Flight Control for the F-8 Oblique Wing Research Aircraft

This paper will discuss multivariable flight control laws for the F-8 Oblique Wing Research Aircraft. The control laws were developed using a loopshaping methodology to support the NASA/Navy program to ultimately flight test a supersonic aircraft with an oblique wing with as much as 65 degrees wing skew. The objective of the control laws 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 will be presented. Stability robustness properties of the control laws will be presented using singular value and structured singular value techniques. Handling qualities will be analyzed using the equivalent systems technique. Responses of the controlled aircraft to pilot inputs will be presented using time histories.