Effect Of Rotary Disturbances On Aircraft Response

Abstract

A numerical model is introduced to study the effect of rotary disturbances on aircraft response. The model follows the technique proposed by the senior author for solving the coupled equations of motion of an aircraft. The general small-disturbance equations of motion are obtained as a system of linearized first-order differential equations. These equations are written in the form of a state equation. The latter equation is integrated by trapezoidal integration, which is stable for all increment sizes. The proposed numerical model simulates the aircraft response due to rotary disturbances that arise from variations in loads applied on the aircraft. Computer-generated illustrations of these responses are presented for initial pitching velocity disturbance, rolling disturbance, and yawing disturbance during straight flight. For an initial longitudinal rotary disturbance, the responses exhibit overshoots, short-period critically damped modes, and low-amplitude long-period oscillation modes for the symmetrical perturbations of the aircraft. On the other hand, a lateral initial disturbance causes heavily damped short period oscillation modes, exponentially decaying or increasing modes, and also critically damped modes for asymmetrical motion. Based on such responses, it is possible to extract the aircraft stability criteria.