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Rotor map of dynamic stall locations for all conditions. Stage 4: full separation of the flow on the upper surface of the airfoil can be observed, accompanied by the peak of nose-down pitch moment. Stage 5: the full flow reattachment is achieved as the AoA gradually decreases until it is fairly smaller than the static stall angle. [10]
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]
In aviation, and in particular in helicopters, servo transparency (also called servo reversibility or jack stall), [1] is a phenomenon affecting the servomechanisms (or servos) that assist a helicopter's flight controls, which, in certain flight conditions, can result in a significant stiffening of the controls handled by the pilot.
Helicopter rotor joints Illustration of the shift in the location of the center of mass of a helicopter rotor caused by the individual blades' rotation in their respective vertical joints. Articulated rotor systems with drag hinges allow each blade to advance or lag in its rotation to compensate for the stress on the blade caused by the ...
The static rollover critical angle can be determined by measuring the angle between level ground and an imaginary line drawn from skid to skid, when the helicopter's center of gravity is located on the upward pivot line. [4] [5] Static rollover also pertains to automobiles. In the study of roll stability of vehicles, the static rollover ...
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 ...
In a helicopter the maximum forward speed is defined by the turn speed of the rotor; at some point the helicopter will be moving forward at the same speed as the spinning of the backwards-moving side of the rotor, so that side of the rotor sees zero or negative airspeed, and begins to stall. This limits modern helicopters to cruise speeds of ...
In fact, it can be enjoyable to have zero gravity in the cockpit. To produce 0g, the aircraft has to follow a ballistic flight path, which is essentially an upside down parabola. This is the only method to simulate zero gravity for humans on earth. In helicopters. In contrast, low-g conditions can be disastrous for helicopters.