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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 ...
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.
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 .
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.
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.
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.
Phase lag may vary depending on rotor tilt rate, ratio of aerodynamic damping to blade inertial forces (Lock number), offset of flapping hinge from axis of rotation (e/R ratio), and coupling of blade flap, drag, and feather motions, and often results in cross-coupling between the aircraft control axes. Phase lag is a property of all rotating ...
Single rotor helicopters are limited in forward speed by a combination of sonic tip speed and retreating blade stall. As the advance ratio increases, the relative velocity experienced by the retreating blade decreases so that the tip of the blade experiences zero velocity at an advance ratio of one.