Rotor wing
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A rotor wing is a lifting rotor or wing which spins to provide aerodynamic lift. In general, a rotor may spin about an axis which is aligned substantially vertically, fore-and aft, or side to side (spanwise). All three classes have been studied for use as lifting rotors, although only vertical-axis rotorcraft such as the helicopter have come into common use.
Some types provide lift at zero forward airspeed, allowing for vertical takeoff and landing (VTOL), as in the helicopter. Others require forward airspeed in the same manner as a fixed-wing aircraft. Many can also provide forward thrust if required.
Classes of rotor wing include:
Conventional rotorcraft have vertical-axis rotors. The main types include the helicopter with powered rotors providing both lift and thrust, and the autogyro with unpowered rotors providing lift only. There are also various hybrid types.
Some rotor wing aircraft are designed to stop the rotor for forward flight, so that it then acts as a fixed wing to provide some or all of the lift required. For vertical flight and hovering it spins to act as a rotary wing or rotor, and for forward flight at speed it stops to act as a fixed wing. Additional fixed wings may also be provided to help with stability and control and to provide auxiliary lift.
An early American proposal was the conversion of the Lockheed F-104 Starfighter with a triangular rotor wing. The idea was later revisited by Hughes. The Sikorsky S-72 research aircraft underwent extensive flight testing.
The later canard rotor/wing (CRW) concept added a "canard" foreplane as well as a conventional tailplane, offloading the rotor wing and providing control during forward flight. For vertical and low-speed flight, the main airfoil is tip-driven as a helicopter's rotor by exhaust from a jet engine, and there is no need for a tail rotor. In high-speed flight the airfoil is stopped in a spanwise position, as the main wing of a three-surface aircraft, and the engine exhausts through an ordinary jet nozzle. Two Boeing X-50 Dragonfly prototypes were flown from 2003 but the program ended after both had crashed, having failed to transition successfully.
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Wikipedia