The Utility of a Ghost Horizon and Climb/Dive Ladder Tapering on a Head-Up Display

Abstract

As part of an Air Force effort to standardize HUD symbology, an unusual attitude recovery task was employed to investigate the utility of a cue, the ghost horizon, that indicates the direction of the actual horizon when the climb/dive ladder horizon line is not within the HUD field of view. Six HUD-experienced and 6 non-HUD-experienced military pilot subjects were used to determine whether there was improvement, with the ghost horizon, in ability to recover from nose-down unusual attitudes in a flight simulator. The ghost horizon was evaluated with 3 different climb/dive ladder line configurations (tapered, non-tapered, reverse tapered). In terms of accuracy of the initial stick input, the ghost-horizon configurations resulted in significantly better performance (about 11% better) than did the non-ghost-horizon configurations. The ghost horizon had no effect on initial stick input reaction time or total recovery time. The climb/dive ladder line taper configuration did not affect accuracy, initial stick input reaction time, or total recovery time. Subjective data indicated that the pilots did not have a strong preference for any of the configurations. These findings suggest that the ghost horizon is a useful aid to unusual attitude recovery performance, and may reduce spatial disorientation.