Token Allocation Strategy for Free-Flight Conflict Solving

For the last 10 years, airlines have widely supported research on the development of airspaces where aircraft would be free to decide their trajectory: these areas where called Free-flight airspaces. However, as soon as two aircraft are in the same area, their separation must be guaranteed. FACES is an autonomous and coordinated embarked (on board) conflict solver for Free Flight airspace. It solves conflict by computing simple manoeuvres that guarantees conflict free trajectories for the next minutes (min). Coordination is ensured by giving sequential manoeuvres to aircraft with a token allocation strategy. FACES can be implemented with the current positioning, broadcasting and flight management technology. Moreover, it is robust to communication or system failure for time up to one or two minutes. FACES was tested with a traffic simulator on busy traffic days over France. Airspace over flight level 320 was considered as Free Flight.