Future airborne collision avoidance — Design principles, analysis plan and algorithm development

As the aviation community moves toward the Next Generation Air Transportation System (NextGen), the current Traffic Alert and Collision Avoidance System (TCAS II) may become inadequate. This paper presents a novel approach to detection and resolution of air traffic conflicts in a 3-dimensional (3-D) airspace between two aircraft. The inputs to the detection algorithm are the current 3-D position and speed vector of both aircraft and a cylindrical minimum safety protection zone (PZ). For collision avoidance systems (CASs), the size of the configurable PZ can be assigned values that the Federal Aviation Administration (FAA) considers as a near mid air collision (NMAC¹) incident. When available, additional inputs, such as measurement uncertainties and intruder type (e.g., manned/unmanned), can be used to alter the default protection zone. The conflict detection takes into account the 3-D encounter (e.g., closure rate, miss distance, relative converging maneuver). The resolution algorithm initially computes a set of six resolution advisories (RAs) and associated resolution alert times that ensure no violation of the protection zone. Two solutions are computed for each of the three dimensions: ground track, ground speed, and vertical speed. The initial resolution advisories (RAs) solutions take into account ownship capability (i.e., max climb/descent rate, max turn rate, max speed/stall speed) and ownship pilot response delay (e.g., autonomous vs. manual RA execution). These six solutions are subsequently down-selected in two steps: first, based on the encounter geometry, a single implicitly coordinated, independent solution is selected for each of the three dimensions; then, based on ownship preferences and operational considerations a final RA solution is computed.