Predictive ground collision avoidance system for the low-level terrain flight

Abstract

Controlled Flight Into Terrain (CFIT) is reported as a major cause of today’s aircraft accidents. To mitigate these accidents, Predictive Ground Collision Avoidance System (PGCAS) has been used since the mid-70s. In PGCAS algorithm, however, relatively large safety margin for the terrain searching pattern could arise some drawbacks, such as nuisance alarms or unnecessary pull-up commands, during a tactical terrain-following or low-level terrain flight to evade enemy’s air defense network. In this paper, a modified algorithm based on weighted terrain searching pattern and performance diagram is proposed to improve PGCAS more efficiently on the modern tactical fly missions. At first, the weighted terrain searching pattern is set to reflect the aircraft’s performance and give more reasonable safety margin in the system. The terrain elevation data lying in the exterior of the terrain searching pattern are now set to give lower terrain elevation than the data in the interior. Secondly, performance diagram is used to generate reference flight trajectory, which gives terrain-neighboring as well as safe ensured flight path. Finally, the proposed algorithm is further analyzed through simulations to evaluate its performance.