Air Traffic Concept Utilizing 4d Trajectories and Airborne Separation Assistance

Funding for this work was provided by the Advanced Air Transportation Technologies (AATT) project office of NASA's Airspace Systems Program. This paper presents a concept – with the potential for increasing airspace system-wide efficiency and safety – which combines strategic, 4-D userpreferred trajectories with tactical, Airborne Separation Assistance Systems (ASAS). First, prior research and concepts for improving air traffic management are reviewed. Second, the concept for integrating trajectory-orientation and airborne separation assistance is described. Using an example traffic scenario, we then examine how the conflicts might be resolved using A) current day tactical operations, B) current day tactical operations with airborne separation assistance added, and C) a pure trajectory-oriented approach. INTRODUCTION Today’s sector-oriented air traffic control (ATC) is characterized by tactical controller actions protecting separate sections of airspace. This may cause inefficiencies for individual flights, because controllers can not always be aware of the impact of their actions on downstream sectors. The sector-oriented approach also requires controllers to issue multiple instructions to each aircraft in high-traffic-density sectors. The resulting ATC workload and radio frequency congestion limits the number of aircraft that can be safely managed in a sector at any given time. Different approaches for ameliorating these operating inefficiencies and workload have been proposed and pursued by air traffic management researchers. Next the example traffic problem is examined in the context of the proposed mixed TrajectoryOriented and ASAS Limited Delegation Clearances concept. Trajectory-based operations are first used to precondition the flow, sufficient to avoid overloading local airspace sectors. Subsequently, ground controllers issue limited delegation clearances to aircraft to cross behind, merge with, or follow proximal aircraft. Flight crews execute these clearances using ASAS aircraft automation. TRAJECTORY-ORIENTED APPROACHES Trajectory-oriented approaches focus on shifting the air traffic control paradigm from one of tactical sector-based operation toward strategic planning and execution of flight trajectories that span several sectors. Trajectory-based solutions to NAS traffic management are postulated as promoting efficiency by taking a longer-term, flight costeffectiveness approach, as opposed to simply looking at localized traffic constraints. Major projects devoted to the trajectory-oriented concept include the 1) Programme for Harmonized Air traffic Management in Europe – PHARE, 2) Center TRACON Automation System – CTAS, and 3) Distributed Air/Ground Traffic Management – DAG-TM. Each is discussed below. The ASAS Limited Delegation concept, which is not based on a trajectory oriented approach, is discussed in the following section. Finally, the paper describes an evolutionary path for implementing the concept. Initially, advanced trajectory tools can be introduced on the ground (ATC), with aircraft requiring only planned upgrades such as the migration to ADS-B communications technology. With the progressive introduction of more Cockpit Display of Traffic Information (CDTI) technology, flight-deck based trajectory tools and data link, flight crews will be able to select preferred routes using trajectory negotiation, and autonomous operations could be facilitated.