Formal Verification of an Optimal Air Traffic Conflict Resolution and Recovery Algorithm

Highly accurate positioning systems and new broadcasting technology have enabled air traffic management concepts where the responsibility for aircraft separation resides on pilots rather than on air traffic controllers. The Formal Methods Group at the National Institute of Aerospace and NASA Langley Research Center has proposed and formally verified an algorithm, called KB3D, for distributed three dimensional conflict resolution. KB3D computes resolution maneuvers where only one component of the velocity vector, i.e., ground speed, vertical speed, or heading, is modified. Although these maneuvers are simple to implement by a pilot, they are not necessarily optimal from a geometrical point of view. In general, optimal resolutions require the combination of all the components of the velocity vector. In this paper, we propose a two dimensional version of KB3D, which we call KB2D, that computes resolution maneuvers that are optimal with respect to ground speed and heading changes. The algorithm has been mechanically verified in the Prototype Verification System (PVS). The verification relies on algebraic proof techniques for the manipulation of the geometrical concepts relevant to the algorithm as well as standard deductive techniques available in PVS.