Optimal dive recovery maneuvers of a supermaneuvering jet fighter aircraft

Abstract

This paper describes an investigation of dive recovery maneuvers of a jet fighter aircraft capable of flying at angles of attack in the post-stall region. In a dive recovery maneuver, the pilot attempts to return the aircraft to level flight at an airspeed such that level flight can be maintained afterward. This maneuver is needed after either an intentional dive or an unintentional dive, or as the terminal recovery stage from some unusual attitude, namely, combination of extremely low airspeed and very high flight path angle. The optimization criterion is the minimization of the maximum loss of altitude during the dive recovery; hence, the optimization problem is a minimax problem of optimal control. The flight dynamics model accounts for all of the factors necessary to accurately characterize the aircraft motion. The results show that the optimal dive recovery trajectories consist of one to three segments, depending on the initial speed and flight path angle. For relatively high initial speed, the optimal trajectory consists of a single segment: a pitch-up at the limiting load factor. For very low initial speed, the optimal trajectory consists of two segments: a supermaneuver flown at very large angles of attack, followed by a pitch-up at the limiting load factor. For unusual attitude recovery from the combination of very low initial speed and very high initial flight path angle, the optimal trajectory consists of three segments: a dive initiation segment, followed by a supermaneuver at very large angles of attack, followed by a pitch-up at the limiting load factor. For aircraft without supermaneuver capability, the supermaneuver segment is to be replaced by a maximum angle of attack segment. The paper concludes with a discussion of the design benefits accrued via supermaneuver capability as well as the operational benefits accrued via afterburner usage.