Towards higher levels of automation in taxi guidance: Using GBAS Terminal Area Path (TAP) messages for transmitting taxi routes

According to Sheridan and Verplank's classification of levels of automation, taxiing on an airport still has a very low automation level. Key element for increased automation in taxi guidance is a precise and reliable navigation capability. As a Ground Based Augmentation System (GBAS) can fulfill the stringent requirements for a precision approach, it can play an important role in providing the required navigation performance during taxiing as well. This paper will explain the use of GBAS for taxi guidance. It presents, how the required navigation performance for automatic taxiing can be provided using GBAS. Besides the highly precision position service provided via Differential GPS, the Terminal Area Path (TAP) messages will be used to provide the aircraft with accurate and reliable information about the taxi route. Taxi trials with DLR's A320 research aircraft ATPvA (Advanced Technology Research Aircraft) and the GBAS ground station at airport Braunschweig-Wolfsburg (EDVE) showed that over the whole maneuvering area the received VHF signal level was adequate for transmitting such a "Ground- TAP". These tests were performed with an antenna on the aircraft located at a height of 8ft, which is lower than the actual required coverage minimum of 12ft defined in ICAO Annex 10. Together with a re- defined voice communication structure and a list of predefined routes the use of GBAS for taxi routing functionalities of an Advanced Surface Movement Guidance & Control System (A-SMGCS) is feasible. Due to the independency from an on-board database the combination of such a message broadcast and the GNSS based positioning can be the key enabler for a future auto taxiing functionality.