Optimizing eVTOL final approaches: A scheduling and trajectory strategy for high-density urban air traffic

Continuous Descent Operations (CDO) streamline the descent profile and reduce engine thrust requirements, thereby lowering energy consumption. Compared to traditional hover-and-wait approaches, CDO employs less airspace in densely built urban settings and delivers superior safety and energy performance. However, implementing CDO typically necessitates greater separation buffers between flights, making it a challenge to maximize the number of eVTOL aircraft executing CDO procedures, particularly during peak urban air traffic. To address this issue, we develop an eVTOL-specific CDO concept, termed Staging with Continuous Descent Operations (S-CDO), in which aircraft are first sequenced on concentric dynamic loops and then fly a continuous, no-level-off terminal descent to touchdown. A kinematics-based point-mass model with an eVTOL electrical-power representation generates time-energy windows for candidate approach paths obtained via in-annulus path stretching. These windows feed a mixed-integer arrival-scheduling model solved in a rolling-horizon fashion, enforcing time-based separation at shared waypoints on top of a geometrically separated loop design while jointly optimizing total flight time and delay. We validate our model and methodology within a dynamically looped airspace framework designed in accordance with the China Civil Airports Association's group standards (T/CAATB). Numerical results confirm that our trajectory optimization-based eVTOL arrival scheduling approach substantially reduces total flight times and energy consumption, advancing the operational efficiency and sustainability of urban air mobility.