ALTHOUGH the Wright brothers made the first power-controlled flights in an aeroplane, they could have achieved nothing but for the experiments of Otto Lilienthal.
Lilienthal was bom at Anklam, Germany, in 1848. When he was sixteen he went to the Potsdam Technical School (near Berlin), where he was trained as an engineer. Before this, however, he had become interested in aviation, and, with his brother, Gustavus, made several aeronautical experiments. The brothers fastened light wings to their arms and attempted to glide by running down-hill. At a later stage the brothers fastened wings to their backs. Few, if any, real glides were made, however, and Otto Lilienthal realized that if any progress were to be made not only in gliding but also in aviation generally, the study of aeronautics must be put on a scientific basis.
Although Sir George Cayley had made a scientific study of aeronautics, he had devoted himself chiefly to the navigable balloon. Before Lilienthal reduced gliding to an exact science, it had never been studied from a scientific standpoint. He studied and measured bird flight and proved that curved wings were more effective than flat surfaces; he proved also the existence of up-currents of air as an aid to bird flight.
In 1889 he published in a book his theories, the results of twenty-five years of study. Two years later he built his first glider. This weighed about 40 lb and had a supporting surface of some 107 square feet. The wings were fixed to his arms by padded tubes, and Lilienthal gripped a cross-bar in front of his body. By holding this bar he could, when on the ground, adjust the glider’s wings at any angle to the wind; when he was in the air the bar helped him to control the glider as he moved his body backwards, forwards or sideways. He launched himself into the air by jumping from a springboard.
ONE OF THE EARLY GLIDERS with which Otto Lilienthal made successful flights. To hold himself to the glider he passed his arms through padded tubes and gripped a cross-bar. During his gliding experiments Lilienthal used a springboard and an artificial hill to aid the launching of his gliders. The work of this engineer considerably assisted the aviators who in later years made flights in powered machines.
When he built his second glider, in 1893, he launched it by running against the wind down an artificial hill, 50 feet high. From this hill he made several hundred glides and often covered a distance of over 100 yards, at an angle of descent of 1 in 7 or less.
In 1895 he built a glider with two superposed planes. This was the forerunner of the biplane which, many years later, was to be the generally adopted form of aeroplane. The two superposed planes of Lilienthal’s glider had a span of 18 feet and a total area of 200 square feet. These planes enabled Lilienthal to make glides in winds of greater velocity than before. In 1896 he went to the Rhinower Hills, near Stollen, in Germany, and from the 250-feet summit of these hills he made glides of 750 feet and farther.
About this time Lilienthal abandoned the method of control by which he balanced his body or weight in relationship to the machine, and used a horizontal control surface which was worked by a line attached to his head. While he was experimenting-with this form of rudder, Lilienthal was killed on August 10, 1896.
His achievements were of outstanding value to aviation, and in addition to the Wright brothers, other pioneers, such as Pilcher and Octave Chanute, worked on Lilienthal’s principles. Although certain details of his theories and experiments were later proved to be inaccurate (see page 394), the fundamental principles which he had laid down were invaluable to future aeronauts. It is impossible to realize what the future of mechanical flight would have been, or to imagine how slow its realization might have been, but for Otto Lilienthal’s work. Had he lived, he might have forestalled the Wright brothers, for he had already seriously considered the use of mechanical power for his machines.
Although his aeronautical experiments were among the most important ever made, Lilienthal did not devote all his time to aviation. From 1867 to 1870 he was a student at the Berlin Technical Academy. He served as a volunteer in the Franco-Prussian war of 1870-71. After the war he worked in some engineering shops in Berlin. In 1880 he opened his own factory, and invented a steam motor and some marine signals, for which he was awarded the silver State medal.