Collision avoidance: a helicopter simulator study

Six pilots flew a helicopter flight simulator with a helmet-mounted display. The pilot's task was to judge the time to collision with a second helicopter that disappeared at either 2, 2.5, or 3 s before collision. The field of view (FOV) was 66 degrees (vertical) x 127 degrees or 19 degrees x 25 degrees or 3 degrees x 3 degrees.

With a stationary target and ownship forward speed of 60 kt, pilots estimated that collision with a stationary target would occur roughly 200 ms before the actual time to collision in the large and intermediate FOV conditions. In the case of ownship stationary and the target approaching at 60 kt, estimates of collision time showed considerably less lead in the large and intermediate FOV conditions. When the smallest FOV was used, estimates were the same whether closing speed was produced entirely by ownship motion or entirely by target motion.

We suggest that the too-early errors in estimating time to collision were caused by the impression of self-motion produced by stimulating the peripheral retina with a radially-expanding flow pattern.