Field Evaluation of Descent Advisor Trajectory Prediction Accuracy

The Descent Advisor (DA) automation tool has undergone a series of field tests at the Denver Air Route Traffic Control Center to study the feasibility of DAbased clearances and procedures. The latest evaluation, conducted in the fall of 1995, expanded the operational nature of DA testing to include a wider variety of test conditions. A total of 197 commercial flights from three airlines participated in the study over twenty-three days of testing. Aircraft included large and heavy jet transports, both conventionaland flight-managementsystem-equipped, and turboprop commuter types. The primary objective was to measure DA trajectory prediction accuracy for use in validating DA metering advisories and developing conflict-probe error models. Previous evaluations, involving large jet types only, demonstrated an arrival time prediction accuracy within 20 sec. The 1995 test results indicate a mean error of 0.5 sec late with a standard deviation of 14.3 sec. The least variation was found for flight-management-systemequipped jets with a standard deviation of 11.9 sec compared to 15.2 and 15.4 sec for conventionalequipped jets and turboprop types respectively. This paper describes the test and presents an analysis of the descent trajectory prediction accuracy in terms of errors in the horizontal profile, altitude profile, and arrival time. * Research Scientist, Member AIAA. † Aerospace Engineer, Member AIAA. Copyright  1996 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 royalty-free license to exercise all rights under the copyright claimed herein for government purposes. All other rights are reserved by the copyright owner. Introduction The quest to achieve "free-flight" benefits for airspace users is a driving force in the development of new automation systems for both aircraft operations and Air Traffic Control (ATC)1. Substantial benefits, in the form of reduced operating costs (time and fuel), will require new tools and procedures to increase the realization of user preferences (route, altitude, speed, and/or time) while maintaining system safety and robustness. One area with a large potential for benefit gains is the extended terminal area wherein aircraft transition from relatively “unconstrained” en route airspace to high-density terminal airspace. In the extended terminal area, ATC procedural constraints (routes, altitudes, and speeds) are needed to facilitate the safe and orderly handling of aircraft in the en route, arrival, and departure phases of flight. In addition, traffic management constraints (e.g., miles-in-trail or metering) related to terminal area capacity limitations have a significant impact on the cost of flight operations. In this environment, both ATC procedural and traffic management constraints must be addressed simultaneously to improve flight efficiency. The economic benefit of flying an optimized trajectory (e.g., best wind route, speed, and altitude) into a high density terminal area may be negated if the optimization does not account for constraints such as metering delays and separation. The Center TRACON Automation System (CTAS) is a set of ATC automation tools designed to assist controllers in maximizing the efficiency of the extended terminal area airspace.2 The Descent Advisor (DA) is the CTAS element designed to assist Air Route Traffic Control Center (Center) controllers with an emphasis on achieving an efficient transition from the en route to the arrival phase of flight. DA assists controllers by generating accurate, fuel-efficient clearance advisories for the merging, sequencing, and separation of high-density arrival traffic while providing automation assistance for