Low Altitude RA Virtual Pilot Tabletop: Preliminary Results Summary

A virtual tabletop activity was conducted in support of NASA Airspace Operations and Safety Program’s (AOSP) Air Traffic Management and Safety (ATMS) project. The primary aim of this study was to collect pilot feedback and opinion on the impact(s) of modifications to the alerting behavior of a next-generation collision avoidance system known as the Airborne Collision Avoidance System X for Active operations (ACAS Xa), particularly at low altitudes and in the terminal environment. In response to the January 29, 2025 midair collision between PSA Airlines Flight 5342 and PAT25 at DCA, a tiger team was established within RTCA SC-147 to investigate potential modifications to alerting standards that would increase overall safety in the terminal area. In particular, there is a question of whether lowering the “inhibit” thresholds in Xa’s low-altitude regime could improve safety. Accordingly, the goal of the current protocol was to expose pilots recruited for the study to narrative scenarios that feature variations of existing and modified ACAS Xa alerting behavior to collect opinions regarding safety impacts. Pilots experienced narrative scenarios, including visual storyboards mocking up the situations and relevant flightdeck displays, in a virtual, semi-structured tabletop (i.e., focus group) setting facilitated by Microsoft Teams. Following the presentation of each scenario, pilots responded to several questionnaire items and participated in a short open-ended discussoin. There was also an open-ended discussion at the end of the 4-hour virtual tabletop session. Pilots were unanimously in favor of lowering the alert inhibit thresholds, with the caveat that the change does not significantly increase the rate of nuisance alerts when flying close to the ground.