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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.

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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## autogiro

autogiro (ôtōjī´rō) or gyroplane (jī´rəplān), type of aircraft supported in the air by a horizontally mounted airfoil similar to that of a helicopter but unpowered. Invented by the Spaniard Juan de la Cierva, it was first flown successfully in Jan., 1923, in Spain. Most of the lift is supplied by large airfoils which are mounted horizontally above the craft and rotated by the airflow created by the craft's forward movement. The autogiro has fixed wings that are smaller than those of an ordinary airplane; the body and tail assembly is of conventional design. Thrust is supplied by an ordinary engine and propeller, and control is maintained by a rudder, elevators, and ailerons. In one type, fixed wings are absent, and the rotor provides all the lift. Control of pitch and roll are accomplished by tilting the rotor forward, backward, or to either side. Some advantages of the machine are that its descent will be slowed by the turning of the rotor if the engine fails; that it becomes airborne with a very short takeoff run and can land in small areas; and that with a moderate headwind it can virtually hover with zero ground speed. However, it cannot match the vertical climbing performance of the helicopter.

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## Cierva, Juan de la

Juan de la Cierva (hwän dā lä thyār´vä), 1895–1936, Spanish aeronautical engineer, inventor of a rotary-wing aircraft called an autogiro. He flew his first autogiro in 1923 and crossed the English Channel in an improved model in 1928.

See his Wings of Tomorrow (1931).