Forebody vortex control - A progress review

Conventional fighter aircraft control surfaces, such as the rudder, become ineffective at high angles of attack resulting in a serious deficiency in lateraldirectional controllability in the angle of attack range for maximum lift and in the post stall regime. Development of robust control methods for high angle of attack flight has focused primarily on thrust vector control and forebody vortex control. This paper is an attempt to review the forebody vortex control research that has taken place in the last two to three years. Some earlier research results are also shown to provide a historical perspective and to document the state of our knowledge of this rapidly advancing technology. The techniques that have been investigated include large deployable or hinged strakes, pneumatic techniques using either nozzles or slots, suction through small holes or ports, and miniaturized rotatable nose-tip and nose-boom strakes. Optimized versions of all of these techniques are effective in producing primarily yawing moments at high AOA, with, for some configurations, some interactions in rolling moment. Mass flow rates required for pneumatic techniques are at levels that can be obtained from today's engine bleed systems. Application of techniques developed for conventional forebodies with rounded cross sections are just beginning to be evaluated for advanced forebodies with chined cross sections.