Evaluation of Trajectory Errors in an Automated Terminal-Area Environment

Summary A piloted simulation experiment was conducted to document the trajectory errors associated with use of an airplane’s Flight Management System (FMS) in conjunction with a ground-based Air Traffic Control (ATC) automation system, called CTAS (Center-TRACON (Terminal Radar Approach Control) Automation System) in the terminal area. Integrating the trajectory prediction capabilities of the two automation systems in the terminal area could enable airplanes to fly accurate FMS trajectories that are matched by CTAS-predicted trajectories, resulting in better arrival-time predictions over current-day procedures. This more accurate match could help to implement reduced spacing operations at some of the nation’s busiest terminal areas, thereby contributing to capacity increase. Three different arrival procedures into Dallas Fort Worth International airport (DFW) were compared, beginning at the metering fix and ending at the final approach fix. The three procedures used were current-day (vectors from ATC), modified arrival (using current-day procedures with minor procedure updates), and data link with FMS lateral navigation. All represent current or near-term capabilities, with the data link procedure requiring the most changes to current-day operations. Six active airline pilots flew the simulated arrivals in a fixed-base simulator, and provided subjective comments (in addition to the simulator data collected). The FMS-datalink procedure resulted in the smallest time and path distance errors, indicating that use of this procedure could reduce the CTAS arrival-time prediction error by approximately half over the current-day procedure. The modified procedure did not result in a substantial improvement in arrival-time accuracy or path distance errors over current-day procedures, but had smaller crosstrack errors. Significant sources of error which contributed to the arrival-time error were crosstrack errors (in particular through the turns to base and final), and early speed reduction in the 2-4 miles prior to the final approach fix. Pilot comments were all very positive, indicating the FMS-datalink procedure was easy to understand and use, and the increased head-down time and workload did not detract from the benefit. Significant issues need to be resolved before this method of operation would be ready for commercial use. These issues include development of procedures acceptable to controllers, changes to procedures to account for speed differences, and certification of FMS database procedures to support the FMS approach transitions.