Flight Inspection of GAST-D Approach and Taxi Guidance Systems
Claus-Sebastian Wilkens, Aerodata AG, Germany; Thomas Feuerle, Mirko Stanisak, Technische Universität Braunschweig - Institute of Flight Guidance, Germany; Patrick Thomsen, Aerodata AG, Germany
Location: Regency Ballroom
Date/Time: Tuesday, Apr. 17, 4:30 p.m.
The term “Ground Based Augmentation System (GBAS)” describes a method for instrument landing using ILS look-alike guidance computed from real-time differential corrections for global navigation satellite systems (GNSS). At the moment, GBAS approach service type C (GAST-C) installations are certified for approaches down to CAT I minima, i.e. decision altitudes of at least 200 ft. While the number of approved ground installations and certified aircraft are increasing continuously, many parties are waiting for a CAT II/III GBAS in order to allow approaches in significantly worse weather conditions. For this, the GBAS approach service type D (GAST-D) is currently developed in the frame of the ICAO. The publication of ICAO “Standards and Recommended Practices” (SARPs) regarding the implementation of GAST-D is expected for the year 2018. First installations at airports are assumed to become operational in the 2020 time frame.
GBAS GAST-D installations require a commissioning flight inspection prior to operational approval. This in turn requires the availability of appropriate flight inspection equipment and procedures. Flight inspection procedures and certified flight inspection systems (FIS) are available for GAST-C, but currently not for GAST-D. This is addressed by the research project MEGA (Inspection of GNSS-based CAT-III Approach and Taxi Guidance Systems) funded by the German Federal Ministry for Economic Affairs and Energy as part of the national “Aeronautical Research Programme V” (LuFo V). Within this project, the institutions represented by the authors will provide a suggestion as basis of future GAST-D inspection.
The project focuses on the development of GAST-D flight inspection procedures and equipment as a possible complement of an existing GAST-C capable FIS. For this, after having identified the differences between GAST-C and GAST-D, the requirements for GAST-D flight inspection, regarding both the FIS equipment and the flight procedures are gathered. Based on these requirements, work is ongoing to define future flight inspection standards and to integrate experimental GAST-D equipment into a flight inspection demonstrator system. In parallel, measurement procedures are developed, including an assessment of the complete process and measurement chain. At the end of project MEGA, demonstration flights will be conducted. The data of these flights will be combined with data recorded by other vehicles in order to demonstrate an exemplary GAST-D commissioning.
An additional focus is set on GBAS ground operations, both on runways (GAST-D) and on taxiways. As GBAS is currently only approved for landings but not for ground taxiing, the requirements for future GBAS-based taxi guidance systems are currently analyzed in order to define measurement procedures to enable such operations.
This paper presents some intermediate results and the ongoing work within project MEGA. Based on the GAST-C standards, the main differences to the GAST-D standards are pointed out. Flight inspection requirements for equipment and procedures are derived and presented. A new GBAS receiver with special flight inspection functionality and future GAST-D capability is introduced. Finally, the current state of the GAST-D flight inspection system demonstrator and procedure design is presented. In addition, a general overview of GBAS-based taxiing is given, comprising the requirements, challenges, and technical limitations of such operations.