:t,-fc! ,/:- : .:';:i:' TEXTBOOK OF MILITARY AERONAUTICS i We miiiit hiiild iHrjfrr «ir f\rrU nnd put the fenr of Oofl in the Oormnn hpnrt hy rondiictiriff miijor HerinI o]>eratinnii nfrninst the (Jcrmnti flrrt. I'-IkmiI hnncs, militnrv Imscs, innniifnctiirinK renters, supply depot* nnd r«llroHd«. This illuKtrntion vUualixed the destruction of GennHn bases across the Hhlne by Allied Air Kleet*. TEXTBOOK OF MILITARY AERONAUTICS BY HENRY WOODHOUSE Author of "Textbook of Naval Aeronautics" member of the board of governors of aero club of america, vice-president aerial league of america, member of national aibeal coast patrol com- mission, chairman of committee of flying equipment cooperating with commandant of third naval district in organizing naval reserve forces, trustke and chairman of committee on aeronautics national institute of efficiency, mem- ber of the society of automotive engineers, educational and industrial delegate, pan-american federation, etc., etc. NEW YORK THE CENTURY CO. 1918 Copyright, 1918, by The Cehtury Co. Publuhsd, May, 1918 i PREFACE One of the purposes of this book is to make avaihible to our prospective American aviators the educational information regarding the man- ner in which aviators fight the enemy — informa- tion which the enemy gets whenever Alhed avi- ators are brought down and printed instructions are found on them, and by daily observations of what the Allied aviators do. The author has found by talking to Allied officers and from the score or so of periodicals of the European countries engaged in this war that all information about modus operandi and aero- planes and devices becomes known to the enemy almost immediately, through the capture of aeroplanes and aviators and through observa- tion of repetition of actions. Another purpose of this book is to supply to military authorities an illustrated pen picture of the history of the evolution of military aeronau- tics, its present status, and the direction of its development. The hundreds of letters received from naval officers regarding the value to them of the "Textbook of Naval Aeronautics" convinced the author of the need for a similar book about military aeronautics rather than for a book deal- ing with the mechanics of military aircraft and their equipment, an extensive subject that would fill a book as large as this volume. The following excerpts of letters from the commanding officers of war-ships give the gen- eral sentiment expressed in the letters received about the "Textbook of Naval Aeronautics," which are close to one thousand in number. Acknowledging the receipt of two copies of the text-book, one for himself and one for the ship's library, for the use of the crew, the com- manding officer of a United States war-ship writes : I know they will be of inestimable value. I have already spent, some pleasant and instructive hours in reading a copy and must admit I knew little of the state of the art as applied to naval aeronautics until this time, and I am sure officers and men will be aston- ished to know how far this science has progressed in our service, and I am further satisfied it will awaken keener interest in this branch of naval activity and produce recruits for this service among our skilled mechanicians and those daring souls to whom the rou- tine life aboard battle-ships may become irksome. There is as much difference between aerial warfare in connection with army operations and aerial warfare in connection with naval opera- tions as there is between the operations of the army and navy proper. The naval aviator who has to hunt submarines, convoy troop-ships, lo- cate submarine mines, patrol the sea-lanes, and manoeuver his aircraft over the sea in scouting or bomb-dropping expeditions must have a training which is entirely different from that of the military aviator, who locates and watches the movements of the enemy's artillery and in- fantry, photographs the enemy's positions, and cooperates in attacking soldiers in the trenches or on the march, etc. Hence the necessity of the two books. Supremacy in the air is the key to victory. "Had the Allies one thousand more aero- planes, we could have easily defeated the Ger- mans." This is the general expression that one hears as the German offensive is raging. - It is an of- ficial as well as a public expression, and every- body scans the reports to find out what the aero- planes are doing and whether the Allies have sufficient aeroplanes to maintain that supremacy in the air which is necessary to decide the war in favor of the Allies. With one thousand additional warplanes, the Allies would have been able to prevent German aviators from mapping the Allied positions; and could have destroyed the militarj- bases, muni- tion-dumps, gun emplacements, the railroads upon which the troops, munitions, and supplies were transported. In short, they could have prevented the massing of such a huge body of 382116 PREFACE troops as the Germans massed for this drive. Aeroplanes are the only things that can pass the German lines. Thev can flv over the Ger- man lines and they can do so at night, when neither the anti-aircraft batteries nor the Ger- man aeroplanes can see them. Unfortunately, the Allies did not have this additional aerial force. To keep one thousand well-trained aviators on the fighting fronts, em- ploying them daily, involves about forty per cent, replacements in aviators, and from one hundred to two hundred per cent, replace- ments in machines per month. In other words, it takes six hundred aviators per month to keep one thousand fighting continuously, operating day and night. Xot all of these aviators are killed or hurt. A large number just "wear out" after a few weeks or months of intensive service, and cannot continue. They must be sent back to rest or to be employed in other work. As for machines, they are used fast and in large numbers. The anti-craft guns are quite accurate at heights of fifteen thousand feet; and speeds up to one hundred and forty miles an hour are necessary to maintain supremacy in the air. Landing such fast machines in small fields leads to damaging a great many. However, when we consider the tremendous value of each aviator, we find that the air service is the most im|)ortant and economic branch of the fighting forces. The accounts show that in 1918 night opera- tions by aeroplanes are used more extensively. One of the despatclies summarizes some of the activities of the aviators as follows: In moonlight of sufficient brilliance to permit the reading of a newspaper, bombing planes and warplanes swarm out, carrying high explosives, far behind the battle zone. They broaden the area of death scores of miles, few villages escaping. When the sun rises, the bombers, like prowling night birds, return to their roost ; ground fighting speeds up, and scout fleets, succeeding the bombers, fly low over the clashing infantry, harassing enemy columns and observing for the artillery. One of the reports of the daytime aerial op- erations reads as follows : The enemy's low-flying aeroplanes were most per- sistent in their attack on our infantry in the forward areas. Many of these machines were attacked and brought down by our pilots. A total of twenty-nine hostile machines were brought down and twenty-five others were driven down out of control. Two enemy balloons were also destroyed. Nine of our machines are missing. Our machines on Saturday carried out another suc- cessful raid on factories in Mannheim. Nearly one and a half tons of bombs were dropped, and bursts were seen on a soda factory, the railway, and docks. Several fires were started, one of which was of great size, with flames reaching to a height of 200 feet and smoke to 5000 feet. The conflagration was visible for a distance of thirty-five miles. The weather Saturday again favored operations, and our aeroplanes were constantly emj)loyed in re- connoitering positions of troops, in photography and bombing, and in reporting suitable targets for our artillery. Many thousands of rounds were fired by our pilots from low altitudes on hostile troops massed in villages and in the open continuously throughout the day. More than fourteen tons of bombs were dropped on enemy billets, on his high-velocity guns, and on rail- road stations in the battle area. Our bombing-aeroplanes were attacked by thirty- two hostile machines, and a fierce fight ensued. One of the enemy's aeroplanes was brought down in flames, and another was downed, and fell in the center of Mannheim. Five others were driven down out of con- trol. Despite this severe combat and the enemy's heavy anti-aircraft gunfire, all our machines returned except two. During the night ten heavy bombs were dropped on an important railway's bridge and works at Konz, just south of Treves, in Germany. Eight of these bombs were clearly seen to be bursting among the railway's works. It is stated officially that this is only the be- ginning of the intensive warfare that is to fol- low, one of the great drives that are to follow each other in quick succession hereafter. We must, therefore, concentrate efforts on our air- craft program and put all the manufacturing facilities now standing virtually idle in the United States to turn out aircraft and parts. No time .should be lost in adopting the plan which is to give the Allies the supremacy in the air that is so vital, as it will decide the war in favor of the AHies. Henry Woodhouse. INTRODUCTION As President Wilson has repeatedly pointed out, it is most important that the country be educated to its task. The workers for aerial preparedness have found in the past that the principal work was to teach the public the hnportance of aerial pre- paredness, the tremendous possibilities for the employment of aircraft in connection with every branch of the army and navy,* and independ- ently. To teach the busy military man, so that he would recommend the expansion of the air service to the legislator, so the legislator would support the military man's recommenda- tions; to teach the engineer, so that he woidd develop better aircraft especially suited for mili- tary purposes; and the general public, in order to inspire j^oung men to volunteer their services and men and women to work for the develop- ment of our air forces. Now that the world's strategists agree that the present war is to be decided in the air, and this country has been asked and has undertaken to supply the thousands of aviators and tens of thousands of machines needed to maintain aerial supremacy on the side of the Allies, the great demand is for reliable information regarding the use of aircraft for military purposes. Executive military officers who want to know the exact status of military aeronautics and the principles of aerial strategy; students learning military aviation who want to know in detail the various phases of aerial warfare; aeronautic en- gineers and manufacturers who want to know the duties of aircraft, in order to design and make more efficient machines; and the average patriot who wants to learn about aeronautics in the hope of finding an opening to employ his or her efforts to help the Government in carrying the war to a successful conclusion, will find in this book the publication they have been looking for. Another commendable point — it has many — is the strong message which the book carries to the American authorities and public. The au- thor brings out once more the importance of air power and urges full-size measures. In this again every one will agree. It is time that we shun half-measures. The greatest of our na- tional sins in aeronautic matters has been over- reliance on minimums — minimum plans, based on minimum understanding of the military and aeronautic situation, further weakened by mini- mum appropriations. We have also had some minimum men, having minimum knowledge and experience, who did not realize, as one must do in war-times, the possible necessity of quick ex- pansion, the possibility of delays, due to trans- portation of materials, labor conditions, mis- takes, etc., The one national resolution that we ought to make in dealing with aeronautics should be to eliminate minimums of all kinds and adopt maximums in programs, men, appropriations, manufacturing facilities, etc. Having adopted maximums, let us add to each, so as to have a substantial margin of safety to insure success under any circumstances. Alan R. Hawley, President Aero Club of America. CONTENTS Chapter I The War to be Decided in the Air Aerial Supremacy Must be Maintained Day and Night Air Service the First Line of Offence and Defence — Tlie Use of Aircraft in Connection with Military Op- erations — Aerial Operations Independent of Land Forces— Cooperation Between the Army and the Navy in Conducting Major Operations Chapter II The Warplane for Bombing AND Torpedo Attacks 9 The New Revolutionary Weapon Which Combines Power, Mobility, and Control, and Permits Major Aerial Operations Against German Military Centers and Naval Bases — Night Raids Can be Conducted Without Difficulty — Allies Have Never Had Enough Large Aeroplanes With Which to Conduct Major Aerial Operations — Huge Warplanes to do at Long Range What Huge Guns Can Only do at Short Range — Proportion of Bombing Planes to be Increased — Huge Warplanes and Torpedoplanes Capable of Car- rying Tons of Explosives— Tlie Marvelous Giant Ca- proni Warplane — French and British Bomb-dropping Machines — The Huge Curtiss Triplane — Long-distance Bombing Raids not New — Long-distance Allied Raids Into Enemy Country in tlje Western Theatre of War — Extensive Damage Can be Done by Bombs — Night Facilitates Bombing at Close Range — Need of Silencers to Eliminate Noise of Approach — Bombs and Bomb- dropping Mechanism— Bomb Sights — The Scientific Side of Bomb Dropping — Night Bombing Requires Knowledge of Aerial Navigation by Instruments — Night Landing Lights — Navigation Lights — The Sperry Automatic Pilot — Turn Into the Wind to Avoid Drift — Formation for Boml)ing Raids — Rules for For- mation Flying — How 1,000 Warplanes Could Raid Kiel Chapter III Dropping Bombs from Aero- planes 31 Chapter IV Battleplanes AND Aircraft Guns — The Dominant Factors in Main- taining the Supremacy of the Air . Proportions of Different Types of Armed Aeroplanes in the Air Service — Tlie Five Fundamental Factors in Maintaining Supremacy in the Air — Types of Aero- planes and Their Armament — Avions de Chasse or Combat Machines — Avions Types "Corps d'arme" — Used for Spotting Artillery Fire, Aerial Photograph, etc. — Pursuit, or Combat Machines — The Triplane — A Scientific Solution of the Problem of Getting Speed and High Factor of Safety — Triplane Safe, Even if Wing is Shot Away — Battleplanes That Collapsed in the Air — Loss of Factor Safety Not Compensated — Large Aerial Destroyers — Aeroplane Guns and Can- non — Large Aeroplane Guns — Problems of Armoring — Vulnerable Parts of the Aeroplane — Bullets vs. High Explosive Shells — Fast vs. Slow Muzzle Velocity — Re- coil ; a Solved Problem — Tactics in Air Duels — ( 1 ) Air Duels in Which Participants are Both Air Fighters Whose Only Function is to Keep the Sky Clear of En- emy Machines — (2) Air Duels Between Combat Ma- chines and Armed Photographing, Spotting, or Bomb- ing Machines — (3) Air Duels Between Large Armed Aeroplanes — Formation in Air Fighting — Lamp Sig- nals for Use of Leaders of Formations — Offensive Fighting Tactics — Thorough Knowledge of Weapons is Requir^ 39 PAGE Chapter V The Fundamental Principles OF Aerial Combat 63 Chapter VI Directing Artillery Fire by Night and Day Signaling to and from Aircraft "^^ Methods and Codes Used for Communicating From and to Aircraft — Tlie Observer's Special Map — Signaling With Very's Lights — Kite Balloons for Spotting Artil- lery Fire — The Dubilier-GoU Semi-Radio Telephone System for Captive Balloons — Signaling Between Air- craft — Cooperation Between Balloons and Artillery Chapter VII Kite Balloons the Eyes of the Artillery 81 Maneuvering — Camp Equipment of a Kite Balloon Unit — An Artillery Captain's Experience — Personnel of Kite Balloon Company — Preparations for Ascen- sion — What You Can See from a Kite Balloon — Aero- plane vs. Captive Balloon — A Leap Into Space from a Kite Balloon — A Curious Maneuver — A Drama at the End of a Cable Chapter VIII Aero Photography ... 91 Tliousands of Miles of Photographic Maps — Twenty Per Cent of Aeroplanes at the Front Used for Aerial Pho- tography — The Aerophotographic Organization of an Army — Seven Aeroplane Bombs Photographed Soon After Release by the French Aviator That Released Them on a German Plant — Aeroplane Photography That Shows Minutest Details of a Factory Cliimney Being Repaired — A Photographic Officer Should be Fa- miliar With the Following Technical Subjects — Cam- eras and Fittings — Loading of Plates — Negative Devel- oping — Finish of Work — A Squadron Photographic Non-commissioned Officer With His Three Men Should be Familiar With the Following — Science of Aeropho- tography Still Young — Essentials in Aerophotographs — Relative Elevations Hard to Show — Interpreting Photographs Requires Skill — Problems of Aerophotog- raphy — Different Types of Cameras — Possible Troubles in Taking Aero Photographs and Their Remedy Chapter IX Reconnaissance and Contact Patrol Work by Aeroplane .... Ill Five Types of Reconnaissance — Procedure in Issuing Orders "for Reconnaissance — How Reconnaissance Aero- planes are Guarded and Protected — Protecting Recon- naissance Machines — Navigation Rules for Reconnais- sance — Pilots and Observers — Aircraft Report Diary Contact Patrol (Aeroplanes De Liason) Chapter X Night Flying 126 Zeppelin Raids Forced Aeroplane Night Flying — Long- distance Bombing Night Raids — Aeroplanes Cannot be Seen One Hundred Feet Away — The Operation of Aeroplanes by Night — Lighting the Aerodromes — The "Honig Circles" Signals for Night Flyers — Lights for Night Landing Grounds — Returning from Night Flights — The Signals — Lighting Equipment of Aero- planes — Instruments Painted with Luminous Com- pounds — Adventures in Night Flying Chapter XI Radio for Aeroplanes 139 CONTENTS Chaptee XII Military Aerostatics Dirigible Balloons — Rigid, S«>mi-Ripid. and \on-Rigid Dirigibles — Military Observation Balloons — Employed at Nght as Well as in the Daytime — For Directing Artillery Fire — Hydrogen Supply and the "Nurse" — The Windlass — Free Balloon Training Necessary — The Free Balloons — Synopsis of the Course of Training at United States Army Balloon School Chapter XIII Hydrogen for Military Pur- poses page 157 167 Proportii-s of Hydrogen — Vitriol Process — Electrolytic Metiiod — Silicol Process — Iron Contact Process — Alu- minum Caustic Soda Process — Hydrolithe — Hydroge nite — Hydrogen from Water — Gas — Aluminum Potas- sium Cyanide Process — Acetylene Process — Iron and Water Process — Silico-Acetylene Process — Decarbura- tion of Oils Chapter XIV Training Aviators for the United States Army ; Home and For- eign Service Schools of Military Aeronautics (Ground Schools) — Instruction in the Junior Wing — Instruction in the Senior Wing — Training at Army Aviation Schools — Tests for an Aviator's Certificate — Spherical Balloon Pilot's Certificate — Dirigible Balloon Pilot's Certifi- cate — Aviator's Certificate — Hydroaeroplane Pilot's Certificate — United States Army Preliminary Flying Test — United States Army Reserve Military Aviator Test Chapter XV' Regulations for Uniforms of U. S. Aeronautic Personnel Uniform Specifications — Coats, Aviator, Anti-sinking — Face Mask, Aviators — Flying Suit — Gloves, Aviator, Winter — Gloves, Aviator, Summer — Goggles — Helmet, Aviators, Summer — Helmet, Aviators, Winter — Avia- tion Service — Mufflers — Shoes, Aviator, Winter — Boots, Rubber, Wading (Wading Pants) — Breeches, Winter, Motorcycles — Insignia, SU-eve — Changes in Regulations for the Uniforms of the United States Army, 1014, to Cover Aviation — Uniforms of the United States Army — Officers — Enlisted Men Chapter XVI Aeronautic Maps Five Types of Aeronautic Maps — Tlie Map With Pho- tographic Reproduction of Route and Information Re- garding Prevailing Winds — The War Prevented an International Convention on Aeronautic Cartography — Existing Aeronautic Maps are the Result of Work by Aero Clubs Chapter XVII History of United States Army Aeronautics Aeroplanes of All Types Purchased by the Signal Corps — The Mexican Campaign Found the United States 179 190 197 204 PAQB Army Unprepared Aeronautically — Aircraft Board Created— The $1,0.32,294,260 Army Air Program— Long Delay in Extending Plans and €retting Appropria- tions Causes Trouble Chapter XVIII The Evolution of Mili- tary Aviation 222 Signal Corps Specification, No. 486 — General Condi- tions of French Military Competition of 1910-1911 — The Kaiser's Prize for a Motor Competition — Aero- planes First Used for Military Purposes in the Italian- Turkish War — French Aviation Developed by Public Interest — Firing Guns, Dropping Large Bombs, and Two-engined Aeroplanes Once Considered Impossibil- ities — British Army Tests for Aeroplanes in 1914 — Aeronautics at the Outbreak of the War — Advent of Large Warplanes in 1917 Permitted Conducting Major Aerial Operations — The United States Lagged Behind for Seven Years — Aero Club of America's Monumental Work in Developing Our Aerial Forces — America's En- try Into the War Brings Decision to Concentrate Ef- forts to Strike Germany Tlirough tlie Air — Tlie Prob- lem of Delivering Aeroplanes to Europe — British Air Ministry Created Chapter XIX Some Problems in Aero- plane Construction Military Functions of Aeroplanes— Some Problems in Construction — Propeller Stresses — Suggestions for Im- provements in Design Chapter XX Methods of Measuring Air- craft Performances Aeroplane Testing — Speeds 245 259 Chapter XXI The Sperry Automatic Pilot 269 Incorporating a Gyroscopic Reference Plane and Clin- ometer for Aeroplanes — Its Application for Military Purposes Chapter XXII The Case for the Large Aeroplane 274 Aerodynamical Bases of Comparison — The Effect of an Increase in Size on the Structural Weight of Aero planes — The Effect of an Increase in Siz.e Upon an Aeroplane's Performance — Tlie Large Machine from the Pilot's Standpoint Chapter XXIII Every Military Aviator Ought to Know What His Own and the Enemy's Machine Can do and How They Look 282 Index 293 TEXTBOOK OF MILITARY AERONAUTICS A squadron of Gotha biplanes which raided I.ondon in full daylight on July 7th, 1917. They were equipped with two 260 horse- power Mercedes engines and carried 800 pounds of explosives. Forty people were killed and 19-1 injured. CHAPTER I THE WAR TO BE DECIDED IN THE AIR This war is to be decided in favor of the side which maintains its supremacy in the air through having the largest number of efficient aircraft and airmen. The world's strategists agree on this point, and the struggle for command of the air is rag- ing. The air service is the balance of power, a most marvelous power combined with unlimited mobility and control to such a tremendous ex- tent that it makes of the aircraft a new arm of revolutionary potentiality. Aerial Supremacy Must Be Maintained Day and Night Command of the air means maintaining su- premacy in the air by day and by night. Holding supremacy of the air during the day- time avails little if the enemy has supremacy of the air at night, and vice versa. Aerial supremacy at night can be main- tained by conducting extensive night-bombing operations against German military centers, military supply bases, and railroads, and by sub- stantial naval aerial operations, also at night, against the German fleet and U-boat bases, striking the ships of the German fleet with tor- pedoes launched from torpedoplanes, and the U-boats and their bases with bombs dropped from the air. Aerial supremacy during the daytime means guarding the different fronts with an overwhelming number of aeroplanes of the fighting type, as well as with the types used for regulating artillery fire, for aerial photography, for scouting, and in connection with infantry and cavalry operations; and by short, daylight, bombing expeditions. Major aerial operations, supported by ener- getic military operations on land and naval operations at sea, could, as Admiral Fiske has pointed out repeatedly, in a comparatively brief period of time destroy Germany's strength as nothing else can. They could do more than the addition of a million men on land and five TEXTBOOK OF ^IILITARY AERONAUTICS Caproni warplanc — one of the largest warplanes In the world. naval squadrons at sea could accomplish: be- cause, as is generally admitted, additional men would avail little against the entrenched Ger- man lines. Capturing lines at present involves going through many lines of trenches ; and that involves lengthy preparatory activities. The same thing is true at sea; ships and men can do little against the protected German fleet, because of the miles of mines and other defenses which guard it. As Admiral Fiske has pointed out in the "Textbook of Naval Aeronautics," the large warplane combines power, mobility, and control as no other weapon does, and permits the quick concentration on any given point of large jnasses of explosives. • Aircraft can flj' over all obstructions, both at sea and on the land, as though they did not ex- ist. True, during daylight squadrons of Ger- man battleplanes and hundreds of German anti- aircraft guns would attempt to prevent the progress of the Allies' raiding forces, which would involve casualties, although only a frac- tion of the casualties that result every day in the least important land operations. Air Service the First Line of Offense and Defense The air service has become the first line of of- fen.se and defense. Every military operation is preceded by aerial operations which include: (1) Bombing the enemy's bases, destroyin<)- railroads, trains, and enemy material. This is done with bombing aeroplanes, self- sufficient, or protected by fighting machines. (See chapters on "Battleplanes and Aircraft Guns" and "Warplanes for Bombing and Tor- pedo Attacks.") (2) Fighting hostile aeroplanes, preventing- them from making aerial reconnaissance or tak- ing photographs of one's positions, thus direct- ing the fire of their artillery, etc. Small, fighting aeroplanes are used for this purpose. (See chapter on "Battleplanes and Aircraft Guns.") (3) Reconnoitering. Determining the strength of the enemy, its composition, disposi- tions, and probable intentions. Aeroplanes of different types are used for this purpose. (4) Photographing the enemy ])ositions. These photogi-aphs, by giving accurate details of the enemy's position, permit conducting op- erations based on exact information, and there- fore afl'ord the greatest chance for success. Aeroplanes and kite-balloons are used for this purpose. (5) Directing artillery fire. This is done with both aeroplanes and kite-balloons, and has become an exact science. (6) Contact patrol. Coordinating the ac-, tivities of the different arms during attacks. Tn| this role the aviator becomes the master-mind that watches over everv movement of the eneiiiv. THE WAR TO BE DECIDED IN THE AIR as well as of his own forces, and transmits to his own forces information regarding the advance, retreat, and other movements of the enemy, di- recting the sending of reinforcements to the weak or threatened points, and controlling the fire of the machine-gun batteries as well as of the artillery. Aeroplanes of different types are used for this purpose. (7) Cooperating with the infantry and other arms in taking trenches, by flj'ing low over the trenches and attacking the enemy with machine- guns. Different types of one- or two-passen- ger aeroplanes are used. (8) Cooperating with the artillery and other arms by attacking the crews of hostile batteries with machine-guns. Different types of one- or two-passenger aeroplanes are used for this pur- pose. (9) Making attacks with bombs or gims against land forces, to engage the enemy and distract his attention from ope^-ations which are about to be conducted ; in other words, perform- ing the functions of cavalry, which has been used but httle along the western front. (10) Conducting aerial attacks from the rear with bombs and machine-guns against enemy land-forces, to relieve the pressure being brought by the enemy's forces against any one point, or to wear down the strength of the ene- my's land-forces. Different types of battle- planes are used for this purpose. (11) Preventing reinforcements from reach- ing the enemy, by flying far into the enemy lines, watching for trains and attacking them with bombs and machine-guns. Different types of battleplanes are used for this purpose. The Use of Aircraft in Connection with Military Operations The use of aircraft in connection with mili- tary operations has become so extensive that it may be said that the air service, cooperating with the land-forces, is, in itself, an aerial army, J A remarkable pliotojiraph of the capture of German trenrhes by the French infantry on the Somme. This photograph was taken by a French aviator at a height of only 500 feet. The trench in the left foreground, named the Guillaume Trench, had formed the German front line. Slanting up to it from the right-hand corner is a communication-trench, by which French reinforcements are seen arriving. Shell craters are seen everywhere. 6 TEXTBOOK OF MILITARY AERONAUTICS Air craft can go over all obstructions which stop the pnif^rc^s of .snii)s and armies. How conipktc is its supremacy may be seen from the above photograph, taken from an Italian military aeroplane (part of which is shown in the photograph) while crossing the Alps. Italian aviators connected with the Trentin Army flew daily under such conditions. the aeroplanes performing the function of cav- alry, artillery, and infantry. General Haig, commander-in-chief of the British forces in France, in his official reports has stated repeatedly that the employment of aeroplanes in connection with military opera- tions is practically unlimited. In one of his latest reports he speaks of the work of the Royal Flying Corps as follows : "In this combination between infantry and artillery the Royal Flying Corps jAayed a highly important part. The admirable work of this Corps has been a very satisfactory fea- ture of the battle. Under the conditions of modern war the duties of the Air Service are many and varied. They include the rcgu'ation and control of artillery fire by indicating targets and observing and reporting the results of rounds; the taking of photographs of enemy trenches, strong points, battery positions, and the effect of bombardments; and the observa- tion of the movements of the enemy beliind his lines. "The greatett ikUl and daring has been ihown in the performance of all these duties, as well as in bombing expeditions. Our Air Serv- ice has also cooperated with our infantry in their assaults, signaling the position of our attacking troops and turning machine-guns on the enemy infantry and even on his batteries in action. "Not only has the work of the Royal Flying Corps to be carried out in all weathers and under constant fire from the ground, but fight- ing in the air has now become a normal pro- cedure, in order to maintain the mastery over the enemy's Air Service. In these flights the greatest skill and determination have been shown, and great success has attended the ef- forts of the Royal Flying Corps. I desire to point out, however, that the maintenance of 7nastery in the air, xchich is essential, entails a constant and libera! supply of the most up-to- date machines, without which even the most skilful pilots cannot succeed. "The style of warfare in which we have been engaged offered no .scope for cavalry action, with the exception of the one instance already mentioned, in which a small body of cavalry gave useful assistance in the advance on High Wood." THE WAR TO BE DECIDED IN THE AIR Aerial Operations Independent of Land-Forces Aerial operations independent of the land- forces are increasing in number and extent. The advent of large battleplanes with a flying radius of close to 1000 miles, and capable of carrying one ton or more of explosives, will in- crease the extent of bombing operations. It is, roughly, between 450 and 500 miles from Great Britain to Kiel, Wilhelmshaven, and Helgoland. It is less than 300 miles from the Allies' lines to Essen and Diisseldorf, and it is less than 100 miles from the main Allied aeronautic bases to Zeebrugge and Ostend, which are important bases for U-boats and German destroyers. Details regarding the types of warplanes used for bombing and major operations are given in the chapter on "The Warplane for Bombing and Torpedo Attacks." Cooperation Between the Army and the Navy in Conducting Major Operations As pointed out in the "Textbook of Naval Aeronautics," it is difficult to define the lines of demarcation where the navy ceases to operate and the army begins to operate, and vice versa. The Allies have, very wisely, combined their aerial resources to conduct major aerial opera- tions. It would be hard to figure out under whose jurisdiction a raid should be conducted which involves flying over land and sea; therefore all lines of demarcation have been wiped out in so far as major operations are concerned, the bombing squadrons usually including army and naval aviators of two or three of the allied na- tions. It is to be expected, therefore, that army aviators will be called upon to participate in operations in which their aeroplanes will carry torpedoes, to be used in attacks against the German fleet, just as naval aviators have been called upon to conduct bombing operations against German military bases, as in the case of the raids on Essen and Obendorf . In the United States the army has charge of the coast defense ; therefore the army air service uses land and water aeroplanes, airships, and captive balloons. The functions of aircraft for coast defense are: ( 1 ) For reconnaissance, patrolling the coasts, looking for hostile ships of all types, enemy sub- A French Nieuport fighting aeroplane photographed as it was passing another military aeroplane in midair. 8 TEXTBOOK OF MILITARY AERONAUTICS marine bases, and mines. Aeroplanes, large and small, land and water, and dirigibles are used. (2) To prevent the landing of enemy forces by attacking the hostile ships and transports with torpedoes, guns of large caliber, and bombs. Aeroplanes, land and water, and dirig- ibles are used. (3) To attack hostile bombarding and block- ading ships with torpedoes, guns, and bombs. Aeroplanes, land and water, and dirigibles are used. (4) To direct and spot the fire of coast de- fense batteries. Aeroplanes, land and water, dirigibles, and captive balloons are used. (5) To fight off enemy aircraft, preventing them from gathering and transmitting informa- tion about the location and disposition of our coast defenses. Aeroplanes and dirigibles are used. (6) To transmit confidential information be- . tween militarj' stations. Aeroplanes and dirig- ibles are used. (7) To convoy troopships, merchantships and army transports on coastwise trips. Aero- planes, land and water, and dirigibles are used. (8) To locate mine-fields and assist trawlers in destroying mines. Aeroplanes, dirigibles, and captive balloons are used. (9) To serve as the "eyes" in planting mines. Captive balloons, dirigibles, and aeroplanes are used. The effect of a bomb dropped on an aeiodioiiie at ftaionica by a Cjeniian aeroplane. It just missed hitting the hangars and garage. CHAPTER II THE WARPLANE FOR BOMBING AND TORPEDO ATTACKS The New Revolutionary Weapon Which Combines Power, Mobility, and Control, and Permits Major Aerial Operations Against German Military Centers and Naval Bases It is generally agreed that the most effective and quickest way of achieving victories of de- cisive importance over Germany is : ( 1 ) By conducting substantial bombing oper- ations against German military centers, military supply bases, and railroads; (2) By conducting substantial aerial opera- tions against the German fleet and U-boat bases, striking the Gei-man fleet with torpedoes launched from torpedoplanes and the U-boats and the bases with bombs dropped from the air, as well as with shots from aeroplane guns of large caliber. Such major aerial operations, supported by energetic military operations on land, and naval operations at sea, could, as Admiral Fiske has pointed out repeatedly, in a comparatively brief period of time destroy Germany's strength as nothing else can. They could do more than the addition of a million men on land and five naval squadrons at sea, because, as it is gener- ally admitted, additional men could do but lit- tle against the entrenched German lines. Cap- turing lines at present involves going through many lines of trenches, and that involves lengthy preparatory^ activities. The same thing is true at sea; ships and men can do but little against the entrenched German fleet, because of the miles of mines and other defenses which protect the German fleet. As Admiral Fiske has pointed out in the "Textbook of Naval Aeronautics," the large warplane combines power, mobility and control as no other weapon does, and permits the quick concentration on any given point of large masses of explosives. Aircraft can fly over all obstructions, both in the sea and on the land, as though they did not exist. Tnie, during daylight, squadrons of German battleplanes and hundreds of German anti-aircraft gims would attempt to prevent the progress of the Allies' raiding forces, which 10 TEXTBOOK OF MILITARY AERONAUTICS would involve casualties — although only a frac- tion of the casualties that result every day in the least important land operations. Night Raids Can Be Conducted Without Difficulty A thousand aeroplanes could flj' from the nearest Allied bases to the German bases at Kiel and Wilhehnshaven, or to Essen, Berlin, and other German military centers, almost un- seen. At night aeroplanes can hardly be seen a hun- dred feet away by other aeroplanes, and it is a most difficult thing for searchlights to locate them in the sky. Under the best weather con- ditions and a fairly clear night, a squadron of Allied aeroplanes started from Salonica re- cently to bomb the German lines. They ar- rived over the German lines, and were surprised when all at once the lights of the German aero- drome were lighted. The Allied aviators dropped their bombs and returned to their own aerodrome — to find that German aviators had in the meantime bombed the Allied lines. The squadrons had passed each other en route, but neither side had sighted the other. In each case the officers in charge of the aerodromes lighted the aerodromes when they heard the noise of motors, thinking that their aviators were returning from their bombing raid. In scores of cases single aeroplanes or fleets of five or more aeroplanes have carried on bombing raids during the night without being seen by Germans. Therefore, the solution of striking Germany through the air rests in night raids. Allies Have Never Had Enough Large Aeroplanes with Which to Conduct Major Aerial Operations Neither the Allies nor the Teutons have had a sufficient number of large aeroplanes to per- mit them to conduct major aerial operations against the other side. While there are now thousands of aeroplanes employed, whereas there were only a few hundred in the beginning of the war, the use of aeroplanes has been so greatly extended, and they are used for so many miportant purposes in connection with military, coast patrol, and naval operations, that it has been impossible to accumulate the number of aeroplanes recjuired for major aerial operations. It is also true that until recently there were not available the types of large aeroplanes re- quired for long distance bombing or torpedo launching operations. Huge Warplanes to Do at Long Range What Huge Guns Can Only Do at Short Range Major R. Perfetti, the head of the Special Italian Commission for Aeronautics in the United States, brought to the attention of the Tlie Gcriiinii Gotliii warpliinc. THE WARPLANE FOR B03IBIXG AND TORPEDO ATTACKS 11 When the "Emergency Air Fleet" Crosses the Rhine! Allied military authorities the fact that huge warplanes can do at long range what huge guns can only do at short range. He pointed out that, just as reducing the fortresses and posi- tions which were supposed to be invulnerable was done by concentration of the fire of many huge guns, the reducing of distant military and naval bases can be accomplished by the drop- ping of tons of explosives simultaneously by hundreds of warplanes. This was an obvious truth, which heretofore could only be figured out theoretically, but not proven in practice, because of the lack of war- planes powerful enough to carry tons of explo- sives. jSIajor Perfetti could state it as a tested and proven truth, because Italy has the huge warplanes needed for these operations, and has been using them on a limited scale in her oper- ations against the Austrians over the moun- tains and across the Adriatic Sea. If the United States takes steps promptly to build thousands of these huge triplanes, it is possible that substantial deliveries will begin to be made in six months, making it possible to figure on aerial operations against the German naval and military bases next spring and sum- mer. Nothing else affords such possibilities. Proportion of Bombing Planes to Be Increased Heretofore, owing to limited production, the proportion of bombing planes to the number of aeroplanes used has been only about ten per cent. Twenty per cent, have been small, fast 12 TEXTBOOK OF MILITARY AERONAUTICS A British aviator throwing a bomb. fighting machines to fight enemy aviators en- gaged in similar work, or in photographing, di- recting artillery fire, reconnoitering, etc. Now that the United States has entered the war, and has mobilized manufacturing resources to the point where a program to munufacture 100,000 aeroplanes could be completed in three years, the proportion of bombing planes can be increased by the addition of thousands of huge bombing warplanes, many of which can be man- ufactured in America, the Italian Government, like the British and French Governments, hav- ing offered to cooperate with the United States Government. Huge Warplanes and Torpedoplanes Cap- able of Carrying Tons of Explosives The Allies now have huge warplanes and tor- pedoplanes capable of carrying from two to three tons of explosives or torpedoes. The gigantic Caproni torpedoplanes permit aerial o])erations from any of the Allied bases to any German naval or military base and return — with substantial reserve fuel. The Curtiss triplane air-cruiser, while handi- capped by the heavy flying-boat hull, is also a good possibility. The twin-motored Handley- Page biplane and the new three-motored Gal- laudet seaplane are among other possibilities for long-distance aerial raids. The Marvelous Giant Caproni Warplane Italy leads in types of bombing and gun-car- rying aeroplanes. The following are some of the most important types of Italian aeroplanes, types which, if built by thousands, will make it possible for the Allies to conduct the major aerial operation a'?ainst Germany which is to ensure her down- fall: (1) The largest Caproni triplane. This re- markable warplane is equipped with three large h.p. Fiat motors. The details about this ma- chine are kept secret, but it is known that the machine, as a whole, follows the characteristics of the Caproni warplanes. This machine, judged by the smaller types, must carry about five tons of explosives and fuel for twelve hours, at a speed of about eighty miles an hour. (2) The small bombing type Caproni tri- plane. This machine, which is illustrated here- with, is a triplane, with two fuselages, equipped with three Fiat or Isotta-Fraschini motors, two in front fitted with one propeller respectively, and one in the rear, also fitted with one pro- peller. Each of the engines is independent of Italian Battleplane.. From left to rl.ht: th- C.pronl triplane. .•,uipp,-.l v.i.1. .h"-^ •-.> '< tors. THE WARPLANE FOR BOMBING AND TORPEDO ATTACKS 13 The Italian Caproni warplane returning from a flight. the others, so that if two of the engines should stop, the machine could still keep in the air with the power of one motor. (3) The bombing type Caproni biplane. This type of machine is most remarkable for its speed. It is equipped with three Fiat or Isotta-Fraschini motors of 200 h.p., and three propellers, two tractors and one pusher. French and British Bomb -Dropping Machines The following are a few of the many French and British bomb-dropping, gun-carrying ma- chines: The British Handley Page, equipped with two Rolls-Royce motors. This biplane has carried 21 passengers in one flight and has a top wing-spread of 98 ft. and a lower wing of 98 ft. It has mountings for large guns. The twin-motored Avro biplane, a triplace equipped with various kinds of motors. In the "short distance" class of bombers are: The Sopwith 130 h.p. triplane known as the "Tripe Hound." This is a single seater equipped with a Clerget motor. The two seater 1Y2 strut Sopwith biplane equipped with a Clerget motor. This is used extensively by the Royal Naval Air Service for bombing, and the Royal Flying Corps for fighting. To these must be added the machines de- signed by the Royal Aircraft ISIanufactory, which include the BE-2C, R. A. F. motor, rather Caproni biplane: the small Italian fifljhting Monoplane, and the Caproni bombing biplane. 14 TEXTBOOK OF MILITARY AERONAUTICS POSITION OF SIGHT when bomhs arc rcleasi-d on lo 2nd Tari(ct The l*f>in!cr (sec dUij(rani inset) was first set at 12 dc4rcc\ ; then vktial ray aJvjnccd to 2nd '1 .irSct hy tiltinjt prisni, the '.:i4i.-l bcinit held in sntht by ^: .iiJually reducing anfilc until lidt-^rtts rtachcd, when pointer :iiiil bi^nihs arc rcIcawJ Dmawixo muM THE Ix>MtK>N Okai*i(u SiiowiNti IIow Tiir (itmiA AiMH Its Homiim Thr art of arrlal iMmibardmrnt \h liirjrrly n ?imttrr of lurk. To n'tliirr this i-Innrnt thr rnrmy bus pnKlutvd the instruinciit lllus- tratrd, thr Grorz boinlwIroppcr'H trloM-opic hijrht, which Is included In the equipment of the Uotha, wliich lias u speed of ninct/- thrrc miles an hour, therefore make« accurate hitting dlfHcult. THE WARPLANE FOR BOMBING AND TORPEDO ATTACKS 15 British airmen taking the offensive against a German brigade concentrating for .ittnck near Arras. The aviators discovered the Germans concentrating for an attack and dropped heavy bombs on them, destroying their machine guns and ammunition and dispersing them. In addition, the aviators advised the British artillery which opened fire on the German concentration, so that the German attack was never even launched. — (Drawing by the "Illustrated London News'" artist.) slow and a poor climber, but a good machine for night flying, on account of its inherent stabil- ity; the BE-2E, the FE, which is a two-seater pusher fighting machine ; which is a faster scout, just being tested, and the BE-12. Also the two- passenger Avro, armed with one or two guns. The French also use a great many different types of machines, the following being used for bomb-dropping: The Breguetj equipped with a single motor. The Caudron G-4, pilot and observer; equipped with two La Rhone motors. The Caudron R-4, three-passenger. The Farman, pusher type, two-passenger, equipped with one Renault motor. The Germans have several tj^pes of bombing machines, of which the Gotha is most prom- inent. It is a biplane equipped with two 260 h.p. jVIercedes motors, carries fourteen bombs, and is armed with three guns. The Huge Curtiss Triplane The huge Curtiss triplane air-cruiser built for the British Government is a good possibility The Caudron G-6, two-passenger; equipped as a long-distance bomb carrier, for aerial oper- with two La Rhone motors. ations against Germany. For such a purpose The Dorand A-R, two-passenger; equipped the boat-hull can be eliminated, and its weight- with one motor. carrying ability increased thereby. Having The Farman, pusher type, two-passenger; multiple power-plants, it can make the flight equipped with 170 h.p. Renault motor, carry- from an Allied base to Kiel or Berlin or Essen ing one or two Lewis guns forward. The Letort, equij^ped with two motors. The Moineau, three-passenger; one motor, connected to drive two propellers. The Voisin-Peugeot, two-passenger ; equipped with a Peugeot motor. with a good margin of flying ability. The big Curtiss triplane, with a few changes in construction, will make a most efficient tor- pedoplane, capable of carrying a magazine of torpedoes. The new three-motored Gallaudet seaplane 16 TEXTBOOK OF MILITARY AERONAUTICS The Twin-Motored Handlcv Pajrc Bomhinfr Biplane. A Handley Pape has flown from London to Asia Minor, with stops, and dropped bombs on Constantinople. It carried seven men, spare motors and supplies. Larger Handley Pages can fly across the Atlantic and bomb the German bases and munition plants. The Krrnrh Farmnn mnrhinc rquip|>red by naval aeroplanes. September 23 — .\djutant Baron bombards by night military establishments at Ludwigshafen, and continuing his route, bombs Mannheim. .September 2+ — Captain de Beauchnmp and Lieutenant Oauoourt bomb the factories of Essen (Westphalia). September 24-25 — French bombarding squadrons effect by night an attack on the blast furnaces of Dillingen (Rhineland) and .Saarlnuis. .September 27— Naval raid on airship shed.s at Ev^re. Berchem St. Agathe. and Ettcrbeik. October 5 — French bombard aviation ground at Colmar (.\1- sace). THE WARPLANE FOR BOMBING AND TORPEDO ATTACKS 19 Night raid by French aeroplanes on electric searchlights and buildings at Zeebrugge. October 9-10 — Adjutants Baron and Chazard bombard by night the Bosch magneto factory at Stuttgart. October 10-11 — French night raid on Lorrach establishment, Colmar aviation ground, and Mulheim railway station. October 13— Franco-British squadron of 40 aeroplanes bom- bard the Mauser works at Oberndorf. October 32 — French aeroplanes bombard blast furnaces of Ilagondange. October 23— British aeroplanes carry out a further attack on Hagondange. November 9 — French aviator bombs railway station of Ofen- burg. November 10 — Xaval raid on Zeebrugge Ostend. Seventeen British aeroplanes bombard the steel works of Frocklingen (northwest of Sarrebruck) and other factories in the Sarr region. November 10-11 — Further night attack by French aeroplanes on same factories. November 12 — A squadron of naval aeroplanes carry out an at- tack on Ostend harbor. November 15— Further naval attack on harbor and submarine shelters at Ostend and Zeebrugge. November 17 — Successful raid on Ostend and Zeebrugge by naval aeroplanes. Captain de Beauchanip bombs Munich as a reprisal for the bombardments of Amiens. November 22 — Xaval aviators drop bombs on torpedo craft and seaplane sheds at Zeel)rugge. November 23-24 — French aviators again bombard Volklingen blast furnaces. November 24— British naval aeroplanes bombard the blast fur- naces of Dillingen. November 28 — Xaval aeroplanes carry out an attack on Zee- brugge harbor. December 27— Thirteen machines of the R.X.A.S. bombard blast furnaces at Dillingen. French dirigible l)ombards factories at Hagondange and iron- works at X'eunkirchen. Septe.mber 26 — Russian aviators again attack German air-sta- tion on Lake Angern. December 13 — Successful Russian air-raid on Tarnopol-Zloczow rallwav. Italian Theater Januaby 14 — Italian air squadron bombards Aisovizza aero- drome. Jaxuahy IT^Italian aviator bombs Austrian headquarters at Volano. February 12 — Austrian seaplanes raid on Ravenna. February 18 — Italian machines carry out reprisal raid on Laibach. April 3 — Italian aeroplanes bomb railway at Adelsberg. Apkil 17 — Franco-Italian raid on Trieste. April 20 — Italian air-raid on Trieste. May 3 — Italian airship falls into ,\ustrian hands. May 7 — Italian air-raid over the Adige Valley. Juxe 3 — ^Italian squadrons bomb encampments in the Astico val- ley. June 12 — Italian seaplanes bomb Trieste. June 16 — Italian squadron of thirty-seven machines bomb en- campments in the N'os Valley. August 1 — Italian squadrons bombard the Whitehead Torpedo and Submarine Works at Flume. August 2 — Italian aviators bomb Durazzo. August 15 — Italian X''leuport chasers bomb Austrian encamp- ments near Gorizia. August 16 — Italian aviators bomb railway at Relnenberg. August 25 — Italian air-squadron bombs railway-station at San Cristoforo. September 13 — Italian machines bomb Trieste. Septe.mber 15 — Italian squadrons bomb Comignano. Septe.mber 17 — Italian squadrons bomb station at Dottogliano and Scoppo. October 31 — Italian squadrons successfully bomb Trieste rail- way. X'ovember 1 — Italian X^ieuport-Caproni squadron bombs enemy camps in the Vippacco Valley. November 7 — Franco-Italian aircraft carry out raid on the Istrian coast. Xovember 14-15 — Italian aviators attack airsheds at Prosecco and the pier at Trieste. December 30 — Italian raid on Volano and RIfemberga. December 3 — Italian aviators attack Dottogliano and Scoppo railway stations. Southeastern Theater January 23— Thirty-two French aeroplanes bomb Ghevgeli and Monastir. One of the three Sperry bomb sights. The Sperrys, after gaining world-wide fame in making scientific instruments for ships, undertook to solve the most difficult problems in aerial navigation and aerial warfare. Having begun in the early days of aeronautics they were able, through their long experience in aeronautics, and thorough knowledge of the problems, to evolve some most efficient instruments. 20 TEXTBOOK OF MILITARY AERONAUTICS Jakuasy 28 — Fourteen French aeroplanes bomb Bulgar camp northwest of Lake Doiran. May ^4 — Allied raid on Ghevgeli. July 3 — Allied aeroplane droi)s bombs on Sofia. AuocsT 18 — Nineteen Allied aeroplanes attack Monastir. August 23 — Russian seaplanes bombard Varna. August ^5-31 — Naval air raids behind Kavala. August ^8 — French aviators destroy aviation park at Mrzenci. August -29 — English aeroplanes bomb Drama. September -2 — Raid on Constanza. September 9 — Rumanian aviators bomb Rustchuk. September 13-2^ — Naval seaplanes bomb Bulgarian coasts. September 14 — French aviators bomb Sofia. SEPTE.MBER 18 — English aviators drop bombs on Prosenik. September 26 — The R.N..\.S. bomb Angista. October 11 — French aviators bomb Prilep. October 15 — R.N..\.S. bomb the Buk bridge. October -23 — Naval aeroplanes bomb Buk and Drama. October 26-2'i — English aviators reach Bucharest. October -29 — News of the evacuation of Constanza carried to Odessa by seaplane. October 31 — Naval aircraft bomb railway bridge at Simsirli. No\'E.MBER 3 — English aviators bomb Bursuk. No\'ember 11 — Naval aircraft bomb Seres-Drama railway. Bombs dropped on Campulung. November 18 — British squadrons bombard Karjani, Pravishta, and Senultos. Xo\-ember 22 — French aeroplanes bomb enemy encampments in tlie Topolchani and Prilep regions. November J3-J9 — Naval squadrons bomb Bulgarian coast. November 29 — British naval aeroplanes effect great damage at Gereviz. December I — Russian air raid near Constanza. December 14 — Naval air squadron bombs Kuleli-Burgas bridge, on the railway to Constantinople. ' The Levant February 20 — English aviator destroys enemy's power station at El He.ssana. April 12 — English bomb Smyrna. April 14 — British naval aeroplanes bomb Constantinople. May 18 — English machines bombard El Arish. May 25 — The R.F.C. bomb advanced posts in Sinai Desert. May 29 — English drop more bombs on Smyrna. June 13— The U.F.C. bomb El Arish. August 25-29 — English aviators cany out many raids in Pales- tine. September 4 — R.F.C. bomb Mazar. September 5 — English aviators bomb Turkish aerodrome at El Arish. October 1— English bombs dropped on Kut-el-Amara. Octobek 10 — U.F.C. bombs Tigris camp. Novembeb 1 — Russian aviators carry out successful raid on the Euphrates. Nove.mbeh 11 — English aviators carry out two successful raids on Maghdaba and Birsaba. Xove.mber 15 — English aviators bomb Turkish base near Sinai. December 4 — English aviators carry out reprisal on Turkish camps. December 14-15 — British aviators attack Tigris pontoon bridges by night. Aeroplane Raids on England, 1916 Casualties Date District Killed Injured Jax. 23 East Coast of Kent 1 6 Feb. 20 East and Soutlieast Coasts — Lowes- toft and Walmer 3 "h ■ Mae. 1 Southeast Coast 1 — 19 East Kent — Dover and Ramsgate 9 31 April 24 Dover — — May 3 Deal ,. — 1 20 East Coast of Kent 1 2 Aug. 12 Dover — • 7 Oct. 22 Sheerness — — 23 Margate — 3 Total 15 59 Nov. 28 London — 9 Extensive Damage Can Be Done by Bombs The damage that can be done by bombs is extensive, particularly in thickly settled places. In fast raids, whole factories and magazines Incendiary bombs dropped on English soli by Zeppelins, some bum<-o Hattiell, N. Y., Nof. 19, J916, 590 mlle» in 4 hr*. 17 min. -30 sec Victor Carlitronii Chicago to Em, Pa., Nov. 2, 1S16, 452 milas. Newport Newt to New York, May 20, 1916, 400 miles. A. Seguin, duratioB flight _ France, Oct 13^ 1913, 648 miles. R. Boehm, duration flight — Germany, July 12, 1914, re. mained in air 24 hrs. 12 min. Sketch-plan showing an outline topographic view of the Allies po- sitions in relation to Heligoland, Kiel and Essen. The distance from the nearest Allied aeronautic centers on British soil to Kiel is only about 275 miles. There are now warplanes which are capable of carrying over one ton of ex- plosives over a distance of seven hundred miles or more, and there- fore capable of reaching Kiel at night. One thousand warplanes dropping a ton of bombs on the German fleet and U-boat bases could severely damage the Ger- man fleet. 26 TEXTBOOK OF MILITARY AERONAUTICS A huge mountain of supplies for tlic A..-li: i";., -, (_nriMi::\ hi- ouniu' niountain- "i Mi^ijiiie^ for lirr .-innic^ whirli can be destroyed by conducting major aerial operations against the German bases, thereby seriously impairing the efficiency of the work of the German forces. known that these impressions are susceptihle to serious error, due to centrifugal force or acceler- ation pressures, which are capable of reproduc- ing and even multiplying gravitational sensa- tions, when the machine approaches an unaccus- tomed inclination. The misinterpretation of these sensations has often resulted disastrously. "Bomb-Dropjnng. In bomb-dropping it is quite needless for us to discuss the absolute ne- cessity of having a gjToscopic horizontal refer- ence plane of integrity and accuracy, or to enu- merate the inaccuracies to which pendulums, mercury tubes, and other gravity devices are susceptible. Our experts have long ago ex- posed the total unreliability of all of these de- vices. "The gjToscopic apparatus is capable of stay- ing within one-quarter of one degree to the true horizontal. A sensitive aeroplane is held, through the intermediary of the servo motor and follow-up system, within three quarters of one degree of the position of this gj'roscopic plane. This variation of three quarters of a degree might seem to the layman to be, in eflFect, a cor- responding inaccuracy, but any one accustomed to reading a baragraph, the index of which is designed to tremb'e or vibrate constantly, will appreciate the eas'j and accuracy with which the pilot bomb-dropper can secure his objective in the mean of two extreme positions, especially when close to each other. In this way more ac- curate results can be obtained than with non- oscillating conditions, because this motion makes all the parts of the follow-up mechanism ex- tremely sensitive, as in the case of the baragraph. Furthermore, the slight motion assures the op- erator that the apparatus is functioning prop- erly, while he need only consult his clinometer, located on the g>'ro unit, to check up accuracies. "The proposition to connect the bomb sight directly to the gj^roscopic element involves ham- pering its freedom by friction of the connection links, and by the inertia vibrations of the sight; in addition, pressure of the hand in making ad- justments is likely to cause inaccuracies. It is always advisable to leave the gyro as free and unmolested from outside forces as possible. "With the bomb sight rigidly fixed to the side of the machine or to the floor, the method of sighting is somewhat as follows: "With the gyro manual-control the position of the aeroplane is adjusted until both clinometers read zero. The operator then seciu-es by his rudder the motion of some objective in his field of vision, parallel to the longitudinal cross-wire. During this time the deviation angle is set by taking the usual stop-watch reading, or by other steps involving this very simple oijcration. The pilot bomb-dro])per has now only to keep his ultimate objective moving along the longitudi- nal wire, before releasing the bomb when it reaches and crosses the lateral wire. THE WARPLANE FOR BOMBING AND TORPEDO ATTACKS 27, i' "The increased accuracy of bomb-dropping from an aeroplane equipped with the Automatic Pilot is due to: "1. Being able to get the aeroplane more ac- curately lateral over the target. "2. Being able to release the bomb at the proper angular distance from the target. "3. Simplifying the operation of bomb-sight- ing, since the sight is held automatically and ab- solutely horizontal, the reby allowing the pilot bomb-dropper to focus his entire attention on adjusting the sight and steering the aeroplane. "During the long night bombardments, the elimination of the extra passenger has the ad- vantage of either increasing the radius of action or of enlarging the bomb-carrying capacity of the machine; while, of course, in the event of failure, one man is lost instead of two. The physical work of which the pilot is entirely re- lieved in long bombardment trips, especially with the larger types of aeroplanes, would fre- quently be too much for the ordinary pilot." Turn into the Wind to Avoid Drift In bombing-raids drift is one of the most dif- ficult factors to conquer by the use of instru- ments, because of the difficulty of calculating with accuracy, especially at night. There is a simple solution to this problem, however, which is always to turn into the wind when about to drop the bombs, and thus avoid the drift en- tirely. Formation for Bombing Raids Suppose one thousand large bombing ma- chines were sent to bomb Kiel, Essen, or any other important German base. They would probably set out from five to ten aeronautic An official air-photopraph of Ostend after the Rritisli naval bombardment. It will be seen that the bombardment was directed against the Germans' submarine lair, the letters indicatinft the principal hits. Thus B represents the damaged entrance pates to basin; C, Q and R, destroyers struck; D, U and Z, pier and jetties hit. The other letters indicate damage to the submarine har- bor and adjacent buildings. Ostend is an important German naval base. 28 TEXTBOOK OF MILITARY AERONAUTICS bases, on carefully drawn plans. As there would be no advantage in having all the ma- chines arrive at the same time, since there would be possibility of confusion and crowding, the plan would probably be to divide the thousand aeroplanes into from six to ten wings, each wing to consist of a given number of squadrons in charge of a squadron commander. The raid would have to be carried out in the darkness between sundown and sunrise. In the autumn, winter, and spring, when the nights are longer, such raids can be conducted entirely un- der cover of darkness, and the raiders have little to fear from anti-aircraft guns and enemy air- craft. In the first large night-raid, made in August, 1917, by 232 Italian aeroplanes, only one machine was lost, the others being protected by darkness. In a raid of a thousand aeroplanes, the best effect can be obtained by sending units of 200 to follow each other at intervals of half an hour. The second imit arrives after the first unit has done its work, and finds the theater of war ablaze with the fires started by the first unit. ^ The lights assist in picking out the im- portant points and objects to be bombed. The succeeding units find their work correspond- ingly easy. Rules for Formation Flying The rules for formation in this case would be the same as prescribed by the General Stafi" of different countries. These are practically uni- form, since each country adopts improvements as fast as they become known, which happens whenever a squadron or flight commander is brought down and printed or written instruc- tions are found on his person. The instructions of the British General Staff to squadron and flight commanders of bombing units — which are also applicable to fighting, reconnoitering, photographing, and other branches of the air service, are as follows: A leader must be appointed, and a sub- leader, in case the leader has to leave the forma- tion for any reason; i.e., engine trouble. The leader cannot efficientlj^ control more than a certain number of machines. If, there- fore, this number is exceeded, the mission must be carried out by two formations acting in con- cert, but each with its own leader. A French BrcKUct tractor binlune used fur buiiibing, photographing and artillery spotting. THE WARPLANE FOR BOMBING AND TORPEDO ATTACKS 29 Drawn by Frank ilerritt Courtesy of Motor Boating Reducing the German fleet at Kiel with present day warplanes. 30 TEXTBOOK OF MILITARY AERONAUTICS How 1000 Warplanes Could Raid Kiel Suppose 1000 warplanes were to start from the Allies' lines in a major operation against German bases. They would start from differ- ent aerotlromes, probably about one hundred from each aerodrome, the machines following each other at intervals of 30 seconds. Squadrons of 2.5 machines would probably be fonned, with a flight commander to each squad- ron, who would start first. The aviators of each squadron would follow as fast as possible, each aviator following the navigation lights of his s(juadron commander. A prearranged signal from the aerodrome woidd tell the squadron commander when the last machine of his squad- ron left the ground, and he would then, after a brief delay to give time for the machines to climb up, give the signal to fall in line, and the squadron would travel on in V formation. Every aviator, of course, would have studied the specially prepared chart and would be fa- miliar with the route — as it looks to the aviator from the air. Thus they would travel the 450 or so miles between the Allied bases and the German naval bases, or about the same to the important Ger- man militarj^ bases. There being a crew of three men to each warplane, the aviators would not be as lonesome as they often are in bombing raids alone. The distance woidd be covered in five to six hours. And then? Then, with the tor- pedoplanes attacking the German ships from the sides and the bombs attacking from above, the hardest blow yet struck at Germany, the most effective blow in the fight for humanity's rights, would be struck! Just as the battles of Manila, Santiago, and Tshushima lasted only about an hour, so the battle of Kiel would be over in one hour, because the destruction of the German fleet from the air would make it possible for the Allies' mine- sweepers to clear away the German mines and open the way for the Allies' ships to deal with U-boats in their bases at close range. And Germany's naval power would be crippled thereby — and its total destruction would follow, through repeated raids on the less important U-boat bases. So let us not lose a minute ; let us concentrate the nation's efforts on turning out the thousands of torpedoplanes and warplanes needed. Five different sizes of bombs dropped from aeroplanes. The weight of aeroplane bombs to-day varies Irom Hi to oOO pounds. CHAPTER III DROPPING BOMBS FROM AEROPLANES By Jean- Abel Lefrance Last February a French aviator, Captain Guynemer, succeeded in bringing down inside the French lines, one of a raiding squad of 20 German bombarding planes of the newest type, manufactured by the Gotha Wagonen Fabrik. A peculiarly interesting feature of the aeroplane was its Goerz sighting telescope or range-finder, designed to facilitate the taking of correct aim at objects to be bombarded. A careful study of this, with a discussion of the laws governing the dropping of bombs, appears in "La Nature" (Paris), together with the accompanying dia- grams. Any projectile dropped from a height is sub- ject, of course, to two constant forces, the re- sistance of the air and the acceleration due to gravity. Its trajectory is a vertical line from the point of discharge. A, to the striking point, B (Fig. l) . If the bomb be dropped from an airship in motion, it will have an initial speed equal to and in the same direction as that of the latter. This new force is compounded with 31 32 TEXTBOOK OF MILITARY AERONAUTICS Inae.x and bti5e 6 Index I CrortoaraY>h Uo.versol j-^tnt Eut-pieccfJt— ■ Chronograph Controlling Disk for Prism Rodcontrollinq PrI.rr. ^ Fig. 1. Trejectorj' of a bomb falling from an aeroplane as affected by the di- rection of the wind. Fig. -2. The Goerz range-finder. Fig. 3. Diagram showing construction of the Goerz range-finder. the two former, and the result is the curved trajectory' A C. If this bomb, having a given initial velocity, is dropped into a layer of air in motion, that is, into the wind, it is acted on by the latter, and is said to undergo "drift." If the wind is at the back, the trajectory is lengthened, as in A D; if there is a head wind, the trajectory will be shortened, as in A E. If the bomb be dropped from an avion which the strength of the wind causes to be stationary' with respect to the ground, i.e., when the ve- locity of the wind is exactly equal to that of the avion and in the opposite direction, the projectile will have no initial velocity and the curve of its trajectory will be a function solely of the drift produced by the wind, as in A b; it will therefore fall to the rear of the point of departure. This latter case, however, is ex- ceedingly rare, since it presupposes a wind of 120 to 1.50 kilometers per hour; but this is a gale too high to permit the sending up of avia- tors. These trajectories being given, the angle of aiming will be the angle formed by the vertical line A V at the point of departure A with the straight line joining this point A with the strik- ing point O, i.e., the angle VAO. Since these trajectories are curves, the height of the avion above the object aimed at is an element which modifies the value of the trajec- tory. Since the wind causes drift, this drift will vary with the form of the projectile and with the velocity of the fall. Here we have two ele- ments which are constant for each type of bomb. To sum up, the trajectory of a bomb dis- charged from an avion is the resultant of the following forces: Weight Form Drift Speed of avion in wind Elements constant for a given type of bomb Considered as a constant for a given type of avion A Vobin bombing machine u^cU bj Uic llusslunii and Uic French. Other Elements Height of shot Initial speed of bomb, i.e., of avion with respect to ground Velocity of head wind Variable elements DROPPING BOMBS FROM AEROPLANES 88 Of these three principal variable elements which it is necessary to know for each case of bombardment, one of them, the velocity of the head wind, can be immediately deduced when the velocity of the avion with reference to the earth is known, since this velocity of the wind is the difference between the velocity of the avion with respect to the earth and its normal velocity in the wind, an element which is fixed for a given type of avion. Take an avion having a normal speed of 150 km. per hour; if it is only going 100 km. per hour with reference to the earth, then it is fly- ing against a head wind of 50 km. per hour. Hence it is only necessary to know the height of the avion and the initial speed of the bomb to determine a trajectory. This method of cal- culating trajectories seeks to base itself on science in order to obtain a mathematical pre- cision in its results. Unfortunately it is based upon a probable knowledge of atmospheric con- ditions, which are essentially capricious. Par- ticularly, the speed of the wind at the height of the avion is taken into account, e.g., at 4000 meters, but it is supposed that this remains unmodified down to the ground, which is rarely the case in reality. It may also be that, starting from 3000 meters, the wind changes its direction so much that the best calculations, the best tele- scopes, and the best bombardiers, are unable to secure a correct aim, so that some authorities despair of ever being able to get results in aerial bombardment comparable to the efforts made. Goerz Range-Finder. — This is certainly the test and most highly perfected effort of German science to find means of destroying railroads, factories, and populations outside the range. of their big guns. It consists of a telescope about ■one meter long; mounted on a universal joint, it can be oriented in every direction and kept strictly vertical whatever be the position of the •avion (Fig. 2). The accompanying diagram (Fig. 3) shows the ensemble of the optical sys- tem; the field obtained is 500/1000 and the en- largement is 1.5. At the base of this telescope is a prism mounted on a pivot and controlled by a grad- uated disk. The telescope remaining vertical, the play of the prism permits the visual ray to Direct to*^ o^ ^ovKmcrtt of Airopfortc^^ Figs. 4, 5, 6. Direction of aim in the finder. be inclined a number of degrees corresponding to the graduations of the disk. On this disk are two indexes, one correspond- ing to the vertical speed, or dead point of the range-finder, and the other to the vision of 22° 30'. Another index serves as a basis ; it is fixed on the body of the range-finder. At 0° the marksman sees the ground along the vertical (Fig. 4) ; at 20° the inclination of the visual ray is 20° in front of the avion (Fig. 5) ; at 5° the inclination is 5° behind the avion (Fig. 6). A small index is movable upon the disk, but this can be made solid with it bv means of a little Three different types of bombs dropped by Allied aviators at Salonica. 34 TEXTBOOK OF MILITARY AERONAUTICS I Ignilion Device Thermtt Reiinoui matter MclUo nkite piosphonm Section of Incendiarj- Bomb dropped from Zeppelins. The Incendiarj- bomb illustrated herewith is being used by German airships for the purpose of setting afire enemy towns and mili- tarj' establishments; it is described in a poster published by the British Fire Prevention Committee as follows: "The usual fire-bomb dropped by a Zeppelin is of conical shape, the diam- eter at the base being about ten inches. It is wrapped round with inflammable cord, which gives it rather a nautical appear- ance, enhanced by a handle at the apex for lowering it over the gunwale of the airship — if airships have gunwales. The base is a flat cup, and from this to the handle runs a hollow metal funnel forming the center and business part of the bomb. This center funnel is filled with thermite. Thermite is the prepara- tion which on ignition produces a heat so intense as to melt steel. The ignition of thermite creates a tremendous glare of light, and the heat melts the metal funnel. The molten metal spreads when the bomb strikes. It sets up at once a fierce fire if it strikes anything combustible, but at the beginning it is only a small fire, and if it is tackled at once with water it can be put out before it does any damage to speak of. detent. This index once fixed before a gradu- ation of the disk, after passing the dead point falls into a small notch, and thus informs the gunner that he sees the ground according to the inclination which he had marked with this index ; this is disengaged by a slightly stronger pres- sure of the hand. In the body of the telescope is a spirit-level. The edges of the air-bubble are refracted in such manner that they ap})ear in the form of a black circle, which sen'es as a sighting center for the telescope. In the course of all his range-finding operations the gunner must keep this bubble in the center of the ocular, which will keep the range-finder vertical no matter what the inclina- tion of the avion. The universal joint permits the finder to in- cline freely from right to left or from front to rear, but when it revolves around its vertical axis, i.e., when the visual ray, instead of being directed in front of oi- behind the avion, is di- rected to the right or the left of the route fol- lowed, the finder acts upon a route corrector. This consists of an electric device. Resistances act upon a very sensitive galvanometer placed in front of the pilot and indicate to him how to cor- rect his route in order to make it pass exactly above the object to be bombarded. Method. — There are only a few of the ele- ments constituting a trajectory which can differ in the course of each bombardment: the height of the avion above the object, the initial velocity of the bomb, the speed of the wind. The Ger- man method of the Goerz finder enables a calcu- lation of these three elements to be made. 1. The height is obtained by subtracting from the altitude range shown on the altimeter of the avion the altitude of the object bombarded; e.g., if the avion is flying at 4200 meters above sea- level, and if the factory to be bombarded is 200 meters, then the height to be reckoned with will be 4200— 200— 400€ meters. This method, moreover, is subject merely to ii ivu iu a stuck of Imy on EiigliUi wil. DROPPING BOMBS FROM AEROPLANES 85 very slight errors where high altitudes are in question. Example: At 90 km. an error of altitude of 500 meters for an avion at 4000 meters, corresponds to an error of only 25 meters at the ground level (Fig. 7) . 2. Initial Velocity of the Bomb. — In reality this is the speed of the bomb with reference to the ground. This element is the most difficult to know, because it varies with the velocitj^ of the wind, which is in a state of perpetual insta- bility. If an avion possesses a speed of 150 km. and the wind is blowing at the rate of 50 km., then with a following wind the avion will travel at 200 km. per hour, while with a head wind it will go only 100, This difference of speed con- siderably modifies the trajectories, as can readily be seen by examining the curves in Fig. 7, in which the avion is going 120 and 60 km. per hour respectively. In place of being simply added or subtracted, this speed of the wind and speed of the avion may be compounded if the avion receives the wind, for example, three quar- ters to the rear (175 km. per hour) or three quarters head on (125 km. per hour) . In principle, to simplify the calculations, the avion should bombard with the wind head on, i.e., with the speed as much reduced as possible. To determine this kilometric speed of the avion we calculate the time required by a fixed point on the groimd O to traverse an angle fixed at 45° or 22° 30'. It is easy to see by the figure that the time required by an avion to find the range of the the initial horizontal speed of the bomb same point successively, first with an angle of 22° 50' and then vertically, is proportional to the speed of the avion with respect to the earth. A value in sec- onds is obtained. A previous prepared table will indicate that if the avion be- ing at an altitude of 4000 meters, a point on the ground takes 36 seconds to pass through an an- gle of 22° 30', then the avion is going 100 km. per hour, with reference to the earth; if the point takes only 18 seconds to pass through the same angle, the A bomb liropped from a Zeppelin, Another Speriy bomb sight which practically does all thinking necessary for accurate bomb-dropping. avion is going 200 km. per hour. This value is 36 TEXTBOOK OF MILITARY AERONAUTICS woo '^iOOO 100 300jMtociM$eonetMt«c loaei \ ^ \ X \ < •A I o 1 ' \ V \ K 3 C 3000 < t 1 \ \ \ mo \ i c too 300 300 4O0 SOO 600 700 800 900 fOOO Oev.alion m Meters Fig. 7. The falling curves of bombs at different speeds. D-recliOrt Control Gurtoe>-'» seot Fig. 8. Location of the finder upon an aeroplane. 3. Moreover, it is known that avions of the Gotha type have 150 km. per hour speed when the motors are revolving at their usual velocity ; if the preceding range-finding shows the speed at the ground to be only 100 km. per hour, the obvious deduction is that the head wind has a value of 50 km. Thus all the elements of the trajectory sought are known ; it remains only to read on the chart which firing angle is suitable to cause the Iximb to fall on the given object, in view of the given elements. Several minutes before arriving over the ob- ject to be bombarded it is necessary to ac(}uire a knowledge of two elements which will enable the gunner to read on the chart the proper firing angle. The altitude range on the ba- Fijr. 9. Device for releasing bombs. rometer less the altitude of the object gives the height of the fall of the projectile. To obtain the second element, which will give a knowledge of all the values of speeds, we have recourse to the method of previous range- finding of the ground, explained previously. The index of the graduated disk is fixed at 22° 30'. The range of any point whatever on the ground forward of the avion is found — a Copyright by Underwood & Undprwooil. Bombs in the fuselage of an aeroplane. DROPPING BOMBS FROM AEROPLANES 87 A 100 11). bomb dropped by a Zeppelin. route perpendicular to the one followed, a river, a house, the edge of a wood. This point is caught in the circle formed by the air-bubble and followed while turning the disk until the index falls into the notch at the dead point; at this instant the seconds chronograph is re- leased and the terrestrial point continues to be followed in the range-finder until the 0° of the disk is checked at the dead point. The chrono- graph, immediately stopped, gives a number of seconds which, when found upon the chart in the line of altitude, indicates the speed of the avion with respect to the ground and the sight- ing angle to make use of, for example, 10°. The index is immediately set at the number of degrees of the sighting angle, i.e., 10°. The observer is ready to operate. About 2 or 3 km. before flying over the object the latter is caught in the field of vision, then in the circle of the bubble. At this instant the route corrector op- erates and the galvanometer indicates to the pilot whether he is following a route which will make the avion pass directly above the object. At the precise moment when the index fixed at the number of degrees of the sighting angle falls into the notch at the dead point, i.e., at the moment when the finder aims with an angle of 10°, the bombardier operates the bomb re- leaser and the bombs fall toward the object. Throughout the whole bombardment the pilot must keep his craft strictly head on to the wind ; the air-bubble must be kept rigorously in the center of the ocular, the play of the prism alone serving to seek the object. This Goerz range-finder is of an elementary simplicity for any one who has manipulated it in a few brisk actions. Its movable prism en- ables the object to be found with ease, and its annular bubble permits it to be immediately centered in the vertical position. Marvelously constructed, it appears to show marked prog- ress over all previously made range-finders. It eliminates errors, except from new and practically incalculable elements, such as varia- tions of forces and directions of the wind be- tween the altitude at which the sighting is done and the ground, or when it becomes impossible to keep the avion head on toward the wind. American-made Barlow aircraft bombs. Photo courtesy New York Times & Western Newspaper Union 88 TEXTBOOK OF MILITARY AERONAUTICS The aim being at times scientifically perfect, as the application of a method derived from calculations, does it follow that the bombs will fall directly upon the objects aimed at? Re- sults loudly proclaim a negative. Hundreds of bombs discharged on railway stations, on famous ironworks, on important aviation ter- rains, have been without result, except for a few shell "funnels" in the ballasts, a few labor- ers killed, some holes in hangars. Range-find- ing is a delicate task to execute in an avion sur- rounded by bursting shells. ^Memoranda : The master of the air. A Voisin armed bombardment machine equipped with aircraft gun of large caliber photographed in mid- air. This machine is equipped with a Canton-Unne motor. CHAPTER IV BATTLEPLANES AND AIRCRAFT GUNS— THE DOMINANT FACTORS IN MAINTAINING THE SUPREMACY OF THE AIR Supremacy in the air, the all important fac- tor which leads to victory on land and sea, de- pends greatly on battleplanes and aircraft guns. About twenty per cent, of the service aero- planes used by the warring nations at present are the very fast avians de chasse or pursuit ma- chines used exclusively for fighting; seventy per cent, are the slower types used for regulat- ing artillery fire, aerial photography, scouting, and in connection with infantry and cavalry operations; five per cent, are the slower, large bombing aeroplanes. All of these aeroplanes carry machine guns ; some carry cannons. Proportions of Different Types of Armed Aeroplanes in the Air Service The proportions vary continually in accord- ance with developments, and the future will see an increase in the number of bombing machines, with possibly an increase of fighting machines. Raiding from now on is to be carried out more and more extensively, and in connection with the protection of bombing planes, as well as the protection of artillery "spotters" and photog- raphy planes, aerial fighting will increase. Pursuit machines will always be needed to fight enemy aviators, but the practice of send- 39 40 TEXTBOOK OF MILITARY AERONAUTICS ing pursuit machines to protect the artillery spotters and photography planes will grow less and less, because it is more economical to employ large machines capable of carrying two or more guns and to defend themselves. Otherwise it is hard to protect a plane with less than four to six fighting machines. To pro- tect themselves these planes must carry from three to four guns. JNIany a photography plane, equipped with only one gun, has been brought down by an enemy aviator who darted at it suddenly and riddled it with shots while the observer was taking photographs and did not see it approach. Therefore a change is taking place toward larger machines to do this work, which are ca- pable of carrying three to four guns. The Five Fundamental Factors in Maintain- ing Supremacy in the Air The five fundamental factors in maintaining supremacy in the air are: (1) Speed. (2) Position of the aeroplane. (3) Skill in piloting the aeroplane and in manipulating the guns. (4) Number of aeroplanes. (5) Destructiveness of the projectiles. Speed is incontestably the most important factor. The value of position as a command- ing factor was first demonstrated by the fa- mous German aviators. Captains Boelke and Immelmann, who would climb high and take a position as near as possible to a cloud. There they would wait for an Allied aeroplane, then dive down towards it, firing the machine gun at the same time. If they missed their prey, they would not attempt to challenge the Allied aviators or to manceuver to a commanding posi- tion and give battle. Failing in their first dive, they would land and go up again later to try it all over. It cost the Allies a great many avia- tors and aeroplanes before thej' found out the value of position as a fundamental factor in maintaining supremacj' in the air. A 37 millimetre Hotchkiss cannon mounted on tt French "\'oisin" battleplane. BATTLEPLANES AND AIRCRAFT GUNS 41 The famous French aviator Vedrines examining the two guns of a German battleplane, which are so mounted that they can be shot in a half circle and up and down — -through the hole in the fuselage. Skill is an important factor, and often makes it possible for an aviator whose machine makes five miles less than his adversary to fight on an equal basis. Number makes up for lack of speed or posi- tion. Having two or three machines to the enemy's one, makes up for the handicap due to lack of speed. Destructiveness of projectiles is a very im- portant factor. The bullet of a machine gun must strike either the pilot, or the propeller, or the motor, or the gas tank, or the control wires, to put the machine hors de combat. The shell, on the other hand, will put the machine hors de combat if it strikes practically any part of the machine. Types of Aeroplanes and Their Armament The types of aeroplanes used by the warring countries, and their armament, have been changing continually. At the date of writing, the following types are used: Avions de Chasse or Combat Machines (1) The "Spad" carrying one or two pas- sengers. A number of these machines have, un- fortunately, fallen in the hands of the Germans, so we may say that their horse-power ranges from 150 h.p. to 250 h.p. and are equipped with Lewis and Vickers machine guns. They are used extensively by the French. (2) The "Nieuport," one passenger, equipped with one 110-horse-power Le Rhone motor, capable of a speed of 150 kilometers per hour; equipped with two and three Vickers or Lewis machine gun synchronized to shoot through the propeller. (3) The "Avro," carrying one or two pas- sengers, equipped with one lOO-horse-power Gnome motor, carrying one or two gims. 42 TEXTBOOK OF MILITARY AERONAUTICS The A. E. G. 1917 single motored type of German biplane, equipped with a 175 h.p. Mercedes motor. Avions Types "Corps d'arme" — Used for Spotting Artillery Fire, Aerial Pho- tography, Etc. (4) The "Caudron" G-4; pilot and ob- sen'cr; equipped with two 80-horse-power Le Rhone motors, Lewis and Vickers guns forward and rear. (5) The "Caudron" G-6; two passengers; equipped with two 110-horse-power La Rhone motors, carrying one machine gun forward and one in the rear. (6) "Dorand" A-R; two passenger; equipped with one 150-horse-power Hispano- Suiza motor or a 170-horse-power Renault, carrying one Vickers gun forward, and two Lewis guns in the rear. (7) Farmaii; pusher type, two passenger; equipped with one 170-horse-power Renault motor, carrying one or two Lewis guns for- ward. (8) Morane Parasol; two passenger; one 110-horse-power La Rhone motor, mounting one Lewis gun in the rear. (6) Caudron R-4; three passengers; equipped with two 150-horse-power Hispano- Suiza motors, with two Vickers guns mounted forward in turrets, and two Lewis guns in the rear. (9) Letort; equipped with two 150-horse- power Hispano-Suiza motors; two Vickers guns mounted forward in turrets and two Lewis guns in the rear. (10) Moineau; three passengers; one 220- horse-power Samson motor, connected to drive two propellers; equijiped with two Vickers guns mounted forward in turrets, and two Lewis guns in the rear. (11) Sopmth TripMue. This type of machine has, unfortunately, fallen in the hands of the enemy, therefore we may note its existence as a combat machine used by the British. (12) Sopwith biplane; two passenger; A "G-4" Caudron biplane, equipped with two HO li.p. I>e ithone motors. The gun mounting is si-rn in front. BATTLEPLANES AND AIRCRAFT GUNS ^8 The ofScers of a squadron of Voisin bombing ma chines being decorated for their successful raids. equipped with 130-horse-power Clerget motor, carrying eight bombs; Vickers machine gun forward, shooting through propeller, and one Lewis gun in the rear. (13) Voisin-Peugeot; two passenger; equipped with a 220-horse-power Peugeot mo- tor ; carrying two Vickers or 37 millimeter guns forward. (14) Breguet-Michelin; two passenger; equipi^ed with one 220-horse-power Peugeot motor; mounting two Vickers or 37 millimeter machine guns forward. (15) Farman; pusher type, two passenger; equipped with one 170-horse-power Renault motor, mounting one Lewis gun forward, (16) The Caproni; the various tyjies men- tioned in the chapter on "Warplanes for Bomb- ing and Torpedo Launching," are with Fiat machine guns and cannons and Davis non-re- coil guns. So are the Pomilio SIA, Sa- voya-Verduzio and ]Macchi machines. At date of writing, the British, French, and Germans can be said to have more or less the same types of aeroplanes, with the same amount of armament. As a matter of fact, the warring nations are never far from each other in either types or armament, because as fast as they cap- ture each other's machines and find important improvements, they copy them. Pursuit, or Combat Machines Among the comparatively new machines of the British Royal Flying Corps, there is the Soptiith triplane, which has given such a good account of itself as a combat, or pursuit ma- chine on the Western fronts. Other machines of this type are the De Haviland scout biplane, a "pusher" with a fixed gun in front, and the Vickers biplane, two passenger, equipped with Beardmore or Clerget motors. The German combat machines include the Ago, the Fokker, the Halberstadt, the Roland, which are equipped with Mercedes, Oberunsel (rotary), Benz, and Argus motors of 165 to 175 horse-power. They are armed with Para- beilum or Vickers and Lewis guns. "Two Tails," twin fuselage simple mo- tored German Ago biplane equipped with a 150 h.]). Benz motor and Parabellum and Vickers guns. 44 TEXTBOOK OF MILITARY AEROXAUTICS The Gentian "Rump' liipbmr, I «(i-seater, equipped with two iruns. The two smallest machines, the Halberstadt and the Albatros Bii, are single seaters, all the others being two-seaters. Where the gunner occupies the rear cockpit, it is found that in many cases the pilot is equipped with a syn- chronized gun, fired forward and sighted by steering the machine itself. The same applies to the single-seaters. Some of the single- seaters are equipped with two synchronized guns, fired directly in front. The top wing of the Albatros Bii is 28 feet, 4> inches, the bot- tom wing 26 feet, nine inches ; gap, 5 feet, three inches; chord, five feet, nine inches; length over all, 24 feet. The measurements of the Hal- berstadt are: top wing, 28 feet, 6 inches; bot- tom wing, 26 feet; gap, four feet, 6 inches; chord, 5 feet; length, 24 feet. The measurements of the Nieuport and the Spad are: Nieuport; top plane, 24 feet 6 inches; bottom plane, 23 feet; chord, top plane, 3 feet 11 inches; bottom plane, 2 feet 4 inches; gap, 4 feet 2 inches to 3 feet ii inches; length, 18 feet 6 inches. Spad type 5 VII, one passenger; top plane, 25 feet 8 inches; chord, 4 feet 7 inches; gap, 4 feet 10 inches; length, 20 feet. The speed of these machines varies with the horse-power, ranging from 95 miles to 125 miles per hoiu" high speed, to from 56 miles to 80 miles slow speed. The climbing speed ranges from 4000 to 10,000 feet in ten minutes. Owing to lack of demand, few machines of this type were built in the United States until recently. But efficient types existed. The Cur- tiss wireless scout of 1915-16 was followed by the Curtiss triplane, the characteristics of wliich cannot be made public. The Italian I'onillio curiibat plane, salU tu be tlie fu«tei>t buttlcplune in vxititence. (Uliieiiil Ualian Photo.) BATTLEPLANES AND AIRCRAPT GUNS 45 The German "Spatl," tlie MflTelU-.s lliolill'cil "\ll];lil nized to shoot through the propeller. It carries two Maxim guns which are synchro- The Triplane — A Scientific Solution of the Problem of Getting Speed and High Factor of Safety The triplane solves the problem of getting high speed with the low landing speed and high factor of safety. The additional plane affords sufficient increase in carrying capacity to lift the additional weight of stronger construction, and also makes slower landing possible, without much additional head resistance. The battleplane, while representing only one fifth of the types of machines used in the pres- ent war, is the key to command of the air, be- cause the skies must be cleared of enemy avia- tors before the scouts, bombing, artillery, and infantry aeroplanes can w^ork efficiently. Of course, if one side could outnumber the other side, the equivalent of the fighting power af- forded by the fast battleplanes could be obtained by the advantage afforded by number, which makes up for having a few miles less in speed or less skilful aviators. But neither side has been able to outdistance the other appreciably in numbers; therefore command of the air is still decided by speed, the pilot's skill, and the pilot's ability to gain an advantageous position, like the famous Captain Boelke, who used "position" as a winning fac- tor. As a general rule, however, speed is the basic factor for achieving command of the air. Hence every effort is made to get speed, and the factor of safety in construction is only given second consideration, when it is considered at all. Triplane Safe, Even if Wing Is Shot Away The triplane is safe, even if a wing is shot away; the remaining wings will support it for the rest of the flight under any normal condi- tions. A biplane usually collapses soon after a wing has been shot away, and a monoplane collapses immediately. Triplane construction removes the speed limitations imposed upon the small biplanes and monoplanes by their limited lifting power; 46 TEXTBOOK OF MILITARY AERONAUTICS A squadron of Xicuport combat machines. therefore speed can be increased to close to 150 ment just in time to avoid a collision. One of miles, going beyond the margin of safety of the average biplane battleplane. Battleplanes that Collapsed in the Air — Loss of Factor Safety Not Compensated A recent despatch stated that German bat- tleplanes have been collapsing in the air, at the wings of the British aeroplane, however, scraped one of the German's wings, whereupon the latter began to fall. The British pilot dived after him and was startled to see the German's damaged wings fly completely off, while the tail dragged as if its back was broken." The causes are evident. In the struggle for times without being hit, often when but slightly additional speed, there has been sacrificed the damaged. The despatch follows in part: "With the British armies in France, via Lon- don — British pilots continue to bring in ac- counts of German aeroplanes breaking to pieces in the air soon after being attacked. That factor of safety. The machines are merely shells of machines. Triplane construction is a scientific solution of getting greater speed and high factor of safety, but there is, of course, nothing to pre- tendency has been notable for more than a fort- vent cutting down the factor of safety, so as to night. Once shot out of control, the German get a few miles more in speed, aeroplanes have lost their wings, tails, and other Considering the fact that low factor of safety gear to such an extent that when they finally involves the loss of aviators and machines crash on the ground, very little wreckage can through accidents, as well as through machines be seen. collapsing when slight damages are inflicted by "A British pilot recently flew at an enemy gun-fire or other causes, and that this loss in- machine head-on, manoeuvering at the last mo- volv^es a decrease of skilled aviators and number of machines, the writer contends that this loss is not compensated for by the advantages afforded by the slight gain in speed. As already pointed out, while speed is the most important fac- tor in maintaining supremacy in the air, five miles or so less speed than that of the adversary' can be compen- sated for by having skilful aviators, or The Gennan "Koiaiui" two siaiir, so imiit thai the i>iiot .scc-s ovlt tho jj greater nimibcr of aviators and aero- npprr plane and hag but a single stmt, like the "wireless" Curtiss of 1916. . It U equipped with • 140 h.p. Bcnz motor. plones. BATTLEPLANES AND AIRCRAFT GUNS 47 Triplanes being assembled at one of tlie Sopwith factories in Eiighiiul, being inspected by tiie King and Queen of England. These triplanes are equipped with 130 h.p. Clerget motors. Large Aerial Destroyers The larger army machines are four: The "Moineau," the "Voisin-Peugeot," the " Bre- guet-JNIichelin" and the "Farman." These may be called "destroyers," no matter what they may be used for. The most popular British machine of this type is the "Handley-Page." This machine is equipped with two twelve- cylinder Rolls-Royce cylinders of 280 horse- power each; the top wing has a 98-foot span; the lower wing, 65 feet. It has mountings for three Lewis guns. The Germans have several machines of this type. The twin "A. E. G." (manufactured by the Allegemeine Electricitats Gesellschaft) is a three-seated tractor biplane with two i80-horse- power Mercedes motors. Like all machines of this type, including the French, British, Italian, and Russian, it is equipped with two pairs of wheels. Its armament consists of Maxim guns forward and rear, and a bomb-dropping device in front of the passenger's seat. The "A. G. O.," a twin-bodied pusher, usually equipped with a single Bentz 175-horse- power motor; the latest are equipped with a Bentz 220-horse-power motor. It carries two guns mounted on turrets in front. The twin-motored 520-horse-power "Gotha" is a three-passenger biplane usually equipped with two six-cylinder Mercedes motors of 260 horse-power. The wings are 76 feet in span. The length of the machine is 38 feet. It is usually armed with Maxim guns forward and rear, and it fires downward through a hole in the rear fuselage. It is equipped with three bomb-dropping devices and carries 144 bombs. In the smaller German armed machines not already mentioned, are the following: The "Pfalz" monoplane, equipped with a 100-horse- power Obei-rusael rotary motor. Its arma- ment consists of two fixed guns, mounted on each side of the pilot and firing through the propeller. The "Fokker" is also equipped with two Maxim guns firing through the propellers. The "Albatross C-3"; the "Aviatik"; the "L. V. W."; and the "Rumpler" represent the aver- age type of German biplanes. The size of the top wing is from 39 to 42 feet, 10 inches; the bottom wings from 35 to 38 feet ; and the length from 26 feet 3 inches to 27 feet; thev are all 48 TEXTBOOK OF MILITARY AERONAUTICS A view of the French "Spacl" equipped with the Hispano-Suizti 100 h.j). motor and Nickers gun in front and Lewis in the rear. armed with Maxim guns shooting through the propellers; some carry Maxim or Parabellum guns mounted on turrets in the rear. They are equipped with from two to four bomb-dropping apparatuses. In the United States there are, at date of writing, about a dozen types of twin-motored aeroplanes, all suitable for arming; but until the United States entered the war, no steps were taken to arm the machines with machine guns or equip them with bomb-dropping devices. Aeroplane Guns and Cannon The aeroplane guns and cannon employed to-day were developed in the year 1912-1914 and perfected, as far as their perfection goes, during the war. Considered from the stand- point of the guns of six years ago, the aeroplane guns of to-day are marvelously efficient. The most extensively used aeroplane guns of small caliber are the Lewis and the Vickers by the Allies, and the Maxim and the Para- bellum by the Germans. The I>ewis macliine- ^n is an air-cooled, gas-operated, magazine- fed gun, weighing about 26 pounds with the jacket, or 18 pounds without the jacket. The gun is at present used almost entirely without the jacket, without any loss of efficiency. Its extreme mobility makes it a most efficient gun for aeroplane work, being capable of operating in any position, firing straight up or straight down, or in any direction. The speed of get- ting into action and the ability to function auto- matically in any position are due to the use of detachable, drum-shaped, rotating magazines, each magazine holding 47 or 97 cartridges. ^\Tien a magazine is latched on the magazine post, it temporarily becomes a part of the gun, requiring no further attention until empty, when it is snatched off and another snapped on, as quickly as an empty magazine is dropped out of an automatic pistol and a loaded one inserted. Further details of this gun will be given later, with the detailed description of its construction. The Vickers is a water-cooled, recoil-oper- ated, belt-fed machine-gun. Like the Lewis gun, it is capable of being fired at the rate of 300 to .500 shots per minute, maximum. Its advan- tage over the Lewis gim is that it is capable of being fired continuously up to .'jOO shots, whereas the I^ewis requires changing of maga- zines after 97 shots. On the other hand, it has the disadvantage of being belt-fed, so it does not afford the mobility which the Lewis gun af- fords. The water-cooling in the Vickers, like BATTLEPLANES AND AIRCRAFT GUNS 49 the air-cooling device in the Lewis, has been dis- pensed with for aerial work, as unnecessary. Therefore, in most of the French and British planes one finds the Vickers gun fixedly mounted in front, and the pilot points the aero- plane at the enemy, instead of pointing the gun. The Lewis guns are mounted in the rear or in front, on mobile or fixed mountings. The Ger- man Maxim is practically the same as the Vick- ers gun used by the Allies. The Lewis shoots .33 ammunition, and the Vickers shoots .30 am- munition. The Colt, a gas-operated, air-cooled, belt-fed, automatic gun, was used as an aeroplane gun in the beginning of the war, but there are few in use now. That is also true of the Hotchkiss and the Benet-Mecier, which is a modification of the Hotchkiss. All belt-fed guns are subject to jamming, particularly when cotton is used instead of linen webbing, but in the air the one thing to be feared is jamming, due to the fact of the tremendous wind-jDressure on the belt. The present method of mounting Vickers on aeroplanes has prac- tically solved this problem. The Fiat aircraft gun used by Italy is in the order of the Vickers, and shoots 400 shots per minute. Large Aeroplane Guns Details about the larger aeroplane guns have been kept secret, but there are many in use, there ■M^ WsaM^-S"., ^Q 1 reudi isieupoit "Avion de cliasse" flying over a stretch of "no man's land" in France. being squadrons of large aeroplanes equipped with them. A Hotchkiss one pounder, or one- inch gun, has been used in France and England. A Vickers pom-pom, or one inch, weighing 180 or 190 pounds, is reported as giving good re- sults and the Fiat 37 millimeter has been a great success. The Davis gun, the invention of Com- mander Davis of the United States Navy, made in one-inch and three-inch sizes, is a most re- markable weapon. The two pounder, six pounder, and 12 pounder are entirely non-recoil The French "Corps d'Armee" type, "Letort" battleplane equipped with two ISO h.p. Hispano-Suiza motor.", and mounting two Lewis and two Vickers guns. 50 TEXTBOOK OF MILITARY AERONAUTICS -1 The three motored Italian Caproni biplane equipped with three Frasohini motors. guns. The two pounder is 10 feet long, weighs 75 pounds, shoots 1.575 projectile with a muz- zle velocity of 1200 feet per second. The three- inch Davis weighs 130 pounds. It fires a pro- jectile weighing between 12 and 13 pounds at a guaranteed muzzle velocity of 1000 feet per second, but it has shown a velocity of 1200 feet in tests. Another American aeroplane gun is the Driggs one-pounder, now being manufactured. It fires one pound shells at the rate of fifty per minute, weighs one hundred and sixty pounds, including twenty rounds of ammunition, and the recoil pull amounts to six hundred pounds. The Driggs Aeroplane Machine Gun, an- other new American gim, is similar to the Lewis gun in that it has a self-contained magazine, which holds one hundred cartridges, and the gun is operated by recoil, instead of by gas. The larger guns, while not so mobile as the smaller, have greater destructive power and can reach further than the smaller guns. When they hit a plane, almost any part of it, they are almost certain of wrecking it, whereas the bul- lets of smaller guns are only effective when they hit the pilot or the vulnerable parts of the aero- plane. Problems of Armoring — Vulnerable Parts of the Aeroplane So far no progress has been made in the ar- moring of aeroplanes. To have an effective ar- mor to protect the pilot and the vulnerable parts would involve prohibitive weight, which would cut down the efficiency of the aeroplane beyond the safety point. The vulnerable parts of the aeroplane are: (1) the pilot; (2) the gasoline tank; (3) the propeller ; (4) the motor; (5) the control wires. Of course, the pilot could be encased in a steel cabin, but that would limit his mobility, and the enemy aviator could fly close and hit the other vulnerable parts of the aero- plane without interference. The gas-tank and the motor can be armored to some extent with- out great additional weight, but when the mat- ter is considered, it always appears that the One of the Fokkers hrou^tlit down l>y a French aviator. This shows the armored liody and the Maxim pni mounted on top. General fioiiraiid, the late Freneh Conmiandcr-in-Chief at the Dardanelles, is standing by tlie propeller. BATTLEPLANES AND AIRCRAFT GUNS 51 The French Br^guet-Michelin bombing biplane equipped with a 230 Peugeot motor and two guns weight involved could be invested to better ad- vantage in adding a gun, thereby increasing the armament of the aeroplane by one unit. The proj^eller and the wires cannot, of course, be armored. Air fighters always aim to hit the pilot of a machine. The gasoline tank, the motor, the propeller, and other parts of the aerojilane get hit as a result of the effort of the gunner to hit the pilot. Next to the pilot, the propeller, the gas tank, and the motor are the vulnerable parts of an aeroplane which get hit oftener. Only occasional^ are aeroplanes brought down through the wrecking of the con- trols or other parts of the aeroplanes. Many aeroplanes come down at the end of a few hours' flight with several hundred holes in their planes, made by bullets from hostile aeroplanes and bits of shrapnel from the anti-aircraft guns. Bullets vs. High Explosive Shells A bullet striking the strut or the rib of an aeroplane merely leaves a hole, but very rarely does more damage than that. A shell striking the same part will wreck the plane. Hence the shell has its advantages. The mobility of a larger gun would, of course, be less than the mobility of the smaller gun, but that is compen- sated by the destructiveness of the shot. However, the necessity of having rapid fire in aerial fighting precludes the possibility of the larger gun replacing the smaller gun. One supplements the other. Another thing; it would not be possible to mount the larger gun so as to fire through the propeller with the syn- chronizing device. A shell hitting the pro- peller would wreck it, and possibly result in tearing the motor loose, breaking the gaso- line pipes, and setting the machine on fire. With the smaller gun, a bullet "hanging fire" and striking the propeller seldom does more than make a hole in or splinter the pro- peller. However, hardly more than one bullet in 5000 hits the propeller. In firing with the synchronizing device, it releases a shot at every 52 TEXTBOOK OF MILITARY AERONAUTICS four turns of the propeller, permitting the fir- ing of about 300 shots per minute. Explosive shells are used with Lewis, Vickers, Fiat, Parabellum and JNIaxim guns. Fast vs. Slow Muzzle Velocity Fast muzzle velocity has certain advantages, but has the disadvantage of involving greater weight, due to the necessity of having a stronger gun to withstand the additional discharge, and stronger mounting to withstand the greater recoil. The same result can be obtained with slow muzzle velocity by aiming ahead of the target. In the beginning of the war, there being no precedent in aerial gunnery, considerable con- fusion resulted and there was accepted an ex- tremely high muzzle velocity. Then it was de- cided that a maximum muzzle velocity of 800 feet per second was sufficient, giving the de- sired results, but eliminating considerable weight. As a general rule, outside of aeronautics a gun weighs one hundred times the weight of the projectile. This weight is necessary to give it the velocity needed to carry the projectile ver- tically or horizontally over considerable dis- tances. Shooting down from a height only re- quires a portion of that muzzle velocity, the pro- jectile acquiring velocity in its downward tra- jectory. A Lewis gun mounted on a French avion cle combat. Recoil; a Solved Problem Up to the time of the war, it was feared that the recoil of a gun would affect the stability of the aeroplane. Even the recoil of small ma- chine-guns was feared. It is now a solved problem for large machines. It has been found The 1917 type Nieuport avion de rhassc, rqulpjicd with two Lewis guns slioofing over the planes, and a -Vickers gun to slioot through the pro|)cller. In the rear can be seen a "Spad" and several N'ieuports. BATTLEPLANES AND AIRCRAFT GUNS 53 This photograph shows the mounting of the two Lewis guns on top of tlie plane and one Vicliers gun in front of the pilot seat of the single-seater Nieuport biplane. French official photo, passed by French censor. {Courtesy of "Flying.") that aircraft absorb the recoil of any gun of a size suitable for firing from an aeroplane; that is, the aeroplane acts as its own recoil cylinder. This was first discovered in the early part of 1914 when a small naval cannon was mounted on the first Voisin gun-plane. That fear proved to be helpful, as it resulted in developing light, efficient machine-guns and cannon. Tactics in Air Duels For the sake of avoiding confusion, it is well to separate air duels into four classes, as fol- lows : (1) Air Duels in Which Participants are Both Air Fighters Whose Only Func- tion is to Keep the Sky Clear of Enemy Machines The aviator having this mission to perform usually flies out with a speedy machine equipped with from one to three aeroplane guns. He flies as high as he can and remains high until he sees an enemy machine. Then he dives down toward it and tries to bring it down by opening fire on it as he gets to firing distance, keeping up the stream of fire until he sees the enemy machine fall. If he missed hit- ting a vital part, he must either land, if he is near his own lines, or manoeuver to a point of vantage to shoot at the enemy again, or try to rise vertically as quickly as possible, and ma- ncEuver for a high position again, before the enemy gets to the point of vantage to open fire on him. The first method, that of flying to a height and then diving down upon the enemy machine, opening a stream of fire on him, and landing in case of failure, was originated and adopted by Immelman and Boelke, the famous German aviators, who brought down a large number of Allied aviators before their tactics were known. But the success of that method is based on fight- ing enemy machines that are operating over one's territory and that in itself is basically faulty, as control of the air means striking the enemy aviators over the enemy's territory, never permitting the enemy aviators to come as far as one's own lines. A very sound principle of tactics in air duels is to fly to a height, and then dive down on the enemy aviator, pouring a rain of bullets on him. This is, of course, the maneuver that every aviator would like to perform. Being above the enemy is an advantage. Unless the enemy is hit and fluttering away, and needs only a few more shots to be put hors de combat, the practice is to make a sharp turn 54 TEXTBOOK OF MILITARY AERONAUTICS and quickly climb to a height, and regain a point of vantage before the enemy can do so. Having reached a height, the pilot is again at the point of vantage from which he can shoot down on the enemy. In aerial combats, as in naval combats, one's movements are often changed by the enemy's movements. The strongest and ablest drives the other into "tight corners" at sea. But in the air one can fly over, under, and aroimd the enemy, and as both combatants are flying at tremendous speed, which reaches 1.50 miles per hour in dives, the combatants often fly about for many minutes before they get to a point of vantage from which they can shoot at the pilot, gunner, or vulnerable parts of the machine. (2) Air Duels Between Combat Machines and Armed Photographing, Spotting, or Bombarding Machines A duel between a combat machine and an armed photographing, spotting, or bombing machine is quite different from the duel between combat machines. The combat machine will dive on the armed larger machine, which will re- ceive it with upward fire from one or more guns. If the combat machine succeeds in hitting one of the gunners, it only silences one of the guns, but still has to deal with the other gunners and guns. If the aviator does not succeed in hit- ting one of the gunners, then there is a regular battery of guns to shoot at him, and he will need A 37 millimeter gun mounted on a Voisin-Peugeot gun plane. all the skill that he can command to so ma- noeuver as to avoid their fire. But while he may manoeuver swiftly, the enemy machine does not manoeuver so swiftly ; it is not necessary, for it depends on driving away the small combat machine by sheer gun-fire and skill in gun ma- nipulation. In the first year of the war, when few machines were armed with aircraft guns and rifles and pistols were used for aerial com- A Davis non-recoil jiun mounted on R British biittleplane. Tlie three inch pun of this type shoots a 15 pounder. BATTLEPLANES AND AIRCRAFT GUNS 56 A Ilciuy Fariuan "Lo;pa dWr uRc' type, photographed as it was passing another French battleplane, 6,000 feet up. bats, small, fast German machines attacked the large, slow, Russian Sykorsky machines and the Russian gunners were able to bring down the Germans with their rifle-fire from the plat- form of the Sykorsky machines. (3) Air Duels Between Large Armed Aeroplanes In air duels between large armed aeroplanes the tactics are different. These types of ma- chines, being usually busy with taking photo- graphs, spotting, or bomb-dropping, seldom go to great heights; and they are not so well adapted to diving and swift manoeuvering as the combat machines. But that is where the na- ture of the gun and the marksmanship are the main factor in deciding the victoiy. As most of these large machines are either twin-motored or are of the pusher type, with the motor in the rear, they mount aeroplane guns of large cali- ber in front, and can shoot at the enemy from front and sides. The twin-motored aeroplanes also permit mounting guns in the rear, so that they can fight from almost any angle of attack. The employment of aerial gims of large caliber, and the employment of shells instead of bullets, brings a new factor of dominant importance in aerial combat. Whereas a bullet must hit one of the vulnerable parts of the aeroplane to do serious damage, a shell will wreck the aeroplane practically every time it makes a hit. Formation in Air Fighting Formation in air fighting is part of the latest developments in the aerial part of the war. Fighting in formation began in the early part of 1916, and by the spring of 1917, in the in- tensive air fighting that preceded the Allies' drives, aerial combats had taken place in which as many as forty aeroplanes participated on each side. Since then the ofiicial reports contain many incidents such as the following, which was dated June 6, 1917: "Five hostile formations, all of which consisted of over thirty machines, were attacked and dis- persed with heavy casualties. In the course of the fighting, nine German aeroplanes were brought down and at least nine others were driven down, out of control. Six of our aero- planes are missing." There are many instances of individual avia- tors who fought from 4 to 10 enemy aeroplanes and came out victorious, although not, of course, bringing down the 10 machines. 56 TEXTBOOK OF MILITARY AERONAUTICS Launp Signals for Use of Leaders of Formations The code letters are painted on the machine where visible to the observer and within reach of the pilot's hand. When the leader wishes to give an order, he places his finger on the letter required, which the observ^er then sends to the machines concerned with the lamp. The order can be acknowledged by the lamp or by a "waggle" of the machine if lamps are not car- ried. Single-seaters working with two-seaters can take such messages. The principles of formation defined by the British General Staff (see chapter on "War- planes for Bombing and Torpedo-Launching") are applicable to fighting patrols, as well as to bombing, reconaissance, and other patrols. The British General Staff also points out that in the face of opposition of any strength offen- sive patrols usually have to fly in formation, in order to obtain the advantage of mutual sup- port, but the formation adopted may be gov- erned solely by the requirements of offensive fighting. Single-seater scout machines, or even A \'ickers gun mounted on the "Spad" of a menilier nf the Lafayette Flying Corps, and the belt with which it is fed. two-seaters, if superior in speed and chmbing ability to the great majority of the enemy's machines, may be able to patrol very success- Onc of Franre's Short Distance Bombing Machines. BATTLEPLANES AND AIRCRAFT GUNS 57 A squadron of German speed bi- planes of the Albatros type, painted in variegated colors. fully alone or in pairs, taking advantage of their power of manoeuvering and acting largely by surprise attacks; but in the case of machines which do not enjoy any marked superiority, formation-flying is essential. Fighting in the air, however, even when many machines are in- volved on each side, tends to resolve itself into German silver- 1 o o o o o o ORDINARY ARMOR INCENDIARY EXPLOSIVE PIERCING TRACING German ammunition. 3WAY GASOLINE VAtves MOTOR SPEED INDICATOR, FIXED hAACHINE- GON STARTING MAGNETO . MAGAZINE MAONETO 1 FOR FILLED SWITCH EMPTY cAnTA.OOt BELT DCLT Position of the fixed macliine gun in the fuselage (as seen by the pilot) Courtesy of Aerial Age Weekly a number of more or less independent combats, and accordingly it has been found advisable to organize a purely fighting formation. As far as possible, the groups should be permanent organizations, in order that the pi- lots may acquire that mutual confidence and knowledge of each other's tactics and methods, which is essential for successful fighting. It must be impressed on pilots that the group is the fighting unit, and not the individual. Normally, a formation shoidd consist of not more than three groups, and if greater strength is required separate formations should be em- ployed, acting independently, but in such a way as to be mutually supporting. k,'f^.^J?V^' «*L.- British aviators figuring out a raid 58 TEXTBOOK OF MILITARY AERONAUTICS The DeHaviland Scout Bi- plane, one of the more recent British pusher-type scouts. Ik ^3u A fighting formation should consist of ma- chines of one type, but single- and two-seater machines can be combined for similar perform- ance. A suitable flying formation with groups of three machines advances in column groups, with flank machines echeloned slightly back, the whole formation being in vertical echelon. The rear group is the highest, and in the case of a mixed formation consists of two-seaters, w^ith machines of equal performance. Fast single-seaters, if combined with two- seaters, should fly above them, circling so as to obtain a good view all aroimd. In the case of groups of two machines a sim- ilar flying formation is in line of groups, the two machines of each group flying one behind the other, the rear machine at a higher altitude. The flank groups should not be echeloned back, as in this position thej' will be unable to use the center group. The BritUb Vickers pusher biplane equipped with 100 h.p. motor. It mounts a gun forward. Offensive Fighting Tactics Realizing the fact that fighting tactics vary with the type of machine, and with the powers and favorite methods of individual pilots, the military authorities of the warring counti'ies have not issued set rules. Rules of Manoeuver Individual skill in manoevering favors sur- prise. A pilot who is thoroughly at home in the air can place his machine by a steep dive, a sharp turn, or the like, in an unexpected posi- tion on the enemj^'s "blind" side, or under his tail. Individual and collective power of manoeu- vering is essential if flying in formation is to be successful, or even possible. It can only be obtained by constant practice. The following points must always be borne in mind: ( 1 ) Pilots and observers must know the fuel capacity of their machine, and its speed at all heights. (2) The direction and strength of tlie wind must be studied before leav- ing the ground and during the flight. This study is most important, since wind limits the range of action, and machines, when fighting, are bound to drift down wind. (3) To guard against surprise, di- rection must be varied fretjucntly, un- less making for a definite i)oint, and a good lookout must be always kept in everv direction. Gnome BATTLEPLANES AND AIRCRAFT GUNS 59 ''^'^WIJS^.. <■?'/?■":'';"■'', '"^^'^.^f^-'T- ' " BOMB RELEASED The fusclagt' of cine df tlie Gotha biplanes which bombed London. Illustration by courtesy of Illustrated London News. (4) Every advantage must be taken of the natural conditions, such as clouds, sun, and haze, in order to achieve surprise. (5) The types of host"le aeroplanes must be carefully studied, so that the performance and tactics of each, its blind side, and the best way to attack it, can be worked out. Some machines have a machine-gun mounted to fire downward and backward through the bottom of the fuse- lage. (6) Height means speed; since it is easier to overhaul a hostile machine on a dive. If a hostile machine seeks safety by diving, it is bound to flatten out eventually and may, there- fore, be overtaken by a machine from above, if the latter dives in front of it. The hostile 60 TEXTBOOK OF MILITARY AERONAUTICS One of the German Parabellum aeroplane guns. Three quarter view of tlie Sopwitli biplane. machine must be watched all the time, in case it turns. (7) The engine must be always kept well in hand in a dive. If it is allowed to choke, the opportimity will be lost. Thorough Knowledge of Weapons is Required Machine-guns in the air, as on the ground, are very powerful weapons of offense, owing to the volume of fire they are capable of pro- An aerotlnmie just back of a line of trenches In France photof;ru))lietl from an aeroplane. A twin-motored ("luidron and some SupwiUiK are shown on the ground. The motor transports arc in the court-lilie place. (French official plioto.) BATTLEPLANES AND AIRCRAFT GUNS «1 A French type of biplane used for aerial photography and to direct artillery fire, showing the gun mounting at the rear seat. (Photo Committee on Public Information.) UWIS AUTOMATIC MACHINC GUN • .. jnODCiLi ISIS ... Section diagrams ot the Lewis Automatic Machine Gun. The gun is an air-cooled gas-operated, magazine-fed arm, weighing 26 pounds. Its speed and ability to function automatically in any position are due to the use of detachable drum-shape rotating magazines holding from 47 to 97 cartridges. It may be used with tripods or mountings of any design. The Lewis gun has shown adversility and sureness of action which makes it equally effective on rigid bases or the undulating, fragil supports in the air. 62 TEXTBOOK OF MILITARY AERONAUTICS ducing. Their effective use in the air demands even more skill and practice than on the ground. It is dependent on: (1) Absokite famiharity with the mechan- ism of the gun, so that the jamming can be rectified in the air. (2) A high degree of skill in manipulation and accuracy in aim, both on the ground and in flight. (3) Constant study of the conditions affect- ing their use in an aeroplane, and continual practice under these conditions. Memoranda: I CHAPTER V THE FUNDAMENTAL PRINCIPLES OF AERIAL COMBAT By Oscar Ribel Chief Instructor in One of the French Military Flying Schools Translation by Augustus Post The fifth arm has taken a very important part in the European war. The warmest ad- vocates of mihtary aviation in times of peace never dreamed of the vital importance of the aeroplane to-day. In 1907 the most remarkable aerial flights were no farther than 1 kilometer, or %ths of a mile, at a height of 30 meters, about 100 feet. The marvelous accomplishments in aviation during the last ten j^ears are astounding. The most optimistic prophecies did not anticipate one half the actual reality. Who dared to be- heve, when Farman timidly tried his wings at Issy-les-JNIoulineaux, that nine years later es- cadrilles of thirty or forty aerial warriors would sail off into space to engage in heroic aerial combat against each other. Aerial fighting has given an opportunity to develop in both the French and English rare qualities of courage, coolness, and hardihood. The Germans, on the other hand, are less well trained and equipped than their adversaries but, as is frequently recorded, exhibit undeniable bravery. The system used in aerial fighting differs in the German and Allied forces. In France we have distinct types of aeroplanes for different purposes, that is to say, for recon- noitering, "spotting" or directing artillery fire, and for carrying bombs. All these aeroplanes are protected by an escort of machines espe- cially adapted for speed and fighting, and they are well armed. The Germans use their ma- chines more indiscriminately for these various military operations. They do not have so many types of machines, and thus those they have are capable of being used for different purposes with equal efficiency. An exception to this statement are the Fokkers and the Wal- vets, which are flown by their most expert avi- ators and are used exclusively for fighting the enemj'. From a technical point of view French avia- tion is about the same as German, but our pilots are superior scientifically to the Germans, and the number of cur "aces" is constantly increas- ing. Practically all of them fly the Nieuport or Spad, and their victories up to date can be numbered by the himdred. Naturally we can- not describe the methods employed by each one 63 Fig. 1 — The "Loop" as an aerial military manoeuver. At- tacked by four or five German machines, a French biplane turned completely over and returned by means of "looping the loop" to attack the squadron which was attacking him in the rear. of these "aces" in fighting the enemy, because almost every one depends upon the marvelous individual skill with which they perform their acrobatic feats. One example among thou- 64 TEXTBOOK OF MILITARY AERONAUTICS sands may be quoted. It is well known among escadrilles at the front and will give an idea of how every pilot must cut the "Gordian Knot." In the course of a reconnoitering flight in the East, sub-Lieut. Navarre found himself sur- rounded by five or six German machines. Three or four were above him and the others ^ t I ill Ol B ZOOmetres, Fig. 2 — The favorite attack of the Walvets. Walvets patrol two by two. A 200 meters above and 200 meters behind B. If a machine C is encountered B engages in combat with it while A remains to survey the zone of battle to prevent surprise on the part of another machine which might come up to render assistance. were below or at the sides, which prevented him from going to the right or to the left, either in rising or descending. It seemed impossible for him to escape. Without losing for an in- stant his remarkable coolness, our valiant "ace" surprised his adversaries by making a complete loop over the entire group of assailants, and following up the nearest machines, discharged an entire belt of cartridges from his machine gun and brought down two machines one after the other. The other pilots retreated as fast as possible to their lines, pursued by the in- trepid Navarre. The German "aces" are much less numerous than our own, the best among them being Cap- tain Boelke, who died the 28th of October, 1916, after having brought down his fortieth adver- sary. We count as victories for our pilots only the enemy machines which fall inside our lines, or fall in flames in unoccupied territory', but the Germans do not hesitate to count every machine which is brought down for one cause or another, and is thus obliged to abandon the fight. If we adopted the same method of counting, it is certain that Guynemer, among others, has brought down more than sixty enemy machines. French aviators often fight twenty or thirty kilometers behind the German front. A Ger- man reconnoitering party must be checked in its operations and brought down if possible. During the course of our ofi'ensive on the Somme and at Verdun, our machines estab- lished a veritable barrier across our front, through which no German aviator was able to penetrate; and this lasted for several days. Speed and climbing ability are essential for a fighting machine, as the aviator has to outfly his adversary and strike him in a vital spot at an opportune moment. The Fokkers, the Walvets, and the L.V.G. are the principle types used for reconnoitering over the front, and have a speed of 1.50 kilometers per hour (about 100 miles). They climb very rapidly, and the altitiade at which aerial combat is gen- erally fought is about 4000 meters (14,000 feet). Generally speaking, the German fighting pilots, especially those who fly the Walvets, employ the following tactics when they come over our lines and engage our aviators. They always go in groups composed of units of two machines each. If an enemy machine is en- gaged by one of these units, the first of the Ger- man aviators begins the battle and the second man remains about two hundred meters above, his mission being to overlook the zone of combat without interfering directly with the fighting. If a second adversary comes to the rescue, how- ever, it is his turn to attack and drive away the rescuer, while if his partner is vanquished, he returns to his lines as quickly as possible. Often the manoeuvers are more involved, and the aviators fly in large squadrons for mutual protection. If an isolated enemy is encoun- tered, he is quickly surrounded and must seek safety in the speed of his flight. The speed of the fighting machines is great, and there is danger therefore of breaking the wings. A machine which flys at 180 kilometers an hour (about 110 miles), rises two thousand FUNDAMENTAL PRINCIPLES OF AERIAL COMBAT 65 meters in seven minutes (about 7000 feet), and dives almost vertically from this height, ex- periences a tremendous strain which, in time, is apt to cause weakness. Fighting machines have to perform extraordinary feats in pur- suing the enemy. They dive vertically, and if the wings break under the jiressure caused by these conditions, the machine at once falls. German machines, generally speaking, have a good factor of safety in their different parts. Many accidents have been caused after a ma- chine has had many repairs, or through some Fig. 3 — The "Dive Attack." To train the machine gun upon its target below the machine must be pointed down at least 60 degrees. hidden fault of constniction. Recently at the front near Verdun an aviator was pursuing a German machine and, in his turn, was pursued by a small Rumpler biplane. At the moment when the French pilot, after bringing down his first adversary, was preparing to face this new assailant, the Rumpler dived straight toward the earth in a sudden bold dash. The wings broke and folded up above the fuselage. Many Rumpler machines have met the same fate in other air battles. The constructors thus invol- untarily contribute to the success of our pilots, and thereby deserve our thanks. The German "aces" generally fight in con- junction with a squadron of accompanying ma- chines. These are charged with the duty of occupying the attention of the enemy until an opportune moment for attack. Boelke adopted the following tactics, as described by M. Jacques Mortane. The German flew with an escadrille of five or six good pilots on Rolands, Walvets, or Fokkers; he preferred a Fokker, but sometimes was seen on a Roland, or a small Aviatik. As soon as the well-known profile of an Allied machine was seen on the horizon, the squadron rose to engage it. The duty of Boelke's support was to surround the enemy and block his path. They would fire from all sides, suddenly ceasing the instant Boelke made his entrance upon the scene. The latter would dash at his prey and attack furiously, firing a thousand cartridges from his machine gun. Boelke followed up the fight, in contrast to the Fig. 4 — The tactics of the famous Boelke. The duty of the machines C, D, E, is to surround their adversary B at a given moment. A, who has been hidden from the view of his adversary, dashes at him, firing his machine gun furiously. custom of many of his compatriots. These rarely continued an engagement with an ad- versary who was not brought down at the first shot. Such was the method adopted by Lieut. Immelmann, one of the best of the German aviators. He would dash up to an enemy's 66 TEXTBOOK OF MILITARY AERONAUTICS machine, and when so close that a collision seemed imminent, would discharge his machine gun at it as he passed by. Once out of range he would not return to the attack, but would fly away, which cannot be considered very heroic. The Germans usually fly very high. When they see French machines they hesitate to cross our lines, which are always well guarded by our fighting machines, especially during the periods of Allied drives. The weather plays an im- portant role in air fighting. Calm days, when the sky is full of dark, gray clouds, are the most favorable for surprise attacks. The clouds act as a screen and allow the aviator to hide until the last moment, before he makes a dash at an unsuspecting enemy. The Germans are ■ well versed in one trick which they invented and which they have often used. When the bank of clouds is thick, one of their machines flies down to an altitude of two or three hundred feet. This machine may be of any class, but it is usually a slow machine of an old type, and not heavily armed. Fig. 5 — The Tactics of IiiiiiicliiKin. The iiiiuliino A daslies straiglit at its enemy B, firing at him furiously. If he failed to bring down his prey he fled and did not return to the charge. It appears to be relatively easy prey, and is quickly discovered by the French machines. They give chase, not hesitating to follow it, even to some distance behind the German lines. At the moment when the French pilot finds conditions most favorable to begin his attack, three or four German fighting machines of the latest and most formidable model appear. Flj'ing above the clouds, they have been follow- ing the two antagonists while hidden from view, and never appear until the enemy is at least twenty or thirty kilometers from his base. The number of attacking machines, and the difficul- ties in getting help in time, make it an extremely precarious predicament for the French avia- tor. An air battle does not necessarily end by the complete destruction of an enemy machine, or the killing or disabling of a pilot. A case has occurred where a German aviator was at- tacked by a French "ace." The German was convinced that he had no chance, lost his nerve, and preferred to come down in safety to having his body riddled with bullets. He directed the observer with him to throw up his hands, while he steered his captured machine, and following his vanquisher to the nearest aviation field, landed by the side of his captor. In this way Lieut. Laffon gathered out of a clear sky a Fokker of the latest model, and brought it to the aviation center of Plessis-Belleville. The feat was all the more remarkable and creditable to the officer because he had no arms aboard, except a revolver. Before the war the question of arming ma- chines received only superficial study, at least in France. At the beginning of hostilities only a few aeroplanes were equipped with machine guns. ]Many of the aviators had only a rifle with which to defend themselves against attack. To-day, as the enemy well knows, our machines are very efficiently armed for both attack and defense. The position of a machine gun on the aeroplane plays a great part in the success of air fighting. We know that the Germans have studied the problem with great care, and their machine guns are mounted in one of the five following positions: (1) Above the upper plane (machine guns stationarjs firing through the propeller). (2) Along the fuselage (gun stationary, shooting through the propeller). FUNDAMENTAL PRINCIPLES OF AERIAL COMBAT 67 (3) In rear of the lower plane (guns mova- ble in a revolving turret) . (4) In front of the cockpit (gun movable and able to fire in all directions ; single-motored machine with a pusher propeller). (5) Both in front and in rear of the cockpit (gun movable; twin-motored machine, tractor propellers, with a central cockpit). The first arrangement has been adopted by several manufacturers of small speedy bi-planes in Germany, and is similar in almost all points to the system used on our Nieuports. The ma- chine gun is stationary on the upper plane, par- allel with the fuselage, and is controlled by a "Bowden" flexible wire control fastened to a rod beside the pilot. To train the gun upon its mark in the vertical plane one must point the aeroplane up or down; and to aim in the longitudinal plane, the aeroplane must be pointed in the direction of fire, since the gun is firmly mounted on the axis of the nlachine. When the aeroplane attacked is just below the pursuing machine, the latter must dive verti- cally and attack its adversary while inclined at ninety degrees, in order to bring the machine gun into range. In practice, the angle of at- tack is not quite as steep as this, for the attacked machine is not exactly beneath its adversary's gun. It is at least 100 meters (300 feet) away, and when the attacking machine opens fire, it angle. The difficulty of hitting the mark is great, since the gunner and his object are mov- ing rapidly, and the movements in steering an aeroplane are complex and relatively slow. The mounting of the gun on the upper plane is best adapted to the machine which has the Mitrailleuse fine -Mitrailleuse mobile a tourelle Fig. 6 — Mounting of the two machine guns on the new bi- plane L. G. V. The machine gun in front shoots through the propeller and is fired by the pilot. The rear gun mounted in a revolving turret is fired by the observer. is at an angle of 55 or 65 degrees. This, when compared with the horizontal, is a considerable Fig. 7 — Arrangement of a machine gun with a limited field of fire. The gun is mounted in front of the car on an elevated support. The field is limited by the extremities of the aero- plane. pilot's seat behind the wings. Consequently, to gain the best chance to reach the aviator him- self, his adversary must strive to attack from above. The mounting of guns for firing through the propeller was first attempted by Roland Gar- ros, who was taken prisoner before he was able to destroy his machine. The Germans were quick to copy this method of mounting guns, and have made many improvements, as it was well adapted to the Fokker machine and gave very good results. On the Fokkers, the gun is mounted stationary above the hood, a little to the right of the axis, on a level with the head of the pilot. The propeller causes only slight in- convenience, but on account of the gun being firmly fixed, the entire machine must be aimed, with the attendant difficulties already men- tioned. It is also possible to shoot through the propeller by using an automatic device to momentarily stop the fire during the passage of the propeller-blade in front of the gun. The latter is mounted directly behind the propeller. In this device the motor is connected with the machine gun, and a cam controls a mechanism 68 TEXTBOOK OF MILITARY AERONAUTICS which stops the fire for /^oo of a second, while the blades of the propeller are in the path of the bullets. When the propeller has passed, the gun is free to fire again. If a pilot wishes to shoot, he presses a small lever placed on the steering post, which is connected to the trigger of the gun. The company licensed to make the Nieuports Fig. 8 — Vertical field of a machine gun mounted on a pivot. In the vertical plane the fire is very extended. It is only lim- ited by the parts of the aeroplane. in Italy recently invented a device which en- ables one to shoot through the propeller, prac- tically identical with that used on the Fokker. It is based on the difference between the speed of the gun and the speed of the propeller ; that is to say, the ratio between the bullet and the propeller-blade is 700 to 160. This difference is used to regulate the stopping of the machine gun during the passage of the blade of the pro- peller in front of the barrel of the gun. The arrangement which Garros used was ex- tremely crude. It consisted simply of a small piece of steel, hard enough to resist a bullet, placed on each blade of the propeller opposite the barrel of the gun. If a bullet chanced to hit the propeller, the metal deflected it without causing damage to the propeller-blade. The German bi-planes, like the Ij. V. G., for example, have two machine gims. One is sta- tionary on the upper plane, the other movable and mounted on the fuselage behind the observ- er's seat, on a revolving turret. This gives it a great range of fire. The turret is a ring of wood which turns freely around the cock-pit on ball-bearings, with a bracket arm which holds the gun and permits it both to be trained in the vertical plane and swung around in the hori- zontal plane to either side of the fuselage, so as to point in any direction. Two small clamps hold the turret and gun firmly in any position. This arrangement gives a wide range or fire to- ward the rear in all directions, and on either side, both above and below. It is even possible to fire ahead, above the wings of the machine. The rear machine gun is often replaced by a "fusil mitrailleuse," or automatic rifle. To pro- tect the blank sector of this gun arrangement, the fuselage is provided with a tube-like open- ing, inclined at an angle of forty-five degrees. This tube allows the gunner to see and fire through the fuselage at the enemy, if he tries to hide from view of the gunner below the rear of the machine. The machine guns, when mounted in front and rear, are both fired by the observer, but in a recent type the forward gim was placed be- tween the two planes beside the motor and parallel to it, being fired by the pilot. At the beginning of the war some German machines had a cockpit, like the French Far- mans, with a gun mounted on an elevated sup- port. This mounting left a large blank sector of fire, and was afterward abandoned. The gun did not have much sweep, and its zone of fire was restricted by passengers, wings, pro- peller, cables, struts, etc. This was remedied in a measure by mounting it on a turret, which allowed it to fire in all directions, but not at all angles. This type of machine is not used to- day at the front. It has been replaced by the A. G. O., which is provided with two motors and tractor propellers, and a central car armed with two machine-gun turrets. One machine gun is placed forward, sweeping the horizon for 180 degrees and the other is in the rear, its range also controlling 180 degrees of the horizon. Between them the entire horizon is covered. All of the German machines are armed with one or two Maxims, Lewis, or Parabcllum machine FUNDAMENTAL PRINCIPLES OF AERIAL COMBAT 69 guns. Some aeroplanes have three machine guns, and these are considered the best for ac- tual service. The Parabellum has a belt of cartridges which contains not less than a thou- sand projectiles. If each pilot has his own method of fighting, each type of machine has its weak points; and these points must be well known, in order to make a successful attack upon it. When at- tacking a machine it is necessary to learn how its guns are mounted, in order to know whether to attack it from above, below, or from the side. If the field of fire of the machine gun has cer- tain dead points, it is thereby handicapped, and may be attacked to advantage. A pilot who is attacked by an Aviatik is exposed to fire from all directions, except in the zone in front of the propeller. In the case of ordinary Aviatiks, with the gunner in front, the machine gun can be placed at will on the right or left side of the fuselage. It is placed upon a pivot mounted on a carriage. This carriage can be moved on two guides, or slide bars, that run along the fuselage to a convenient point for firing. A clamp holds the carriage at any spot, so that one can fire in all directions. An aviator who attacks an L. V. G. which, as we have explained, has two machine guns, must decide whether it is better to stay in front or in the rear of the line of fire between the forward and the rear gun. Thus we see that the identification of the type of enemy aeroplane is absolutely necessary for ^-•' -^,.^ X ■•x^ X ^N / \ / \ / N / \ / \ / / \ \ t \ \ 1 Propul^ur Propufaeur 'j ' --^^ -(K-- -ir' ' r-----'-":.'i. *\ a 1 ^J..J-— — — r ' 1 1 1 L*J 1 1 \ ! \ t \ • / \ / \ / X, y ^ — — ^^.,'' Fig. 9 — Mounting of two machine guns in a bi-motored ma- chine. The arcs of fire in the horizontal plane meet each other when the guns are mounted in this manner. an air warrior. Unfortunately, the diversity of types of machines employed by the Germans, and the frequent changes made in service, ren- ders this identification extremely difficult. German positions reduced by Frencli artillery through the directions given by aero observers. The center pho- tograph shows the trenches and German position in broad perspective. The im- portant positions are shown by numbers and are shown in detail in the smaller pho- tographs. The aero observ- ers directed the artillery fire on these positions. Photograph No. 1 shows the effects of the French shells on a typical one of many German points d'appui. No. 2 shows the condition in which the captured German trenches were found. No. 3 shows the remains of the emplacement of a German battery. No. 4 shows the ruins of a small l)ut very strong German fortified post. No. 6 shows the result of the French bombardment on the German defensive line be- fore the River Suiiipe. No. (!, like No. 2, is another typical scene in the captured Germnn trenches, showing their general appearance after the bombard- ment. No. 7 shows all that re- ma ine• J)--' 't n^f T.ll, o off-'*' 's"*— '1 dr* 1 -r,».. ^t *'.nJ^«H^»4 '•/< T* ''IC * 1. J c ME.r-ie •1 *.« cations of a section for this reason : although the greater part of the hnes are laid by the signal companies, when once laid, the balloon section is responsible for their upkeep, and it will be seen, on referring to the sketch, that it is a pretty big job for the small telephone detach- ment allotted to a balloon section. Therefore it is of the greatest help when batteries assist, as much as is in their power, with the laying and maintenance of the line from their position to the advanced exchange ( see Fig. 1 ) . The work chiefly allotted to the balloon con- sists of: 1. Destruction of villages; 2. Destruction of strong points behind the line; 3. Registering on cross roads; 4. Registering on exits from villages, woods, and ravines; 5. Counter-batterj' work. The method of observation employed it to observe on the line balloon-target, and, bj' the use of graticuled glasses, to send to the battery such observations as 1°20' Right, 30' Left, Line and over. Line and short. When the battery sends "Gun fired," the chart room officer sets his stop-watch going and says, "Bun fired" to the observer, then, at the correct time: "10 seconds to burst"; "5 seconds to burst"; "4"; "3"; "2"; "1"; "Burst." This relieves the observer in the balloon of watching with his glasses the whole time. He nmst keep his eyes fixed on the target, but need not strain them by peering through his glasses during the whole time of flight. When he hears "10 seconds" he gets ready, and at "5" puts them up. i A French captive balloon of the Caqout type just behind the firing lines. CHAPTER VII KITE BALLOONS -THE EYES OF THE ARTILLERY Written by a French Officer; Translated by Augustus Post (From "Lectures Pour Tous") Another of the marvelous developments of the war is the captive balloon, which, in view of the wonderful progress made with dirigibles and aeroplanes, seemed doomed to be relegated to the storehouse. Captive balloons, on the contrary, have developed with the increasing importance of artillery until we now receive most valuable service from our "sausages," which are exposed to great dangers and whose officers have had most dramatic adventiu'es. Holding the lines of the enemy under con- tinuous observation, transmitting to the com- mander every operation that goes on, directing artillery fire — this is the role that the captive balloon plays. Before the beginning of the war, the Germans had foreseen their value and although we had only spherical captive balloons, they were already using the elongated shape, familiarly called "sausage." As is the case with many other inventions, this model was originally French, and was copied and adapted by the Germans under the name of "drachen," or "kite" balloon. It has proven its superior- ity since the spring of 1915, because it acts ex- actly as a kite and is supported by the force of the wind, when a spherical balloon woidd be beaten down by a wind of from eight to ten meters a second. Manoeuvering A balloon company consists of a crew, who take charge of the manoeuvering of a kite bal- loon; that is to say, filling, observation, trans- porting, and making the ascension. In addi- tion, there are several wagons and automo- biles. The most important is the "voiture- treuil," or "windlass wagon." A steel cable about the size of a pencil, that can stand a heavy pull, is wound up on an immense reel. In the center of this cable is a telephone wire, con- necting with the basket. A motor turns the reel 81 82 TEXTBOOK OF MILITARY AERONAUTICS in one direction or the other to allow the balloon to ascend, or to draw it down. The automobile windlass has almost entirely superseded the old- fashioned steam winch with six or eight horses ; it moves three or four times as fast, needs not more than ten meters to turn, and is less vul- nerable. Always ready, it is easily concealed with a cover of branches. Camp Equipment of a Kite Balloon Unit ^^^len the balloon is in use, the "treuil" is ac- companied by a "camion aux agres," or "rig- ging truck" containing a store of extra ropes, the basket, the "godets," or cup-shaped pieces which are attached back to back and make an immense kite-tail to head the balloon into the wind. The equipment includes the field- glasses, maps, and scientific instruments. Be- sides the windlass wagon, there are two equally important wagons that hold the encampment paraphernalia and the telephone equipment. The first has all the things necessary to set up a new observation station when the old one has to be abandoned for some cause — shell-fire, for instance, coming too near. They carry cork- screw stakes and pegs which hold the stays of the balloon, sacks of ballast, a ground-cloth to prevent the balloon touching the ground, and all the other things that are a necessary part of the equipment. In one day a company changed its location four times, because the posi- tions were shelled each time after the balloon had been set up and inflated. The telephone car contains all the material necessary to establish communication, — miles of wire, apparatus, tables, bells, spurs for climbing high trees, insulators and brackets for laying lines to connect the balloon with the commander of the artillerv or batteries of anti-aircraft ffuns, if they are a long way from the place of ascen- sion. An Artillery Captain's Experience During an advance, the observer in the basket is directly in touch with the gunners and regu- lates their fire, a very interesting occupation for the observer, especially when it is necessary to pick off some convoy or troop on the march. One day an old captain of artillery who had lit- tle confidence in the usefulness of the captive balloon was invited to ascend, in order to see how easy it was to control the artillery fire. They had not ascended one hundred meters be- fore he marveled at the panorama, at three hun- dred he was converted, at eight hundred he was enthusiastic. The observer who accompanied him kept revealing new possibilities to him all the time. The time passed until the ofiicer com- manding the company of the balloon corps saw his telephone operators bursting with laughter. He called them to order, thinking that they were telling each other funny stories, but one of them said to him, "Take the receiver and listen to the observer and the captain in the balloon." They were directing fire upon a long train on the march, at the extreme range of a battery. One of the monster British guns on the West- ern front. The efficiency of these guns Hei>ends en- tirely on the spotting of tlie (lerial ohservers, there- fore. The Kite halloons are usually stationed in the rear of heavy artil- lery, held anchored by means of cnhles. The ob- servers in the basket of the balloon have a clear view of the enemy's posi- tion and observe the re- sults of the gun firing, and advise the battery commanders by telephone. KITE BALLOONS— THE EYES OF THE ARTILLERY 88 f Photograph taken from kite balloon showing how the earth appears to an observer. The captain was amazed and could not restrain himself. "Bang! in the center; one wagon de- molished. Oh! and the horses — bang! — an- other. Eh! — Ah! it is wonderful, wonderful. I never believed it. Bang! At least, we do not fire blindly." Personnel of Kite Balloon Company The personnel of a company of balloonists is divided into two classes of about equal num- bers; that is to say, the men who pull on the ropes, and the others. In order, they are: the captain, sometimes a lieutenant, in command of the company. It is he who, assisted by his offi- cers, chooses the best point for observation and the most convenient for locating the balloon and the camp. Under the direction of the officers, the sergeants assign the corporals to their ropes, and lay out and transport the balloon over ob- stacles. Eight men handle the envelope, and the rigging, place the basket, and adjust the maps and instruments, four or five mechanicians work the winch, and one cyclist and one motor- cyclist serve as messengers. As in all other troops, there is a doctor, a quartermaster, a fur- rier, tailor, shoemaker, barber, orderlies, and all the little world of specialists who go to make up an efficient unit. Preparations for Ascension When a company arrives at a new position the captain, accompanied by his observers, im- mediately gets in touch with the commanders of artillery, inquires the location of the enemies' batteries, their habits and activities, and the strength of their artillery and aeroplanes. In another direction a mounted officer with a detail- map searches for a good location to station the balloon. This is a very delicate matter to de- cide. The best place is in a forest, which pro- tects the balloon from high winds. Trees are cut down to make a clearing large enough for the manoeuvers of ascending and descending without risk of tearing the envelope on the branches, and for leaving room to handle the tail of parachutes. Next the work of making camp is begun. The ground-cloth is spread, ten stakes set, to attach the balloon, 80 ballast sacks of ten kilos are placed with their hooks in the network, and a bag containing the balloon is placed in the center of the ground-cloth. The valve is attached, the cords straightened out, 84 TEXTBOOK OF MILITARY AERONAUTICS and the filling pipe securely connected. All this takes about half an hour, and the balloon is ready for inflation. Hydrogen is brought in from the tube wagons, each tube containing 150 cubic meters of gas, compressed to a small vol- ume. It takes over one hundred tubes to fill the balloon, and from two to three hours, unless you have enough tube wagons, when it can be done in half an hour. When filled, the "sausage" is ready to ascend, if the weather permits and the wind is moderate. In fifteen minutes the balloon is in the air, not to come down till nightfall, and the regular rou- tine of life begins. At daylight the company return to the balloon. Some detach the ropes from the fastenings and unhook the bags of bal- last which hold it down, while others connect the appendix, and replace the gas lost during the preceding ascension by expansion, due to the altitude. This takes only fifteen or twenty min- utes at most, and soon all is ready for another ascension. When circumstances permit, the balloon remains in the air all the time, with one or two observers who take their meals with them. As night falls, or when the weather renders it useless to remain in the air, or dangerous storms with rain or high winds, come up, the balloon is brought down, disconnected, and made fast for the night under the watch of sentinels, so that the rest of the men can return to camp. Fre- quently, it is necessary to remain ujj all night. to search out the batteries of the enemy by the flashes from his guns. An observer who has passed many days in a balloon becomes famihar with the countrj^ and can determine in the dark various points in the landscape and tell where certain woods and villages lie, or he can even lo- cate very exactly a batterj' whose position could not be located in the daytime. This routine con- tinues with great regularity, until the company receives orders to take up a new position. In three or four hours at most the convoy is on the march, the balloon being deflated in twenty-five minutes, and packed in its sack, and all other materials loaded on the wagons. What You Can See from a Kite Balloon Here is a story of a lieutenant of artillerj^ on his first ascension. "The order to 'let go' has been given. ]My basket is a charming little boudoir, hardly big enough to take two steps in. At my hand, hter- ally, are three binoculars, maps, and the tele- phone which connects with the ground and puts me in direct connection with the commander of the artillery station. At my feet, I see my com- panions looking up, with their heads thrown back. The perspective rapidly extends. The horizon, limited by the trees and surrounding hills, slips farther and farther away; the land- scape stretches out below in relief; the picture changes to a geographical map, but the map is One of the hundreds ot French motor batteries en route to its firing point, the Are of which is directed by Kite balloons and aeroplanes. KITE BALLOONS— THE EYES OF THE ARTILLERY 85 vivid and brilliant with soul-inspiring color ; ser- pentine roads and rivers stretch away in the dis- tance. Just below me is a farm, and those mi- nute dots are animals. In the east, a few kilo- meters away, are the zigzag lines of the enemy's trenches ; they cross and re-cross. In the center runs a slender green ribbon which seems to be intact. This is the ground between the trenches of our first line, and the enemy. Here and there are some ruined villages, the houses de- mohshed. The desolation of the scene makes one feel sad. Scattered all about, we can see black and white places. These are the shell- holes, where the enemy has trained a battery upon some spot and sprinkled it with terrific fire. There are also our own works, and batteries which we know well by the puffs of smoke when the guns are fired. From the basket all this is perfectly clear. It is the ideal observatory for artillery. It is true that the basket is not al- ways above the positions of the enemy, as is the case with the aeroplane, but it is stable, and you can use glasses without difficulty. There is also another great advantage in that the observer is in constant communication with his batteries, which is more accurate and rapid work than in the case of the aeroplane." Aeroplane vs. Captive Balloon The captive balloon has a dangerous enemy — the aeroplane. When the weather is clear and An aeroplane having approached the balloon, the observer has jumped into space and is descending by means of the para- chute. the clouds high, the aeroplane is not a formid- able enemy. The telephone signal and white pufPs of smoke from the "75's" give warning from afar. If the balloon is too high, it is hauled down 300, 400, or 500 meters, but not down to the ground, for if it is on the ground, the enemy aviator has only to consult his map A French Kite balloon being inflated. The Ger- mans were first to em- ploy Kite balloons for directing artillery fire. The Allies promptly adopted them and now there are thousands of Kite balloons in use on both sides and are con- sidered absolutely inval- uable. The English call it "Kite balloon," the French "balloon captif" or "saucisse," the Russian "Kolbasa," the German "drachen," the Italian "Pallone — Cervo Vo- lante." 86 TEXTBOOK OF MILITARY AERONAUTICS and altimeter to know his exact lieight above his target and release his bombs with some chance of success. If the balloon is at an unknown height, it is impossible for the aviator to calcu- late the instant to let fall his projectile. When he descends low enough to attack with his ma- chine gun, he must risk being hit by the ob- server's gun-fire and the machine-gun below the balloon. Descending to 2000 meters is dan- gerous for the aviator, but there are some excep- tions of which the following incident is one : Last jNIarch, in ideal weather, the balloon of the Company was in a clear sky at sunset. Suddenly the signal came that a German aero- plane was seen on the horizon. In truth, all one could see was the white puffs from the "75's" shells, high in the sky. But soon the silhouette of an aeroplane appeared, making right for the balloon. A whistle, two or three sharp com- mands, and the windlass commenced to haul in while the machine-guns and muskets were trained on the aeroplane, and the observer warned by telephone. There was no more doubt, for not only had the aeroplane headed for the balloon, but again, without heeding the bursting shells, pointed directly at the "sau- sage." Descending with great daring to the same height, so that it was difficult for the anti- aircraft guns to regulate their fire, the machine- guns only were brought into action. In the basket Adjutant T., just promoted, prepared to christen his chevrons; his carbine came into play. Seeing the balloon descend, the German aviator volplaned down, so near that we hoped each instant he would be caught in the manoeu- vering rope. While turning, the aviator was furiously firing his machine gun. As luck would have it, the carbine of the observer jammed. He kept cool, however, which was easily done, for it was 6° above zero, and calmly sat down in the bottom of the basket trying to fix his gun. Believing him wounded the "boche," despite the bullets which whistled around him, tried to set fire to the "sausage" with a specially constructed cannon. He launched an incendiary bomb, and we saw a train of glowing sparks go toward the balloon. But Adjutant T. had fixed his gun. He rose in the basket and fired point blank at the enemy. Alas ! he fired only four shells when the breech- block broke, leaving him completely disarmed, while the German, with a new machine-gun, merely unrolled a new belt of 250 cartridges. Finally a French aviator, who had seen the struggle from afar, flew up to the rescue. The aviatik flew away, pursued by the "75's." Brave Adjutant T. was safe and sound, but the basket and envelope were riddled with bullets. This damage was repaired with a few patches. Such a bold attack is exceptional, but some- times the aviator uses other tactics to attack the balloon. He chooses a day when great clouds A Russinn observntion balloon and its "nurse." An oljserva- tion balloon after inflation may stay in the air for an entire day without receiving additional gas. When it needs replenishing a smaller balloon, the "nurse," is brought up and the gns it eon- tains is pressed info the larger balloon, the pressing being done by the men, who squeeze the "nurse." KITE BALLOONS— THE EYES OF THE ARTILLERY 87 form in a layer above the balloon, two or three thousand meters high. Flying above the clouds, the aviator, seeing his prey through a rift, or judging he is near enough, darts down, releasing his incendiary bombs covered with fish- hooks, which catch in the envelope and are sure to set it afire. Another of these tactics is to take advantage of the clouds that pass between the balloon and the ground, hiding the aeroplane from the eyes of the balloon company, who are unable to train their machine guns upon the enemy. A Leap Into Space from a Kite Balloon Experience has taught that the counter -move for this manoeuver is not to allow the balloon to rise out of sight above the clouds and, when necessary, to haul it down by the winch every lit- tle while. The observer is also provided with a parachute, which he attaches to his back by stout suspenders which pass under his arms and around his waist. If he finds his balloon on fire, or if warned by the telephone from the ground, he jumps out. The parachute, folded in a spe- cial sack, opens in less than sixty meters, land- ing him gently on the ground. This is of quite frequent occurrence. Within three days the life of an observer was saved on two occasions by this means. On the 19th of March, during a violent wind-storm, the rigging broke, and two The observer descending with the parachute to escape an aero- plane attack. seconds later the basket started to fall. In- stinctively the observer saw his danger, gathered up his papers, jumped into space and descended with his parachute. When his feet touched the Turning on the gas from gas cylinders to in- flate a Kite balloon. M'herever a Kite balloon is established there are brought the gas cylinders on specially constructed trucks. They are then unloaded and placed on a .special stand, as shown in the photo, and pipes are connected to each cylin- der and to the main pipe which is connected to the rubber tube which leads to the ai)pendix of the Kite balloon. 88 TEXTBOOK OF MILITARY AERONAUTICS Members of the Canadian Kite Balloon Section patcliing up a kite balloon on the Somme front. ground, the eighty square meters of cloth made a sail in the strong wind and he was dragged 1200 meters over the fields, finally bringing up with only a few scratches. A Curious Manoeuver "When the wind rages and the rain falls, the windlass is used to bring the balloon down, but if it breaks, they use a "tiraudes," or snatch block with eight large ropes attached to it. !Men pull on this rope, marching straight away, bringing the balloon down to the ground one half as fast as the winch. A serious situation may arise if the windlass is destroyed by shell- fire and the balloon cut away when the wind is blowing toward the enemy's lines. When this happens, they move the automobile winch away, dragging the balloon like a kite. Of course the observer can always descend by opening the valve and allowing the gas to escape. \ A Drama at the End of a Cable Accidents will happen despite all precautions. Last spring there was a tragic day for our bal- loons when several were torn away by the wind and driven over the enemy's lines. The weather kept the balloons down all day until about 5 :30 P. M., when it cleared and the wind fell to a flat calm, the kite tails hanging vertically along the cable. Two officers went up in one of the bal- loons. They wished to go high enough to ob- serve a battery that had had the cover which con- cealed it blown away. To lighten the balloon, they left the only parachute in the equipment on the ground. Suddenly the telephone op- erator called the observer and said, "Heavy clouds are forming in the southwest." Rapidly the sky became overcast and in an instant the balloon, which had been hanging directly over- head, started northeast. The wind rose, and the Captain ordered the windlass to haul down as quickly as possible. Two hundred meters were wound on the drum, and a thousand still remained. The winch puffed and labored, and finally stopped altogether. "Raise the pres- sure," ordered the Captain. "I have eight kil- ograms," answered the engineer. The pressure cannot be raised in a moment, and time was fly- ing. The windlass turned slowly, and again it stopped. "Ever}" one on the hauling ropes," came the order, as a last resort. Two hundred meters were hauled in this way, when the men walking away with the rope were blocked by a large farm building and had to halt. At this moment the engineer signaled that the pressure was at ten, the extreme limit of the gage, and again the winch began to turn. Hopes arose, but the wind arose, too. The rope jumped the groove of the pulley, became jammed, and the winch stopped. "To the haul- ing ropes again," the Captain cried. INIean- while there was another drama at the other end of the cable on which hung the life of two men. The "sausage" tugged at its mooring line, like a horse champing his bit. The basket swayed, capsized and swung like a .stone in a sling. The telephone was not yet broken. From the bot- tom of the basket one of the unfortunates shouted, "One more jerk will be our la.st." The other cried, "It is all over with us." Alas, his presentiment was only too true. The basket tossed in the air. The .stabilizing wings of the balloon were torn off. The balloonet ripi)ed KITE BALLOONS— THE EYES OF THE ARTILLERY 80 into shreds, diabolically whipping the air. One after another the strands of the cable broke. The balloon, freed from its leash, leaped into the air, the light car swaying below. It was a tragic moment ; there was a lull in the midst of the con- fusion, but the poor men in the basket were per- fectly calm. No more jerks terrified them, but what was worse, they were borne in the direction of the enemy's line. We saw objects fall from the car. They were, as we found out later, the maps and secret papers which the brave men had had the presence of mind to think of and throw down before passing over the lines. This drama had taken only thirty-five minutes. The "sausage," which the Germans fired at as it came down low over the trenches, landed, and the French officers were made prison- ei's. Memoranda: \ 90 TEXTBOOK OF MILITARY AERONAUTICS The trenches and shell lioles and advancing; allied troops photographed by an allied aviator. How aero photofiiaphs ai<- put tci;;. Iher to make a continuous photographic map. These photographs were taken by Allied aviators at the Dardenelles the early part of the war. The city of Tchanak and the estuary of the Kodja Chai; on the right shore is fort Tchimalik and on tlie left fort Hamidie. CHAPTER VIII AERO PHOTOGRAPHY In the official reports of military and naval operations in the present war daily items can be found reading more or less as follows : On May 20th the French prepared to rush the im- pregnable positions on Mount Cornillet and Mount Teton. Photographs taken by their aviators showed an immense system of tunnels which apparently con- cealed German reserves. A single entrance was lo- cated and the operator of a French 15-inch gun ten miles away was told to put a shell in the entrance. The gun started firing thousand-pound shells, and the infantry was ordered to advance at a certain minute. Two hours before the time set for the ad- vance a half-ton shell planted itself squarely in the mouth of the tunnel, killing half of the men inside, blockading the exit, and wrecking the transverse cor- ridors. The French advanced and took several hun- dreds of prisoners without suffering any loss. Thousands of Miles of Photographic Maps The mihtary and naval authorities of the warring countries have thousands of miles of photographic maps. These are kept up to the minute by the constant stream of aerophoto- graphs brought to headquarters by aviators, where they are developed, studied, and the mi- nutest changes noted on the map. The following report gives an idea of how exact a science aerophotography has become, and what its value is in connection with military and naval operations : Several series of photographic plates, taken by British naval observers after the bombardment of Ostend by the British forces on June 5th, have arrived at the Admiralty in London and afford a remarkable example of the development of photo- graphic observations and record by aeroplane. They show in undeniable fashion that the British bombard- ment of Ostend on that date was the most successful thing of its kind yet accomplished, insuring that Ostend will be crippled as a useful German base for weeks, if not permanently. The first series shows the German base before the attack, while a second group shows the effects of the bombardment. In the pictures of the harbor one is immediately struck by a slight change in the appear- ance of the great lock-gates on which all the activity of the harbor depends. These gates are 100 feet long and 25 feet high, and they seem somehow to have lost a little of their rectilinear character over- night. The magnifying glass reveals some of the reasons for this change. The breaking down of the 91 92 TEXTBOOK OF MILITARY AERONAUTICS One of the large French apparatus for taking photographs from aeroplanes. locks prevents the retention of water in the basin and the canals which feed it, incapacitating the entire port machinery. Equally effective in crippling the harbor is a hit on the operating machinery, jamming the locks so that ingress and egress is impossible until elaborate repairs are made. The pictures confirm tiie statement in the official communique that more than half the buildings in the factory section of the town have been either destroyed or badly damaged. It is easy to see that there may have been a heavy loss of life, although the residential section apparently was untouched. Some of the ruined factories necessarily operate night and day and many men are employed at night on the shipping and docks. British shells, dropped from a height of miles by the high-angle fire of the British monitors, located at a point far below the horizon, frequently fell straight through the roof of a shed or factory, blowing out great sections of the sides and roofs and hurling a shrapnel-like shower of splintered wood, steel and rock into the adjacent buildings. Twenty Per Cent, of Aeroplanes at the Front Used for Aerial Photography Every military operation is preceded by an extensive photographic survey of the enemy's position and hundreds of photographs are taken by the aero photographers, until headquarters has obtained all the information necessary to complete the photographic map upon which the operation is to be based. , Fully twenty per cent, of the aeroplanes used at the different fronts are employed in taking photographs of the enemy's positions. For this purpose are usually employed ma- chines having a speed of about eighty miles an hour, and the aerophotographer must go down as low as jjossible over the enemy's lines, with- out actually going below the "safety" point, which varies under different circumstances. When one side has command of the air, and there are plenty of fighting machines about to keep the sky clear of enemy aeroplanes, the task of the aerophotographer is comparatively easy, because he only has to contend with the enemy's anti-aircraft guns. Firing these is not always thought advisable by the enemy, as it gives the location and range of the batteries to the kite balloons and artillery aeroplanes of the other side. Till recently the aerophotographer was sent out in a fairly slow aeroplane, with a num- ber of fighting-machines to protect him. The fighting-machines, flying at a speed of about 1 i ■■'^^^ ! ^^''^iSHPiHB? ^ ■ ft ... - ,-' . Ill m M\ ''iMSBtBf^^ A French machine used for pho- tography in 1917. AERO PHOTOGRAPHY 98 Side view of one of the Farman aeroplanes used for aerial photography. 120 miles an hour, would fly around in circles looking for enemy machines, while the photo- graphing-machine went about its business of taking photographs. But oftentimes a lonely German aviator, who had taken his position high up in the sky while waiting to dive on Allied aeroplanes, in accordance with the tactics estab- lished by Immelmann and Captain Boelke, would spy the slow photographing-machine and dive for it, shooting as it drew near and landing immediately, whether it brought down the pho- tographing-machine or not. In this case the fighting-machines which es- corted the photographing-aeroplane were un- able to defend it, because the battle was all over before they could manceuver to a position which would permit them to intercept or fight the at- tacking German aeroplane. As they were fly- ing over German territory, they could not fol- low the German machine in its flight downward over the German lines, because of the German anti-aircraft batteries. This method involved sending out from four to six machines to convoy a single photograph- ing-machine, but did not permit as good protec- tion as is afforded by sending a larger photo- graphing-machine equipped with several ma- chine-guns mounted forward and rear. These permit the gunners of the photographing-ma- chine to defend themselves against attacks from even two or three enemy aeroplanes. With this larger type of machine the effect of an attack does not involve the loss of the aeroplane, the aviator, and the photographer, as in the case of the smaller machine which is unable to defend itself. In the former, if the photographer or one of the gunners is hit, the other two members of the crew can keep up the fight while flying back to their own lines, or until reinforcements arrive. Therefore the tendency is toward the employment of larger and well-armed aero- planes for aerophotography. The Aerophotographic Organization of an Army Since the value of aerophotography became recognized, the armies in the field have had spe- cial aerophotographic corps. The size of these corps has been increasing steadily. As many of the American aviators now being trained, or to be trained, will undoubtedly be employed in photographic work, the following detailed description of the British aerophoto- graphic organization will be of great assistance in giving the student a comprehensive pen-pic- ture of this work. 94 TEXTBOOK OF MILITARY AERONAUTICS Seven Aeroplane Bombs Photographed Soon After Release by the French Aviator That Released Them on a German Plant The above is one of the most remarkable snapshots of an aerial bombardment. It Is an enlargement of a photoirraph taken by a French aviator at a heipht of over 13,000 feet during a raid on a German nmnitions jilant between Metz and Briey, in the occui)ied part of Ixirraine. The bombs are shown the moment after they were released from the aeroplane, and by reason of the persiK-ctive ajipear as if they would fall in different directions far from the object aimed at. But the aviator has to throw the bombs in such a way as to allow for the fact that he is traveling at a great speed and for what corresponds to the trajectory of a projtx-- tile from a cannon. The bombs used for aerial attacks are known as "M" (Michelin) bombs, and are of two kinds, weighing from 20 to 100 ]K>unds. In this case all the bombs were thrown together and succeeded in hitting their object, the German munitions factory 1h-1ow. The district chosen for attack is a great manufacturing region the Germans liave turned into a huge war factory. The British and French armies arc confining their air raids exclusively to military ol)jects, such as the bombing of the sulnnarinc establishments l>ehind the German lines. Although we receive reports of only the more important aerial attacks, these attacks are of daily occurrence, and have caused far more tlamage than the Germans care to admit. (French Official Photo.) AERO PHOTOGRAPHY 05 Aeroplane Photography That Shows Minutest Details of a Factory Chimney Being Repaired ! M^* This remarkable photograph taken from a French aeroplane shows how the Allied aviators can fly low and choose their target in bombing German munition plants, provided there are sufficeint aeroplanes to fire on and silence anti-aircraft batteries. Also the clearness of the target on an aerial photograph for use by the artillery. 96 TEXTBOOK OF MILITARY AERONAUTICS Film-picture taking in mid-air: a piiotographer and liis cameri in a icite-balloon. The prints are kept in wallets in series b\ squadrons, e.g., all Xo. 25 squadron prints from 2.5 w 1 to 25 w 1000 would be kept in this serial order in probate wallets. Thus it is possible to refer to photographs in every way by date, squadrons, area, and so on. Cioiiifi uj) ill a Ciuqiiul halliim. l.» ..Imcrvc artillery firing in France, and taking photos at close range. * ni. . L- nttc OL ij L c- -1. How scale varies with height, and focal A Photographic Urricer Should be ramihar i +1 f i u/:iL ..u- c-ii :__ T I • _i o__L- -1- lengtn or lens. With the Following Technical Subjects Detection from prints of bad work; differ- The necessarj' accommodation for the work at ^"^^ ^'^^^^^^ S^od prints from poor negatives, present demanded from a section. Apparatus used — function of each item — ■ which essential and which non-essential. Rough and ready substitutes. Construction and care of cameras. Details of mechanism and weaknesses. Properties of focal plane shutter, and of Anastigmatic lens. Function of color filters, and Panchromatic plates, advantages, and disadvantages. Causes of failure. Attachment of cameras to machines; advan- tages of the various systems and the reasons. Vibration; results of investigations in the field. The Canadian official kineniatogniiihrr gmng iilmi in nn ob- servation balloon. AERO PHOTOGRAPHY 97 A German Scout photographed by a French Scout early in 1915 when aerial fighting was not in practice. and poor prints from good negatives. Stains, and their cause and cui-e. Identification with map — this of the first importance — recognition of roads, trenches, tracks, wire, batteries, etc. JNIap square system co-ordinates. System of central registry and fihng of pho- tographs. Possible output of prints in a given time. Any section should, in times of stress, be able to send out for a week without breakdown. Time necessarily taken by the various processes. Simple intelligence reading of photographs. Cameras and Fittings It is the duty of the non-commissioned officer in charge of the photographic section to see that the camera fitting is jiroperh" fixed to the machine and to place the camera in it, adjust slit, clear lens from dust and wind the tension. On no account should cameras be kept in the hangars. Cameras can be taken from hot to cold, but the reverse causes condensation to form on lens. Care should be taken to avoid this, or the recon- naissance will be a failure. Loading of Plates All plates should be loaded in absolute darkness, and the metal sheaths should al- ways be cleaned from dust and rust before loading. It is advisable to load magazines as required, and not keep them loaded, as metal dust ac- cumulates and particles of such dust set up chemical action. Cameras should be kept scru- pulously free from dust, which is one of the worst enemies. Nothing spoils the appearance of a print so much as innumerable pin holes. Negative Developing Discrimination must be shown not to treat the development of all subjects alike. A town requires less exposure than green fields, and must be treated accordingly. Over-development is the usual fault. In some countries with chalky soils, much detail is lost unless great care be shown in timing the rate of development. A thin negative with plenty of detail printing through the lantern in about six seconds is about the ideal. Finish of Work Work is not allowed to stop on any account until all orders are finished. All dishes, measures, etc., must be thoroughly cleansed before the men are allowed to leave. Cleanliness in the dark room is essential to efficiency. I 98 TEXTBOOK OF MILITARY AERONAUTICS A French photography twin motored biplane. I.lnot of trenches on the Western front photogruj)hcd from an aeroplane. Soldiers arc shown walking along the trenches. I AERO PHOTOGRAPHY 99 The war-kite in mid-air. A Squadron Photographic Non-Commissioned Officer With His Three Men Should be Familiar With the Following: Details of mechanism of camera. Properties of focal plane shutter, and An- astigmatic lenses. Color filters. Panchromatic plates. Attachment of cameras to machines. Perfect fitting is essential. Care of cameras and lenses generally. How to put in a filter and re-lock the lens. Simple repairs to cameras. Jams. How they occiu", and how they can be avoided. Loading of magazines in complete darkness. Use of special size plate and sheath gage for loaded sheaths to prevent jams. Formulae at present in use. Development of How to obtain thin, quick-printing negatives full of detail. Value of "color." Big dishes are preferable to tanks. Cleanliness. Washing and drying of negatives; use of spirit; avoidance of spirit-fog due to sunshine and change of temperatiu-e. The observer and photograplier in mid-air supported by kites. Use of hydrochloric acid to take out occa- sional excess of color. Printing; speed is essential. Hand-shading. Every man should be able to make at least good prints per hour. Substitutes for apparatus. Gasoline tanks as fixing tanks, etc. The excellence of old doped fabric with which to make big dishes. Development of prints. One man should be able to develop at least 12 prints at once, in one dish with one hand, and to fix them in an- other dish with the other hand. Washing: thoroughness. Drying; spirit and burning-off processes. Identification of photographs with maps. Characteristic natural and artificial features. Reversed writing for marking negatives. A sound idea of the shutter slits and expo- sures to be used. System of catalogue, and filing. Lantern-plate and positive making both on sy^ by 31/4 and by contact, Science of Aerophotography Still Young The science of aerophotography is still in its infancy. Up to the present time it may be said that only existing forms of cameras, or modi- 100 TEXTBOOK OF MILITARY AERONAUTICS The Herbert & Husgen multiple aeroplane camera. fied cameras, have been used to take aeropho- tographs. Little has been done to develop spe- cial photographic apparatus to take better pho- tographs from the air at different altitudes in order to show in sharper detail the topography of the country, either straight below or in per- spective. Essentials in Aerophotographs The essential thing in taking aerophotographs is to bring back a perfect record or map of the Four type* of nrroplnne rnniprns used by tlic Frencli Air Serv- ice. (Official Phiito, from the Illustratwl Liindoii News.) surface below, with the component objects in their true proportions. The military commander mainly wants to know: (1) The distance between points. (2) The location of objects, such as enemy batteries, structures, trenches, camps, roads, ridges, bodies of water, etc. (3) The disposition, or traces of movements, or actions of the enemy. If a battery is shown, it is essential to know that it is not a dummy battery. (4) The elevation of ridges or depth of de- pressions where his own forces may hide in advances. (5) The nature of the country, whether it is solid ground, marshes, forests, cultivated land, brush, etc. To take an accurate map of the surface be- low and eliminate distortions, the axis of the camera must be kejjt vertical to the gx'ound. Relative Elevations Hard to Show Relative elevations cannot be shown in an aerophotograph, except l)y contrast, when the elevation occurs near bodies of water, or tlic photograph is taken close to the ground or in perspective. AERO PHOTOGRAPHY 101 Whenever airmen bomb places they must bring back photos showing the damage done. As the anti-aircraft guns begin to fire as soon as the bombing plane is detected, the aviator takes the photos of the damage as he climbs to safe altitudes. This photo shows buildings on fire after bombs were dropped. In the last case the image is distorted, al- though, of course, the information that it con- veys regarding elevations is invaluable. But a trained reader of aerophotographs can detect elevations in the prints, as well as the nature of the surface. The nature of the surface is harder to detect ■even in ballooning. Messrs. Alan R. Hawley and Augustus Post, during their forty-six-hour balloon trip, which started at St. Louis and ter- minated in the wilds of Canada, were deceived by the look of the country from a height of 15,000 feet, at which elevation they were trav- eling. It was in October and the leaves were turning yellow. The contrast of spots where the leaves were green, extending over miles of country comprised in their perspective, led them to believe they were traveling over cultivated country, when they were, in fact, traveling over unexplored country. Interpreting Photographs Requires Skill Interpreting or reading photographs requires skill gained by long experience. The expert "interpreter" of photographs must be able to gage distances and elevations at a glance, and also tell the nature of the surface. The camera always flattens the field and de- stroys perspective, but the trained "interpreter" The pistol-camera for German airmen — the right side. The pistol-camera for German airmen — the left side. 102 4 •//;;:: -TEXTBOOK OF MILITARY AERONAUTICS Camera mounted on a British R, E. liiplane, Major Campbell in the pilot seat, demonstrating it. (Photo Bureau of Public Information.) reaches a point where he is able to tell at a glance the nature of the surface from a photo- graph. Problems of Aerophotography The problems of aerophotography resolve themselves into the one big problem of showing the nature of the things photographed. Thr Ragtman aeroplane cnmera. The important factors in aerophotography are: ( 1 ) Tiie plate. Experiments should be con- ducted to develop special plates, so that lumi- nosity, water-vapor, haze, and smoke can be filtered, and good photographs taken under any condition. (2) The method of development. (3) The lens. (4) The mechanical constniction of the cam- era and the facilities which it may afford for taking photographs in number, with the records of compass direction and altitude as far as pos- sible. (5) Skill in taking the photographs. This has been elinu'natcd to some extent, and it should be fiirtlicr cliininated by evolving rules which anybody can follow in taking acroplioto- graphs. Skill in developing the photographs and printing them is another matter entirely, AERO PHOTOGRAPHY 103 ■nrts Itelonging to the nero Kqundriin. The seven huge hungars ciin house about (iO aeroplanes. AERO PHOTOGRAPHY 107 \ 4 « '"^^^N^. ■^ '^—"^^ ^s^ffiaEsss^"' The Allies' command of the air on the western front, which permits Allies' airmen to map the enemy's trenches. A French airman flew over the enemy's lines and brought back to headquarters in a few minutes this perfect map of the enemy's trenches, with French shells bursting over the trenches. Kodak Co. The first makes it possible to take 750 pictures with one loading. As a standard size film is used, it may easily be projected on a screen for military purposes. The action of the camera is automatic. One pull of a flexible cable sets the shut- ter, makes the exposure, winds up the pre- vious exposiu'e and registers the number of pho- tographs. It is universal in focus. The lens is exactlj' the same as that used by professional operators of motion picture cameras, being the highest grade astigmat, with a speed of f.4.8. It is easy to operate, and the military aeropho- tographer can take hundreds of photographs of important positions in quick succession and yet operate a gun to defend himself. This camera weighs only 6 pounds and is constructed entirely of metal and, therefore, is not easily broken. Altitude photographs may be taken with this camera from a height of 10,000 feet with a lens of special focal length, supplied with the cam- era. jVIotion-pictiu'e films of standard make are used, which give minute definitions and great capacity in a small space. Film vs. Plate On accoimt of its lightness, unbreakability, and simplicity, the film is preferred for aerial work, especially since there are cameras which permit loading for hundreds of exposures. The possibility of turning out films which give as good results as plates is excellent. A great ad- 108 TEXTBOOK OF MILITARY AERONAUTICS Possible Troubles in Taking Aero Photographs and Their Remedy FaulU. Probable Cause. Remedies. Plates fogged. leakage. Examine all screws on cone, changer and lens plate. Open silt In blind and place an electric lamp Inside the cone and examine for light In the dark room. Take off changer, and fit the magazines with lids open, place a lamp In- side the magazines and examine for leakage be- tween magazine and changer. Examine also the magazine lld.s. Movement on Slit too wide. Examine cord, pulley plate, plates. Shutter sticking. teeth on "set" wheel and Bad fitting on machine. pinion. Examine blind and notice If the slit Is true. Negatives out ol Lens working out of Tighten up, re-focus, and fit tociu. flange. grub screw. Test with gage. Sheaths not dropping true on changer Test with sheath In gage. slide. Changer Jam- Changer handle not be- ming. ing pushed forward to end of movement, and not allowing the plate to drop clear of the aperture In changer slide Into receiving magazine Take camera oft machine. Sheaths being Inserted In the wrong side of and turn upside down, al- the magazine, thus lowing sheaths to drop allowing the open back In the magazine. edge to jam In the Close lid In this position. forward movement. and re-fit the sheaths In their proper position In the magazine. Changer working Small chips of glass Take off top half of changer sttn. worked Into changer. and clean out ; oil run- ners. Take oft top half of changer, Changer handle bush working loose. remove changer slide plate, and tighten screws holding bush on to plate, file off any protruding screw ends on reverse side. Pulley bracket slide Take off inspection cover not working freely. and examine. Changer handle Shutter setting cord Release retainer screws and not able to fin- too tight. allow handle to finish the ish vbole ol forward movement, then forward move- pull In cord enough to ment. give a V4. turn on pinion. Changer working Cord retainer screws easily but not loose. setting ihutter. Broken cord. 1. Remove the changer 2. Take off "set" Indicator comer plate ; the pulley on shutter pinion will now be exposed. 3. Thread the cord from the Inside of the pulley through the hole on the Probable Cause. Changer working easily but not setting shutter. Continued. Releasing lever not working freely. Sheath not pass- ing through changer. Changer Jam mlng at end of forward stroke of handle. Changer handle Jammed at re- leasing posi- tion. Broken cord. Camera being fitted on outside of m/c and having a cord on re- lease lever which Is exposed to the wind. Induces a resistance which the lever can- not overcome. Setting pin In pulley bracket slide broken. Changer Inlet and out- let being of wood are liable owing to damp to swell. Changer slide plate jamming between top half of changer and the small stop- lips on the end of runners. Sheaths fitted In mag azlne wrong way. Remedies. roller side thereof, and secure by means of a knot. Wrap the cord around the pulley five times, first passing it un- der and then over the groove. 4. Thread end of cord through eyeletted hole In the corner plate. 5. Replace corner plate and changer. G. Pull cord, so as to set the shutter. 7. Pass cord around sliding pulley on changer and push up changer slide as far as it will go. and ad- just the cord to the cord grip which is attached to the corner plate. S. To Test. — Release shut- ter and re-set by means of the changer slide han- dle. If the shutter does not set, the cord is not tight enough, and must be adjusted by pulling a lit- tle further through the grip. N.B. — It is very important to notice that while it Is necessary to have a cer- tain amount of tightness on the cord In order that this shutter may set, it is equally Important that this tightness should be only just sufficient to set the shutter, as other- wise, when working the changer, the cord lt.self acts as a stop for the travel of the changer- handle. Instead of the handle slotted plates. The result Is that the cord will snap with the greatest of ease. If the cord Is properly adjusted so that It does not act as a stop to the travel of the changer, the cord will last a long time. Fit additional spring from lever to cone. Release cord from retainer and take off pulley bracket slide and re-fit pin. Test with changer gage and ease woodwork. Bend the stop-lips, UkInK care the changer plate has the full movement forward when refitted. AERO PHOTOGRAPHY 109 vantage will be gained by developing an effi- exacting. Instructions for operating a camera cient film to replate plates. The demands made under these extraordinary conditions are as upon a mihtary aviator at the front are very follows: Memoranda: 110 TEXTBOOK OF MILITARY AERONAUTICS ;ular (hiily rcionnaissancc was ciinductccl between Columbus, X. ,M., and Colonia Dublan, Mcxicd, tlu- headquarters of General Pershing's punitive expedition and other points by the first aero squadron during the Mexican trouble. CHAPTER IX RECONNAISSANCE AND CONTACT PATROL WORK BY AEROPLANE Wellington said: "Victory belongs to the commander who makes the best guess as to what is happening on the other side of the hill," and winning battles has always depended mainly on quickly obtaining accurate information concern- ing the enemy. Until the advent of aircraft, military opera- tions depended largely on skilful guessing. This guessing was made necessary by the fact that scouts, whether mounted or on foot, could only observe the movements of a fraction of the enemy's forces, and the length of time required for scouts to report their observation was suf- ficient to permit the movement of army corps in an entirely different direction than that re- ported. Aircraft, by permitting a scout to observe the enemy from a height where the composition and disposition of military forces can easily and quickly be estimated, have removed the neces- sity of guessing; and by making it possible for air scouts to ti'ansmit with a sixty to one hun- dred miles per hour speed the movements of an army which can travel at a rate of only fifteen to twenty miles per day, they have removed the elements of surprise. Balloons were used for observation as early as 1794. At the battle of Fleurus, June 26, 1794, the French employed captive balloons, and thereby gained a decided advantage over the Austrians. Balloons were used in practically every war thereafter. During the Franco-Ger- man War of 1870-71, sixty-six balloons were sent up by the French from besieged Paris be- tween September 23, 1870, and January 28, 1871. Five Types of Reconnaissance Reconnaissance consists in gathering infor- mation from actual observation. The air scout must report facts and may draw conclusions, but must not report conclusions instead of facts. There are five types of reconnaissance, as fol- lows: (1) Distant reconnaissance, which is essen- tially an examination of the enemy's country for about 100 miles, made for the general staff for strategical purposes. This is Line Reconnais- sance and deals more with the enemy's general location and apparent purpose. (2) Close Reconnaissance, which is more 111 112 TEXTBOOK OF MILITARY AERONAUTICS minute in detail and extends about 30 miles into the enemy's territoiy. It is more tactical and is intended for the use of the local staff. This is area reconnaissance and deals with the details of the enemy's position and defenses. (3) Local or artillery reconnaissance, which is a minute examination of the trenches and de- fenses. It is seldom more than 8 or 10 miles in extent. (4) Special reconnaissance, which includes obsen-ations for artillery spotting, locating new targets, and other special purposes. (5) Contact patrol reconnaissance, which aims: (a) To keep headquarters of formations in- formed as to the progress of their troops during an attack. (b) To report on the positions of the enemy opposing the advance, the movements of his im- mediate reser\'es, and the state of his defenses. ( c ) To transmit messages from the troops en- gaged to the headquarters of their formation. Procedure in Issuing Orders for Reconnaissance The following is the normal procedure in issu- ing orders for reconnaissance : Orders are issued by the General Staff to the wing commander, who in turn issues orders to the squadron commander, who in turn may issue them to the flight commander. The orders by the general staff usually ex- plain the general situation and so much of the commander's intention as it may be necessary for observers to know in order that they may un- dei-stand the objects of the reconnaissance. The information which the commander re- quires is definitely stated, and the best results are obtained if the information is asked for in question form. The orders of the wing commander and other officers usually include: (a) Information as to the enenw and of our own advanced troops. (b) The object of the reconnaissance. (c) Route to be followed if general informa- tion is required. (If certain definite informa- tion is required, the route should not be given.) (d) Special points to be watched for. (e) Time of starting if necessaiy. (f) Method of reporting and where to send messages. (g) Procedure to be adopted in case of breakdown. (h) What other aircraft are reconnoitring Balloons were the first type of aircraft to be used for ob- servation. An early artist's interpretation of the employ- ment of eaptive balloons by the French at the Bafth- of Flcunis, June 26, 179+. Being thus su])plied witli "aerial eyes" tlie French had tlie ad- vantage over the Austrian ar- mies. RECONNAISSANCE AND CONTACT PATROL WORK - 113 The change forced by aerial observers. This shows a lieavy French gun in 1914^15. It was not protected from the aerial eyes. the same objective or on the flanks of the route detailed. (i) Number and type of fighting aeroplanes assigned to guard and protect the observer, if any are so assigned. All orders and instructions should be in writ- mg, except in very special circumstances. They must be given as early as possible in order to allow the pilots time to study their course, plot compass bearings, etc. Squadron and detached flight commanders keep a record of the general situation, so as to enable them to give pilots any information they may require before starting on a reconnaissance. The best method of keeping this record is by means of maps marked with colored flags. Full information as to the general situation should be given to the pilots and observers, and they should study the map kept up by the squadron commander in order that, in the event of their discovering some unexpected informa- tion, they may be able to decide whether it is of such importance as to justify them giving up their original mission and returning at once. As a general rule, however, when an aircraft is given a definite route to follow or a definite ob- jective to discover, it must complete its mission. General information of importance regarding procedure, signaling map used by observers, etc., can be found in the chapters on "Directing Artillery Fire" and "Areas Photography." Detailed information regarding scientific instru- 1 '*" 6 ^ ^ \ ■ 7 1 A' ■f- — "^ r\1 fc^-tj, •- , /"^i ^^«« ^i sf^-, ^^yW\ 2 1£ ^C^^ -' ,,' M IBti*"" m^Tk This shows a heavy French gun in 1917, pro- tected from the aerial eyes by a cover of cloth, branches of trees, and other devices that are part of the art of camouflage. 114 TEXTBOOK OF MILITARY AERONAUTICS A dummy gun half hidden by trees to mislead the enemy aerial observers. ments can be found in the "Textbook of Naval Aeronautics," also published by the Century Co., X. Y. How Reconnaissance Aeroplanes Are Guarded and Protected • The protection afforded the pilots and ob- server is naturally of great importance. The danger to the reconnaissance machines comes from: (l) Attacks by enemy fighting aero- planes, (2) Anti-aircraft guns. Against the latter aviators can only protect themselves by gaining information of their location whenever possible from other aviators, and by manoeuver- ing their airoplanes to dodge shots. Against the former there are two methods of protection : (1) By using larger and more powerful aero- planes, capable of carrying two or three men and from two to four guns, thereby permitting each aeroplane to defend itself ; (2) By sending with the reconnaissance patrol a guard of fight- ing machines to protect them from attacks. The former is becoming more and more popu- lar, because it makes every aeroplane self-pro- tecting and eliminates the possibility of recon- naissance aeroplanes being brought down by a lonely enemy machine which can dive down on a helpless reconnaissance machine, shoot the pilot, and land before the protecting machines can act. As the fight takes place over the enemy's lines, the fighting machines cannot follow the enemy machines in their downward flight without ex- posing themselves to the fire of the anti-aircraft guns. Three men in a machine equipped with dual controls and several guns can withstand the attack of any machine or of several ma- chines, and one of the three is usually able to fly the machine back to his line, whereas in a single or two-passenger machine the loss of one man often leads to the loss of the other man and the machine. The first duty of the fighting reconnaissance machines is to gain information and get back with it. They do not go out with the intent to fight, but must be capable of doing so, since fighting is often necessary to enable them to obtain the required information. With two- seaters, the pilot operates the machine and the observer carries out the reconnaissance, and both operate the guns if necessary. In three-seaters the pilot operates the machine, the observer car- ries out the reconnaissance, and the third man watches for enemy machines. It is best for all three to know how to pilot the machine and op- erate the guns. Reconnaissance machines are seldom called upon to act alone, but fly in formation, one or more machines carrying out the reconnaissance, while the remainder act as escort, on the same RECONNAISSANCE AND CONTACT PATROL WORK 115 principle as an escort on the ground. That is to say, they do not seek an engagement, but fight if necessary, to enable the reconnaissance machines to do their work. See chapter on "Fighting Planes and Aircraft Guns." Protecting Reconnaissance Machines In protecting reconnaissance machines from attacks, important use may be made of the di- rections which have been supplied to the person- nel of reconnaissance machines of different coun- tries. These directions have been found on cap- tured flight commanders or pilots, and should therefore be carefully examined by students. In reconnaissance, the whole object is to pro- tect the reconnaissance machine or machines, and enable them to complete their work. Opposi- tion will usually take one of two forms. The enemy's scouts may employ guerilla tactics, hanging on the flanks and rear of the formation, ready to cut off stragglers, or attacking from several directions simultaneously, or else the formation may be attacked by a hostile forma- tion. A suitable type of two-seater fighting reconnaissance machine will often be able to deal with either class of opposition without as- sistance. The machines must fly in close for- mation, keep off enemy scouts which employ guerilla tactics by long-range fire, and be ready to attack a hostile formation, if the enemy's opposition takes that form. Reconnaissance formations, like fighting for- mations, can be organized in groups, each with its sub-leader, but as the object is to secure the safety of the reconnaissance machine, the whole formation must keep together and act as one. If scouts are used in combination with two- seater machines on a reconnaissance, it is usually preferable to keep the two types of machines as distinct formations, each under a separate leader. The two-seaters act as described, and the scouts fly above them in such a position as to obtain the best view of them and the great- est freedom of manoeuver in any direction. Their role is : ( 1 ) To break up an opposing formation. ( 2 ) To prevent the concentration of superior force on any part of the reconnaissance forma- tion. (3) To assist any machine which loses forma- tion through engine or any other trouble. A fake battery planted to deceive the aerial observer. k 116 TEXTBOOK OF MILITARY AERONAUTICS Gothu bombing acroi)lane brought down in Belgium while returning from u rail un Englcuul. Navigation Rules for Reconnaissance The height at which aircraft will fly during reconnaissance is governed by the state of the atmosphere and the consequent ease of observa- tion. The duty of gaining information must be the primary consideration, and aircraft person- nel must always be prepared to expose them- selves to hostile fire if they cannot otherwise carry out efficient obsen^ation. The difficulty of replacing trained personnel and aeronautical material must, however, always be borne in mind. Shells of the big guns hiildtn trmn the aerial observer's eyes. Once obtained, information must he delivered at headquarters as safely and rapidly as pos- sible. Consequently, aircraft retin-ning from reconnaissances should fly at such a height as to render them absolutely immune from fire from the ground. The chances of being hit from the ground will be diminished by following an imeven course both in direction and elevation. Advantage may also be taken of cloud for concealment. The action to be taken against hostile aircraft will vary according to the mission which the pilot has been given. Should he have been despatched to clear up some important point, or should he be retm-n- ing with valuable information, he must be care- ful to concentrate his energies on avoiding hos- tile aircraft. If, on the other hand, having seen nothing, he should neet a hostile aircraft over or near a place where it is obvious that it must have gained valuable information, he must attack it. It must be borne in mind that the side whose aircraft show the greater determination to fight on every opportimity Avill rapidly gain a moral ascendancy which will largely contribute to ob- taining the command of the air. Pilots and Observers In order that good results may be obtained from aerial reconnaissance, the same |)ilot and observer should Avork together as far as possible. Mutual confidence is of the utmost importance. It has been found inadvisable to lav down any RECONNAISSANCE AND CONTACT PATROL WORK 117 rules as to the respective duties of pilots and ob- servers. These must depend largely upon the personality and air experience of the indi- viduals. On receipt of orders, the pilot and ob- server should consult together with the aid of a map as to the best manner of fulfilling their task and the route to be followed. Compass bearings, distances, and times must be worked out, and, if necessary, tabulated and fixed to the machine, so as to be clearly visible during flight. Allowance must be made for the probable drift due to the wind at the height at which the aeroplane will fly. The pilot is responsible that his machine, if in flying order, is ready to go up whenever re- quired. Before starting, he must test his en- gine, verify the quantity of oil and petrol in his tanks, and make a final inspection of the ma- chine with his mechanics. He marks the route on his map and places it in readiness. The observer also marks his map, and in cer- tain cases, when a detailed reconnaissance is re- quired, makes an enlargement of it and dupli- cates it with the aid of carbon paper. He pre- pares his apparatus, notebook or writing block, pencils, weighted message bags, watch, field- glasses and, in some cases, a camera. No person going up in an aircraft should carry written matter or maps which, in the event of an accident, would be found on him and give information to the enemy. The responsibility of finding the way must be shared by the pilot and the observer; the actual method of navigation adopted depends on the nature of the country, the state of the weather, and the type of aeroplane used. The pilot will conform to the direction of the observer as regards moving slightly to right or left, so as to gain a clearer view of a road, cir- cling round so as to examine a place more thor- oughly, or coming lower down to get a clearer view. The pilot should assist in observation by look- ing out on the opposite side to the observer. Observers must be constantly on the look out for information both on the way out or returning from their reconnaissance ; and, though they may have accomplished the tasks specifically allotted To deceive the aerial enemy's observers the art of camouflage is applied to men as well as machines- The crew of a French antiaircraft gun dressed with a view to invisibility. to them, they must not consider their duty finished. In addition to using a speaking tube, a simple code of signals should be arranged so that the observer can communicate his wishes to the pilot without the latter having to switch off or throttle down his engine. In the case of a forced landing inside the enemy's lines, when it is evident that the machine must be captured, the pilot is responsible for taking such steps as will render it useless to the enemy; setting fire to it will generally be the most effective method. The pilot will assist the observer in making out his report. All reports will be signed by the observer. Messages should be written out fully in the recognized manner, headings being as far as possible filled in before leaving the ground. It must be remembered that the omission of any of the usual headings will reduce the value of a re- port or may even render it useless. The positions of troops on the ground, espe- ciallj^ when they are scattered, can often be most easily explained by showing them on a carbon tracing or enlargement of the map. A rough diagram will frequently be of great value in 118 TEXTBOOK OF MILITARY AERONAUTICS ■uiwi I. . J immmimim i!x m> fii mne. doubt regarding the reliability of his observa- tions. In cases when an aircraft has been out for some hours and seen a number of small details, it is advisable to add the general impression formed by the observer as a result of what he has seen, but it must be made quite clear that this is merely an opinion and not necessarily a fact. It is of great importance that reports from aerial observers should reach their destination as soon as possible. INIuch of the value of aerial reconnaissance will be lost if the information so quickly gained is delayed in transmission to headquarters. Aircraft Report Diary An aircraft report diary should be kept in each scpiadron or detaclicd fliglit. A summary of the information collected IIECONNAISSANCE AND CONTACT PATROL WORK 119 A Russian air scout operating under difficult conditions. should be made out daily and sent to the head- quarters concerned, to prevent the possibility of any message having been overlooked or having gone astray without the knowledge of those concerned. Contact Patrol (Aeroplanes De Liason) The contact patrol, which came in the year 1916, is one of the latest developments in mih- tary science. Established at first as a con- venience, it is now a distinct service of extraor- dinary importance, and binds together the aerial and land forces. As a writer pointed out in Aerial Age Weekly recently, Contact Patrol, which is one of the chief raisons d'etre of the aeroplane, is a special tactical reconnaissance carried out dur- ing the progress of an attack. It establishes a liaison between the front line infantry and their battalion headquarters, corps, or division head- quarters in the rear. The aeroplane is the most valuable means of connection, and accomplishes the following objects: (a nnderwood &, Underwood Remarkable photo of a French Spad Chaser plane, taken from above, under great difficulties. 120 TEXTBOOK OF MILITARY AERONAUTICS r One of the Hrrjfuct homWmii tyiM- bipliinrs used by the French, which arc most rcinarkuble clhiibers, thouL'h they arc limited in the load they ean carry. I'nfortunately the Germans have hroiiirht down several of this tyi>c and will be able to copy it. (French Official Photo.) RECONNAISSANCE AND CONTACT PATROL WORK 121 A Farraan reconnaissance biplane passing another reconnaissance machine. 1. Keeps higher command informed of own troops' movements. 2. Keeps higher command informed of en- emy troop movements. 3. Carries messages from battahon headquar- ters to corps and division headquarters. 4. Reports the state of enemy trenches dur- ing an attack, and also reports any new enemy trenches. There are four methods of signaling from the ground to an aeroplane engaged in contact patrol. They are: 1. Ground strips. This method consists in white strips of cloth which are placed on the ground in various shapes according to prear- ranged code. Thus, a ground strip in the shape of a "T" might mean "Need Ammunition," or some similar message. 2. Signal Lamps. These are colored lamps with a special slide which pennits light to ap- pear in flashes, long and short, and the mes- sages are sent according to the Morse Code, or some other prearranged code. 3. The Shutter. The shutter is a device very similar to the ordinary window bhnd, with one side of each shutter painted white and the other side black. It is operated by a cord, and the code used is generally the INIorse International. 4. Flares. These, as the name suggests, are simply oil-soaked cloths which are lighted by the front line troops to show their position during the attack. On sunny days the method most used is the panel, but on dull days the lamp is used. Gen- erally an infantry battalion has either the lamp or the panel (Shutter), sometimes both. The battalion headquarters always has both. All messages are sent from battalion headquarters. The following are the methods used by the aeroplane to communicate with headquarters: 1. Wireless. 2. Signaling Lamp. 3. Klaxon Horn. 4. Skeleton maps, and messages dropped in weighted message bags. In some brigades, by Very's lights and smoke bombs. In the Very's light method a red and green flare are used, and the succession in which they are fired indicates the message. Wireless is very rarely used in contact patrol work, and is never used to refer to the position of our own troops, as the code might be intercepted by the enemy very easily. As our own barrage fire is regulated by the aeroplanes on contact patrol, the pilot of the aeroplane must be absolutely certain that the troops signaling they are the first line are the first line, as a mistake would place them di- rectly vmder their own barrage from the rear. Thus in very doubtful cases the aeroplane flies so low that the pilot recognizes the uniforms of our own troops. This, of course, makes the A "protecting" Xieuport fighting biplane photographed by the observer of a reconnaissance machine. 122 TEXTBOOK OF MILITARY AERONAUTICS A two seater Morane-Laulnier contact patrol machine. work very dangerous. The procedure of con- tact patrol work during an attack is as follows : The hour for the attack is known as the "Zero Hour," and all watches and time pieces are care- fully set to coincide to the second. Exactly at the Zero Hour the aeroplane must arrive over the front line trenches, in such a position to be over, or imder the expected barrage, generally just over it, at a height of 1500 to 2500 feet. The pilot watches the attack until the infantry reaches its first objective, then signals "Where are you?" by one of the methods described above. The infantry, in response, lights a flare to show their position, and the pilot traces it on a skeleton map, and flies directly back to head- quarters. Arriving at this position, he places the map in a weighted message bag, together with any other message he wishes to send, and, coming down to an altitude of about 200 feet, drops the bag. If the ground does not acknowl- 1 . ^^ 1 P >i^K ^^>flHK; i4|H 1 - ll>>^ii.i.^ ■iB^Bii An Allii-d /,c|i|)flin ••■.••'..'.■■.-. .'iJ^'J'^...'.' '->- Cross-sectional view of one of flie new German aviation iK-acons Couneay acientiflc AmtrUxm NIGHT FLYING 131 I Lighting stand, serving the double purpose of guiding nocturnal flyers to a safe landing and detecting hostile aeroplanes. -I.e. with- 1. Flying by instruments alone- out using the horizon as a guide, 2. Gliding slowly. 3. Making small sideslips and quick recov- eries. 4. Checking the speed of the machine and identifying it with the sound of the wires under certain conditions. 5. Turning, using instruments alone, 6. Landing slowly." The "Honig Circles" Signals for Night Flyers The ingenious arrangement of signals for night fliers, patented by the German architect Edgar Honig, was described in the Technische Monatsnefte and translated in the Literary Di- gest. The apparatus consists of two concentric circles or rings of incandescent lamps standing on edge a few feet from the ground, with the smaller one placed at a distance of several yards behind the larger one, which stands back of the landing stage. The working of this arrangement depends on the wellknown fact that a circle appears as an ellipse as soon as the eye ceases to be directly opposite the center. Hence two circles of light, arranged as Figure 1, must be perceived as two upright or slanting ellipses which either inter- sect each other or have the smaller contained in the larger, until the eye of the beholder is directly in line with the axis passing through the middle point of the two circles. In the case of the X'hotograph of the IliiTiig Circle.^. :^";5 132 TEXTBOOK O^ MILITARY AERONAUTICS i. — From above, the aviator sees two ellipses only. 3. — As he descends, the circles round out and cut each other. Honig Signal Circles whose central axis stands about 13 feet above ground, this occurs when the airman is from two to three feet (according to the build of the machine) above the ground. Figure 2 shows how the circles appear to a flier who finds himself at a great height above the signal and flies directly down in the direc- tion of the central axis of the circles. When he comes farther down, probably flying in a spiral and thus nearing tbe ground, the rings begin to intersect, and appear to him, for instance, as in Figure 3. This position of the light-circles re- veals to him not only that he has approached the earth, but also that he has diverged from the di- rection of the middle axis, and that he must steer his machine to the right in order to obtain -"Earth level! Steer left!" 5. — ■'"Home !" the right direction again. He does this, still continuing to descend until he sees the signal, perhaps as in Figure 4. He knows then that he has approached the level of the ground. Consequently he steers, and the operation con- sists merely of turning on the current when a machine is heard approaching at night, in cases where the lights are not needed to bum con- tinuously. Where the signal is part of the equipment of an aviation corps in an army, it is easily arranged so that the rings can be fastened together and transported without difficulty when camp is changed. The invention is like- wise specially valuable for water landings. Lights for Night Landing Grounds Mr. Bright the British authority in his report on the best lights for night landing grounds says in this connection: "While undoubtedly the I. — How the. circles of light guide the night- fliers. The relative positions of the two con- centric light-circles reveal to the aviators, as the dotted lines show (and as the diiigranis of the opposite page indicate), their angle of approach to the aviation-ground. See article on next page. NIGHT FLYING 133 light obtained from the ordinary petrol flare is better suited for the purpose than the white light from a conmion arc lamp, the same does not ap- ply in the case of the comparatively new flame arc lamps which are recommended for this pur- pose. The value of the petrol flare was settled as far back as 1885 when the South Foreland experiments were conducted at the instance of Trinity House (see "Report of the Committee on Experiments at South Foreland relative to Electricity, Gas, and Oil as Lighthouse Illumi- nants") . The new flame arc lamps give a yel- low red arc when the carbons are made in a manner separately communicated. Indeed, the light produced by the yellow flame carbon has the highest penetrating power of any known il- luminant, and has great advantages over all others (including petrol flares) in foggy or hazy weather. The light obtained from these special flame arc lamps (fitted with yellow flame car- bons) is very near in color to petrol flares, but is considerably more powerful. A further im- portant advantage in an electric lighting system of the special type named would be that, unlike petrol flares, all the lights can be simultaneously switched on and off at a moment's notice." Returning from Night Flights — The Signals To the aviator engaged in long-distance night raids night flying still holds difficulties to be sur- A convenient French aerial beacon. Portable aerial beacon of 2400 decimal C.P. mounted. There. are a few difficulties however, confronting the aviator on "Zep duty" who does not venture far from his base. The long dis- tance raider may lose his way in the darkness; the aviator on "Zep duty" only has to flash the signals, and since the landing stations in Great Britain and France are numerous, the signal is usually answered by one of the stations lighting up so that the aviator may land. Naturally, the signals are changed daily. The authorities issue daily signals and the me- chanics load the signal pistols accordingly for the aviators. The lights or flares can be seen from a distance of from ten to fifteen miles. Aeroplanes are also equipped with lights placed beneath the bottom wings and with automobile lamps so that in case of a forced landing they may come down with little trouble. These lights are turned down by pressing a button. Lighting Equipment of Aeroplanes The lighting equipment of aeroplanes varies considerably. Following are the British Gov- 134 TEXTBOOK OF MILITARY AERONAUTICS T:-,^v/■^?r?,7l!^5,r«!2P'5SS«: -?-^-^^ 0k |NO IcHrr ppw^^ww ^^^T^^g IHHI^P '^^B Aeria/ i..., „„.,t ernment's specifications for the lighting equip- ment of certain battleplanes and the passenger's bay. Electric lighting equipment. This will be fixed in a suitable manner. Dry batteries of the life of 4iA hours to be provided to light up the dashboard. As the machine will not be fly- ing for a longer period than 8 hours, the extra dry battery provided can be used in emergency. When these dry batteries are exhausted, they can be thrown away. They weigh about 21 lbs. each. The lighting to be arranged as follows : 2. Lights to throw light on the instrument board, and arranged so as not to throw it in the pilot's eyes. 1. Light at the bottom of the fuselage, to throw light on the floor in case the pilot wishes to throw light there for any purpose. This is also to be shaded so that it will not throw light in his eyes. 1. Light for the compass, arranged in the same way. 1. Portable torch to be provided with each machine. Instruments Painted with Luminous Compounds The instruments used by aviators in night flying have the indicators and dials painted with luminous compounds, which eliminate the blind- ing glare of electricity and the necessity of using flash lamps. The parts so painted can be seen clearly by the pilot who for the time being is en- tirely wrapped in darkness. Aerial Lighthouses It is as essential that air men have hghthouses to guide them through the atmospheric ocean as for navigators at sea. The aerial beacons are of several types, the most powerful having a candle-power of 50,000 and being visible for up- ward of fifty miles. As the result of much ex- perimenting a general type of beacon has been developed. It consists of several belts of lenses, with a powerful lamp at their focus which sends out its rays uniformly in all directions. It is necessary, of course, that the light be clearly visible to the air man, whether flying above or below the light. Each lighthouse must have a distinctive mark of its own, so that the air man will be in no danger of confusing them and losing his way. A series of light- flashes are thrown out, corresponding to the dots and dashes of the JSIorse code. The air man soon learns to read these signals, or to ver- ify them by a code book, and can thus readily learn his position, even when the earth beneath him is completely hidden. ■ Adventures in Night Flying Following is a letter from Lieut. Red. H. Mulock, R. N., the Canadian pilot who was the first to succeed in chasing a Zep at night, and did so at a time when arrangements for signal- ing between aeroplanes and aerodromes had not yet been completed. "Dear "We have had a little fun around here. A signal, indicated bjr dots and dashes, flashed from aerial lighthouses. NIGHT FLYING 185 Showing the luminous tracks of three aeroplanes landing at night at a military aerodrome. week ago, or rather Mondaj% the 17th, a Zep blew along evidently looking for our aerodrome. We heard him coming and presently saw him flying in from the sea. I asked our C. O. if I could go after him, and got away with some bombs, grenades, and a revolver. He was steer- ing a.bout due south, so I laid a course east of south, and started to head him off. It was in the middle of the night — a little after 1 a. m. and no moon, very dark with clouds around and the stars so dark you could not see the horizon. He passed over here about 2,000 ft. up, and, by the time he got to I was up even with him and to seaward. I then changed my course straight for him. He had stopped to drop his bombs on and with his engine shut down, heard me coming, and of course, as soon as he heard me, looked in my direction and must have seen the flames from my exhaust. "Anyway he did not wait to throw anj^ more bombs, and I saw the most wonderful sight. I was about 1,500 ft. from him. He opened fire with maxims, but without effect, and majestic- ally stuck his nose up and went up like a balloon. He was then higher than I, so I opened out again, and tried to round him back again at , where we both turned out to sea and steered about east. I chased him up to 8,000 ft. and over to the Belgian coast, and we both changed courses to S. E. and a little later went into the clouds together over . "Having lost him in the clouds, I climbed to 9,000 ft. and rambled around waiting for him. But he had gone. There were two of them; 136 TEXTBOOK OF MILITARY AERONAUTICS one was given a warm reception by the chaps at , wliile the other one and I had a picnic all to ourselves. He ran away so fast I could not keep up with him and climb at the same time. I waited around for him, but no Zep ap- peared; evidently he stopped his engines and listened for me, and then went off in another di- rection. There was no use waiting, so I started for home. I swung around out to sea from coast, going north by compass. It was very dark, and I could not see the sea or land and no stars or moon, as I was in the clouds. Talk about being alone in the world, very few people know what it means. I came down to 7,500 ft. and turned west finally, picking up some search- lights in the distance. I thought they were at and headed for them, and after some time. three big searchlights jumped out of the dark- ness below. Instantl}' I knew they were from a cruiser and were looking for me, having heard my engine. At night they fire on any one, as they cannot see our large red circles. So, not being particularly anxious to see how near they could come, I started to dodge the large beams and headed out north into the open sea again. I worked my way gradually back to the and later on saw the lightship, and then the coast, which looked very dim way down below, but it was home and once more I felt in the world. "I could not come down for two reasons. First, it was not light enough to land and sec- ondly, I knew I would be fired on if I w^ent low. So I had to play around up in the sky over the sea 7,500 ft. up waiting for the sun to rise. As soon as it was light enough I came down and every one seemed glad to see me back, as they had given me up. I cannot begin to tell you all about it, as one has to go through a night like that to realize what wonderful things we have. I enjoyed every minute of it, and every minute Avas different. "]My engine gave out once over the North Sea but was able to keep her going slowly, and finally as I was gliding down to the ocean for some unknown reason, it picked up again. I was going to glide for one of the searchlights and land in the water alongside and be picked up by a torpedo boat, but luck was with me. Dodging searchlights over the North Sea is the finest sport in the world. Funny, is n't it, that we have to dodge our own guns and lights? They cannot distinguish between the Germans and ourselves, and take no chances, so they fire on any engine they hear in the sky." Since the above was written arrangements have been made for signaling between aero- planes and the aerodromes. Lieut. William L. German i>ortable gag beacon. Aerial beacon with eicctric flashliglit. Tlie aerial brnron at Johnnnistal, Germany. NIGHT FLYING 187 Robinson who, on September 2d, 1916, brought airship fall, he looped the loop with joy, then, down the first Zeppelin on British soil, in relat- "showed my signals to stop firing, and came ing his exploit states that after seeing the huge down to earth." Memoranda: 138 TEXTBOOK OF ^IILITARY AERONAUTICS Fig. 9. Installation by German government. Fig. 11. A Zeppelin wireless outfit. Fig. 12. A motor car wireless station. Fig. 18. Airman's helmet with wireless re- ceiver. Aero wireless apparatus. The use of wireless for communication be- tween areoplanes and their bases has gradually become more and more necessary and to-day the aviators on all the fronts are equipped with the most improved instruments available. For every type of aircraft a suitable wireless set has been developed. Fig. 10. Large 5 K. W. Zeppelin apparatus. Fig. 19. Apparatus for seeing wire- less signals. Fig. 16. Early German Taube carrying wireless masts on wings. I'ig. 15. Wireless on 1913-14 monoplane used in I-'landcrs. 138 A double-motored Caudron biplane used extensively for observation, in France. It is equipped with a Lewis gun. CHAPTER XI RADIO FOR AEROPLANES By William Dubilier Unless one has made personal observations as to the working of wireless and air craft in this present war, it is difficult to appreciate how the art of warfare has been transformed by these two branches of science; and, in turn, modern one day, and have been solved the next. One incident may be mentioned where, in the early months of the war, wireless stations were used for directing the artillery. The shots from the guns, however, were so constant and continuous methods of fighting have changed the art of that they caused disturbances in the atmosphere, radio and aeronautic engineering. Recent which, in turn, seemed to affect the receptor of events and progress of wireless communications the wireless station, and so a continuous noise or have established this branch of science as an in- click was heard, such as is produced by static, dispensable means of transmitting intelligence Immediately physicists were set to work and this from one place to another. objection removed, and so, many other problems Radio and aeronautic communication may be in wireless have come up, as communication be- termed the nervous systems of the army and came necessary under different conditions, navy. Even for the directing of artillery fire and communication between trenches, it has been necessary to resort to electro-magnetic waves from aeroplanes. Problems have arisen which enlisted almost every radio and aero worker in the fighting countries. They had no time to try out new apparatus, except where new conditions arose, and the instruments pre- 139 140 TEXTBOOK .OF MILITARY AERONAUTICS U. S. Army biplane used in Capt. Culver's experiments, siiowing radio apparatus and aerials. viously used were not suitable; so immediately the departments were divided up into sections. The practical men were set to work installing and making stations as fast as the factories could turn them out, and the experimenters and physicists were ready to try out new apparatus and rectify new objections. Wireless and aeroplane companies in France, England, and the other countries, except Ger- many, were not so numerous or as large as they are in this country, and so their output was soon limited, which was much below the demand. Everything obtainable was used for wireless. The old type induction coils, apparatus which was placed in the junk heap 10 years ago, all became very handy, due to the fact that the Virw of the ejr Ji, /7/vc zzo/f /fa fie /"aaai £ ~Azzcnaff & /fofir -ff/fSArr TTie Spherical lialloon — used mainly to train pilots for military observation balloons. The balloons range in size from 30,000 to 80,000 cubic feet. in MILITARY AEROSTATICS 150 ent war for directing artillery fire and observa- tion. The great advantage of the captive balloon is that the observer is constantly in direct tele- phonic communication with the artillery com- manders in his vicinity; constant and thor- ough inspection of the enemy's positions with the aid of powerful glasses and telescopes reveals every movement of bodies of troops or anything new that has appeared during the previous niglit, and the targets thus pre- sented can be immediately taken under fire. Continuous and searching observation of the same sector enables an observer to note even slight changes in the color of the earth and to make important deductions therefrom. Changes in trench construction can thus be easily detected. One observer on the western battle front in France states that he was able to count twenty- six balloons in sight at one time ; this is convinc- ing testimony of their extensive use. It is an interesting development of the present war that battle type aeroplanes ai'e assigned for the pro- tection of the captive balloons and for this pur- pose cruise about at a height of several thousand feet above the balloon, ready to swoop down upon any enemy aeroplanes that attempt to destroy it. Frequently, anti-aircraft guns are located sufficiently near balloons to maintain barage fire over them to prevent hostile aeroplanes from approaching within range of their in- cendiary rockets or bullets. The spherical type of captive balloon has been abandoned in favor of the elongated type, often referred to as "sausage" or "drachen" (German for kite) balloon, since the latter type has much greater steadiness in the winds; the pres- sure of the moving air against the under side of the balloon holds it steady in the same manner as in the case of the common paper kite. The kite balloon is fitted with a tail consisting of several conical canvas cups, to assist in main- taining its stability, with the same result as is secured by affixing a tail to the toy kite. The latest type of captive balloons are made with stream line shape and fins so that the kite tail- cups are not required for steadiness, and conse- quently should not properly be referred to as kites. Employed at Night as Well as in the Daytime In Europe the observation balloons are placed from two to four miles in rear of the line of trenches, and are separated by intervals de- pending upon the artillery activity in various sectors. The altitude at which they are held is dependent upon the atmospheric condi- tions and upon the distance of the enemy's artillery. They are usually sent up at daylight, and remain in the air until dark, being drawn down every few hours to change observers. Occasionally they remain up at night, and it is frequently found that enemy guns that are not visible by daylight may be located at night by their flashes. Even after dark it has been found that observers who have studied every feature of the ground for days are able to see The winch for the kite-balloon mounted on a ^7? truck. 160 TEXTBOOK OF MILITARY AERONAUTICS One of the new Cacquou type observation balloons used exten- sively by the Allies. enough to fix accurately the position of the flashes. The strain of constant observation with high-power glasses, or telescopes makes it advisable to change the observers at frequent in- tervals. It is customary to have two officers in the car of the balloon, and they are connected with the ground by telephone. One method is to have an insulated telephone wire in the center of the cable which holds the balloon; another method is to drop a strong, light-weight wire from the basket of the balloon to connect with the tele- phone circuits directly underneath. In both cases the steel wires of the holding cable serve to complete the electric circuit for the tele- phones. Balloon companies are provided with tele- phone switchboards so that the observer in the basket can communicate directly with any bat- tery or higher artillery commander in his vi- cinity. Buildings, hills, or specially constructed towers concealed by the trees are frequently utilized in conjunction with captive balloons to provide an auxiliary observing station, so that the two may serve as the end stations of a base line for the accurate location of targets. In some cases another balloon is used as the second observing station. For Directing Artillery Fire It has been learned that at the beginning of the war various special codes of signals were experimented with for the purpose of enabling observers to report the error in the fall of shots, but these have been discontinued in favor of the brief annoimcement of "over," "short," "right," and "left." Field glasses having a milled scale permit of the observer reporting in degrees the distance of shots from the target. For service with the mobile army it was cus- tomary in Europe before the war to have highly trained balloon companies, able to inflate a bal- loon and have it, with its observers, several thousand feet in the air in about twenty min- utes after the organization had halted; this speed was attained by using compressed hy- drogen carried in special vehicles. Hydrogen Supply and the "Nurse" The information of three or more years ago indicated that the peace strength of the balloon companies in Europe averaged about sixty men. The arduous and continuous service that has been required during the war has necessitated an increase in the number, there being at the present time in some cases 160 officers and men assigned to one balloon; this number pro- vides for three reliefs for the captive balloon, the observation tower personnel, the telephone switchboard operators, and details for the manufactiH-e of hydrogen. Since the service along the western battle front has been in the nature of siege warfare, it has been practicable to supply hydrogen from portable field generators, instead of furnishing it compressed in cylinders. TEXTBOOK OF MILITARY AERONAUTICS 161 The average capacity of the balloon is 32,000 cubic feet. There is continuous loss of hydrogen due to leakage through the fabric and to losses from expansion at high altitudes ; these losses are ordinarily replaced at night. A com- mon method of replacing gas is to fill small bal- loons called "nurses" at the nearest field gen- erating plant; a small detachment of men can easily conduct this supply balloon to the hangar and transfer hydrogen from the "nurse" to the captive balloon as it may be required. The Windlass The most modern tj^pe of windlass for hold- ing captive balloons consists of a winding drum constructed on a motor truck. Whenever enemy aircraft attempt to destroy a captive balloon, it is customary to haul it down rapidly or to keep it moving around the field, to lessen the chances of its being hit. The moving is often done by using twenty-five or more men, each having a rope attached to a snatch block, through which the cable is passed. These men then walk to various points in the field, and their movement changes the position of the balloon not only horizontally but verti- cally as well. Captive balloons are occasionally destroyed by incendiary bullets, arrows, or bombs dropped by aviators. Destruction in this maimer is not necessarily fatal to the observers, as they are usually provided with parachutes attached to body harness, which permit their safe descent to the ground. About eight years ago, while Fort Omaha was garrisoned by signal corps troops only, a large balloon hangar was constructed at that point, together with a plant for generating hy- drogen by the electrolysis of water and the ma- chinery for compressing the gas. After its completion, the equipment was used for about two years for free and captive balloon instruc- tion, but its employment for this purpose was later discontinued for the reasons previously stated. The U. S. Army Balloon School is now estab- lished at Fort Omaha. Commissioned and en- listed personnel are assembled there, organ- ized into companies and squadrons, provided with equipment and given considerable train- ing before being sent out to serve the artillery and divisions. Free Balloon Training Necessary In case the cable holding a captive balloon should break, it then becomes necessary for the observer to descend and land in the same man- ner as in manoeuvering the ordinary free balloon, for which reason an essential part of the prelim- inary training of students at the Balloon School One of the American Blimps manufactured by the Goodrich Company. (Passed by the Censor.) III ^»MJL^ ^ 162 MILITARY AEROSTATICS 168 consists in the navigation of free balloons and qualifying as pilots thereof. The Free Balloons ITS CONSTRUCTION, INFLATION, AND OPERATION The present war has brought out the value of free balloon training, and the sportsmen who took up ballooning as a sport in the past twelve years are now as valuable to the cause of na- tional preparedness as if they had had military training for that same length of time. A free balloon is the simplest of all aircraft. It is essentially a spherical bag made of silk, or cotton varnished or rubberized to prevent too rapid diffusion of the contained gas. Coal gas of light density (4) and hydrogen are the gases ordinarily used for the inflation of spherical bal- loons. A net is spread over the spherical gas envelope and by means of a loading ring the basket for passengers is attached to the lower terminal ropes of the net. In the top of the envelope is a manceuvering valve the opening of which permits the escape of gas and consequent descent of the balloon. The valve cord, usually white in color, hangs vertically passing down through the appendix opening within reach of the pilot. When a free balloon lands in a wind it is necessary to deflate it veiy quickly in order to avoid being dragged along the ground ; to provide for this a special ripping panel is made into the upper surface of the envelope, so arranged that when the pilot pulls the cord (colored red) attached to the up- per end of this panel the stitching rips, thereby opening several feet of the gas bag and empty- ing all gas in a few seconds. A free balloon usually is provided with a long guide rope and anchor (with separate rope). The navigating instruments consist of a record- ing barometer (baragraph) calibrated for alti- tude measurements, a statoscope, which is also a sensitive barometer and will indicate changes in altitude of only six or seven feet. Synopsis of the Course of Training at United States Army Balloon School The course of technical training is both prac- tical and theoretical, so arranged that the prac- One ot till- first kite-balloons used by the Aerostatic Section, U. S. Army at Omatia. (Photo passed by the censor.) tical instruction will have preference at all times when weather conditions are suitable. When- ever high winds or rain interfere with the out- door training the class room instruction is held and consists principally of conferences. The instructor covers the subject thoroughly and students are expected to ask questions and join freely in discussion. Practical instruction in the measurement of density of gases, testing and adjustment of instruments and sim- ilar laboratoiy indoor work is conducted when weather conditions outside are unfavor- able. PRACTICAL INSTRUCTION Generation and compression of hydrogen. Hydraulic testing of gas cylinders. Spreading envelopes and assembling parts of free and captive balloons. Inflation of balloons. Balancing free balloons. Use of ballast and balloon instruments while on voyages. Selection of landing spots and drag-roping. Deflation by valve and rip panel. Folding, packing, and shipment of bal- loons. 164 TEXTBOOK OF MILITARY AERONAUTICS One of hundreds of Kite Balloons, which serve as the eyes of the artillery on all the fronts, be- ing towed by its mooring-rope to its anchorage. There is a Kite Balloon for every heavy gun. An account of how Kite Balloons are operated for artillery was given in "Flying" for Decem- ber. Replacing of rip panel, repairs and inspec- tion of envelope and net. Qualification as balloon pilot according to F. A. I. rules. Testing of cordage and fabric for breaking strength. Testing of fabric for permeability to gases. Practical handling of captive balloon wind- lass. Filling kite balloons rapidly from cylinders of compressed hydrogen. Motor truck operation and maintenance. Determining course and position of free bal- loon by use of maps and compass. conferences: obganization, equipment and training of balloon companies Assignment of duties, commissioned and en- listed personnel. Transportation and special technical vehicles. Replacing gas lost by diffusion and expan- sion. Replacement of empty hydrogen cylinders. Field hydrogen generators. Field compressing outfits. Meth(Mls of observing and indicating targets and plotting shots. Telephone sen-ice from balloons, instniments and circuits. Photography and sketching from balloons. Visual signal codes from balloons. Property damage caused by descent in free balloons. conferences: balloon construction Kinds of fabric suitable for balloons. Preparation and application of varnishes for cotton balloons. Cordage for nets and suspensions. Shapes of balloon envelopes and standard sizes. Strip and panel construction for envelopes. Laying out patterns for envelopes. Various types of seams. Designs and tests of suspension patches. Manufacture of nets. Tj'pes and sizes of manoeuvering valves and pressure valves. Size, location, cord attachment and replace- ment of rip panel. Appendix ring, neck and cord. Kite balloon steering bags and substitutes. Number, size and shape of tail cups. Strength, weight, flexibility and construction of cable for captive balloons. Sizes, types, weight and attacliment of bal- loon cars. Essential features of concentrating rings. MILITARY AEROSTATICS 165 conferences: gases Kinds of gas suitable for free, captive and dirigible balloons. Specific gravity of gases and methods of de- termining. Manufacture of coal-gas and water-gas. Production of hydrogen by electrolysis of water. Hydrogen by steam and iron method. Hydrogen by compression and refrigeration method. Hydrogen by decarburation of oils. Hydrogen by silicon-soda process. Hj'drogen from hydrogenite and hydrolythe. Testing hydrogen for purity. Compression of gases. Flow of gases through pipes and orifices. Types of gas-holders and their maintenance. conferences : meteorology Indicating and recording, barometers, ther- mometers, hygrometers and anemometers. Tests, maintenance and method of mounting instruments. Various changes in atmosphere with increas- ing altitude. Movement of high and low pressure areas; direction and rate at various seasons. Movement of atmosphere over large areas. Local effect of vertical currents. Cloud formations and deductions from them. Weather maps, weather predictions; storm warnings and weather signal codes. Tornadoes and cyclones; seasons and locali- ties. Average wind velocity in sections of the United States. conferences: dirigible balloons General types of rigid, semi-rigid and non- rigid balloons, and employment of each type. Rigid dirigibles : Dimensions, shapes and ma- terials used. Semi-rigid: Dimensions, shape, materials, important structural features and methods of car suspension. Non-rigid: Dimensions and shapes; main- Drawing reproduced fruiii the "lllublraled Lumlun News," showing the extent of the employment of observation balloons on the Somme front. 166 TEXTBOOK OF MILITARY AERONAUTICS taining shape; material for envelopes; methods of ear suspension. Air resistance to various shapes and skin re- sistance. Size and arrangement of ballonets. EmplojTnent of ballast. Vertical and horizontal stabilizing fins. Rudders for altitude and direction. Xumber and arrangement propellers. Gasoline engines suitable for dirigibles. Number and distribution and sizes of motors. Gas engine principles and maintenance. Dj'namic reaction of atmosphere on under surface. Velocity with respect to wind direction and earth. Na\ igating instruments. Hangars and methods of entry and exit in wind. Designs for descending on water or land. Bomb dropping devices. Armament. Memoranda: This pliotogrui)h, passed by Uic censor, shows one of the hangars and some of the balloons at liie L. cj. Army Balloon School at Omaha, Nebraska. (International Photo.) CHAPTER XIII HYDROGEN FOR MILITARY PURPOSES Notes Prepaked by Lieut.-Colonel C. DeF. Chandler, Signal Corps, U. S. A., for Army Balloon School The production of hydrogen for commercial purposes has naturally been toward the develop- ment of methods which insure low cost, and the equipment designed is usually for permanent installations. Greatest efficiency in the pro- duction of hydrogen for the military service in- volves processes which permit of easily trans- portable generating equipment, ample avail- able supplies of chemical substances, and purity of gas. It is often practicable for the army to use hydrogen plants of commercial types, ship- ping the gas compressed in cylinders, so that it is important that officers assigned to the lighter- than-air service become familiar with all prac- ticable methods. Properties of Hydrogen Hydrogen is a colorless and odorless gas, when pure. Frequently in the manufacture of hydrogen by chemical processes impurities in materials cause combinations of sulphur, carbon and arsenic, which with hydrogen even in mi- nute quantities, produces an odor often incor- rectly referred to as that of hydrogen. Hydrogen is the lightest known gas, having a density of .0696, referred to air at the same pressure and tempei'ature ; this is equivalent to a weight of .005621 pounds per cubic foot at temperature of zero degrees C, and 76 cm. (.001476 grams per cubic centimeter, at zero de- grees C. 76 cm.). 1 Gram (15.43 grains) at 0° C. 76 cm. equals 11.11 liters equivalent to 678 cubic inches of hydrogen. One grain of hydrogen at 60° F. and 30 inches barometric pressure equals 46.45 cubic inches. Compared to other gases, hydrogen is ab- sorbed very slightly in water. At 0° C, the ab- sorption in water is .00192 and at 80 degrees C, the absorption is .00079 referring to weight in grams H2 absorbed in 1000 grams of water. Hydrogen becomes liquid at a temperature of 167 168 TEXTBOOK OF MILITARY AERONAUTICS A British airship about to ascend. minus 220 degrees C. when subjected to a pres- sure of 20 atmospheres. No matter how low the temperature, the pressure must be at least 14 atmospheres, and, at this critical pressure, hydrogen liquefies at minus 240.8 C. The coefficient of expansion of hydrogen due to temperature changes is .00366 per degree Centigrade at a pressure of 100 centimeters of mercury, and between the temperature of 1° and 100° Centigrade. This coefficient of expansion should be particularly noted for the reason that in less than 24 hours changes in temperature of 72° F. (40° C.) in the north temperate zone are not unusual. A lowering of the temperature 40° C. reduces the volume of gas nearly 15 per cent, causing a balloon of 25,000 cubic feet capacity to become flabby and have the appear- ance of losing 3200 cubic feet of gas. Boyle's Law states that for a constant tem- perature the volume of gas diminishes in direct proportion to the pressure, but this applies only to ideal gases, of which there are none. The di- vergence of actual gases from Boyle's Law does not follow any formula ; a curve plotted for any one gas is irregular at various pressures. ( See Smithsonian Physical Tables.) Hydrogen is less compressible than indicated by Boyle's Law, while nearly all other gases are more compress- ible. At normal temperatures and a pressure of 2000 pounds per sq. inch (136 atmospheres), the quantity of free hydrogen in commercial cylinders of 2640 cubic inches, should be, accord- ing to Boyle's Law, 208 cu. ft. whereas experi- ments show only 191 cu. ft. (Bureau of Stand- ards.) Hydrogen will burn in air when the percent- age is as low as 4i/4, the flame traveling upward when ignited below. As the percentage of H2 increases to 9, the flame will travel downward or in any direction. Further increases in per- centage H2 increase the intensity of the flame propagation, which when very rapid and violent is called an explosion. The flame propagation is increased when the hydrogen is mixed with oxygen not diluted with nitrogen as in air. Ex- amples of this power and effect are occasionally observed when hydrogen and oxygen are acci- dentally compressed in the same cylinder. Vitriol Process One of the oldest and best known methods for hydrogen production is the vitriol process. The action of sulphuric acid on iron, or zinc evolves hydrogen as shown by the following chemical equation: Fe + H2SO4 Aq = FeS04 + 2H It is essential that dilute acid be used for the reason that concentrated sulphuric acid forms a film of sulphate of iron on the surface, which is soluble in water but not dissolved by the con- centrated acid. This process is so well kno^^^l that a detailed description here seems unneces- sary. The generating equipment can often be improvised by using substantial barrels or vats of wood or large glass or earthenware carboys, and lead pipes for conducting tlie acid. The caution to always pour the acid into the water and never the water into concentrated acid can not be repeated too often. Furthermore, when using improvised equipment or even specially constructed generators that are not positively gas tight, never strike a match or carry an open light such as a lantern near the generators. HYDROGEN FOR MILITARY PURPOSES 169 It is found in practice that the washing and purifying of the gas by the usual methods does not entirely remove the water vapor carrying traces of sulphuric acid, which is most injurious to rubberized balloon fabrics ; for this reason the vitriol process is not favored when it is prac- ticable to secure hydrogen by other processes, but if it must be used then special precautions should be taken such as multiplying the number of washers and purifiers and frequently chang- ing the lime in the purifiers. Fresh unslaked lime is used in the purifier to absorb the moisture charged with traces of sulphuric acid which passes out of the hot generating tanks. The lime (CaO)' has a great affinity for water (CaO -(- H2O ^ Ca (011)2) changing it to slaked lime (calcium hydroxide) upon absorbing the water. The lime also combines chemically with the sulphuric acid forming calcium sulphate (2CaO + H2SO4 = CaSO, + Ca(0H)2). Greater purity of hydrogen can be insured when the weight of apparatus is unimpor- tant, as in permanent installations, by add- ing in series more purifiers containing chemical substances such as Caustic Soda (NaOH) and Calcium Chloride (CaCl2) both of which have property of absorbing moisture which is carried along with the hydrogen. In order to determine the quantities of chem- icals required to produce a certain quantity of hydrogen by any jjrocess, apply the atomic weights of the elements in the chemical equa- tions in the manner shown below; for example. making the object of the computation 1000 cu. ft. of hydrogen, it is necessary to determine first the number of cubic feet of hydrogen in one pound of the gas. This is found to be about 178 feet by taking 12.388 cu. ft. of air as weigh- ing one pound and considering air as 14.4 times heavier than hydrogen, which figures are suffi- ciently accurate for this purpose. Example : Fe + H2SO4 = FeSO* + H2 55.84 (2 + 32 + 64)= 152 + 2 Then by Proportion: 3256 cu. ft. H : 1000 cu. ft. :: 55.84 lbs. Fe, : X X = 157 lbs. iron Similarly for sulphuric acid, 356 : 1000 : : 98 X X = 275 lbs. It is seen from the foregoing that 157 lbs. of iron and 275 lbs. sulphuric acid are theoretically required to produce 1000 cubic ft. hydrogen, but in estimating or purchasing these materials it is always advisable to increase the amounts by at least 5 and better 10 per cent, to allow for im- purities in chemicals, incomplete chemical ac- tion, and losses of gas due to generators and pipes not being gas-tight in improvised ap- paratus. The atomic weight of zinc is 65 and by a sim- ilar chemical equation it is found that theoreti- cally 182.5 lbs. of zinc and 275 lbs. of sulphuric acid are required to produce 1000 cubic feet of hydrogen. i tkiSiitiSmh&fii "I L .--^^ jrMr 1^6^^ '.jfe^i^MitoWaisSfcai Wm finS'^ inii d?9inK3 JiKqoiBfi BmlSra The motor transports, including hydrogen carriers of a U. S. Army balloon company photographed at Umaha. (Passed by the Censor.) 170 TEXTBOOK OF MILITARY AERONAUTICS Portable hydrogen gas plant constructed for the chief engineer- ing department of the Imperial Russian War OfBce. Zn + HoS04 . Aq==ZnS04 . Aq + 2H. 65+(2 + 32 + 64) = (65 + 32 +64) +2. At least 5 per cent, should be estimated above the theoretical amounts, for supplies of zinc and acid. Zinc usually contains some lead as im- purity; the lead is not objectionable, but on the contrary, is said to assist in promoting rapid chemical combination due to galvanic action. Using only the quantities of iron and acid ac- cording to the theoretical computation and as- simiing the cost of iron turnings at 2 cents per pound and acid at 3 cents per pound, the cost of materials alone to produce 1000 cu. ft. hydrogen would be $11.39. Electrolytic Method Hydrogen of greatest purity is obtained in commercial practice by the electrolysis of water, the hydrogen collecting on the negative elec- trode and the oxygen on the positive electrode where current enters the cell. A direct current of electricity is passed through water in a suit- able cell which is provided with pipes for col- lecting both gases. The electro-chemical equiv- alent of hydrogen is .0000104 grams per cou- lomb which in larger units amounts to nearly 15 cubic feet of hydrogen for a current of 1000 ampere hours. The theoretical electromotive force required to dissociate water into its con- stituent elements is 1.47 volts between elec- trodes. Therefore, due to the internal resist- ance of the cell, if the voltage required is 2, then the computation shows that one kilowatt hour of electric power will produce 7^/2 cubic feet of hydrogen. The internal resistance of cells increases with the distance between the electrodes, and de- creases as the size of the electrode increases. It varies also depending upon the nature and spe- cific gravity of the electrolyte in the cell. Pure distilled water is a very poor conductor of electricity and extremely high E.INI.F. would be necessary unless the conductivitj^ is improved by adding suitable chemicals to the water. Or- dinarily, pure caustic soda (NaOH) is used, bringing the solution to specific gravity between 1.2 and 1.25 at 60° F. It is found experiment- ally that 2^/4 pounds of chemicallj^ pure caustic soda are required to bring one gallon of distilled water to 1.25 specific gravity. This is about 17 per cent, caustic soda and is the point at which the solution has the greatest conductivity. Adding more caustic soda increases the internal resistance. Caustic potash (KOH) may also be used for electrolyte but larger quantity is re- quired and the present cost is much greater than that of caustic soda. There are two general types of construction for electrolizers, one being the unit type which consists of separate cells, each containing the positive and negative electrodes, connected elec- trically in series; the other general type being called by various names, "bi-polar," "multiple- plate," and "filter-press" types. These electro- lizers are usually constructed by assembling large plates very close together separating the positive and negative electrodes by sheets of as- bestos; where 110 volt power is available these generators have 60 pairs of plates. The ad- vantage of the multiple plate type over the unit cell type is principally lower first cost and less floor space required; the disadvantages being in greater maintenance cost and difficulty of preventing leakage of gas. ^lost of the electro- lizers made in the United States, both unit type and bi-i)olar, utilize a special weave of asbestos cloth as separator for the hydrogen and oxygen within the cell. The foreign-made cells at Fort Omaha have a very fine wire gauze to separate the gases. The quantity of hydrogen produced by this method is proportional to the amjjerage passed HYDROGEN FOR MILITARY PURPOSES 171 through the cell. For American made electro- lizers the current varies from 35 amperes to 1000 amperes, and for the Siemens cells at Fort Omaha the normal current is 1500 amperes. The E. M. F. required for each unit cell or for one pair of plates in the multiple type will aver- age 2 volts, but depends entirely upon the in- ternal resistance of the cell, which in turn de- pends upon the size of the electrodes, distance between them, nature and specific gravity of the electrolyte and the temperature. It is observed in practice that in starting the plant when cells are cold the E.M.F. per cell is often more than 3I/2 volts, which reduces to less than 2 volts after the cells become hot. As the water in the cells is converted into gas, it must be replaced by pure distilled water. The quantity being 5.76 gallons for 1000 cubic feet of hydrogen. It is seldom necessary to add caustic soda to the solution and then only enough to replace the very small quantity which is carried off from the cells by the moisture with the hot gases, but even this vapor may be con- densed and recovered to some extent by mois- ture traps of various kinds. Most manufacturers of electrolizers in the United States claim an output of 7V2 cubic feet of hydrogen per kilowatt hour. As shown in the preceding paragraphs, this means an E. M. F. of not to exceed 2 volts per cell. When it is possible to secure electric power at 1 cent per K. W. H. the cost of 1000 cubic feet or hydro- gen for power alone is $1.57 (assuming motor- generator efficiency of 85 per cent., and electro- lizer efficiency of 7^ cubic feet hydrogen per K. W. H.). The electrolytic plant installed by the armj' at Fort Omaha in 1908 consists of 30 large cells made by Siemens Bros. Company, Ltd., Lon- don, the normal current being 1500 amperes and the voltage varying fi'om 4 to 2.2 per cell, depending on temperature. The temperature should be maintained at 150 degrees F. Higher than this is likely to damage the insula- tion and produce an excess of moisture with the gas. Lower temperature increases the internal resistance and cost of electric power. Each cell produces 23.3 cubic feet of hydrogen per hour, a total of 699 cubic feet per hour for the 30 cells, equivalent to 16,776 cubic feet per day of 24 hours for the plant. Silicol Process The production of hydrogen by dropping ferro-silicon into hot caustic soda is, in the French and British Armies, known as the "silicol" method; in Germany it is called the Schuckert process, and for manj' j'ears the de- tails of it were carefully concealed. The chemical reaction producing hydrogen is between silicon and caustic soda without any • .f '*t i^. vl -V -^j^jatSl! . . A batteiy of hydrogen gas cylinders attached to supply pipe of balloon being filled. 172 TEXTBOOK OF MILITARY AERONAUTICS change in the iron. The following chemical equation will serve to explain the process: Si + 2XaOH + 2H2O = NaaSiOs + 4H. + HoO. In Germany it was customary to use pure or nearly pure silicon. In France this method was developed for the military service by Capt. Le Large and Dr. Jaubert ; the gene- rating apparatus being designed in three types ; viz: Auto truck transportable size, semi- fixed and for permanent installations. Ferro- silicon is used, being more easily secured and at less cost than pure silicon as in the Schuckert generators. The steel indus- try in this countrj' uses large quantities of ferro-silicon containing 50 to 75 per cent, silicon. Experiments have shown that more satisfactory chemical action is secured by having the silicon content 80 to 85 per cent. Commercial caustic soda of 97 per cent. NaOH is suitable. Except in very cold weather the mixing of caustic soda with water produces sufficient heat to start the chemical combination of silicon and soda. It is necessary to agitate the solution constantly to secure best results and avoid sud- den generation of large quantities of gas of ex- plosive violence. The solution resulting from the chemical combination is sodium silicate, which may be easily drawn off at the bottom of the mixing tank. According to the chemical equation, the pro- duction of one thousand cubic feet of hydrogen would require 39.6 pounds of pure silicon and 112.3 pounds of pure caustic soda. The actual quantities which should be supplied depend German railway truck with itccl cylinders. upon the silicon content of the ferro-silicon and the percentage of purity of the caustic soda. An experiment conducted for the army deter- mined that 58 pounds of 80 per cent, ferro-sili- con and 125Y2 pounds caustic soda would pro- duce 1000 cubic feet hydrogen. Ferro-silicon at 15 cents per pound and caustic soda at 3 cents per pound would bring the total cost for ma- terials to $12.46 per 1000 cubic feet. Ferro-silicon may be stored without deteriora- tion by moisture and without any special pre- caution for its care. The caustic soda must be protected from moisture and is usually supplied in air-tight drums containing 100 pounds. In connection with silicol generators, there are required washers and purifiers to remove from the gas the hot vapors carrying caustic soda solution. Field generators of this process should alwaj^s be set up for operation near a stream or other ample supply of water. It is possible to design the generating equipment with radiators for cooling the circulating water for situations where water economy is important. Iron Contact Process The iron contact process for production of hydrogen is often referred to as the regenera- tive steam and iron and method, the principle being that when steam passes over red hot iron it is decomposed into its constituent elements, the iron absorbing oxygen from the steam and the hydrogen collected. The chemical reaction is represented by the equation : 2Fe -f 3H2O = Fe203 + 6H. To utilize this principle commercially, it is necessary to reduce the ferric-oxide back again to metallic iron which can be done by passing carbon monoxide over the iron oxide, the carbon monoxide (CO) tak- ing an atom of oxygen from the iron becomes carbon dioxide (COo) represented by the fol- lowing equation: SCO + FejOs = 2Fe + SCO^ The conmiercial equipment for production of hydrogen by the iron contact process utilizes the well-known water-gas process for making the carbon monoxide which is needed to reduce the iron from the oxide to pure metallic state. HYDROGEN FOR MILITARY PURPOSES 173 Close view of the carriage of a British Blimp. The water-gas generator is filled with coke which is heated to redness by a blast of air for a very brief period. When steam is turned on to this red hot coke, it is decomposed, the hy- drogen freed from the oxygen is combined with the carbon of the coke forming carbon monox- ide (CO). The water-gas consists principally of hydrogen and carbon monoxide, but must be passed through washers and purifiers to remove dust and particularly sulphuretted hydrogen. Sulphur is removed by passing the gas over trays of iron. The purified water-gas, usually referred to as "blue gas," is then stored in a holder, available for use as reducing agent. After steam has passed over the red hot iron for a few minutes, the temperature is lowered to such an extent that it no longer decomposes the steam and it is then necessary to raise its heat and at the same time change the ferric oxide to metallic iron by turning the blue gas into the ovens. The period of heating the iron and re- ducing the oxide requires about twice the amount of time for the hydrogen production phase. Temperature is a most important factor and must be constantly watched in all phases of the process. In the water-gas generator, if the temperature is too slow, carbon dioxide is formed instead of carbon monoxide. In reduc- ing the ferric oxide, if the temperature is not sufficiently high the reduction will be only from the ferric oxide FcaOs to Fe^Oi or at still lower temperature to FeO instead of to the pure metallic Fe. The reduction ovens are originally filled with hematite (Fe203) which should be as porous as possible in order to expose greater surface to the action of the steam and carbon monoxide, and this ore should be free from sulphur com- pounds and other impurities. It is necessary to replace the ore in the ovens about every six months. The iron contact process was developed long ago by Coutelle and perfected by Giffard in France, then developed commercially in Eng- land by Lane using several retorts for the iron. In Germany it was further developed by A. Messerschmitt, utilizing one large regenerative oven instead of many small retorts. The Mes- serschmitt regenerative oven is patented in the United States. The patents relate only to the oven and retorts; the steam and iron process is not patented. At least two firms in this coun- try install iron contact plants, which produce 3500 cubic feet of hydrogen per hour. Plants of this size and type are now under construction for the Navy Department at Pensacola, for the Army at Langley Field, and for a private firm near Akron, Ohio. Hydrogen produced by the iron contact proc- 174 TEXTBOOK OF MILITARY AERONAUTICS Filling cylinders on the railway truck. ess has a purity of at least 98 per cent. The impurities consist principally of nitrogen and carbon dioxide which have no deleterious effect on balloon fabric, nor are these gases inflam- mable. It is claimed that hydrogen can be pro- duced by this process from 25 cents to 75 cents per thousand cubic feet. Aluminum Caustic Soda Process During the war between Russia and Japan both armies used field hydrogen generators em- ploying the chemical reaction of alkaline hy- drates upon aluminum. Sodium hydrate (XaOH) ordinarily known as caustic soda, is preferred to the potassium hydrate on account of the lower cost of the soda. The chemical reaction taking placfe is represented by the fol- lowing equation: 6XaOH + 2 Al = AI2 ( OXa ) « + 6H The generating apparatus was constructed in two types, one of small size installed on vehicles for rapid transportation, and a larger size called "semi-fixed." An iron basket is filled with aluminum sqrap, lowered into the solution of caustic soda, the cover being immediately clamped to make it gas tight. The gas passes from the generator to a washing and cooling de- vice which removes the traces of alkaline matter. In the generator the aluminum is attacked by the sf)da solution with great energ>', the gas com- ing off rapidly and the liquid heating to the boiling point, but as the proportion of free soda in the solution diminishes, the rate becomes slower. In order to finish the gas production without delay, the generator is charged with caustic soda considerabh^ above the theoretical requirement. According to the theoretical computation, it is found that to produce 1000 cubic feet of hy- drogen there are required 224 pounds of caustic soda and 51 pounds of aluminum. With caus- tic soda at 3 cents per pound and aluminum at 50 cents per pound, the cost of the one thousand cubic feet of hydrogen by this process is $32.22. The actual quantity of materials to be carried will be considerably in excess of 275 pounds and the cost per thousand more than the foregoing computation indicates, on account of the neces- sity for using an excess of caustic soda and the fact that commercial caustic soda contains im- purities, the most common grade containing only 77 per cent, sodium hydrate. The aluminum and alkali method has the ad- vantage of requiring about 20 per cent, less weight of material than the viti-iol process and both materials being dry are easily transported without the especial care which is necessary for the transportation of sulphuric acid. Further- more, the hydrogen produced is of greater pur- ity, does not contain volatile hydrocarbons, nor the dangerous gases produced by combinations of hydrogen and arsenic. U. S. patent was issued in September, 1901, for a modification of the aluminum-caustic-soda process. The inventor prepared the material by pouring molten caustic soda into a mass of aluminum in the form of powder, filings, or turnings, which was thoroughly mixed before the mass cooled. This mixture of material must be kept in sealed containers to avoid de- terioration due to moisture in the atmosphere. When the mixed substance is placed in water the chemical reaction produces sodium alumi- nate and free hydrogen, probably according to the following equation : 2A1 + 2XaOH + xH^O = NasAljO* + xH.O + 8H2 or 2A1 + eXaOH -f xH,0 = NaeAUOa + xHsO + 8H, HYDROGEN FOR MILITARY PURPOSES 175 Hydrolithe "Hydrolyte" is calcium hydride (CaHz) manufactured by heating pure metalhc calcium in retorts containing hydrogen. To produce hydrogen it is only necessary to drop the gran- ulated hydrolythe into water. Generating equipment similar to the ordinary acetylene gas outfits are suitable. The reason hydrolythe is not more extensively used is on account of its high cost. About ten years ago the Signal Corps purchased a sufficient quantity to con- duct experiments, which confirmed all claims for it, but chemical manufacturers in the United States do not produce it at present. It will be seen from the following chemical equations that only 59 pounds of hydrolythe are required to produce 1000 cubic feet of hydrogen: CaH2 + H2O = CaO + 4H. At 80 cents per pound for hydrolythe the cost of 1000 cubic feet of hydrogen by this method would be $47.20. Pure sodium or lithium dropped in water will produce hydrogen and it is possible to make hydrides of lithium the same as calcium which will similarly produce hydrogen upon contact with water. On account of the light weight of lithium this would be particularly desirable for field hydrogen generation, and experiments are now in progress to determine whether it is prac- ticable to manufacture lithium hydride at rea- sonable cost. Dropping pure lithium in water would the- oretically require only 40 pounds to produce 1000 cubic feet of hydrogen: 2Li + H2O = Li^O + 2H. And of lithium hydride 221/2 pounds would produce 1000 cubic feet hydrogen 2LiH + H.O = LiaO + 4H. About ten years ago an American manufac- turer proposed the use of lead compounds hav- ing great affinity for water known as "Hydrone A, B, and C," and experiments were conducted by the Signal Corps. It developed that the chemical reaction upon dropping the substance into an alkaline solution was so violent that the oxygen of the air above the generating tank would burn the hydrogen, — the ignition being due to heat of the chemical action. This diffi- culty was overcome by manufacturing a lower grade which evolved hydrogen slowly. The One of the Goodyear "Blimps." Photo passed by the Censor. 176 TEXTBOOK OF MILITARY AERONAUTICS y A military balloon ascending. low-grade material was first dropped into the generator until the escaping gas had carried with it all oxygen above the water, then the high-grade substance was fed into the generator. On account of the extreme care that was neces- sary to avoid explosions with this method and the considerable weight of the hydrone, its fur- ther development for field hydrogen generation in the army was discontinued. One pound of hydrone produced only 2.88 cubic feet hydro- gen at a cost of QYo cents per foot. Hydrogenite This hydrogen process is a modification of the "silicol" process already described. The chemical substances and reaction are the same as the silicol, but the materials are prepared and used in somewhat different manner. Pul- verized ferro-silicon and caustic soda properly proportioned are thoroughly mixed and pre- served in hermetically sealed cartridges, each containing .50 kilograms. The field generators to use these cartridges consist of metal container slightly larger than the cartridge, having a lid which can be clamped down gas tight. After placing the cartridge in the apparatus, the top of the can is opened and the mixed powders ignited. Around the inside of the cylindrical burning oven in which the cartridge is placed, is a trough to contain a measured quantity of water. The heat pro- duced by the burning of the chemicals quickly converts this water into steam, the silicon, soda, and water combining as in the previously shown equation describing silicol method. Ignition may be started by a fuse or taper in- serted in the powder or by placing on top a small quantity of some easily combustible powder in order to produce sufficient heat in one spot to start the combustion. The hydro- genite burns rapidly and without flame, like tinder; a cartridge of 50 kilograms being con- sumed in about ten minutes. When the mixture is first ignited, the air in the chamber and products of combustion are permitted to escape until the pure hydrogen ap- pears. The gas is passed through washing and cooling purifiers before being used. It is learned that even with the greatest care generators ai'e frequently destroyed by explo- sions, for which reason the process is not in gen- eral use. Hydrogen from Water-Gas A German chemist developed and advocated some years ago the production of hydrogen for aeronautical purposes by first manufacturing water-gas in the usual manner, which consists principally of hydrogen and carbon monoxide, passing the water-gas over red hot calcium car- bide in the form of powder. The hot calcium carbide decomposes the carbon monoxide form- ing lime (CaO) and leaving carbon in the form of crystalline graphite. The inventor claims that minor impurities in the water-gas are al- most entirely removed in the reaction, produc- ing hydrogen of 99 per cent, purity. The re- port further stated that generating equipment was devised to produce 70,000 cubic feet of hy- drogen daily. Hydrogen may also be separated from water- gas or coal gas by the fractional refrigeration HYDROGEN FOR MILITARY PURPOSES 177 process. Hydrogen liquefies under pressure at lower temperature tlian other common gases, so that from illuminating gas having a consid- erable percentage of hydrogen it is possible to cool and compress it with liquid air apparatus, drawing off first all other gases as they liquefy and leaving the hydrogen. This method is not in general use for commercial production for the reason that other methods offer more simple and more economical means of securing hydro- gen. The Electrical Review (Vol. 40) reported that M. D'Arsonval passed coal gas previously cooled to minus 80° C. through a Linde liquid air machine, obtaining 3500 cubic feet of hydro- gen per hour, expending 12 to 15 horse-power. Assuming coal gas to cost $1 per thousand and containing 50 per cent, hydrogen, the cost of material would be about $2 per thousand cubic feet hydrogen, to which must be added approxi- mately 60 cents per thousand for power, plus cost of expert attendance. Aluminum-Potassium Cyanide Process A French chemist a few years ago advocated the generation of hydi'ogen for aeronautical purposes by mixing aluminum filings with pul- verized bichloride of mercury and potassium cyanide. After these ingredients are thor- oughly mixed hydrogen will be produced by adding water. The powder has a density of 1.42 and must be kept in hermetically sealed cans. It is stated that experiments indicated 187 pounds of this material were required to produce 1000 cubic feet of hydrogen. The chemical reactions which take place should properly be represented by three or four stages, but may be sufficiently explained by the follow- ing single equation: 6KCN + 6H2O + 4A1 + 3 HgCla = 2K3AIO3 + 12H + 3Hg(CN)2 + 2A1C18 Acetylene Process In 1901 Mr. H. Houbon, a resident of Eng- land, invented and patented a process for mak- ing pure hydrogen from acetylene. He com- pressed the acetylene to 5 atmospheres in a Caillet steel bomb and ignited it by electric spark. The carbon precipitates in the form of fine soot leaving the pure hydrogen. It is stated that the process is without danger and A British "Blimp" passing over an anti-aircraft post. 178 TEXTBOOK OF MILITARY AERONAUTICS calcium carbide for producing acetylene is very cheap, but it is not known that this process has ever been perfected for producing hydrogen in large quantities for aeronautical service. By computation it is found that 180 pounds of calcium carbide are required to produce 1000 cubic feet of hydrogen by this method. C2H2 + Heat = 2C + 2H Iron and Water Process Recently an article in a German technical journal described a new method for securing compressed hj'drogen of great purity. So far as known it has been employed only in labora- tories, but it may be developed later on a com- mercial scale. Powdered iron is mixed in water in a vertical steel cylinder, the liquid being subjected to a pressure of 300 atmospheres (5,410 pounds per square inch) and the temperature raised to 350° C. The chemical reaction that takes place is sufficiently explained by the following equa- tion : 2Fe + 3H2O = Fe^Os + 6H from which it is seen that under this great heat and pressure the iron combines with the oxygen from the water, and the hydrogen may be re- moved at the top of the cylinder already com- pressed for storage in cylinders. The iron ox- ide may be easily reduced again to metallic iron, which is facilitated by its porous condition, due to the peculiar manner in which it is oxidized. Hydrogen obtained is said to have 99 per cent, purity, which can be further increased to 99.95 per cent, by being passed over charcoal. When iron contains sulphur, the sulphur is not at- tacked, but any carbon content in the iron is converted into carbon monoxide. Silico-Acetylene Process The silicides of calcium, barium and stron- tium (CaSi2 : BaSi2 : SrSi2) are made in the electric furnace similar to the manufacture of calcium carbide. When calcium silicide is added to aciduated water, it is decomposed, leaving sihco-acetylene in solution; the calcium oxide is precipitated. The solution is drawn off and evaporated, leaving yellow ciystals of sihco-acetylene SiaHa. When these crystals are added to alkahne solution such as caustic soda or potash, the silico-acetylene is decom- posed, evolving hydrogen. It is reported that 163 pounds of silico-acetylene are required to produce 1000 cubic feet of hydrogen. Decarburation of Oils About four years ago the Scientific American described equipment developed by the German Army for the generation of hydrogen by the method of decarburizing hydro-carbon oils. The apparatus was designed for installation on two railway cars, the main part of the equipment consisting of two gas producers. To fire up these producers to the proper heat requires from one to two hours. The producers are filled with coke which is heated to redness by air-blast. Crude petro- leum or any petroleum distillates are first va- porized and then passed through the producer ovens containing the hot coke, which decom- poses the oil. After about twenty minutes the coke has been reduced in temperature so much that it is necessary to heat it again to redness by hot air blast. This requires only two or three minutes. The gas produced is passed through water scrubbers and purifiers to remove sulphur. It contains considerable carbon monoxide which is removed by passing the gas through an oven, the details of which process are not stated. The resultant gas is said to be OS.! per cent, hydro- gen, 1.2 per cent, nitrogen, and 0.4 per cent, carbon monoxide, and to have a specific gravity between 0.087 and 0.092. Courtesy Underwood & Underwood. Group of students seated around big relief map. Photo passed by the Censor. CHAPTER XIV TRAINING AVIATORS FOR THE UNITED STATES ARMY; HOME AND FOREIGN SERVICE The training of aviators for the United States Army, for home and foreign service, is con- ducted by the Organization and Training Sec- tion of the Aviation Division, Signal Corps, whose offices are in the War Department, Washington, D. C. According to a recently issued official state- ment, this Section deals with the organization of aviation school squadrons and standard aerosquadrons, the latter composed of gradu- ated Reserve jSIilitary Aviators. There are but a few officers with the title "Military Aviator " and "Junior Military Av- iator." These are in administrative positions. This Section has nothing to do with training of men for aerostatic work, which is handled by the Balloon Division. The Aviation Division of the Signal Corps is composed, originally, of officers and enlisted men of the Regular Army, limited by law to a definite number. Additional personnel is pro- vided through the Signal Officers' Reserve Corps, the Signal Enlisted Reserve Corps, and the employment of civilians in instructive, ad- visory, administrative, or other capacities. Civilians may be employed (1) as such; (2) by passing standard physical and mental ex- aminations and by going through the routine Practically the entire new flying personnel is of joining the Signal Officers' Reserve Corps, to be composed of Reserve Military Aviators, in which event, if satisfactory, they may be 179 180 TEXTBOOK OF MILITARY AERONAUTICS given commissions therein commensurate in grade with their attainments and duties, as fol- lows: (a) Non-flj'ing duty, (b) Flying duty (as pilots or observers), (c) By enlistment in the Signal Enlisted Reserve Corps. The Organization and Training Section also handles original applications for commissions in the S.O.R.C. from civilians. Regular Army or National Guard officers and men are needed as supply, engineer, or field-inspector officers. Opportunity is afforded by personal interview to obtain first-hand knowledge of the particular attainments of each man. If pre- liminary investigation is satisfactory, the ap- plicant fills out his blank and is turned over to the Personnel Division, which attends to the routine of physical and mental examination. Upon the obtaining of his commission he is as- signed to such place as his services are required. Form of letter of application for examination for commission in Officers' Reserve Corps. [Under section 37, Act of June 3, 1916.] I have served years in 19- To Sir: I have the honor to apply for examina- tion for a commission as ^ aviation section, in the Signal Officers' Reserve Corps, organized under the authority of Congress. 1 Insert grade, first lieutenant, captain, or major. I have pursued a regular course of instruc- tion for years m I graduated in the year from after having creditably pursued the course of military instruction therein provided. I was born , , at , and am "• a citizen of the United States. A.g& . Color . Height . Weight . My business is . My experience is . I inclose letters of recommendation and ad- dresses of three citizens who know me as fol- lows : . Respectfully, Permanent post office address The correctness of the statements above made was sworn to and subscribed before me , 19—. The duties of the Aero-Personnel Division consist of matters affecting the commissioned and enlisted men of the Aviation Section of the Signal Corps, which may be more conveniently termed the Army Air Service. All communi- 2 Insert service in the Regular Army of the United States, or Volunteer forces of the United States, or Organized Militia of any State, Territory, or District of Columbia; also state in what capacity. s Insert name and location of the school or college. * Insert the name and location of the educational institution. 5 Insert "not" if in accordance with fact. 8 Oath to be taken before, and signature to be made by, officer authorized by law to administer oaths. Group of army aviation students at one of the training fields. TRAINING AVIATORS FOR UNITED STATES ARMY 181 students learning the assembling ot aeroplanes at a University, somewhere in America cations to the Chief Signal Officer, or higher authority, that are concerned with the subject of aviation personnel must pass through this Division, except when such communications deal with civilian employees. The personnel of the Army Air Service com- prises the following groups: (a) Enhsted men of the Regular Army. (b) Signal Enlisted Reserve,^ throughout this chapter referred to as "Enlisted Reserve Proper." (c) Men (flying duty) enlisted temporarily in the Signal Enlisted Reserve in order to ob- tain training for a commission in the Aviation Section of the Signal Officers' Reserve Corps. (Throughout this chapter they are referred to as the "Enhsted Reserve.") (d) Reserve Officers (flying duty). (e) Reserve Officers (non-flying duty). (f) Officers (of the Regular Army). The Aero-Personnel Division is also con- cerned with two other groups of men : (g) Enlisted applicants of the Regular Army for transfer to the Air Service. (h) Commissioned applicants of the Regular Army for detail to the Air Service. (a) Present provisions in regard to the first of these groups continue as now prescribed by law and Army Regulations. The Aero-Per- sonnel Division has charge of the records of en- listed men of the Regular Army. (b) The purpose of the "Enlisted Reserve Proper" has been to secure a body of trained 1 Inasmuch as all enlistments are for the period of the war and the policy of the office is to accept men for the Regular Army only, paragraph (b) is modified to this extent. mechanicians, machinists, electricians, chauf- feurs, and other qualified men, who may be quickly called in time of need. Cards giving the home addresses and information about the enlistments of such reservists are kept in the Aero-Personnel Division. Similar informa- tion is in the service record of each reservist, in the hands of the department commander in whose territorial jurisdiction he resides. No more enlistments in this group as reservists are being made at present, there being no desirabil- ity during wartime to increase the number of reserves not on active duty. At date of writing the entire personnel of this group is being called into active service by department commanders immediately upon enlistment. They are as- signed to aviation stations and placed in train- ing. (c) The enlisted reservists who are appli- cants for commissions as reserve officers, flying duty, and are enlisted in the Signal Enlisted Re- serve Corps simply for the purpose of prelimi- nary training prior to receiving their commis- sions, comprise an extremely important group. From their number will come almost exclusively the aviators of the Army Air Service. The procedure in regard to the enlistment of these men is in the hands of the Aero-Personnel Di- vision. All applicants for commission in the Aviation Section of the Signal Officers' Reserve Corps must forward their applications to the Aero-Personnel Division for approval or disap- proval. If the application is approved, its sender is given an examination to determine his physical condition, and a second examination to test his moral, professional, and educational 182 TEXTBOOK OF MILITARY AERONAUTICS qualifications for a commission. Boards to give the complete examinations are situated at each of the Schools of ^lilitary Aeronautics; also at the several Signal Corps flying schools in the different states and at Washington. If the candidate is successful in passing these examinations, he is reexamined with a view to enlistment as first-class private in the Signal Enlisted Reserve, and is then either sent home with a certificate of enlistment to await further orders, or is sent immediately to one of the "ground schools" (Schools of Military Aero- nautics) for instruction. From this time until the receipt of his commis- sion the candidate is under the jurisdiction of: First, the Schools of Military Aeronautics Di- vision; and later the Organization and Train- ing Division. The Aero-Personnel Division asks for the transfer to the "ground schools" of suitahle students on duty at the Federal Re- serve Officers' Training Camps. Such re- quests, if recommended, are made weekly. (d) Upon successful completion of the fly- ing-school course, the candidate is commissioned as a reserve officer, whereupon his relation to the Aero-Personnel Division becomes like that of a regular officer of the Air Service. Competent civilian flyers, who pass the physi- cal and mental examinations and are satisfac- tory otherwise, may at once be commissioned in the Signal Officers' Reserve Corps and ordered to active duty. (e) Civilian apj)licants for commissions in the S. O. R. C. for non-flying duty in capacities such as engineer, supply or other officer, may take mental and physical examinations (the lat- ter less rigid than that for flying duty), and if qualifications are satisfactory, may be commis- sioned and ordered to active duty. America's future airmen are here shown ]iracticing tlie Morse Interna- tional Code as one of tlie first steps in masterinjr the science of radio transmis- sion which they will soon he using over the German trenches in France. Photo passed hy Censor. (f) All communications in regard to officers of the Arm}' Air Service pass through the Aero-Personnel Division. Similarly, all orders for officers of the Air Service that are requested from the Adjutant-General pass through this division. Complete military records of officers are also kept there. (g) Applications of enlisted men of the Sig- nal Corps proper, or of other staff corps or de- partments or arms, for transfer to the Air Serv- ice should be approved by the Aero-Personnel Division before orders are issued for such trans- fer. (h) Any officer of the Regular Army, who is an applicant for detail to the Air Service, has his military record and correspondence concerning him kept by the Aero-Personnel Division while he is undergoing training at the Signal Corps flying schools. Upon detail to the Air Service, the status of such an officer in relation to this division is precisely like that of other officers of the Army Air Service. In all cases application for enlistment, trans- fer, detail, or commission, is made direct to the Aero-Personnel Division. Schools of Military Aeronautics (Ground Schools) Successful candidates for flying duty are di- rected by the Aero-Personnel Division to one of the ground schools located at the following in- stitutions : Massachusetts Institute of Technology, Bos- ton, Mass. Cornell University, Ithaca, New York. Ohio State University, Columbus, Ohio. University of Illinois, I''"rbana. Illinois. Texas University, Austin, Texas. TRAINING AVIATORS FOR UNITED STATES ARMY 188 One of the Army aviation training fields, showing Curtis JN-4 scJiool planes. (Committee on Public Information.) University of California, Berkeley, Calif. Princeton University, Princeton, N. J. Georgia Institute of Technology, Atlanta, Ga., Jolm Hopkins University, etc. (Additional institutions are being added to this list at date of writing.) Upon arrival, the S. M. A. Division is advised thereof, with a list of candidates, which list is kept by the S. M. A. Division in cooperation with the Organization and Training Section. Now the students are under the charge of the S. M. A. Division, Here the students serve eight weeks with the pay of a first-class private, about a dollar a day, and with the allowance of a dollar a day for rations. Quarters are provided in barracks. The candidate upon entering the Ground Schools of Military Aeronautics becomes a ca- det. He is assigned to a "Junior Squadron," where he remains for three weeks; then he is transferred to a "Senior Squadron." Each squadron consists of between twenty to thirty cadets in charge of a first sergeant. At these ground schools the cadets are given a general course in military discipline and drill, as well as intensive instruction in aeronautical engines, telegraphy, machine-guns, bombing and fighting, aerial observation and cooperation with artillery and infantry, including map- reading, contact patrol and reconnaissance; army regulations and military subjects; flying with meteorology, instruments, compasses, pho- tography; rigging, care and repair of aero- planes, engines and cameras. Guns and other apparatus are provided for practical study. Upon completion of this course the students are assigned through the Aero-Personnel Di- vision to the aviation school squadrons, as noted under "Organization and Training." The daily schedule at the ground schools of military areonautics is more or less as follows: Reveille, 5 :35 a. m. First call, 5 :40. All calls are by bugles, the same as in the army. Assembly is blown at 5 :50 A. M., when all cadets must be in ranks in their respective places. On. all assembly calls the first sergeant of each squadron orders his men to fall in. Then he receives his corporal's report of "lates" or "ab- sentees," about faces to the officer of the day, and reports concerning lates or absentees from his squadron; whereupon the officer of the day commands the senior first sergeant or cadet cap- tain to take charge of the men for calisthenics. The senior cadet sergeant marches all the squadrons to the court, and when they have taken their respective places leads them through ten minutes of calisthenics. At the end of this time the squadrons are placed in command of their respective sergeants, the two senior squad- rons being marched immediately to mess, the re- maining squadrons returning to the quadrangle, awaiting their turn for mess. The mess takes about an hour for each squad- ron. At 6 :55 A. M. first call for drill is blown. At 7 A. M. assembly is blown, whereupon the men are marched to the drill field and given one hour of military drill. As the men in this school are training to become aviator officers, a full course in military drill is not required, the reason being that the man getting his commis- 184 TEXTBOOK OF MILITARY AERONAUTICS sion wiU have hardly any enhsted men under him to drill. Saturday: 8-9 A. M. 9-10 10-11 Study Hour Reconnaissance Map-Reading The work after drill is different for different 11-12 Art of Observation wings of the school. The first three weeks, or For the second week it is as follows: Jimior Wing, and the last five weeks, or Senior Monday: 8-9 A. .M 9-10 Study Hour Art of Observation Wing, have the following schedules: 10-11 Map-Reading 11-12 Nomenclature FIB8T THREE WEEKS LAST FIVE WEEKS 2- 3:50 P.M. Miniature range JUNIOR WING SENIOR WING Tuesday; 8-9 A. M. Machine-guns 7- 8 A. M. DrIU 7- 8 A. M. Drill 9-10 Study Hour 8-9 " Class 8- 9 " Class 10-12 " Gasoline engines 9-10 " DrUl 9-10 " Class 2- 2:50 P.M. Art of Observation 10-11 " Class 10-11 " Class 3- 3:50 " Instruments, including Compasses 11-12 " Calisthenics 11-12 " Class Wednesday 8- 9 A. M. Study Hour 12 M. Mess 12 M. Mess 9-10 Reconnaissance 2- 3 p. M. Drill 2- 3 P. M. Class 10-12 " Gasoline engines S- 4 " Calistiienics 3-4 " Class 2- 3:50 P.M. Miniature range *- 5 " DriU 4-5 " Calisthenics Thursday: 8-11 A. M. Rigging and Landing Gear 5:45 P.M. First Call 11-12 Study Hour 5:50 " Retreat 2- 3:50 P.M. Gasoline engines 5:55 " Assembly Friday: 8-9 A. M. Tools March to mess 9-10 " Study Hour 7 :55 p. M. School Call 10-11 Machine-guns 8:55 " Dismissed or Recall 11-12 Art of Observation 9:10 " Tatoo 2- 3:50 P.M. Gasoline engines 9:15 " Roll Call in barracks Saturday: 8-9 A. M. Study Hour 9:30 « In bed — and lights out 9-10 10-11 Instruments, including Compasses Wireless Every Saturday morning between 7 and 8 inspection of the 11-12 Reconnaissance entire student company is held under arms on the drill field. and is followed by inspection of barracks by the commandant. During the third week it is as follows: Monday: 8-10 A. M. 10-12 Gasoline engines Machine-gun test Instruction in the Junior Wing 2- 3 p. M. 3-4 Instruments, including Compasses Study Hour Instruction in the Junior Wing consists of Tuesday: 8- 9 A.M. 9-10 Theory of Wireless Lecture on Photography elementary work in wireless, such as sending 10-11 11-12 " Machine-guns Study Hour Miniature range and receiving, machine-gun instruction and ma- 2- 3:50 P. M. chine-gun theory. Wednesday. 8-9 A.M. 9-10 10-11 11-12 Study Hour Meteorology Astronomy Lecture on Fighting In the Air Instruction in the Senior Wing Thursday: 2- 3:50 P.M. 8-9 A. M. Gas-engines Study Hour Instruction for the first week in the Senior Wing is as follows: 9-10 10-11 " Instruments, including Compasses Contact patrol Tools MOXDAT: 7- 8 A. M. Drill 11-12 8-10 Wireless 2- 3:50 P. M. Miniature range 10-12 Gas-engines Friday: 8- 9 A. SI. Study Hour 2- 3:50 P. M. Machine-guns 9-12 Rigging and Landing Gear TUMBOAX: 8-9 A. M. Lecture, Type of Machine 2- 3 P. M. Signal Instruction 9-10 " Lecture, Bombs and Bombing 3-4 Map-reading 10-11 Lecture, Wireless Saturday: 8-9 A. M. Buzzer Practice 11-12 Lecture, Theory of Flight 9-10 Machine-guns 2- 330 P.M. Lecture, Gasoline Engines 10-12 Bombs and Bombing Weoxesoay: 8-9 a.m. Theory of Wireless 9-10 Nomenclature For the fourth week it is as follows: 10-11 Reconnaissance Monday: 8-9 A. M. Study Hour 11-12 « Map-Reading 9-12 Rigging and Landing Gear ■ 2- SaO P. M. Gas-engines 2- 3:50 P. M. Gasoline engines Thuudat: 8-9 a.m. Nomenclature Tuesday: 8-9 A. M. Study Hour 9-10 Study Hour 9-10 Machine-guns 10-11 « Bomlis and Bombing 10-12 Miniature range 11-12 Machine-guns 2- 3:50 P.M. Gasoline engines 2- 2:50 P. M. Wireless Wednesday: 8-10 A. M. Gasoline engines 3- 3:40 " Theory of Wireless 10-1 1 Meteorology PUDATi 8-9 A. M. Study Hour 11-12 Photography 9-10 " Art of Observation 2-3 P. M. Radio and Wireless 10-11 Theory of Wireless 3-4 Signal telegraphy 11-12 Machine-guns TaUlSDATi 8-9 A. M. Theory of Wireless 9- S'M r. M. Gasoline engines 9-10 Theory of Sending and Receiving TRAINING AVIATORS FOR UNITED STATES ARMY 185 Lieutenant Montariol, French Flying Corps, in- structing a class of avia- tion students somewhere in America. Thursday: 10-12 A. M. 2- 3 P. M. 3- 4, (t Friday : 8-10 10-12 A. M. 2- 4 P. M. Saturday : 8-10 A. M. 10-12 (( For th Monday: 8- 9 A. M. 9-12 t< 2- 4 P.M. Tuesday: 8-11 A. M. 11-13 t( 2- 3:50 P. M. Wednesday: 8- 9 A. M. 9-10 n 10-11 n 11-12 (( 2- 3:50 p. jr. Thursday : 8-10 A. M. 10-12 (( 2- 3:50 p. M. Friday: Saturday : 8-10 10-12 7- 8 Examination in theory of Sending and Receiving Wireless Machine-guns Instruction in Wigwag and Sema- phore Gasoline Engines Examination in the Theory of Flight Machine-guns Gasoline Engines Examination in Gunnery, includ- ing bombs and bombing, and machine-guns e fifth week: Examination in Wigwag and Semaphore Work in the field with a field wire- less set, as used by the United States Army in the field Study Hour Sail-making and Rope-splicing Study Hour Examination on the theory of Gas- oline Engines Study Hour Lecture on Magnetos Signal Telegraphy Meteorology Care of machine Rotary gasoline engines Miniature range examination Transportation of machines. Ver- bal examination on motor- trucks Aerial observation, which consists of fighting in the air, recon- naissance and map-reading Engines Inspection Training at Army Aviation Schools Graduates of the Schools of Mihtary Aero- nautics (ground schools) are assigned through the Aero-Personnel Division in cooperation with the O. & T. Section, to the various aviation school squadrons for instruction in actual fly- ing. From this point on the flying students are in charge of the O. & T. Section. Following is a list of the location of aviation school squadrons organized and to be organized in the near future. As time goes on, doubtless this schedule will be extended. Mineola, N. Y. — Operating. Mt. Clemens, Mich. (Selfridge Field).— Operating. Fairfield, O. (Wilbur Wright Field) .—Op- erating. Rantoul, 111. (Chanute Field). — Operating. So. Mississippi Valley. — Under investiga- tion. San Antonio, Tex. — Operating. San Diego, Calif.^Now operating. Belleville, 111. — Operating. One station to be in Rocky Mountain Re- gion. Fort Sill, Okla. (advanced school operating) . At the above schools training is done with as much rapidity as possible. At the conclusion of from fifteen to twenty-five hours' flying, it is expected students will be able to pass tests for certificates as Reserve Military Aviators. While undergoing this flying instruction, the 186 TEXTBOOK OF MILITARY AERONAUTICS Training America's first thousand aviators. The photo shows three training aeroplanes in the air at one of the training fields. pupil is required to study radio, gunnery, pho- tograph}', motors and aeronautical engineering. This study is practical; the student handles and operates everj' instrument, assembling and dis- assembling engines, and does construction and repair of aeroplanes to the extent that he must assemble, disassemble, line-up, etc. In the ^nnery instruction, for instance, the student uses a machine in which a gun is mounted and is given target practice at objects moving in the air. Upon receiving their certificate, these flying students are commissioned as First Lieuten- ants, Signal Officers' Reserve Corps, Aviation Section, and when on duty involving frequent or continuous flying, receive twenty-five per ■cent, increase in pay. The base pay is $2,000 a year. When on foreign duty ten per cent, in- crease on the base pay is allowed. Quarters are also furnished. Standard aero-squadrons of the army are formed at the aviation school squadrons. The flying and enlisted personnel for these squad- rons is furnished from these flying schools. The officers, of course, are Reserve Military Aviators by this time, though some may be Junior Military Aviators. The enlisted men are of the Enlisted Reserve Corps, or of the Regular Army. These areo-squadrons, thus formed, will be fully equipped, save as to aeroplanes, and trans- ported to England or France for advanced training. These graduated aviators (R. M. A.'s) may also be sent to complete the complement of areo- squadrons already in process of formation or partially filled, to be maintained at certain points. Tests for an Aviator's Certificate In different stages of training the student or mihtary aviator may go through tests and ob- tain the following certificates: (1) The F. A. I. Certificate. This is the international certificate issued under the rules of the International Aeronautic Federation by the Aero Club of America. It represents the federation in the United States and in other countries on the American continent which do not have a national areo club affiliated with the International Aeronautic Federation. It is necessary to have this certificate to enter aeronautic meets, and to have records homolo- TRAINING AVIATORS FOR UNITED STATES ARMY 187 gated and accepted by the International Aero- nautic Federation. Following are the rules under which F. A. I. certificates are granted by the Aero Club of America : 1. A person desiring a pilot's certificate must apply in writing to the Secretary of the Aero Club of America. He must state in his letter the date and place of his birth, and enclose therein two unmounted photographs of himself about 2^/4 X 21/^ inches, together with a fee of five dollars. In case the applicant is a natural- ized citizen of the United States he must sub- mit proof of naturalization. 2. On receipt of an application the Secretary will forward it promptly to the Contest Com- mittee, which, in case of an application for an aviator's certificate, will designate a representa- tive to supervise the test prescribed by the In- ternational Aeronautical Federation, and will advise the representative of the name and loca- tion of the applicant and, through the Secre- tary, advise the applicant of the appointment of the representative to take the test. 3. In case the application is for a spherical balloon or for a dirigible balloon pilot's certifi- cate the applicant will be fully advised by the Contest Committee. 4. All applications for aviator's certificates must reach the Secretary a reasonable time in advance of the date that the applicant may ex- pect to take the required test. 5. No telegraphic applications for certificates will be considered. Applicants for each class of certificate must be of the age of 18 years, and in the case of dir- igible certificates 21 years, and must pass, to the satisfaction of the properly designated rep- resentatives of the Aero Club, the tests pre- scribed by the F. A. I., as follows: Spherical Balloon Pilot's Certificate Candidates must pass the following tests: (A) Five ascensions without any conditions. (B) An ascension of one hour's minimum duration undertaken by the candidate alone. (C) A night ascension of two hours' mini- mum duration, comprised between the setting and the rising of the sun. The issue of a certificate is always optional. Dirigible Balloon Pilot's Certificate Candidates must be 21 years of age. They must hold a spherical balloon pilot's certificate and furnish proof of having made twenty (20) flights in a dirigible balloon at different dates. They must also undergo a technical examina- tion. A group of aviation students at one of the army training fields. 188 TEXTBOOK OF MILITARY AERONAUTICS In case, however, the candidate does not al- ready possess a spherical balloon certificate, he must have made twenty-five (25) ascensions in dirigibles before he can apply for a certificate. The application for the certificate must be countersigned by two dirigible balloon pilots, ■who have been present at at least three of the departures and landings of the candidate. The issue of the certificate is always optional. Aviator's Certificate 1. Candidates must accomplish the three following tests, each being a separate flight : A and B. Two distance flights, consisting of at least 5 kilometers (16,404 feet) each in a closed circuit, without touching the ground or water, the distance to be measured as described below. C. One altitude flight, during which a height of at least 100 meters (328 feet) above the point of departure must be attained; the de- scent to be made from that height with the motor cut off. A barograph must be carried on the aeroplane in the altitude flight. The landing must be made in view of the observers, without restarting the motor. 2. The candidate must be alone in the air- craft during the three tests. 3. Starting from and landing on the water is only permitted in one of the tests A and B. 4. The course on which the aviator accom- plishes tests A and B must be marked out by two posts or buoys situated not more than 500 meters (547 yards) apart. 5. The turns around the posts or buoys must be made alternately to the right and to the left, so that the flight will consist of an uninter- rupted series of figures of 8. 6. The distance flown shall be reckoned as if in a straight line between the two posts or buoys. 7. The landing after the two distance flights is tests A and B shall be made: (a) By stopping the motor at or before the moment of touching the ground or water; (6) By bringing the aii-craft to rest not more than 50 meters (164 feet) from a point indicated previously by the candidate. 8. All landings must be made in a normal manner, and the observers must report any ir- regularities. The issuance of the certificate is always op- tional. Official observers must be chosen from a hst drawn up by the governing organization of each country. Hydroaeroplane Pilot's Certificate The tests to be successfully accomplished by candidates for this certificate are the same as An instructor enlifthtening future air- men in the intricacies of coast defense. TRAINING AVIATORS FOR UNITED STATES ARMY 189 those for an aviator's certificate, except that starting from and landing on the water is per- mitted in all of the tests. United States Army Preliminary Flying Test (a) Three sets of figures 8 around pylons 1600 feet apart. In making turns around pylons, all parts of machine will be kept within a circle whose radius is 800 feet. (b) Stop motor at a minimum height of 300 feet and land, causing machine to come to rest within 150 feet of a previously designated point. (c) An altitude test consisting of rising to a minimum height of 1000 feet. (d) Glides with motor throttled, changing direction 90° to right and left. Note. — (a) and (b) may be executed in one flight; (c) and (d) in one flight. The same rules apply in starting from and landing on water. Special attention will be paid to the character of landings made. Report of these tests will be submitted to the officer in charge of the aviation section, with the information as to whether or not the school will complete the training of the aviator through the reserve military aviator stage. If the preliminary flying test is passed satis- factorily and a candidate qualifies in other re- spects, he will be eligible for further instruction to qualify as a reserve military aviator. United States Army Reserve Military Aviator Test Reserve Military Aviator Test. The reserve military aviator test will be as follows : (1) Climb out of a field 2000 feet square and attain 500 feet altitude, keeping all parts of ma- chine inside of square during climb. (2) Glides at normal angle, with motor throttled. Spirals to right and left. Change of direction in gliding. (3) At 1000 feet cut off motor and land within 200 feet of a previously designated point. (4) Land over an assumed obstacle 10 feet high and come to rest within 1500 feet from same. (5) Cross-country triangular flight of 30 miles, passing over two previously designated points. Minimum altitude 2500 feet. (6) Straight-away cross-country flight of 30 miles. Landing to be made at designated des- tination. Both outward and return flight at minimum altitude of 2500 feet. (7) Fly for 45 minutes at an altitude of 4000 feet. Any candidate who successfully passes the Reserve Military Aviator tests will, on apphca- tion, be granted the "Expert Aviator" certifi- cate by the Aero Club of America. An aviator desiring this certificate must apply in writing to the Secretary of the Aero Club of America, 297 Madison Avenue, New York City, sending the report of his R.M.A. tests, certified by the com- manding officer of the school, by one of the of- ficers who witnessed the tests, or by one of the officers of the administrative staff, together with the sum of $5. The tests for the R.M.A. certificate are ac- cepted in place of the club's own tests for the Expert Certificate. These are as follows : 1. A cross-country flight from a designated starting point to a point at least 25 miles distant, and return to the starting point without alight- ing. 2. A glide, without power, from a height of 2500 feet, coming to rest within 164 feet of a previously designated point, without the use of brakes. 3. A figure 8 around two marks 1640 feet apart. In making turns the aviator must keep all parts of his apparatus within semicircles of 164 feet radius from each turning mark as a cen- ter. Enlisted Aviators Observer Junior Military Aviator Aviation Mechanicians. All enlisted men except aviation mechanics and en- listed aviators. The uniform insignia of the U. S. Aviation Service. Military Aviator CHAPTER XV REGULATIONS FOR UNIFORMS OF U. S. AERONAUTIC PERSONNEL Regulations and Specifications for the Uniform of Officer Aviators and Enlisted Men OF the Aviation Section of the Signal Corps Approved June 22, 1917, by the Secretary of War Uniform Specifications Body, to be double breasted, loose sack coat of soft russet leather, standard-lined through- out with kersey; to be easy fitting throughout, buttoned down the side with five large horn but- tons. Collar, standing and falling; standing, to be closed in front with hook and eye, and to be about one inch high ; cloth of the collar to be of the same material as the coat, and not less than four inches, or more than five inches in width, an attachable flap of the same material as the coat, five inches in length and two inches in width, with buttonhole in each end to close the front of the collar when worn closed. Pockets, two large hip pockets covered with a flap, slightly rounded at the corners, the open- ing to be horizontal and nine inches across ; one large breast pocket on the left side with eight- inch vertical opening at the center line of the body, the pocket to slope down to the left. All pockets to be patch. 190 Skirt, to extend one third of the distance from the point of the hip to the bend of the knee, ac- cording to the height of the wearer. Shoulder Looj^s, on each shoulder a loop of the same material as the coat, let in at the sleeve head-seam and reaching to the edge of the col- lar, buttoning up at the upper end with a small horn button, loops to be about two inches wide at the lower end, and one inch wide at the collai end, and cross-stitched throughout the entire length. Sleeves, to have flaps with buttons to tighten sleeve around the wrist, one buttonhole in the flap, with two buttons on the sleeve for adjust- ing. Coats, Aviator, Anti-Sinking Body, to be single-breasted, sack coat of ga- berdine with the anti-sinking material quilted between the outside and the lining, quality and quantity of the anti-sinking material to be of the approved standard, to button down the front with five horn buttons; sleeves not to be quilted. I REGULATIONS FOR UNIFORMS OF U. S. AERONAUTIC PERSONNEL 191 Collar, to be a folding collar with a fold not more than two inches, the coat to fit snugly around the neck. Pockets, two pockets, patch, one on each hip. Six inches horizontal opening without flaps. Skirts, quilted skirt to extend one third of way to knee from the hip, according to the height of the wearer. Shoulder Loops, on each shoulder a loop of same material as the coat, let in at the sleeve head-seam, and reaching to the edge of the col- lar, buttoning at the upper end with a small coat button ; loops to be about two inches wide at the lower end and one inch wide at the collar end, and cross-stitched throughout the entire length. Face Mask, Aviators To be made of chamois in the proper shape to conform to the general shape of the head ; skirts to lay flat on the shoulder and chest, and to be about six inches long. Eye, nose, and mouth holes to be cut in the proper place for each in- dividual wearer. Flying Suit To be made of gaberdine of approved quality, unlined. Body, a one-piece suit with opening in front from crotch to neck; fastened together with seven horn buttons. Collar, a falling collar with one and one half inch fall, fitting snugly around the neck. Shoulder Loops, on each shoulder a loop of gaberdine let in at the sleeve head-seam, and reaching to the edge of the collar, buttoning at the upper end with a small coat button ; loops to be about two inches wide at the lower end, and one inch wide at the collar end, and cross- stitched throughout. Pockets, to have two breast pockets, one on the right breast to have an eight-inch horizontal opening with button flap the height of armpit; the one on the left side to have a vertical open- ing nine inches in length without flap, but with button provided for closing; pocket to be large and extend in a downward direction toward the left hip. Sleeves, sleeves to extend well down on the hand, and to be furnished with flaps for tighten- ing around the wrist, flaps to be of the same ma- terial as the suit, with two buttons for adjusting. Legs, to extend down to the ankles, fitting rather loosely, with a flap at the bottom of each leg for tightening around the ankle; two but- tons for adjusting to be furnished. Buttons, all buttons to be of horn, and of suit- able size for the purposes for which they are to be used. Gloves, Aviator, Winter To be made of buckskin or pliable russet leather of approved quality, lined with fleece of unborn lamb. Hand of glove to be of the mitten type, with the thumb compartment sufficiently large to permit of its being withdrawn and placed with the fingers. There shall be a slit across the in- Summer flying suit of moleskin cloth, unlined, with winter cap of soft tan-colored leather. 192 TEXTBOOK OF MILITARY AERONAUTICS terior of the hand, which will permit the fingers being extended in the opening, the slit must be sufficiently overlapped so that ordinarily it will remain closed. Cuffs to be of the gauntlet type, made of soft leather and extending about one half the way up to the elbow, and to be the same color and material as the glove proper; the fur in the glove to extend two inches up the gauntlet from the wrist joint; a strap to be furnished for tight- ening the glove around the wrist. Gloves, Aviator, Summer To be the regular gauntlet type of soft un- lined buckskin or russet leather, with soft gaunt- let extending about one half the way to the elbow. Goggles Transparent part to be made of triplex glass ; mounting for the glass to extend well away from the eyes; the part of the goggles nearest to the face to fit snugly, and conform to the general shape of the face in order to keep out the wind ; an adjustable elastic tape to be furnished to hold the goggles in place. Amber or clear glass to be used, according to the desire of those wearing them. Helmet, Aviators, Summer To be of the football type, of brown pliable sole leather, to be shaped to conform to the head and cover the entire head except the face. Ear flaps are to be attached for the protection of the ears, and by having shields to keep out the wind. The entire helmet is to be lined with felt one inch thick, and to be fastened under the chin with an elastic tape and tie string; proper holes for ventilation will be placed over the entire top of the helmet. Helmet, Aviators, Winter To be of soft russet leather lined with fur; to he shaped so as to cover the entire head ex- cept the face; to be fastened under the chin with a .strap and buckle or patent snap, the front of the helmet to extend down to the eyebrow. Aviation Service Officers of the Aviation Service who are Mil- itary Aviators shall wear an insignia on the left breast, the insignia to be embroidered in silver on blue background, and shall be two wings with the shield between; the wings shall be three inches from tip to tip, each wing shall be one and one eighth inches long, and nine sixteenths inch wide at the contour ends; the shield shall be nine sixteenths inch high and five eighths inch wide, with the letters "U. S." one quarter inch high in the center below the horizontal cross lines. See exhibit A. Junior Military Aviators shall wear on their left breast the same insignia described for the Military Aviator, except that the right-hand wing shall be omitted, the insignia consisting of one wing to the left of the shield. All officers in the Aviation service shall wear the Signal Corps crossed flags on their collar. See Ex- hibit A. C'liiiiiKii^ skin iiiii^k iinil Ic.'itlicr coat REGULATIONS FOR UNIFORMS OF U. S. AERONAUTIC PERSONNEL 198 Mufflers Mujflers: To be closely- woven wool or cam- els' hair, O. D. color, sixteen inches wide and one and one half yards long, the ends to be made up with a fringe the same as those in common use. Shoes, Aviator, Winter To be of soft russet leather, lined with fleece, and extending one half way to knee; to have heavy sole, and made in the boot form or to be laced up wholly or partially in the front. Boots, Rubber, Wading (wading pants) To have regular boot feet, but the legs to ex- tend up in regular trouser form, the top to be at a height just under the armpits; adjustable sus- penders to be furnished for holding the tops up. Breeches, Winter, Motorcycles To be made of gaberdine, the same shape and style as the service breeches as issued. They will be lined with kersey throughout. Face Mash, Goggles, Helmet: Same as for summer. Hood: To be closely -woven O. D. wool, and cover the entire head except face; to fit snugly ■and extend well down on shoulders; must cover forehead down to eyebrows. Insignia, Sleeve Enlisted men of the Aviation Section shall have a navy blue cap let in at the sleeve head- seam and extending down the sleeve five and one half inches from the point of the shoulder. All men as hereinafter specified will wear the in- signia as described. A four-bladed propeller with center three and three fourths inches from point of shoulder, embroidered in white; the propellers to be two inches in diameter, two of the blades horizontal and the other two vertical; three fourths of an inch above the top tip of the vertical propeller l)lade a figure showing the number of the squad- ron to which the man belongs, one inch high, and embroidered in white. See Exhibit C. Aviation mechanician, same as above with a white embroidered circle added, inside of circle to be one and one fourths inches from center of the propellers, outside of the circle to be one and three eighths inches from the center of the pro- pellers. See Exhibit B. Enlisted aviator, on the same blue back- ground shall be embroidered in white, the in- signia as hereafter described. A pair of wings with a five-inch spread with crossed propellers between them, each wing to be one and seven eighths inches long and seven eighths of an inch high at the inner edge. Propellers to be one inch across. One fourth inch above the top tip of the vertical propeller shall be embroidered the number of the squadron to which the man belongs in figures one half an inch high. See Exhibit C. Leg gins: All mounted men, and enlisted men of the Aviation Section, Signal Corps, canvas with leather reenforcement, as issued. Muffler: Same as for aviators. Overalls, Mechanics: To be of standard denim material, but made in one piece, to open up in front from crotch to neck, and button up with seven small buttons, to fit snugly around the neck, with no collar, each sleeve to be pro- vided with a flap for tightening around the wrist; to have two hip and two back pockets, each pocket to have a six-inch opening, the legs to extend to the ankles, and to be provided with flaps for tightening around the ankles. Changes In Regulations for the Uniforms of the United States Army, 1914, to Cover Aviation Special articles of clothing for aviation pur- poses are provided and authorized as indicated hereafter. They are in addition to the usual ar- ticles of clothing for garrison and field service. All officers and enlisted men on duty in the Aviation Section will obtain them on memoran- dum receipt from the Quartermaster. They will be held in addition to all the other clothing as required by these regulations. Breeches for Motorcycle Messengers: In cold weather motorcycle messengers in the Avi- ation Section will wear kersey-lined gaberdine 194 TEXTBOOK OF MILITARY AERONAUTICS breeches of standard pattern over their service breeches. Officers detailed in the Aviation Section and qualified as Mihtary Aviators will wear the double or if quahfied as Junior Military Av- iator the single wing shield over their left breast. Officers detailed in the Aviation Section of the Signal Corps will wear the following insig- nia to show their qualifications : Military Aviator: A silver-embroidered double wing shield on the left breast, above the line prescribed for badges and medals. Junior Military Aviator: A single wing sil- ver-embroidered shield on the left breast, above the line prescribed for badges and medals. Rubber Wading Boots (wading pants): For use of officers and enlisted men on duty with Hydroaeroplane Squadrons, rubber wading boots with the top extending up, in the form of breeches, well beneath the armpits will be fur- nished. They will be held up by adjustable suspenders. Coats, Leather, Aviator (or in case of water squadron, anti-sinking coats) : Will be worn while engaged in flying, except in the trop- ics, where the leather coat may be dispensed with. Face Mask: Of chamois, will be worn by of- ficers and enlisted men flying or enlisted men riding motorcycles in cold weather. Flying Suit: A one-piece flying suit of gab- erdine used by all officers and enlisted men while flying. It will be worn under the leather coat. Winter: They will be worn by chauffeurs and motorcycle messengers of the Aviation Section of the Signal Corps during cold weather. Aviator: While engaged in flying, aviators will wear gloves prescribed, fur-lined mittens with gauntlet tops will be worn in cold weather, and the plain buckskin or leather gauntlets in warm weather. Goggles: Improved type of triplex goggles will be worn by all aviators and motorcycle mes- sengers in the Aviation Section of the Signal Corps while engaged m their respective duties. Chauffeurs will wear them in the winter. Clear Brigadier-General B. D. Foulois, wearing the military aviator insignia. or amber colored glass, according to the desire of the person using them. Blue denim hat will be worn by enlisted men of the Coast Artillery, Quartermaster Corps, Aviation Section of the Signal Corps and Field Companies of the Signal Corps, when on duty on cable ships, with the fatigue uniform. Helmets. Aviators and Motorcycle Messen- gers, will wear special helmets prescribed. In the summer they shall be of pliable russet leather, lined with felt ; in the cold weather, avia- tors will wear a fur-lined soft russet leather helmet. On the shoulder loops of the ser\'ice and white uniforms, and aviators' outside suits or coats, metal insignia of rank will be worn as fol- lows: Enlisted men of the Aviation Service will wear embroidered insignia on the right sleeve just below the shoulder as follows: Enlisted men in the Aviation Section will wear a white embroidered insignia with crossed propellers, with the number of their squadron REGULATIONS FOR UNIFORMS OF U. S. AERONAUTIC PERSONNEL 195 above, on blue background, on the upper, right sleeve. Aviation mechanicians will have in addition, a white, embroidered, circle around the propel- lers. Enlisted aviators will wear an insignia with double wing, crossed propellers with the numer- ical designation of the squadron embroidered on the blue background on the upper right sleeve. Mufflers: Aviators, motorcycle messengers and chauffeurs of the Aviation Section will wear an O. D., closely-woven wool muffler dur- ing cold weather. While doing fatigue, enlisted men of the Avi- ation Section will wear a one piece denim me- chanic's overalls, as authorized. Officers, Aviation: A soft russet leather fleece-lined, high-top shoe with heavy sole will be worn by officer aviators while flying during cold weather. Enlisted men aviators, and motorcycle messengers will wear high-top russet leather, heavy-soled shoes, lined with fleece, dur- ing cold weather, while flying or riding motor- cycles. Aviators and Motorcycle Messengers will wear special, closely-knit, all-wool, coat sweater during cold weather. Aviation Officers: In addition to the articles listed under "a" and "b" for mounted and dis- mounted officers, officers acting as pilot will se- cure and have in their possession the following articles : I 1. Aviator's winter helmet. 2. Aviator's summer helmet. 3. Clear or amber, triplex glass goggles. 4. Muffler. 5. One-piece flying suit. 6. Leather coat. 7. Aviator's winter gloves. 8. Aviator's summer gloves. 9. Aviator's winter shoes. 10. Aviator's sweater. 11. Aviator's face mask. Note: In case of the officer being with a water squadron, an anti-sinking coat will be sub- stituted for the leather coat. UNIFORMS OF THE UNITED STATES ARMY Table of Occasions Officers Service Uniform and Equipment Occasions By whom Articles E. In minter. 1. Aviator's winter helmet. 2. Face mask. 3. Goggles. 4. Muffler. S. Flying suit. 6. Aviator's winter gloves. 7. Aviator's shoes. 8. Sweater. 9. O. D. Shirt. 1. For all offi- 10. Service breeches. cer aviators U. Leather Coat. , ,-, . and observ- 4. For garri- ^^^ E. ^°° ''"ty engaged in In summer. flying land 1. Aviator's summer hel- machines. met. 2. Goggles. 3. One-piece flying suit. 4. Leather coat. 5. Aviator's summer gloves. 6. O. D. Shirt. 7. Service breeches. 8. Russet leather shoes. 9. Russet leather leggins. In tropics. Same as summer except omit leather coat. Note 1. For water machines substitute in winter anti-sinking coat for leather coat. In summer, substitute anti- sinking coat for leather coat. In tropics, substitute anti-sinking coat for flying suit and leather coat. E. Add to garrison uniform. On person 1. Identification tag. 2. First aid packet and pouch. For all officer 3. Watch, aviators a n d 4. Notebook and pencil. 5. For field observers while 5. Compass. duty engaged in fly- inff. In machine 1. Haversack containing meat can, knife and fork, and spoon. 2. Canteen with cover. 3. Cup. 4. Field Glasses for Observ- ers only. Note: — When not flying, aviators and observers will substitute campaign hat for aviator's head gear. helmet. la. Enlisted Men Winter 1. Aviator's winter 2. Face mask. 3. Goggles. For garri- All enlisted avi- 4. Muffler. son duty ators and ob- 5. Flying suit. while en- servers. 6. Aviator's winter gaged in T. Aviator's shoes. flying- 8. Sweater. 9. O. D. Shirt. 10. Service breeches. 11. Leather coat. gloves. 196 TEXTBOOK OF MILITARY AERONAUTICS Occasion* By whom. Articles Summer. I. Aviator's summer helmet. J. Goggles. 3. One-piece flying suit. 4. Leather coat. 5. Aviator's summer gloves. 6. O. D. Shirt. 7. Service breeches. 8. Russet leather shoes. 9. Russet leather leggins. In tropics. Same as summer. Omit leather coat. Ic. Ic. For men tend- ing. t'oT garri- son duty, For Chauffeurs. .\ VI all on Section. Winter. For garri- son duty. For mechanl- Aviation cians. Section. Winter cap. Alasl«an Pea Jacket. One piece mechanic's suit. O. D. Shirt. Service breeches. Russet Shoes. Arctics. Gloves, woolen. 1. 2. 3. 4. S. 6. 7. 8. Summer. 1. Blue Denim hat. 2. One piece suit, me- chanics. 3. O. D. Shirt. 4. Service breeches. 5. Russet shoes. Tropics. Same as summer. Omit shirt and breeches. Water Machines. Add wading pants, and omit one piece suit. Winter 1. Winter cap. 2. Goggles. 3. Muffler. 4. Alaskan Pea Jacket. 5. Aviator's winter gloves. 6. O. D. Shirt. 7. One piece mechanic's suit. 8. Service breeches. 9. Leggins, leather. 10. Russet shoes. Oceation lb. For garri- son duty. Aviation Section. By who m. A rticles Summer. 1. Service cap. 2. One piece mechanic's suit. 3. O. D. Shirt. 4. Service breeches. S. Leather leggins. 6. Russet shoes. Tropics. Same as summer, except. omit O. D. Shirt, and service breeches. Winter. 1. Aviator's winter helmet. 2. Hood. 3. Goggles. 4. Face Masks. S. Muffler. 6. Alaskan Pea Jacket. 7. Fleece-lined gauntlets. 8. Kersey-lined breeches. 9. Aviator's winter shoes. 10. O. D. Shirt. 11. Service breeches. 12. Leather leggins. For all motor- Summer. cycle messen- 1. Aviator's summer hel- gers. met. 2. Goggles. 3. One piece mechanic's suit. 4. Gloves, summer, aviators. 5. Leather leggins. 6. O. D. Shirt. 7. Service breeches. 8. Russet shoes. 6a. For Field Service for Aviation Tropical. Same as summer, except omit gloves, O. D. Shirt, and service breeches. For enlisted aviators. For motorcycle men. ^dd to garrison uniform. For mechani- 1. Identification tag. cians. For Chauf- feurs. J CHAPTER XVI AERONAUTIC MAPS Maps have always been most important fac- tors in military and naval operations, as they have been important factors in peaceful travel over land and water. A map is as important to the aviator as it is to the navigator at sea. As the mariner's chart must tell the navigator of currents, depths of water, and location of rocks and reefs, so the aeronautic map must tell the aviator the char- acter of the land and the configuration of the bodies of water below him. It must show the land as it is, the exact shape of cities, woods, and lakes; the trend of rivers, railroads, and roads; it must indicate clearly the prominent land- marks and the established aerodromes and open fields suitable for landings, etc., etc. In other words, the aeronautic map must show the con- tours and configuration of the land as closely as possible to the way it looks to the aviator from the air. Five Types of Aeronautic Maps There are four types of aeronautic maps used in the present war, and one type is in prepara- tion in the United States. The former are as follows : (1) The General Aeronautic Map. — This is based on existing maps, usually on a scale of 1 :200,000, but differs from the average maps in that the roads are shown in red, the railroads in black, forests and woods in green, and water- ways in blue. (2) The Special Aeronautic Map. — (Illus- trated herewith.) Besides including every- thing in the first chart, this shows aerodromes for aeroplanes and dirigibles, landing fields where there are no hangars, stations where gas for dirigibles is obtainable, the approximate shape of cities, towns, and villages, and such landmarks as prominent churches, railroad sta- tions, windmills, smokestacks, castles, and mon- uments. These maps are used in long-distance flights and raids. When a flight is planned the avia- tors go over the map, lay down the route to be followed, and study the details given on the map, together with any other information they may be able to obtain regarding the configura- tion of the land over which they will fly, possible landing places, etc. It is needless to add that the aviators make every effort to ascertain as nearly as possible the nature of the enemy coun- try, in order to recognize the locations where bombs are to be dropped, as well as where anti- aircraft guns are most apt to be waiting. (3) The Special Aeronautic Map for Per- manent Aerial Routes. — This gives only im- portant information required by the aviator to travel over a certain route. This type of map, which is illustrated herewith, originated in Italy, and has not yet been put into general use out- side of Italy. It is a most remarkable map. The rivers and lakes are shown in blue, in their exact form. The roads are given in brown, the railroads in black. The ajiproximate shape of cities and towns is given in black, and the most prominent building of each city or town, to be used as a landmark, is reproduced. The woods and forests are also shown; and the elevation at different points is given in meters, so that the pilot can rise in case he is caught in a fog after passing a given place, and thus avoid flying into a hill. In view of the fact that his altimeter or barograph gives only the altitude above sea- level, or the altitude from the point of start, it is necessary for the aviator to know the ap- proximate elevation of the land below. The aerial route to be followed, which is permanent, is marked in red dotted lines. The aerodromes are shown in red circles; the land- ing-places which permit landing from two points 197 198 TEXTBOOK OF MILITARY AERONAUTICS are indicated by two red dots of the same size, connected with a red line; the landing-places which permit landing only from one side are indicated by one red dot, connected by a short line and a smaller red dot. These dots are most important, as the large dot represents the ap- proximate place where the wheel of the aero- plane must touch on landing. The line that connects it with the smaller dot shows the direc- tion toward which the aeroplane must run in landing. The distance between the first dot and the second is usually about 300 meters, and the width is usually about 100 meters. This type of map greatly facilitates aerial navigation. (4) The Photographic Map of Sectors. — Military operations are based on these maps. This style of map is most important, and is cor- rected daily, often several times a day, to include the changes shown by photographs taken by aviators from their aeroplanes. These photo- graphic maps show the configuration to the most minute detail and with the utmost care, as the success of certain operations depends upon the exactness of the smallest topographical detail. Aerial photography is now almost an exact science. An aviator at a height of from 6000 to 8000 feet can take a photograph which will include and show clearly all of Manhattan Is- land; and the photograph can be enlarged to show the main streets, docks, bridges, and, of course, the buildings. A series of photographs could be taken from New York to Albany which would permit making photographic maps of the entire route, and show every detail on an exact scale. This could not be accomplished, even with the expenditure of years of time and large sums of money, by any other method. The expert maker of photographic maps quickly fig- ures out the scale, and combines photographs to make a continuous map. An aviator might fly from Albany to New York in what is considered a slow aeroplane at about 70 miles an hour, and take a motion-pic- ture of the entire route, giving the exact topo- graphical conditions, thus permitting the mili- tary authorities within twenty-four hours to conduct operations with absolute certainty as to conditions obtaining throughout this region. (5) The Sj^erry Aeronautic Map. — This type of map is made on the basic principle of the "Special Aeronautic Map for Permanent Air Routes" described above, although it was evolved entirely independently of the latter, and has several improvements. Mr. Lawrence B. Sperry has been working on these maps and with the cooperation of the Committee on Aeronautic Maps and Landing Places of the Aero Club of America, the Aerial League of America, and the Aeronautic Li- brary is preparing a map of the Wilson Airway from New York to San Francisco, which will make it possible for an aviator to fly across the continent without the possibility of losing his way. Maps of the air-routes between New York and Chicago, New York and Newport News, 200 TEXTBOOK OF MILITARY AERONAUTICS Va., and about Long Island, have also been pre- pared and are ready for the insertion of the aerodromes now being established by the Army Air Service and civil organizations, and of other landmarks. The plan is to also show on the map the land- ing-places for twenty-five or fifty miles on either side of the straight route, and eventually to give sketches of the shape of cities and towns, or the more prominent landmarks which strike the eye of the air-traveler. The map being prepared of the Wilson Aerial Highway will cover a straight route from New York to San Francisco, but there will be lines leading from the main line to central land- ing-places, such as Erie, Cleveland, and Detroit. All the headings are magnetic on these maps, and the arrows indicate headings in either di- rection. The true heading from one city to another is determined by projecting the line of flight be- tween these two cities, and then transferring this line, by means of parallel rulers, to the nearest compass rose, from which the true head- ing is obtained. As the difference between the geographical and magnetic North Pole differs at various places on the earth's surface, it is necessary to correct frequently for this differ- ence, which is known as "variation." In the vicinity of Chicago the magnetic needle is found to point to true geographical north, but as the journey is continued eastwardly, the error will be noticed to increase to almost 10 degrees west at New York. As all the headings on this chart have been laid out "magnetic," or with variation taken into consideration, the pilot simply steers his craft on the charted headings. Wherever the variation is east, it is necessary to subtract from the true heading, and when it is west, one must add the necessary number of degrees, in order to obtain the proper indication. As soon as regular air-lines are established to carry passengers and mail, and aircraft start from a given station at a given time daily, there will be added to this map the approximate time at which aircraft will pass certain places, so that the aviator can navigate the air with even less trouble than the sailor navigates the sea. In fact, an aeroplane equipped with the Sperry automatic pilot could be set to follow the com- pass direction in trips of a few hundred miles, and thereafter the pilot would have practically nothing to do, as the automatic pilot would con- trol his machine completely. The pilot would only have to guard against the drift due to side- winds, which he would do by occasionally glanc- ing at his map and looking below to see whether the prominent landmarks checked with the land- marks shown on his map. Knowing the speed of his machine, and having the approximate time required to reach different places, a glance at the watch would tell him at what point he should be at that hour, when he could ascertain whether the landmarks below were similar to those shown on the map. The Map with Photographic Reproduction of Route and Information Regarding Prevailing Winds As soon as large aeroplanes with a broad dash-board are used, it will be possible to make maps larger, and to include on the ipiargins a film reproduction of the entire route, or merely important places. It may also be found advis- able to print on the margin information regard- ing prevailing winds to be met at different altitudes. It may later be found that films can easily be taken of the entire route from New York to San Francisco, and between other control points. Such a film can be enlarged to have a width of between 9 and 12 inches, and the water can be painted blue, the forests and woods green, the roads brown, the railroads black, the aerodromes red, etc. This will furnish an exact map, not only for the aviator, but for other commercial and scientific purposes, such as de- veloping railroads and highways, and surveying for various purposes. It is quite possible that the entire cost of making a photograj)hic aeronautic map of the route between New York and San Francisco will not be found as high as that of surveying a few miles to make an average topographic map. The War Prevented an International Con- vention on Aeronautic Cartography The war prevented the assembling of an in- ternational convention, held under the auspices AERONAUTIC MAPS 201 of the Aero Club of America, to discuss and decide on the basic principles for an aeronautic map of the world to be adopted by all nations. This convention was being ai'ranged in the United States by the Aero Club at the suggestion of Rear- Admiral Robert E. Peary, Chair- man of the Committee on Aeronautic Maps and Landing-Places of the Aero Club of America. Admiral Peary at- tended the Tenth International Geo- graphical Congress, held at Rome in January, 1913, at which the subject of aeronautic maps was discussed. The report of this congress and the principal address delivered were translated from Italian by the writer and printed in "Flying," the organ of the Aero Club of America, for September and October, 1913. At this conference no decision was reached, or action taken, toward adopt- ing basic principles for the making of aeronautic maps, because it was agreed by the delegates, as it had been agreed by the delegates that attended the congress of the International Aeronautic Federation at Vienna in June, 1912, that the first step to be taken should be to agree on a scale and conventional signs to be adopted for an aeronautic map of the world. The aero- nautic map of the world was then to be supple- mented by aeronautic maps of different coun- tries, and of parts of different countries, to be made on the accepted scale with the use of the same conventional signs. It was to bring about this international agree- ment that the Aero Club of America was ar- ranging to hold an international convention in the United States, the object being to do for the world aeronautic map what was done for the world chart, as proposed by the International Geographical Congress at Geneva in 1908. The purpose of this congress was not only to agree on a scale and conventional signs to be adopted for the world aeronautic map, but also to make the necessary arrangements, through diplomatic channels or otherwise, to facilitate the execution of those sheets of this map which overlapped the frontiers of different countries. A Sperry map-holder and map. The war prevented the holding of this con- vention, but the committee on aeronautic maps and landing-places of the Aero Club of America continued its work to advance this project. The members of this committee are as follows: Rear Admiral Robert E. Peary, Chairman; Henry Woodhouse, Vice-Chairman; Bion J. Arnold, Vincent Astor, A. G. Batchelder, George F. Baker, Jr., Captain Robert A. Bart- lett, Bernard H. Baruch, August Belmont, James Gordon Bennett, Cortlandt F. Bishop, Captain Mark L. Bristol, U. S. N.; Starling Burgess, Godfrey L. Cabot, President Aero Club of Xew England; President Manuel Es- trada Cabrera of Guatemala; ISIajor Joseph E. Carberry, U. S. A.; Major C. C. Culver, U. S. A.; Newcomb Carlton; Lieut. Col. Charles De F. Chandler, U. S. A.; Captain W. I. Cham- bers, U. S. 'N.; J. Parke Canning, Roy D. Chapin, Alexander Smith Cochran, Robert J. Collier, Howard E. Coffin, Chairman Aircraft Production Board; Roy U. Conger, Glenn H. Curtiss, Commander Cleveland Davis, U. S. N.; Lieut. F. Trubee Davison, N. R. F. C; Lieut. Col. E. A. Deeds, S. O. R. C; Charles de San Marsano, Charles Dickinson, President Aero 202 TEXTBOOK OF MILITARY AERONAUTICS MIHt&ICItO MLLA OUCAftA SpecUI aeronautic map of permanent aerial routes. Club of Illinois; F. G. Diffin, W. Earl Dodge, Brig. General Robert K. Evans, U. S. A. ; Rear Admiral Bradley A. Fiske, U. S. N.; Elbert H. Gary, John Hays Hammond, Jr.; W. Av- erill Harriman, Alan R. Hawley, William Hawley, Henry B. Joy, Frank S. Lahm, Cap- tain A. B. Lambert, A. S. R. C; Henry Lock- hart, Jr.; Lieut. Robert A. Lovett, R. N. F. C; Harold F. MeCormick, Captain J. C. McCoy, Emerson McMillan, Eugene Meyers, Jr. ; Cap- tain James E. Miller, S. O. R. C; Lieut. Com- mander Henry C. Mustin, U. S. N.; George M. Myers, President Aero Club of Kansas City; J. D. Park, George W. Perkins, Prof. Charles L. Poor, Augustus Post, Ralph Pulit- zer, Col. Samuel Reber, U. S. A.; Ogden Mills Reid, Thomas F. Ryan, Alberto Santos Du- mont, Frank A. Seiberling, Hon. William G. Sharp, Edwin C. Shaw, I^awrence B. Sperry, Brig. General George O. Squier, Chief Signal Officer, U. S. A.; James S. Stephens; Lieut. Commander J. H. Towers, U. S. N.; K. M. Turner, George W. Turney, Col. Cornelius Vanderbilt, W. K. Vanderbilt, L. A. Vilas, Rodman Wanamaker, Monroe Wheeler, Schuy- ler Skaats Wheeler, Harry Payne Whitney, G. Douglas Wardrop, Hugh L. Willoughby, Henry A. Wise Wood, Orville Wright, Wil- liam Wallace Young, A. Francis Zahm. Existing Aeronautic Maps Are the Result of Work by Aero Clubs The existing aeronautic majjs are the result of work done by the Aero Clubs of France, Italy, and United States. The same pioneer sportsmen and volunteers who were responsible for developing aeronautics in the different coun- tries up to the time of the war, were also respon- sible for the first aeronautic maps. The writer well remembers how these pio- neers, now considered as "pioneers and authori- ties in aeronautics" and given credit for having had "wonderful foresight" at that time, were considered visionaries in 1910, as even in 1914f. Few people were willing to admit that aircraft would develop within fifty or one hundred years to such a point that aeronautic maps would be needed for aerial navigation. These pioneers nevertheless went on with their work. AERONAUTIC MAPS 208 In 1910 officials of the Automobile Club of America and the Aero Club of America com- bined their efforts to make a topographical map of Western Long Island for aeronautic pur- poses. The Aero Club of France started, in 1911, to make an aeronautic map of France. This aero- nautic map was to consist of about 100 sheets, 24 of which have already been issued and are used extensively by the French and British Fly- ing Corps. Mr. Charles Lallemand, the well- known French scientist, is the chairman of the aeronautic maps committee of the Aero Club of France. The basic principle on which aero- nautic maps are now being made by the Aero Club of France has been revised so as to bring them up to date and meet military needs. In Italy the work of making aeronautic maps has been shared between the aeronautic authori- ties, the authorities of the Touring Club of Italy, and the members of the National Com- mission of Aerial Touring. The Italian pio- neers in aeronautic toj)ography include Senator G. Celoria, the chairman of the National Com- mission on Aerial Touring; Commander Gio- vanni Roncagli, Royal Italian Navy and secre- tary general of the Tenth International Geo- graphical Congress; Mr. C. Usuelli, and other well-known Italian scientists. The pioneer work of these organizations has been of great value to the military authorities of their re- spective countries during the present war. In France and Italy the Aero Clubs were practi- cally the only sources from which the necessary information covering aeronautic maps could be obtained, as no attention had been paid to this subject before the war by the military authori- ties. CHAPTER XVII HISTORY OF UNITED STATES ARMY AERONAUTICS As related in the chapter on "The Evolution of the ^lilitary Aeroplane," the United States Army holds the distinction of being the first army in the world to acquire an aeroplane. The order for the first Wright machine was placed early in 1908, and tests were made at Fort Myer, Va., in September of that year. These resulted in an accident on September 17, in which Orville Wright, the pilot, was severely which officers of line organizations could serve on special details. Lieut. Foulois was sent to San Antonio to teach himself to fly with the Wright machine. Owing to the failure of Congress to allow an appropriation for army aeronautics, the work of developing this branch of the service practically ceased in 1910-11, and officers attached to the Aeronautic Division kept up their practice injured, and Lieutenant E. Self ridge, the pass- mainlv by attending aviation meets and follow- enger, was killed. The next tests took place at Fort Myer in July, 1909. This machine was accepted by the Government, and Lieutenants Frank Purdy Lahm and Benjamin D. Foulois were assigned to receive instruction from the Wrights. An aviation camp was established at College Park, Md., and Captain Charles DeF. Chand- ler, then disbursing officer of the Signal Corps, was appointed Officer in Charge of the Aero- nautic Division. The following officers were taught to pilot the Wright machine by Wilbur Wright during October and November, 1909: Captain Charles DeF. Chandler, Lieutenant F. P. Lahm, Lieutenant Benjamin D. Foulois, Lieutenant Frederick E. Humphreys, Lieuten- ant T. deWitt Milling, Lieutenant H. H. Ai-- nold, and Lieutenant George C. Sweet, the last being assigned by the Navy Department. The first dirigible, delivered to the United States Army by Captain Thomas G. Baldwin, was first flown at Fort Myer with Lieutenant Frank P. Lahm of the 7th Cavalry in charge, and then was sent to Omaha in the autumn of 1909, with I^ieutenants R. S. Bamberger of the 2nd Cavalry, John G. Winter of the 6th Cav- alr)% and Oliver A. Dickinson of the .5th Infan- try in charge. These officers and I^ieutenant Frank P. Lahm were subsequently returned to duty with their respective regiments, because of regulations prescribing a time limit during 204 ing the development of civilian aviation. During the jNIexican outbreak in February and JNIarch, 1911, the United States Army had no aeroplanes to send to the Mexican border. It was enabled to put an air scout at the dis- posal of the Government through the courtesy of ^Ir. Robert J. Collier, the president of the Aero Club of America, who loaned the army his Wright aeroplane. With this machine Lieu- tenant B. D. Foulois and Mr. P. O. Parmalee, made a number of flights along the Mexican border, reconnoitering and carrying messages from General Carter to jSIajor George O. Squier. During the winter of 1911 I^ieutenant Paul W. Beck, G. E. :M. Kelley, and John C. Walker were assigned to take a course of training at the Curtiss Aviation School at San Diego, Cal. They were assigned to duty at San Antonio, Texas, in April, 1911, to fly the Curtiss ma- chines acquired by the United States Army. The first army officer to be granted an F. A. I. pilot's certificate was Lieutenant F. P. Labni. Lieutenants II. H. Arnold and T. deWitt Mil- ling, Captain Charles DeF. Chandler, Lieuten- ant Benjamin D. Foulois, Captain Paul W. Beck, Lieutenant R. Carrington Kirtland. Lieutenant J. W. McClaskey, Ijieutenant Wil- liam C. Sherman, Lieutenant Harry Graiiam, and Captain Frederick B. Hennessey, were the HISTORY OF UNITED STATES ARMY AERONAUTICS 205 next ten army officers to obtain a pilot's certifi- cate. By the Act of Congress of March 3, 1911, there was made available the sum of $125,000 for army aeronautics. This appropriation made it possible to establish a substantial avia- tion camp at College Park, Md. This was moved to Augusta, Ga., during the four winter months of 1912-13. Seven aeroplanes were bought for the United States Army in 1911. Three were Wrights, three were Curtiss machines, and one was a Bur- gess biplane. Important experiments were conducted at College Park during 1911-12, in- cluding the testing of the Lewis gun and the Scott bomb-dropping device; also experiments in sending wireless messages from an aeroplane, map-making, and other pioneer work. Early in 1912 steps were taken to form an aviation section in the Philippines, and one aero- plane in charge of Lieutenant Frank P. Lahm was sent to the islands for that purpose. Lack of funds and shortage of personnel pre- •■^SOfSW^J^^R? The Baldwin dirigible, first and only dirigible acquired by the United States Army up to 1917, being put through the tests, August, 1908. Col. (now Gen.) Squier was the Chairman of the Joint Army and Navy Committee ordered to conduct the tests of the first Army aeroplane in 1908. The above photograph shows the aero- plane in the air at Fort Meyer, Va., on September 12th, 1908, when Orville Wright and Col. Squier, who was the first passen- ger, made a flight of 9 minutes six seconds, which was a record for many months. vented expansion of the air service and exten- sion of the work of the existing organization. The Act of August 24, 1912, appropriated $100,000 for the purchase, maintenance, oper- ation, and repair of aircraft. Twelve aero- planes were bought in that year. Major Sam- uel Reber was put in charge of the Aeronautic Division. The exact number of machines and aviators and the distribution of the United States Army Aviation Squadron in June, 1913, was as fol- lows: Machines OflScers Training High-powered Texas City, Texas 11 6 4 San Diego, Cal 5 1 1 Philippine Islands 1 1 1 Four officers were on temporary duty learn- ing to fly, and Fort Leavenworth, Kansas, had one high-powered machine. 206 TEXTBOOK OF MILITARY AERONAUTICS This photograph, which was taken by James H. Hare, at the Mexican border in 1911, shows Col. (now Gen.) Squier on the left after receiving a message carried by Captain (now Brig.-Gen.) Benjamin D. Foulois and Philip O. Parmalee. The aeroplane was loaned to the Army by Mr. Robert J. Collier, then president of the Aero Club of America. The general equipment of this handful of avi- ators consisted of the barest necessities. The allowances made by Congress in 1911 and 1912 were too meager to afford more than the neces- sar\' aeroplanes, tents, and spare parts, while the 1913 allowance of $12.5,000 was bartely sufficient to replace the wornout machines and afford maintenance. It was not possible, therefore, to acquire motor-truck repair-shops, motor-trail- ers, extra motors, and such other equipment as was absolutely necessary to create an efficient organization. Lacking funds, the Signal Corps was unable to replace the army dirigible, or to extend the aerostatic section. Therefore work in that branch of the service practically ceased. Aeroplanes were first u.sed in military ma- noeuvers in August, 1912. Two machines were assigned to these manoeuvers, in charge of I.,ieu- tenants B. D. Foulois and Harold Geiger, Cap- tain F. B. Hennessey, lieutenant T. deW. Mil- ling, and Lieutenant Harry Graham. A plan to give the army 120 aeroplanes and to establish a number of aviation centers was pro- posed by the Secretary of War in a special re- port to Congress in response to Resolution 444, House of Representatives, March 26, 1912, (House Document No. 718, 62d Congress, 2d Session), but Congress took no action on it. The Act of March 2, 1913, allowed a detail not to exceed thirty officers of the line of the army to aviation duty, and gave extra pay to officers engaged in flying. The Act approved July 18th, 1914, author- ized an increase of the Signal Corps by the addi- tion of an Aviation Section. Previous to the passage of this Act there was no definite provi- sion of law covering the duties of the Signal Corps with respect to aviation. Under this Act the Aviation Section was authorized to have sixty officers and 250 enlisted men. But the shortage of officers in every branch of the service prevented getting more than half that HISTORY OF UNITED STATES ARMY AERONAUTICS 207 number of officers for the aviation section. In 1912 twelve aeroplanes were bought, and in 1913 eight more were added. In 1914 eleven machines were bought, and in 1915 twenty more were secured. The following table gives a list of aeroplanes purchased by the Signal Corps between 1908 and 1916, with their disposition: Aeroplanes of All Types Purchased by the Signal Corps Date. Year 1908 19U 1912 Maker. Disposition. Date. Total. Original Wrightin Smith.sonian Institution 1 Curtiss Condemned February, 1914 Wriglit do do Do Destroyed by accident. . .September, 1912 Burgess Condemned February, 1914 Curtiss do do Wright Destroyed by accident .. .August, 1913.. Curtiss Condemned June, 1914. . . . Burgess do do Wriglit Destroyed by accident. . .February, 1914 Do do July, 1913 .... Do do November, 1913 Do do October, 1913. . Do do November, 1913 Curtiss do April, 1913 .... Wright do June, 1914 .... Burgess do January, 1915. Do do September, 1913 Wright Condemned June, 1914.... Do do do 1913 Curtiss do do Do do October, 1914 . . Do do June, 1914.... Burgess do April, 1915. . . . Do do January, 1915. Do Out of repair August, 1915.. 1914 Year. Maker. DLsposltion. Burgess-Dunne . In commission Wright Condemned June, 1915. . . . Burgess Out of repair Do Condemned August, 1916. . Curtiss do January, 1915. Do do November, 1915 Martin In commission Do Condemned June, 1915. . . . Do do do ...... Curtiss In commission Do do Martin do Do do Burgess Out of repair Curtiss In commission Do do Do do Do do Do do Do Condemned October, 1915. . Do flo August, 1915 . . Do In commission Do do Total. 1915 U Martin do Do do Curtiss do Do do Martin do Do Undergoing tests Do In commission . Do do Do do Do do 12 Total SUMMARY In Smithsonian Institution Destroyed and condemned Out of repair Now in service, distributed as follows : Manila — Hydroplanes 4 San Diego — Flying boats 2 Training machines 9 Mexican expedition 20 59 1 32 3 — 23 Total 59 View of the Signal Corps Aviation Field, College Park, Md., 1912, taken from an Army machine. (From "Flying.") 208 TEXTBOOK OF MILITARY AERONAUTICS The first tests of the now famous Lewis gun were made by United States Aviators. Cap- tain Charles de F. Chan- dler and Lieutenant T. De Witt Milling at Col- lege Park, Md., June 7th- Sth, 1912. The Mexican Campaign Found the United States Army Unprepared Aeronautically Our utter aeronautic unpreparedness was shown in ^larch, 1916, when Villa raided Co- lumbus, Xew JNIexico, and other American lo- calities along the Mexican Border, killing Americans and destroying property. Villa raided Columbus on March 9, and on ^larch 11, Secretary of War Baker ordered General Scott, Chief of Staff, to instruct General Funston to use, as far as possible, the Aero-Squadron sta- tioned at Fort Sam Houston, San Antonio, Texas, in his expedition against Villa. General Funston realized that an aeroplane was easilj' worth 5000 men in the Mexican campaign, and that scouts, other than aerial, faced death in crossing the Mexican Border. As General Funston pointed out: "Villa parties will at times surprise these scouting parties. In ordi- nary warfare our men might, if hopelessly out- nunil)ered and resistance were futile, surrender with safety. To surrender to Villa, however, would be worse than suicide. Villa's men will kill every American they can lay their hands pn. Every encounter with them means a fight to the death for our men." The aero-squadron at Fort Sam Houston in- cluded Captain Benjamin D. Foulois, Captain T. S. Dodd, Lieutenant J. E. Carberry, Lieu- tenant T. S. Bowen, Lieutenant Ira D. Rader, Lieutenant C. C. Chapman, Lieutenant H. A. Dargue, Lieutenant Edgar S. Gorrell, Lieuten- ant W. G. Kilner, and Lieutenant R. H. Willis. These aviators joined General Pershing at Casas Grandes, JSIexico, about 110 miles from the border. The squadron had only eight small, low-pow- ered scout-aeroplanes, not suitable for flights of over 50 miles from their own base and certainly not adapted for the difficult conditions under which the aviators had to fly. It also lacked general equipment required to keep an aero- squadron in the field. On IMarch 27, Secretary Baker made known tliat there were only two aeroplanes in commission for use by the Mexi- can Expedition, and that General Funston had asked for more. In his statement Secretary Baker said: "The wireless coninnuiication is reported to be intermittent, because of the static conditions in the electric field there. For this reason additional importance is given to the re- quest for aeroplane facilities." Congress was asked for an emergency ap- propriation of $500,000 for aeroplanes. Tliis sum was provided on March 28, wlicii the Army Deficiency Bill passed the House by a vote of 878 to 1. HISTORY OF UNITED STATES ARMY AERONAUTICS 209 Lieutenant Colonel George O. Squier, who had been military attache at the United States Embassy at London, was appointed to take charge of the Aeronautic Division of the United States Army. Meanwhile the two available aeroplanes were kept in daily service carrying despatches and reconnoitering between General Pershing's camp at the front and Columbus, N. M. On April 22 a despatch stated that they were out of commission, being repaired at Columbus, and the expeditionary force in Mexico was without air scouts. It was soon evident that the $.500,000 emer- gency appropriation would only meet a frac- tion of the needs, and that the appropriation of $1,222,000 asked for aeronautics for the next fiscal year would be too small to permit start- ing a substantial air service. The Aero Club of America then undertook not only to arouse the country to the need of a substantial air service, but also to create a reserve of trained aviators. For several years previously the Aero Club of America had been urging the expansion of the army air service, and while it had succeeded in creating what little interest there was in the subject, it was far from achieving its aims. These aims were: "To give the United States 5000 aviators, placing this country in the posi- tion of the porcupine, which goes about its daily peaceful pursuits, harms no one, but is ever ready to defend itself." Finding it impossible to get authorization for assigning even 500 army officers to aviation, the Aero Club turned to forming a reserve of Na- tional Guard officers from different states. Pa- triotic citizens contributed to carrying out this plan. Mrs. William H. Bliss contributed through the club the funds necessary to purchase an aero- plane and train officers of the National Guard of New York, starting an aero company at Mineola, Long Island. Lieutenant Raynal C. Boiling was commanding officer of this com- pany, which some months later gave the country a score of good aviation reserve officers. Messrs. Emerson McMillin, T. Jefferson Coolidge, Barend Van Gerbig, and others, made substantial contributions, and the Curtiss Com- pany offered to train an officer from the Na- tional Guard of each state. When Villa raided Columbus the Aero Club offered to present a number of aeroplanes to the United States Army and to supply a number of volunteer aviators. This offer was declined. But when the two aeroplanes in Mexico went out of service and the Carrizal tragedy took place, a request was sent to the club by the sig- The Hangars at the U. S. Army Aviation School at College Park, Md., 1911. 210 TEXTBOOK OF MILITARY AERONAUTICS _! < ! " fijy. Four of the aeroplanes of the First Aero Squadron at Columbus, New Mexico. nal officer for volunteers, and an officer was as- signed to work with the club in mobilizing civil- ian aeronautic resources. The list of volunteers submitted by the club included about fifty civilian aviators and the following National Guard officers. The latter were assigned by their respective Adjutant- Generals, whose names also follow : Arkansas. — Brigadier-General Lloyd Eng- land, the Adjutant-General, detailed Second Lieutenant Forrest Ward to report at the Cur- tiss Aviation School, Newport News, Va., for training. Colorado. — Brigadier General John Chase, the Adjutant-General, detailed Lieutenant Cummings, Signal Corps, National Guard of Colorado, to report to the Curtiss Aviation School, Newport News, Va., for training. Connecticut. — Brigadier General George INI. Cole, the Adjutant-General, detailed Captain Ralph L. Taylor, of the Connecticut Coast Ar- tillery of Stamford, Conn., to report to the Cur- tiss Aviation School, Newport News, Va., for training. Georgia. — Brigadier General Van Holt Nash, the Adjutant-General, detailed Sergeant L. V. Smith to report at the Curtiss Aviation School, Newport News, Va., for training. Kentucky. — Brigadier General II. Tandy Ellis, the Adjutant-General, detailed Lieu- tenant B. Osborn, of the Signal Corps, to report at the Curtiss Aviation School, Newport News, Va., for training. Minnesota. — Brigadier General Fred W. Wood, the Adjutant-General, detailed Geo. M. Palmer to report at the Curtiss Aviation School, Newport News, Va., for training. Nehra.ika.~Br\frad\er General P. L. Hall, the Adjutant-General, detailed Captain Ralph E. McMillin, a licensed pilot, to report at the Curtiss Aviation School, Newport News, Va., to qualify for the "Superior" or "Expert" Li- cense issued by the Aero Club of America. This was in response to the Aero Club of Amer- ica's telegrams sent out March 12. The cost of obtaining tliis license was borne by the National Aeroplane Fund. Netc York.— The Aviation Company of the National Guard of New York, which had been training at the Mineola Aviation Field com- prised the following gentlemen: Captain Raynal C. Boiling; Lieutenant N. Carolin; J. E. Miller; A. B. Thaw, 2d Master Signal Electrician; R. J. Gilmore; First-Class Sergeants P. R. Stockton, F. R. Dick; Quar- termaster Sergeant W. T. Odell; Sergeants J. H. Stevenson and E. A. Kruss; Corporals D. G. Frost, D. R. Noyes, K. B. Hagerty, W. P. Willetts, J. R. Speyers, H. H. Salmon, .Ir., P. J. Roosevelt, F. .1. Hoppin; Privates E. C. Best, F. Boger, Jr., K. J. Bevens, W. W. Con- ant, Jr., A. M. Craig, J. T. Dwyer, A. L. Favre. C. C. Goodrich, P. J. Heiiry, W. T. Howell, J. F. Hubbard, W. C. Jenkins, W. J. Johnson, R. .1. Knowlson, E. McCormick, E. Martin. I). P. Morse, R. M. Olyphant. Jr.. C. H. Reynolds. R. F. Russell, P. I). Smith, J. D. Sullivan, T. F Ward, and Trumpeter W. L. Rockwell. Buffalo, N. v. — Two members of the Buffalo Aero Squadron reported at the Curtiss Aviation .School, Newport News, Va., to receive the same course of training given the militia officers of the various states, detailed for instruction by the Ad- HISTORY OF UNITED STATES ARMY AERONAUTICS 211 jutant-Generals of their respective states. These two men were: Messrs. Willis G. Hick- man and Morgan More. Lieutenant Edward Bagnell was detailed to accompany Captain McMillin to Newport News for training. New Hampshire, — Brigadier General C. W. Howard, the Adjutant-General, detailed Lieu- tenant Ai'thur J. Coyle, of the 1st Infantry, to report at the Curtiss Aviation School, Newport News, Va., for training. North Carolina. — Brigadier General L. W. Young, the Adjutant-General, detailed liieu- tenant D. B. Byrd, of Company F, 2nd In- fantry, to report at the Curtiss Aviation School, Newport News, Va., for training. Ohio. — Brigadier General W. B. Hough, the Adjutant General, detailed Lieutenant R. H. Hoyer, to report at the Curtiss Aviation School at Newport News, Va., for training. Oklahoma. — Brigadier General F. M. Can- ton, the Adjutant-General, detailed Sergeant Harrison Handley, of the Infantry, to report at the Curtiss Aviation School, Newport News, Va., for training. Oregon. — Brigadier General Geo. H. White, the Adjutant-General, detailed Captain Frank W. Wright to report to the Curtiss Aviation School at San Diego, California, for training. Chief Mechanic Bairn, an experienced avi- ator, was detailed to accompany Captain Wright to San Diego to qualify for the "Su- perior," or "Expert," License issued by the Aero Club of America. Tennessee. — Brigadier General C. B. Rogan, the Adjutant-General, detailed Lieutenant Curry A. McDaniels, of the Infantry, to report at the Curtiss Aviation School, Newport News, Va., for training. Texas. — Brigadier General H. Hutchings, Mustering into the Federal Service the First Aero Company, X. Y. X. G., at Mineola, which was started tliicJUL'li tlic icmtrihu- tion of Mrs. William H. Bliss and trained at private expense, dose to $60,000 contributed largely through the Aero Club of America. Most of these men became members of the Signal Officers Reserve Corps. The personnel of the Aero Company, which includes many members of prominent New York families, as mustered in, was as follows: Captain Raynal C. Boiling, Lieutenant N. Carolin, J. E. Miller, A. B. Thaw, 3nd Master Signal Electrician; R. J. Gilmore; First-CIass Sergeants, P. R. Stockton, F. R. Dick; Quartermaster Sergeant, W. T. Odell; Sergeants, J. H. Stevenson, E. A. Kruss; Corporals, D. G. Frost, D. R. Noyes, E. B. Hagerty, W. P. Willets, J. R. Speyers, H. H. Salmon, Jr., P. J. Roosevelt, F. J. Hoppin; Privates, E. C. Best, F. Boger, Jr., K. J. Bevens,"w. W. Conant, Jr., A. M. Craig, J. T. Dwyer, A. L. Favre, C. C. Goodrich, P. J. Henry, W. T. Howell, J. F. Hubbard, W. C. Jenkins, W. J. Johnson, R. J. Knowlson, E. McCormick, E. Martin, D. P. Morse, R. M. Olyphant, Jr., C. H. Reynolds, R. F. Russell, P. D. Smith, J. D. Sullivan, T. F. Ward, and Trumpeter, W. L. Rockwell. 212 TEXTBOOK OF MILITARY AEROXAUTICS i?*- A squadron of American training uiacliincs at one of the Army Aviation Schools in 191G. the Adjutant-General, detailed Lieutenant Byron McMuUen to report at the Curtiss Avia- tion School, Xewport News, Va., for training. Vermont. — Brigadier General Lee S. Tillot- ton, the Adjutant-General, detailed Lieutenant Harold P. Sheldon, of the 1st Infantry, to re- port at the Curtiss Aviation School, Newport News, Va., for training. Virginia. — Brigadier General W. W. Sales, the Adjutant-General, detailed Corporal Greenhow Johnston, of the Signal Corps, Vir- ginia National Guard, to report at the Curtiss Aviation School, Newport News, Va., for train- ing. West Virginia. — Brigadier General John C. Bond, the Adjutant-General, detailed Lieu- tenant Howard F. Wehrle, to report at the Cur- tiss Aviation School, Newport News, Va., for training. As the United States Army had no authoriza- tion to enroll civilians in an aerial reserve corps, the latter applied to the Aero Club of Amer- ica. Applications were received at the rate of one thousand per month. The club urged Con- gress to provide for an aerial reserve, and on May 25, 1916, Mr. Alan R. Hawley, the presi- dent of the club, flew from New York to Wash- ington with Victor Carlstrom, carrying a special edition of the "New York World" containing indorsements from governors and other state authorities of the plan to train 2000 aviators. As soon as the National Defense Act of June 3, 1916, was passed, — an act which provided for the enrolling of officers and men in the Officers' and Enlisted Men's Reserve Corps, — a commit- tee of the club, consisting of jNIessrs. Alan R. Hawley, Congressman Murray Hulbei't, Ralph Pulitzer, Robert J. Collier, and the writer, waited on President Wilson and urged him to authorize the organization of the Aerial Reserve Corps. On July 13, 1916, a telegram from the White House advised the club that the President had authorized the organization of the Aerial Re- serve Corps. In the meantime a most energetic campaign of public education was conducted by the club to bring about an increase of the aeronautical appropriation from $1,222,000, as estimated, to $29,000,000, the sum urged by the club. An Some of the arroplanes In uhp nt the Army Avliitlon Field at Sun Oiego In 1916. i HISTORY OF UNITED STATES ARMY AERONAUTICS 218 The International Aircraft Standardization Committee, which met in Washington, August 14—15, for the first time. Seated, left to right, F. G. Diffin, U. S., Chairman; G. I.. Xorris, U. S.; Lieut. M. Mignot, France; Capt. J. Herck, France; A. B. Rogers, England, and S. G. Payne, England. Standing, P. D. Merica, Bureau of Standards; F. G. Ericson, Canada; W. F. Prentice, Eng- land; Capt. A. Pomilio, Italy; J. S. MacGregor, U. S.; H. Chase and Dr. G. K. Burgess, both of the U. S. Bureau of Standards. amendment, proposed by Congressman Murray Hulbert when it first came before the House, to increase the appropriation to $14,000,000, was defeated on a point of order. An amendment proposed by Congressman James Mann, was adopted, however. This amendment increased the appropriation to $3,500,000. Senator George E. Chamberlain, the chairman of the Committee on Mihtary Affairs, next introduced the amendment in the Senate, and while it met with difficulties, it finally was adopted, the ap- propriation allowed being $13,861,000. This appropriation permitted the Signal Corps to develop the aeronautic division on a more substantial basis, and gave this country a year's start toward improved aerial develop- ments. The Chief Signal Officer, in his report dated October 3, 1916, has stated that there were thirty-nine officers detailed in, and forty-six stu- dents attached to, the Aviation Section. An official report issued October 20 stated that the Aviation Section, "ordered 175 aero- planes for the Army and soon will order 100 hydroaeroplanes and 100 training school ma- chines to be used in training the Army and the National Guard." The report also announced that orders had been signed on that date for the formation at San Diego of the Second and Third Aero Squadrons for the Army, The Report stated further that "the Army has 45 junior military aviators, with a tactical staff of six officers, has 38 officers under instruc- tion at San Diego, where they have been turned out at the rate of eight a month. "Major Charles de F. Chandler of the Signal Corps, who has had practical experience in bal- looning, has been placed in charge of all military balloon work, and bids have been advertised for four army balloons, two spherical and two kite. The balloon section may be established at Omaha or at Akron. "The Army will train officers in flying at San Diego, where it has eleven training machines which are to be increased by eighteen hydroaero- planes. There are six machines at the Mineola training school on Long Island, and twelve un- der order for use there. There are four ma- chines at the Chicago training station and twelve ordered. The army bill appropriated $300,000 for purchase of land in California for aviation school purposes and $300,000 for an- other large tract. A special board is now consid- ering the selection of the second site in the East. "The army has only one thoroughly equipped areo squadron. It is at Columbus, N. M., and has twelve 160-horse-power reconnoissance type of Curtiss aeroplanes, one Curtiss twin-tractor of 200 horse-power. The army also has one aero company stationed in the Philippines for 214 TEXTBOOK OF MILITARY AERONAUTICS coast defense work. It will be raised to aero squadron strength." General Orders Xo. 55 provided that the Re- serve OjBicers of the Aviation Section of the Sig- nal Corps should consist of 296 officers. An order issued September 8, 1916, limited the number of National Guard Officers to be trained in aviation at army schools to fifty. On October 11, 1916, President Wilson au- thorized the creation of the Council of National Defense and appointed seven civihan members of the Advisory Committee of the Council, as follows : Daniel Willard ; Samuel Gompers ; Dr. Franklin H. Martin; Howard E. Coffin; Ber- nard Baruch; Dr. HoUis Godfrey; Julius Ro- senwald. On February 7, 1917, when it became known that the House Committee on Military Affairs in reporting the appropriation for Army aero- nautics for the ensuing year had allowed only $8,000,000 for equipment and $1,000,000 for aeronautic stations, the Aero Club of America started another campaign of public education to get the appropriation inci'eased to a minimum of $50,000,000 and to insure the training of 2000 aviators during 1917. After a meeting of the National Advisory Committee on Aeronautics held March 20-31 an official statement was issued outlining the plans of the Ai-my and Navy regarding the number of aviators to be trained and machines to be or- dered, which read in part as follows : "There are many estimates of our reasonable needs, and the one herewitli presented has been prepared after conferences with as many men as could be reached who have experience or judg- ment quahfying them to express an opinion, and after obtaining as many data as possible from Europe. "Tentative estmiate of annual requirements of aeroplanes ( assumed to be possible of accom- plishment in 1916) : "Attached to an army of 1,000,000 men, 1,000 planes and 1,000 aviators. Thl« photo^aph shows the First Aircraft Production Board in its mcetinff room in the Munsey Huildinp, Wnshintrton, I). C. Prom left to rl(fht: A. G. Cahle, Secretary of the Board; R. L. Montgomery, .Sidney I). Waldon, K. A. Heeds. Hear Admiral David W. Taylor, Chief of the Bureau of Construction and Repair, U. S. N.; Brigadier-General George O. Squler, Chief Signal Oflcer, U. S. A.| Howard E. Coffin, Chairman of the Board. HISTORY OF UNITED STATES ARMY AERONAUTICS 215 Officers at the Mineola aviation station. From left to ripht, sitting: Capt. li. L. Taylor, oliircr in eliarge ul' flying; l.L. Cliurlcs Reed, first aero reserve squadron; Capt. P. A. Carroll, first aero reserve squadron; Capt. Frank T. Coffyn, S. O. R. C. ; Maj. W. G. Kilner, C. O., S. C. A. S., Mineola; Capt. S. W. Fitzgerald, Commanding officer; Capt. Henry, Adjutant, S. C. A. S., Mine- ola. From left to right, standing: Lt. Stroman, photographic department; I,t. Jones, training department; I,t. L. C. Ricker, quar- termaster; Lt. W. P. Willetts, technical department; Lt. Olyphant, fir.st aero reserve squadron; Lt. B. O. Watkins, supply depart- ment; Lt. D. R. Wheeler, supply officer; Lt. H. H. Simons, training department; Lt. Montarial, instructor detailed from French F. C; Lt. Page, technical department. "Attached to our fleet at sea, 200 planes and 200 aviators. "For harbor and seaport defense, 800 planes and 800 aviators. "Total, 2,000 planes and 2,000 aviators. "For training pilots (worn out or broken), 2,000 planes and 400 aviators. "Total, 4,000 planes and 2,400 aviators." Seven weeks after the United States' entry in the war, on May 21, 1917, there was created the Aircraft Production Board, in the Council of National Defense, the personnel of which was as follows: Howard E. Coffin, Chairman; Brig. Gen. George O. Squier, Chief Signal Officer, U. S. A.; Rear Admiral David M. Taylor, of the navy; S. D. Waldon; E. E. Deeds; and R. L. Montgomery. The preliminary announcement of the Air- craft Production Board was as follows : "We now believe America has started on the right road toward working out her destiny in the air and taking the place to which her capacity •entitles her and which the world expects of her. We have been in constant touch for weeks with the aircraft manufacturers on the problem of the quantity production of machines, and the Government authorities are already signing contracts for as many machines as our present appropriation permits. The United States can depend on a minimum of 3500 aircraft of all types for the first year, if Congress authorizes us to proceed. The program we now have in mind would provide for both training and com- bat machines. "The country has made progress in develop- ing aviators. Last month a group of army offi- cers visited the training camp of the Royal Fly- ing Corps at Borden, Ontario, one of the four camps established in Canada and the aviation school at Toronto, where cadets are trained un- der militaiy discipline for the service. In these schools there has been incorporated the latest European experience in the development of this new art of the air. "Our officers were deeply impressed with their observations, and as a result we called together here the heads of six prominent engineering schools which also have military training, and 216 TEXTBOOK OF MILITARY AERONAUTICS made plans to estahlisli u similar system in the United States. The six institutions are the Universities of California, Texas, Illinois, Ohio, JMassachusetts Institute of Technology, and Cornell University. Three technical instruct- ors from each of these places were sent to Toronto. They returned on May 8 after a comprehensive study of the course given there, prepared to teach it themselves. On May 10 these six engineering schools opened similar cadet aviation schools at their respective insti- tutions. At the end of two months of this pre- liminary work, the cadet is given a final test to determine whether he shall go on to the aviation camp. "The manufacturing capacity can easily he doubled the second year. A prominent Brit- ish General has asserted that America's great- est contribution to the war will be aircraft and aviators. We believe that once started upon quantity production, American mechanical gen- ius will overcome any present obstacles to the progress of the art." The Deficiency Bill to provide for the Army's needs at that time carried an appropriation of only $54,000,000 for aeronautics. Appreciating the fact that the plans for the building of our Air Forces on a scale propor- tionate to the need were restricted by lack of prospects to get sufficient appropriations and believing that the American ])ublic would favor the adoption of a plan extensive enough to pro- vide for the training and ecjuipping of ten thou- sand aviators and sending tens of thousands of aeroplanes to the Allies, the Aero Club of America undertook to get public support for such a plan. The canipaign started a few days after the announcement of the Aircraft Production Board. The slogan "We m ust Strike Germani/ Through the Air" was adopted. In the first statement Mr. Alan R. ITawley, the President of the Aero Club of America, pointed out that, "Germany's U-boat warfare and the necessity of keeping the German Heet Imttled up are occupying the navies of the Allies and no decisive victory over the Germans is ex- pected in naval actions in the near future. Likewise advances against the Germans on land are slow, and Germany has seemed able so far to always throw new thousands of men and new lines of trenches and countless guns to meet the advance of the Allies. The only victories on the part of the Allies so far have been as a result of supremacy of the air, as a result of the matching of skilful, daring Allied aviators against German aviators and observation bal- loons; the recent British and Italian victories wei-e preceded by countless aerial fights in which hundreds of aviators took part, and it was not until the skies had been cleared of German avi- ators and of German observation balloons — and the Germans were thereby deprived of the aerial eyes of the infantry, of the aerial scouts, and the Allies' aviators, being masters of the air, could follow the movements of the enemy and locate their batteries and their strongholds, that the victories became possible. "While the United States is beginning to help substantially now, effective help of the kind that leads to permanent victory can only come at the end of months of preparation, and in consider- ing in which way we can best prepare to help to achieve permanent victories it is found that the aerial branch of the service affords the greatest possibilities. British, French, Russian, Italian and American authorities who have studied the matter closely have come to the conclusion that the addition of 10,000 aviators to-day to the Allies' present aerial forces would insure blind- ing the German batteries and preventing Ger- man aviators from conducting operations over or near the Allies' lines. An additional 10,000 aviators would make it possible to conduct aerial raids on a large scale and to strike Germany in the most vital places, to strike hard enough to lead to permanent victories." A billion .dollar appropriation was urged for Army aeronautics. It soon became evident that the pul)lic favored the appropriation of this sum. One of the most important factors in creating favorable public sentiment for this appropri- ation was the hearings held by the Senate Sub- Committee on Military Affairs on the Shep- pard-Hulbert Bill to create a Department of Aeronautics. This brought forth the endorse- ment of leading authorities of not only the plan HISTORY OF UNITED STATES ARMY AERONAUTICS 217 to train thousands of aviators and build tens of thousands of aeroplanes, but also strong general endorsements of the Sheppard-Hulbert Bill. The hearings began June 12th, and lasted for two weeks. Those who testified before the Sen- ate Sub-Committee of the House of Representa- tives, and endorsed the plan to establish a De- partment of Aeronautics, were as follows; Rear Admiral Robert E. Peary: Major L. W. B. Rees, of the British Royal Flying Corps, member of the British Commission in the United States; Howard E. Coffin, Chairman, Aircraft Production Board; Brigadier General George O. Squier, Chief Signal Officer, U. S. A.; Alan R. Hawley, President, Aero Club of America; Henry Woodhouse, Henry A. Wise Wood, Augustus Post, Rear Admiral Bradley A. Fiske ; Lieut. Rumsey and Lieut. Prince, mem- bers of the Lafayette Flying Corps; J. Bernard Walker; F. H. Allen, one of the Directors of the Lafayette Flying Corjjs; INIajor General Goethals; Joseph A. Steinmetz, President of the Aero Club of Pennsylvania. The forceful statements made by these au- thorities were pubhshed daily by the press throughout the United States and brought out hundreds of editorials urging prompt action and large appropriations. Brigadier General George O. Squier, the Chief Signal Officer of the Army, in endorsing the aerial preparedness program said, in part: "The way to beat Germany is to flood the air with aeroplanes. Take the war out of the trenches and off the ground. Put it in the air." On June 18th Secretary Baker came out for a vast air fleet. "The War Department is behind the aircraft plans with every ounce of energy and enthusi- asm at its command," said Secretary Baker. "The aircraft program seems by all means the most effective way in which to exert Amer- ica's force at once in telling fashion. "We can train thousands of aviators and build thousands of machines without interfering in the slightest with the plans for building up our armies and for supplying the allies with food and munitions. To train and equip our armies and send them abroad will take time, however, and in the meantime we can be devoting to this most important service vast quantities of pro- ductive machinery and skilled labor which other- wise could not be contributing to the nation's cause in full proportion to its capacity. "The aircraft j)lans meet the demands of the situation. Under existing conditions of fight- ing, where the allies and the Germans are fight- ing on practically even terms as regards man power and aircraft, the addition which we can contribute to the allied air forces will be propor- tionately of far greater value than the immediate aid which we can furnish on land. According to the best obtainable information, there are about 7,000,000 men on the western front to- day. The addition of a few infantry units, while of great moral value, is of little use in forcing a decision. A few thousand trained aviators, however, with the machines for their use, may spell the whole difference between vic- tory and defeat. The supremacy of the air, in modern warfare, is essential to a successful Army. America must make sure that the Al- lies and not Germany, secure the permanent domination of the air, and that within the year." On June 22 President Wilson himself en- dorsed the movement, in the following letter to Secretary Baker: The White House, Washington. My Dear Mr. Secretary: I have your letter of yesterday about the produc- tion of aircraft and the training of men to operate them, and want to say that I am entirely willing to back up such a program as you suggest. I hope that you will present it in the strongest possible way to the proper committee of the Congress. Cordially and sincerely yours, (Signed) Woodrow Wilson. Hon. Newton D. Baker, Secretary of War. A bill appropriating $640,000,000 was intro- duced and passed the House of Representa- tives on July 14, without a dissenting vote. It passed the Senate on July 21, and was signed by President Wilson July 24. The estimate showed that only $363,000,000 was to be spent for aeroplanes, the rest going to pay for the service squadron, supply squadrons, training stations, machine guns, etc., and that 218 TEXTBOOK OF MILITARY AERONAUTICS the number of aeroplanes to be ordered under that appropriation would be only about 22,000, a good portion of which would be training machines needed for the training of aviators. The Aero Club of America thereupon imme- diately started a campaign to make known the necessity of an additional appropriation of $1,000,000,000 to build the thousands of large warplanes needed to conduct major aerial op- erations against the German bases. Being told that the shortage of tonnage would preclude shipping thousands of aeroplanes to France, the Aero Club started to develop plans for delivering the aeroplanes by flying them across the Atlantic. Aircraft Board Created It became evident that to get quicker action and remove confusion in the production of air- craft it would be best to have an Air Board with full authority, or better still, a separate De- partment of Aeronautics. The Aero Club of America had recommended the separate de- partment of aeronautics in 1915, and urged it continuously ever since. Getting an Air Board with sufficient author- ity the Aircraft Production Board and the Signal Corps were prompt in acting and carry- ing the plans into effect. Their work in estab- lishing and putting into operation huge train- ing aviation camps was extraordinary. Carry- ing out the aircraft production program was slower. Among the most striking accomplishments were the developing of the "Liberty motor" de- signed l)y Messrs. J. C. Vincent and E. S. Hall, and the creation of the International Aircraft Standards Board with Mr. F. G. Diffin as chair- man, was a step towards it. A bill to create the Air Board was introduced in the Senate by Senator Morris Sheppard of Texas and in the House of Representatives by Congressman ^lurray Hulbert of New York. It passed the Senate on September 12 and the House on Sep- temljer 26. It was signed by President Wilson onOctol)er 1st, 1917. The act creating the Aircraft Board and the endorsements of Secretary Baker and Secretary Daniels may be found in "Flying" for Sep- tember, 1917. Unfortunately the provisions contained in Section 4 and Section 5 of the Act confined this Board to a merely advisory capacity and pre- vented its getting an organization adequate to do the important work of building Air Forces extensive enough to cope with the fastly devel- oping German Air Forces. The following were appointed on the new Aircraft Board: Howard E. Coffin, chairman; Major-General George O. Squier; Colonel E. A. Deeds; Colonel R. L. Montgomery; Ad- miral D. W. Taylor; Captain Noble E. Irwin; Lieutenant-Commander A. K. Atkins; R. F. Howe, appointed November 6, 1917; and H. B. Thayer, appointed February 26, 1918. While these plans were being made in the United States, two changes took place in the situation in Europe, as follows: 1. Aerial warfare became more and more intensified. Aerial combats became more nu- mez'ous; the employment of aeroplanes to attack infantry and artillery formations grew more and more extensive; bombing at short- and long-distance range became an every-day mat- ter. This greatly increased the number of aeroplanes in use, and more than quadrupled the percentage of casualties among aviators and the loss of aeroplanes due to different causes. 2. The Italian reverses and the Russian collapse brought about serious conditions, ne- cessitating a much greater contribution in air- craft and aviators from the United States than was planned and greater speed in carrying out the plan. A committee of the Aero Club of America, headed by Mr. Alan R. Hawley, the ])resident of the club, and including Congress- man Murray Hulbert, Admiral I'eary, and the writer, called on some of the Washington au- thorities to urge the necessity. We found the authorities divided in two groups: those who felt certain that Congress would give additional appropriations for aeronautics immediately after convening in December; those who be- lieved the program under way to be sufficient to meet the changed condition, and would not con- sider increasing it. HISTORY OF UNITED STATES ARMY AERONAUTICS 219 It soon became apparent that the Russian and Itahan reverses could have been prevented had those countries had about two hundred additional warplanes each, and that an auxiliary air fleet was needed to meet the swift manceuvers of the enemy. At the annual meeting of the Aero Club of America on November 12, 1917, the following resolution was adopted, which was transmitted to President Wilson; Secretary of War Newt(ni D. Baker; Secretary of the Navy Josephus Daniels; Mr. Howard E. Coffin, the chairman of the Aircraft Board; and Major- General George O. Squier, the chief signal officer : Whereas, Tlio greatest difficulty of the Allies has been to move their forces fast enough to meet unex- pected German attacks on weak points of the Allied lines, and to overcome the advantage which the Ger- mans have of being able to transport large bodies of troo])s, ammunition and supplies from one point to another by interior lines ; and Whereas, It is evident that powerful warplanes af- ford the needed combination of power and mobility in a higher degree than do any other appliances, and that the recent occupation of the Baltic Islands by Germans and the Italian reverses in the province of Venetia could have been prevented if the Allies had been able to send a sufficient number of torpedoplanes and bomb- dropping aeroplanes to assist the Russians and Ital- ians at the first evidence of danger ; and Whereas, It is generally accepted by the recognized authorities on aeronautics that aeroplanes can easily be built which can fly across the Atlantic and thereby solve the problem of delivering large units of aero- nautic power to England, France, Italy and Russia, without dependence on ocean transportation, or inter- fering with it ; and Whereas, There are in the United States unutilized manufacturing facilities and resources which could build thousands of powerful warplanes during the com- ing year without interfering with the present aero- nautical program of the Army and Navy; and Whereas, These aeroplanes can conduct major aerial operations against the German fleet and U-boat bases, as well as against the German lines of communi- cation and military industries and forces; be it Resolved, That these facts be brought to the atten- tion of the President, the Council of National Defense, the Secretary of War, the Secretary of the Navy, the Aircraft Production Board, and to the American pub- lic, through the press, and that the coming Congress be urged to expand the present aeronautical program by appropriating not less than $1,000,000,000 for build- ing an "Emergency Air Fleet" of huge warplanes, and also appropriate $1,000,000,000 to carry out a com- prehensive aeronautic program of training aviators and building the tens of thousands of fighting, photog- raphy, artillery and contract patrol aeroplanes ; dirig- ibles and balloons, which are needed to assure the Allies' supremacy in the air. The $1,032,294,260 Army Air Program In December, 1917, were made public the Signal Corps estimates for 1919, in which was asked the sum of $1,032,294,260 for aeronau- tics, including the following items : Lighter-than-air equipment Aeroplanes and seaplanes Spare parts and accessories Extra engines and spare parts . . Maintenance, upkeep, and opera- tion of aero squadrons Aero stations, United States . . . Aero stations, Panama Aero stations, Hawaii Maintenance, repair, etc., build- ings in Europe Purchase of land Warehouse and su])ply depots . . Aviation clothing equipment .... Expenses of officers, enlisted men, and civilians on special duty . . Vocational training Mileage to officers and traveling exjienses of civilian employees Development of new types of aeroplanes and engines Schools of military aeronautics . . Machine-guns for aero])lanes . . . Photographic equipment, mate- rial, etc Contingent expenses, office equip- ment, etc Construction Leasing of land Reserve officers and men Anemometers, barographs, avia- tors' garments and other spe- cial accessories Miscellaneous $8,171,000.00 235,866,000.00 47,173,200.00 553,289,120.00 20,950,000.00 20,400,000.00 5,420,000.00 4,420,000.00 9,127,000.00 16,700,000.00 5,595,000.00 1,358,440.00 67,200.00 120,000.00 3,050,000.00 2,000,000.00 8,050,000.00 77,475,000.00 3,405,500.00 100,000.00 $279,388.27 6,240,634.55 752,930.96 1367,110.95 1,249,120.62 70,462.39 3,061,293.77 77,512.13 400,000.00 2,841.45 358,314.90 Total aviation $1,032,294,260.00 $14,159,351.89 PAY OF OKFICKRS AXD MEN' Pay of 11,941 officers $27,619,533.00 Aviation increase, officers ; 10,030,800.00 Additional pay for length of service, oflBcers .... 1 00,000.00 Pay of 153,94.5 enlisted men 60,606,607.05 Aviation increase, men 4,916,800.00 Additional pay for length of service, men 150,000.00 Total $103,423,740.05 Long Delay in Extending Plans and Getting Appropriations Causes Trouble It was most unfortunate that the necessity of extending the aeronautic program was not rec- ognized and steps were not taken to extend the program in the autumn of 1917. 220 TEXTBOOK OF MILITARY AERONAUTICS In official statements dated September 13 and 31, Secretaiy of War Xewtoti D. Baker an- nounced the creation of the Liberty Motor and the passing of its "final tests." On February 21, 1918, he announced that the first "American- built battleplanes" were en route for France. In March and April, 1918, it was made pub- lic that the aircraft program was late by several months. The following letter, written by Mr. Alan R. Hawley, president of the Aero Club of Amer- ica, to President Wilson, on April 2, 1918, gives the status of the situation at the time, and the recommendations made to solve the problems: Mif dear Mr. President: A niimlHT of men who had applied for admission in the Air Service of the Army have advised tlie Aero Cluh of America that they have Iwen notified hy the Signal Corps autlioritics that no further enlistments are heinp accepted at this time. As Secretary Baker's rejwrt, published recently, stated there were less than four thousand aviators under training, and know- ing that it will take twenty thousand aviators to keep five thou- s»nil aviators on the fighting front continuously for one year, and realizing that to lack the trained aviators to supply the necessary replacements would mean defeat for the cause of the Allies, we were amazed to find this condition. In answer to our inquiries, we were advised that the reason no further enlistments arc accepted for the Air Service is that there is a lack of training fields and of aeronautic equipment and that these cannot he provided heeause there are no funds available for the extension of the Air Service. This is only one of the evidences that the aircraft program is slowing down l>e<"ause of lack of funds. We have been advised by factories that have completed their orders that they also do not have orders to look forward to and to prepare. We submit, Mr. President, Ihat this is a mournful condition which threatens the cause of tlie .\llies more seriously tlian any- thing else. Supremacy in the air is to be the key to victory. To achieve and maintain supremacy in the air, the Allies must be able to count on not less than twenty-five thousand American aviators, .so as to insure keeping five thousand at the front con- tinuously for the various duties of the Air Service and for the iHimliing expeditions. Tlie [H-rcenlage of replacements needed in the Air Service has increased greatly in the past six months and will further in- crea.s*' in tlie coming year, becau.se there is mii<-h more aerial fighting, attacking troops from the air, bomliing at low altitudes .ind night raiding. Aerial fighting is becoming more and more intense; and the anti-aircraft guns are firing more and more accurately anil hitting aeroplanes at altitudes of sixteen thou- sand feet. This increases the casualties among aviators enor- mously. Thiii condition to-day is analogous to the condition which exi>leer in the American aircraft situatiim as a wlwlc. A largi- numU-r of training camps had b«vn estalilished, at a cost of i^«K),(KK»,(KH), orders for aeroplanes and motors had l)c«-n placed, and the funds had practically been exhausted. Tliereu|Mm the work of developing additional sources of sui)plies for aircraft and motors practically slopped, notwithstanding the fact Ihat the Italian reverses and the Uussian collapse demanded lni|>rrafively Unit our program Iw tripled in siw. TIm' Aero Cluh of America officials urged aiul pleaded for prompt omsiderntion of this new condition at the time, and pointed out that It was aiisolutely necessary to immediately give two l>ill)4>n dollars addilioiinl a])propriations for extending the aircraft program. That wa« f>ix inontliii ago, when prompt action would have prevented the confusion and mistakes which were subsequently made, partly owing to lack of sufficient ap- propriations. Tlie main cau.se of tlie present deploralile condition of our aircraft program was that tlie authorities in charge tried to make twenty thousand aeroplanes do the work of eighty thou- sand. The original program did not take into consideration that it takes an average of two aeroplanes to give an aviator the one hundred hours of preliminary and advanced training needed to make him fit for the present-day highly specialized work of a military aviator. Xor did it take into consideration that it takes close to one hundred per cent, replacements per month in aeroplanes and motors to keep aviators equipped for fighting. Xor did it take into consideration that it takes forty per cent, replacements in aviators per month to keep up the fighting personnel of aero squadrons. In making this program the fact was overlooked that if the plan was to keep five thousand American aviators at the front, it was necessary to train twenty-five thousand. Therefore, there would be required fifty thousand preliminary and advanced train- ing aeroplanes with which to train them speedily. The number of aeroi)Ianes under construction to-day is not sufficient to even give the preliminary and advanced training to the number of aviators the I'nited States must supply within the coming twelve months. There was also overlooked the fact that to keep five thousand aviators equipped for action, there would be required an average of two thousand aeroplanes of different types per month, or a total of twenty-four tlioiisand machines of different types during the twelve months. Having overlooked these very important considerations, the authorities could not undertake to supply all the aeroplanes needed out of the twenty-two thousand planned. The Italian and Russian reverses created imperative needs, and the authori- ties received caliles requesting thousands of aeroplanes of dif- ferent types, l^acking the funds necessary to place additional ortlers, the authorities changed the orders of aeroplanes under construction, so as to meet the requests from France. As the requests from France and the suggestions from the different Allies were for different types of machines, the authorities kept on changing the orders, so as to supply these machines for which there seemed to be the most pressing need. This led to the continuous changes which caused the set-backs which have re- sulted in the aircraft program — which is still the same program made at the time when Italy was victorious and Russia was still fighting — being behind by several months. Mad the authorities been in a position to place additional orders whenever they received cables asking for a given num- ber of machines of a given type, instead of having to change orders for machines under construction, to-day the original pro- gram would be nearly delivered and an additional program would be well under way. To-day we are making the same mistake that was made then. We are stopping the enlisting of aviators and no .steps have lieen taken to extend the program to meet the new conditions which have arisen, and which, unless they are met ])r(nnptly, may result in Allied reverses and )>ublic condemnation of your .Vdministra- tion, not only from the .\niericaii pulilic liut also from the Allies. It is tragic to us, .Mr. President, to know that while aeroplanes and aviators are needed so badly to fight this figlit lor civiliza- tion and humanity, hundreds of manufacturers who could lie making aeroplanes and motor parts are kept in forced idleness for lack of orders, and thousands of patriotic young men who are anxious to join the Air Service and go to France and do their share towards winning the war, are told that no further men are lieing taken in the Air Services. The delay in ])rodiicing the I.ilierty motor cannot be held re- spike Ader's experiment, it was wrecked in the attempt to fly it, and the military 222 THE EVOLUTION OP^ MILITARY AVIATION 223 authorities, who had been expecting to get a practical craft out of the first experiment, were disappointed and withdrew their support. In 1908 the Board of Ordnance and Fortifi- cations of tlie United States Army directed Samuel P. Langley to construct a large-sized model of the "aerodrome" he had designed, and made an aj)propriation of $.30,000 to defray the cost of the experiment. Langley's machine was a tandem monoplane, 48 feet from tip to tip and 52 feet from bowsprit to the end of its tail. It was fitted with a .50 horse-power en- gine and weighed 830 pounds. Two attempts to launch it were made, one on October 7 and the other on December 8, 1903. On both occa- sions, according to reports, the "aerodrome" be- came entangled in the defective launching ap- paratus and was thrown headlong into the Po- tomac River, on which the launching trials were made. Following the last failure, when the "aerodrome" was wrecked, the press ridiculed the whole enterprise, and Congress refused to appropriate money for further experiments. The first requisition for a military aeroplane, giving definite specifications of what the aero- plane should accomplish to be acceptable for military service, was made by the United States War Department in an advertisement issued December, 1907. This advertisement is a won- derful document. It exacted the utmost, with- out going into the impossible. It shows that at that time — when Bleriot, Farman, and Cur- tiss had only made a few jumps, and the per- formances of the Wrights had not been made public — the authorities at Washington had a thorough knowledge of the aeroplane and a lucid conception of its possibilities. The full text of the advertisement is reproduced herewith for its historical value: Signal Corps Specification, No. 486 ADVERTISEMENTS AND SPECIFICATION FOR A A HEAVIER-THAN-AIR FLYING MACHINE To the pub ic: Sealed proposals, in duplicate, will be re- " ceived at this office until 12 o'clock noon on February 1, 1908, on behalf of the Board of Ordnance and Fortification for furnishing the Signal Corps with a heavier-than-air flying ma- chine. All proposals received will be turned over to the Board of Ordnance and Fortifica- tion at its first meeting after February 1 for its official action. Persons wishing to submit proposals under this specification can obtain the necessary forms and envelopes by application to the Chief Signal Officer, United States Army, War Depart- ment, Washington, D. C. The United States reserves the right to reject any and all pro- posals. Unless the bidders are also the manufacturers of the flymg machine, they must state the name and place of the maker. Preliminary. — This specification covers the construction of a flying machine supported en- tirely by the dynamic reaction of the atmos- phere and having no gas bag. Acceptance. — The flying machine will be ac- cepted only after a successful trial flight, dur- ing which it will comply with all requirements of this specification. No payments on account will be made until after the trial flight and acceptance. Inspection.— The Government reserves the right to inspect any and all processes of manu- facture. GENERAL REQUIREMENTS The general dimensions of the flying ma- chine will be determined by the manufacturer, subject to the following conditions: 1. Bidders must submit with their proposals the following: (a) Drawings to scale show- ing the general dimensions and shape of the fly- ing machine which they propose to build under this specification, (b) Statement of the speed for which it is designed, (c) Statement of the total surface area of the supporting planes. (d) Statement of the total weight, (e) De- scription of the engine which will be used for motive power, (f) The material of which the frame, planes, and propellers will be con- structed. Plans received will not be shown to other bidders. 2. It is desirable that the flying machine should be designed so that it may be quickly and easily assembled, and taken apart and packed 224 TEXTBOOK OF MILITARY AERONAUTICS for transportation in army wagons. It should will be required of at least one hour, during be capable of being asseml)led and put in opera- which time the flying machine must remain con- ting condition in al)out one hour. tinuously in the air without landing. It shall 3. The flying machine must be designed to return to the starting point and land without carry two persons having a combined weight of any damage that would prevent it immediately about S.'iO pounds, also sufficient fuel for a flight starting upon another flight. During this trial of 12.) miles. flight of one hour it must be steered in all direc- 4. The flying machine should be designed to tions without difficulty, and must be at all have a speed of at least 40 miles pei- hour in still times under perfect control and equihbrium. air, but bidders must submit quotations in their 7. Three trials will be allowed for speed as proposals for cost depending upon the speed at- provided for in paragraphs 4 and 5. Three tained during the trial flight, according to the trials will be for endurance, as provided for in following scale: paragraph 6, and both tests must be completed 40 miles per hour 100 per cent. ^'t.^^'" ^ P^;""^ "f thirty days from the date of 39 miles per hour 90 per cent. delivery. The expcnsc of the tests is to be borne S S: ;::; iZ ;:::::;;::;:::::::::; ;?o i::: Zl ^y t'^e manufacturer. The place of delivery to 36 miles per hour 60 per cent. the (iovemmcnt and trial flights will be at Fort Less than 36 miles per hour rejected. JMver Virj>"inin 41 miles per hour 110 per cent. o Ti i i i l i • *2 miles i>er hour 1:.>0 i.er cent. »• At Shouid DC SO dCSlgUCd aS tO aSCCud lU any 43 miles p<-r hour 130 per cent. countrv which may be encountered in Held serv- 44 nnles per hour 140 per cent. . * . ice. I he starting device must be simple and 5. The speed accomplished during the trial transportable. It should also land in a field flight will be determined by taking an average without requiring a specially prepared spot and of the time over a measured course of more than without damaging its structure. five miles, against and with the wind. The time 9. It should be provided with some device to will be taken by a flying start, passing the start- permit of a safe descent in case of an accident to ing point at full speed at both ends of the course, the propelling machinery. This test is subject to such additional details as 10. It should be sufficiently simple in its con- the Chief Signal Officer of the army may pre- struction and operation to permit an intelligent scribe at the time. man to become proficient in its use within a rea- 6. Before acceptance a trial endurance flight sonable length of time. Next the British Government engaged Sir Hiram Maxim to bulla :i mllil.ii) a. mpLiiK. Sir .Maxun's multipldnc ul>o < auic to grief In an attempt to show its flying qualities. THE EVOLUTION OF MILITARY AVIATION 225 11. Bidders must furnish evidence that the Government of the United States has the lawful right to use all patented devices or appur- tenances which may be part of the flying ma- chine, and that the manufacturers of the flying machine are authorized to convey the same to the Government. This refers to the unrestricted right to use the flying machine sold to the Gov- ernment, hut does not contemplate the exclusive purchase of patent rights for duplicating the flying machine. 12. Bidders will be required to furnish with their proposal a certified check amounting to ten per cent, of the price stated for the 40-mile speed. LTpon making the award for this flying machine, these certified checks will be returned to the bidders, and the successful bidder will be required to furnish a bond, according to army regulations, of the amount equal to the price stated for the 40-mile speed. 13. The price quoted in proposals must be understood to include the instruction of two men in the handling and operation of this flying machine. No extra charge for this service will be allowed. 14. Bidders must state the time which will be required for delivery after receipt of order. James Aixen, Brigadier-General, Chief of Signal Officer of the Army. Signal Office, Washington, D. C, December 23, 1907. The Wright brothers were the only persons to submit a complete machine and fulfil the require- ments. The first trials, made by Orville Wright at Fort Myer in September, 1908, re- sulted in a record flight of 1 hour, 14 minutes, 20 seconds. An accident prevented the fulfil- ment of the passenger-carrying requirement and caused a delay of one year. The Wright machine, which fulfilled the con- ditions in August, 1909, was the old-type Wright biplane. It had a spread of 40 feet, a 25 horse-power motor, front elevator, skids in- stead of wheels, and was started by catapult and monorail. The record flights made during the tests at Fort Myer included a flight of 1 hour, 20 minutes, 30 seconds, and one of 1 hour, 28 minutes, 20 seconds, with Lieutenant Frank P. Lahm as passenger. It was most appropriate that the distinction of supplying the first aeroplane to the United States Government should have gone to the Wrights, who gave the world the first practical aeroplane. Wilbur Wright and his brother, Orville Wright, two men of remarkable char- acteristics, sons of the Rev. Milton Wright, were presented in their boyhood, thirty odd years ago, with a toy helicopter, a butterfly- shaped contrivance, consisting of paper wings fitted with a tin propeller which, when made to revolve by twisted rubber, caused the toy to shoot forward through the air. That toy fired their imagination, and they saw it, in magnified form, capable of carrying a man. Their attempt to fly large helicopters con- structed on the idea of the toy did not bring practical results, and until 1896 they did not give the matter of artificial flight more than passing attention. In the summer of that year, however, the news of the accident and death of Otto Lilienthal, the German champion of glid- ing flight, stirred them to action, and they set themselves to study aerodjmamics and the works of Lilienthal, ]\Iouillard, Chanute, Maxim and Langley, the most prominent experimenters at that time. Their experiments with a glider began in the autumn of 1900 at Kitty Hawk, North Caro- lina. There, on the barren sand-dunes of North Carolina, these two intrepid investigators took all the theories of flight and tried them one by one, only to find after two years of hard, dis- couraging work, that they were based more or less on guesswork. Thereupon they cast aside old theories and patiently put the apparatus through innumerable gliding tests, ever chang- ing, adding, and modifying. They set down the results after each glide, comparing and changing details again and again, advancing inch by inch, until they at last developed a glider wonderfully exact, which, when fitted with -a light motor also built by them, made initial flights on December 17, 1903, of from twelve to fifty -nine seconds' duration. This, then, was the birth of the aeroplane, — the flimsy, icono- clastic thing which seems to evade Newton's 226 TEXTBOOK OF MILITARY AERONAUTICS The first "gun-plane" was the French Voisin armored and armed with a 37 mill, gun, Itbled early in liHi. It (li.-.jinnru iljc theory that the recoil of a gun would upset the aeroplane. laws, eliminates frontiers, and promises to ex- pand civilization as much as have the steamship, the railway, and electricity. On September 15, 1904, Orville Wright, flying the Wright biplane near Dayton, Ohio, made the first turn in a heavier-than-air ma- chine. On September 20, he made the first circle; on October 4, 1905, he made the first flight of over half an hour, a flight lasting 33 minutes, 17 seconds. The Wrights did not make their achieve- ments public at the time; in fact, until 1908 they flew only in private. The report of their wonderful achievement, nevertheless, spread far and wide. It stimu- lated those who had given up experimenting and inspired others to take up experiments. Octave Chanute, in 1902, went to France and related the early successes of the Wrights with their glider, describing the general shape of the Wright machine. The result of this trip was that half a dozen enthusiasts, including Louis Bleriot, Captain Louis Ferber, Ernest Arch- deacon, and later the Voisin brothers and Al- berto Santos-Dumont, took up the work, thus founding the mighty French school, which has increased so greatly and done so much ever since. The first member of this school to succeed was Santos-Dumont, the Brazilian aeronaut sports- man. He constructed a machine of original design, and in 1906 made short sustained flights of from fifty to seven hundred feet in a straight line. This created a world-wide sensation at the time. Meanwhile, others of the French school graduated and won honors. The Voisin brothers became constructors and teachers, and with their cooperation Leon Delagrange, Henry Farman, Louis Bleriot, and others, prosecuted practical experiments and succeeded in getting their creations to leave the ground for modest flights. At this juncture, during the summer of 1908, the Wrights started to give pubhc demonstrations. Their methods supplied and suggested to the French experimenters the means to modify and improve their aeroplanes, particularly the method of balancing them, which had, until then, been a perplexing prob- lem. The conditions set by the United States Gov- ment in its specification of 1907-08 formed the standard by which most governments judged aeroplanes acquired for military work until the close of 1911, when the French Military Com- petition took place. This competition was or- ganized by the French War Department at the close of 1910, after the military manoeuvers, with a view to develop better aeroplanes for military purposes. The conditions to be fulfilled by the competing aeroplanes and the prizes to be awarded to the winners were as follows : General Conditions of French Military Competition of 19101911 1. The aeroplane and its engine must have been constructed in France of the best ma- terials. THE EVOLUTION OF MILITARY AVIATION 227 2. Each aeroplane must make a circular flight of 300 kilometers (186 miles) without a stop. 3. Each aeroplane on this circular flight must carry a load of 300 kilograms (660 pounds) over and above the requisite petrol, oil, water, etc. 4. JMachines must provide accommodation for three passengers: the pilot, a mechanic, and an observer. 5. The mean speed must be not less than 60 kilometers per hour (37.3 miles) . 6. Machines must be able to land without dif- ficulty or damage on plowed fields, meadows, stubble, etc., and must start again from ground of this character, 7. Machines must be easily transportable, whether packed or not, by road or rail, and should be easily assembled. The following hints were given to construct- ors: 1. It is desirable that the aeroplane be fitted with a double control; or, at all events, that the pilot and his assistant should be able to relieve one another by taking over the control in flight. 2. It is desirable that machines should be ca- pable of starting without outside assistance. 3. The observer's field of vision should not be obstructed by any parts of the machine. with their full load. The final classification will be made according to the best performance dur- ing this test. PRIZES The prizes will be awarded as follows: The machine accomplishing the best performance will be bought by the Ministry of War for the sum of 100,000 francs and its constructor will re- ceive an order for 10 machines of a similar type at 40,000 francs each. An extra premium of .500 francs will be granted in addition for each kilometer of average speed above 60 kilometers per hour that the machine has attained. The constructors of the machines accomplishing the second and third best performances will receive orders for six and four machines respectively, at the same prices. In the case where only two machines come through the tests satisfactorily, the constructor of the first will receive an order for twelve machines and the constructor of the second an order for eight machines ; and if only one machine has satisfactorily passed the tests its constructor will receive an order for 20 ma- chines. The genei'al conditions of this contest were i';'f4'-l>*ss''' -irnm?T^^m PRELIMINARY TESTS 1. Three flights must be made with the above stated load on board, and a landing accom- plished on ground of the nature indicated in paragraph 6 above. On each occasion machines must reascend, start from the ground and land again after a flight of a few minutes. 2. The machine carrying its full load must make a flight over a circular course for the pur- pose of testing its speed. 3. Two altitude flights, with the full load, must be made, during which machines must reach a height of 500 meters (1640 feet) within 15 minutes. TWO FINAL TESTS On a day appointed beforehand all the ma- chines that have successfully passed the prelimi- nary tests shall make a non-stop flight over a circular course of 300 kilometers (186 miles) How they tried to shoot over the propeller up to 1915, before the method of synchronl/.inf; the gun with the propeller to per- mit shooting through it was found, a French improvement. 228 TEXTBOOK OF MILITARY AERONAUTICS French Caudron biplane equipped with two motors. (Official French photo.) over 100 per cent, more severe and more detailed than the general conditions of the American competition. The aeroplane had been tried in the military manoeuvers of 1910, and from its accompli-shments the authorities had deduced its great possibilities — if further developed — to give the amount and quality of service exacted as minimum in the competition. The conditions show that the authorities had a thorough knowl- edge of what an aeroplane would have to do to suit for general military work, and the large prizes offered show that they were aware that to develop the required standard efficiency was to involve lengthy and costly experiments, which few of the constructors could carry out unless a liberal inducement was given. As it was, the contest had to be postponed for six months to give an opportunity to constructors to develop the required qualities. Encouraged by the inducements given, six- teen French constructors built special aero- planes, thirty-four in number, whose general characteristics were as follows: Make Type Span Length Motor „p Weight ^^- Kilo. Antoinette Monoplane Aktra Biplane '■ Triplane Antra-Wrlght Biplane Bitriot Monoplane Brtgnet Biplane Deperduuio Monoplane U. Karman Biplane M. Pannan OoupT Moru>*-Bor«l Monoplane 52' 6" 40' 43' 52' 36' 36' 63' 41' 4" 41' 4" 63' 41' 4" 53' 40' 6- 39' 0" 40' G' 64' 64' 62' 10" 62' 10" 64' 64' 41' 44' 36' 34' 3" 31' 34' 27' 27' 20' 28' G" 28' G" 29' 28' 6" 29' 80' 30' . 30' 38' 82' 6" 82' 82' 87' 8" 88' 88' 83' Antoinette Chcnu Renault GnAme Dancette Canton-Une It <( OnOme Anzanl ClergPt Renault OnAme Renault Cbenu OoAma 60 75 75 50 100 130 100 130 100 110 110 80 100 80 100 76 76 70 100 76 76 76 100 180 936 862 760 G24 4G5 515 652 637 652 722 703 700 462 626 691 691 471 689.B 618 637 Make Type Span Length Motor H.P. Weight Kilo. Nieuport •• 41' 29' " 100 483 " " 41' 29' " 100 483 Paulhan Triplane 41' 6" 33' Renault 75 R E P. Biplane 30' 33' R. E. P. 60 Savary " 62' 38' Labor 70 708 " «« 62' 38' " 70 708 Voisin rent services of the sum of $18,000,000. As can be seen from the reports covering the differ- ent lines of activity developed by the National Aero- plane Fund, which was started in the spring of 1915, when American aeronautics was at its lowest ebb, the National Aeroplane Fund succeeded in developing aeronautics in the Army, Navy, National Guard, Na- val Militia ; among college men, in the Coast Guard, and a dozen other fields. This movement was started in the early spring of 1915, after Congress had adjourned and the inter- national situation grew serious enough to make this country take stock of its defenses. There were at the time only about a dozen aeroj)lanes in commission in the Army and Navy combined, when we should have had one hundred times that number, and there were no prospects of relief, since the last Congress had al- lowed but a fraction of the amount needed for aero- nautics. The maneuvers of the National Guard and Naval Militia of the states were being planned, but in no case was an aeroplane to be employed — the reason being that there were no funds available to pay for aeroplanes or for training Militia officers in aviation. The Aero Club of America, the National aeronautic body, which has fostered the development of aeronau- tics in America since 1905, realizing the necessity of bringing immediate relief, decided to wait no longer for the Government to do its duty. It took steps to contribute materially toward })roviding aeronautical The flr»t tractor liiplanc in America. Constructed l)y Captain Jiiims V. .Martin in August, 1911. 'Vhv first fliglit toolt place in November, 1911, at Nassau Boulevard, I,. I. It was equipped with a 100 h.p. Gnome motor. THE EVOLUTION OF MILITARY AVIATION 285 equipment and instituted the National Aeroplane Fund for the purpose of developing our aeronautical resources, oi-ganizing aviation units in the Militia of the States, building an aeronautical reserve, and creat- ing in a general way sources of supply of personnel and equipment. In the educational campaign, which was the back- bone of the National Aeroplane Fund, which resulted in 2,000,000 })ieces of literature being distributed dur- ing eighteen months, the committee has had the hearty cooperation of the press of the United States. We have received an average of sixty clippings a day re- garding the work of the Aero Club of America during these eighteen months, including hundreds of editori- als, not a single one of which spoke unfavorably of the National Aeroplane Fund or the work of the Aero Club of America. The work of the National Aerojilane Fund has been highly commended by leading Congressmen and Sena- tors, and was favorably mentioned on the floor of the House of Representatives. We have also been warmly praised by Washington officials, also by the governors and adjutants-general of the States and by hundreds of contributors to the fund, and others. Some of the most important movements started or endorsed by the Executive Committee in connection with the campaign to develop our aerial defenses have been adopted and endorsed by the Administration and are as follows: The Council of National Defense, which was advo- cated by the Aero Club of America and other organ- izations cooperating through the Conference Commit- tee on National Preparedness in May, 1915, was adopted by Congress, and President Wilson has just appointed the seven civilian members of the council, which include two prominent members of the Aero Club of America. The organizing of the Council of National Defense is undoubtedly the most important step taken so far to develop real national preparedness. This country as a nation has been like a house divided. There has been practically no cooperation between the Govern- ment, the industries, the patriotic organizations, and the people. So our enormous resources and extensive industries have never been coordinated as the best in- terests of the nation demand. The Council is to do the coordinating, and we expect that aeronautics will greatly benefit from the coordination of our aero- nautical resources which the council may bring about. The large appropriation asked by the Aero Club of America for aerial defense, which seemed excessive when it was proposed, as it was six times greater than the estimates submitted to Congress by the secretaries of war and the navy, was adopted by Congress, and close to $18,000,000 was allowed for aerial defense, instead of ,$3,200,000 asked by the secretaries of war and the navy. The plan to organize an Aerial Reserve Corps pro- posed by the "New York World" and the Aero Club of America, was authorized on July 13 by President Wilson, after a committee of the club's Executive Committee called at the White House and recom- mended the authorization of the plan. The j)lan of the Aerial Coast Patrol was promptly endorsed by President Wilson and the secretaries of war and navy, and an appropriation of $1,500,000 has been ]iromised for putting the plan into effect. Steps were taken to establish aerial coast patrol units, and a complete unit was established at Port Washington, Long Island — the Volunteer AerisJ Coast Patrol Unit No. 1, organized by F. Trubee Davison and eleven other patriotic young men. This unit rendered valuable service in connection with the "Mosquito Fleet" manoeuvers. A Bill was introduced in the Senate to appropriate the sum of $1,500,000 for establishing units of the Aerial Coast Patrol under the auspices of the Navy, and in connection with the Naval Militia and Naval Reserves, but owing to the shortness of time, and the pressure of legislative business, Congress could not act upon it during the past session. The plan to use aeroplanes in connection with the Coast Guard, for the Life-Saving Service and Revenue Cutter Service, first recommended by me five years ago, and since advocated by the Aero Club of Amer- ica, and substantially supported by Byron R. New- ton, the assistant secretary of the treasury, has been adopted by Congress. The plan to use aeroplanes for mail-carrying, ad- vocated by the Aero Club of America for several years, has been adopted and the postmaster-general has invited bids for mail-carrying over different routes where there is now spent $330,000 for carrying mail by other methods. This sum would be spent for aeroplane mail-carrying if suitable bids could be ob- tained. The post-office authorities are anxious to put this plan in operation and are giving every en- couragement. The plan to interest the universities in aerial de- fense, which the Aero Club of America has been car- rying out in so far as it concerns aerial defense, and which was frowned upon some time ago, has been fol- lowed by a request from President Wilson to the heads of the leading universities to consider ways and means to arrange for the training in military science of stu- dents in sixteen of the country's leading universities and colleges under the auspices of the War Depart- ment. Our committee, with the cooperation of Robert Bacon, offered a bonus of $50 for each Harvard un- dergraduate who learned to fly and passed the F. A. I. pilot tests. Twenty-one undergraduates took a course; twelve have already passed the tests. We have also offered three medals of merit to each of the 236 TEXTBOOK OF MILITARY AERONAUTICS First use of aeroplane in w,ir oonditions. Lieut, (now Brifr.-Gen.) B. D. Foulois and P. Pariuelee at Eagle Pass, March, 1911, with the aeroplane loaned to the Army by Robert J. Collier, President of the Aero Club of America. hundred largest universities, having a total of about 850,000 students, the medals to be awarded to the three students who, by March 15, 1917, write the best essays on (a) Military Aeronautics; (b) Mechanics of the Aeroplane and Possible Technical Development in Aeronautics; (c) Possible Application of Aircraft for Utilitarian Purposes. To foster progress in the technical branch of aero- nautics and begin the Work of standardizing, the com- mittee, at the request of Thomas A. Edison, organ- ized the American Society of Aeronautic Engineers, which now includes in its membership all the promi- nent aeronautic engineers. The society is now being combined with the Society of .Automobile Engineers, and Motor-Tractor Engineers, and a new organiza- tion being created which is to be called the American Society of Automotive Engineers. Appreciating the basic value of Pan-Americanism from the standpoint of national defense, the commit- tee started a movement to develop Pan-American aeronautics. Alberto Santos-Dumont was invited to conic to the United States to cooperate in this move- ment. He came, and has been traveling through South and Central America, as the club's representative, and has already done some very constructive work. The organization of the Pan-American Aeronautic Fed- eration was a direct result of the work of the Execu- tive Committee. This federation is already a most powerful organization, and will be more so as time goes on. A large Pan American Aeronautic Exposi- tion is now being organized to be held next February, Mr. Henry Woodhouse, who, with Mr. Henry A. Wise Wood, has been the father of the Pan-American move- ment, is raising the $10,000 needed for the Pan- American Aviation Trophy, and prizes to be com- peted for at Rio de Janeiro next summer. Giving a national defense aspect to the sport of fly- ing resulted in two score of sportsmen taking up aviation and acquiring their own aeroplanes for use of national defense in case of emergency. The success of the aviation meet, held at Sheeps- hcad Bay last spring, was a direct result of the work of the National Aeroplane Fund. Remarkable rec- ords were made at this meet, including non-stop flights from Newport News to New York with passengers. Subsequently, and with the hearty cooperation of the " New York World," a flight was made from New York to Washington, in which I was a passenger, for the purpose of carrying to Washington a special edition of the "New York World," which advocated the training of 2000 aviators, wiiich plan was en- dorsed by the governors of practically all the States. This plan to train 2000 aviators was favorably con- sidered by Congress, and when a letter sent to one of the Congressmen with a copy of the "World" was read on the floor of the House of Representatives, the House applauded and the letter was ordered printed in the "Congressional Record." Subsequently, and with the hearty cooperation of Rear-Admiral Robert E. Peary, Congressmen Kahn, Lieb, Hulbert, and Senators Johnson and Sheppard, and Government officials, an exhibition of four aero- planes was held in Washington. It lasted about two weeks and assisted greatly in educating the members of both Houses and making them realize the necessity of increasing the appropriations for aerial defense. It was also through the interest created by the Na- tional Aeroplane Fund that Mr. Ralph Pulitzer of- THE EVOLUTION OF MILITARY AVIATION 287 fered the Pulitzer trophy, instituting the National Aerial Derby, which is to take place annually, and for which there has been set aside $20,0C0 to be given as prizes, this sum being part of the contributions made to the National Aeroplane Fund by Mr. Emerson Mc- Millin, who requested that his contributions be spent at the discretion of the Board for whatever purposes the Board deemed best. To interest the younger generation in aeronautics, prizes were offered from the National Aeroplane Fund for model aeroplane contests, in which more than twenty model aero clubs in different parts of the coun- try participated. Knowing that the Wright Broth- ers themselves became interested in aeronautics through a toy helicopter, we realized that offering prizes to encourage the younger generation may re- sult in finding geniuses who may eventually create, or develop or invent something which will be of great value to mankind. To interest the still younger gen- eration, at the time when the National Educational Association of the United States held its convention in New York, steps were taken to interest in aeronau- tics the 60,000 school teachers who attended the con- vention. An aeroplane exhibition was arranged espe- cially for the teachers, and they were given copies of "Flying," donated by the publishers, containing the history of the development of aeronautics from the earliest ages ; and a diploma to be awarded to a pupil in each school who writes the best composition on aeronautics. The foregoing is only a brief outline of what has been accomplished by the National Aeroplane Fund. It would take many pages to give the less prominent achievements. The committee received substantial and hearty sup- port from the following governors of the club: Rear- Admiral Robert E. Peary, Cortlandt F. Bishop, John Hays Hammond, Jr., Evert Jansen Wendell, diaries Jerome Edwards, Albert Bond Lambert, George M. Myers, Henry B. Joy, Rodman Wanamaker, and the late Samuel H. Valentine. It is hard for me to find words that will adequately express the value of the work done by Mr. Henry Woodhouse in connection with the National Aero- plane Fund. He subscribed the first $1000 to make it possible to begin the National Aeroplane Fund, and then made additional contributions during the cam- paign. He has given his entire time, practically six- H jmm '^y"-mmy^_ r-^ M 1" __ — : ^z!!32£*JBSLaH^HHHBI^^^^^I Looking down on a German Gotha resting on the ground. (British official photo.) 238 TEXTBOOK OF MILITARY AERONAUTICS teen hours a day, every day, including Sundays and holidays, to this work, practically only leaving the club house on occasions when he had to deliver ad- dresses and to attend meetings or make trips of in- spection in connection with the furthering of this campaign. He has done this without compensation or expectation of compensation. Very sincerely yours, Alan R. Hawley, Chairman. Firing Guns, Dropping Large Bombs, and Two-Engined Aeroplanes Once Consid- ered Impossibilities The writer clearly remembers that in 1910-13 the firing of machine-guns and the dropping of large bombs from aeroplanes were considered impossibilities. It was lield that tlie recoil of a gun would upset the aeroplanes ; while the drop- ping of weight of more than fifty pounds would upset the aeroplane. For that reason it was held that aeroplanes could only be used for scouting, directing artillery fire, and taking photographs. The development of speedy aero- planes was discouraged. Those who expressed the possibility of equipping aei'oplanes with two or more motors were considered visionary, the general opinion being that an aeroplane equipped with two motors would fail. Two reasons were given: First, the machine would be unable to lift its own weight ; secondly, if one motor stopped, the other motor would make the machine spin. Speed in aeroplanes was developed, there- fore, entirely by private efforts, mainly by sportsmen and aero-clubs in connection with the annual competition for the Gordon-Bennett Cup. As early as 1912 this trophj' was won by a flight of over one hour at a speed of 10.5 miles per hour. In 1913 tlie winner of the Gordon- Bennett Cup made a speed of 124 miles an hour for about one hour. In 1913 a prize of $15,000 was offered by Mr. Edwin Gould, a member of the Aero Club of America, in a competition for twin-motored aeroplanes, but it was not won, although the conditions required only a flight of about one hour. Following is given, for historic purposes, a table of the performances required by the British War Office for aeroplanes of different types on February 9, 1914. British Army Tests for Aeroplanes in 1914 1. The Chief Inspector of Military Aero- nautics is prepared, on the request of an aero- plane constructor, to put an aeroplane through Onrille Wright and Lieutmant .S<-lfri — r 3 'r-- X j= j= CJ w T -7 X J= J= 00 I c c o fe £ g -^ S I 2 2 o « ^ « t'^ "^ g i! "> O .2 .2 .2 •M w "2 ^ !^rf .w * uX. ^^t- <- ^ « j: 3 ST 3 = '^ Cfl CA K V3 CA CA gj ij ^ ^ V ^ ^ U u QJ ^ U •C TO i .S ''I <5» 0» 01 Q> s I s s ' ' ' ' ' • 0» (5* W 0» ^ —^1 I J J J • o. m > 1^ i^ 1^ '^ "7 « to ? t ? ? 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F. Dodd, Signal Corps, United States Army; and D. E. Strahlmann, Engineer, War Department, Office of the Chief Signal Officer. (Paper presented January 1917 to the Society of Automotive Engineers.) In this paper we shall advance for discussion, should be entirely defenseless against the attack with hopes of solution, some important problems of hostile aeroplanes, connected with the construction of aeroplanes intended for military uses in the United States. Many of these problems also apply to aero- planes built for commercial and sporting pur- poses. Although the lessons on type develop- ment that are being learned in the European war are of immense value to us, many conditions that we must meet are peculiar to this country. Military Functions of Aeroplanes We will first consider the various military functions (becoming more and more distinct), as we understand them at present. It must be borne in mind that other important uses will, in all likelihood, develop. The aeroplane itself This and all other service types should carry one or more machine guns, and the general ar- rangement of the system should be such as to permit extensive fields of fire in important direc- tions. The useful load, that is, fuel plus the military load, and the speed range, determine the power required. A powerplant of about 200 h.p. would apparently satisfy most economically this problem, the primary requirements of the powerplant being reliability and fuel efficiency. Assuming this, the fuel will weigh between 700 and 800 lbs. The military load will be al- most 600 lbs. The complete aeroplane, fully loaded, will weigh over 3,.500 lbs. This aeroplane would also be adapted for and its uses in war are so new that it is impos- long-distance transportation of important com- sible to predict, with any degree of accuracy, munications or officers, the developments in even a few months. At present the aeroplane is being used in war for reconnaissance, fire control, rapid transporta- tion of important officers or communication, de- molition of valuable structures by bombing, and to attack hostile aeroplanes in order to prevent them from performing these functions. la — STRATEGICAL-RECONNAISSANCE MACHINES For this work the fuel capacity should insure a flight of at least 500 miles without stop. The average speed during this flight should not be less than 80 m.p.h. The military load consists of one pilot, one observer, a sketching outfit, a camera, a wireless set, and navigating instru- ments. The general rule is becoming more and more firmly established that no military aeroplane 245 lb — TACTICAL-RECONNAISSANCE MACHINES The fuel capacity of this type should insure a continuous flight of at least 250 miles at a speed of not less than 85 m.p.h. The military load should be about the same as that carried in the strategical-reconnaissance machine. A powerplant of about 125 h.p. is desired, the primary requirement being reliability. The fuel will weigh about 225 lbs., the aeroplane loaded somewhat less than 2,400 lbs. 2 — FIELD-ARTILLERY FIRE-CONTROL The tactical-reconnaissance machine can per- haps perform this duty, but it appears that the fire-control machine should be slower, and that one of its primary requirements should be an 246 TEXTBOOK OF MILITARY AERONAUTICS extremely good field of vision. The engine should be of 125 h.p., or perhaps less. 3 LOXG-KAXGER BOMBERS We here attack a more difficult problem, owing to the heavy useful load with which we must cHmb from the starting field. There will probabh^ be a wide range in sizes of machines intended for this duty. We will discuss what we might call an average type at the present time. The fuel capacity should permit going out at least 200 miles and returning safely, starting with a load of bombs weighing, say, 400 lbs. The machine should be capable of defending it- self from hostile aircraft, so that it can operate independently of escort. It appears that we need at least 250 h.p. and that, depending upon the total useful load, 300 h.p., or even 350, would not be too great. If we assume 300 h.p., the fuel weight will be at least 900 lbs. and the total military load, in- cluding bombs, about the same. This aeroplane will weigh, loaded, between 5,000 and 6,000 lbs. 4 — PURSUIT MACHINES The function of this type is to attack and drive off hostile aeroplanes of any of the three first-mentioned types, preventing them from ac- complishing their purpose. In fact, the em- ployment of this type should afford a sort of of- fensive defense against hostile aircraft of all descriptions. "While the types la, lb, 2 and 3 are interested primarily in objects on the ground, the pursuit type is occupied solely with events in the air. This type is at present divided into the one and two-place subclasses. a. — The one-place machine carries fuel for two hours at full speed, about 130 m.p.h. The pilot is the only occupant. He controls the ma- chine and operates the machine gun, or guns, of which there can be from one to four. He usu- ally aims the gun, in action, by "pointing" his aeroplane. All characteristics are sacrificed to reason- able limits in order to obtain rapid climbing ability, high speed, rapid climbing ability at high speed, and the greatest possible dodging ability, or "handiness." In the engine, reliability must be sacrificed to a great extent to obtain low weight per horse- power, in order that the necessary attributes of the aeroplane can be obtained. Between 90 and 130 h.p. is desired. At present by far the greatest percentage of engines in this type of machine are of the rotary air-cooled type. b. — The tiico-place machine carries fuel for three hours at full speed, about 110 m.p.h. Space is provided for two men, the pilot and the gun operator. This is, of course, somewhat larger and less agile than the one-place machine and, it is believed, is rapidly losing its popu- larity in favor of the smaller type. The power required is from 110 to 160 h.p. 5 — oat:rseas reconnaissance a. — The long-range machine of this type must carry fuel for six hours at not less than 75 m.p.h. Two men, wireless-transmitting set and navigating instruments are carried. The 300-h.p. plant used on the bomber should an- swer for this t\'pe satisfactorily, the greatest requirements being reliability and fuel effi- ciency. b. — The machine used for short-range recon- naissance and coast-artillery fire-control must carry fuel for three to four hours at speed of not less than 75 m.p.h. Two men, navigating in- struments, wireless and other signaling ajipa- ratus will be required. The 200-h.i:). engine used in the land strategical-reconnaissance ma- chine should answer. Some Problems in Construction It is important that engineers work out the mechanical details of a gi-eat many problems in construction, among which are the two-propeller system, the reduction of vibration, the develop- ment of light engine starters, gasoline supply systems, devices required for safe landing and improvements in wing and propeller design. THE TWO-PROPEEEER SYSTEM "When an all-around field of fire is necessary, the best arrangement is to carry the two or three SOME PROBLEMS IN AEROPLANE CONSTRUCTION 247 operators and the main supply of gasoline in a central body, and to drive the machine by two propellers — one at each side of this central body. By such an arrangement machine guns can be fired forward, in attack, and to the rear, in re- treat, with extensive fields of fire in both direc- tions, above and below, to right and to left. This attribute is always desirable, and, in some types, as for instance in the bombers and recon- naissance machines, is essential. These propellers can be either tractor screws or "pushers," The left-hand propeller should turn clockwise and the right-hand propeller counter-clockwise. This symmetrical arrange- ment is a great advantage, in that it permits equalized torque and gyroscopic efforts when turning in different directions. In addition, it makes for safety, because the downward velocity imparted to the inboard parts of the two slip- streams that strike the horizontal tail-surfaces produces an inherent tendency toward nose heaviness without power and toward tail heavi- ness with power. We can, therefore, design so that the line of thrust is considerably above the center of gravity, compensating for this, and obtaining another convenient feature. A fourth great advantage of such a system is the fact that great power can be transmitted with good propeller efficiency without demand- ing excessive diameter and retaining satisfac- tory structural safety factors. It is highly de- sirable that the line of thrust of the propeller be kept below the center of gravity of the aero- plane, unless the two-propeller arrangement, as described above, be used; a propeller of large diameter, with sufficient clearance, necessitates a high landing gear with its many great disad- vantages. It appears extremely difficult to build a propeller of wood, of satisfactory strength (if the speed of revolution be high), giving good efficiency, to transmit more than 160 h.p. Peculiarly stringent climatic condi- tions making for rapid deterioration have in- creased this difficulty. In fact the tendency to reduce cylinder diameter and increase crank- shaft revolution speed is already necessitating a gear between crankshaft and propeller-shaft in order to keep the propeller speed below 1,300 r.p.m., which is considered desirable. A fifth advantage of the two-propeller ar- rangement is that the total resistance of the air to progress through it of the complete aeroplane while flying under power will be diminished owing to the fact that less total projected area of bodies will lie in the propeller slip-streams. The velocity of the air striking objects lying in the slip stream is, say, 20 per cent, higher than the velocity of air not in the slip stream. The resistance varies about as the square of the velocity. Therefore, all other things being equal, less power will be required to overcome the total resistance. ARRANGEMENTS WITH TWO PROPELLERS Four different systems for two-propeller in- stallation have been suggested: 1. Two engines, one on each side, mounted out on the wings. The fundamental weakness of this system is that these great masses, re- moved so far from the center of gravity of the aeroplane, produce great moments of inertia, and consequently slow periods of oscillation. The machine is "logy" and probably not satis- factory for any but "hydro" purposes, in which case a "snappy" machine is impossible at best. 2. Two engines mounted in the central body between pilot and observer, each driving its own pi'opeller through bevel gears and shafts, or by other method, the two systems being independ- ent. 3. One large engine, mounted in the central body, driving both propellers, one propeller at each side. 4. Two engines, mounted in the central body, with a system of clutches connected with the transmission system in such a manner that either engine, or both engines, can drive both pro- pellers, it being possible for the pilot to shift during flight. The last system presents many advantages over the others, but it is entirely possible that excessive weight and complexity will render it impracticable. The system, as a whole, must be reliable. In the design of any system of transmission for the two-propeller arrangement, the en- gineer must bear in mind that the structure of the wings supporting the propeller and trans- 248 TEXTBOOK OF MILITARY AERONAUTICS mission is very light and rather flexible, usually vibrating during flight. The information at hand indicates that, to date, no successful aeroplane of the two-pro- peller type has been developed, but it is urged that the possible advantages are such as to war- rant great effort on the part of engineers to- ward this improvement. METHODS OF REDUCING VIBRATION The problem of reducing vibration of the aeroplane in flight, initiated by the engine, is a serious one. It is difficult to realize, without actual experience, the viciousness of this vibra- tion, especially when the engine is of the eight- cylinder type, even though it is running nor- mally. After one experiences this vibration, it is easy to understand why ignition systems, gasoline-supply joints, water-cooling systems, delicate instruments, and even wire terminals and structural joints of the aeroplane itself, de- teriorate so rapidly. The vibration throughout the aeroplane can of course be reduced by better design of the en- gine mounting, but we cannot hope to eliminate it entirely in this manner, if the engine itself is not of the proper design. We must not, in this connection, get the idea that the engine is al- ways operating at the same speed during flight. We can, for instance, if flying at extremely high speed, turn the crankshaft over at, say 2,000 r.p.m.; whereas, if our sole object is to remain in the air without losing altitude, as when spot- ting for artillery fire, we can use a crankshaft speed of, say, not more than 1,200 r.p.m. The vibration at any speed should not be excess- ive. STARTING MOTOR FOR ENGINES The development of light starters is a matter of immediate importance. For instance, a sea- plane cfjuipped with two engines, one out on each wing, would be utterly useless without re- liable starters. It seems quite probable that electric starters will be preferable, if the weight can he reduced sufficiently, and if the danger of spilling electrolyte be eliminated. It appears that any engine of over 140 h.p. requires a starter. Reliable provision for starting the engine in extremely cold weather is necessary. GASOLINE SUPPLY-SYSTEM To date none of our pilots is anxious to fly across country with any except gravity feed. The gasoline supply-systems Figs. 1 and 2, required by the U. S. Army for twin-engine seaplanes, is as follows: The flow of fuel shall be from the main sup- ply tank in central bodj^ to the gravity service- tank located at the center of the upper wing; from gravity service-tank by gravity, along the lower wing panels, to the small headers at the carbureters of the two engines, and from the small headers in each case to the carbureter. These tanks shall have fuel capacities suf- ficient for operation at full rated power, as fol- lows : Main supply tank, 4 hr. 3.5 min. ; gravity service-tank, 25 min. ; each header to carbureter, 1 min. The design and material of the gasoline sup- ply-system throughout shall be such as to ob- tain extreme lightness as far as consistent with strength and resistance to corrosion. MAIN GASOLINE-SUPPLY TANK IN CENTR^VL BODY This shall be divided by one vertical longitu- dinal bulkhead and one vertical transverse bulk- To"k fv Cariurtfr^S '*(]-Ofi RFT^P^ Fig. 1 — Gasoline supply system (suction pump) for military seaplane head into four gasoline-tight compartments. Proper swash-baffle plates shall bo installed. The tank shall be of sturdy construction throughout. The main tank shall be of such shape as to SOME PROBLEMS IN AEROPLANE CONSTRUCTION 249 properly fit the central body. It shall be se- curely fastened in the structure of the central body in such a way as to be undisturbed by any possible motion of the aeroplane. The struc- ture shall be such that the tank will withstand an internal pressure of at least 7 lbs. per sq. in. without leakage of gasoline. The design shall be such that there will be no ill effects from drumhead vibration. Suitable means shall be provided for quickly and conveniently filling and for completely draining all four compartments. Each filling hole shall have a suitable screen filter, 100 mesh to the inch. Plugs or caps for filling holes shall be air- tight and provision shall be made for "safety- ing" them positively in place. Suitable gaskets shall be used. Provision for reducing to a minimum the rate of leakage due to bullet holes by lining the in- side of the tank with a special material, is highly desirable. Suitable gasoline-supply gage shall be in- stalled. There shall be leads from the bottoms of the four compartments to the upper gravity serv- ice-tank. SUPPLY OF GASOLINE FROM MAIN TO GRAVITY- SERVICE TANK This shall be by two methods : First. — Air fan driven pump, so designed as to maintain proper air pressure in or suction from the main tank system, and to operate satis- factorily during flight. An alternative and bet- ter method will be to install two such fans, each fan maintaining pressure in any two of the four compartments of the main tank. When any one or two of the four compartments of the main tank leaks (because of bullet hole or through other cause) , an arrangement by which pressure or suction can be maintained through the leads from the tight compartments is highly desirable. Second. — A hand air-pressure pump in or at the side of the pilot's cockpit, which can be used when not in flight or in an emergency. This pump shall be located in the cockpit at a point as high as will permit convenient operation by the pilot in his seat. It shall be provided with a suitable air-pressure gage, visible to the pilot. Its connections with the compartments of the main tank shall be at a point as high as prac- ticable to prevent the pump becoming flooded <^>{>ft f3F7 Fig. 2 — Gasoline supply system (air pressure) for military sea- plane with gasoline. An arrangement by which pres- sure can be maintained by the hand air-pressure pump on tight compartments of the main tank when one or two compartments leak is highly de- sirable. CONSTRUCTION OF GRAVITY SERVICE-TANK This tank shall be of sturdy construction, se- curely supported in place, and provided with the proper number of swash-baffle plates. It is considered desirable to protect this tank. with light V-shaped armor on the under side. An automatic ball-float valve shall be pro- vided to prevent overfilling of this tank. A suitable overflow pipe out of the top center of the gravity service-tank shall be provided. The gravity service-tank shall be of good stream-line form. A suitable gage, visible to the pilot in his seat, shall be in the gravity service-tank. This gage shall be connected at such a point that it will register accurately through the range of normal flight attitudes. From the gravity service-tank the gasoline shall be led to a small header at each engine by leads within or along the lower wing panels. Between gravity service-tank and each header shall be two independent, and, as far as prac- ticable, isolated tube leads. Each of these four 250 TEXTBOOK OF MILITARY AERONAUTICS leads shall connect with the lower part of the gravity sen'ice-tank at such a point that the supply will not be interrupted at any normal flight attitude. At the connection of lead to the gravity serv- ice-tank shall be a suitable wire gauze strainer, mesh 100 to the inch. Provision shall be made to prevent the possibility of air pockets in the gasoline leads from the gravity service-tank. Provision shall be made for permitting the pilot, while in his seat, to cut off the gasoline supply, through all leads, from the gravity service-tank to the carbureter headers. HEADERS BETWEEN CARBURETEE AND SERVICE- TANK A small cylindrical or stream-line tank or header shall be installed in the immediate vicinity of each carbureter. The gasoline shall pass through this header after coming from the gravity service-tank. Its capacity shall be sufficient for one min- ute's running at full-rated horsepower. The central portion of this header shall be on a level with the jets of the carbureter. The axis of the cylinder shall be vertical. The cylinder shall be of sufficient length to give satisfactory head, either when the aero- plane is in normal attitudes or when it is upside ■down. Provision shall be made to prevent gasoline from backing up into the service lead instead of coming into the carbureter when the engine is upside down. Suitable gasoline cutoff shall be installed near this header in such a position as to be convenient for operation to a man standing on the ground or on the wing. TUBING FOE FUEL LEADS At every point these shall be of the highest grade material best suited for the purpose. It shall he approved by the inspection department. Flexible tubing shall be ^e-in. No, 2 copper tubing. Non-flexible leads shall be piping as approved by the inspection department. Tubing .shall in all cases be of diameter suffi- cient to give free and continuous flow under se- vere vibratory conditions. In the absence of other instructions the bore shall be %6-in. All tubing shall be securely fastened in such a way as to resist wear, vibration, and chafing. The number of joints and fittings shall be re- duced to a minimum. Unions, ells, tees, and fittings, to be S. A. E. standard, approved by the inspection depart- ment. The method of connecting all leads shall be aj^proved by the inspection department. All fittings shall be readily accessible for inspection, adjustment, repair, or removal. It will be seen that it will require consider- able ingenuity to work out satisfactorily the me- chanical details of this complicated arrange- ment. For instance, a satisfactory method of insuring feed from the compartments of the main tank, up to the gravity tank, when one or more of the main compartments are punctured by shot, is required. MET^VL CONSTRUCTION FOR AEROPLANES It is suggested that the field for development of steel aluminum alloy in the structure of aero- planes is one offering considerable inducement. The authors have gone briefly through the lay- out of an aeroplane in which every strength member is of metal. In this design it was found most convenient to use seamless steel tube at some places, welded tube at others, channel section at others, I-section and L-section, at others. At a few points aluminum alloy was used, at other points pure aluminum, assump- tion being made that this aluminum was rolled in such a way as to give it certain desired phj'si- cal characteristics. It is suggested that, even with the present standard method of construction, there is great room for improvement in the material and method of heat treatment of the metal fittings used in conjunction with wood and wire. Es- pecially where fittings are bent both with and across the grain, a special alloy appears advis- able. The same holds for fittings shaped by die-forging. Chrome vanadium steel, to com- ply with S. A. E. specifications 6130, and heat treated in such a way as to render it best in each case, is suggested. It is believed that the total weight of an aeroplane can be materially de- SOME PROBLEMS IN AEROPLANE CONSTRUCTION 251 creased, without sacrifice of strength, and hence superior performance obtained, by the use of better steel. The construction of floats of metal for sea- planes appears to be a possibility as is also the use of metal for aeroplane propellers. It is possible that the entire body might be made of light pressed steel, or aluminum, with holes to decrease the weight cut at proper places, and covered with linen. ri,EXIBLE PIPING Satisfactory flexible gasoline lead has not yet been developed. Such a lead should resist the action of vibration, should be light in weight and resist cutting or denting. The method of mak- ing joints is important. The duct should be carefully sweated into proper terminal fittings. Tube ends of fittings should have spiral springs wound around them for at least 2/4 in., thus pre- venting sharp bends and disturbing the effects of vibration. All unions should be ground, with spherical seats, and threads should be cut clear and sharp, with all burrs removed. The inside diameter of tube should not be less than 0.35 in. A flexible pipe, light in weight, of material suitable for leading the exhaust away from the engine would be useful. MUFFLER REQUIREMENTS In military service a hostile aeroplane is usually first discovered by hearing it. A muf- fler satisfactory as to low weight, flexibility, loss of power through back pressure, durability against corrosion, and efficiency as a muffler, is highly desirable. SHOCK ABSORBERS FOR LANDING GEAR Rubber is not satisfactory as a shock absorber for heavy aeroplanes. Neither is it satisfactory as a military supply, especially when it is sub- jected to heat and the direct rays of the sun. It seems necessary to develop a steel-spring shock-absorber. The action of this steel spring must, however, be damped by an oil cylinder. Without this damping the action is such as to cause the aeroplane to bound excessively upon striking the ground. BRAKES REQUIRED WHEN LANDING The development of a brake to reduce the run of the aeroplane after it has touched the ground, thus permitting it to land in restricted areas, appears to be a difficult problem. It is a moot question whether such a brake is desirable when the simple two-wheel landing gear is used, as its action has a tendency to throw the aeroplane over on its nose. Where more than two wheels are used, however, a brake fitted to the two main rear outside wheels in such a way that the pilot can, from his seat, operate either brake, or both brakes together, would be desirable. Such an arrangement would permit him not only to stop his machine quickly, but also to steer it on the ground to some extent. FOLDING LANDING GEAR The development of a landing gear that can be submerged within the body by the pilot, dur- ing flight, would materially increase the speed of the aeroplane by reducing the "parasite" re- sistance. Such a mechanism should be light in weight, sturdy and simple. GASOLINE SUPPLY GAGE The development of a gage to indicate the supply of gasoline remaining in the tanks to the pilot, whose seat can be out of view of the tanks, is necessary. Such a gage should be simple and sturdy. The accuracy and re- liability with which it registers should not be affected by any change in altitude of the aero- plane. It should not form a possible source of leakage. It should be adapted to both the pres- sure and suction systems of feed. FIRE SAFETY-DEVICE Many casualties have occurred because the aeroplanes have caught fire in the air. While it has been impossible to determine from the wreck just what led to the fire, it is quite prob- able that many of these accidents were due to back fire into the carbureter that forced burn- ing gasoline out into the surrounding structure, or to a leaking gasoline tank. The develop- ment of a device that will render such an acci- dent impossible would save many lives. 252 TEXTBOOK OF MILITARY AERONAUTICS In this connection it should always be a rule for aeroplane constructors never to have any electric lead near a gasoline supply or lead. ALTITUDE ADJUSTMENT FOR A CARBURETER The development of a device to regulate auto- matically the mixture for variations in density of air incident to changes in altitude, would be valuable. VIBRATIOX-ABSORBING MATERIAL The development of a material more suitable than ordinary felt for padding the points of support of radiators, and the like, is highly de- sirable. VARIABLE RADIATORS A more suitable method of permitting the pilot to adjust the amount of cooling done by the radiator in order to compensate for changes in temperature of air, or changes in speed through the air, is necessary. Such arrange- ment should permit operation by the pilot from his seat during flight, or, better yet, might be automatic ; the device being operated as a func- tion of the temperature of the water. It should be durable and should act with reliability. VARIABLE-CAMBER AVING Great speed range is a desirable attribute of an aeroplane, as it permits high speed of travel in the air and yet low speed while landing, which of course makes for safety if the landing place be small or rough. Great improvement in the speed range can be brought about by use of a variable-camber wing surface, that is to say, if the section form of the aerofoil could be changed at will during flight from a shape such as A to one similar to B, Fig. 3. tive wind). At small angles of attack, where the lift coefficient is low, this shape has a rela- tively high resistance and will consequently re- quire a gi'eat power to drive it through the air at speed high enough for the necessary support. The reverse is true of such a shape as A, which, though the lift coefficient is poor, has an appreciably lower resistance or "drag." If, then, we could utilize the section B for slow speed, as in making landings, and section A for high speed, the safe limits of speed be- tween which the aeroplane could fly would be extended. The variable-camber would permit changing the characteristics of the wing to suit conditions. Performance curves (Figs. 4 and 5) have Fig. 3 — Variable forms of aerofoil sections An aerofoil such as shown in B, has a high lift coefficient at large angles of attack (the angle of attack being the angle between the chord tangent to the lower surface and the rela- SP£ED MILCS PER HOUR Fig. 4 — Performance curves for aeroplane with ftxed-camber wing been worked out for a pursuit machine having a good aerofoil (ffxed-camber) in common use to- day ; and a similar series of curves for a machine with an assumed variable-camber wing. It has been assumed that otherwise both aeroplanes are similar. No allowance has been made for the probable increase in weight of the variable- camber machine due to the operating mechanism and structure. The slow speed of the fixed-cambered wing aeroplane is 61 m.p.h. This will only permit landing the aeroplane on an ideal field by a very skilful pilot. On the other hand the variable-cambered wing aeroplane can be flown at a slow speed of 56 m.p.h. The curves show that with the variable cam- ber a higher speed, 127 m.p.h., as against 120 for the fixed camber, can be obtained with the SOME PROBLEMS IN AEROPLANE CONSTRUCTION 253 same power. The same speed might be ob- tained with less power. SPEED MILES PER HOWR Fig. S — Performance curves for aeroplane with variable-camber wing // the same high speed were desired the vari- able-camber wing might have a greater area. It would then have a slow speed of 46 m.p.h. as against 61 for the fixed camber (allowing for increased weight due to added surface), which would permit its being flown and being landed in an ordinary field, by the ordinarily skilful pilot. It can, therefore, be seen that the invention of a suitable variable-cambered wing would be a big step in advance. APPENDIX In calculating the values used in plotting the performance curves. Figs. 4 and 5, the weight of machine was assumed as 1150 lbs., and the engine was assumed to develop 140 b.h.p. The lifting power of a wing is given hy L = KvA V^, where L is the lift, Kv the lift coefficient (which varies for different altitudes of the wing to the relative wind and must be determined by experiment), A is the area of the wings and V the air speed. Similarly the resistance of a wing is expressed by D = K):A V^, Kx being a variable coefficient that must be found by experiment. The speed at which the aeroplane must fly for any assumed angle of attack can be found from the lift formula. The lift in all cases, of course, is assumed to be the weight of the aeroplane. The resistance of the wings at these speeds can then be determined and the total resistance found by adding the parasite resistance, that is, the resistance of the body, landing gear, etc. From the total resistance the horsepower re- quired can be calculated and plotted against speed. The horsepower available is obtained by multiplying the efficiency of the propeller by the brake horsepower delivered by the engine. I SECTION Fig. 6 — Rib used in present type of wing construction The ribs as ordinarily used in the present type of wing construction are as shown in Fig. 6. The weight of such a rib for a small pur- suit machine, as assumed in the above calcula- tions would be less than I/2 lb. The ribs would be spaced from 12 to 15 in. along the spars. A wing complete with cover, internal bracing, etc., weighs from 0.6 to 0.7 lb. PKOPELI,ERS WITH VARIABLE-PITCH ANGLE Improved performance of an aeroplane, espe- cially as regards radius of action, can be brought about by means of a propeller whose pitch angle can be varied by the pilot while in flight. The liability of failure, the complexity of the mecha- nism and the weight added, must be weighed against the gain obtained in the performance. The gain in efficiency of the variable-pitch propeller over the fixed-blade type is consider- able. This increased efficiency makes available more horsepower for climbing, giving faster climbing, and permits throttling down to attain the economical speed, and hence increases the flight radius and the time in the air with a given quantity of fuel. These facts are more clearly brought out by the approximate curves given in Fig. 7, which give the horsepower required, and horsepower available at various speeds for a fast reconnais- sance type of aeroplane of refined design. The full lines give the power available for a fixed- blade propeller; the dotted lines for a variable- angle blade. It is assumed that the propeller was designed for maximum efficiency at the high speed of the aeroplane. The most evident gain made by using the variable pitch as observed from the curves is the 254 TEXTBOOK OF MILITARY AERONAUTICS increased reserve horsepower available for climbing. This particular assumed aeroplane, with full load, climbs: With fixed blade: 650 ft. the first minute. Fig. 7 — Performance curves for reconnaissance type of aeroplane With variable-pitch blade: 715 ft. the first minute. The increase in the radius of action is very great, the greatest radius of action being ob- u» ««0 /f / / J'^' / / / V ^ ^ / / \,^ — --' 1 ■J ^^- 1 to «a 70 so SPCCO. MILCS PCR HOUR Fig. 9 — Showing economical speeds of aeroplanes with flxed- bUde (full lines) and variable-blade (dotted lines) propellers tained when flying at the economical speed of the aeroplane. Figure 8 shows the economical speed in each case. On one filling of the gasoline tanks the fixed blade would carry the machine about 690 miles in 10^ hours. The variable-pitch blade would carry the same machine a distance of about 10.50 miles in 15i/^ hours. (Were this machine driven at fuU power it could go but 600 miles with either propeller. ) These cures, while only approximate, will at least give some indication as to the value of a variable-angle propeller, especially where great distances are to be covered. The greater efficiency of the variable pitch would be of value in giving increased climbing Angle of Attach ability at high altitudes and the possibility of reaching greater heights with a given machine. Another feature possible, of secondary impor- tance, in a variable-pitch blade is that it can be rotated to give a large negative angle of attack, or possibly reversed, when the aeroplane is on the ground making a landing, thus serving as a brake and cutting down the distance the ma- chine rolls on the ground, APPENDIX The weight of assumed aeroplane fully loaded is 2400 lbs. The brake horsepower of engine is as given in Fig. 11. The fuel capacity is six hours at full power. If A denotes the angle that the helix line makes with the base line. Fig. 9, V the transla- tional velocity in feet per second and iV the pro- peller speed in revolutions per second, then the distance advanced each revolution, neglecting slip, is (r-^2V) ft., which is the effective pitch of the propeller. Suppose the chord XF of the blade section at any radius V , makes an angle a with the lielix line. Fig. 9. Angle a is called the angle of at- tack of the section. As {V-^N) changes owing to a variation in either V or N, or in both the blade section will liave a varying angle of attack, an increase in {V -^ N) decreasing the angle of attack and vice versa. SOME PROBLEMS IN AEROPLANE CONSTRUCTION 255 The efficiency of such an element is expressed by c = tan^ tan {A + G) where G is the gliding angle, which is a func- tion of the angle of attack and varies with the --^ ^ \" ' >' ^■■/ y \ i / / \ / / / \ 1 f 1 1 1 t / / / ■cpeller Propeller __w Van fble-f>ifth 1 ! / / 1 / 1 / t / t / 1/ 2 DISTANCE 4 ADVANCE f >tR REVOLU TiOH.FErr • Fig. 10 type of section employed. With the usual sec- tion used in propeller design G is a minimum when the angle of attack is about 4 deg. It 750 1000 nV> IKK) REVOLUTIONS PER MINUTE This can be accomplished by means of a flex- ible blade whose pitch angles could be changed a varying amount from the tip of the blade to the root or hub section. Such a blade is out of the question in the light of present day practice. A good approximation to such a blade could be more simply had by rotating the blade about its axis perpendicular to the shaft. With the usual type of section employed the approximation is good as the value of G does not change greatly for a degree or so on either side of the best angle of attack. A mean value for the angle of at- tack could therefore be found giving practically the same efficiency as though all the sections were at the best angle of attack. Fig. 10 shows curves in which efficiency of a propeller is plotted against {V-^'N). The full line gives the efficiency for a fixed blade, the dotted line the efficiency of the same blade were the angle of attack kept at approximately 4 deg. It is assumed that the fixed-blade propeller was designed for a maximum efficiency at a value of (r^2V),of about 6 ft. Propeller Stresses In connection with the subject of propellers, it may be of interest to give a brief review of the variation of stress that occurs in a propeller blade under an assumed condition of flight. The blades of a propeller are subject to the following stresses when an aeroplane is in any but a straight-line flight: Fig. 13 — Points of maximum propeller stress Fig. 11- -Assumed brake horsepower of Engine Driving variable- pitch propeller 1. Shear due to aerodynamical forces. 2. Torsion due to the distance between the would therefore be advantageous from the view- center of gravity of the blade section and the point of efficiency of the section to keep the point of application of the resultant of the air angle of attack at 4 deg. throughout the speed reactions. of the aeroplane. 3. Tension due to centrifugal force. 256 TEXTBOOK OF MILITARY AERONAUTICS 4. Steady bending due to aerodynamic forces ; torque and thrust imposing a distributed load on the blade, the hub being the fixed point of support. 5. Reverse bending due to gjToscopic forces, which occurs only when the aeroplane has rota- tion about an axis, as in making a turn or pull- ing out of a dive. As a matter of fact, an aero- plane is continually turning to some extent if the flight be in disturbed air. Each of these forces produces a maximum stress of tension and compression in different parts of the blade, hence the resultant fiber stress at any point will be equal to the algebraic sum of the individual stresses at that point. It is sufficient to calculate the stress at the points a, b, c, (Fig. 12) along the blade, as these points will be those of maximum stress. The shear in any case is small and can be neg- lected in design. The torsion is also small. In good designs, when the thrust is great, the point of application of the air reactions is but little removed from the axis passing through the cen- ter of gravity of the section. The curves of stress given are for a three- blade propeller of about S^A ft. diameter, 5 ft. pitch, absorbing 150 h.p. at 1300 r.p.m. The ^ r JIABIUS IN rccT 5h5» Pig. IS— Fiber stress In propeller blade at point o (See Fig. 12) curves are not accurate, as they are intended merely to give a general idea of the order of magnitude of the stresses likely to occur in such a propeller. The stress caused by centrifugal force is uni- form over any section of the blade and varies in intensity at points along the blade, as shown ap- proximately in Figs. 18, 14 and 15. Steady bending due to aerodjmamic forces is caused by torque and thrust. These forces act along X — X and Y — Y, respectively for any section, such as shown in Fig. 12. When re- solved along I — I and II — II they induce bend- ing moments that cause the fiber stress as shown in Figs. 13, 14 and 15. Gyroscopic moments are only induced when the aeroplane is changing its direction of flight. In order to estimate the stress set up in the blades an assumption must be made as to the angular velocitj^ of the propeller axis; that is, as to the precession. There is some question as to the assumption it is reasonable to make in computing the stresses. The type of aeroplane, size and disposition of the larger masses, such as engines, etc., will affect the rate at which a machine can be turned in flight. In general, the angular velocity in yaw will not greatly exceed 0.35 radians per second. It must be re- membered, however, that a steeply -banked turn also involves rotation in pitch. The maximum angular velocity attained in coming out of a steep dive can be estimated from the characteristics of the aeroplane and the fac- tor of safety, which determine the maximum RAOWS IN FCCT Fig. 14 — Stress in propeller blade at point 6 (See Fig. 12) high speed attainable and the radius of curva- ture of the path along which it is possible to pull the machine out of its dive safely. A safe value for the angular velocity in pitch for the usual type of present-day aeroplanes is about one ra- dian per second. Loops have been turned in about 6 seconds, which gives about the value mentioned of the angular velocity. A precession of one radian per second at the SOME PROBLEMS IN AEROPLANE CONSTRUCTION 257 normal speed of the engine should therefore be assumed in computing the stresses. The stresses set up by gyroscopic forces are alternating, changing in sign (tension to com- pression) twice in each revolution of the propel- ler about its axis. RADIUS m FEET Fig. 15 — Stress in propeller blade at point c (See Fig. 12) The fiber stress caused by the gyroscopic mo- ments is given in Figs. 13, 14 and 15. Alge- braically adding the fiber stress at the three points chosen gives the approximate value of the resultant fiber stress at those points, as shown in the same figures. It will be noticed that the maximum stresses occur at some distance out from the hub. To insure a good wearing blade, which will stand up under the necessarily hard usage given it in the field, a factor of safety of not less than 5 is suggested as being the minimum consistent with requirements when the three principal stresses are taken into consideration. Suggestions for Improvements in Design These suggestions on powerplants are based on the experience of the First Aero Squadron, United States Army, in the field. It is considered extremely poor practice to use shims under caps of crankpin and crankshaft bearings. JNIany American crankcases are not suf- ficiently rigid in construction. It is believed that crankcase castings are not designed and built, in this country, with sufficient care. Some of the jigs for boring crankshaft and camshaft bearing seats are not so accurate as desirable. In some cases it has been found that pistons are not of uniform weight, and are not carefully made. Lack of inter changeability of parts and care- less workmanship have been great faults in this country. OILING SYSTEM This should be by pressure to all important bearings, preferably from a gear pump. Screens should be provided to protect the suc- tion pumps. For engines that have push-rod and rocker-arm valve mechanism, means should be provided to reduce the friction on the ex- haust-valve rocker-arm bearing, especially if the valves are more than 1^/4 in. diameter, IGNITION All military aeroplanes, except possibly the pursuit type, should have two complete and in- dependent ignition systems. Engines larger than 140 h.p. should have a booster system for starting on battery spark, if a starter is not provided. It is believed that our magnetos would have much longer life if a more suitable shock-ab- sorbing device between the driving gear and the magneto shaft were provided, A magneto mounting should be machined so that the mag- neto shaft will be exactly in line with its driving shaft; dowel pins and dowel-pin holes to pre- serve this alignment should be provided. No shims should be used here. We have had con- siderable trouble because of non-uniform and warped carbon brushes. FUEL SUPPLY Carbureters should be located in such a way that oil, water and impurities cannot enter them. They should be supported from the engine and not from the frame work of the aeroplane. They should be supported independently of the intake manifolds, if practicable. Gaskets for connections in intake manifolds should be as thin as practicable. Manifolds built of copper, brazed, or of steel, welded, are considered preferable to cast manifolds. Steel is considered preferable, but should, of course, be heat treated after welding. 258 TEXTBOOK OF MILITARY AERONAUTICS It is urged that more study and care should be put into the design relating to shape and fin- ish of the interior of intake manifolds and pas- sages. It is believed, in this connection, that much greater efficiency can be obtained by at- tention to fluid flow. COOLING SYSTEM Radiators should preferably be placed at the leading edge of the upper wing, the header be- ing shaped so as to form part of this leading edge. If it is necessary to place the radiator between the engine and the propeller, the radia- tor should be circular. The radiator should be provided with a sufficient number of points of support to prevent deformation of the shell ow- ing to shocks on landing. Care should be taken with the alignment of tubes at the connections in the water-circulating system. A ring reinforcement might be welded to a flanged end of the thin tubing and the face machined so as to make a good fit to the cylin- der jacket. It is considered bad practice to ex- pand thin tubing. Memoranda: CHAPTER XX METHODS OF MEASURING AIRCRAFT PERFORMANCES By Capt. H. T. TizAKi), R.F.C. Aeroplane Testing The accurate testing of aeroplanes is one of the many branches of aeronautics which have been greatly developed during the war, and es- pecially during the last year. For some months after the war began a climb of 3,000 to 5,000 ft. by aneroid and a run over a speed course was considered (juite a sufficient test of a new aeroplane; now we all realize that for mili- tary reasons certainly, and probably for com- mercial reasons in the future, it is the perform- ance of a machine at far greater heights with which we are mainly concerned. In this paper I propose to give a short general account of some of the methods of testing now in use at the Testing Squadron of the Royal Flying Corps, and to indicate the way in which results of actual tests may be reduced, so as to represent as ac- curately as possible the performance of a ma- chine independently of abnormal weather con- ditions, and of the time of the year. For ob- vious reasons full details of the tests and meth- ods employed cannot yet be given. So far as England is concerned, I believe that the general principles of what may be called the scientific testing of aeroplanes were first laid down at the Royal Aircraft Factory, Our methods of re- duction were based on theirs to a considerable extent, with modifications that were agreed upon between us; thejj^ have been still further modified since, and recently a joint discussion of the points at issue has led to the naval and military tests being coordinated, so that all of- ficial tests are now reduced to the same stand- ard. It should be emphasized that once the methods are thought out scientific testing does not really demand anv high degree of scientific knowledge ; in the end the acciu-acy of the results really depends upon the flyer, who must be pre- pared to exercise a care and patience unneces- sary in ordinary flying. Get careful flyers whose judgment and reliabilitj'^ you can trust and your task is comparatively easy; get care- less flyers and it is impossible. At the outset it may be useful to point out by an example the nature of the problems that drise in aeroplane testing. Suppose that it is desired to find out which of two wing sections is most suitable for a given aeroplane. The aeroplane is tested with one set of wings, which are then replaced by the other set and the tests repeated some days later. The results might be ex- pressed thus: A Wings. Speed at 10,000 ft Rate of climb at 10,000 ft 250 ft 90 m.p.h.. B Wings. 93 m.p.h. a minute. 300 ft. a minute. 259 Now, the intelligent designer knows, or soon will know, that, firstly, an aneroid may indicate extremely misleading "heights": and, secondly, that even if the actual height above the ground is the same in the two tests, the actual conditions of atmospheric pressure and temperature may have been very different on the two days. He will therefore say. What does that 10,000 mean? Do you mean that yoiu* aneroid read 10,000 ft., or do you mean 10,000 ft. above the spot you started from, or 10,000 ft. above sea-level? If he proceeds to think a trifle further he will say, What was the density of the atmosphere at your 10,000 ft.; was it the same in the two tests? If not, the results do not convey much. There he will touch the keynote of the whole problem, for it is on the density of the atmosphere that the whole performance of an aeroplane depends; the power of the engine and the efficiency of the machine depends essentially on the density, the resistance to the motion of the machine through 260 TEXTBOOK OF MILITARY AERONAUTICS the air is proportional to the density, and so finally is the lift on the wings. None of these properties are proportional solely to the pres- sure of the atmosphere, but to the density — that is, the weight of air actually present in unit vol- ume. It follows that it is essential when com- paring the performances of machines to com- pare them as far as possible under the same conditions of atmospheric dcnmti/, not as is loosely done at the same height above the earth, since the density of the atmos])here at the same height above the earth may vary considerably on different days, and on the same day at different places. -zoooo I6O0O ISOOO fiooo VartJtl Fig. I. ions of lemaerature uiilh Heiifht. -' \\ \ \& \ \''* V-. \ 1 v^,_ Jo So la TEMPERATURE 90 At the same time, in expressing the final re- .sults, this principle may be carried too far. Thus, if the speed of a machine were exjiressed as 40 meters a second at a density of 0.8 kilogs. per cubic meter, the statement, though it may be strictly and scientifically accm-ate, will convey nothing to 99 per cent, of those directly con- cerned with the results of the test. The result is rendered intelligible and, indeed, useful by the form, "90 m.p.h. at 10,000 ft.," or whatever it is. With this form of statement, in order that all the statements of results may be con- sistent and comparative, we must be careful to mean by "10,000 ft." a certain definite density — in fact, the average density of the atmosphere at a height of 10,000 ft. above mean sea-level. This is what the problem of "reduction" of tests Imils down to: what is the relation between at- mospheric density and height above sea-level? This knowledge is obtained from meteorological observations. We have collected all the avail- able data, mostly unpublished, with results shown in the following table: — Table 1. — Mean Atmospheric Pressure, Temperature and Density at various Heights above Sea-level. Mean temp. Mean Height Height in Mean in absolute density in in equivalent pressure m degrees kgm. per Kiloms. feet. millibars. Centigrade. cubie meter 1,014 282 1.253 1 3,280 900 278 1.128 2 6,560 795 273 1.014 3 9,840 699 268 0.909 4 13,120 615 262 0.818 5 16,400 568 255 0.735 6 19,680 469 248 0.658 7 22,960 407 241 0.589 These are the mean results of a long series of actual observations made mainly by Dr. J. S. Dines. It is convenient to choose some density as standard, call it unity, and refer to all other densities as fractions or percentages of this "standard density." We have taken, in con- formity with the R.A.F., the density of dry air at 760 mm. pressure and 16° C. as our stand- ard density; it is 1.221 kilog. per cubic meter. The reason this standard has been taken is that the air speed indicators in use are so constructed as to read correctly at this density, assuring the law : p = VipY^, where V is the air s])eed. p the pressure oI)tained, i> the standard density. In some ways it would doubtless be more con- venient to take the average density at sea-level as the standard density, but it does not really matter what you take so long as you make your units quite clear. Translated into feet, and fraction of the standard density, the above table becomes : — Table II. Height in feet. Percentage of standarc density. Height in feet. Percentage of standard Height density. in feel. Percentage of standard density. 102.6 7.000 81.9 15,000 63.0 1,000 99.4 8,000 79.2 16.000 61.1 2.000 96.3 9,000 76.5 1 16.500 60.1 3,000 93.2 tl 0,000 74.0 17.000 .59.1 4.000 90.3 11.000 71.7 18.000 .57.1 5.000 87.4 12,000 69.5 19.000 .55.2 6,000 84.6 1 13,000 67.3 20.000 53.3 t6,500 83.3 14,000 65.2 METHODS OF MEASURIXG AIRCRAFT PERFORMANCES 261 Let us briefly consider what these figures mean. For example, we say that the density at 10,000 ft. is 74 per cent, of our standard density, but it is not meant that at 10,000 ft. above mean sea level the atmospheric density will always be 74 per cent, of the stand- ard density. Unfortunately for aeroplane tests this is far from true. The atmospheric density at any particular height may vary con- siderably from season to season, from day to day, and even from hour to hour; what we do mean is that if the density at 10,000 ft. could be measured everj^ day, then the average of the re- sults would be, as closely as we can tell at pres- ent, 74 per cent, of the standard density. The above table may therefore be taken to represent the conditions prevailing in a "nor- mal" or "standard" atmosphere, and we en- deavor, in order to obtain a strict basis of comparison, to reduce all observed aeroplane performances to this standard atmosphere, i.e., to express the final results as the performance which may be expected of the aeroplane on a day on which the atmospheric density at every point is equal to the average density at the point. Some days the aeroplane may put up a better performance, some days a worse, but on the average, if the engine power and other charac- teristics of the aeroplane remain the same, its performance will be that given. It must be remembered that a standard at- mosphere is a very abnormal occurrence; be- sides changes in density there may occur up- and-down air currents which exaggerate or diminish the performance of an aeroplane, and which must be taken carefully into account. They show themselves in an otherMise imac- countable increase or decrease in rate of climb or in full speed flj'ing level at a particular lieight. We now pass to the actual tests, beginning with a description of the observations which have to be made and thereafter to the instru- ments necessary. The tests resolve themselves mainly into (a) A climbing test at the maxi- mum rate of climb for the machine, {h) Speed tests at various heights from the "ground" or some other agreed low level upwards. Experience agrees with theory in showing that the best climb is obtained by keeping that which is frecjuently called the air speed of an aeroplane, viz., the indications of the ordinary air speed indicator, nearly constant whatever the height — in other words, pV is kept con- stant. We can look at this in this way. There is a limiting height for every aeroplane above which it cannot climb; at this limiting height, called the ceiling of the machine, there is only one speed at which the aeroplane will fly level, at any other air speed higher or lower it will descend. Suppose this speed be 55 m.p.h. on the air speed indicator. Then the best rate of climb from the ground is obtained by keeping the speed of the machine to a steady indicated 55 m.p.h. Fortunately a variation in the speed does not make very much diff'erence to the rate of climb; for instance, a B.E.2c with a maxi- mum rate of climb at 53 m.p.h. climbs just as fast up, say, 5,000 ft. at about 58 m.p.h. This is fortunate as it requires considerable concen- tration to keep climbing at a steady air speed, especially with a light scout machine; if the air is at all "bumpy" it is impossible. At great heights the air is usually very steady, and it is much easier to keep to one air speed. It is often difficult to judge the best climbing speed of a new machine; flyers differ very much on this point, as on most. The Testing Squadron, therefore, introduced some time ago a rate of climb indicator intended to show the pilot when he is climbing at the maximum rate. It con- sists of a thermos flask, communicating with the outer air through a thermometer tube leak. A liquid pressure gage of small bore indicates the difference of pressure between the inside and outside of the vessel. Now, when climbing, the atmospheric pressure is diminishing steadily; the pressvu'e inside the thermos flask tends therefore to become greater than the outside atmospheric pressure. It goes on increasing until air is being forced out through the ther- mometer tubing at such a rate that the rate of change of pressure inside the flask is equal to the rate of change of atmospheric pressure due to climbing. When chmbing at a maximum rate, therefore, the pressure inside the thermos flask is a maximum. The pilot therefore varies his air speed until the liquid in the gage is as 262 TEXTBOOK OF MILITARY AERONAUTICS high as possible, and this is the best climbing speed I'or the machine. What observations during the test are neces- sary in order that the results may be reduced to the standard atmosphere? Firstly, we want the time from the start read at intervals, and the height reached noted at the same time. Here we encounter a difficulty at once, for there is no instrument which records height with accuracy. The aneroid is an old friend now of aeronauts as well as of mountaineers, but although it has riCuKE 2 X^OAr ^•-■86; g S^*.oseOPf often been tentatively exposed, it is doubtful whether 1 i)er cent, of those who use it daily realize how extraordinarily rare it is that it ever does what it is supposed to do, that is, indicate the correct height above the ground, or starting jjlace. The faults of the aeroplane aneroid are partly unavoidable and partly due to those who first laid down the conditions of its manufac- ture. An aneroid is an instrument which in the first place measures only the pressure of the surrounding air. Now if pi and po are the pressure at two points in the atmosphere, the difference of height between these points is given very closely by the relation, h — <^ log, '"/p2 where ^ is the average temperature, ex- pressed in "absolute" degrees, of the air between the two ])oints. It is obvious that if we wish to graduate an aneroid in feet we must choose arbitrarily sonie value for *. The temperature that was originally chosen for aero|)lnne ane- roids was .50'' F. or 10'' C. An aneroid, as now graduated, will therefore only read the correct height in feet if the atmosphere has a uniform temperature of .50° F. from the ground up- wards, and it will be the more inaccurate the greater the average temperature between the ground and the height reached differs from .50^ F. Unfortunately 50° F. is nuich too high an average temperature ; to take an extreme exam- ple, it is only on the hottest days in summer, and even then very rarely, that the average tempera- ture between the ground and 20,000 ft. will be as high as 50° F. On these very rare occasions an aneroid will read approximately correctly at high altitudes; otherwise it will always read too high. In winter it may read on cold days 2,000 ft. too high at 16,000 ft., i.e., it will indicate a height of 16,000 ft. when the real height is only 14,000 ft. It is always necessary, therefore, to "correct" the aneroid readings for temperature. The equation Tx _ 273 + t , gives us the necessary correction. Here H is the true difference in height between any two points, t the average temperature in degrees Centigrade between the points, and h the differ- ence in height indicated by aneroid. It is con- venient to draw a curve showing the necessary correction factors at different temperatures, some of which are given below: — Tabi.e III. — .Aneroid Correction Factors. Temperature Correction Temperature Correction ° F. factor. " F. factor. 70 1.04.0 10 0.9522 50 1.000 —10 0.833 30 0.961 For example if a climb is made through 1,000 ft. by aneroid and the average temperature is 10° v., the actual distance in feet is only 1,000 X 0.922 = 922 ft. The above equation is probably quite accurate enough for small dif- ferences of height — up to 1,000 ft. say — and ap- j)roximately so for bigger differences. The magnitude of the correction which may be nec- essary shows how important it is that observa- tions of temperature should be made during every test. P"'or this purpose a special tlier- mometer is attached to a strut of the machine, well away from the fuselage, and so clear of any warm air which may come from the engine. METHODS OF MEASURING AIRCRAFT PERFORMANCES 263 The p^'rench, I believe, do not measure tempera- ture, but note the ground temperature at the start of a test, and assume a uniform fall of temperature with height. This, undoubtedly, may lead to serious errors. The change of tem- perature with height is usually very irregular, and only becomes fairlj^ regular at heights well above 10,000 ft. The aneroid being what it is, one soon comes to the conclusion that the only way to make use of it in aeroplane tests is to treat it purely as a pressure instrument. For this reason it is best to do away with the zero adjustment for all test purposes and lock the instrument so that the zero point on the height scale corresponds to the standard atmospheric pressure of 29.9 ins. or 760 mm. of mercury. Every other height then corresponds to a definite pressure; for in- stance, the locked aneroid reads 5,000 ft. when the atmospheric pressure is 24.88 ins., and 10,000 ft. when it is 20.70 ins., and so on, If the temperature is noted at the same time as the aneroid reading, we then know both the atmos- pheric pressure and temperature at the point, and hence the density can be calculated, or, more conveniently, read off curves drawn for the purpose. The observations necessary (after noting the gross aeroplane weight and net or useful weight carried) are therefore: (i) Aneroid height every 1,000 ft.; (ii) time which has elapsed from the start of the climb; and (iii) temperature. To these should be added also (iv) the air speed and (v) engine revolutions at frequent intervals. The observed times are then plotted on squared pa])er against the ane- roid heights and a curve drawn through them. From this curve the rate of climb at any part (also in aneroid feet) can be obtained by meas- uring tlie tangent to the curve at the point. This is done for every 1,000 ft. by aneroid. The true rate of climb is then obtained by mul- tiplying the aneroid rate by the correction fac- tor corresponding to the observed temperature. These true rates are then plotted afresh against standard heights, and from this curve we can obtain the rate of climl) corresponding to the standard heights, 1,000. 2,000, 3,000, etc. Knowing the change of rate of climb with height, the time to any required height is best obtained by graphical integration. The table below gives the results of an actual test. At least two climbing tests of every new ma- chine are carried out up to 16,000 ft. or over by aneroid. If time permits three or more tests are made. The final results given are the aver- age of the tests and represent as closely as pos- sible the performance on a standard day, with temperature effects, up and down currents and other errors eliminated. If we i^roduce the rate of climb curve up- wards it cuts the height axis at a point at which the rate of climb would be zero, and therefore the limit of climb reached. This is the "ceiling" of the machine. SPEEDS His 16,000 ft., or whatever it is, reached, the flyer's next duty is to measure the speed flying level by air speed indicator at regular intervals of heiglit (generally every 2,000 ft.) from the highest point downwards. To do this, he re- quires a sensitive instrument which will tell him when he is flying level. The aneroid is quite useless for this purpose, and a "statoscope" is used. The principle of this instrument is really the same as that of a climb meter. It consists of a thermos flask connected to a small glass gage, slightly cun^ed, but placed about hori- zontally (see Fig. 2). In this gage is a small drop of liquid, and at either end are two glass traps which prevent the liquid from escaping either into the outside air or into the thermos flask. As the machine ascends and the atmos- pheric pressure being smaller, and the pressure in the flask being higher than the external pres- sure, the liquid is pushed up to the right hand trap, where it breaks, allowing the air to escape. On descending the reverse happens; the liquid travels to the left, breaks, and air enters the flask. When flying truly level the drop re- mains stationary, moving neither up nor down. The instrument is made bv the British Wright Co. The flyer or the observer notes the maximum speed by the air speed indicator — i.e., the speed at full engine throttle. At one or more heights, also, he observes the speeds at various positions of the throttle down to the minimum speed 264 TEXTBOOK OF MILITARY AERONAUTICS wliich will keep the machine flying at the height in question. The petrol consumption and the engine revolutions are noted at the same time, as well, of course, as the aneroid height and temperature. Accurate observation of speeds needs very careful flying — in fact much more so than in climbing tests. If the air is at all bumpy observations are necessarily subject to much greater error, since the machine is always accelerating and decelerating. The best way to carry out the test seems to be as follows. The machine is flown first just down hill and then just up hill, and the air speeds noted. This K Ficunc 3 will ^'e a small range between which the real level speed must lie. The flyer must then keep the speed as steadily as possible on a reading midway between these limits, and watch the statoscope with his other eye. If it shows steady movement, one way or the other, the air speed must be altered accordingly by 1 m.p.h. In this way it is always possible at heights where the air is steady to obtain the reading correct at any rate to 1 m.p.h., even with light machines, provided always sufficient ])atience is exercised. The r.p.m. at this speed are then noted. One difficulty, however, cannot be avoided. If at any height there is a steady up or down air current, then though the air may appear calm, i.e., there may be no "bumps," the air speed indicator reading may be wrong, since to keep the machine IcxtI in an up current it is necessary to fly slightly down hill relatively to the air. Such unavoidable errors are. however, eliminated to a large extent by the metliod of taking speeds every 2,000 ft., and finally aver- aging the results. We must now consider how the true speed of the aeroplane is deduced from the reading of the air speed indicator. It is well known that an air speed indicator reads too low at great heights — for example, if it reads 70 m.p.h. at 8,000 ft. the real speed of the machine through the air is nearer 80 m.p.h. The reason for this is that the indicator, like the aneroid, is only a pressure gage — a sensitive pressure gage, in fact, which registers the difl'erence of pressure between the air in a tube with its open end point- ing forward along the lines of flight of tlie ma- cliine, and the real pressure (the static ])ressure) of the external air. This difference of pressure is as nearly as we can judge by experiment — Vi p V^ (where p is the density of the air and V the speed of the machine) , provided that the open end of the tube is well clear of Avings, fuselage, etc., and so is not affected by eddies and other disturbances. Now, assuming this law, air speed indicators are graduated to read correctly, as I have said above, at a density of 1.221 kgm. per cubic meter, which we have taken as our standard density and called "unity." It corresponds on an average to a height of about 800 feet above sea level. Then suppose the real air sj^eed of an aero- plane at a height of "h" feet is V m.p.h., and the indicated air speed is 70 m.p.h., this means that the excess pressure in the tube due to the speed is proportional to 1 X 70^, or P X F'^ = 1 X 70^ where p is the density at the height in question, expressed as a fraction of the standard density. To correct the observed speed, we therefore divide the reading by the square root of the density. Thus, observation of the maximum speed of an aeroplane at a height of 8,000 ft. by the locked aneroid gave 80 m.p.h. on the indi- cator, the temperature })eing 31° Fahr. From the cun'e we find that the density corresponding to 8.000 ft. and 31" is 0.8.'> of standard density. The corrected air speed is therefore: 80 V .8.) 86.7 m.p.h. This "corrected" air speed will only be true if the above law holds, that is to say, if there are no disturbances due to the jjressure head being in close proximity to struts or wings. It is always necessary to find out the magnitude METHODS OF MEASURING AIRCRAFT PERFORMANCES 265 of this possible error, that is, to calculate the air speed meter, and the only waj' to do this is to measure a real air speed at some reasonable altitude for easy observation of the aeroplane by actual timed observations from the ground, and from these timed results check those de- duced from the air speed indicator readings. This calibration is the most important and diffi- cult test of all, since on the accuracy of the re- sults depends the accuracy of all the other speed measurements. It can either be done by speed trials over a speed course close to the ground, or when the aeroplane is flying at a considerable height above the ground. In the Testing Squadron we have always attached much more importance to the latter method, mainly be- cause the conditions approximate more to the conditions of the ordinary air speed measure- ments at different heights, and because the weather conditions are much steadier and the flyer can devote more attention to flying the machine at a constant air speed than he can when very close to the ground. One method is to use two camera obscuras, one of which points vertically upwards and the other is set up sloping towards the vertical camera. At one important testing center the cameras are a mile apart, and the angle of the sloping camera is 45°. By this arrangement, if an aeroplane is directly over the vertical camera it will be seen in the field of the sloping camera if its height is anywhere between 1,500 and 15,000 feet, although at very great heights it would be too indistinct for measurements except on a very clear day. The height the tests are usually carried out is 4,000 ft. to 0,000 ft. The aeroplane is flown as nearly as possible directly over the vertical camera and in a direc- tion approximately at right angles to the line joining the two cameras. The pilot flies in as straight a line and at as constant an air speed as he can. Observers in the two cameras dot in the position of the aeroplane every second. A line is drawn on the tables of each camera point- ing directly towards the other camera, so that if the image of the aeroplane is seen to cross the lines in the one camera it crosses the line in the other simultaneously. From these ob- servations it is possible to calculate the height of the aeroplane with considerable accuracy; the error can be brought down to less than 1 part in a 1,000 with care. Knowing the height, we can then calculate the speed over the ground of the aeroplane by measuring the average dis- tance on the paper passed over per second by the image in the vertical camera. If j? inches is this distance, and / the focal length of the lens, the ground speed is a? X h/f feet per sec- ond. It is necessary to know also the speed and direction of the wind at the height of the test. For this purpose the pilot or his observer fires a smoke puff' slightly upwards when over the cameras, and the observer in the vertical camera dots in its trail every second. The height of the smoke puff is assumed to be the same as that of the aeroplane — it probably does not differ from this enough to introduce any appreciable error in the results. The true speed through the air is then found graphically as shown in Fig. 4. Here the length AB represents the ground speed of the aeroplane as measured in the camera and CB represents on the same scale the velocity and direction of the wind. The length AC represents, also on the same scale, the true air speed of the machine. The tests are done in any direction relative to the wind, and generally at three air speeds, four runs being made at each air speed. The advantages of this method are: (1) Being well above the earth the pilot can devote his whole attention to the test. (2) Within reasonable limits any height can be chosen, so that it is generally possible to find a height at which the wind is steady. (3) It does not matter if the pilot does not fly along a level path so long as he does so ap- proximately. What is more important is that he should fly at a constant air speed. (4) It is not necessary that there should be any communication between the two cameras, although it is convenient. The two tracks are made quite independently, and synchronized afterwards from the knowledge that the image must have passed over the center line simul- taneously in the two cameras. The main disadvantage is that somewhat elaborate apparatus is necessary, but this is of 266 TEXTBOOK OF MILITARY AERONAUTICS not much importance in a permanent testing station. There are often jjcriods in war time, however, when an aeroplane has to be tested quickly, and low cloud layers and other causes prevent the camera test from being carried out. It is then necessary' to rely on measurements of speeds near the ground for the calibration of the air speed indicator. In this method the aeroplane is flown about 10 ft. off the ground, and is timed over a measured run. There are two observ- ers, one at each end of the course: when the aeroplane passes the starting point the observer ocfc^lowfc 0" H<» ground Thi^tto" AC 'tyrmnft rtic r
    . This iiiailiiiir hns ii wing spreiid of 101 fi-ot. THE CASE FOR THE LARGE AEROPLANE 279 are correctly placed in respect of one another for all heights. This method of plotting and the curves so obtained give the necessary basis for a comparison between different machines, and reference will be made to them again later in the pajjcr, after discussing the structiu'al side of the question. The Effect of an Increase in Size on the Structural Weight of Aeroplanes ^Vttention has already been drawn to the fact that an improvement in the aerodynamical qual- 4i^ Ut V ^ - lU ti -tt Mt. ^ dnU^ " ■ m ^ tkt /// - - — ->tt 1^ tt Jj M- //^ ^■^ a_ U<>_. i i ities of the machine as the size increases may be partially or completely nullified if the increase in size is accompanied by a disproportionate in- crease in weight. I will, therefore, accordingly examine the rate at which the weight increases with increase hi size. In this discussion we shall leave out the weight of the power unit comprising engine, tanks, and fuel, as well as the useful load, whether consisting of men or dead weight, such as guns, bombs, etc. We will confine our argu- ment to the weight of the machine structure, that is, the portion which supports the load whether on the ground or in the air, with the necessary directing surfaces and their attach- ment to the main portion of the aeroplane. In the latter category come the planes, the fuse- lage, and the chassis, and these will be considered seriatim. In all discussions on weight saving there is the general question as to the best utilization of materials with the varying size of machines. As the machine is made smaller, so eventually a limit is reached beyond which it is not possible to decrease the minimum thickness of the material and retain adecjuate local strength. Especially is this the case in aeroplane work, where the members are usually stressed as struts, and for which, therefore, a hollow tubu- lar construction is the most efficient form from the point of view of mininumi strength for a given weight. In making tubular members, whether these be plane spars, fuselage, struts, or longerons, it is not advisable to decrease the thickness of the walls below ^/u\ in. to Vi in. Even this is on the small side when allowance is made for errors in workmanship, and the fit- ting in of the necessary tongue piece to make a secure joint. Considerable economies can be effected in weight-saving with increase in size in this manner. Local strength, too, determines the construc- tion of subsidiary parts of the machine, such as the tail skid, the ribs, tail planes, a local strength that does not need to be increased with inci'case in size of the machine, and here, again, weight economy can be effected. This better utilization of material more than offsets the increase in weight that would occur in the planes provided that they were increased in a geometrically similar manner and the load- ing aspect ratio and section kept the same. In a machine of which I can show you the })hotos later the plane weight per square foot is less than a small one for the same factor of safety, and the total plane weight is a lesser percentage of the gross weight. The fuselage weight, owing to the better util- ization of material, is considerably decreased. The chassis weight remains about the same. The Effect of an Increase in Size Upon an Aeroplane's Performance A general comparison can now be effected be- tween aeroplanes of different sizes on the basis 280 TEXTBOOK OF MILITARY AEROXAUTICS of the curves described in Section II, the total weight of the aeroplanes considered being modi- fied according to the size in accordance with the conclusions of Section III. An examination of equation Xo. 9 in which H.P. equals /; X Kx/Kv XVl/Kv shows that, provided that similar planes are used and that the weight per H.P. remains the same, the same plane curve repre- sents all machines. These curves as plotted are, in fact, curves of H.P. required per pound weight of the machine for a given loading per square foot. Let us now examine the lower curve of H.P. required for body resistance and refer to equation 14. Provided that the area of the body increases in the same ratio as the plane area, this lower curve will still, for any size of machine, be correct in relation to the plane curve plotted above, and the summation of the two ordinates or the distance between the two cin-ves will represent the total H.P. required, the scale being increased in proportion to the increase in ratio. The greatest resistance of an aeroplane is that of the body. This, for smaller shaped bodies, would increase as the square of its lineal dimensions, whereas its volume would increase as the cube. It follows, therefore, that the re- sistance of the fuselage per unit of volume will decrease with the increase in size of the aero- plane. The lower curve will have to be modi- fied to meet these changed conditions. This de- crease in weight will have the usual cumulative effect of decreasing the weight of all the rest of the machine. The curves which are plotted are for H.P. per unit weight of the whole machine, and do not show so graphically the su])eriority of the large machine as if the curves of H.P. per imit of useful weight had been plotted instead of gross weight. In this case the curves for jjlanes and body would have their vertical ordinance increased with the projjortion of useful to total weight. The balance in favor of the large ma- chine is tiujs apparent directly we com])are ma- chines of approximately the same total weight per H.P. The conclusion that may be drawn from the above theoretical considerations of the aero- dynamical and structural ({ualities of the large machine are that for the same total weight car- ried per H.P. the big machine will effect the better performance. The Large Machine from the Pilot's Standpoint There has been very much less experience in the flying of large machines than with small ones, and, therefore, pilots are not so accus- tomed to their use, neither is the experience wide enough to draw general conclusions. It may, however, be safely said that large machines can be built to operate quite as easily and fly with as little fatigue as the best of the small ones. Xo Servo-motors are required for the controls, provided the controlling surfaces are properly balanced. There is less work in flying a large machine owing to the wind gusts, which seem large to a small machine, being relatively small in their effect on a large one. A large machine will plow its way through gusts without any control being necessary, whereas a good deal of war})ing might be necessary on a small machine. 1 ?* M / 1 / f // / Vi- J y ft ' ~ — ■^^ s ^k \ s, \ The large machine can be handled more easily on the ground and can alight in smaller places. When considered from the point of view of load to be carried or long distance to be flown the large machine has it all its own way. ^Vhere a large load is to be carried the size of the machine to do it must be increased until the THE CASE FOR THE LARGE AEROPLANE 281 These men coni])ri.sc the first firniip of Ainerieiin aviators wlio rejiresentcd U. S. on the i-'rench front. In tlie group, ielt lo right are: Lieiitcnant de Laage, Sergeant C. C. Johnson, New York City; Corporal Lawrence Uunisey, Buffalo, N. Y.; Sergeant J. H. MeConnell, Carthage, N. C; Lieutenant William Thaw, Pittsburgh; Sergeant H. I.ufhery, N'ew Haven, Conn.; Sergeant Kiffin Rockwell, Atlanta, Ga.; Adjutant Didier Masson, Los Angeles, Cal.; Sergeant Norman Prince, Boston, and Adjutant Bert Hall, Galveston, Tex. [Photo Courtesy N. Y. Times.] useful load is sufficiently great. The size of the machine that is required for the purpose de- pends on the total weight per H.P. that can he carried. There is here no (juestion of competi- tion between large and small machines, it is a case of the correct machine for the purpose. For future commercial developments the large machine scores with plenty of room for passengers to sit in comfort, or mails or lug- gage to be carried, and with its steadier move- ment will afford great comfort to those who travel by it. It is probable that commercial aerojilane work will be undertaken for long-dis- tance journeys. Where delays at the com- mencement of the journey are a large percent- age in time of that necessary to complete the distance, the possible time taken to traverse a given space may be as great or even greater than that taken by a more certain means of transit. It is the old question of the hare and the tortoise. Where, however, the distance to be traversed is great, such as 1,000 to 2,000 miles, or with journeys such as crossing the At- lantic, the passengers or mails could afford to wait a day or two and will accomplish the jour- ney far quicker than any other means of transit. Were the commercial development of aviation confined to journeys of from 50 to 200 miles, delays at starting or the cost of organizing to prevent them would cause the aeroplane's use to be considerably nullified. It is this question of certainty in operation that requires careful attention, for it is the one thing at the present time that the aeroplane re- quires in order that it may take its proper place in commercial work. Engines for this will probably be more heavilj' built to reduce the possibility of breakdown, and multi-engine ma- chines will be used which can fly satisfacto- rily even if one engine breaks down. Here again this points to the use of the larger ma- chine. Finally, it must be pointed out that the same improved performance can be obtained from a large machine, whether for scouting, fighting, or weight carrying, provided that the specifica- tions are the same in both cases. It is absurd to compare the performance of a weight-carry- ing machine with high values of useful weight per H.P. with a small scout of very small use- ful weight per H.P., and particular attention is, therefore, drawn to the methods of com])arison set out in Section II, so that careful comparison mav result. Memoranda: CHAPTER XXIII EVERY MILITARY AVIATOR OUGHT TO KNOW WHAT HIS OWN AND THE ENEMY'S MACHINE CAN DO AND HOW THEY LOOK (Courtesy of Aerial Age Weekly) "If you see an aeroplane that does not look like any of the machines shown in this leaflet, you are to make every eflFort to bring it down." This, in eflFect. is the instruction that every French and Italian aviator receives, not only while he is being instructed, but periodically, whether he is at one of the permanent military aerodromes or temporarily stationed on the front. The Allied Governments found it necessary to teach their aviators and students all about their own machines and as much as possible about the enemy's machines, particularly their appearance. As a basic principle, the aviator is taught that what does not look like one of the Allied machines must be an enemy machine. Therefore every effort should be made to bring it down. The anti-aircraft forces are taught the same thing, and knowledge of the features of the different types of aeroplanes is one of the prime factors in making anti-aircraft forces efficient. Lacking that knowledge, the Allied air forces, as well as the anti-aircraft defenses, get confused and pernn't the enemy to obtain temporary ad- vantages which cost the lives of Allied aviators, as well as of the ])opulation of cities which are raided, without mentioning the strategic advan- tages that the enemy gains through gathering information or surprising the Allies. It has also been found of extreme importance to have every aviator know what the enemy's machines, as well as his own machines, can do. It will be recalled that when the first "Spad" appeared, the CJerman aviators did not give it credit for the speed it had, so they ventured too much and too far for their own good. The Cigogne S(|uadron and the Lafayette S(]uadr()n were enabled thereby to maintain supremacy in the air and to bring down a number of German aviators who did not know the fighting charac- teristics of the "Spad." In several cases some of the machines which were thought to have " blind sides " were found to have guns mounted at front and rear, and to shoot below as well. An aviator in a single- seater fighter would attack what appeared to be a "pusher type," and all at once a gunner would emerge from the small cock-pit and turn a stream of fire on him. The United States is to train thousands- of aviators, observers, aerial photograjjhers, and anti-aircraft gunners. Many are taking their ])reliminaiy course, and thousands are waiting their turn. Thousands more of prospective candidates are not yet of age, or have passed the draft age and will volunteer as they learn more about military aeronautics. INIilitary and aeronautic authorities agree that a valuable service can be rendered to the nation by contin- uing to publish descriptions of machines used by the enemy, as well as by the Allies. In the last case it is necessary, of course, not to publish details of machines which the enemy has not yet caj)tured, or to give details of performances of newly adopted types. In a general way, any type that has not been used in number at the front for a period of at least two months must be considered as new, and details of perform- ances must not be published. The publication of details of German ma- chines is encouraged. The Boche knows, of course, all about his own types; he also knows how the Allied aeroplanes look, as soon as one or two are captured. But he docs not always know all about performances. Thcrcfoi'e, in- formation about performances of new types should be withheld. 282 Sopwjtli Triplane (British), 'i'lie motor, a rotary Clcrget, is completely surrounded by an aluminum cowling. The planes are equal in span, very narrow in chord, and braced by a single strut at either side of the fuselage. Planes highly staggered. De Havilland 2 (British). Somewhat resembles the F. E. 8, but the outriggers meet one another at the vertical rudder in- stead of at the tail plane. Sopwith single-seater (Britisli). Used by the French and British. Also the Sopwith two-seater. Equipped with a rotary engine, Clerget or Rhone. Identified by the central set of struts, which stagger outward at the upper end. The fixed triangular fin is rounded off at its leading end. Planes are considerably staggered. Ailerons on both upper and lower ]ilanes. Koland two-sealcr ((jerniaii). The engine is a fixed .Merce- des, 175 h.p. A machine-gun and bombs are carried. The body is exceptionally deep, reaching as high as the upper j)lane. Windows are provided in tlie sides of the fuselage for observa- tion. There is but a single interplane strut at either side of the body. Planes are considerably staggered. Fin and rudder placed very high. F. E. ^b and 2d (British) (Farman Experimental). Pusher type with a nacelle which carries a fixed Beardmore or liolls- Hoyce engine. Empennage carried on four outriggers. Land- ing gear consists of two main wheels and two smaller auxiliary wheels below the forward cock. 283 F. F,. 8 (British). Scout type single-seater pusher with a rotary Monosoupape-Gnome engine. Fin and rudder area simi- larly disposed above and below the tail-plane. Two-wlieel land- ing-gear and tail-skid below the fin. A movable Lewis ma-, chine-gun is carried on the deck of the nacelle. Xioiiport. I '.'■ed hy the French, 15riti''h, Belgians, and Italians. Jlade in single-seater scouts which have rotary Rhone or Clcrgct engines and having a small wing sjian, and also two-seaters with fix<'d Hispano-Suiza engines and a larger wing span. Struts be- tween the planes arc V shaped. Two sealers have two sets of struts at either side, the outer sets inclined outward at the top. Other struts are vertical. Urcguet Av. (FrcTuhV Has a fixed Renault engine. Di- hedral on the upper plane only. There are ailerons on the uj)|)er and lower jilanes, the lower ones being exce])tionally long and extending from the wing-tip nearly to the body. The elevators are lialaiucd. Hristol Scout (British). Called the "bullet." One of the fastest scouts. I'ses a rotary Bhone engine. There is also a Bristol two-sealer which has two pairs of struts at either side of the body. The two-seater is equipped with a fi.xcd engine. H. K. .'e nncl the B. K. U (British) (Bleriot Kxperiimnlnl). Thev mnrhlnr', are equipped with fixed H. A. F. (Hoyal Air- craft Factory) engincK with n four-bladed propeller. The plntM^ are ttagfrrrrd and have a pronounced dihedral on lK)th planes. Vickers Scout (British). Rotary Clerget engine Single pair of struts at either side of the body. I'lanes eqmd in area and .similar in outline. High stagger. The engine is com- pletely surrounded by an aluminum cowling. 284 13. E. 2e and H. K. 8 (British). There Is a single pair of struts at either side of the l)ody, in addition to one strut which connects each pair of ailerons on upper and lower wings. R. E. 7 (Kcconnaissance Kxperimental) (British). Upi)cr plane of greater span than the lower. Two pairs of vertical struts at either side of the body and a pair of inclined struts which carry the overhang. Ariiistrong-Witworth (British). I'pper and lower planes are practically similar in sha])e. They are not staggered nor swept bacli, and have but a little dihedral. Two sets of struts at either side of the fuselage. The fin surface is rather large and carries the rudder quite high. Paul Schmitt (French). Made in two types; the type B. K. A. H. (Bombardment Henault, Ailes hautes) and the B. K. A. B. (Ailes basses). The planes of this machine are arranged to be altered while the machine is in flight, changing the angle of incidence according to the lift recjuired. Caudron G. (j (French). Quite similar to the R. 4, but two rotary engines are used. It has only four landing wheels and a very narrow lower plane. The upper ])lane overhangs con- siderably and is braced by sloping outer struts. Trailing edge very flexible. Caudron R. 4. Used by the French and British. Twin- motored tractor type with a fuselage. The landing gear is composed of a pair of wheels below each motor corajtartment and a fifth wheel at the nose of the fuselage. Aviatik (Aviatik-u. .Autumohil-Gesellschaft) (German). A fixed Mercedes 17.5 h.p. engine is installed. The familiar ex- haust stock carries the gases from the engine and leads them over the top plane. Albatros CHI. A German "all purposes" machine which carries a fixed and movable gun. Radiator carried in the upper plane. Exhaust pipes similar to that of the Aviatik. 285 I.. V. O. (Luft-Verkehrs-Gosellschaft) (German). Made in two tj-pes: Type "D9" wliioh lias a 175 Ii.p. Mercedes or Benz engine, nml Tyiw "1)11," having a 235 h.p. engine. Distinguishable by its "half-negative" ailerons and tlie long span of the Dll, tlie wing- cbord of which is greater near the body than at the wing-tips. AGO (Aktien Gesellschaft Otto). A German single-seater. Rotary Olterursol ciigiiu- with propeller spinner or nose-piece. The vertical rudder is balanced much in the manner of the French Nicuport. The upper plane is but slightly greater in span than the lower and both planes have practically the same chord, whereas Ihe Nieuj)ort has a narrow lower plane. Albatros D.III (German). Single-seater scout equipped with a vertical Mercedes engine. A'ery apt to be mistaken for a Nieuport, as it has V struts and a narrow lower plane. It has, however, a high vertical fin and an undcr-fin tail-skid. Fokkrr (German). Sinple-sonter scoiit machine, with a rotary OIktutscI 100 h.p. or a fixed Mercedes 170 h.p. engine. Tills ninchinc Is very similar to the Mornne-Saulnler, but Is dis- tin|riii'>hflli)e l>y Its commn-shnped balanced directional rudder ami ll« two pairs of interplnnr strnls. F.vidently if'! conslrue- tors apprrriate the vnhw of adhering to Morane-Saulnier lines. Halberstndt (German). Single-seater equipped with a fixed Argus or Mercedes engine. The planes are staggered I'e", and the upper plane slightly overhanging, thereby differing from the Morane. Over-all length, 2V0'. Span, upper plane, 28' 0" 5 lower plane. 25' 10". Chord, both planes. S' 2". Gap. 4' 4". The bidanced tail-flaps measure 10' from tip to tip, and are S" 4" wide. iM Morane-Suuliiicr. Employed by the British. A rotary en- gine is used, preceded by a streamline nosei)late. The under- carriage structure resembles the letter M (initial of "Mora&e"). Martinside (British). Kngine is fixed. Ailerons on uji|)er and lower planes which are about equal in span. The tail- plane is narrow in comparison with its span. Moruiie-Saulnier monoplane (used by French and British). The Parasol type is equii)])ed with a rotBTy engine and resem- bles the Morane-Saulnier biplane. ,. « ♦ JIorane-SAulnier monocoques 11 and 13 niq. It is often mis- taken for a German Fokker, which is a copy of the earlier Morane-Saulnier. Farman Freres F. 40 (French). A pusher type biplane with a fixed engine. The nacelle is situated above the lower plane. Lower plane has the same chord, but about one third less area than tlie ii])i)er. Ailerons on the ui)))er plane only. De Havilland 4 (British). Uses a V-type engine and four- bladed propeller. Plane's are slightly staggered, but not swept back and very slight dihedral. Two pairs of struts used at either side of the fuselage. A balanced type rudder used. Salmson-Moineau (French). A tractor biplane with twin propellers driven by a single Salmson engine. The propellers are carried lietween the planes l)y means of X-shaped .struts. The empennage surfaces are rectangular in shape. Caproni H. K. P. (Italian and French). This is a .'?-motored biplane with two motors in tractor position, located at the front of the fuselages, and a pusher engine at the rear of the central nacelle. 287 Spad single-sciitfr scout (Sooictc pour TAviation et sos Derives). Used by the French and British. All Spads are equipped with either IjO or :200 h.j). engines. This machine Is easily confused with the Albatros, a German scout. Alh.itros D. 1. Single-seater scout. (German.) One of the fastest of German aeroplanes. It is equipped witli a 170 h.p. Mercedes engine or a 25 h.p. Benz and provided with two fixed machine-guns arranged to fire through tlie propeller. A.K. or .\.1,.U. I'renili niacliine for all uses. Planes are Jnvertly staggered and the fuselage is set above the lower plane. Uumjiler. (German.) Has the Mercedes 17,5 h.)). engine, a fixed and a movable gun. Radiator semi-circular, set into the upper plane. ["fc-* Spad two-seater. (French.) Fixed engine. Similar in out- line (and eonstruetion) to the Spad scout. The two-seater car- ries a movable gun at the rear, in addition to a fixed machine- gun syriclironized with the propeller and firing directly ahead. A. E. G. (Allgemeine Elektrlzitiits Gesellsehaft.) A Ger- man two-seater witli a 175 h.p. Merceiles engine. It carries a gun synchronized with the propeller and one movable i^t the red r. I.rlonl. (Frrncli.) A three-pliini- twjn-iiiotiirrd biplane Imrtor inlnji nxrchlne the engines are carried on the lower plane, with exhaust stacks running up over the upper plane. Vertical engines ■re uxed. A wheel Is located beneath each of the two engines. The two-seater Avro has highly st«ggereeratinK 182 Fairfield, O. (Wilbur Wright Field) oper- ating 182 Port Sin. Okla,, advanced 182 Hineola. N. Y., oi>erating 182 Mt. Clements. Mich. (Selfridge Field) operating 182 Rantonl. 111. (Chanute Field) 0|>erating 182 Rock.v Mountain Reserve 182 San Antonio. Texas, operating 182 San Diego. Cal.. operating 182 So. Mississippi Valley. Under investi- gation 182 Aviation students 187 Aviator. AUied 90. 91 Aviators. American 93. 282 certificates 186. 187 face masks 191 glovea 191. 192 messengers 19.5 service 192. 194 nniforms 195 Avion. Clement Ader's 240 Avro aeroplane 15, 298 Back pressure 251 Bagnell. Lieut. Edward 211 Bairn, Chief mechanic 211 Baker, George F. Jr 201 Baker. Secretar>- of War 298 Balance of jKiwer 3 Balancing free balloons t 163 Baldwin. Ca|>tain Thomas S 204 Baldwin dirigible 205 Balkan Mountains 17 Ballast, sacks 83 BaOoons 83. 84. 157. 159. 163 ballast 163 ears 164 capacit}- 161 captive 74. 75, 81. 85 Caquot 81. 160 companies 160 dirigible pilot certificates 187 Division 179 envelope 158. 164 equator 158 fabrics 164 historic Ill, 112 inflation 82 kite 76, 81. 83. 84. 87. 96, 157 maneuver 88 nurse 86. 160 observation 84. 96. 156 school. Fort Omaha 161. 167, 213 Bamberger, Lieut. R. S 204 Barometer 157 Barrage fire 70 Bartlett, Capt. Robert A 201 Baruch. Bernard II 201. 214 Batchelder, A. G 201 Battery, hydrogen cylinders 171 Battleplanes 39 B. K. (Bleriot Kx|>erimeutal) 284 Beachy air ships 157 Beacon, aerial 133 B«a«on, electric flashlight 136 Beacons, ilermamt' 130 Beck, Lieut. Paul W 204 Belgian cities 25 Belgium, invasion 240, 241 Bellanger, Capt 234 Belmont, August 201 Bennett. James Gordon 201 Benoist Aircraft Co. 242 Berlin 25 Best, E. C 210 Betbenods high frequency generator. . . . 143 Bethenods resonance alternator 143 Boveoa, K. J 211 Biiishaiii, Prof. Uiram 215 Bishop, Oourtland F 201 Blades, variable pitch propeller . . . .254, 255 Bliriol, Louis 226 "Blimp" 157 American 156, 161 BriUah 173, 177 Ooodyesr 176 BUsa, Un. WiUUm H 209, 211 Board of Governors, Aero Club of America 234 Board of Ordnance and Fortification. .222. 223 Body resistance 275 Boring Airplane Oo. 242 Boelke, CaiiMin 64, 66, 93, 241 Borer, F. Jr 210. 211 Boilinf. Capt. Raynal 20S, 210, 211 Bomb 87 Barlow 87 daacription 22 dropping 26. SI, 289. 278 lalliog enrves 86 iDiUal vrlocitr 85 releaaiog drvlc* 86 •t*!"!* 22, 278 ■ ■■i l iardlng maebioaa 64 Boabardment 70, 269, 371, 273 Boabardmant, French 70 Bombing 122 attacks 9 enemy bases 4 night raids 125 parties 125 raids, list of 18 raids, long distance 17 damage done 20 incendiary 20, 34 types of 22. 31 Bond. Brig. General John 212 Bonvalot, Gabriel 232 Boots, rubber wading 193 Bowen. Lieut. T. S 208 Brake horse power 255 Brake, for landing 251 Breeches, winter motorcycle 193 Breese Penguin 300 Brequet aeroplane 292, 298 BrequetMichelin war plane 21 Bright, British authority 132 Bristol, Capt. Mark L 201 Bristol Scout Aero]>lunc 292 British aero photographs 93 British aeroplane. Vickers pusher biplane 58 airship 107 armies 171 army tests 239 blimps 173 Commission in U. S 217 De Haviland scout biplane 58 flying corps 217 forces 91 General staff sg Government 241 Government specification, wireless 145 funs 82 Naval Air Service, instruments 24 Royal Navy Air Service 76. 104 War Office 239 Wright Co 263 Brush discharge 145 Buc, France 230 Buffalo Aero Squadron 210 Buffalo, N. y 210 Bulkheads 248 Bullets vs. high exjilosive shells 51 Bureau of Construction and Repair 214 13urgcss aerojilanc 207, 244 Burgess Dunne aeroplane 207 Burgess, Dr, G. K 213 Burgess, W^ Starlmg 201 Burns, K. J 210 Byrd, Lieut. D. B 211 Cable, A. G 214 Cabot, Godfrey L 201 Coffyn, Capt. Frank T 215 Calcium chloride 169 Calibration tests 267, 268 California Aviation School 213 Camera 91, 106, 107. 117. 264 care of 97 construction 104 Eastman aero 102 Pabbri 103 Howorth 102 long focus 102 stereoscopic 102 types of 105 Camouflage 113 Camshaft 257 Canadian photographer 96 Chauning, J. I'arki: 201 Canton, Brigadier General F. M 211 Cauton-Unne 228 Capacity tanks 230 Caproui planes 12, 13, 50, 241, 278, 295 Caproui triplane 4, 13, 297 Captain de Beauchamp 17 Captain de Kerillis 17 Captive baloons 71, 74, 76, 81, 85, 167, 159. 161 Captive balloons vs, aeroplanes 85 Caquot balloon 78, 81 96, 160 Coquot, Capt 78 Carbcrry, Major Josejih E 201, 208 Carburetor 252 Carburetor headers 250 Carlstroni. Victor , 211 Carlton. Newconib 201 Carolian. Lieut. M 210, 211 Carrizal tragedy 209 Carroll. Capt. P. A 213 Carter. General 204 Cases for a balloon inflation 165 Case for large aeroplane 374 Cartography aeronautic 200 Caudron biplane .16. 42. 73. 139, 285-290-298 Caustic jiotash 170 Ceiling of machine 261 Celoria. Senator 203 Central Powers, wirelcaa 141 Centrifugal forces 266 Oertificate. dirigible balloons 187 bydroaeronlanes 188 spherical balloons 187 ChamlMTlain, Senator George E 218 Chamber of Drputies. French 282 Chambers. Capt. W. 1 201 Chandler, Major Charles de F 167, 201. 204, 208, 213 Changes of uniforms J93 Changing speed . . . . 252 Chanute. Octave ' 226 Chapin. Roy D [] 20I Chapman. Lieut. C. C 208 Chase, Brig.-Gen. John ] . ! ! ! 210 Chicago Training Station ..'.', 213 Chief Aeronautic Engineers 245 Contractor of Navy .['. 219 Inspector Military Aeroplanes . ... .239, 240 Signal Officer . 181, 202, 213, 219, 223, 224, 225 Cnristofferson 244 Chrome vanadium steel ] 250 Circuit of Eastern Prance ' 232 Clark. Capt. V. E 245 Clerget motor 228 Climbing ; ; ; 253 Clinometer 269 Close formation flying 115 Close reconnaissance m Coast artillery 71. 194 Coast defence .' igg Coast defence, function of aircraft 7 Coast guard 237 Coats, aviator, antisinking 190 Coats, aviator, leather 194 Cochran. Alex. Smith 201 Coffin. Howard E 201. 214, 215, 217 College Park. Md 204. 205, 207, 208, 209 Collier, Robert J 201, 204. 206. 212 Colonia Dubliin m Colorado 210 Color filters 99 Colt 49 Columbus, N. M 208, 209, 210, 213 Combat machines, tactics 54 Commissioned personnel 161 Committee on Aeronautic Maps and Land- ing Places 199, 201 Committee on Military Affairs 213 Committee of National Aviation 233 Communication by Wireless 139 Compass 24 Comjiass bearings 117 Conant, W. M 210 Concealment 116 Concentrating rings 158 Condenser charging device 149, 150 Condensers, wireless 145, 146 Conger. Roy U 201 Cougress, Acts of 206, 206, 222, 237 Connecticut 210 Connecticut Coast Artillery 210 Continental Pusher 291 Construction of aeroplanes 245 Construction of balloons 163 Contact patrol 4. 112, 121 Contact patrol machines 122 Contest Committee, Aero Club of America 187 Coolidge, T. Jefferson 209 Cooling system 257 Cooperation between balloon and artillery 77 Council of National Defense 215, 235. 237, 248 Coutelle 178 Coyle, Lieut. Arthur J 211 Craig, A. M 211 Crankshaft bearings 257 Culver, Major C. C 140, 201 Culver radio apparatus 140 Culver wireless set 146, 164 Cummings, Lieut 210 Ourtiss aeroplane . . . .204, 207, 236, 244, 300 Curtiss Aviation School . . . .204, 210. 211, 212 Curtiss, Glenn H 201. 207. 222 Curtiss JN. 4-B tractor model 291 Curtiss triplane 12, 44. 291 Curtiss Wireless Scout 44 Curves of stress 256 Dansette 228 Dardanelles 91 Dargue. Lieut. Herbert 76 D'Arsonval 177 Daucort, Lieut 17 Davis, Commander Cleland 201 Davis, Driggs 60 Davison, Lieut. F. Trubee 201 Day signalling 71 Dayton. Ohio 826 Dayton Wright Co 244 Decarburatiou of oils 378 Deeds. Lieut. Col. E. A 301, 214 Defensive line 70 Deficiency Bill 218 De Havilland 288-287 Delivering aeroplanes to Europe 246 Density 269, 280 Density of gases 368 Density tables 868 Department of Arronautios 817, 319 Deaigner 859 Designs and tests of suspension patohea. . 164 Deatrnotivrnrs* of proleetUes 40 Detached flight 118 Dick. P. R 310. 311 Dickson, Charles tOl INDEX 295 . .302 Dickinson, Lieut. Oliver P. . Die-forging Dielectric constants Diffln, F. O Directing artillery flr^e ^^- ^^i isi: li^. Dirigibles 125, 157, 158, Baldwin i>ilot's certificate first U. S military naval wireless Distance reconnaissance District of Columbia Dive attack ■ ■ • Dodii. Capt. T. F 208. Dodge, W. Earl Dope, inflammable Drag Drag roping Drift Drift coefficient Drift indicator Dropping bombs Dubilier condenser Dubilier system ■ ■ • Dubilier, William l**"- Dugouts, German Dumont, Alberto Santos Duesenberg motor Dusseldorf Duties of balloon personnel • ■ ■• Dwyer, J. T 210. 204 250 146 213 160 165 205 187 204 157 157 143 111 219 65 245 202 72 275 163 117 275 272 22 145 137 253 70 202 242 7 164 211 First aero appropriation — Contintted dirigibilo 204 «i«ht 222 gunplane *•''' militar.v aero review 230 Eastman aero camera Economical speeds Effect of size on performance Effect of size on structural weight Electric flashlight beacon Electric headlights Electrical Review Electrolyzers Electrolyzers, American Electrolytic method Electrolytic plant • • Electro magnetic controlled oscillator .... Ellis, Brig. Gen. H. Handy Elongated balloons ol- Emergency Air Fleet Enemv aircraft • • England I''"' England, Brig. Gen. Lloyd England, night flying in English wireless apparatus Enlisted aviators, insignia Enlisted men. Aviation section Begular Army uniforms Enlisted personnel Enlisted Reserve Enlisted Reserve Proper Equipment, balloons companies Equipment, cost of Ericson, P. G i' .V Essen T, 10, Etampes • • ■ • • • ' • European War -^^i. -*=>• Evans, Gen. Robert K Evolution of military aeroplane Expansion of hydrogen .... ■ Experiments at South Foreland Expert Aviator certificate 102 254 279 279 136 25 177 170 171 170 171 l.'Jl 210 159 11 160 259 210 127 140 190 193 181 195 161 1«1 181 164 213 213 27 287 259 202 204 168 133 189 Pabbri photo apparatus ■ ■ . ■ • Face masks for aviators 191. 1«''. Factors of air supremacy Factors of safety • • • • P. A. I. Certificates 18"- F. A. I. rules Pall of shots Pan driven generator • • • . ■ ■ • Farman, Henri. 15. 16. 93, 222. 282. 287. Parman biplane Parman reconnaissance biplane .... ■ • ■ ■ Favre. A. L : ...... .210, Federal Reserve Officers' Training Camps . . Federal service Ferber, Cajrt. Louis Ferro-silicon • • • Fiat motors '■^• Fibre stress Field artillery Field artillery control Field companies Field compression outfits Field generators Field generators, hydrogen Fifth arm ; , ■ ■ ■ ■■■ Fighting in the air 57. .2bH. Fighting machines Fighting pilots Fighting tactics . Filling hydrogen cylinders Filling kite balloons Films vs. plates Fire control Fire safety device First aero appropriation iiA'Vi'i' Aero squadron ^i"> ^^^ requisition 222 specifications ^^^ spotting artillery fire JjJ tractor bijdane. U. S 2-7 use of aeroplane in war -^9 Piske, Rear Admiral Bradlej A 202 PiUgerald, Capt. S. \V 215 Fixed blade propeller 253, 255 Fixed camber wings 252 Flare lighting Ijf Flares Ig" Flare up "° Flashlight beacon i^o Plexilile pijiing ^"1 Flight commanders 11^ Flint Aircraft Mfg. Co ^** Floats, metal ^gi Flying Corps ^»^ instruments iJJ level 261 ^r. ;.;.• .•.•.;.■.•;.• .■.•.■.■;.;;i9i,ib4; 195 suit, summer i^^ Fokker. batteries • ■ . • • ■ • • »' Pokker nionoi)lane 241. 286, ^'^^) Folding landing gear 251 Folding, packiug, shipping balloons lOd Forces of gases 1°^ Formation, aerial fighting Oi flying, lamp signals 68 flying, rules ^» opposing {|^ reconnaissance • Jip Form of application. Officers Corps 180 1^ Syr'". ■.::::■.■.:■.:• 264; •205.- 22^ 225 Port Omaha 161. 167. 169. 170 Port Sam Houston • . • • • f"8 Foulois. Benjamin . . 194. 204, 206, 208. 225 French aerial beacon 133 Aero Club 202 aeroplane ^^j? air raids f" air raids with British i» Army 230 artillery ^0 aviation '"; aviation camp ^^" aviators j" balloons . 'Ij: bombardment •'; bombing plane ;>} French cameras zi dirigible • ■ ■ • l|?^ Flying Corps 185. •i"'' front \l\ government *^^ kite balloon g* landing system ■ ■ • 1^» Military competition ^^0. ^o" Ministry of War ^27. iii nightflying observers 127 105 128 German armed machines 47 Automobile Constructor's Ass 231 aviation beacons 130 bases SI biplane, A. E. 42 cities 25 combat machines 43 costly failure 240 defensive line 70 dugouts 70 government wireless 154 hydrogen making 171 hydrogen trucks 172 naval bases 27 positions 70 Roland jilane 46 Rumpler plane .... 44 Scout 97 Spad 45 Taube 154 trenches 70 War Department 231 German wireless apparatus 140, 141 communication 154 stations 152 Gillmore, R. J 211 Gliding angle 229 Gloves for aviators, summer 192 Gloves for aviators, winter 191 Gnome 228 Godfrey. Dr. Hollis 214 Goerz range finder 31, 32. 33 Goerz sighting telescope 31 Goethals, Maj. Gen 21'7 Goggles ... 192, 193, 194 Gompers, Samuel < 214 Goodrich, C. C 161. 210. 211 Goodyear Blimp 175 Goodyear School. Akron, Ohio 156 Gorrell, Lieut. E. S 208 Gotha 14. 289 Gotha battleplane 79 Gotha biplanes 3 Gotha biplane, fusilage 59 Gotha gunners 79 Graduate School of Military Aeronautics. . 185 Graham. Lieut. Harry 204.208 Graig, AM 210 Gravity service tanks 240 Great Britain's Dirigibles 157 Ground cloth °| Ground School of Military Aeronautics. . . . 183 Ground signal sheets 121 Guerilla tactics 115 Guide and anchor rofie toggle 158 Guide rope lo3 Guillaume. Trench 5 Gunners, aero 71 Guns, largo caliber 72 Itewis 1^9 mounting on aeroplanes 67 mounts 54 Vickers 73 Guynemer, Capt 31 Gyroscope efforts 247 Gyro manual control 26, - /3 Gyroscopic moments 256 Gyroscopic unit 269. 271 pilots scout «' trenches 107 103 194 40 46 204 164 160 154 295 55 121 211 182 211 226 176 288 256 71 245 194 165 160 165 63 270 286 64 58 174 164 108 245 251 221 257 War Deiiartment 226 wireless aii|)aratus 1*0 wireless trucks 144 wireless set 14]J Franco Prussian War 221 Free balloons 163 Free balloon training 161. 163 Frost, Cori>. B. C ^10 Frost, D. O jll Fuel capacity ^*;? Fuel leads 2j0 Fuel supply Pull loads 254 Funston. Gen ^"g Fuselage ■ ■'°% Fuselage of aeroplane "o Gallaudet Aircraft Corp 244 Garrison uniforms 195 Garros. Roland „%l Gary. Elbert H 202 Gas beacon 1^° Gas cylinders " ' Gasoline supply J*J Gasoline supiily system ^4» Geiger, Lieut, Harold 206 General Aeronautic maps J97 General aeroplane , ,■ '. Tco Generation and compression of hydrogen . . 10^ Generator -69 Generator, wireless 1* ' Geographical Congress 201 Se?mi"ny ■::::: ; : : ; : : .'8i.' i^iVHo: Vie. 233 German aerial beacon ■•■ t-?" aero camera l"l' i"^ aerodromes at night ••■■■■• J^ ak' oV log aeroplanes 57. 79, HO, ad. i-» German ammunition 5 / Hagerty, Corp. E. B 210, Halberstadt Hall, Brig.-Gen. P. L Hall, E. S Hammond, John Hays Hand air pressure i)umps Hand control lever 269. 270. HandleyPage warplane. .12, 47, 274, 276. Handley, Sergent Harrison Hangars Hangars, illumination Handling captive balloon windlass Haunay, Maj. D. R Hare, James H Harriman, W. Averill ■ ■ Hawley, Alan R 101, 202, 216, 217, Hawley. William Heavier than air machines Heinrich Corp Helicopters • ■ Heligoland • -7. Helmets, aviator s -Im^- Hennessey. Capt. Frederick B 204. Henrj. P. J 210, Herbert and Husgen 100, Herck, Capt J Hertz wireless experiments Hickman, Willis G High explosive shells Hindenburg statue • . . • History of aeronautics 20b, History of U. S. Army aeronautics. . . .204. Homogeneous dielectrics Honig, Edgar 131. Honig circles Hood Hoppin, F, L. V Horizontal reference Horizontal surfaces Hotchkiss, Gen 211 286 210 219 202 249 272 287 211 209 127 164 77 206 202 243 202 223 244 226 25 193 206 211 106 213 141 211 51 156 211 219 146 210 131 193 211 272 247 49 296 INDEX Hough, Brig. Gen. W. B 211 House Committee on Military Affairs .... 214 Howard. Brig. Gen. C. W 211 HoweU, W. T. 210. 211 Howitzers 71 Hoyer. Lieut. R. H 211 Hobbard. J. P 210. 211 Hulbert, Congressman Murray 219. 243 Humphreys. Lieut. Frederick E 204 Hutchings, Brig. Gen. H 211 Hydraulic tests of gas cylinders 163 Hydroaeroplane pilot's certificate 188 Hydrogen 84 American manufacturers 175 carriers 169 eylinders 160 field generators 176 for military purposes 167 from water gas 176 portable gas j>lant 170 Silicol process 171 supply 160 trucks, German 172 Hydrogenite 176 Hydolite 175 Immelmann, Lieut 65, 66. 241 Imperial Aero Club 231 Imperial Automobile Club 231 Improvements in design 257 Incendiary bombs 20 Incendiary rockets 159 Inclinometer 24, 126 Identification badge . 196 Indenting for stores 97 Independent interrupter 142 Induction coil 142 Inflammable doi>e 72 Inflation of balloons 82. 163 Insignia 190. 199 Insignia, sleeve 193 Inspection, balloon envelope and net 164 Inspection window 158 Installation, wireless 138 Instructions for aero photography 91. 109 Instructional aeroplanes 240 Instruments 14, 23, 24. 126 Instruments, sighting telescope 31 International Aeronautic Federation. .186, 201 International Aircraft Standardization Committee 213 International Convention on Aeronautic Cartography 200 International Geographical Congress 201 Invisibility of aeroplanes 125 Iron contact process 172 Isotta Fraschini motors 12, 13 Italian Aeronautic Topography 203 aeroplanes 157 airscout 229 Commission on Aeronautics in U. S. . . 10 raids 19 theatre of war 19 Turkish War 232 Italians 241 Italy, aeronautic map 202 Janney Aircraft Co 244 Jenkins. W. C 210. 211 Johannistal beacon 136 Johnson, Corp. Greenhow 212 Johnson. W. J 210. 211 Joint Army and Navy Committee 204 Joy. Henry B ; 202 Junior MiliUrj' Aviators ..179. 186. 192, 194 Junior Military Aviator's insignia 190 Junior Squadron 183 Junior \N ing. instruction 184 Kaiser's prise 230 Karlshrnhe raid 17 KeBey. O. E. M 204 Kentucky « 210 Kid 7. 10. 25. 27. 29 Kiel Canal 18. 25 Kiel, raid on 30 Kilmer. Lieut. W. G 208. 215 Kinematograph , 96 King and Queen of England 47 Kirtland. Lieut. R. Carrtngton 204 Kite balloon 71. 77. 81 83. 84, 85. 87. 91, 06. 157. 163, 164 Canadian 88 eompany 83 steering bags 164 truck 169 unit 82 Kit* obaerrer 99 Kitty Hawk 226 Klaxon horn 121 KnowUon. R. J 210. 211 Kodja Chai 91 Kolbasa 86 Konaot. W, W. Jr 211 Kruaa, Berj. E. A 210. 211 Laffoo. Lieut. 66 Lahm. Maj Frank Vurdy 76. 202. 204, 205 Laird Aviation Co. 244 Laml>prt, Capt. A. B 202 Lallemand, ChAries 208 Lamp signals, formation flying 56 Landing brakes 251 gear 251 ground 127. 132 places 198. 199 spots for balloons 163 stations 127 Langley. C. P 222. 223. 226 Langley Aerodrome 223 Langley Field 173 Lanzuis Aircraft Co 244 Large aeroplane, case of 274 Large warplanes 2-41 Large Zeppelin apparatus 138 Law, Ruth 25 Lawson "M T-1" 292 Leading American aeroplane 244 Lebaudy dirigible 157 Lefrance, Jean-Abel 31 Le Large, Capt 172 Leggins 193 Lenses 104 Letord 15. 288 Levant air raids 20 Lewis gun 48, 52, 61, 72, 139, 208 Life Saving Service 237 Lift coefficient 275 Lighthouses, aerial 134 Lighting aerodromes 127 Lighting equipment for aeroplanes 133 Light scout aeroplanes 240 Lighting stand 131 Lights for landing grounds 132 Liquid pressure gauge 261 Line of direction 102 Line of reconnaissance Ill Literary Digest 131 Local strength 279 Local or artilh'ry reconnaissance 112 Lockhart, Henry, Jr 202 Logj- 247 London 126 London Aeronautics 127 Long distance flights 187 Lend distance raids 125 Long Island Map 200 Lovett, Lieut. Robert A 202 L-section . 250 Ludwigshafen raid 17 L. W. F. aeroplane ■ 271 L. W. F. Engineering Co 244 L. V. G 287 Machine guns, mounting 67 Magnetic forces, wireless 151 Magnetos 257 Major aerial operations 241 Mann, Congressman James R 213 Manoeuvering and pressure valves 164 Manoeuvering valve 163 Map holder, Sperry 201 Maps 74. 75, 91, 113, 197 Map with photograph of route 200 Marconi Co., wireless 155 Marconi wireless experiments 141 Mariner's chart 197 Martin aeroplane 207 Martin, Dr. Franklin 214 Martinside 286 Massachusetts Institute of Technology .... 216 Maurice Farman biplane, wireless 147 Mauser Work.s, Oberndorf IS Maximotor 244 Maxim, Sir Hiram 48. 222 McClasky, Lieut. J. W 204 McCormick. E 210 McCormick. Harold F 202 McCoy, Capt. J. C 202 McDaniels, Lieut. Curry A 211 McGregor, J. S 213 McMillin, Capt. Ralph E 210 McMillin, Emerson 202, 209, 232 McMullen. Lieut. Byron 211 Mean density 260 Mean pressure 260 Mean temperature 260 Measuring aircraft performances 259 Mechanical interrupters 150 Mechanics of the aeroplane 238 Mercedes engines 3, 288 Merrica, P. D 213 Messengers, motorcycle 194 Messerschmitt. A 173 Metal construction for aeroplanes 250 Metal floats 251 Meteorology 166 Mexican campaign 206. 208, 231 Mexico, punitive expedition Ill Mexican War 204 Meyers, Eugene. Jr 202 M. F. P. Aero Co 244 Micbelln. M 47 Mignot, Lieut. M 213 Military aeroplanes 245. 240. 257 afroplanes, evolution 222 aerodromes 106, 135 arroKtntics 157 aviftlors 179. 1»2. 194 aviator's insignia 190 dirigibles 167 loaortation. balloons 81 Trenches 70. 71. 75. 90. 105, 159 Trenches. British 130 Trench shelters 70 Trentino Army 6 Trent iuo front 72 Trial flights 224 Trieste Raids 19 TripUine scout "8-3" 244 Triplane. advantages of 45 Tri|>lane. Caproni 278 "Triiie Hound" 13 Tripoli 229 Tropics, uniforms 195 Tubing for fuel leads ... 250 Tulie wagon 84 Tuning vibrator 142 Turkish-German iKwitions 125 Tnrney, George W 202 Turner. K. M 202 Twin motored .J N Tractor 244 Twin motored Handley Page 276 Two engined aeroplanes 239 Two place machines 246 Two propeller system 246 Types of Aeronautic Maiw 197 Ubmt biues 9. 21 TTnifomi* reguUtions 193 Uniforms, specifications 190 Uniforms, U. S. Aeronautic Personnel 190. 193 United Eastern Aero Con 242. 299 United SUtea 7. 170. 173 18S, 11)3. 195. 201, 212, 224. 245. 282 aero maiM 197 •ertmautic p<-rsonnel, regulations for uni forma 190. 193 aeronautics, history of 204 armed machine* 47 United States — Continued aviation students 181 dirigibles . 157 Government 223 Government wireless seta 153 Navy Radio Division 154 training of aviators 179 training fields 186 War Department 222 wireless students 141 United States Army 76, 204, 205, 208, 209, 245 Aviation School 210 Balloon Co 169 Balloon School 161, 163 Balloon School, Ft. Omaha 167 biplanes, V. S 140 gasoline supply system 242 Reserve Military aviators test 189 service insignia 190 uniforms 195 University of California 216 Illinois 216 Ohio 216 Texas 216 University students studying aviation .... 181 Use maps and compass with free balloon . 164 Useful load 245 UsueUi, C 203 Valve cord 163 Valve line 258 Vanderbilt, Col. Cornelius 202 Vanderhilt. W. K 202 Variable-camber wing 252 inductance 148 pitch blade 254. 255 pitch propeller 253. 265 pull 128 radiators 252 Varnishing cotton balloons 164 Velocity 247 Velocity of aeroplane 275 Verdun 64. 128 Vermont 212 Verys Light 75. 76. 128 Verys jtistol 73, 76 V formation 30 Vibration 248 Vibration absorbing material 252 Vickers gun 48. 72 Vickers Scout 286 Vienna International Aeronautical Federa- tion 201 Vilas, L. A 202 Villa's raid 208 Vincent. J. C 219 Virginia 212 Virginia National Guard 212 Visual signal codes for balloons 164 Vitriol process 168 Voisin 32. 47. 222, 228. 269. 290 Voisin Brothers 226 Voisin-Peugeot gun plane 54 Volunteer forces 180 Waldon, Sidney D 214, 215 Walker. J. Bernard 217 Walker. .John C 204 Walvets 64 Wanamaker. Rodman 210 War. decision of 3 War Department 179. 217 245 Wardrop. G. Douglas 202 Wards. Lieut. Forest 210 Ward. T. P 211 War kites 99 War office 229 War with Mexico 204 Washington, Cutting A., radio set 153 Washington, D. C 179 Washington Signal Corps Flying School . . 182 Water gas for hydrogen 176 Watkins, Lieut. B. O . 215 Wave length, wireless 142 Weight saving 279 Wellington, quotation Ill Wendell, Evert Jansen 237 Western battle front ] 107 Western front 's2, 98 Western theater of war .' 13 West Virginia ' ' 212 Wheeler, Lieut. D. R '.'..'. 215 Wheeler, Monroe ' 202 Wheeler. S. S ,,] 202 White. Brig.-Gen. George H 211 White House 212. 217 Whitney, Harry Payne .' 202 Wilhelmshavcn 7, 10 WiUard. Daniel .' 214 Willets. Lieut. W. P 210. 211. 215 William, I. R _' 230 Williams Aero Co ,'. 244 Willis. Lieut. R. H , . , 208 Willoughby. Hugh L 202 Wilson Aerial Highway 200 Winch for kite balloons 159 Wind channel experiments 275 Winding drum igi Windlass 16I Windlass wagon gi Wing construction 253 Wing section 259 Winter gloves for aviators 191 Winter. Lieut. .John C 204 Wire gauze strainer 250 Wireless 75, 76, 77, 121, 138 aerials ... 142 aero transmitter 150 apparatus. Breguet 148 communication 139 control of artillery fire 142. 149 Culver .".et 154 equipment 138 observer 147 helmet 138 installation 148 receiving apparatus 152 receiving station 151 receiving trucks 144 sets for U. S. Gov 153 signaling 147 speed of sending 141 station, German .... 151 transmission 141, 142 transmission sets 246 trucks 145 units 150 Washington set 153 Wire telephone 140 Wise Wood. Henry A 202, 217. 238 WittemannLewis Co 244. 291 Wood, Brig. Gen. J'red. W 210 Woodhouse, Henry 201, 217, 234, 237 Woods bulls eye 158 Wright 222 Wright aeroplane 204, 207, 226 236 Wright. Captain Frank W 211 Wright-Martin Co 237, 291-292 Wright. Orville . . . .202. 204, 205, 222, 224, 225. 226 Wright, Rev. Milton 225 Wright. Wilbur 221. 225 Young. Brig.-Gen. L. W 211 Young, William Wallace 202 Zahm, Francis A 202 Zeebrugge 7 Zeppelins 20. 126, 134, 135. 137. 143. 157. 240 bomb 37 bomb dropping mechanism 22 duly 127. 133 raids 24, 125 incendiary Ijomb 34 over Berlin 156 radio 154 (See Textbook of Naval Aeronautics and D'Orcy's Airship manual.) wireless 138 wireless stations 152 wreck 110 Zone call system 122 ^^ ^iAiIi2£i^(i 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books ate subject to immediate recall. ian29'62U'-^^ REC'D LD ,IAN 1 8 iqfi? 5Apr'62MW REC'D LD APR 51962 V RfeC D LD WAY 2 2^04 5PM ^27^969 oX RgCElVgp FFtil9-F.c)-f^K,vi l - OAN DCP T . f^P'C'D LD *«^ JOM gUfW^ -^ 6*N\ KhC'U LD MAY ■X 8 I95r 2 6/U 'i>HIVl 8 8 LD 21A-50m-8,'61 (Cl795sl0)476B tJETrnrj^fc; I Library University of California Berkeley <^0040t3io?