Short-Term Conflict Alert Algorithm for Urban Air Mobility Operations Based on Conflict Detection and Resolution

Although short-term conflict alert (STCA) is a well-established safety net in air traffic management, STCA tailored to low-altitude urban air mobility (UAM) operations under the provider-of-services-for-UAM (PSU)-centered framework remains underexplored. This study proposes an STCA algorithm for UAM comprising a conflict-prediction module, which detects simultaneous horizontal and vertical separation violations using the closest point of approach, and a conflict-resolution module, which analytically derives alert distances for horizontal turning and vertical climbing in four encounter geometries classified by crossing angle. For each of 25 speed pairs between 180 and 320 km/h, 108 pairwise encounters were simulated. The alert rate increased with intruder speed, whereas the effect of object speed reversed depending on intruder speed. With controller and pilot reaction times sampled from kernel density estimates, the margin distances satisfying the target level of safety of 5 × 10−9, extrapolated using a generalized Pareto distribution, ranged from 1031 to 1882 m. A sensitivity analysis further showed that the required margin decreased with larger bank angles and climb rates. The proposed algorithm can serve as an alerting function for initial UAM operations involving onboard pilots and the PSU.