Trajectory Specification for Terminal Air Traffic: Arrival Spacing

Abstract

“Trajectory specification” is the explicit bounding and control of aircraft trajectories such that the position at each point in time is constrained to a precisely defined volume of space. The bounding space is defined by cross-track, along-track, and vertical tolerances relative to a reference trajectory that specifies position as a function of time. The tolerances are dynamic and are based on the aircraft navigation capabilities and the current traffic situation. A standard language will be developed to represent these specifications and to communicate them by datalink. Assuming conformance, trajectory specification can guarantee safe separation for an arbitrary period of time, even in the event of an air traffic control system or datalink failure; hence, it can help to achieve the high level of safety and reliability needed for air traffic control automation. As a more proactive form of air traffic control, it can also maximize airspace capacity and reduce the reliance on tactical backup systems during normal operation. It applies to both en route airspace and the terminal area around airports, but this paper focuses on arrival spacing in the terminal area and presents algorithms and software for achieving a specified delay of runway arrival time.