Algorithms for airborne conflict detection, prevention, and resolution

Airborne conflict management (ACM) is part of an air traffic safety and separation management concept wherein a degree of responsibility - sometimes total responsibility - for determining and executing maneuvers necessary to avoid conflicts with other traffic is assigned to the flight crew. The concept offers the promise of user-selected routing, improved safety, shorter flights, lowered flight costs, more efficient airspace utilization, and increased airspace capacity. The central and most crucial elements of ACM are the aircraft-based systems that provide pilots with the information needed to autonomously and safely maneuver within the airspace. The necessary information is awareness of a) existing conflicts, b) maneuvers that would create conflicts and c) maneuvers that can resolve conflicts. The ACM application is enabled by the automatic dependent surveillance-broadcast (ADS-B) reports of position, velocity, and other information. In Europe and in the U.S., government and private organizations have worked to advance the understanding, acceptance, and utilization of ACM technologies and practices. RTCA has published an ACM concept of operations document (RTCA Special Committee 186, 2003) and application description (RTCA Special Committee 186, 2000), Rockwell Collins has developed and tested the algorithms necessary to implement an ACM system. The three major components of the system are: conflict detection (CD) - algorithm that uses measures of a projected conflict's "severity", "stability", and "temporal proximity" in determining when to issue a CD alert; conflict prevention (CP) - mechanism that utilizes mathematical and numerical "conflict probes" to determine ground speeds, headings, altitudes, rates of climb, and bank angles that would conflict with the trajectories of other aircraft and conflict resolution (CR) - algorithms that use "repulsive force field"-like mechanisms to calculate conflict resolution guidance. This paper discusses each of these components, as developed and implemented by Rockwell Collins, in substantial detail.