HE NEW ART 
 DF FLYING 
 
 UNIVERSITY OF CALIFORNIA LIBRARY 
 
 
 
 WALDEMAR KAEMPFFERT 
 
LIBRARY 
 
 OF THE 
 
 UNIVERSITY OF CALIFORNIA. 
 
 Class 
 
THE NEW ART OF FLYING 
 
Photograph by Edwin Levick 
 
 Fig. 36. The Hanriot monoplane in flight. The 
 
 entire framework is covered with canvas 
 
 to reduce resistance 
 

 
 
 
 The 
 New Art of Flying 
 
 
 
 BY 
 
 WALDEMAR KAEMPFFERT 
 
 With Numerous Illustrations 
 
 
 
 v i , 
 
 
 
 >-, >' T* ;\ } , -, } i s T V%? HI *;i 
 
 
 
 NEW YORK 
 DODD, MEAD AND COMPANY 
 1911 
 
 
 
 
 
Copyright iplO, 
 BY WALDEMAR KAEMPFFERT 
 
 Copyright 1911 
 BY HARPER & BROS. 
 
 Published, April, 1911 
 
 LIBRARIAN'S FIK3 
 
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PREFACE 
 
 WHEN the time comes for some historian of 
 the far-distant future to survey critically the 
 technical achievements of the nineteenth and 
 twentieth centuries and to weigh the compara- 
 tive economic importance of those achievements, 
 it may be that the invention of the aeroplane 
 flying-machine will be deemed to have been of 
 less material value to the world than the dis- 
 covery of Bessemer and open-hearth steel, or 
 the perfection of the telegraph, or the intro- 
 duction of new and more scientific methods in 
 the management of our great industrial works. 
 To us, however, the conquest of the air, to use 
 a hackneyed phrase, is a technical triumph so 
 dramatic and so amazing that it overshadows 
 in importance every feat that the inventor has 
 accomplished. If we are apt to lose our sense 
 of proportion, it is not only because it was but 
 yesterday that we learned the secret of the bird, 
 but also because we have dreamed of flying 
 long before we succeeded in ploughing the water 
 in a dug-out canoe. 
 
 From Icarus to the Wright Brothers is a far 
 cry. In the centuries that have elapsed more 
 
 218707 
 
vi PREFACE 
 
 lives have been lost in aeronautic experimenta- 
 tion than in devising telephones and telegraphs. 
 These tragedies of science have lent a glamour 
 to the flying-machine; so much so, indeed, that 
 the romance rather than the technique of flying 
 interests the reading public. Yet this attitude 
 of wonder is pardonable. Only a few years ago 
 the inventor of a flying-machine was classed, 
 even by scientists, with the misguided enthusi- 
 ast who spends his life in devising perpetual 
 motion machines or in fruitless attempts at 
 squaring the circle. It is hard to realise that 
 the building of aeroplanes is now elevated to 
 the dignity of a legitimate engineering pursuit. 
 
 Although the romantic aspects of aviation 
 have not been ignored in the following pages, 
 it is the chief purpose of this book to explain as 
 simply and accurately as possible the principles 
 of dynamic flight and aeroplane construction, 
 so that an intelligent reader will learn why a 
 machine many times heavier than the air stays 
 aloft for hours at a time and why it is con- 
 structed as it is. The limitations imposed by 
 a popular book are such that it is impossible to 
 discuss with anything like thoroughness such 
 difficult matters as equilibrium and stability, the 
 correct proportioning of supporting surfaces to 
 weight and speed, and the resistance encoun- 
 
PREFACE vii 
 
 tered in the air by planes in motion. Indeed, 
 these questions are not definitely settled in the 
 minds of technical men. Besides presenting an 
 elementary account of a flying-machine's way 
 in the air, it has been deemed advisable to dis- 
 cuss the screw and the internal-combustion 
 motor as applied to the flying-machine. There 
 can be little doubt that the propeller and the 
 engine offer many a problem for solution be- 
 fore the aeroplane can compete successfully with 
 other forms of locomotion, and a discussion of 
 the driving mechanism of an aeroplane should, 
 therefore, constitute an essential part of even 
 a popular book on flying. 
 
 So marked have been the changes that have 
 been made in the construction of well-known 
 biplanes and monoplanes and so many are the 
 new machines that appear almost from week 
 to week that it is almost a hopeless task to 
 present anything like a complete account of 
 existing aeroplanes. Hence it has been deemed 
 advisable to limit the descriptions of types to 
 those machines which have been in a measure 
 standardized. 
 
 In the preparation of this volume the author 
 has been ably assisted by several friends to 
 whom he wishes to make due acknowledgment. 
 He is indebted to Mr. Carl Dienstbach for a 
 
viii PREFACE 
 
 critical reading of the entire manuscript before 
 it passed to the press, and for many valuable 
 suggestions; to Mr. C. Fitzhugh Talman, li- 
 brarian of the United States Weather Bureau, 
 for a painstaking revision of the chapter en- 
 titled " The New Science of the Air "; to Mr. 
 H. A. Toulmin for information on the points 
 at issue in the various suits brought by the 
 Wright Brothers for the alleged infringement 
 of their patents; to Francis W. Aymar, Pro- 
 fessor of Law in the New York University 
 Law School, for valuable aid in the prepara- 
 tion of the chapter on " The Law of the 
 Air " ; and to the Smithsonian Institution and 
 the Wright Brothers for various photographs. 
 
 Acknowledgment is also made to Messrs. 
 Harper & Brothers for permission to use ma- 
 terial which appeared in an article written by 
 the author and published in " Harper's Monthly 
 Magazine." 
 
 NEW YORK, N. Y., January, 1911. 
 
CONTENTS 
 
 CHAPTER PAGI 
 
 I WHY FLYING-MACHINES FLY .... i 
 
 II FLYING-MACHINE TYPES 15 
 
 III THE PLANE IN THE AIR 26 
 
 IV STARTING AND ALIGHTING 42 
 
 V How AN AEROPLANE is BALANCED . 58 
 
 VI MAKING A TURN 85 
 
 VII THE PROPELLER 94 
 
 VIII AEROPLANE MOTORS in 
 
 IX THE NEW SCIENCE OF THE AIR . . 133 
 
 X THE PERILS OF FLYING 163 
 
 XI THE FLYING-MACHINE IN WAR . . . 185 
 
 XII SOME TYPICAL BIPLANES 208 
 
 XIII SOME TYPICAL MONOPLANES .... 222 
 
 XIV THE FLYING-MACHINE OF THE FUTURE 23 1 
 XV THE LAW OF THE AIR 246 
 
 GLOSSARY 269 
 
 INDEX fc . . 281 
 
ILLUSTRATIONS 
 
 Fig. 36. The Hanriot monoplane in flight. The entire frame- 
 work is covered with canvas to reduce resistance frontispiece 
 
 FACING PAGE 
 
 Fig. i . Lilienthal gliding in the machine in which he was killed 4 
 Fig. a . Chanute trussed biplane glider in flight 8 
 
 fig. 3. Langley's steam-driven model, the first motor flying- 
 machine that ever flew ia 
 
 Fig. 4. Langley's aerodrome in flight on May 6, 1X96, on the 
 Potomac River at Quantico. This is the first photo- 
 graph ever made of an aeroplane in flight .... 1 6 
 
 Fig. 5. Roe's triplane in flight. The best engineering opinion 
 is against the triplane because of its large head resist- 
 ance and consequent low speed 20 
 
 Fig. 6. Cornu's helicopter or screw-flyer. In this machine the 
 lifting and propulsive force is obtained entirely by 
 screws 4 
 
 Fig. IO. Langley's device for launching his aerodromes. The 
 machine was mounted on a houseboat, which could be 
 turned in any direction so as to face the wind ... 30 
 
 Fig. 1 1 . Langley's model aerodrome photographed immediately 
 
 after a launch . . % 34 
 
 Fig. 13. Starting derrick and rail of the Wright Brothers. The 
 
 machine is about to be hauled up on the rails ... 38 
 
 Fig. 14. Combined wheels and skids employed on the later Wright 
 
 machines 44 
 
 Fig. 15. Bleriot starting from the French coast on his historic 
 
 flight across the English Channel 48 
 
 Fig. ao. Mr. Wilbur Wright in the old type Wright biplane . 54 
 
 Fig. ai. The first type of Wright biplane, showing the general dis- 
 position of the main planes, forward horizontal rudders 
 and rear vertical rudders 60 
 
 Fig. aa. A machine devised by the Wrights for the instruction of 
 
 pupils 7* 
 
 Fig. 24. Glenn H. Curtiss winning the Scientific American Trophy 
 
 on July 4, 1908 76 
 
 Fig. 25. Glenn H. Curtiss in one of his flying-machines, equipped 
 
 with balancing-planes between the main planes . . 80 
 
 Fig. 27. The Farman biplane. The ailerons are the flaps on the 
 planes, which, as shown in this picture, hang down 
 almost vertically when the machine is at rest ... 8z 
 
 xi 
 
ILLUSTRATIONS 
 
 FACING PAGE 
 
 Fig. 28. Henry Farman seated in his biplane. His hand grasps 
 
 the lever by which the ailerons are operated ... 88 
 
 Fig. 29. One of the new Curtiss biplanes in flight. The ma- 
 chine is fitted with ailerons similar to those of the 
 Farman machine pictured in Fig. 27 92 
 
 Fig. 32. In the Antoinette monoplane the horizontal or elevating 
 rudder is operated by means of a vertical hand-wheel 
 by the pilot's right hand. The aviator here pictured 
 is Hubert Latham . o,g 
 
 Fig- 33- The Antoinette monoplane of 1909 in which ailerons 
 
 were employed to control the machine laterally . . 102 
 
 Fig. 34. Voisin machine of 1909. Machines such as this are 
 
 no longer made 106 
 
 Fig- 35- The Voisin biplane of 1910. The old cellular con- 
 struction is abandoned. Instead of vertical curtains 
 between the main planes Farman ailerons are adopted 112 
 
 Fig. 37. Gyrostat mounted in an aeroplane according to the system 
 of A. J. Roberts. The gyrostat is controlled by a 
 pendulum which swings to the right or to the left, 
 according to the tilt of the aeroplane . . . . 1 1 6 
 
 Fig. 38. The new Wright biplane in which horizontal or elevat- 
 ing rudder is mounted in the rear 128 
 
 Fig. 40. A Farman biplane making a turn. The entire machine 
 is canted so that its weight is opposed to the centrif- 
 ugal force generated by rounding an arc at high speed 130 
 
 Fig. 43. A Wright propeller. Wright propellers turn at com- 
 paratively low speeds (400 revolutions a minute). 
 They have an estimated efficiency of 76 per cent . 136 
 
 Fig. 44. The Wright machine is driven by two propellers driven 
 in opposite directions by chains connecting the pro- 
 peller shafts with the motor shaft 140 
 
 Fig. 45. The Santos-Dumont "Demoiselle" monoplane is the 
 smallest flying-machine that has ever flown success- 
 fully with a man. In the later "Demoiselles" 
 fabric propellers are supplanted by wooden screws of 
 the usual type 144 
 
 Fig. 46. A Bleriot monoplane showing a seven-cylinder, fifty- 
 horse power rotary Gnome motor. The motor spins 
 around with the propeller at the rate of about 1400 
 revolutions a minute 148 
 
 Fig. 47. The motor and the propeller of a R. E. P. (Robert 
 Esnault-Pelterie) monoplane. Robert Esnault-Pel- 
 terie has abandoned this four-bladed metal propeller 
 for the more efficient two-bladed wooden propeller . 152 
 
 Fig. 48. Henry Farman seated in his biplane with three passengers 156 
 
 xii 
 
ILLUSTRATIONS 
 
 FACING PAGE 
 
 Fig. 63. Motor of the Wright biplane 1 60 
 
 Fig. 64. Two-cylinder Anzani motor on a Letourd-Niepce mono- 
 plane 1 66 
 
 Fig. 65. The kite and the balloon-house of the Mt. Weather 
 
 Observatory 17 
 
 Fig. 66. Sending up the first of a pair of tandem kites at the Blue 
 
 Hill Observatory 174 
 
 Fig. 67. Mechanism of a meteorograph which records the velocity 
 of the wind, the temperature, the humidity, and the 
 barometric pressure 178 
 
 Fig. 69. A glimpse through a Wright biplane. The two planes 
 are trussed together like the corresponding members 
 of a bridge, so as to obtain great strength . . . . 182 
 
 Fig. 70. One of the numerous accidents that happened to Louis 
 
 , Bleriot before he devised his present monoplane . . 1 88 
 
 Fig. 71. A biplane that came to grief because of defective lateral 
 
 control IQ2 
 
 Fig. 72. An old style Voisin biplane of cellular construction 
 wrecked because the pilot tried to make too short a 
 turn near the ground 196 
 
 Fig. 73- A Krupp 6.5 cm. gun for airship and aeroplane attack. 
 The gun fires a projectile weighing about 8 Ibs. 1 3 oz. 
 to a height of about 18,700 feet 200 
 
 Fig. 74. A Krupp 7. 5 cm. gun mounted on an automobile truck. 
 The gun fires a 12 Ib. 2 oz. projectile to a height 
 of about 4 miles. The automobile has a speed of 
 28^ miles an hour. Under its seats 62 projectiles 
 can be stored 104 
 
 Fig. 75. A Krupp 10.5 cm. naval gun for repelling aircraft . . 210 
 
 Fig. 76. The projectiles employed for the repulsion of airships 
 and aeroplanes leave a trail of smoke behind them so 
 that the gun crew can determine the amount of error 
 in sighting 214 
 
 Fig. 77. A projectile that hit its mark 216 
 
 Fig. 78. ' A Voisin biplane equipped with a Hotchkiss machine 
 gun, exhibited at the 1910 Salon de 1'Aeronautique, 
 Paris. This is probably the first attempt to mount 
 a machine gun on an aeroplane, and was a rather 
 poor attempt 2*O 
 
 Fig. 79. The Wright biplane that Wilbur Wright flew in France 
 
 in 1908 224 
 
 Fig. 80. The Wright biplane of 1910. The elevating rudder 
 has been placed in the rear of the machine, where it 
 also serves as a tail 228 
 
 xiii 
 
ILLUSTRATIONS 
 
 _. FACING PAGE 
 
 rig. si. The machine in the air is a Farman biplane of the latest 
 type. The machine on the ground is a Bleriot 
 monoplane 232 
 
 Fig. 82. Sommer biplane 236 
 
 Fig. 83. The 100 horsepower Antoinette monoplane that Hubert 
 Latham flew at Belmont Park during the Interna- 
 tional Aviation Tournament of 1910 240 
 
 Fig. 84. The Santos-Dumont " Demoiselle " in flight . . . 150 
 
 Fig. 85. A Bleriot racing monoplane. Six men are exerting 
 
 every muscle to hold back the machine . . . . 256 
 
 Fig. 86. The Bleriot monoplane XII. This is a passenger- 
 carrying type. The pilot and his companion sit side 
 by side below the wings 262 
 
 XIV 
 
DIAGRAMS 
 
 PAGE 
 
 Fig. 7. CD is the " entering edge." The lifting power of the 
 forward half A of the curved plane is greater than the 
 lifting power of the rear half 2?, although both are 
 of equal area 28 
 
 Fig. 8. A is a simple inclined plane j S, a curved plane at the 
 same angle of incidence or inclination ; C, the type 
 of curved plane which has thus far given the best 
 results in the air 29 
 
 Fig- 9 . The plane B S is at a greater angle of incidence than 
 the plane A A. If its speed be 10 miles an hour, it 
 will, while travelling horizontally 25 feet, overcome 
 its tendency to fall to D. If its speed be 20 miles 
 an hour, it will have 50 feet to travel while over- 
 coming its tendency to fall to E. Unless the angle 
 of B S, therefore, were decreased to that of A A for 
 the greater speed, the plane would not move hori- 
 zontally but would ascend 32 
 
 Fig. 12. The special launching device invented by the Wright 
 Brothers. The device consists of an inclined rail, 
 about seventy feet long ; a pyramidal derrick j a heavy 
 weight arranged to drop within the derrick ; and a 
 rope, which is fastened to the weight, passed around 
 a pulley at the top of the derrick, then around a second 
 pulley at the bottom of the derrick over a third pulley 
 at the end of the rail, and finally fastened to a car 
 running on the rail. The car is placed on the rail, 
 and the aeroplane on the car. When a trigger is 
 pulled, the weight falls, and the car is jerked forward. 
 So great is the preliminary velocity thus imparted that 
 the machine is able to rise in a few seconds from the 
 car, which is left behind 52 
 
 Fig. 1 6. Path of an aeroplane driven forward but with a speed too 
 
 low for horizontal flight, and with too flat an angle . 58 
 
 Fig. 17 Path of a plane inclined at the angle C to the horizontal. 
 The arrow A indicates the direction of travel. If the 
 speed is sufficient the plane will rise because of the 
 upward inclination of the plane 59 
 
 Fig. 18. How a plane is laterally balanced by means of ailerons 
 and a vertical rudder. The plane A is provided with 
 hinged tips C and D and with a vertical rudder E. 
 The tips are swung in opposite directions to correct 
 any tipping of the plane, and the vertical rudder E is 
 
 XV 
 
DIAGRAMS 
 
 PACK 
 
 swung over to the side of least resistance (the side of the 
 tip D in the example here given) in order to prevent 
 the entire machine from rotating on a vertical axis . 62 
 Fig. 19. The system of control on an old Wright model ... 64 
 
 Fig. 13. The Curtiss system of control 66 
 
 Fig. 26. The system of ailerons and rudders devised by Henry 
 Farman for maintaining fore-and-aft and side-to-side 
 balance 68 
 
 Fig. 30. The Bleriot system of control 70 
 
 Fig. 31. The steering and control column of the Bleriot mono- 
 plane. The wheel Z,, the post AT, and the bell-shaped 
 member M form one piece and move together. Wires 
 connect the bell with the yoke G, carrying the 
 pulley F, around which the wires H running to the 
 flexible portions of the supporting planes are wrapped. 
 By rocking the post and bell from side to side in a 
 vertical plane the wires H are respectively pulled and 
 relaxed to warp the planes. By moving the post K 
 back and forth the horizontal rudder is operated through 
 the wires P. These various movements of the post 
 can be effected by means of the wheel L, which is 
 clutched by the aviator's hands, or by means of the 
 bell My which can be clutched by the aviator's feet 
 if necessary 71 
 
 Fig. 39. An aeroplane of 40 feet spread of wing rounding an arc 
 of 60 feet radius. Since the outer side of the aeroplane 
 must travel over a given distance in the same time that 
 the inner side must travel a considerably shorter distance, 
 gravitation must be opposed to centrifugal force in 
 order that the turn may be effected with safety . . 86 
 
 Fig. 41. A single-threaded and a double- threaded screw. A two- 
 bladed aeroplane propeller may be conceived to have 
 been cut from a double-threaded screw, /. ., the sec- 
 tions AznA A' and the sections B and B' ... 97 
 
 Fig. 42. How the Wright propeller is cut from three planks laid 
 
 upon one another fan-wise 109 
 
 Figs. 49, 50, 51, and 52. The four periods of a four-cycle engine. 
 During the first period (Fig. 49) the explosive mix- 
 ture is drawn in ; during the second period (Fig. 50) 
 the explosive mixture is compressed j during the third 
 period (Fig. 51) the mixture is exploded ; and during 
 the fourth period the products of combustion are 
 discharged 114 
 
 Fi S* 53 The U8ual arrangement of the four cylinders of a four- 
 cylinder engine .......... .118 
 
 xvi 
 
DIAGRAMS 
 
 PAGE 
 
 Figs, 54 and 55. Side and plan views of a four-cylinder engine 
 
 with diagonally-placed cylinders 120 
 
 Figs. 56 and 57. Engine with horizontally opposed cylinders . . 1 21 
 
 Figs. 58 and 59. Engine with four cylinders radially arranged . 123 
 
 Fig. 60. Arrangement of connecting-rods of an engine with four 
 
 radial cylinders ..124 
 
 Fig. 6 1 Arrangement of cylinders and crank case of one type of 
 
 three-cylinder engine ....125 
 
 Fig. 62. Disposition of cylinders, crank case and connecting-rods 
 
 in one type of engine 126 
 
 Fig. 68. The extent of the atmosphere in a vertical direction. 
 
 Heights in kilometres ...147 
 
 XV11 
 
THE 
 
 NEW ART OF FLYING 
 CHAPTER I 
 
 WHY FLYING-MACHINES FLY 
 
 AN aeroplane is any flat or slightly curved sur- 
 face propelled through the air. Since it is con- 
 siderably heavier than air, an inquiring mind 
 may well ask: Why does it stay aloft? Why 
 does it not fall? 
 
 It is the air pressure beneath the plane and 
 the motion of the plane that keep it up. A 
 balloon can remain stationary over a given spot 
 in a calm, but an aeroplane must constantly 
 move if it is to remain in the air. The mono- 
 planes and biplanes of Bleriot, Curtiss, and the 
 Wrights are somewhat in the position of a 
 skater on thin ice. The skater must move fast 
 enough to reach a new section of ice before he 
 falls; the aeroplane must move fast enough 
 to reach a new section of air before it falls. 
 Hence, the aeroplane is constantly struggling 
 with gravitation. 
 
2 THE NEW ART OF FLYING 
 
 The simplest and most familiar example of 
 an aeroplane is the kite of our boyhood days. 
 We all remember how we kept it aloft by hold- 
 ing it against the wind or by running with it if 
 there happened to be only a gentle breeze. 
 When the wind stopped altogether or the string 
 broke, the kite fell. Above all things it was 
 necessary to hold the kite's surface toward the 
 wind, an end which we accomplished with a 
 string. 
 
 The eagle is an animated kite without a string ; 
 it keeps its outspread wings to the wind by 
 muscular power. If we can find a substitute for 
 the string, some device in other words which 
 will enable us to hold the kite in the proper 
 direction, we have invented a flying-machine. 
 The pull or the thrust of an engine-driven pro- 
 peller is the accepted substitute for the string of 
 a kite and the muscles of an eagle. 
 
 If only these simple principles were involved 
 in a solution of the age-old problem of artificial 
 flight, aeroplanes would have skimmed the air 
 decades ago. Many other things must be 
 considered besides mere propelling machinery. 
 Chief among these is the very difficult art of 
 
WHY FLYING-MACHINES FLY 3 
 
 balancing the plane so that it will glide on an 
 even keel. Even birds find it hard to maintain 
 their balance. In the constant effort to steady 
 himself a hawk sways from side to side as he 
 soars, like an acrobat on a tight rope. Occa- 
 sionally a bird will catch the wind on the top of 
 his wing, with the result that he will capsize and 
 fall some distance before he can recover himself. 
 If the living aeroplanes of nature find the feat 
 of balancing so difficult, is it any wonder that 
 men have been killed in endeavouring to dis- 
 cover their secret? 
 
 If you have ever watched a sailing yacht in 
 a stiff breeze you will readily understand what 
 this task of balancing an aeroplane really 
 means, although the two cases are mechani- 
 cally not quite parallel. As the pressure of the 
 wind on the sail heels the boat over, the ballast 
 and the crew must be shifted so that their 
 weight will counterbalance the wind pressure. 
 Otherwise the yacht will capsize. In a yacht 
 maintenance of equilibrium is comparatively 
 easy; in an aeroplane it demands incessant 
 vigilance, because the sudden slight variations 
 of the wind must be immediately met. The 
 
4 THE NEW ART OF FLYING 
 
 aeroplane has weight; that is, it is always fall- 
 ing. It is kept aloft because the upward air 
 pressure is greater than the falling force. The 
 weight or falling tendency is theoretically con- 
 centrated in a point known as the centre of 
 gravity. Opposed to this gravitative tendency 
 is the upward pressure of the air against the 
 under surface of the plane, which effect is 
 theoretically concentrated in a point known 
 as the centre of air pressure. Gravitation 
 (weight) is constant; the air pressure, because 
 of the many puffs and gusts of which even a 
 zephyr is composed, is decidedly inconstant. 
 Hence, while the centre of gravity remains in 
 approximately the same place, the centre of 
 air pressure is as restless as a drop of quick- 
 silver on an unsteady glass plate. 
 
 The whole art of maintaining the side-to- 
 side balance of an aeroplane consists in keeping 
 the centre of gravity and the centre of air 
 pressure on the same vertical line. If the 
 centre of air pressure should wander too far 
 away from that line of coincidence, the aero- 
 plane is capsized. The upward air pressure 
 being greater than the falling tendency and 
 
WHY FLYING-MACHINES FLY 5 
 
 having been all thrown to one side, the aero- 
 plane is naturally upset. 
 
 Obviously there are two ways of maintain- 
 ing side-to-side balance, the one by con- 
 stantly shifting the centre of gravity into coin- 
 cidence with the errant centre of air pressure; 
 the other by constantly shifting the centre of air 
 pressure into coincidence with the centre of 
 gravity. 
 
 The first method (that of bringing the centre 
 of gravity into alignment with the centre of air 
 pressure) involves ceaseless, flash-like move- 
 ments on the part of the aviator; for by shift- 
 ing his body he shifts the centre of gravity. It 
 happened that one of the first modern experi- 
 menters with the aeroplane met a tragic death 
 after he had succeeded in making over two 
 thousand short flights in a gliding-machine of 
 his own invention, simply because he was not 
 quick enough in so throwing his weight that 
 the centres of air pressure and gravity coin- 
 cided. He was an engineer named Otto Lilien- 
 thal, and he was killed in 1896. Birds were 
 to him the possessors of a secret which he felt 
 that scientific study could reveal. Accordingly, 
 
6 THE NEW ART OF FLYING 
 
 he spent many of his days in the obscure 
 little hamlet of Rhinow, Prussia. The cottage 
 roofs of that hamlet were the nesting places of 
 a colony of storks. He studied the birds as 
 if they were living machines. After some 
 practical tests, he invented a bat-like appa- 
 ratus composed of a pair of fixed, arched 
 wings and a tail-like rudder. Clutching the 
 horizontal bar to which the wings were fast- 
 ened, he would run down a hill against the wind 
 and launch himself by leaping a few feet into 
 the air. In this manner he could finally soar 
 for about six hundred feet, upheld merely by 
 the pressure of the air beneath the outstretched 
 wings. In order to balance himself he was com- 
 pelled to shift his weight incessantly so that the 
 centre of gravity coincided with the centre of 
 air pressure. Since they rarely remain coin- 
 cident for more than a second, Lilienthal had 
 to exercise considerable agility to keep his 
 centre of gravity pursuing the centre of air 
 pressure, which accounts for the apparently 
 crazy antics he used to perform in flights. One 
 day he was not quick enough. His machine 
 was capsized, and his neck was broken. Pil- 
 
WHY FLYING-MACHINES FLY 7 
 
 cher, an Englishman, slightly improved on Lili- 
 enthal's apparatus, and after several hundred 
 flights came to a similar violent end. Crude 
 as Lilienthal's machine undoubtedly was, it 
 startled the world when its first flights were 
 made. It taught the scientific investigator of 
 the problem much that he had never even 
 suspected, and laid the foundation for later 
 researches. 
 
 Octave Chanute, a French engineer resident 
 in the United States, continued the work of the 
 ill-fated Lilienthal. Realising the inherent 
 danger of a glider in which the operator must 
 adapt himself to the changing centre of air 
 pressure with lightning-like rapidity, he devised 
 an apparatus in which the centre of air pressure 
 was made to return into coincidence with the 
 centre of gravity, the second of the two ways 
 of maintaining side-to-side balance. Thus 
 Chanute partly removed the perilous necessity 
 of indulging in aerial gymnastics. In his glid- 
 ing-machines the tips of the planes, when struck 
 by a gust of wind, would fold slightly backward, 
 thereby curtailing the tendency of the centre 
 of air pressure to shift. 
 
8 THE NEW ART OF FLYING 
 
 Chanute built six motorless, man-carrying 
 gliders, with three of which several thousand 
 short flights were successfully undertaken. The 
 best results were obtained with an apparatus 
 consisting of two superposed planes, a construc- 
 tion which had been previously adopted by 
 Lilienthal. It remained for the Wright 
 Brothers to provide a more perfect mechanism 
 for controlling the movement of the centre of 
 air pressure. 
 
 The principle of sitting or lying still in the 
 aeroplane and, by means of mechanical devices, 
 bringing the centre of air pressure back into 
 alignment with the centre of gravity is now fol- 
 lowed by every designer of aeroplanes. The 
 old, dangerous method of shifting weights is 
 quite abandoned. The greatest contribution 
 made by the Wright Brothers to the art of fly- 
 ing was that of providing a trustworthy mech- 
 anism for causing the centre of air pressure 
 to return into coincidence with the centre of 
 gravity. 
 
 The aeroplane must be balanced not only 
 from side-to-side but fore-and-aft as well. The 
 same necessity exists in the eld-fashioned, 
 
WHY FLYING-MACHINES FLY 9 
 
 single-surface kite. To give it the necessary 
 fore-and-aft stability, we used to adorn it with 
 a long tail of knotted strips of rags. If the tail 
 was not heavy / or long enough, the kite dived 
 erratically and sometimes met its destruction 
 by colliding with a tree. To insure longitud- 
 inal stability, many aeroplane flying-machines 
 are similarly provided with a tail, which con- 
 sists generally of one or more horizontal plane 
 surfaces. Some aeroplanes, however, are tail- 
 less, among them the earlier Wright machines. 
 Usually, they are less stable than the tailed 
 variety. 
 
 In order to relieve the .aviator of the neces- 
 sity of more or less incessantly manipulating 
 levers, which control centres of air pressure, 
 many inventors have tried to provide aero- 
 planes with devices which will perform that 
 task automatically. Some of them are ingen- 
 ious; but most of them are impracticable be- 
 cause they are too heavy, too complicated, or 
 not responsive enough. 
 
 In order to fly, an aeroplane, like a kite or 
 a soaring bird, is made to rise preferably in 
 the very teeth of the wind. What is more, it 
 
io THE NEW ART OF FLYING 
 
 must be in motion before it can fly. How this 
 preliminary motion was to be obtained long 
 baffled the flying-machine inventor. Eagles, 
 vultures, and other soaring birds launch them- 
 selves either by leaping from the limb of a 
 tree or the edge of a cliff, or by running along 
 the ground with wings outspread, until they 
 have acquired sufficient speed. To illustrate 
 the difficulty that even practised soaring birds 
 find in rising from the ground, the late Prof. 
 Samuel P. Langley used to quote the following 
 graphic description of the commencement of 
 an eagle's flight (the writer, one of the founder 
 members of the old aeronautical society of 
 Great Britain, was in Egypt, and the " sandy 
 soil " was that of the banks of the Nile) : 
 
 " An approach to within 80 yards arouses 
 the king of birds from his apathy. He partly 
 opens his enormous wings, but stirs not yet 
 from his station. On gaining a few feet 
 more he begins to walk away with half- 
 expanded, but motionless, wings. Now for the 
 chance. Fire ! A charge of No. 3 from eleven 
 bore rattles audibly but ineffectively upon his 
 
WHY FLYING-MACHINES FLY n 
 
 densely feathered body; his walk increases to 
 a run, he gathers speed with his slowly wav- 
 ing wings, and eventually leaves the ground. 
 Rising at a gradual inclination, he mounts aloft 
 and sails majestically away to his place of 
 refuge in the Libyan range, distant at least 
 five miles from where he rose. Some frag- 
 ments of feathers denote the spot where the 
 shot has struck him. The marks of his claws 
 were traceable in the sandy soil, as, at first 
 with firm and decided digs, he forced his way; 
 but as he lightened his body and increased his 
 speed with the aid of his wings, the imprints 
 of his talons gradually merged into long 
 scratches. The measured distance from the 
 point where these vanished to the place where 
 he had stood proved that with all the stimulus 
 that the shot must have given to his exertions 
 he had been compelled to run full 20 yards 
 before he could raise himself from the earth." 
 
 We have not all had a chance of seeing this 
 striking illustration of the necessity of get- 
 ting up speed before soaring, but many of 
 us have disturbed wild ducks on the water 
 
12 THE NEW ART OF FLYING 
 
 and noticed them run along it, flapping their 
 wings for some distance to get velocity before 
 they could fly, and the necessity of initial 
 velocity is at least as great with an artificial 
 flying-machine as it is with a bird. From this, 
 we can readily understand why a vulture can 
 be confined in a small cage, which is entirely 
 open at the top. 
 
 To get up preliminary speed many methods 
 have been adopted. Langley tried every con- 
 ceivable way of starting his small model, and 
 at last hit on the idea of launching it from 
 ways, somewhat as a ship is launched into the 
 water. The model rested on a car which fell 
 down at the extremity of its motion and thus 
 released the model for its free flight. On 
 May 6, 1896, he saw his creation really fly 
 like a living thing, the first time in history that 
 a motor-driven aeroplane ever flew. 
 
 The Wright Brothers used to obtain their 
 preliminary speed by having their machine 
 carried down the side of a sandhill, partly sup- 
 ported by a head-wind. Their first perfected 
 motor-driven, man-carrying biplane was started 
 on an inclined track. Most aviators of the 
 
O (D 
 
 !1 
 
 1 S 
 1 
 
 bfl 
 
 j 
 
WHY FLYING-MACHINES FLY 13 
 
 present time, however, mount their aeroplanes 
 on pneumatic-tired wheels, and like the eagle, 
 in the foregoing quotation, run along the 
 ground for a short distance. Aeroplanes have 
 also been dropped into the air from balloons. 
 
 Just as a soaring bird uses his legs in leap- 
 ing into the air or running on the ground to 
 start his flight and also in alighting, so many 
 aeroplanes alight with the wheels that serve 
 them during the brief moments of launching. 
 Sometimes, however, special alighting devices 
 are provided, a conspicuous example of which 
 is to be found in the skids or runners of the 
 Wright machine. 
 
 The problem of steering an aeroplane, when 
 it is launched, is solved, as it must be, by two 
 sets of rudders. A steamboat is a vehicle that 
 travels in two dimensions only; hence, it re- 
 quires only a single, vertical rudder, which 
 serves to guide it from side to side. An aero- 
 plane moves not only from side to side, but 
 up and down as well. Hence, it is equipped 
 with a vertical rudder similar to that of a 
 steamboat's, and also with a horizontal rudder, 
 which serves to alter its course up or down, 
 
14 THE NEW ART OF FLYING 
 
 and which is becoming more widely known as 
 an elevator. Fore-and-aft stability is attained 
 in tailless machines entirely by manipulation 
 of this elevator. Even in tailed machines its 
 use for that purpose is quite imperative. 
 
CHAPTER II 
 
 FLYING-MACHINE TYPES 
 
 THE flying creatures of nature insects, 
 birds, fishes, and bats spread wings that lie 
 in a single plane. Because their wings are thus 
 disposed birds may be properly regarded as 
 single-decked flying-machines or " monoplanes," 
 in aviation parlance, and because the earliest 
 attempts at flying were more or less slavish imi- 
 tations of bird-flight, it was but natural that 
 the monoplane was man's first conception of a 
 flying-machine. Since birds are the most effi- 
 cient flying-machines known, so far as power 
 consumption for distance travelled and surface 
 supported are concerned, the monoplane will 
 probably always be regarded as the ideal type 
 of aeroplane flying-machine. 
 
 It is a circumstance of considerable scientific 
 moment that the wings of a gliding bird, such 
 as an eagle, a buzzard, or a vulture, are wide 
 in spread and narrow in width. Much pains- 
 taking experimentation by Langley and others 
 
1 6 THE NEW ART OF FLYING 
 
 has shown that the best shape of plane is that 
 which is oblong; the span must be considerably 
 greater than the width. In other words, science 
 has experimentally approved the design of a 
 bird's wings. In nature the proportion of span 
 to width varies in different birds. The spread 
 of an albatross' wings is fourteen times the 
 width; the spread of a lark's wings is four times 
 the width, which is the smallest ratio to be 
 found among birds. The albatross is a more 
 efficient flying-machine than the lark. Hence the 
 albatross is a better model to follow and four- 
 teen to one a better ratio than four to one. 
 
 Long spans are unwieldy, often too unwieldy 
 for practical, artificial flight. Suppose we cut 
 a long plane in half and mount one half over 
 the other. The result is a two-decked machine, 
 a " biplane." Such a biplane has somewhat 
 less lifting power than the original monoplane, 
 and yet it has the same amount of entering 
 edge. Moreover, the biplane is a little steadier 
 in the air than the monoplane and therefore 
 a little safer, just as a box-kite is steadier than 
 the old-fashioned single-surface kite. Still, 
 the difference in stability between biplane and 
 
From an instantaneous photograph by Dr. Alexander Graham Bell 
 
 Fig. 4. Langley's aerodrome in flight on May 6, 
 
 1896, on the Potomac River at Quantico. 
 
 This is the first photograph ever made 
 
 of an aeroplane in flight 
 
FLYING-MACHINE TYPES 17 
 
 monoplane is so slight that designers base 
 their preferences for one type or the other on 
 other considerations. Both types are inher- 
 ently so unstable that it requires a skilled hand 
 to correct their capsizing tendencies. 
 
 By placing one plane over another certain 
 structural advantages are obtained. It is com- 
 paratively easy to tie two superposed planes 
 together and to form a strong, bridge-like truss, 
 which was first done by Chanute. The proper 
 support of the outstretched surfaces of a mono- 
 plane, on the other hand, is a matter of some 
 difficulty. 
 
 To correct the inherent instability of both 
 monoplanes and biplanes and to make them 
 safer machines, tails are frequently added. 
 Stability and safety are thus gained at the 
 expense of driving power; for the increased 
 surface of the tail means more resisting sur- 
 face and therefore less speed. An engine of 
 twenty horse-power will drive a tailless Wright 
 machine; tailed Voisin machines with large, 
 heavy cellular tails have refused to rise at 
 times even when equipped with fifty horse- 
 power motors. 
 
1 8 THE NEW ART OF FLYING 
 
 If a monoplane were to fall vertically like 
 a parachute, it would offer the resistance of its 
 entire surface to the fall; if a biplane were to 
 fall, it would offer the resistance of only one 
 of its planes to the fall. Hence the monoplane 
 is a better parachute than the biplane. The 
 point is perhaps of slight value, because if a 
 skilful aviator is high enough when his motor 
 fails him, he can always glide to the ground 
 on a slant which may be miles in length. Para- 
 doxical as it may seem, the greater the distance 
 through which he may fall, the better are an 
 aviator's chances of reaching the ground with 
 an unbroken neck. At a slight elevation from 
 the ground, both monoplanes and biplanes are 
 in a precarious position in case of motor stop- 
 pages. There is no distance to glide. Hence 
 they must fall. 
 
 Whether the biplane is a better type of ma- 
 chine than the monoplane, it would be difficult, 
 if not impossible, to maintain. It is certain, 
 however, that the biplane has been brought to 
 a higher state of perfection than the mono- 
 plane, probably because it was the first success- 
 ful type of a man-carrying, motor-driven flying- 
 
FLYING-MACHINE TYPES 19 
 
 machine. The older the type, the more marked 
 will be the improvements to which it will be 
 subjected. It is curious, too, that most of the 
 pioneer aviators have been advocates of the 
 biplane type. Lilienthal met his death in a 
 biplane. Chanute, who brilliantly continued 
 Lilienthal's work, and the Wright Brothers 
 brought the motorless biplane glider to its 
 highest pitch of perfection. The first flight 
 ever made by a man-carrying, motor-driven 
 machine was that of a Wright biplane. Voisin, 
 Curtiss, and Farman, all of them experienced 
 designers, have performed their most brilliant 
 feats in designing or flying biplanes. 
 
 Chanute made many experiments with glid- 
 ing-machines having more than two superposed 
 surfaces; but he found in the end that the bi- 
 plane type was most satisfactory. Despite the 
 lessons to be learned from his painstaking ex- 
 periments, inventors have not been wanting 
 who have worked on the three-deck or triplane 
 principle. One of these is Farman, who de- 
 signed the Farman-Voisin three-decked ma- 
 chine. Others are A. V. Roe in England and 
 Vanniman in France. Vanniman and Farman 
 
20 THE NEW ART OF FLYING 
 
 have since abandoned their triplane structures, 
 and thus rather confirmed Chanute's conclu- 
 sions. It is interesting to know that the tri- 
 plane goes back as far as 1868, in which year 
 an inventor named Stringfellow built a three- 
 decked model. 
 
 The many-planed flying-machine was prob- 
 ably carried to its extreme by an Englishman, 
 Mr. Horatio Phillips. Between 1881 and 
 1894 he made a series of experiments which 
 resulted in his building a multiplane, not un- 
 like a Venetian blind in appearance. It con- 
 sisted primarily of a series of numerous super- 
 posed slats, which had extraordinary lifting 
 power. Perhaps the chief objections to such a 
 multiplane are its weight and its height. Con- 
 sequently it is less stable in the air than biplanes. 
 
 Since an aeroplane, whether it be of single- 
 deck or double-deck construction, must be 
 driven at considerable speed to keep it in the 
 air, and must, furthermore, get up a certain 
 preliminary speed before it can fly at all, some 
 inventors have thought of rotating the planes, 
 as if they were huge propellers, instead of driv- 
 ing them along in a straight line. Such screw- 
 
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 r^ ^"H ? 
 
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 S-c 1 S 
 
 J -M 
 
FLYING-MACHINE TYPES 21 
 
 propellers, to push a machine from the ground, 
 are mounted on a vertical shaft, the whole con- 
 stituting a machine which goes by the name 
 " helicopter." A helicopter should theoretically 
 screw its way up into the air. Because no screw- 
 propeller can possibly support a weight in air 
 with anything like the aeroplane's economy of 
 power, the helicopter has never been a practical 
 success. In a helicopter, the screw-propeller 
 must be designed not only for propulsion but 
 for support as well. As far back as 1812 Pon- 
 ton d'Amecourt and de la Landelle maintained 
 that the heavier-than-air machine would be sup- 
 ported by a screw, the " sacred screw," to 
 use d'Amecourt's ecstatic Gallic phrase. They 
 found in the Academician Babinet a stout sup- 
 porter of their view, and he it was who invented 
 the term " helicoptere." The familiar little 
 screw-fliers which are whirled into the air by 
 hand or by twisted rubber bands seemed to offer 
 experimental evidence enough in support of any 
 helicopter theories. It was recognised, how- 
 ever, that one screw would cause the entire 
 apparatus to rotate. Hence two screws turning 
 in opposite directions were early recommended. 
 
22 THE NEW ART OF FLYING 
 
 Thus the rotating effect of one screw was coun- 
 teracted by the other, and the lifting effects of 
 the two were combined. 
 
 The most earnest student of the problem of 
 the lifting screw-flier or helicopter has been 
 Colonel Renard, of the French Army. It was 
 he who first pointed out in 1903 that the ordi- 
 nary screw would not answer. A helicopter's 
 screw must not only propel, but must also sup- 
 port, for which reason it must be differently 
 constructed from a screw designed for propul- 
 sion only. Renard even went so far as to plan 
 a composite machine, an apparatus which was 
 a helicopter for lifting itself from the ground 
 and an aeroplane in the air. Thus he hoped 
 to overcome the necessity of that preliminary 
 run which aeroplanes must make in order that 
 they may be launched in the air. His ma- 
 chine would theoretically leap straight up from 
 the ground. 
 
 The pathway of aeronautic invention is 
 strewn with wrecked helicopters. Men just 
 as distinguished as Renard have pinned their 
 faith to the blades of its revolving screws. 
 Among them have been Thomas A. Edison 
 
FLYING-MACHINE TYPES 23 
 
 and Emil Berliner. Yet the only perfectly 
 operative screw-flier constructed on the lifting- 
 screw principle is the little toy to which ref- 
 erence has been made. In France, where 
 fashions in aeroplanes are created with the 
 same facility as fashions in clothes, the heli- 
 copter still engages the attention of a few en- 
 thusiasts, despite the brilliant success of the 
 aeroplane. Cornu is one of these. His ma- 
 chine undoubtedly lifts; but thus far it has 
 not been allowed to display its capabilities in 
 that direction more than two feet from the 
 ground. Breguet, the inventor of a helicopter 
 aeroplane, is said to have flown in 1908 a dis- 
 tance of sixty-four feet at a height of fifteen 
 feet. He is now building aeroplanes. 
 
 Even less encouraging than these experi- 
 ments with helicopters, have been the efforts 
 of a few misguided aviators who have sought 
 to build what are known as ornithopters 
 machines that flap wings like a sparrow. It 
 seems very natural to adopt the flapping-wing 
 principle, because all birds depend upon it to 
 a certain extent. Apart from the myth of 
 Daedalus the earliest recorded proposal of 
 
24 THE NEW ART OF FLYING 
 
 this kind was made in 1500, by Leonardo da 
 Vinci, but he does not seem to have made a 
 practical test. The first actual experiment 
 with flapping wings, according to tradition, 
 seems to have been made by a French tight- 
 rope dancer named A'llard, in the reign of 
 Louis XIV. Allard attempted a demonstra- 
 tion before the court but failed in his strength, 
 fell, and was seriously hurt. Since that time 
 many aviators in ornithopters have broken 
 their wings and sometimes their bones. The 
 most earnest experimenter was Hargrave, who 
 ultimately gave the world the box-kite, the pro- 
 totype of the biplane. He built eighteen flap- 
 ping-wing models between 1883 and 1893. 
 With one of these at least, a flight of three 
 hundred and forty-three feet was made in 
 1891. It must be said that Hargrave relied 
 on flapping wings solely for propulsion and 
 not for support. His efforts to devise an 
 efficient sustaining surface gave us his box- 
 kite. Only a few French inventors still per- 
 sist in working on the ornithopter principle. 
 The most persistent of these is Adh. de la 
 Hault. His machine, exhibited at Brussels in 
 
FLYING-MACHINE TYPES 25 
 
 1908, has wings that describe, when in motion, 
 a figure-of-eight curve. His results have been 
 meagre. 
 
 In order to build a flying-machine with flap- 
 ping wings, so as to imitate birds exactly, a very 
 complicated system of levers, cams, cranks, and 
 links must be employed, all of which usually 
 weigh more than the wings can lift. 
 
CHAPTER III 
 
 THE PLANE IN THE AIR 
 
 A ROWBOAT, a mud-scow, a battleship, and a 
 racing yacht, whatever aesthetic differences they 
 may present, are roughly similar in form. The 
 swifter the vessel the finer will be the lines of 
 its hull. Naval architects after some centuries 
 of experimenting have laid down certain rules 
 of construction to be followed in building ves- 
 sels of a certain class. 
 
 The plane surface is to the aeroplane what 
 a hull is to a ship. Like a ship's hull it must 
 be fashioned to cleave the medium through 
 which it must travel with the least possible 
 resistance. Aeronautical engineers have not 
 solved that problem entirely as yet, for the 
 simple reason that flying has only recently be- 
 come an assured fact. But their experiments 
 have given them certain standards which they 
 invariably follow when they design an aero- 
 plane. Young as the art of flying is, it may 
 well be questioned whether the aeronautical en- 
 
THE PLANE IN THE AIR 27 
 
 gineer is not in possession of a set of empirical 
 formulae almost as good as those of the naval 
 architect. 
 
 .So far as the manner of cleaving their re- 
 spective media is concerned, there is this im- 
 portant difference between ships and planes : 
 A vessel is propelled through the water along 
 the line of least resistance, the line of its length; 
 an aeroplane, whether it be a bird or a Wright 
 biplane, is driven through the air at right 
 angles to the line of greatest length or 
 resistance. 
 
 What is known as the " entering edge " of 
 an aeroplane, in other words the character of 
 the cutting part of a plane, gives the aero- 
 nautical engineer much concern. It is the enter- 
 ing edge that strikes the air first. The lifting- 
 power of a plane gradually dwindles from the 
 entering edge backward. A plane one hundred 
 feet long and one foot wide has greater lifting 
 power than a plane ten feet square, although 
 both planes have exactly the same amount of 
 surface. That explains why the wings of a 
 bird are longer in span than in width, and why 
 the aeroplanes of man are as long and as nar- 
 
28 THE NEW ART OF FLYING 
 
 row as possible. If the entire surface of a plane 
 were struck by the air, it would be just as ad- 
 vantageous to employ square planes. But since 
 the air bears directly only on the front or enter- 
 ing edge, we must adopt planes that give us 
 
 FIG. 7. CD is the " entering edge." The lifting power of 
 the forward half A of the curved plane is greater than 
 the lifting power of the rear half B, although both are 
 of equal area. 
 
 as great an entering edge as possible without 
 making the plane too unwieldy. 
 
 Otto Lilienthal demonstrated, after much 
 experiment, that if an oblong surface were 
 curved, the loss in power in the rear half of a 
 plane might be overcome. The investigations 
 of others, notably Horatio Phillips, Prof. S. P. 
 Langley, Sir Hiram Maxim, and the Wright 
 Brothers, have confirmed his opinion. Hence, 
 despite their name, the best aeroplanes of to- 
 
THE PLANE IN THE AIR 29 
 
 day are made not with flat, but with surfaces 
 slightly curved from front to rear (Fig. 7), so 
 that the rear part of a plane can " grip " the 
 air almost as well as the entering edge. De- 
 
 B 
 
 FIG. 8 A is a simple inclined plane; B, a curved plane at 
 the same angle of incidence or inclination; C, the type 
 of curved plane which has thus far given the best results 
 in the air. 
 
 spite the curvature, however, there is an ap- 
 preciable loss in lifting power, back of the 
 entering edge. 
 
 The general shape which a plane should have 
 must be considered as well as the entering 
 edge. Much experimental research has shown 
 that the best plane is not only curved back and 
 
30 THE NEW ART OF FLYING 
 
 down, but is also convex on top. What is more, 
 it has been found that it should be somewhat 
 thicker nearer the front. Just where the thick- 
 est part should lie is still a matter of doubt; 
 but most designers place the thickest part at a 
 distance from the front edge not more than 
 a third of the total width of the plane (Fig. 8) . 
 A kite must be held at an angle to the wind 
 if it is to fly. So must an aeroplane. Just what 
 that angle should be varies with the circum- 
 stances of flight. The flatter the angle (in 
 other words, the more horizontal the position 
 of the aeroplane) the speedier will be the fly- 
 ing-machine. The greater the angle of the 
 plane, the greater will be the resistance offered 
 and the greater will be the power required to 
 drive the plane. Still, this greater angle will 
 enable the flying-machine to rise more quickly 
 in the air, because the lifting power is greater. 
 It is easy to see that the aviator must select such 
 an angle for his planes that his machine will be 
 as speedy as possible, as economical of power 
 as possible, and that it will have as much lifting 
 power as possible. The angle in practical flying- 
 machines varies usually from one in seven to 
 
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THE PLANE IN THE AIR 31 
 
 one in twenty. What does that mean? It 
 means that a plane having an angle of one in 
 ten will push the air down at one tenth of the 
 forward velocity and that the plane will rise 
 one foot in ten relatively to the forward 
 movement. 
 
 An aeroplane driven through the air is acted 
 upon by two forces, its weight and its hori- 
 zontal momentum. Because it has weight it 
 is always falling. If its horizontal momentum 
 (its speed) is greater than the rate of its fall, 
 it will stay in the air, which means not only that 
 it has not time enough to fall visibly but that 
 it may even ascend. Suppose that a plane trav- 
 elling at the rate of ten miles an hour has just 
 sufficient horizontal momentum to prevent its 
 falling. If the speed be increased to twenty 
 miles an hour, the plane will not only be pre- 
 vented from falling, but will actually rise in the 
 air, because of the plane's angle of inclination. 
 Hence to prevent the plane from rising at a 
 speed of twenty miles an hour, the angle must 
 be flattened. Therefore substantially horizon- 
 tal flight may be maintained by proper adjust- 
 ment of speed and angle (Fig. 9). 
 
32 THE NEW ART OF FLYING 
 
 The angle of incidence varies with the wind, 
 with the power of the motor, with every devia- 
 tion of the plane from a uniform line, and with 
 every variation of the load. If a machine car- 
 ries two men, the angle will be greater than if 
 
 E D 
 
 FIG. 9. The plane B B is at a greater angle of incidence 
 than the plane A A. If its speed be 10 miles an hour, it 
 will, while travelling horizontally 25 feet, overcome its 
 tendency to fall to D. If its speed be 20 miles an hour, 
 it will have 50 feet to travel while overcoming its ten- 
 dency to fall to E. Unless the angle of B B, therefore, 
 were decreased to that of A A for the greater speed, the 
 plane would not move horizontally but would ascend. 
 
 one is carried; when the fuel tank is full the 
 angle will be greater than when the tank is 
 empty, and will vary as the fuel is used. More- 
 over, when the power of the motor increases or 
 decreases, the speed correspondingly increases 
 or decreases and causes the angle of incidence 
 to increase or decrease. Even with constant- 
 power, the speed is different in ascending and 
 
THE PLANE IN THE AIR 33 
 
 descending, and the angle of incidence varies 
 accordingly. The Wright Brothers state that 
 during a flight of one hour the angle of inci- 
 dence will be either greater or less than any 
 angle which may be termed normal, for more 
 than fifty-nine minutes, and that it will be ex- 
 actly at the normal angle less than one minute. 
 In their experience the angle of incidence varies 
 in flight throughout a range of ten degrees 
 or more and is particularly great when the 
 wind is turbulent. For that reason, among 
 others, the control of an aeroplane in flight 
 requires incessant vigilance on the part of the 
 pilot. 
 
 In most forms of locomotion, increased speed 
 is obtained at the expense of power. When you 
 run, you expend more energy than when you 
 walk. A locomotive driven at high speed uti- 
 lises more power than at low speed. Paradoxi- 
 cally enough, the aeroplane follows no such 
 rule. The late Professor Langley discovered 
 that the higher the speed of an aeroplane, the 
 less power is required to drive it. Langley 
 was considering surfaces only. Wires and 
 struts must also be considered, and their re- 
 
34 THE NEW ART OF FLYING 
 
 sistance (increasing with the square of the 
 velocity) is such that, as Herring has pointed 
 out, flight without motor is impossible on ac- 
 count of the resistance offered by wires alone. 
 Theoretically at least, it seemed to Langley 
 that a speed could be reached where the power 
 received would be nil. The Wrights and other 
 aviators maintain, however, that there is a 
 close limit to this economy of power with ac- 
 celerated speed. The early experiments of 
 Langley, Maxim and Chanute seemed to show 
 that at high speed increased lifting power is 
 obtained, but how much the increase may 
 be not all the experimenters agree. Con- 
 trary, to the early experimenters, the Wright 
 Brothers maintain that there is no practical 
 advantage in increasing speed to obtain in- 
 creased lifting power. High speed renders it 
 possible to reduce the size and weight of the 
 machine, which in turn means a reduction in 
 atmospheric resistance. 
 
 The first glimpse of a flying-machine in the 
 air is a disappointment, not because the flying- 
 machine really flies, but because it apparently 
 flies so slowly. The speed appears less than 
 
THE PLANE IN THE AIR 35 
 
 it really is, and it is only when it is accurately 
 measured that it reaches the hoped-for figure. 
 The speed of many of the early biplanes was 
 not much above thirty miles an hour, and most 
 of the modern biplanes probably do not exceed 
 forty miles. Monoplanes now travel often at 
 a speed of not less than sixty miles. Many of 
 the Bleriot monoplanes make considerably over 
 seventy miles an hour on a straight line. At 
 Reims, in 1910, over seventy miles an hour was 
 attained. It is evident that in the near future 
 eighty miles an hour on a straight course is 
 well within the bounds of probability. 
 
 In an aeroplane speed is of more importance 
 than any other vehicle, because the aeroplane 
 is far more affected by the wind. A boat, to 
 be sure, is affected by both tide and wind, but 
 not to such an extent as the aeroplane. A 
 strong tide runs only about two knots, while 
 the speed of a fast boat is some ten times this, 
 so that her speed is reduced only ten per cent 
 when running against the tide. An aeroplane, 
 however, is very much more influenced, simply 
 because an ordinary breeze has a velocity of 
 fifteen miles an hour, a strong wind thirty to 
 
36 THE NEW ART OF FLYING 
 
 forty miles an hour, and a gale, sixty miles an 
 hour. The aeroplane, in order to be a service- 
 able vehicle of sport, must be able to make 
 good speed against a thirty-mile wind. In 
 other words, it should be able to obtain a ve- 
 locity of sixty or seventy miles an hour, under 
 favourable conditions. Such fast flying, how- 
 ever, complicates the problem of starting and 
 alighting. Landing at high speed is especially 
 dangerous. As long as the method of alight- 
 ing is what it is now, that is, as long as the 
 machine runs along the ground for some dis- 
 tance, it can hardly be safe to land at speeds 
 in excess of those used at present. It is evi- 
 dent, therefore, that it may be necessary to 
 devise a machine which will fly over a consider- 
 able range of speed, so that it can be slowed 
 down before landing. The minimum speed at 
 which an aeroplane will fly is dependent chiefly 
 on the ratio of wing surface to weight. There- 
 fore, to fly slowly we must have large wings 
 in proportion to the weight. Small wings, on 
 the other hand, give high speed, and the small 
 wings on Bleriot and Wright racers seem to 
 be very small indeed. 
 
THE PLANE IN THE AIR 37 
 
 In order that the aeroplane may have a vari- 
 able speed, it must either have large wings, so 
 designed that they can be driven fast without, 
 resistance, or else we must have some me^ns 
 of reducing the surface of the wings in the air. 
 In the former case, the angle of incidence of 
 the wings is reduced, which would seem to be 
 at least theoretically obtainable, whatever may 
 be the difficulties in making the curves of the 
 wings suitable for various speeds. 
 
 Reefing the wing surfaces is a still better 
 method of obtaining variable speeds, but the 
 practical difficulties are formidable. Furling a 
 wing when travelling at forty miles an hour in 
 the air can hardly be easy. Taking in sail in 
 a gale of wind on a boat has its difficulties, 
 and an aeroplane travels at the speed of a 
 gale. For all that, we find that attempts are 
 made, even now, to build machines on this 
 principle. 
 
 Before we can advance much farther in aero- 
 plane construction we must conduct more sys- 
 tematic investigations of various kinds of sup- 
 porting surfaces. Several laboratories are now 
 engaged in such researches, but the results of 
 
38 THE NEW ART OF FLYING 
 
 their labours will hardly be available for some 
 years to come. 
 
 It is the general practice of ship-builders 
 to test new forms of hulls by towing models of 
 a few yards in length through the water and by 
 measuring the resistance opposed to their mo- 
 tion. No large ocean steamer is now con- 
 structed without such preliminary experiments. 
 Tests with aeroplane models are still more 
 necessary, because in the air we are, as yet, 
 more or less inexperienced. In both cases one 
 of the chief objects of study is the total resist- 
 ance to motion, and the discovery of the form 
 which will reduce this resistance to the lowest 
 possible point. Other important questions con- 
 cern the distribution of pressure and skin fric- 
 tion in their dependence upon the form and 
 character of surface. The investigation of sta- 
 bility and steering qualities also requires ex- 
 periments with models, which may likewise 
 give interesting information on the lifting 
 power or kite action of an aeroplane when 
 inclined to the horizontal. It is necessary to 
 study thoroughly the magnitude and direction 
 of the resultant force on single surfaces of 
 
3 <L> 
 
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 3 
 
 <u 
 
 h 
 
 O > 
 
 1^ 
 
 PQ 2 
 
 s 
 
 vy 
 
 1-s 
 
 -S .2 
 
 bfi 
 
 C 
 
THE PLANE IN THE AIR 39 
 
 various forms, on combinations of surfaces, 
 and finally on complete aeroplanes, as well as 
 the stability and steering qualities of these com- 
 binations. It is easier and cheaper to learn from 
 models all that they can teach us than to make 
 the experiments with large and expensive craft, 
 which has been the practice in the past. It is 
 a question, however, how far the results ob- 
 tained from models can be applied to the large 
 vessels. Even small models of ships' hulls, 
 which are tested in towing tanks, do not give 
 absolute results. In aeroplanes, the method 
 may be still more untrustworthy because the 
 aerial craft is completely surrounded by the 
 medium through which it travels and because 
 the carriage generally creates more disturbance 
 in the air than the model, a disturbance suffi- 
 ciently great to make exact measurements im- 
 possible. By substituting for the towing car- 
 riage a cord wound on a windlass, this objec- 
 tion is removed, but it remains very difficult to 
 distinguish sharply between the comparatively 
 small air resistances and the great force of 
 inertia of the heavy model. M. Eiffel has made 
 some excellent experiments with bodies freely 
 
40 THE NEW ART OF FLYING 
 
 falling through the air. The method fre- 
 quently employed of carrying the model around 
 in a circle by means of a long rotating arm, 
 or on a whirling table, is open to the objec- 
 tion that the model is always moving in air 
 which has been disturbed by its last passage. 
 There is still a third method, which consists 
 in maintaining the model at rest in a current 
 of air produced, for example, by a blower. 
 The mutual action between the model and the 
 air is exactly as in the former system, if the 
 condition of the moving air before it strikes 
 the model is as uniform as that of still air. 
 The trustworthiness of results obtained by this 
 method depends, therefore, upon obtaining a 
 uniform current free from eddies, which end 
 can be attained by the employment of various 
 appliances. When a uniform current has been 
 secured, the advantages of this method are 
 great and obvious. The duration of the ex- 
 periment is unlimited, and the model can be 
 attached to its support much more easily and 
 securely than if it were in motion. Further- 
 more, the difficulties produced by the accelera- 
 tion and inertia of the model on a measuring 
 
THE PLANE IN THE AIR 41 
 
 apparatus are here avoided. The model is 
 continuously in sight, so that any irregularities 
 can be at once detected. This system has been 
 adopted in the Goettingen Experimental Insti- 
 tute, planned and directed by Professor Prandtl. 
 
CHAPTER IV 
 
 STARTING AND ALIGHTING 
 
 IN a previous chapter it has been pointed out 
 that like every soaring bird an aeroplane must 
 be in motion before it can fly. Even the early 
 dreamers appreciated the fact. How that pre- 
 liminary leap into the air is to be effected gave 
 Langley no little concern. With the motorless 
 gliders of Lilienthal, Pilcher, and Chanute, it 
 was no difficult matter for the aeronaut to 
 launch himself into the air. He simply carried 
 his apparatus to the top of a hill, grasped the 
 handle-bar, ran down the hill at top speed for 
 a short distance, and then drew up his legs, like 
 any bird. Thus he would slide down the air 
 for several hundred feet as if upon an invisible 
 track. 
 
 When Langley succeeded in building a small, 
 motor-driven model of a flying-machine, the 
 problem of launching his contrivance long 
 baffled him. Eventually he invented a launch- 
 ing device, which has served as a pattern for 
 
STARTING AND ALIGHTING 43 
 
 later inventors. The difficulties which beset 
 him were eloquently and lucidly described in 
 an article from his pen, published in McClure's 
 Magazine for June, 1897. The whole prob- 
 lem is there so well and so simply presented 
 that we cannot do better than to let Mr. Lang- 
 ley set it forth himself, even though launching 
 a flying-machine is now regarded as a simple 
 matter: 
 
 " In the course of my experiments I had 
 found out . . . that the machine must begin 
 to fly in the face of the wind and just in the 
 opposite way to a ship, which begins its voyage 
 with the wind behind it. 
 
 " If the reader has ever noticed a soaring 
 bird get upon the wing he will see that it does 
 so with the breeze against it, and thus when- 
 ever the aerodrome * is cast into the air it must 
 face a wind which may happen to blow from 
 the north, south, east or west, and we had 
 better not make the launching station a place 
 like the bank of a river, where it can go only one 
 way. It was necessary, then, to send it from 
 something which could be turned in any direc- 
 tion, and taking this need in connection with 
 
 * * Langley's term for an aeroplane flying-machine, signifying 
 " air-runner." 
 
44 THE NEW ART OF FLYING 
 
 the desirability that at first the airship should 
 light in the water, there came at last the idea 
 (which seems obvious enough when it is stated) 
 of getting some kind of a barge or boat and 
 building a small structure upon it which could 
 house the aerodrome when not in use, and from 
 whose flat roof it could be launched in any 
 direction. Means for this were limited, but a 
 little " scow " was procured, and on it was 
 built a primitive sort of house, one story high, 
 and on the house a platform about ten feet 
 higher, so that the top of the platform was 
 about twenty feet from the water, and this 
 was to be the place of the launch. This boat it 
 was found necessary to take down the river 
 as much as thirty miles from Washington, 
 where I then was since no suitable place 
 could be found nearer to an island having 
 a stretch of quiet water between it and the main 
 shore; and here the first experiments in at- 
 tempted flight developed difficulties of a new 
 kind difficulties which were partly antici- 
 pated, but which nobody would probably have 
 conjectured would be of their actually formi- 
 dable character, which was such as for a long 
 time to prevent any trial being made at all. 
 They arose partly out of the fact that even 
 such a flying-machine as a soaring bird has to 
 get up an artificial speed before it is on the 
 
11 
 
 4 a 
 
 s "^ 
 
 I 
 
 1 
 
 u 
 
STARTING AND ALIGHTING 45 
 
 wing. Some soaring birds do this by an initial 
 run upon the ground, and even under the most 
 urgent pressure cannot fly without it. 
 
 u To get up this preliminary speed many 
 plans were proposed, one of which was to put 
 the aerodrome on the deck of a steamboat, and 
 go faster and faster until the head-wind lifted 
 it off the deck. This sounds reasonable, but it 
 is absolutely impracticable, for when the aero- 
 drome is set up anywhere in the open air, we 
 find that the very slightest wind will turn it 
 over, unless it is firmly held. The whole must 
 be in motion, but in motion from something to 
 which it is held until that critical instant when 
 it is set free as it springs into the air. 
 
 " The house boat was fitted with an appara- 
 tus for launching the aerodrome with a certain 
 initial velocity, and was (in 1893) taken down 
 the river and moored in the stretch of quiet 
 water I have mentioned; and it was here that 
 the first trials at launching were made, under 
 the difficulties to which I have alluded. 
 
 " It is a difficult thing to launch a ship, al- 
 though gravity keeps it down upon the ways, 
 but the problem here is that of launching a kind 
 of ship which is as ready to go up into the air 
 like a balloon as to go off sideways, and readier 
 to do either than to go straight forward, as it 
 is wanted to do, for though there is no gas in 
 
46 THE NEW ART OF FLYING 
 
 the flying-machine, its great extent of wing 
 surface renders it something like an albatross 
 on a ship's deck the most unmanageable and 
 helpless of creatures until it is in its proper 
 element. 
 
 " If there were an absolute calm, which never 
 really happens, it would still be impracticable 
 to launch it as a ship is launched, because the 
 wind made by running it along would get under 
 the wings and turn it over. But there is always 
 more or less wind, and even the gentlest breeze 
 was afterward found to make the airship un- 
 manageable unless it was absolutely clamped 
 down to whatever served to launch it, and when 
 it was thus firmly clamped, as it must be at 
 several distinct points, it was necessary that 
 it should be released simultaneously at all these 
 at the one critical instant that it was leaping 
 into the air. This is another difficult condi- 
 tion, but that it is an indispensable one may be 
 inferred from what has been said. In the first 
 form of launching piece this initial velocity was 
 sought to be attained by a spring, which threw 
 forward the supporting frame on which the 
 aerodrome rested; but at this time the extreme 
 susceptibility of the whole construction to in- 
 jury from the wind and the need of protecting 
 it from even the gentlest breeze had not been 
 appreciated by experience. On November 18, 
 
STARTING AND ALIGHTING 47 
 
 1893, the aerodrome had been taken down the 
 river, and the whole day was spent in waiting 
 for a calm, as the machine could not be held in 
 position for launching for two seconds in the 
 lightest breeze. The party returned to Wash- 
 ington and came down again on the 2Oth, and 
 although it seemed that there was scarcely any 
 movement in the air, what little remained was 
 enough to make it impossible to maintain the 
 aerodrome in position. It was let go, notwith- 
 standing, and a portion struck against the edge 
 of the launching piece, and all fell into the 
 water before it had an opportunity to fly. 
 
 " On the 24th another trip was made and 
 another day spent ineffectively on account of 
 the wind. On the zyth there was a similar 
 experience, and here four days and four 
 (round-trip) journeys of sixty miles each had 
 been spent without a single result. This may 
 seem to be a trial of patience, but it was re- 
 peated in December, when five fruitless trips 
 were made, and thus nine such trips were made 
 in these two months and but once was the 
 aerodrome even attempted to be launched, and 
 this attempt was attended with disaster. The 
 principal cause lay, as I have said, in the un- 
 recognised amount of difficulty introduced even 
 by the very smallest wind, as a breeze of three 
 or four miles an hour, hardly perceptible to the 
 
48 THE NEW ART OF FLYING 
 
 face, was enough to keep the airship from rest- 
 ing in place for the critical seconds preceding 
 the launching. 
 
 " If we remember that this is all irrespective 
 of the fitness of the launching piece itself, which 
 at first did not get even a chance for trial, some 
 of the difficulties may be better understood; 
 and there were many others. 
 
 " During most of the year of 1894 there was 
 the same record of defeat. Five more trial 
 trips were made in the spring and summer, dur- 
 ing which various forms of launching apparatus 
 were tried with varied forms of disaster. Then 
 it was sought to hold the aerodrome out over 
 the water and let it drop from the greatest at- 
 tainable height, with the hope that it might ac- 
 quire the requisite speed of advance before the 
 water was reached. It will hardly be anticipated 
 that it was found impracticable at first to simply 
 let it drop without something going wrong, but 
 so it was, and it soon became evident that even 
 were this not the case, a far greater time of fall 
 was requisite for this method than that at com- 
 mand. The result was that in all these eleven 
 months the aerodrome had not been launched, 
 owing to difficulties which seem so slight that 
 one who has not experienced them may wonder 
 at the trouble they caused. 
 
* 
 
 I I 
 
STARTING AND ALIGHTING 49 
 
 " Finally, in October, 1894, an entirely new 
 launching apparatus was completed, which em- 
 bodied the dozen or more requisites, the need 
 for which had been independently proved in 
 this long process of trial and error. Among 
 these was the primary one that it was capable 
 of sending the aerodrome off at the requisite 
 initial speed, in the face of a wind from 
 whichever quarter it blew, and it had many 
 more facilities which practice had proved 
 indispensable." 
 
 Langley's account has a certain historical 
 interest, because never before had a motor- 
 driven machine been brought to such a pitch of 
 perfection that it could fly, if once launched. 
 After his repeated failures, Langley finally 
 succeeded in launching his craft from " ways," 
 as shown in Fig. n, somewhat as a ship is 
 launched into the water, the machine resting on 
 a car, which fell down at the end of the car's 
 motion. 
 
 A launching device identical in principle was 
 afterwards employed to start the man-carrying 
 machine built by Langley for the United States 
 Government. Once, according to Major Ma- 
 comb, of the Board of Ordnance, u the trial was 
 
50 THE NEW ART OF FLYING 
 
 unsuccessful because the front guy post caught 
 in its support on the launching car and was not 
 released in time to give free flight, as was in- 
 tended, but, on the contrary, caused the front 
 of the machine to be dragged downward, bend- 
 ing the guy post and making the machine plunge 
 into the water about fifty yards in front of the 
 house boat." Of another trial Major Macomb 
 states . . . " the car was set in motion and the 
 propellers revolved rapidly, the engine working 
 perfectly, but there was something wrong with 
 the launching. The rear guy post seemed to 
 drag, bringing the rudder down on the launch- 
 ing ways, and a crashing, rending sound, fol- 
 lowed by the collapse of the rear wings, showed 
 that the machine had been wrecked in the 
 launching; just how it was impossible to see.'* 
 Because it was never launched, the machine 
 never flew. The appropriation having been 
 exhausted, Langley was compelled to abandon 
 his tests. The newspaper derision which 
 greeted him undoubtedly embittered him, short- 
 ened his life, and probably set back the date 
 of the man-carrying flying-machine's advent 
 several years. Langley's trials have been here 
 
STARTING AND ALIGHTING 51 
 
 set down at some length to show the practica- 
 bility and impracticability of various launching 
 methods and to demonstrate that his machine 
 was far from being the failure popularly sup- 
 posed. No man has contributed so much to 
 the science of aviation as the late Samuel Pier- 
 pont Langley. 
 
 That his work was not lost on the Wright 
 Brothers at least, is evidenced by the manner 
 in which they attacked the difficulty of getting 
 up starting speed. The Wright Brothers in- 
 vented an arrangement, which was simpler than 
 Langley's, more efficient, and not so likely to 
 imperil the aeroplane. As illustrated in Fig- 
 ures 12 and 13, it consisted in its early stage 
 of an inclined rail, about seventy feet long; a 
 pyramidal " derrick " ; a heavy weight ar- 
 ranged to drop within the derrick; and a rope 
 which was fastened to the weight, led around 
 a pulley at the top of the derrick, passed around 
 a second pulley at the bottom of the derrick 
 and over a third pulley at the end of the rail, 
 and then secured to a car. The car was placed 
 on the rail, and the aeroplane itself on the 
 car. When a trigger was pulled, the weight 
 
52 THE NEW ART OF FLYING 
 
 fell, and the car was jerked forward. So great 
 was the preliminary velocity thus imparted 
 that the machine was able to rise from the car 
 in a few seconds. 
 
 FIG. 12. The special launching device invented by the 
 Wright Brothers. The device consists of an inclined 
 rail, about seventy feet long; a pyramidal derrick; a 
 heavy weight arranged to drop within the derrick; and 
 
 [ a rope, which is fastened to the weight, passed around 
 a pulley at the top of the derrick, then around a 
 second pulley at the bottom of the derrick over a third 
 pulley at the end of the rail, and finally fastened to 
 a car running on the rail. The car is placed on the 
 rail, and the aeroplane on the car. When a trigger is 
 pulled, the weight falls, and the car is jerked forward. 
 So great is the preliminary velocity thus imparted that 
 the machine is able to rise in a few seconds from the 
 car, which is left behind. 
 
 Neither a falling weight nor a starting car- 
 riage on rails can be carried with an aero- 
 plane. Hence, a machine thus launched must 
 always return to its derrick. Clearly, an aero- 
 plane which can start up under its own power 
 is preferable to one which is wedded to a start- 
 ing derrick or any other extraneous launching 
 
STARTING AND ALIGHTING 53 
 
 apparatus. Inasmuch as more power is re- 
 quired for starting by running on the ground 
 (i. e., for accelerating the machine) than for 
 actual flight, the Wright Brothers continued to 
 employ their starting rail long after other avi- 
 ators had adopted wheels. The result was that 
 they could equip their machine with motors of 
 far less power than their rivals. 
 
 Even before the Wright Brothers threw 
 aside all secrecy and flew publicly in France 
 and the United States during the summer of 
 1908, Curtiss and Farman had made short 
 flights on machines which were mounted on 
 pneumatic-tired wheels. Their machines would 
 run on the wheels for several hundred feet. 
 When sufficient velocity had been attained the 
 pilot would give a slight upward tilt to the ele- 
 vating rudder, and the machine would leave 
 the ground. The only essential was a fairly 
 smooth, fairly hard piece of ground for the 
 preliminary run. So successful has this system 
 been that in somewhat improved form it is 
 embodied in every modern aeroplane. Even 
 the Wright Brothers, who long persisted in 
 using the starting derrick in the face of the 
 
54 THE NEW ART OF FLYING 
 
 obvious advantages of wheels, abandoned the 
 starting derrick as soon as they had increased 
 the power of their motors. In Fig. 14 one of 
 their later machines is pictured, mounted on 
 wheels. 
 
 Although starting wheels enable the aviator 
 to rise from any suitable piece of ground, he 
 pays for that advantage in engine power. A 
 well-made machine, having ample power to 
 fly, but dependent only on its engine and 
 rubber-tired wheels for its initial run, may be 
 unable to rise if the ground is too rough. The 
 engine cannot overcome the loss due to fric- 
 tion. On hard asphalt the cyclist can readily 
 attain a speed of twenty-five miles an hour in 
 a few seconds; on a ploughed field, he may 
 labour hard and yet not make more than ten 
 miles an hour. The aeroplane is in the same 
 position as the bicycle. To start a flying- 
 machine on rough ground requires more power 
 than is afterwards needed for propulsion. 
 Hence we find that the earlier Wright ma- 
 chines, although they could rise only from the 
 perfect surface of a starting rail, were fitted 
 with engines of remarkably low power. 
 
Photograph by Edwin Levick 
 
 Fig. 20. Mr. Wilbur Wright in the old type 
 Wright biplane 
 
STARTING AND ALIGHTING 55 
 
 The wheels on which the preliminary run is 
 made may also serve the aviator in alighting. 
 After he shuts off his engine he glides down 
 and runs on the wheels until his momentum is 
 expended. The shock may be sufficient to 
 wreck a machine piloted by an unskilled hand, 
 and the run may be long, unless some form of 
 brake is provided. Recognising these disad- 
 vantages early in the course of their experi- 
 ments, the Wright Brothers fitted their aero- 
 planes with skids or runners on which the 
 machine alighted. The shock is almost im- 
 perceptible, and the machine stops in the course 
 of a few yards without the assistance of a 
 brake. Many machines are now equipped with 
 skids similar to those embodied long ago by 
 Herring and by the Wright Brothers in their 
 early models. 
 
 Starting wheels and alighting skids are not 
 easily combined in the same machine. The 
 skids must be elevated sufficiently to clear the 
 ground in making the preliminary run, and yet 
 they must become effective as soon as the ma- 
 chine touches the ground. For that reason the 
 wheels are usually connected with springs, 
 
56 THE NEW ART OF FLYING 
 
 which are compressed as the aeroplane strikes 
 the ground so as to allow the skids to perform 
 the function for which they are designed. 
 
 In the Farman biplane, for example, the 
 wheels are mounted on the skids and are at- 
 tached to rubber springs. When the machine 
 alights the wheels yield, and the skids come into 
 play. 
 
 In the Sommer biplane, the framework is 
 carried on two large wheels at the front and 
 two smaller wheels at the rear. The front 
 wheels are attached by rubber springs to two 
 skids, built under the frame. As in the Farman 
 machine, the wheels yield by virtue of this 
 spring mounting. 
 
 In Santos-Dumont's monoplane " Demoi- 
 selle," springs are dispensed with. The ma- 
 chine starts on two wheels in front and the 
 shock of alighting is broken by a skid at the 
 rear. 
 
 An arrangement similar to that of Santos- 
 Dumont is to be found in the Antoinette ma- 
 chines. The mounting consists of two wheels 
 at the front and a skid at the rear. No springs 
 are provided for the wheels. 
 
STARTING AND ALIGHTING 57 
 
 In the Curtiss and Voisin biplane machines, 
 as well as in some others of minor importance, 
 no skids at all are employed. The machine 
 starts and alights on the same set of wheels, 
 and is usually stopped by brakes. On the whole 
 the combination of wheels and skids seems to 
 be more desirable, particularly for a heavy 
 machine. 
 
CHAPTER V 
 
 HOW AN AEROPLANE IS BALANCED 
 
 DROP a flat piece of cardboard from your hand. 
 It will fall. But as it falls its surface will offer 
 a certain resistance, so that it becomes in effect 
 a parachute. The amount of its resistance will 
 
 FIG. 16. Path of an aeroplane driven forward but with a 
 speed too low for horizontal flight, and with too flat an 
 angle. 
 
 depend on the amount of its surface. If the 
 cardboard be driven to the left, as shown in 
 Fig. 1 6, it will still fall, but along an inclined 
 path. In other words it will fall while advanc- 
 ing and advance while falling. 
 
 Suppose that this same piece of cardboard, 
 this aeroplane, as we may call it, is inclined to 
 
BALANCING AEROPLANES 59 
 
 the wind and that it is driven along a horizontal 
 path B in the direction of the arrow A as shown 
 in Fig. 17. If it were not driven forward the 
 cardboard plane would fall by reason of its 
 weight. But since it is driven forward and since 
 it is inclined to the air, it offers resistance, which 
 means that pressure is exerted upward against 
 
 Rear Edge 
 
 FIG. 17. Path of a plane inclined at the angle C to the 
 horizontal. The arrow A indicates the direction of 
 travel. If the speed is sufficient the plane will rise be- 
 cause of the upward inclination of the plane. 
 
 its lower surface. The driving power, what- 
 ever it may be, overcomes the resistance or 
 pressure; yet the effect of the resistance or 
 pressure is to keep the plane up in the air. So, 
 the plane tends to slide up diagonally on the 
 resisting air; gravity (weight) tends to draw 
 the plane down toward the earth; and the diag- 
 onal sliding action tends to move the plane 
 farther from the earth. This climbing effect is 
 obviously dependent on the angle of the plane. 
 
60 THE NEW ART OF FLYING 
 
 If the angle is large, it is great; if the angle is 
 small, it is slight. Given a very high speed of 
 propulsion, a speed greater than the falling 
 tendency, and the plane is bound to rise. Given 
 a speed of propulsion less than the falling ten- 
 dency and the plane will sooner or later settle 
 to the ground. Horizontal flight can therefore 
 be maintained by proper adjustment of speed 
 and angle. 
 
 This angle at which the plane moves against 
 the air is known as the " angle of incidence." 
 It is positive, because it has a tendency to lift. 
 If the plane were tilted forward or dipped, the 
 sliding effect would be earthward. Indeed, so 
 marked would be this effect that the plane 
 would reach the ground much more quickly than 
 if it fell simply by its own weight. In that case 
 the angle of incidence is negative, because it 
 depresses. 
 
 It is therefore evident that an advancing 
 aeroplane may be caused to travel up or down 
 simply by making the angle of incidence posi- 
 tive or negative. 
 
 During flight, a Wright or Curtiss or Bleriot 
 machine is subjected to every whim of the air. 
 
n 
 
 111 
 us 
 
 C 
 
 II 
 
 ! 
 
 *- 2 
 
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 IH 
 
 ' O 
 
 M 
 
 Q, 
 
 5J 
 
 cs - 
 
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 bJD O 
 
BALANCING AEROPLANES 61 
 
 These incessant variations of the air must all 
 be counteracted; otherwise the machine will 
 capsize. 
 
 It happens during flight that the aeroplane, 
 because of the wind's caprice, will drop more 
 on one side than on the other. To maintain his 
 balance, the aviator must in some way lift the 
 falling side or lower the rising side, or do both. 
 It was this problem that long baffled the in- 
 ventor of aeroplane flying-machines. The 
 whole art of machine-flying is summed up in its 
 successful solution. To the Wright Brothers of 
 Dayton, Ohio, belongs the full credit of having 
 devised the first and thus far the most efficient 
 means of solving that problem, a means now em- 
 bodied in almost every successful flying-machine. 
 
 Suppose that the plane A in Fig. 1 8 is pro- 
 vided at each side with tips C and D, hinged 
 so that they can be swung up or down. If these 
 two tips (ailerons the French call them) are 
 swung so that they lie flush with the main 
 plane A, they have no effect whatever beyond 
 adding to the amount of aeroplane surface. 
 Suppose that the near side of the plane drops. 
 In that case, the tip C is thrown down as shown 
 
62 THE NEW ART OF FLYING 
 
 in Fig. 1 8. What happens? More resistance 
 is offered to the air at that side and greater 
 upward pressure is consequently exerted, so 
 that the plane is restored to its former position 
 
 Direction of Plane's Motion 
 
 Direction of Air Pressure 
 
 FIG. 18. How a plane is laterally balanced by means of 
 ailerons and a vertical rudder. 
 
 The plane A is provided with hinged tips C and D and with 
 a vertical rudder E. The tips are swung in opposite 
 directions to correct any tipping of the plane, and the 
 vertical rudder E is swung over to the side of least re- 
 sistance (the side of the tip D in the example here given) 
 in order to prevent the entire machine from rotating on 
 a vertical axis. 
 
 of equilibrium. To assist in this restoration, 
 the tip D at the farther side of the plane can be 
 tilted down, so that the angle of incidence is 
 negative or depressive. Hence the far end of 
 the plane is lowered while the near end is raised. 
 In all flying-machines this dropping of one tip 
 and raising of the other is effected simultane- 
 ously by a system of cables and levers. When 
 
BALANCING AEROPLANES 63 
 
 the plane's balance has been regained, the tips 
 are swung so that they lie flush with the plane 
 A, and become virtually part of the plane. 
 
 As a result of inclining the tips at opposite 
 angles, the near side of the plane offers more 
 resistance to the air than the far side. Hence 
 the near side will be retarded and the far side 
 accelerated. This will cause the entire plane 
 to swerve from its course. It was a brilliant 
 discovery of the Wright Brothers to correct this 
 swerving by means of a vertical rudder E, 
 which is thrown over to the side of least resist- 
 ance the far side in the particular instance 
 pictured in Fig. 18. The wind pressure on the 
 rudder exerts a counteracting force at the rear 
 of the machine and opposes the tendency of the 
 machine to turn. Hence the vertical rudder in 
 flying-machines serves not nearly so much for 
 steering as for preventing the spinning of the 
 machine. 
 
 The actual controlling method devised by 
 the Wrights is shown in Fig. 19. Instead of 
 one plane, the Wrights employ two superposed 
 planes A and A' trussed together. In front or 
 rear is a horizontal rudder or elevator to steer 
 
64 THE NEW ART OF FLYING 
 the machine up or down, which rudder in the 
 example before us (an old Wright type al- 
 though the principle is the same in the new) 
 consists of two superposed planes, 5 and 6, 
 and which is operated by the lever F' through 
 the medium of connecting rods. In the 
 
 FIG. 19. The system of control on an old Wright model. 
 
 rear is the vertical rudder C, which serves to 
 steer the machine from side to side and to coact 
 with the planes A and A' in keeping the ma- 
 chine on its course. Instead of employing 
 pivoted tips like those shown in Fig. 18, the 
 Wrights warp the corners of the planes A and 
 A'. Thus, when the corners i and 2 are ele- 
 vated, the corners 3 and 4 are depressed. This 
 simultaneous elevation and depression of cor- 
 ners is produced by a cable E, attached to a 
 lever F'. By throwing the lever from side to 
 
BALANCING AEROPLANES 65 
 
 side the planes are warped. The vertical rud- 
 der C is connected by tiller ropes with the same 
 lever F', and is swung by moving the lever P 
 back and forth. Hence the planes are warped 
 and the vertical rudder properly turned by the 
 one lever F'. The photograph reproduced in 
 Fig. 20 shows Mr. Wilbur Wright seated in 
 his machine /with his hands on the controlling 
 levers. Fig. 2 1 pictures the Wright machine on 
 the ground and shows the disposition of the main 
 planes, horizontal or elevation rudders, and ver- 
 tical rudder. Fig. 22 depicts an instruction 
 machine with an extra lever for the pupil. 
 
 Some of the machines which Mr. Glenn H. 
 Curtiss has flown are similarly provided with 
 two superposed main planes A and J9, as 
 shown in Fig. 23, with a box-like rudder in 
 front and with a rear vertical rudder D. The 
 front horizontal rudder is swung up or down 
 by means of the rod R connected with the 
 wheel TV, the wheel being pushed or pulled by 
 the pilot for that purpose. The same wheel JV, 
 when rocked like the pilot wheel of a steam- 
 boat serves to swing the vertical rudder D by 
 drawing on one or the other of two tiller ropes, 
 
66 THE NEW ART OF FLYING 
 
 S. In his earlier machines, as, for example, 
 the one illustrated in Fig. 24, Curtiss employed 
 supplementary plane tips, very much like those 
 represented in Fig. 18. In his later machines, 
 however, one of which is shown in Fig. 25, he 
 
 FIG. 23. The Curtiss system of control. 
 
 has transferred the tips from the sides of the 
 main planes to positions between the main 
 planes, beyond which they project, as indicated 
 by the letters C C in Fig. 23. Despite the trans- 
 fer their purpose still remains the same. To 
 swing the supplementary planes C C in opposite 
 directions, cables T T are connected with the 
 seat-back G, which is movable from side to side 
 
BALANCING AEROPLANES 67 
 
 and which partly encircles the pilot's body. By 
 throwing his body from side to side the pilot 
 swings the planes C C in opposite directions. 
 The effect is the same as if the main planes 
 A B were warped, as in the Wright machine. 
 Whether or not it is necessary to throw over 
 the vertical rudder when the balancing planes 
 C C are- swung is the question at issue in 
 the patent infringement suit instituted by 
 the Wright Brothers against Curtiss. The 
 Wrights claim that Curtiss cannot fly unless the 
 vertical rudder is operated simultaneously with 
 the balancing planes. Curtiss claims that he 
 can. Much testimony has been taken on both 
 sides. A United States Circuit Judge thought 
 that the preponderance of expert evidence was 
 on the side of the Wrights, particularly since 
 Curtiss himself admitted that he did sometimes 
 use the vertical rudder to offset the swerving 
 of the machine caused by changing the incli- 
 nation of the balancing planes. A preliminary 
 injunction was therefore issued, which, on ap- 
 peal, however, was dissolved. Whether or not 
 Curtiss can fly without simultaneously operat- 
 ing his vertical rudder and his balancing planes 
 
68 THE NEW ART OF FLYING 
 
 FIG. 26. The system of ailerons and rudders devised 
 by Henry Farman for maintaining fore-and-aft and 
 side-to-side balance. 
 
BALANCING AEROPLANES 69 
 
 will be decided when the question of infringe- 
 ment is settled at the final hearing. 
 
 In the Farman biplane, which the Wright 
 Brothers allege likewise infringes their patent, 
 the ailerons, as illustrated in Fig. 26, form part 
 of the main planes A B. They are the hinged 
 flaps D D at the rear corners of the main planes. 
 The inclination of the ailerons D D is varied by 
 means of cables leading to the lever C. By 
 moving the lever C from side to side, the aile- 
 rons are moved up and down in opposite direc- 
 tions. To the rear of the main planes two ad- 
 justable rudders E E are placed, from which two 
 wires lead to a tiller F operated by the pilot's 
 feet. When the aeroplane tips to the left, for 
 example, the pilot swings his control-lever C to 
 the right, thus pulling down on the flaps on the 
 left-hand side of the planes and creating more 
 lift on that side. The right-hand flaps remain 
 horizontal, held out by the air pressure. When 
 the machine is at rest on the ground, the flaps 
 hang down vertically, as shown in Fig. 27. In 
 Fig. 28 Mr. Farman is shown seated in his 
 biplane. His hand grasps the lever by means 
 of which both the ailerons or flaps and the 
 
70 THE NEW ART OF FLYING 
 
 forward horizontal or elevation rudder are 
 operated. 
 
 In his later machines Mr. Curtiss has pro- 
 vided ailerons similar to those of Farman, as 
 shown in Fig. 29. 
 
 The Bleriot monoplane, which is also in- 
 volved in this Wright litigation, is outwardly at 
 
 FIG. 30. The Bleriot system of control. 
 
 least more like the Wright machine in the mech- 
 anism for maintaining side-to-side balance. Its 
 single supporting plane is warped at the sides 
 by a lever and a system of cables, as shown in 
 Fig. 30. The single supporting plane is rigidly 
 trussed along its front edge, but a cable is at- 
 tached to one rear corner at / and passes down- 
 ward, and toward the centre to a pulley F 
 (Fig. 31) actuated by a lever K, and upward 
 
BALANCING AEROPLANES 71 
 
 to the opposite rear corner of the plane /' 
 (Fig. 30). By moving the lever K to one side, 
 the cable pulls down the side rear portion of the 
 
 FIG. 31. The steering and control column of the Bleriot 
 monoplane. The wheel L, the post K, and the bell-shaped 
 member M form one piece and move together. Wires O 
 connect the bell with the yoke G, carrying the pulley F, 
 around which the wires H running to the flexible por- 
 tions of the supporting planes are wrapped. By rocking 
 the post and bell from side to side in a vertical plane 
 the wires H are respectively pulled and relaxed to warp 
 the planes. By moving the post K back and forth the 
 horizontal rudder is operated through the wires P. 
 These various movements of the post can be effected by 
 means of the wheel L, which is clutched by the aviator's 
 hands, or by means of the bell M, which can be clutched 
 by the aviator's feet if necessary. 
 
72 THE NEW ART OF FLYING 
 
 plane at one tip to a greater angle of incidence 
 than the normal plane of the body of the aero- 
 plane, and permits the opposite side rear por- 
 tion to rise to an angle of less incidence. Thus 
 the whole plane is warped, and the portions 
 lying at the opposite tips are presented to the 
 air at different angles of incidence. The ver- 
 tical adjustable rudder R (Fig. 30) is located 
 at some distance to the rear of the main plane, 
 and wires lead from it to a tiller operated by 
 the feet. When the pilot warps the plane he 
 swings the rudder to prevent the machine from 
 spinning. By moving the lever K back and 
 forth the horizontal rudder is rocked up and 
 down. 
 
 In the Antoinette monoplane the horizontal 
 or elevation rudder and the stabilising mech- 
 anism are quite independent. The vertical 
 rudder consists of two vertical triangular sur- 
 faces at the rear. They are moved jointly by 
 means of wire cables running from a tiller 
 worked by the aviator's feet. When this tiller, 
 which moves in a horizontal plane, is turned 
 to the left, the aeroplane will turn to the left. 
 The elevation rudder in the Antoinette mon- 
 
II 
 
 E 3 
 
 bD 
 
BALANCING AEROPLANES 73 
 
 oplane consists of a single triangular horizon- 
 tal surface placed at the extreme rear. It 
 is governed by cables leading from a wheel 
 placed at the aviator's right hand (Fig. 32). 
 To ascend, the wheel is turned up. This 
 causes a decrease in the inclination of the ele- 
 vation rudder relatively to the line of flight, and 
 the machine, therefore, rises. Side-to-side bal- 
 ance was at one time maintained by ailerons, as 
 shown in Fig. 33. Latterly it is maintained by 
 warping the outer ends of the main plane very 
 much as in the Wright machine. But the front 
 ends are movable and the rear ends rigid 
 throughout in the new Antoinette, while the 
 opposite is the case in the Wright biplane. The 
 wheel at the aviator's left hand, through cables 
 and a sprocket gear, placed at the lower end of 
 the central mast, controls the warping. For cor- 
 recting a dip downward on the right the right 
 end of the wing is turned up, and at the same 
 time the left end is turned down, thus restoring 
 balance. 
 
 Warping a plane and rocking an aileron are 
 not the only ways of maintaining side-to-side 
 balance. The late Professor S. P. Langley dis- 
 
74 THE NEW ART OF FLYING 
 
 covered that by cutting a plane in two and ar- 
 ranging the two parts so that they would form 
 a rather wide V when viewed from the front 
 or rear (" dihedral angle " is the proper tech- 
 nical term), a certain amount of automatic sta- 
 bility would be obtained. He constructed his 
 own successful small models on that principle. 
 Bleriot, too, adopted it in at least one of his 
 earlier machines. Although wasteful of power 
 it is still a conspicuous feature of many French 
 machines of the present day. Even in some 
 recent biplanes, notably the racing Farman, it 
 is to be found. 
 
 Still another way of obtaining a certain 
 amount of automatic stability is to employ ver- 
 tical surfaces to prevent tilting and to distribute 
 the pressure more evenly over the main sur- 
 faces. An example is to be found in the earlier 
 Voisin machine, which is a biplane divided into 
 cells by vertical curtains or partitions (Fig. 
 34). In practice, these partitions are found in- 
 adequate, for which reason the pilot of this 
 Voisin type must right his machine by steering 
 with the rudder. Thus, if the machine cants up 
 on the left and down on the right, he steers to 
 
BALANCING AEROPLANES 75 
 
 the left. This brings the right side up again 
 because it is suddenly called upon to travel more 
 quickly through the air than the left side, in- 
 creased speed resulting in increased elevation. 
 This Voisin type is one of the few construc- 
 tions that does not fall within the scope of the 
 Wright patent. Farman, who was one of the 
 first pilots that ever tried a Voisin, abandoned 
 it for the aileron machine, which bears his name. 
 In the new Voisin machines (Fig. 35) no cells 
 at all are to be found, but instead ailerons sim- 
 ilar to those adopted by Farman. On the whole 
 it must be confessed that the most successful 
 machines at the present time are those in which 
 the side-to-side balance is maintained either by 
 warping the wings or by means of ailerons. 
 
 Sometimes the vertical surfaces are distrib- 
 uted along the frame of the machine in the 
 form of keels. Although they contribute a cer- 
 tain stability, it cannot be denied that they also 
 increase the resistance and lower the speed. 
 To prevent this so far as possible, and yet to 
 retain whatever advantages they may have, it 
 is customary to taper them. Examples of such 
 tapering keels will be found on the Antoinette 
 
76 THE NEW ART OF FLYING 
 
 and Hanriot monoplanes (Fig. 36, Frontis- 
 piece). In a few years keels will probably dis- 
 appear altogether. The advantages hardly 
 offset the disadvantages. No special arrange- 
 ment or design of keels has really ever suc- 
 ceeded in insuring automatic stability. Even 
 now the best designers confine them to the 
 extreme rear of the machine, where they act 
 somewhat like a bird's tail. 
 
 Mr. F. W. Lanchester, the distinguished 
 English authority, has suggested that auto- 
 matic stability can be insured by driving the 
 aeroplane at speeds higher than those of the 
 gusts, that are so liable to upset it. Just as 
 the " Lusitania " at twenty-five knots dashes 
 through waves and winds that would drive a 
 fishing-smack to cover, so the high-speed aero- 
 plane, in his opinion, would sail on, undeterred 
 by the fiercest blast. Sixty miles an hour is 
 the minimum speed that a machine should have, 
 if his idea is correct. Moreover, he believes 
 that, if the aeroplane is to have any extended 
 use, it must travel very much faster than the 
 motor-car. 
 
 Another means of attaining automatic sta- 
 
,3 S 
 
 
 00 
 
 u 
 
 c 
 c 
 
 <u 
 
 3 
 
 ci 
 
BALANCING AEROPLANES 77 
 
 bility consists in varying the angle of incidence 
 by rocking the whole plane on a horizontal 
 axis, which is done by Esnault-Pelterie. 
 
 The foregoing explanation of stability and 
 stabilizing devices applies only to side-to-side 
 balance. Fore-and-aft balance can be obtained, 
 as in birds, by tails, such as are found in the 
 Curtiss, Bleriot, Antoinette, Santos-Dumont, 
 Esnault-Pelterie, and indeed most machines. 
 
 The tail may be either a single horizontal 
 surface or a cell, like a box kite. 'Almost every 
 machine that now flies is provided with a tail 
 to secure steadiness in flight. In the new 
 Wright biplanes (Fig. 38) a single horizontal 
 surface is used at the rear of the machine, a 
 surface which also serves as an elevation 
 rudder; for the Wrights have removed from 
 the front of the machine those two parallel 
 horizontal surfaces, which, in the early days 
 of their work, were to them like the antennae 
 of an insect, a means of feeling their way. The 
 Wrights were the first who ever placed the 
 rudder in front, and their example was quickly 
 followed by Curtiss, Farman, Sommer, Voisin 
 and other biplane makers. Whatever advan- 
 
78 THE NEW ART OF FLYING 
 
 tages this forward position of the horizontal 
 rudder may have, it is certain that it increases 
 the tendency of the machine to pitch in flight, 
 because of the long lever-arm provided by the 
 rods connecting the forward rudders with the 
 main framework. When the Wrights reversed 
 themselves and removed the horizontal rudder 
 from the front and placed it at the rear, where 
 it performed not only its old function, but also 
 served as a tail (an instrument with which the 
 earlier Wright machines were not provided), 
 their example was promptly followed by 
 Voisin (Fig. 35), Breguet, Goupy, Caudron 
 Freres and other constructors. It is safe to 
 predict that in the future most biplanes will be 
 provided with rear horizontal stabilising and 
 elevating surfaces. 
 
 From the very first, monoplanes have been 
 provided with rear horizontal or elevation 
 rudders, probably because such is the example 
 offered by every bird and because the late Pro- 
 fessor Langley adopted them after much ex- 
 perimenting. The Bleriot, Antoinette and 
 other monoplanes have rear horizontal rudders 
 and also tails. 
 
BALANCING AEROPLANES 79 
 
 The tail corrects the see-saw motion or pitch- 
 ing of a flying-machine in flight. The further 
 back that it is placed the greater will be the 
 steadying effect. If placed too far back, how- 
 ever, a " dead centre " will be reached. If 
 there is no tail the pilot must manipulate the 
 horizontal rudder to check the see-saw motion. 
 The Wrights have taken out a patent for a 
 mechanical device, which maintains fore-and- 
 aft stability automatically. In this device the 
 human brain is supplanted by the pressure of 
 the air on a plane. Compressed air is substi- 
 tuted for muscular action. Lateral stability is 
 
 automatically maintained by means of a pendu- 
 
 
 
 lum. The plane and pendulum open valves 
 which admit compressed air to an engine oper- 
 ating the horizontal or elevation rudder and 
 warping mechanism. 
 
 To relieve the pilot of the physical strain of 
 more or less constantly warping planes or ma- 
 nipulating ailerons, it was suggested long be- 
 fore the day of the Wrights that the flying- 
 machine be provided with some automatic 
 device which would prevent any capsizing 
 tendency. The more important of such ap- 
 
8o THE NEW ART OF FLYING 
 
 pliances are moving weights, pendulums, and 
 gyrostats. A gyrostat is any rapidly rotating 
 body, which, by virtue of its rotation, resists 
 any force tending to move it from its plane of 
 rotation. The greater the weight and the 
 higher the speed of the gyrostat the greater 
 must be the force expended to shift it from its 
 plane of rotation. Hence if a gyrostat could 
 be mounted on an aeroplane it certainly would 
 tend to resist any unbalancing force, such as a 
 gust of wind. Paul Regnard in France is said 
 to have conducted very successful experiments 
 with gyrostatically controlled aeroplanes. Rob- 
 erts in England has also made more or less en- 
 couraging tests. In his machine the gyrostat 
 is applied as shown in Fig. 37. 
 
 The pilots of present machines object to any 
 device that will relieve them entirely of all hand 
 control. They would much prefer an auto- 
 matic device which is immediately thrown out 
 of operation when the hand-devices are manipu- 
 lated. It is argued that a machine must be 
 humoured, that with an automatic device such 
 as the gyrostat, it is impossible to accommo- 
 date the machine to variations in the wind. 
 
2 
 
 S-jg 
 
 I '* 
 
 
 
 15 
 
 too c 
 .S 6 
 
 j.l 
 
 C it 
 
 1 
 
 C 
 S 
 
 3 
 
BALANCING AEROPLANES 81 
 
 Moreover, there is the objection that the ma- 
 chine must be elevated rapidly in starting, with 
 a fairly large angle of incidence, but must after- 
 wards assume a fairly flat angle for horizontal 
 flight, with all of which a steadily running gyro- 
 stat would seriously interfere. Soaring down 
 a steep angle with motors at full speed could 
 hardly be accomplished with a gyrostat run- 
 ning at a fixed rate, for it is the gyrostat's 
 tendency to resist movement. Besides, there 
 is always the possibility that the motor which 
 drives the gyrostat may stop, so that the avi- 
 ator is helpless if no hand-controlled devices 
 enable him to prevent rocking from side to side 
 and pitching fore and aft. 
 
 The pendulum, as we have seen, has been 
 suggested by the Wrights as well as by other 
 inventors to relieve the aviator of his present 
 duties. The underlying idea is that a freely 
 suspended weight will always tend to hang 
 down, and that it would be an easy mat- 
 ter to connect with it elevation rudders and 
 ailerons, in such a manner that pitching fore 
 and aft, or rocking from side to side could be 
 controlled by the effort of the pendulum to 
 
82 THE NEW ART OF FLYING 
 assume a perfectly normal position relatively 
 to the earth. The pendulum, however, will 
 hardly be likely to attain the desired end. It 
 cannot control a flying-machine automatically, 
 as Professor Prandtl has pointed out. The 
 very force which causes an aeroplane to change 
 its horizontal position in flight also retards it, 
 accelerates it, or inclines it from side to side. 
 Consequently a pendulum, which has the mo- 
 mentum of the entire machine, will follow the 
 direction of the aeroplane's inclination and, 
 so far from hanging down, will deviate from 
 the vertical. The result will be, curiously 
 enough, that it will always maintain its posi- 
 tion relatively to the planes, whatever their 
 inclination fore-and-aft and side-to-side may be. 
 Hence the pendulum is inoperative. Further- 
 more, when an aeroplane is rounding a curve 
 at the rate of from forty to sixty miles an hour, 
 centrifugal force would completely nullify the 
 action of the pendulum. 
 
 If a gyrostat is to be used, it is likely that 
 it will be combined with some system of hand 
 control, so that the aviator can depend upon the 
 one or the other, as circumstances may dictate. 
 
SOJ 
 c 
 
 f "a 
 
 I * 
 
 en O .22 
 
 OJ 
 
 .3 5 IS 
 
 J S- 
 
 j* s 
 
 H 2 -c 
 
 OJ 
 
 C CA 
 
 -2 -C 
 a, -^ 
 
 c 
 
 ^ 
 
 o 
 
 o, c 
 
BALANCING AEROPLANES 83 
 
 But how this combination would really im- 
 prove the situation it is difficult to see. .Auto- 
 matic control is necessarily complicated. Hand 
 control is admittedly dependent upon a cool 
 head and an expert hand. Moreover, an auto- 
 matic device must be made as small and as light 
 as possible, for the aeroplane as it now stands is 
 a machine in which the weight of every part 
 has been reduced to a minimum. Can control 
 mechanism, dependent upon a gyrostat, be 
 made sufficiently light to meet the requirements 
 of present construction? The more one con- 
 siders the question, the more likely are we to 
 believe that the best automatic machine is a 
 well-trained hand. 
 
 Any one who has seen a skilled man steering 
 a small boat in a heavy sea must realise that 
 there is no possibility of making any automatic 
 device which would take his place, and that 
 any attempt to make the steering automatic 
 by such means as a gyrostat would mean the 
 certain swamping of the boat in a sea through 
 which it could be steered quite simply by hand. 
 The aeroplane is very much in the position of 
 this small boat. 
 
84 THE NEW ART OF FLYING 
 
 The danger of hand control is to be found 
 in the possibility of making a false move. 
 Locomotive engineers, signal men, automobile 
 chauffeurs, are all of them in a position where 
 a false move means a bad accident. Yet for 
 all that, the number of errors which are made 
 is comparatively small. A ship is dependent 
 upon the engines and skill of the men in the 
 pilot house ; yet it is but rarely that we hear 
 of shipwrecks due to bad judgment in the 
 wheel house. All things considered, it is very 
 likely that aeroplanes will be hand controlled 
 for years to come. 
 
CHAPTER VI 
 
 MAKING A TURN 
 
 IN straightaway flight an aeroplane is balanced 
 to a certain extent by the main supporting sur- 
 faces (the large spread of which counteracts 
 sudden inclination) and also by the position of 
 the centre of gravity, which lies below the sup- 
 porting surfaces in many machines. But when 
 the vertical rudder is thrown over to swing the 
 machine around, new forces come into play. 
 
 When a line of soldiers wheels around a 
 street corner the man at the inner end of the 
 line does little more than mark time; the man 
 in the centre of the line marches along at a 
 steady pace; while the man on the outside all 
 but runs. In order that the line may be straight 
 the movement must be progressively faster 
 from the inner to the outer end. An aeroplane 
 as it turns horizontally is in exactly the same 
 predicament as a line of soldiers. The outer 
 end of the machine must move faster than the 
 inner end. 
 
86 THE NEW ART OF FLYING 
 
 The accompanying illustration, Fig. 39, will 
 make this clearer. Let us assume that the arc 
 to be described is sixty feet in diameter, and 
 
 \ 
 
 FIG. 39. An aeroplane of 40 feet spread of wing round- 
 ing an arc of 60 feet radius. Since the outer side of the 
 aeroplane must travel over a given distance in the same 
 time that the inner side must travel a considerably 
 shorter distance, gravitation must be opposed to centrif- 
 ugal force in order that the turn may be effected with 
 safety. 
 
 that the aeroplane has a spread of forty feet. 
 The outer end of the machine must describe its 
 large arc of sixty feet radius while the inner 
 end is describing its small arc of twenty feet 
 
MAKING A TURN 87 
 
 radius. Evidently the outer end must travel 
 considerably faster than the inner. 
 
 As the speed of an aeroplane increases, its 
 lifting power also increases. Hence the more 
 rapidly moving outer end of an aeroplane will 
 be subjected to a greater lifting effort than the 
 slowly moving inner end, and hence the entire 
 machine is canted at a more or less sharp angle 
 on a turn. This natural canting or banking has 
 its advantages. It counteracts the effects of 
 centrifugal force, which are unavoidable in any 
 rotary movement. 
 
 What centrifugal force means we see when 
 a weight at the end of a cord is whirled around. 
 If whirled fast enough, the weight will describe 
 a circle, because the centrifugal force is very 
 much greater than the force of gravitation. If 
 the whirling be slackened below a certain criti- 
 cal point, the weight will drop back to the 
 hand. A flying-machine is like the whirling 
 stone. It has a very large centrifugal force 
 as it turns. So great is that force that it must 
 be checked by the force of gravitation, in other 
 words, the weight of the machine. The more 
 the machine is heeled over, the more marked 
 
88 THE NEW ART OF FLYING 
 
 will be the action of gravitation. Hence the 
 natural canting of the machine on a curve is of 
 advantage in counteracting the effect of centrif- 
 ugal force. 
 
 If the canting be very pronounced, it is pos- 
 sible that gravitation may overcome the centrif- 
 ugal force, so that the machine will slide down 
 to the ground. To forestall that possibility the 
 aviator may either sweep his circle on so long 
 a radius that there will be but little canting, or 
 he may employ wing-warping devices or aile- 
 rons to counterbalance the canting action. Since 
 most aeroplanes are provided with either warp- 
 ing devices or ailerons, it is the usual practice 
 to depend upon them in turning. The result is 
 that we see skilful pilots swinging in an arc at 
 a speed that cants their machines at an angle 
 which may be more than seventy degrees to the 
 horizontal and which almost causes the specta- 
 tor's heart to stop beating, so perilous does the 
 exploit seem to the eye. 
 
 The inquiring reader may ask: How does 
 wing-warping or the manipulation of ailerons 
 prevent the machine from slipping down ? The 
 principle involved is exactly the same as that 
 
A 
 
 Photograph by Edwin Levick 
 
 Fig. 28. Henry Farman seated in his biplane. His 
 
 hand grasps the lever by which the 
 
 ailerons are operated 
 
MAKING A TURN 89 
 
 which underlies the balancing of the machine 
 in straightaway flight when it is subjected to cap- 
 sizing gusts. As soon as the pilot wheels, he in- 
 creases the angle of incidence on the inner end 
 and hence the upward pressure, with the result 
 that the tendency of the inner end of the ma- 
 chine to fall is checked. Simultaneously the 
 angle of incidence of the outer side is decreased 
 and the downward pressure increased, with the 
 result that the .tendency of the outer side to rise 
 is checked. 
 
 All this sounds very easy; yet, even after a 
 successful aeroplane had been invented, many 
 machines were wrecked before the trick of 
 making a turn was learned. It took the French 
 two years to learn the art of turning. Indeed, 
 a wealthy Parisian, named Armengaud, offered 
 a prize to the first Frenchman who performed 
 the feat. Henry Farman won that prize so 
 recently as July 6, 1908. The Wright Brothers 
 spent the whole flying season of 1904 in 
 learning how to sweep a circle when the wind 
 was blowing. Octave Chanute, the only en- 
 gineer who was allowed to see them at work 
 during that period of apprenticeship, gives 
 
9 o THE NEW ART OF FLYING 
 this interesting account of their trials and 
 tribulations : 
 
 " I witnessed a flight at Dayton on October 
 15, 1904, of 1,377 f eet > performed in twenty- 
 four seconds. The start was made from level 
 ground, and the machine swept over about one- 
 quarter of a circle at a speed of thirty-nine 
 miles an hour. The wind was blowing diag- 
 onally to the starting rail at about sixteen miles 
 an hour. 
 
 " After the machine had progressed some 
 five hundred feet and then risen about fifteen 
 feet it began to cant over to the left and as- 
 sumed an oblique transverse inclination of fif- 
 teen to twenty degrees. Had this occurred at 
 an elevation of, say, one hundred feet above 
 the ground, Orville Wright, who was in the 
 machine on this occasion, could have recovered 
 an even balance even with the rather imperfect 
 arrangement for control at that time employed. 
 But he felt himself unable to do so at the height 
 then occupied and concluded to come down. 
 
 * This was done while still turning to the 
 left, so that the machine was going with the 
 wind instead of against it, as practiced where 
 possible. 
 
 " The landing was made at a speed of forty- 
 five to fifty miles an hour, one wing striking the 
 
MAKING A TURN 91 
 
 ground in advance of the other, and a breakage 
 occurred, which required one week for repairs. 
 The operator was in no wise hurt. 
 
 " This was flight No. 71 of the 1904 series. 
 On the preceding day the brothers had made 
 alternately three circular flights, one of 4,001 
 feet, one of 4,902 feet, and one of 4,936 feet, 
 the last covering rather more than a full circle. 11 
 
 A steady wind is imperceptible to the man in 
 a flying-machine, and turning is effected as 
 easily with as against the wind. When the 
 wind is unsteady not only is balancing difficult 
 but turning also, since the machine must be 
 simultaneously balanced and turned. The two 
 operations are more or less confused. When 
 the wind is very gusty the pilot may find it 
 harder to turn and travel with the wind instead 
 of against it. 
 
 A sharp turn on an aeroplane is like one of 
 those moments on a yacht when you slack away 
 quickly on the main sheet and prepare for the 
 boom to jibe. There is none of the yacht's 
 hesitancy, however; for the machine slides 
 away on the new slant without a quiver. An 
 inexperienced passenger on an aeroplane is 
 
92 THE NEW ART OF FLYING 
 
 tempted to right the machine, as it swings 
 around and tilts its wings, by throwing over his 
 body toward the descending side. In a canoe 
 or on a bicycle it would be natural to use the 
 body. In an aeroplane the movement is un- 
 necessary because the machine does its own 
 banking. 
 
 In the Curtiss and Santos-Dumont machines 
 any such instinctive movement on the part of 
 the aviator to right the careening machine actu- 
 ates the ailerons or wing-warping devices in 
 the proper way. In the Curtiss biplane, as we 
 have seen, the seat-back is pivoted and is con- 
 nected by cables with the ailerons. Hence, 
 should the pilot involuntarily throw his weight 
 over to right the machine, the ailerons are 
 tilted to regulate the pressure on the planes in 
 the proper manner. 
 
 The effect of the vertical rudder in turning 
 varies with the speed of the aeroplane relatively 
 to the speed of the wind. The higher the 
 speed of the aeroplane the more marked is the 
 influence of the vertical rudder on its course. 
 
 The form that the vertical rudder assumes 
 is various. In monoplanes it consists of a 
 
a -a 
 
 s 
 
 l 
 
 .S c 
 
 V) G 
 < C 
 
 3 s 
 
 si 
 
 aj C 
 
 2 
 
 O JJ 
 
 
MAKING A TURN 93 
 
 single vertical surface, mounted at the rear of, 
 the machine: in biplanes it usually consists of 
 a pair of parallel vertical surfaces, as in the 
 Wright machine. Occasionally these parallel 
 vertical surfaces form the sides of a box, as 
 in the Voisin and Farman machines, the top 
 and bottom of the box serving as horizontal 
 stabilising surfaces, as in the old cellular Voisin 
 biplane. 
 
CHAPTER VII 
 
 THE PROPELLER 
 
 FEATHERING paddles, somewhat like those to 
 be found on steamboats, beating wings, like 
 those of a bird, sweeps or oars have all been 
 suggested as means for propelling the flying- 
 machine; but the screw propeller is the only 
 device that has met with any success. The screw 
 propeller is the most important adjunct of the 
 aeroplane, and also the most deficient. The 
 circumstance is remarkable because the screw 
 or helical rotating propeller was associated 
 with schemes of aerial navigation no less than 
 four centuries ago, and by no less a personage 
 than the great artist-mechanician, Leonardo da 
 Vinci, at the end of the fifteenth century. 
 
 Leonardo da Vinci's propeller was a screw 
 or helix of a single " worm " or thread prac- 
 tically all " worm " comprising an entire 
 convolution, of which the modern equivalent 
 would be a single-bladed screw, blades being 
 a much later development. It is not difficult 
 
THE PROPELLER 95 
 
 to imagine how the original screw propeller 
 came to be of the single " worm " type, and 
 why one complete turn of the " worm " should 
 be deemed essential. These were matters of 
 subsequent development, the departures being 
 suggested by experiment and trial. 
 
 It was first discovered by actual comparative 
 trials that half a convolution of the " worm " 
 was fully as efficient as a whole turn, and then 
 that a quarter turn was more efficient than half. 
 But with this curtailment of the helix a for- 
 midable difficulty arose. It had now developed 
 Into a one-bladed screw; it was unsymmetrical 
 and, consequently, unbalanced. Centrifugal 
 force and one-sided thrust jointly interposed, 
 with poor results. 
 
 Eventually it dawned on the minds of the 
 pioneer experimenters that to produce a more 
 efficient, symmetrical, and compact screw pro- 
 peller while employing only a fraction of 
 a convolution two or more " worms," now 
 reduced to blades, were necessary. 
 
 No perfect definition of a screw propeller 
 has ever been given. It is usually defined as 
 an organ which, by pressing upon a fluid, pro- 
 
96 THE NEW ART OF FLYING 
 
 pels the vehicle to which it is attached. In a 
 sense, the screw propeller may be regarded as 
 a rotating aeroplane, with an angle of inci- 
 dence, known as its " pitch," and a " camber," 
 which is its curve. But the propeller differs 
 from the aeroplane in that the blades are con- 
 tinually passing over the same spot many times 
 in a second in air already disturbed. This is 
 one reason why the propeller offers a far more 
 difficult problem than the plane. 
 
 By the " pitch " of a propeller is meant the 
 theoretical distance that the propeller would 
 move forward in one revolution in a solid. 
 Because a propeller revolves in air, a very 
 thin and yielding medium, it loses a certain 
 amount of power, which loss is known as its 
 " slip." If the propeller in one revolution 
 moves forward theoretically six inches, but actu- 
 ally only three inches, the loss of power or 
 " slip " is fifty per cent. The slip varies with 
 different speeds. To find the best pitch, the best 
 curvature, the best diameter, the best speed, is 
 the problem that confronts the propeller designer. 
 
 The ideal aerial propeller is one that can 
 move through the air without friction. If the 
 
THE PROPELLER 97 
 
 ideal could be attained, the entire power of the 
 motor would be transformed into useful work, 
 and a maximum thrust would be transmitted to 
 the propeller shaft. The actual aerial propeller 
 
 FIG. 41. A single-threaded and a double- threaded screw. 
 A two-bladed aeroplane propeller may be conceived to 
 have been cut from a double-threaded screw, i. e., the 
 sections A and A' and the sections B and B r . 
 
 falls far short of that ideal. Its blades are not 
 plane, but are curved in a manner skilfully de- 
 signed to obtain a maximum efficiency. In order 
 to give an idea of this curvature and its pos- 
 sible variations, consider a vertical section of 
 an Archimedes screw (Fig. 41), Let us study 
 
98 THE NEW ART OF FLYING 
 
 the small slice, M. This small element is not 
 a plane surface, but has a curvature which de- 
 pends upon the pitch of the screw and its radius. 
 Two such elements attached, opposite each 
 other, to the same shaft represent a two-bladed 
 propeller of definite curvature. 
 
 It is evident that this curvature cannot be a 
 matter of indifference, for it is intimately con- 
 nected with the distance A 5, between two 
 points on the same generatrix of the screw; 
 that is to say, upon the pitch of the screw. The 
 form of a propeller blade can be imitated by 
 holding one end of a rectangular strip of paper 
 and twisting the other end about an axis parallel 
 with the length of the strip. The Wrights form 
 such a surface in deforming aeroplanes in steer- 
 ing. If the aeroplane were attached to a fixed 
 vertical axis, it would revolve about this axis 
 like an ordinary propeller during a turn. The 
 true screw-propeller in its simplest and most 
 efficient type is but a very short length cut from 
 a two-thread screw, in which the thread is rela- 
 tively very deep, with a pitch equal to about 
 two thirds of its diameter. A twist or curve in 
 a propeller blade is necessary because the hub 
 
THE PROPELLER 99 
 
 and the outer edge of the blade revolve at 
 different speeds. The outer edge of the blade 
 clearly must sweep through a greater distance 
 in a given time than the hub. In order that all 
 parts may theoretically grip the air equally, the 
 angle is steeper at the centre than at the outer 
 edge. In practice the hub portion has a much 
 lower efficiency than the outer edge of the 
 blade. 
 
 Just how many blades the propeller should 
 have once gave us much concern. Some air- 
 propellers have two blades, some three, some 
 four. It is now generally conceded that nothing 
 is to be gained by three and four blades, and 
 that the two-bladed propeller is indeed the most 
 efficient. 
 
 The Ericsson propeller (marine) was 
 formed of a short section of a 12-thread screw 
 of very coarse pitch and proved very ineffi- 
 cient. The aerial fan propeller of Moy (not 
 a screw) had six broad vanes enclosed in a 
 hoop and was but little better. The same re- 
 mark applies to the propellers of Henson, 
 Stringfellow, Linfield, Du Temple, and many 
 others. Even the first propeller fans used by 
 
ioo THE NEW ART OF FLYING 
 
 Langley on his earliest aerial model were six- 
 bladed. In his subsequent and highly success- 
 ful model aerodrome the twin propellers were 
 two-bladed true screws, as also were those of 
 the Maxim machine. 
 
 It is a significant fact that the conspicuous 
 successes have all been achieved with two- 
 bladed propellers. All recent systematic and 
 comparative experiment points to the fact that 
 a two-bladed propeller is the most efficient, and, 
 at the same time, fortunately, the simplest and 
 lightest. 
 
 Authorities are not in accord on the proper 
 position of the propeller. Most of them, how- 
 ever, hold, with Sir Hiram Maxim, that the 
 proper position is in the rear. Bleriot (Fig. 
 46), Levavasseur (who builds the Antoinette 
 machine), and many monoplane designers 
 mount the propeller in front. In its usual posi- 
 tion just in advance of the centre, the front pro- 
 peller interrupts the entering edge. To obviate 
 this, some monoplane builders, among them 
 Santos-Dumont and Bleriot (in his passenger- 
 carrying monoplane XII), place the engine and 
 pilot below the plane. 
 
THE PROPELLER 101 
 
 On the position of the propeller Maxim 
 says: 
 
 " Many experimenters have imagined that a 
 screw is just as efficient placed in front of a 
 machine as at the rear, and it is quite probable 
 that in the early days of the steamship a similar 
 state of things existed. For several years there 
 were steamboats running on the Hudson River, 
 New York, with screws at their bows instead 
 of at their stern. Inventors of, and experi- 
 menters with, flying-machines are not at all 
 agreed by any means as to the best position for 
 the screw. It would appear that many, having 
 noticed that a horse-propelled carriage always 
 has the horse attached to the front, and that 
 their carriage is drawn instead of pushed, have 
 come to the conclusion that in a flying-machine 
 the screw ought, in the very nature of things, 
 to be attached to the front of the machine, so 
 as to draw it through the air. Railway trains 
 have their propelling power in front, and why 
 should it not be the same with flying-machines? 
 But this is very bad reasoning. There is but 
 one place for the screw, and that is in the imme- 
 diate wake, and in the centre of the greatest 
 atmospheric disturbance. ... If the screw is 
 in front, the backwash strikes the machine and 
 certainly has a decidedly retarding action. The 
 
102 THE NEW ART OF FLYING 
 
 framework, motor, etc., offer a good deal of 
 resistance to the passage of the air, and if the 
 air has already had imparted to it a backward 
 motion, the resistance is greatly increased." 
 
 When mounted in front, the screw draws 
 the machine along. Hence the front propeller 
 is sometimes called a " tractor screw." When 
 the screw is mounted in the stern, as in a ship, 
 it pushes the machine along (Fig. 48) and is 
 then truly a propeller. 
 
 The question of position is not yet settled 
 by any means. The propeller at the rear has a 
 free discharge, but, on the other hand, its feed 
 is disturbed. In front it has a clear feed, but 
 is hampered in discharging, and also modifies 
 the streams impinging on the supporting planes, 
 as Maxim points out. 
 
 The number of the propellers is also a moot 
 point. Kress, a well-known experimenter, be- 
 lieved that there should be at least four pro- 
 pellers, so attached that their shafts could be 
 directed to different angles. Thus, he imag- 
 ined, they could be employed to sustain the 
 machine in the air without driving it forward. 
 This is the helicopter or screw-flier principle, 
 
s "8 
 8> 
 
 11 
 
 W 
 
 t 
 
 f 
 
 
 " " 
 
 s i 
 
 u 
 
 = 
 E 8 
 
 bfl 
 
THE PROPELLER 103 
 
 briefly considered in the chapter on flying- 
 machine types. 
 
 The Wrights have always advocated the use 
 of two propellers rotating in opposite direc- 
 tions (Fig. 44). There is always the danger, 
 however, that one propeller may break down 
 and that the machine may be imperilled. In- 
 deed, an accident of that kind occurred during 
 the official tests of the Wright machine at 
 Fort Myer, Virginia, in 1908. A propeller 
 struck a loose guy-wire and broke. The biplane 
 crashed to the ground. Orville Wright, the 
 pilot, was painfully injured, and Lieutenant 
 Selfridge, a passenger, was killed. It must be 
 stated, however, that had the machine been 
 higher, Mr. Wright would probably have glided 
 down in safety. 
 
 Should propellers be of very small diameter 
 and high speed, or of large diameter and low 
 speed? Both systems have their advocates. 
 We know something about the power of heavy 
 gales; and when we consider that an aero- 
 plane propeller is capable of producing a 
 little cyclone, it is easy to conceive of its 
 exerting sufficient force to drive a i,ooo-pound 
 
io 4 THE NEW ART OF FLYING 
 
 aeroplane at high velocity. Flying-machines 
 have attained a speed of seventy miles an 
 hour. In order to do this, the propellers must 
 have turned fast enough to have produced a 
 current of air considerably more than this veloc- 
 ity, because the fluidity and elasticity of the air 
 are sufficient to cause a considerable " slip " of 
 the propellers, which reduces their efficiency to 
 a large extent. Hence even the slowest of pro- 
 pellers (the Wright) turns at the fairly high 
 speed of four hundred revolutions a minute, 
 while the swiftest turns at the rate of about 
 fifteen hundred revolutions a minute, which is 
 about the speed of an electric fan. A high- 
 speed Chauviere propeller is a mere glittering 
 disk of light about eight feet in diameter. The 
 blades move so fast that it is possible to cast 
 a shadow upon them; for the eye cannot per- 
 ceive the interval which elapses before another 
 blade has taken the place of that which has left 
 a given spot. The phenomenon. is simply one 
 of the persistence of retinal images ; but it serves 
 to drive home the enormous speed of some 
 aeroplane propellers. 
 
 It is generally believed that much better re- 
 
THE PROPELLER 105 
 
 suits could be obtained by the use of propellers 
 of fifteen or twenty feet diameter rotating 
 slowly. But there are two disadvantages in- 
 volved in this feature of construction, which 
 make its adoption in the machines of the future 
 rather doubtful. The first is the greatly added 
 weight of so big a propeller; and the second, 
 the difficulty of building a good chassis high 
 enough to enable the propeller to clear the 
 ground. 
 
 Like the marine turbine, the aerial engine 
 runs too fast for the best propeller speeds. 
 The Wright brothers overcame this difficulty 
 by the somewhat unmechanical expedient of 
 chain gearing, one chain being crossed. A 
 French firm has utilised the half-time cam-shaft 
 of the engine, suitably enlarged, to drive the 
 propeller, thus getting a speed reduction of two 
 to one, but the Bleriot, Antoinette, Farman, 
 Voisin, and indeed most types continue to drive 
 the propeller directly without reduction. It is 
 probable that the direct drive will prevail, for 
 any form of gearing, however simple, intro- 
 duces an element of risk with doubtful benefits. 
 At present there is scarcely any machine which 
 
*io6 THE NEW ART OF FLYING 
 
 has the propeller well under control, so that it 
 can be stopped and started and altered in speed, 
 without stopping the motor. This is due, of 
 course, to the weight of clutches, change-speed 
 gears, etc. Probably some enterprising engi- 
 neer may produce a suitable gear for this pur- 
 pose before long. 
 
 In this outline we have used the word " effi- 
 ciency." How is efficiency determined, may 
 well be asked. The true efficiency of a pro- 
 peller driving an aeroplane is the ratio between 
 the work of propulsion and the energy con- 
 sumed, the work of propulsion being the prod- 
 uct of the travel of the aeroplane multiplied by 
 the resistance opposed to its forward move- 
 ment. The efficiency is measured at a fixed 
 point by causing the propeller to revolve, with- 
 out advancing or receding, and measuring the 
 thrust produced, in the direction of the axis, 
 by a given horse-power. 
 
 The conditions of the experiment are very 
 different from those of rapid flight through the 
 air, in which the friction between the air and 
 the propeller is enormously increased; no ac- 
 count is taken of the resistance opposed by the 
 
* -2 
 
 .22 
 IS 
 
 O 
 
THE PROPELLER 107 
 
 air to the forward movement of the aeroplane. 
 In fact, no work of propulsion is performed or 
 even imitated, the sole result being a thrust 
 which may be employed for propulsion. Under 
 these conditions the propeller is comparable 
 with a lever which supports a motionless weight 
 and thus exerts a stress, but performs no work. 
 For this reason absolute reliance cannot be 
 placed on the results of many propeller tests. 
 
 A fair imitation of the conditions of flight 
 as they directly affect the propeller itself can 
 be obtained by placing the propeller in a tube 
 in which an air current of any desired velocity 
 is produced by blowers. Some experimenters 
 mount the propeller so that it revolves freely 
 in air and yet drives a boat or a road vehicle. 
 
 Some of the best results obtained, in recent 
 times, of thrust for horse-power applied are: 
 Maxim, nine pounds; Langley, about seven 
 pounds; Spencer (with a Maxim type pro- 
 peller), six pounds; Farman, and other experi- 
 menters in France, six pounds (about). 
 
 It is now a widely recognised fact that the 
 aerial propellers at present in use are lament- 
 ably inefficient. Most aeroplane successes, ex- 
 
io8 THE NEW ART OF FLYING 
 
 cept those of the Wrights, are achieved at an 
 enormous cost; for the propellers waste prob- 
 ably more than half the power applied. 
 
 A propeller of large diameter and slow revo- 
 lution is more efficient than one of small diam- 
 eter and high speed, a circumstance borne out 
 especially in the case of the Wright machine, 
 in which more thrust is obtained per unit of 
 power than in any other type (Fig. 43). 
 
 We are beginning to realise that the abuse 
 lavished on the motor should be bestowed in 
 very large measure on the propeller. The in- 
 ternal-combustion engine fitted to the aero- 
 plane must have all the vital parts cut to the 
 narrowest margin, and must be worked at very 
 nearly break-down rate in order to produce an 
 enormous amount of surplus power wasted by 
 the screw. For this reason all our more serious 
 investigators are carrying out scientific experi- 
 ments to determine propeller efficiency. Per- 
 haps when they have completed their work we 
 may be able to build a propeller which will 
 drive a flying-machine with something like econ- 
 omy of power. 
 
 The construction of the aerial propeller is 
 
THE PROPELLER 109 
 
 the more delicate, because it depends to a large 
 extent upon the peculiarities of the vessel to 
 which it is to be attached. The methods em- 
 ployed in all establishments are the same; yet 
 a Chauviere propeller is very different from a 
 Wright propeller. 
 
 FIG. 42. How the Wright propeller is cut from three 
 planks laid upon one another fan-wise. 
 
 A Wright propeller is made of American 
 spruce and is of very light construction. The 
 extremities of the blades are covered with 
 canvas, which is varnished with the rest, for 
 the purpose of increasing the rigidity of the 
 thin outer ends. The whole propeller is 
 built up of three planks arranged as shown in 
 Fig. 42, so that they overlap like the sticks of 
 a fan, to an extent which diminishes as the dis- 
 
no THE NEW ART OF FLYING 
 
 tance from the hub increases. The superfluous 
 parts of the wood, represented by the darker 
 and triangular areas of the upper diagram in 
 Fig. 42, are then cut away, and the curvature 
 is tested at every point by patterns. 
 
 Chauviere propellers are made of ash, fumed 
 oak, and walnut, and include six or seven over- 
 lapping planks. The finished propeller contains 
 only about eight and one half per cent of the 
 wood of the original planks. 
 
 It should be added that constructors show 
 little disposition to furnish exact details of their 
 methods. Their industry is so new that they 
 jealously guard their secrets, for which reti- 
 cence they cannot be blamed. 
 
 Propellers are also made of metal. In these 
 the blades are soldered or riveted to the arms, 
 which are steel tubes riveted to the hub. The 
 blades are shaped by hammering them upon a 
 form. In some cases they are cast, or twisted 
 into shape, but this construction is not so good. 
 
CHAPTER VIII 
 
 AEROPLANE MOTORS 
 
 MARVEL as we may at the wonderful ingenuity 
 displayed in the modern flying-machine, we have 
 still much to learn from soaring birds. Little 
 as we know of the efficiency of curved surfaces 
 in the air, we know still less how to drive those 
 surfaces without an inordinate expenditure of 
 power, fuel, and lubricant. We have only to 
 compare the amount of energy expended by the 
 great flying creatures of the earth with that 
 expended by our machines to realise how much 
 we have to learn. 
 
 The late Professor Langley long ago pointed 
 out that the greatest flying creature which the 
 earth has ever known was probably the extinct 
 pterodactyl. Its spread of wing was perhaps 
 as much as twenty feet ; its wing surface was in 
 the neighbourhood of twenty-five square feet; 
 its weight was about thirty pounds. Yet this 
 huge creature was driven at an expenditure of 
 energy of probably less than 0.05 horse-power. 
 
ii2 THE NEW ART OF FLYING 
 
 The condor, which is preeminently a soaring 
 bird, has a stretch of wing that varies from nine 
 to ten feet, a supporting area of nearly ten 
 square feet, and a weight of seventeen pounds. 
 Its approximate horse-power has been placed 
 by Professor Langley at scarcely 0.05. The 
 turkey-buzzard, with a stretch of wing of six 
 feet, a supporting area of a little over five 
 square feet, and a weight of five pounds, uses, 
 according to Langley, about 0.015 horse-power. 
 Langley's own successful, small, steam-driven 
 model had a supporting area of fifty-four feet, 
 and a weight of thirty pounds. Yet it required 
 one and a half horse-power to drive it. How 
 much power is required to fly at high speeds in 
 machines may be gathered from the fact that 
 although Bleriot crossed the Channel with a 
 25 horse-power Anzani motor, and the Wright 
 machine uses a 25-30 horse-power motor, aero- 
 planes usually have engines of 50 horse-power 
 and upwards. When we consider that one 
 horse-power is equal to the power of at least 
 ten men, we see that even the smallest power 
 successfully used in an aeroplane represents the 
 combined continuous effort of more than two 
 
AEROPLANE MOTORS 113 
 
 hundred men. To be sure, our flying-machines 
 are very much larger than any flying creature 
 that ever existed; but comparing their weights 
 and supporting surfaces with the corresponding 
 elements of a bird, their relative inefficiency be- 
 comes immediately apparent. Mr. F. W. Lan- 
 chester has expressed the hope that some day 
 we may learn the bird's art of utilising the cur- 
 rents and counter-currents of the air for propul- 
 sion, so that we may ultimately fly without 
 wasting power. 
 
 Aeroplanes are driven by what are known as 
 " explosion engines " or " internal combustion 
 engines." The fuel is not used externally, as 
 in the steam-engine, but is fed to the engine in 
 the form of an explosive gas. The gas is det- 
 onated within the engine to drive a piston. 
 Most of these internal combustion engines oper- 
 ate on what is known as the Otto four cycle. 
 A complete cycle comprises four distinct pe- 
 riods, which are diagrammatically reproduced 
 in the accompanying drawings (Figs. 49, 50, 
 51, and 52). 
 
 During the first period (illustrated in Fig. 
 49) the piston is driven forward, creating a 
 
ii 4 THE NEW ART OF FLYING 
 vacuum in the cylinder and simultaneously draw- 
 ing in a certain quantity of air and gas. During 
 
 FIG. 49- 
 
 FIG. 50. 
 
 FIG. 52. 
 
 FIGS. 49, 50, 51, -and 52. The four periods of a four-cycle 
 engine. During the first period (Fig. 49) the explosive 
 mixture is drawn in; during the second period (Fig. 50) 
 the explosive mixture is compressed; during the third 
 period (Fig. 51) the mixture is exploded; and during 
 the fourth period the products of combustion are dis- 
 charged. 
 
AEROPLANE MOTORS 115 
 
 the second period the piston returns to its initial 
 position; all the admission and exhaust valves 
 are closed; and the mixture of air and gas 
 drawn in during the first period is compressed. 
 The third period is the period of explosion. 
 The piston having reached the end of its return 
 stroke, the compressed mixture is ignited by an 
 electric spark, and the resulting explosion drives 
 the piston forward. During the fourth period 
 the exploded gases are discharged; the piston 
 returns a second time ; the exhaust valve opens ; 
 and the products of combustion are discharged 
 through the opened valve. These various 
 cycles succeed one another, passing through the 
 same phases in the same order. 
 
 The fuel employed in the internal combustion 
 engines of aeroplanes is gasoline, called petrol in 
 England, which is volatilised, so that it is sup- 
 plied to the engine in the form of vapour. In 
 order that it may explode, this vapour is mechan- 
 ically mixed with a certain amount of air. To 
 obtain what is called cyclic regularity and to carry 
 the piston past dead centres, a heavy fly-wheel is 
 employed, the momentum of which is sufficient 
 to keep the piston in motion on the return stroke. 
 
n6 THE NEW ART OF FLYING 
 
 Since considerable heat is developed by the 
 incessant explosions, the cylinders naturally be- 
 come hot. To cool them, water is circulated 
 around them in a " water-jacket," or else a fan 
 is used to blow air against them. 
 
 The memorable experiments of Professor 
 Langley on the Potomac River gave rise to the 
 idea that only an engine of extreme lightness 
 could be employed if the flying-machine was 
 ever to become a reality. Since his time bi- 
 planes have lifted three and four passengers 
 besides the pilot over short distances. While 
 the ultimate achievement of dynamic flight was 
 due to the lightness of the internal combustion 
 motor in relation to the power developed, subse- 
 quent experiment has demonstrated how the 
 efficiency of the sustaining surfaces can be in- 
 creased so as to diminish head resistance and to 
 make extreme lightness in the motor desirable 
 only on the score of freight-carrying capacity. 
 The original motor used by the Wrights was 
 comparatively heavy for the power developed. 
 
 Saving of weight in the motor permits the 
 construction of a more compact and controllable 
 machine than would be possible if the sustain- 
 
Photograph by Edwin Levick 
 
 ^y. Gyrostat mounted in an aeroplane accord- 
 ing to the system of A. J. Roberts. The gyrostat 
 is controlled by a pendulum which swings 
 to the right or to the left, according 
 to the tilt of the aeroplane 
 
AEROPLANE MOTORS 117 
 
 ing surfaces were designed to carry consider- 
 able dead weight. To gain freight-carrying 
 capacity the weight of the motor must be kept 
 low. The fuel needed for a six-hour flight, for 
 example, is equal in load to an engine weighing 
 three pounds per brake horse-power, assuming 
 that the hourly fuel consumption is one half a 
 pound per horse-power. Clearly the motor 
 must be light if the flight is to be long. 
 
 There are various ways of securing lightness 
 in a motor. One way is to increase the power 
 developed by cylinders of a certain size. An- 
 other is to reduce the weight for a given cylin- 
 der capacity by the use of thin steel cylinders 
 and by constructing the parts as lightly as pos- 
 sible. A third way is to arrange the cylinders 
 in such a manner that more than one connect- 
 ing-rod is assigned to each crank with a conse- 
 quent reduction in the weight of the crank- 
 case. A fourth way is to cool the cylinders 
 with air instead of water. 
 
 Many motor builders have abandoned the 
 fly-wheel because it is the heaviest part of the 
 engine. In order that the motor may run 
 steadily without a fly-wheel and may be prop- 
 
n8 THE NEW ART OF FLYING 
 
 erly balanced, it has been necessary to rearrange 
 the cylinders and to increase their number. 
 The whole subject was recently considered by 
 an anonymous writer in Engineering (London) . 
 The following lucid paragraphs on the arrange- 
 
 FIG. 53. The usual arrangement of the four cylinders of 
 a four-cylinder engine. 
 
 ment of cylinders in present aeroplane motors 
 present his views: 
 
 * The weight of an engine consists princi- 
 pally of the cylinders and pistons on the one 
 hand, and the crank, crank shaft, etc., on the 
 other. Roughly speaking, the weight of the 
 cylinders will be proportionate to the cube of 
 the dimensions. That is to say, if the cylinders 
 are arranged vertically in a row, for instance, 
 the weight of the crank case, shaft, etc., will be 
 practically proportionate to the cylinder ca- 
 
AEROPLANE MOTORS 119 
 
 pacity. If we can mount the cylinders in such 
 a manner that we can get a great cylinder ca- 
 pacity with a very short crank case, we shall, 
 however, save weight. If, for instance, we start 
 with the vertical four-cylinder engine of the or- 
 dinary type, as shown in Fig. 53, the crank case 
 has necessarily to be as long as the length over 
 the cylinders. In this and the following figures 
 the valves are omitted for the sake of clearness, 
 and in all the figures the cylinders are the same 
 size, so that the size of crank case necessary for 
 a given cylinder capacity can easily be seen. 
 
 '* Two common plans for reducing the length 
 and weight of the crank case are to place the 
 cylinders either diagonally, as in Figs. 54 and 
 55, or horizontally opposed, as in Fig. 56. In 
 either of these arrangements the length of the 
 crank case, etc., is almost halved, and a consid- 
 erable saving of weight is effected. Any of 
 these arrangements can be made with two, four, 
 six, eight, or more cylinders. In the case of the 
 diagonal engine the impulses are not evenly 
 divided with two or four cylinders, though they 
 can be so with six, if the angle between the cyl- 
 inders be made one hundred and twenty degrees. 
 With eight cylinders at ninety degrees the im- 
 pulses are evenly divided, and this is the most 
 usual number. In this type each diagonal pair 
 of cylinders is connected with one crank. The 
 
120 THE NEW ART OF FLYING 
 
 diagonal engine, with the cranks at ninety de- 
 grees, can be balanced for all practical purposes, 
 even where there are only two cylinders, by 
 placing a balance weight opposite the crank 
 
 FIGS. 54 and 55. Side and plan views of a four-cylinder 
 engine with diagonally-placed cylinders. 
 
 equal to the weight of the whole rotating parts 
 and the reciprocating parts of one cylinder. 
 With four cylinders the cranks are usually 
 placed opposite, but balance weights are still 
 necessary to avoid a rocking moment. With 
 eight cylinders the cranks are set so that the two 
 
AEROPLANE MOTORS 
 
 end ones are opposite the two middle ones, and 
 no balance weights are required. 
 
 " In the case of the opposed horizontal en- 
 gine the two connecting rods work on opposed 
 
 FIG. 56 
 
 FIG. 57. 
 
 FIGS. 56 and 57. Engine with horizontally opposed 
 cylinders. 
 
 cranks, as in Fig. 57. In this case the engine, 
 even the two-cylinder, is in many ways better 
 balanced than the vertical or diagonal types, as 
 the error in balancing, due to the angle of the 
 connecting rods, is allowed for. If only two 
 cylinders are used, there is, however, a very 
 
122 THE NEW ART OF FLYING 
 
 small rocking moment, due to the fact that the 
 cylinders are not actually opposite each other; 
 but this is usually a negligible quantity. . . . 
 With four cylinders the rocking moment is bal- 
 anced. The impulses in the horizontal opposed 
 engine are always evenly divided, whether two, 
 four, or eight cylinders are used. 
 
 " Comparing the horizontal opposed with the 
 diagonal engine, the former appears to have all 
 the advantages, as the impulses are more even 
 with a small number of cylinders, and the bal- 
 ance better. The latter point will enable some- 
 what shorter connecting rods to be used with- 
 out excessive vibration, thus lightening the 
 engine. . . . 
 
 '* While the crank case, etc., is distinctly 
 lightened by these arrangements, it can be still 
 more reduced if the cylinders are all arranged 
 radially on to one crank. This has been done 
 in. a great many different ways by different 
 makers. For comparison, with the previously- 
 mentioned four-cylinder engines, a four-cylinder 
 radial engine is shown in Figs. 58 and 59, the 
 cylinders being the same size as before. It will 
 be seen that in this case the crank case and shaft 
 are very much shorter and lighter than in any of 
 the previous arrangements. In practice four is 
 not a good number of cylinders, as the impulses 
 cannot be evenly divided, and an odd number 
 
AEROPLANE MOTORS 123 
 
 of cylinders must be used to effect this. This 
 type of engine can be satisfactorily balanced as 
 long as the cylinders are evenly spaced round 
 the crank case, for all the pistons are attached 
 
 FIG. 58 
 
 FIGS. 58 and 59. Engine with four cylinders radially 
 arranged. 
 
 to one crank pin, and therefore form one revolv- 
 ing weight, which can be balanced by a suitable 
 balance weight. 
 
 ' When many cylinders are used it is imprac- 
 ticable actually to put all the connecting rods 
 to work onto one crank pin, as either the big 
 
124 THE NEW ART OF FLYING 
 
 ends would have to be very narrow, or the crank 
 pin impracticably long. This can, however, be 
 got over by the arrangement shown in Fig. 60. 
 
 " Probably the greatest difficulty in making 
 the radial engine satisfactory is that of lubrica- 
 
 FIG. 60. Arrangement of connecting-rods of an engine 
 with four radial cylinders. 
 
 tion. This is a matter which does not seem to 
 have had nearly as much attention paid to it as 
 it needs. . . . The even distribution of the oil 
 to the various cylinders of a radial engine is 
 very difficult, and further, however well it might 
 be managed when the engine is running, as soon 
 as it stops the oil runs into the lower cylinders, 
 and probably fouls the plugs, so that it is diffi- 
 
AEROPLANE MOTORS 125 
 
 cult to start it again. In order to get over this, 
 the engine has occasionally been mounted on its 
 side, with the crank shaft vertical, the propeller 
 being driven through bevel gear. If it is desired 
 to run the propeller slower than the engine, there 
 is no great objection to this, and there is little 
 doubt that the slow-running propeller is much 
 the more efficient. Another plan is to mod- 
 ify the arrangement of the cylinders. Thus in 
 
 FIG. 61. Arrangement of cylinders and crank case of one 
 type of three-cylinder engine. 
 
 one make of three-cylinder engine the cylinders 
 are all at the top of the crank case (Fig. 61), 
 all the connecting rods leading to one crank pin. 
 In this case it is impossible to divide the im- 
 pulses evenly, and the balancing is not so good. 
 In practice this type of engine is made with in- 
 side fly-wheels of considerable weight, and runs 
 well, but the fly-wheels necessarily add to the 
 
126 THE NEW ART OF FLYING 
 
 weight. Another plan is to put all the cylinders 
 at the top of the crank case, and to place those 
 which should have been at the bottom in a com- 
 plete radial engine on a crank opposite to the 
 others, as shown in Fig. 62. 
 
 " In some cases the radial engine is made 
 with the crank shaft fixed and the cylinders re- 
 volving. As constructed by the Societe des 
 Moteurs Gnome, this type (Fig. 46) has given 
 very good results, but it may be doubted 
 
 FIG. 62. Disposition of cylinders crank case and connect- 
 ing-rods in one type of engine. 
 
 whether they are due simply to making the cyl- 
 inders revolve. A very small amount of con- 
 sideration will show that the radial engine will 
 be of the same weight whether the cylinders re- 
 volve or the crank shaft, all other details of 
 construction being, of course, assumed to be 
 the same. This being so, the only way in which 
 
AEROPLANE MOTORS 127 
 
 the revolving cylinders can be an advantage is 
 either by obtaining a lighter construction of 
 cylinder or crank case, or else by increasing the 
 power obtained from a given sized cylinder. 
 There does not seem any reason for supposing 
 that revolving the cylinders secures either of 
 these results. 
 
 '* The advantages of the revolving cylinders 
 are : ( i ) That they act as a fly-wheel, and ( 2 ) 
 that they render air-cooling more efficient. 
 Where the propeller is directly coupled, how- 
 ever, no fly-wheel is required in any case. No 
 doubt there is a distinct advantage in the air- 
 cooling from the fact that the cylinders revolve, 
 but it is not likely to be very great. 
 
 " Assuming that the ends of the cylinders are 
 fifteen inches from the crank shaft, and the 
 engine runs at twelve hundred revolutions per 
 minute, the ends of the cylinders move through 
 the air at about ninety-five miles an hour. 
 When the engine with fixed cylinders is placed 
 just behind the propeller, it probably always 
 works in a current of air moving sixty miles an 
 hour or more, so it will be seen that the differ- 
 ence is not so great as might be expected. In 
 practice the power given per cubic inch of cylin- 
 der capacity by the Gnome engine is very small, 
 and there seems no reason to doubt that the 
 same power could be obtained from fixed cylin- 
 
128 THE NEW ART OF FLYING 
 
 ders of smaller size. The good results appear 
 to be due to the fact that the weight of the parts 
 is reduced by machining practically all parts, in- 
 cluding the cylinders and crank case, from steel 
 forgings to such an extent that the engine 
 weighs only 0.35 pounds per cubic inch of cyl- 
 inder capacity. It seems probably that with 
 fixed cylinders at least equally good results 
 could be obtained if the same amount of trouble 
 and money were spent." 
 
 The prime difficulty with the radial rotating 
 engine shown in Fig. 46 is the lubrication, and 
 until some means of reducing the consumption 
 of lubricating oil is devised, the rotating cylin- 
 der motor must have at least that compensat- 
 ing defect. On occasions such as a flight from 
 Chicago to New York for a prize the use of 
 large quantities of lubricating oil may not mat- 
 ter, but in an everyday motor for the aeroplane 
 in the hands of the " chauffeur," or whatever 
 his aerial equivalent may be called, the lubri- 
 cation must be relied upon more than in the 
 motor car; for while failure in the one case 
 means only inconvenience, in the other it may 
 entail disaster. 
 
AEROPLANE MOTORS 129 
 
 The horse-power required for flight varies to 
 a certain extent as the speed. Hence the factor 
 that governs the maximum velocity of flight is 
 the horse-power that can be developed on a 
 given weight. At present the weight per horse- 
 power of featherweight motors appears to range 
 from two and one quarter up to seven pounds 
 per brake horse-power. A few actual figures 
 are given in the following list : 
 
 Antoinette 5 Ibs. per brake horse-power. 
 
 Fiat 3 " " 
 
 Gnome under 3 Ibs. 
 
 Metallurgic 8 Ibs. 
 
 Renault 7 " 
 
 Wright 6 " 
 
 Automobile engines, on the other hand, com- 
 monly weigh 12 pounds to 13 pounds to the 
 brake horse-power. 
 
 Because lightness and durability are oppo- 
 site qualities, and because the more trustworthy 
 a machine must be, the heavier must be its con- 
 struction, it may well be inferred that the aero- 
 plane motor is not a model either of durability 
 or trustworthiness. The aeroplane builder ap- 
 
130 THE NEW ART OF FLYING 
 
 pears, at present, willing to tolerate very little 
 reliability, largely because the aeroplane is still 
 in the hands of record-breakers and prize- 
 winners, rather than of ordinary tourists. In 
 making records the start takes place when the 
 motor is ready. In a race it takes place at some 
 determinate time, and if the motor be not ready, 
 then the chance is lost. The record is also the 
 result of frequent trials; a race is gained or 
 lost in one. Thus, if one motor will make an 
 aeroplane fly fifty miles whenever required and 
 without unreasonable tuning up, but another 
 makes it fly one hundred miles once out of ten 
 attempts, the latter takes the record, though on 
 its nine failures it may have broken down in a 
 few miles, and may have required hours tuning 
 up for each trial. If, however, the aeroplane 
 is ever to be of the slightest practical use, the 
 reliability of the engine must not only be 
 brought up to that of the racing machine, but 
 very much beyond it. This lack of reliability 
 was strikingly evinced in the famous Circuit 
 de I'Est of 1910, a circular cross-country race 
 which started from Paris and finished there, and 
 which included the towns of Troyes, Mezieres, 
 
AEROPLANE MOTORS 131 
 
 Douai, and Amiens. The contest was remark- 
 able because the airmen were expected to per- 
 form what they had never attempted before. 
 They had to fly over a given course on specified 
 days without being able to choose weather con- 
 ditions most favourable to them. Eight ma- 
 chines started from Paris, but after the second 
 day the only competitors left were Leblanc and 
 Aubrun on their Bleriot monoplanes. The fail- 
 ures of the others were due solely to engine 
 troubles. 
 
 A resume of aeroplane motors compiled by 
 Warren H. Miller is appended below in the 
 concise form of a table of comparative costs 
 and weights per horse-power based on the fifty 
 horse-power size. It will be noticed that the 
 Clement-Bayard is by far the heaviest, in spite 
 of using aluminium for the case, thus adding to 
 the already large amount of proof that for equal 
 strength steel is always lighter than aluminium. 
 The table also brings out the increased cost ne- 
 cessitated by multiplication of cylinders, to ob- 
 tain increased horse-powers at light weights. 
 The Anzani, with only three cylinders, is by far 
 the cheapest, but its weight is about midway be- 
 
i 3 2 THE NEW ART OF FLYING 
 
 tween the Clement and the Gnome, the lightest 
 of them all. 
 
 TABLE OF FRENCH AVIATION MOTORS 
 
 Make H. P. Weight per h. p. Cost per h. p. Speed. 
 
 Antoinette ... 50 3 -84 Ibs. $48.00 ,200 
 
 Anzani 50 4.6 Ibs. 20.00 ,400 
 
 Gnome 50 3-3<5 Ibs. 52.00 ,200 
 
 E. N. V 40 3-85 Ibs. 37.50 ,500 
 
 Clement-Bayard 40 6.05 Ibs. 47.50 ,500 
 
 R. E. P 40 3.96 Ibs. 70.00 ,500 
 
 Wright 25 7-2 Ibs. 
 
CHAPTER IX 
 
 THE NEW SCIENCE OF THE AIR 
 
 So far as the earth is concerned, the sun is very 
 much in the position of a man who practically 
 utilises only a single cent out of a fortune of 
 $22,000,000 and throws the rest away; for only 
 1/2,200,000,000 of the sun's heat ever reaches 
 us. That pittance must be conserved, for which 
 reason the earth is wrapped in a wonderful, 
 transparent, and invisible garment which we call 
 the air and which serves the very utilitarian pur- 
 pose of keeping the world warm. Of the thick- 
 ness of that wrapping we know but little. Per- 
 haps it may extend outward from the earth for 
 a distance of two or three hundred miles if we 
 may judge from observations of meteor trains 
 and auroras. Some idea of its depth may be 
 gained by stating that if this planet were a 
 globe only six feet in diameter, the air would be 
 not much more than two inches thick. The tex- 
 ture of this gaseous garment and its peculiar 
 relation to the sun have but recently been made 
 
134 THE NEW ART OF FLYING 
 the subject of rigorous investigation; for only 
 in our own day has it been perceived that the 
 vagaries of the weather may thus be satisfac- 
 torily explained and a system of weather fore- 
 casting devised more far-reaching and accurate 
 than that which at present serves us. 
 
 One step in this investigation is the study of 
 the physical attributes with which the air is en- 
 dowed. The air has a weight which fluctuates 
 from day to day and from hour to hour. It is 
 sometimes warm and sometimes cold, sometimes 
 moist and sometimes dry, sometimes calm and 
 sometimes turbulent. All this our senses taught 
 us long ago. But so crude are our senses that 
 they can never tell us exactly how much it weighs 
 at a given moment, how wet it is, how fast it 
 moves, and how warm or cold it is. The physi- 
 cist has, therefore, been constrained to devise 
 subtler senses. He has given us a remarkable 
 balance which is known to every one as a barom- 
 eter and which weighs the air to a nicety; a del- 
 icate measurer of moisture, which he calls a 
 hygrometer ; a motion or wind recorder, known 
 as an anemometer; and a heat-measurer in the 
 form of the familiar thermometer. These re- 
 
THE NEW SCIENCE OF THE AIR 135 
 
 sponsive artificial senses have been used on the 
 surface of the earth for many years, and by 
 their means are gathered the main facts upon 
 the basis of which the weather bureaus at 
 home and abroad venture to predict the mor- 
 row's weather. 
 
 Because we have learned practically all there 
 is to learn of the lower air and because weather 
 forecasters have in the past ignored the upper 
 levels of the air, levels which unquestionably 
 have their influence on the weather, it was felt 
 that some effort must be made to measure the 
 thickness of the earth's invisible wrapping and 
 to determine the weight, temperature, velocity, 
 and moisture of the air miles above us. 
 
 In order to accomplish this task it was essen- 
 tial to invent an artificial arm which would 
 grasp the sensitive barometer, thermometer, 
 hygrometer, and anemometer devised by the 
 physicist and hold them for us in the upper 
 reaches of the air. The problem of providing 
 such an arm was not easily solved. In fact, it 
 is not completely solved even now, for which 
 reason the hand of science has not yet suc- 
 ceeded in touching the uppermost layer of air 
 
136 THE NEW ART OF FLYING 
 
 the hem of the earth's mysterious robe. 
 Meteorological observations with manned bal- 
 loons have been made sporadically for much 
 more than a century. An ascent was made by 
 Jeffries, at London, in 1784, with a remarkably 
 complete equipment of meteorological appara- 
 tus. Hardly a year passes but that experiment 
 is repeated. Because a human being cannot 
 breathe the tenuous air of great altitudes and 
 live, the experiment has sometimes proved 
 fatal. To overcome the difficulty, the meteor- 
 ologist has torn a leaf from the book of the 
 marine biologist, who plumbs the deep sea with 
 scientific instruments and brings to the surface 
 living facts for subsequent study. The meteor- 
 ologist, accordingly, now sounds the air, as if it 
 were a great invisible ocean at the bottom of 
 which we live. 
 
 The artificial arm that reaches upward has 
 assumed the form either of a kite or of a small 
 unmanned balloon, and thus it has become pos- 
 sible to elevate to great heights the mechanical 
 senses that weigh the air, feel its moisture and 
 its heat, and note its motion. The men to 
 whom most of the credit is due for all that has 
 
S 
 
 gas 
 
 o c \C 
 
 * 8 
 
 II 
 
 ^ 8 
 
 I h & 
 
 a ^ ^> 
 
 Si's 
 
 sii 
 
 C c3 
 
 o wu 
 
 ^ Q 
 
 fcJC 
 
THE NEW SCIENCE OF THE AIR 137 
 
 been gleaned in the last few years are Teis- 
 serenc de Bort, of France, Prof. A. Lawrence 
 Rotch, of the United States, and Dr. Richard 
 Assmann, of Germany. 
 
 During the past decade the work has been 
 taken up by the official meteorological services 
 of the world, and is now carried on systemati- 
 cally under the direction of an international 
 commission, appointed by the International 
 Meteorological Committee. This commission 
 has a permanent office at Strassburg, and holds 
 triennial meetings in different cities, in which 
 meteorologists from all civilised countries par- 
 ticipate. The next meeting will take place at 
 Vienna, in 1912. 
 
 In the United States, in addition to the ad- 
 mirable work done at Blue Hill, by Professor 
 Rotch and his staff, regular observations of the 
 upper air are carried on by the Weather Bureau 
 at the Mt. Weather Observatory, near Blue- 
 mont, Va., and the data obtained are tele- 
 graphed daily to Washington, for the informa- 
 tion of the official weather-forecasters. 
 
 In Europe there are now several institutions 
 devoted entirely to this branch of investiga- 
 
138 THE NEW ART OF FLYING 
 
 tions. The most elaborate of these is the Royal 
 Prussian Aeronautical Observatory at Linden- 
 berg, not far from Berlin, and Germany has ob- 
 servatories of similar character, on a somewhat 
 smaller scale, at Hamburg, Aachen, Friedrichs- 
 hafen, and elsewhere. The observatory at 
 Friedrichshafen is unique in possessing a small 
 steamboat which plies the waters of Lake Con- 
 stance and is especially equipped for sending up 
 kites and balloons. Other " aerological obser- 
 vatories, " as the institutions of this character are 
 now called, are situated at Trappes, near Paris ; 
 Pavia, Italy; and Pavlovsk, Russia; while in 
 the British Isles the chief centre for aerological 
 observations is the Glossop Moor Observatory, 
 near Manchester. Similar observatories exist 
 in subtropical regions, in Egypt and India. A 
 very important station is located on the peak 
 of Teneriffe, in the Canary Islands. In the 
 southern hemisphere upper-air researches are 
 now regularly carried on at two places, viz., 
 in Samoa; and at Cordoba, in the Argentine 
 Republic. In addition to these fixed observa- 
 tories, mention should be made of the aero- 
 logical work now frequently carried out by ex- 
 
THE NEW SCIENCE OF THE AIR 139 
 
 ploring expeditions, especially in the polar 
 regions. 
 
 The scientific projection of the human mind 
 to the upper atmosphere was not achieved 
 merely by the invention of instruments and 
 means for elevating them. Our eyes could not 
 read the instruments when they were suspended 
 in the air, and so it became necessary to make 
 the artificial senses self-recording. Ingenious 
 scientific artisans have provided the barometer, 
 thermometer, hygrometer, and wing-gauge with 
 clock-driven fingers that write a continuous, 
 colourlessly impersonal, and therefore unbiassed 
 story of atmospheric happenings at great 
 heights, a story which, to those who are 
 versed in the hieroglyphic script in which it is 
 written, gives a coherent account of the condi- 
 tions that prevail at various elevations. The 
 unselfish inventive genius which has been dis- 
 played in devising these self-recording instru- 
 ments would have been richly rewarded had it 
 been applied to the needs of every-day life. 
 
 The lifting power of kites and balloons is 
 limited, for which reason the instruments are 
 made of feathery lightness and are ingeniously 
 
i 4 o THE NEW ART OF FLYING 
 
 combined. The combination is generically 
 known as a " meteorograph." Thus the ther- 
 mometer and barometer are merged into a 
 meteorograph specifically known as a " baro- 
 thermograph," a contrivance which is provided 
 with two automatic hands, one of which writes 
 down the weight (pressure) of the air and the 
 other its temperature. Sometimes the barom- 
 eter, thermometer, and hygrometer are joined 
 in a single instrument, which notes the humidity 
 as well as the pressure and temperature. When 
 the instruments return to the ground, their 
 records inform the meteorologist of the height 
 of the kite or balloon at any given minute 
 during its ascent and of the temperature and 
 barometric pressure at that particular minute. 
 Because no ink has been found which will not 
 freeze in the bitter cold of the upper air, the 
 writing fingers of these instruments trace their 
 story on smoked cylinders. At lower levels 
 special inks and paper can be employed. Sam- 
 ples of air have been collected by Teisserenc de 
 Bort at heights which no human being can ever 
 hope to reach, by devices that operate as if they 
 were endowed with brains. To explain this 
 
t- a 
 
 " s 
 
 o *n 
 
 f. T3 
 
 2 2 
 
 bo - 
 o QJ 
 
 "O Tl 
 
 1> Pi 
 
 D. O 
 O *H 
 
 I * 
 
 O "S 
 
 B ^^ 
 
 B s ii 
 
 > 
 
 r w 6 
 
 u !^ 
 
 U en j 
 
 C S ^ 
 
 E.o a 
 
 oi .a 
 
 *c ^3 
 
 > <u 
 
THE NEW SCIENCE OF THE AIR 141 
 
 remarkable feat, it may be stated that at a pre- 
 determined altitude the barometer was made 
 to complete an electric circuit (just as we push 
 a bell-button), whereupon a little hammer fell 
 and broke a closed, exhausted glass tube. Air 
 rushed into the tube, and the glass was there- 
 upon automatically sealed by a current which 
 heated a platinum wire coiled around the broken 
 end of the tube, thereby fusing the glass. 
 
 These are but a few of a long list of scien- 
 tific inventions which might be cited and of 
 which the world hears nothing. Meteorology 
 has more than one unheralded Edison and 
 Tesla, men who labour year after year in scien- 
 tific obscurity, and who deem themselves richly 
 rewarded if their instruments aid in the dis- 
 covery of some new atmospheric phenomenon 
 which may illumine the very dark subject of 
 meteorology. 
 
 The elevation of these instruments by kites 
 has probably been carried to the greatest per- 
 fection by Prof. A. Lawrence Rotch, of the Blue 
 Hill Meteorological Observatory at Hyde Park, 
 Massachusetts. His exploration of the lower 
 four miles of air is the most complete that has 
 
I 4 2 THE NEW ART OF FLYING 
 
 yet been made. The kites employed by him, 
 and, for that matter, by most air explorers, are 
 of the open box type, which every boy now 
 flies in preference to the old-fashioned single- 
 surface contrivance distinguished by its long tail 
 of rags knotted together. For meteorological 
 purposes, however, the box kite assumes dimen- 
 sions that utterly dwarf its toy prototype. Some 
 of the Blue Hill kites measure nine feet in 
 length. Despite the great lifting capacity im- 
 parted by its expansive surface, an air-exploring 
 kite could not attain a considerable height 
 if it were held only by hemp. A cord or 
 rope would necessarily be so heavy and thick 
 that a kite would be severely taxed in pulling it 
 up. Hence it is the practice to employ fine 
 piano-wire, which is both strong and light. 
 
 So powerful is the pull of a large kite that 
 human muscles are hardly able to cope with it. 
 An engine-driven winch is therefore utilised to 
 haul in the long line. Devices are employed 
 to register the pull of the kite and the length 
 of the wire in use. Often it happens that as 
 much as ten miles of line may be paid out. 
 The elevation of the kite is determined in clear 
 
THE NEW SCIENCE OF THE AIR 143 
 
 weather from data obtained by means of special 
 optical instruments (theodolites) placed on the 
 ground. At night and in hazy weather the 
 meteorograph readings themselves must be 
 depended upon. 
 
 Four miles may be considered the maximum 
 height that a kite is capable of attaining. To 
 explore the air above that limit and above the 
 six miles that mark the end of human endurance 
 in manned balloons, the " sounding-balloon " 
 is employed, of which the most skilful use has 
 been made by Teisserenc de Bort and by Dr. 
 Richard Assmann. 
 
 The balloons are filled with hydrogen gas, 
 which expands with increasing elevation. The 
 degree of inflation therefore depends upon the 
 height to be attained. Thus, if the balloon is 
 to reach a point where the air is one half as 
 dense as it is at the level of the sea, the gas- 
 bag is half filled. If at the objective point the 
 density of the air is one fourth the density at 
 the level of the sea, the bag is filled only one 
 fourth. Obviously, if very great heights are 
 to be attained, heights where the air is exceed- 
 ingly rare and thin, the balloon's capacity must 
 
i 4 4 THE NEW ART OF FLYING 
 
 be great and the construction wonderfully light. 
 Paper balloons were, therefore, adopted by 
 Teisserenc de Bort. Latterly, however, Ass- 
 mann's India-rubber balloons, varying in diam- 
 eter from three to five feet, have come into use, 
 because they reach greater heights. At the 
 maximum elevation of the balloon the expansion 
 of the hydrogen gas is so powerful that the 
 balloon bursts. Retarded in their fall by a para- 
 chute, the instruments glide gently down to the 
 ground. Instead of a parachute a slightly 
 inflated auxiliary balloon may be employed 
 which does not explode, and which has sufficient 
 buoyancy to prevent a too rapid descent of the 
 instruments and to indicate the position of the 
 basket in a thicket or at sea. To the basket 
 in which the instruments are contained a printed 
 notice is attached which offers a reward for 
 their return. More than ninety-five per cent of 
 the sounding-balloons liberated find their way 
 back to the observatories. Indeed, the zeal 
 of the finder is sometimes such that he even 
 takes the trouble to polish the smoked cylinder 
 on which the records are traced. 
 
 Sounding-balloons reach astonishing eleva- 
 
THE NEW SCIENCE OF THE AIR 145 
 
 tions and generally travel at railroad speed. 
 Often they rise to heights of over fifteen miles 
 
 PROVISIONAL SELECTION OF DATES FOR INTERNATIONAL 
 AEROLOGICAL OBSERVATIONS 
 
 (From "Wiener Luftschiffer Zeitung" Dec. I, 1909, with correc- 
 tions subsequently announced by the International Commission 
 for Scientific Aeronautics) 
 
 1910 
 
 1911 
 
 1912 
 
 1913 
 
 January 
 
 February 
 
 March 
 
 April 
 
 May 
 
 June 
 
 July 
 
 August 
 
 September 
 
 October 
 
 November 
 
 December 
 
 6 
 
 2-4 
 3 
 
 H 
 11-13 
 
 2 
 
 7 
 8-13 
 
 i 
 
 6 
 2-4 
 
 i 
 
 May 3i-June 2 
 
 6 
 
 3 
 4-9 
 
 5 
 
 9 
 6-8 
 
 3-S 
 i 
 
 7 
 11-13 
 
 2 
 
 6 
 
 1-6 
 i 
 
 5 
 2-4 
 
 7 
 5 
 
 6 
 
 4 
 5-io 
 
 5 
 
 Is 
 
 4 
 
 2 
 
 5-7 
 4 
 
 In general, observations are made on the first Thursday 
 of each month. Once a year observations on an especially 
 extensive scale are made during six successive days; this 
 is the so-called "International Week" and is the occasion 
 of special aerological expeditions, in which the naval ves- 
 sels of many countries participate. The month in which 
 the International Week occurs varies from year to year. 
 Shorter series of observations, covering three days, are 
 made during other months as shown in this table. 
 
 The results of the international observations are col- 
 lected and published by the International Commission for 
 Scientific Aeronautics, which has its headquarters at Strass- 
 burg. 
 
 and cover distances of seven and eight hundred 
 miles at the rate of forty to eighty miles an 
 
i 4 6 THE NEW ART OF FLYING 
 
 hour. A paper balloon will reach its greatest 
 height in about six hours; a rubber balloon, 
 in three hours. 
 
 Ascents with kites and sounding-balloons are 
 regularly made on agreed dates by the air- 
 exploring stations of the entire world. The 
 dates noted in the table on page 145 were 
 chosen for kite and balloon ascents for the 
 years 1910 to 1913, inclusive. 
 
 As a result of many hundred flights made 
 by kites and sounding-balloons by day and by 
 night, in fair weather and foul, in spring and 
 summer, in autumn and winter, over land and 
 sea, in the tropics and within the arctic circle, 
 we know that even in midsummer we live in a 
 comparatively thin stratum of warm air. We 
 know, too, that if we could transport ourselves 
 to a height of ten miles and live in the bitter 
 cold, thin air which would there surround us, 
 we should find the aspect of the heavens won- 
 derfully changed. The sky would no longer 
 appear azure and suffused with light. By day as 
 well as by night it would appear strangely black. 
 Like brilliant points pricked in a sable canopy, 
 the stars would shine both at noon and at mid- 
 
THE NEW SCIENCE OF THE AIR 147 
 
 night. They would shine, moreover, not with 
 the scintillation to which we are accustomed but 
 with relentless steadiness. The sun would blaze 
 
 KV. 
 
 FIG. 68. The extent of the atmosphere in a vertical 
 direction. Heights in kilometres. 
 
 so fiercely in that cloudless sky of jet that the 
 human skin would blister under its rays. So 
 tenuous would be the air that it could not propa- 
 
1 48 THE NEW ART OF FLYING 
 
 gate sound. I could not call to my friend and 
 be heard, even though my hand touched his. 
 
 Much of this might have been guessed with- 
 out the aid of the elaborate machinery that has 
 been invented to explore the air. Much, how- 
 ever, has been discovered that was undreamed 
 of in our meteorology, among other things, 
 that the air is stratified above us in three more 
 or less distinct layers. 
 
 The lowermost of these layers, the layer in 
 which we live and which extends upward for 
 about two miles from the surface of the earth, 
 is a region of turmoil, warm to-day and cold 
 to-morrow. This is the region of whimsical 
 winds, of cyclones and anti-cyclones, of cool 
 descending currents and warm ascending cur- 
 rents. All our weather forecasting is at present 
 based upon what can be learned from the gen- 
 eral circulation of the air in this lowermost 
 layer, the layer in which men navigate the air. 
 
 Beginning at the two-mile level that marks 
 the end of the lowermost layer and extending 
 upward for a distance of some five miles, we 
 find a second stratum of air, a stratum less 
 capricious, and one in which the air grows 
 
a a ,_ 
 
 *fe ^ <U 
 
 ' ' O *"5 
 
 - 1 s 
 a* s. 
 
 V S c 
 
 c p o 
 
 1> O '^J 
 
 I -I 
 
 rt ls 
 
 M & 
 
 c ^ o 
 
 II: 
 jj 
 
 f 
 
 o . "o 
 
 ifl 
 
 M 
 < 
 
 'bio 
 
THE NEW SCIENCE OF THE AIR 149 
 
 steadily colder and drier with increasing height. 
 The lowest temperature thus far recorded is 
 152 below the Fahrenheit freezing point. 
 Whatever thermal irregularities there may be 
 are caused by wide temperature changes on the 
 surface of the earth and by the reflection of 
 solar heat by the clouds. Here the air moves 
 in great planetary swirls, produced by the spin- 
 ning of the earth on its axis, so that the wind 
 always blows in the same eastward direction. 
 The greater the height the more furious is the 
 blast of this relentless gale. 
 
 Last of all comes a layer which was dis- 
 covered by Teisserenc de Bort and Dr. Richard 
 Assmann almost simultaneously, and which is 
 generally called the " isothermal stratum " be- 
 cause the temperature varies but little with alti- 
 tude. The lower part of the isothermal layer 
 shows a slight increase in temperature with 
 increasing height. Hence this part of the iso- 
 thermal layer is sometimes referred to as the 
 " inversion layer," or region of the upper 
 inversion. 
 
 Above the inversion layer the vertical tem- 
 perature gradient is practically zero ; i. e., there 
 
150 THE NEW ART OF FLYING 
 
 is little or no change of temperature with alti- 
 tude. Teisserenc de Bort now calls the isother- 
 mal layer " stratosphere," and the use of this 
 latter name is increasing. 
 
 Although the air is warmer than in the layer 
 immediately below, the temperature lies far 
 below the Fahrenheit zero and may be placed 
 somewhere near 100 below the Fahrenheit 
 freezing point in middle latitudes. Here we 
 have a region of meteorological anomalies 
 which have not yet been satisfactorily explained. 
 In passing from the second to the isothermal 
 layer, the wild blasts of wind are stilled to a 
 breeze, the velocity decreasing from twenty- 
 five to eighty per cent. The air no longer 
 whirls in a planetary circle. Indeed, the wind 
 may blow in a direction quite different from 
 that in the second layer. Whatever may be 
 the moisture of the air below, it is always exces- 
 sively dry in the permanent inversion layer. 
 Just where this isothermal layer begins depends 
 on the season, the latitude, the barometric pres- 
 sure, and perhaps on other factors still unknown. 
 Just where it ends no one knows; for although 
 sounding balloons have risen to heights of over 
 
THE NEW SCIENCE OF THE AIR 151 
 
 eighteen miles, its upper limit has not yet been 
 discovered. In summer time the isothermal 
 layer over middle latitudes begins at a height 
 of about seven miles above the earth. We know 
 that the higher it lies the colder it is, that the 
 lower it lies the warmer it is. We know, too, 
 that there is no bodily shifting up and down of 
 warm and cold masses of air in that mysterious 
 region. The result is that a current ascending 
 from the lower level spreads out when it en- 
 counters the " permanent-inversion " layer as if 
 a solid barrier had been interposed. 
 
 Up to the height of the " permanent-inver- 
 sion " layer the temperature falls at a rate 
 which increases somewhat with altitude, but 
 which may be placed roughly at rather over 
 y 2 C. per hundred metres (say i F. per three 
 hundred to four hundred feet), so that on a 
 hot summer's day with a temperature of 90 
 Fahrenheit at the earth's surface, a man could 
 place himself in fairly cool surroundings if he 
 could rise only fifteen hundred feet. Because 
 of the constant upheavals to which the air is 
 subject in its lower levels, this average rate of 
 temperature reduction, as we ascend, is not 
 
i S 2 THE NEW ART OF FLYING 
 
 often observed. It may even happen that for 
 a short distance the thermometer may rise 
 and not fall at all. Ultimately, the tempera- 
 ture drops at a uniform rate until it reaches a 
 point lower than that reported by any North- 
 pole explorer. 
 
 To these fluctuating temperatures in the 
 lowermost layer clouds and rain are due. Warm 
 air tends to rise and to cool as it rises. The 
 cooling air in turn condenses its water vapor 
 into clouds. This process, as well as others that 
 need not be considered here, leads ultimately 
 to the precipitation of the condensed water of 
 atmosphere, as rain, snow, or hail. 
 
 The three layers of air which have been dis- 
 closed to us by the sensitive instruments of 
 modern meteorology intermingle but slightly. 
 The one floats upon the other as oil floats upon 
 water. Of the great ocean of air at the bottom 
 of which we move and live, three fourths by 
 mass lie below the isothermal layer. All our 
 storms, our clouds, and all dust, except such as 
 may be of volcanic or cosmical origin, are phe- 
 nomena of the lower two layers. 
 
 When the meteorologist has fully discovered 
 
Photograph by Edwin Levick 
 
 Fig. 47. The motor and the propeller of a R. E. P. 
 
 (Robert Esnault-Pelterie) monoplane. Robert 
 
 Esnalt-Pelterie has abandoned this four- 
 
 bladed metal propeller for the more 
 
 efficient two-bladed wooden propeller 
 
THE NEW SCIENCE OF THE AIR 153 
 
 the influence which the upper region exerts upon 
 the lower, there is reason to hope that he will 
 be able to foretell the weather not merely a 
 day but perhaps a week or more in advance, 
 and to prepare charts which will be as useful to 
 the aviator as the charts which warn the mariner 
 of shoals and reefs. 
 
 The currents in the various levels of the 
 atmosphere are of as much importance to the 
 aviator as are the ocean currents to the mariner. 
 Hence the necessity of charting the sea of air 
 with scientific care, and hence the value of the 
 work here outlined. The International Commis- 
 sion for Scientific Aeronautics has already accu- 
 mulated sufficient data to chart aerial routes, 
 comparable with the ocean routes laid down 
 by the various hydrographic officers of the 
 world. Every government will have a special 
 branch of research and will distribute infor- 
 mation for aeronauts. The daily weather 
 reports will be amplified to suit the flying man. 
 
 Thus far more interest has been shown in 
 Europe than in this country in this matter of 
 vital importance to the aeronaut. A detailed 
 analysis of the wind data available for the 
 
154 THE NEW ART OF FLYING 
 
 German Empire was undertaken by Dr. Richard 
 Assmann at the instance of the " Motorluftschiff- 
 Studiengesellschaft," founded by the Kaiser. 
 That society, whose name translated into Eng- 
 lish reads u Society for the Study of Motor 
 Airships," recently published the results of Ass- 
 mann. The Italian Aeronautical Society has 
 performed a similar service for Italy. Such 
 data will be useful to the aeronaut in selecting 
 sites for practising grounds or for aerial har- 
 bours, or in choosing the seasons most appro- 
 priate for experiment. 
 
 Dr. Richard Assmann, director of the Royal 
 Prussian Aeronautical Observatory of Linden- 
 berg, in an article entitled " The Dangers of 
 Aerial Navigation and the Means of Diminish- 
 ing Them," contributed to the Deutsche Zeit- 
 schrift fur Luftschifahrt, describes the aeronau- 
 tical weather service that he is organising, and 
 of which Lindenberg Observatory is to be the 
 centre. According to Dr. Assmann at least 
 three similar tentative schemes have already 
 been put into execution in the German Empire. 
 The first was undertaken by the Lindenberg 
 Observatory in 1907, during trial trips made 
 
THE NEW SCIENCE OF THE AIR 155 
 
 by the " Parseval " airship. Observations of 
 the upper air currents were made simultaneously 
 at five stations by means of pilot balloons and 
 communicated to the crew of the airship, who 
 were thus materially aided in guiding their 
 craft. The second similar undertaking was 
 Dr. Linke's special weather service for aero- 
 nauts, conducted at the Frankfort Aeronautical 
 Exposition of 1910. The third aeronautical 
 service was organised by Dr. Polis, at Aachen. 
 It is still in existence, and is intended especially 
 for the benefit of the aero clubs of the Rhein- 
 land. Its usefulness was demonstrated during 
 the army manoeuvres in West Prussia in 1910. 
 
 Next to the United States, Germany has 
 probably the best organised weather service in 
 the world. It is therefore not astonishing that 
 Germany should be better prepared than any 
 other European state for the adaptation of 
 modern meteorological science to the needs of 
 the airman. Lindenberg Observatory is now 
 equipping the Public Weather Service stations 
 with the apparatus needed for daily observa- 
 tions of the upper air, not primarily for the 
 purpose of improving the weather forecasts, 
 
1 56 THE NEW ART OF FLYING 
 
 but in order to lessen the dangers of aerial 
 navigation, dangers, in Assmann's opinion, 
 largely avoidable and to which the loss of 
 twenty valuable lives in Germany during 1910 
 may be attributed. At the present time the 
 navigator of the air launches his craft with 
 no more knowledge of the meteorological con- 
 ditions in the upper air than can be surmised 
 from those depicted in the ground-service 
 weather map. The day is not far distant when 
 he will have a weather map all his own. 
 
 In Dr. Assmann's plan, a number of the 
 Public Weather Service stations are to be fur- 
 nished by the Lindenberg Observatory with a 
 theodolite, an inflating-balance for determining 
 the ascensional force of the balloons, a sufficient 
 number of balloons, and the necessary graphic 
 tables for rapidly working up the observations. 
 
 At 8 A. M. every day, assuming the weather 
 is favourable, the stations will be expected to 
 send up a pilot balloon and to trace its course 
 with the theodolite as long as possible. The 
 observation will then be worked up a matter 
 of barely a quarter of an hour for a practised 
 observer and telegraphed to Lindenberg. 
 
Photograph by Edwin Levick 
 
 Fig. 48. Henry Farman seated in his biplane with 
 three passengers 
 
THE NEW SCIENCE OF THE AIR 157 
 
 Here the observations received from all other 
 stations will be assembled and re-distributed in 
 a single telegram sent to each of the cooperat- 
 ing stations. If they arrive in time, the tele- 
 grams can be utilised in connection with the 
 ordinary daily weather forecast, as well as for 
 the preparation of special forecasts and warn- 
 ings for airmen. At Lindenberg the regular 
 observation with a kite or capture balloon is 
 made daily at 8 A. M., and in summer an ob- 
 servation is also made about 5 or 6 A. M. 
 Assmann also proposes to conduct daily ob- 
 servations at Lindenberg with a pilot balloon 
 at ii A. M., and, whenever necessary, another 
 about 2 p. M., so that soundings of the air to 
 an altitude of several miles will be made three 
 or four times a day within a period of six to 
 nine hours. Thus valuable information will be 
 gathered which ought to enable the weather 
 forecaster to warn airmen of impending changes 
 in the lower atmosphere, on the basis of act- 
 ually occurring rapid changes in the upper 
 atmosphere. 
 
 That the German Public Weather Service 
 stations will ultimately be supplemented with 
 
158 THE NEW ART OF FLYING 
 
 stations especially erected for the purpose at 
 the larger aviation fields and the like, would 
 seem to follow from the work now done 
 at the experimental observatory at Bitterfeld, 
 from the erection of the aeronautical observa- 
 tory on the Inselberg, near Gotha, from the 
 probability of the erection of the long-promised 
 aerological station at Taunus, and lastly, from 
 the contemplated installation of aerological 
 stations at nautical schools on the coast. 
 
 The difficulty of following pilot ballqons in 
 hazy weather and at dusk leads Assmann to 
 propose the utilisation of balloons of two sizes, 
 the smaller and cheaper to be used when it is 
 evident that the state of the sky will not per- 
 mit the balloon to be followed with the the- 
 odolite to a great distance. Observations at 
 night could be made by illuminated balloons, 
 but at considerable expense. 
 
 Undoubtedly there will be many days on 
 which few, if any, observations can be secured 
 with pilot balloons, so that only the observa- 
 tions made at stations equipped with captive 
 balloons and kites will be available. In order 
 to meet this serious difficulty, Assmann is con- 
 
THE NEW SCIENCE OF THE AIR 159 
 
 sidering the plan of supplying a few selected 
 stations with a central and easily manageable 
 kite outfit. 
 
 Thus far the plan outlined by Dr. Assmann 
 has been approved only for a limited part of 
 the Empire. Political heterogeneity still ham- 
 pers imperial undertakings in Germany. Ulti- 
 mately, however, the field of observations 
 will be extended to include the south German 
 states, where some very important stations are 
 located, chief among which is the admirably 
 equipped station at Friedrichshafen on Lake 
 Constance. 
 
 Assmann himself realises that his plan can- 
 not hope to provide detailed information and 
 forecasts of local conditions except in so far 
 as may be inferred from the general outlook. 
 Some experiments which were recently made 
 in Germany, after the appearance of Dr. Ass- 
 mann's article, show that it is feasible to secure 
 a corps of special thunderstorm observers who 
 can report by telegraph and telephone, and who 
 are numerous enough to enable the weather 
 forecaster to follow the progress of sudden 
 atmospheric disturbances across the country, 
 
i6o THE NEW ART OF FLYING 
 
 and to give timely warning to the aeronaut to 
 avoid them. 
 
 Apart from enlightening the aeronaut on the 
 condition of the atmosphere, it will be obviously 
 necessary to provide the equivalent of automo- 
 bile road maps, something that will tell the 
 man of the air where he is. It is very difficult 
 to recognise even familiar country from above. 
 During his flight down the Hudson River, Cur- 
 tiss decided to alight on what looked to him 
 like a fine green field. Swooping down, he 
 found that his green field was a terrace, an un- 
 avoidable error in judgment which might have 
 cut short his triumphal flight. With a map on a 
 scale of half an inch to the mile, showing the 
 lines of the roads and the shapes of the villages, 
 it would seem easy enough to ascertain one's 
 whereabouts; but the aviator travels quickly 
 and a full equipment of half-inch maps would 
 be a serious item in the weight of his load. 
 The man in a balloon is often above clouds, 
 and when he views the earth again it is very 
 difficult and frequently impossible to pick up 
 the route again. The aviator in a flying-ma- 
 chine is more favourably placed. He knows his 
 
Fig. 63. Motor of the Wright biplane 
 
THE NEW SCIENCE OF THE AIR 161 
 
 direction approximately, although he is often 
 unable to make proper allowance for the drift- 
 ing effect of the wind. If caught by varying 
 currents or by storms above the clouds, he easily 
 loses track of the course. There will be need 
 of large distinctive ground marks for day and 
 lights for night at distances of ten miles apart, 
 marks which will correspond with those on an 
 air-chart. Zeppelin proposes maps showing 
 heights by colours, and marks indicating the 
 influence of streams, marshes, and woods on 
 the static equilibrium of the airship. The scale 
 he suggests is three miles to the inch. Colour 
 is the main consideration. In the opinion of 
 Mr. Charles Cyril Turner, an English aero- 
 naut, the colours should approximate to the 
 colours of the landscape as seen from above. 
 The roads should be white, the water blue, the 
 fields light green, woods a darker green, habi- 
 tations grey, and railways black. 
 
 Besides guiding the aerial traveller on his 
 way some means must be devised of conveying 
 useful information to him. It will often be of 
 great importance to know the strength and exact 
 direction of the wind. Skimming the air at the 
 
1 62 THE NEW ART OF FLYING 
 
 rate of fifty miles an hour, the aviator will find 
 it difficult if not impossible to make these obser- 
 vations. The German Aerial Navy League has 
 suggested that special light-houses be con- 
 structed for that purpose. These are to send 
 a long beam of light in the direction in which 
 the wind is blowing. For day flights it will 
 probably be necessary to have a long arrow 
 painted white and swinging on a pivot so that 
 it can be turned in the proper direction. 
 
CHAPTER X 
 
 THE PERILS OF FLYING 
 
 FROM what has been said in the foregoing 
 chapter it may well be inferred that a man who 
 attempts to fly in the unsteady lower stratum 
 of the atmosphere in which we live is almost 
 in the same position as a drop of quicksilver on 
 an exceedingly unsteady glass plate. Unlike the 
 drop of quicksilver, however, he is provided 
 with a more or less imperfect apparatus for 
 maintaining a given course on the unsteady 
 medium to which he trusts himself. 
 
 Were it not that the whirling maelstroms, 
 the quiet pools, the billows and breakers of the 
 great sea of air are invisible, the risks of flying 
 would perhaps not be so great. Only the man 
 in the air knows how turbulent is the atmosphere 
 even at its calmest. " The wind as a whole," 
 wrote Langley a decade ago, " is not a thing 
 moving along all of a piece, like the water in 
 the Gulf Stream. Far from it. The wind, 
 when we come to study it, as we have to do 
 
1 64 THE NEW ART OF FLYING 
 
 here, is found to be made of innumerable cur- 
 rents and counter-currents which exist altogether 
 and simultaneously in the gentlest breeze, which 
 is in reality going fifty ways at once, although, 
 as a whole, it may come from the east or the 
 west; and if we could see it, it would be some- 
 thing like seeing the rapids below Niagara, 
 where there is an infinite variety of motion in 
 the parts, although there is a common move- 
 ment of the stream as a whole." 
 
 Through these invisible perils the airman 
 must feel his way in the brightest sunshine, like 
 a blind man groping his way in a strange room. 
 He can tell you that against every cliff, every 
 mountain side, every hedge, every stone wall, 
 the air is dashed up in more or less tumultuous 
 waves. The men who crossed the English 
 Channel found that against the chalk cliffs of 
 Dover a vast, invisible surf of air beats as furi- 
 ously as the roaring, visible surf in the Channel 
 below, a surf of air that drove nearly all of 
 them out of their course and imperilled their 
 lives. There are whirlpools, too, near those 
 cliffs of Dover, as Moisant used to tell. He 
 was sucked down into one of them within two 
 
THE PERILS OF FLYING 165 
 
 hundred feet of the sea. His machine lurched 
 heavily, and it was with some difficulty that 
 he managed to reascend to a height at 
 which he could finish the crossing of the 
 Channel. 
 
 Sometimes there are descending currents of 
 air with very little horizontal motion, just as 
 dangerous as the breakers. Into such mael- 
 stroms the pilot may drop as into unseen quick- 
 sands. On his historic flight down the Hudson 
 River, Curtiss ran into such a pitfall, fell with 
 vertiginous rapidity, and saved himself only by 
 skilful handling of his biplane. A less experi- 
 enced pilot would have dropped into the river. 
 A sudden strong gust blowing with the machine 
 would have a similar effect. 
 
 Such are the concentration of mind and the 
 dexterity required by very long cross-country 
 flights that a man's strength is often sapped. 
 During the Circuit de I'Est of 1910, in which 
 the contestants were compelled to fly regardless 
 of the weather, the German, Lindpaintner, had 
 to give up because of physical and nervous ex- 
 haustion. Another competitor crawled under 
 his machine, as soon as he alighted, and went 
 
1 66 THE NEW ART OF FLYING 
 
 asleep. Wilbur Wright has been credited with 
 the remark: " The more you know about the 
 air, the fewer are the chances you are willing to 
 take. It 's your ignorant man who is most 
 reckless." 
 
 Because of the air's trickiness, starting and 
 alighting are particularly difficult and dangerous. 
 More aeroplanes are wrecked by novices in the 
 effort to rise than from any other cause. As a 
 general rule a new man tilts his elevating rudder 
 too high, and because he has not power enough 
 to ascend at a very steep angle, he slides back 
 with a crash. In high winds even practised 
 airmen find it hard to start. During the meeting 
 at Havre in August, 1910, Leblanc and Morane 
 were invited to luncheon at Trouville. Like 
 true pilots of the air they decided to keep their 
 engagements by travelling in their machines. 
 At half past eleven they ordered their Bleriots 
 trundled from their sheds. Twice they were 
 dashed back by the wind before they succeeded 
 in taking the air. An untried man would have 
 wrecked his machine in that wind. 
 
 The pneumatic tired wheels on which a ma- 
 chine runs in getting up preliminary speed serve 
 
Photograph by Edwin Levick 
 
 Fig. 64. Two-cylinder Anzani motor on a Letourd- 
 Niepce monoplane 
 
THE PERILS OF FLYING 167 
 
 also for alighting, as we have seen. When a 
 monoplane glides down at the rate of forty- 
 five miles an hour and strikes the ground, some 
 disposition must be made of its energy. Usu- 
 ally skids or runners, like those of a sled, are 
 employed for that purpose, the bicycle wheels 
 giving way under the action of springs, so as 
 to permit the skids to arrest the machine. Men 
 like the Wrights can bring an aeroplane to a 
 stop without spilling a glass of water; but your 
 unpractised hand often comes down with a 
 shock that makes splinters of a high-priced 
 biplane. 
 
 Inexperience in the correct manipulation of 
 stabilising devices is a fruitful cause of acci- 
 dents, perhaps the most fruitful. The ma- 
 nipulation of these corrective devices is no easy 
 art. Machines and necks have been broken in 
 the effort to acquire it. Man and aeroplane 
 must become one. The horizontal rudder, 
 which projects forward from many biplanes, is 
 like the cane of a blind man. With it the pilot 
 feels his way up or down, yet without touching 
 anything. -Balancing from side to side is even 
 more difficult. Curiously enough, it is when the 
 
1 68 THE NEW ART OF FLYING 
 
 machine is near the ground that it is hardest 
 of all to bring the aeroplane back to an even 
 keel. Imagine yourself for the first time in your 
 life seated in a biplane with a forty-foot span 
 of wing, sailing along at the rate of thirty-five 
 miles an hour, about ten feet from the ground. 
 If your machine suddenly drops on one side, it 
 will scrape on the ground before you can twist 
 your planes and lift the falling side by increasing 
 the air pressure beneath it. You will come 
 down with a crash. If, on the other hand, you 
 are an old air-dog, you will tilt up your hori- 
 zontal or elevation rudder and glide up before 
 you attempt to right yourself. So, too, if you 
 see a stone wall or a hedge in your course, you 
 will lift yourself high above it. Why? To 
 avoid the waves of air dashed up against the 
 wall or hedge. For if you did not rise, the 
 waves would catch you and toss you about, and 
 you might lose your aerial balance. 
 
 In this connection Prof. G. H. Bryan has 
 pointed out that the distinction between equi- 
 librium and stability should be kept in mind. 
 An aeroplane is in equilibrium when travel- 
 ling at a uniform rate in a straight line, or, 
 
THE PERILS OF FLYING 169 
 
 again, when being steered round a horizontal 
 arc of a circle. A badly balanced aeroplane 
 would not be able to travel in a straight line. 
 The mathematics of aeroplane equilibrium are 
 probably very imperfectly understood by many 
 interested in aviation, but they are compara- 
 tively simple, while the theory of stability is 
 of necessity much more difficult. 
 
 It is necessary for stability that if the aero- 
 plane is not in equilibrium and moving uniformly 
 it shall tend toward a condition of equilibrium. 
 At the same time it may commence to oscillate, 
 describing an undulating path, and if the oscil- 
 lations increase in amplitude the motion will be 
 unstable. It is necessary for stability that an 
 oscillatory motion shall have a positive modulus 
 of decay or coefficient of subsidence, and the 
 calculation of this is an important feature of 
 the investigation. 
 
 At the present time it is certain that aviators 
 rely entirely on their own exertions for control- 
 ling machines that 'are unstable, or at least 
 deficient in stability, and they go so far as to 
 declare that, owing to the danger of sudden 
 gusts of wind, automatic stability is of little 
 
1 70 THE NEW ART OF FLYING 
 
 importance. Moreover, even in the early exper- 
 iments of Pilcher, it was found that a glider 
 with too V-shaped wings, or with the centre of 
 gravity too low down, is apt to pitch danger- 
 ously in the same way that increasing the meta- 
 centric height of a ship while increasing its 
 " statical " stability causes it to pitch danger- 
 ously. It thus becomes important to consider 
 what is the effect of a sudden change of wind 
 velocity on an aeroplane. If the aeroplane was 
 previously in equilibrium, it will cease to be so, 
 but will tend to assume a motion which will 
 bring it into the new state of equilibrium con- 
 sistently with the altered circumstances, provided 
 that this new motion is stable. Thus an aero- 
 plane of which every steady motion is stable 
 within given limits will constantly tend to right 
 itself if those limits are not exceeded. Exces- 
 sive pitching or rolling results from a short 
 period of oscillation combined with a modulus 
 of decay which is either negative (giving insta- 
 bility) or of insufficient magnitude to produce 
 the necessary damping. 
 
 More difficult than the maintenance of sta- 
 bility is the making of a turn. The dangers that 
 
THE PERILS OF FLYING 171 
 
 await the unskilled aviator who first tries to 
 sweep a circle have been sufficiently dwelt upon 
 in Chapter VI. The canting of a machine at 
 a considerable angle, which is necessary in order 
 that the weight of the machine may be op- 
 posed to the centrifugal force generated in 
 turning, necessarily implies that the aeroplane 
 shall be at a height great enough to clear the 
 ground. Yet many of the early experimenters 
 wrecked their apparatus because they tried to 
 make turns when too near the ground, with , 
 the result that one wing would strike the turf 
 and crumple up like paper. 
 
 Even at great heights the making of a turn 
 is not unattended with danger, particularly when 
 the machine is brought around suddenly. If a 
 turn is made too abruptly, parts of the structure 
 are sometimes strained to the breaking-point. 
 There is good reason to believe that the Hon. 
 C. S. Rolls was killed because he made too 
 quick a turn. 
 
 Flying exhibitions, which tempt the prize- 
 winning airmen to be overbold, are responsible 
 for many of the tragedies that have occurred 
 within the last few years. At the Reims meeting 
 
172 THE NEW ART OF FLYING 
 
 of 1910, as many as eighteen machines were 
 circling around one another, swooping down, 
 hawklike, from great heights, or cutting figure- 
 of-eight curves to the plaudits of an enthusi- 
 astic multitude. It was not the possibility of 
 collision that was so perilous, but the disturb- 
 ance created in the air. The wake that every 
 steamer leaves behind it has its counterpart in 
 the wake that trails behind an aeroplane in the 
 air. A rowboat may ride safely through the 
 steamer's wake with much bobbing; an aero- 
 plane caught in the wake of another pitches 
 alarmingly. That was how the Baroness de la 
 Roche met with such a terrible accident at the 
 Reims meeting in question. 
 
 The various accidents which have occurred 
 recently to aeroplanes raise the whole question 
 of whether the construction of the wings is such 
 as to give the requisite margin of safety to 
 insure their not breaking under the loads which 
 are likely to be thrown upon them in use. In 
 all ordinary construction, as in building a steam- 
 boat or a house, engineers have what they call 
 a factor of safety. An iron column, for instance, 
 will be made strong enough to hold five or ten 
 
THE PERILS OF FLYING 173 
 
 times the weight that is ever going to be put 
 upon it, but if we try anything of the kind in 
 flying-machines the resultant structure will be 
 too heavy to fly. Everything in the work must 
 be so light as to be on the edge of disaster. 
 Some of the worst accidents on record are to 
 be attributed to this necessarily flimsy construc- 
 tion. It is, of course, very difficult in the case 
 of aeroplane accidents to ascertain which part 
 broke first, for the fabric is generally so utterly 
 destroyed that no details of the first breakage 
 can be seen. Further, the aviator, who is the 
 only man who can tell accurately what happened, 
 is frequently killed, so that the only information 
 available is what can be seen of the fall while 
 the machine is in the air, and accidents occur 
 so suddenly that different people do not always 
 get the same impression of the sequence of 
 events. There seems, however, little doubt that 
 in several cases the wings collapsed in some way 
 while the machine was flying, and that it fell 
 in consequence. 
 
 In the case of a biplane (Fig. 69) the framing 
 of the main wings usually consists of four longi- 
 tudinals running the whole span of the wings, 
 
i 7 4 THE NEW ART OF FLYING 
 
 and these are braced together, both vertically 
 and horizontally, with numerous cross-struts 
 and wire diagonals, so as to give them very 
 great strength, both vertically and horizontally. 
 In fact, if the stresses of the diagonal wires be 
 worked out, they are found to be very much 
 below those usual in ordinary engineering work. 
 Still, the wires are so numerous that, even if one 
 of them breaks from vibration, the extra stress 
 thrown on the adjacent ones will not bring the 
 load up to the ordinary stresses allowed in 
 girder work. The horizontal strength is also 
 practically equal to the vertical, as the trussing 
 is generally of the same character. 
 
 In the monoplane the trussing is much 
 simpler. Often there is no horizontal trussing 
 at all. The vertical strength of the main plane 
 is entirely dependent on stays, generally four to 
 each side, which go to the bottom of a strut 
 under the backbone. Should one of these break, 
 the probability is that the wing will collapse 
 with disastrous results. These stays are often 
 single parts of steel wire or ribbon, a material 
 which has not been found sufficiently reliable 
 for use as supports to the masts of small sailing 
 
Photograph by George Brayton 
 
 Fig. 66. Sending up the first of a pair of tandem 
 kites at the Blue Hill Observatory 
 
THE PERILS OF FLYING 175 
 
 boats, where wire rope is always preferred, on 
 account of the warning it gives before breakage. 
 
 The structure of each wing in a monoplane 
 is, in fact, very much like that of the mast and 
 rigging of a sailing boat, the main spars taking 
 the place of the mast, while the wire stays take 
 that of the shrouds. A very important differ- 
 ence, however, is that the mast of a sailing 
 boat is almost invariably provided with a fore- 
 stay to take the longitudinal pressure when 
 going head to wind, while the wing of an ae'ro- 
 r : me, as we have already noted, often has no 
 such provision, the longitudinal pressure due 
 to the air resistance being taken entirely by the 
 spar. 
 
 When a monoplane is flitting through the 
 air at the rate of sixty miles an hour, the wire 
 stays often vibrate so fast that they emit a 
 distinct musical note. The small boy who wants 
 to break a piece of wire simply bends it back and 
 forth many times at a given point. Rapid 
 vibration of wires and ribbons on monoplanes 
 will ultimately produce the same result. For 
 safety's sake either wire rope should be used 
 (heavier and therefore undesirable from the 
 
176 THE NEW ART OF FLYING 
 
 record-breaker's standpoint), or the number of 
 stays must be increased so that the parting of 
 one will not necessarily spell a wreck and pos- 
 sibly death. 
 
 The horizontal stresses thrown on the single 
 supporting surface of an aeroplane are greater 
 than most pilots realise. In one of those breath- 
 less downward swoops which almost bring your 
 heart to your throat, or in one of those quick 
 turns in which the machine seems to stand on 
 end, the stresses are enormously increased. It 
 was the breaking of a wing by overstrain that 
 killed Delagrange at Pau on January 4, 1910; 
 it was overstrain that killed Wachter at Reims 
 on July i, 1910; it was overstrain, due to sharp 
 turning, that killed Rolls on July 12, 1910, at 
 Bournemouth, England; and it was probably 
 overstrain that weakened the wings of Chavez's 
 monoplane in its battle with the Alpine winds 
 and resulted in the fatal accident that occasioned 
 the intrepid Peruvian's death on September 27, 
 1910. 
 
 In commenting upon the lack of horizontal 
 strength in monoplanes, a writer in Engineering 
 observe? ; 
 
THE PERILS OF FLYING 177 
 
 " It is, no doubt, assumed that the weight 
 of the machine rests on the wings, and that 
 this is the main stress to be provided for. This 
 is no doubt true, but a careful consideration of 
 the horizontal stresses will show that these are 
 much greater than might at first sight appear. 
 When flying horizontally the horizontal stress 
 cannot, of course, exceed the thrust of the pro- 
 peller, and must in practice be considerably less 
 than this, as part of that thrust is spent in over- 
 coming the resistance of the body of the ma- 
 chine, the tail, etc. The ratio of lifting power 
 to horizontal stress will vary considerably in 
 different machines with the efficiency of the 
 planes, but even with the machine flying hori- 
 zontally the horizontal stress will probably be 
 in the neighbourhood of ten per cent of the 
 vertical. 
 
 " It appears, however, that there are circum- 
 stances in which the horizontal stress may be 
 very much greater than this, for it increases with 
 the speed of the aeroplane through the air, and 
 this may be very much greater when descending 
 than when flying level. The wings contribute 
 the greater part of the air resistance, and there- 
 fore, if the aeroplane is descending, it will accel- 
 erate till the horizontal stress on the wings 
 balances the acceleration due to gravity. Thus, 
 if the aeroplane descends at a slope of one in 
 
178 THE NEW ART OF FLYING 
 
 five, the horizontal pressure on the planes may 
 be approximately twenty per cent of the weight 
 of the machine. If the engine is kept running, 
 it will be more than this by the amount of the 
 propeller thrust. It is quite clear, therefore, 
 that circumstances might arise in which the hori- 
 zontal stress would be some twenty-five per cent 
 of the vertical. 
 
 " Now, if we examine the framework of many 
 of the monoplanes, we find that the horizontal 
 strength of the wings is nothing like twenty-five 
 per cent of the vertical; in fact, it is often prob- 
 ably under five per cent. The framework of 
 the wing consists of two longitudinals, and nu- 
 merous cross-battens carrying the fabric. The 
 longitudinals are the only part fixed to the back- 
 bone, and therefore take practically the whole 
 stress. These longitudinals are generally made 
 very deep in proportion to their height, and are 
 often channelled on the sides to make them into 
 I-section girders. It is obvious, therefore, that 
 their horizontal strength is very small indeed 
 compared with the vertical. True, the numer- 
 ous cross-battens stiffen the wing perceptibly, 
 but the extent to which this is the case can hardly 
 be calculated; and as they are often only about 
 24 inch by % i ncn and fastened with very small 
 nails, they cannot be relied on to any great 
 extent. It seems, therefore, that either the 
 
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THE PERILS OF FLYING 179 
 
 wings should have diagonal bracing or should 
 have stays in front corresponding to those down 
 below." 
 
 That the question of speed in descent is a 
 matter for which provision should be made is 
 shown by the fatal death of Wachter at Reims 
 in 1910. The speed in descending is higher 
 than when flying level. In some cases the hori- 
 zontal strength of the wings appears to pro- 
 vide a very small margin for this increased 
 stress, and the accidents seem to have happened 
 exactly as suggested, for in each case, when 
 rapidly descending from a height, the wing 
 collapsed. 
 
 It may be said that when descending the en- 
 gine ought to be stopped and the descent made 
 at a speed not exceeding that which can be 
 maintained on the level. Still, it is hardly prac- 
 ticable to adhere to any such principle; for 
 in alighting it is necessary to travel at top speed 
 to clear the ground eddies. Moreover, if the 
 aeroplane is to be of any practical use, it must 
 be made to stand any reasonable usage to which 
 it is likely to be subjected. Bicycles and motor- 
 cars are often run down hill, or before a wind, 
 
i8o THE NEW ART OF FLYING 
 
 at speeds far higher than can be maintained on 
 the flat, and it is quite certain that a machine 
 which is unsafe under these circumstances is 
 not fit for ordinary work. Most men run down 
 a hill as fast as they can without losing control 
 of their cars, and aviators will doubtless do the 
 same. The machine must, therefore, be made to 
 stand the stresses set up under these conditions. 
 
 Very little is known of the air's power of 
 breaking aeroplanes travelling at high speeds. 
 Designers work from tables that indicate the 
 breaking strength of wire and wood and the 
 percussive force of the wind at different veloci- 
 ties. But the actual buffeting to which a ma- 
 chine is subjected in the air is still an engineer- 
 ing uncertainty. A storm will tear the roof 
 from a house and toss it a hundred yards ; yet 
 aeroplane designers require a machine to travel 
 through the air at hurricane speed and bear up 
 under the sledge-hammer blows of the air, 
 a machine that is the flimsiest vehicle in which 
 man has risked his life, composed, as it is, of 
 fragile wires, the lightest wood cut as finely as 
 possible, and fabric that is affected by varia- 
 tions in the weather. 
 
THE PERILS OF FLYING 181 
 
 In some of the tragedies of the flying-machine 
 the propeller and the motor have each played 
 their part. Lieutenant Selfridge's death at Fort 
 Myer on August 17, 1908, was due to the snap- 
 ping of a propeller blade, which struck a loose 
 wire, an accident that for months crippled 
 Orville Wright, who was piloting the machine. 
 This, of course, was not due to any inherent 
 defect in the propeller. Indeed, the Wright 
 propellers, because of their low speed (four 
 hundred to five hundred revolutions a minute), 
 are probably the safest in use. The propellers 
 of most monoplanes and biplanes travel at 
 speeds as high as fifteen hundred revolutions 
 a minute, or about as fast as an electric fan. 
 Propellers mean more to an aeroplane than 
 stout axles on an automobile; for if a flying- 
 machine stops it must glide down. Nearly 
 every contestant at a flying-machine meeting 
 is equipped with spare propellers, which are as 
 near alike as brains and hands can make them. 
 Yet the same engine will not be able to turn 
 two propellers seemingly alike at the same 
 speed. Why? Because man can make steel, 
 but he cannot make wood. That is grown 
 
1 82 THE NEW ART OF FLYING 
 
 by nature. And because woods from different 
 trees are not alike the propellers formed from 
 them are not alike. Untraceable and insur- 
 mountable variations create the differences. 
 In aeroplaning science success or failure de- 
 pends on just such slight differences. 
 
 The propeller's mechanical cousin, the motor, 
 is also not what it ought to be. At very great 
 heights it is impossible to obtain adequately 
 high compressions in the motor cylinders. 
 Hence the motor stops, and the aviator must 
 glide down, vol plane, as the French call 
 it. Such glides can be made with comparative 
 safety if the pilot is skilful. Occasionally it 
 happens that motor stoppages have been the 
 cause of death. It was the stopping of his 
 motor that killed Leblon at San Sebastian on 
 April 2, 1910, and Van Maasdysk at Amster- 
 dam on August 22, 1910. 
 
 To prevent such accidents, Mr. Edwin Gould 
 in 1910 offered through the Scientific American 
 a prize of $15,000 to the designer and demon- 
 strator of a successful machine equipped with 
 more than one motor, the arrangement being 
 either such that should one motor be disabled 
 
Fig. 69. A glimpse through a Wright biplane. The 
 two planes are trussed together like the corre- 
 sponding members of a bridge, so as 
 to obtain great strength 
 
THE PERILS OF FLYING 183 
 
 another can be immediately thrown into gear, 
 or that if all the motors should be running si- 
 multaneously the stoppage of one will not nec- 
 essarily leave the apparatus without power. 
 The progress which has been made since the 
 Wright Brothers gave us the first success- 
 ful man-carrying motor-driven aeroplane can 
 hardly be called scientific progress. Much of 
 it has been progress of the trial and error vari- 
 ety, very costly and not always productive of 
 valuable results. It may be retorted that, de- 
 spite the highly scientific experiments of Langley 
 and Maxim, we really owe the successful ma- 
 chine to such men as the Wright Brothers, who 
 are not profound mathematicians but skilful, 
 practical mechanics. If the whole truth were 
 known about the years of patient experiment- 
 ing which finally led the Wright Brothers to 
 the invention of a successful flying-machine, it 
 would probably be discovered that they were 
 no less scientific in their methods than was 
 Langley himself. 
 
 The problem of building a flying-machine is 
 in quite a different position from what it was. 
 If flying-machines are not to be subjected to 
 
1 84 THE NEW ART OF FLYING 
 
 frequent accidents and are to be made acces- 
 sible to the million, the sooner aeronauts learn 
 engineering the better. Not until engineers are 
 employed to design and build flying-machines 
 shall we be able to skim the air as safely as we 
 now roll along the ground in motor-cars. 
 
CHAPTER XI 
 
 THE FLYING-MACHINE IN WAR 
 
 UNLIKE any battle that has ever been fought 
 in the world's history, the battle of the future 
 will be a conflict waged in three dimensions. 
 Long before its artillery will have volleyed 
 and thundered, each great military power will 
 have endeavoured to secure the command of 
 the air by building more dirigible airships and 
 aeroplanes than its rivals. The fighting arm 
 of a nation will henceforth be extended not 
 merely over land and sea, but upward into the 
 hitherto unconquerable air itself. Of all this 
 we had some indication during the remarkable 
 French military manoeuvres of 1910. Then for 
 the first time aeroplanes were tested under condi- 
 tions that approximated those of actual warfare. 
 To the laymen the aeroplane's chief function 
 in this battle of the future would seem to be 
 the dropping of explosives on a hapless and 
 helpless army below. The military strategist 
 knows better. In the first place he knows that 
 
1 86 THE NEW ART OF FLYING 
 
 the actual amount of damage which could thus 
 be inflicted would be disappointingly small. A 
 hole may be torn in the ground; the windows 
 of a few buildings may be broken; a battle- 
 ship's superstructure may be blown away; but 
 that wholesale destruction of life and property 
 which would seem obviously to follow from 
 the mere existence of military flying-machines, 
 freighted with bombs and grenades, is not to 
 be looked for. Even were it possible thus to 
 destroy part of a stronghold, the difficulty of 
 hitting the object aimed at is nearly insur- 
 mountable. Every small boy has attempted to 
 hit some passer-by in the street with a missile 
 hurled from a third-story window. Usually 
 he failed, because the target was moving and 
 because the wind deflected the projectile. The 
 air-marksman is much worse off. Seated in a 
 craft which is not only skimming at a speed 
 hardly less than thirty-five miles an hour and 
 possibly as great as eighty miles an hour, but 
 skimming at a height of perhaps half a mile, 
 the chance that he will ever be able to hit his 
 target by making the proper allowance for the 
 horizontal momentum which his bomb would 
 
THE FLYING-MACHINE IN WAR 187 
 
 receive, as well as for the prevailing wind, 
 seems wofully remote. If bombs are to be 
 dropped on forces below, it must be by means 
 of tubes which will both project and direct the 
 missile and which will be provided with wind 
 gauges and height indicators for the proper 
 guidance of the marksman. We must not allow 
 ourselves to be misled by the skill displayed at 
 flying exhibitions in dropping oranges on mini- 
 ature battleships. Oranges are not bombs, nor 
 are the heights at which they are dropped the 
 half mile at which a military aeroplane must 
 soar if it is to elude gun-fire. 
 
 Nevertheless some such possibility may have 
 been at the bottom of the declaration signed 
 by the delegates of the United States to the 
 Second International Peace Conference held at 
 The Hague in 1907, a declaration which 
 prohibited the discharge of projectiles and ex- 
 plosives from the air. The declaration reads: 
 
 " The contracting powers agree to prohibit, 
 for a period extending to the close of the Third 
 Peace Conference, the discharge of projectiles 
 and explosives from balloons or by other new 
 methods of a similar nature." 
 
1 88 THE NEW ART OF FLYING 
 
 The countries which did not sign the decla- 
 ration forbidding the launching of projectiles 
 and explosives from air-craft were: Germany, 
 Austria-Hungary, China, Denmark, Ecuador, 
 Spain, France, Great Britain, Guatemala, Italy, 
 Japan, Mexico, Montenegro, Nicaragua, Para- 
 guay, Roumania, Russia, Servia, Sweden, 
 Switzerland, Turkey, Venezuela. 
 
 To be effective, a bomb must be fairly large. 
 Moreover, a considerable supply of bombs must 
 be available. The aeroplane is a thing of com- 
 parative lightness. It cannot carry much am- 
 munition of that sort. Hence, even admitting 
 the possibility of dropping explosives upon any 
 desired spot, the destruction wrought must nec- 
 essarily be limited in extent. Lastly, there is 
 also considerable danger in unbalancing the 
 machine, by the sudden removal of the load 
 from one side. 
 
 During the French manoeuvres of 1910 no 
 attempt seems to have been made to drop 
 explosives from either airships or aeroplanes, 
 an omission which implies the ineffective- 
 ness of that mode of attack. In the war of 
 the future the aeroplane will be employed 
 

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THE FLYING-MACHINE IN WAR 189 
 
 primarily for the transmission of orders 
 and despatches; for discovering an enemy in 
 a region in which his presence is suspected, his 
 strength and the disposition of his forces being 
 unknown; for ascertaining the strength of an 
 enemy at points where he is known to be lo- 
 cated; and for collecting sufficient information 
 to permit siege guns to plant their shells where 
 they will be most effective. In other words, the 
 future military aeroplane will do the work of 
 a scouting force; for its chief function will be 
 that of reconnaissance. Two men will be 
 seated in its frame, one to pilot the machine, 
 and one to sketch and photograph the terrane 
 below. From the trained eye of the spy in the 
 air nothing will be concealed. He will be like 
 a vulture wheeling in the blue, watching for 
 carrion below. The click of his camera-shutter 
 may be a death-knell, for it will record instan- 
 taneously the position of some battery cun- 
 ningly hidden behind a ridge, an earthwork 
 thrown up across a pass, a stream spanned by 
 military pontoon bridges. His pencil, when it 
 touches the page of a notebook, may spell the 
 death sentence of a regiment; for it will un- 
 
1 9 o THE NEW ART OF FLYING 
 
 erringly note those details of position and num- 
 bers which the photographic plate may not be 
 able to register. When he has learned all that 
 he can learn, he signals his companion to re- 
 turn. Hardly two hours may have elapsed since 
 he was despatched on his quest. Yet within 
 that time he may be able to give his command- 
 ing officer information that a regiment of cav- 
 alry could not have gathered with almost unlim- 
 ited time. 
 
 Both Generals Picquart and Meunier, the 
 opposing commanders during the French ma- 
 noeuvres of 1910, expressed their satisfaction 
 with the performance of aerial scouts. The 
 machines were sent up practically whenever 
 they were ordered to do so. What is more, 
 the aviators carried out orders to the letter, and 
 often under very unfavourable weather condi- 
 tions. It was doubted at first whether they 
 would be able to report with any degree of 
 definiteness upon the position and number of 
 the enemy. At a height of fifteen hundred feet, 
 it seems quite possible, however, for a prac- 
 tised man to discover the character of the 
 troops below him and to ascertain whether they 
 
THE FLYING-MACHINE IN WAR 191 
 
 are infantry, cavalry, or artillery. Artillery is 
 easily enough distinguished by the intervals be- 
 tween the horses. By counting the number of 
 gun caissons the strength of the battery can be 
 ascertained. The strength of cavalry and in- 
 fantry is arrived at by counting the companies 
 or other group formations. 
 
 During the manoeuvres in question it was 
 sometimes difficult at the first glance to gain 
 definite information of troops in battle forma- 
 tion, and at times it was possible to distinguish 
 friend from foe only by the direction of fire. 
 Lieutenant Sido, a French army officer and 
 aerial scout, in commenting upon the possibility 
 of discovering at a very great height the posi- 
 tion of an enemy's forces, stated that a man 
 who goes up in an aeroplane for the first time 
 cannot distinguish anything below him; that 
 many flights are necessary before he can form 
 a judgment of the terrane below; that good 
 eyesight, coupled with experience, are neces- 
 sary; that field glasses are needed only rarely; 
 and that at a very great height cavalry is some- 
 what harder to make out than artillery. 
 
 Although aeroplanes carrying but a single 
 
i 9 2 THE NEW ART OF FLYING 
 
 man did much valuable work during the ma- 
 noeuvres, it is generally agreed that the military 
 aeroplane must carry at least two men, one of 
 whom shall act as a pilot, and the other as an 
 observer. As the field of the military aero- 
 plane is extended, it is very likely that non- 
 commissioned officers, and even ordinary sol- 
 diers, will be entrusted with the piloting of the 
 machine. The observer must always be an in- 
 telligence officer of experience. Lieutenant 
 (now Captain) Bellenger, who distinguished 
 himself by his effective reconnaissances in a 
 Bleriot, maintains that one man will answer 
 for ordinary scouting. When it is considered, 
 however, that the machine is to be controlled, 
 that maps are to be read, that the enemy's 
 strength and disposition are to be discovered, 
 that notes and sketches are to be made, it 
 seems obvious that more than one man will be 
 required. 
 
 It may be doubted whether the aeroplane 
 will entirely supplant the usual forces employed 
 for reconnaissance. The mist which usually 
 conceals the ground early in the morning will 
 probably interfere seriously with the activities 
 
Photograph by Edwin Levick 
 
 Fig. 71. A biplane that came to grief because of 
 defective lateral control 
 
THE FLYING-MACHINE IN WAR 193 
 
 of the aerial scout, not to mention ordinary 
 fogs. Night marches and cavalry raids will 
 probably be necessary as they have been in 
 the past, and troops will mask themselves as 
 they always have by natural and artificial 
 concealments. 
 
 No doubt new stratagems will be devised to 
 deceive the aerial eye. It is conceivable that a 
 regiment may group itself in battalion or even 
 brigade form, so that its strength may be over- 
 estimated. Other stratagems suggest them- 
 selves, such as the feigned movements which 
 completely misled the observers in dirigible 
 airships during the German army-manoeuvres 
 of 1910. 
 
 It is highly advisable that the aeroplane be 
 fitted, if possible, with some form of wireless 
 telegraph apparatus, so that the commanding 
 officer may be kept fully informed of each new 
 discovery. The necessity of reporting in per- 
 son means the return of the aeroplane to head- 
 quarters. Up to the present time, no very 
 successful attempt has been made in this direc- 
 tion, although the success of the wireless instal- 
 lation on the dirigible " Clement-Bayard II " 
 
i 9 4 THE NEW ART OF FLYING 
 
 would seem to indicate that the problem is not 
 beyond solution. 
 
 For ordinary reconnaissance on the battle- 
 field elaborate notes are not essential. The 
 notes that Captain Bellenger took were of 
 the most meagre character, simply sufficient 
 to refresh his memory. They were mere mem- 
 oranda which read, for example, " 7 h. 47 m. 
 Mortvillers, 3 batteries." Such a note was all 
 that he required when making his oral report 
 to refresh his memory. For siege work, on 
 the other hand, Bellenger insists on much more 
 detailed information. In reconnoitring of that 
 character the chief work to be performed by 
 the man in the air will be the precise indica- 
 tion of the point to be shelled. An error of 
 only one hundred and fifty feet in giving that 
 position may nullify the besieging commander's 
 best efforts. Reconnaissances in force to as- 
 certain the enemy's disposition, a tactical neces- 
 sity which may require a detachment of sev- 
 eral thousand men from the main army for a 
 considerable period of time will probably be 
 of infrequent occurrence in the future war- 
 fare. An aeroplane will accomplish the same 
 
THE FLYING-MACHINE IN WAR 195 
 
 result in a fraction of the time. One of 
 the bloodiest encounters the world has ever 
 seen was the Japanese attack on " 203 Meter 
 Hill." Yet the sole purpose of that great 
 slaughter was the placing of two or three men 
 at the summit of the hill to direct the fire of the 
 Japanese siege guns upon the Russian fleet in 
 the harbour of Port Arthur. 
 
 Major G. O. Squier of the United States 
 Signal Corps has pointed out that the realisa- 
 tion of aerial navigation for military purposes 
 brings forward new questions as regards the 
 limitation of frontiers. As long as military 
 operations are confined to the surface of the 
 earth, it has been the custom to protect the 
 geographical limits of a country by ample 
 preparations in time of peace, such as a line 
 of fortresses properly garrisoned. At the out- 
 break of war these boundaries represent real 
 and definite limits to military operations. Ex- 
 cursions into the enemy's territory usually re- 
 quire the backing of a strong military force. 
 Under the new conditions, however, these geo- 
 graphic boundaries no longer offer the same 
 definite limits to military movements. With a 
 
196 THE NEW ART OF FLYING 
 
 third dimension added to the theatre of opera- 
 tions, it will be possible to pass over this boun- 
 dary on rapid raids for obtaining information, 
 accomplishing demolitions, etc., returning to 
 safety in a minimum time. Major Squier, 
 therefore, regards the advent of military scouts 
 of the air as, in a measure, obliterating pres- 
 ent national frontiers in conducting military 
 operations. 
 
 Is the enemy altogether defenceless? Can 
 he offer no resistance? It is inconceivable that 
 he shall lie at the mercy of a great artificial 
 vulture, as helpless as a carcass. Undoubtedly 
 he will have his special artillery, field pieces 
 so constructed that they can be elevated for 
 high angle fire. Against that military bird of 
 prey which he sees hovering far above him and 
 whose errand he divines only too well, he will 
 train this weapon. If his whistling shrapnel 
 should strike a motor, a propeller blade, or an 
 ignition device, if it should cut a tiller rope or 
 splinter a steering rod, that great bird above 
 him must glide down, wounded at least. It is 
 not necessary to kill the pilot, but merely to 
 strike a vital part of the driving mechanism. 
 

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THE FLYING-MACHINE IN WAR 197 
 
 The spy in the air may glide down in safety; 
 but his information is lost to his commanding 
 officer. The question arises, can the aeroplane 
 be struck so easily? Probably not. A moving 
 object is always difficult to hit, but trebly so 
 when it soars half a mile up in the sky. 
 
 Such guns are made in Germany by Krupp 
 and by the Rheinische Metallwaaren und Ma- 
 schinenfabrik, of Diisseldorf. The guns have 
 small bores and use light projectiles, so that 
 they can be fired quickly. The barrels are com- 
 paratively long, so that a high initial velocity 
 and a low trajectory are obtained. Telescope 
 sights and a range finder are provided, the 
 latter fitted with an arrangement which gives 
 the necessary elevation as the distance is read 
 off. 
 
 The ordinary Krupp field gun has a 6.5 cm. 
 bore (Fig. 73), and is fitted with an hydraulic 
 brake and a spring recoil. A coiled spring is 
 provided to balance the gun as it is pointed 
 above the horizontal. The upper part of the 
 gun-carriage is movable, and the wheels can also 
 be given a half-turn away from the body, which 
 assists in quick aiming. This equipment weighs 
 
198 THE NEW ART OF FLYING 
 
 875 kilos, 352 kilos of this being in the gun, 
 523 kilos in the carriage. The projectile 
 weighs 4 kilos about 81 Ibs. 13 oz. The ini- 
 tial velocity is given as 620 m. roughly 
 2,034 ft. a second; the extreme range, 8,650 m. 
 9,450 yards; and the height of fire obtain- 
 able, 5,700 m. roughly 18,700 ft. The gun 
 can be elevated through an angle of 70 degrees 
 above the horizontal, and depressed 5 degrees 
 below it, and it can be revolved right round 
 through an angle of 360 degrees. 
 
 A heavier type of Krupp field gun (Fig. 74) 
 has a bore of 7.5 cm., and weighs when ready 
 for firing 1,065 kilos. The weight of the pro- 
 jectile is 5.5 kilos about 12 Ibs. 2 oz. The 
 initial velocity is stated to be 625 m. per sec- 
 ond, and 9,100 m. and 6,300 m. are given as the 
 extreme range and height attained at trials. 
 The motor-car on which the weapon is carried 
 is designed for an average speed of 45 kilome- 
 tres 2%y 2 miles an hour, and weighs 3,250 
 kilos 7,163 Ibs. without the gun. It car- 
 ries 62 projectiles under the seats, and is 
 propelled by a 50 horse-power motor. It is 
 steadied during firing by a special arrangement 
 
THE FLYING-MACHINE IN WAR 199 
 
 which presses the platform against the axles. 
 The gun can be elevated to an angle of 75 
 degrees from the horizontal, and can be re- 
 volved through a complete circle. 
 
 A 10.5 cm. naval gun (Fig. 75) is also made 
 by Krupps. It weighs 3,000 kilos when ready 
 for firing, the projectile 18 kilos, the gun 1,400, 
 the carriage 1,600. Its initial velocity is 700 m. 
 per second, and 13,500 m. and 11,400 m. are 
 given as the extreme range and height attain- 
 able. As in the case of the 7.5 cm. gun, it can 
 be elevated through an angle of 75 degrees 
 from the horizontal, and revolved through a 
 complete circle. All these three guns are 35 
 calibres long. 
 
 The guns made by the Diisseldorf firm are 
 of a somewhat different construction. The bore 
 is 5 cm., and the barrel is 30 calibres long. The 
 gun is worked from a centre pivot by a hand- 
 wheel and weighs 140 kilos 400 kilos with 
 shield. It can be elevated to an angle of 70 
 degrees above the horizontal, and depressed 
 5 degrees below it, and can be revolved through 
 a complete circle. The total weight of the gun, 
 ammunition, five men and car comes to 3,200 
 
200 THE NEW ART OF FLYING 
 
 kilos. The car is built at the factory of Ehr- 
 hardt, at Zella, and is driven by a motor of 50 
 to 60 horse-power, which propels it at a normal 
 speed of 45 kilometres per hour. It is said to 
 be capable of negotiating gradients of 22 per 
 cent even on bad roads. The whole, including 
 the wheels, can be protected by nickel-steel plate 
 shields. 
 
 During the French manoeuvres of 1910 a 
 special gun was used for the repulsion of air- 
 ships and aeroplanes, the invention of Captain 
 Houbernat. It was a weapon of 75 millimetres 
 (3 inches) diameter carried on an. automobile. 
 The maximum elevation of fire was 66 degrees. 
 The piece was so mounted that it could be 
 swung down for its whole length with the 
 muzzle beside the driver of the car. When ele- 
 vated, the entire weight of the piece was thrown 
 on the rear of the motor-car. Hence it was 
 necessary to stake down the front wheels. The 
 weapon had a range of 5,000 metres (3 miles). 
 The projectiles fired were Robin shells which ex- 
 plode at a maximum elevation of 2,500 metres 
 (7,200 feet). Besides this piece, a mitrailleuse 
 was used of the usual type employed by French 
 
THE FLYING-MACHINE IN WAR 201 
 
 infantry and cavalry, but modified so that it 
 could be elevated at a high angle and fired from 
 an automobile if necessary. 
 
 The question of ammunition most suitable 
 for guns is also receiving attention in Germany. 
 The Diisseldorf firm mentioned has introduced 
 a combined shrapnel and ordinary shell for use 
 against both dirigibles and aeroplanes. This 
 new form of shrapnel differs from that which is 
 ordinarily fired in so far as, after the explosion 
 of the shrapnel part, the shell part is carried 
 on to the target, or to the ground, where it det- 
 onates, giving off in its flight an observable 
 cloud of smoke. A somewhat similar projectile 
 is also made by the Krupps. The trail of 
 smoke serves the purpose of indicating how close 
 the projectile came to its mark (Figs. 76 and 
 
 77)- 
 
 Not upon such artillery and shells and shrap- 
 nel will the enemy rely, but on aeroplanes and 
 airships of his own. He must fight steel with 
 steel. When he sees a black speck in the sky, 
 moving toward him, he gives a quick command. 
 A monoplane or a biplane, perhaps two, start 
 with a whirr from his camp and soar to meet 
 
202 THE NEW ART OF FLYING 
 
 that speck. When machine encounters machine 
 in the sky, what will happen? They dare not 
 ram each other. That would mean the inevit- 
 able destruction of both; for the two would 
 surely fall, a mass of twisted and splintered 
 metal and wood. They must fire at each other. 
 But with what? Not with revolvers or rifles, 
 for their range is too small for effective shoot- 
 ing at an aeroplane wheeling around some 
 thousands of yards away; not with a field-piece, 
 for it could not be carried on so light a contriv- 
 ance; but with a machine-gun of especially light 
 construction, a mitrailleuse which will pour forth 
 so many hundred shots a minute in a steady 
 stream, like a jet of water spouting from a 
 hose. That battle in the sky will be won by 
 the swiftest and most readily controlled flying- 
 machine, by the aeroplane, in a word, which 
 can run and choose its own position and 
 range. 
 
 The question may well be asked: What will 
 be the relation of dirigible to aeroplane? Will 
 the one type displace the other? Both types 
 will probably be necessary. The dirigible and 
 the aeroplane will bear to each other the rela- 
 
THE FLYING-MACHINE IN WAR 203 
 
 tion of battleship to torpedo boat. In actual 
 war each combatant will have a fleet of both 
 airships and aeroplanes. When an enemy ap- 
 pears it will be the first duty of the opposing 
 fleet to attack him. The home fleet will have a 
 certain advantage because it will be nearer its 
 base. It is not likely that an attacking fleet will 
 sail over an enemy's country unless it is able to 
 destroy the home fleet. 
 
 What chance has the dirigible against the 
 aeroplane in an aerial battle? Because of its 
 greater speed the aeroplane has the advantage 
 of fighting or running. Moreover, the dirigible 
 being a most expensive machine, there are al- 
 ways likely to be more aeroplanes than air- 
 ships, so that many aeroplanes can be opposed 
 to a single dirigible, just as many torpedo 
 boats are sent against a single battleship on 
 the theory that one at least will deal a fatal 
 blow. 
 
 Its great speed gives the aeroplane an im- 
 measurable advantage over the dirigible even 
 in scouting. Suppose that a frontier several 
 miles long is patrolled by a fleet of dirigibles, 
 and suppose that a considerable number of hos- 
 
204 THE NEW ART OF FLYING 
 
 tile aeroplanes is available to ascertain the 
 position and strength of the enemy beyond that 
 frontier. No reasonable number of dirigibles 
 could alone protect that frontier from invasion. 
 The blockade can always be run. However well 
 the line may be protected, there will be 
 spaces where the aeroplane can cross and 
 recross after having taken all the observations 
 required. 
 
 For actual fighting purposes the aeroplane 
 cannot as yet be reckoned with. It can be armed 
 only with the lightest gun and can carry only 
 a very limited amount of ammunition and men. 
 The dirigible, on the other hand, can carry a 
 crew of twenty-six and can be fitted with guns 
 much above rifle-calibre. It can remain in the 
 air thirty or forty hours, and in that time travel 
 several hundred miles. When the aeroplane 
 can carry a couple of fighting men in addition 
 to the pilot, and these can be armed with some- 
 thing in the nature of a machine-gun, the effi- 
 ciency of aeroplanes will be far increased if 
 they can cruise in fleets against isolated dirigi- 
 bles. The small target and high speed of the 
 aeroplane will be in its favour, even though its 
 
THE FLYING-MACHINE IN WAR 205 
 
 opponent will be more heavily armed. More- 
 over the inevitable confusion attending a com- 
 bat waged upwards and downwards and on all 
 sides should offer many a chance to a daring 
 fighter of delivering a telling blow. 
 
 It has been urged that if the aeroplane once 
 gets above the dirigible the fate of the latter 
 is sealed; for the gas bag prevents the dirigible 
 from firing at the aeroplane. It may well be 
 that gun-platforms will be arranged on top 
 with a conning-tower projecting from the car 
 below, through the gas bag. Such a construc- 
 tion has been proposed in Germany. At pres- 
 ent the dirigible can ascend to heights which 
 the aeroplane has not yet reached. The rarity 
 of air at altitudes of over a mile has an im- 
 portant effect on the operation of the aeroplane 
 engine. Most of the men who have soared to 
 great heights in aeroplanes have found that 
 their motors stopped at a certain elevation, and 
 a motor that stops places the pilot in the posi- 
 tion of a balloonist whose gas has leaked away. 
 If the aeroplane can choose its own range be- 
 cause of superior speed, the dirigible can at 
 least choose its own elevation. Yet even here 
 
206 THE NEW ART OF FLYING 
 
 there are limitations to be observed. As a 
 dirigible rises its gas expands. To prevent the 
 bursting of the envelope, gas must be allowed 
 to escape. Hence when the dirigible drops 
 again to a lower level, its ascensional power 
 has been considerably curtailed. 
 
 Command of the air, like command of the 
 sea, will depend on men and material. With- 
 out men of courage and skill, flying-machines 
 are useless. Without efficient flying-machines, 
 on the other hand, it is obvious that men cannot 
 fly. The situation is much the same in that re- 
 spect as in naval affairs. England has domi- 
 nated the sea because she has had the ships 
 and a well-trained industrious body of civilians 
 to fight them. Acquisition of material is merely 
 a matter of spending money. The nation that 
 spends the most money will have the most 
 numerous and best equipped air navy. In the 
 case of war in the air, as at sea, success will 
 depend not only on abundant material, but on 
 the ability to supply wastage of war, which is 
 enormous and increases in enormity as the ma- 
 terial becomes more complicated and costly. 
 In matters of armament, however, cost is not 
 
THE FLYING-MACHINE IN WAR 207 
 
 the guiding principle. Nothing is so expensive 
 as defeat, and to avoid defeat the most efficient 
 aircraft must be provided in sufficient numbers. 
 Battles, aerial or terrestrial, are won as much 
 by money as by hard fighting. 
 
CHAPTER XII 
 
 SOME TYPICAL BIPLANES 
 
 ALL biplanes, no matter by whom designed, 
 have certain features in common. Besides the 
 two superposed supporting surfaces from which 
 they take their name, they all have a horizontal 
 rudder or elevator, by means of which the ma- 
 chine is guided up or down and is prevented 
 from pitching; a vertical rudder, by means of 
 which the machine is kept on an even course 
 and turned to the right or to the left; and 
 some means by which the amount of main sur- 
 face exposed to the pressure of the air can be 
 varied, so as to keep the machine in balance 
 from side to side. To these essential elements 
 a tail, consisting of a small horizontal surface, 
 is usually added, because it serves to steady 
 the machine in flight. 
 
 Just how these elements shall be disposed is 
 a matter of more or less difference of opinion 
 among biplane designers, and this difference of 
 opinion has given us the various biplanes of the 
 
SOME TYPICAL BIPLANES 209 
 
 Wrights, Curtiss, Farman, Goupy, Sommer, 
 Breguet, and others. Biplanes as a class fol- 
 low the lines of the Wright machine. It is here 
 impossible and unnecessary to describe in de- 
 tail all the biplanes in use at the present day. 
 For our purpose it will be quite sufficient to con- 
 fine ourselves to the Wright, Curtiss, Farman, 
 and Sommer machines, inasmuch as they rep- 
 resent the chief systems of control to be found 
 in the two-surface machine. 
 
 THE WRIGHT BIPLANE 
 
 The two supporting surfaces of the Wright 
 machine consist of canvas stretched over and 
 under ribs of spruce. At a point near the centre 
 these surfaces are three inches thick. The 
 dimensions of the planes vary. In the earlier 
 machines they measured 41 feet in spread, 
 6.56 feet in depth, and 538 square feet in area. 
 In the later machines the spread has been re- 
 duced to 39 feet, the depth to 5.5 feet, and the 
 area to 410 square feet. A smaller model has 
 also been designed in which the spread has been 
 reduced to 26 feet. 
 
 In the first Wright machines (Fig. 79) the 
 
210 THE NEW ART OF FLYING 
 
 horizontal or elevation rudder was mounted in 
 front, and was so constructed that it was auto- 
 matically curved concavely on the under side 
 when elevated, and in the opposite way when 
 depressed. A long wooden rod connected the 
 horizontal rudder with a lever, which was ma- 
 nipulated by the operator's left hand (Fig. 20). 
 By pulling the lever toward him the operator 
 inclined the rudder upward; by pushing the 
 lever away from him the operator depressed 
 the rudder. 
 
 The vertical rudder, which not only served 
 to steer the machine in a horizontal plane but 
 also to prevent it from spinning on a vertical 
 axis, was mounted in the rear of the machine as 
 at present. It consisted and still consists of 
 two parallel vertical surfaces, swung by a lever 
 in the operator's right hand. By pushing the 
 lever away from him the operator turns the 
 machine to the left; by pulling it toward him 
 he turns the machine to the right. 
 
 Side-to-side balance has always been main- 
 tained in the Wright biplane by warping the 
 main planes in the manner explained in Chap- 
 ter V. The entire front of the two supporting 
 
Fig. 75- A Krupp 10.5 cm. naval gun for repelling 
 aircraft 
 
SOME TYPICAL BIPLANES 211 
 
 surfaces is rigid; but the rear corners are mov- 
 able. The central sections of the two planes 
 are rigid and are never moved in balancing the 
 machine. Only the rear corners of both planes 
 play any part in controlling the apparatus. 
 These flexible rear corners of both planes are 
 connected by means of cables with the lever in 
 the operator's right hand (Fig. 20), in other 
 words, the lever which controls the vertical rud- 
 der. By throwing the lever from side to side 
 the rear corners are flexed in opposite direc- 
 tions; in other words, as one corner of one 
 plane is bent down, the other corner of the 
 same plane is bent up, with the result that the 
 entire plane is given what the Wrights call a 
 " helicoidal warp." The same lever controls 
 both the vertical rudder and the warping of the 
 planes, because the Wrights found that as the 
 planes were bent the machine would spin on a 
 vertical axis, as explained in Chapter V. This 
 lever is therefore swung in a circular or ellip- 
 tical path so that the planes are warped and 
 the vertical rudder swung in the proper direc- 
 tion at the same time. 
 
 In the newer Wright biplanes a modified form 
 
212 THE NEW ART OF FLYING 
 
 of lever has been adopted to warp the wings 
 and turn the vertical rudder, the principle, how- 
 ever, remaining substantially the same. The 
 new lever is provided with an auxiliary grip, 
 which can be worked by the fingers to operate 
 the vertical rudder, while the main portion of 
 the lever is pushed forward or backward to 
 warp the wings. 
 
 In the European Wright machine a tail was 
 soon added, because it was found that the ma- 
 chine pitched markedly in flight. This pitching 
 was corrected, to be sure, by manipulation of 
 the horizontal rudder, but this required con- 
 siderable skill on the pilot's part. Hence a 
 horizontal surface was placed in the rear to act 
 as a steadying tail, which surface could be 
 turned up and down to aid the elevation rudder 
 in its action. In the American machines, made 
 by the Wrights themselves, this horizontal tail 
 has also been incorporated (Fig. 80). What 
 is more, the front horizontal rudders have been 
 abandoned altogether and the rear horizontal 
 surface or tail employed both as an elevator and 
 a steadying surface. The result has been that the 
 machine flies far more steadily than formerly. 
 
SOME TYPICAL BIPLANES 213 
 
 The earlier Wright machines were mounted 
 on skids. The machines were launched on a 
 starting rail (Fig. 12) in the manner described 
 in Chapter IV. The European manufacturers 
 of Wright machines soon introduced wheels on 
 which the machine ran in the usual manner, the 
 skids serving for alighting as before. This im- 
 provement has been adopted by the Wrights 
 (Fig. 14). 
 
 The motors which drive the American 
 Wright machines are made by the Wrights 
 themselves. The horse-power, except in small 
 racers, varies from 25 to 30, which is consider- 
 ably below that of most European biplanes. 
 The motor drives two propellers revolving in 
 opposite directions at the rate of 400 revolu- 
 tions a minute, which is remarkably slow as 
 propeller speeds go. 
 
 The Wright racing aeroplane, which made 
 its first appearance at the Belmont Par!: Inter- 
 national Aviation Meet of 1910, is not essen- 
 tially different from the regular Wright biplane. 
 In order to attain high speed, the planes have 
 been reduced in spread, and consequently in 
 area, and a V-motor of high power has been in- 
 
2i 4 THE NEW ART OF FLYING 
 
 stalled. The planes are 21 feet in length and 
 3 l / 2 feet wide. The combined area of both 
 planes is 180 square feet. It is stated that the 
 motor develops about 60 horse-power. The 
 machine was used by Johnstone when he made 
 an altitude flight of 9,714 feet. The machine 
 is credited with a speed of 685^ miles an hour. 
 
 THE CURTISS BIPLANE 
 
 Like the Wrights, Mr. Glenn H. Curtiss 
 has departed somewhat from the type that he 
 originally evolved. In his earlier machines 
 (Fig. 25) the supporting planes consisted of 
 " rubberized " silk stretched over the top of 
 a light spruce frame. The spread of the planes 
 was 26.42 feet, the depth 4.5 feet, the dis- 
 tance between the planes 5 feet, and the area 
 220 square feet. In the more recent machines 
 the spread is 32 feet, the depth 5 feet, and 
 the area 316 square feet. 
 
 The horizontal or elevation rudder of the 
 Curtiss biplane consists of two parallel hori- 
 zontal surfaces mounted in front of the ma- 
 chine and moved in unison by means of a steer- 
 
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 rll 
 
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 1-5 
 
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 a 
 
SOME TYPICAL BIPLANES 215 
 
 ing-wheel. A long bamboo rod connects the 
 horizontal rudder with the steering-wheel, the 
 arrangement being such that by pushing or pull- 
 ing the steering-wheel backward or forward, the 
 rudder is respectively turned down or up. 
 
 The vertical rudder of the Curtiss machine 
 is a single surface placed in the rear and also 
 operated by the steering-wheel through the 
 medium of cables. To work the vertical rud- 
 der the steering-wheel is rocked like the pilot- 
 wheel of a steamboat. To secure steadiness 
 in flight and to reduce the pitching effect a hori- 
 zontal surface or tail is mounted in the rear. 
 
 Side to side balance was maintained in the 
 Curtiss machine up to 1910 by means of two 
 balancing planes of about 12 square feet in 
 area, mounted between the two main planes. 
 These balancing planes were swung in opposite 
 directions by cables connected with a yoke 
 partially surrounding the aviator's body and 
 mounted to rock. By leaning from side to side 
 the aviator moved the yoke and consequently 
 the balancing-planes. The arrangement was 
 such that the instinctive motion of the body 
 swung the balancing-planes. 
 
216 THE NEW ART OF FLYING 
 
 In the late Curtiss machines ailerons (Fig. 
 29) similar to those of the Farman biplane 
 (q. v.) are employed. They are operated in 
 the same manner as the old balancing-planes. 
 
 The motors which drive the machine are 
 made by Mr. Curtiss himself. On the larger 
 machines the motors are of the well-known 
 V-type and develop 50 horse-power. On the 
 smaller machines 25 horse-power vertical cylin- 
 der motors are used. The engine is controlled 
 by an accelerator pedal on the left of the steer- 
 ing column. There is also a throttle lever close 
 to the pilot's seat. Another pedal under the 
 action of the pilot's right foot is employed to 
 cut off the ignition and to apply a brake to the 
 front wheel of the chassis by which the machine 
 is carried on the ground. Mr. Curtiss himself 
 has driven machines with 100 horse-power 
 motors. 
 
 The propellers are made of wood and are 
 two-bladed. Their diameter is 6 feet, the 
 pitch 5 feet, and the speed 1,200 revolutions 
 a minute. 
 
 The machine starts and alights on three 
 rubber-tired wheels. 
 
SOME TYPICAL BIPLANES 217 
 
 For the Belmont Park aviation meeting of 
 1910 Mr. Curtiss made a machine which was 
 practically a monoplane. The upper plane was 
 reduced to a surface of almost negligible area. 
 At the meeting in question the machine was 
 not given a very extensive trial, so that it could 
 not be compared with the Bleriot and other 
 machines that were entered. 
 
 THE FARMAN BIPLANE 
 
 The Farman biplane is the outcome of Henry 
 Farman's experience with the old, cellular 
 Voisin biplanes (Fig. 34). Like Curtiss, he 
 was manifestly influenced by the Wrights, as, 
 indeed, was every French maker of flying- 
 machines after the memorable flights of Wilbur 
 Wright in France in 1908. As it now stands, 
 the Farman is probably the most widely used 
 biplane in Europe and deservedly so by reason 
 of its ingenious and extraordinarily staunch 
 construction. 
 
 The main supporting surfaces of the Farman 
 biplane are made of what is known as " Conti- 
 nental " cloth, a special fabric manufactured 
 for aeronautic purposes. The cloth is stretched 
 
218 THE NEW ART OF FLYING 
 
 over ribs of ash. Although the dimensions 
 vary somewhat, the average Farman biplane 
 has a spread of 33 feet, a depth of 6.6 feet, 
 and a total area of 430 square feet. In the 
 later machine the upper plane has a greater 
 spread than the lower. The planes are sepa- 
 rated by a distance of 7 feet. 
 
 The elevation or horizontal rudder is car- 
 ried out in front of the machine, after the early 
 Wright fashion. Wires run from the rudder 
 to a lever held by the pilot's right hand (Fig. 
 28). By pushing the lever away from him, 
 the pilot depresses the rudder; by pulling 
 the lever toward him, he tilts the rudder 
 up. 
 
 The same lever controls the lateral balance 
 of the machine. Four hinged flaps, constitut- 
 ing the rear corners of the main planes, are 
 connected by cables with the lever. By throw- 
 ing the lever from side to side the flaps (aile- 
 rons) on one side are pulled down, and the 
 flaps on the other side are relaxed so that 
 they lie practically flush with the main planes. 
 When the machine is standing still on the 
 ground, the flaps hang down. As soon as the 
 
SOME TYPICAL BIPLANES 219 
 
 machine is in flight, they stream out behind the 
 main planes. 
 
 The vertical rudder consists of two parallel 
 vertical surfaces in the rear of the machine, 
 which surfaces are connected by means of tiller 
 cables with a lever worked by the pilot's 
 feet. 
 
 Somewhat in advance of the vertical rudder 
 are two horizontal surfaces which constitute a 
 steadying tail. The top surface of this tail can 
 be swung up and down in conjunction with the 
 front horizontal rudder. 
 
 The motors used on the Farman machine are 
 usually Gnome rotary motors of 50 horse- 
 power, although 100 horse-power motors have 
 been used on occasion. The propeller is a 
 Chauviere wooden propeller of two blades, with 
 a speed of 1,200 revolutions a minute. The 
 pitch of the propeller is 4.62 feet, the diameter 
 8.5 feet. 
 
 The machine is mounted on two skids, each 
 of which is fitted with a pair of wheels. Heavy 
 elastic bands connect the skids with the axles 
 of the two wheels. In alighting the bands yield 
 and allow the skids to take the main shock. 
 
220 THE NEW ART OF FLYING 
 
 This is a most ingenious, efficient, and simple 
 invention, which has been widely copied. 
 
 THE SOMMER BIPLANE 
 
 The biplane built by Farman's former pupil 
 Roger Sommer (Fig. 83) follows the Farman 
 type rather closely. The supporting surfaces 
 consist of rubber cloth stretched over wooden 
 ribs. The spread is 33 feet, the depth, 5.2 feet, 
 and the total area 326 feet. 
 
 The horizontal rudder is carried well out in 
 front of the machine. It consists of a single 
 horizontal surface. As in the Farman machine, 
 it is controlled by a single lever, which, instead 
 of being placed at the right, is mounted at the 
 left. The operation of this lever and the con- 
 sequent elevation and depression of the rudder 
 are exactly the same as in the Farman machine. 
 
 As in the Farman machine, ailerons are em- 
 ployed to maintain side-to-side balance. These 
 ailerons are to be found either on both planes 
 or only on the upper plane. They are not oper- 
 ated, as in the Farman machine, by the lever 
 which controls the horizontal rudder. Instead, 
 the Curtiss principle of using the instinctive 
 
SOME TYPICAL BIPLANES 221 
 
 movements of the pilot's body is adopted. 
 Wires leading from the ailerons are attached 
 to a yoke partially surrounding the aviator's 
 body. In obedience to the movements of the 
 body the ailerons are pulled down and up 
 respectively. 
 
 The vertical rudder is a single surface at the 
 rear of the machine operated, as in the Farman 
 machine, by a foot lever. 
 
 To steady the machine a single horizontal 
 surface is mounted in the rear. This surface 
 is movable, not for the purpose of acting as an 
 elevation rudder, but to increase or decrease the 
 stabilising effect. A lever at the aviator's right 
 controls this tail. 
 
 The machine is mounted on skids and wheels, 
 the skids serving for alighting. Rubber springs 
 are employed in connection with the wheels, as 
 in the Farman machine. 
 
 As a general rule Sommer machines are 
 driven by 50 horse-power Gnome motors, which 
 turn a two-bladed Chauviere propeller at the 
 rate of 1,200 revolutions a minute. Some ma- 
 chines have been fitted with 100 horse-power 
 motors. 
 
CHAPTER XIII 
 
 SOME TYPICAL MONOPLANES 
 
 MONOPLANES differ less from one another 
 than biplanes. Nearly all of them have the 
 same system of lateral control, and the same 
 method of mounting the motor. As a general 
 rule this system of lateral control is the Wright 
 wing-warping method. The motors are usu- 
 ally Gnome motors mounted in front of the 
 machines. 
 
 THE ANTOINETTE MONOPLANE 
 
 Antoinette monoplanes (Fig. 84) are de- 
 signed and built by Levavasseur, a well-known 
 manufacturer of motors. 
 
 The single silk surface of an Antoinette mon- 
 oplane is constructed in two halves which are 
 so mounted that they form a slight dihedral 
 angle. This plane is braced to a central mast 
 or spar, and is carried on a girder-like frame 
 of aluminium, cedar, and ash. The spread of 
 the plane is 49 feet ; the area 405 square feet. 
 
SOME TYPICAL MONOPLANES 223 
 
 The horizontal rudder is a single surface at 
 the extreme rear of the machine and is con- 
 trolled by a hand-wheel at the aviator's right 
 
 (Fig. 32). 
 
 The vertical rudder comprises two surfaces 
 at the rear of the machine. Tiller cables lead 
 from the surfaces to a lever operated by the 
 aviator's feet. 
 
 To balance the machine from side to side the 
 plane is warped after the Wright principle. In 
 contradistinction to the Wright machine, how- 
 ever, the front edges are flexible and the rear 
 edges fixed. To warp the plane a hand-wheel 
 is provided at the aviator's left. 
 
 The mast, to which the plane-halves are 
 braced, contains a pneumatic shock-absorber in 
 its lower end, besides which there are two 
 wheels with heavy pneumatic tires and a for- 
 ward plough-like skid. A skid in the rear is 
 used to support the tail. 
 
 On each side of the body is a horizontal, fan- 
 shaped keel at the rear to steady the machine 
 longitudinally. A vertical fin above this hori- 
 zontal fin gives a certain amount of lateral 
 stability. 
 
224 THE NEW ART OF FLYING 
 
 An 8-cylinder V-type water-cooled Antoinette 
 motor of 50 horse-power is placed in front of 
 the machine and drives a y-foot propeller. At 
 the International Aviation Meeting held in 
 1910 at Belmont Park, Latham flew a 100 
 horse-power Antoinette. 
 
 The Antoinette monoplanes which are built 
 in Germany are equipped with 100 horse-power 
 Gnome motors of fourteen cylinders. The area 
 of the wings can be reduced by about one square 
 metre, the smaller area being employed when 
 the aviator is flying alone. When three pas- 
 sengers are carried besides the aviator, the 
 span can be increased to fifteen metres, so that 
 the area amounts to four square metres. The 
 passengers are placed symmetrically, so that 
 the centre of gravity of the machine is not dis- 
 turbed. This large Antoinette machine is some- 
 what longer than the normal Antoinette, built 
 in France. Since the utilisation of the Gnome 
 motor means the abandonment of the usual 
 Antoinette water-cooling plant, and such auxil- 
 iary apparatus as radiators, pumps, etc., it was 
 necessary to redistribute the weight. Accord- 
 ingly the German machine is longer than the 
 
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SOME TYPICAL MONOPLANES 225 
 
 French, so that the motor can be placed out 
 further. 
 
 THE BLERIOT MONOPLANES 
 
 Louis Bleriot is a well-to-do manufacturer 
 of automobile lamps whose attention was di- 
 rected to flying-machines in 1906. He has the 
 distinction of having broken more machines 
 and more frequently risked his life than any 
 other man interested in the new sport. What 
 is more, he was the first man who ever flew a 
 monoplane. 
 
 Bleriot's remarkable experience has resulted 
 in the development of two types of machines 
 known respectively as the Bleriot XI (Fig. 81) 
 and the Bleriot XII (Fig. 88). The Bleriot 
 XI is a fast model patterned after that with 
 which Bleriot flew across the English Channel; 
 the Bleriot XII is a passenger-carrying machine, 
 which differs somewhat from the XI. 
 
 The main plane of the No. XI is built in 
 halves and consists of " Continental rubber " 
 stretched over a wooden frame. In order that 
 the machine may be readily transported the 
 halves of the plane can be detached from a 
 
226 THE NEW ART OF FLYING 
 
 central joint. This detachability, moreover, 
 renders it possible to interchange wings of large 
 and small area. The spread is normally 28.2 
 feet, the depth 6.5 feet, and the total area 151 
 square feet. 
 
 To steady the machine longitudinally in flight 
 a horizontal surface or tail is employed. The 
 horizontal or elevation rudder consists of two 
 movable surfaces, one at each side of this tail. 
 The horizontal rudder is operated by a central 
 lever in the manner described in Chapter V. 
 
 The vertical rudder of the Bleriot XI con- 
 sists of a vertical surface in the rear of the 
 machine. It is operated by tiller wires con- 
 nected with a foot lever. 
 
 Lateral control of the machine is obtained 
 by wing-warping, as in the Wright biplane, 
 For this purpose the central lever or bell- 
 column, described in Chapter V, is employed, 
 the column being thrown from side to side to 
 pull on one wing-warping wire and to slacken 
 the other. 
 
 In the machine with which he flew across 
 the English Channel, Bleriot used a 25 horse- 
 power Anzani motor. Since then 50 horse- 
 
SOME TYPICAL MONOPLANES 227 
 
 power Gnome motors have usually been em- 
 ployed, the motor being mounted in front of 
 the machine and driving a two-bladed Chau- 
 viere propeller 6.87 feet in diameter at the 
 rate of 1,200 to 1,400 revolutions a minute. 
 
 The starting and alighting gear of the Ble- 
 riot XI consists of rubber-tired wheels and 
 rubber shock-absorbers. For the rear wheel, as 
 shown in Fig. 86, a skid has been substituted. 
 
 In the smaller type of Bleriot a fuel tank is 
 placed very far below the frame in order to 
 lower the centre of gravity. In the larger type 
 two fuel tanks are placed between the wings 
 in the body of the machine right in front of the 
 pilot's seat. In order that the lowered fuel 
 tank of the small Bleriot XI may offer as little 
 resistance to the air as possible, it is given a 
 fish form (Fig. 86) for the reason that Prandtl 
 has proven that such shapes offer the least 
 resistance. 
 
 Racing machines are also made on the lines 
 of the Bleriot XI, but with a smaller wing- 
 spread and 100 horse-power, fourteen-cylinder 
 Gnome motors. 
 
 The passenger-carrying Bleriot XII is so con- 
 
228 THE NEW ART OF FLYING 
 
 structed that the aviator sits with his passen- 
 gers under the main plane, back of the motor. 
 This type is now practically abandoned. In 
 the Bleriot XI he sits with his body above the 
 main plane. A later passenger-carrying model 
 has been evolved in which the two occupants 
 of the machine sit side by side above the plane, 
 as in the regular Bleriot XL 
 
 Early in 1911 Bleriot brought out a remark- 
 able 10 passenger monoplane, the lateral sta- 
 bility of which was controlled by ailerons and 
 the 100 horse-power motor of which was placed 
 with the propeller directly behind the plane, 
 following Maxim's suggestion. A front hori- 
 zontal rudder was also provided, similar to 
 that of the Farman biplane. 
 
 THE SANTOS-DUMONT MONOPLANE 
 
 By far the smallest flying-machine of the day 
 is the monoplane designed by Santos-Dumont. 
 Because of its littleness it is extremely fast. 
 
 The supporting surface consists of silk 
 stretched over bamboo ribs. This silken sur- 
 face is braced by wires to a central frame of 
 bamboo and metal tubing. The spread is 18 
 

SOME TYPICAL MONOPLANES 229 
 
 feet, the depth 6.56 feet, and the area 113 
 square feet. 
 
 The vertical rudder and the horizontal rud- 
 der, usually entirely distinct, in most biplanes 
 and monoplanes, are here combined after the 
 Langley principle. This combined rudder is 
 carried on a universal joint so that it can be 
 turned in any direction. Although they are 
 mounted together, the horizontal and vertical 
 members of the rudder are operated indepen- 
 dently. The vertical surface is controlled by 
 a hand-wheel or lever at the pilot's left hand. 
 The horizontal rudder is operated by a lever 
 held in the aviator's right hand. 
 
 Following the principle of Curtiss, lateral 
 control is effected by the instinctive movements 
 of the aviator's body; but instead of employ- 
 ing balancing planes or ailerons Santos-Dumont 
 warps the plane. The wires leading from the 
 plane are connected with a steel member sewed 
 on the pilot's coat. Hence the pilot has 
 only to sway his body in order to warp the 
 wings. 
 
 The starting and alighting gear consists of 
 two wheels at the front and a skid at the rear. 
 
230 THE NEW ART OF FLYING 
 
 No tails or other stabilising surfaces are 
 used, although the horizontal member of the 
 rudder undoubtedly acts as a tail, as in the newer 
 Wright biplane. 
 
 The motor may be of any type. Darracq, 
 Clement-Bayard, and Panhard motors of 30 
 horse-power have been used. The propeller is 
 a two-bladed Chauviere. 
 
CHAPTER XIV 
 
 THE FLYING-MACHINE OF THE FUTURE 
 
 WHAT will the flying-machine of the future be 
 like? He would be a wise man indeed who 
 could predict with any degree of accuracy the 
 exact form and dimensions of the coming aero- 
 plane. The dreams of the old-time imaginative 
 novelist seem almost to be realised now. Our 
 more modern Kipling, looking back in his 
 mind's eye at our feeble efforts, talks with scorn 
 in the " Night Mail " of " the days when men 
 flew wooden kites over oil-engines." Yet it is 
 not likely that we shall graduate from that 
 crude type for many years to come. A scien- 
 tific forecast of the flying-machine's possibili- 
 ties and its effect on human affairs must 
 therefore be deduced from present aeroplane 
 facts. 
 
 The aeroplane of our time is a thing of 
 almost feathery lightness. In its construction 
 the lightest and toughest woods and the small- 
 est possible amount of metal must be used. As 
 
2 3 2 THE NEW ART OF FLYING 
 
 a result, it is wellnigh as delicate as a watch, 
 and like a watch it must be handled with some 
 care. Since the motor is the heaviest part of 
 a flying-machine, it offers the most serious ob- 
 stacle to the attainment of lightness. Because 
 of the motor's necessarily small size its power 
 is none too generous, and because of its delicate 
 construction it breaks down with awkward 
 ease. Hence it is safe to prophesy that the 
 flying-machine of the future will be equipped 
 with motors far higher in power than those at 
 present in use. 
 
 It is probable that the future aeroplane will 
 carry two motors, instead of one, each motor 
 independently operative, so that if one fails, 
 the other will still be able to drive the machine 
 safely through the air. For military purposes 
 at least, such a double-motor aeroplane is abso- 
 lutely necessary. Imagine a spy in the air 
 compelled to glide ignominiously down in an 
 enemy's camp, because his engine failed him! 
 Mere considerations of safety demand the in- 
 stallation of two motors on a flying-machine. 
 In March, 1910, the French aviator Crochon 
 fell to the ground in a cross-country flight from 
 
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THE FUTURE FLYING-MACHINE 233 
 
 Mourmelon to Chalons, because his motor 
 broke down. Le Blon was killed at San Sebas- 
 tian on April 2, 1910, as a result of a similar 
 motor trouble. During the Nice meeting in 
 April, 1910, Chavez and Latham mercifully 
 dropped into the Mediterranean, also because 
 of motor trouble. All of these accidents might 
 have been avoided if the aviators could have 
 relied upon a second motor. 
 
 The aviator of the present day is somewhat 
 in the position of a bicycle rider on a slack wire, 
 armed with a parasol. He must exercise inces- 
 sant vigilance, lest he lose his balance. The 
 strain upon nerves and muscles, for the begin- 
 ner at least, is tremendous. Hence, even now, 
 we hear of automatic devices which will prevent 
 the loss of a flying-machine's equilibrium and 
 which will enable the aviator to soar in the sky 
 more blithely than he can at present. 
 
 Balloonists find difficulty in ascertaining their 
 location, particularly after descending from a 
 cloud bank. It is true that the aviator can 
 swoop down to the earth and find out where he 
 is. Nevertheless, it is very likely that in the 
 future he will be provided with charts and in- 
 
234 THE NEW ART OF FLYING 
 
 struments which will obviate that necessity, 
 charts which will indicate landmarks and instru- 
 ments which will indicate the angle of the flight 
 path and which will include convenient field 
 glasses and day and night signalling devices. 
 Needless to say the aviator will carry a com- 
 pass, probably a prismatic compass from which 
 directions can be taken with great accuracy so 
 long as fixed objects on the earth are visible. 
 No doubt the compass will have a dial covered 
 with luminous material, visible in the dark. 
 At night a trailing-line will be cast overboard, 
 fitted with some electrical indicator, which will 
 ring a bell if some object should be struck, to 
 warn the pilot that he is flying too low. The 
 German Aerial Navy League has proposed 
 that special beacon lights be erected at certain 
 points. The aviator of the future will certainly 
 need some such guidance if he flies by night, 
 some light which will send a long beam in the 
 direction in which the wind is blowing. 
 
 Two men at least will be carried by the aero- 
 plane of the future, one to look after the 
 controlling mechanism and the other to navi- 
 gate. The military aeroplane will surely be so 
 
THE FUTURE FLYING-MACHINE 235 
 
 manned; for one man alone cannot perform 
 the duties of mechanician and observer. 
 
 Explorations into unknown lands will be 
 robbed of their perils by the flying-machine. 
 The hummocks of the Arctics, the jungles of 
 Africa, the morasses of a country untrodden by 
 the foot of man can hide nothing from the ex- 
 ploring aviator. Tasks which formerly occu- 
 pied years for -their achievement will hence- 
 forth be accomplished in as many months, 
 weeks, or even days. If Lieutenant Shackleton 
 found the motor-car of service in Antarctic ex- 
 ploration, what shall be said of the flying-ma- 
 chine which speeds on its journey unimpeded by 
 mountains of snow or grinding pack-ice? The 
 character of the information gathered by the 
 future explorer-aviator will be of greater scien- 
 tific value than that which is at present so pain- 
 fully collected. A Livingstone or a Stanley chop- 
 ping his way through dense tropical vegetation 
 brings back no complete map of the region trav- 
 ersed. All that he can show is his itinerary, 
 a mere fringe of the new country. Mountains 
 and rivers he indicates rather than charts. In- 
 stead of crawling over the face of our planet, 
 
236 THE NEW ART OF FLYING 
 
 the sky-explorer will some day survey it from 
 a height. He will see his Africa or Asia or 
 India spread before him like a map. His eye 
 will sweep an area measuring hundreds of 
 square miles in extent. The camera will record 
 those topographical peculiarities which he came 
 to note, and he will be spared the necessity of 
 imperilling his life to discover the source of a 
 river or the secret of some Tibetan Forbidden 
 Kingdom. 
 
 So far as actual appearance goes, the opin- 
 ions of present-day flying experts differ as to the 
 flying-machine of the future. Mr. R. W. A. 
 Brewer, an English authority, sees a larger and 
 a heavier machine than we have at present, a 
 kind of air yacht, weighing at least three tons, 
 and built with a boat-body. The craft of his 
 fancy will be decked in. It will carry several 
 persons conveniently and will be provided with 
 living and sleeping accommodations. He proph- 
 esies that it will fly at speeds of one hundred and 
 fifty to two hundred miles an hour, for the rea- 
 son that high speeds in flying, according to some 
 authorities, mean less expenditure of power than 
 lower speeds. Mr. F. W. Lanchester, as we 
 
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 tj) 
 
THE FUTURE FLYING-MACHINE 237 
 
 have pointed out in a previous chapter, enter- 
 tains similar views on the necessity of high 
 speed. If it is ever possible for an aeroplane 
 to travel at such terrific velocities, whole conti- 
 nents will become the playgrounds of aviators. 
 Daily trips of one thousand miles would not 
 be extraordinary. It is even conceivable that 
 there will be aeroplane liners which will travel 
 from Europe to America in twenty-four hours. 
 
 It seems certain that special starting and 
 alighting grounds will be ultimately provided 
 throughout the world. If tramcars must have 
 their stables and their yards, it is not unreason- 
 able to demand the provision of suitable aero- 
 plane stations. Depots or towers will be erected 
 for the storage of fuel and oil, garages on 
 stilts, in a word. The aviator in need of sup- 
 plies will signal his wants, lower a trailing line 
 and pick up gasoline by some such device as 
 we now employ to catch mail sacks on express 
 trains. 
 
 It may well be that the advent of the flying- 
 machine will have a marked effect on our archi- 
 tecture. Some day houses will be provided with 
 landing stages, assuming that the aeroplane 
 
238 THE NEW ART OF FLYING 
 
 will be able to alight more easily than at pres- 
 ent and without the necessity of running along 
 the ground for some distance before it expends 
 its momentum. Ely's remarkable feat in land- 
 ing on the deck of a warship in the harbour of 
 San Francisco shows that the thing is not re- 
 motely possible. When that day dawns, roofs 
 will disappear in favour of flat terraces suited 
 for launching and landing. A business man in- 
 stead of travelling in a lift from the ground 
 floor of a building to his office on the twenty- 
 first floor, will start from the roof of the build- 
 ing and proceed downward. 
 
 Above all things, flyirg must be safer than 
 it is now. Although the dangers of a sport 
 will inevitably attract to it adventurous spirits, 
 a really commercial machine must satisfy the 
 requirements of the highly nervous man or 
 woman to whom sailing a yacht seems a suicidal 
 pastime. 
 
 The early days dl the bicycle and the auto- 
 mobile industries offer a close parallel to the 
 present position of the aeroplane industry. 
 The pioneers having shown the way, the ma- 
 chine immediately became an instrument of 
 
THE FUTURE FLYING-MACHINE 239 
 
 sport. Speed was the thing first desired, and 
 the speed of anything that moves can best be 
 demonstrated in a competition. Bicycle and 
 automobile races became and still are, to some 
 extent, the manufacturer's opportunity of test- 
 ing and demonstrating the quality of his ma- 
 chines. Long before the manufacture of either 
 touring bicycles or touring automobiles as- 
 sumed their present proportions, the production 
 of the racing machine was all important. The 
 flying-machine is now in this stage. Races and 
 endurance tests will be the battles from which 
 will emerge the flying-machine of the future, 
 the machine capable of sustained flights, many 
 hours in duration, at speeds of eighty and one 
 hundred miles an hour. The racer will give 
 birth to the touring flyer, just as the touring car 
 of to-day was evolved from the racing car of 
 five years ago. 
 
 Incredible as it may seem, in less than a year 
 from the date when Blerioc flew over the Eng- 
 lish Channel, a feat which set France aeroplane- 
 mad, the actual sales of flying-machines out- 
 numbered the actual sales of automobiles in 
 the first year of their commercial development. 
 
240 THE NEW ART OF FLYING 
 
 A flying Frenchman clamours for his Bleriot 
 or Farman as impatiently as an automobiling 
 American millionaire for his high-powered car, 
 ordered months in advance. The one is no 
 more inclined to bide his time than the other. 
 Hence agents have sprung up in Paris, who 
 order machines from the manufacturer on spec- 
 ulation, and receive as much as $500 to $1,000 
 above the factory price for immediate delivery. 
 In Paris at least such signs as " Bouvard et 
 Pecuchet, Agents pour Monoplanes Antoi- 
 nette " can be seen even now, the harbinger 
 of a great industry of the future and of flying- 
 machine quarters in our large cities. 
 
 Compared with the flying-machine of the 
 future, the motor-car will seem as tame and dull 
 as a cart, drawn by a weary nag on a dusty 
 country road. Confined to no route in particu- 
 lar, unhampered by speed restrictions, the speed 
 maniac can drink his fill in the high-powered 
 monoplane. Even the most leisurely of air- 
 touring machines will travel at speeds that only 
 a racing automobile now attains, while the air 
 racer will flit over us, a mere blur to the eye 
 a buzz to the ear. In an hour or two a 
 
Photograph by Edwin Levick 
 
 Fig. 83. The 100 horsepower Antoinette monoplane 
 
 that Hubert Latham flew at Belmont Park 
 
 during the International Aviation 
 
 Tournament of 1910 
 
THE FUTURE FLYING-MACHINE 241 
 
 whole province will be traversed; in a day a 
 whole continent. An air tourist, a few years 
 hence, will breakfast in Paris and sup the same 
 evening in Moscow. His air-charts, the equiva- 
 lent of our present road automobile maps will be 
 an atlas, a book in which the air-routes of all 
 Europe are laid down. Swifter than any storm 
 will be his flight. If the black, whirling mael- 
 strom of a cyclone looms up before him, he can 
 make a detour or even outspeed it; for the 
 velocity of his machine will be greater than that 
 of the fiercest of howling, wintry blasts. At a 
 gale which now drives every aviator timorously 
 to cover, he snaps a contemptuous finger, 
 plunges through it in a breathless dash and 
 emerges again in the sunshine, as indifferent to 
 his experience as a locomotive engineer after 
 running through a shower. 
 
 The aspect of the heavens will be wonder- 
 fully changed when the pleasure plane of the 
 air has arrived. Black specks will dot the blue 
 sky, more like birds than machines, specks that 
 the practised will recognise as impetuous and 
 daring high flyers. Lower down the less reck- 
 less will perform their evolutions, and the whirr 
 
242 THE NEW ART OF FLYING 
 
 of their motors will be as the droning of bees, 
 so numerous will they be. 
 
 All this deals with the sport. Has the aero- 
 plane no mercantile future? Shall we see 
 flocks of gigantic artificial birds, freighted with 
 heavy cargoes, darkening the sky as they wing 
 their way across the Atlantic or the continent? 
 Will travelling by steamship and railway give 
 way to the aeroplane? 
 
 The most sanguine aeronautic engineer would 
 not venture to predict the supplanting of the 
 freight train or the steamer by the aeroplane. 
 For many, many years to come the flying- 
 machine will remain what it is now, a vehicle of 
 sport and war only. Perhaps it may never be 
 anything more. Why? Because it cannot be 
 made big enough. The carrying capacity of an 
 aeroplane depends on its spread of plane. To 
 increase the load means so important an in- 
 crease in spread that an unmanageable area of 
 supporting surface would be necessary. In 
 order to secure the necessary strength to uphold 
 this increased area an increased weight per 
 square yard is entailed. Hence it is unlikely 
 that aeroplanes carrying many passengers will 
 
THE FUTURE FLYING-MACHINE 243 
 
 be built in our time. Not so very long ago Mr. 
 Orville Wright expressed the opinion that aero- 
 planes " will never take the place of trains or 
 steamships for the carrying of passengers. My 
 brother and I have never figured on building 
 large passenger-carrying machines. Our idea 
 has been to get one that would carry two, three, 
 or five passengers, but this will be the limit of 
 our endeavours." 
 
 The late Prof. Samuel P. Langley discovered 
 in the course of his classic experiments that the 
 higher the speed at which a plane travels 
 through the air the less is the supporting sur- 
 face required. Hence there is a chance that a 
 machine may be constructed in the future which, 
 taking advantage of this law, will be provided 
 with a supporting surface adjustable in area, 
 so that it can start with a large surface, and 
 fold up its planes at full speed. In such a 
 machine the supporting surface would be ulti- 
 mately reduced until it is a thin edge. We 
 would have an aeroplane propelled by great 
 power, supported largely by the pressure against 
 its body, its wings reduced to mere fins, serving 
 to guide its motion. 
 
244 THE NEW ART OF FLYING 
 
 As a future commercial possibility, the air- 
 ship is far more promising than the aeroplane. 
 To the size of the airship there is no limit. 
 Indeed, the larger it can be built the more eco- 
 nomically can it be driven, when we measure 
 economy by ratio of carrying power to cost of 
 operation. Just how large an airship can be 
 constructed is a question of constructive en- 
 gineering. In considering that question the late 
 Prof. Simon Newcomb pointed out that econ- 
 omy is gained only when the dimensions of an 
 airship are so increased that it will carry more 
 than an ocean steamer or a railroad train. To 
 attain that end he estimated that it would be 
 necessary to build an airship at least half a mile 
 in length and six hundred feet in diameter. 
 Such an airship might carry a cargo of ten thou- 
 sand tons or fifteen thousand passengers. The 
 construction of so huge a craft is not an utter 
 engineering absurdity, remote as it may seem 
 to us now. We recently witnessed something 
 like this when Count von Zeppelin's passenger- 
 carrying airship made a voyage that excited 
 the admiration of the world, even though the 
 vessel was wrecked in a storm. Some fourteen 
 
THE FUTURE FLYING-MACHINE 245 
 
 passengers were transported on that remark- 
 able trip, for whom adequate seating and dining 
 accommodations were provided. But the cost 
 of operating such a giant of the air is enormous. 
 After all is said, money will decide the ques- 
 tion of the commercial possibilities of flying- 
 machines and airships. How much does it cost 
 to build? How much does it cost to maintain? 
 How much does it cost to operate? Not until 
 these questions are answered satisfactorily can 
 we tell whether or not the aeroplane will ever 
 be anything more than a racing machine for 
 gilded youth and the dirigible an air-yacht for 
 bankers too old for the more perilous aeroplane. 
 
CHAPTER XV 
 
 THE LAW OF THE AIR 
 
 IT is one of the most difficult tasks of govern- 
 ment to adapt existing laws to those incessant 
 changes in the relationships of nations and in- 
 dividuals which are brought about by the in- 
 vention of new arts and industries. The rail- 
 road, the telegraph, the telephone, and wire- 
 less signalling have each given the legislatures 
 of the world no little concern in developing 
 codes which would enable the new inventions 
 to take their place in our daily lives without too 
 greatly disturbing vested rights. 
 
 Englishmen and Americans are fortunate in 
 having a common law, which, although based 
 upon custom and precedent, is nevertheless so 
 flexible that it is able to adapt itself to the new 
 conditions which the flying-machine will create. 
 To supplement whatever shortcomings the com- 
 mon law may have, there can be no doubt that 
 special statutes will be passed in this country 
 and England to define the relations of the air- 
 
THE LAW OF THE AIR 247 
 
 men to people on the earth below. European 
 nations develop their laws more consciously. 
 They even anticipate conditions that may arise 
 by the introduction of a new invention. Thus 
 we find that continental jurists have given con- 
 sideration to questions of such detail as the 
 nationality to be ascribed to persons born on 
 board voyaging air-craft, rights in respect of 
 salvage, and other doctrines drawn from mari- 
 time law. Twenty years hence it will be inter- 
 esting to compare Anglo-Saxon air-laws evolved 
 from custom and actual experience, with the air- 
 laws of the continent, many of them enacted 
 before aerial navigation was really established. 
 The mere fact that aeroplanes and airships 
 plough the air above us is in itself a circum- 
 stance that gives rise to a new legal situation. 
 As Professor Meli of Zurich has put it, a careful 
 man must now look not simply in front of him 
 and on either side, but above him as well. 
 
 Has the airman any inherent right to navi- 
 gate the air at all? That is the first question 
 that must be decided by civilised countries, 
 whether they be Anglo-Saxon, European, or 
 Asiatic. The question of an inherent right must 
 
248 THE NEW ART OF FLYING 
 
 be considered both from the standpoint of the 
 private property owner and from the standpoint 
 of international law. 
 
 Even among lawyers the old saying that to 
 the owner of a piece of land belongs not only 
 the earth beneath his feet to the very centre of 
 the globe, but the air above his property to an 
 infinite height, is regarded as a basic principle 
 of the English common law. Yet, to use the 
 words of Brett, Master of the Rolls, in the case 
 of Wandsworth Board of Works v. United 
 Telephone Company, (1884) 13 Q. B. D. 904, 
 this old maxim is at best a u fanciful phrase. " 
 The maxim can be traced to Coke upon Littleton 
 and to Blackstone. In all the vast body of deci- 
 sions on which the English common law is based, 
 there can be found none in which the ownership 
 of the air to a height above that at which a prop- 
 erty owner could make reasonable use of it, is 
 the point at issue. It is true that Coke's old 
 saw and its reiteration by Blackstone have been 
 approved in many a dictum; but dicta are not 
 decisions. If the doctrine were really good 
 common law, every man who sailed over the 
 land of another would be a trespasser. Sup- 
 
THE LAW OF THE AIR 249 
 
 pose that an action were brought to collect dam- 
 ages for trespass. It is hardly likely that even 
 nominal damages could be recovered, for the 
 simple reason that no injury has been worked 
 to the landowner's estate and no nuisance has 
 been created. Decisions enough can be found 
 to justify the action of trespass in all cases of 
 encroaching signs, buildings, trees, overhang- 
 ing telegraph and telephone wires; but in all 
 these cases the defendant's possession and the 
 use of the land have been interfered with. It 
 may well be concluded that rights in the air 
 must be strictly appurtenant to the soil beneath, 
 and that unless a reasonable use of the land is 
 interfered with, no action for trespass will lie. 
 The actual interference with the enjoyment 
 of the land as the sole justification for legal 
 action is fully recognised in Europe. Even be- 
 fore the advent of the flying-machine and the 
 airship the code of the Canton of Grisons pro- 
 vided that " property in land extends to the air 
 space (above) and the earth beneath, so far as 
 these may be of productive value to the owner." 
 In the German Civil Code the rights of the air- 
 man are recognised in a clause in which the 
 
2 5 o THE NEW ART OF FLYING 
 
 property holder " cannot prohibit such interfer- 
 ences undertaken at such a height or depth that 
 he has no interest in the prevention." 
 
 It is probable that one of the first of the fu- 
 ture laws of the air will fix the height at which 
 air-craft must travel. In all likelihood the aero- 
 naut will be compelled to sail at a height not 
 less than fifteen hundred feet over inhabited 
 districts and navigable inland waters, leaving 
 him free to fly at any height he pleases over 
 wildernesses and the high seas. A man who 
 sails over a city not only takes his own life into 
 his hands, but also endangers the lives of others, 
 because he cannot readily alight should his 
 motor fail him. The French advocate, Fau- 
 chille, has therefore proposed a law which will 
 forbid flying over communities without the per- 
 mission of the authorities. 
 
 That an action can be brought against an 
 aviator who alights upon a piece of land with- 
 out the owner's permission, even though he be 
 compelled to do so against his will, is even now 
 well established. In a New York case (Guille 
 v. Swann, 19 Johns. 381 ; 10 Amer. Dec. 234) 
 decided in 1822, an aeronaut was held respon- 
 
THE LAW OF THE AIR 251 
 
 sible not only for the direct damage caused by 
 the descent of his balloon into a garden, but 
 even for the remote damage caused by the 
 crowding of strangers upon the property to sat- 
 isfy their curiosity. Such unpremeditated de- 
 scents will be frequent in coming years. The 
 obvious necessity of sometimes alighting against 
 one's will demands some law which will enable 
 the airman to land without necessarily incurring 
 a suit for damages or imprisonment. Judge 
 Simeon Baldwin questions whether it will not 
 be advisable to prescribe a mode of indicating 
 where a landing is prohibited and where it is 
 permitted. If, for instance, a red flag were 
 made the sign of prohibition, it may fairly be 
 provided, in his opinion, that to land in the face 
 of such a warning the aviator subjects himself 
 to an action for double damages, enforcible by 
 his arrest. The Berlin Conference relating to 
 wireless telegraphy imposed on all coast and 
 shipping stations the duty of exchanging wire- 
 less messages, regardless of the system em- 
 ployed. A similar arrangement would probably 
 apply to the right of air-craft to use local areas 
 set apart for alighting, mooring, and embarka- 
 
252 THE NEW ART OF FLYING 
 
 tion. It would seem that a distinction should 
 be made between an accidental landing, which 
 is due to negligence and which causes damage, 
 and a landing which is made with all due care 
 in order to save the airman from death. In 
 the one case a penalty of some kind should be 
 imposed, but in the other the airman should be 
 allowed to escape by simply paying the amount 
 of the actual damage which he has inflicted. 
 Judge Baldwin has even raised the question 
 whether the law of self-preservation cannot be 
 invoked by an airman who is compelled to 
 make an immediate landing to save his own life 
 and by so doing accidentally causes the death 
 of another. 
 
 It is certain that in order to reduce the possi- 
 bility of accidents to a minimum only a licensed 
 pilot will be permitted to navigate the air in 
 the future. Judge Baldwin advises that the 
 government issue such licenses only on the 
 filing of a proper indemnity bond for the bene- 
 fit of those who may suffer such accidents. 
 He has pointed out that the same result could 
 be obtained by compelling the owners of air- 
 craft to take out blanket policies of accident 
 
THE LAW OF THE AIR 253 
 
 insurance, covering all injuries occasioned by 
 the use of the ship and authorising the injured 
 to bring suit upon it in the name of the insured, 
 but for their own benefit. 
 
 In European countries a tendency is shown 
 to subject air navigation to the monopolistic 
 control of the state. In the United States and 
 in England private enterprises will have a freer 
 hand, subject, of course, to strict governmental 
 supervision by registration, license, and inspec- 
 tion. But shall such a government license 
 issued in one state or country be respected in 
 another? There seems to be no good reason 
 why it should not. Automobile licenses are so 
 respected for a limited number of hours. 
 Treaties and agreements will undoubtedly be 
 drawn which will secure the recognition of air 
 licenses by foreign governments. But to har- 
 monise the aeronaut's rights with those of other 
 men and those of foreign lands over which he 
 may take his course, demands not only ade- 
 quate local legislation but adequate interna- 
 tional agreements. Professor Meli of Zurich, 
 in a recent address before the International 
 Vereinigung fur vergleichende Rechtswissen- 
 
254 THE NEW ART OF FLYING 
 
 schaft of Berlin, strongly advocated the 
 convening of an international conference for 
 this purpose. Such a conference was held at 
 Paris in 1910, but accomplished very little in 
 the way of practical results. The British 
 Government demanded more time for con- 
 sideration before approving the measures of 
 the Conference. 
 
 Although every reasonable concession will 
 be made to the man who builds and flies air- 
 craft, it must not be supposed that those below 
 are altogether at the mercy of the man in the 
 air. Every moment of an atmospheric voyage 
 is fraught to some extent with danger to those 
 below. If actual physical injury is sustained 
 by a man on the ground, the civil or criminal 
 courts may be appealed to for justice. The 
 man who is wounded by an object dropped 
 from an air-craft certainly has a right of action 
 for damages, whether or not he be the owner 
 of the land upon which he happens to be stand- 
 ing at the time. The master and servant rule 
 would apply here as well as in other cases. 
 An action for damages would lie against the 
 pilot of the flying-machine, whether he be the 
 
THE LAW OF THE AIR 255 
 
 owner of the craft or not, or the master by 
 whom he is employed. It is even conceivable 
 that an injunction could be obtained to abate 
 a nuisance caused by a fleet of air-craft travel- 
 ling in a defined roadway day after day and 
 week after week, so as to annoy a tenant or a 
 property holder by their noise, odours, exhaust, 
 and the like. 
 
 Besides these rights of the man below, 
 whether he be a landowner or not, there are 
 broader national questions to be considered. 
 In a sense the state is the ultimate owner of 
 the soil, and as such it has the right to regulate 
 the air above its territory, and to state the con- 
 ditions under which it will permit the naviga- 
 tion of the air. That air-craft will sooner or 
 later become the subject of governmental reg- 
 ulation and authorisation seems almost self- 
 evident when we consider the history of the 
 railroad, the telegraph, the telephone and wire- 
 less telegraphy. In the United States the indi- 
 vidual states will regulate the air-craft that ply 
 the air wholly within the state; the federal 
 government those vessels that travel from state 
 to state. 
 
256 THE NEW ART OF FLYING 
 
 The international aspects of the question are 
 somewhat more difficult to dispose of. Before 
 the American Political Science Association, Mr. 
 Arthur K. Kuhn suggested that the right of 
 the craft of one nation freely to traverse the 
 air-space of another might be compared with 
 that of the vessel of one state freely to navi- 
 gate the river of a coriparian state, especially 
 when the river becomes navigable within its 
 own territory. Dr. Hazeltine, reader in Eng- 
 lish law at Cambridge, believes, however, that 
 the analogies of the high seas and the maritime 
 belt of coastal waters as applied by advocates 
 of limited sovereignty are far from being sound 
 and applicable. Still it is not unlikely that, in 
 settling the international problems that must in- 
 evitably arise in the future, some of the prin- 
 ciples of maritime law will be applied to the 
 navigation of the air. Because the airship, and 
 to a lesser degree the aeroplane, may be an 
 instrument of commerce as well as a ship sail- 
 ing the high seas, Judge Baldwin has suggested 
 that provision must be made for ship's papers; 
 that the number of passengers to be carried on 
 an air vessel must be fixed; that the qualifica- 
 
THE LAW OF THE AIR 257 
 
 tions of those in charge must be determined; 
 that machinery must be inspected; and that 
 pilotage must be provided for. 
 
 Freedom of the seas is based on the impos- 
 sibility of an effective control by any one state. 
 It has been urged by one school of German 
 advocates, among them Meurer, Holtzendorff, 
 and Griinwald, that the air-space over a state 
 is an appurtenance of it, and as such the right 
 to navigate it is not as free as the right to navi- 
 gate the high seas. By another school the rela- 
 tion of the state to its overlying air-space is 
 compared with that of its coastal waters. The 
 abortive Convention drafted by the International 
 Conference on Aerial Navigation of 1910 was 
 based entirely upon the provisions of inter- 
 national maritime law. There are the same re- 
 quirements as to registration and nationality of 
 air-vessels, certificates of fitness of the craft 
 and the competence of its navigators and navi- 
 gation in territorial waters using the mari- 
 time phrase for the sake of convenience and 
 the same regulations applying to the sojourn 
 of alien craft in distress. It is laid down that 
 aerial navigators must keep a very detailed 
 
258 THE NEW ART OF FLYING 
 
 log, giving the names, nationality and domicile 
 of all persons on board, and embodying a record 
 of the course, altitude and all the events of the 
 voyage. This log must be preserved for at 
 least two years from the date of the last entry, 
 and must be produced on the demand of the 
 authorities. Each state would have to exercise 
 the right of police and customs supervision in 
 the atmosphere over its territory. It would 
 have power to regulate passenger and goods 
 traffic between points in its own territories, and 
 it could prohibit navigation in certain zones of 
 reasonable extent, indicated with sufficient pre- 
 cision to permit of their being shown on aero- 
 nautical charts. There is such a thing as a three- 
 mile limit in maritime law, a limit originally set 
 by the range of a cannon. Why then, we are 
 asked, should there not be sovereignty within a 
 certain zone, the height of which is determined 
 by gun fire? The analogy and the rule re- 
 sulting from it were strongly supported by 
 Westlake before the Institute of International 
 Law; but they were rejected in favour of a 
 negative sovereignty, saving the right of self- 
 protection. The range of Krupp ordnance, 
 
THE LAW OF THE AIR 259 
 
 which has been especially designed for airship 
 repulsion, would no doubt aid in determining 
 the height of such a zone. Holtzendorff, Fau- 
 chille, and Holland would restrict absolute sov- 
 ereignty within a zone of isolation varying from 
 three hundred and thirty metres (the altitude 
 of the Eiffel Tower as the highest artificial 
 object) to fifteen hundred metres. The topog- 
 raphy of the earth is in itself a sufficient objec- 
 tion to that proposal. Dr. Hazeltine has 
 expressed the view that any theory of sover- 
 eignty limited in height is open to the same 
 objection as the theory of a zone of protection 
 in which free passage is allowed to non-military 
 craft. In his opinion the state should have full, 
 sovereign dominion in the entire air space 
 above its territory. Furthermore, he main- 
 tains that the recognition of each territorial 
 state's full right of sovereignty in the air space 
 above it would constitute a basis for the fu- 
 ture development of national and international 
 aerial law, leaving, as it would, to aerial navi- 
 gators as well as states and their inhabitants 
 the full legal enjoyment of their proper interests. 
 A nation's sovereignty can hardly extend 
 
260 THE NEW ART OF FLYING 
 
 to a domain that it cannot defend from invasion. 
 When Balboa stood upon a peak in the Andes 
 and, surveying the Pacific, claimed in the name 
 of Spain all the land that its waters might wash, 
 he was as ridiculous as he was grandiloquent. 
 Even in that age of limited geographical knowl- 
 edge he must have felt that his country could 
 never uphold the claim by force of arms. To be 
 sure, it would be easier for a nation to defend all 
 the air-space above its territory than to restrain 
 encroachments upon land washed by the waters 
 of a vast ocean. The maximum height at which 
 air-craft can sail may be placed at about five 
 miles, with the probability that the average 
 height will be about one mile. It would not be 
 a task of extraordinary difficulty for any nation 
 equipped with a formidable aerial navy to police 
 its air-space more or less effectively. Whatever 
 zone is adopted, self-interest alone will impel 
 each state to grant access to and passage 
 through its air-space in time of peace, subject 
 only to such rules as its reasonable interests may 
 require. As to the liberty to navigate the air, 
 the following rule was accepted at the Inter- 
 national Conference of 1910: 
 
THE LAW OF THE AIR 261 
 
 " Each of the contracting States shall permit 
 the navigation of the airships of the other con- 
 tracting States within and above its territory, 
 reserving the restrictions necessary to guaran- 
 tee its own safety and that of the persons and 
 property of its inhabitants." 
 
 The restrictions referred to relate chiefly to 
 the question of certain zones, over which, if they 
 are properly indicated in advance, no airship 
 may fly unless compelled to by necessity. If 
 an aeroplane is carried by accident or by adverse 
 air conditions over an interdicted zone, it must 
 descend at once and indicate its disability. It 
 must also descend if signalled to from the 
 earth. 
 
 The matter of jurisdiction over crimes com- 
 mitted by airmen or their passengers is likewise 
 a matter of international concern. Fauchille has 
 proposed that crimes committed on air-craft " fall 
 under the competence of the tribunals of the 
 nation to which the air-craft belongs." Ameri- 
 can and English lawyers will object to any such 
 principle because Anglo-Saxon law has always 
 been territorially administered. Probably con- 
 current jurisdiction will be agreed upon, as in 
 
262 THE NEW ART OF FLYING 
 
 the case of crimes committed on foreign vessels 
 in territorial waters. 
 
 Besides crimes committed on air-craft, there 
 are also crimes committed on the ground which 
 involve the rights of airmen. Balloons have 
 been shot at in pure wantonness. Jurisdiction 
 in such cases obviously belongs to the country 
 in which the firearms were discharged. If a 
 man is killed in a flying-machine in the United 
 States by a bullet discharged over the border- 
 line in Canada, there is no reason why murder 
 has not been done in the United States and why 
 the murderer should not be extradited and tried 
 in a United States court. 
 
 Lastly, there remains to be considered the 
 legal status of the airship and the aeroplane in 
 time of war. Balloons were used in war long 
 before the dirigible airship or the aeroplane 
 were brought to a state of practical perfection, 
 but they never played so conspicuous a part in 
 military operations that it was necessary to de- 
 fine their status according to the principles of 
 international law. It is true that Bismarck said 
 that an Englishman who manned a French 
 balloon would be subject to arrest and trial 
 
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THE LAW OF THE AIR 263 
 
 " because he had spied out and crossed our out- 
 posts in a manner which was beyond the* con- 
 trol of the outposts, possibly with a view to 
 making use of the information thus gained to 
 our prejudice." That dictum of blood and iron 
 seems much too drastic even to German com- 
 mentators. A spy is supposed to act clandes- 
 tinely. An air-craft is so conspicuous an object 
 that even though bent on ascertaining the 
 enemy's strength and the disposition of its 
 forces, its errand can hardly be secret. On the 
 other hand, Mr. Kuhn has pointed out that the 
 impossibility of flying secretly by day, at least, 
 is in itself no reason why the use of the air- 
 craft may not be clandestine. The Hague 
 Peace Conference in 1907 left the matter in a 
 very unsatisfactory condition. It provided that 
 aeronauts were not to be regarded as spies if 
 they carried despatches or maintained commu- 
 nication between different parts of an army or 
 territory, but it failed to fix the status of the 
 reconnoitring airman. In the war of the future 
 the aeroplane and the airship will perform 
 much the same function as a cavalry reconnais- 
 sance in force; yet even Bismarck would not 
 
264 THE NEW ART OF FLYING 
 
 have shot as a spy a trooper captured on a 
 scouting raid. The international complica- 
 tions which may arise even at the present time 
 will undoubtedly be considered when the next 
 Hague International Conference takes place. 
 The possibility that an alert military spy, float- 
 ing serenely over a fortress which has cost a 
 nation millions, may photograph or sketch 
 every battery, manifestly necessitates the adop- 
 tion of some restrictive measures. So jealously 
 are many of the fortifications of Europe 
 guarded from the watchful eyes of spies, that 
 entry within their portals is granted only on 
 certain conditions. No cameras may be taken 
 within the lines; nor is admission granted with- 
 out credentials. What a spy on land might be 
 unable to discover in months by cunning, cajol- 
 ery, and bribery, will be exposed to an aeronaut 
 in half an hour. Some check must therefore be 
 placed upon the scout in the air. At the Inter- 
 national Conference on Aerial Navigation of 
 1910 it was proposed that a state should have 
 the privilege of developing photographic nega- 
 tives found on board an airship coming to earth 
 in its territory, and if necessary to seize them 
 
THE LAW OF THE AIR 265 
 
 and the photographic apparatus. Wireless tele- 
 graphic instruments, too, could not be used, 
 according to another provision, without special 
 permission, for any other purpose than to secure 
 the vessel's safety. Perhaps, although no Inter- 
 national Conference has thus far suggested it, 
 the pilots of the future will be constrained 
 to avoid fortifications entirely, or run the risk 
 of arrest by air sentry, military lookouts 
 gliding along in aeroplanes ready to act if a 
 too closely approaching atmospheric tourist ap- 
 pears. Arrests will undoubtedly be made by 
 these sentinels in the air; the captured aeronaut 
 will be asked for his credentials and will be 
 searched for sketches that may implicate him. 
 If he is caught red-handed, he will be punished 
 
 how, must be determined by international 
 agreement. 
 
 The war of the future will be a conflict of air- 
 craft as well as of infantry and artillery. How 
 shall the aeroplane of any warring country be 
 distinguished from those of any other? Every 
 ship on the high seas, whether it be merchant- 
 man or battleship, flies the flag of its country, 
 
 a challenge to its foes in time of war, a 
 
266 THE NEW ART OF FLYING 
 
 badge of peace to its friends. The question 
 of nationality brought up some interesting points 
 during the International Conference of 1910. 
 It was decided that it should be determined by 
 the nationality of the owner or by his domicile. 
 It was also voted that: 
 
 " A State may require its subject to be at the 
 same time domiciled on its territory, or it may 
 admit domiciled foreigners as well as its sub- 
 jects. Airships belonging to companies must 
 take the nationality of the State in which their 
 head office is situated. In the case of an airship 
 belonging to several owners, at least two-thirds 
 must be owned by subjects of, or foreigners 
 domiciled in, the State conferring nationality." 
 
 The Swiss delegates protested that this article 
 would permit the establishment of many foreign 
 airships in one nation without the supervision of 
 their own, and then drew attention to a sugges- 
 tion already made by them that no nationality 
 be attributed to airships, but that each airship 
 be compelled to acknowledge a " certain port 
 of register or domicile." This system, the Swiss 
 believe, " offers, from the point of view of the 
 safety of States, guarantees very superior to 
 
THE LAW OF THE AIR 267 
 
 those secured by the system of owner's na- 
 tionality." But the Swiss proposal was rejected. 
 
 Fully as important as these considerations 
 are the rights of neutral air-craft in time of 
 war. If France and Russia are at war, has 
 Germany the right to prevent the v vessels of 
 either nation from crossing her boundaries be- 
 cause her neutrality is violated? The right of 
 exclusion is absolute, if no neutral zone be 
 agreed upon internationally. But if a free 
 zone be agreed upon, the aerial equivalent of 
 the maritime three-mile limit, have belligerents 
 the right to engage in battle over neutral ter- 
 ritory with a possibility of injuring those below? 
 There is such a force as gravitation and 
 with that force airships and aeroplanes must 
 constantly reckon. 
 
 Will the air-craft that seeks refuge on neutral 
 ground or in neutral air be compelled to leave 
 within a stipulated time, as in the case of a 
 warship that seeks refuge in a neutral harbor? 
 Will an air-craft so badly injured that it cannot 
 leave, even when ordered to do so, be disarmed? 
 
 The military reports of the question were 
 discussed at the International Conference of 
 
268 THE NEW ART OF FLYING 
 
 1910, but more with regard to the status of 
 air-craft in time of peace than in time of war. 
 The departing or landing of military airships 
 of one state in the territory of another was 
 prohibited, unless with the authorization of 
 the state whose territory is involved; -while 
 each contracting state was at liberty to pro- 
 hibit or regulate in accordance with its interests 
 the passage over its territories of military air- 
 ships belonging to other contracting states. A 
 clause in the Convention relating to the extra- 
 territoriality of military airships and their crews 
 while within the limits of jurisdiction of a for- 
 eign state, appears not to have met with the full 
 approval of the delegates of several Powers, 
 Great Britain and Austria being among those 
 who reserved their adhesion. The Convention 
 stipulated that nothing it contained should in- 
 terfere with the liberty of action of belligerents 
 or with the rights and duties of neutrals. As 
 bearing on this point, it is of interest that all 
 the participating nations agreed that the aerial 
 transport of explosives, firearms, ammunitiqn, 
 and carrier-birds must be forbidden. 
 
GLOSSARY 
 
 Adjusting Plane or Adjusting Surface: A surface 
 of small area for regulating lateral stability; usually 
 located at the side edge or rear edge of a supporting 
 plane. It is to be distinguished from an aileron (q. v.) 
 in that it is capable of adjustment but not of inde- 
 pendent movement by special operating devices. 
 
 Advancing Edge: See Entering Edge. 
 
 Advancing Surface: The forward supporting sur- 
 face of a machine provided with supporting planes in 
 tandem, as in the Langley aerodrome, or with super- 
 posed surfaces arranged in step formation. 
 
 Aerocurve: Any arched supporting surface. The 
 term has been proposed because few supporting sur- 
 faces are true aeroplanes. See also Aerofoil. 
 
 Aerodrome: A term invented by the late Prof. 
 Samuel P. Langley and used by him to designate 
 an aeroplane flying-machine. Etymologically the term 
 signifies " air-runner." It is more commonly used to 
 designate a flying-course by analogy with " hippo- 
 drome." Mr. F. W. Lanchester and Dr. Alexander 
 Graham Bell have sought to restrict the term to th& 
 use which Langley intended. 
 
 Aerodromics: Langley 's term for the science and art 
 of flying with an aeroplane flying-machine. 
 
 Aerofoil: The supporting surface of a flying- 
 machine, coined, like Aerocurve, because the sup- 
 porting surfaces of a flying-machine are not, strictly 
 speaking, flat planes. 
 
270 GLOSSARY 
 
 Aeronaut: One who navigates the air. 
 
 Aeronautics: The science of aerial navigation. 
 
 Aeronef: A term invented in France and intro- 
 duced into English-speaking countries to designate any 
 heavier-than-air flying-machine. The term is not much 
 employed either in French or in English. 
 
 Aeroplane: Any plane surface propelled through the 
 air. The term was invented before it was discovered 
 that curved surfaces are better than flat surfaces. 
 Hence it is not strictly applicable to modern support- 
 ing surfaces. 
 
 Aileron: A French word meaning " winglet," in- 
 troduced into English to designate any freely swinging 
 surface controlled by the aviator and designed to main- 
 tain lateral stability. Ailerons may be either tips 
 hinged to the side edges or rear edges of the main 
 supporting surface, or they may be small independent 
 planes. See also Adjusting Surface, Balancing Plane 
 or Surface, Stabiliser, and Wing-Tip. 
 
 Airship: A term originally employed to designate 
 any aerial craft, whether heavier or lighter than air, 
 but now restricted by the best writers to dirigible 
 balloons. 
 
 Air Speed: The velocity of a machine in the air as 
 distinguished from its velocity on the ground. 
 
 Airman: An aeronaut; one who navigates the air. 
 
 Alighting Gear: The wheels or skids or combina- 
 tions of both on which a machine alights. See 
 Skids. 
 
 Angle of Attitude: See Angle of Incidence. 
 
 Angle of Entry: The angle formed by a tangent to 
 the entering edge with the line x>f motion. 
 
 Angle of Incidence: The angle made by the main 
 
GLOSSARY 271 
 
 planes with the line of travel. Sometimes called 
 " angle of attitude " and " angle of attack." The angle 
 may be positive or negative, depending on the direction 
 in which the plane is turned to the line of flight. 
 
 Angle of Trail: The angle formed by a tangent to 
 the rear edge with the line of travel in curved sup- 
 porting surfaces. 
 
 Apteroid: Lanchester's term for a short, broad form 
 of wing. 
 
 Arch: The downward curve or droop to the ends 
 of supporting surfaces. 
 
 Aspect: The top plan view of an aeroplane flying- 
 machine. 
 
 Aspect Ratio: The ratio of the length to the width 
 of a plane or curved supporting surface. 
 
 Aspiration: The suction produced by a current of 
 air which strikes a curved supporting surface. 
 
 Attitude: See Angle of Incidence. 
 
 Automatic Stability: See Stability. 
 
 Auxiliary Surface: See Supplementary Surface. 
 
 Aviation: Flight with heavier-than-air machines as 
 distinguished from ballooning. 
 
 Aviator: The pilot of a heavier-than-air machine. 
 
 Balance: The maintenance of equilibrium by means 
 of balancing surfaces. A distinction is sometimes made 
 between Balancing and Stabilising (q. v.). 
 
 Balancing Plane or Balancing Surface: A surface for 
 establishing and maintaining equilibrium as well as to 
 assist in turning. Such surfaces may be operated either 
 automatically or by hand; they maintain both longi- 
 tudinal and lateral balance. 
 
 Beat: A periodically recurring movement in a pro- 
 peller blade or in a wing of a flapping-wing machine. 
 
272 GLOSSARY 
 
 Biplane: A flying-machine with two superposed sup- 
 porting surfaces. 
 
 Body: See Fuselage. 
 
 Box-Kite: A kite invented by Hargrave and pro- 
 vided with two parallel vertical and two parallel hori- 
 zontal surfaces in the form of an open box. 
 
 Brace: A compression member. 
 
 Camber: The curve of a supporting surface meas- 
 ured from port to starboard. 
 
 Caster-Wheel: A small wheel of the alighting gear, 
 so pivoted that, like the caster of a chair, it automati- 
 cally suits itself to the direction of the flying-machine's 
 motion on the ground. 
 
 Carburetter: An apparatus by which air is charged 
 with a hydrocarbon so that it will either burn or ex- 
 plode. In the gasoline flying-machine motor it serves 
 the purpose of mixing the gasoline vapor with air 
 in the right proportion to form an explosive when 
 ignited. 
 
 Chassis: The under framework of a flying-machine. 
 
 Cell: An open box-like unit. Its parallel vertical 
 and parallel horizontal surfaces serve to maintain 
 stability. 
 
 Centre of Effort: The point in which the effect of 
 an axially exerted force is theoretically concentrated, 
 as, for example, the thrust of a propeller. 
 
 Centre of Gravity: A point in which the weight of 
 a flying-machine is theoretically concentrated. 
 
 Centre of Lift: See Centre of Pressure. 
 
 Centre of Pressure: An imaginary centre in which 
 the air pressure on a supporting surface is theoretically 
 concentrated. 
 
 Centre of Thrust: See Centre of Effort. 
 
GLOSSARY 273 
 
 Chord: The line connecting the ends of the segment 
 of a circle. 
 
 Compound Control: A system of hand-levers and 
 ropes or hand-wheels and ropes by which two con- 
 trolling operations are simultaneously carried out with 
 but a single operating device, as, for example, the 
 single lever in a Wright machine, which serves not 
 only to warp the main planes, but also to swing the 
 vertical rudder at the same time. 
 
 Compression Side: The side of a surface, such as an 
 aeroplane or air-propeller, which faces the flow of air 
 current. 
 
 Curtain: A vertical plane, as in the Voisin cellular 
 biplane, between the main planes, serving to insure a 
 certain amount of lateral stability. 
 
 Diagonal: A diagonal brace in a framework. 
 
 Derrick: A pyramidal structure from the top of 
 which a weight can be mechanically dropped in order 
 to start a flying-machine in motion on a rail. Some- 
 times called a " pylon." 
 
 Dihedral Angle: The angle formed by two planes 
 placed at opposite sides of a median line, so as to form 
 a very wide " V." 
 
 Double-Decker: A synonym of biplane (q. v.). 
 
 Double Monoplane: A machine having two sets of 
 supporting surfaces arranged in a single tier. Such 
 a machine is also called a " following-surface " 
 machine. 
 
 Double Rudder: A rudder having two surfaces of 
 more or less similar surface and outline, which sur- 
 faces may or may not act simultaneously. 
 
 Doubled-Surfaced: Covering both sides of the 
 framework of a supporting surface. 
 
274 GLOSSARY 
 
 Drift: The resistance offered to forward motion of 
 a plane or curved surface in the air by the horizontal 
 component of the air pressure against the plane. It is 
 to be carefully distinguished from mere head resist- 
 ance (q. v.). 
 
 Elevator: The horizontal rudder of a flying-machine, 
 used for steering in a vertical plane. 
 
 Entering Edge: The front or leading edge of an 
 aeroplane. 
 
 Equilibrator: The tail of a flying-machine. 
 
 Equilibrium: In flying-machine parlance the term 
 is used in the same sense as " stability." Properly 
 speaking, an aeroplane is in equilibrium when travelling 
 at a uniform rate in a straight line, or, again, when it 
 is steered around a horizontal arc or circle. It is 
 necessary for stability that if the aeroplane be not in 
 equilibrium and moving uniformly it shall tend toward 
 a condition of equilibrium. 
 
 Equivalent Head Area: The area which would offer 
 head resistance equal to that of the supporting sur- 
 faces of a flying-machine plus the struts, stays, wires, 
 chassis, etc. 
 
 Feathering: Said of surfaces which are manoeuvred 
 in a manner to pass edgewise and flatwise in alternate 
 directions while in motion. 
 
 Fin: A rigid vertical surface which acts somewhat 
 like the keel of a sailing yacht. 
 
 Fish Section: A section resembling in shape the body 
 of a fish. Such sections are commonly found in flying- 
 machine struts. 
 
 Fixed Wheel: In contradistinction to a caster-wheel 
 (q. v.), a wheel that always preserves its relative posi- 
 tion in the alighting-gear. 
 
GLOSSARY 275 
 
 Flapping-Wing Flight: Flight by means of beating 
 wings as distinguished from flight obtained by means 
 of rigid aeroplanes. See Ornithopter. 
 
 Flexible Propeller: A fabric propeller, capable of 
 adjusting itself in flight. 
 
 Flying Angle: Flying attitude. See Angle of 
 Incidence. 
 
 Following Edge: The rear edge of an aeroplane 
 surface. 
 
 Following Surface: The rear surfaces of two similar 
 surfaces arranged in tandem. 
 
 Fore-and-Aft: Longitudinally. 
 
 Front Control: Front Rudder: The framework and 
 planes situated at the extreme front of the aeroplane, 
 in advance of the operator. 
 
 Fusiform : Spindle-shaped. 
 
 Fuselage: The framework or body of an aeroplane. 
 
 Gap: The distance between two planes in a multi- 
 plane machine. 
 
 Glide: To travel without power. 
 
 Glider: An aeroplane without a motor. 
 
 Gliding Angle: The angle at which a machine glides 
 down without power. 
 
 Ground Attitude or Incidence: The difference in the 
 angle formed by the aeroplane surface when on the 
 ground and when in flight. 
 
 Guy-Wire: A wire connecting two members of an 
 aeroplane, usually parts of the controlling system. 
 
 Gyroplane: A flying-machine with rotating planes. 
 See Heliocopter. 
 
 Gyroscope: A freely-hung, rapidly-rotating fly-wheel, 
 which resists forces that tend to throw it from its plane 
 of rotation. 
 
276 GLOSSARY 
 
 Hangar: A term said to be of Hungarian origin, 
 now also used in English, to designate a shed for hous- 
 ing aeroplanes or airships. 
 
 Head Area: The total head resistance offered by the 
 entire framework of an aeroplane. 
 
 Head Resistance: The resistance a surface offers to 
 movement through the air. 
 
 Heavier-than-Air: A term applied to all air-craft 
 not sustained by a buoyant gas. 
 
 Helicopter or Helicopter e: A heavier-than-air ma- 
 chine in which flight is secured by lifting screw pro- 
 pellers revolving in more or less horizontal planes. 
 
 Helix: The path of a point moving uniformly 
 around a cylinder and uniformly along the cylinder. 
 
 Horizontal Rudder: See Elevator. 
 
 Keel: The under framing of an aeroplane to stiffen 
 it both laterally and vertically. Sometimes used as a 
 synonym of fin ( q. v. ) . 
 
 Land Speed: The rate of travel of an aeroplane on 
 the ground before ascension. 
 
 Landing Area: A special allotment of ground on 
 which a machine can land safely. 
 
 Landing Skid: See Skid. 
 
 Lateral: A strut for side wise bracing in the frame- 
 work of an aeroplane. 
 
 Lateral Stability: Lateral equilibrium in the side-to- 
 side direction. 
 
 Lattice Girder: A girder with many crossed mem- 
 bers, resembling in appearance a lattice window. 
 
 Leeway: Lateral drift in the direction in which the 
 air current is flowing due to the air current. 
 
 Lift: The ascensional force of an aeroplane surface. 
 
 Longitudinal Stability: Lengthwise stability. 
 
GLOSSARY 277 
 
 'Magneto: An apparatus for generating electric cur- 
 rent to produce a spark wherewith to ignite the explo- 
 sive mixture in the cylinder of an internal-combustion 
 motor. 
 
 Main Plane: The largest supporting wing in a 
 multiplane. 
 
 Mast: A spar or strut for fastening trussing wires 
 or stays to stiffen the planes. 
 
 Monoplane: An aeroplane with one or more sup- 
 porting surfaces, all in the same plane. 
 
 Monorail: A rail used as a track in starting some 
 machines. 
 
 Multiplane: An aeroplane with more than one main 
 supporting surface. 
 
 Nacelle: See Fuselage. In some monoplanes the en- 
 closed, boat-like part of the body, containing the seat 
 for the pilot and his passenger. 
 
 Negative Angle of Incidence: The angle formed by 
 a plane inclined downwardly to the direction of travel. 
 
 Ornithopter, Ornithoptere, Orthopter, or Orthop- 
 tere: A machine which attains flight by bird-like flap- 
 ping of wings. 
 
 Orthogonal Action: The vertical reaction of the air 
 in affording equilibrium by means of wing motion. 
 
 Panel: The vertical planes in a box-like or cellular 
 structure. 
 
 Pendular Movement: To-and-fro movement like 
 that of a pendulum. 
 
 P hug old: Lanchester's designation for the undulat- 
 ing course naturally adopted by plane surfaces when 
 moving in the air. 
 
 Pitch: The forward movement that would be pro- 
 duced by one turn of a propeller in a solid. 
 
278 GLOSSARY 
 
 Plane: Literally a flat surface; in aeroplanes a flat 
 or curved surface. 
 
 Poly plane: See Multiplane. 
 
 Pylon: The tower required by some types of aero- 
 planes to start. Also, the pillars that mark a definite 
 course to be taken by a flying-machine at a flying- 
 machine meeting. 
 
 Radiator: A coil of piping or any circuitous conduit 
 in which water is cooled by radiation after having cir- 
 culated around the hot cylinder of an internal com- 
 bustion engine. 
 
 Rarefaction Side: The side opposite the compression 
 side, as, for example, the top of an aeroplane in motion. 
 
 Reactive Stratum: The compressed or rarefied layer 
 of free air flowing along an aeroplane surface. 
 
 Rear Control: A stabilising tail surface which may 
 also be a rear horizontal rudder. 
 
 Rising Angle: The maximum angle of ascension.- 
 
 Rudder: A horizontal or vertical plane used for 
 steering. 
 
 Runner: See Skids. 
 
 Screw: A propeller. 
 
 Single-Decker: A monoplane. 
 
 Single-Surfaced: Aeroplane surfaces covered only on 
 one side. Compare with Double-Surfaced. 
 
 Skids: Runners underneath some types of machines, 
 used for landing. 
 
 Skin Friction: The friction of the air against sur- 
 faces. 
 
 Slip : The difference between the pitch of a propeller 
 and its actual forward travel. 
 
 Soaring Flight: Flight with rigid wings. 
 
 Spar: A strut, a brace, etc. 
 
GLOSSARY 279 
 
 Stability: Maintenance of balance in flight by auto- 
 matic devices such as a shifting weight or a gyroscope 
 (q. v.) ; or hand-operated devices such as ailerons, wing- 
 tips, and plane-warping devices. 
 
 Stabilise: To maintain equilibrium by means of 
 surfaces and not by mechanism. 
 
 Stabiliser: The tail of a flying-machine. 
 
 Stabilising Plane: A surface for the maintenance of 
 equilibrium ; small horizontal planes hinged to the main 
 planes, and suiting the angle of the wind. 
 
 Starting Frame: See Chassis. 
 
 Starting Rail: See Monorail. 
 
 Stay: A brace or wire in an aeroplane framework. 
 
 Steadying Vane: Small vertical planes, usually placed 
 in the front control of the old Wright machine. 
 
 Straight Pitch: In propellers, a flat instead of a 
 helical blade surface. 
 
 Strainer: A turnbuckle. 
 
 Strut: A compression member in a structure. In 
 biplanes the posts separating the main planes. 
 
 Supplementary Surface or Auxiliary Surface: A 
 small surface such as an aileron or wing-tip, which 
 acts in unison with a larger one for a specific purpose. 
 
 Supporting Surfaces: The main planes. 
 
 Tail: A collective term for the framework and 
 planes in the rear of the main plane. 
 
 Tail Planes: The rear planes supported by the tail 
 framework. 
 
 Tail Wheel: A small wheel under the tail of some 
 machines to support the tail on the ground. 
 
 Tie: A tension member in a framework; used also 
 for wire stays. 
 
 Tractor Screw: A propeller set in front of the sup- 
 
280 GLOSSARY 
 
 porting surface instead of in the rear, so that the ma- 
 chine is drawn through the air and not pushed. 
 
 Triplane: An aeroplane with three superposed sup- 
 porting surfaces. 
 
 Turnbuckle: A combined right and left-hand screw 
 for taking up the slack in a loose wire stay. 
 
 Up-Wind: Moving against the wind. 
 
 Variable Pitch: In propellers, a varying angle of 
 blade width in contradistinction to uniform pitch. 
 
 Vol-Plane: See Glide. 
 
 Wake: The wash of an aeroplane in flight. 
 
 Warping: The act of twisting a plane for the main- 
 tenance of equilibrium. 
 
 Wash: See Wake. 
 
 Wing Arc: The arc described by a moving wing. 
 
 Wing-Bar: A longitudinal strip so placed as to 
 strengthen an aeroplane surface. 
 
 Wing Section: The longitudinal curvature with re- 
 lation to the arc of travel. 
 
 Wing-Skid: A runner under a wing-tip. 
 
 Wing-Tip: The hinged outer side of a plane. 
 
 Wing-Wheel: A wheel under a wing-tip to support 
 the wing when the machine strikes on the ground. 
 
INDEX 
 
 ACCIDENTS 
 
 perils of flight, 161 
 
 AEROCURVES (See Aeroplanes, 
 Entering Edge, Lift, and 
 Planes) 
 
 AERODYNAMICS 
 
 empirical formulae, 27; 
 laboratories and their work, 
 38; towing carriage, 39; 
 Eiffel's experiments, 39; whirl- 
 ing tables, 40; relative ad- 
 vantages of fixed and moving 
 models, 40; Gottingen studies, 
 41; propeller-thrust tests, 106 
 
 AEROLOGY (See Meteorology) 
 
 AEROPLANE (See also Entering 
 Edge, Planes, Lift, Drift) 
 
 definition, i; compared 
 with kite, 2; with screw- 
 propeller, 96; military uses, 
 185; dirigible airships vs. 
 aeroplanes in war, 202; aero- 
 plane of the future, 236, 240 
 
 AILERONS (See also Stability) 
 
 use in maintaining stabil- 
 ity, 61, 75; Farman system, 
 69; early Antoinette system, 
 73; use in turning, 88 
 
 AIR 
 
 relation of scientific study 
 of air to flight, 133 et seq.; 
 study by de Bort at great 
 heights, 140; charting ocean 
 of air, 153 et seq., 241; dangers 
 of unsteady air, 163 et seq.; 
 air resistance and effect on 
 structure of machines, 177, 
 1 80; military command of 
 the air, 186, 206; effect of 
 rarefied air on engines, 205 
 
 AIRSHIPS IN WAR (See Explo- 
 
 sives, Hague Peace Conference, 
 and War) 
 
 ALBATROSS 
 
 aspect ratio, 16 
 
 ALIGHTING 
 
 birds and machines com- 
 pared, 13; alighting at high 
 speed, 36; use of wheels and 
 shock absorbers, 55, 167; 
 skids, 55; brakes, 57; dangers, 
 167, 179; alighting gear of 
 Farman, 56, 219; of Sommer, 
 56; of Santos-Dumont, 56, 
 229; of Antoinette mono- 
 plane, 56, 223; Wright 
 alighting gear, 213; Curtiss' 
 alighting gear, 216; Bleriot 
 XI alighting gear, 227; alight- 
 ing grounds of the future, 
 237; landing on warships, 
 238; legal aspects of com- 
 pulsory landing, 251 
 
 ALLARD 
 
 ornithopter experiments, 24 
 
 ANEMOMETER 
 
 use in meteorology, 134, 
 
 139 
 
 ANTOINETTE (See Monoplanes, 
 
 Motors, Stability) 
 ANZANI MOTOR (See Motors) 
 ARCHITECTURE 
 
 effect of flying on building 
 design, 237 
 ARMENGAUD PRIZE 
 
 won by Farman, 89 
 ARTILLERY, AERIAL (See Ord- 
 nance) 
 ASSMANN, RICHARD 
 
 meteorological studies, 137, 
 143, 144, 149, 154, 156, 158, 
 159 
 
282 
 
 INDEX 
 
 ASPECT RATIO 
 
 in birds, 16; in biplanes 
 and monoplanes, 16; relation 
 to entering edge and lift, 27 
 ATMOSPHERE 
 
 its purpose, 133; results 
 of study, 146; isothermal 
 stratum, 151; permanent- 
 inversion layer, 151 
 AUBRUN 
 
 in Circuit de I'Est, 131 
 AUTOMOBILE MOTORS (See 
 
 Motors) 
 AUTOMOBILES 
 
 motor-car guns, 198; Ehr- 
 hardt car, 200 
 
 BALANCING (See Stability) 
 
 BALANCING-PLANES (See Sta- 
 bility) 
 
 BALDWIN, SIMEON 
 
 on law of the air, 251, 252, 
 256 
 
 BALLOONS IN WAR (See Explo- 
 sives, Hague Peace Conference, 
 and War) 
 
 BALLOONS, SOUNDING 
 
 use in meteorology, 136, 
 139, 143 et seq. 
 
 BANKING (See Steering and 
 Gravitation) 
 
 BAROMETER 
 
 its use in flying, 134 
 
 BAROTHERMOGRAPH 
 
 meteorological use, 140 
 
 BELLENGER, CAPTAIN 
 
 performances as an air- 
 scout, 192, 194 
 
 BIPLANE 
 
 distinguished from mono- 
 plane, 15, 16, 208; structural 
 advantages, 17; defects of its 
 double surface, 18; relative 
 perfection of monoplane and 
 biplane, 18; compared with 
 skate, I; control of center 
 of air-pressure on Wright 
 machine, 8, 210; tailed and 
 tailless Wright biplanes, 9, 17, 
 
 95, 98, 103, 105, 209; small 
 wings of Wright racers, 36, 
 209, 213; alighting gear of 
 Wright machine, 55, 213; of 
 Farman, 56, 219; of Sommer, 
 56; _of Curtiss, 57; of old 
 Voisin, 57; structure of 
 Wright machine, 63, 77, 209; 
 structure of Curtiss biplane, 
 6 5> 77, 9 2 > 2I 4J structure of 
 Farman machine, 69, 74, 77, 
 105, 217 et seq.; Voisin (old 
 tyP e )> 74; Voisin (new type), 
 75> 77) 7 8 > I0 5; structure of 
 Sommer machine, 77, 220 et 
 seq.; structure of Breguet 
 machine, 78; structure of 
 Voisin (new type), 78, 105; 
 structure of Goupy, 78; struc- 
 ture of Caudron Freres, 78; 
 margin of safety, 172 et seq. 
 
 BIRDS 
 
 relation to aeroplanes, 2, 5, 
 9; launching devices of birds, 
 10, 45; vultures in open 
 cages and reason therefor, 12; 
 birds and machines in alight- 
 ing, 13; efficiency, 15, in, 
 113; proportions and shapes 
 of wings, 16, 27; Lanchester 
 on bird flight, 113 
 
 BISMARCK 
 
 on air-spies, 262 
 
 BlTTERFELD 
 
 aerological observatory, 158 
 BLACKSTONE 
 
 on ownership of the air, 248 
 BLADES, PROPELLER (See Screw) 
 BLERIOT, Louis (See also Mono- 
 planes) 
 
 his use of the dihedral angle, 
 
 74; his cross-Channel flight, 
 
 112, 239; his experiences, 225 
 
 BLUE HILL OBSERVATORY (See 
 
 Rotch, A. Lawrence) 
 BOATS 
 
 comparison of wind effects 
 on boats and planes, 35 
 BOMBS (See also War) 
 
 as an offensive weapon, 186 
 
INDEX 
 
 283 
 
 BRAKES 
 
 use in alighting, 57 
 BRETT, MASTER OF THE ROLLS, 
 
 on law of the air, 248 
 BREWER, R. W. A. 
 
 his aeroplane of the future, 
 236 
 BRYAN, G. H. 
 
 on equilibrium and stabil- 
 ity, 1 68 
 
 CAMBER 
 
 of propellers, 96 
 CAUDRON FRERES (See Bi- 
 planes} 
 
 CANNON, AERIAL (See Ordnance} 
 CANTING (See Gravitation, Steer- 
 ing) 
 CENTRIFUGAL FORCE 
 
 its effect in steering, 87; 
 in screw propellers, 95 
 CHANUTE, OCTAVE 
 
 his gliders, 7, 19, 42; his 
 use of the truss, 17; his de- 
 scription of Wright Brothers' 
 learning to turn, 89 
 CHAUVIERE PROPELLERS (See 
 - Screw} 
 CHAVEZ 
 
 cause of death, 176; acci- 
 dent at Nice, 233 
 CIRCUIT DE L'EST 
 
 motor trouble, 130; physi- 
 cal endurance test, 165 
 CLEMENT-BAYARD MOTORS (See 
 
 Motors) 
 COKE UPON LITTLETON 
 
 ownership of the air, 248 
 COMPASS 
 
 for aerial use, 234 
 CONDOR (See also Birds) 
 
 efficiency as a flying ma- 
 chine, 112 
 CORNU 
 
 his helicopter, 23 
 CRIME IN THE AIR (See Law, 
 
 Aerial 
 CROCHON 
 
 cause of his death, 232 
 
 CURTISS, GLENN H. (See also 
 Biplane, Monoplane, and 
 Motors 
 Hudson River flight, 160, 165 
 
 DAEDALUS 
 
 his ornithopter, 23 
 D'AMECOURT, PONTON 
 
 relation to helicopter, 21 ^ 
 DANGERS OF AIRMEN (See Acci- 
 dents) 
 DA VINCI, LEONARDO 
 
 his ornithopter, 24; his 
 screw propeller, 94 
 DE BORT, TEISSERENC 
 
 meteorological studies, 137, 
 140, 143, 144, 149 
 DELAGRANGE 
 
 cause of death, 176 
 DE LA HAULT, ADH. 
 
 ornithopter experiments, 24 
 DE LA LANDELLE 
 
 his relation to helicopter, 21 
 DE LA ROCHE, BARONESS 
 
 accident at Reims (1910), 
 172 
 
 DIHEDRAL ANGLE (See Sta- 
 bility) 
 DIRIGIBLE AIRSHIP IN WAR (See 
 
 War} 
 DOVER 
 
 wind surf, 164 
 DUCKS 
 
 their difficulty in starting, 
 ii 
 Du TEMPLE 
 
 his propeller, 99 
 
 EAGLE 
 
 compared with kite, 2; how 
 launched in flight, 10 
 EHRHARDT AUTOMOBILES (See 
 
 Automobiles) 
 EIFFEL 
 
 aerodynamic experiments, 
 
 ELY 
 
 his landing on deck of war- 
 ship, 238 
 ENGINES (See Motors) 
 
284 
 
 INDEX 
 
 ENTERING EDGE 
 
 relation to lifting power, 27; 
 Lilienthal's investigation, 28; 
 Phillip's study, 28; Langley's 
 results, 28; Wright Brothers' 
 studies, 28 
 
 E. N. V. MOTORS (See Motors) 
 EQUILIBRIUM (See also Stability) 
 of yachts and aeroplanes, 
 3; distinguished from stabil- 
 ity, 1 68 
 ERICSSON 
 
 his marine propeller, 99 
 ESNAULT-PELTERIE, ROBERT 
 his stability control system, 
 
 EXPLORATION 
 
 geographical and topo- 
 graphical value of the flying- 
 machine, 235 
 EXPLOSIVES 
 
 use on aeroplanes, 186; 
 shrapnel for repelling attack, 
 20 1 
 
 FARMAN, HENRY 
 
 his launching device, 53; 
 
 use and abandonment of 
 
 early Voisin biplane, 75; 
 
 winning of Armengaud prize, 
 
 89; influence of Wright 
 
 Brothers, 217 
 FAUCHILLE 
 
 on permissible altitude, 
 
 2 S> 2 S9> criminal aerial 
 
 jurisdiction, 261 
 FIAT MOTORS (See Motors) 
 FLAPPING-WING MACHINES (See 
 
 Ornithopters) 
 FLY-WHEEL 
 
 its function, 115,' 117; 
 
 rotary engines as fly-wheels, 
 
 127 
 
 FRICTION (See Skin Friction) 
 FRIEDRICHSHAFEN 
 
 observatory, 138, 159 
 FUEL (See Petrol and Gasoline) 
 FUTURE, FLYING-MACHINE OF 
 
 THE, 231 et seq., 240, 242 
 
 GASOLINE 
 
 its use as a fuel, 115, 117 
 GLIDING 
 
 its relation to safe flight, 
 18, 189 
 GLOSSOP MOOR 
 
 aerological observatory, 138 
 GNOME MOTORS (See Motors) 
 GOULD, EDWIN 
 
 prize for multimotor ma- 
 chine, 182 
 
 GOUPY (See Biplanes) 
 GRAVITATION 
 
 its part in aeroplane flight, 
 J 4 3i 59; in steering, 87 
 GRAVITY, CENTER OF 
 
 relation to center of air 
 pressure, 4; shifting center 
 of gravity to maintain bal- 
 ance, 5, 8; in Lillienthal's 
 machine, 6; in Pilcher's 
 machine, 7; in Chanute's 
 gliders, 7; relation to stabil- 
 ity, 85 
 GRUNWALD 
 
 on international law of the 
 air, 257 
 
 GUNS, AERIAL (See Ordnance) 
 GYROSTAT 
 
 its use in automatically 
 maintaining balance, 80, 82 
 
 HAGUE PEACE CONFERENCE 
 
 on use of bombs, 187; on 
 spies in the air, 263 
 HARGRAVE, LAWRENCE 
 
 ornithopter experiments, 24 
 HAZELTINE 
 
 on international law of 
 air, 256, 259 
 HELICOPTERS 
 
 principle of screw-fliers, 20; 
 d'Amecourt and de la Lan- 
 delle, 21 ; Renard's screw- 
 flier, 22; Edison's helicopter, 
 22; Berliner's helicopter, 23; 
 Cornu's helicopter, 23; Bre- 
 guet, 23; Kress, 102 
 HELIX (See Screw) 
 
INDEX 
 
 285 
 
 HENSON 
 
 his propeller designs, 99 
 HERRING 
 
 determination of effect of 
 wires and struts on speed, 34; 
 invention of skids, 55 
 
 HOLTZENDORFF 
 
 on international law of the 
 air, 257, 259 
 
 HOUBERNAT GUN (See Ordnance} 
 HYGROMETER 
 
 use in meteorology, 134, 
 139 
 
 INCIDENCE, ANGLE OF 
 
 maintenance of horizontal 
 flight by adjustment of angle 
 of incidence, 31, 59, 60; 
 cause of variations in the 
 angle, 32; gyrostat and angle 
 of incidence, 80 
 INSELBERG 
 
 Aerological Observatory, 
 
 T IS8 
 
 INSURANCE 
 
 Baldwin on accident in- 
 demnities, 252 
 
 INTERNATIONAL CONFERENCE 
 ON AERIAL NAVIGATION (See 
 Paris Conference) 
 
 ISOTHERMAL STRATUM (See At- 
 mosphere) 
 
 JEFFRIES 
 
 meteorological studies, 136 
 
 KEELS (See also Stability) 
 
 their stabilizing effect, 75 
 
 KITES 
 
 kites and aeroplanes com- 
 pared, 2; stability of kites 
 and manner of maintaining 
 it, 9; launching, 9; stability 
 of box and single-surface 
 kites compared, 16; use in 
 meteorology, 136, 139, 142, 
 143 
 
 KRESS 
 
 his propeller system, 102 
 KRUPP AERIAL ARTILLERY (See 
 
 Ordnance) 
 KUHN, ARTHUR K. 
 
 on international law of 
 the air, 236 et seq.', spies in 
 the air, 263 
 
 LANCHESTER, F. W. 
 
 on automatic stability, 76; 
 on speed, 236 
 LANDING (See Alighting) 
 LANGLEY, SAMUEL PIERPONT 
 
 comparison of eagle and 
 aeroplane, 10; his launching 
 experiments, 12, 42; ex- 
 periments with planes, 16; 
 determination of lift of aero- 
 curves, 28; determination of 
 power ratio for given speed, 
 33, 243; his trials with large 
 aerodrome, 49; newspaper 
 derision, 50; use of the dihe- 
 dral angle, 74; adoption of 
 rear horizontal rudder, 78; 
 his propellers, 100, 107; study 
 of bird efficiency, in; motor 
 designs, n6j wind studies, 
 
 T l63 
 
 LARK 
 
 aspect ratio, 16 
 
 LATHAM, HUBERT (See also 
 Monoplanes) 
 
 at Belmont Park (1910), 
 224; accident at Nice, 233 
 
 LAUNCHING 
 
 necessity of preliminary 
 run, 9, 10, 42; methods of 
 getting up preliminary speed, 
 12, 44; Langley's experi- 
 ments, 12; Wright Brothers' 
 methods, 12; wheels for 
 launching, 12, 13; Langley's 
 difficulties, 42; Wright start- 
 ing derrick and rail, 52; 
 power consumed in launching, 
 
 e; adoption of wheels by 
 irtiss and Farman; Wright 
 
286 
 
 INDEX 
 
 adoption of wheels, 54; gyro- 
 stats and their effect, 80; 
 launching grounds of the 
 future, 237 
 
 LAW, AERIAL 
 
 adaptability of common 
 law, 246; salvage, 247; own- 
 ership of air, 248; code of 
 Canton of Grisons, 249; 
 German Civil Code, 249; 
 permissible altitude, 250, 
 258; trespass, 250; com- 
 pulsory alighting, 251; li- 
 censes, 253; international 
 aspects, 253, 256 et seq.; 
 aerial equivalent of maritime 
 three-mile limit, 258; crimi- 
 nal jurisdiction, 261; spies 
 in the air, 263; rights of 
 neutrals, 267 
 
 LEBLANC 
 
 in Circuit de I'Est, 131; at 
 Havre (1910), 166 
 
 LEBLON, HUBERT 
 
 cause of death, 182, 233 
 
 LEVAVASSEUR (See also Mono- 
 planes [Antoinette]) 
 propeller mounting, 100 
 
 LICENSES 
 
 Baldwin on licenses, 252 
 
 LIFT 
 
 relation to entering edge, 
 27; to angle of incidence, 31; 
 Maxim's experiments, 28; 
 Phillip's work, 28; Langley's 
 studies, 28, 34; Wright Broth- 
 ers' studies, 28, 34; effect of 
 turning on lift, 87 
 
 LIGHTHOUSES 
 
 beacons for aviators, 234 
 
 LlLIENTHAL, OTTO 
 
 cause of his death, 5; his 
 gliders, 6, 8, 19, 42; experi- 
 ments in determining lifting 
 effect, 28 
 
 LlNDENBERG 
 
 Aeronautical Observatory, 
 138, 154, ISS, 156 
 
 LlNDPAINTNER 
 
 In Circuit de FEst, 131 
 
 LlNFIELD 
 
 his propeller design, 99 
 LINKE 
 
 his aeronautic weather ser- 
 vice, 155 
 LUBRICATION 
 
 of motors, 124, 128 
 
 MACOMB, MAJOR 
 
 on Langley's aerodrome, 49 
 MAPS 
 
 use by aviators, 160 
 MAXIM, SIR HIRAM 
 
 experiments on lift of 
 curved surfaces, 28; pro- 
 peller designs, 100, 101, 107 
 MEURER 
 
 on international law of 
 
 on law of the air, 247, 253 
 METALLURGIC (See Motors) 
 METEOROGRAPHS (See Mete- 
 
 orology) 
 METEOROLOGY 
 
 relation to flying, 133 et 
 seq.\ dates for international 
 aerological investigations, 145 
 MEUNIER, GENERAL 
 
 on aerial scouting, 190 
 MILITARY USES OF FLYING 
 MACHINES 
 
 aeroplane in war, 186 et seq. 
 MILLER, WARREN H. 
 
 his table of motor efficien- 
 cies, 131 
 MODELS 
 
 relative advantages of fixed 
 and moving models in re- 
 search work, 40 
 MOISANT 
 
 cross-Channel flight, 164 
 MONOPLANE 
 
 compared' with skate, i; 
 distinguished from biplanes, 
 15; structural defects, 17; 
 advantage of its single sur- 
 face, 18; relative perfection 
 of monoplane and biplane, 
 
INDEX 
 
 287 
 
 1 8; speed of Bleriot, 35; 
 alighting gear of Antoinette, 
 56, 223; of Pelterie, 57; 
 Bleriot construction, 70, 78, 
 100, 105, 225; Antoinette 
 construction, 72, 75, 78, 100, 
 105, 222; use of dihedral 
 angle by Langley and Bleriot, 
 74; Hanriot monoplane, 76; 
 Santos-Dumont monoplane, 
 92, 100, 228; Curtiss mono- 
 plane, 217; margin of safety, 
 172 
 
 MORANE 
 
 at Havre meeting (1910), 
 166 
 
 MOTOR-CAR GUNS (See Auto- 
 mobiles) 
 
 MOTORS 
 
 relation to speed, 17; to 
 angle of incidence, 32; di- 
 minishing power required with 
 increasing speed (Langley's 
 law) 33; power consumed 
 in starting machine, 53, 54; 
 low power of early Wright 
 motors, 54; relation to pro- 
 pellers, 108; efficiency, in, 
 116, 129, 205; Anzani, 112, 
 132, 226; Wright, 112, 116, 
 129, 132, 213; 4-cycle princi- 
 ple, 113; lightness, 117, 232; 
 cylinder arrangements, 117; 
 lubrication, 124; radial en- 
 gines, 124; Gnome motors, 
 126, 127, 129, 132, 219, 220, 
 224, 227; Antoinette motors, 
 129, 132, 224; Fiat motors, 
 129; Metallurgic, 129; Re- 
 nault, 129; automobile mo- 
 tors, 129, 224; E. N. V. 
 motors, 13 2; Clement-Bayard, 
 132, 230; Curtiss, 216; R. E. 
 P. motors, 132; motor-break- 
 downs, 182, 205; effect of 
 rarefied air on compression,2O5 
 
 MOY 
 
 his fan-propeller, 99 
 
 MT. WEATHER OBSERVATORY 
 its functions, 137 
 
 MULTIPLANE 
 
 triplanes, 19, 20; Phillips, 
 20 
 
 NEUTRALITY IN AIR WARFARE 
 (See Law, Aerial) 
 
 ORDNANCE, AERIAL 
 
 for repulsion of aerial at- 
 tacks, 196; Krupp guns, 
 197 et seq., 258; Rheinische 
 Metallwaaren und Maschi- 
 nenfabrik (Dlisseldorf) aerial 
 guns, 199, 201; Houbernat 
 gun, 200; machine-guns on 
 aeroplanes, 202, 204; range 
 of Krupp guns to determine 
 neutral zone, 258 
 
 ORNITHOPTERS 
 
 underlying principle, 23 ; 
 Leonardo da Vinci's, 24; 
 Allard's experiments, 24; Har- 
 grave's models, 24; de la 
 Hault's experiments, 24; dis- 
 advantages of the type, 25 
 
 OTTO ENGINE (See Motors) 
 
 PARIS CONFERENCE 
 
 international law of the 
 air, 253, 260, 266, 267 
 PATENTS 
 
 Wright patents and their 
 scope, 67, 68, 69, 70, 75; 
 Wright pendulum patents, 79 
 PAVIA 
 
 Aerological Observatory, 
 
 T,' 38 
 
 PAVLOVSK 
 
 Aerological Observatory, 
 
 T,' 38 
 
 PENDULUM 
 
 Wright automatic pendu- 
 lum for stabilizing, 79; faults 
 of the pendulum as an auto- 
 matic control device, 81 
 
 PERMANENT INVERSION LAYER 
 (See Atmosphere) 
 
288 
 
 INDEX 
 
 PETROL 
 
 as a motor fuel, 115, 117 
 PHILLIPS, HORATIO 
 
 his multiplane, 20; study 
 of lifting effect of curved 
 planes, 28 
 PHOTOGRAPHY 
 
 the camera in war, 189, 
 264; in exploration, 236 
 PICQUART, GENERAL 
 
 on aerial scouting, 190 
 
 PlLCHER 
 
 his death, 7; gliders, 42, 
 170 
 PITCH 
 
 definition, 96 
 
 PLANES (See also Lift, Entering 
 Edge) 
 
 Proper shape and size, 16; 
 relation to hull of a ship, 26, 
 27; entering edge and lift, 
 27; Lilienthal's results, 28; 
 Wright Brothers' studies of 
 aerocurve lifts, 28; Phillips 
 study of lifts, 28; force act- 
 ing on plane in motion, 31; 
 angle of incidence and speed, 
 31; relation of power to 
 speed, 33, 243 (Langley's 
 law); speed and size of 
 planes, 36; reefing wings, 
 37; aerodynamic studies, 38; 
 margin of safety, 172 
 
 POLIS 
 
 his aeronautic weather ser- 
 vice, 155 
 
 POWER (See Motors) 
 
 PRANDTL 
 
 aerodynamic work at Goet- 
 tingen, 41; exposure of pen- 
 dulum defects for automatic 
 control, 82; study of form 
 for airship gas bags, 227 
 
 PRESSURE 
 
 relation of pressure to 
 entering edge, 28; aero- 
 dynamic study of pressure, 
 38; pressure and support of 
 machine in flight, 59; effect 
 on construction, 177 
 
 PRESSURE, CENTER OF 
 
 relation of center of gravity 
 to, 4; shifting center of pres- 
 sure to maintain balance, 5; 
 in Lilienthal's glider, 6; in 
 Pilcher's machine, 7; in 
 Chanute's glides, 7; in Wright 
 machines, 8; automatic con- 
 trol, 9 
 
 PROJECTILES (See Explosives') 
 
 PROPELLERS (See Screw) 
 
 PTERODACTYL 
 
 efficiency compared with 
 flying machine, in 
 
 RACING 
 
 its effect on commercial 
 development of aeroplane, 
 240 
 RADIATORS 
 
 in motors, 116 
 RAILS IN LAUNCHING (Set 
 
 Launching) 
 RECONNAISSANCE 
 
 scouting aeroplanes, 189, 
 190 
 REGNARD, PAUL 
 
 his gyrostatic system of 
 control, 80 
 REIMS 
 
 meeting of 1910 and speeds 
 attained, 35; accidents, 172, 
 ^176, 179 
 RENARD, COLONEL 
 
 his combined aeroplane and 
 helicopter, 22 
 
 RENAULT MOTORS (See Motors) 
 R. E. P. (See Esnault-Pelterie 
 
 and Motors') 
 
 RESISTANCE (See Pressure) 
 RHEINISCHE METALLWAAREN 
 UNO MASCHINENFABRIK AE- 
 RIAL ARTILLERY (See Ord- 
 nance) 
 RHINOW 
 
 Lilienthal's experiments 
 at, 6 
 
 ROLLAND 
 
 on international law of the 
 air, 259 
 
INDEX 
 
 289 
 
 ROLLS, C. S. 
 
 cause of death, 171, 176 
 
 ROTCH, A. LAWRENCE 
 
 meteorological studies, 137, 
 141 
 
 RUDDERS, HORIZONTAL (See also 
 Steering) 
 
 their purpose, 13, 167; 
 Wright system, 64, 77, 210; 
 Curtiss system, 65, 77, 214; 
 Farman system, 69, 77, 218; 
 Bleriot system, 72, 226; An- 
 toinette system, 72, 223; 
 stabilizing effect when used 
 as tails, 77; Langley system, 
 78, 129; Sommer system, 
 220; Santos-Dumont (De- 
 moiselle) system, 229 
 
 RUDDERS, VERTICAL (See also 
 Steering) 
 
 their necessity, 13; use 
 in maintaining stability as 
 taught by the Wrights, 63; 
 Curtiss system, 65, 215; 
 Farman system, 69, 219; 
 Bleriot system, 72, 226; An- 
 toinette system, 72, 223; 
 Wright system, 210; Santos- 
 Dumont system, 229; effect of 
 vertical rudder in steering, 92; 
 types of vertical rudders, 92 
 
 SAFETY (See Occidents) 
 
 SALVAGE (See Law, Aerial) 
 
 SCOUTING 
 
 aeroplane reconnaissances, 
 189, 190 
 
 SCREW 
 
 lifting propellers in heli- 
 copters, 21 ; inefficiency of 
 screw, 94, 106, 108; da Vin- 
 ci's screw, 94; principle of 
 screw, 95 et seq.; Ericsson's 
 marine propeller, 99; Moy's 
 fan propeller, 99; Henson's 
 propeller, 99; Stringfellow's 
 propeller, 99; Linfield's pro- 
 peller, 99; du Temple's pro- 
 peller, 99; Langley's pro- 
 
 pellers, 100; Maxim's pro- 
 pellers, ico; Kress system, 
 102; Wright system, 103, 
 109; Chauviere, 104, 109, 
 no, 219, 227, 230; danger of 
 breakage, 181; Curtiss pro- 
 pellers, 216 
 
 SCREW-FLIERS (See Helicopters) 
 
 SELFRIDGE 
 
 his death, 103, 181 
 
 SHELLS (See Explosives) 
 
 SHIPS (See also Yachts, Boats) 
 
 difference between aero- 
 planes and ships in axis of 
 propulsion, 27; comparison of 
 towing-tank experiments and 
 aerodynamic researches, 38 
 
 SHOCK-ABSORBERS (See also 
 Alighting) 
 
 necessity of, 55 
 
 SHRAPNEL (See Explosives) 
 
 SIDO, LIEUTENANT 
 
 performances as an aerial 
 scout, 191 
 
 SKIDS (See also Alighting) 
 
 use in alighting, 55; intro- 
 duction by Herring and 
 Wrights, 55; use by Farman, 
 56, 219; Sommer, 56; Santos- 
 Dumont and Antoinette, 56 
 
 SKIN-FRICTION 
 
 its laboratory study, 38; 
 in screw propellers, 96 
 
 SLIP 
 
 definition, 96; speed and 
 slip, 104 
 
 SOMMER, ROGER 
 his biplane, 220 
 
 SOUNDING-BALLOONS (Set Bal- 
 loons) 
 
 SPAN (See Aspect Ratio) 
 
 SPEED (See also Motors) 
 
 tails and their effect, 17; 
 relation of speed to form, 26; 
 relation to gravitation, 31; 
 effect on angle of incidence, 
 32; power and speed in aero- 
 planes, 33, 34; monoplane 
 speeds, 35; relation of speed 
 to wind, 35; landing at high 
 
290 
 
 INDEX 
 
 speed, 36; necessity of vari- 
 able speed, 36, 243; speec 
 and stability, 75; speed and 
 steering, 87; speed and mo- 
 tors, 130; speed and struc- 
 tural design, 177, 179; speec 
 of future aeroplane, 236 
 SPY, AERIAL 
 
 repulsion of, 196 
 SQUIER, MAJOR G. O. 
 
 on military possibilities oJ 
 aerial navigation, 195 
 STABILITY 
 
 in birds, 3; in machines, 
 4; methods of maintaining 
 stability, 5; fore-and-aft sta- 
 bility, 8, 14, 167; automatic 
 control, 9, 75, 79, 83, 169, 
 223; monoplane and biplane 
 stability compared, 16; sta- 
 bility explained, 58; aile- 
 rons and their use, 61; Wright 
 warping system, 63, 210; 
 Curtiss system, 65, 92, 215; 
 Wright-Curtiss infringement 
 suit, 67; Farman control, 69, 
 218, 220; Bleriot control, 70, 
 226; Antoinette control, 72, 
 223; the efficiency of the 
 dihedral angle, 74, 170; use of 
 vertical curtains (Voisin), 74; 
 effect of keels, 75; Lanchester 
 on speed and stability, 75; 
 Esnault-Pelterie control, 77; 
 use of tails to maintain 
 fore-and-aft stability, 77, 210; 
 gyrostatic control, 80; au- 
 tomatic vs. hand control, 80; 
 stability and steering, 88; 
 effect of wind, 91; Santos- 
 Dumont control system, 92; 
 dangers of bad manipulation 
 of stabilizers, 167; equilib- 
 rium and stability distin- 
 guished, 168; Sommer system 
 of control, 220 
 STARTING (See Launching) 
 STAYS (See also Wires) 
 
 in monoplanes and bi- 
 planes, 173 et seq. 
 
 STEERING (See also Rudders) 
 
 necessity for two sets of 
 rudders, 13; Wright system, 
 64; Curtiss system, 65; Far- 
 man system, 69; Antoinette 
 system, 72; principles in- 
 volved in steering, 85 et seq.' t 
 perils of steering, 170 
 
 STRINGFELLOW 
 
 his triplane, 20; his pro- 
 peller designs } 99 
 
 TAILS 
 
 their part in maintaining 
 stability, 9, 14, 17, 77, 79, 
 212, 219, 221, 226 
 TAUNUS 
 
 Aerological Observatory, 
 158 
 TELEGRAPHY, WIRELESS 
 
 on aeroplanes in war, 193; 
 Berlin Conference, 251 
 THEODOLITES 
 
 use in meteorology, 143 
 THERMOMETER 
 
 use in meteorology, 134, 
 139 
 
 THRUST (See Screw) 
 TOWING-CARRIAGES 
 
 defects of, 39 
 TRACTOR SCREWS (See Screws) 
 TRAPPES 
 
 aerological work, 138 
 TRESPASS (See Law of the Air) 
 TRIPLANE (See Multiplane) 
 TURKEY-BUZZARD (See also 
 Birds) 
 
 efficiency as a flying-ma- 
 chine, 112 
 TURNING (See Steering) 
 
 VAN MAASDYSK 
 
 cause of death, 182 
 VOL-PLANE (See Gliding) 
 VOISIN FRERES (See Biplanes) 
 VULTURES 
 
 how launched for flight, 10; 
 how caged and reason there- 
 for, 12 
 
INDEX 
 
 291 
 
 WACHTER 
 
 cause of death, 176, 179 
 
 WAR, 
 
 flying-machines in, 185 et 
 seq.\ dirigibles vs. aeroplanes 
 in war, 202; double-motor 
 military machine, 232; inter- 
 national law and aerial war- 
 fare, 262 
 
 WARPING (See Stability) 
 
 WATER-JACKET 
 use in motors, n 6 
 
 WEATHER 
 
 weather and flight, 133 
 et seq. 
 
 WESTLAKE 
 
 on international law of the 
 air, 258 
 
 WHEELS FOR ALIGHTING AND 
 LAUNCHING (See Launching 
 and Alighting) 
 
 WHIRLING-TABLES 
 their defects, 40 
 
 WIND 
 
 relation of speed to wind, 
 35; effect on launching, 46; 
 effect on steering, 91; use 
 of anemometer, 134; wind- 
 data of German Empire, 154; 
 wind perils, 163, 170; wind- 
 gauges for dropping explo- 
 sives, 187 
 
 WINGS (See Planes) 
 
 WIRES 
 
 effect on speed, 33; use in 
 
 stiffening monoplanes and 
 biplanes, 173 et seq. 
 
 WIRELESS TELEGRAPHY (See 
 Telegraphy) 
 
 WRIGHT BROTHERS 
 
 their contribution to flight 
 problem, 8; launching de- 
 vices, 12, 51; study of lift 
 of curved surfaces, 28; on 
 variability of angle of inci- 
 dence, 33; study of relation 
 of power to speed (Langley's 
 law), 34; influence of Langley 
 on Wrights, 51; introduc- 
 tion of skids, 55; their solu- 
 tion of stability problem, 61, 
 63; rudder studies, 77; 
 automatic stability patents, 
 79; Chanute on their early 
 turning experiments, 89; ac- 
 cident to Orville Wright at 
 Ft. Myer, 103, 181; skill in 
 aviation, 166, 167; scientific 
 character of their work, 183; 
 influence on Farman, 217; 
 Orville Wright on future of 
 aeroplane, 243 
 
 YACHTS (See also Boats, Ships) 
 compared with aeroplanes 
 in stability, 3; compared with 
 aeroplane in making a turn, 
 91 
 
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