Tangential Forebody Blowing-yaw control at high alpha

Abstract

Aircraft yaw control at high angles of attack by Tangential Forebody Blowing has been investigated experimentally. Tests were performed in the University of Bath 2. lm x 1.5m low speed wind tunnel using an approximately 6% scale generic combat aircraft model fitted with blowing slots in the nose cone. Six component strain gauge balance force and moment data was measured for angles of attack up to 90 and for a number of different slot geometries and locations. The performance of momentum and mass flow based aerodynamic scaling parameters was assessed. It was found that small blowing rates from short slots at the front of the forebody could produce large controlled yawing moments up to around 60 angle of attack, however longer slots at larger blowing rates could provide control at angles of attack up to 90, where no coherent vortical flow is present. The effect of slot angular position is demonstrated and a slot stall phenomenon described. A geometry dependent forebodylwing flow-field coupling has been identified which can lead to unexpected yawing moments and uncommanded rolling moments.