Transforming the Nas: the next Generation Air Traffic Control System

The next-generation air-traffic control system will have to be able to handle, safely and efficiently, a traffic density that will be two or three times that accommodated by the present system. Capacity of the en route and transition (arrival/departure) airspace of the present system is principally limited by the controller workload associated with monitoring and controlling aircraft separation. Therefore, the key to achieving a large increase in the capacity of this airspace is a reduction in controller workload, which can be accomplished by automating the monitoring and control of separation and by using an air-ground data link to send trajectories directly between groundbased and airborne computers. In the proposed next-generation system design, the Advanced Airspace Concept (AAC), computer logic on the ground monitors aircraft separations and uplinks modified trajectories when potential conflicts between aircraft develop. During flight, pilots can downlink requests for trajectory changes to the ground system; their requests are revised by the ground system only as necessary to eliminate possible conflicts and to comply with other control system restrictions. If adapted to approach control, the system could increase landing rates by 25%. An AAC system architecture, consisting of software and hardware components on the ground and onboard aircraft, is defined. A separationassurance system, which activates in the event of a failure in the primary ground-based system, is an essential element of the AAC. It is recommended that there be a phased transition from the present air-traffic control system to the AAC in order to minimize risks and to begin realizing the benefits of the AAC as soon as possible. Results from a safety analysis indicate the potential for the system to reduce the collision risk substantially compared to that of the current system.