Knowledge-based Runway Assignment for Arrival Aircraft in the Terminal Area

A knowledge-based system for scheduling arrival traffic in the terminal area, referred to as the Final Approach Spacing Tool (FAST), has been implemented and operationally tested at the Dallas/Fort Worth Terminal Radar Approach Control (TRACON) facility. Two types of controller advisories are generated by FAST: sequence number and runway assignment. The knowledge base for runway assignment employs a set of hierarchical rules and decision logic that evaluates both performance and workload criteria. This formulation is based on over 2,000 hours of controller-in-the-loop, real-time simulations. In the field tests, controllers had the option to accept or reject the FASTgenerated runway assignments. Results indicate strong adherence to the advisories and increased capacity, with no significant impact on controller workload. Introduction Runway assignment of arrival aircraft is a tactical decision made by controllers. Strategic reassignments, or allocations, assist in balancing controller workload and reducing delay, but are difficult for controllers because of the high workload already associated with the traffic load. As terminal area controllers become consumed with the task of separation, strategic runway allocation becomes neglected. During high workload periods, controllers simply assign runways to fill available landing slots when aircraft are well within TRACON airspace. This process of tactical adjustments to the arrival schedule requires coordination between controllers and ultimately leads to higher workload and increased delay. Any system which attempts to alleviate this problem must consider controller workload. This report describes such a system; the knowledge-based runway allocation algorithm for an Copyright © 1997 by the American Insitute of Aeronautics and Astronautics Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental Purposes. All other rights are reserved by the copyright owner. * Research Scientist, Terminal Area ATM Research Branch air traffic automation tool called the Final Approach Spacing Tool (FAST).1,2,3 FAST is the terminal area component of the Center/TRACON Automation System (CTAS).4 The runway allocation algorithm in FAST attempts to achieve runway load balancing and increased capacity without increasing controller workload. Previous research focused on optimization of delay reduction. Optimization of a cost function requires that all relevant inputs be quantified. Therefore, if controller workload is considered important, it must be quantified. Brinton attempted to represent workload as a series of terms in a cost function, however, his implicit enumeration algorithm did not adequately address this issue and was found unacceptable by controllers.5 The runway allocation function provided by FAST employs a knowledge base obtained through thousands of hours of simulation with expert controllers. This knowledge base incorporates controller preferences and workload into the runway allocation problem. By doing this, FAST emulates the decision patterns of expert controllers, while using accurate calculations of aircraft performance to reduce delay in a manner acceptable to controllers. This paper begins by defining the motives and potential benefits of runway allocation. The runway assignment algorithm employed by FAST is described, as well as the rules used to create the knowledge base. Results of operational testing of FAST at the Dallas/Fort Worth TRACON facility are briefly discussed, followed by some concluding remarks. Runway Allocation Motives and Benefits As aircraft enter TRACON airspace, they are typically assigned by the controller to the closest runway to the arrival feeder gate. This default assignment defines an initial arrival plan. Adjustments are made to the arrival plan, as the aircraft approach the runway, by assigning aircraft to alternate runways. This process is known as runway allocation, and is the primary means of balancing arrivals to each runway and controller workload. Runway allocation decisions made by controllers in