Side gust loads on a fighter aircraft during maneuver

Abstract

The aerodynamic response of an aircraft to side gust loads was experimentally examined. The investigation was carried out in a wind tunnel with side flow supplied from the test section side wall, such that it simulates side gust. The model employed is similar to the F-4 fighter. Since fighter aircraft are designed to fulfill high maneuverability requirements, the orientations considered in the investigation assumed various incidence, sideslip and bank angles. It was found that side gust causes reduction in lift for certain settings. Fortunately, this loss of lift could not only be made up for but additional lift could be obtained by changing the aircraft bank angle. Side winds had profound effect in increasing the drag. Once again, it was possible to obliterate the effect of gust loads on the drag force by rolling the aircraft to certain bank angles. Unfortunately, it was not possible to secure both advantages at the same aircraft setting. The longitudinal stability curves featured additional nose-up pitching moment and gain in the longitudinal stability for all cases considered as side flow was applied. In response to the laterally supplied side flow, the aircraft model side force exhibited constant drift in the direction of the lateral flow. The influence of side gust on the rolling and yawing moments was less significant in terms of magnitude. According to these results, the recommended aircraft maneuver configuration during side gust encounter is the one where lift is enhanced, though this will imply drag build up. The latter is to be made up by applying more thrust.