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 wingspread 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 14th, 1897, tried out his third machine at the 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 accomplishment, 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 practiced 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 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 deserve—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 construction, was ready for trial. This was fitted with two steam motors of twenty horse-power each, driving two four-bladed propellers; the wings warped automatically: 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 movement of the tail planes.
On October the 12th, 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 controversy 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 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 continually 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 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 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 '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 order to achieve flight. The wrecked 'Avion' and the refusal of the French War Ministry to grant any more funds for further experiment are sufficient evidence of the need for working along the lines taken by the pioneers of gliding rather than on those which Ader himself adopted.
Let it not be thought that in this comment there is any desire to derogate from the position which Ader should occupy in any study of the pioneers of aeronautical enterprise. If he failed, he failed magnificently, and if he succeeded, then the student of aeronautics does him an injustice and confers on the Brothers Wright an honour which, in spite of the value of their work, they do not deserve. There was one earlier than Ader, Alphonse Penaud, who, in the face of a lesser disappointment than that which Ader must have felt in gazing on the wreckage of his machine, committed suicide; Ader himself, rendered unable to do more, remained content with his achievement, and with the knowledge that he had played a good part in the long search which must eventually end in triumph. Whatever the world might say, he himself was certain that he had achieved flight. This, for him, was perforce enough.
Before turning to consideration of the work accomplished by the Brothers Wright, and their proved conquest of the air, it is necessary first to sketch as briefly as may be the experimental work of Sir (then Mr) Hiram Maxim, who, in his book, Artificial and Natural Flight, has given a fairly complete account of his various experiments. He began by experimenting with models, with screw-propelled planes so attached to a horizontal movable arm that when the screw was set in motion the plane described a circle round a central point, and, eventually, he built a giant aeroplane having a total supporting area of 1,500 square feet, and a wing-span of fifty feet. It has been thought advisable to give a fairly full description of the power plant used to the propulsion of this machine in the section devoted to engine development. The aeroplane, as Maxim describes it, had five long and narrow planes projecting from each side, and a main or central plane of pterygoid aspect. A fore and aft rudder was provided, and had all the auxiliary planes been put in position for experimental work a total lifting surface of 6,000 square feet could have been obtained. Maxim, however, did not use more than 4,000 square feet of lifting surface even in his later experiments; with this he judged the machine capable of lifting slightly under 8,000 lbs. weight, made up of 600 lbs. water in the boiler and tank, a crew of three men, a supply of naphtha fuel, and the weight of the machine itself.
Maxim's intention was, before attempting free flight, to get as much data as possible regarding the conditions under which flight must be obtained, by what is known in these days as 'taxi-ing'—that is, running the propellers at sufficient speed to drive the machine along the ground without actually mounting into the air. He knew that he had an immense lifting surface and a tremendous amount of power in his engine even when the total weight of the experimental plant was taken into consideration, and thus he set about to devise some means of keeping the machine on the nine foot gauge rail track which had been constructed for the trials. At the outset he had a set of very heavy cast-iron wheels made on which to mount the machine, the total weight of wheels, axles, and connections being about one and a half tons. These were so constructed that the light flanged wheels which supported the machine on the steel rails could be lifted six inches above the track, still leaving the heavy wheels on the rails for guidance of the machine. 'This arrangement,' Maxim states, 'was tried on several occasions, the machine being run fast enough to lift the forward end off the track. However, I found considerable difficulty in starting and stopping quickly on account of the great weight, and the amount of energy necessary to set such heavy wheels spinning at a high velocity. The last experiment with these wheels was made when a head wind was blowing at the rate of about ten miles an hour. It was rather unsteady, and when the machine was running at its greatest velocity, a sudden gust lifted not only the front end, but also the heavy front wheels completely off the track, and the machine falling on soft ground was soon blown over by the wind.'
Consequently, a safety track was provided, consisting of squared pine logs, three inches by nine inches, placed about two feet above the steel way and having a thirty-foot gauge. Four extra wheels were fitted to the machine on outriggers and so adjusted that, if the machine should lift one inch clear of the steel rails, the wheels at the ends of the outriggers would engage the under side of the pine trackway.
The first fully loaded run was made in a dead calm with 150 lbs. steam pressure to the square inch, and there was no sign of the wheels leaving the steel track. On a second run, with 230 lbs. steam pressure the machine seemed to alternate between adherence to the lower and upper tracks, as many as three of the outrigger wheels engaging at the same time, and the weight on the steel rails being reduced practically to nothing. In preparation for a third run, in which it was intended to use full power, a dynamometer was attached to the machine and the engines were started at 200 lbs. pressure, which was gradually increased to 310 lbs per square inch. The incline of the track, added to the reading of the dynamometer, showed a total screw thrust of 2,164 lbs. After the dynamometer test had been completed, and everything had been made ready for trial in motion, careful observers were stationed on each side of the track, and the order was given to release the machine. What follows is best told in Maxim's own words:—
'The enormous screw-thrust started the engine so quickly that it nearly threw the engineers off their feet, and the machine bounded over the track at a great rate. Upon noticing a slight diminution in the steam pressure, I turned on more gas, when almost instantly the steam commenced to blow a steady blast from the small safety valve, showing that the pressure was at least 320 lbs. in the pipes supplying the engines with steam. Before starting on this run, the wheels that were to engage the upper track were painted, and it was the duty of one of my assistants to observe these wheels during the run, while another assistant watched the pressure gauges and dynagraphs. The first part of the track was up a slight incline, but the machine was lifted clear of the lower rails and all of the top wheels were fully engaged on the upper track when about 600 feet had been covered. The speed rapidly increased, and when 900 feet had been covered, one of the rear axle trees, which were of two-inch steel tubing, doubled up and set the rear end of the machine completely free. The pencils ran completely across the cylinders of the dynagraphs and caught on the underneath end. The rear end of the machine being set free, raised considerably above the track and swayed. At about 1,000 feet, the left forward wheel also got clear of the upper track, and shortly afterwards the right forward wheel tore up about 100 feet of the upper track. Steam was at once shut off and the machine sank directly to the earth, embedding the wheels in the soft turf without leaving any other marks, showing most conclusively that the machine was completely suspended in the air before it settled to the earth. In this accident, one of the pine timbers forming the upper track went completely through the lower framework of the machine and broke a number of the tubes, but no damage was done to the machinery except a slight injury to one of the screws.'
It is a pity that the multifarious directions in which Maxim turned his energies did not include further development of the aeroplane, for it seems fairly certain that he was as near solution of the problem as Ader himself, and, but for the holding-down outer track, which was really the cause of his accident, his machine would certainly have achieved free flight, though whether it would have risen, flown and alighted, without accident, is matter for conjecture.
The difference between experiments with models and with full-sized machines is emphasised by Maxim's statement to the effect that with a small apparatus for ascertaining the power required for artificial flight, an angle of incidence of one in fourteen was most advantageous, while with a large machine he found it best to increase his angle to one in eight in order to get the maximum lifting effect on a short run at a moderate speed. He computed the total lifting effect in the experiments which led to the accident as not less than 10,000 lbs., in which is proof that only his rail system prevented free flight.
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