The Rise of the Flying Machine

Henson and Stringfellow

The weight of the man-carrying machine was estimated by Cayley to be about 500 lbs, complete with engine and propeller. He thus arrived at a requirement of 10 hp for every 1000 lbs lifted. This fired the imagination of William Samuel Henson to such an extent that in 1843 he proposed an “Aerial Transit Company” bill in the House of Commons.

His object was the construction of a flying machine powered by a steam engine developing 25 to 30 hp and weighing over 600 lbs. The complete aeroplane would weigh about 3000 lbs with a wing surface of 6000 sq ft. This would, in Henson’s opinion, enable him to organize aerial transit to several distant points of the globe.

Henson’s proposals received a great deal of publicity but, if he had ever been given the green light to proceed with his Transit Company, the business would have floundered because of the lack of adequate power, as well as by the enormous surface requirement of the wing and the tail.

But Henson and his engineering associate John Stringfellow went to work anyway on small-scale models. If there is one thing that continually amazes the historian, it is the optimism with which the early pioneers tackled the host of difficulties that lay before them.

Henson realized that high steam pressures would be required so he set to and designed and built a model engine to work on a pressure of 100 lbs/sq in. After many discouraging years without result, Henson gave up in 1849, whilst Stringfellow continued alone and was at last able to build a small model steam engine which was said to produce about one-third hp for a weight of 13 lbs, including the steam generator.

France takes up the challenge

After Henson’s experiments, aviation in the UK was allowed to lapse but, curiously enough, interest in dynamic flight arose again in France, in spite of Navier’s calculations, which could have been forgotten in the meantime.

It is significant to note that Cayley was asked to contribute and he subsequently wrote several articles for the Bulletin Trimestriel of the first aeronautical society in the world, the Société Aérostatique et Météorologique de France, founded by a well-known French aeronaut J. F. Dupuis Delcourt. As will be noted, the title does not mention dynamic flight.

Yet Cayley, in 1853, proposed rather slyly that “As aerial navigation on the balloon principle, can only be carried out on an enormous scale of magnitude and expense ... it may not be unworthy of the Society to turn its attention towards making some cheap preliminary experiments to ascertain practically what can be done on the principle of the inclined plane, which appears to be applicable on any small scale from that of a bird to the uses of man, ... whenever a first mover, combining sufficient power, within a certain limit as to weight, is discovered.”

There is no evidence that directly links Cayley’s articles and proposals in this French Bulletin to the first attempts by Frenchmen to start experiments with fixed-wing aeroplanes, but the analogies are striking.

In 1857, a French naval officer, Félix du Temple, patented a fixed-wing flying machine moved by a motor. The machine was calculated to weigh one ton and du Temple, with more optimism than Cayley’s, estimated the power requirement as 6 hp.

Du Temple’s machine had a tail in the rear and a slight dihedral of the monoplane wing. One interesting original feature was the proposal that the aeroplane should take off by rolling across a field in the modern manner. Due consideration was also given to the question of stability.

Experiments were on small-scale models but, as soon as full-scale construction began around 1874, “the inadequacy of all motors known became apparent” as O. Chanute wrote. Du Temple had experimented with steam at high pressures and in due course designed an efficient boiler consisting of small water tubes as advocated by Cayley in 1809. This boiler produced no flight, but it was adopted by the French Navy, so du Temple was in some measure rewarded for his pains.

A second experimenter was Joseph Pline, a pioneer of great originality, who presented a patent in 1855 using a fixed plane in conjunction with a balloon, in an effort to get the best of both aeronautical systems. One interesting feature in this patent was that the fixed plane was for the first time designated with the word aéroplane.

Pline’s mixed system was not built; it would have been a failure as were all others that followed, trying to add wings to an airship, but Pline soon began to experiment with small flying models and stated that he was certain that it was possible for a plane to rise, sustain itself and fly around in the atmosphere without the use of hydrogen.

After carefully observing aerial currents as well as the organs used for flight by different animals (nature has produced more flying creatures than earthbound ones), Pline came to the conclusion that curved surfaces were the most efficient and he designed several paper models that had wings consisting of half-cylindrical surfaces arranged in the direction of flight, somewhat in the manner of F. M. Rogallo’s flexible wings designed in 1948.

Pline’s model aeroplanes flew gracefully and, under the name Papillons de Pline (Pline’s Butterflies), acquired great fame in France during the 1860s. All aeronautical experimenters were able to witness the flights of these flying models, which proved that in case of engine failure, a fixed-wing machine would not fall like a stone but could glide safely to earth.

The fruitful decade

Human progress sometimes proceeds by leaps and bounds and the 1860s and 1870s were a case in point in the field of flight. In 1860 J. E. Lenoir invented and then built the first internal combustion engine “firing inflammable air with a due portion of common air under a piston” as Cayley had proposed in 1809.

It is true that, as soon as illuminating gas was invented by Philippe Lebon in 1799, means were sought to use gas as a fuel for machines that produced power, with the principal difficulty being thought to lie in the means of mixing gas and air before combustion could take place. Lenoir solved the problem in one masterful stroke by effecting the mixing inside the working cylinder itself. He simply built a copy of a steam engine that admitted a quantity of gas and air during the first part of the working stroke which was then ignited half-way, producing an explosion that did useful work during the rest of the stroke. The return stroke was used to expel the burned gases and then the cycle began anew.

Lenoir’s engine generated much enthusiasm among aircraft pioneers, but this enthusiasm soon waned when it was found that the heavy, shaking gas motor, needing water to cool the cylinder and consuming great amounts of gas and lubricating oil, was less suitable as an aeronautical powerplant than the steam engine in use at that time.

However, several other initiatives began to encourage the aeronautical movement both in England and in France. After the demise of Dupuis Delcourt’s society in 1853, a group of enthusiasts gathered in Paris on 30 July 1863 at the instigation of the well-known photographer Jules Nadar to hear a manifesto concerning aerial locomotion which caused considerable agitation.

Nadar founded a journal with title L’Aéronaute which had a short life due to a lack of subscribers but set the ball rolling. The idea was to single-mindedly promote the art of flying by means of machines heavier than air. Gustave Vicomte Ponton d’Amécourt, one of Nadar’s principal collaborators, had written in 1853, “We will try in vain to solve the problem of aerial navigation as long as we do not suppress the balloon.” Nevertheless, as Navier had calculated that fixed-wing flight was impossible, all minds were set on developing a machine lifted by airscrews.

Another enthusiast, Guillaume Joseph Gabriel de La Landelle, published a book in 1863 with the title Aviation ou Navigation Aérienne (sans ballons) in which the word aviation was used for the first time. This book showed a drawing of a flying vessel that was moved and supported by several horizontal propellers and de La Landelle asserted that by such means 1000 kg could be lifted by a force of 4 hp.

De La Landelle’s flying ship was never built for obvious reasons but it fired the imagination of Jules Verne, who published the best-seller Robur the Conqueror (also translated into English as The Clipper of the Clouds) describing a flying ship moved by multiple horizontal airscrews as in de La Landelle’s vision.

Ponton d’Amécourt went to the trouble of building an extremely light engine for helicopter use which worked with steam at a pressure of 150 lbs/sq in. from a generator built almost entirely of aluminium, which thereby made its initial appearance as a lightweight metal for light aircraft engines.

The Aeronautical Society

On 12 January 1866, the Aeronautical Society of Great Britain was founded in London, with the Duke of Argyll as president and Francis H. Wenham as one of the founding members.

On 27 January, Wenham read a paper before the Society, entitled On Aerial Locomotion and the Laws by which Heavy Bodies impelled through Air are Sustained. Wenham proposed rigid leading edges of the wings, a high aspect ratio and the use of several superposed planes in order to increase the wing surface without increasing its dimensions and weight in the same proportion. The paper had a great impact on the aeronautical movement in the English-speaking countries.

In the same year an equally important paper was published by Jean-Charles de Louvrié in France with the suggestive title Vol des Oiseaux, équation du travail, erreur de Navier. De Louvrié declared emphatically that Navier’s calculations were wrong, that the bird was similar to the kite “in which the line is replaced by the living force working on the mass (of air) by the propeller” (the wing tips which in a bird act as propellers). This was certainly a new point of view and de Louvrié went on to state that a bird could soar on rising currents of air, determined by the unevenness of the ground and that flight was nothing more than a balancing act.

All this was true, but it led several French enthusiasts, eager to copy the bird’s balancing act, to think along lines that deviated from what Cayley had shown, as will be discussed in a later chapter.

The most important event of the decade was the organization by the Aeronautical Society of the first Aeronautical Exhibition in the world. It opened on the 25 June 1868 at the Crystal Palace in London, and among the seventy-seven exhibits were engines, models and kites.

The Exhibition lasted eleven days, and was especially important because the French were also present. Earlier during the year, the publication L’Aéronaute had been revived by Abel Hureau de Villeneuve and on 23 May a Société Aéronautique et Météorologique de France was constituted on the model of the Aeronautical Society of Great Britain.

The new L’Aéronaute started its publication by reporting extensively on the Aeronautical Exhibition of London. A prize of 100 pounds was to be given for the best engine. Sixteen engines were entered and the prize was unanimously awarded to the steam engine built by John Stringfellow for the Henson experiments referred to above.

The committee, for some mysterious reason, accorded Stringfellow’s engine a power output of one hp. It was later acquired by S. P. Langley for the Smithsonian Institution but on test never approached even the 1/3 hp originally claimed for it. It was also installed in a neat triplane model plane built by Stringfellow but was incapable of making it fly, so the Exhibition produced no artefacts capable of flight.

The French would have liked to submit Ponton d’Amécourt’s aluminium steam engine but Hureau de Villeneuve refused permission to have it fired up, on the grounds that the manometer was lacking. He was criticized for his decision at the time, but he was probably right.

Another steam engine at the Exhibition was built by R. E. Shill, whose “turbine injector power unit” was said to be capable of achieving 1 hp. Shill subsequently collaborated with Thomas Moy, who became bitten by the aeronautical bug at about that time (having exhibited “a mariner’s kite for use in rough weather” at the Exhibition), and subsequently built what was called “Thomas Moy’s Aerial Steamer”. The engine for the first experimental model worked at a pressure of 160 lbs/sq in. and produced three hp for a weight of 80 lbs in 1874.

The model was tested in 1875 but instead of the hoped-for 35 mph take-off speed, only 12 mph was reached and no flight was achieved. Again we see the sanguine response of the pioneers when, after the unsuccessful tests, Moy proposed building a full-size aeroplane with a steam engine of 100 hp “capable of carrying several men” according to Chanute.

It was no wonder that, in one of his reports on the Exhibition to Paris, Hureau de Villeneuve stated sadly that the great enthusiasm aroused in France at the prospect of realizing aerial locomotion in the very near future in 1863 had all but died out and, like Cayley sixty years before, he reflected on the fact that the big problem remained the engine, or rather the lack of a satisfactory one.

In his opinion, it was not a matter of cost and he declared: “At the present stage it does not really matter whether the aero engine consumes alcohol, ether, diamonds or attar of roses. The important thing is to fly at any price.” Economy would be achieved by subsequent practice.

The year 1868 saw another outstanding feat, the invention of the aileron system for controlling the lateral movements of an aeroplane. M. P. W. Boulton registered a patent (No. 392) that year for a system “to prevent [aerial vessels] turning over by rotating on the longitudinal axis”. In his specification Boulton referred to Cayley’s proposals to achieve inherent lateral stability by using a dihedral angle of the wing but he thought that it could become “desirable to provide a more powerful action preventing rotation of the body in this direction”.

The system described (“vanes or moveable surfaces attached to arms projecting from the vessel laterally”), the aileron system as it is called today, was proposed as a safety device in order to redress the aircraft if, for some reason it should begin to roll as a result of a gust of wind or an upset balance. The purpose of the invention was to ensure that “the balance of the vessel is redressed and its further rotation prevented”.

This was aileron action as it is used on the great majority of modern aeroplanes although no mention was made for its use in order to make a turn. That had not yet entered the vision of the aviation pioneers and would come much later.

Thus, the modern aeroplane was slowly taking shape. A light and powerful engine, fixed and rigid wings of high aspect ratio, a horizontal and vertical movable rudder at the rear, ailerons for controlling unwanted rolling movements were contemplated in theory before the end of the 1860s.

There was only one quality lacking: inherent stability in the longitudinal sense. Cayley’s speculations in 1809 were not yet adequate for that purpose. Longitudinal stability, the most important of all, would now be shown shortly afterwards to an admiring aeronautical community in Paris by the second great aeronautical genius of the nineteenth century, after Sir George Cayley, a figure who would dominate the aeronautical movement during the next decade: Alphonse Pénaud.

Alphonse Pénaud

As Hureau de Villeneuve sadly remarked in 1869, most of the enthusiasm for aviation that had been aroused earlier had again been lost. But at the end of the decade it was revived with great force by a single man whose genius dominated the next few years.

A complete biography of the extraordinary and talented Alphonse Pénaud is still lacking but a special issue of the French aeronautical monthly Icare (Nº 38 of 1966) was devoted to him. Compiled by the late Charles Dollfus, at that time France’s most respected historian of aeronautics, it is the best source of information about Pénaud’s life and work.

Born on 31 May 1850, Pénaud was the son of an admiral but he was unable to follow a naval career because he was incapacitated from the age of nineteen by a hip ailment. His great mental energy then found another outlet in the furtherance of dynamic flight.

In 1869 he started his aeronautical activities by building a small-scale helicopter along the lines followed by Launoy et Bienvenu in 1784 and by Sir George Cayley in 1796. In the course of his experiments he found that rubber, when cut into fine strands and suitably twisted would provide more energy than an equal weight of rubber working under tension, as had hitherto been used.

His twisted-rubber helicopter model was shown for the first time on 20 April 1870 to de La Landelle and Hureau de Villeneuve, but Pénaud, who had become very interested in the flying exhibitions of Joseph Pline’s Papillons was gripped by the possibilities of fixed-wing flight and decided to find out if he could build a self-propelled flying aeroplane by using his twisted-rubber engine. No aeroplane type, not even Stringfellow’s steam-powered triplane of 1868, had been able to achieve flight so far.

Beginning his research by observing the fall of diverse surfaces and by studying Pline’s models, Pénaud soon designed a small-scale aeroplane which used twisted rubber as a power source. He had to apply the full keenness of his mind to make this model fly in perfect balance and find a solution to the hitherto unsolved problem of how to obtain longitudinal stability.

The model plane which was built according to his calculations received the name “Planophore” and flew for the first time in public on 18 August 1871 before an admiring group of fellow associates of the newly founded Société Française de Navigation Aérienne.

His flying model bore a decided resemblance to a modern aeroplane as it had a monoplane wing in front and a small fixed tail at the rear. It weighed only 16 grams (0.56 oz) and with a wing that had a surface of 490 square centimetres (0.53 sq ft) the wing loading amounted to merely 0.0714 lbs/sq ft.

It was driven by a single propeller at the rear and, in order to counteract the torque of the revolving propeller, one side of the wing was made longer than the other.

After applying the necessary energy to his rubber strands by giving the propeller 240 turns, the little aeroplane flew for 11 to 13 seconds, covering between 40 and 60 metres (130 to 200 ft.). Because of the low wing loading it flew very slowly at 3.6 m/s (about 13 kph or 8 mph) and yet showed a remarkable steadiness in flight.

Pénaud had discovered the secret of inherent longitudinal stability. He described his discoveries and the calculations related to them in a remarkable article published in L’Aéronaute of January 1872 under the simple title “Aéroplane Automoteur” and with the revealing subtitle “Stabilité Automatique”.

As he stated in the article, “Luckily, after a few investigations, I imagined a very simple device, which achieved the desired goal.” This simple device was a small fixed horizontal tail, inclined downwards with reference to the main lifting wing and at a certain distance to the rear. Just as Cayley had indicated the way to obtain lateral stability by giving a small dihedral to the wings so that they looked like a flattened V when seen from the front, Pénaud now proposed to use the same means in a longitudinal direction because the angle formed by the wing and the stabilizing tail also formed a very flat V.

Because this tail surface was restraining, it produced a certain amount of drag and hence power was wasted by this kind of construction, but it is the toll that has to be paid in return for safety in the air.

The propeller of the “Planophore” was at first situated at the rear, but in 1875 he also flew a planophore with a tractor propeller at the front. The little model plane was so stable that it flew without a vertical fin, but it could only fly in a windless atmosphere, preferably indoors, where most of Pénaud’s exhibitions were held.

His article ended as follows: “Whatever the results, my planophore proves the possibility of the aeroplane system, the possibility of a stable equilibrium surrounded by air and promises a considerable speed for great machines.”

In 1871 it may be said that all the elements of the modern aeroplane form were in existence, excepting again, the engine. Inspired by Pénaud’s research, a new branch of the existing aeronautical society was formed as the Société Française de Navigation Aérienne. Hureau de Villeneuve was appointed its president and Pénaud was the archivist and librarian. He thus had access to all the publications of the society and he studied every one of them.

In the January 1873 issue of L’Aéronaute, he published a theory of the aeroplane entitled “Laws of Gliding through the Air” in which he made reference to Newton, to Navier’s error, to Wenham and to Cayley, whose articles, published in France in 1853, he had also read.

Cayley’s writings aroused his interest and he began to search through British technical literature of the early nineteenth century, eventually coming across Cayley’s triple paper “On Aerial Navigation” in Nicholson’s Journal in 1809 and 1810, referred to previously.

Pénaud thus encountered a mind equal to his own and was astounded by the clarity of Cayley’s essay: “These writings,” wrote Pénaud, “which have lain dormant and forgotten on the dusty shelves of old libraries, are among the most important which exist relating to aerial navigation.”

“Nobody has understood the impact of this mind, nobody has encouraged or helped him, or was stimulated by these life-giving ideas. The tree died before it bore fruit and Cayley’s very existence was unknown in France. It is our duty to raise his name from oblivion.” And he duly did so, as Cayley’s triple paper was translated into French and published in L’Aéronaute during 1877.