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A greater amount of rotor energy is required to stop a helicopter with a high rate of descent than is required to stop a helicopter that is descending more slowly. Therefore, autorotative descents at very low or very high airspeeds are more critical than those performed at the minimum rate of descent airspeed.
Location of flight controls in a helicopter. Helicopter flight controls are used to achieve and maintain controlled aerodynamic helicopter flight. [1] 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.
Turbulent airflow results in loss of rotor efficiency. If allowed to continue, uncommanded pitch-and-roll oscillations may occur, with a large descent rate. [1] The vortex ring state (VRS) is a dangerous aerodynamic condition that may arise in helicopter flight, when a vortex ring system engulfs the rotor, causing severe loss of lift.
Helicopters which lose power do not simply fall out of the sky. In a maneuver called autorotation, the pilot configures the rotors to spin faster driven by the upward moving air, which limits the rate of descent. Very shortly before meeting the ground, the pilot changes the momentum stored in the rotor to increase lift to slow the rate of ...
The number of rotors is also important, many helicopters have two rotors in a single line, and another configuration is 4 rotors. [22] An example of two-blade rotor is the Bell 212 , and four blade version of this helicopter is the Bell 412 . [ 23 ]
Helicopter blade tip vortex simulation by DLR Tip vortex rollup. A blade vortex interaction (BVI) is an unsteady phenomenon of three-dimensional nature, which occurs when a rotor blade passes within a close proximity of the shed tip vortices from a previous blade.
The helicopter that crashed into a canal in late December near Miami, killing a 71-year-old pilot and hospitalizing his daughter, broke into two with the tail landing hundreds of feet away from ...
[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 ...