AEROPLANES

The writer of this record of "Progress in Flying Machines" originally hesitated whether he should include therein the account of the experiments of Captain [e Bris, which is about to follow. Not because he deemed it incredible in itself, nor because, if correctly stated, the experiments were not most interesting and instructive, but because the only account of them which he had been able to procure was contained in a novel, in which the author, to make the book more attractive, had mixed up a love story with the record of the aerial experiments, which combination, in the present state of disbelief, the writer feared might be too much for the credulity of the reader. It is true that the author of the novel²³ said that the account of the experiments was scrupulously correct, and that in this, the principal object of the book, he had endeavored to he very exact, even at the risk of detracting from his hero. It is also a fact that the Aéronaute²⁴ in reviewing the book, said:

Throughout the novel are to be found absolutely historical data concerning the artificial bird of Le Bris his experiments, his partial success, his mischances, and his deplorable final failure, the latter not through a radical defect, but through lack of method, steadiness in thought, and attention to details.

But still the writer hesitated to reproduce this tale of an ancient mariner.

Fortunately, after a year's seeking, he succeeded in getting a copy of an historical book, now quite out of print, by the same author,²⁵ which gives without any embellishments an account of Captain Le Bris's experiments, and quite confirms that given in the novel, wherein it is said to have been related " with scrupulous exactness." From the historical work, therefore, of M. de la Landelle, supplemented by his novel, the following account has been compiled of what seems to have been a very remarkable series of experiments on "aspiration."

Captain Le Bris was a French mariner, who had in his younger days made several voyages around the Cape of Good Hope and Cape Horn, and whose imagination had been fired by the sight of the albatross, sporting in the tempest on rigid wings, and keeping up with the fleetest ships without exertion. He had killed one of these birds, and claimed to have observed a very remarkable phenomenon. In his own words, as quoted by M. de la Landelle:

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.

Possessed with an ardent imagination, he early became smitten with the design of building an artificial bird capable of carrying him, whose wings should be controlled by means of levers and by a system of rigging; and when he returned to France, and had become the captain of a coasting vessel, sailing from Douarnenez (Finistère), where he was born, and where he had married, he designed and constructed with his own hands the artificial albatross shown in fig. 48.

FIG. 48. -- LE BRIS -- 1867

This consisted of a body in the shape of a "sabot," or wooden shoe, the front portion being decked over, provided with two flexible wings and a tail. The body was built like a canoe, being 13 1/2 ft. Iong and 4 ft. wide at its broadest point, made of light ash ribs well stayed, and covered on the outside with impermeable cloth, so it could float. A small inclined mast in front supported the pulleys and cords intended to work the wings. The latter were each 23 ft. long, so that the apparatus was 50 ft. across, and spread about 215 sq. ft. of supporting surface; the total weight, without the operator, being 92 Ibs. The tail was hinged so as to steer both up and down and sideways, the whole apparatus being, as near as might be, proportioned like the albatross. The front edge of the wings was made of a flexible piece of wood, shaped like the front edge of the wing of the albatross, and to this, cross wands were fastened and covered with canton flannel, the flocculent side down. An ingenious arrangement, which Le Bris called his rotules (knee pans), worked by two powerful levers, imparted a rotary motion to the front edge of the wings, and also permitted of their adjustment to various angles of incidence with the wind. Le Bris was to stand upright in the canoe (an excellent position), his hands on the levers and cords, and his feet on a pedal to work the tail. His expectation was that, with a strong wind, he would rise into the air and reproduce all the evolutions of the soaring albatross, without any flapping whatever.

Le Bris's first experiment was conducted on a public road at Trefeuntec, near Douarnenez. Believing, like Count D' Esterno that it was necessary that the apparatus should have an initial velocity of its own, in addition to that of the wind, he chose a Sunday morning, when there was a good 10-knot breeze from the right direction, and setting his artificial albatross horizontally on a cart, he started down the road against the brisk wind, the cart being driven by a peasant. The bird, with extended wings, 50 ft. across, was held down by a rope passing under the rails of the cart and terminating in a slip knot fastened to Le Bris's wrist, so that with one jerk he could loosen the attachment and allow the rope to run. He stood upright in the canoe, unincumbered in his movements, his hands being on the levers and depressing the front edge of the wings, so that the wind should press upon the top only and hold them down, their position being, moreover, temporarily maintained by assistants walking along on each side.

When they came to the right turn in the road the assistants were directed to let go, and the driver was told to put his horse on a trot. Then Le Bris, pressing on his levers, slowly raised the front edge of the wings to a very slight angle of incidence; they fluttered a moment, and then took the wind like a sail on the under side, relieving the weight upon the cart so much that the horse began to gallop. With one jerk Le Bris loosened the fastening rope, but lo ! it did not run, and the bird did not rise. Instead of this, its ascending power counterbalanced the weight of the cart, and the horse galloped as if at full liberty. It was afterward ascertained that the running rope had been caught on a concealed nail, and that the apparatus had remained firmly fastened to the cart. Finally the rails of the latter gave way, the machine rose into the air, and Le Bris said he found himself perfectly balanced, going up steadily to a height of nearly 300 ft., and sailing about twice that distance over the road.

But an accident had taken place. At the last moment the running rope had whipped and wound around the body of the driver, had lifted him from his seat, and carried him up into the air. He involuntarily performed the part of the tail of a kite; his weight, by an extraordinary chance, Just balancing the apparatus properly at the assumed angle of incidence, and with the strength of the brisk wind then blowing. Up above, in the machine, Le Bris felt himself well poised in the breeze, and exulted that he was about to pass two hours in the air; but below, the driver was hanging on to the rope and howling with fright and anguish.

As soon as Le Bris became aware of this state of affairs, and this was doubtless in a very short time, he took measures to descend. He changed the angle of incidence of his wings, came down slowly, and manoeuvred so well that the driver gently reached the soil, entirely unharmed and ran off to catch his horse, who had stopped when he again felt the weight of the cart behind him; but the equilibrium of the artificial albatross was no longer the same, because part of the weight had been relieved, and Le Bris did not succeed in reascending. He managed with his levers to retard the descent, and came down entirely unhurt, but one wing struck the ground in advance of the other and was somewhat damaged.

This exploit naturally caused a great deal of local talk. Captain Le Bris was considered a visionary crank by most persons, and as a hero by others. He was poor, and had to earn his daily bread, so that it was some little time before, with the aid of some friends, he repaired his machine and was ready to try it again.

He determined this time to gain his initial velocity by dropping from a height, and for this purpose erected a mast, with a swinging yard, on the brink of a quarry, excavated in a sort of pocket, the bottom of which was well protected from the wind. In this quarry bottom he put his apparatus together, and standing in the canoe, it was suspended to a rope and hoisted up aloft to a height of some 30 ft. above the ridge, and nearly 100 ft. above the quarry bottom. A fresh breeze was blowing inland, and the yard was swung so that the apparatus should face both the wind and the quarry, while Le Bris adjusted his levers so that only the top surfaces of the wings should receive the wind. When he had, by trial, reached a proper balance, he raised upward the front edge of the wings, brought the tail into action through the pedal, and thought he felt himself well seated on the air, and, as it were, "aspired forward into the breeze." At this moment he tripped the hook suspending the apparatus, and the latter glided and sailed off toward the quarry.

Scarcely had it reached the middle of the pocket, when it met a stratum of wind inclined at a different angle from that prevailing at the starting_point¤a vertical eddy, so to speak¤probably caused by the reaction of the wind against the sides of the quarry. The apparatus then tilted forward, Le Bris pressed on his levers to alter the plane of the wings, but he was not quick enough. The accounts of the bystanders were conflicting, but it was thought that the apparatus next oscillated upward, and then took a second downward dip, but in any event it finally pitched forward, and fell toward the bottom of the quarry. As soon as the apparatus became sheltered from the wind it righted up, and fell nearly vertically; but as it exposed rather less than 1 sq. ft. of surface to each pound of weight, it could scarcely act as a parachute, and it went down so violently that it was smashed all to pieces, and Le Bris, who at the last moment suspended himself to the mast of the canoe and sprang upward, nevertheless had a leg broken by the rebound of the levers.

This accident practically ruined him, and put an end for 12 or 13 years to any further attempt to prove the soundness of his theory. He had failed in both experiments for want of adequate equilibrium. He fairly provided for the transverse balance by making his wings flexible, but the longitudinal equilibrium was defective, as he could not adjust the fore_and_aft balance as instantly as the circumstances changed. The bird does his like a flash by instinct; the man was compelled to reason it out, and he could not act quickly enough.

M. de la Landelle makes the following comment:

He lacked the science of Dante (of Perugia), but he was ingenious, persevering, and the most intrepid of men. He was entirely in the right in locating himself upright, both arms and legs quite free, in an apparatus which was besides exceedingly well designed. None was better fitted than he to succeed in sailing flight (vol-à-voile) in imitation of his model, the albatross.

In 1867 a public subscription at Brest enabled Le Bris to build a second artificial albatross, and this is the one represented by fig. 48. It was much like the first, but a trifle lighter, although a movable counterweight was added, intended to produce automatic equilibrium. The apparatus when completed was publicly exhibited, and attracted much attention; but the inventor no longer had the audacity of youth, and he was influenced by numberless contradictory counsellors. He wanted to proceed as at Douarnenez, by giving an initial velocity to his apparatus, but he was dissuaded from this. He was also urged to test his machine with ballast, instead of riding in it himself, which at once changed all the conditions of equilibrium, as there was no longer command over a varying angle of incidence, and yet a first mischance led him to resort to the method of experimenting without riding in the machine.

M. de la Landelle relates the incident as follows:

Once only did he obtain something like an ascension, by starting from a light wagon, which was not in motion. He was on the levee of the port of commerce at Brest, the breeze was light, and the gathered public was impatient, through failure to realize that success depended wholly on the intensity of the wind. Le Bris was hoping for a gust which should enable him to rise; he thought it had come, pulled on his levers, and thus threw his wings to the most favorable angle, but he only ascended a dozen yards, glided scarcely twice that distance, and after this brief demonstration came gently to the ground without any jerk.

This negative result occasioned a good many hostile comments, and so the inventor no longer experimented in public; but he had further bad luck; the machine was several times capsized at starting, and more or less injured, being repaired at the cost of Le Bris, whose means were nearly exhausted. Then he tried it in ballast with varying success, and on one occasion, the breeze being just right, it rose up some 50 yds., with a light line attached, and advanced against the wind as if gliding over it. Very soon the line became slack, and the assisting sailors were greatly astonished, for the bird, without waver, thus proceeded some 200 yds.; but at the approach of some rising ground, which undoubtedly altered the direction of the aerial current, the bird, shielded from the wind, began settling down, without jolt, very gently, and alighted so lightly that the grass was scarcely bruised.

Encouraged by this partial success, Le Bris tried to reproduce the same results, but he met many mishaps, in which the apparatus was upset and injured. At last, one day, by a stiff northeast breeze, he installed his bird on top of the rising ground near which it had performed so well a few weeks before, and this time he meant to ride in the machine himself. He was dissuaded by his friends, and probably made a serious mistake in yielding to them, for the uncontrolled apparatus was not intended to adjust itself to a gusty wind.

At any rate, the empty machine rose, but it did not sustain itself in the air. It gave a twist, a glide, and a plunge, and pitched forward to the ground, where it was shattered all to bits. The wings were broken, the covering cloth of the canoe was rent to pieces, while the bowsprit in front was broken and forced back like a dart into the canoe.

The friends claimed that if the operator had been aboard, he surely would have been spitted and killed, but Le Bris maintained that if he had been aboard he could, with his levers, have changed the angle of the wings in time to avoid the wreck; he blamed himself for having surrendered his better judgment, and he gave way to profound despair.

For this was the end. His second apparatus was smashed, his means and his credit were exhausted, his friends forsook him, and perhaps his own courage weakened, for he did not try again. He retired to his native place, where, after serving with honor in the war of 1870 he became a special constable, and was killed in 1872 by some ruffians whose enmity he had incurred.

Le Bris had made a very earnest, and, upon the whole, a fairly intelligent effort to compass sailing flight by imitating the birds. He finally failed for want of sufficient pecuniary backing, and also, perhaps, for lack of scientific methods and knowledge, for even at that day Captain BÙlÙguic a French naval officer, had called attention to the importance of securing longitudinal equilibrium, the lack of which caused the failure of poor Le Bris. Had he secured this he might have succeeded far better, especially if he had adhered to his original conception as to the necessity for that initial velocity against the wind, which served him so well upon the first trial and so ill upon the second. Singularly enough, he does not seem in all his subsequent experiments to have sought to give his apparatus that forward motion of its own, which he, like Count D'Esterno, originally held to be indispensable. He had also proposed to carry on his experiments at sea, from a steam vessel under way, and whatever may have been the cause that made him give up this idea, it was a misfortune, for his apparatus was capable of floating, he was himself an excellent swimmer, and had he experimented from a vessel under motion, not only would he have been safe, but he would have had no lack of wind to rise upon the air.

He seems, if the accounts given be correct, to have exhibited some very remarkable phenomena of "aspiration" which we shall find reproduced in one or two experiments yet to be noticed, and which the soaring birds exhibit every day to the observer, but he was baffled by the lack of fore-and-aft equilibrium.

In 1867 Mr.Smyth patented, in Great Britain, a combination of aeroplanes with lifting and driving screws, which is shown in end view by fig. 49. It consisted of a cylindrical car with pointed ends, to carry the passengers and the motor; of two aeroplanes, or light frames covered with silk, one at the front of the car and one at the rear, to furnish the supporting power when driven through the air by the propellers--one of which is shown in end view--and of two lifting screws, one above and the other below the car. These latter vanes were to be mounted at an adjustable angle upon vertical shafts passing through a tube in the car, the weight of the latter being transferred to them by means of a disk placed on rollers. This set of vanes was to be driven by one engine, and the horizontal propellers by another, so that the apparatus could be simultaneously lifted and driven forward if desired.

Fig. 49 -- SMYTH -- 1867.

This arrangement is open to the objection that the resistance of the aeroplane has to be overcome in rising, and it is quite inferior to the proposal of Crowell patented in the United States in 1862 in which he had shown a pair of propellers (revolving in contrary directions), pivoted at the car, so that they might be brought overhead to ascend, and gradually dropped to the horizontal line to drive the apparatus forward, at which time a pair of aeroplanes, hinged at the car, and hanging vertically during the ascent, was also to be brought to a horizontal position to furnish a sustaining reaction.

Mr. Smyth seems to have apprehended that there might be some difficulty with his own arrangement, for he provides in his patent for a modification, in which he dispenses with the elevating propellers, and proposes to flap the sustaining surfaces or modified aeroplanes.

The principal feature of novelty, however, in Mr. Smyth's proposal was in the motor, which was to be a non-metallic apparatus, within which to explode gases to produce motion. This was to consist of a wooden cylinder, lined with a water-proof coating, and containing a series of india-rubber cells surrounded with water and connected with each other. Inside of these cells, which could be alternately collapsed or expanded, explosive mixtures of hydrogen and air were to be fired by electric sparks, the resulting expansion driving out a folding extension of the wooden cylinder, arranged like a concertina, and imparting motion to a jointed rod from which it was conveyed to the propellers.

The object was evidently to save the weight incumbent upon metallic engines, the patentee asserting that India rubber cells are not injured by exploding mixed gases in them, so long as they are kept moist. It is probable that experiments were made with some models of this novel motor, but no account of them seems to have been published. Mr. Smyth had described his proposed machine at the 1867 meeting of the Aeronautical Society of Great Britain, but had no model in the exhibition of that society in the ensuing year, where, however, an analogous idea was brought forward by Mr. D. S. Brown, through a model in which the ordinary cylinder and piston of a steam-engine were replaced by an india-rubber cloth bag, the alternate inflation and expansion of which produced the stroke. It was stated that the first steam-engine constructed by Hancock ran on the common road with an engine of this description, but that as the process of vulcanizing india-rubber was not then known, the steam speedily softened the texture and escaped through the canvas.

Fig. 50 shows the form of aeroplane patented in Great Britain in 1867 by Butler and Edwards, and was evidently due to some recollection of their school-boy days, when they threw paper arrows in class. The stability of these Iittle projectiles is quite good fore-and-aft, because the supporting surfaces increase in area while the intensity of the pressures diminish toward the rear, but the power required is great, and there is probably no aviating merit in this form. Butler and Edwards proposed to combine it in a variety of ways, superposing the sustaining planes, or placing two machines side by side, or both, and bracing between by diagonal ties. The form here shown is the simplest, the top planes being set at a slight diedral angle, in order to procure lateral stability.

FIG. 50 -- BUTLER & EDWARDS-- 1867.

The motive power was to be placed in a car, forward of the centre of figure, and capable of being moved forward and back, so as to shift the center of gravity to correspond with the center of pressure at varying angles of flight. The power was to consist in jets of steam issuing against the air in the rear; but, suspecting that this would be enormously wasteful, the patentees reserved the right of using screw propellers, driven either by the reaction of jets of steam issuing from curved arms (Hero's aeolipile) or by an ordinary steam-engine, in which case the steam was to be exhausted and condensed back into water, in cells formed by doubling the surfaces of the planes and thus providing hollow spaces.

We now come to a celebrated experiment, which attracted great attention at the time; not so much because of the results obtained with the entire apparatus, for these were unsatisfactory, but because of the unprecedented lightness of the steam-engine in proportion to its estimated power.

Mr. Stringfellow whose experiments in connection with Henson's machine have already been noticed, was much impressed with Mr. Wenham's proposal for superposing planes, and when the Aeronautical Society of Great Britain advertised an exhibition and offered prizes, he constructed and entered two models for competition in 1868.

One of these models was the apparatus shown in fig. 51 and consisted of three superposed planes and of a tail, driven by a screw propeller moved by a steam-engine The aggregate frontage was 21 lineal feet and the sustaining area of the three planes was 28 sq. ft., while the tail added some 8 ft. more, thus making some 36 sq. ft. The weight, including the aeroplane, engine, boiler, fuel and water. was under 12 Ibs., thus giving a proportion of about; sq. ft. per pound, which was certainly ample for support. The engine was rated at one-third of a horse power but its weight is not stated.

FIG. 51 -- STRINGFELLOW -- 1868.

The machine ran suspended along a wire, in the central transept of the Crystal Palace in London. It was forced by its propellers at great speed, but generally failed to lift itself from the wire, although Mr. Stringfellow said that it occasionally did so, and was then sustained by its superposed planes alone. this failure to rise may have been due to the fact, stated by M. Hureau de Villeneuve, |hat the axis of the screw was parallel with the sustaining planes so that there was no angle of incidence, but a better explanation lies in the fact that the equilibrium was so imperfect that it was not safe, for fear of breakage, to liberate the machine. This however, was done at the basement of the Crystal Palace, after the close of |he public exhibition, a canvas being held to break the fall, and M. Brearey, an eye-witness, says:

When freed, it descended an incline with apparent lightness until caught in the canvas; but the impression conveyed was that had there been sufficient fall, it would have recovered itself.... It was intended at the last to set this model free in the open country, when the requirements of the Exhibition were satisfied, but it was found that the engine, which had done much work, required repairs. Many months afterward, the presence of the author (M. Brearey) an experiment was tried in a field at Chard, by means of a wire stretched across it. The engine was fed with methylated spirits, and during some portion of its run under the wire, the draft occasioned thereby invariably extinguished the flames, and so these interesting trials were rendered abortive.

This apparatus (restored) is now in the National Museum of the Smithsonian Institution at Washington, where it is said that the engine cannot now develop anything like the power originally claimed.

The remark has well been made that so far as concerns he motive power, this apparatus ought to have flown. Its weight was only that of a goose, and it was said to have one-third of a horse-power. This may have been overestimated, but then Mr. Maxim estimates the power of a goose at 0.083 of a horse-power, and so there is ample margin.

There were two reasons for the failure. In the first place the sustaining surfaces were at least three times those of the goose, and hence the "drift, "or horizontal component of the air pressure, would be much greater in the aggregate, so that the discrepancy in power is not as great as at first sight appears; and in the second place, and more important, the equilibrium was so defective that the inventor did not dare liberate his model, while freedom of action is the first condition of successful experiment in flight. He had done better with single planes on the previous occasion which has been mentioned, but the failure with superposed planes in 1868 does not necessarily condemn them. It merely indicates that the surfaces must be of correct shape and skilfully arranged, and, if possible, produce automatic stability. If the equilibrium be unstable, like that of the bird it is well enough to have more power than the goose but it is much more important to possess its skill.

The second model of Mr. Stringfellow consisted in a steam-engine, similar to that applied to the complete apparatus, but larger. It was entered in the catalogue thus:

Light engine and machinery for aerial purposes, about half horse-power, cylinder 2 in. diameter, 3 in. stroke generating surface of boiler, 3 1/2 ft.; starts at 100 lbs. pressure in three minutes, works two propellers of 3 ft. diameter, about 300 revolutions per minute. With 3 1/2 pints of water and 10 oz. of liquid fuel, works about ten minutes. Weight of engine, boiler, water, and fuel, 16 1/4 Ibs.

Subsequently the examining jury estimated the power at one full horse-power, the weight of the engine and boiler alone being 13 Ibs., and it awarded a prize of $500 to Mr. Stringfellow for "the lightest engine in proportion to its power, from whatever source that power may be derived."

With this prize money Mr. Stringfellow erected a building over 70 ft. long, in which to experiment with a view of ultimately constructing a large machine to carry a person to guide and conduct it, his experience with models having evidently impressed him with the necessity for intelligent control of any aerial apparatus not possessing automatic stability; but he was already 69 years of age, his sight became impaired, and he died in 1883 without having accomplished any advance on his previous achievements.

A reference is made by M. de la Landelle in "Dans les airs" to an "Essay upon the theory of Flight," published in 1869 at Copenhagen by Professor Krarup-Hansen, giving an account of an apparatus carrying a man who, by means of pedals, put into action horizontal wings whose action imparted motion to the machine, but the account is too scanty to determine whether this refers to beating wings or to an aeroplane.

Almost the same may be said concerning a large artificial bird, whose wings covered with feathers were more than 32 ft across constructed in 1845 by M Duchesnay and exhibited in Paris, but which does not seem to have been tried in the open air. Somewhat more definite is he account given of some experiments by M. Marc Seguin, he celebrated French civil engineer, who in 1846 tried :two series of experiments, one with lifting screws, and he other with an apparatus weighing 50 Ibs., with a pair of canvas wings measuring 65 sq. ft. in area, from which he drew rather discouraging conclusions. He, however, tried another series of experiments in 1849 with an apparatus weighing 35 Ibs. and worked by a man, the total weight, including ballast and operator being 232 lbs. This actually left the ground, and raised up some 6 to 8 in., but the effort required was evidently so violent as not to warrant further experimenting with man-power.

Continues