The most significant pre-Wright brothers aeronautical experimenter was the German glider pioneer Otto Lilienthal. In Germany, Otto Lilienthal make an intensive study of bird anatomy and flying characteristics, inspired by the storks which he and his brother Gustav watched wheel¬ing over the rooftops of Potsdam, their home town. He sought to discover precisely how birds flew, altering the dihedral angle of their wings for lateral stability, and varying the camber of the surfaces for lift or drag. Lilienthal was quick to appreciate the importance of curved wing surfaces. In 1889 he published the results of his findings in his book Der Vogelflug als Grundlage der Fliegekunst (Bird Flight as the Basis of the Flying Art), and set about testing his theories.
Between 1891 and 1896, he built and flew a series of highly successful full-size gliders. During this period, Lilienthal made close to 2,000 brief flights in 16 different designs based on aerodynamic research he conducted in the 1870s and 1880s. Most were monoplanes with stabilizing tail surfaces mounted at the rear. Control was achieved by shifting body weight fore-and-aft and from side-to-side.
Lilienthal began testing gliders in his backyard on a one metre platform and made hundreds of flights there before moving to a small hill, two and a half metres high.
By 1893 his gliders had cambred wings with radiated tip, fixed rear fin and tailplane, and could be folded to fit through an ordinary door.
On the evening of 9 August 1896, Otto was at Stöllen in the Rhinower Hills testing a new kind of head-movement control arrangement when a sudden gust upturned his No. 11 monoplane glider and he crashed heavily from 15 m (49 ft) breaking his spine. He died in a Berlin clinic the next day. His last words were ‘Opfer mussen gebracht werden’ (‘Sacrifices must be made’).
Gustav Lilienthal (1849-1933) was the younger brother of glider pioneer Otto Lilienthal. He spent the last 20 years of his life developing ornithopters, based on his studies of bird flight. The 1914 “Big Bird” spanned 17.5 metres and was tested at the research station of Altwarp, on the Stettiner Haff, but never left the ground. Lilienthal continued working at the Berlin Tempelhof and Adlershof airfields until his death.
