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https://www.nationalacademies.org/trb/events

Use of a Monocular Head-Worn Display (HWD) With and Without an Enhanced Flight Vision System (EFVS) to Conduct Lower-than-Standard Approach and Landing Minima Flight Operations

When flying a Special Authorization Category I (SA CAT I) instrument landing system (ILS) approach, pilots may use a Head-Up Display (HUD), which presents flight symbology on a transparent screen so that the pilot can view primary flight information while looking out the window, along the flightpath. Pilots can also use an Enhanced Flight Vision System (EFVS) on a HUD during this operation, which provides a real-time sensor image of the forward view to enhance runway awareness when transitioning to visual flight references. The Head-Worn Display (HWD) is an emerging technology in civil aviation that is designed to provide the benefits of a HUD; however, the unique optical and physical characteristics of the HWD may change the existing levels of pilot performance and workload during SA CAT I operations flown with a HUD. When flying with a monocular HWD, binocular rivalry occurs, which may impact pilot performance and workload. This raises questions about whether pilot performance and workload are significantly impacted during manual SA CAT I flight operations where the pilot flying (PF) uses a monocular HWD with and without an EFVS. To address this concern, a study was carried out in which 11 pilot crews, made up of 22 Airline Transport Pilot (ATP) Captains, flew manual SA CAT I approach, landing, and rollout scenarios in a Boeing 737 Level D-equivalent flight simulator with a HUD and monocular HWD, with and without an EFVS, and in day and night ambient lighting conditions. Pilots rated their workload during each scenario using the National Aeronautics and Space Administration Task Load Index (NASA-TLX). The findings of the study suggest that a monocular HWD may not have a significant negative impact on a pilot’s ability to manage most aspects of the flightpath during an SA CAT I operation; however, the monocular HWD elevated pilot workload. The monocular HWD also caused increased glideslope deviation during the instrument segment and increased deviation from the runway centerline during rollout. However, these increases were small, and may not translate to operational significance. While the use of an EFVS did not impact any aspects of pilot performance or workload, pilots reported that it enhanced their awareness of the runway environment when transitioning from instrument to visual flight references; however, it was reported to be a hindrance when transitioning to flare, landing, and rollout regardless of whether it was implemented on a HUD or a monocular HWD.