Clément Ader, (b. Feb. 4, 1841, Muret, France--d. March 5, 1926, Toulouse) was an early enthusiast of aviation who constructed a balloon at his own expense during the Franco-German War of 1870-71. In 1876 he quit his job in the Administration of Bridges and Highways to make more money to support his hobby. His early inventions in electrical-communications included a microphone and a public-address device.

He then focused on the problem of heavier-than-air flying machines and in 1890 built a steam-powered, bat-winged monoplane, which he named the Eole. On October 9 he flew it a distance of 50 m (160 feet) on a friend's estate near Paris. The steam engine was unsuitable for sustained and controlled flight, which required the gasoline engine; nevertheless, Ader's short hop was the first demonstration that a manned heavier-than-air machine could take off from level ground under its own power.

Between 1894 and 1897 Clément Ader built a larger but still 'batlike' twin screw machine which he named the Avion.

Clément Ader's 'Eole' in Flight

Clément Ader's 'Eole' Patent Drawings

Clément Ader's 'Eole', (Front Elevation)

Clément Ader's 'Eole', (Plan)

Clément Ader's 'Eole', Fuselage, (Plan)

Clément Ader's Eole, (Side Elevation Alt.)

Clément Ader's Eole, Motor

Clément Ader's Eole

Clément Ader's Avion III, otherwise known as the "Bat", one of the centrepieces at the Musée des arts et métiers, was restored in the 1980s by the Musée de l'air et de l'espace at its workshop in Meudon, near Paris.

The aircraft, which has a wingspan of over 15 metres and is equipped with two 20-HP steam engines and two propellers, was built between 1894 and 1897 in Paris, in the rue Jasmin workshop. The materials used were basically wood and, for a small number of parts, steel, brass and aluminium. The web on the wings was made from silk pongee which, in spite of its tight weave, is permeable to air.

Experiments on the prototype, which required a considerable amount of work, began in October 1897. Interrupted after an accident, the work was not continued due to a lack of financial resources. However, Ader claimed that a 300-metre flight had taken place, a fact confirmed by two witnesses.

Biruta Kresling was given the opportunity of studying the airplane close at hand when it was 'dissected' - 'taken to pieces', enabling her to find out all the details relating to its manufacture and produce a series of drawings. She was immediately struck by the great intuition shown by Ader in transposing the mechanical principles of bat flight, particularly that of the flying fox.

Clément Ader's Avion III in 1908

With the impression of experiencing a remarkable adventure, Biruta Kresling laid bare the aircraft's design, revealing the astonishingly bionic (before the term was coined) elements which inspired Clément Ader, engineer and prodigious inventor, and examining the new ideas he introduced.

Although the 'Bat' plane remains virtually unknown outside France, and in spite of the fact that Ader's copy of the natural model (faithful right down to the terms he used - 'arm', 'forearm', 'fingers', 'elbow', 'wood') seems naive and clumsy today, all these technical concepts, for which Ader had no theoretical bases or experimental means at his disposal other than those he used himself (large flying models, a glider, the Eole aircraft and, finally, the life-size plane itself), were extremely advanced for the time.

The resemblances between the aircraft and the animal are by no means coincidental. Ader did in fact recommend building the wings of low-speed planes on the model of a bat's wing, and those of high-speed planes on the model of a bird's wing.

Among the many similarities between 'Avion III' and the flying fox or birds, we will look at just a few examples.

Doubtless aware that the pilot would be unable to steer such a complex aircraft without the assistance of self-stabilizing devices, depending on the shapes and materials used, Ader invented mechanisms such as propeller blades inspired by the quills in birds' wings, made of paper and bamboo - a sort of 'propfan' and blade 'with automatic variable pitch'. The shaft of the propeller blades consisted in a central strand made of cork onto which thin sheets of split bamboo were assembled and stuck. The unit was mounted in such a way as to flatten out at high speeds, automatically regulating the angle of incidence.

The 'thumb' of the flying fox combines two functions: firstly, the unfurling and automatic tensing of a membrane similar to the 'leading edge flap' in an aircraft, followed by the folding back of the wing, with the thumb now acting as a hook enabling the bat to grip onto the branch of a tree. The same coupled mechanism - a safety device for the animal - gave Ader's flying machine, designed for military aviation, an essential, dual function: the wing could be tensed and then folded back, meaning that large wing surface areas could be reduced. A single mechanism thus facilitated the processes of putting the aircraft into operation rapidly by unfurling the wings, bringing it to rest, transporting it from the airfield to the hangar, followed by fast, easy removal and dissimulation once it had landed.

X-rays of the 'arm' of Avion III showed its hollow inner space to be criss-crossed with thin wooden rods driven into the sides of the tube. These make the arm rigid, similar to the bony trabeculae - the thin rods which reinforce the humerus in birds.

As Director of the Musée de l'air et de l'espace, General Pierre Lissarrague supervised restoration work on the plane. He began by carrying out a critical study of the countless technical notes in Clément Ader's workshop notebooks. In order to check that Ader's ribless wing did indeed have the hollow profile announced in the patent, Lissarrague came up with the idea of testing an original half-wing from the plane, with its 'arm-bones' and 'fingers', covering it with a new layer of silk pongee, just like the one on the original wing which was used as a model, and exposing it to natural wind. The experiment took place outdoors, on the west coast of the Cottentin peninsula. The 'automatic ' curve of the thin 'fingers' and the membrane of the aircraft could thus be observed in simulated flight, as could the profiles along its wingspan. The placing of reflective strips under the wing enabled the shape of these profiles to be photographed, while measuring the way in which they are positioned in relation to one another.