Abstract
Rotary wing aircraft are being tactically flown closer and closer to the ground in an effort to take maximum advantage of concealment and protection afforded by trees, man-made structures and terrain features. In recent years, night vision goggles have been used to aid the pilot in his/her flight duties. It has been noted, however, that visual transition from the outside environment into the cockpit (and vice versa) requires manual refocusing of the goggles. This requires the pilot to remove his hand from one or the other of the controls, thus compromising safe flight. In this study, eight U.S. Army aviators hovered an instrumented Army JUH-1H helicopter ten feet above the ground at night under four visual conditions using the unaided eye (normal night vision) and three configurations of the AN/PVS-5 night vision goggles (NVG).
The NVG configurations included: (1) 40° field-of-view piano tubes focused at infinity; (2) a bifocal arrangement in which the bottom 14% of the field was focused at approximately 22 inches; and (3) a bifocal arrangement with the bottom 24% focused at 22 inches. Aircraft status and control position monitors were scanned at a rate of 20 times per second and recorded on a seven-track magnetic tape via the helicopter in-flight monitoring system (HIMS).
Subsequent review and analysis of these data indicate no significant difference between configurations in terms of control movements. In terms of aircraft status variables, radio measured altitude indicated a large variability under the 40° piano NVG. However, hover behavior stabilized significantly in the bifocal condition. Subjective pilot responses supported these observations.
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