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Aircraft which are required to fly effectively at high angles-of-attack must overcome two fundamental difficulties: generally poor dynamic characteristics, especially with respect to damping, and low control authority of conventional aerodynamic effectors. One solution to improve closed-loop tracking of pilot commands is to employ a model-following controller approach, whereby an aircraft with poor dynamics at high angle-ofattack is made to track the outputs of a model of the same aircraft at low angle-of-attack, thereby emulating its good dynamics. An improved solution is the extension to combine the model-following controller with a controller that can augment the yaw control power by effectively modulating forebody pneumatic vortex flow nozzles. This paper presents the synthesis and design of both high angleof-attack lateral/directional controllers for a generic X-29A equipped with forebody vortex flow control nozzles. Results demonstrate that both controllers are effective in improving closed-loop tracking of input commands and high angle-of-attack maneuverability, compared to a conventional flight control scheme using only aerodynamic control effectors, and without model-following.

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