Controlling the aircraft

The 1880s became a period of intense study, characterized by the "gentleman scientists" who represented most research efforts until the 20th century. Starting in the 1880s advances were made in construction that led to the first truly practical gliders. Three people in particular were active: Otto Lilienthal, Percy Pilcher and Octave Chanute. One of the first modern gliders appears to have been built by John J. Montgomery; it flew one flight outside of San Diego on August 28, 1883. It was not until many years later that his efforts became well known. Another hang-glider had been constructed byWilhelm Kress

as early as 1877 near Vienna.

Otto Lilienthal of Germany duplicated Wenham's work and greatly expanded on it in 1874, publishing his research in 1889. He also produced a series of gliders, and starting in 1891 was able to make flights of 25 meters or more routinely. He rigorously documented his work, including photographs, and for this reason is one of the best known of the early pioneers. He also promoted the idea of "jumping before you fly", suggesting that researchers should start with gliders and work their way up, instead of simply designing a powered machine on paper and hoping it would work. His type of aircraft is now known as a hang glider.

Lilienthal died in 1896 when a gust of wind cause him to lose control: he fell from a height of roughly 50 feet (15 m) and broke his back. He died the next day. By the timeof his death he had made 2500 flights of up to 250 meters using a number of designs. Lilienthal had been working on small engines suitable for powering his designs at the time of his death.

The Australian Lawrence Hargrave invented the box kite and dedicated his life to constructing flying machines. In the 1880s he experimented with monoplane models and by 1889 Hargrave had constructed a rotary airplane engine, driven by compressed air.

Picking up where Lilienthal left off, Octave Chanute took up aircraft design after an early retirement, and funded the development of several gliders. In the summer of 1896 his team flew several of their designs many times at Miller Beach, Indiana, eventually deciding that the best was a biplane design. Like Lilienthal, he documented his work and also photographed it, and was busy corresponding with like-minded resarchers around the world. Chanute was particularly interested in solving the problem of aerodynamic instability of the aircraft in flight, which birds compensate for by instant corrections, but which humans would have to address either with stabilizing and control surfaces or by moving the center of gravity of the aircraft, as Lilienthal did. The most disconcerting problem was longitudinal instability (divergence), because as the angle of attack of a wing increases, the center of pressure moves forward and made the angle increase more. Without immediate correction, the craft would pitch up and stall. Much more difficult to understand was the relationship between lateral and directional control.

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