TRANSFORMING THE NAS: THE NEXT GENERATION AIR TRAFFIC CONTROL SYSTEM

Heinz Erzberger


ABSTRACT

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 ground-based 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 
separation-assurance 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.