Flight trials: "runway-to-runway" required time of arrival evaluations for time-based ATM environment

Flight trials were conducted by Smiths Aerospace with Scandinavian Airlines in the spring of 2001 evaluating the use of the Four-Dimensional Flight Management System (4-D FMS) and it's Required-Time-of-Arrival (RTA) function for a future Air Traffic Management (ATM) environment. 4-D FMS, along with air-ground datalink capability, is central to the ATM operational environment established by the European Commission's AFAS (Aircraft in the Future ATM System) program. These RTA trials supported this project's development by assessing the current generation FMS RTA algorithm's performance in an AFAS-like flight environment, and identifying necessary improvements for the next generation avionics. The Swedish CAA participated in these trials by providing priority servicing to the trials' flights allowing the evaluation of 4-D FMS performance in an "undisturbed AFAS operational scenario". Required-Time-of-Arrival (RTA) points were established at takeoff targeted for waypoints as late in the flight plan as the top of the Standard Terminal Arrival (STAR) and the destination runway threshold. The Smiths Aerospace standard FMS equipment on the Boeing "Next Generation" B737 was then responsible to guide the aircraft for the entire flight while an observer in the jump seat recorded performance data. The preliminary results from the 33 trial flights and subsequent analysis indicate that aircraft equipped with the current generation Smiths FMS can reliably predict and maintain a 4-D trajectory over an entire flight in real-world fleet operations. Time-of-arrival errors at waypoints located at the top of the Standard Arrival procedures were demonstrated to be less than 7 seconds with a standard deviation of 4.8 seconds. In cases targeting the runway with an RTA constraint, errors were bounded to 21 seconds with a standard deviation of 12.7 seconds. This precise "runway-to-runway" trajectory prediction and control capability is a critical building block in the AFAS "gate-to-gate" 4-D ATM concept. This paper describes the background and setup of these trials. Five supporting research objectives are introduced including RTA accuracy assessment, wind modeling effects, and the evaluation of trajectory time-control authority. Preliminary results and analysis are presented.