Head-up display symbology for ground collision avoidance

Four ground collision avoidance displays were tested using a fixed-base T-3 8 simulator with a simulated head-up display. Twelve participants flew thro ugh 6 terrain encounters in each of the 4 display formats with 2 terrain pr ofiles and 3 initial aircraft attitudes. The displays were: an X icon, depi cted when projected altitude was below a given threshold; a chevron display that moved 2 triangular symbols laterally according to altitude; a mountai n display that moved a single triangle symbol vertically based on altitude; and a highway display providing a preview, perspective depiction of terrai n altitude, and a target altitude. When given the X-icon display, pilots we re able to spend only 40% of the flight time at the desired altitude and cr ashed in 20% of the runs. The chevron and mountain symbols allowed 70% and 80% of the flight time to be spent at the desired altitude, respectively, a nd resulted in a crash in 8% of the runs. The highway depiction was the bes t display for the task, allowing over 90% of the time to be spent at the de sired altitude with a crash rate of 2%.