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The signs of VRS are a vibration in the main rotor system [8] followed by an increasing sink rate and possibly a decrease of cyclic authority. [9]In single rotor helicopters, the vortex ring state is traditionally corrected by slightly lowering the collective to regain cyclic authority and using the cyclic control to apply lateral motion, often pitching the nose down to establish forward flight.
The critical rollover angle is 5°-8°. Once exceeded, main rotor thrust continues the roll, and recovery via cyclic control is impossible. [1] A helicopter is susceptible to a rolling tendency, called dynamic rollover, when close to the ground, especially when taking off or landing. For dynamic rollover to occur, some factor has to first cause ...
During takeoff, ground effect can cause the aircraft to "float" while below the recommended climb speed. The pilot can then fly just above the runway while the aircraft accelerates in ground effect until a safe climb speed is reached. [2] For rotorcraft, ground effect results in less drag on the rotor during hovering close to the ground. At ...
Above, the rotor is powered and pushing air downward, generating lift and thrust. Below, the helicopter rotor has lost power, and the craft is making an emergency landing. Autorotation is a state of flight in which the main rotor system of a helicopter or other rotary-wing aircraft turns by the action of air moving up through the rotor, as with ...
The winds passing on both sides of the tail rotor make it teeter between being effective (providing thrust) and ineffective (not providing thrust). This creates a lot of pedal work for the pilot to eliminate unintended yaw. Tail rotor vortex ring state - Wind moving in the same direction as the tail rotor moves air. With pusher tail-rotors ...
Rotordynamics (or rotor dynamics) is a specialized branch of applied mechanics concerned with the behavior and diagnosis of rotating structures. It is commonly used to analyze the behavior of structures ranging from jet engines and steam turbines to auto engines and computer disk storage .
Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a desired way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating ...
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]