Longitudinal-Plane Simultaneous Non-Interfering Approach Trajectory Design for Noise Minimization

Runway-independent aircraft (RIA) operating under simultaneous non-interfering (SNI) traffic procedures have been proposed to alleviate airspace congestion at crowded urban airports. This paper introduces a methodology for designing minimum-noise longitudinal SNI approach trajectories for rotorcraft. An analytical model for ground noise annoyance associated with out-of-plane Blade-Vortex Interaction (BVI) noise is introduced and its application as the cost function for SNI trajectory optimization is described. The noise model relies on a physics-based semi-empirical expression developed to approximate the average annoyance levels associated with BVI noise on a representative ground plane. To guarantee strictly SNI trajectories, fixed-wing traffic corridors are treated as impenetrable obstacles modeled by their cross-sections in the longitudinal approach plane. Two optimization procedures are employed: a heuristic strategy that specifies trajectories using a small approach waypoint set and a globally-optimal cell-based algorithm. The feasibility and practicality of example minimum-BVI noise solutions are discussed.