Flight control for the F-8 oblique wing research aircraft

Multivariable flight control laws for the supersonic F-8 oblique wing research aircraft are discussed. The control laws are developed using a loopshaping methodology. The goal is to perform flight tests on a supersonic aircraft with an oblique wing with as much as 65 degrees wing skew. The objective of the control law is to obtain decoupling of the longitudinal and lateral-directional motions of the unsymmetrical aircraft, as well as to satisfy conventional flight control objectives, including gust attenuation, good command tracking, good handling qualities, and stability robustness with respect to model uncertainty. A multivariable proportional-plus-integral element is the basic ingredient of the control laws, along with sensor blending into regulated variables and pilot command precompensation. Various analyses, including frequency and time responses, are presented. Stability robustness properties of the control laws are presented using structured and unstructured singular-value techniques. Handling qualities are analyzed using the equivalent systems technique. Responses of the controlled aircraft to pilot inputs are illustrated using time histories.<>