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Rotorcraft
From Wikipedia, the free encyclopedia
Rotorcraft is a category of heavier-than-air flying machines that use lift generated by wings that revolve around a mast called rotor blades. Several rotor blades mounted to a single mast is referred to as a rotor. Rotorcraft may also include the use of static lifting surfaces, but the primary distinguishing feature being lift provided by one or more rotors. Rotorcraft include helicopters, autogyros, gyrodynes and tiltrotors. A qualified applicant receives a pilot license in the category of rotorcraft, with a class rating for either helicopter or gyrocopter, depending on which aircraft is to be flown. Tiltrotors, while using rotors and principles that govern flight of rotorcraft, are classified by the United States Federal Aviation Administration as powered lift aircraft.
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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 one driven main rotor require some sort of antitorque device such as a tail rotor, fantail, or NOTAR, although some rare examples of helicopters use tip jet propulsion which generates almost no torque.
Unlike a helicopter, the rotor of an autogyro is driven by aerodynamic forces alone once it is in flight, and thrust is provided by an engine-powered propeller similar to that of a fixed-wing aircraft. The autogyro is a distinct type of aircraft and not a hybrid between fixed-wing aircraft and helicopters. The U.S. Federal Aviation Administration refers to autogyros as gyrocopters.
A Gyrodyne is a heavier-than-air aircraft with a rotor system that is normally driven by its engine for takeoff, hovering and landing like a helicopter, but which also has an additional propulsion system that is independent of the rotor system. At higher speeds, the rotor system acts similar to that of an autogyro, no longer driving the aircraft but simply providing lift. A technology proposal by Carter Copter Technologies, as well as a research project funded by DARPA both refer to gyrodyne-type concepts as heliplanes.
As the name implies, a tiltrotor aircraft uses tiltable (rotating) propellers, or proprotors, for lift and propulsion. For vertical flight the proprotors are positioned horizontally to direct their thrust downwards, providing lift for vertical take off and landing, and hover. In this mode of operation the craft is essentially identical to a helicopter. As the craft gains speed, the proprotors are slowly tilted forward, eventually becoming perpendicular to the ground. In this mode the wing provides the lift, and the wing's greater efficiency helps the tiltrotor achieve its high speed.