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[1] [2] Unlike fixed-wing aircraft, of which the stall occurs at relatively low flight speed, the dynamic stall on a helicopter rotor emerges at high airspeeds or/and during manoeuvres with high load factors of helicopters, when the angle of attack(AOA) of blade elements varies intensively due to time-dependent blade flapping, cyclic pitch and ...
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]
This causes the innermost portions of the blades to begin to stall. [citation needed] As the inner blade sections stall, a second set of vortices, similar to the rotor-tip vortices, begins to form in and around the center of the rotor system. This, combined with the outer set of vortices, results in severe loss of lift.
The inner 25 percent of the rotor blade is referred to as the stall region and operates above its maximum angle of attack (stall angle) causing drag, which slows rotation of the blade. A constant rotor rotational speed is achieved by adjusting the collective pitch so blade acceleration forces from the driving region are balanced with the ...
A helicopter's main rotor hub. The vertical rods are at the end of the control chain that starts with the pilot controls. Helicopter flight controls are connected to the main and tail rotors, and include a cyclic stick, broadly to control forward-aft and left-right movements, a collective lever, broadly to control vertical movements, and anti-torque pedals, to control left and right yaw.
This is done by blade flapping and cycling feathering. Blade flapping is the primary means of countering dissymmetry of lift. [1]: 2–14 Rotor blades are designed to flap: the advancing blade flaps up and develops a smaller angle of attack due to a change in relative wind vectors, thus producing less lift than a rigid blade would. Conversely ...
Rotor stalls are not recoverable because the descending helicopter has airflow moving upwards through the rotor disc, so even full down collective will not restore normal airflow. When the helicopter rotor stalls, it does not do so symmetrically, because forward airspeed causes higher airspeed on the advancing blade than on the retreating blade ...
At the top of the mast is the attachment point (colloquially called a Jesus nut) for the rotor blades called the hub. The rotor blades are then attached to the hub, and the hub can have 10-20 times the drag of the blade. [1] Main rotor systems are classified according to how the main rotor blades are attached and move relative to the main rotor ...