Examining and explaining the effects of non-iconic conformal features in advanced head-up displays on pilot performance.

摘要

The primary objective of this study was to assess the impact of Synthetic Vision System (SVS) and Enhanced Vision System (EVS) depictions of terrain features on pilot performance when displayed in an advanced head-up display (HUD) during various phases of a landing approach under instrument meteorological conditions (IMCs). SVS is a display system that presents terrain features using a wireframe grid rendered polygons by integrating terrain databases with a global positioning system. EVS displays present an actual out-of-cockpit view using a forward looking infrared camera.;In the experiment as part of this study, video stimuli presenting varied HUD configurations were pre-recorded using a high-fidelity flight simulator at NASA Langley and presented to eight pilots later in a lab environment. The HUD videos from the high-fidelity simulator were combined with out-of-cockpit views from a lab simulator. The flight scenario consisted of an approach and landing on a runway (Reno, Nevada International Airport (KRNO), 16R (right)) under IMC. Each pilot completed eight trials based on a within-subjects experimental design and one additional trial to collect verbal protocols on specific display feature use. The independent variables included four display configurations (baseline, SVS-only, EVS-only, and a combination of SVS and EVS features) and two visibility conditions (IMC-day versus IMC-night). Every display configuration included tunnel features (highway-in-the sky) showing the designated flight path. The experiment involved observing pilot performance in four segments during the approach and landing. Dependent variables included flight path control performance, pilot SA, workload, and subjective preferences. Flight path control performance was determined based on pilot errors in tracking a flight path marker in the pre-recorded videos with a super-imposed cursor using test pilots yoke controls. Pilot situation awareness (SA) was measured using SAGAT (the Situation Awareness Global Assessment Technique) in order to evaluate pilot perception, comprehension, and projection for three types of pilot SA (spatial, system, and task awareness). Workload measures were recorded using the NASA-TLX (Task Load Index) and heart-rate. In order to develop explanations of pilot behavior under the various HUD conditions, a video record of the additional test trial was reviewed by each subject using a verbal protocol analysis and probing technique.;Results revealed SVS to support overall pilot SA but to degrade flight path control performance due to confusion of visual features, EVS caused pilots to focus on path control but decreased System awareness because of visual distractions of some imagery. The combination of SVS and EVS features generated offsetting effects; however there were decrements in performance in the final landing phase due to clutter effects. In general, display configurations did not affect spatial awareness but pilot awareness of system information was impacted. The IMC-day condition produced worse flight performance than night flight due to the low visual saliency of HUD imagery in daylight. Flight performance was not different among phases of flight but different levels and types of pilot SA were affected by segment. Because the main task in the study was the tracking task, results did not reveal differences of conditions in terms of workload measures. Interestingly, patterns of pilot preference for displays did not match with the results of objective performance and SA measures. Pilots gave higher ratings of SA support and safety for the SVS and EVS displays with the lowest ratings for the combination. Ratings on annoyance increased with increases in display visual content. The verbal protocol analysis yielded sequential and non-sequential lists of pilot tasks and behaviors and critical pilot comments. The analysis also identified the required information and alternative methods of performance for specific flight tasks in the scenario. This analysis was used to explain the experimental results and describe pilot behaviors with the SVS and EVS displays in the flight scenario.;This study assessed advanced HUD feature effects on pilot performance, using an elaborate SAGAT method for measuring pilot SA, and developed a CTA for interpreting experimental results. Further studies need to be conducted to evaluate the advanced HUDs under various flight situations using a more realistic flight simulator as a basis for optimal design. In addition, cognitive model of pilot behavior based on CTA needs to be developed for predicting performance and SA implications of HUD design.