Towards higher level of A-SMGCS: Handshake of electric taxi and trajectory-based taxi operations

This paper focuses on newly developed alternative ground propulsion systems of aircraft for airport surface operations and their dependencies with decision support tools for air traffic controller in the airport tower. Both issues refer to functionalities from the Advanced Surface Movement Guidance and Control System (A-SMGCS) concept specifically the route planning and guidance functions. The route planning functionality generates the optimal surface movement plan for every aircraft. This plan consists of conflict-free optimized routes with associated speed values called four dimensional taxi trajectories (4DT). The 4DT must be generated by dedicated planning systems that support the air traffic controller in their daily work. Several research studies have shown that the implementation of trajectory-based taxi operations mainly depends on the ability of the aircraft to follow the optimal surface movement plan which is still a challenge. The guidance functionality primarily addresses the support of pilots and vehicle drivers equipped with displays for increased situation awareness especially in low visibility conditions. However, ICAO's A-SMGCS manual also states that predetermined taxi speeds have to be maintained so that a timely arrival at the runway holding position and at the stands can be ensured. Autonomous engine-off taxi technologies with electric engines — called eTaxi — is an alternative ground propulsion system (AGPS) that promises to accomplish this performance. At the same time, AGPS are able to reduce the environmental impact, through less noise and emissions, and the economic impact, through less fuel consumption, while taxiing. This paper addresses the research question of how AGPS and trajectory-based taxi operations are interdependent. As a starting point to answer this research question, two conceptual investigations are conducted. First, the trajectory-based taxi operations concept is reviewed. Second, the investigation of necessary ATC procedures to manage aircraft with autonomous engine-off taxi technologies is considered. Both processes have to be considered in order to develop a viable concept of e-taxi.