autogyro/autogiro

A heavier-than-air rotorcraft which, throughout its flight, derives the whole or part of its lift from a freely rotating rotor. The rotors are not driven by any engine, although an autogyro must be provided with a source of horizontal thrust. Unlike the helicopter, the autogyro maintains its speed of rotation in the air because of the aerodynamic forces acting upon the rotor blades and is without direct mechanical drive from the engine. All the power required to maintain flight is supplied through the propeller of the autogyro at the front (tractor type) or rear (pusher type) of the fuselage. The rotor is thereby pulled through the air and creates a lifting force. Also known as a gyroplane.