Otto Lilienthal(1848-1896): Founder of aeronautics

OTTO LILIENTHAL was born on May 23, 1848 in Anklam, Prussia. He attended the Technical School at Postdam, after which he studied engineering at the Berlin Technical Academy (1867-70). For a short time he served in the Franco-Prussian War.

Lilienthal they established a factory to produce engineering goods - light steam motors, steel pulleys, sirens to give marine signals; many of these products were his own inventions. Here spent ten years (till 1880) before he was able to devote himself to his life-work.

As a boy at the age of 13, he used to study, with his brother Gustav, the flights of birds, especially of the stork. He quickly realised that it was `not enough to acquire the art of the bird'; but it was also necessary to develop the problem of flight on a scientific basis.

From these studies he learnt that curved wings allow horizontal flight without an angle of incidence to the wind and established the importance of rising air-currents for soaring.

In 1889 he published his monumental work ``Bird Flight as a Basis for Aviation'' which had a tremendous impact on the early pioneers. It was perhaps the conclusion - a few of his colleagues also held the same, that birds produce thrust by the action of their outer primary feathers that kept Lilienthal on the path of the ``Ornithopter''. The latter was a machine which simulated the winged flight of a bird as the ultimate means of powered flight.

After exhaustive experimentation with gliders and flying models with flapping models with flapping wings, he eventually built his first man carrying glider in 1891. This consisted of two curved, fabric covered wings to which he attached himself by his arms using his hanging body for balance. He even built an artificial hill, outside Berlin 50 feet high, from which he was able to take off regardless of the direction of the wind.

Lilienthal's work could produce enormous influence, during and after his death because of the simultaneous advances in photography and printing - the dry-plate negative and half-tone printing process. Magnifcient series of pictures could get circulated around the world, which produced a tremendous impact at that time.

About his trials he wrote ``the fact of launching by running down a slope into the wind until sufficient velocity is reached to lift the operator and his 40 pound wings requires practice. In the beginning the height should be moderate and the wings not too large or the wind will soon show that it is not to be trifled with.''

Lilienthal's gliding experiments (since 1881) with winged apparatus convinced Lilienthal that the key to eventual powered flight was in glider-flying, by which men could master the elements of control and design. Among other things, he was the first to demonstrate the principle of the aerofoil and establish the superiority of cambered wings over flat wings.

By 1893 the size of his glider had reached a wingspan of 23 ft, a surface area of 16.7 sq. yard, and a weight of 44 lb. He achieved glides of more than 1000 ft; his activities gave a boost to gliding as a sport.

The year 1894 was momentous, as Lilienthal introduced a shock- absorbing hoop which certainly helped on 9th November to save his life on a crash. A detailed description of this incident caused the Wright Brothers to build elevators in front of their machines, the idea being to prevent damage in the event of a nose-dive. Lilienthal had already made a provision with the introducing leading-edge flaps to counteract the above tendency.

In 1895 Lilienthal experimented with a biplane. He added a carbon dioxide motor to flap the wings despite the fact that petrol engines had been built by that time. He considered means of control other than body swinging. Till then the pilot was suspended by his arms, the rest of him dangling free after the take-off. Movement was produced by swinging the body, altering the centre of gravity. The idea of the body harness was introduced, an echo of something Leonardo da Vinci had sketched five centuries ago.

Before he could progress with this innovation, he met with a fatal accident on August 1, 1896, through the upper plane of his glider coming loose in the air. His spine was broken, he died the following day. His work was continued by his brother Gustav who survived him by nearly forty years. His name is commemorated by the Lilienthal Medal, one of the world's highest awards in aviation. His essays on flying machines (1894) were acclaimed as the basic work on aeronautics.

Lilienthal's favourite saying ``Sacrifices have to be made'' is inscribed on his tombstone. (The Biographical Dictionary of Scientists, Vol. 6 - Engineers and Inventors, Blond Educational Series, 1984)

R. Parthasarathy

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