Gps Receiver Operation - Garmin G1000 NXi Pilot's Manual

SYSTEM OVERVIEW
GPS INPUT FAILURE
In-flight initialization of ADAHRS/AHRS, when operating without any valid source of GPS data and at
NOTE:
true air speed values greater than approximately 200 knots, is not guaranteed. Under these rare conditions,
it is possible for in-flight ADAHRS/AHRS initialization to take an indefinite amount of time which would
result in an extended period of time where valid ADAHRS/AHRS outputs are unavailable.
The system provides two sources of GPS information. If a single GPS receiver fails, or if the information
provided from one of the GPS receivers is unreliable, the ADAHRS/AHRS seamlessly transitions to using
the other GPS receiver. An alert message informs the pilot of the use of the backup GPS path. If both GPS
inputs fail, the ADAHRS/AHRS continues to operate in reversionary No-GPS mode so long as the air data and
magnetometer inputs are available and valid.
AIR DATA INPUT FAILURE
A failure of the air data input has no effect on ADAHRS/AHRS output while ADAHRS/AHRS is operating in
normal mode. A failure of the air data input while the ADAHRS/AHRS is operating in reversionary No-GPS
mode results in invalid attitude and heading information on the PFD (as indicated by red "X" flags).
MAGNETOMETER FAILURE
If the magnetometer input fails, the ADAHRS/AHRS transitions to one of the reversionary No-Magnetometer
modes and continues to output valid attitude information. However, if the aircraft is airborne, the heading
output on the PFD does become invalid (as indicated by a red "X").

GPS RECEIVER OPERATION

Each GIA 63W Integrated Avionics Unit (IAU) contains a GPS receiver. Information collected by the specified
receiver (GPS1 for the #1 IAU or GPS2 for the #2 IAU) may be viewed on the Aux - GPS Status Page.
These GPS sensor annunciations are most often seen after system power-up when one GPS receiver has
acquired satellites before the other, or one of the GPS receivers has not yet acquired a SBAS signal. While
the aircraft is on the ground, the SBAS signal may be blocked by obstructions causing one GPS receiver to
have difficulty acquiring a good signal. Also, while airborne, turning the aircraft may result in one of the GPS
receivers temporarily losing the SBAS signal.
If the sensor annunciation persists, check for a system failure message in the Messages Window on the PFD.
If no failure message exists, check the GPS Status Page and compare the information for GPS1 and GPS2.
Discrepancies may indicate a problem.
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Garmin G1000 NXi Pilot's Guide for Cessna Nav III
190-02177-00 Rev. A