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Collision avoidance is of concern to all aircraft, requiring the detection and identification of hazardous terrain or obstacles in sufficient time for clearance maneuvers. The collision avoidance requirement is even more demanding for helicopters, as their unique capabilities result in extensive operations at low-altitude, near to terrain and hazardous obstacles. To augment the pilot's visual collision avoidance abilities, some aircraft are equipped with “enhanced-vision” systems or terrain collision warning systems. Enhanced-vision systems typically project raw images from infrared or radar sensors, and can require a high degree of pilot interpretation and attention, as the sensor returns may be sparse and are devoid of memory from previous sensor returns. Terrain collision warning systems rely on stored terrain maps that are of low resolution and accuracy which do not represent hazards to the aircraft placed after map sampling.

NASA and the U.S. Army have designed, developed, and tested a Computer Aiding for Low-Altitude Helicopter Flight guidance system. This system provides guidance to the pilot for near-terrain covert helicopter operations. The guidance is presented to the pilot through symbology on a helmet mounted display. This system has demonstrated the feasibility of a pilot-centered concept of terrain flight guidance that preserves pilot flexibility and authority. The system was developed using extensive piloted simulation and then implemented in a UH-60 Blackhawk helicopter for flight development and evaluation. A close correlation between simulation and actual flight was found; however, in flight overall pilot workload increased and performance decreased. This paper presents a description of the basic system design, simulation, and flight evaluations.