The ICAO defines the GBAS system as "a system by which augmentation information received by the user comes directly from the land transmitter". GBAS complements the GNSS system, improving its features, supplied within a local service area. It is designed to be used in an airport environment and thus to offer positioning and navigation services during the instrumental approach, taxiing and departure phases. The nominal range of these systems is set at around 50 NM.
Aena plays an essential and internationally recognised role in the operational implementation of GBAS CAT I systems through its project in Malaga. This project, along with parallel projects by DFS in Bremen, ASA in Sydney and the FAA in Memphis and Newark, leads the start of operations of this new service with multiple operational benefits. Proof of this is the cooperation with Air Berlin to monitor the system installed in Malaga, and the cooperation agreements with FAA and Boeing.
The GBAS station in Malaga will be the third station in the world to begin operation after the German station in Bremen (February 2012) and the US station in Newark (October 2012). The new precision instrumental approach service based on GBAS at Malaga airport will be available in early 2014.
GBAS will perform the following functions:
- Provide local pseudorange corrections.
- Provide final approach segment data.
- Provide monitoring integrity for GNSS ranging sources.
The following illustration describes how GBS operation works:
The GBAS operation involves, from a technical perspective:
- A space segment that provides both aircraft and the GBAS system with the information needed to determine pseudorange.
- A ground segment (GBAS system) that monitors satellite signals, calculates and issues pseudorange corrections, integrity parameters, relevant local data such as the Final Approach Segment (FAS) data block, which defines the flight path in space to allow for precision approaches.
- An air segment, on the aircraft, that receives signals from both the satellites and the GBAS station, supplying navigation and guiding information to the autopilot (Automatic Flight Control System-AFCS) and the flight crew.
A gradual implementation approach is considered suitable to implement GBAS. This gradual approach consists of developing and implementing GBAS CAT I as a look-alike ILS, to then build on the experience acquired. Development of GBAS CAT III is planned in two stages: a short-term GBAS CAT III solution based on the GPS constellation, and a long-term solution based on multi-constellation and multi-frequency concepts.
GNSS applications potentially include aircraft and vehicle movements on the aerodrome surface (A-SMGCS). The ICAO has highlighted the need to standardise a series of elements, include non-visual guide systems. A series of facilitators are required to achieve this. The potential features of GBAS seem to place it as the best candidate to support the guide function. The first goal is to improve aircraft and vehicle safety during surface movements, particularly under conditions of reduced visibility. In fact, invading the runway is probably the first cause of ATM-related accidents.
Meanwhile, airports with reduced visibility approaches and departures (CAT II / III) may even have a greater interest in the A-SMGCS guide function.
Aena is already certified as a GBAS service provider.
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