A HISTORY OF AERONAUTICS Trial of full-size Langley Aerodrome, 8th December, 1903. Langley Memoir on Mechanical Flight, Smithsonian Institution, Washington. Frontispiece. A History of Aeronautics by E. CHARLES VIVIAN WITH A SECTION ON PROGRESS IN AEROPLANE DESIGN h LIEUT.-COL. W. LOCKWOOD MARSH, O.B.E. NEW YORK HARCOURT, BRACE AND COMPANY 1921 To MY WITNESS OCT. 2 1ST 1919 V. 481742 FOREWORD ALTHOUGH successful heavier-than-air flight is less than two decades old, and successful dirigible propulsion antedates it by a very short period, the mass of experi- ment and accomplishment renders any one-volume history of the subject a matter of selection. In addition to the restrictions imposed by space limits, the material for compilation is fragmentary, and, in many cases, scattered through periodical and other publications. Hitherto, there has been no attempt at furnishing a detailed account of how the aeroplane and the dirigible of to-day came to being, but each author who has treated the subject has devoted his attention to some special phase or section. The principal exception to this rule Hildebrandt wrote in 1906, and a good many of his statements are inaccurate, especially with regard to heavier-than-air experiment. Such statements as are made in this work are, where possible, given with acknowledgment to the authorities on which they rest. Further acknowledgment is due to Lieut.-Col. Lockwood Marsh, not only for the section on aeroplane development which he has con- tributed to the work, but also for his kindly assistance and advice in connection with the section on aerostation. The author's thanks are also due to the Royal Aero- nautical Society for free access to its valuable library of aeronautical literature, and to Mr A. Vincent Clarke vii FOREWORD for permission to make use of his notes on the develop- ment of the aero engine. In this work is no claim to originality it has been a matter mainly of compilation, and some stories, notably those of the Wright Brothers and of Santos Dumont, are better told in the words of the men themselves than any third party could tell them. The author claims, however, that this is the first attempt at recording the facts of development and stating, as fully as is possible in the compass of a single volume, how flight and aerostation have evolved. The time for a critical history of the subject is not yet. In the matter of illustrations, it has been found very difficult to secure suitable material. Even the official series of photographs of aeroplanes in the war period is curiously incomplete, and the methods of censorship during that period prevented any complete series being privately collected. Omissions in this respect will probably be remedied in future editions of the work, as fresh material is constantly being located. E. C. V. October^ 1920. viii CONTENTS / PART I THE EVOLUTION OF THE AEROPLANE CHAP. PAGB I. THE PERIOD OF LEGEND 3 II. EARLY EXPERIMENTS 15 III. SIR GEORGE CAYLEY THOMAS WALKER 43 IV. THE MIDDLE NINETEENTH CENTURY 56 V. WENHAM, LE BRIS, AND SOME OTHERS 7! VI. THE AGE OF THE GIANTS 83 VII. LILIENTHAL AND PILCHER 95 VIII. AMERICAN GLIDING EXPERIMENTS loy IX. NOT PROVEN 121 X. SAMUEL PIERPOINT LANGLEY 133 XI. THE WRIGHT BROTHERS 145 XII. THE FIRST YEARS OF CONQUEST Ij6 XIII. FIRST FLIERS IN ENGLAND l88 XIV. RHEIMS, AND AFTER 199 XV. THE CHANNEL CROSSING 211 XVI. LONDON TO MANCHESTER 21 7 XVII. A SUMMARY TO I 9! I 221 XVIII. A SUMMARY TO 1914 233 XIX. THE WAR PERIOD 1 246 XX. THE WAR PERIOD II 259 XXI. RECONSTRUCTION 264 xxn. 1919-1920 270 CONTENTS PART II 1903-1920: PROGRESS IN DESIGN CHAP. I. THE BEGINNINGS 277 II. MULTIPLICITY OF IDEAS 289 III. PROGRESS ON STANDARDISED LINES 296 IV. THE WAR PERIOD 306 PART III AEROSTATICS I. BEGINNINGS 317 II. THE FIRST DIRIGIBLES 331 III. SANTOS-DUMONT 342 IV. THE MILITARY DIRIGIBLE 348 V. BRITISH AIRSHIP DESIGN 359 VI. THE AIRSHIP COMMERCIALLY 372 VII. KITE BALLOONS 37^ PART IV ENGINE DEVELOPMENT I. THE VERTICAL TYPE 383 II. THE VEE TYPE 404 III. THE RADIAL TYPE 417 IV. THE ROTARY TYPE 428 V. THE HORIZONTALLY-OPPOSED ENGINE 440 VI. THE TWO-STROKE CYCLE ENGINE 447 VII. ENGINES OF THE WAR PERIOD 458 APPENDICES 469 A SHORT BIBLIOGRAPHY OF AERONAUTICS 504 PART I THE EVOLUTION OF THE AEROPLANE THE PERIOD OF LEGEND THE blending of fact and fancy which men call legend reached its fullest and richest expression in the golden age of Greece, and thus it is to Greek mythology that one must turn for the best form of any legend which foreshadows history. Yet the prevalence of legends regarding flight, existing in the records of practically every race, shows that this form of transit was a dream of many peoples man always wanted to fly, and imagined means of flight. In this age of steel, a very great part of the inventive genius of man has gone into devices intended to facilitate transport, both of men and goods, and the growth of civilisation is in reality the facilitation of transit, improvement of the means of communication. He was a genius who first hoisted a sail on a boat and saved the labour of rowing; equally, he who first harnessed ox or dog or horse to a wheeled vehicle was a genius and these looked up, as men have looked up from the earliest days of all, seeing that the birds had solved the problem of transit far more completely than themselves. So it must have appeared, and there is no age in history in which some dreamers have not dreamed of the conquest of the air; if the caveman had left records, these would without doubt have showed that he, too, dreamed this dream. His main aim, 3 A HISTORY OF AERONAUTICS probably, was self-preservation; when the dinosaur looked round the corner, the prehistoric bird got out of the way in his usual manner, and prehistoric man such of him as succeeded in getting out of the way after his fashion naturally envied the bird, and con- cluded that as lord of creation in a doubtful sort of way he ought to have equal facilities. He may have tried, like Simon the Magician, and other early experimenters, to improvise those facilities; assuming that he did, there is the groundwork of much of the older legend with regard to men who flew, since, when history began, legends would be fashioned out of attempts and even the desire to fly, these being compounded of some small ingredient of truth and much exaggeration and addition. In a study of the first beginnings of the art, it is worth while to mention even the earliest of the legends and traditions, for they show the trend of men's minds and the constancy of this dream that has become reality in the twentieth century. In one of the oldest records of the world, the Indian classic Mahabarata, it is stated that ' Krishna's enemies sought the aid of the demons, who built an aerial chariot with sides of iron and clad with wings. The chariot was driven through the sky till it stood over Dwarakha, where Krishna's followers dwelt, and from there it hurled down upon the city missiles that destroyed everything on which they fell.' Here is pure fable, not legend, but still a curious fore- cast of twentieth century bombs from a rigid dirigible. It is to be noted in this case, as in many, that the power to fly was an attribute of evil, not of good it was the demons who built the chariot, even as at Friedrichshavn. Mediaeval legend, in nearly every case 3 attributes flight 4 THE PERIOD OF LEGEND to the aid of evil powers, and incites well-disposed people to stick to the solid earth though, curiously enough, the pioneers of mediaeval times were very largely of priestly type, as witness the monk of Malmesbury. The legends of the dawn of history, however, distribute the power of flight with less of prejudice. Egyptian sculpture gives the figure of winged men; the British Museum has made the winged Assyrian bulls familiar to many, and both the cuneiform records of Assyria and the hieroglyphs of Egypt record flights that in reality were never made. The desire fathered the story then, and until Clement Ader either hopped with his Avion, as is persisted by his critics, or flew, as is claimed by his friends. While the origin of many legends is questionable, that of others is easy enough to trace, though not to prove. Among the credulous the significance of the name of a people of Asia Minor, the Capnobates, 4 those who travel by smoke,' gave rise to the assertion that Mongolfier was not first in the field or rather in the air since surely this people must have been responsible for the first hot-air balloons. Far less questionable is the legend of Icarus, for here it is possible to trace a foundation of fact in the story. Such a tribe as Daedalus governed could have had hardly any know- ledge of the rudiments of science, and even their ruler, seeing how easy it is for birds to sustain themselves in the air, mig^t be excused for believing that he, if he fashioned wings for himself, could use them. In that belief, let it be assumed, Daedalus made his wings; the boy, Icarus, learning that his father had determined on an attempt at flight, secured the wings and fastened 5 A HISTORY OF AERONAUTICS them to his own shoulders. A cliff seemed the likeliest place for a ' take-off/ and Icarus leaped from the cliff edge only to find that the possession of wings was not enough to assure flight to a human being. The sea that to this day bears his name witnesses that he made the attempt and perished by it. In this is assumed the bald story, from which might grow the legend of a wise king who ruled a peaceful people 'judged, sitting in the sun,' as Browning has it, and fashioned for himself wings with which he flew over the sea and where he would, until the prince, Icarus, desired to emulate him. Icarus, fastening the wings to his shoulders with wax, was so imprudent as to fly too near the sun, when the wax melted and he fell, to lie mourned of water-nymphs on the shores of waters thenceforth Icarian. Between what we have assumed to be the base of fact, and the legend which has been invested with such poetic grace in Greek story, there is no more than a century or so of re-telling might give to any event among a people so simple and yet so given to imagery. We may set aside as pure fable the stories of the winged horse of Perseus, and the flights of Hermes as messenger of the gods. With them may be placed the story of Empedocles, who failed to take Etna seriously enough, and found himself caught by an eruption while within the crater, so that, flying to safety in soi.ie hurry, he left behind but one sandal to attest that he had sought refuge in space in all probability, if he escaped at all, he flew, but not in the sense that the aeronaut understands it. But, bearing in mind the many men who tried to fly in historic times, trie legend of Icarus and Daedalus, in spite of the impossible form 6 THE PERIOD OF LEGEND in which it is presented, may rank with the story of the Saracen of Constantinople, or with that of Simon the Magician. A simple folk would naturally idealise the man and magnify his exploit, as they magnified the deeds of some strong man to make the legends of Hercules, and there, full-grown from a mere legend, is the first record of a pioneer of flying. Such a theory is not nearly so fantastic as that which makes the Capnobates, on the strength of their name, the inventors of hot-air balloons. However it may be, both in story and in picture, Icarus and his less conspicuous father have inspired the Caucasian mind, and the world is the richer for them. Of the unsupported myths unsupported, that is, by even a shadow of probability there is no end. Although Latin legend approaches nearer to fact than the Greek in some cases, in others it shows a disregard for possibilities which renders it of far less account. Thus Diodorus of Sicily relates that one Abaris travelled round the world on an arrow of gold, and Cassiodorus and Glycas and their like told of mechanical birds that flew and sang and even laid eggs. More credible is the story of Aulus Gellius, who in his Attic Nights tells how Archytas, four centuries prior to the opening of the Christian era, made a wooden pigeon that actually flew by means of a mechanism of balancing weights and the breath of a mysterious spirit hidden within it. There may yet arise one credulous enough to state that the mysterious spirit was precursor of the internal combustion engine, but, however that may be, the pigeon of Archytas almost certainly existed, and perhaps it actually glided or flew for short distances or else Aulus Gellius was an utter liar, like Cassiodorus and H.A. , 7 B A HISTORY OF AERONAUTICS his fellows. In far later times a certain John Muller, better known as Regiomontanus, is stated to have made an artificial eagle which accompanied Charles V. on his entry to and exit from Nuremberg, flying above the royal procession. But, since Muller died in 1436 and Charles was born in 1500, Muller may be ruled out from among the pioneers of mechanical flight, and it may be concluded that the historian of this event got slightly mixed in his dates. Thus far, we have but indicated how one may draw from the richest stores from which the Aryan mind draws inspiration, the Greek and Latin mythologies and poetic adaptations of history. The existing legends of flight, however, are not thus to be localised, for with two possible exceptions they belong to all the world and to every civilisation, however primitive. The two exceptions are the Aztec and the Chinese; regarding the first of these, the Spanish conquistadores destroyed such civilisation as existed in Tenochtitlan so thoroughly that, if legend of flight was among the Aztec records, it went with the rest; as to the Chinese, it is more than passing strange that they, who claim to have known and done everything while the first of history was shaping, even to antedating the discovery of gunpowder that was not made by Roger Bacon, have not yet set up a claim to successful handling of a monoplane some four thousand years ago, or at least to the patrol of the Gulf of Korea and the Mongolian frontier by a fore- runner of the l blimp.' The Inca civilisation of Peru yields up a myth akin to that of Icarus, which tells how the chieftain Ayar Utso grew wings and visited the sun it was from the sun, too, that the founders of the Peruvian 8 THE PERIOD OF LEGEND Inca dynasty, Manco Capac and his wife Mama Huella Capac, flew to earth near Lake Titicaca, to make the only successful experiment in pure tyranny that the world has ever witnessed. Teutonic legend gives forth Wieland the Smith, who made himself a dress with wings and, clad in it, rose and descended against the wind and in spite of it. Indian mythology, in addition to the story of the demons and their rigid dirigible, already quoted, gives the story of Hanouam, who fitted himself with wings by means of which he sailed in the air and, according to his desire, landed in the sacred Lauka. Bladud, the ninth king of Britain, is said to have crowned his feats of wizardry by making himself wings and attempting to fly but the effort cost him a broken neck. Bladud may have been as mythic as Uther, and again he may have been a very early pioneer. The Finnish epic, * Kalevala,' tells how Ilmarinen the Smith * forged an eagle of fire,' with * boat's walls between the wings/ after which he * sat down on the bird's back and bones,' and flew. Pure myths, these, telling how the desire to fly was characteristic of every age and every people, and how, from time to time, there arose an experimenter bolder than his fellows, who made some attempt to translate desire into achievement. And the spirit that animated these pioneers, in a time when things new were accounted things accursed, for the most part, has found expression in this present century in the utter daring and disregard of both danger and pain that stamps the flying man, a type of humanity differing in spirit from his earth- bound fellows as fully as the soldier differs from the priest. Throughout mediaeval times, records attest that 9 A HISTORY OF AERONAUTICS here and there some man believed in and attempted flight, and at the same time it is clear that such were regarded as in league with the powers of evil. There is the half-legend, half-history of Simon the Magician, who, in the third year of the reign of Nero announced that he would raise himself in the air, in order to assert his superiority over St Paul. The legend states that by the aid of certain demons whom he had prevailed on to assist him, he actually lifted himself in the air but St Paul prayed him down again. He slipped through the claws of the demons and fell headlong on the Forum at Rome, breaking his neck. The * demons ' may have been some primitive form of hot-air balloon, or a glider with which the magician attempted to rise into the wind; more probably, however, Simon threatened to ascend and made the attempt with apparatus as unsuitable as Bladud's wings, paying the inevitable penalty. Another version of the story gives St Peter instead of St Paul as the one whose prayers foiled Simon apart from the identity of the apostle, the two accounts are similar, and both define the attitude of the age toward investigation and experiment in things untried. Another and later circumstantial story, with similar evidence of some fact behind it, is that of the Saracen of Constantinople, who, in the reign of the Emperor Comnenus some little time before Norman William made Saxon Harold swear away his crown on the bones of the saints at Rouen attempted to fly round the hippodrome at Constantinople, having Comnenus among the great throng who gathered to witness the feat. The Saracen chose for his starting-point a tower in the midst of the hippodrome, and on the top of the 10 THE PERIOD OF LEGEND tower he stood, clad in a long white robe which was stiffened with rods so as to spread and catch the breeze, waiting for a favourable wind to strike on him. The wind was so long in coming that the spectators grew impatient. * Fly, O Saracen! ' they called to him. ' Do not keep us waiting so long while you try the wind!' Comnenus, who had present with him the Sultan of the Turks, gave it as his opinion that the experiment was both dangerous and vain, and, possibly in an attempt to controvert such statement, the Saracen leaned into the wind and * rose like a bird ' at the outset. But the record of Cousin, who tells the story in his Histoire de Constantinople ', states that * the weight of his body having more power to drag him down than his artificial wings had to sustain him, he broke his bones, and his evil plight was such that he did not long survive/ Obviously, the Saracen was anticipating Lilienthal and his gliders by some centuries; like Simon, a genuine experimenter both legends bear the impress of fact supporting them. Contemporary with him, and belonging to the history rather than the legends of flight, was Oliver, the monk of Malmesbury, who in the year 1065 made himself wings after the pattern of those supposed to have been used by Daedalus, attaching them to his hands and feet and attempting to fly with them. Twysden, in his Historic Anglican* Scrip tores X y sets forth the story of Oliver, who chose a high tower as his starting-point, and launched himself in the air. As a matter of course, he fell, permanently injuring himself, and died some time later. After these, a gap of centuries, filled in by impossible stones of magical flight by witches, wizards, and the II A HISTORY OF AERONAUTICS like imagination was fertile in the dark ages, but the ban of the church was on all attempt at scientific develop- ment, especially in such a matter as the conquest of the air. Yet there were observers of nature who argued that since birds could raise themselves by flapping their wings, man had only to make suitable wings, flap them, and he too would fly. As early as the thirteenth century Roger Bacon, the scientific friar of unbounded inquisitiveness and not a little real genius, announced that there could be made * some flying instrument, so that a man sitting in the middle and turning some mechanism may put in motion some artificial wings which may beat the air like a bird flying.' But being a cautious man, with a natural dislike for being burnt at the stake as a necromancer through having put forward such a dangerous theory, Roger added, * not that I ever knew a man who had such an instrument, but I am particularly acquainted with the man who contrived one/ This might have been a lame defence if Roger had been brought to trial as addicted to black arts; he seems to have trusted to the inadmissibility of hearsay evidence. Some four centuries later there was published a book entitled Perugia Augusta^ written by one C. Crispolti of Perugia the date of the work in question is 1648. In it is recorded that ' one day, towards the close of the fifteenth century, whilst many of the principal gentry had come to Perugia to honour the wedding of Giovanni Paolo Baglioni, and some lancers were riding down the street by his palace, Giovanni Baptisti Danti unexpectedly and by means of a contrivance of wings that he had constructed proportionate to the size of his body took off from the top of a tower near by, and with 12 THE PERIOD OF LEGEND a horrible hissing sound flew successfully across the great Piazza, which was densely crowded. But (oh, horror of an unexpected accident!) he had scarcely flown three hundred paces on his way to a certain point when the mainstay of the left wing gave way, and, being unable to support himself with the right alone, he fell on a roof and was injured in consequence. Those who saw not only this flight, but also the wonderful construction of the framework of the wings, said and tradition bears them out that he several times flew over the waters of Lake Thrasimene to learn how he might gradually come to earth. But, notwithstanding his great genius, he never succeeded.* This -reads circumstantially enough, but it may be borne in mind that the date of writing is more than half a century later than the time of the alleged achieve- ment the story had had time to round itself out. Danti, however, is mentioned by a number of writers, one of whom states that the failure of his experiment was due to the prayers of some individual of a conservative turn of mind, who prayed so vigorously that Danti fell appropriately enough on a church and injured himself to such an extent as to put an end to his flying career. That Danti experimented, there is little doubt, in view of the volume of evidence on the point, but the darkness of the Middle Ages hides the real truth as to the results of his experiments. If he had actually flown over Thrasimene, as alleged, then in all probability both Napoleon and Wellington would have had air scouts at Waterloo. Danti's story may be taken as fact or left as fable, and with it the period of legend or vague statement may be said to end the rest is history, both of genuine 13 A HISTORY OF AERONAUTICS experimenters and of charlatans. Such instances of legend as are given here are not a tithe of the whole, but there is sufficient in the actual history of flight to bar out more than this brief mention of the legends, which, on the whole, go farther to prove man's desire to fly than his study and endeavour to solve the problems of the air. II EARLY EXPERIMENTS So far, the stories of the development of flight are either legendary or of more or less doubtful authenticity, even including that of Danti, who, although a man of remarkable attainments in more directions than that of attempted flight, suffers so far as reputation is concerned from the inexactitudes of his chroniclers; he may have soared over Thrasimene, as stated, or a mere hop with an ineffectual glider may have grown with the years to a legend of gliding flight. So far, too, there is no evidence of the study that the conquest of the air demanded; such men as made experiments either launched themselves in the air from some height with made-up wings or other apparatus, and paid the penalty, or else constructed some form of machine which would not leave the earth, and then gave up. Each man followed his own way, and there was no attempt without the printing press and the dissemina- tion of knowledge there was little possibility of attempt on the part of any one to benefit by the failures of others. Legend and doubtful history carries up to the fifteenth century, and then came Leonardo da Vinci, first student of flight whose work endures to the present day. The world knows da Vinci as artist; his age knew him as architect, engineer, artist, and scientist 15 A HISTORY OF AERONAUTICS in an age when science was a single study, comprising all knowledge from mathematics to medicine. He was, of course, in league with the devil, for in no other way could his range of knowledge and observation be explained by his contemporaries; he left a Treatise on the Flight of Birds in which are statements and deductions that had to be rediscovered when the Treatise had been forgotten da Vinci anticipated modern knowledge as Plato anticipated modern thought, and blazed the first broad trail toward flight. One Cuperus, who wrote a Treatise on the Excellence of Man, asserted that da Vinci translated his theories into practice, and actually flew, but the statement is unsupported. That he made models, especially on the helicopter principle, is past question; these were made of paper and wire, and actuated by springs of steel wire, which caused them to lift themselves in the air. It is, however, in the theories which he put forward that da Vinci's investigations are of greatest interest; these prove him a patient as well as a keen student of the principles of flight, and show that his manifold activities did not prevent him from devoting some lengthy periods to observations of bird flight. * A bird/ he says in his Treatise ', * is an instrument working according to mathematical law, which instru- ment it is within the capacity of man to reproduce with all its movements, but not with a corresponding degree of strength, though it is deficient only in power of maintaining equilibrium. We may say, therefore, that such an instrument constructed by man is lacking in nothing except the life of the bird, and this life must needs be supplied from that of man. The life which resides in the bird's members will, without doubt, 16 EARLY EXPERIMENTS better conform to their needs than will that of a man which is separated from them, and especially in the almost imperceptible movements which produce equilibrium. But since we see that the bird is equipped for many apparent varieties of movement, we are able from this experience to deduce that the most rudimentary of these movements will be capable of being compre- hended by man's understanding, and that he will to a great extent be able to provide against the destruction of that instrument of which he himself has become the living principle and the propeller/ In this is the definite belief of da Vinci that man is capable of flight, together with a far more definite statement of the principles by which flight is to- be achieved than any which had preceded it and for that matter, than many that have succeeded it. Two further extracts from his work will show the exactness of his observations : * When a bird which is in equilibrium throws the centre of resistance of the wings behind the centre of gravity, then such a bird will descend with its head downward. This bird which finds itself in equilibrium shall have the centre of resistance of the wings more forward than the bird's centre of gravity; then such a bird will fall with its tail turned toward the earth.' And again: * A man, when flying, shall be free from the waist up, that he may be able to keep himself in equilibrium as he does in a boat, so that the centre of his gravity and of the instrument may set itself in equilibrium and change when necessity requires it to the changing of the centre of its resistance.' Here, in this last quotation, are the first beginnings of the inherent stability which proved so great an A HISTORY OF AERONAUTICS advance in design, in this twentieth century. But the extracts given do not begin to exhaust the range of da Vinci's observations and deductions. With regard to bird flight, he observed that so long as a bird keeps its wings outspread it cannot fall directly to earth, but must glide down at an angle to alight a small thing, now that the principle of the plane in opposition to the air is generally grasped, but da Vinci had to find it out. From observation he gathered how a bird checks its own speed by opposing tail and wing surface to the direction of flight, and thus alights at the proper * landing speed.' He proved the existence of upward air currents by noting how a bird takes off from level earth with wings outstretched and motionless, and, in order to get an efficient substitute for the natural wing, he recommended that there be used something similar to the membrane of the wing of a bat from this to the doped fabric of an aeroplane wing is but a small step, for both are equally impervious to air. Again, da Vinci recommended that experiments in flight be conducted at a good height from the ground, since, if equilibrium be lost through any cause, the height gives time to regain it. This recommendation, by the way, received ample support in the training areas of war pilots. Man's muscles, said da Vinci, are fully sufficient to enable him to fly, for the larger birds, he noted, employ but a small part of their strength in keeping themselves afloat in the air by this theory he attempted to encourage experiment, just as, when his time came, Borelli reached the opposite conclusion and discouraged it. That Borelli was right so far and da Vinci wrong, detracts not at all from the repute of the earlier IS EARLY EXPERIMENTS investigator, who had but the resources of his age to support investigations conducted in the spirit of ages after. His chief practical contributions to the science of flight apart from numerous drawings which have still a value are the helicopter or lifting screw, and the parachute. The former, as already noted, he made and proved effective in model form, and the principle which he demonstrated is that of the helicopter of to-day, on which sundry experimenters work spasmodi- cally, in spite of the success of the plane with its driving propeller. As to the parachute, the idea was doubtless inspired by observation of the effect a bird produced by pressure of its wings against the direction of flight. Da Vinci's conclusions, and his experiments, were forgotten easily by most of his contemporaries; his Treatise lay forgotten for nearly four centuries, over- shadowed, mayhap, by his other work. There was, however, a certain Paolo Guidotti of Lucca, who lived in the latter half of the sixteenth century, and who attempted to carry da Vinci's theories one of them, at least, into practice. For this Guidotti, who was by profession an artist and by inclination an investigator, made for himself wings, of which the framework was of whalebone; these he covered with feathers, and with them made a number of gliding flights, attaining considerable proficiency. He is said in the end to have made a flight of about four hundred yards, but this attempt at solving the problem ended on a house roof, where Guidotti broke his thigh bone. After that, apparently, he gave up the idea of flight, and went back to painting. One other, a Venetian architect named Veranzio, 19 A HISTORY OF AERONAUTICS studied da Vinci's theory of the parachute, and found it correct, if contemporary records and even pictorial presentment are correct. Da Vinci showed his con- ception of a parachute as a sort of inverted square bag ; Veranzio modified this to a * sort of square sail extended by four rods of equal size and having four cords attached at the corners,' by means of which * a man could without danger throw himself from the top of a tower or any high place. For though at the moment there may be no wind, yet the effort of his falling will carry up the wind, which the sail will hold, by which means he does not fall suddenly but descends little by little. The size of the sail should be measured to the man.' By this last, evidently, Veranzio intended to convey that the sheet must be of such content as would enclose sufficient air to support the weight of the parachutist. Veranzio made his experiments about 1617-1618, but, naturally, they carried him no farther than the mere descent to earth, and since a descent is merely a descent, it is to be conjectured that he soon got tired of dropping from high roofs, and took to designing architecture instead of putting it to such a use. With the end of his experiments the work of da Vinci in relation to flying became neglected for nearly four centuries. Apart from these two experimenters, there is little to record in the matter either of experiment or study until the seventeenth century. Francis Bacon, it is true, wrote about flying in his Syfoa Syfoarum, and mentioned the subject in the New Atlantis , but, except for the insight that he showed even in superficial mention of any specific subject, he does not appear to have made attempt at serious investigation, ' Spreading of 20 EARLY EXPERIMENTS Feathers, thin and close and in great breadth will likewise bear up a great Weight,' says Francis, * being even laid without Tilting upon the sides.' But a lesser genius could have told as much, even in that age, and though the great Sir Francis is sometimes adduced as one of the early students of the problems of flight, his writings will not sustain the reputation. The seventeenth century, however, gives us three names, those of Borelli, Lana, and Robert Hooke, all of which take definite place in the history of flight. Borelli ranks as one of the great figures in the study of aeronautical problems, in spite of erroneous deductions through which he arrived at a purely negative conclusion with regard to the possibility of human flight. Borelli was a versatile genius. Born in 1608, he was practically contemporary with Francesco Lana, and there is evidence that he either knew or was in correspondence with many prominent members of the Royal Society of Great Britain, more especially with John Collins, Dr Wallis, and Henry Oldenburgh, the then Secretary of the Society. He was author of a long list of scientific essays, two of which only are responsible for his fame, viz., Theorice Medic*earum Planetarum y published in Florence, and the better known posthumous De Motu Animalium. The first of these two is an astronomical study in which Borelli gives evidence of an instinctive knowledge of gravitation, though no definite expression is given of this. The second work, De Motu Animalium^ deals with the mechanical action of the limbs of birds and animals and with a theory of the action of the internal organs. A section of the first part of this work, called De Volatu^ is a study of bird flight; it is quite independent of Da Vinci's earlier 21 A HISTORY OF AERONAUTICS work, which had been forgotten and remained un- noticed until near on the beginning of practical flight. Marey, in his work, La Machine Animale^ credits Borelli with the first correct idea of the mechanism of flight. He says: * Therefore we must be allowed to render to the genius of Borelli the justice which is due to him, and only claim for ourselves the merit of having furnished the experimental demonstration or a truth already suspected.' In fact, all subsequent studies on this subject concur in making Borelli the first investigator who illustrated the purely mechanical theory of the action of a bird's wings. Borelli's study is divided into a series of propositions in which he traces the principles of flight, and the mechanical actions of the wings of birds. The most interesting of these are the propositions in which he sets forth the method in which birds move their wings during flight and the manner in which the air offers resistance to the stroke of the wing. 1 With regard to .the first of these two points he says: ' When birds in ' repose rest on the earth their wings are folded up close against their flanks, but when wishing to start on their flight they first bend their legs and leap into the air. Whereupon the joints of their wings are straightened out to form a straight line at right angles to the lateral surface of the breast, so that the two wings, outstretched, are placed, as it were, like the arms of a cross to the body of the bird. Next, since the wings with their feathers attached form almost a plane surface, they are raised slightly above the horizontal, and with a most quick impulse beat down in a direction almost perpendicular to the wing-plane, upon the underlying air; and to so intense a beat the air, notwithstanding it to be fluid, 22 EARLY EXPERIMENTS offers resistance, partly by reason of its natural inertia, which seeks to retain it at rest, and partly because the particles of the air, compressed by the swiftness of the stroke, resist this compression by their elasticity, just like the hard ground. Hence the whole mass of the bird rebounds, making a fresh leap through the air; whence it follows that flight is simply a motion composed of successive leaps accomplished through the air. And I remark that a wing can easily beat the air in a direction almost perpendicular to its plane surface, although only a single one of the corners of the humerus bone is attached to the scapula, the whole extent of its base remaining free and loose, while the greater transverse feathers are joined to the lateral skin of the thorax. Nevertheless the wing can easily revolve about its base like unto a fan. Nor are there lacking tendon ligaments v/hich restrain the feathers and prevent them from opening farther, in the same fashion that sheets hold in the sails of ships. No less admirable is nature's cunning in unfolding and folding the wings upwards, for she folds them not laterally, but by moving upwards edgewise the osseous parts wherein the roots of the feathers are inserted; for thus, without encountering the air's resistance the upward motion of the wing surface is made as with a sword, hence they can be uplifted with but small force. But thereafter when the wings are twisted by being drawn transversely and by the resistance of the air, they are flattened as has been declared and will be made manifest hereafter.' Then with reference to the resistance to the air of the wings he explains: * The air when struck offers resistance by its elastic virtue through which the particles of the air compressed by the wing-beat strive to expand H.A. 23 c A HISTORY OF AERONAUTICS again. Through these two causes of resistance the downward beat of the wing is not only opposed, but even caused to recoil with a reflex movement; and these two causes of resistance ever increase the more the down stroke of the wing is maintained and accelerated. On the other hand, the impulse of the wing is continuously diminished and weakened by the growing resistance. Hereby the force of the wing and the resistance become balanced; so that, manifestly, the air is beaten by the wing with the same force as the resistance to the stroke/ He concerns himself also with the most difficult problem that confronts the flying man of to-day, namely, landing effectively, and his remarks on this subject would be instructive even to an air pilot of these days: * Now the ways and means by which the speed is slackened at the end of a flight are these. The bird spreads its wings and tail so that their concave surfaces are per- pendicular to the direction of motion; in this way, the spreading feathers, like a ship's sail, strike against the still air, check the speed, and so that most of the impetus may be stopped, the wings are flapped quickly and strongly forward, inducing a contrary motion, so that the bird absolutely or very nearly stops.' At the end of his study Borelli came to a conclusion which militated greatly against experiment with any heavier-than-air apparatus, until well on into the nine- teenth century, for having gone thoroughly into the subject of bird flight he states distinctly in his last proposition on the subject that * It is impossible that men should be able to fly craftily by their own strength.' This statement, of course, remains true up to the present day, for no man has yet devised the means by which 24 EARLY EXPERIMENTS he can raise himself in the air and maintain himself there by mere muscular effort. From the time of Borelli up to the development of the steam engine it may be said that flight by means of any heavier-than-air apparatus was generally regarded as impossible, and apart from certain deductions which a little experiment would have shown to be doomed to failure, this method of flight was not followed up. It is not to be wondered at, when Borelli's exaggerated estimate of the strength expended by birds in proportion to their weight is borne in mind; he alleged that the motive force in birds' wings is 10,000 times greater than the resistance of their weight, and with regard to human flight he remarks : * When, therefore, it is asked whether men may be able to fly by their own strength, it must be seen whether the motive power of the pectoral muscles (the strength of which is indicated and measured by their size) is proportionately great, as it is evident that it must exceed the resistance of the weight of the whole human body 10,000 times, together with the weight of enormous wings which should be attached to the arms. And it is clear that the motive power of the pectoral muscles in men is much less than is necessary for flight, for in birds the bulk and weight of the muscles for flapping the wings are not less than a sixth part of the entire weight of the body. Therefore, it would be necessary that the pectoral muscles of a man should weigh more than a sixth part of the entire weight of his body; so also the arms, by flapping with the wings attached, should be able to exert a power 10,000 times greater than the weight of the human body itself. But they are far below such excess, for the aforesaid pectoral A HISTORY OF AERONAUTICS muscles do not equal a hundredth part of the entire weight of a man. Wherefore either the strength of the muscles ought to be increased or the weight of the human body must be decreased, so that the same pro- portion obtains in it as exists in birds. Hence it is deducted that the Icarian invention is entirely mythical because impossible, for it is not possible either to increase a man's pectoral muscles or to diminish the weight of the human body; and whatever apparatus is used, although it is possible to increase the momentum, the velocity or the power employed can never equal the resistance; and therefore wing flapping by the contraction of muscles cannot give out enough power to carry up the heavy body of a man/ It may be said that practically all the conclusions which Borelli reached in his study were negative. Although contemporary with Lana, he perceived the one factor which rendered Lana's project for flight by means of vacuum globes an impossibility he saw that no globe could be constructed sufficiently light for flight, and at the same time sufficiently strong to with- stand the pressure of the outside atmosphere. He does not appear to have made any experiments in flying on his own account, having, as he asserts most definitely, no faith in any invention designed to lift man from the surface of the earth. But his work, from which only the foregoing short quotations can be given, is, nevertheless, of indisputable value, for he settled the mechanics of bird flight, and paved the way for those later investigators who had, first, the steam engine, and later the internal combustion engine two factors in mechanical flight which would have seemed as impossible to Borelli as would wireless telegraphy to a student of 26 EARLY EXPERIMENTS Napoleonic times. On such foundations as his age afforded Borelli built solidly and well, so that he ranks \ as one of the greatest if not actually the greatest of the investigators into this subject before the age of steam. The conclusion, that * the motive force in birds' wings is apparently ten thousand times greater than the resistance of their weight/ is erroneous, of course, but study of the translation from which the foregoing excerpt is taken will show that the error detracts very little from the value of the work itself. Borelli sets out very definitely the mechanism of flight, in such fashion that he who runs may read. His reference to ' the use of a large vessel/ etc., concerns the suggestion made by Francesco Lana, who antedated Borelli's publication of De Motu Animalium by some ten years with his suggestion for an * aerial ship/ as he called it. Lana's mind shows, as regards flight, a more imaginative twist; Borelli dived down into first causes, and reached mathematical conclusions; Lana conceived a theory and upheld it theoretically, since the manner of his life precluded experiment. Francesco Lana, son of a noble family, was born in 1631; in 1647 ne was received as a novice into the Society of Jesus at Rome, and remained a pious member of the Jesuit society until the end of his life. He was greatly handicapped in his scientific investigations by the vows of poverty which the rules of the Order imposed on him. He was more scientist than priest all his life; for two years he held the post of Professor of Mathematics at Ferrara, and up to the time of his death, in 1687, he spent by far the greater part of his time in scientific research. He had the dubious advantage of living in 27 A HISTORY OF AERONAUTICS an age when one man could cover the whole range of science, and this he seems to have done very thoroughly. There survives an immense work of his entitled, Magisterium Nature et Artis^ which embraces the whole field of scientific knowledge as that was developed in the period in which Lana lived. In an earlier work of his, published in Brescia in 1670, appears his famous treatise on the aerial ship, a problem which Lana worked out with thoroughness. He was unable to make practical experiments, and thus failed to perceive the one insuper- able drawback to his project of which more anon. Only extracts from the translation of Lana's work can be given here, but sufficient can be given to show fully the means by which he designed to achieve the conquest of the air. He begins by mention of the celebrated pigeon of Archytas the Philosopher, and advances one or two theories with regard to the way in which this mechanical bird was constructed, and then he recites, apparently with full belief in it, the fable of Regiomontanus and the eagle that he is said to have constructed to accompany Charles V. on his entry into Nuremberg. In fact, Lana starts his work with a study of the pioneers of mechanical flying up to his own time, and then outlines his own devices for the construction of mechanical birds before proceeding to detail the construction of the aerial ship. Concerning primary experiments for this he says: ' I will, first of all, presuppose that air has weight owing to the vapours and halations which ascend from the earth and seas to a height of many miles and surround the whole of our terraqueous globe; and this fact will not be denied by philosophers, even by those who may have but a superficial knowledge, because it can be 28 EARLY EXPERIMENTS proven by exhausting, if not all, at any rate the greater part of, the air contained in a glass vessel, which, if weighed before and after the air has been exhausted, will be found materially reduced in weight. Then I found out how much the air weighed in itself in the following manner. I procured a large vessel of glass, whose neck could be closed or opened by means of a tap, and holding it open I warmed it over a fire, so that the air inside it becoming rarified, the major part was forced out; then quickly shutting the tap to prevent the re-entry I weighed it; which done, I plunged its neck in water, resting the whole of the vessel on the surface of the water, then on opening the tap the water rose in the vessel and filled the greater part of it. I lifted the neck out of the water, released the water contained in the vessel, and measured and weighed its quantity and density, by which I inferred that a certain quantity of air had come out of the vessel equal in bulk to the quantity of water which had entered to refill the portion abandoned by the air. I again weighed the vessel, after I had first of all well dried it free of all moisture, and found it weighed one ounce more whilst it was full of air than when it was exhausted of the greater part, so that what it weighed more was a quantity of air equal in volume to the water which took its place. The water weighed 640 ounces, so I concluded that the weight of air com- pared with that of water was i to 640 that is to say, as the water which filled the vessel weighed 640 ounces, so the air which filled the same vessel weighed one ounce.' Having thus detailed the method of exhausting air from a vessel, Lana goes on to assume that any large vessel can be entirely exhausted of nearly all the air 29 A HISTORY OF AERONAUTICS contained therein. Then he takes Euclid's proposition to the effect that the superficial area of globes increases in the proportion of the square of the diameter, whilst the volume increases in the proportion of the cube of the same diameter, and he considers that if one only constructs the globe of thin metal, of sufficient size, and exhausts the air in the manner that he suggests, such a globe will be so far lighter than the surrounding atmosphere that it will not only rise, but will be capable of lifting weights. Here is Lana's own way of putting it: ' But so that it may be enabled to raise heavier weights and to lift men in the air, let us take double the quantity of copper, 1,232 square feet, equal to 308 Ibs. of copper; with this double quantity of copper we could construct a vessel of not only double the capacity, but of four times the capacity of the first, for the reason shown by my fourth supposition. Consequently the air contained in such a vessel will be 718 Ibs. 4 ounces, so that if the air be drawn out of the vessel it will be 4 1 o Ibs. 4! ounces lighter than the same volume of air, and, consequently, will be enabled to lift three men, or at least two, should they weigh more than eight pesi each. It is thus manifest that the larger the ball or vessel is made, the thicker and more solid can the sheets of copper be made, because, although the weight will increase, the capacity of the vessel will increase to a greater extent and with it the weight of the air therein, so that it will always be capable to lift a heavier weight. From this it can be easily seen how it is possible to construct a machine which, fashioned like unto a ship, will float on the air.' With four globes of these dimensions Lana proposed 30 UCVO METE.DO D o de A suggestion for applying hydrogen gas to Lana's 'Aerial Ship.' Rome, 1784. Jo face page 30 EARLY EXPERIMENTS to make an aerial ship of the fashion shown in his quaint illustration. He is careful to point out a method by which the supporting globes for the aerial ship may be entirely emptied of air; this is to be done by connecting to each globe a tube of copper which is * at least a length of 47 modern Roman palmi.' A small tap is to close this tube at the end nearest the globe, and then vessel and tube are to be filled with water, after which the tube is to be immersed in water and the tap opened, allowing the water to run out of the vessel, while no air enters. The tap is then closed before the lower end of the tube is removed from the water, leaving no air at all in the globe or sphere. Propulsion of this airship was to be accomplished by means of sails, and also by oars. Lana antedated the modern propeller, and realised that the air would offer enough resistance to oars or paddle to impart motion to any vessel floating in it and propelled by these means, although he did not realise the amount of pressure on the air which would be necessary to accomplish propulsion. As a matter of fact, he foresaw and provided against practically all the difficulties that would be encountered in the working, as well as the making, of the aerial ship, finally coming up against what his religious training made an insuperable objection. This, again, is best told in his own words: ' Other difficulties I do not foresee that could prevail against this invention, save one only, which to me seems the greatest of them all, and that is that God would surely never allow such a machine t be successful, since it would create many disturbances in the civil and political governments of mankind.' He ends by saying that no city would be proof 31 A HISTORY OF AERONAUTICS against surprise, while the aerial ship could set fire to vessels at sea, and destroy houses, fortresses, and cities by fire balls and bombs. In fact, at the end of his treatise on the subject, he furnishes a pretty complete resume of the activities of German Zeppelins. As already noted, Lana himself, owing to his vows of poverty, was unable to do more than put his suggestions on paper, which he did with a thoroughness that has procured him a place among the really great pioneers of flying. It was nearly 200 years before any attempt was made to realise his project; then, in 1843, M. Marey Monge set out to make the globes and the ship as Lana detailed them. Monge's experiments cost him the sum of 25,000 francs 75 centimes, which he expended purely from love of scientific investigation. He chose to make his globes of brass, about .004 in thickness, and weighing 1.465 Ibs. to the square yard. Having made his sphere of this metal, he lined it with two thicknesses of tissue paper, varnished it with oil, and set to work to empty it of air. This, however, he never achieved, for such metal is incapable of sustaining the pressure of the outside air, as Lana, had he had the means to carry out experi- ments, would have ascertained. M. Monge's sphere could never be emptied of air sufficiently to rise from the earth; it ended in the melting-pot, ignominiously enough, and all that Monge got from his experiment was the value of the scrap metal and the satisfaction of knowing that Lana's theory could never be translated into practice. Robert Hooke is less conspicuous than either Borelli or Lana; his work, which came into the middle of the seventeenth century, consisted of various experiments 32 EARLY EXPERIMENTS with regard to flight, from which emerged * a Module, which by the help of Springs and Wings, raised and sustained itself in the air.' This must be reckoned as the first model flying machine which actually flew, except for da Vinci's helicopters; Hooke's model appears to have been of the flapping-wing type he attempted to copy the motion of birds, but found from study and experiment that human muscles were not sufficient to the task of lifting the human body. For that reason, he says, ' I applied my mind to contrive a way to make artificial muscles,' but in this he was, as he expresses it, * frustrated of my expectations/ Hooke's claim to fame rests mainly on his successful model; the rest of his work is of too scrappy a nature to rank as a serious contribution to the study of flight. Contemporary with Hooke was one Allard, who, in France, undertook to emulate the Saracen of Con- stantinople to a certain extent. Allard was a tight-rope dancer who either did or was said to have done short gliding flights the matter is open to question and finally stated that he would, at St Germains, fly from the terrace in the king's presence. He made the attempt, but merely fell, as did the Saracen some centuries before, causing himself serious injury. Allard cannot be regarded as a contributor to the development of aeron- autics in any way, and is only mentioned as typical of the way in which, up to the time of the Wright brothers, flying was regarded. Even unto this day there are many who still believe that, with a pair of wings, man ought to be able to fly, and that the mathematical data necessary to effective construction simply do not exist. This attitude was reasonable enough in an unlearned age, and Allard was one a little more conspicuous 33 A HISTORY OF AERONAUTICS than the majority among many who made experiment in ignorance, with more or less danger to themselves and without practical result of any kind. The seventeenth century was not to end, however, without practical experiment of a noteworthy kind in gliding flight. Among the recruits to the ranks of pioneers was a certain Besnier, a locksmith of Sable, who somewhere between 1675 and 1680 constructed a glider of which a crude picture has come down to Besnier's Flying Apparatus. modern times. The apparatus, as will be seen, consisted of two rods with hirged flaps, and the original designer of the picture seems to have had but a small space in which to draw, since obviously the flaps must have been much larger than those shown. Besnier placed the rods on his shoulders, and worked the flaps by cords attached to his hands and feet the flaps opened as they fell, and closed as they rose, so the device as a whole must be regarded as a sort of flapping glider. Having by experiment proved his apparatus successful, 34 EARLY EXPERIMENTS Besnier promptly sold it to a travelling showman of the period, and forthwith set about constructing a second set, with which he made gliding flights of considerable height and distance. Like Lilienthal, Besnier projected himself into space from some height, and then, according to the contemporary records, he was able to cross a river of considerable size before coming to earth. It does not appear that he had any imitators, or that any advantage whatever was taken of his experiments; the age was one in which he would be regarded rather as a freak exhibitor than as a serious student, and possibly, considering his origin and the sale of his first apparatus to such a client, he regarded the matter himself as more in the nature of an amusement than as a discovery. Borelli, coming at the end of - the century, proved to his own satisfaction and that of his fellows that flapping wing flight was an impossibility; the capabilities of the plane were as yet undreamed, and the prime mover that should make the plane available for flight was deep in the womb of time. Da Vinci's work was forgotten flight was an impossibility, or at best such a useless show as Besnier was able to give. The eighteenth century was almost barren of experiment. Emanuel Swedenborg, having invented a new religion, set about inventing a flying machine, and succeeded theoretically, publishing the result of his investigations as follows: * Let a car or boat or some like object be made of light material such as cork or bark, with a room within it for the operator. Secondly, in front as well as behind, or all round, set a widely-stretched sail parallel to the machine, forming within a hollow or bend, which could 35 A HISTORY OF AERONAUTICS be reefed like the sails of a ship. Thirdly, place wings on the sides, to be worked up and down by a spiral spring, these wings also to be hollow below in order to increase the force and velocity, take in the air, and make the resistance as great as may be required. These, too, should be of light material and of sufficient size; they should be in the shape of birds' wings, or the sails of a windmill, or some such shape, and should be tilted obliquely upwards, and made so as to collapse on the upward stroke and expand on the downward. Fourth, place a balance or beam below, hanging down perpen- dicularly for some distance with a small weight attached to its end, pendent exactly in line with the centre of gravity; the longer this beam is, the lighter must it be, for it must have the same proportion as the well-known vectis or steel-yard. This would serve to restore the balance of the machine if it should lean over to any of the four sides. Fifthly, the wings would perhaps have greater force, so as to increase the resistance and make the flight easier, if a hood or shield were placed over them, as is the case with certain insects. Sixthly, when the sails are expanded so as to occupy a great surface and much air, with a balance keeping them horizontal, only a small force would be needed to move the machine back and forth in a circle, and up and down. And, after it has gained momentum to move slowly upwards, a slight movement and an even bearing would keep it balanced in the air and would determine its direction at will.' The only point in this worthy of any note is the first device for maintaining stability automatically Swedenborg certainly scored a point there. For the rest, his theory was but theory, incapable of being put 36 EARLY EXPERIMENTS to practice he does not appear to have made any attempt at advance beyond the mere suggestion. Some ten years before his time the state of knowledge with regard to flying in Europe was demonstrated by an order granted by the King of Portugal to Friar Lourenzo de Guzman, who claimed to have invented a flying machine capable of actual flight. The order stated that * In order to encourage the suppliant to apply himself with zeal toward the improvement of the new machine, which is capable of producing the effects mentioned by him, I grant unto him the first vacant place in my College of Barcelos or Santarem, and the first professorship of mathematics in my University of Coimbra, with the annual pension of 600,000 reis during his life. Lisbon, I7th of March, 1709.* What happened to Guzman when the non-existence of the machine was discovered is one of the things that is well outside the province of aeronautics. He was charlatan pure and simple, as far as actual flight was concerned, though he had some ideas respecting the design of hot-air balloons, according to Tissandier. (La Navigation Aerienne^) His flying machine was to contain, among other devices, bellows to produce artificial wind when the real article failed, and also magnets in globes to draw the vessel in an upward direction and maintain its buoyancy. Some draughts- man, apparently gifted with as vivid imagination as Guzman himself, has given to the world an illustration of the hypothetical vessel; it bears some resemblance to Lana's aerial ship, from which fact one draws obvious conclusions. A rather amusing claim to solving the problem of flight was made in the middle of the eighteenth century 37 A HISTORY OF AERONAUTICS by one Grimaldi, a * famous and unique Engineer ' who, as a matter of actual fact, spent twenty years in missionary work in India, and employed the spare time that missionary work left him in bringing his invention to a workable state. The invention is described as a * box which with the aid of clockwork rises in the air, and goes with such lightness and strong rapidity that it succeeds in flying a journey of seven leagues in an hour. It is made in the fashion of a bird; the wings from end to end are 25 feet in extent. The body is composed of cork, artistically joined together and well fastened with metal wire, covered with parchment and feathers. The wings are made of catgut and whalebone, and covered also with the same parchment and feathers, and each wing is folded in three seams. In the body of the machine are contained thirty wheels of unique work, with two brass globes and little chains which alternately wind up a counterpoise; with the aid of six brass vases, full of a certain quantity of quicksilver, which run in some pulleys, the machine is kept by the artist in due equilibrium and balance. By means, then, of the friction between a steel wheel adequately tempered and a very heavy and surprising piece of lodestone, ' the whole is kept in a regulated forward movement, given, however, a right state of the winds, since the machine cannot fly so much in totally calm weather as in stormy. This prodigious machine is directed and guided by a tail seven palmi long, which is attached to the knees and ankles of the inventor by leather straps; by stretching out his legs, either to the right or to the left, he moves the machine in whichever direction he pleases. . . . The machine's flight lasts only three hours, after which the wings gradually close 38 EARLY EXPERIMENTS themselves, when the inventor, perceiving this, goes down gently, so as to get on his own feet, and then winds up the clockwork and gets himself ready again upon the wings for the continuation of a new flight. He himself told us that if by chance one of the wheels came off or if one of the wings broke, it is certain he would inevitably fall rapidly to the ground, and, therefore, he does not rise more than the height of a tree or two, as also he only once put himself in the risk of crossing the sea, and that was from Calais to Dover, and the same morning he arrived in London.' And yet there are still quite a number of people who persist in stating that Bleriot was the first man to fly across the Channel! A study of the development of the helicopter principle was published in France in 1868, when the great French engineer Paucton produced his Theorie de la Vis cC Ar chime de. For some inexplicable reason, Paucton was not satisfied with the term ' helicopter,' but preferred to call it a * pterophore,' a name which, so far as can be ascertained, has not been adopted by any other writer or investigator. Paucton stated that, since a man is capable of sufficient force to overcome the weight of his own body, it is only necessary to give him a machine which acts on the air * with all the force of which it is capable and at its utmost speed,' and he will then be able to lift himself in the air, just as by the exertion of all his strength he is able to lift himself in water. * It would seem,' says Paucton, * that in the pterophore, attached vertically to a carriage, the whole built lightly and carefully assembled, he has found something that will give him this result in all perfection. In construction, one would be careful that the machine H.A. 39 D A HISTORY OF AERONAUTICS produced the least friction possible, and naturally it ought to produce little, as it would not be at all compli- cated. The new Daedalus, sitting comfortably in his carriage, would by means of a crank give to the pte*rophore a suitable circular (or revolving) speed. This single pterophore would lift him vertically, but in order to move horizontally he should be supplied with a tail in the shape of another pterophore. When he wished to stop for a little time, valves fixed firmly across the end of the space between the blades would automatically close the openings through which the air flows, and change the pterophore into an unbroken surface which would resist the flow of air and retard the fall of the machine to a considerable degree/ The doctrine thus set forth might appear plausible, but it is based on the common misconception that all the force which might be put into the helicopter or ' pterophore ' would be utilised for lifting or propelling the vehicle through the air, just as a propeller uses all its power to drive a ship through water. But, in applying such a propelling force to the air, most of the force is utilised in maintaining aerodynamic support as a matter of fact, more force is needed to maintain this support than the muscle of man could possibly furnish to a lifting screw, and even if the helicopter were applied to a full-sized, engine-driven air vehicle, the rate of ascent would depend on the amount of surplus power that could be carried. For example, an upward lift of 1,000 pounds from a propeller 15 feet in diameter would demand an expenditure of 50 horse-power under the best possible conditions, and in order to lift this load vertically through such atmospheric pressure as exists 40 EARLY EXPERIMENTS at sea-level or thereabouts, an additional 20 horse- power would be required to attain a rate of 1 1 feet per second 50 horse-power must be continually provided for the mere support of the load, and the additional 20 horse-power must be continually provided in order to lift it. Although, in model form, there is nothing quite so strikingly successful as the helicopter in the range of flying machines, yet the essential weight increases so disproportionately to the effective area that it is necessary to go but very little beyond model dimensions for the helicopter to become quite ineffective. That is not to say that the lifting screw must be totally ruled out so far as the construction of aircraft is concerned. Much is still empirical, so far as this branch of aeronautics is concerned, and consideration of the structural features of a propeller goes to show that the relations of essential weight and effective area do not altogether apply in practice as they stand in theory. Paucton's dream, in some modified form, may yet become reality it is only so short a time ago as 1896 that Lord Kelvin stated he had not the smallest molecule of faith in aerial navigation, and since the whole history of flight consists in proving the impossible possible, the helicopter may yet challenge the propelled plane surface for aerial supremacy. It does not appear that Paucton went beyond theory, nor is there in his theory any advance toward practical flight da Vinci could have told him as much as he knew. He was followed by Meerwein, who invented an apparatus apparently something between a flapping wing machine and a glider, consisting of two wings, which were to be operated by means of a rod; the venturesome one who would fly by means of this A HISTORY OF AERONAUTICS apparatus had to lie in a horizontal position beneath the wings to work the rod. Meerwein deserves a place of mention, however, by reason of his investigations into the amount of surface necessary to support a given weight. Taking that weight at 200 pounds which would allow for the weight of a man and a very light apparatus he estimated that 126 square feet would be necessary for support. His pamphlet, published at Basle in 1784, shows him to have been a painstaking student of the potentialities of flight. Jean-Pierre Blanchard, later to acquire fame in connection with balloon flight, conceived and described a curious vehicle, of which he even announced trials as impending. His trials were postponed time after time, and it appears that he became convinced in the end of the futility of his device, being assisted to such a con- clusion by Lalande, the astronomer, who repeated Borelli's statement that it was impossible for man ever to fly by his own strength. This was in the closing days of the French monarchy, and the ascent of the Mongolfiers' first hot-air balloon in 1783 which shall be told more fully in its place put an end to all French experiments with heavier-than-air apparatus, though in England the genius of Cayley was about to bud, and even in France there were those who understood that ballooning was not true flight. Ill SIR GEORGE CAYLEY THOMAS WALKER ON the fifth of June, 1783, the Montgolfiers* hot-air balloon rose at Versailles, and in its rising divided the study of the conquest of the air into two definite parts, the one being concerned with the propulsion of gas lifted, lighter-than-air vehicles, and the other being crystallised in one sentence by Sir George Cayley: ' The whole problem,' he stated, ' is confined within these limits, viz.: to make a surface support a given weight by the application of power to the resistance of the air/ For about ten years the balloon held the field entirely, being regarded as the only solution of the problem of flight that man could ever compass. So definite for a time was this view on the eastern side of the Channel that for some years practically all the progress that was made in the development of power- driven planes was made in Britain. In 1800 a certain Dr Thomas Young demonstrated that certain curved surfaces suspended by a thread moved into and not away from a horizontal current of air, but the demonstration, which approaches perilously near to perpetual motion if the current be truly horizontal, has never been successfully repeated, so that there is more than a suspicion that Young's air-current was not horizontal. Others had made and were making experi- ments on the resistance offered to the air by flat surfaces, 43 A HISTORY OF AERONAUTICS when Cayley came to study and record, earning such a place among the pioneers as to win the title of ' father of British aeronautics.' Cayley was a man in advance of his time, in many ways. Of independent means, he made the grand tour which was considered necessary to the education of every young man of position, and during this excursion he was more engaged in studies of a semi-scientific character than in the pursuits that normally filled such a period. His various writings prove that throughout his life aeronautics was the foremost subject in his mind; the Mechanic's Magazine, Nicholsons Journal, the Philosophical Magazine, and other periodicals of like nature bear witness to Cayley's continued research into the subject of flight. He approached the subject after the manner of the trained scientist, analysing the mechanical properties of air under chemical and physical action. Then he set to work to ascertain the power necessary for aerial flight, and was one of the first to enunciate the fallacy of the hopes of successful flight by means of the steam engine of those days, owing to the fact that it was impossible to obtain a given power with a given weight. Yet his conclusions on this point were not altogether negative, for as early as 1810 he stated that he could construct a balloon which could travel with passengers at 20 miles an hour he was one of the first to consider the possibilities of applying power to a balloon. Nearly thirty years later in 1837 he made the first attempt at establishing an aeronautical society, but at that time the power-driven plane was regarded by the great majority as an absurd dream of more or less mad inventors, while ballooning ranked on about the same 44 SIR GEORGE CAYLEY THOMAS WALKER level as tight-rope walking, being considered an adjunct to fairs and fetes, more a pastime than a study. Up to the time of his death, in 1857, Cayley main- tained his study of aeronautical matters, and there is no doubt whatever that his work went far in assisting the solution of the problem of air conquest. His principal published work, a monograph entitled Aerial Navigation, has been republished in the admirable series of ' Aeronautical Classics' issued by the Royal Aeronautical Society. He began this work by pointing out the impossibility of flying by means of attached wings, an impossibility due to the fact that, while the pectoral muscles of a bird account for more than two-thirds of its whole muscular strength, in a man the muscles available for flying, no matter what mechanism might be used, would not exceed one-tenth of his total strength. Cayley did not actually deny the possibility of a man flying by muscular effort, however, but stated that ' the flight of a strong man by great muscular exertion, though a curious and interesting circumstance, inasmuch as it will probably be the means of ascertaining this power and supplying the basis whereon to improve it, would be of little use.' From this he goes on to the possibility of using a Boulton and Watt steam engine to develop the power necessary for flight, and in this he saw a possibility of practical result. It is worthy of note that in this con- nection he made mention of the forerunner of the modern internal combustion engine; ' The French/ he said, ' have lately shown the great power produced by igniting inflammable powders in closed vessels, and several years ago an engine was made to work in this country 45 A HISTORY OF AERONAUTICS in a similar manner by inflammation of spirit of tar.' In a subsequent paragraph of his monograph he anticipates almost exactly the construction of the Lenoir gas engine, which came into being more than fifty-five years after his monograph was published. Certain experiments detailed in his work were made to ascertain the size of the surface necessary for the support of any given weight. He accepted a truism of to-day in pointing out that in any matters connected with aerial investigation, theory and practice are as widely apart as the poles. Inclined at first to favour the helicopter principle, he finally rejected this in favour of the plane, with which he made numerous experiments. During these, he ascertained the peculiar advantages of curved surfaces, and saw the necessity of providing both vertical and horizontal rudders in order to admit of side steering as well as the control of ascent and descent, and for preserving equilibrium. He may be said to have anticipated the work of Lilienthal and Pilcher, since he constructed and experimented with a fixed surface glider. ' It was beautiful,' he wrote concerning this, * to see this noble white bird sailing majestically from the top of a hill to any given point of the plain below it with perfect steadiness and safety, according to the set of its rudder, merely by its own weight, descending at an angle of about eight degrees with the horizon/ It is said that he once persuaded his gardener to trust himself in this glider for a flight, but if Cayley himself ventured a flight in it he has left no record of the fact. The following extract from his work, Aerial Navigation^ affords an instance of the thoroughness of his investigations, and the concluding paragraph also 46 Sir George Caley, Bart. The Father of British Aeronautics.' To face page 46 SIR GEORGE CAYLEY THOMAS WALKER shows his faith in the ultimate triumph of mankind in the matter of aerial flight : ' The act of flying requires less exertion than from the appearance is supposed. Not having sufficient data to ascertain the exact degree of propelling power exerted by birds in the act of flying, it is uncertain what degree of energy may be required in this respect for vessels of aerial navigation; yet when we consider the many hundreds of miles of continued flight exerted by birds of passage, the idea of its being only a small effort is greatly corroborated. To apply the power of the first mover to the greatest advantage in producing this effect is a very material point. The mode universally adopted by Nature is the oblique waft of the wing. We have only to choose between the direct beat over- taking the velocity of the current, like the oar of a boat, or one applied like the wing, in some assigned degree of obliquity to it. Suppose 35 feet per second to be the velocity of an aerial vehicle, the oar must be moved with this speed previous to its being able to receive any resistance; then if it be only required to obtain a pressure of one-tenth of a Ib. upon each square foot it must exceed the velocity of the current 7.3 feet per second. Hence its whole velocity must be 42.5 feet per second. Should the same surface be wafted down- ward like a wing with the hinder edge inclined upward in an angle of about 50 deg. 40 feet to the current it will overtake it at a velocity of 3.5 feet per second; and as a slight unknown angle of resistance generates a Ib. pressure per square foot at this velocity, probably a waft of a little more than 4 feet per second would produce this effect, one-tenth part of which would be the pro- pelling power. The advantage of this mode of 47 A HISTORY OF AERONAUTICS application compared with the former is rather more than ten to one. * In continuing the general principles of aerial navigation, for the practice of the art, many mechanical difficulties present themselves which require a consider- able course of skilfully applied experiments before they can be overcome; but, to a certain extent, the air has already been made navigable, and no one who has seen the steadiness with which weights to the amount of ten stone (including four stone, the weight of the machine) hover in the air can doubt of the ultimate accomplishment of this object/ This extract from his work gives but a faint idea of the amount of research for which Cayley was respon- sible. He had the humility of the true investigator in scientific problems, and so far as can be seen was never guilty of the great fault of so many investigators in this subject that of making claims which he could not support. He was content to do, and pass after having recorded his part, and although nearly half a century had to pass between the time of his death and the first actual flight by means of power-driven planes, yet he may be said to have contributed very largely to the solution of the problem, and his name will always rank high in the roll of the pioneers of flight. Practically contemporary with Cayley was Thomas Walker, concerning whom little is known save that he was a portrait painter of Hull, where was published his pamphlet on The Art of Flying in 1 8 1 o, a second and amplified edition being produced, also in Hull, in 1831. The pamphlet, which has been reproduced in extenso in the Aeronautical Classics series published by the Royal Aeronautical Society, displays a curious mixture SIR GEORGE CAYLEY THOMAS WALKER of the true scientific spirit and colossal conceit. Walker appears to have been a man inclined to jump to con- clusions, which carried him up to the edge of discovery and left him vacillating there. The study of the two editions of his pamphlet side by side shows that their author made considerable advances in the practicability of his designs in the 21 intervenirg years, though the drawings which accompany the text in both editions fail to show anything really capable of flight. The great point about Walker's work as a whole is its suggestiveness; he did not hesitate to state that the * art ' of flying is as truly mechanical as that of rowing a boat, and he had some conception of the necessary mechanism, together with an absolute convic- tion that he knew all there was to be known. * Encouraged by the public,' he says, * I would not abandon my purpose of making still further exertions to advance and complete an art, the discovery of the true -principles (the italics are Walker's own) of which, I trust, I can with certainty affirm to be my own.' The pamphlet begins with Walker's admiration of the mechanism of flight as displayed by birds. ' It is now almost twenty years,' he says, * since I was first led to think, by the study of birds and their means of flying, that if an artificial machine were formed with wings in exact imitation of the mechanism of one of those beautiful living machines, and applied in the very same way upon the air, there could be no doubt of its being made to fly, for it is an axiom in philosophy that the same cause will ever produce the same effect.' With this he confesses his inability to produce the said effect through lack of funds, though he clothes this delicately in the phrase * professional avocations 49 A HISTORY OF AERONAUTICS and other circumstances/ Owing to this inability he published his designs that others might take advantage of them, prefacing his own researches with a list of the very early pioneers, and giving special mention to Friar Bacon, Bishop Wilkins, and the Portuguese friar, De Guzman. But, although he seems to suggest that others should avail themselves of his theoretical know- ledge, there is a curious incompleteness about the designs accompanying his work, and about the work itself, which seems to suggest that he had more know- ledge to impart than he chose to make public or else that he came very near to complete solution of the problem of flight, and stayed on the threshold without knowing it. After a dissertation upon the history and strength of the condor, and on the differences between the weights of birds, he says : * The following observations upon the wonderful difference in the weight of some birds, with their apparent means of supporting it in their flight, may tend to remove some prejudices against my plan from the minds of some of my readers. The weight of the humming-bird is one drachm, that of the condor not less than four stone. Now, if we reduce four stone into drachms we shall find the condor is 14,336 times as heavy as the humming-bird. What an amazing disproportion of weight! Yet by the same mechanical use of its wings the condor can overcome the specific gravity of its body with as much ease as the little humming-bird. But this is not all. We are informed that this enormous bird possesses a power in its wings, so far exceeding what is necessary for its own conveyance through the air, that it can take up and fly away with a whole sheep in its talons, with as much 50 SIR GEORGE C A YLEY THOMAS WALKER case as an eagle would carry off, in the same manner, a hare or a rabbit. This we may readily give credit to, from the known fact of our little kestrel and the sparrow- hawk frequently flying off with a partridge, which is nearly three times the weight of these rapacious little birds.' After a few more observations he arrives at the following conclusion: * By attending to the progressive increase in the weight of birds., from the delicate little humming-bird up to the huge condor, we clearly discover that the addition of a few ounces, pounds, or stones, is no obstacle to the art of flying; the specific weight of birds avails nothing, for by their possessing wings large enough, and sufficient power to work them, they can accomplish the means of flying equally well upon all the various scales and dimensions which we see in nature. Such being a fact, in the name of reason and philosophy why shall not man, with a pair of artificial wings, large enough, and with sufficient power to strike them upon the air, be able to produce the same effect ? ' Walker asserted definitely and with good ground that muscular effort applied without mechanism is insufficient for human flight, /out he states that if an aeronautical boat were constructed so that a man could sit in it in the same manner as when rowing, such a man would be able to bring into play his whole bodily strength for the purpose of flight, and at the same time would be able to get an additional advantage by exerting his strength upon a lever. At first he concluded there must be expansion of wings large enough to resist in a sufficient degree the specific gravity of whatever is attached to them, but in the second edition of his work he altered this to * expansion of flat passive surfaces 51 A HISTORY OF AERONAUTICS large enough to reduce the force of gravity so as to float the machine upon the air with the man in it.' The second requisite is strength enough to strike the wings with sufficient force to complete the buoyancy and give a projectile motion to the machine. Given these two requisites, Walker states definitely that flying must be accomplished simply by muscular exertion. ' If we are secure of these two requisites, and I am very confident we are, we may calculate upon the success of flight with as much certainty as upon our walking/ Walker appears to have gained some confidence from the experiments of a certain M. Degen, a watch- maker of Vienna, who, according to the Monthly Magazine of September, 1809, invented a machine by means of which a person might raise himself into the air. The said machine, according to the magazine, was formed of two parachutes which might be folded up or extended at pleasure, while the person who worked them was placed in the centre. This account, however, was rather misleading, for the magazine carefully avoided mention of a balloon to which the inventor fixed his wings or parachutes. Walker, knowing nothing of the balloon, concluded that Degen actually raised himself in the air, though he is doubtful of the assertion that Degen managed to fly in various directions, especially against the wind. Walker, after considering Degen and all his works, proceeds to detail his own directions for the construction of a flying machine, these being as follows: * Make a car of as light material as possible, but with sufficient strength to support a man in it; provide a pair of wings about four feet each in length; let them be horizontally expanded and fastened upon the top edge of each side SIR GEORGE CAYLEY THOMAS WALKER of the car, with two joints each, so as to admit of a vertical motion to the wings, which motion may be effected by a man sitting and working an upright lever in the middle of the car. Extend in the front of the car a flat surface of silk, which must be stretched out and kept fixed in a passive state; there must be the same fixed behind the car; these two surfaces must be perfectly equal in length and breadth and large enough to cover a sufficient quantity of air to support the whole weight as nearly in equilibrium as possible, thus we shall have a great sustaining power in those passive surfaces and the active wings will propel the car forward.' A description of how to launch this car is subsequently given: * It becomes necessary/ says the theorist, * that I should give directions how it may be launched upon the air, which may be done by various means; perhaps the following method may be found to answer as well as any: Fix a poll upright in the earth, about twenty feet in height, with two open collars to admit another poll to slide upwards through them; let there be a sliding platform made fast upon the top of the sliding poll; place the car with a man in it upon the platform, then raise the platform to the height of about thirty feet by means of the sliding poll, let the sliding poll and platform suddenly fall down, the car will then be left upon the air, and by its pressing the air a projectile force will instantly propel the car forward; the man in the car must then strike the active wings briskly upon the air, which will so increase the projectile force as to become superior to the force of gravitation, and if he inclines his weight a little backward, the projectile impulse will drive the car forward in an ascending direction. When the car is brought to a sufficient 53 A HISTORY OF AERONAUTICS altitude to clear the tops of hills, trees, buildings, etc., the man, by sitting a little forward on his seat, will then bring the wings upon a horizontal plane, and by con- tinuing the action of the wings he will be impelled forward in that direction. To descend, he must desist from striking the wings, and hold them on a level with their joints; the car will then gradually come down, and when it is within five or six feet of the ground the man must instantly strike the wings downwards, and sit as far back as he can; he will by this means check the projectile force, and cause the car to alight very gently with a retrograde motion. The car, when up in the air, may be made to turn to the right or to the left by forcing out one of the fins, having one about eighteen inches long placed vertically on each side of the car for that purpose, or perhaps merely by the man inclining the weight of his body to one side/ Having stated how the thing is to be done, Walker is careful to explain that when it is done there will be in it some practical use, notably in respect of the con- veyance of mails and newspapers, or the saving of life at sea, or for exploration, etc. It might even reduce the number of horses kept by man for his use, by means of which a large amount of land might be set free for the growth of food for human consumption. At the end of his work Walker admits the idea of steam power for driving a flying machine in place of simple human exertion, but he, like Cayley, saw a drawback to this in the weight of the necessary engine. On the whole, he concluded, navigation of the air by means of engine power would be mostly confined to the construction of navigable balloons. As already noted, Walker's work is not over practical, 54 SIR GEORGE CAYLEY THOMAS WALKER and the foregoing extract includes the most practical part of it; the rest is a series of dissertations on bird flight, in which, evidently, the portrait painter's observations were far less thorough than those of da Vinci or Borelli. Taken on the whole, Walker was a man with a hobby; he devoted to it much time and thought, but it remained a hobby, nevertheless. His observations have proved useful enough to give him a place among the early students of flight, but a great drawback to his work is the lack of practical experiment, by means of which alone real advance could be made; for, as Cayley admitted, theory and practice are very widely separated in the study of aviation, and the whole history of flight is a matter of unexpected results arising from scarcely foreseen causes, together with experiment as patient as daring. H.A. IV THE MIDDLE NINETEENTH CENTURY BOTH Cayley and Walker were theorists, though Cayley supported his theoretical work with enough of practice to show that he studied along right lines; a little after his time there came practical men who brought to being the first machine which actually flew by the application of power. Before their time, however, mention must be made of the work of George Pocock of Bristol, who, somewhere about 1840, invented" what was described as a * kite carriage,' a vehicle which carried a number of persons, and obtained its motive power from a large kite. It is on record that, in the year 1846, one of these carriages conveyed sixteen people from Bristol to London. Another device of Pocock's was what he called a * buoyant sail,' which was in effect a man- lifting kite, and by means of which a passenger was actually raised 100 yards from the ground, while the inventor's son scaled a cliff 200 feet in height by means of one of these ' buoyant sails.' This constitutes the first definitely recorded experiment in the use of man- lifting kites. A History of the Charvolant or Kite- Carriage^ published in London in 1851, states that * an experiment of a bold and very novel character was made upon an extensive down, where a large wagon with a considerable load was drawn along, whilst this huge machine at the same time carried an observer 56 THE MIDDLE NINETEENTH CENtURY aloft in the air, realising almost the romance of flying. Experimenting, two years after the appearance of the * kite-carriage/ on the helicopter principle, W. H. Phillips constructed a model machine which weighed two pounds; this was fitted with revolving fans, driven by the combustion of charcoal, nitre, and gypsum, producing steam which, discharging into the air, caused the fans to revolve. The inventor stated that * all being arranged, the steam was up in a few seconds, when the whole apparatus spun around like any top, and mounted into the air faster than a bird; to what height it ascended I had no means of ascertaining; the distance travelled was across two fields, where, after a long search, I found the machine minus the wings, which had been torn off in contact with the ground/ This could hardly be described as successful flight, but it was an advance in the construction of machines on the helicopter principle, and it was the first steam- driven model of the type which actually flew. The invention, however, was not followed up. After Phillips, we come to the great figures of the middle nineteenth century, W. S. Henson and John Stringfellow. Cayley had shown, in 1809, how success might be attained by developing the idea of the plane surface so driven as to take advantage of the resistance offered by the air, and Henson, who as early as 1840 was experimenting with model gliders and light steam engines, evolved and patented an idea for something very nearly resembling the monoplane of the early twentieth century. His patent, No. 9478, of the year 1842, explains the principle of the machine as follows: * In order that the description hereafter given may 57 A HISTORY OF AERONAUTICS be rendered clear, I will first shortly explain the principle on which the machine is constructed. If any light and flat or nearly flat article be projected or thrown edgewise in a slightly inclined position, the same will rise on the air till the force exerted is expended, when the article so thrown or projected will descend; and it will readily be conceived that, if the article so projected or thrown possessed in itself a continuous power or force equal to that used in throwing or projecting it, the article would continue to ascend so long as the forward part of the surface was upwards in respect to the hinder part, and that such article, when the power was stopped, or when the inclination was reversed, would descend by gravity aided by the force of the power contained in the article, if the power be continued, thus imitating the flight of a bird. Now, the first part of my invention consists of an apparatus so constructed as to offer a very extended surface or plane of a light yet strong construction, which will have the same relation to the general machine which the extended wings of a bird have to the body when a bird is skimming in the air; but in place of the movement or power for onward progress being obtained by movement of the extended surface or plane, as is the case with the wings of birds, I apply suitable paddle-wheels or other proper mechanical propellers worked by a steam or other sufficiently light engine, and thus obtain the requisite power for onward movement to the plane or extended surface; and in order to give control as to the upward and downward direction of such a machine I apply a tail to the extended surface which is capable of being inclined or raised, so that when the power is acting to propel the machine, by 58 Henson's proposed flying machine. Stringfellow's power-driven model the first model to achieve engine-driven flight. To face page 59 THE MIDDLE NINETEENTH CENTURY inclining the tail upwards, the resistance offered by the air will cause the machine to rise on the air; and, on the contrary, when the inclination of the tail is reversed, the machine will immediately be propelled downwards, and pass through a plane more or less inclined to the horizon as the inclination of the tail is greater or less; and in order to guide the machine as to the lateral direction which it shall take, I apply a vertical rudder or second tail, and, according as the same is inclined in one direction or the other, so will be the direction of the machine.' The machine in question was very large, and differed very little from the modern monoplane; the materials were to be spars of bamboo and hollow wood, with diagonal wire bracing. The surface of the planes was to amount to 4,500 square feet, and the tail, triangular in form (here modern practice diverges) was to be 1,500 square feet. The inventor estimated that there would be a sustaining power of half a pound per square foot, and the driving power was to be supplied by a steam engine of 25 to 30 horse-power, driving two six-bladed propellers. Henson was largely depen- dent on Stringfellow for many details of his design, more especially with regard to the construction of the engine. The publication of the patent attracted a great amount of public attention, and the illustrations in contemporary journals, representing the machine flying over the pyramids and the Channel, anticipated fact by sixty years and more; the scientific world was divided, as it was up to the actual accomplishment of flight, as to the value of the invention. Strongfellow and Henson became associated, 59 A HISTORY OF AERONAUTICS after the conception of their design, with an attorney named Colombine, and a Mr Marriott, and between the four of them a project grew for putting the whole thing on a commercial basis Henson and Stringfellow were to supply the idea; Marriott, knowing a member of Parliament, would be useful in getting a company incorporated, and Colombine would look after the purely legal side of the business. Thus an application was made by Mr Roebuck, Marriott's M.P., for an act of incorporation for ' The Aerial Steam Transit Company,' Roebuck moving to bring in the bill on the 24th of March, 1843. The prospectus, calling for funds for the development of the invention, makes interesting reading at this stage of aeronautical develop- ment; it was as follows: PROPOSAL. For subscriptions of sums of ^100, in furtherance of an Extraordinary Invention not at present safe to be developed by securing the necessary Patents, for which three times the sum advanced, namely, 300, is con- ditionally guaranteed for each subscription on February I, 1844, in case of the anticipations being realised, with the option of the subscribers being shareholders for the large amount if so desired, but not otherwise. An Invention has recently been discovered, which if ultimately successful will be without parallel even in the age which introduced to the world the wonderful effects of gas and of steam. The discovery is of that peculiar nature, so simple in principle yet so perfect in all the ingredients required 60 THE MIDDLE NINETEENTH CENTURY for complete and permanent success, that to promulgate it at present would wholly defeat its development by the immense competition which would ensue, and the views of the originator be entirely frustrated. This work, the result of years of labour and study, presents a wonderful instance of the adaptation of laws long since proved to the scientific world combined with established principles so judiciously and carefully arranged, as to produce a discovery perfect in all its parts and alike in harmony with the laws of Nature and of science. The Invention has been subjected to several tests and examinations and the results are most satisfactory, so much so that nothing but the completion of the undertaking is required to determine its practical operation, which being once established its utility is undoubted, as it would be a necessary possession of every empire, and it were hardly too much to say, of every individual of competent means in the civilised world. Its qualities and capabilities are so vast that it were impossible and, even if possible, unsafe to develop them further, but some idea may be formed from the fact that as a preliminary measure patents in Great Britain, Ireland, Scotland, the Colonies, France, Belgium, and the United States, and every other country where protection to the first discoveries of an Invention is granted, will of necessity be immediately obtained, and by the time these are perfected, which it is estimated will be in the month of February, the Invention will be fit for Public Trial, but until the Patents are sealed any further disclosure would be most dangerous to the principle on which it is based. 61 A HISTORY OF AERONAUTICS Under these circumstances, it is proposed to raise an immediate sum of 2,000 in furtherance of the Projector's views, and as some protection to the parties who may embark in the matter, that this is not a visionary plan for objects imperfectly considered, Mr Colombine, to whom the secret has been confided, has allowed his name to be used on the occasion, and who will if referred to corroborate this statement, and convince any inquirer of the reasonable prospects of large pecuniary results following the development of the Invention. It is, therefore, intended to raise the sum of 2,000 in twenty sums of jioo each (of which any subscriber may take one or more not exceeding five in number to be held by any individual) the amount of which is to be paid into the hands of Mr Colombine as General Manager of the concern to be by him appropriated in procuring the several Patents and providing the expenses incidental to the works in progress. For each of which sums of 100 it is intended and agreed that twelve months after the ist February next, the several parties subscribing shall receive as an equivalent for the risk to be run the sum of 300 for each of the sums of 100 now subscribed, provided when the time arrives the Patents shall be found to answer the purposes intended. As full and complete success is alone looked to, no moderate or imperfect benefit is to be anticipated, but the work, if it once passes the necessary ordeal, to which inventions of every kind must be first subject, will then be regarded by every one as the most astonishing discovery of modern times; no half success can follow, and therefore the full nature of the risk is immediately ascertained. 1 62 THE MIDDLE NINETEENTH CENTURY The intention is to work and prove the Patent by collective instead of individual aid as less hazardous at first and more advantageous in the result for the Inventor, as well as others, by having the interest of several engaged in aiding one common object the development of a Great Plan. The failure is not feared, yet as perfect success might, by possibility, not ensue, it is necessary to provide for that result, and the parties concerned make it a condition that no return of the subscribed money shall be required, if the Patents shall by any unforeseen circumstances not be capable of being worked at all ; against which, the first application of the money subscribed, that of securing the Patents, affords a reasonable security, as no one without solid grounds would think of such an expenditure. It is perfectly needless to state that no risk or responsibility of any kind can arise beyond the payment of the sum to be subscribed under any circumstances whatever. As soon as the Patents shall be perfected and proved it is contemplated, so far as may be found practicable, to further the great object in view a Company shall be formed but respecting which it is unnecessary to state further details, than that a preference will be given to all those persons who now subscribe, and to whom shares shall be appropriated according to the larger amount (being three times the sum to be paid by each person) contemplated to be returned as soon as the success of the Invention shall have been established, at their option, or the money paid, whereby the Sub- scriber will have the means of either withdrawing with a large pecuniary benefit, or by continuing his interest in the concern, lay the foundation for participating in 63 A HISTORY OF AERONAUTICS the immense benefit which must follow the success of the plan. It is not pretended to conceal that the project is a speculation all parties believe that perfect success, and thence incalculable advantage of every kind, will follow to every individual joining in this great under- taking; but the Gentlemen engaged in it wish that no concealment of the consequences, perfect success, or possible failure, should in the slightest degree be inferred. They believe this will prove the germ of a mighty work, and in that belief call for the operation of others with no visionary object, but a legitimate one before them, to attain that point where perfect success will be secured from their combined exertions. All applications to be made to D. E. Colombine, Esquire, 8 Carlton Chambers, Regent Street. The applications did not materialise, as was only to be expected in view of the vagueness of the proposals. Colombine did some advertising, and Mr Roebuck expressed himself as unwilling to proceed further in the venture. Henson experimented with models to a certain extent, while Stringfellow looked for funds for the construction of a full-sized monoplane. In November of 1843 ne suggested that he and Henson should construct a large model out of their own funds. On Henson's suggestion Colombine and Marriott were bought out as regards the original patent, and Stringfellow and Henson entered into an agreement and set to work. Their work is briefly described in a little pamphlet by F. J. Stringfellow, entitled A few Remarks on what has been done with screw-propelled Aero-plane Machines THE MIDDLE NINETEENTH CENTURY from 1809 to 1892. The author writes with regard to the work that his father and Henson undertook: * They commenced the construction of a small model operated by a spring, and laid down the larger model 20 ft. from tip to tip of planes, 3^ ft. wide, giving 70 ft. of sustaining surface, about 10 more in the tail. The making of this model required great consideration; various supports for the wings were tried, so as to combine lightness with firmness, strength and rigidity. * The planes were staid from three sets of fish- shaped masts, and rigged square and firm by flat steel rigging. The engine and boiler were put in the car to drive two screw-propellers, right and left-handed, 3 ft. in diameter, with four blades each, occupying three-quarters of the area of the circumference, set at an angle of 60 degrees. A considerable time was spent in perfecting the motive power. Compressed air was tried and abandoned. Tappets, 'cams, and eccentrics were all tried, to work the slide valve, to obtain the best results. The piston rod of engine passed through both ends of the cylinder, and with long connecting rods worked direct on the cranlc of the propellers. From memorandum of experiments still preserved the following is a copy of one: June, 2yth, 1845, water 5 ozs -> spirit 10 ozs., lamp lit 8.45, gauge moves 8.46, engine started 8.48 (100 Ib. pressure), engine stopped 8.57, worked 9 minutes, 2,288 revolu- tions, average 254 per minute. No priming, 40 ozs. water consumed, propulsion (thrust of propellers), 5 Ibs. 4^ ozs. at commencement, steady, 4 Ibs. J oz., 57 revolutions to i oz. water, steam cut off one-third from beginning. 65 A HISTORY OF AERONAUTICS * The diameter of cylinder of engine was i\ inch, length of stroke 3 inches. ' In the meantime an engine was also made for the smaller model, and a wing action tried, but with poor results. The time was mostly devoted to the larger model, and in 1847 a tent was erected on Bala Down, about two miles from Chard, and the model taken up one night by the workmen. The experiments were not so favourable as was expected. The machine could not support itself for any distance, but, when launched off, gradually descended, although the power and surface should have been ample; indeed, according to latest calculations, the thrust should have carried more than three times the weight, for there was a thrust of 5 Ibs. from the propellers, and a surface of over 70 square feet to sustain under 30 Ibs., but necessary speed was lacking/ Stringfellow himself explained the failure as follows : ' There stood our aerial protegee in all her purity too delicate, too fragile, too beautiful for this rough world; at least those were my ideas at the time, but little did I think how soon it was to be realised. I soon found, before I had time to introduce the spark, a drooping in the wings, a flagging in all the parts. In less than ten minutes the machine was saturated with wet from a deposit of dew, so that anything like a trial was impossible by night. I did not consider we could get the silk tight and rigid enough. Indeed, the frame- work altogether was too weak. The steam-engine was the best part. Our want of success was not for want of power or sustaining surface, but for want of proper adaptation of the means to the end of the various parts, ' 66 THE MIDDLE NINETEENTH CENTURY Henson, who had spent a considerable amount of money in these experimental constructions, consoled himself for failure by venturing into matrimony; in 1849 he went to America, leaving Stringfellow to continue experimenting alone. From 1846 to 1848 Stringfellow worked on what is really an epoch-making item in the history of aeronautics the first engine- driven aeroplane which actually flew. The machine in question had a 10 foot span, and was 2 ft. across in the widest part of the wing; the length of tail was 3 ft. 6 ins., and the span of tail in the widest part 22 ins., the total sustaining area being about 14 sq. ft. The motive power consisted of an engine with a cylinder of three-quarter inch diameter and a two-inch stroke; between this and the crank shaft was a bevelled gear giving three revolutions of the propellers to every stroke of the engine; the propellers, right and left screw, were four-bladed and 16 inches in diameter. The total weight of the model with engine was 8 Ibs. Its successful flight is ascribed to the fact that String- fellow curved the wings, giving them rigid front edges and flexible trailing edges, as suggested long before both by Da Vinci and Borelli, but never before put into practice. Mr F. J. Stringfellow, in the pamphlet quoted above, gives the best account of the flight of this model: ' My father had constructed another small model which was finished early in 1848, and having the loan of a long room in a disused lace factory, early in June the small model was moved there for experiments. The room was about 22 yards long and from 10 to 12 ft. high. . . . The inclined wire for starting the machine occupied less than half the length of the room and left space at the end for the machine to clear the 6? A HISTORY OF AERONAUTICS floor. In the first experiment the tail was set at too high an angle, and the machine rose too rapidly on leaving the wire. After going a few yards it slid back as if coming down an inclined plane, at such an angle that the point of the tail struck the ground and was broken. The tail was repaired and set at a smaller angle. The steam was again got up, and the machine started down the wire, and, upon reaching the point of self-detachment, it gradually rose until it reached the farther end of the room, striking a hole in the canvas placed to stop it. In experiments the machine flew well, when rising as much as one in seven. The late Rev. J. Riste, Esq., lace manufacturer, Northcote Spicer, Esq., J. Toms, Esq., and others witnessed experiments. Mr Marriatt, late of the San Francisco News Letter brought down from London Mr Ellis, the then lessee of Cremorne Gardens, Mr Partridge, and Lieutenant Gale, the aeronaut, to witness experi- ments. Mr Ellis offered to construct a covered way at Cremorne for experiments. Mr Stringfellow repaired to Cremorne, but not much better accommo- dations than he had at home were provided, owing to unfulfilled engagement as to room. Mr Stringfellow was preparing for departure when a party of gentlemen unconnected with the Gardens begged to see an experi- ment, and finding them able to appreciate his endeavours, he got up steam and started the model down the wire. When it arrived at the spot where it should leave the wire it appeared to meet with some obstruction, and threatened to come to the ground, but it soon recovered itself and darted off in as fair a flight as it was possible to make at a distance of about 40 yards, where it was stopped by the canvas. 68 THE MIDDLE NINETEENTH CENTURY ' Having now demonstrated the practicability of making a steam-engine fly, and finding nothing but a pecuniary loss and little honour, this experimenter rested for a long time, satisfied with what he had effected. The subject, however, had to him special charms, and he still contemplated the renewal of his experiments/ It appears that Stringfellow's interest did not revive sufficiently for the continuance of the experiments until the founding of the Aeronautical Society of Great Britain in 1 866. Wenham's paper on Aerial Locomotion read at the first meeting of the Society, which was held at the Society of Arts under the Presidency of the Duke of Argyll, was the means of bringing Stringfellow back into the field. It was Wenham's suggestion, in the first place, that monoplane design should be aban- doned for the superposition of planes; acting on this suggestion Stringfellow constructed a model triplane, and also designed a steam engine of slightly over one horse-power, and a one horse-power copper boiler and fire box which, although capable of sustaining a pressure of 500 Ibs. to the square inch, weighed only about 40 Ibs. Both the engine and the triplane model were exhibited at the first Aeronautical Exhibition held at the Crystal Palace in 1868. The triplane had a supporting surface of 28 sq. ft.; inclusive of engine, boiler, fuel, and water its total weight was under 12 Ibs. The engine worked two 21 in. propellers at 600 revolu- tions per minute, and developed 100 Ibs. steam pressure in five minutes, yielding one-third horse-power. Since no free flight was allowed in the Exhibition, owing to danger from fire, the triplane was suspended from a A HISTORY OF AERONAUTICS wire in the nave of the building, and it was noted that, when running along the wire, the model made a per- ceptible lift. A prize of ^100 was awarded to the steam engine as the lightest steam engine in proportion to its power. The engine and model together may be reckoned as Stringfellow's best achievement. He used his 100 in preparation for further experiments, but he was now an old man, and his work was practically done. Both the triplane and the engine were eventually bought for the Washington Museum; Stringfellow's earlier models, together with those constructed by him in conjunction with Henson, remain in this country in the Victoria and Albert Museum. John Stringfellow died on December I3th, 1883. His place in the history of aeronautics is at least equal to that of Cayley, and it may be said that he laid the foundation of such work as was subsequently accomplished by Maxim, Langley, and their fellows. It was the coming of the internal combustion engine that rendered flight practicable, and had this prime mover been available in John Stringfellow's day the Wright brothers' achievement might have been ante- dated by half a century. 70 WENHAM, LE BRIS, AND SOME OTHERS THERE are few outstanding events in the development of aeronautics between Stringfellow's final achievement and the work of such men as Lilienthal, Pilcher, Mont- gomery, and their kind ; in spite of this, the later middle decades of the nineteenth century witnessed a consider- able amount of spade work both in England and in France, the two countries which led in the way in aeronautical development until Lilienthal gave honour to Germany, and Langley and Montgomery paved the way for the Wright Brothers in America. Two abortive attempts characterised the sixties of last century in France. As regards the first of these, it was carried out by three men, Nadar, Ponton d'Amecourt, and De la Landelle, who conceived the idea of a full-sized helicopter machine. D'Amecourt exhibited a steam model, constructed in 1865, at the Aeronautical Society's Exhibition in 1868. The engine was aluminium with cylinders of bronze, driving two screws placed one above the other and rotating in opposite directions, but the power was not sufficient to lift the model. De la Landelle's principal achievement consisted in the publication in 1863 of a book entitled Aviation, which has a certain historical value; he got out several designs for large machines on the helicopter principle, but did little more until the three combined H.A. 71 F A HISTORY OF AERONAUTICS in the attempt to raise funds for the construction of their full-sized machine. Since the funds were not forth- coming, Nadar took to ballooning as the means of raising money; apparently he found this substitute for real flight sufficiently interesting to divert him from the study of the helicopter principle, for the experiment went no further. The other experimenter of this period, one Count d'Esterno, took out a patent in 1864 for a soaring machine which allowed for alteration of the angle of incidence of the wings in the manner that was subsequently carried out by the Wright Brothers. It was not until 1883 that any attempt was made to put this patent to practical use, and, as the inventor died while it was under construction, it was never completed. D'Esterno was also responsible for the production of a work entitled Du Vol des Oiseaux, which is a very remarkable study of the flight of birds. Mention has already been made of the founding of the Aeronautical Society of Great Britain, which, since 1918, has been the Royal Aeronautical Society. 1866 witnessed the first meeting of the Society under the Presidency of the Duke of Argyll, when in June, at the Society of Arts, Francis Herbert Wenham read his now classic paper Aerial Locomotion. Certain quotations from this will show how clearly Wenham had thought out the problems connected with flight. 1 The first subject for consideration is the proportion of surface to weight, and their combined effect in descending perpendicularly through the atmosphere. The datum is here based upon the consideration of safety, for it may sometimes be needful for a living being to drop passively, without muscular effort. One 72 WENHAM, LE BRIS, AND SOME OTHERS square foot of sustaining surface for every pound of the total weight will be sufficient for security. * According to Smeaton's table of atmospheric resistances, to produce a force of one pound on a square foot, the wind must move against the plane (or which is the same thing, the plane against the wind), at the rate of twenty-two feet per second, or 1,320 feet per minute, equal to fifteen miles per hour. The resistance of the air will now balance the weight on the descending surface, and, consequently, it cannot exceed that speed. Now, twenty-two feet per second is the velocity acquired at the end of a fall of eight feet a height from which a well-knit man or animal may leap down without much risk of injury. Therefore, if a man with parachute weigh together 143 Ibs., spreading the same number of square feet of surface contained in a circle fourteen and a half feet in diameter, he will descend at perhaps an unpleasant velocity, but with safety to life and limb. 1 It is a remarkable fact how this proportion of wing- surface to weight extends throughout a great variety of the flying portion of the animal kingdom, even down to hornets, bees, and other insects. In some instances, however, as in the gallinaceous tribe, including pheasants, this area is somewhat exceeded, but they are known to be very poor fliers. Residing as they do chiefly on the ground, their wings are only required for short distances, or for raising them or easing their descent from their roosting-places in forest trees, the shortness of their wings preventing them from taking extended flights. The wing-surface of the common swallow is rather more than in the ratio of two square feet per pound, but having also great length of pinion, it is both swift and enduring in its flight. When on a 73 A HISTORY OF AERONAUTICS rapid course this bird is in the habit of furling its wings into a narrow compass. The greater extent of surface is probably needful for the continual variations of speed and instant stoppages for obtaining its insect food. * On the other hand, there are some birds, particularly of the duck tribe, whose wing-surface but little exceeds half a square foot, or seventy-two inches per pound, yet they may be classed among the strongest and swiftest of fliers. A weight of one pound, suspended from an area of this extent, would acquire a velocity due to a fall of sixteen feet a height sufficient for the destruction or injury of most animals. But when the plane is urged forward horizontally, in a manner analogous to the wings of a bird during flight, the sustaining power is greatly influenced by the form and arrangement of the surface. ' In the case of perpendicular descent, as a parachute, the sustaining effect will be much the same, whatever the figure of the outline of the superficies may be, and a circle perhaps affords the best resistance of any. Take, for example, a circle of twenty square feet (as possessed by the pelican) loaded with as many pounds. This, as just stated, will limit the rate of perpendicular descent to 1,320 feet per minute. But instead of a circle sixty-one inches in diameter, if the area is bounded by a parallelogram ten feet long by two feet broad, and whilst at perfect freedom to descend perpendicularly, let a force be applied exactly in a horizontal direction, so as to carry it edgeways, with the long side foremost, at a forward speed of thirty miles per hour just double that of its passive descent: the rate of fall under these conditions will be decreased most remarkably, probably 74 WENHAM, LE BRIS, AND SOME OTHERS to less than one-fifteenth part, or eighty-eight feet per minute, or one mile per hour/ And again: * It has before been shown how utterly inadequate the mere perpendicular impulse of a plane is found to be in supporting a weight, when there is no horizontal motion at the time. There is no material weight of air to be acted upon, and it yields to the slightest force, however great the velocity of impulse may be. On the other hand, suppose that a large bird, in full flight, can make forty miles per hour, or 3,520 feet per minute, and performs one stroke per second. Now, during every fractional portion of that stroke, the wing is acting upon and obtaining an impulse from a fresh and undisturbed body of air; and if the vibration of the wing is limited to an arc of two feet, this by no means represents the small force of action that would be obtained when in a stationary position, for the impulse is secured upon a stratum of fifty-eight feet in length of air at each stroke. So that the conditions of weight of air for obtaining support equally well apply to weight of air and its reaction in producing forward impulse. * So necessary is the acquirement of this horizontal speed, even in commencing flight, that most heavy birds, when possible, rise against the wind, and even run at the top of their speed to make their wings available, as in the example of the eagle, mentioned at the com- mencement of this paper. It is stated that the Arabs, on horseback, can approach near enough to spear these birds, when on the plain, before they are able to rise; their habit is to perch on an eminence, where possible. 1 The tail of a bird is not necessary for flight. A 75 A HISTORY OF AERONAUTICS pigeon can fly perfectly with this appendage cut short off; it probably performs an important function in steering, for it is to be remarked, that most birds that have either to pursue or evade pursuit are amply provided with this organ. * The foregoing reasoning is based upon facts, which tend to show that the flight of the largest and heaviest of all birds is really performed with but a small amount of force, and that man is endowed with sufficient muscular power to enable him also to take individual and extended flights, and that success is probably only involved in a question of suitable mechanical adaptations. But if the wings are to be modelled in imitation of natural examples, but very little consideration will serve to demonstrate its utter impracticability when applied in these forms/ Thus Wenham, one of the best theorists of his age. The Society with which this paper connects his name has done work, between that time and the present, of which the importance cannot be overestimated, and has been of the greatest value in the development of aeronautics, both in theory and experiment. The objects of the Society are to give a stronger impulse to the scientific study of aerial navigation, to promote the intercourse of those interested in the subject at home and abroad, and to give advice and instruction to those who study the principles upon which aeronautical science is based. From the date of its foundation the Society has given special study to dynamic flight, putting this before ballooning. Its library, its bureau of advice and information, and its meetings, all assist in forwarding the study of aeronautics, and its twenty- three early Annual Re-ports are of considerable value, 76 WENHAM, LE BRIS, AND SOME OTHERS containing as they do a large amount of useful informa- tion on aeronautical subjects, and forming practically the basis of aeronautical science. Ante to Wenham, Stringfellow and the French experimenters already noted, by some years, was Le Bris, a French sea captain, who appears to have required only a thorough scientific training to have rendered him of equal moment in the history of gliding flight with Lilienthal himself. Le Bris, it appears, watched the albatross and deduced, from the manner in which it supported itself in the air, that plane surfaces could be constructed and arranged to support a man in like manner. Octave Chanute, himself a leading exponent of gliding, gives the best description of Le Bris's experiments in a work, Progress in Flying Machines, which, although published as recently as 1894, is already rare. Chanute draws from a still rarer book, namely, De la Landelle's work published in 1884. Le Bris himself, quoted by De la Landelle as speaking of his first visioning of human flight, describes how he killed an albatross, and then * I took the wing of the albatross and exposed it to the breeze; and lo! in spite of me it drew forward into the wind; notwithstanding my resistance it tended to rise. Thus I had discovered the secret of the bird! I comprehended the whole mystery of flight.' This apparently took place while at sea; later on Le Bris, returning to France, designed and constructed an artificial albatross of sufficient size to bear his own weight. The fact that he followed the bird outline as closely as he did attests his lack of scientific training for his task, while at the same time the success of the experiment was proof of his genius. The body of his 77 A HISTORY OF AERONAUTICS artificial bird, boat-shaped, was 13^ ft. in length, with a breadth of 4 ft. at the widest part. The material was cloth stretched over a wooden framework; in front was a small mast rigged after the manner of a ship's masts to which were attached poles and cords with which Le Bris intended to work the wings. Each wing was 23 ft. in length, giving a total supporting surface of nearly 220 sq. ft.; the weight of the whole apparatus was only 92 pounds. For steering, both vertical and horizontal, a hinged tail was provided, and the leading edge of each wing was made flexible. In construction throughout, and especially in that of the wings, Le Bris adhered as closely as possible to the original albatross. He designed an ingenious kind of mechanism which he termed ' Rotules,' which by means of two levers gave a rotary motion to the front edge of the wings, and also permitted of their adjustment to various angles. The inventor's idea was to stand upright in the body of the contrivance, working the levers and cords with his hands, and with his feet on a pedal by means of which the steering tail was to be worked. He anticipated that, given a strong wind, he could rise into the air after the manner of an albatross, without any need for flapping his wings, and the account of his first experiment forms one of the most interesting incidents in the history of flight. It is related in full in Chanute's work, from which the present account is summarised. Le Bris made his first experiment on a main road near Douarnenez, at Trefeuntec. From his observation of the albatross Le Bris concluded that it was necessary to get some initial velocity in order to make the machine rise; consequently on a Sunday morning, with a breeze 78 WENHAM, LE BRIS, AND SOME OTHERS of about 12 miles an hour blowing down the road, he had his albatross placed on a cart and set off, with a peasant driver, against the wind. At the outset the machine was fastened to the cart by a rope running through the rails on which the machine rested, and secured by a slip knot on Le Bris's own wrist, so that only a jerk on his part was necessary to loosen the rope and set the machine free. On each side walked an assistant holding the wings, and when a turn of the road brought the machine full into the wind these men were instructed to let go, while the driver increased the pace from a walk to a trot. Le Bris, by pressure on the levers of the machine, raised the front edges of his wings slightly; they took the wind almost instantly to such an extent that the horse, relieved of a great part of the weight he had been drawing, turned his trot into a gallop. Le Bris gave the jerk of the rope that should have unfastened the slip knot, but a concealed nail on the cart caught the rope, so that it failed to run. The lift of the machine was such, however, that it relieved the horse of very nearly the weight of the cart and driver, as well as that of Le Bris and his machine, and in the end the rails of the cart gave way. Le Bris rose in the air, the machine maintaining perfect balance and rising to a height of nearly 300 ft., the total length of the glide being upwards of an eighth of a mile. But at the last moment the rope which had originally fastened the machine to the cart got wound round the driver's body, so that this unfortunate dangled in the air under Le Bris and probably assisted in maintaining the balance of the artificial albatross. Le Bris, congratulating himself on his success, was prepared to enjoy just as long a time in the air as the pressure of the wind would 79 A HISTORY OF AERONAUTICS permit, but the howls of the unfortunate driver at the end of the rope beneath him dispelled his dreams; by working his levers he altered the angle of the front wing edges so skilfully as to make a very successful landing indeed for the driver, who, entirely uninjured, disen- tangled himself from the rope as soon as he touched the ground, and ran off to retrieve his horse and cart. Apparently his release made a difference in the centre of gravity, for Le Bris could not manipulate his levers for further ascent; by skilful manipulation he retarded the descent sufficiently to escape injury to himself; the machine descended at an angle, so that one wing, striking the ground in front of the other, received a certain amount of damage. It may have been on account of the reluctance of this same or another driver that Le Bris chose a different method of launching himself in making a second experiment with his albatross. He chose the edge of a quarry which had been excavated in a depression of the ground; here he assembled his apparatus at the bottom of the quarry, and by means of a rope was hoisted to a height of nearly 100 ft. from the quarry bottom, this rope being attached to a mast which he had erected upon the edge of the depression in which the quarry was situated. Thus hoisted, the albatross was swung to face a strong breeze that blew inland, and Le Bris manipulated his levers to give the front edges of his wings a downward angle, so that only the top surfaces should take the wing pressure. Having got his balance, he obtained a lifting angle of incidence on the wings by means of his levers, and released the hook that secured the machine, gliding off over the quarry. On the glide he met with the inevitable upward current 80 WENHAM, LE BRIS, AND SOME OTHERS of air that the quarry and the depression in which it was situated caused; this current upset the balance of the machine and flung it to the bottom of the quarry, breaking it to fragments. Le Bris, apparently as in- trepid as ingenious, gripped the mast from which his levers were worked, and, springing upward as the machine touched earth, escaped with no more damage than a broken leg. But for the rebound of the levers he would have escaped even this. The interest of these experiments is enhanced by the fact that Le Bris was a seafaring man who con- ducted them from love of the science which had fired his imagination, and in so doing exhausted his own small means. It was in 1855 that he made these initial attempts, and twelve years passed before his persistence was rewarded by a public subscription made at Brest for the purpose of enabling him to continue his experi- ments. He built a second albatross, and on the advice of his friends ballasted it for flight instead of travelling in it himself. It was not so successful as the first, probably owing to the lack of human control while in flight; on one of the trials a height of 150 ft. was attained, the glider being secured by a thin rope and held so as to face into the wind. A glide of nearly an eighth of a mile was made with the rope hanging slack, and, at the end of this distance, a rise in the ground modified the force of the wind, whereupon the machine settled down without damage. A further trial in a gusty wind resulted in the complete destruction of this second machine; Le Bris had no more funds, no further subscriptions were likely to materialise, and so the experiments of this first exponent of the art of gliding (save for Besnier and his kind) came to an end. They Si ' A HISTORY OF AERONAUTICS constituted a notable achievement, and undoubtedly Le Bris deserves a better place than has been accorded him in the ranks of the early experimenters. Contemporary with him was Charles Spencer, the first man to practise gliding in England. His apparatus consisted of a pair of wings with a total area of 30 sq. ft., to which a tail and body were attached. The weight of this apparatus was some 24 Ibs., and, launching himself on it from a small eminence, as was done later by Lilienthal in his experiments, the inventor made flights of over 120 feet. The glider in question was exhibited at the Aeronautical Exhibition of 1868. 82 VI THE AGE OF THE GIANTS UNTIL the Wright Brothers definitely solved the problem of flight and virtually gave the aeroplane its present place in aeronautics, there were three definite schools of experiment. The first of these was that which sought to imitate nature by means of the ornithopter or flapping-wing machines directly imitative of bird flight; the second school was that which believed in the helicopter or lifting screw; the third and eventually successful school is that which followed up the principle enunciated by Cayley, that of opposing a plane surface to the resistance of the air by supplying suitable motive power to drive it at the requisite angle for support. Engineering problems generally go to prove that too close an imitation of nature in her forms of recipro- cating motion is not advantageous; it is impossible to copy the minutiae of a bird's wing effectively, and the bird in flight depends on the tiniest details of its feathers just as much as on the general principle on which the whole wing is constructed. Bird flight, however, has attracted many experimenters, including even Lilienthal; among others may be mentioned F. W. Brearey, who invented what he called the ' Pectoral cord,' which stored energy on each upstroke of the artificial wing; E. P. Frost; Major R. Moore, and especially Hureau de Villeneuve, a most enthusiastic student of this form 83 A HISTORY OF AERONAUTICS of flight, who began his experiments about 1865, and altogether designed and made nearly 300 artificial birds. One of his later constructions was a machine in bird form with a wing span of about 50 ft.; the motive power for this was supplied by steam from a boiler which, being stationary on the ground, was connected by a length of hose to the machine. De Villeneuve, turning on steam for his first trial, obtained sufficient power to make the wings beat very forcibly; with the inventor on the machine the latter rose several feet into the air, whereupon de Villeneuve grew nervous and turned off the steam supply. The machine fell to the earth, breaking one of its wings, and it does not appear that de Villeneuve troubled to reconstruct it. This experiment remains as the greatest success yet achieved by any machine constructed on the ornithopter principle. It may be that, as forecasted by the prophet Wells, the flapping-wing machine will yet come to its own and compete with the aeroplane in efficiency. Against this, however, are the practical advantages of the rotary mechanism of the aeroplane propeller as compared with the movement of a bird's wing, which, according to Marey, moves in a figure of eight. The force derived from a propeller is of necessity continual, while it is equally obvious that that derived from a flapping movement is intermittent, and, in the recovery of a wing after completion of one stroke for the next, there is necessarily a certain cessation, if not loss, of power. The matter of experiment along any lines in connection with aviation is primarily one of hard cash. Throughout the whole history of flight up to the out- break of the European war development has been handicapped on the score of finance, and, since the THE AGE OF THE GIANTS arrival of the aeroplane, both ornithopter and helicopter schools have been handicapped by this consideration. Thus serious study of the efficiency of wings in imitation of those of the living bird has not been carried to a point that might win success for this method of propulsion. Even Wilbur Wright studied this subject and pro- pounded certain theories, while a later and possibly more scientific student, F. W. Lanchester, has also contributed empirical conclusions. Another and earlier student was Lawrence Hargrave, who made a wing-propelled model which achieved successful flight, and in 1885 was exhibited before the Royal Society of New South Wales. Hargrave called the principle on which his propeller worked that of a * Trochoided plane ' ; it was, in effect, similar to the feathering of an oar. Hargrave, to diverge for a brief while from the machine to the man, was one who, although he achieved nothing worthy of special remark, contributed a great deal of painstaking work to the science of flight. He made a series of experiments with man-lifting kites in addition to making a study of flapping-wing flight. It cannot be said that he set forth any new principle; his work was mainly imitative, but at the same time by developing ideas originated in great measure by others he helped toward the solution of the problem. Attempts at flight on the helicopter principle consist in the work of De la Landelle and others already mentioned. The possibility of flight by this method is modified by a very definite disadvantage of which lovers of the helicopter seem to take little account. It is always claimed for a machine of this type that it possesses great advantages both in rising and in landing, since, if it were effective, it would obviously be able to 85 A HISTORY OF AERONAUTICS rise from and alight on any ground capable of containing its own bulk; a further advantage claimed is that the helicopter would be able to remain stationary in the air, maintaining itself in any position by the vertical lift of its propeller. These potential assets do not take into consideration the fact that efficiency is required not only in rising, landing, and remaining stationary in the air, but also in actual flight. It must be evident that if a certain amount of the motive force is used in maintaining the machine off the ground, that amount of force is missing from the total of horizontal driving power. Again, it is often assumed by advocates of this form of flight that the rapidity of climb of the helicopter would be far greater than that of the' driven plane ; this view overlooks the fact that the maintenance of aerodynamic support would claim the greater part of the engine-power; the rate of ascent would be governed by the amount of power that could be developed surplus to that required for maintenance. This is best explained by actual figures: assuming that a propeller 15 ft. in diameter is used, almost 50 horse-power would be required to get an upward lift of 1,000 pounds; this amount of horse-power would be continually absorbed in maintaining the machine in the air at any given level; for actual lift from one level to another at a speed of eleven feet per second a further 20 horse-power would be required, which means that 70 horse-power must be constantly provided for; this absorption of power in the mere maintenance of aero- dynamic support is a permanent drawback. The attraction of the helicopter lies, probably, in the ease with which flight is demonstrated by means 86 THE AGE OF THE GIANTS of models constructed on this principle, but one truism with regard to the principles of flight is that the problems change remarkably, and often unexpectedly, with the size of the machine constructed for experiment. Berriman, in a brief but very interesting manual entitled Principles of Flight^ assumed that ' there is a significant dimension of which the effective area is an expression of the second power, while the weight became an expression of the third power. Then once again we have the two-thirds power law militating against the successful construction of large helicopters, on the ground that the essential weight increases disproportion- ately fast to the effective area. From a consideration of the structural features of propellers it is evident that this particular relationship does not apply in practice, but it seems reasonab/e that some such governing factor should exist as an explanation of the apparent failure of all full-sized machines that have been con- structed. Among models there is nothing more strikingly successful than the toy helicopter, in which the essential weight is so small compared with the effective area.' De la Landelle's work, already mentioned, was carried on a few years later by another Frenchman, Castel, who constructed a machine with eight propellers arranged in two fours and driven by a compressed air motor or engine. The model with which Castel ex- perimented had a total weight of only 49 Ibs.; it rose in the air and smashed itself by driving against a wall, and the inventor does not seem to have proceeded further. Contemporary with Castel was Professor Forlanini, whose design was for a machine very similar to de la Landelle's, with two superposed screws. This H.A. 87 G A HISTORY OF AERONAUTICS machine ranks as the second on the helicopter principle to achieve flight; it remained in the air for no less than the third of a minute in one of its trials. Later experimenters in this direction were Kress, a German;' Professor Wellner, an Austrian; and W. R. Kimball, an American. Kress, like most Germans, set to the development of an idea which others had originated; he followed de la Landelle and Forlanini by fitting two superposed propellers revolving in opposite directions, and with this machine he achieved good results as regards horse-power to weight; Kimball, it appears, did not get beyond the rubber-driven model stage, and any success he may have achieved was modified by the theory enunciated by Berriman and quoted above. Comparing these two schools of thought, the helicopter and bird-flight schools, it appears that the latter has the greater chance of eventual success that is, if either should ever come into competition with the aeroplane as effective means of flight. So far, the aeroplane holds the field, but the whole science of flight is so new and so full of unexpected developments that this is no reason for assuming that other means may not give equal effect, when money and brains are diverted from the driven plane to a closer imitation of natural flight. Reverting from non-success to success, from con- sideration of the two methods mentioned above to the direction in which practical flight has been achieved, it is to be noted that between the time of Le Bris, Stringfellow, and their contemporaries, and the nineties of last century, there was much plodding work carried out with little visible result, more especially so far as 88 THE AGE OF THE GIANTS English students were concerned. Among the incidents of those years is one of the most pathetic tragedies in the whole history of aviation, that of Alphonse Penaud, who, in his thirty years of life, condensed the experience of his predecessors and combined it with his own genius to state in a published patent what the aeroplane of to-day should be. Consider the following abstract of Penaud's design as published in his patent of 1876, and comparison of this with the aeroplane that now exists will show very few divergences except for those forced on the inventor by the fact that the internal combustion engine had not then developed. The double surfaced planes were to be built with wooden ribs and arranged with a slight dihedral angle; there was to be a large aspect ratio and the wings were cambered as in Stringfellow's later models. Provision was made for warping the wings while in flight, and the trailing edges were so designed as to be capable of upward twist while the machine was in the air. The planes were to be placed above the car, and provision was even made for a glass wind-screen to give protection to the pilot during flight. Steering was to be accomplished by means of lateral and vertical planes forming a tail; these controlled by a single lever corresponding to the 1 joy stick ' of the present day plane. Penaud conceived this machine as driven by two propellers; alternatively these could be driven by petrol or steam-fed motor, and the centre of gravity of the machine while in flight was in the front fifth of the wings. Penaud estimated from 20 to 30 horse-power sufficient to drive this machine, weighing with pilot and passenger 2,600 Ibs., through the air at a speed of 60 miles an hour, with the wings set at an angle of A HISTORY OF AERONAUTICS incidence of two degrees. So complete was the design that it even included instruments, consisting of an aneroid, pressure indicator, an anemometer, a compass, and a level. There, with few alterations, is the aeroplane as we know it and Penaud was twenty-seven when his patent was published. For three years longer he worked, experimenting with models, contributing essays and other valuable data to French papers on the subject of aeronautics. His gains were ill health, poverty, and neglect, and at the age of thirty a pistol shot put an end to what had promised to be one of the most brilliant careers in all the history of flight. Two years before the publication of Penaud's patent Thomas Moy experimented at the Crystal Palace with a twin-propelled aeroplane, steam driven, which seems to have failed mainly because the internal com- bustion engine had not yet come to give sufficient power for weight. Moy anchored his machine to a pole running on a prepared circular track; his engine weighed 80 Ibs. and, developing only three horse-power, gave him a speed of 12 miles an hour. He himself estimated that the machine would not rise until he could get a speed of 35 miles an hour, and his estimate was correct. Two six-bladed propellers were placed side by side between the two main planes of the machine, which was supported on a triangular wheeled under- carriage and steered by fairly conventional tail planes. Moy realised that he could not get sufficient power to achieve flight, but he went on experimenting in various directions, and left much data concerning his experi- ments which has not yet been deemed worthy of publi- cation, but which still contains a mass of information 90 THE AGE OF THE GIANTS that is of practical utility, embodying as it does a vast amount of painstaking work. Penaud and Moy were followed by Goupil, a French- man, who, in place of attempting to fit a motor to an aeroplane, experimented by making the wind his motor. He anchored his machine to the ground, allowing it two feet of lift, and merely waited for a wind to come along and lift it. The machine was stream lined, and the wings, curving as in the early German patterns of war aeroplanes, gave a total lifting surface of about 290 sq. ft. Anchored to the ground and facing a wind of 19 feet per second, Goupil's machine lifted its own weight and that of two men as well to the limit of its anchorage. Although this took place as late as 1883 the inventor went no further in practical work. He published a book, however, entitled La Locomotion Aerienne^ which is still of great importance, more especially on the subject of inherent stability. In 1884 came the first patents of Horatio Phillips, whose work lay mainly in the direction of investigation into the curvature of plane surfaces, with a view to obtaining the greatest amount of support. Phillips was one of the first to treat the problem of curvature of planes as a matter for scientific experiment, and, great as has been the development of the driven plane in the 36 years that have passed since he began, there is still room for investigation into the subject which he studied so persistently and with such valuable result. At this point it may be noted that, with the solitary exception of Le Bris, practically every student of flight had so far set about constructing the means of launching humanity into the air without any attempt at ascertaining 91 A HISTORY OF AERONAUTICS the nature and peculiarities of the sustaining medium. The attitude of experimenters in general might be compared to that of a man who from boyhood had grown up away from open water, and, at the first sight of an expanse of water, set to work to construct a boat with a vague idea that, since wood would float, only sufficient power was required to make him an efficient navigator. Accident, perhaps, in the shape of lack of means of procuring driving power, drove Le Bris to the form of experiment which he actually carried out; it remained for the later years of the nineteenth century to produce men who were content to ascertain the nature of the support the air would afford before attempting to drive themselves through it. Of the age in which these men lived and worked, giving their all in many cases to the science they loved, even to life itself, it may be said with truth that * there were giants on the earth in those days,' as far as aeronautics is in question. It was an age of giants who lived and dared and died, venturing into uncharted space, knowing nothing of its dangers, giving, as a man gives to his mistress, without stint and for the joy of the giving. The science of to-day, compared with the glimmerings that were in that age of the giants, is a fixed and certain thing; the problems of to-day are minor problems, for the great major problem vanished in solution when the Wright Brothers made their first ascent. In that age of the giants was evolved the flying man, the new type in human species which found full expression and came to full development in the days of the war, achieving feats of daring and endurance which leave the commonplace landsman staggered at thought of that of which his fellows prove themselves capable. 92 THE AGE OF THE GIANTS He is a new type, this flying man, a being of self- forgetfulness; of such was Lilienthal, of such was Pilcher; of such in later days were Farman, Bleriot, Hamel, Rolls, and their fellows; great names that will live for as long as man flies, adventurers equally with those of the spacious days of Elizabeth. To each of these came the call, and he worked and dared and passed, having, perhaps, advanced one little step in the long march that has led toward the perfecting of flight. It is not yet twenty years since man first flew, but into that twenty years have been compressed a century or so of progress, while, in the two decades that preceded it, was compressed still more. We have only to recall and recount the work of four men : Lilienthal, Langley, Pilcher, and Clement Ader to see the immense stride that was made between the time when Penaud pulled a trigger for the last time and the Wright Brothers first left the earth. Into those two decades was compressed the investigation that meant knowledge of the qualities of the air, together with the development of the one prime mover that rendered flight a possibility the internal combustion engine. The coming and progress of this latter is a thing apart, to be detailed separately; for the present we are concerned with the evolution of the driven plane, and with it the evolution of that daring being, the flying man. The two are inseparable, for the men gave themselves to their art; the story of Lilienthal's life and death is the story of his work; the story of Pilcher's work is that of his life and death. Considering the flying man as he appeared in the war period, there entered into his composition a new 93 A HISTORY OF AERONAUTICS element patriotism which brought about a modi- fication of the type, or, perhaps, made it appear that certain men belonged to the type who in reality were commonplace mortals, animated, under normal con- ditions, by normal motives, but driven by the stress of the time to take rank with the last expression of human energy, the flying type. However that may be, what may be termed the mathematising of aeronautics has rendered the type itself evanescent; your pilot of to-day knows his craft, once he is trained, much in the manner that a driver of a motor-lorry knows his vehicle ; design has been systematised, capabilities have been tabulated; camber, dihedral angle, aspect ratio, engine power, and plane surface, are business items of drawing office and machine shop; there is room for enterprise, for genius, and for skill; once and again there is room for daring, as in the first Atlantic flight. Yet that again was a thing of mathematical calculation and petrol storage, allied to a certain stark courage which may be found even in landsmen. For the ventures into the unknown, the limit of daring, the work for work's sake, with the almost certainty that the final reward was death, we must look back to the age of the giants, the age when flying was not a business, but romance. 94 VII LILIENTHAL AND PILCHER THERE was never a more enthusiastic and consistent student of the problems of flight than Otto Lilienthal, who was born in 1848 at Anklam, Pomerania, and even from his early school-days dreamed and planned the conquest of the air. His practical experiments began when, at the age of thirteen, he and his brother Gustav made wings consisting of wooden framework covered with linen, which Otto attached to his arms, and then ran downhill flapping them. In consequence of possible derision on the part of other boys, Otto confined these experiments for the most part to moonlit nights, and gained from them some idea of the resistance offered by flat surfaces to the air. It was in 1867 that the two brothers began really practical work, experimenting with wings which, from their design, indicate some knowledge of Besnier and the history of his gliding experiments; these wings the brothers fastened to their backs, moving them with their legs after the fashion of one attempting to swim. Before they had achieved any real success in gliding the Franco-German war came as an interruption; both brothers served in this campaign, resuming their experiments in 1871 at the conclusion of hostilities. The experiments made by the brothers previous to the war had convinced Otto that previous experimenters 95 A HISTORY OF AERONAUTICS in gliding flight had failed through reliance on empirical conclusions or else through incomplete observation on their own part, mostly of bird flight. From 1871 onward Otto Lilenthal (Gustav's interest in the problem was not maintained as was his brother's) made what is probably the most detailed and accurate series of observations that has ever been made with regard to the properties of curved wing surfaces. So far as could be done, Lilienthal tabulated the amount of air resistance offered to a bird's wing, ascertaining that the curve is necessary to flight, as offering far more resistance than a flat surface. Cayley, and others, had already stated this, but to Lilienthal belongs the honour of being first to put the statement to effective proof he made over 2,000 gliding flights between 1891 and the regrettable end of his experiments; his practical conclusions are still regarded as part of the accepted theory of students of flight. In 1889 he published a work on the subject of gliding flight which stands as data for investigators, and, on the conclusions embodied in this work, he began to build his gliders and practise what he had preached, turning from experiment with models to wings that he could use. It was in the summer of 1891 that he built his first glider of rods of peeled willow, over which was stretched strong cotton fabric; with this, which had a supporting surface of about 100 square feet. Otto Lilien- thal launched himself in the air from a spring board, making glides which, at first of only a few feet, gradually lengthened. As his experience of the supporting qualities of the air progressed he gradually altered his designs until, when Pilcher visited him in the spring of 1895, he experimented with a glider, roughly made of LILIENTHAL AND PILCHER peeled willow rods and cotton fabric, having an area of 150 square feet and weighing half a hundredweight. By this time Lilienthal had moved from his spring- board to a conical artificial hill which he had had thrown up on level ground at Grosse Lichterfelde, near Berlin. This hill was made with earth taken from the excavations incurred in constructing a canal, and had a cave inside in which Lilienthal stored his machines. Pilcher, in his paper on ' Gliding,' 1 gives an excellent short summary of Lilienthal's experiments, from which the following extracts are taken : * At first Lilienthal used to experiment by jumping off a springboard with a good run. Then he took to practising on some hills close to Berlin. In the summer of 1892 he built a flat-roofed hut on the summit of a hill, from the top of which he used to jump, trying, of course, to soar as far as possible before landing. . . . One of the great dangers with a soaring machine is losing forward speed, inclining the machine too much down in front, and coming down head first. Lilienthal was the first to introduce the system of handling a machine in the air merely by moving his weight about in the machine; he always rested only on his elbows or on his elbows and shoulders. . . . 'In 1892 a canal was being cut, close to where Lilienthal lived, in the suburbs of Berlin, and with the surplus earth Lilienthal had a special hill thrown up to fly from. The country round is as flat as the sea, and there is not a house or tree near it to make the wind unsteady, so this was an ideal practising ground; for practising on natural hills is generally rendered very difficult by shifty and gusty winds. . . . This 1 Aeronautical Classes, No, 5. Royal Aeronautical Society's publications, 97 A HISTORY OF AERONAUTICS hill is 50 feet high, and conical. Inside the hill there is a cave for the machines to be kept in. ... When Lilienthal made a good flight he used to land 300 feet from the centre of the hill, having come down at an angle of i in 6; but his best flights have been at an angle of about i in 10. 1 If it is calm, one must run a few steps down the hill, holding the machine as far back on oneself as possible, when the air will gradually support one, and one slides ofF the hill into the air. If there is any wind, one should face it at starting ; to try to start with a side wind is most unpleasant. It is possible after a great deal of practice to turn in the air, and fairly quickly. This is accomplished by throwing one's weight to one side, and thus lowering the machine on that side towards which one wants to turn. Birds do the same thing crows and gulls show it very clearly. Last year Lilienthal chiefly experimented with double-surfaced machines. These were very much like the old machines with awnings spread above them. ' The object of making these double-surfaced machines was to get more surface without increasing the length and width of the machine. This, of course, it does, but I personally object to any machine in which the wing surface is high above the weight. I consider that it makes the machine very difficult to handle in bad weather, as a puff of wind striking the surface, high above one, has a great tendency to heel the machine over. ' Herr Lilienthal kindly allowed me to sail down his hill in one of these double-surfaced machines last June. With the great facility afforded by his conical hill the machine was handy enough; but I am afraid LILIENTHAL AND PILCHER I should not be able to manage one at all in the squally districts I have had to practise in over here. * Herr Lilienthal came to grief through deserting his old method of balancing. In order to control his tipping movements more rapidly he attached a line from his horizontal rudder to his head, so that when he moved his head forward it would lift the rudder and tip the machine up in front, and vice versa. He was practising this on some natural hills outside Berlin, and he apparently got muddled with the two motions, and, in trying to regain speed after he had, through a lull in the wind, come to rest in the air, let the machine get too far down in front, came down head first and was killed.' Then in another passage Pilcher enunciates what is the true value of such experiments as Lilienthal and, subsequently, he himself made : * The object of experimenting with soaring machines,' he says, ' is to enable one to have practice in starting and alighting and controlling a machine in the air. They cannot possibly float horizontally in the air for any length of time, but to keep going must necessarily lose in elevation. They are excellent schooling machines, and that is all they are meant to be, until power, in the shape of an engine working a screw propeller, or an engine working wings to drive the machine forward, is added; then a person who is used to soaring down a hill with a simple soaring machine will be able to fly with com- parative safety. One can best compare them to bicycles having no cranks, but on which one could learn to balance by coming down an incline/ It was in 1895 tnat Lilienthal passed from experiment with the monoplane type of glider to the construction 99 A HISTORY OF AERONAUTICS of a biplane glider which, according to his own account, gave better results than his previous machines. * Six or seven metres velocity of wind/ he says, * sufficed to enable the sailing surface of 18 square metres to carry me almost horizontally against the wind from the top of my hill without any starting jump. If the wind is stronger I allow myself to be simply lifted from the point of the hill and to sail slowly towards the wind. The direction of the flight has, with strong wind, a strong upwards tendency. I often reach positions in the air which are much higher than my starting point. At the climax of such a line of flight I sometimes come to a standstill for some time, so that I am enabled while floating to speak with the gentlemen who wish to photograph me, regarding the best position for the photographing. ' Lilienthal's work did not end with simple gliding, though he did not live to achieve machine-driven flight. Having, as he considered, gained sufficient experience with gliders, he constructed a power-driven machine which weighed altogether about 90 Ibs., and this was thoroughly tested. The extremities of its wings were made to flap, and the driving power was obtained from a cylinder of compressed carbonic acid gas, released through a hand-operated valve which, Lilienthal anticipated, would keep the machine in the air for four minutes. There were certain minor accidents to the mechanism, which delayed the trial flights, and on the day that Lilienthal had determined to make his trial he made a long gliding flight with a view to testing a new form of rudder that as Pilcher relates was worked by movements of his head. His death came about through the causes that Pilcher states; he fell 100 LILIENTHAL AND PILCHER from a height of 50 feet, breaking his spine, and the next day he died. It may be said that Lilienthal accomplished as much as any one of the great pioneers of flying. As brilliant in his conceptions as da Vinci had been in his, and as conscientious a worker as Borelli, he laid the foundations on which Pilcher, Chanute, and Professor Montgomery were able to build to such good purpose. His book on bird flight, published in 1889, with the authorship credited both to Otto and his brother Gustav, is regarded as epoch-making; his gliding experiments are no less entitled to this description. In England Lilienthal's work was carried on by Percy Sinclair Pilcher, who, born in 1866, completed six years* service in the British Navy by the time that he was nineteen, and then went through a course of engineering, subsequently joining Maxim in his experimental work. It was not until 1895 that he began to build the first of the series of gliders with which he earned his plane among the pioneers of flight. Probably the best account of Pilcher's work is that given in the Aeronautical Classics issued by the Royal Aeronautical Society, from which the following account of Pilcher's work is mainly abstracted. 1 The ' Bat,' as Pilcher named his first glider, was a monoplane which he completed before he paid his visit to Lilienthal in 1895. Concerning this Pilcher stated that he purposely finished his own machine before going to see Lilienthal, so as to get the greatest advantage from any original ideas he might have; he was not able to make any trials with this machine, however, until after witnessing Lilienthal's experiments 1 Aeronautical Classes, No. 5. Royal Aeronautical Society publications. 101 A HISTORY OF AERONAUTICS and making several glides in the biplane glider which Lilienthal constructed. The wings of the * Bat ' formed a pronounced dihedral angle; the tips being raised 4 feet above the body. The spars forming the entering edges of the wings crossed each other in the centre and were lashed to opposite sides of the triangle that served as a mast for the stay- wires that guyed the wings. The four ribs of each wing, enclosed in pockets in the fabric, radiated fanwise from the centre, and were each stayed by three steel piano-wires to the top of the triangular mast, and similarly to its base. These ribs were bolted down to the triangle at their roots, and could be easily folded back on to the body when the glider was not in use. A small fixed vertical surface was carried in the rear. The framework and ribs were made entirely of Riga pine; the surface fabric was nainsook. The area of the machine was 150 square feet; its weight 45 Ibs.; so that in flight, with Pilcher's weight of 145 Ibs. added, it carried one and a half pounds to the square foot. Pilcher's first glides, which he carried out on a grass hill on the banks of the Clyde near Cardross, gave little result, owing to the exaggerated dihedral angle of the wings, and the absence of a horizontal tail. The * Bat ' was consequently reconstructed with a horizontal tail plane added to the vertical one, and with the wings lowered so that the tips were only six inches above the level of the body. The machine now gave far better results; on the first glide into a head wind Pilcher rose to a height of twelve feet and remained in the the air for a third of a minute; in the second attempt a rope was used to tow the glider, which rose to twenty feet and did not come to earth again until 102 Rear view of Pileher's ' Beetle.' The ' Beetle,' side view. Pilcher starting on glide with the ' Bat.' ^0 face page 103 LILIENTHAL AND PILCHER nearly a minute had passed. With experience Pilcher was able to lengthen his glide and improve his balance, but the dropped wing tips made landing difficult, and there were many breakages. In consequence of this Pilcher built a second glider which he named the * Beetle,' because, as he said, it looked like one. In this the square-cut wings formed almost a continuous plane, rigidly fixed to the central body, which consisted of a shaped girder. These wings were built up of five transverse bamboo spars, with two shaped ribs running from fore to aft of each wing, and were stayed overhead to a couple of masts. The tail, consisting of two discs placed crosswise (the horizontal one alone being movable), was carried high up in the rear. With the exception of the wing-spars, the whole framework was built of white pine. The wings in this machine were actually on a higher level than the operator's head; the centre of gravity was, consequently, very low, a fact which, according to Pilcher's own account, made the glider very difficult to handle. Moreover, the weight of the * Beetle,' 80 Ibs., was considerable; the body had been very solidly built to enable it to carry the engine which Pilcher was then contemplating; so that the glider carried some 225 Ibs. with its area of 170 square feet too great a mass for a single man to handle with comfort. It was in the spring of 1896 that Pilcher built his third glider, the * Gull,' with 300 square feet of area and a weight of 55 Ibs. The size of this machine rendered it unsuitable for experiment in any but very calm weather, and it incurred such damage when experiments were made in a breeze that Pilcher found \t necessary to build a fourth, which he named the H.A. lOj H A HISTORY OF AERONAUTICS * Hawk.' This machine was very soundly built, being constructed of bamboo, with the exception of the two main transverse beams. The wings were attached to two vertical masts, 7 feet high, and 8 feet apart, joined at their summits and their centres by two wooden beams. Each wing had nine bamboo ribs, radiating from its mast, which was situated at a distance of 2 feet 6 inches from the forward edge of the wing. Each rib was rigidly stayed at the top of the mast by three tie-wires, and by a similar number to the bottom of the mast, by which means the curve of each wing was maintained uniformly. The tail was formed of a tri- angular horizontal surface to which was affixed a triangular vertical surface, and was carried from the body on a high bamboo mast, which was also stayed from the masts by means of steel wires, but only on its upper surface, and it was the snapping of one of these guy wires which caused the collapse of the tail support and brought about the fatal end of Pilcher s experiments. In flight, Pilcher's head, shoulders, and the greater part of his chest projected above the wings. He took up his position by passing his head and shoulders through the top aperture formed between the two wings, and resting his forearms on the longi- tudinal body members. A very simple form of under- carriage, which took the weight off the glider on the ground, was fitted, consisting of two bamboo rods with wheels suspended on steel springs. Balance and steering were effected, apart from the high degree of inherent stability afforded by the tail, as in the case of Lilienthal's glider, by altering the position of the body. With this machine Pilcher made some twelve glides at Eynsford in Kent in the summer 104 LILIENTHAL AND PILCHER of 1896, and as he progressed he increased the length of his glides, and also handled the machine more easily, both in the air and in landing. He was occupied with plans for fitting an engine and propeller to the ' Hawk,' but, in these early days of the internal combustion engine, was unable to get one light enough for his purpose. There were rumours of an engine weighing 15 Ibs. which gave i horse-power, and was reported to be in existence in America, but it could not be traced. In the spring of 1897 Pilcher took up his gliding experiments again, obtaining what was probably the best of his glides on June 1 9th, when he alighted after a perfectly balanced glide of over 250 yards in length, having crossed a valley at a considerable height. From his various experiments he concluded that once the machine was launched in the air an engine of, at most, 3 horse-power would suffice for the maintenance of hori- zontal flight, but he had to allow for the additional weight of the engine and propeller, and taking into account the comparative inefficiency of the propeller, he planned for an engine of 4 horse-power. Engine and propeller together were estimated at under 44 Ibs. weight, the engine was to be fitted in front of the operator, and by means of an overhead shaft was to operate the propeller situated in rear of the wings. 1898 went by while this engine was under construction. Then in 1899 Pilcher became interested in Lawrence Hargrave's soaring kites, with which he carried out experiments during the summer of 1899. It is believed that he intended to incorporate a number of these kites in a new machine, a triplane, of which the fragments remaining are hardly sufficient to reconstitute the complete glider. This new machine was never given a trial, for on September 3oth, 1899, 105 A HISTORY OF AERONAUTICS at Stamford Hall, Market Harborough, Pilcher agreed to give a demonstration of gliding flight, but owing to the unfavourable weather he decided to postpone the trial of the new machine and to experiment with the * Hawk/ which was intended to rise from a level field, towed by a line passing over a tackle drawn by two horses. At the first trial the machine rose easily, but the tow-line snapped when it was well clear of the ground, and the glider descended, weighed down through being sodden with rain. Pilcher resolved on a second trial, in which the glider again rose easily to about thirty feet, when one of the guy wires of the tail broke, and the tail collapsed; the machine fell to the ground, turning over, and Pilcher was unconscious when he was freed from the wreckage. Hopes were entertained of his recovery, but he died on Monday, October 2nd, 1899, aged only thirty- four. His work in the cause of flying lasted only four years, but in that time his actual accomplishments were sufficient to place his name beside that of Lilienthal, with whom he ranks as one of the greatest exponents of gliding flight. 106 'The Hawk' front view, rear view, and in flight with Pilcher. To face page icb VIII AMERICAN GLIDING EXPERIMENTS WHILE Pilcher was carrying on Lilienthal's work in England, the great German had also a follower in America; one Octave Chanute, who, in one of the statements which he has left on the subject of his experiments acknowledges forty years' interest in the problem of flight, did more to develop the glider in America than with the possible exception of Mont- gomery any other man. Chanute had all the practicality of an American ; he began his work, so far as actual gliding was concerned, with a full-sized glider of the Lilienthal type, just before Lilienthal was killed. In a rather rare monograph, entitled Experiments in Flying, Chanute states that he found the Lilienthal glider hazardous and decided to test the value of an idea of his own; in this he followed the same general method, but reversed the principle upon which Lilienthal had depended for maintaining his equilibrium in the air. Lilienthal had shifted the weight of his body, under immovable wings, as fast and as far as the sustaining pressure varied under his surfaces; this shifting was mainly done by moving the feet, as the actions required were small except when alighting. Chanute's idea was to have the operator remain seated in the machine in the air, and to intervene only to steer or to alight; moving mechanism was provided to adjust the wings 107 A HISTORY OF AERONAUTICS automatically, in order to restore balance when necessary. Chanute realised that experiments with models were of little use; in order to be fully instructive, these experiments should be made with a full-sized machine which carried its operator, for models seldom fly twice alike in the open air, and no relation can be gained from them of the divergent air currents which they have experienced. Chanute's idea was that any flying machine which might be constructed must be able to operate in a wind; hence the necessity for an operator to report upon what occurred in flight, and to acquire practical experience of the work of the human factor in imitation of bird flight. From this point of view he conducted his own experiments; it must be noted that he was over sixty years of age when he began, and, being no longer sufficiently young and active to perform any but short and insignificant glides, the courage of the man becomes all the more noteworthy; he set to work to evolve the state required by the problem of stability, and without any expectation of advancing to the construction of a flying machine which might be of commercial value. His main idea was the testing of devices to secure equilibrium; for this purpose he employed assistants to carry out the practical work, where he himself was unable to supply the necessary physical energy. Together with his assistants he found a suitable place for experiments among the sandhills on the shore of Lake Michigan, about thirty miles eastward from Chicago. Here a hill about ninety-five feet high was selected as a point from which Chanute's gliders could set off; in practice, it was found that the best observation 108 AMERICAN GLIDING EXPERIMENTS was to be obtained from short glides at low speed, and, consequently, a hill which was only sixty-one feet above the shore of the lake was employed for the experimental work done by the party. In the years 1896 and 1897, with parties of from four to six persons, five full-sized gliders were tried out, and from these two distinct types were evolved: of these one was a machine consisting of five tiers of wings and a steering tail, and the other was of the biplane type; Chanute believed these to be safer than any other machine previously evolved, solving, as he states in his monograph, the problem of inherent equilibrium as fully as this could be done. Unfortunately, very few photographs were taken of the work in the first year, but one view of a multiple wing-glider survives, showing the machine in flight. In 1897 a series of photographs was taken exhibiting the consecutive phases of a single flight; this series of photographs represents the experience gained in a total of about one thousand glides, but the point of view was varied so as to exhibit the consecutive phases of one single flight. The experience gained is best told in Chanute's own words. ' The first thing/ he says, ' which we discovered practically was that the wind flowing up a hill-side is not a steadily-flowing current like that of a river. It comes as a rolling mass, full of tumultuous whirls and eddies, like those issuing from a chimney; and they strike the apparatus with constantly varying force and direction, sometimes withdrawing support when most needed. It has long been known, through instrumental observations, that the wind is constantly changing in force and direction; but it needed the experience of an operator afloat on a gliding machine 109 A HISTORY OF AERONAUTICS to realise that this all proceeded from cyclonic action; so that more was learned in this respect in a week than had previously been acquired by several years of experiments with models. There was a pair of eagles, living in the top of a dead tree about two miles from our tent, that came almost daily to show us how such wind effects are overcome and utilised. The birds swept in circles overhead on pulseless wings, and rose high up in the air. Occasionally there was a side-rocking motion, as of a ship rolling at sea, and then the birds rocked back to an even keel; but although we thought the action was clearly automatic, and were willing to learn, our teachers were too far off to show us just how it was done, and we had to experiment for our- selves.' Chanute provided his multiple glider with a seat, but, since each glide only occupied between eight and twelve seconds, there was little possibility of the operator seating himself. With the multiple glider a pair of horizontal bars provided rest for the arms, and beyond these was a pair of vertical bars which the operator grasped with his hands; beyond this, the operator was in no way attached to the machine. He took, at the most, four running steps into the wind, which launched him in the air, and thereupon he sailed into the wind on a generally descending course. In the matter of descent Chanute observed the sparrow and decided to imitate it. * When the latter,' he says, * approaches the street, he throws his body back, tilts his outspread wings nearly square to the course, and on the cushion of air thus encountered he stops his speed and drops lightly to the ground. So do all birds. We tried it with misgivings, but found it perfectly effective. The soft sand was a no AMERICAN GLIDING EXPERIMENTS great advantage, and even when the experts were racing there was not a single sprained ankle.' With the multiple winged glider some two to three hundred glides were made without any accident either to the man or to the machine, and the action was found so effective, the principle so sound, that full plans were published for the benefit of any experimenters who might wish to improve on this apparatus. The American Aeronautical Annual for 1897 contains these plans; Chanute confessed that some movement on the part of the operator was still required to control the machine, but it was only a seventh or a sixth part of the movement required for control of the Lilienthal type. Chanute waxed enthusiastic over the possibilities of gliding, concerning which he remarks that * There is no more delightful sensation than that of gliding through the air. All the faculties are on the alert, and the motion is astonishingly smooth and elastic. The machine responds instantly to the slightest movement of the operator; the air rushes by one's ears; the trees and bushes flit away underneath, and the landing comes all too quickly. Skating, sliding, and bicycling are not to be compared for a moment to aerial conveyance, in which, perhaps, zest is added by the spice of danger. For it must be distinctly understood that there is constant danger in such preliminary experiments. When this hazard has been eliminated by further evolution, gliding will become a most popular sport.' Later experiments proved that the biplane type of glider gave better results than the rather cumbrous model consisting of five tiers of planes. Longer and more numerous glides, to the number of seven to eight hundred, were obtained, the rate of descent being III A HISTORY OF AERONAUTICS about one in six. The longest distance traversed was about 1 20 yards, but Chanute had dreams of starting from a hill about 200 feet high, which would have given him gliding flights of 1,200 feet. He remarked that ' In consequence of the speed gained by running, the initial stage of the flight is nearly horizontal, and it is thrilling to see the operator pass from thirty to forty feet overhead, steering his machine, undulating his course, and struggling with the wind-gusts which whistle through the guy wires. The automatic mechan- ism restores the angle of advance when compromised by variations of the breeze; but when these come from one side and tilt the apparatus, the weight has to be shifted to right the machine . . . these gusts sometimes raise the machine from ten to twenty feet vertically, and sometimes they strike the apparatus from above, causing it to descend suddenly. When sailing near the ground, these vicissitudes can be counteracted by movements of the body from three to four inches; but this has to be done instantly, for neither wings nor gravity will wait on meditation. At a height of three hundred or four hundred feet the regulating mechanism would probably take care of these wind-gusts, as it does, in fact, for their minor variations. The speed of the machine is generally about seventeen miles an hour over the ground, and from twenty-two to thirty miles an hour relative to the air. Constant effort was directed to keep down the velocity, which was at times fifty-two miles an hour. This is the purpose of the starting and gliding against the wind, which thus furnishes an initial velocity without there being undue speed at the landing. The highest wind we dared to experiment in blew at thirty-one miles an hour ; when the 112 AMERICAN GLIDING EXPERIMENTS wind was stronger, we waited and watched the birds.' Chanute details an amusing little incident which occurred in the course of experiment with the biplane glider. He says that * We had taken one of the machines to the top of the hill, and loaded its lower wings with sand to hold it while we went to lunch. A gull came strolling inland, and flapped full-winged to inspect. He swept several circles above the machine, stretched his neck, gave a squawk and went off. Presently he returned with eleven other gulls, and they seemed to hold a conclave about one hundred feet above the big new white bird which they had discovered on the sand. They circled round after round, and once in a while there was a series of loud peeps, like those of a rusty gate, as if in conference, with sudden flutterings, as if a terrifying suggestion had been made. The bolder birds occasionally swooped downwards to inspect the monster more closely; they twisted their heads around to bring first one eye and then the other to bear, and then they rose again. After some seven or eight minutes of this performance, they evidently concluded either that the stranger was too formidable to tackle, if alive, or that he was not good to eat, if dead, and they flew off to resume fishing, for the weak point about a bird is his stomach.* The gliders were found so stable, more especially the biplane form, that in the end Chanute permitted amateurs to make trials under guidance, and throughout the whole series of experiments not a single accident occurred. Chanute came to the conclusion that any young, quick, and handy man could master a gliding machine almost as soon as he could get the hang of a A HISTORY OF AERONAUTICS bicycle, although the penalty for any mistake would be much more severe. At the conclusion of his experiments he decided that neither the multiple plane nor the biplane type of glider was sufficiently perfected for the application of motive power. In spite of the amount of automatic stability that he had obtained he considered that there was yet more to be done, and he therefore advised that every possible method of securing stability and safety should be tested, first with models, and then with full- sized machines; designers, he said, should make a point of practice in order to make sure of the action, to proportion and adjust the parts of their machine, and to eliminate hidden defects. Experimental flight, he suggested, should be tried over water, in order to break any accidental fall; when a series of experiments had proved the stability of a glider, it would then be time to apply motive power. He admitted that such a process would be both costly and slow, but, he said, that * it greatly diminished the chance of those accidents which bring a whole line of investigation into contempt/ He saw the flying machine as what it has, in fact, been; a child of evolution, carried on step by step by one investigator after another, through the stages of doubt and perplexity which lie behind the realm of possibility, beyond which is the present day stage of actual perform- ance and promise of ultimate success and triumph over the earlier, more cumbrous, and slower forms of the transport that we know. Chanute's monograph, from which the foregoing notes have been comprised, was written soon after the conclusion of his series of experiments. He does not appear to have gone in for further practical work, but PH I I O AMERICAN GLIDING EXPERIMENTS to have studied the subject from a theoretical view-point and with great attention to the work done by others. In a paper contributed in 1900 to the American Independent^ he remarks that * Flying machines promise better results as to speed, but yet will be of limited commercial application. They may carry mails and reach other inaccessible places, but they cannot compete with railroads as carriers of passengers or freight. They will not fill the heavens with commerce, abolish custom houses, or revolutionise the world, for they will be expensive for the loads which they can carry, and subject to too many weather contingencies. Success is, however, probable. Each experimenter has added something to previous knowledge which his successors can avail of. It now seems likely that two forms of flying machines, a sporting type and an exploration type, will be gradually evolved within one or two generations, but the evolution will be costly and slow, and must be carried on by well-equipped and thoroughly informed scientific men; for the casual inventor, who relies upon one or two happy inspirations, will have no chance of success whatever.' Follows Professor John J. Montgomery, who, in the true American spirit, describes his own experiments so well that nobody can possibly do it better. His account of his work was given first of all in the American Journal, Aeronautics^ in January, 1909, and thence transcribed in the English paper of the same name in May, 1910, and that account is here copied word for word. It may, however, be noted first that as far back as 1860, when Montgomery was only a boy, he was attracted to the study of aeronautical problems, and in 1883 he built his first machine, which was of "5 A HISTORY OF AERONAUTICS the flapping-wing ornithopter type, and which showed its designer, with only one experiment, that he must design some other form of machine if he wished to attain to a successful flight. Chanute details how, in 1884 and 1885, Montgomery built three gliders, demonstrating the value of curved surfaces. With the first of these gliders Montgomery copied the wing of a seagull; with the second he proved that a flat surface was virtually useless, and with the third he pivoted his wings as in the Antoinette type of power-propelled aeroplane, proving to his own satisfaction that success lay in this direction. His own account of the gliding flights carried out under his direction is here set forth, being the best description of his work that can be obtained : * When I commenced practical demonstration in my work with aeroplanes I had before me three points; first, equilibrium; second, complete control; and third, long continued or soaring flight. In starting I con- structed and tested three sets of models, each in advance of the other in regard to the continuance of their soaring powers, but all equally perfect as to equilibrium and control. These models were tested by dropping them from a cable stretched between two mountain tops, with various loads, adjustments and positions. And it made no difference whether the models were dropped upside down or any other conceivable position, they always found their equilibrium immediately and glided safely to earth. ' Then I constructed a large machine patterned after the first model, and with the assistance of three cowboy friends personally made a number of flights in the steep mountains near San Juan (a hundred miles 116 AMERICAN GLIDING EXPERIMENTS distant). In making these flights I simply took the aeroplane and made a running jump. These tests were discontinued after I put my foot into a squirrel hole in landing and hurt my leg. The following year I commenced the work on a larger scale, by engaging aeronauts to ride my aeroplane dropped from balloons. During this work I used five hot-air balloons and one gas balloon, five or six aeroplanes, three riders Maloney, Wilkie, and Defolco and had sixteen applicants on my list, and had a training station to prepare any when I needed them. ' Exhibitions were given in Santa Cruz, San Jose, Santa Clara, Oaklandff and Sacramento. The flights that were made, instead of being haphazard affairs, were in the order of safety and development. In the first flight of an aeronaut the aeroplane was so arranged that the rider had little liberty of action, consequently he could make only a limited flight. In some of the first flights, the aeroplane did little more than settle in the air. But as the rider gained experience in each successive flight I changed the adjustments, giving him more liberty of action, so he could obtain longer flights and more varied movements in the flights. But in none of the flights did I have the adjustments so that the riders had full liberty, as I did not consider that they had the requisite knowledge and experience necessary for their safety; and hence, none of my aero- planes were launched so arranged that the rider could make adjustments necessary for a full flight. * This line of action caused a good deal of trouble with aeronauts or riders, who had unbounded confidence and wanted to make long flights after the first few trials ; but I found it necessary, as they seemed slow 117 A HISTORY OF AERONAUTICS in comprehending the important elements and were willing to take risks. To give them the full knowledge in these matters I was formulating plans for a large starting station on the Mount Hamilton Range from which I could launch an aeroplane capable of carrying two, one of my aeronauts and myself, so I could teach him by demonstration. But the disasters consequent on the great earthquake completely stopped all my work on these lines. The flights that were given were only the first of the series with aeroplanes patterned after the first model. There were no aeroplanes constructed according to the two other models, as I had not given the full demonstration of the iworkings of the first, though some remarkable and startling work was done. On one occasion Maloney, in trying to make a very short turn in rapid flight, pressed very hard on the stirrup which gives a screw-shape to the wings, and made a side somersault. The course of the machine was very much like one turn of a corkscrew. After this movement the machine continued on its regular course. And afterwards Wilkie, not to be outdone by Maloney, told his friends he would do the same, and in a subsequent flight made two side somersaults, one in one direction and the other in an opposite, then made a deep dive and a long glide, and, when about three hundred feet in the air, brought the aeroplane to a sudden stop and settled to the earth. After these antics, I decreased the extent of the possible change in the form of wing-surface, so as to allow only straight sailing or only long curves in turning. ' During my work I had a few carping critics that I silenced by this standing offer : If they would deposit a thousand dollars I would cover it on this proposition. 118 AMERICAN GLIDING EXPERIMENTS I would fasten a 1 50 pound sack of sand in the rider's seat, make the necessary adjustments, and send up an aeroplane upside down with a balloon, the aeroplane to be liberated by a time fuse. If the aeroplane did not immediately right itself, make a flight, and come safely to the ground, the money was theirs. * Now a word in regard to the fatal accident. The circumstances are these: The ascension was given to entertain a military company in which were many of Maloney's friends, and he had told them he would give the most sensational flight they ever heard of. As the balloon was rising with the aeroplane, a guy rope dropping switched around the right wing and broke the tower that braced the two rear wings and which also gave control over the tail. We shouted Maloney that the machine was broken, but he probably did not hear us, as he was at the same time saying, "Hurrah for Montgomery's airship," and as the break was behind him, he may not have detected it. Now did he know of the breakage or not, and if he knew of it did he take a risk so as not to disappoint his friends ? At all events, when the machine started on its flight the rear wings commenced to flap (thus indicating they were loose), the machine turned on its back, and settled a little faster than a parachute. When we reached Maloney he was unconscious and lived only thirty minutes. The only mark of any kind on him was a scratch from a wire on the side of his neck. The six attending physicians were puzzled at the cause of his death. This is remark- able for a vertical descent of over 2,000 feet/ The flights were brought to an end by the San Francisco earthquake in April, 1 906, which, Montgomery states, * Wrought such a disaster that I had to turn my H.A. 119 i A HISTORY OF AERONAUTICS attention to other subjects and let the aeroplane rest for a time.' Montgomery resumed experiments in 1911 in California, and in October of that year an accident brought his work to an end. The report in the American Aeronautics says that ' a little whirlwind caught the machine and dashed it head on to the ground; Professor Montgomery landed on his head and right hip. He did not believe himself seriously hurt, and talked with his year-old bride in the tent. He complained of pains in his back, and continued to grow worse until he died/ 120 IX NOT PROVEN THE early history of flying, like that of most sciences, is replete with tragedies; in addition to these it contains one mystery concerning Clement Ader, who was well known among European pioneers in the development of the telephone, and first turned his attention to the problems of mechanical flight in 1872. At the outset he favoured the ornithopter principle, constructing a machine in the form of a bird with a wing-spread of twenty-six feet; this, according to Ader's conception, was to fly through the efforts of the operator. The result of such an attempt was past question and naturally the machine never left the ground. A pause of nineteen years ensued, and then in 1886 Ader turned his mind to the development of the aeroplane, constructing a machine of bat-like form with a wing- spread of about forty-six feet, a weight of eleven hundred pounds, and a steam-power plant of between twenty and thirty horse-power driving a four-bladed tractor screw. On October 9th, 1890, the first trials of this machine were made, and it was alleged to have flown a distance of one hundred and sixty-four feet. Whatever truth there may be in the allegation, the machine was wrecked through deficient equilibrium at the end of the trial. Ader repeated the construction, and on October I4th, 1897, tried out his third machine at the 121 A HISTORY OF AERONAUTICS military establishment at Satory in the presence of the French military authorities, on a circular track specially prepared for the experiment. Ader and his friends alleged that a flight of nearly a thousand feet was made ; again the machine was wrecked at the end of the trial, and there Ader's practical work may be said to have ended, since no more funds were forthcoming for the subsidy of experiments. There is the bald narrative, but it is worthy of some amplification. If Ader actually did what he claimed, then the position which the Wright Brothers hold as first to navigate the air in a power-driven plane is nullified. Although at this time of writing it is not a quarter of a century since Ader's experiment in the presence of witnesses competent to judge on his accom- plishment, there is no proof either way, and whether he was or was not the first man to fly remains a mystery in the story of the conquest of the air. The full story of Ader's work reveals a persistence and determination to solve the problem that faced him which was equal to that of Lilienthal. He began by penetrating into the interior of Algeria after having disguised himself as an Arab, and there he spent some months in studying flight as practised by the vultures of the district. Returning to France in 1886 he began to construct the * Eole,' modelling it, not on the vulture, but in the shape of a bat. Like the Lilienthal and Pilcher gliders this machine was fitted with wings which could be folded; the first flight made, as already noted, on October 9th, 1890, took place in the grounds of the chateau d'Amainvilliers, near Bretz; two fellow- enthusiasts named Espinosa and Vallier stated that a flight was actually made; no statement in the history 122 NOT PROVEN of aeronautics has been subject of so much question, and the claim remains unproved. It was in September of 1891 that Ader, by permission of the Minister of War, moved the ' Eole ' to the military establishment at Satory for the purpose of further trial. By this time, whether he had flown or not, his nineteen years of work in connection with the problems attendant on mechanical flight had attracted so much attention that henceforth his work was subject to the approval of the military authorities, for already it was recognised that an efficient flying machine would confer an inestimable advantage on the power that possessed it in the event of war. At Satory the ' Eole * was alleged to have made a flight of 109 yards, or, according to another account, 164 feet, as stated above, in the trial in which the machine wrecked itself through colliding with some carts which had been placed near the track the root cause of this accident, however, was given as deficient equilibrium. Whatever the sceptics may say, there is reason for belief in the accomplishment of actual flight by Ader with his first machine in the fact that, after the inevitable official delay of some months, the French War Ministry granted funds for further experiment. Ader named his second machine, which he began to build in May, 1892, the * Avion,' and an honour which he well deserves that name remains in French aeronautics as descriptive of the power-driven aeroplane up to this day. This second machine, however, was not a success, and it was not until 1897 that the second ' Avion,' which was the third power-driven aeroplane of Ader's con- struction, was ready for trial. This was fitted with 123 A HISTORY OF AERONAUTICS two steam motors of twenty horse-power each, driving two four-bladed propellers; the wings warped auto- matically: that is to say, if it were necessary to raise the trailing edge of one wing on the turn, the trailing edge of the opposite wing was also lowered by the same movement; an under-carriage was also fitted, the machine running on three small wheels, and levers controlled by the feet of the aviator actuated the move- ment of the tail planes. On October the I2th, 1897, the first trials of this ' Avion ' were made in the presence of General Mensier, who admitted that the machine made several hops above the ground, but did not consider the performance as one of actual flight. The result was so encouraging, in spite of the partial failure, that, two days later, General Mensier, accompanied by General Grillon, a certain Lieutenant Binet, and two civilians named respectively Sarrau and Leaute, attended for the purpose of giving the machine an official trial, over which the great con- troversy regarding Ader's success or otherwise may be said to have arisen. We will take first Ader's own statement as set out in a very competent account of his work published in Paris in 1910. Here are Ader's own words: * After some turns of the propellers, and after travelling a few metres, we started off at a lively pace; the pressure- gauge registered about seven atmospheres; almost immediately the vibrations of the rear wheel ceased; a little later we only experienced those of the front wheels at intervals. Unhappily, the wind became suddenly strong, and we had some difficulty in keeping the " Avion " on the white line. We increased the pressure to between eight and nine atmospheres, and 124 NOT PROVEN immediately the speed increased considerably, and the vibrations of the wheels were no longer sensible; we were at that moment at the point marked G in the sketch; the " Avion " then found itself freely supported by its wings; under the impulse of the wind it con- tinually tended to go outside the (prepared) area to the right, in spite of the action of the rudder. On reaching the point V it found itself in a very critical position; the wind blew strongly and across the direction of the Landing of the Course of the Avion's Flight, October 14, 1897. white line which it ought to follow; the machine then, although still going forward, drifted quickly out of the area; we immediately put over the rudder to the left as far as it would go; at the same time increasing the pressure still more, in order to try to regain the course. The " Avion " obeyed, recovered a little, and remained for some seconds headed towards its intended course, but it could not struggle against the wind; instead of going back, on the contrary it drifted farther and farther 125 A HISTORY OF AERONAUTICS away. And ill-luck had it that the drift took the direction towards part of the School of Musketry, which was guarded by posts and barriers. Frightened at the prospect of breaking ourselves against these obstacles, surprised at seeing the earth getting farther away from under the " Avion," and very much impressed by seeing it rushing sideways at a sickening speed, instinctively we stopped everything. What passed through our thoughts at this moment which threatened a tragic turn would be difficult to set down. All at once came a great shock, splintering, a heavy concussion: we had landed.' Thus speaks the inventor; the cold official mind gives out a different account, crediting the 4 Avion ' with merely a few hops, and to-day, among those who consider the problem at all, there is a little group which persists in asserting that to Ader belongs the credit of the first power-driven flight, while a larger group is equally persistent in stating that, save for a few ineffectual hops, all three wheels of the machine never left the ground. It is past question that the ' Avion ' was capable of power-driven flight; whether it achieved it or no remains an unsettled problem. Ader's work is negative proof of the value of such experiments as Lilienthal, Pilcher, Chanute, and Montgomery conducted; these four set to work to master the eccentricities of the air before attempting to use it as a supporting medium for continuous flight under power; Ader attacked the problem from the other end; like many other experimenters he regarded the air as a stable fluid capable of giving such support to his machine as still water might give to a fish, and he reckoned that he had only to produce the machine in 126 I oo c ? jc 4-> '? end of the, race was a great fight between Beaumont and Vedrines, both of whom scorned weather conditions in their determination to win. Beaumont made the distance in a flying time of 22 hours 28 minutes 19 seconds, and Vedrines covered the journey in a little over 23! hours. Valentine came third on a Deperdussin monoplane and S. F. Cody on his Cathedral biplane was fourth. This was in 1911, and by that time heavier-than-air flight had so far advanced that some pilots had had war experience in the Italian campaign in Tripoli, while long cross-country flights were an everyday event, and bad weather no longer counted. 220 XVII A SUMMARY, TO 19 1 1 THERE is so much overlapping in the crowded story of the first years of successful power-driven flight that at this point it is advisable to make a concise chronological survey of the chief events of the period of early develop- ment, although much of this is of necessity recapitulation. The story begins, of course, with Orville Wright's first flight of 852 feet at Kitty Hawk on December I9th, 1903. The next event of note was Wright's flight of 1 1 . 1 2 miles in 1 8 minutes 9 seconds at Dayton, Ohio, on September 26th, 1905, this being the first officially recorded flight. On October 4th of the same year, Wright flew 20.75 miles ln 33 minutes 17 seconds, this being the first flight of over 20 miles ever made. Then on September I4th, 1906, Alberto Santos-Dumont made a flight of eight seconds on the second heavier- than-air machine he had constructed. It was a big box-kite-like machine; this was the second power- driven aeroplane in Europe to fly, for although Santos- Dumont's first machine produced in 1905 was reckoned an unsuccessful design, it had actually got off the ground for brief periods. Louis Bleriot came into the ring on April 5th, 1907, with a first flight of 6 seconds on a Bleriot mcnophne, his eighth but first successful construction. Henry Farman made his first appearance in the 221 A HISTORY OF AERONAUTICS history of aviation with a flight of 935 feet on a Voisin biplane on October I5th, 1907. On October 25th, in a flight of 2,530 feet, he made the first recorded turn in the air, and on March 29th, 1908, carrying Leon Delagrange on a Voisin biplane, he made the first passenger flight. On April loth of this year, Delagrange, in flying ij miles, made the first flight in Europe exceeding a mile in distance. He improved on this by flying io| miles at Milan on June 22nd, while on July 8th, at Turin, he took up Madame Peltier, the first woman to make an aeroplane flight. Wilbur Wright, coming over to Europe, made his first appearance on the Continent with a flight of if minutes at Hunaudieres, France, on August 8th, 1908. On September 6th, at Chalons, he flew for i hour 4 minutes 26 seconds with a passenger, this being the first flight in which an hour in the air was exceeded with a passenger on board. On September I2th, 1908, Orville Wright, flying at Fort Meyer, U.S.A., with Lieut. Selfridge as passenger, crashed his machine, suffering severe injuries, while Selfridge was killed. This was the first aeroplane fatality. On October 3oth, 1908, Farman made the first cross-country flight, covering the distance of 17 miles between Bouy and Rheims. The next day, Louis Bleriot, in flying from Toury to Artenay, made two landings en route^ this being the first cross-country flight with landings. On the last day of the year, Wilbur Wright won the Michelin Cup at Auvours with a flight of 90 miles, which, lasting 2 hours 20 minutes 23 seconds, exceeded 2 hours in the air for the first time. On January 2nd, 1909, S. F. Cody opened the New 222 A SUMMARY TO 1911 Year by making the first observed flight at Farnborough on a British Army aeroplane. It was not until July 1 8th of 1909 that the first European height record deserving of mention was put up by Paulhan, who achieved a height of 450 feet on a Voisin biplane. This preceded Latham's first attempt to fly the Channel by two days, and five days later, on the 2th of the month, Bleriot made the first Channel crossing. The Rheims Meeting followed on August 22nd, and it was a great day for aviation when nine machines were seen in the air at once. It was here that Farman, with a 1 1 8 mile flight, first exceeded the hundred miles, and Latham raised the height record officially to 500 feet, though actually he claimed to have reached 1,200 feet. On September 8th, Cody, flying from Aldershot, made a 40 mile journey, setting up a new cross-country record. On October I9th the Comte de Lambert flew from Juvisy to Paris, rounded the Eiffel Tower and flew back. J. T. C. Moore-Brabazon made the first circular mile flight by a British aviator on an all-British machine in Great Britain, on October 3oth, flying a Short biplane with a Green engine. Paulhan, flying at Brooklands on November 2nd, accomplished 96 miles in 2 hours 48 minutes, creating a British distance record; on the following day, Henry Farman made a flight of 150 miles in 4 hours 22 minutes at Mourmelon, and on the 5th of the month, Paulhan, flying a Farman biplane, made a world's height record of 977 feet. This, however, was not to stand long, for Latham got up to 1,560 feet on an Antoinette at Mourmelon on December ist. December 3ist witnessed the first flight in Ireland, made by H. Ferguson on a monoplane which he himself had constructed at Downshire Park, Lisburn. 223 A HISTORY OF AERONAUTICS These, thus briefly summarised, are the principal events up to the end of 1 909. 1910 opened with tragedy, for on January 4th Leon Delagrange, one of the greatest pilots of his time, was killed while flying at Pau. The machine was the Bleriot XI which Delagrange had used at the Doncaster meeting, and to which Delagrange had fitted a 50 horse-power Gnome engine, increasing the speed of the machine from its original 30 to 45 miles per hour. With the Rotary Gnome engine there was of necessity a certain gyroscopic effect, the strain of which proved too much for the machine. Delagrange had come to assist in the inauguration of the Croix d'Hins aerodrome, and had twice lapped the course at a height of about 60 feet. At the beginning of the third lap, the strain of the Gnome engine became too great for the machine; one wing collapsed as if the stay wires had broken, and the whole machine turned over and fell, killing Delagrange. On January yth Latham, flying at Mourmelon, first made the vertical kilometre and dedicated the record to Delagrange, this being the day of his friend's funeral. The record was thoroughly authenticated by a large registering barometer which Latham carried, certified by the officials of the French Aero Club. Three days later Paulhan, who was at Los Angeles, California, raised the height record to 4,146 feet. On January 25th the Brussels Exhibition opened, when the Antoinette monoplane, the Gaffaux and Hanriot monoplanes, together with the d'Hespel aeroplane, were shown; there were also the dirigible Belgica and a number of interesting aero engines, including a German airship engine and a four-cylinder 50 horse-power Miesse, this last air-cooled by means of 224 A SUMMARY TO 1911 fans driving a current of air through air jackets sur- rounding fluted cylinders. On April 2nd Hubert Le Blon, flying a Bleriot with an Anzani engine, was killed while flying over the water. His machine was flying quite steadily, when it suddenly heeled over and came down sideways into the sea; the motor continued running for some seconds and the whole machine was drawn under water. When boats reached the spot, Le Blon was found lying back in the driving seat floating just below the surface. He had done good flying at Doncaster, and at Heliopolis had broken the world's speed records for 5 and 10 kilometres. The accident was attributed to fracture of one of the wing stay wires when running into a gust of wind. The next notable event was Paulhan's London- Manchester flight, of which full details have already been given. In May Captain Bertram Dickson, flying at the Tours meeting, beat all the Continental fliers whom he encountered, including Chavez, the Peruvian, who later made the first crossing of the Alps. Dickson was the first British winner of international aviation prizes. C. S. Rolls, of whom full details have already been given, was killed at Bournemouth on July I2th, being the first British aviator of note to be killed in an aeroplane accident. His return trip across the Channel had taken place on June 2nd. Chavez, who was rapidly leaping into fame, as a pilot, raised the British height record to 5,750 feet while flying at Blackpool on August 3rd. On the 1 1 th of that month, Armstrong Drexel, flying a Bleriot, made a world's height record of 6,745 feet. It was in 1910 that the British War Office first began fully to realise that there might be military 225 A HISTORY OF AERONAUTICS possibilities in heavier-than-air flying. C. S. Rolls had placed a Wright biplane at the disposal of the military authorities, and Cody, as already recorded, had been experimenting with a biplane type of his own for some long period. Such development as was achieved was mainly due to the enterprise and energy of Colonel J. E. Capper, C.B., appointed to the superintendency of the Balloon Factory and Balloon School at Farn- borough in 1906. Colonel Capper's retirement in 1910 brought (then) Mr Mervyn O'Gorman to command, and by that time the series of successes of the Cody biplane, together with the proved efficiency of the aeroplane in various civilian meetings, had convinced the British military authorities that the mastery of the air did not lie altogether with dirigible airships, and it may be said that in 1910 the British War Office first began seriously to consider the possibilities of the aeroplane, though two years more were to elapse before the formation of the Royal Flying Corps marked full realisation of its value. A triumph and a tragedy were combined in September of 1910. On the 23rd of the month, Georges Chavez set out to fly across the Alps on a Bleriot mono- plane. Prizes had been offered by the Milan Aviation Committee for a flight from Brigue in Switzerland over the Simplon Pass to Milan, a distance of 94 miles with a minimum height of 6,600 feet above sea level. Chavez started at 1.30 p.m. on the 23rd, and 41 minutes later he reached Domodossola, 25 miles distant. Here he descended, numbed with the cold of the journey; it was said that the wings of his machine collapsed when about 30 feet from the ground, but however this may have been, he smashed the machine on landing, 226 Chavez flying across the Alps. To face page ^26 A SUMMARY TO 1911 and broke both legs, in addition to sustaining other serious injuries. He lay in hospital until the 2yth September, when he died, having given his life to the conquest of the Alps. His death in the moment of success was as great a tragedy as were those of Pilcher and Lilienthal. The day after Chavez's death, Maurice Tabuteau flew across the Pyrenees, landing in the square at Biarritz. On December 3oth, Tabuteau made a flight of 365 miles in 7 hours 48 minutes. Farman, on December i8th, had flown for over 8 hours, but his total distance was only 282 miles. The autumn of this year was also noteworthy for the fact that aeroplanes were first successfully used in the French Military Manoeuvres. The British War Office, by the end of the year, had bought two machines, a military type Farman and a Paulhan, ignoring British experimenters and aeroplane builders of proved reliability. These machines, added to an old Bleriot two-seater, appear to have constituted the British aeroplane fleet of the period. There were by this time three main centres of aviation in England, apart from Cody, alone on Laffan's Plain. These three were Brooklands, Hendon, and the Isle of Sheppey, and of the three Brooklands was chief. Here such men as Graham Gilmour, Rippen, Leake, Wickham, and Thomas persistently experimented. Hendon had its own little group, and Shellbeach, Isle of Sheppey, held such giants of those days as C. S. Rolls and Moore Brabazon, together with Cecil Grace and Rawlinson. One or other, and sometimes all of these were deserted on the occasion of some meeting or other, but they were the points where the spade 227 A HISTORY OF AERONAUTICS work was done, Brooklands taking chief place. ' If you want the early history of flying in England, it is there,' one of the early school remarked, pointing over toward Brooklands course. 1911 inaugurated a new series of records of varying character. On the I7th January, E. B. Ely, an American, flew from the shore of San Francisco to the U.S. cruiser Pennsylvania, landing on the cruiser, and then flew back to the shore. The British military designing of aeroplanes had been taken up at Farn- borough by G. H. de Havilland, who by the end of January was flying a machine of his own design, when he narrowly escaped becoming a casualty through collision with an obstacle on the ground, which swept the undercarriage from his machine. A list of certified pilots of the countries of the world was issued early in 1911, showing certificates granted up to the end of 1910. France led the way easily with 353 pilots; England came next with 57, and Germany next with 46; Italy owned 32, Belgium 27, America 26, and Austria 19; Holland and Switzer- land had 6 aviators apiece, while Denmark followed with 3, Spain with 2, and Sweden with i. The first certificate in England was that of J. T. C. Moore- Brabazon, while Louis Bleriot was first on the French list and Glenn Curtiss, first holder of an American certificate, also held the second French brevet. On the 7th March, Eugene Renaux won the Michelin Grand Prize by flying from the French Aero Club ground at St Cloud and landing on the Puy de Dome. The landing, which was one of the conditions of the prize, was one of the most dangerous conditions ever attached to a competition; it involved dropping 228 A SUMMARY TO 1911 on to a little plateau 150 yards square, with a possibility of either smashing the machine against the face of the mountain, or diving over the edge of the plateau into the gulf beneath. The length of the journey was slightly over 200 miles and the height of the landing point 1,465 metres, or roughly 4,500 feet above sea-level. Renaux carried a passenger, Doctor Senoucque, a member of Charcot's South Polar Expedition. The 1911 Aero Exhibition held at Olympia bore witness to the enormous strides made in construction, more especially by British designers, between 1908 and the opening of the Show. The Bristol Firm showed three machines, including a military biplane, and the first British built biplane with tractor screw. The Cody biplane, with its enormous size rendering it a prominent feature of the show, was exhibited. Its designer anticipated later engines by expressing his desire for a motor of 150 horse-power, which in his opinion was necessary to get the best results from the machine. The then famous Dunne monoplane was exhibited at this show, its planes being V-shaped in plan, with apex leading. It embodied the results of very lengthy experiments carried out both with gliders and power-driven machines by Colonel Capper, Lieut. Gibbs, and Lieut. Dunne, and constituted the longest step so far taken in the direction of inherent stability. Such forerunners of the notable planes of the war period as the Martin Handasyde, the Nieuport, Sopwith, Bristol, and Farman machines, were features of the show; the Handley-Page monoplane, with a span of 32 feet over all, a length of 22 feet, and a weight of 422 Ibs., bore no relation at all to the twin-engined giant which later made this firm famous. In the matter 229 A HISTORY OF AERONAUTICS of engines, the principal survivals to the present day, of which this show held specimens, were the Gnome, Green, Renault air-cooled, Mercedes four-cylinder dirigible engine of 115 horse-power, and 120 horse- power Wolseley of eight cylinders for use with dirigibles. On April I2th of 1911, Paprier, instructor at the Bleriot school at Hendon, made the first non-stop flight between London and Paris. He left the aerodrome at 1.37 p.m., and arrived at Issy-les-Moulineaux at 5.33 p.m., thus travelling 250 miles in a little under 4 hours. He followed the railway route practically throughout, crossing from Dover to nearly opposite Calais, keeping along the coast to Boulogne, and then following the Nord Railway to Amiens, Beauvais, and finally Paris. In May, the Paris-Madrid race took place; Vedrines, flying a Morane biplane, carried off the prize by first completing the distance of 732 miles. The Paris-Rome race of 916 miles was won in the same month by Beaumont, flying a Bleriot monoplane. In July, Kcenig won the German National Circuit race of i, 1 68 miles on an Albatross biplane. This was practically simultaneous with the Circuit of Britain won by Beaumont, who covered 1,010 miles on a Bleriot monoplane, having already won the Paris- Brussels-London-Paris Circuit of 1,080 miles, this also on a Bleriot. It was in August that a new world's height record of 11,152 feet was set up by Captain Felix at Etampes, while on the 7th of the month Renaux flew nearly 600 miles on a Maurice Farman machine in 1 2 hours. Cody and Valentine were keeping interest alive in the Circuit of Britain race, although this had long been won, by determinedly plodding on at finishing the course. 230 A SUMMARY TO 1911 On September 9th, the first aerial post was tried between Hendon and Windsor, as an experiment in sending mails by aeroplane. Gustave Hamel flew from Hendon to Windsor and back in a strong wind. A few days later, Hamel went on strike, refusing to carry further mails unless the promoters of the Aerial Postal Service agreed to pay compensation to Hubert, who fractured both his legs on the nth of the month while engaged in aero postal work. The strike ended on September 25th, when Hamel resumed mail-carrying in consequence of the capitulation of the Postmaster- General, who agreed to set aside 500 as compensation to Hubert. September also witnessed the completion in America of a flight across the Continent, a distance of 2,600 miles. The only competitor who completed the full distance was C. P. Rogers, who was disqualified through failing to comply with the time limit. Rogers needed so many replacements to his machine on the journey that, expressing it in American fashion, he arrived with practically a different aeroplane from that with which he started. With regard to the aerial postal service, analysis of the matter carried and the cost of the service seemed to show that with a special charge of one shilling for letters and sixpence for post cards, the revenue just balanced the expenditure. It was not possible to keep to the time-table as, although the trials were made in the most favourable season of the year, aviation was not sufficiently advanced to admit of facing all weathers and complying with time-table regulations. French military aeroplane trials took place at Rheims in October, the noteworthy machines being H.A. 231 Q A HISTORY OF AERONAUTICS Antoinette, Farman, Nieuport, and Deperdussin. The tests showed the Nieuport monoplane with Gnome motor as first in position; the Breguet biplane was second, and the Deperdussin monoplanes third. The first five machines in order of merit were all engined with the Gnome motor. The records quoted for 1911 form the best evidence that can be given of advance in design and performance during the year. It will be seen that the days of the giants were over; design was becoming more and more standardised and aviation not so much a matter of individual courage and even daring, as of the reliability of the machine and its engine. This was the first year in which the twin-engined aeroplane made its appearance, and it was the year, too, in which flying may be said to have grown so common that the * meetings ' which began with Rheims were hardly worth holding, owing to the fact that increase in height and distance flown rendered it no longer necessary for a would-be spectator of a flight to pay half a crown and enter an enclosure. Henceforth, flying as a spectacle was very little to be considered; its commercial aspects were talked of, and to a very slight degree exploited, but, more and more, the fact that the aeroplane was primarily an engine of war, and the growing German menace against the peace of the world combined to point the way of speediest development, and the arrangements for the British Military Trials to be held in August, 1912, showed that even the British War Office was waking up to the potentialities of this new engine of war. 232 XVIII A SUMMARY, TO 1914 CONSIDERATION of the events in the years immediately preceding the War must be limited to as brief a summary as possible, this not only because the full history of flying achievements is beyond the compass of any single book, but also because, viewing the matter in perspective, the years 1903-1911 show up as far more important as regards both design and performance. From 1912 to August of 1914, the development of aeronautics was hindered by the fact that it had not progressed far enough to form a real commercial asset in any country. The meetings which drew vast concourses of people to such places as Rheims and Bournemouth may have been financial successes at first, but, as flying grew more common and distances and heights extended, a great many people found it other than worth while to pay for admission to an aerodrome. The business of taking up passengers for pleasure flights was not financially successful, and, although schemes for com- mercial routes were talked of, the aeroplane was not sufficiently advanced to warrant the investment of hard cash in any of these projects. There was a deadlock; further development was necessary in order to secure financial aid, and at the same time financial aid was necessary in order to secure further development. Consequently, neither was forthcoming. 333 A HISTORY OF AERONAUTICS This is viewing the matter in a broad and general sense; there were firms, especially in France, but also in England and America, which looked confidently for the great days of flying to arrive, and regarded their sunk capital as investment which would eventually bring its due return. But when one looks back on those years, the firms in question stand out as exceptions to the general run of people, who regarded aeronautics as something extremely scientific, exceedingly dangerous, and very expensive. The very fame that was attained by such pilots as became casualties conduced to the advertisement of every death, and the dangers attendant on the use of heavier-than-air machines became greatly exaggerated; considering the matter as one of number of miles flown, even in the early days, flying exacted no more toll in human life than did railways or road motors in the early stages of their development. But to take one instance, when C. S. Rolls was killed at Bourne- mouth by reason of a faulty tail-plane, the fact was shouted to the whole world with almost as much vehemence as characterised the announcement of the Titanic sinking in mid-Atlantic. Even in 1911 the deadlock was apparent; meetings were falling off in attendance, and consequently in financial benefit to the promoters; there remained, however, the knowledge for it was proved past question that the aeroplane in its then stage of development was a necessity to every army of the world. France had shown this by the more than interest taken by the French Government in what had developed into an Air Section of the French army; Germany, of course, was hypnotised by Count Zeppelin and his dirigibles, to say nothing of the Parsevals which had been proved useful military A SUMMARY TO 1914 accessories; in spite of this, it was realised in Germany that the aeroplane also had its place in military affairs. England came into the field with the military aeroplane trials of August ist to I5th, 1912, barely two months after the founding of the Royal Flying Corps. When the R.F.C. was founded and in fact up to two years after its founding in no country were the full military potentialities of the aeroplane realised; it was regarded as an accessory to cavalry for scouting more than as an independent arm; the possibilities of bombing were very vaguely considered, and the fact that it might be possible to shoot from an aeroplane was hardly considered at all. The conditions of the British Military Trials of 1912 gave to the War Office the option of purchasing for 1,000 any machine that might be awarded a prize. Machines were required, among other things, to carry a useful load of 350 Ibs. in addition to equipment, with fuel and oil for 4^ hours; thus loaded, they were required to fly for 3 hours, attaining an altitude of 4,500 feet, maintaining a height of 1,500 feet for i hour, and climbing 1,000 feet from the ground at a rate of 200 feet per minute, ' although 300 feet per minute is desirable/ They had to attain a speed of not less than 55 miles per hour in a calm, and be able to plane down to the ground in a calm from not more than 1,000 feet with engine stopped, traversing 6,000 feet horizontal distance. For those days, the landing demands were rather exacting; the machine should be able to rise without damage from long grass, clover, or harrowed land, in 100 yards in a calm, and should be able to land without damage on any cultivated ground, including rough ploughed land, and, when landing on smooth turf in a calm, be able to pull up 235 A HISTORY OF AERONAUTICS within 75 yards of the point of first touching the ground. It was required that pilot and observer should have as open a view as possible to front and flanks, and they should be so shielded from the wind as to be able to communicate with each other. These are the main provisions out of the set of conditions laid down for competitors, but a considerable amount of leniency was shown by the authorities in the competition, who obviously wished to try out every machine entered and see what were its capabilities. The beginning of the competition consisted in assembling the machines against time from road trim to flying trim. Cody's machine, which was the only one to be delivered by air, took i hour and 35 minutes to assemble; the best assembling time was that of the Avro, which was got into flying trim in 14 minutes 30 seconds. This machine came to grief with Lieut. Parke as pilot, on the yth, through landing at very high speed on very bad ground; a securing wire of the under- carriage broke in the landing, throwing the machine forward on to its nose and then over on its back. Parke was uninjured, fortunately; the damaged machine was sent off to Manchester for repair and was back again on the 1 6th of August. It is to be noted that by this time the Royal Aircraft Factory was building aeroplanes of the B.E. and F.E. types, but at the same time it is also to be noted that British military interest in engines was not sufficient to bring them up to the high level attained by the planes, and it is notorious that even the outbreak of war found England incapable of providing a really satisfactory aero engine. In the 1912 Trials, the only machines which actually completed all their tests were the Cody 236 A SUMMARY TO 1914 biplane, the French Deperdussin, the Hanriot, two Bleriots and a Maurice Farman. The first prize of 4,000, open to all the world, went to F. S. Cody's British-built biplane, which complied with all the conditions of the competition and well earned its official acknowledgment of supremacy. The machine climbed at 280 feet per minute and reached a height of 5,000 feet, while in the landing test, in spite of its great weight and bulk, it pulled up on grass in 56 yards. The total weight was 2,690 Ibs. when fully loaded, and the total area of supporting surface was 500 square feet; the motive power was supplied by a six-cylinder 120 horse- power Austro-Daimler engine. The second prize was taken by A. Deperdussin for the French-built Deper- dussin monoplane. Cody carried off the only prize awarded for a British-built plane, this being the sum of 1,000, and consolation prizes of $oo each were awarded to the British Deperdussin Company and The British and Colonial Aeroplane Company, this latter soon to become famous as makers of the Bristol aeroplane, of which the war honours are still fresh in men's minds. While these trials were in progress Audemars accomplished the first flight between Paris and Berlin, setting out from Issy early in the morning of August 1 8th, landing at Rheims to refill his tanks within an hour and a half, and then coming into bad weather which forced him to land successively at Mezieres, Laroche, Bochum, and finally nearly Gersenkirchen, where, owing to a leaky petrol tank, the attempt to win the prize offered for the first flight between the two capitals had to be abandoned after 300 miles had been covered, as the time limit was definitely exceeded. 237 A HISTORY OF AERONAUTICS Audemars determined to get through to Berlin, and set off at 5 in the morning of the 1 9th, only to be brought down by fog; starting off again at 9.15 he landed at Hanover, was off again at 1.35, and reached the Johannisthal aerodrome in the suburbs of Berlin at 6.48 that evening. As early as 1910 the British Government possessed some ten aeroplanes, and in 1911 the force developed into the Army Air Battalion, with the aeroplanes under the control of Major J. H. Fulton, R.F.A. Toward the end of 1911 the Air Battalion was handed over to (then) Brig.-Gen. D. Henderson, Director of Military Training. On June 6th, 1912, the Royal Flying Corps was established with a military wing under Major F. H. Sykes and a naval wing under Commander C. R. Samson. A joint Naval and Military Flying School was established at Upavon with Captain Godfrey M. Paine, R.N., as Commandant and Major Hugh Trenchard as Assistant Commandant. The Royal Aircraft Factory brought out the B.E. and F.E. types of biplane, admittedly superior to any other British design of the period, and an Aircraft Inspection Department was formed under Major J. H. Fulton. The military wing of the R.F.C. was equipped almost entirely with machines of Royal Aircraft Factory design, but the Navy preferred to develop British private enterprise by buying machines from private firms. On July ist, 1914, the establishment of the Royal Naval Air Service marked the definite separation of the military and naval sides of British aviation, but the Central Flying School at Upavon continued to train pilots for both services. It is difficult at this length of time, so far as the military wing was concerned, to do full justice to the 238 A SUMMARY TO 1914 spade work done by Major-General Sir David Henderson in the early days. Just before war broke out, British military air strength consisted officially of eight squadrons, each of 1 2 machines and 1 3 in reserve, with the necessary complement of road transport. As a matter of fact, there were three complete squadrons and a part of a fourth which constituted the force sent to France at the outbreak of war. The value of General Henderson's work lies in the fact that, in spite of official stinginess and meagre supplies of every kind, he built up a skeleton organisation so elastic and so well thought out that it conformed to war requirements as well as even the German plans fitted in with their aerial needs. On the 4th of August, 1914, the nominal British air strength of the military wing was 179 machines. Of these, 82 machines proceeded to France, landing at Amiens and flying to Maubeuge to play their part in the great retreat with the British Expeditionary Force, in which they suffered heavy casualties both in personnel and machines. The history of their exploits, however, belongs to the War period. The development of the aeroplane between 1912 and 1914 can be judged by comparison of the require- ments of the British War Office in 1912 with those laid down in an official memorandum issued by the War Office in February, 1914. This latter called for a light scout aeroplane, a single-seater, with % fuel capacity to admit of 300 miles range and a speed range of from 50 to 85 miles per hour. It had to be able to climb 3,500 feet in five minutes, and the engine had to be so constructed that the pilot could start it without assistance. At the same time, a heavier type of machine for reconnaissance work was called for, carrying fuel 239 A HISTORY OF AERONAUTICS for a 200 mile flight with a speed range of between 35 and 60 miles per hour, carrying both pilot and observer. It was to be equipped with a wireless telegraphy set, and be capable of landing over a 30 foot vertical obstacle and coming to rest within a hundred yards' distance from the obstacle in a wind of not more than 15 miles per hour. A third requirement was a heavy type of fighting aeroplane accommodating pilot and gunner with machine gun and ammunition, having a speed range of between 45 and 75 miles per hour and capable of climbing 3,500 feet in 8 minutes. It was required to carry fuel for a 300 mile flight and to give the gunner a clear field of fire in every direction up to 30 degrees on each side of the line of flight. Comparison of these specifications with those of the 1912 trials will show that although fighting, scouting, and reconnaissance types had been defined, the development of performance compared with the marvellous development of the earlier years of achieved flight was small. Yet the records of those years show that here and there an outstanding design was capable of great things. On the 9th September, 1912, Vedrines, flying a Deperdussin monoplane at Chicago, attained a speed of 105 miles an hour. On August I2th G. de Havilland took a passenger to a height of 10,560 feet over Salisbury Plain, flying a B.E. biplane with a 70 horse-power Renault engine. The work of de Havilland may be said to have been the principal influence in British military aeroplane design, and there is no doubt that his genius was in great measure responsible for the excellence of the early B.E. and F.E. types. On the 3ist May, 1913, H. G. Hawker, flying at Brooklands, reached a height of 1 1,450 feet on a Sopwith 240 A SUMMARY TO 1914 biplane engined with an 80 horse-power Gnome engine. On June i6th, with the same type of machine and engine, he achieved 12,900 feet. On the 2nd October, in the same year, a Grahame White biplane with 120 horse-power Austro-Daimler engine, piloted by Louis Noel, made a flight of just under 20 minutes carrying 9 passengers. In France a Nieuport monoplane piloted by G. Legagneaux attained a height of 6,120 metres, or just over 20,070 feet, this being the world's height record. It is worthy of note that of the world's aviation records as passed by the International Aeronautical Federation up to June 3oth, 1914, only one, that of Noel, is credited to Great Britain. Just as records were made abroad, with one exception, so were the really efficient engines. In England there was the Green engine, but the outbreak of war found the Royal Flying Corps with 80 horse-power Gnomes, 70 horse-power Renaults, and one or two Antoinette motors, but not one British, while the Royal Naval Air Service had got 20 machines with engines of similar origin, mainly land planes in which the wheeled under- carriages had been replaced by floats. France led in development, and there is no doubt that at the outbreak of war, the French military aeroplane service was the best in the world. It was mainly composed of Maurice Farman two-seater biplanes and Bleriot monoplanes the latter type banned for a period on account of a number of serious accidents that took place in 1912. America had its Army Aviation School, and employed Burgess-Wright and Curtiss machines for the most part. In the pre-war years, once the Wright Brothers had accomplished their task, America's chief accomplish- ment consisted in the development of the * Flying 241 A HISTORY OF AERONAUTICS Boat,' alternatively named with characteristic American clumsiness, * The Hydro-Aeroplane/ In February of 1911, Glenn Curtiss attached a float to a machine similar to that with which he won the first Gordon- Bennett Air Contest and made his first flying boat experiment. From this beginning he developed the boat form of body which obviated the use and troubles of floats his hydroplane became its own float. Mainly owing to greater engine reliability the duration records steadily increased. By September of 1912 Fourny, on a Maurice Farman biplane, was able to accomplish a distance of 628 miles without a landing, remaining in the air for 13 hours 17 minutes and just over 57 seconds. By 1914 this was raised by the German aviator, Landemann, to 21 hours 48! seconds. The nature of this last record shows that the factors in such a record had become mere engine endurance, fuel capacity, and capacity of the pilot to withstand air conditions for a prolonged period, rather than any exceptional flying skill. Let these years be judged by the records they produced, and even then they are rather dull. The glory of achievement such as characterised the work of the Wright Brothers, of Bleriot, and of the giants of the early days, had passed; the splendid courage, the patriotism and devotion of the pilots of the War period had not yet come to being. There was progress, past question, but it was mechanical, hardly ever inspired. The study of climatic conditions was definitely begun and aeronautical metereology came to being, while another development already noted was the fitting of wireless telegraphy to heavier-than-air machines, as instanced in the British War Office specification of 242 CJ w CD o c 03 A SUMMARY TO 1914 February, 1914. These, however, were inevitable; it remained for the War to force development beyond the inevitable, producing in five years that which under normal circumstances might easily have occupied fifty the aeroplane of to-day; for, as already remarked, there was a deadlock, and any survey that may be made of the years 1912-1914, no matter how superficial, must take it into account with a view to retaining correct perspective in regard to the development of the aeroplane. There is one story of 1914 that must be included, however briefly, in any record of aeronautical achieve- ment, since it demonstrates past question that to Professor Langley really belongs the honour of having achieved a design which would ensure actual flight, although the series of accidents which attended his experiments gave to the Wright Brothers the honour -)f first leaving the earth and descending without accident in a power-driven heavier-than-air machine. In March, 1914, Glenn Curtiss was invited to send a flying boat to Washington for the celebration of ' Langley Day,' when he remarked, * I would like to put the Langley aeroplane itself in the air.' In consequence of this remark, Secretary Walcot of the Smithsonian Institution authorised Curtiss to re-canvas the original Langley aeroplane and launch it either under its own power or with a more recent engine and propeller. Curtiss completed this, and had the machine ready on the shores of Lake Keuka, Hammondsport, N.Y., by May. The main object of these renewed trials was to show whether the original Langley machine was capable of sustained free flight with a pilot, and a secondary object was to determine more fully the advantages of the tandem monoplane type; thus the aeroplane was first 243 A HISTORY OF AERONAUTICS flown as nearly as possible in its original condition, and then with such modifications as seemed desirable. The only difference made for the first trials consisted in fitting floats with connecting trusses; the steel main frame, wings, rudders, engine, and propellers were substantially as they had been in 1903. The pilot had the same seat under the main frame and the same general system of control. He could raise or lower the craft by moving the rear rudder up and down; he could steer right or left by moving the vertical rudder. He had no ailerons nor wing-warping mechanism, but for lateral balance depended on the dihedral angle of the wings and upon suitable movements of his weight or of the vertical rudder. After the adjustments for actual flight had been made in the Curtiss factory, according to the minute descriptions contained in the Langley Memoir on Mechanical Flight, the aeroplane was taken to the shore of Lake Keuka, beside the Curtiss hangars, and assembled for launching. On a clear morning (May 28th) and in a mild breeze, the craft was lifted on to the water by a dozen men and set going, with Mr Curtiss at the steering wheel, esconced in the little boat- shaped car under the forward part of the frame. The four- winged craft, pointed somewhat across the wind, went skimming over the wavelets, then automatically headed into the wind, rose in level poise, soared grace- fully for 150 feet, and landed softly on the water near the shore. Mr Curtiss asserted that he could have flown farther, but, being unused to the machine, imagined that the left wings had more resistance than the right. The truth is that the aeroplane was perfectly balanced in wing resistance, but turned on the water 244 A SUMMARY TO 1914 like a weather vane, owing to the lateral pressure on its big rear rudder. Hence in future experiments this rudder was made turnable about a vertical axis, as well as about the horizontal axis used by Langley. Hence- forth the little vertical rudder under the frame was kept fixed and inactive. 1 That the Langley aeroplane was subsequently fitted with an 80 horse-power Curtiss engine and successfully flown is of little interest in such a record as this, except for the fact that with the weight nearly doubled by the new engine and accessories the machine flew successfully, and demonstrated the perfection of Langley's design by standing the strain. The point that is of most importance is that the design itself proved a success and fully vindicated Langley's work. At the same time, it would be unjust to pass by the fact of the flight without according to Curtiss due recognition of the way in which he paid tribute to the genius of the pioneer by these experiments. * Smithsonian Publications No. 2329. 24* XIX THE WAR PERIOD- FULL record of aeronautical progress and of the accom- plishments of pilots in the years of the War would demand not merely a volume, but a complete library, and even then it would be barely possible to pay full tribute to the heroism of pilots of the war period. There are names connected with that period of which the glory will not fade, names such as Bishop, Guynemer, Boelcke, Ball, Fonck, Immelmann, and many others that spring to mind as one recalls the * Aces * of the period. In addition to the pilots, there is the stupendous develop- ment of the machines stupendous when the length of the period in which it was achieved is considered. The fact that Germany was best prepared in the matter of heavier-than-air service machines in spite of the German faith in the dirigible is one more item of evidence as to who forced hostilities. The Germans came into the field with well over 600 aeroplanes, mainly two-seaters of standardised design, and with factories back in the Fatherland turning out sufficient new machines to make good the losses. There were a few single-seater scouts built for speed, and the two-seater machines were all fitted with cameras and bomb- dropping gear. Manoeuvres had determined in the German mind what should be the uses of the air fleet; there was photography of fortifications and field works ; 246 THE WAR PERIOD I signalling by Very lights; spotting for the guns, and scouting for news of enemy movements. The methodical German mind had arranged all this before- hand, but had not allowed for the fact that opponents might take counter-measures which would upset the over-perfect mechanism of the air service just as effectually as the great march on Paris was countered by the genius of Joffre. The French Air Force at the beginning of the War consisted of upwards of 600 machines. These, unlike the Germans, were not standardised, but were of many and diverse types. In order to get replacements quickly enough, the factories had to work on the designs they had, and thus for a long time after the outbreak of hostilities standardisation was an impossibility. The versatility of a Latin race in a measure compensated for this; from the outset, the Germans tried to over- whelm the French Air Force, but failed, since they had not the numerical superiority, nor this equally a determining factor the versatility and resource of the French pilots. They calculated on a 50 per cent superiority to ensure success; they needed more nearly 400 per cent, for the German fought to rule, avoiding risks whenever possible, and definitely instructed to save both machines and pilots wherever possible. French pilots, on the other hand, ran all the risks there were, got news of German movements, bombed the enemy, and rapidly worked up a very respectable anti- aircraft force which, whatever it may have accomplished in the way of hitting German planes, got on the German pilots* nerves. It has already been detailed how Britain sent over 82 planes as its contribution to the military aerial force H.A. 247 R A HISTORY OF AERONAUTICS of 1914. These consisted of Farman, Caudron, and Short biplanes, together with Bleriot, Deperdussin and Nieuport monoplanes, certain R.A.F. types, and other machines of which even the name barely survives the resourceful Yankee entitles them ' orphans/ It is on record that the work of providing spares might have been rather complicated but for the fact that there were none. There is no doubt that the Germans had made study of aerial military needs just as thoroughly as they had perfected their ground organisation. Thus there were 21 illuminated aircraft stations in Germany before the War, the most powerful being at Weimar, where a revolving electric flash of over 27 million candle-power was located. Practically all German aeroplane tests in the period immediately preceding the War were of a military nature, and quite a number of reliability tests were carried out just on the other side of the French frontier. Night flying and landing were standardised items in the German pilot's course of instruction while they were still experimental in other countries, and a system of signals was arranged which rendered the instructional course as perfect as might be. The Belgian contribution consisted of about twenty machines fit for active service and another twenty which were more or less useful as training machines. The material was mainly French, and the Belgian pilots used it to good account until German numbers swamped them. France, and to a small extent England, kept Belgian aviators supplied with machines throughout the War. The Italian Air Fleet was small, and consisted of 248 THE WAR PERIOD I French machines together with a percentage of planes of Italian origin, of which the design was very much a copy of French types. It was not until the War was nearing its end that the military and naval services relied more on the home product than on imports. This does not apply to engines, however, for the F.I.A.T. and S.C.A.T. were equal to practically any engine of Allied make, both in design and construction. Russia spent vast sums in the provision of machines : the giant Sikorsky biplane, carrying four 100 horse- power Argus motors, was designed by a young Russian engineer in the latter part of 1913, and in its early trials it created a world's record by carrying seven passengers for i hour 54 minutes. Sikorsky also designed several smaller machines, tractor biplanes on the lines of the British B.E. type, which were very successful. These were the only home productions, and the imports consisted mainly of French aeroplanes by the hundred, which got as far as the docks and railway sidings and stayed there, while German influence and the corruption that ruined the Russian Army helped to lose the War. A few Russian aircraft factories were got into operation as hostilities proceeded, but their products were negli- gible, and it is not on record that Russia ever learned to manufacture a magneto. The United States paid tribute to British efficiency by adopting the British system of training for its pilots ; 500 American cadets were trained at the School of Military Aeronautics at Oxford, in order to form a nucleus for the American aviation schools which were subsequently set up in the United States and in France. As regards production of craft, the designing of the Liberty engine and building of over 20,000 aeroplanes 249 A HISTORY OF AERONAUTICS within a year proves that America is a manufacturing country, even under the strain of war. There were three years of struggle for aerial supremacy, the combatants being England and France against Germany, and the contest was neck and neck all the way. Germany led at the outset with the standardised two-seater biplanes manned by pilots and observers, whose training was superior to that afforded by any other nation, while the machines themselves were better equipped and fitted with accessories. All the early German aeroplanes were designated Taube by the uninitiated, and were formed with swept-back, curved wings very much resembling the wings of a bird. These had obvious disadvantages, but the standardisation of design and mass production of the German factories kept them in the field for a consider- able period, and they flew side by side with tractor biplanes of improved design. For a little time, the Fokker monoplane became a definite threat both to French and British machines. It was an improvement on the Morane French monoplane, and with a high- powered engine it climbed quickly and flew fast, doing a good deal of damage for a brief period of 1915. Allied design got ahead of it and finally drove it out of the air. German equipment at the outset, which put the Allies at a disadvantage, included a hand-operated magneto engine-starter and a small independent screw which, mounted on one of the main planes, drove the dynamo used for the wireless set. Cameras were fitted on practically every machine; equipment included accurate compasses and pressure petrol gauges, speed and height recording instruments, bomb-dropping 250 THE WAR PERIOD I fittings and sectional radiators which facilitated repairs and gave maximum engine efficiency in spite of variations of temperature. As counter to these, the Allied pilots had resource amounting to impudence. In the early days they carried rifles and hand grenades and automatic pistols. They loaded their machines down, often at their own expense, with accessories and fittings until their aeroplanes earned their title of Christmas trees. They played with death in a way that shocked the average German pilot of the War's early stages, declining to fight according to rule and indulging in the individual duels of the air which the German hated. As Sir John French put it in one of his reports, they established a personal ascendancy over the enemy, and in this way compensated for their inferior material. French diversity of design fitted in well with the initiative and resource displayed by the French pilots. The big Caudron type was the ideal bomber of the early days; Farman machines were excellent for recon- naissance and artillery spotting; the Bleriots proved excellent as fighting scouts and for aerial photography; the Nieuports made good fighters, as did the Spads, both being very fast craft, as were the Morane-Saulnier monoplanes, while the big Voisin biplanes rivalled the Caudron machines as bombers. The day of the Fokker ended when the British B.E.2.C. aeroplane came to France in good quantities, and the F.E. type, together with the De Havilland machines, rendered British aerial superiority a certainty. Germany's best reply this was about 1916 was the Albatross biplane, which was used by Captain Baron von Richthofen for his famous travelling circus, manned by German star pilots and sent to various parts 251 A HISTORY OF AERONAUTICS of the line to hearten up German troops and aviators after any specially bad strafe. Then there were the Aviatik biplane and the Halberstadt righting scout, a cleanly built and very fast machine with a powerful engine with which Germany tried to win back superiority in the third year of the War, but Allied design kept about three months ahead of that of the enemy, once the Fokker had been mastered, and the race went on. Spads and Bristol fighters, Sopwith scouts and F.E.'s played their part in the race, and design was still advancing when peace came. The giant twin-engined Handley-Page bomber was tried out, proved efficient, and justly considered better than anything of its kind that had previously taken the field. Immediately after the conclusion of its trials, a specimen of the type was delivered intact at Lille for the Germans to copy, the innocent pilot responsible for the delivery doing some great disservice to his own cause. The Gotha Wagon-Fabrik Firm immediately set to work and copied the Handley-Page design, producing the great Gotha bombing machine which was used in all the later raids on England as well as for night work over the Allied lines. How the War advanced design may be judged by comparison of the military requirements given for the British Military Trials of 1912, with performances of 1916 and 1917, when the speed of the faster machines had increased to over 150 miles an hour and Allied machines engaged enemy aircraft at heights ranging up to 22,000 feet. All pre-war records of endurance, speed, and climb went by the board, as the race for aerial superiority went on. Bombing brought to being a number of crude 252 THE WAR PERIOD I devices in the first year of the War. Allied pilots of the very early days carried up bombs packed in a small box and threw them over by hand, while, a little later, the bombs were strung like apples on wings and under- carriage, so that the pilot who did not get rid of his load before landing risked an explosion. Then came a properly designed carrying apparatus, crude but fairly efficient, and with 1916 development had proceeded as far as the proper bomb-racks with releasing gear. Reconnaissance work developed, so that fighting machines went as escort to observing squadrons and scouting operations were undertaken up to 100 miles behind the enemy lines; out of this grew the art of camouflage, when ammunition dumps were painted to resemble herds of cows, guns were screened by foliage or painted to merge into a ground scheme, and many other schemes were devised to prevent aerial observation. Troops were moved by night for the most part, owing to the keen eyes of the air pilots and the danger of bombs, though occasionally the aviator had his chance. There is one story concerning a British pilot who, on returning from a reconnaissance flight, observed a German Staff car on the road under him; he descended and bombed and machine-gunned the car until the German General and his chauffeur abandoned it, took to their heels, and ran like rabbits. Later still, when Allied air superiority was assured, there came the phase of machine-gunning bodies of enemy troops from the air. Disregarding all anti- aircraft measures, machines would sweep down and throw battalions into panic or upset the military traffic along a road, demoralising a battery or a transport 253 A HISTORY OF AERONAUTICS train and causing as much damage through congestion of traffic as with their actual machine-gun fire. Aerial photography, too, became a fine art; the ordinary long focus cameras were used at the outset with automatic plate changers, but later on photographing aeroplanes had cameras of wide angle lens type built into the fuselage. These were very simply operated, one lever registering the exposure and changing the plate. In many cases, aerial photographs gave information which the human eye had missed, and it is noteworthy that photographs of ground showed when troops had marched over it, while the aerial observer was quite unable to detect the marks left by their passing. Some small mention must be made of seaplane activities, which, round the European coasts involved in the War, never ceased. The submarine campaign found in the spotting seaplane its greatest deterrent, and it is old news now how even the deeply submerged submarines were easily picked out for destruction from a height and the news wirelessed from seaplane to destroyer, while in more than one place the seaplane itself finished the task by bomb dropping. It was a seaplane that gave Admiral Beatty the news that the whole German Fleet was out before the Jutland Battle, news which led to a change of plans that very nearly brought about the destruction of Germany's naval power. For the most part, the seaplanes of the War period were heavier than the land machines and, in the opinion of the land pilots, were slow and clumsy things to fly. This was inevitable, for their work demanded more solid building and greater reliability. To put the matter into Hibernian phrase, a forced landing at sea is a much more serious matter than on the ground. Thus 254 THE WAR PERIOD I there was need for greater engine power, bigger wing- spread to support the floats, and fuel tanks of greater capacity. The flying boats of the later War period carried considerable crews, were heavily armed, capable of withstanding very heavy weather, and carried good loads of bombs on long cruises. Their work was not all essentially seaplane work, for the R.N.A.S. was as well known as hated over the German airship sheds in Belgium and along the Flanders coast. As regards other theatres of War, they rendered valuable service from the Dardanelles to the Rufiji River, at this latter place forming a principal factor in the destruction of the cruiser Konigsberg. Their spotting work at the Dardanelles for the battleships was reponsible for direct hits from 15 in. guns on invisible targets at ranges of over 12,000 yards. Seaplane pilots were bombing specialists, including among their targets army headquarters, ammunition dumps, railway stations, submarines and their bases, docks, shipping in German harbours, and the German Fleet at Wilhelmshaven. Dunkirk, a British seaplane base, was a sharp thorn in the German side. Turning from consideration of the various services to the exploits of the men composing them, it is difficult to particularise. A certain inevitable prejudice even at this length of time leads one to discount the valour of pilots in the German Air Service, but the names of Boelcke, von Richthofen, and Immelmann recur as proof of the courage that was not wanting in the enemy ranks, while, however much we may decry the Gotha raids over the English coast and on London, there is no doubt that the men who undertook these raids were not deficient in the form of bravery that is of more A HISTORY OF AERONAUTICS value than the unthinking valour of a minute which, observed from the right quarter, wins a military decoration. Yet the fact that the Allied airmen kept the air at all in the early days proved on which side personal superiority lay, for they were outnumbered, out-manoeuvred, and faced by better material than any that they themselves possessed; yet they won their rights or died. The stories of their deeds are endless; Bishop, flying alone and meeting seven German machines and crashing four; the battle of May 5th, 1915, when five heroes fought and conquered twenty-seven German machines, ranging in altitude, between 12,000 and 3,000 feet, and continuing the extraordinary struggle from five until six in the evening. Captain Aizlewood, attacking five enemy machines with such reckless speed that he rammed one and still reached his aerodrome safely these are items in a long list of feats of which the character can only be realised when it is fully comprehended that the British Air Service accounted for some 8,000 enemy machines in the course of the War. Among the French there was Captain Guynemer, who at the time of his death had brought down fifty-four enemy machines, in addition to many others of which the destruction could not be officially confirmed. There was Fonck, who brought down six machines in one day, four of them within two minutes. There are incredible stories, true as incredible, of shattered men carrying on with their work in absolute disregard of physical injury. Major Brabazon Rees, V.C., engaged a big German battleplane in September of 1915 and, single-handed, forced his enemy out of action. Later in his career, with a serious wound in 255 THE WAR PERIOD I the thigh from which blood was pouring, he kept up a fight with an enemy formation until he had not a round of ammunition left, and then returned to his aerodrome to get his wound dressed. Lieutenants Otley and Dunning, flying in the Balkans, engaged a couple of enemy machines and drove them off, but not until their petrol tank had got a hole in it and Dunning was dangerously wounded in the leg. Otley improvised a tourniquet, passed it to Dunning, and, when the latter had bandaged himself, changed from the observer's to the pilot's seat, plugged the bullet hole in the tank with his thumb and steered the machine home. These are incidents; the full list has not been, and can never be recorded, but it goes to show that in the pilot of the War period there came to being a new type of humanity, a product of evolution which fitted a certain need. Of such was Captain W est, who, engaging hostile troops, was attacked by seven machines. Early in the engagement, one of his legs was partially severed by an explosive bullet and fell powerless into the controls, rendering the machine for the time unmanageable. Lifting his disabled leg, he regained control of the machine, and although wounded in the other leg, he manoeuvred his machine so skilfully that his observer was able to get several good bursts into the enemy machines, driving them away. Then, desperately wounded as he was, Captain West brought the machine over to his own lines and landed safely. He fainted from loss of blood and exhaustion, but on regaining consciousness, insisted on writing his report. Equal to this was the exploit of Captain Barker, who, in aerial combat, was wounded in the right and left thigh and had his left arm shattered, subsequently bringing 257 A HISTORY OF AERONAUTICS down an enemy machine in flames, and then breaking through another hostile formation and reaching the British lines. In recalling such exploits as these, one is tempted on and on, for it seems that the pilots rivalled each other in their devotion to duty, this not confined to British aviators, but common practically to all services. Sufficient instances have been given to show the nature of the work and the character of the men who did it. The rapid growth of aerial effort rendered it necessary in January of 1915 to organise the Royal Flying Corps into separate wings, and in October of the same year it was constituted in Brigades. In 1916 the Air Board was formed, mainly with the object of co-ordinating effort and ensuring both to the R.N.A.S. and to the R.F.C. adequate supplies of material as far as construction admitted. Under the presidency of Lord Cowdray, the Air Board brought about certain reforms early in 1917, and in November of that year a separate Air Ministry was constituted, separating the Air Force from both Navy and Army, and rendering it an independent force. On April ist, 1918, the Royal Air Force came into existence, and unkind critics in the Royal Flying Corps remarked on the appropriate- ness of the date. At the end of the War, the personnel of the Royal Air Force amounted to 27,906 officers, and 263,842 other ranks. Contrast of these figures with the number of officers and men who took the field in 1914 is indicative of the magnitude of British aerial effort in the War period. 258 XX THE WAR PERIOD II THERE was when War broke out no realisation on the part of the British Government of the need for encouraging the enterprise of private builders, who carried out their work entirely at their own cost. The importance of a supply of British-built engines was realised before the War, it is true, and a competition was held in which a prize of 5,000 was offered for the best British engine, but this awakening was so late that the R.F.C. took the field without a single British power plant. Although Germany woke up equally late to the need for home produced aeroplane engines, the experience gained in building engines for dirigibles sufficed for the production of aeroplane power plants. The Mercedes filled all requirements together with the Benz and the Maybach. There was a 225 horse- power Benz which was very popular, as were the 100 horse-power and 170 horse-power Mercedes, the last mentioned fitted to the Aviatik biplane of 1917. The Uberursel was a copy of the Gnome and supplied the need for rotary engines. In Great Britain there were a number of aeroplane constructing firms that had managed to emerge from the lean years 1912-1913 with sufficient manufacturing plant to give a hand in making up the leeway of con- struction when War broke out. Gradually the 259 A HISTORY OF AERONAUTICS motor-car firms came in, turning their body-building depart- ments to plane and fuselage construction, which enabled them to turn out the complete planes engined and ready for the field. The coach-building trade soon joined in and came in handy as propeller makers; big upholstering and furniture firms and scores of concerns that had never dreamed of engaging in aeroplane construction were busy on supplying the R.F.C. By 1915 hundreds of different firms were building aero- planes and parts; by 1917 the number had increased to over 1,000, and a capital of over a million pounds for a firm that at the outbreak of War had employed a score or so of hands was by no means uncommon. Women and girls came into the work, more especially in plane construction and covering and doping, though they took their place in the engine shops and proved successful at acetylene welding and work at the lathes. It was some time before Britain was able to provide its own magnetos, for this key industry had been left in the hands of the Germans up to the outbreak of War, and the ' Bosch ' was admittedly supreme even now it has never been beaten, and can only be equalled, being as near perfection as is possible for a magneto. One of the great inventions of the War was the synchronisation of engine-timing and machine gun, which rendered it possible to fire through the blades of a propeller without damaging them, though the growing efficiency of the aeroplane as a whole and of its armament is a thing to marvel at on looking back and considering what was actually accomplished. As the efficiency of the aeroplane increased, so anti-aircraft guns and range-finding were improved. Before the War an aeroplane travelling at full speed was reckoned 260 THE WAR PERIOD II perfectly safe at 4,000 feet, but, by the first month of 1915, the safe height had gone up to 9,000 feet, 7,000 feet being the limit of rifle and machine gun bullet trajectory; the heavier guns were not sufficiently mobile to tackle aircraft. At that time, it was reckoned that effective aerial photography ceased at 6,000 feet, while bomb-dropping from 7,000-8,000 feet was reckoned uncertain except in the case of a very large target. The improvement in anti-aircraft devices went on, and by May of 1916, an aeroplane was not safe under 15,000 feet, while anti-aircraft shells had fuses capable of being set to over 20,000 feet, and bombing from 15,000 and 16,000 feet was common. It was not till later that Allied pilots demonstrated the safety that lies in flying very near the ground, this owing to the fact that, when flying swiftly at a very low altitude, the machine is out of sight almost before it can be aimed at. The Battle of the Somme and the clearing of the air preliminary to that operation brought the fighting aeroplane pure and simple with them. Formations of fighting planes preceded reconnaissance craft in order to clear German machines and observation balloons out of the sky and to watch and keep down any further enemy formations that might attempt to interfere with Allied observation work. The German reply to this consisted in the formation of the Flying Circus, of which Captain Baron von Richthofen's was a good example. Each circus consisted of a large formation of speedy machines, built specially for fighting and manned by the best of the German pilots. These were sent to attack at any point along the line where the Allies had got a decided superiority. The trick flying of pre-war days soon became an 261 A HISTORY OF AERONAUTICS everyday matter; Pegoud astonished the aviation world before the War by first looping the loop, but, before three years of hostilities had elapsed, looping was part of the training of practically every pilot, while the spinning nose dive^ originally considered fatal, was mastered, and the tail slide, which consisted of a machine rising nose upward in the air and falling back on its tail, became one of the easiest ' stunts ' in the pilot's repertoire. Inherent stability was gradually improved, and, from 1916 onward, practically every pilot could carry on with his machine-gun or camera and trust to his machine to fly itself until he was free to attend to it. There was more than one story of a machine coming safely to earth and making good landing on its own account with the pilot dead in his cock-pit. Toward the end of the War, the Independent Air Force was formed as a branch of the R.A.F. with a view to bombing German bases and devoting its attention exclusively to work behind the enemy lines. Bombing operations were undertaken by the R.N.A.S. as early as 1914-1915 against Cuxhaven, Dusseldorf, and Friedrichshavn, but the supply of material was not sufficient to render these raids continuous. A separate Brigade, the 8th, was formed in 1917 to harass the German chemical and iron industries, the base being in the Nancy area, and this policy was found so fruitful that the Independent Force was constituted on the 8th June, 1918. The value of the work accomplished by this force is demonstrated by the fact that the German High Command recalled twenty fighting squadrons from the Western front to counter its activities, and, in addition, took troops away from the fighting line in large numbers for manning anti-aircraft batteries and 262 THE WAR PERIOD II searchlights. The German press of the last year of the War is eloquent of the damage done in manufacturing areas by the Independent Force, which, had hostilities continued a little longer, would have included Berlin in its activities. Formation flying was first developed by the Germans, who made use of it in the daylight raids against England in 1917. Its value was very soon realised, and the V formation of wild geese was adopted, the leader taking the point of the V and his squadron following on either side at different heights. The air currents set up by the leading machines were thus avoided by those in the rear, while each pilot had a good view of the leader's bombs, and were able to correct their own aim by the bursts, while the different heights at which they flew rendered anti-aircraft gun practice less effective. Further, machines were able to afford mutual protection to each other and any attacker would be met by machine- gun fire from three or four machines firing on him from different angles and heights. In the later formations single-seater fighters flew above the bombers for the purpose of driving off hostile craft. Formation flying was not fully developed when the end of the War brought stagnation in place of the rapid advance in the strategy and tactics of military air work. H.A. 263 XXI RECONSTRUCTION THE end of the War brought a pause in which the multitude of aircraft constructors found themselves faced with the possible complete stagnation of the industry, since military activities no longer demanded their services and the prospects of commercial flying were virtually nil. That great factor in commercial success, cost of plant and upkeep, had received no consideration whatever in the War period, for armies do not count cost. The types of machines that had evolved from the War were very fast, very efficient, and very expensive, although the bombers showed promise of adaptation to commercial needs, and, so far as other machines were concerned, America had already proved the possibilities of mail-carrying by maintaining a mail service even during the War period. A civil aviation deparanent of the Air Ministry was formed in February of 1919 with a Controller General of Civil Aviation at the head. This was organised into four branches, one dealing with the survey and preparation of air routes for the British Empire, one organising meteorological and wireless telegraphy services, one dealing with the licensing of aerodromes, machines for passenger or goods carrying and civilian pilots, and one dealing with publicity and transmission of information generally. A special Act of Parliament 264 RECONSTRUCTION entitled * The Air Navigation Acts, 1911-1919,' was passed on February 27th, and commercial flying was officially permitted from May ist, 1919. Meanwhile the great event of 1919, the crossing of the Atlantic by air, was gradually ripening to per- formance. In addition to the rigid airship, R-34, eight machines entered for this flight, these being a Short seaplane, Handley-Page, Martinsyde, Vickers- Vimy, and Sopwith aeroplanes, and three American flying boats, N.C.I, N.C.j, and N.C. 4 . The Short seaplane was the only one of the eight which proposed to make the journey westward; in flying from England to Ireland, before starting on the long trip to Newfound- land, it fell into the sea off the coast of Anglesey, and so far as it was concerned the attempt was abandoned. The first machines to start from the Western end were the three American seaplanes, which on the morning of May 6th left Trepassy, Newfoundland, on the 1,380 mile stage to Horta in the Azores. N.C.I and N.C.3 gave up the attempt very early, but N.C.4, piloted by Lieut.-Commander Read, U.S.N., made Horta on May iyth and made a three days* halt. On the 2oth, the second stage of the journey to Ponta Delgada, a further 190 miles, was completed and a second halt of a week was made. On the 27th, the machine left for Lisbon, 900 miles distant, and completed the journey in a day. On the 3oth a further stage of 340 miles took N.C.4 on to Ferrol, and the next day the last stage of 420 miles to Plymouth was accomplished. Meanwhile, H. G. Hawker, pilot of the Sopwith biplane, together with Commander Mackenzie Grieve, R.N., his navigator, found the weather sufficiently auspicious to set out at 6.48 p.m. on Sunday, May i8th, 265 A HISTORY OF AERONAUTICS in the hope of completing the trip by the direct route before N.C.4 could reach Plymouth. They set out from Mount Pearl aerodrome, St John's, Newfoundland, and vanished into space, being given up as lost, as Hamel was lost immediately before the War in attempting to fly the North Sea. There was a week of dead silence regarding their fate, but on the following Sunday morning there was world-wide relief at the news that the plucky attempt had not ended in disaster, but both aviators had been picked up by the steamer Mary at 9.30 a.m. on the morning of the I9th, while still about 750 miles short of the conclusion of their journey. Engine failure brought them down, and they planed down to the sea close to the Mary to be picked up; as the vessel was not fitted with wireless, the news of their rescue could not be communicated until land was reached. An equivalent of half the 10,000 prize offered by the Daily Mail for the non-stop flight was presented by the paper in recognition of the very gallant attempt, and the King conferred the Air Force Cross on both pilot and navigator. Raynham, pilot of the Martinsyde competing machine, had the bad luck to crash his craft twice in attempting to start before he got outside the boundary of the aerodrome. The Handley-Page machine was withdrawn from the competition, and, attempting to fly to America, was crashed on the way. The first non-stop crossing was made on June I4th- i^th in 1 6 hours 27 minutes, the speed being just over 117 miles per hour. The machine was a Vickers-Vimy bomber, engined with two Rolls-Royce Eagle VIII's, piloted by Captain John Alcock, D.S.C., with Lieut. Arthur Whitten-Brown as navigator. The journey 266 RECONSTRUCTION was reported to be very rough, so much so at times that Captain Alcock stated that they were flying upside down, and for the greater part of the time they were out of sight of the sea. Both pilot and navigator had the honour of knighthood conferred on them at the conclusion of the journey. Meanwhile, commercial flying opened on May 8th (the official date was May ist) with a joy-ride service from Hounslow of Avro training machines. The enterprise caught on remarkably, and the company extended their activities to coastal resorts for the holiday season at Blackpool alone they took up 10,000 passengers before the service was two months old. Hendon, beginning passenger flights on the same date, went in for exhibition and passenger flying, and on June 2 ist the aerial Derby was won by Captain Gathergood on an Airco 4R machine with a Napier 450 horse-power * Lion ' engine; incidentally the speed of 129.3 miles per hour was officially recognised as constituting the world's record for speed within a closed circuit. On July iyth a Fiat B.R. biplane with a 700 horse-power engine landed at Kenley aerodrome after having made a non-stop flight of 1,100 miles. The maximum speed of this machine was 160 miles per hour, and it was claimed to be the fastest machine in existence. On August 25th a daily service between London and Paris was inaugurated by the Aircraft Manufacturing Company, Limited, who ran a machine each way each day, starting at 12.30 and due to arrive at 2.45 p.m. The Handley-Page Company began a similar service in September of 1919, but ran it on alternate days with machines capable of accommodating ten passengers. The single fare in each case was fixed 267 A HISTORY OF AERONAUTICS at 15 guineas and the parcel rate at ys. 6d. per pound. Meanwhile, in Germany, a number of passenger services had been in operation from the early part of the year; the Berlin-Weimar service was established on February 5th and Berlin-Hamburg on March ist, both for mail and passenger carrying. Berlin-Breslau was soon added, but the first route opened remained most popular, 538 flights being made between its opening and the end of April, while for March and April combined, the Hamburg-Berlin route recorded only 262 flights. All three routes were operated by a combine of German aeronautical firms entitled the Deutsche Luft Rederie. The single fare between Hamburg and Berlin was 450 marks, between Berlin and Breslau 500 marks, and between Berlin and Weimar 450 marks. Luggage was carried free of charge, but varied according to the weight of the passenger, since the combined weight of both passenger and luggage was not allowed to exceed a certain limit. In America commercial flying had begun in May of 1918 with the mail service between Washington, Philadelphia, and New York, which proved that mail carrying is a commercial possibility, and also demonstrated the remarkable reliability of the modern aeroplane by making 102 complete flights out of a possible total of 104 in November, 1918, at a cost of 0.777 of a dollar per mile. By March of 1919 the cost per mile had gone up to 1.28 dollars; the first annual report issued at the end of May showed an efficiency of 95.6 per cent and the original six aeroplanes and engines with which the service began were still in regular use. In June of 1919 an American commercial firm 268 RECONSTRUCTION chartered an aeroplane for emergency service owing to a New York harbour strike and found it so useful that they made it a regular service. The Travellers Company inaugurated a passenger flying boat service between New York and Atlantic City on July 25th, the fare, inclusive of 35 Ibs. of luggage, being fixed at 25 each way. Five flights on the American continent up to the end of 1919 are worthy of note. On December I3th, 1918, Lieut. D. Godoy of the Chilian army left Santiago, Chili, crossed the Andes at a height of 19,700 feet and landed at Mendoza, the capital of the wine-growing province of Argentina. On April 1 9th, 1919, Captain E. F. White made the first non-stop flight between New York and Chicago in 6 hours 50 minutes on a D.H.4 machine driven by a twelve-cylinder Liberty engine. Early in August Major Schroeder, piloting a French Lepere machine flying at a height of 18,400 feet, reached a speed of 137 miles per hour with a Liberty motor fitted with a super-charger. Toward the end of August, Rex Marshall, on a Thomas-Morse biplane, starting from a height of 17,000 feet, made a glide of 35 miles with his engine cut off, restarting it when at a height of 600 feet above the ground. About a month later R. Rohlfe, piloting a Curtiss triplane, broke the height record by reaching 34,610 feet. 269 XXII INTO the later months of 1919 comes the flight by Captain Ross-Smith from England to Australia and the attempt to make the Cape to Cairo voyage by air. The Australian Government had offered a prize of 10,000 for the first flight from England to Australia in a British machine, the flight to be accomplished in 720 con- secutive hours. Ross-Smith, with his brother, Lieut. Keith Macpherson Smith, and two mechanics, left Hounslow in a Vickers-Vimy bomber with Rolls-Royce engine on November I2th and arrived at Port Darwin, North Australia, on the i oth December, having completed the flight in 27 days 20 hours 20 minutes, thus having 51 hours 40 minutes to spare out of the 720 allotted hours. Early in 1920 came a series of attempts at com- pleting the journey by air between Cairo and the Cape. Out of four competitors Colonel Van Ryneveld came nearest to making the journey successfully, leaving England on a standard Vickers-Vimy bomber with Rolls-Royce engines, identical in design with the machine used by Captain Ross-Smith on the England to Australia flight. A second Vickers-Vimy was financed by the Times newspaper and a third flight was under- taken with a Handley-Page machine under the auspices of the Daily Telegraph. The Air Ministry had already prepared the route by means of three survey parties which cleared the aerodromes and landing grounds, 270 CD CD 1919-1920 dividing their journey into stages of 200 miles or less. Not one of the competitors completed the course, but in both this and Ross-Smith's flight valuable data was gained in respect of reliability of machines and engines, together with a mass of meteorological information. The Handley-Page Company announced in the early months of 1920 that they had perfected a new design of wing which brought about a twenty to forty per cent improvement in lift rate in the year. When the nature of the design was made public, it was seen to consist of a division of the wing into small sections, each with its separate lift. A few days later, Fokker, the Dutch inventor, announced the construction of a machine in which all external bracing wires are obviated, the wings being of a very deep section and self-supporting. The value of these two inventions remains to be seen so far as commercial flying is concerned. The value of air work in war, especially so far as the Colonial campaigns in which British troops are constantly being engaged is in question, was very thoroughly demonstrated in a report issued early in 1920 with reference to the successful termination of the Somaliland campaign through the intervention of the Royal Air Force, which between January 2ist and the 3ist practically destroyed the Dervish force under the Mullah, which had been a thorn in the side of Britain since 1907. Bombs and machine-guns did the work, destroying fortifications and bringing about the sur- render of all the Mullah's following, with the exception of about seventy who made their escape. Certain records both in construction and performance had characterised the post-war years, though as design advances and comes nearer to perfection, it is obvious 271 A HISTORY OF AERONAUTICS that records must get fewer and farther between. The record aeroplane as regards size at the time of its con- struction was the Tarrant triplane, which made its first and last flight on May 28th, 1919. The total loaded weight was 30 tons, and the machine was fitted with six 400 horse-power engines; almost immediately after the trial flight began, the machine pitched forward on its nose and was wrecked, causing fatal injuries to Captains Dunn and Rawlings, who were aboard the machine. A second accident of similar character was that which befell the giant seaplane known as the Felixstowe Fury, in a trial flight. This latter machine was intended to be flown to Australia, but was crashed over the water. On May 4th, 1920, a British record for flight duration and useful load was established by a commercial type Handley-Page biplane, which, carrying a load of 3,690 Ibs., rose to a height of 13,999 ^ eet an< ^ remained in the air for I hour 20 minutes. On May 27th the French pilot, Fronval, flying at Villacoublay in a Morane- Saulnier type of biplane with Le Rhone motor, put up an extraordinary type of record by looping the loop 962 times in 3 hours 52 minutes 10 seconds. Another record of the year of similar nature was that of two French fliers, Boussotrot and Bernard, who achieved a continuous flight of 24 hours 19 minutes 7 seconds, beating the pre-war record of 21 hours 48! seconds set up by the German pilot, Landemann. Both these records are likely to stand, being in the nature of freaks, which demonstrate little beyond the reliability of the machine and the capacity for endurance on the part of its pilots. Meanwhile, on February I4th, Lieuts. Masiero and Ferrarin left Rome on S.V.A. Ansaldo V. machines 272 fitted with 220 horse-power S.V.A. motors. On May 3oth they arrived at Tokio, having flown by way of Bagdad, Karachi, Canton, Pekin, and Osaka. Several other competitors started, two of whom were shot down by Arabs in Mesopotamia. Considered in a general way, the first two years after the termination of the Great European War form a period of transition in which the commercial type of aeroplane was gradually evolved from the fighting machine which was perfected in the four preceding years. There was about this period no sense of finality, but it was as experimental, in its own way, as were the years of progressing design which preceded the war period. Such commercial schemes as were inaugurated call for no more note than has been given here; they have been experimental, and, with the possible exception of the United States Government mail service, have not been planned and executed on a sufficiently large scale to furnish reliable data on which to forecast the prospects of commercial aviation. And there is a school rapidly growing up which asserts that the day of aeroplanes is nearly over. The construction of the giant airships of to-day and the successful return flight of R34 across the Atlantic seem to point to the eventual triumph, in spite of its disadvantages, of the dirigible airship. This is a hard saying for such of the aeroplane industry as survived the War period and consolidated itself, and it is but the saying of a section which bases its belief on the fact that, as was noted in the very early years of the century, the aeroplane is primarily a war machine. Moreover, the experience of the War period tended to discredit the dirigible, since, before the introduction of helium gas, the inflammability of its 273 A HISTORY OF AERONAUTICS buoyant factor placed it at an immense disadvantage beside the machine dependent on the atmosphere itself for its lift. As life runs to-day, it is a long time since Kipling wrote his story of the airways of a future world and thrust out a prophecy that the bulk of the world's air traffic would be carried by gas-bag vessels. If the school which inclines to belief in the dirigible is right in its belief, as it well may be, then the foresight was uncannily correct, not only in the matter of the main assumption, but in the detail with which the writer embroidered it. On the constructional side, the history of the aeroplane is still so much in the making that any attempt at a critical history would be unwise, and it is possible only to record fact, leaving it to the future for judgment to be passed. But, in a general way, criticism may be advanced with regard to the place that aeronautics takes in civilisation. In the past hundred years, the world has made miraculously rapid strides materially, but moral development has not kept abreast. Conception of the responsibilities of humanity remains virtually in a position of a hundred years ago; given a higher conception of life and its responsibilities, the aeroplane becomes the crowning achievement of that long series which James Watt inaugurated, the last step in inter- communication, the chain with which all nations are bound in a growing prosperity, surely based on moral wellbeing. Without such conception of the duties as well as the rights of life, this last achievement of science may yet prove the weapon that shall end civilisation as men know it to-day, and bring this ultra-material age to a phase of ruin on which saner people can build a world more reasonable and less given to groping after purely material advancement. 274 II -I ifl C S 2 c O 399 A HISTORY OF AERONAUTICS was 440 Ibs., or 3.66 Ibs. per horse-power. One of these engines was used on the machine which, in 1909, won the prize of 1,000 for the first circular mile flight, and it may be noted, too, that S. F. Cody, making the circuit of England in 1911, used a four-cylinder Green engine. Again, it was a Green engine that in 1914 won the 5,000 prize offered for the best aero engine in the Naval and Military aeroplane engine competition. Manufacture of the Green engines, in the period of the War, had standardised to the production of three types. Two of these were six-cylinder models, giving respectively 100 and 150 brake horse-power, and the third was a twelve-cylindered model rated at 275 brake horse-power. In 1910 J. S. Critchley compiled a list showing the types of engine then being manufactured; twenty-two out of a total of seventy-six were of the four-cylindered vertical type, and in addition to these there were two six-cylindered verticals. The sizes of the four-cylinder types ranged from 26 up to 118 brake horse-power; fourteen of them developed less than 50 horse-power, and only two developed over 100 horse-power. It became apparent, even in the early stages of heavier-than-air flying, that four-cylinder engines did not produce the even torque that was required for the rotation of the power shaft, even though a flywheel was fitted to the engine. With this type of engine the breakage of air-screws was of frequent occurrence, and an engine having a more regular rotation was sought, both for this and to avoid the excessive vibration often experienced with the four-cylinder type. Another point that forced itself on engine builders was that the 400 THE VERTICAL TYPE increased power which was becoming necessary for the propulsion of aircraft made an increase in the number of cylinders essential, in order to obtain a light engine. An instance of the weight reduction obtainable in using six cylinders instead of four is shown in Critchley's list, for one of the four-cylinder engines developed 118.5 brake horse-power and weighed 1,100 Ibs., whereas a six-cylinder engine by the same manufacturer developed 117.5 brake horse-power with a weight of 880 Ibs., the respective cylinder dimensions being 7.48 diameter by 9.06 stroke for the four-cylinder engine, and 6.1 diameter by 7.28 stroke for the six-cylinder type. A list of aeroplane engines, prepared in 1912 by Graham Clark, showed that, out of the total number of 112 engines then being manufactured, forty-two were of the vertical type, and of this number twenty-four had four-cylinders while sixteen were six-cylindered. The German aeroplane engine trials were held a year later, and sixty-six engines entered the competition, fourteen of these being made with air-cooled cylinders. All of the ten engines that were chosen for the final trials were of the water-cooled type, and the first place was won by a Benz four-cylinder vertical engine which developed 102 brake horse-power at 1,288 revolutions per minute. The cylinder dimensions of this engine were 5.1 inch diameter by 7.1 inch stroke, and the weight of the engine worked out at 3.4 Ibs. per brake horse-power. During the trials the full-load petrol consumption was 0.53 pint per horse-power per hour, and the amount of lubricating oil used was 0.0385 pint per brake horse-power per hour. In general construction this Benz engine was somewhat similar to the Green engine already described; the overhead valves, fitted in the tops of the cylinders, 401 A HISTORY OF AERONAUTICS were similarly arranged, as was the cam-shaft; two springs were fitted to each of the valves to guard against the possibility of the engine being put out of action by breakage of one of the springs, and ignition was obtained by two high-tension magnetos giving simultaneous sparks in each cylinder by means of two sparking plugs this dual ignition reduced the possibility of ignition troubles. The cylinder jackets were made of welded sheet steel so fitted around the cylinder that the head was also water-cooled, and the jackets were corrugated in the middle to admit of independent expansion. Even the lubrication system was duplicated, two sets of pumps being used, one to circulate the main supply of lubricating oil, and the other to give a continuous supply of fresh oil to the bearings, so that if the supply from one pump failed the other could still maintain effective lubrication. Development of the early Daimler type brought about the four-cylinder vertical Mercedes-Daimler engine of 85 horse-power, with cylinders of 5.5 diameter with 5.9 inch stroke, the cylinders being cast in two pairs. The overhead arrangement of valves was adopted, and in later designs push-rods were eliminated, the overhead cam-shaft being adopted in their place. By 1914 the four-cylinder Mercedes-Daimler had been partially displaced from favour by a six-cylindered model, made in two sizes; the first of these gave a nominal brake horse-power of 80, having cylinders of 4-1 inches diameter by 5.5 inches stroke; the second type developed 100 horse-power with cylinders 4-7 inches in diameter and 5.5 inches stroke, both types being run at 1,200 revolutions per minute. The cylinders of both these types were cast in pairs, and, instead of the water jackets forming part of the casting, 402 THE VERTICAL TYPE as in the design of the original four-cylinder Mercedes- Daimler engine, they were made of steel welded to flanges on the cylinders. Steel pistons, fitted with cast-iron rings, were used, and the overhead arrange- ment of valves and cam-shaft was adopted. About *55 P mt P er brake horse-power per hour was the usual fuel consumption necessary to full load running, and the engine was also economical as regards the consump- tion of lubricating oil, the lubricating system being ' forced ' for all parts, including the cam-shaft. The shape of these engines was very well suited for work with aircraft, being narrow enough to admit of a stream- line form being obtained, while all the accessories could be so mounted as to produce little or no wind resistance, and very little obstruction to the pilot's view. The eight-cylinder Mercedes-Daimler engine, used for airship propulsion during the War, developed 240 brake horse-power at 1,100 revolutions per minute; the cylinder dimensions were 6-88 diameter by 6 .5 stroke one of the instances in which the short stroke in relation to bore was very noticeable. Other instances of successful vertical design the types already detailed are fully sufficient to give particulars of the type generally are the Panhard, Chenu, Maybach, N.A.G., Argus, Mulag, and the well-known Austro-Daimler, which by 1917 was being copied in every combatant country. There are also the later Wright engines, and in America the Wisconsin six-cylinder vertical, weighing well under 4 Ibs. per horse-power, is evidence of the progress made with this first type of aero engine to develop. 403 II THE VEE TYPE AN offshoot from the vertical type, doubling the power of this with only a very slight if any increase in the length of crankshaft, the Vee or diagonal type of aero engine leaped to success through the insistent demand for greater power. Although the design came after that of the vertical engine, by 1910, according to Critchley's list of aero engines, there were more Vee type engines being made than any other type, twenty- five sizes being given in the list, with an average rating of 5 7' 4 brake horse-power. The arrangement of the cylinders in Vee form over the crankshaft, enabling the pistons of each pair of opposite cylinders to act upon the same crank pin, permits of a very short, compact engine being built, and also permits of reduction of the weight per horse- power, comparing this with that of the vertical type of engine, with one row of cylinders. Further, at the introduction of this type of engine it was seen that crankshaft vibration, an evil of the early vertical engines, was practically eliminated, as was the want of longi- tudinal stiffness that characterised the higher-powered vertical engines. Of the Vee type engines shown in Critchley's list in 1910, nineteen different sizes were constructed with eight cylinders, and with horse-powers ranging from 404 THE VEE TYPE thirty to just over the hundred; the lightest of these weighed 2.9 Ibs. per horse-power a considerable advance in design on the average vertical engine, in this respect of weight per horse-power. There were also two sixteen-cylinder engines of Vee design, the larger of which developed 134 horse-power with a weight of only 2 Ibs. per brake horse-power. Subse- quent developments have indicated that this type, with the further development from it of the double- Vee, or engine with three rows of cylinders, is likely to become the standard design of aero engine where high powers are required. The construction permits of placing every part so that it is easy of access, and the form of the engine implies very little head resistance, while it can be placed on the machine supposing that machine to be of the single-engine type in such a way that the view of the pilot is very little obstructed while in flight. An even torque, or great uniformity of rotation, is transmitted to the air-screw by these engines, while the design also permits of such good balance of the engine itself that vibration is practically eliminated. The angle between the two rows of cylinders is varied according to the number of cylinders, in order to give working impulses at equal angles of rotation and thus provide even torque; this angle is determined by dividing the number of degrees in a circle by the number of cylinders in either row of the engine. In an eight- cylindered Vee type engine, the angle between the cylinders is 90 degrees; if it is a twelve-cylindered engine, the angle drops to 60 degrees. One of the earliest of the British-built Vee type engines was an eight-cylinder 50 horse-power by the Wolseley Company, constructed in 1908 with a cylinder 405 A HISTORY OF AERONAUTICS bore of 3-75 inches and stroke of 5 inches, running at a normal speed of 1,350 revolutions per minute. With this engine, a gearing was introduced to enable the propeller to run at a lower speed than that of the engine, the slight loss of efficiency caused by the friction of the gearing being compensated by the slower speed of the air-screw, which had higher efficiency than would have been the case if it had been run at the engine speed. The ratio of the gearing that is, the speed of the air- screw relatively to that of the engine, could be chosen so as to suit exactly the requirements of the air-screw, and the gearing itself, on this engine, was accomplished on the half-speed shaft actuating the valves. Very soon after this first design had been tried out, a second Vee type engine was produced which, at 1,200 revolutions per minute, developed 60 horse-power; the size of this engine was practically identical with that of its forerunner, the only exception being an increase of half an inch in the cylinder stroke a very long stroke of piston in relation to the bore of the cylinder. In the first of these two engines, which was designed for airship propulsion, the weight had been about 8 Ibs. per brake horse-power, no special attempt appearing to have been made to fine down for extreme lightness; in this 60 horse-power design, the weight was reduced to 6-1 Ibs. per horse-power, counting the latter as normally rated; the engine actually gave a maximum of 75 brake horse-power, reducing the ratio of weight to power very considerably below the figure given. The accompanying diagram illustrates a later Wolseley model, end elevation, the eight-cylindered 126 horse-power Vee type aero engine of the early war period. With this engine, each crank pin has two 406 Sikh, 12-eylinder magneto, end view. Sikh, 12-cylinder, side view. To face page 407 THE VEE TYPE connecting rods bearing on it, these being placed side by side and connected to the pistons of opposite cylinders, and the two cylinders of the pair are staggered by an amount equal to the width of the connecting rod- bearing, to afford accommodation for the rods. The crankshaft was a nickel chrome steel forging, machined hollow, with four crank pins set at 180 degrees to each other, and carried in three bearings lined with anti- friction metal. The connecting rods were made of tubular nickel chrome steel, and the pistons of drawn steel, each being fitted with four piston rings. Of these the two rings nearest to the piston head were of the ordinary cast-iron type, while the others were of phosphor bronze, so arranged as to take the side thrust of the piston. The cylinders were of steel, arranged in two groups or rows of four, the angular distance between them being 90 degrees. In the space above the crankshaft, between the cylinder rows, was placed the valve-operating mechanism, together with the carburettor and ignition system, thus rendering this a very compact and accessible engine. The combustion heads of the cylinders were made of cast-iron, screwed into the steel cylinder barrels; the water-jacket was of spun aluminium, with one end fitting over the combustion head and the other free to slide on the cylinder; the water-joint at the lower end was made tight by a Dermatine ring carried between small flanges formed on the cylinder barrel. Overhead valves were adopted, and in order to make these as large as possible the combustion chamber was made slightly larger in diameter than the cylinder, and the valves set at an angle. Dual ignition was fitted in each cylinder, coil and accumulator being used for starting and as a reserve in case of failure 1 1. A. 407 2 D A HISTORY OF AERONAUTICS of the high-tension magneto system fitted for normal running. There was a double set of lubricating pumps, ensuring continuity of the oil supply to all the bearings of the engine. The feature most noteworthy in connection with the running of this type of engine was its flexibility; End View of Wolseley 120 horse-power Vee-type Engine. the normal output of power was obtained with 1,150 revolutions per minute of the crankshaft, but, by accelerating up to 1,400 revolutions, a maximum of 147 brake horse-power could be obtained. The weight was about 5 Ibs. per horse-power, the cylinder dimensions being 5 inches bore by 7 inches stroke. Economy in running was obtained, the fuel consumption being 0-58 pint per brake horse-power per hour at full load, with an expenditure of about 0-075 P m * f lubricating oil per brake horse-power per hour. 408 THE VEE TYPE Another Wolseley Vee type that was standardised was a 90 horse-power eight-cylinder engine running at i, 8 oo revolutions per minute, with a reducing gear introduced by fitting the air screw on the half-speed shaft. First made semi-cooled the exhaust valve was left air-cooled, and then entirely water-jacketed this engine demonstrated the advantage of full water cooling, for under the latter condition the same power was developed with cylinders a quarter of an inch less in diameter than in the semi-cooled pattern; at the same time the weight was brought down to 4^ Ibs. per horse- power. A different but equally efficient type of Vee design was the Dorman engine, of which an end elevation is shown; this developed 80 brake horse-power at a speed of 1,300 revolutions per minute, with a cylinder bore of 5 inches; each cylinder was made in cast-iron in one piece with the combustion chamber, the barrel only being water-jacketed. Auxiliary exhaust ports were adopted, the holes through the cylinder wall being uncovered by the piston at the bottom of its stroke the piston, 4.75 inches in length, was longer than its stroke, so that these ports were covered when it was at the top of the cylinder. The exhaust discharged through the ports into a belt surrounding the cylinder, the belts on the cylinders being connected so that the exhaust gases were taken through a single pipe. The air was drawn through the crank case, before reaching the carburettor, this having the effect of cooling the oil in the crank case as well as warming the air and thus assisting in vaporising the petrol for each charge of the cylinders. The inlet and exhaust valves were of the overhead type, as may be gathered from the diagram, 409 A HISTORY OF AERONAUTICS and in spite of cast-iron cylinders being employed a light design was obtained, the total weight with radiator, piping, and water being only 5 .5 Ibs. per horse-power. Here was the antithesis of the Wolseley type in the matter of bore in relation to stroke; from about 1907 up to the beginning of the war, and even later, there was controversy as to which type that in which the bore exceeded the stroke, or vice versa gave greater Dorman 80 horse-power Vee-type Engine. efficiency. The short-stroke enthusiasts pointed to the high piston speed of the long-stroke type, while those who favoured the latter design contended that full power could not be obtained from each explosion in the short - stroke type of cylinder. It is now generally conceded that the long-stroke engine yields higher efficiency, and in addition to this, so far as car engines are concerned, the method of rating horse-power in relation to bore 410 THE VEE TYPE without taking stroke into account has given the long- stroke engine an advantage, actual horse-power with a long stroke engine being in excess of the nominal rating. This may have had some influence on aero engine design, but, however this may have been, the long-stroke engine has gradually come to favour, and its rival has taken second place. For some time pride of place among British Vee type engines was held by the Sunbeam Company, which, owing to the genius of Louis Coatalen, together with the very high standard of construction maintained by the firm, achieved records and fame in the middle and later periods of the war. Their 225 horse-power twelve- cylinder engine ran at a normal speed of 2,000 revolutions per minute ; the air screw was driven through gearing at half this speed, its shaft being separate from the timing gear and carried in ball-bearings on the nose-piece of the engine. The cylinders were of cast-iron, entirely water-cooled; a thin casing formed the water-jacket, and a very light design was obtained, the weight being only 3.2 Ibs. per horse-power. The first engine of Sunbeam design had eight cylinders and developed 150 horse-power at 2,000 revolutions per minute; the final type of Vee design produced during the war was twelve-cylindered, and yielded 310 horse-power with cylinders 4 .3 inches bore by 6 -4 inches stroke. Evidence in favour of the long-stroke engine is afforded in this type as regards economy of working; under full load, working at 2,000 revolutions per minute, the consumption was 0.55 pints of fuel per brake horse-power per hour, which seems to indicate that the long stroke permitted of full use being made of the power resulting from each explosion, in spite of the high rate of speed of the piston. 4U A HISTORY OF AERONAUTICS Developing from the Vee type, the eighteen-cylinder 475 Dra ke horse-power engine, designed during the war, represented for a time the limit of power obtainable from a single plant. It was water-cooled throughout, and the ignition to each cylinder was duplicated; this engine proved fully efficient, and economical in fuel consumption. It was largely used for seaplane work, where reliability was fully as necessary as high power. The abnormal needs of the war period brought many British firms into the ranks of Vee-type engine- builders, and, apart from those mentioned, the most notable types produced are the Rolls-Royce and the Napier. The first mentioned of these firms, previous to 1914, had concentrated entirely on car engines, and their very high standard of production in this department of internal combustion engine work led, once they took up the making of aero engines, to extreme efficiency both of design and workmanship. The first experimental aero engine, of what became known as the ' Eagle * type, was of Vee design it was completed in March of 1915 and was so successful that it was standardised for quantity production. How far the original was from the perfection subsequently ascertained is shown by the steady increase in developed horse-power of the type; originally designed to develop 200 horse-power, it was developed and improved before its first practical trial in October of 1915, when it developed 25^5 horse- power on a brake test. Research and experiment pro- duced still further improvements, for, without any enlargement of the dimensions, or radical alteration in design, the power of the engine was brought up to 266 horse-power by March of 1916, the rate of revolutions of i, 800 per minute being maintained throughout, 412 THE VEE TYPE July, 1916, gave 284 horse-power; by the end of the year this had been increased to 322 horse-power; by September of 1917 the increase was to 350 horse-power, and by February of 1918 the ' Eagle ' type of engine was rated at 360 horse-power, at which standard it stayed. But there is no more remarkable development in engine design than this, a 75 per cent increase of power in the same engine in a period of less than three years. To meet the demand for a smaller type of engine for use on training machines, the Rolls-Royce firm produced the ' Hawk ' Vee-type engine of 100 horse- power, and, intermediately between this and the * Eagle,' the * Falcon ' engine came to being with an original rated horse-power of 2 05 at i , 8 oo revolutions per minute, in April of 1916. Here was another case of growth of power in the same engine through research, almost similar to that of the * Eagle ' type, for by July of 1 9 1 8 the ' Falcon ' was developing 285 horse-power with no radical alteration of design. Finally, in response to the constant demand for increase of power in a single plant, the Rolls-Royce company designed and produced the * Condor ' type of engine, which yielded 600 horse-power on its first test in August of 1918. The cessation of hostilities and consequent falling off in the demand for extremely high-powered plants prevented the * Condor ' being developed to its limit, as had been the * Falcon ' and 1 Eagle ' types. The * Eagle ' engine was fitted to the two Handley- Page aeroplanes which made flights from England to India it was virtually standard on the Handley-Page bombers of the later War period, though to a certain extent the American ' Liberty ' engine was also used. 4*3 A HISTORY OF AERONAUTICS Its chief record, however, is that of being the type fitted to the Vickers-Vimy aeroplane which made the first Atlantic flight, covering the distance of 1,880 miles at a speed averaging 117 miles an hour. The Napier Company specialised on one type of engine from the outset, a power plant which became known as the ' Lion ' engine, giving 450 horse-power with twelve cylinders arranged in three rows of four each. Considering the engine as * dry/ or without fuel and accessories, an abnormally light weight per horse- power only 1-89 Ibs. was attained when running at the normal rate of revolution. The cylinders and water-jackets are of steel, and there is fitted a detachable aluminium cylinder head containing inlet and exhaust valves and valve actuating mechanism; pistons are of aluminium alloy, and there are two inlet and two exhaust valves to each cylinder, the whole of the valve mechanism being enclosed in an oil-tight aluminium case. Con- necting rods and crankshaft are of steel, the latter being machined from a solid steel forging and carried in five roller bearings and one plain bearing at the forward end. The front end of the crank-case encloses reduction gear for the propeller shaft, together with the shaft and bearings. There are two suction and one pressure type oil pumps driven through gears at half-engine speed, and two 12 spark magnetos, giving 2 sparks in each cylinder. The cylinders are set with the central row vertical, and the two side rows at angles of 60 degrees each; cylinder bore is 5^ inches, and stroke 5^ inches; the normal rate of revolution is 1,350 per minute, and the reducing gear gives one revolution of the propeller shaft to I' 52 revolutions of crankshaft. Fuel consumption Napier ' Lion.' Napier ' Lion/ To face page 414 THE VEE TYPE is 0-48 Ibs. of fuel per brake horse-power hour at full load, and oil consumption is 0*020 Ibs. per brake horse- power hour. The dry weight of the engine, complete with propeller boss, carburettors, and induction pipes, is 850 Ibs., and the gross weight in running order, with fuel and oil for six hours working, is 2,671 Ibs., exclusive of cooling water. To this engine belongs an altitude record of 30-500 feet, made at Martlesham, near Ipswich, on January 2nd, 1919, by Captain Lang, R.A.F., the climb being accomplished in 66 minutes 15 seconds. Previous to this, the altitude record was held by an Italian pilot, who made 25,800 feet in an hour and 57 minutes in 1916. Lang's climb was stopped through the pressure of air, at the altitude he reached, being insufficient for driving the small propellers on the machine which worked the petrol and oil pumps, or he might have made the height said to have been attained by Major Schroeder on February 27th, 1920, at Dayton, Ohio. Schroeder is said to have reached an altitude of 36,020 feet on a Napier biplane, and, owing to failure of the oxygen supply, to have lost consciousness, fallen five miles, righted his machine when 2,000 feet in the air, and alighted successfully. Major Schroeder is an American. Turning back a little, and considering other than British design of Vee and double- Vee or ' Broad arrow ' type of engine, the Renault firm from the earliest days devoted considerable attention to the development of this type, their air-cooled engines having been notable examples from the earliest days of heavier-than-air machines. In 1910 they were making three sizes of eight-cylindered Vee-type engines, and by 1915 they had increased to the manufacture of five sizes, ranging *1J A HISTORY OF AERONAUTICS from 25 to 100 brake horse-power, the largest of the five sizes having twelve cylinders but still retaining the air-cooled principle. The De Dion firm, also, made Vee-type engines in 1914, being represented by an 80 horse-power eight-cylindered engine, air-cooled, and a 1 50 horse-power, also of eight cylinders, water-cooled, running at a normal rate of 1,600 revolutions per minute. Another notable example of French construction was the Panhard and Levassor 100 horse-power eight- cylinder Vee engine, developing its rated power at 1,500 revolutions per minute, and having the for that time low weight of 4-4 Ibs. per horse-power. American Vee design has followed the British fairly closely; the Curtiss Company produced originally a 75 horse-power eight-cylinder Vee type running at 1,200 revolutions per minute, supplementing this with a 170 horse-power engine running at 1,600 revolutions per minute, and later with a twelve-cylinder model Vee type, developing 300 horse-power at 1,500 revolu- tions per minute, with cylinder bore of 5 inches and stroke of 7 inches. An exceptional type of American design was the Kemp Vee engine of 80 horse-power, in which the cylinders were cooled by a current of air obtained from a fan at the forward end of the engine. With cylinders of 4*25 inches bore and 4*75 inches stroke, the rater power was developed at i, 1 50 revolutions per minute, and with the engine complete the weight was only 4-75 Ibs. per horse power. Ill THE RADIAL TYPE THE very first successful design of internal combustion aero engine made was that of Charles Manly, who built a five-cylinder radial engine in 1901 for use with Langley's * aerodrome,' as the latter inventor decided to call what has since become known as the aeroplane. Manly made a number of experiments, and finally decided on radial design, in which the cylinders are so rayed round a central crank-pin that the pistons act successively upon it; by this arrangement a very short and compact engine is obtained, with a minimum of weight, and a regular crankshaft rotation and perfect balance of inertia forces. When Manly designed his radial engine, high- speed internal combustion engines were in their infancy, and the difficulties in construction can be partly realised when the lack of manufacturing methods for this high- class engine work, and the lack of experimental data on the various materials, are taken into account. During its tests, Manly 's engine developed 52*4 brake horse- power at a speed of 950 revolutions per minute, with the remarkably low weight of only 2-4 Ibs. per horse- power; this latter was increased to 3-6 Ibs. when the engine was completed by the addition of ignition system, radiator, petrol tank, and all accessories, together with the cooling water for the cylinders, 417 A HISTORY OF AERONAUTICS In Manly's engine the cylinders were of steel, machined outside and inside to T 5 ^ of an inch thickness; on the side of the cylinder, at the top end, the valve chamber was brazed, being machined from a solid Cross Section, Manly's 5 Cylinder Radial Engine. forging. The casing which formed the water-jacket was of sheet steel, -^ of an inch in thickness, and this also was brazed on the cylinder and to the valve chamber. Automatic inlet valves were fitted, and the exhaust valves were operated by a cam which had two points, 1 80 degrees apart; . the cam was rotated in the opposite direction to the engine at one-quarter engine speed, THE RADIAL TYPE Ignition was obtained by using a one-spark coil and vibrator for all cylinders, with a distributor to select the right cylinder for each spark this was before the days of the high-tension magneto and the almost perfect ignition systems that makers now employ. The scheme of ignition for this engine was originated by Manly himself, and he also designed the sparking plugs fitted in the tops of the cylinders. Through fear of trouble resulting if the steel pistons worked on the steel cylinders, cast- iron liners were introduced in the latter, ^ of an inch thick. The connecting rods of this engine were of virtually the same type as is employed on nearly all modern radial engines. The rod for one cylinder had a bearing along the whole of the crank pin, and its end enclosed the pin; the other four rods had bearings upon the end of the first rod, and did not touch the crank pin. The accompanying diagram shows this construction, together with the means employed for securing the ends of the four rods the collars were placed in position after the rods had been put on. The bearings of these rods did not receive any of the rubbing effect due to the rotation of the crank pin, the rubbing on them being only that of the small angular displacement of the rods during each revolution ; thus there was no difficulty experienced with the lubrication. Another early example of the radial type of engine was the French Anzani, of which type one was fitted to the machine with which Bleriot first crossed the English Channel this was of 25 horse-power. The earliest Anzani engines were of the three-cylinder fan type, one cylinder being vertical, and the other two placed at an angle of 72 degrees on each side, as the possibility 419 A HISTORY OF AERONAUTICS of over-lubrication of the bottom cylinders was feared if a regular radial construction were adopted. In order to overcome the unequal balance of this type, balance weights were fitted insi4e the crank case. The final development of this three-cylinder radial was the * Y ' type of engine, in which the cylinders were regularly disposed at 120 degrees apart; the bore was 4-1, stroke 4-7 inches, and the power developed was 30 brake horse-power at 1,300 revolutions per minute. Critchley's list of aero engines being constructed in 1910 shows twelve of the radial type, with powers of between 14 and 100 horse-power, and with from three to ten cylinders this last is probably the greatest number of cylinders that can be successfully arranged in circular form. Of the twelve types of 1910, only two were water-cooled, and it is to be noted that these two ran at the slowest speeds and had the lowest weight per horse-power of any. The Anzani radial was considerably developed, special attention being paid to this type by its makers, and by 1914 the Anzani list comprised seven different sizes of air-cooled radials. Of these the largest had twenty cylinders, developing 200 brake horse-power it was virtually a double radial and the smallest was the original 30 horse-power three-cylinder design. A six- cylinder model was formed by a combination of two groups of three cylinders each, acting upon a double- throw crankshaft; the two crank pins were set at 180 degrees to each other, and the cylinder groups were staggered by an amount equal to the distance between the centres of the crank pins. Ten-cylinder radial engines are made with two groups of five cylinders acting upon two crank pins set at 180 degrees to each 420 THE RADIAL TYPE other; the largest Anzani * ten ' developed 125 horse- power at 1,200 revolutions per minute, the ten cylinders being each 4 .5 inches in bore with stroke of 5 .9 inches, and the weight of the engine being 3 .7 Ibs. per horse- power. In the 200 horse-power Anzani radial the cylinders are arranged in four groups of five each, acting on two crank pins. The bore of the cylinders in this engine is the same as in the three-cylinder, but the stroke is increased to 5.5 inches. The rated power is developed at 1,300 revolutions per minute, and the engine complete weighs 3 -4 Ibs. per horse-power. With this 200 horse-power Anzani, a petrol con- sumption of as low as o .49 Ibs. of fuel per brake horse- power per hour has been obtained, but the consumption of lubricating oil is compensatingly high, being up to one-fifth of the fuel used. The cylinders are set desaxe with the crank shaft, and are of cast-iron, provided with radiating ribs for air-cooling; they are attached to the crank case by long bolts passing through bosses at the top of the cylinders, and connected to other bolts at right angles through the crank case. The tops of the cylinders are formed flat, and seats for the inlet and exhaust valves are formed on them. The pistons are cast-iron, fitted with ordinary cast-iron spring rings. An aluminium crank case is used, being made in two halves connected together by bolts, which latter also attach the engine to the frame of the machine. The crankshaft is of nickel steel, made hollow, and mounted on ball-bearings in such a manner that practically a combination of ball and plain bearings is obtained; the central web of the shaft is bent to bring the centres of the crank pins as close together as possible, leaving only room for the connecting rods, and the pins are 421 A HISTORY OF AERONAUTICS 1 80 degrees apart. Nickel steel valves of the cone- seated, poppet type are fitted, the inlet valves being automatic, and those for the exhaust cam-operated by means of push-rods. With an engine having such a number of cylinders a very uniform rotation of the crankshaft is obtained, and in actual running there are always five of the cylinders giving impulses to the crankshaft at the same time. An interesting type of pioneer radial engine was the Farcot, in which the cylinders were arranged in a horizontal plane, with a vertical crankshaft which operated the air-screw through bevel gearing. This was an eight-cylinder engine, developing 64 horse- power at 1,200 revolutions per minute. The R.E.P. type, in the early days, was a ' fan * engine, but the designer, M. Robert Pelterie, turned from this design to a seven-cylinder radial, which at 1,100 revolutions per minute gave 95 horse-power. Several makers entered into radial engine development in the years immediately preceding the War, and in 1914 there were some twenty-two different sizes and types, ranging from 30 to 600 horse-power, being made, according to report; the actual construction of the latter size at this time, however, is doubtful. Probably the best example of radial construction up to the outbreak of War was the Salmson (Canton- Unne) water-cooled, of which in 1914 six sizes were listed as available. Of these the smallest was a seven- cylinder 90 horse-power engine, and the largest, rated at 600 horse-power, had eighteen cylinders. These engines, during the War, were made under licence by the Dudbridge Ironworks in Great Britain. The accompanying diagram shows the construction 422 THE RADIAL TYPE of the cylinders in the 200 horse-power size, showing the method of cooling, and the arrangement of the connecting rods. A patent planetary gear, also shown in the diagram, gives exactly the same stroke to all the pistons. The complete engine has fourteen cylinders, Section of 200 h.p. Salmson Radial Engine. of forged steel machined all over, and so secured to the crank case that any one can be removed without parting the crank case. The water-jackets are of spun copper, brazed on to the cylinder, and corrugated so as to admit of free expansion; the water is circulated by means of a centrifugal pump. The pistons are of cast-iron, each fitted with three rings, and the connecting rods are of high-grade steel, machined all over and fitted with H.A. 423 2E A HISTORY OF AERONAUTICS bushes of phosphor bronze; these rods are connected to a central collar, carried on the crank pin by two ball- bearings. The crankshaft has a single throw, and is made in two parts to allow the cage for carrying the big end-pins of the connecting rods to be placed in position. The casing is in two parts, on one of which the brackets for fixing the engine are carried, while the other part carries the valve-gear. Bolts secure the two parts together. The mechanically-operated steel valves on the cylinders are each fitted with double springs, and the valves are operated by rods and levers. Two Zenith carburettors are fitted on the rear half of the crank case, and short induction pipes are led to each cylinder; each of the carburettors is heated by the exhaust gases. Ignition is by two high-tension magnetos, and a compressed air self-starting arrangement is provided. Two oil pumps are fitted for lubricating purposes, one of which forces oil to the crankshaft and connecting-rod bearings, while the second forces oil to the valve gear, the cylinders being so arranged that the oil which flows along the walls cannot flood the lower cylinders. This engine operates upon a six-stroke cycle, a rather rare arrangement for internal combustion engines of the electrical ignition type; this is done in order to obtain equal angular intervals for the working impulses imparted to the rotating crankshaft, as the cylinders are arranged in groups of seven, and all act upon the one crankshaft. The angle, therefore, between the impulses is 77^ degrees. A diagram is inset giving a side view of the engine, in order to show the grouping of the cylinders. The 600 horse-power Salmson engine was designed 424 THE RADIAL TYPE with a view to fitting to airships, and was in reality two nine-cylindered engines, with a gear-box connecting them; double air-screws were fitted, and these were so arranged that either or both of them might be driven by either or both engines; in addition to this, the two engines were complete and separate engines as regards Salmson 200 h.p. Radial Engine, Side View. carburation and ignition, etc., so that they could be run independently of each other. The cylinders were exceptionally 'long stroke,' being 5-9 inches bore to 8.27 inches stroke, and the rated power was developed at 1,200 revolutions per minute, the weight of the 425 A HISTORY OF AERONAUTICS complete engine being only 4.1 Ibs. per horse-power at the normal rating. A type of engine specially devised for airship pro- pulsion is that in which the cylinders are arranged horizontally instead of vertically, the main advantages of this form being the reduction of head resistance and less obstruction to the view of the pilot. A casing, mounted on the top of the engine, supports the air- screw, which is driven through bevel gearing from the upper end of the crankshaft. With this type of engine a better rate of air-screw efficiency is obtained by gearing the screw down to half the rate of revolution of the engine, this giving a more even torque. The petrol consumption of the type is very low, being only 0-48 Ibs. per horse-power per hour, and equal economy is claimed as regards lubricating oil, a consumption of as little as 0.04 Ibs. per horse-power per hour being claimed. Certain American radial engines were made previous to 1914, the principal being the Albatross six-cylinder engines of 50 and 100 horse-powers. Of these the smaller size was air-cooled, with cylinders of 4 .5 inches bore and 5 inches stroke, developing the rated power at 1,230 revolutions per minute, with a weight of about 5 Ibs. per horse-power. The 100 horse-power size had cylinders of 5.5 inches bore, developing its rated power at 1,230 revolutions per minute, and weighing only 2-75 Ibs. per horse-power. This engine was markedly similar to the six-cylindered Anzani, having all the valves mechanically operated, and with auxiliary exhaust ports at the bottoms of the cylinders, overrun by long pistons. These Albatross engines had their cylinders arranged in two groups of three, with each 426 THE RADIAL TYPE group of three pistons operating on one of two crank pins, each 180 degrees apart. The radial type of engine, thanks to Charles Manly, had the honour of being first in the field as regards aero work. Its many advantages, among which may be specially noted the very short crankshaft as compared with vertical, Vee, or * broad arrow ' type of engine, and consequent greater rigidity, ensure it consideration by designers of to-day, and render it certain that the type will endure. Enthusiasts claim that the ' broad arrow * type, or Vee with a third row of cylinders inset between the original two, is just as much a development from the radial engine as from the vertical and resulting Vee; however this may be, there is a place for the radial type in air-work for as long as the internal combustion engine remains as a power plant. 427 IV THE ROTARY TYPE M. LAURENT SEGUIN, the inventor of the Gnome rotary aero engine, provided as great a stimulus to aviation as any that was given anterior to the war period, and brought about a great advance in mechanical flight, since these well-made engines gave a high-power output for their weight, and were extremely smooth in running. In the rotary design the crankshaft of the engine is stationary, and the cylinders, crank case, and all their adherent parts rotate; the working is thus exactly opposite in principle to that of the radial type of aero engine, and the advantage of the rotary lies in the considerable flywheel effect produced by the revolving cylinders, with consequent evenness of torque. Another advantage is that air-cooling, adopted in all the Gnome engines, is rendered much more effective by the rotation of the cylinders, though there is a tendency to distortion through the leading side of each cylinder being more efficiently cooled than the opposite side; advocates of other types are prone to claim that the air resistance to the revolving cylinders absorbs some 10 per cent of the power developed by the rotary engine, but that has not prevented the rotary from attaining to great popularity as a prime mover. There were, in the list of aero engines compiled in 1910, five rotary engines included, all air-cooled. Three 428 THE ROTARY TYPE of these were Gnome engines, and two of the make known as * International/ They ranged from 21.5 to 123 horse-power, the latter being rated at only 1.8 Ibs. weight per brake horse-power, and having fourteen cylinders, 4-33 inches in diameter by 4-7 inches stroke. By 1914 forty-three different sizes and types of rotary engine were being constructed, and in 1913 five rotary type engines were entered for the series of aeroplane engine trials held in Germany. Minor defects ruled out four of these, and only the German Bayerischer Motoren Flugzeugwerke completed the seven-hour test prescribed for competing engines. Its large fuel consumption barred this engine from the final trials, the consumption being some 0.95 pints per horse-power per hour. The consumption of lubricating oil, also was excessive, standing at 0.123 pint per horse-power per hour. The engine gave 37.5 effective horse-power during its trial, and the loss due to air resistance was 4 -6 horse-power, about 1 1 per cent. The accompanying drawing shows the construction of the engine, in which the seven cylinders are arranged radially on the crank case; the method of connecting the pistons to the crank pins can be seen. The mixture is drawn through the crank chamber, and to enter the cylinder it passes through the two automatic valves in the crown of the piston; the exhaust valves are situated in the tops of the cylinders, and are actuated by cams and push-rods. Cooling of the cylinder is assisted by the radial rings, and the diameter of these rings is increased round the hottest part of the cylinder. When long flights are undertaken the advantage of the light weight of this engine is more than counterbalanced by its high fuel and lubricating oil consumption, but there are other 429 A HISTORY OF AERONAUTICS makes which are much better than this seven-cylinder German in respect of this. Rotation of the cylinders in engines of this type is produced by the side pressure of the pistons on the cylinder walls, and in order to prevent this pressure Bayeriseher 7 Cylinder Rotary Engine, 1913. from becoming abnormally large it is necessary to keep the weight of the piston as low as possible, as the pressure is produced by the tangential acceleration and retardation of the pis"ton. On the upward stroke the circumferential velocity of the piston is rapidly increased, which causes it to exert a considerable tangential pressure on the side of the cylinder, and on the return stroke there is a 430 THE ROTARY TYPE corresponding retarding effect due to the reduction of the circumferential velocity of the piston. These side pressures cause an appreciable increase in the tempera- tures of the cylinders and pistons, which makes it necessary to keep the power rating of the engines fairly low. Seguin designed his first Gnome rotary as a 34 horse-power engine when run at a speed of 1,300 revolutions per minute. It had five cylinders, and the weight was 3.9 Ibs. per horse-power. A seven-cylinder model soon displaced this first engine, and this latter, with a total weight of 165 Ibs., gave 61-5 horse-power. The cylinders were machined out of solid nickel chrome- steel ingots, and the machining was carried out so that the cylinder walls were under J of an inch in thickness. The pistons were cast-iron, fitted each with two rings, and the automatic inlet valve to the cylinder was placed in the crown of the piston. The connecting rods, of ' H ' section, were of nickel chrome-steel, and the large end of one rod, known as the ' master-rod ' embraced the crank pin; on the end of this rod six hollow steel pins were carried, and to these the remaining six con- necting-rods were attached. The crankshaft of the engine was made of nickel chrome-steel, and was in two parts connected together at the crank pin; these two parts, after the master-rod had been placed in position and the other connecting rods had been attached to it, were firmly secured. The steel crank case was made in five parts, the two central ones holding the cylinders in place, and on one side another of the five castings formed a cam-box, to the outside of which was secured the extension to which the air-screw was attached. On the other side of the crank case another A HISTORY OF AERONAUTICS casting carried the thrust-box, and the whole crank case, with its cylinders and gear, was carried on the fixed crank shaft by means of four ball-bearings, one of which also took the axial thrust of the air-screw. For these engines, castor oil is the lubricant usually adopted, and it is pumped to the crankshaft by means of a gear-driven oil pump; from this shaft the other parts of the engine are lubricated by means of centri- fugal force, and in actual practice sufficient unburnt oil passes through the cylinders to lubricate the exhaust valve, which partly accounts for the high rate of con- sumption of lubricating oil. A very simple carburettor of the floatless, single-spray type was used, and the mixture was passed along the hollow crankshaft to the interior of the crank case, thence through the automatic inlet valves in the tops of the pistons to the combustion chambers of the cylinders. Ignition was by means of a high-tension magneto specially geared to give the correct timing, and the working impulses occurred at equal angular intervals of 102-85 degrees. The ignition was timed so that the firing spark occurred when the cylinder was 26 degrees before the position in which the piston was at the outer end of its stroke, and this timing gave a maximum pressure in the cylinder just after the piston had passed this position. By 1913, eight different sizes of the Gnome engine were being constructed, ranging from 45 to 180 brake horse-power; four of these were single-crank engines, one having nine and the other three having seven cylinders. The remaining four were constructed with two cranks; three of them had fourteen cylinders apiece, ranged in groups of seven, acting on the cranks, and the one other had eighteen cylinders ranged in two 432 THE ROTARY TYPE groups of nine, acting on its two cranks. Cylinders of the two-crank engines are so arranged (in the fourteen- cylinder type) that fourteen equal angular impulses occur during each cycle; these engines are supported on bearings on both sides of the engine, the air-screw being placed outside the front support. In the eighteen- cylinder model the impulses occur at each 40 degrees of angular rotation of the cylinders, securing an extremely even rotation of the air-screw. In 1913 the Gnome Monosoupape engine was introduced, a model in which the inlet valve to the cylinder was omitted, while the piston was of the ordinary cast-iron type. A single exhaust valve in the cylinder head was operated in a manner similar to that on the previous Gnome engines, and the fact of this being the only valve on the cylinder gave the engine its name. Each cylinder contained ports at the bottom which communicated with the crank chamber, and were overrun by the piston when this was approaching the bottom end of its stroke. During the working cycle of the engine the exhaust valve was opened early to allow the exhaust gases to escape from the cylinder, so that by the time the piston overran the ports at the bottom the pressure within the cylinder was approximately equal to that in the crank case, and practically no flow of gas took place in either direction through the ports. The exhaust valve remained open as usual during the succeeding up-stroke of the piston, and the valve was held open until the piston had returned through about one-third of its downward stroke, thus permitting fresh air to enter the cylinder. The exhaust valve then closed, and the downward motion of the piston, continuing, caused a partial vacuum inside the cylinder; when the 433 A HISTORY OF AERONAUTICS piston overran the ports, the rich mixture from the crank case immediately entered. The cylinder was then full of the mixture, and the next upward stroke of the piston compressed the charge; upon ignition the working cycle was repeated. The speed variation of this engine was obtained by varying the extent and duration of the opening of the exhaust valves, and was controlled by the pilot by hand-operated levers acting on the valve tappet rollers. The weight per horse- power of these engines was slightly less than that of the two-valve type, while the lubrication of the gudgeon pin and piston showed an improvement, so that a lower lubricating oil consumption was obtained. The 100 horse-power Gnome Monosoupape was built with nine cylinders, each 4.33 inches bore by 5.9 inches stroke, and it developed its rated power at 1,200 revolutions per minute. An engine of the rotary type, almost as well known as the Gnome, is the Clerget, in which both cylinders and crank case are made of steel, the former having the usual radial fins for cooling. In this type the inlet and exhaust valves are both located in the cylinder head, and mechanically operated by push-rods and rockers. Pipes are carried from the crank case to the inlet valve casings to convey the mixture to the cylinders, a car- burettor of the central needle type being used. The carburetted mixture is taken into the crank case chamber in a manner similar to that of the Gnome engine. Pistons of aluminium alloy, with three cast-iron rings, are fitted, the top ring being of the obturator type. The large end of one of the nine connecting rods embraces the crank pin and the pressure is taken on two ball-bearings housed in the end of the rod. This carries eight pins, 434 THE ROTARY TYPE to which the other rods are attached, and the main rod being rigid between the crank pin and piston pin determines the position of the pistons. Hollow con- necting-rods are used, and the lubricating oil for the piston pins passes from the crankshaft through the centres of the rods. Inlet and exhaust valves can be Clerget 115 h.p. Rotary Aero Engine, Side Elevation. set quite independently of one another a useful point, since the correct timing of the opening of these valves is of importance. The inlet valve opens 4 degrees from top centre and closes after the bottom dead centre of the piston; the exhaust valve opens 68 degrees before the bottom centre and closes 4 degrees after the top dead centre of the piston. The magnetos are set to give the spark in the cylinder at 25 degrees before the end of the compression stroke two high-tension magnetos are used; if desired, the second one can be 435 A HISTORY OF AERONAUTICS adjusted to give a later spark for assisting the starting of the engine. The lubricating oil pump is of the valveless two-plunger type, so geared that it runs at seven revolutions to 100 revolutions of the engine; by counting the pulsations the speed of the engine can be quickly calculated by multiplying the pulsations by 100 and dividing by seven. In the 115 horse-power nine- cylinder Clerget the cylinders are 4.7 bore with a 6-3 inches stroke, and the rated power of the engine is obtained at 1,200 revolutions per minute. The petrol consumption is 0.75 pint per horse-power per hour. A third rotary aero engine, equally well known with the foregoing two, is the Le Rhone, made in four different sizes with power outputs of from 50 to 160 horse-power; the two smaller sizes are single crank engines with seven and nine cylinders respectively, and the larger sizes are of double-crank design, being merely the two smaller sizes doubled fourteen and eighteen-cylinder engines. The inlet and exhaust valves are located in the cylinder head, and both valves are mechanically operated by one push-rod and rocker, radial pipes from crank case to inlet valve casing taking the mixture to the cylinders. The exhaust valves are placed on the leading, or air-screw side, of the engine, in order to get the fullest possible cooling effect. The rated power of each type of engine is obtained at 1,200 revolutions per minute, and for all four sizes the cylinder bore is 4.13 inches, with a 5.5 inches piston stroke. Thin cast-iron liners are shrunk into the steel cylinders in order to reduce the amount of piston friction. Although the Le Rhone engines are constructed practically throughout of steel, the weight is only 2.9 Ibs. per horse-power in the eighteen-cylinder type. 436 THE ROTARY TYPE American enterprise in the construction of the rotary type is perhaps best illustrated in the ' Gyro ' engine; this was first constructed with inlet valves in the heads of the pistons, after the Gnome pattern, the exhaust valves being in the heads of the cylinders. The inlet valve in the crown of each piston was mechani- cally operated in a very ingenious manner by the oscillation of the connecting-rod. The Gyro-Duplex Gyro- Duplex Rotary Engine, Cross Section. engine superseded this original design, and a small cross-section illustration of this is appended. It is constructed in seven and nine-cylinder sizes, with a power range of from 50 to 100 horse-power; with the largest size the low weight of 2 .5 Ibs. per horse-power is reached. The design is of considerable interest to the internal combustion engineer, for it embodies a piston valve for controlling auxiliary exhaust ports, which also acts as the inlet valve to the cylinder. The 437 A HISTORY OF AERONAUTICS piston uncovers the auxiliary ports when it reaches the bottom of its stroke, and at the end of the power stroke the piston is in such a position that the exhaust can escape over the top of it. The exhaust valve in the cylinder head is then opened by means of the push-rod and rocker, and is held open until the piston has com- pleted its upward stroke and returned through more than half its subsequent return stroke. When the exhaust valve closes, the cylinder has a charge of fresh air, drawn in through the exhaust valve, and the further motion of the piston causes a partial vacuum; by the time the piston reaches bottom dead centre the piston- valve has moved up to give communication between the cylinder and the crank case, therefore the mixture is drawn into the cylinder. Both the piston valve and exhaust valve are operated by cams formed on the one casting, which rotates at seven-eighths engine speed for the seven-cylinder type, and nine-tenths engine speed for the nine-cylinder engines. Each of these cams has four or five points respectively, to suit the number of cylinders. The steel cylinders are machined from solid forgings and provided with webs for air-cooling as shown. Cast- iron pistons are used, and are connected to the crank- shaft in the same manner as with the Gnome and Le Rhone engines. Petrol is sprayed into the crank case by a small geared pump and the mixture is taken from there to the piston valves by radial pipes. Two separate pumps are used for lubrication, one forcing oil to the crank-pin bearing and the other spraying the cylinders. Among other designs of rotary aero engines the E.J.C. is noteworthy, in that the cylinders and crank case of this engine rotate in opposite directions, and 438 THE ROTARY TYPE two air-screws are used, one being attached to the end of the crankshaft, and the other to the crank case. Another interesting type is the Burlat rotary, in which both the cylinders and crankshaft rotate in the same direction, the rotation of the crankshaft being twice that of the cylinders as regards speed. This engine is arranged to work on the four-stroke cycle with the crankshaft making four, and the cylinders two, revolutions per cycle. It would appear that the rotary type of engine is capable of but little more improvement save for such devices as these of the last two engines mentioned, there is little that Laurent Seguin has not already done in the Gnome type. The limitation of the rotary lies in its high fuel and lubricating oil consumption, which renders it unsuited for long-distance aero work; it was, in the war period, an admirable engine for such short runs as might be involved in patrol work * over the lines,' and for similar purposes, but the water- cooled Vee or even vertical, with its much lower fuel consumption, was and is to be preferred for distance work. The rotary air-cooled type has its uses, and for them it will probably remain among the range of current types for some time to come. Experience of matters aeronautical is sufficient to show, however, that prophecy in any direction is most unsafe. H.A. 439 2F THE HORIZONTALLY-OPPOSED ENGINE AMONG the first internal combustion engines to be taken into use with aircraft were those of the horizontally- opposed four-stroke cycle type, and, in every case in which these engines were used, their excellent balance and extremely even torque rendered them ideal until the tremendous increase in power requirements rendered the type too long and bulky for placing in the fuselage of an aeroplane. As power increased, there came a tendency toward placing cylinders radially round a central crankshaft, and, as in the case of the early Anzani, it may be said that the radial engine grew out of the horizontal opposed piston type. There were, in 1 9 1 o that is, in the early days of small power units, ten different sizes of the horizontally opposed engine listed for manufacture, but increase in power requirements practically ruled out the type for air work. The Darracq firm were the leading makers of these engines in 1910; their smallest size was a 24 horse- power engine, with two cylinders each of 5.1 inches bore by 4.7 inches stroke. This engine developed its rated power at 1,500 revolutions per minute, and worked out at a weight of 5 Ibs. per horse-power. With these engines the cranks are so placed that two regular impulses are given to the crankshaft for each cycle of working, an arrangement which permits of very even balancing of 440 THE HORIZONTALLY-OPPOSED ENGINE the inertia forces of the engine. The Darracq firm also made a four-cylindered horizontal opposed piston engine, in which two revolutions were given to the crankshaft per revolution, at equal angular intervals. The Dutheil-Chambers was another engine of this type, and had the distinction of being the second largest con-, structed. At 1,000 revolutions per minute it developed 97 horse-power; its four cylinders were each of 4.93 inches bore by 1 1 -8 inches stroke an abnormally long stroke in comparison with the bore. The weight which owing to the build of the engine and its length of stroke was bound to be rather high, actually amounted to 8 .2 Ibs. per horse-power. Water cooling was adopted, and the engine was, like the Darracq four-cylinder type, so arranged as to give two impulses per revolution at equal angular intervals of crankshaft rotation. One of the first engines of this type to be constructed in England was the Alvaston, a water-cooled model which was made in 20, 30, and 50 brake horse-power sizes, the largest being a four-cylinder engine. All three sizes were constructed to run at 1,200 revolutions per minute. In this make the cylinders were secured to the crank case by means of four long tie bolts passing through bridge pieces arranged across the cylinder heads, thus relieving the cylinder walls of all longitudinal explosion stresses. These bridge pieces were formed from chrome vanadium steel and milled to an * H ' section, and the bearings for the valve-tappet were forged solid with them. Special attention was given to the machining of the interiors of the cylinders and the combustion heads, with the result that the excep- tionally high compression of 95 Ibs. per square inch 441 A HISTORY OF AERONAUTICS was obtained, giving a very flexible engine. The cylinder heads were completely water-jacketed, and copper water-jackets were also fitted round the cylinders. The mechanically operated valves were actuated by specially shaped cams, and were so arranged that only two cams were required for the set of eight valves. The inlet valves at both ends of the engine were connected by a single feed-pipe to which the carburettor was attached, the induction piping being arranged above the engine in an easily accessible position. Auxiliary air ports were provided in the cylinder walls so that the pistons overran them at the end of their stroke. A single vertical shaft running in ball-bearings operated the valves and water circulating pump, being driven by spiral gearing from the crankshaft at half speed. In addition to the excellent balance obtained with this engine, the makers claimed with justice that the number of working parts was reduced to an absolute minimum. In the two-cylinder Darracq, the steel cylinders were machined from solid, and auxiliary exhaust ports, overrun by the piston at the inner end of its stroke, were provided in the cylinder walls, consisting of a circular row of drilled holes this arrangement was subsequently adopted on some of the Darracq racing car engines. The water jackets were of copper, soldered to the cylinder walls; both the inlet and exhaust valves were located in the cylinder heads, being operated by rockers and push-rods actuated by cams on the half- time shaft driven from one end of the crankshaft. Ignition was by means of a high-tension magneto, and long induction pipes connected the ends of the cylinders to the carburettor, the latter being placed underneath 442 THE HORIZONTALLY-OPPOSED ENGINE the engine. Lubrication was effected by spraying oil into the crank case by means of a pump, and a second pump circulated the cooling water. Another good example of this type of engine was the Eole, which had eight opposed pistons, each pair of which was actuated by a common combustion chamber at the centre of the engine, two crankshafts being placed at the outer ends of the engine. This reversal of the ordinary arrangement had two advantages; it simplified induction, and further obviated the need for cylinder heads, since the explosion drove at two piston heads instead of at one piston head and the top of the cylinder; against this, however, the engine had to be constructed strongly enough to withstand the longitudinal stresses due to the explosions, as the cranks are placed on the outer ends and the cylinders and crank-cases take the full force of each explosion. Each crankshaft drove a separate air-screw. This pattern of engine was taken up by the Dutheil- Chambers firm in the pioneer days of aircraft, when the firm in question produced seven different sizes of horizontal engines. The Demoiselle monoplane used by Santos-Dumont in 1909 was fitted with a two-cylinder, horizontally-opposed Dutheil-Chambers engine, which developed 25 brake horse-power at a speed of 1,100 revolutions per minute, the cylinders being of 5 inches bore by 5-1 inches stroke, and the total weight of the engine being some 120 Ibs. The crankshafts of these engines were usually fitted with steel flywheels in order to give a very even torque, the wheels being specially constructed with wire spokes. In all the Dutheil-Chambers engines water cooling was adopted, and the cylinders were attached to the 443 A HISTORY OF AERONAUTICS crank cases by means of long bolts passing through the combustion heads. For their earliest machines, the Clement-Bayard firm constructed horizontal engines of the opposed piston type. The best known of these was the 30 horse-power size, which had cylinders of 4 .7 inches diameter by 5 i inches stroke, and gave its rated power at 1,200 revolutions per minute. In this engine the steel cylinders were secured to the crank case by flanges, and radiating ribs were formed around the barrel to assist the air- cooling. Inlet and exhaust valves were actuated by push-rods and rockers actuated from the second motion shaft mounted above the crank case; this shaft also drove the high-tension magneto with which the engine was fitted. A ring of holes drilled round each cylinder constituted auxiliary ports which the piston uncovered at the inner end of its stroke, and these were of con- siderable assistance not only in expelling exhaust gases, but also in moderating the temperature of the cylinder and of the main exhaust valve fitted in the cylinder head, A water-cooled Clement-Bayard horizontal engine was also made, and in this the auxiliary exhaust ports were not embodied; except in this particular, the engine was very similar to the water-cooled Darracq. The American Ashmusen horizontal engine, developing 100 horse-power, is probably the largest example of this type constructed. It was made with six cylinders arranged on each side of a common crank case, with long bolts passing through the cylinder heads to assist in holding them down. The induction piping and valve-operating gear were arranged below the engine, and the half-speed shaft carried the air- screw. 444 THE HORIZONTALLY-OPPOSED ENGINE Messrs Palons and Beuse, Germans, constructed a light-weight, air-cooled, horizontally-opposed engine, two-cylindered. In this the cast-iron cylinders were made very thin, and were secured to the crank case by bolts passing through lugs cast on the outer ends of the cylinders; the crankshaft was made hollow, and holes were drilled through the webs of the connecting-rods in order to reduce the weight. The valves were fitted to the cylinder heads, the inlet valves being of the automatic type, while the exhaust valves were mechani- cally operated from the cam-shaft by means of rockers and push-rods. Two carburettors were fitted, to reduce the induction piping to a minimum; one was attached to each combustion chamber, and ignition was by the normal high-tension magneto driven from the half- time shaft. There was also a Nieuport two-cylinder air-cooled horizontal engine, developing 35 horse-power when running at 1,300 revolutions per minute, and being built at a weight of 5 Ibs. per horse-power. The cylinders were of 5.3 inches diameter by 5.9 inches stroke; the engine followed the lines of the Darracq and Dutheil- Chambers pretty closely, and thus calls for no special description. The French Kolb-Danvin engine of the horizontal type, first constructed in 1905, was probably the first two-stroke cycle engine designed to be applied to the propulsion of aircraft; it never got beyond the experi- mental stage, although its trials gave very good results. Stepped pistons were adopted, and the charging pump at one end was used to scavenge the power cylinder at the other ends of the engine, the transfer ports being formed in the main casting. The openings of these 445 A HISTORY OF AERONAUTICS ports were controlled at both ends by the pistons, and the location of the ports appears to have made it necessary to take the exhaust from the bottom of one cylinder and from the top of the other. The carburetted mixture was drawn into the scavenging cylinders, and the usual deflectors were cast on the piston heads to assist in the scavenging and to prevent the fresh gas from passing out of the exhaust ports. 446 VI THE TWO-STROKE CYCLE ENGINE ALTHOUGH it has been little used for aircraft propulsion, the possibilities of the two-stroke cycle engine render some study of it desirable in this brief review of the various types of internal combustion engine applicable both to aeroplanes and airships. Theoretically the two-stroke cycle engine or as it is more commonly termed, the * two-stroke/ is the ideal power producer; the doubling of impulses per revolution of the crank- shaft should render it of very much more even torque than the four-stroke cycle types, while, theoretically, there should be a considerable saving of fuel, owing to the doubling of the number of power strokes per total of piston strokes. In practice, however, the inefficient scavenging of virtually every two-stroke cycle engine produced nullifies or more than nullifies its advantages over the four-stroke cycle engine; in many types, too, there is a waste of fuel gases through the exhaust ports, and much has yet to be done in the way of experiment and resulting design before the two-stroke cycle engine can be regarded as equally reliable, economical, and powerful with its elder brother. The first commercially successful engine operating on the two-stroke cycle was invented by Mr Dugald Clerk, who in 1881 proved the design feasible. As is more or less generally understood, the exhaust gases 447 A HISTORY OF AERONAUTICS of this engine are discharged from the cylinder during the time that the piston is passing the inner dead centre, and the compression, combustion, and expansion of the charge take place in similar manner to that of the four-stroke cycle engine. The exhaust period is usually controlled by the piston overrunning ports in the cylinder at the end of its working stroke, these ports communicating direct with the outer air the complica- tion of an exhaust valve is thus obviated; immediately after the escape of the exhaust gases, charging of the cylinder occurs, and the fresh gas may be introduced either through a valve in the cylinder head or through ports situated diametrically opposite to the exhaust ports. The continuation of the outward stroke of the piston, after the exhaust ports have been closed, com- presses the charge into the combustion chamber of the cylinder, and the ignition of the mixture produces a recurrence of the working stroke. Thus, theoretically, is obtained the maximum of energy with the minimum of expenditure; in practice, however, the scavenging of the power cylinder, a matter of great importance in all internal combustion engines, is often imperfect, owing to the opening of the exhaust ports being of relatively short duration; clearing the exhaust gases out of the cylinder is not fully accomplished, and these gases mix with the fresh charge and detract from its efficiency. Similarly, owing to the shorter space of time allowed, the charging of the cylinder with the fresh mixture is not so efficient as in the four- stroke cycle type; the fresh charge is usually compressed slightly in a separate chamber crank case, independent cylinder, or charging pump, and is delivered to the working cylinder during the beginning of the return 448 THE TWO-STROKE CYCLE ENGINE stroke of the piston, while in engines working on the four-stroke cycle principle a complete stroke is devoted to the expulsion of the waste gases of the exhaust, and another full stroke to recharging the cylinder with fresh explosive mixture. Theoretically the two-stroke and the four-stroke cycle engines possess exactly the same thermal efficiency, but actually this is modified by a series of practical conditions which to some extent tend to neutralise the very strong case in favour of the two-stroke cycle engine. The specific capacity of the engine operating on the two-stroke principle is theoretically twice that of one operating on the four-stroke cycle, and consequently, for equal power, the former should require only about half the cylinder volume of the latter; and, owing to the greater superficial area of the smaller cylinder, relatively, the latter should be far more easily cooled than the larger four-stroke cycle cylinder; thus it should be possible to get higher compression pressures, which in turn should result in great economy of working. Also the obtaining of a working impulse in the cylinder for each revolution of the crankshaft should give a great advantage in regularity of rotation which it undoubtedly does and the elimination of the operating gear for the valves, inlet and exhaust, should give greater simplicity of design. In spite of all these theoretical and some practical advantages the four-stroke cycle engine was uni- versally adopted for aircraft work; owing to the practical equality of the two principles of operation, so far as thermal efficiency and friction losses are concerned, there is no doubt that the simplicity of design (in theory) and high power output to weight ratio (also in theory) 449 A HISTORY OF AERONAUTICS ought to have given the * two-stroke ' a place on the aeroplane. But this engine has to be developed so as to overcome its inherent drawbacks; better scavenging methods have yet to be devised for this is the principal drawback before the two-stroke can come to its own as a prime mover for aircraft. Mr Dugald Clerk's original two-stroke cycle engine is indicated roughly, as regards principle, by the accompanying diagram, from which it will be seen that the elimination of the ordinary inlet and exhaust valves of the four-stroke type is more than compensated by a separate cylinder which, having a piston worked from the connecting-rod of the power cylinder, was used to charging, drawing the mixture from the carburettor past the valve in the top of the charging cylinder, and then forcing it through the connecting pipe into the power cylinder. The inlet valves both on the charging and the power cylinders are automatic; when the power piston is near the bottom of its stroke the piston in the charging cylinder is compressing the carburetted air, so that as soon as the pressure within the power cylinder is relieved by the exit of the burnt gases through the exhaust ports the pressure in the charging cylinder causes the valve in the head of the power cylinder to open, and fresh mixture flows into the cylinder, replacing the exhaust gases. After the piston has again covered the exhaust ports the mixture begins to be compressed, thus automatically closing the inlet valve. Ignition occurs near the end of the compression stroke, and the working stroke immediately follows, thus giving an impulse to the crankshaft on every down stroke of the piston. If the scavenging of the cylinder were complete, and the cylinder were to 450 THE TWO-STROKE CYCLE ENGINE receive a full charge of fresh mixture for every stroke, the same mean effective pressure as is obtained with four-stroke cycle engines ought to be realised, and at an equal speed of rotation this engine should give twice the power obtainable from a four-stroke cycle engine of equal dimensions. This result was not achieved, and, with the improvements in construction brought about by experiment up to 1912, the output was found to be only about fifty per cent more than that of a four-stroke Dugald Clerk's Two-stroke Cycle Engine. cycle engine of the same size, so that, when the charging cylinder is included, this engine has a greater weight per horse-power, while the lowest rate of fuel consumption recorded was 0-68 Ib. per horse-power per hour. In 1891 Mr Day invented a two-stroke cycle engine which used the crank case as a scavenging chamber, and a very large number of these engines have been built for industrial purposes. The charge of carburetted air is drawn through a non-return valve into the crank chamber during the upstroke of the piston, and 451 A HISTORY OF AERONAUTICS compressed to about 4 Ibs. pressure per square inch on the down stroke. When the piston approaches the bottom end of its stroke the upper edge first overruns an exhaust port, and almost immediately after uncovers an inlet port on the opposite side of the cylinder and in communi- cation with the crank chamber; the entering charge, being under pressure, assists in expelling the exhaust gases from the cylinder. On the next upstroke the charge is compressed into the combustion space of the cylinder, a further charge simultaneously entering the crank case to be compressed after the ignition for the working stroke. To prevent the incoming charge escaping through the exhaust ports of the cylinder a deflector is formed on the top of the piston, causing the fresh gas to travel in an upward direction, thus avoiding as far as possible escape of the mixture to the atmosphere. From experiments conducted in 1910 by Professor Watson and Mr Fleming it was found that the proportion of fresh gases which escaped unburnt through the exhaust ports diminished with increase of speed; at 600 revolutions per minute about 36 per cent of the fresh charge was lost; at 1,200 revolutions per minute this was reduced to 20 per cent, and at 1,500 revolutions it was still farther reduced to 6 per cent. So much for the early designs. With regard to engines of this type specially constructed for use with aircraft, three designs call for special mention. Messrs A. Gobe and H. Diard, Parisian engineers, produced an eight-cylindered two-stroke cycle engine of rotary design, the cylinders being co-axial. Each pair of opposite pistons was secured together by a rigid con- necting rod, connected to a pin on a rotating crankshaft which was mounted eccentrically to the axis of rotation 45* THE TWO-STROKE CYCLE ENGINE of the cylinders. The crankshaft carried a pinion gearing with an internally toothed wheel on the trans- mission shaft which carried the air-screw. The com- bustible mixture, emanating from a common supply pipe, was led through conduits to the front ends of the cylinders, in which the charges were compressed before being transferred to the working spaces through ports in tubular extensions carried by the pistons. These extensions had also exhaust ports, registering with ports in the cylinder which communicated with the outer air, and the extensions slid over depending cylinder heads attached to the crank case by long studs. The pump charge was compressed in one end of each cylinder, and the pump spaces each delivered into their corresponding adjacent combustion spaces. The charges entered the pump spaces during the suction period through passages which communicated with a central stationary supply passage at one end of the crank case, communication being cut off when the inlet orifice to the passage passed out of register with the port in the stationary member. The exhaust ports at the outer end of the combustion space opened just before and closed a little later than the air ports, and the incoming charge assisted in expelling the exhaust gases in a manner similar to that of the earlier types of two-stroke cycle engine. The accompanying rough diagram assists in showing the working of this engine. Exhibited in the Paris Aero Exhibition of 1912, the Laviator two-stroke cycle engine, six-cylindered, could be operated either as a radial or as a rotary engine, all its pistons acting on a single crank. Cylinder dimensions of this engine were 3.94 inches bore by 5.12 inches stroke, and a power output of 50 horse- 453 A HISTORY OF AERONAUTICS power was obtained when working at a rate of 1,200 revolutions per minute. Used as a radial engine, it developed 65 horse-power at the same rate of revolution, and, as the total weight was about 198 Ibs., the weight of about 3 Ibs. per horse-power was attained in radial use. The Gobe and Diard Co-axial Two-stroke Engine. Stepped pistons were employed, the annular space between the smaller or power piston and the walls of the larger cylinder being used as a charging pump for the power cylinder situated 120 degrees in rear of it. The charging cylinders were connected by short pipes 454 THE TWO-STROKE CYCLE ENGINE to ports in the crank case which communicated with the hollow crankshaft through which the fresh gas was supplied, and once in each revolution each port in the case registered with the port in the hollow shaft. The mixture which then entered the charging cylinder was transferred to the corresponding working cylinder when the piston of that cylinder had reached the end of its power stroke, and immediately before this the exhaust ports diametrically opposite the inlet ports were uncovered; scavenging was thus assisted in the usual way. The very desirable feature of being entirely valveless was accomplished with this engine, which is also noteworthy for exceedingly compact design. The Lamplough six-cylinder two-stroke cycle rotary, shown at the Aero Exhibition at Olympia in 1911, had several innovations, including a charging pump of rotary blower type. With the six cylinders, six power impulses at regular intervals were given on each rotation; otherwise, the cycle of operations was carried out much as in other two-stroke cycle engines. The pump supplied the mixture under slight pressure to an inlet port in each cylinder, which was opened at the same time as the exhaust port, the period of opening being controlled by the piston. The rotary blower sucked the mixture from the carburettor and delivered it to a passage communicating with the inlet ports in the cylinder walls. A mechanically-operated exhaust valve was placed in the centre of each cylinder head, and towards the end of the working stroke this valve opened, allowing part of the burnt gases to escape to the atmosphere; the remainder was pushed out by the fresh mixture going in through the ports at the bottom end of the cylinder. In practice, one or other of the H.A. 455 20 A HISTORY OF AERONAUTICS cylinders was always taking fresh mixture while working, therefore the delivery from the pump was continuous and the mixture had not to be stored under pressure. The piston of this engine was long enough to keep the ports covered when it was at the top of the stroke, and a bottom ring was provided to prevent the mixture from entering the crank case. In addition to preventing leakage, this ring no doubt prevented an excess of oil working up the piston into the cylinder. As the cylinder fired with every revolution, the valve gear was of the simplest construction, a fixed cam lifting each valve as the cylinder came into position. The spring of the exhaust valve was not placed round the stem in the usual way, but at the end of a short lever, away from the heat of the exhaust gases. The cylinders were of cast steel, the crank case of aluminium, and ball- bearings were fitted to the crankshaft, crank pins, and the rotary blower pump. Ignition was by means of a high-tension magneto of the two-spark pattern, and with a total weight of 300 Ibs. the maximum output was 1 02 brake horse-power, giving a weight of just under 3 Ibs. per horse-power. One of the most successful of the two-stroke cycle engines was that designed by Mr G. F. Mort and con- structed by the New Engine Company. With four cylinders of 3.69 inches bore by 4-5 inches stroke, and running at 1,250 revolutions per minute, this engine developed 50 brake horse-power; the total weight of the engine was 155 Ibs., thus giving a weight of 3.1 Ibs. per horse-power. A scavenging pump of the rotary type was employed, driven by means of gearing from the engine crankshaft, and in order to reduce weight to a minimum the vanes were of aluminium. 456 THE TWO-STROKE CYCLE ENGINE This engine was tried on a biplane, and gave very satisfactory results. American design yields two apparently successful two-stroke cycle aero engines. A rotary called the Fredericson engine was said to give an output of 70 brake horse-power with five cylinders 4-5 inches diameter by 4*75 inches stroke, running at 1,000 revolutions per minute. Another, the Roberts two- stroke cycle engine, yielded 100 brake horse-power from six cylinders of the stepped piston design; two car- burettors, each supplying three cylinders, were fitted to this engine. Ignition was by means of the usual high-tension magneto, gear-driven from the crankshaft, and the engine, which was water-cooled, was of compact design. It may thus be seen that the two-stroke cycle type got as far as actual experiment in air work, and that with considerable success. So far, however, the greater reliability of the four-stroke cycle has rendered it practically the only aircraft engine, and the two-stroke has yet some way to travel before it becomes a formidable competitor, in spite of its admitted theoretical and questioned practical advantages. 457 VII ENGINES OF THE WAR PERIOD THE principal engines of British, French, and American design used in the war period and since are briefly described under the four distinct types of aero engine; such notable examples as the Rolls-Royce, Sunbeam, and Napier engines have been given special mention, as they embodied and still embody all that is best in aero engine practice. So far, however, little has been said about the development of German aero engine design, apart from the early Daimler and other pioneer makes. At the outbreak of hostilities in 1914, thanks to subsidies to contractors and prizes to aircraft pilots, the German aeroplane industry was in a comparatively flourishing condition. There were about twenty-two establishments making different types of heavier-than- air machines, monoplane and biplane, engined for the most part with the four-cylinder Argus or the six- cylinder Mercedes vertical type engines, each of these being of 100 horse-power it was not till war brought increasing demands on aircraft that the limit of power began to rise. Contemporary with the Argus and Mercedes were the Austro-Daimler, Benz, and N.A.G., in vertical design, while as far as rotary types were concerned there were two, the Oberursel and the Stahlhertz; of these the former was by far the most 458 ENGINES OF THE WAR PERIOD promising, and it came to virtual monopoly of the rotary-engined 'plane as soon as the war demand began. It was practically a copy of the famous Gnome rotary, and thus deserves little description. Germany, from the outbreak of war, practically, concentrated on the development of the Mercedes engine; and it is noteworthy that, with one exception, increase of power corresponding with the increased demand for power was attained without increasing the number of cylinders. The various models ranged between 75 and 260 horse-power, the latter being the most recent production of this type. The exception to the rule was the eight-cylinder 240 horse-power, which was replaced by the 260 horse-power six-cylinder model, the latter being more reliable and but very slightly heavier. Of the other engines, the 120 horse- power Argus and the 160 and 225 horse-power Benz were the most used, the Oberursel being very largely discarded after the Fokker monoplane had had its day, and the N.A.G. and Austro-Daimler also falling to comparative disuse. It may be said that the develop- ment of the Mercedes engine contributed very largely to such success as was achieved in the war period by German aircraft, and, in developing the engine, the builders were careful to make alterations in such a way as to effect the least possible change in the design of aeroplane to which they were to be fitted. Thus the engine base of the 175 horse-power model coincided precisely with that of the 150 horse-power model, and the 200 and 240 horse-power models retained the same base dimensions. It was estimated, in 1918, that well over eighty per cent of German aircraft was engined with the Mercedes type. 459 A HISTORY OF AERONAUTICS In design and construction, there was nothing abnormal about the Mercedes engine, the keynote throughout being extreme reliability and such simpli- fication of design as would permit of mass production in different factories. Even before the war, the long list of records set up by this engine formed practical application of the wisdom of this policy; Bonn's flight of 24 hours 10 minutes, accomplished on July loth and nth, 1914, is an instance of this the flight was accomplished on an Albatross biplane with a 75 horse- power Mercedes engine. The radial type, instanced in other countries by the Salmson and Anzani makes, was not developed in Germany; two radial engines were made in that country before the war, but the Germans seemed to lose faith in the type under war conditions, or it may have been that insistence on standardisation ruled out all but the proved examples of engine. Details of one of the middle sizes of Mercedes motor, the 176 horse-power type, apply very generally to the whole range; this size was in use up to and beyond the conclusion of hostilities, and it may still be regarded as characteristic of modern (1920) German practice. The engine is of the fixed vertical type, has six cylinders in line, not off-set, and is water-cooled. The cam shaft is carried in a special bronze casing, seated on the immediate top of the cylinders, and a vertical shaft is interposed between crankshaft and cam- shaft, the latter being driven by bevel gearing. On this vertical connecting-shaft the water pump is located, serving to steady the motion of the shaft. Extending immediately below the camshaft is another vertical shaft, driven by bevel gears from the crank-shaft, 460 ENGINES OF THE WAR PERIOD and terminating in a worm which drives the multiple piston oil pumps. The cylinders are made from steel forgings, as are the valve chamber elbows, which are machined all over and welded together. A jacket of light steel is welded over the valve elbows and attached to a flange on the cylinders, forming a water-cooling space with a section of about T 7 ^ of an inch. The cylinder bore is 5.5 inches, and the stroke 6.29 inches. The cylinders are attached to the crank case by means of dogs and long through bolts, which have shoulders near their lower ends and are bolted to the lower half of the crank chamber. A very light and rigid structure is thus obtained, and the method of construction won the flattery of imitation by makers of other nationality. The cooling system for the cylinders is extremely efficient. After leaving the water pump, the water enters the top of the front cylinders and passes successively through each of the six cylinders of the row; short tubes, welded to the tops of the cylinders, serve as connecting links in the system. The Panhard car engines for years were fitted with a similar cooling system, and the White and Poppe lorry engines were also similarly fitted; the system gives excellent cooling effect where it is most needed, round the valve chambers and the cylinder heads. The pistons are built up from two pieces; a dropped forged steel piston head, from which depend the piston pin bosses, is combined with a cast-iron skirt, into which the steel head is screwed. Four rings are fitted, three at the upper and one at the lower end of the piston skirt, and two lubricating oil grooves are cut in the skirt, in addition to the ring grooves. Two small rivets A HISTORY OF AERONAUTICS retain the steel head on the piston skirt after it has been screwed into position, and it is also welded at two points. The coefficient of friction between the cast-iron and steel is considerably less than that which would exist between two steel parts, and there is less tendency for the skirt to score the cylinder walls than would be the case if all steel were used so noticeable is this that many makers, after giving steel pistons a trial, discarded them in favour of cast-iron; the Gnome is an example of this, being originally fitted with a steel piston carrying a brass ring, discarded in favour of a cast-iron piston with a percentage of steel in the metal mixture. In the Le Rhone engine the difficulty is overcome by a cast- iron liner to the cylinders. The piston pin of the Mercedes is of chrome nickel steel, and is retained in the piston by means of a set screw and cotter pin. The connecting rods, of I section, are very short and rigid, carrying floating bronze bushes which fit the piston pins at the small end, and carrying an oil tube on each for conveying oil from the crank pin to the piston pin. The crankshaft is .of chrome nickel steel, carried on seven bearings. Holes are drilled through each of the crank pins and main bearings, for half the diameter of the shaft, and these are plugged with pressed brass studs. Small holes, drilled through the crank cheeks, serve to convey lubricant from the main bearings to the crank pins. The propeller thrust is taken by a simple ball thrust bearing at the propeller end of the crankshaft, this thrust bearing being seated in a steel retainer which is clamped between the two halves of the crank case. At the forward end of the crankshaft there is mounted a master bevel gear on six splines; this 462 ENGINES OF THE WAR PERIOD bevel floats on the splines against a ball thrust bearing, and, in turn, the thrust is taken by the crank case cover. A stuffing box prevents the loss of lubricant out of the front end of the crank chamber, and' an oil thrower ring serves a similar purpose at the propeller end of the crank chamber. With a motor speed of 1,450 r.p.m., the vertical shaft at the forward end of the motor turns at 2,175 r.p.m., this being the speed of the two magnetos and the water pump. The lower vertical shaft bevel gear and the magneto driving gear are made integral with the vertical driving shaft, which is carried in plain bearings in an aluminium housing. This housing is clamped to the upper half of the crank case by means of three studs. The cam-shaft carries eighteen cams, these being the inlet and exhaust cams, and a set of half compression cams which are formed with the exhaust cams and are put into action when required by means of a lever at the forward end of the cam-shaft. The cam-shaft is hollow, and serves as a channel for the conveyance of lubricating oil to each of the cam- shaft bearings. At the forward end of this shaft there is also mounted an air pump for maintaining pressure on the fuel supply tank, and a bevel gear tachometer drive. Lubrication of the engine is carried out by a full pressure system. The oil is pumped through a single manifold, with seven branches to the crankshaft main bearings, and then in turn through the hollow crankshaft to the connecting-rod big ends and thence through small tubes, already noted, to the small end bearings. The oil pump has four pistons and two double valves driven from a single eccentric shaft on which are mounted 463 A HISTORY OF AERONAUTICS four eccentrics. The pump is continuously submerged in oil; in order to avoid great variations in pressure in the oil lines there is a piston operated pressure regulator, cut in between the pump and the oil lines. The two small pistons of the pump take fresh oil from a tank located in the fuselage of the machine; one of these delivers oil to the cam shaft, and one delivers to the crankshaft; this fresh oil mixes with the used oil, returns to the base, and back to the main large oil pump cylinders. By means of these small pump pistons a constant quantity of oil is kept in the motor, and the oil is continually being freshened by means of the new oil coming in. All the oil pipes are very securely fastened to the lower half of the crank case, and some cooling of the oil is effected by air passing through channels cast in the crank case on its way to the carburettor. A light steel manifold serves to connect the exhaust ports of the cylinders to the main exhaust pipe, which is inclined about 25 degrees from vertical and is arranged to give on to the atmosphere just over the top of the upper wing of the aeroplane. As regards carburation, an automatic air valve surrounds the throat of the carburettor, maintaining normal composition of mixture. A small jet is fitted for starting and running without load. The channels cast in the crank chamber, already alluded to in connection with oil-cooling, serve to warm the air before it reaches the carburettor, of which the body is water-jacketed. Ignition of the engine is by means of two Bosch Z H 6 magnetos, driven at a speed of 2,175 revolutions per minute when the engine is running at its normal speed of 1,450 revolutions. The maximum advance 464 ENGINES OF THE WAR PERIOD of spark is 12 mm., or 32 degrees before the top dead centre, and the firing order of the cylinders is I, j, 3, 6, 2, 4. The radiator fitted to this engine, together with the water-jackets, has a capacity of 25 litres of water, it is rectangular in shape, and is normally tilted at an angle of 30 degrees from vertical. Its weight is 26 kg., and it offers but slight head resistance in flight. The radial type of engine, neglected altogether in Germany, was brought to a very high state of prefection at the end of the War period by British makers. Two makes, the Cosmos Engineering Company's * Jupiter' and * Lucifer,' and the A.B.C. ' Wasp II ' and ' Dragon Fly i A ' require special mention for their light weight and reliability on trials. The Cosmos * Jupiter ' was for it is no longer being made a 450 horse-power nine-cylinder radial engine, air-cooled, with the cylinders set in one single row; it was made both geared to reduce the propeller revolutions relatively to the crankshaft revolutions, and ungeared; the normal power of the geared type was 450 horse-power, and the total weight of the engine, including carburettors, magnetos, etc., was only 757 Ibs.; the engine speed was 1,850 revolutions per minute, and the propeller revolutions were reduced by the gearing to 1,200. Fitted to a * Bristol Badger ' aeroplane, the total weight was 2,800 Ibs, including pilot, passenger, two machine-guns, and full military load; at 7,000 feet the registered speed, with corrections for density, was 137 miles per hour; in climbing, the first 2,000 feet was accomplished in i minute 4 seconds; 4,000 feet was reached in 2 minutes 10 seconds; 6,000 feet was reached in 3 minutes 33 seconds, and 7,000 465 A HISTORY OF AERONAUTICS feet in 4 minutes 15 seconds. It was intended to modify the plane design and fit a new propeller, in order to attain even better results, but, if trials were made with these modifications, the results are not obtainable. The Cosmos ' Lucifer ' was a three-cylinder radial type engine of 100 horse-power, inverted Y design, made on the simplest possible principles with a view to quantity production and extreme reliability. The rated 100 horse-power was attained at 1,600 revolutions per minute, and the cylinder dimensions were 5.75 bore by 6-25 inches stroke. The cylinders were of aluminium and steel mixture, with aluminium heads; overhead valves, operated by push rods on the front side of the cylinders, were fitted, and a simple reducing gear ran them at half engine speed. The crank case was a circular aluminium casting, the engine being attached to the fuselage of the aeroplane by a circular flange situated at the back of the case; propeller shaft and crankshaft were integral/ Dual ignition was provided, the generator and distributors being driven off the back end of the engine and the distributors being easily accessible. Lubrication was by means of two pumps, one scavenging and one suction, oil being fed under pressure from the crankshaft. A single carburettor fed all three cylinders, the branch pipe from the carburettor to the circular ring being provided with an exhaust heater. The total weight of the engine, ' all on,' was 280 Ibs. The A.B.C. ' Wasp II,' made by Walton Motors, Limited, is a seven-cylinder radial, air-cooled engine, the cylinders having a bore of 4.75 inches and stroke 6.25 inches. The normal brake horse-power at 1,650 466 ' Dragonfly ' 1 A. ^ 'Dragonfly' piston assembly. Dragonfly ' cylinder. To face page 46 ENGINES OF THE WAR PERIOD revolutions is 160, and the maximum 200 at a speed of 1,850 revolutions per minute. Lubrication is by means of two rotary pumps, one feeding through the hollow crankshaft to the crank pin, giving centrifugal feed to big end and thence splash oiling, and one feeding to the nose of the engine, dropping on to the cams and forming a permanent sump for the gears on the bottom of the engine nose. Two carburettors are fitted, and two two- spark magnetos, running at one and three-quarters engine speed. The total weight of this engine is 350 Ibs., or 1.75 Ibs. per horse-power. Oil consumption at 1,850 revolutions is -03 pints per horse-power per hour, and petrol consumption is -56 pints per horse- power per hour. The engine thus shows as very economical in consumption, as well as very light in weight. The A.B.C. * Dragon Fly lA ' is a nine-cylinder radial engine having one overhead inlet and two over- head exhaust valves per cylinder. The cylinder dimensions are 5-5 inches bore by 6*5 inches stroke, and the normal rate of speed, 1,650 revolutions per minute, gives 340 horse-power. The oiling is by means of two pumps, the system being practically identical with that of the * Wasp II.' Oil consumption is .021 pints per brake horse-power per hour, and petrol consumption .56 pints the same as that of the ' Wasp II.' The weight of the complete engine, including propeller boss, is 600 Ibs., or 1-765 Ibs. per horse-power. These A.B.C. radials have proved highly satisfactory on tests, and their extreme simplicity of design and reliability commend them as engineering products and at the same time demonstrate the value, for aero work, 467 A HISTORY OF AERONAUTICS of the air-cooled radial design when this latter is accompanied by sound workmanship. These and the Cosmos engines represent the minimum of weight per horse-power yet attained, together with a practicable degree of reliability, in radial and probably any aero engine design. 468 APPENDIX A GENERAL MENSIER's REPORT ON THE TRIALS OF CLEMENT ADER'S * AVION.* PARIS, October 21, 1897. Report on the trials of M. Clement Ader's aviation apparatus. M. Ader having notified the Minister of War by letter, July 21, 1897, that the Apparatus of Aviation which he had agreed to build under the conditions set forth in the convention of July 24th, 1894, was ready, and therefore requesting that trials be undertaken before a Committee appointed for this purpose as per the decision of August 4th, the Committee was appointed as follows : Division General Mensier, Chairman; Division General Delambre, Inspector General of the Permanent Works of Coast Defence, Member of the Technical Committee of the Engineering Corps; Colonel Laussedat, Director of the Conservatoire des Arts et Metiers; Sarrau, Member of the Institute, Professor of Mechanical Engineering at the Polytechnic School ; Leaute, Member of the Institute, Professor of Mechanical Engineering at the Polytechnique School. Colonel Laussedat gave notice at once that his health and work as Director of the Conservatoire des Arts et Metiers did not permit him to be a member of 469 APPENDICES the Committee; the Minister therefore accepted his resignation on September 24th, and decided not to replace him. Later on, however, on the request of the Chairman of the Committee, the Minister appointed a new member, General Grillon, commanding the Engineer Corps of the Military Government of Paris. To carry on the trials which were to take place at the camp of Satory, the Minister ordered the Governor of the Military Forces of Paris to requisition from the Engineer Corps, on the request of the Chairman of the Committee, the men necessary to prepare the grounds at Satory. After an inspection made on the i6th an aerodrome was chosen. M. Ader's idea was to have it of circular shape with a width of 40 metres and an average diameter of 450 metres. The preliminary work, laying out the grounds, interior and exterior circumference, etc., was finished at the end of August; the work of smoothing off the grounds began September ist with forty-five men and two rollers, and was finished on the day of the first tests, October I2th. The first meeting of the Committee was held August 1 8th in M. Ader's workshop; the object being to demonstrate the machine to the Committee and give all the information possible on the tests that were to be held. After a careful examination and after having heard all the explanations by the inventor which were deemed useful and necessary, the Committee decided that the apparatus seemed to be built with a perfect understanding of the purpose to be fulfilled as far as one could judge from a study of the apparatus at rest; they therefore authorised M. Ader to take the machine 470 APPENDICES apart and carry it to the camp at Satory so as to proceed with the trials. By letter of August 1 9th the Chairman made report to the Minister of the findings of the Committee. The work on the grounds having taken longer than was anticipated, the Chairman took advantage of this delay to call the Committee together for a second meeting, during which M. Ader was to run the two propulsive screws situated at the forward end of the apparatus. The meeting was held October 2nd. It gave the Committee an opportunity to appreciate the motive power in all its details; firebox, boiler, engine, under perfect control, absolute condensation, automatic fuel and feed of the liquid to be vaporised, automatic lubri- cation and scavenging; everything, in a word, seemed well designed and executed. The weights in comparison with the power of the engine realised a considerable advance over anything made to date, since the two engines weighed together realised 42 kg., the firebox and boiler 60 kg., the condenser 1 5 kg., or a total of 1 1 7 kg. for approximately 40 horse-power or a little less than 3 kg. per horse-power. One of the members summed up the general opinion by saying : * Whatever may be the result from an aviation point of view, a result which could not be foreseen for the moment, it was nevertheless proven that from a mechanical point of view M. Ader's apparatus was of the greatest interest and real ingeniosity. He expressed a hope that in any case the machine would not be lost to science/ The second experiment in the workshop was made in the presence of the Chairman, the purpose being to H.A. 471 2H APPENDICES demonstrate that the wings, having a spread of 17 metres, were sufficiently strong to support the weight of the apparatus. With this object in view, 14 sliding supports were placed under each one of these, represen- ting imperfectly the manner in which the wings would support the machine in the air; by gradually raising the supports with the slides, the wheels on which the machine rested were lifted from the ground. It was evident at that time that the members composing the skeleton of the wings supported the apparatus, and it was quite evident that when the wings were supported by the air on every point of their surface, the stress would be better equalised than when resting on a few supports, and therefore the resistance to breakage would be considerably greater. After this last test, the work on the ground being practically finished, the machine was transported to Satory, assembled and again made ready for trial. At first M. Ader was to manoeuvre the machine on the ground at a moderate speed, then increase this until it was possible to judge whether there was a tendency for the machine to rise; and it was only after M. Ader had acquired sufficient practice that a meeting of the Committee was to be called to be present at the first part of the trials; namely, volutions of the apparatus on the ground. The first test took place on Tuesday, October I2th, in the presence of the Chairman of the Committee. It had rained a good deal during the night and the clay track would have offered considerable resistance to the rolling of the machine; furthermore, a moderate wind was blowing from the south-west, too strong during the early part of the afternoon to allow of any trials. 472 APPENDICES Toward sunset, however, the wind having weakened, M. Ader decided to make his first trial; the machine was taken out of its hangar, the wings were mounted and steam raised. M. Ader in his seat had, on each side of him, one man to the right and one to the left, whose duty was to rectify the direction of the apparatus in the event that the action of the rear wheel as a rudder would not be sufficient to hold the machine in a straight course. At 5.25 p.m. the machine was started, at first slowly and then at an increased speed; after 250 or 300 metres, the two men who were being dragged by the apparatus were exhausted and forced to fall flat on the ground in order to allow the wings to pass over them, and the trip around the track was completed, a total of 1,400 metres, without incident, at a fair speed, which could be estimated to be from 300 to 400 metres per minute. Notwith- standing M. Ader's inexperience, this being the first time that he had run his apparatus, he followed approxi- mately the chalk line which marked the centre of the track and he stopped at the exact point from which he started. The marks of the wheels on the ground, which was rather soft, did not show up very much, and it was clear that a part of the weight of the apparatus had been supported by the wings, though the speed was only about one-third of what the machine could do had M. Ader used all its motive power; he was running at a pressure of from 3 to 4 atmospheres, when he could have used 10 to 12. This first trial, so fortunately accomplished, was of great importance; it was the first time that a com- paratively heavy vehicle (nearly 400 kg., including the 473 APPENDICES weight of the operator, fuel, and water) had been set in motion by a tractive apparatus, using the air solely as a propelling medium. The favourable report turned in by the Committee after the meeting of October 2nd was found justified by the results demonstrated on the grounds, and the first problem of aviation, namely, the creation of efficient motive power, could be considered as solved, since the propulsion of the apparatus in the air would be a great deal easier than the traction on the ground, provided that the second part of the problem, the sustaining of the machine in the air, would be realised. The next day, Wednesday the I3th, no further trials were made on account of the rain and wind. On Thursday the I4th the Chairman requested that General Grillon, who had just been appointed a member of the Committee, accompany him so as to have a second witness. The weather was fine, but a fairly strong, gusty wind was blowing from the south. M. Ader explained to the two members of the Committee the danger of these gusts, since at two points of the circumference the wind would strike him sideways. The wind was blowing in the direction A B, the apparatus starting from C, and running in the direction shown by the arrow. The first dangerous spot would be at B. The apparatus had been kept in readiness in the event of the wind dying down. Toward sunset the wind seemed to die down, as it had done on the evening of the I2th. M. Ader hesitated, which, unfortunately, further events only justified, but decided to make a new trial. At the start, which took place at 5.15 p.m., the apparatus, having the wind in the rear, seemed to run at a fairly regular speed; it was, nevertheless, easy to 474 APPENDICES note from the marks of the wheels on the ground that the rear part of the apparatus had been lifted and that the rear wheel, being the rudder, had not been in constant contact with the ground. When the machine came to the neighbourhood of B, the two members of the Committee saw the machine swerve suddenly out of the track in a semicircle, lean over to the right and finally stop. They immediately proceeded to the point where the accident had taken place and endeavoured to find an explanation for the same. The Chairman finally decided as follows: M. Ader was the victim of a gust of wind which he had feared as he explained before starting out; feeling himself thrown out of his course, he tried to use the rudder energetically, but at that time the rear wheel was not in contact with the ground, and therefore did not perform its function; the canvas rudder, which had as its purpose the manoeuvring of the machine in the air, did not have sufficient action on the ground. It would have been possible without any doubt to react by using the propellers at unequal speed, but M. Ader, being still inexperienced, had not thought of this. Furthermore, he was thrown out of his course so quickly that he decided, in order to avoid a more serious accident, to stop both engines. This sudden stop produced the half-circle already described and the fall of the machine on its side. The damage to the machine was serious; consisting at first sight of the rupture of both propellers, the rear left wheel and the bending of the left wing tip. It will only be possible to determine after the machine is taken apart whether the engine, and more particularly the organs of transmission, have been put out of line. 475 APPENDICES Whatever the damage may be, though comparatively easy to repair, it will take a certain amount of time, and taking into consideration the time of year it is evident that the tests will have to be adjourned for the present. As has been said in the above report, the tests, though prematurely interrupted, have shown results of great importance, and though the final results are hard to foresee, it would seem advisable to continue the trials. By waiting for the return of spring there will be plenty of time to finish the tests and it will not be necessary to rush matters, which was a partial cause of the accident. The Chairman of the Committee personally has but one hope, and that is that a decision be reached accordingly. TV r- i Division General, Chairman of the Committee, MENSIER. BOULOGNE-SUR-SEINE, October list, 1897. Annex to the Report of October list. General Grillon, who was present at the trials of the 1 4th, and who saw the report relative to what happened during that day, made the following observations in writing, which are reproduced herewith in quotation marks. The Chairman of the Committee does not agree with General Grillon and he answers these observations paragraph by paragraph. I. ' If the rear wheel (there is only one of these) left but intermittent tracks on the ground, does that prove that the machine has a tendency to rise when running at a certain speed ? ' Answer. This does not prove anything in any way, and I was very careful not to mention this in my 476 APPENDICES report, this point being exactly what was needed and that was not demonstrated during the two tests made on the grounds. * Does not this unequal pressure of the two pair of wheels on the ground show that the centre of gravity of the apparatus is placed too far forward and that under the impulse of the propellers the machine has a tendency to tilt forward, due to the resistance of the air ? ' Answer. The tendency of the apparatus to rise from the rear when it was running with the wind seemed to be brought about by the effects of the wind on the huge wings, having a spread of 17 metres, and I believe that when the machine would have faced the wind the front wheels would have been lifted. During the trials of October I2th, when a complete circuit of the track was accomplished without incidents, as I and Lieut. Binet witnessed, there was practically no wind. I was therefore unable to verify whether during this circuit the two front wheels or the rear wheel were in constant contact with the ground, because when the trial was over it was dark (it was 5.30) and the next day it was impossible to see anything because it had rained during the night and during Wednesday morning. But what would prove that the rear wheel was in contact with the ground at all times is the fact that M. Ader, though inexperienced, did not swerve from the circular track, which would prove that he steered pretty well with his rear wheel this he could not have done if he had been in the air. In the tests of the I2th, the speed was at least as great as on the I4th. 2. ' It would seem to me that if M. Ader thought 477 APPENDICES that his rear wheels were off the ground he should have used his canvas rudder in order to regain his proper course; this was the best way of causing the machine to rotate, since it would have given an angular motion to the front axle.' Answer. I state in my report that the canvas rudder whose object was the manoeuvre of the apparatus in the air could have no effect on the apparatus on the ground, and to convince oneself of this point it is only necessary to consider the small surface of this canvas rudder compared with the mass to be handled on the ground, a weight of approximately 400 kg. According to my idea, and as I have stated in my report, M. Ader should have steered by increasing the speed on one of his propellers and slowing down the other. He admitted afterward that this remark was well founded, but that he did not have time to think of it owing to the sudden- ness of the accident. 3. * When the apparatus fell on its side it was under the sole influence of the wind, since M. Ader had stopped the machine. Have we not a result here which will always be the same when the machine comes to the ground, since the engines will always have to be stopped or slowed down when coming to the ground ? Here seems to be a bad defect of the apparatus under trial.' Answer. I believe that the apparatus fell on its side after coming to a stop, not on account of the wind, but because the semicircle described was on rough ground and one of the wheels had collapsed. MENSIER. October 27 th, 1897. 478 APPENDIX B Specification and Claims of Wright Patent^ No. 821393. Filed March 23^, 1903. Issued May 22nd y 1906. Expires May iind> 1923. To all whom it may concern. Be it known that we, Orville Wright and Wilbur Wright, citizens of the United States, residing in the city of Dayton, county of Montgomery, and State of Ohio, have invented certain new and useful Improve- ments in Flying Machines, of which the following is a specification. Our invention relates to that class of flying-machines in which the weight is sustained by the reactions resulting when one or more aeroplanes are moved through the air edgewise at a small angle of incidence, either by the application of mechanical power or by the utilisation of the force of gravity. The objects of our invention are to provide means for maintaining or restoring the equilibrium or lateral balance of the apparatus, to provide means for guiding the machine both vertically and horizontally, and to provide a structure combining lightness, strength, convenience of construction and certain other advantages which will hereinafter appear. To these ends our invention consists in certain novel features, which we will now proceed to describe and will then particularly point out in the claims. 479 APPENDICES In the accompanying drawings, Figure I is a per- spective view of an apparatus embodying our invention in one form. Fig. 2 is a plan view of the same, partly in horizontal section and partly broken away. Fig. 3 is a side elevation, and Figs. 4 and 5 are detail views, of one form of flexible joint for connecting the upright standards with the aeroplanes. In flying machines of the character to which this invention relates the apparatus is supported in the air by reason of the contact between the air and the under surface of one or more aeroplanes, the contact surface being presented at a small angle of incidence to the air. The relative movements of the air and aeroplane may be derived from the motion of the air in the form of wind blowing in the direction opposite to that in which the apparatus is travelling or by a combined downward and forward movement of the machine, as in starting from an elevated position or by combination of these two things, and in either case the operation is that of a soaring-machine, while power applied to the machine to propel it positively forward will cause the air to support the machine in a similar manner. In either case owing to the varying conditions to be met there are numerous disturbing forces which tend to shift the machine from the position which it should occupy to obtain the desired results. It is the chief object of our invention to provide means for remedying this difficulty, and we will now proceed to describe the construction by means of which these results are accomplished. In the accompanying drawing we have shown an apparatus embodying our invention in one form. In this illustrative embodiment the machine is shown as comprising two parallel superposed aeroplanes, i and 2 480 < *" APPENDICES may be embodied in a structure having a single aero- plane. Each aeroplane is of considerably greater width from side to side than from front to rear. The four corners of the upper aeroplane are indicated by the reference letters #, b, c, and LD 19 '65 -3PM YC 19422 UNIVERSITY OF CALIFORNIA LIBRARY