The term is particularly used by the United States Federal Aviation Administration for classification purposes. Powered-lift is one of the seven categories of aircraft designated by the Federal Aviation Administration; the other six being Airplane, Rotorcraft, Glider, Lighter-Than-Air, Powered parachute, and Weight-shift control.
Powered-lift means a heavier-than-air aircraft capable of vertical takeoff, vertical landing, and low speed flight that depends principally on engine-driven lift devices or engine thrust for lift during these flight regimes and on nonrotating airfoil(s) for lift during horizontal flight.
A convertiplane is an aircraft which uses rotor power for vertical takeoff and landing (VTOL) and converts to fixed-wing lift in normal flight.
In tiltrotor and tiltwing designs such as the Bell Boeing V-22 Osprey, the rotor swings forward to act as a propeller in forward flight. Some designs have a ducted fan design, in which the propeller is surrounded by a large ring-shaped duct to reduce tip losses.
The powered rotors of a tiltrotor (sometimes called proprotor) are mounted on rotating shafts or nacelles at the end of a fixed wing, and used for both lift and propulsion. For vertical flight, the rotors are angled to provide thrust upwards, lifting the way a helicopter rotor does. As the aircraft gains speed, the rotors progressively rotate or tilt forward, with the rotors eventually becoming perpendicular to the fuselage of the aircraft, similar to a propeller. In this mode, the wing provides the lift and the rotor provides thrust. The wing's greater efficiency helps the tiltrotor achieve higher speeds than helicopters.
The Bell Boeing V-22 Osprey by Bell Helicopter and Boeing is a twin-engine tiltrotor design that has two turbine engines each driving three-blade rotors. The rotors function similar to a helicopter in vertical flight, and similar to an airplane in forward flight. It first flew on 19 March 1989. The AgustaWestland AW609 (formerly Bell/Agusta BA609) tiltrotor is civilian aircraft based on the V-22 Osprey. The aircraft can take off and land vertically with 2 crew and 9 passengers. The aircraft is expected to be certified in 2017.