MODIFICATIONS TO THE DESIGN OF THE MULTI-CENTER TRAFFIC
MANAGEMENT ADVISOR DISTRIBUTED SCHEDULER

Steven Landry

Abstract

In a number of Air Route Traffic Control Centers (ARTCCs) around the 
United States, time-based metering of arrival aircraft is being used 
to control air traffic demand on busy airports. In attempting to 
introduce time-based metering for airports in the Northeast corridor 
(such as Philadelphia International Airport - PHL), several technical 
challenges were identified. Single-center Traffic Management Advisor 
(TMA), the most advanced decision support tool (DST) used for this 
purpose, is limited to managing traffic within one center, and to 
within about a 250 nautical mile (nm) radius. To overcome these 
restrictions, NASA engineers designed a distributed scheduling 
system, which uses a loosely coupled network of schedulers that 
can be extended across ARTCC boundaries and out beyond 400nm. 
The resulting design was incorporated into the Multi-center 
Traffic Management Advisor (McTMA), a traffic management DST whose 
implementation has undergone research and testing on PHL arrivals. 
This testing has yielded several key insights into the distributed 
scheduler, resulting in significant changes to the algorithm and 
underlying software. Three of these are discussed in this paper. 
First, the method used to account for and distribute unused 
capacity has been changed. Second, the resolution of the mechanism 
used to distribute restrictions has been increased. Lastly, an 
inconsistency in behavior between how close-in departures were 
being scheduled as compared to airborne aircraft was corrected.