Lilienthal and two thousand glides
Otto Lilienthal was an engineer who ran a factory in Berlin and spent his spare time on one question: how does a bird's wing lift it? In the 1880s he measured the lift of curved surfaces on a whirling arm and published the results in 1889 in a book, Bird Flight as the Basis of Aviation.
His conclusion was that a curved wing, an arched profile like that of a bird, lifts far better than a flat plate. To test it he built gliders and flew them himself. From 1891 he launched from a hill near Berlin and later from an artificial mound that he had built so that he could always face the wind. In five years he made more than two thousand flights, with the longest glides covering several hundred metres.
The pilot as the controller
Lilienthal steered by moving his body. He hung from the wing by his arms and swung his legs to shift the centre of gravity. It worked in light air and failed in a gust. In August 1896 a glider stalled and he fell from a height of some fifteen metres. He died the next day.
His real legacy was data and photographs. Pictures of his flights were printed around the world, and the numbers in his tables were used by the next generation, among them the Wright brothers, who started from his figures and later found some of them wrong.