Autogyro

An autogyro, also called a gyroplane or gyrocopter, is a rotorcraft that generates lift from an unpowered rotor turning by autorotation as air flows upward through it, while a separate engine-driven propeller supplies forward thrust; unlike a helicopter's rotor, the autogyro's rotor is never engine-driven except to start it spinning. The Spanish engineer and pilot Juan de la Cierva developed the aircraft after a bomber he designed crashed during testing in 1921, and after three unsuccessful prototypes his fourth design, the C.4, made the first documented autogyro flight on January 17, 1923, piloted by Alejandro Gomez Spencer at the Cuatro Vientos airfield near Madrid. De la Cierva originally called his invention the autogiro, a name later trademarked by the Cierva Autogiro Company he founded to develop it commercially.