Experimental study of helmet-mounted display attitude and flow cues on rotorcraft hover performance

A study was conducted to investigate the use of visual flow and attitude cues as an aid to lateral drift awareness during helicopter flight while using night vision goggles (NVG's). Four displays were compared: 1) NVG display: the baseline display simulating an NVG image of the cockpit and external environment; 2) NVG/Attitude display: NVG image with an overlay of an attitude symbol and a surrounding earth-referenced wire-frame globe; 3) Rate display: NVG image with an overlay of a flow cue field; 4) Rate/Attitude display: NVG image with the Rate and NVG/Attitude display overlays. The task objective was to null out lateral rates in the presence of lateral gusts while in a hover (the yaw, longitudinal, and vertical axes of motion were stabilized with an auto-pilot). This task was conducted in a fixed-based helicopter simulator using a helmet-mounted virtual reality device. Three pilots were used in this preliminary study. Cooper Harper subjective ratings (handling qualities) for the aircraft/display combination favored the Rate/Attitude display using an intermediate cube separation, which was consistent with the performance and frequency metric results.