Role of avionics in trajectory based operations

Air Traffic Management automation systems are being developed and fielded to assist controllers in handling more aircraft and larger airspace per controller. Many of these systems are time-based and built upon predicting the aircraft trajectories as accurately as possible. Trajectories of multiple aircraft are strategically de-conflicted by modifying appropriate trajectories and issuing corresponding clearances to the aircraft. However, disturbances and modeling errors will cause aircraft to deviate from their predicted trajectories and the controllers will need to take action to keep the trajectories free from conflict. The associated increase in workload will reduce the usefulness of these automation systems. Onboard avionics can help improve the accuracy of the trajectory prediction system in three ways: sharing aircraft state information to improve the performance of the ground trajectory prediction system, sharing airborne prediction results and allowable minimum and maximum arrival times at key route waypoints, and finally by applying feedback control onboard the aircraft to autonomously correct for disturbances encountered in flight. This paper presents an analysis of trajectory dispersion with and without airborne time of arrival control, presents an operational concept for air/ground trajectory negotiation, discusses integration with airborne merging and spacing algorithms, and raises concerns about challenges in implementing this integrated solution.