Design Challenges Faced by Actively Stabilized High Performance Aircraft

High performance aircraft tend to be slender with heavy components located along their fuselages. They also tend to feature swept wings and fins. On some aircraft, a center of gravity location may be specified so that the bare airframe longitudinal and lateral-directional frequencies are fast enough to avoid pilot (or autopilot) induced oscillations. On others, physical limitations may preclude sufficient static directional stability to ensure satisfactory unaugmented stability, i.e., hard limits on tail sizing or hard requirements on speed and altitude. This paper examines challenges the control law designer may face when the aerodynamic behavior of common control surfaces drives competing control laws which “fight” one another in an attempt to stabilize and control a high-performance aircraft.