Читать книгу The Rise of the Flying Machine - Hugo Byttebier - Страница 17

The Study of Bird Flight

Meanwhile, Professor Etienne Jules Marey had made profound studies of the flight of birds. After it had been discovered that by putting a kite in motion it could fly like a bird, Marey’s observations showed that a bird is also like a kite, meaning that it follows the same aerodynamic laws as the fixed-wing flying machine.

Marey showed that a bird’s wing consists of two sections; a central part that provides lift like an aeroplane’s wing, whilst the bird’s wingtips provide thrust, working like propellers. The bird flies because it acquires horizontal speed and not because it flaps its wings up and down. “Translation gives three times as much lift as down beating”, said Marey and he gave the definitive proof by tying a bird with a long string to the ground. As soon as the wire became taut and the bird’s horizontal progress was arrested, the poor animal, for all its frantic flapping, fell to the ground.

The bird’s wingtip was at that time called “aileron” by the French, a word that was to acquire, quite by accident, a completely different meaning in 1908.

Marey was not the first to have discovered the true movement of the bird’s wing because Cayley had already become aware of the bird’s mode of flying in 1808 and several others after him, notably Wenham (as Pénaud was quick to point out). Marey himself became involved in a heated controversy with S. B. Pettigrew, Professor of Anatomy at the University of St Andrews, who had described a similar theory of bird flight a year earlier.

But Marey’s publications received wide publicity, and even inspired the Wright brothers’ 25 years later. Another effect was that several of Pénaud’s fellow members of the Société, among them the president Hureau de Villeneuve, were dedicated to the building of flapping-wing models which were patterned, or so they thought, after birds.

Pénaud thereupon built a flapping-wing model himself, with the tips providing thrust and the central part providing lift, as with a real bird. It was tested in 1872 and an improved model was built in 1874 and, as Charles Dollfus wrote, “a better result with a flapping-wing machine has never been obtained”.