Garmin G900X Pilot's Manual page 27

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 WAAS signal. While the aircraft
is on the ground, the WAAS 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 WAAS signal. If no failure message exists, check the GPS Status Page and compare the
information for GPS1 and GPS2. Discrepancies may indicate a problem.
GPS RECEIVER STATUS
The GPS solution type (ACQUIRING, 2D NAV, 2D DIFF NAV, 3D NAV, 3D DIFF NAV) for the active
GPS receiver (GPS1 or GPS2) is shown in the upper right of the GPS Status Page. When the receiver is
in the process of acquiring enough satellite signals for navigation, the receiver uses satellite orbital data
(collected continuously from the satellites) and last known position to determine the satellites that should be
in view. ACQUIRING is indicated as the solution until a sufficient number of satellites have been acquired
for computing a solution.
When the receiver is in the process of acquiring a 3D navigational GPS solution, 3D NAV is indicated as the
solution until the 3D differential fix has finished acquisition. Satellite-Based Augmentation System (SBAS)
status should be indicated as INACTIVE at this point. When acquisition is complete, the solution status
changes to 3D DIFF NAV and SBAS becomes active.
In certain situations, such as when the aircraft is outside or on the fringe of the WAAS coverage area, it may
be desirable to disable WAAS (although it is not recommended). When disabled, the SBAS field in the GPS
Status box indicates DISABLED.
Disabling WAAS:
1) Select the GPS Status Page.
2) Select the SBAS Softkey. The RAIM PREDICTION box is replaced by SBAS SELECTION.
3) Press the FMS Knob. 'WAAS' is highlighted.
4) Press the ENT Key to uncheck the box.
5) Press the FMS Knob to remove the cursor.
190-00726-00 Rev. A
Figure 1-12 Enable/Disable WAAS
Garmin G900X Pilot's Guide
SYSTEM OVERVIEW
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