What is meant by dissymmetry of lift?
Dissymmetry of lift in rotorcraft aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. In forward flight the advancing blade has a higher airspeed than the retreating blade, creating unequal lift across the rotor disc.
How is dissymmetry of lift accommodated for?
The tail rotor experiences dissymmetry of lift during forward flight, because it also has advancing and retreating blades. Dissymmetry is corrected for by a flapping hinge action. It is designed so that flapping automatically introduces cyclic feathering which corrects for dissymmetry of lift.
What action of a main rotor system compensates for dissymmetry of lift?
flapping hinge
The horizontal hinge, called the flapping hinge, allows the blade to move up and down. This movement is called flapping and is designed to compensate for dissymmetry of lift. The flapping hinge may be located at varying distances from the rotor hub, and there may be more than one hinge.
What causes dissymmetry of lift in a helicopter?
Dissymmetry of lift is the difference in lift that exists between the advancing half of the rotor disk and the retreating half. It is caused by the fact that in directional flight the aircraft relative wind is added to the rotational relative wind on the advancing blade, and subtracted on the retreating blade.
What do you mean by dissymmetry of lift?
What is dissymmetry of lift? Dissymmetry of lift is the unequal rotor thrust, or lift, produced by the rotor disc due to forward flight or wind. With forward flight, one blade is advancing into the wind while the other blade is retreating, or going with the wind.
Why does the tail rotor have dissymmetry of lift?
The tail rotor also experiences dissymmetry of lift during forward flight, because of its own advancing and retreating blades. Although the plane of rotation is vertical, the effects are the same as for the main rotor in the horizontal plane. Dissymmetry is usually corrected for by a flapping hinge action.
Why does a forward flight helicopter have more lift?
With forward flight, one blade is advancing into the wind while the other blade is retreating, or going with the wind. Uncorrected, the advancing blade produces more lift than the retreating blade, as the airflow over the advancing blade is greater.