Motion of a blade about the lag hinge, in the same direction as rotor rotation; the opposite of lagging.

The angle that the lateral body axis of an aircraft or similar body makes with a chosen reference plane in rolling; usually, the angle between the lateral axis and a horizontal plane. The angle of roll is considered positive if the roll is to starboard.

The angle between the direction of the undisturbed relative airflow and the plane of symmetry.

A large tank into which models are freely launched for observation of their behaviour when landing on water.