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The effect of dynamic stall limits the helicopter performance in several ways such as: The maximum forward flight velocity and thrust; High blade structural loads, which may result in excessive vibrations and blade structural damage; Control system loads, manoeuvre capability, and handling qualities; Helicopter dynamic performance.
There are three general designs. The earliest, and by far, least common design today, is the fully rigid rotor system; the blades are rigidly fixed to the rotor hub but made of a flexible material that allows some degree of flap. Semi-rigid rotor systems have a horizontal hinge at the base of the blades that allow flap as they rotate. By ...
For a given weight, a helicopter with shorter rotors will have higher disk loading, and will require more engine power to hover. A low disk loading improves autorotation performance in rotorcraft. [5] [6] Typically, an autogyro (or gyroplane) has a lower rotor disk loading than a helicopter, which provides a slower rate of descent in ...
Tail rotor vortex ring state - Wind moving in the same direction as the tail rotor moves air. With pusher tail-rotors, that is wind from the opposite side of the tail-rotor. With puller tail-rotors, that is wind from the same side as the tail rotor. For main rotors with clockwise rotation (European), that is wind from 3 o'clock.
A static balance (sometimes called a force balance [2] [3]) occurs when the inertial axis of a rotating mass is displaced from and parallel to the axis of rotation.Static unbalances can occur more frequently in disk-shaped rotors because the thin geometric profile of the disk allows for an uneven distribution of mass with an inertial axis that is nearly parallel to the axis of rotation.
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.
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 .
When a hovering rotor is near the ground the downward flow of air through the rotor is reduced to zero at the ground. This condition is transferred up to the disc through pressure changes in the wake which decreases the inflow to the rotor for a given disc loading, which is rotor thrust for each square foot of its area.