Search results
Results from the WOW.Com Content Network
The effect of airfoil geometry on dynamic stall is quite intricate. As is shown in the figure, for a cambered airfoil, the lift stall is delayed and the maximum nose-down pitch moment is significantly reduced. On the other hand, the inception of stall is more abrupt for a sharp leading-edge airfoil. [8] More information is available here. [13]
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.
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]
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 angle of attack can be increased to compensate, however beyond a certain point the rotor blades stall and lift rapidly decreases. 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 ...
Nasa’s Mars helicopter Ingenuity will never fly again, the space agency gas said.. The pioneering robot vehicle was the first ever to achieve powered and controlled flight on another world. It ...
The fighter aircraft and helicopter responded to a civilian aircraft at 2:25 p.m. Saturday and escorted it to the ground. During the event, the aircraft dispensed flares in an attempt to draw ...
Proper maintenance of the helicopter's damping system components can prevent ground resonance from taking hold. When it does occur, recovery is often possible if action is taken quickly. If sufficient rotor RPM exists, immediate takeoff can restore rotor balance by allowing the airframe to move and help dampen the oscillation freely. [ 1 ]