Otto Lilienthal

All flight is based upon producing air pressure, all flight energy consists in overcoming air pressure -- Otto Lilienthal

Biography

Otto Lilienthal was an aeronautical pioneer, experimenting with wing gliders and flapping wing constructions. His books on the theory of flight formed the basis for aeronautics. His work has formed the inspiration of many aeronautical engineers, including the Wright Brothers.

Lilienthal was born on May 23, 1848 in Anklam, Prussia (currently Germany). Lilienthal developed an early interest in flight in grammar school in Anklam, studying birds. He went on to study engineering at the regional technical school in Potsdam (1864-1866), followed by one year of practical training at the Schwarzkopf company in Berlin as a mechanical engineer (1866-1867). Immediately following the practical training, Lilienthal began his first studies on human flight while enrolled at the Royal Technical Academy in Berlin (1867- 1870).

After graduation, Lilienthal first joined the army for one year, to fight in the French-German war, followed by employment at several engineering firms. Although Lilienthal was not working professionally on gliders, human flight remained his greatest interest. Together with his brother Gustav, he joined the Aeronautical Society of Great Britain, and lectured about the theory of the flight of birds (1873). From 1874, Otto and Gustav began a systematic study on the force of air on wings, the aerodynamics of wind, and an experimental program with kites and model gliders.

Lilienthal remained working as an engineer; he filed his first of 22 patents in 1866, involving a machine for mining purposes. During his life, Lilienthal filed 4 patents dealing with aviation. Ultimately, he started his own mechanical engineering company for boilers and steam engines (1881). This eventually allowed him to dedicate more studying machines for human flight. In 1889, he published a groundbreaking book on aviation: "Der Vogelflug als Grundlage der Fliegekunst" (Bird flight as a Basis of Aviation). The book summarizes all the experiments he carried out, a treatise on the physics of flight, rules for the construction of airplanes.

Having completed the book, Lilienthal was now ready to start building man carrying gliders (1890). In 1891 he made his first flight of approximately 80 feet, in Derwitz/Krilow (near Potsdam). In the years following his first flight, he continued improving his gliders eventually reaching a flight distance of 800 feet, from the Rhinower hills (Stölln/Rhinow, 1893). Lilienthal also experimented with wing flapping machines, but his major successes were with gliders; in 1894 he started serial production of the normal glider.

Lilienthal made over 2000 flights with monoplane and biplane gliders. On August 9, 1896 he made an unfortunate final flight. The steering mechanism of his glider malfunctioned, and he crashed. Lilienthal died one day later from his injuries.

Work

Lilienthals contributions to the field of aerodynamics, and especially the aerodynamics of wings are significant:

• A conclusive account of the fundamental properties of work required to lift a body in still air, compared to the flight work of birds.
• Experimental work, and properties of curved wings. Lilienthal was the first to interpret aerodynamic results using streamlines.
• The physics of wing aerodynamics; decomposition of the resultant air force in lift and drag components.
• The polar diagram; a method of plotting lift and drag that is still used today.
• Analysis of wing constructions in terms of aspect ratio, shape and profile.
• The development of equipment for air force measurements.