Aircraft collision avoidance systems have long been a key factor in keeping our airspace safe. Over the past decade, the FAA has supported the development of a new family of collision avoidance systems called the Airborne Collision Avoidance System X (ACAS X), which model the collision avoidance problem as a Markov decision process (MDP). Variants of ACAS X have been created for both manned (ACAS Xa) and unmanned aircraft (ACAS Xu and ACAS sXu). The variants primarily differ in the types of collision avoidance maneuvers they issue. For example, ACAS Xa issues vertical collision avoidance advisories, while ACAS Xu and ACAS sXu allow for horizontal advisories due to reduced aircraft performance capabilities. Currently, a new variant of ACAS X, called ACAS Xr, is being developed to provide collision avoidance capability to rotorcraft and Advanced Air Mobility (AAM) vehicles. Due to the desire to minimize deviation from the prescribed flight path of these aircraft, speed adjustments have been proposed as a potential collision avoidance maneuver for aircraft using ACAS Xr. In this work, we investigate the effect of speed change advisories on the safety and operational efficiency of collision avoidance systems. We develop an MDP-based collision avoidance logic that issues speed advisories and compare its performance to that of horizontal and vertical logics through Monte Carlo simulation on existing airspace encounter models. Our results show that while speed advisories are able to reduce collision risk, they are neither as safe nor as efficient as their horizontal and vertical counterparts.
翻译:过去十年来,美国航天局支持开发了一套新的避免碰撞系统,称为空中碰撞避免系统X(ACAS XX),该系统将避免碰撞问题作为Markov决定程序(MDP)来模型;为载人飞机(ACAS Xa)和无人驾驶飞机(ACAS Xu和ACAS SXu)创建了ACAS X的变体;由于希望尽可能减少偏离规定的飞机飞行路线,因此建议采用ACAS Xa进行速度调整,作为可能避免飞机碰撞的轨道动作;例如,ACAS Xa发出避免垂直碰撞的警告,而ACAS Xu和ACAS SXu则允许因飞机性能下降而提供横向警告;目前,正在开发ACAS X (ACAS Xr) 的避免碰撞问题新变体,为旋转飞行器和高级空中机动车辆(AAM)提供避免碰撞能力;由于希望尽可能减少偏离规定的飞行路线,因此提议采用ACAS Xr进行速度调整,作为可能避免飞机碰撞的机动机动机动操作。