<title>Visual field information in nap-of-the-earth flight by teleoperated helmet-mounted displays</title>

Abstract

The human ability to derive control-oriented visual field information from tele-operated helmet-mounted displays (HMDs) in nap-of-the-earth flight is investigated. The visual field with these types of displays originates from a forward looking infrared radiation camera, gimbal-mounted at the front of the aircraft and slaved to the pilot''s line-of-sight to obtain wide-angle visual coverage. Although these displays are proven effective in Apache and Cobra helicopter night operations, they demand very high pilot proficiency and work load. Experimental work presented in the paper has shown that part of the difficulties encountered in vehicular control by means of these displays can be attributed to the narrow viewing aperture and head/camera slaving system phase lags. Both these shortcomings will impair visuo- vestibular coordination, when voluntary head rotation is present. This might result in errors in estimating the control-oriented visual field information vital in vehicular control, such as the vehicle yaw rate or the anticipated flight path, or might even lead to visuo-vestibular conflicts (motion sickness). Since, under these conditions, the pilot will tend to minimize head rotation, the full wide-angle coverage of the HMD, provided by the line-of-sight slaving system, is not always fully utilized.