Warnings for Helicopter Terrain Avoidance

This paper develops a new method for identifying terrain threats to produce warnings for low-level helicopter flight. Non-linear programming is used to calculate optimal avoidance paths for a set of predetermined trajectory classes. Warnings will be produced as the number of trajectories that avoid terrain decrease and the level of control authority required to do so increases. The concept is demonstrated for both a simple two dimensional vehicle as well as a three dimensional, fourteen state helicopter model. The results show that it is possible to calculate a discrete set of trajectories that can provide manoeuvre severity weighted warnings through a straightforward on/o format display.