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