Abort landing guidance trajectories in the presence of windshear

Abstract

The problem of flight trajectories in the presence of windshear is discussed. The abort landing problem is considered with reference to flight in a vertical plane. It is assumed that, at the windshear onset, the power setting is increased at a constant time rate until maximum power setting is reached; afterward, the power setting is held constant. Hence, the only control is the angle of attack. Inequality constraints are imposed on both the angle of attack and its time derivative. Optimal trajectories are considered. The performance index being minimized is the peak value of the altitude drop. Numerical results are obtained for several combinations of windshear intensities and initial altitudes. Guidance trajectories are considered, approximating the optimal trajectories, while using local information on the state of the aircraft and the knowledge of two scalar parameters: the initial altitude h 0 and the total wind velocity difference † W x . Simplified guidance trajectories are also considered, employing only local information on the state of the aircraft, while avoiding the use of wind measurements. Comparative numerical results are obtained for the optimal trajectories (OT), the guidance trajectories (GT), the simplified guidance trajectories(SGT), and some alternative trajectories [constant pitch trajectories (CPT) and maximum angle of attack trajectories (MAAT)].