Optimization of Vertical Plane Cobralike Pitch Reversal Maneuvers

Abstract

Four time-optimal, vertical plane, cobralike pitch maneuvers corresponding to different sets of boundary conditions have been studied for the F-18 high-angle-of-attack research vehicle aircraft. These maneuvers are poststall maneuvers that enable an aircraft that is initially followed by a pursuing aircraft to shift positions, that is, the initial evader turns into the pursuer. The initial pursuer is assumed to remain at constant speed and altitude. In addition an 80-deg pitch reversal maneuver has been considered that was optimized using a Chebyshev approach. A nonlinear programming and collocation method was successfully used to find the optimal vertical plane trajectories in open-loop form. All trajectories that were found have been put through a six-degree-of-freedom simulation utilizing a nonlinear inversion closed-loop control technique. The results showed that the optimal vertical plane trajectories can be flown quite accurately, using longitudinal and lateral thrust vectoring, along with the conventional aerodynamic controls.