A Flight Study of the Dynamic Stability of a Tilting-Rotor Convertiplane

A flight investigation was conducted to determine the effect of blade flapping on the stability and control of the XV-3 convertiplane in cruise and high speed flight. The results of the study indicated that the inplane forces on the prop-rotors due to the blade flapping associated with airplane angular rates were in a direction to produce negative damping moments on the airplane. As a result of these inplane forces, the damping ratio of the longitudinal short period and lateral-directional oscillations approached zero at the maximum airspeed of the test airplane.