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An aircraft is scheduled to fly from Brussels (EBBR) to Malaga (LEMG) and the crew intend to use the GBAS Landing System (GLS) approach onto Runway 13 at LEMG. What is the appropriate source of information on the availability of GBAS augmentation at the estimated time of arrival?
  • A
    AIC
  • B
    AIP
  • C
    The AUGUR GPS RAIM prediction tool
  • D
    NOTAM

Refer to figure.
GBAS - GROUND BASED AUGMENTATION SYSTEM
GBAS is a system that attempts to reduce the natural errors within the GNSS system by providing very localised augmentation to the satellite signals, via a VHF data broadcast (VDB) that a suitably equipped aircraft can receive and use to fix any position errors. It is also called "differential GPS", and can correct for errors induced by satellite clocks, ephemeris and ionospheric propagation to make the augmented GNSS signal very accurate. The GBAS can also, like its satellite based cousin, SBAS, give integrity warnings about faulty satellites, as it should be able to detect this at the nearby antennas.

GBAS is limited in the fact that it is very short range, spanning approximately 30km away from the relevant ground station (which is generally an airport). The operation of GBAS allows it to work in the same way as an ILS approach, down to 200ft minimums currently (but with the ability to carry out full auto-lands with appropriate legislation), and this is called the GBAS Landing System or GLS, and is a precision approach. It is tuned using a 5 digit channel number that picks up the correct VHF datalink signals for that approach.

The availability of GBAS augmentation depends solely on the airport in question, in this case, Malaga. They are the ones who run the GBAS receivers, ground station and VDB transmitter, and therefore will mark any planned unserviceabilities as NOTAMs.

It is quite tempting to choose the AUGUR RAIM prediction as the correct answer, and this might give the pilot an idea as to how many satelllites should be available for the GNSS system, but this is not what is being asked in the question.

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