FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM- AM-26/03

Title and Subtitle: Pilot Performance, Workload, and Usability Considerations for the Use of a Monocular Head-Worn Display in Lieu of a Head-Up Display During SA CAT I Approach, Landing, and Rollout with an Enhanced Flight Vision System

Report Date: January 2026

Authors: David C. Newton (0000-0002-3112-3316), Inchul Choi (0000-0002-2048-7026), Hanna Forbat, Rebecca DiDomenica (0009-0009-4726-578X), Farzaneh Shahini (0000-0002-1514-5312), Theodore C. Mofle (0000-0003-2217-9083), and Ryan Weaver

Abstract:
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, in which 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. Simulator motion was disabled to prevent interference with the HWD head tracking system. The PF 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. Pilots reported that the EFVS enhanced their awareness of the runway environment when transitioning from instrument to visual flight references; however, because there was not an EFVS kill switch for the PF, it was reported to interfere with natural vision when transitioning to flare, landing, and rollout, regardless of when implemented on a HUD and monocular HWD. Ultimately, this research contributes to the understanding of how SA CAT I operations that are flown with and without an EFVS may be impacted when pilots fly with a monocular HWD in lieu of a HUD.

Key Words: Advanced vision systems, all-weather operations, enhanced vision system, enhanced flight vision system, equivalent visual operations, extended reality, head-mounted display, head-up display, head-worn display, low-visibility operations, pilot performance, pilot workload

No. of Pages: 109