Effect of rotary atmospheric gusts on fighter airplane

Abstract

In the present study, a computer program developed by the author is used to study the effect of rotary atmospheric gusts on a fighter bomber aircraft. These rotary gusts are selected to be of the step type that have a duration of one nondimensional unit of time. The response of the airplane under these disturbances are illustrated during different stages of its flight such as powered approach at sea level, subsonic cruise at 35 000 ft., and supersonic cruise at an altitude of 55 000 ft. It is noticed that the aircraft experiences both Dutch roll and spiral modes when it encounters rolling and yawing gust disturbances during various stages of its flight. Dutch roll modes that result from yawing gusts are characterized by relatively high amplitudes during the different stages of flight. Spiral modes trailing the rolling gust are relatively steep and tight. On power approach flight and due to exposure to the pitching gust, responses of both the forward velocity and incidence angle experience long-period increasing oscillation modes. During subsonic cruise flight, however, the aircraft suffers from a continuously increasing incidence angle and a decreasing of the forward velocity. Additionally, it is found that all stability modes are remarkably improved during supersonic cruise flight.