From Gaze Allocation to Scan Sequences: A Segment-Sensitive Eye-Tracking Study of Pilot Scan Discipline During Simulated Instrument Landing System Approaches

Instrument Landing System (ILS) approaches impose distinct visual demands across two operational segments, including (i) an intermediate approach segment prior to the final approach fix (FAF), during which pilots intercept and track the localizer while complying with published altitude restrictions and the glideslope-intercept altitude, and (ii) the final approach (FA) segment from the FAF to decision altitude/decision height, during which pilots precisely maintain both localizer and glideslope guidance. Using eye tracking, this study examines segment-specific scan behavior during simulated ILS approaches in low visibility conditions performed by 36 licensed pilots in a Cessna 172 equipped with G1000 avionics. The study results show that successful approaches were characterized by suppressed external viewing, more compact scans, and more organized return-loop patterns, suggesting that effective ILS scan discipline depends not only on looking at task-relevant instruments, but also on organizing those scans into phase-appropriate and functionally integrated sequences. By linking gaze allocation, scan dispersion, and scan sequence patterns to approach outcomes, this study demonstrates how eye tracking can provide segment-sensitive markers of instrument-scan quality. We further propose candidate scan-assessment metrics that may contribute to more precise and objective simulator debriefing, as well as future flightdeck-interface concepts that may support disciplined cross-checking without increasing pilot workload.