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On a helicopter, the main rotor or rotor system is the combination of several rotary wings (rotor blades) with a control system, that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight.
Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the retreating rotor blade has a lower relative blade speed, combined with an increased angle of attack, causing a stall and loss of lift. Retreating blade stall is the primary limiting factor of a helicopter's never exceed speed, V NE. [1]
The Bölkow Bo 46 was a West German experimental helicopter built to test the Derschmidt rotor system that aimed to allow much higher speeds than traditional helicopter designs. [1] Wind tunnel testing showed promise, but the Bo 46 demonstrated a number of problems and added complexity that led to the concept being abandoned.
Dissymmetry of lift in an American-style helicopter. Consider a single-rotor helicopter in still air. For a stationary (hovering) helicopter, whose blades of length of r metres are rotating at ω radians per second, the blade tip is moving at a speed rω meters per second. As the blades rotate, the speed of the blade-tips relative to the air ...
Loss of tail-rotor effectiveness (LTE) [1] occurs when the tail rotor of a helicopter is exposed to wind forces that prevent it from carrying out its function—that of cancelling the torque of the engine and transmission. Any low-airspeed high-power environment provides an opportunity for it to occur.
The tail rotor is powered by the helicopter's main power plant, and rotates at a speed proportional to that of the main rotor. In both piston and turbine powered helicopters, the main rotor and the tail rotor are mechanically connected through a freewheeling clutch system , which allows the rotors to keep turning in the event of an engine ...
Proper maintenance of the helicopter's damping system components can prevent ground resonance from taking hold. When it does occur, recovery is often possible if action is taken quickly. If sufficient rotor RPM exists, immediate takeoff can restore rotor balance by allowing the airframe to move and help dampen the oscillation freely. [1]
The erosion associated with the Kopp–Etchells effect presents costly maintenance and logistics problems, and is an example of foreign object damage (FOD). [ 11 ] Sand hitting the moving rotor blades represents a security risk because of the highly visible ring it produces, which places military operations at a tactical disadvantage when ...