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The helmet mounted display (HMD) system is designed to facilitate the acquisition of visual information. Instead of requiring gaze shifts to the instrument panel or HUD, specifiable information is available at approximately 0° vertically, and displayed on the helmet visor. Are pilots able to make use of this information without extensive training? If having such information available reduces workload, how does the pilot use the "released" time? To answer these questions, we collected steady state evoked responses (SSEP) to the rapidly flickering display, and also evaluated aspects of visual search as reflected in head and eye movements and eye blinks, in simulated flight. Why these variables are of utility and how they may be used will be described in the context of an evaluation made by our laboratory of the Kaiser HMD system. This was performed for AAMRL/HEA at the McDonnell-Douglas flight simulation facility in St. Louis. Data were collected on B-1 pilots flying "ingress" and "refueling" missions. Although we observed SSEPs in the laboratory, and could record EEG in the electrically noisy simulator environment, several factors prevented a clear demonstration of SSEP under simulation conditions and thus precluded a test of the technique as an index of workload. Specifically, there was less than optimal intensity and waveform of the display, and perhaps most important, there was considerable variablity in the angle of regard of the display due to normal scanning under flight conditions. For purposes of oculographic analysis, the ingress condition was divided into segments associated with approaches to waypoints, threat avoidance, and post-threat periods. Use of the HMD reduced horizontal and vertical visual search activity under all conditions except threat avoidance and post-threat recovery. A second measure, frequency of conjoint occurrence of eye blinks and eye movements, also discriminated the HMD from the nonHMD conditions. Our results suggest that pilots rapidly learn to make effective use of the HMD information, i.e., they spend less time looking at their instrument panels. However, they do not appear to use the "released time" to search their environment more actively.
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