Juan de la Cierva

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Cierva Codorniu, Juan de la


Spanish Aeronautical Engineer 18951936

Juan de la Cierva Codorniu was born in Murcia, Spain, in 1895. Today he is remembered as the inventor of the autogiro , a forerunner of the helicopter. For six years he attended the Escuela Especial de Ingenieros de

Caminos, Canales y Puertos in Madrid, Spain, where he studied theoretical aerodynamics . Following this, he entered a competition to design military aircraft for the government and built a biplane bomber with an airfoil (the part of a plane that provides lift) that he designed mathematically. The plane was tested in May 1919, but it crashed when the pilot stalled it.

Cierva believed that fixed-wing aircraft were unsafe, so he experimented with a rotary-wing design , and the world's first working autogiro* flew 200 yards on January 19, 1923. Two days later the autogiro was unveiled to the public and made three flights, the longest of which was two and a half miles. In 1925, he founded the Cierva Autogiro Company in England and later collaborated with the Autogiro Company of America. On September 18, 1928, he flew one of his autogiros across the English Channel, and in 1930, he flew one from England to Spain. Autogiros were used during the 1930s for military liaison, mail delivery, and agricultural purposes.

*The term "autogyration" means that a plane is equipped with a conventional engine and propeller that pull it forward through the air. This forward motion causes the rotor to gyrate automatically, like a windmill.

Aerodynamic Principles

As a student, Cierva had learned that four aerodynamic forces are involved in flight: lift, gravity, thrust, and drag. Lift allows the craft to ascend; gravity is the force that pulls it down. Thrust propels the craft forward; drag is the force that holds it back. For a craft to ascend, the lift must be greater than the force of gravity, and for it to accelerate, thrust must be greater than drag. When the craft is flying straight and level at a constant speed, all four aerodynamic forces are in equilibrium . The foundation of flight is based on Bernoulli's Principle. Bernoulli, an eighteenth-century Swiss scientist, stated that as the velocity of a fluid (such as air) increases, its pressure decreases, causing lift.

In a fixed-wing aircraft, lift is provided by the wing, thrust by the propeller. Cierva, though, believed that the autogiro controlled these forces better than fixed-wing aircraft, which had a tendency in those days to stall, or lose lift suddenly. He also wanted to develop an aircraft that needed only a short takeoff run and could slowly land in small areas. The autogiro was a major step toward those goals. The body and tail assembly were similar to those of an airplane, and thrust was provided by an ordinary engine and propeller. Lift, however, was provided not by fixed wings but by large airfoils similar to helicopter blades, mounted horizontally above the craft and rotated by airflow that resulted from the craft's forward movement. After early unsuccessful attempts, Cierva came up with the idea of mounting the blades on hinges at a hub, allowing them to flap and thus respond differentially to aerodynamic and centrifugal forces as they rotated.

see also Bernoulli Family; Flight, Measurement of.

Michael J. O'Neal

Bibliography

Anderson, David F., and Scott Eberhardt. Understanding Flight. New York: McGraw-Hill, 2000.

Brooks, Peter W. Cierva Autogiros: The Development of Rotary-Wing Flight. Washington, D.C.: Smithsonian Institution Press, 1988.

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au·to·gi·ro / ˌôtōˈjīrō/ (also au·to·gy·ro) • n. (pl. -ros) a form of aircraft with freely rotating horizontal vanes and a propeller. It differs from a helicopter in that the vanes are not powered but rotate in the slipstream, propulsion being by a conventional mounted engine.