Читать книгу The Rise of the Flying Machine - Hugo Byttebier - Страница 37

Stability versus Control

Most of the aviation pioneers of the nineteenth century were handicapped by their inability to differentiate unequivocally between stability and control. Again it was Sir George Cayley who put the problems in their proper perspective. He argued that the first requisite for a flying machine was lift; the second was stability in the air, and once these qualities were assured then control had to be added.

Pénaud’s model aeroplanes were inherently stable, but he later incorporated methods of control in the specifications of his patent. On the other hand, the bird and its admirable way of flying had given too many people the idea that it would be easy to manage an aeroplane in flight by a multitude of controlling devices, while disregarding stability altogether.

In Lilienthal’s case it is easy to see why he abandoned the inherent stability of his most efficient gliders, those which he used from 1892 to 1894. It was because he wanted to achieve longer flights, which in turn demanded larger wings, and as he also wanted to fly in stronger winds, this required better control and, added to that, he also wanted to incorporate a motor. All these factors made for larger and heavier aeroplanes, but the steering of these by means of movements of the body was becoming increasingly hard with every pound of weight that was added.

The idea of introducing movable auxiliary surfaces for better control was correct, but the relinquishment of inherent stability was not. It would take ten more years before the aircraft designers became conscious of the fact that controls had to be superimposed on an inherently stable construction and that to abandon stability in order to obtain better control was a grave mistake.