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. Such hazards could include aircraft parked on a runway and man-made towers or buildings. In this paper, a scanning pencil-beam, millimeter-wave (MMW) radar forward sensor is used to determine whether an aircraft's flight path is clear of obstructions. The 3-dimensional radar's returns are used to construct a terrain and obstruction database surrounding an aircraft, which is presented to the pilot as a synthetic perspective display. The radar and associated display evaluated in flight test on a NASA/Army test helicopter demonstrated its potential usefulness for collision avoidance.