A rotorcraft or rotary-wing aircraft is a heavier-than-air flying machine that generates lift using rotary wings or rotor blades, which revolve around a mast. Several rotor blades mounted on a single mast are referred to as a rotor. The International Civil Aviation Organization (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors".Rotorcraft generally include aircraft where one or more rotors provide lift throughout the entire flight, such as helicopters, autogyros, and gyrodynes. Compound rotorcraft augment the rotor with additional thrust engines, propellers, or static lifting surfaces.
A helicopter is a rotorcraft whose rotors are driven by the engine(s) throughout the flight to allow the helicopter to take off vertically, hover, fly forwards, backwards and laterally, as well as to land vertically. Helicopters have several different configurations of one or more main rotors.
Helicopters with a single shaft-driven main lift rotor require some sort of antitorque device such as a tail rotor, fantail, or NOTAR, except some rare examples of helicopters using tip jet propulsion, which generates almost no torque.
Autogyro
An autogyro (sometimes called gyrocopter, gyroplane, or rotaplane) utilizes an unpowered rotor, driven by aerodynamic forces in a state of autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust. While similar to a helicopter rotor in appearance, the autogyro's rotor must have air flowing up and through the rotor disk in order to generate rotation. Early autogyros resembled the fixed-wing aircraft of the day, with wings and a front-mounted engine and propeller in a tractor configuration to pull the aircraft through the air.
