Modified algorithm of Predictive Ground Collision Avoidance System for the low level terrain flight

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 cause 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 is proposed to improve PGCAS more efficiently for the low level terrain flight. The weighted terrain searching pattern reflects the aircraft´s performance and the flight path to give more reasonable safety margin to the system. The terrain elevation data lying on the exterior of the terrain searching pattern are set to give lower terrain elevation than the data on the interior. The proposed algorithm is further analyzed through simulations to evaluate its performance.