View from rear of helicopter.
A condition in which one side of a rotor disc produces more thrust than the other. The speed of relative airflow over the advancing blade is higher than that of the retreating blade. The rotor thrust of the advancing blade also is higher than that of the retreating blade and thus the dissymmetry. This results in the helicopter rolling toward the retreating side. Suitable methods, like decreasing the angle of attack of the advancing blade and increasing the angle of attack of the retreating blade, are used to prevent this rolling tendency. Also called dissymmetry of lift