Other contributions to Lv

The contributions to lateral static stability from the tail rotor, the fin and the fuselage all arise as a result of the sideforces produced on these components during a sideslip. The magnitude of each contribution will depend on the individual forces and the distances of their lines of action from the rolling axis. Normally all the contributions are stabilizing. The horizontal stabilizer can also contribute to Lv in a similar fashion to that of the main and tail planes of a fixed wing aircraft. If a helicopter is fitted with symmetrical tail surfaces either side of the tail boom then as the aircraft rolls the downgoing side of the stabilizer encounters the relative airflow at an angle which effectively increases its angle of attack and hence its lift force. The upgoing side will
experience the opposite effect and a decrease in angle of attack and lift. The imbalance provides a moment that acts to stop the roll and, in the subsequent sideslip, any dihedral will further increase this restoring moment.