A Knowledge-based Conflict Resolution Algorithm for Terminal Area Air Traffic Control Advisory Generation

NASA researchers, working under the Aviation System Capacity Program and in conjunction with the FAA Free Flight Program Office, have developed a set of decision support tools to assist terminal area air traffic controllers with control of arrival and departure traffic. Two of these tools, the Final Approach Spacing Tool (FAST) and the Expedite Departure Path (EDP) tool, provide air traffic controllers with heading, speed and altitude advisories to assist in spacing aircraft. This paper describes the conflict prediction and resolution algorithm shared by aFAST and EDP to produce conflict-free aircraft trajectories with realistic conflict resolution maneuvers. The process is accomplished in three stages: prediction, classification and resolution. A conflict prediction scheme is documented which incorporates all applicable FAA separation requirements, including automatic detection of separation during transition from staggered to simultaneous parallel approach operations. A method of classifying predicted conflicts with a limited set of criteria is detailed. Finally, a knowledge-based conflict resolution process is presented which allows for resolution of predicted conflicts in a manner consistent with controller practice: including prioritization of resolution tactics and mixture of multiple degrees of freedom to achieve separation. The scheme has been employed in both closed-loop simulations to determine solution stability and controller-in-the-loop simulations to begin development of the resolution tactics knowledge base. Introduction Large increases in air traffic over the past twenty years have led to substantial delays in the United States air traffic system. Traffic is expected to continue growing at the rate of 3-5% annually over the next decade. Budget and environmental constraints make it difficult to significantly increase the capacity of the National Airspace System (NAS) through infrastructure improvements such as additional runways or new airports. Instead, much effort has been devoted to increasing the efficiency of current operational practices through the use of decision support systems for air traffic controllers (or controllers) and traffic management coordinators (TMCs). Tools have been developed to assist TMCs in developing an efficient plan to manage arrival traffic into the terminal area. Decision support systems have also been implemented to assist the terminal area controller in executing this plan. To date, assistance to radar controllers has been in the form of passive advisories; the efficient plan is presented to the controller in a concise format, but the execution of the plan is the responsibility of the controller. Current research is focused on providing the controller with the necessary information to execute an efficient plan with high precision. The precision is improved by providing the controller with active advisories to be issued to the pilot in the form of heading, speed and altitude clearances. However, relying on an advisory system to provide heading, speed and altitude advisories requires the solution be both conflict-free and easily executable by the controller and pilot. Background NASA Ames Research Center has developed a suite of air traffic decision support tools known as the Center/TRACON Automation System (CTAS). Two of these tools have been implemented, tested and included in the FAA Free Flight Phase One deployment plan: the Traffic Management Advisor (TMA) and the passive Final Approach Spacing Tool (pFAST). TMA provides an efficient schedule for arrival aircraft entering congested terminal areas. Within the Air Route Traffic Control Center (ARTCC or Center), the Traffic Management Unit (TMU) employs TMA to generate an efficient arrival schedule and to present this schedule to the radar controllers. TMA employs time-based scheduling to estimate delays required for each aircraft. The controller meets the schedule by vectoring or slowing each aircraft until the required amount of delay for an aircraft is absorbed. During field trials, and subsequent daily operation, TMA has been shown to reduce delay by an average of two minutes per aircraft. The Final Approach Spacing Tool was originally envisioned as an active advisory tool, but early human factors assessments of FAST determined heading and speed advisories unacceptably cluttered the monochrome display available to controllers at the time. It was decided that FAST be implemented in two stages: passive FAST (pFAST) and active FAST (aFAST). Thus, pFAST was developed and tested as a Research Scientist, Terminal Area ATM Research Branch Copyright  2001 by the American Institute 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 royaltyfree license to exercise all rights under the copyright claimed herein for Governmental Purposes. All other rights reserved by the