Flight Time Errors in a Highly Automated Air Traffic Control System

Abstract

Future Air Traffic Control (ATC) systems will include highly-automated and highly-integrated capabilities to safely and efficiently control future traffic loads. Most aircraft will have equipage for three dimensional (3-D) lateral and vertical trajectories that are more predictable and accurate than today. However, highly accurate 4-D trajectories are a key part of future ATC evolution. Recent experiments with actual en route and arrival flights provide initial insights into benefits, procedures, and flight time errors associated with 4-D trajectories in these flight phases. Although in many cases aircraft can limit flight time errors, prediction of accurate flight times along a trajectory will remain a limiting factor for ATC automation performance. With accurate aircraft dynamics data, flight times in still air (without wind errors) can be computed within a small tolerance. However, flight time differences from planned flight times are dependent on many factors such as forecast wind errors, unpredicted severe weather volumes, aircraft conflicts, departure time errors, and traffic flow initiatives. This paper presents results from two simulation experiments to fly a trajectory within a longitudinal tolerance in the presence of forecast wind errors and aircraft speed changes. If aircraft apply up to 20-knot change in True Airspeed (TAS) as an error mitigation technique, average flight time delay due to forecast wind errors was decreased by more than two-thirds. Additionally, flight time differences introduced by aircraft conflict resolution maneuvers were modeled. Future systems will need to plan for flight time delays introduced by conflict resolution maneuvers since more than one-third of the aircraft required conflict resolution maneuvers. In a sample scenario with seventy percent more traffic than today and a large (15 knots) average forecast wind error, flight time errors due to ground-based conflict resolution maneuvers were larger than flight time errors due to forecast wind errors. Speed change was effective at reducing the flight time errors, but did not eliminate all large flight time errors. Flight time errors could be decreased by additional capabilities such as timely detection of large forecast wind errors to allow earlier speed changes, airborne separation to minimize maneuver costs, and integrated departure planning to minimize departure phase conflicts.