Garmin G3X Installation Manual page 176

10.5.2 Heading Red-X
Figure 10-5 – Heading Failure Indication (Full-Screen PFD)
If a Red-X (steady or intermittent) is displayed on the heading (Figure 10-5), check the following while
the aircraft is on the ground:
1. When taxiing without reliable GPS information, heading performance is susceptible to the
presence of magnetic anomalies (metal buildings, underground steel culverts, steel grates in
the ramp, rebar). Localized sources of interference on the ground may consistently cause a
Red-X to be displayed on the heading in the same spot while taxiing, this is not caused by a
failure of the GMU 44 or its calibration.
2. When the aircraft is taxiing on the ground with a yaw rate of less than 1.5 degrees/second
(i.e., taxiing essentially in a straight line) GPS track information is used to update heading
information. This logic is applied regardless of magnetic anomaly detection.
3. The GDU may display Red-X on the heading if the GSU 73 does not have GPS information,
or if it senses a magnetic anomaly.
Page 10-6
Revision E
Figure 10-4 – AHRS Align Message (PFD)
G3X Installation Manual –Troubleshooting
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