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Evaluation of off-boresight helmet-mounted display symbology formats for interpretation of ownship status information

Three variations of the non-distributed flight reference (NDFR) off-boresight helmet-mounted display (HMD) symbology were evaluated along with the Mil-Std-1787C HUD symbology and an off-boresight HMD symbology called the Visually Coupled Acquisition and Targeting System (VCATS), for interpretation of ownship status information. Using twenty predetermined flight path segments lasting 3 to 5 seconds each, the NDFR, NDFR plus climb-dive angle reference, mini-arc NDFR, Standard HUD, and VCATS symbologies were compared for recall of ownship status information. Twelve military or civilian rated pilots participated. Pilots viewed all five symbology formats with ownship status information recalled at the end of each flight path. Pilots provided feedback of ownship status using a free recall methodology. Mil-Std-1787C HUD served as the baseline measure of comparison with the primary comparison of interest being the off-boresight HMD symbology formats. The study's aim was to evaluate the baseline NDFR format along with alternate symbology designs to arrive at an HMD symbology for off-boresight applications that is highly usable in terms of awareness of aircraft state and orientation. The results of the study showed that, although no single NDFR format proved best for all information categories, taken as a group, the NDFR symbology proved to be the preferred symbology format for the information categories investigated. The NDFR format equaled recall performance for Standard HUD and outperformed or equaled the VCATS off-boresight symbology. Further evaluation of the NDFR concept is planned using pilot-in-the-loop HMD simulations evaluating modifications to the NDFR for trend information and attitude determination and investigating display compatibility with the virtual HUD concept.