Adahrs Troubleshooting - Garmin G3X Installation Manual

8. Is the air data information on the PFD intermittently Red-X'ing? If the ADAHRS +5 VDC
transducer power supply is shorted to ground, it will cause an intermittent air data Red-X issue to
occur.
9. If the AMP indication is Red-X'd, check the Alternator Shunt for correct resistance. Refer to the
applicable sensor documentation.
10. If the Position Indication is Red-X'd, check the sensor and wiring.
11. For single wire temperature inputs, ensure that the LO input pin is tied to ground as close as is
practical to the sensor, grounding the LO input pin away from the sensor may result in inaccurate
or invalid readings.

33.6 ADAHRS Troubleshooting

33.6.1 Heading Red-X
Figure 33-4 Heading Failure Indication (Full-Screen PFD)
If a Red-X (steady or intermittent) is displayed on the heading (Figure 33-4), 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 22 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 ADAHRS does not have GPS information, or
if it senses a magnetic anomaly.
4. While a magnetic anomaly is detected and the aircraft is determined to be stationary, the value of
the heading output is frozen. When either the aircraft is determined to be no longer stationary or
the magnetic anomaly ceases, heading will be unfrozen and determined as useable. In this context,
the aircraft is considered to be stationary when its yaw rate is less than 1.0 degrees/second and all
other angular rate and acceleration values are sufficiently small. (moving or shaking the wings or
tail for example can cause a Red-X to be displayed).
5. Check to see if any new equipment has been installed on the aircraft, and reference
minimum distances for installed equipment from the GMU 22 to prevent interference.
If the GMU 22 heading is not present on the GDU, there may be a problem with the RS-232 or
RS-485 line between the ADAHRS and GMU 22. Troubleshoot any possible wiring/connector issues
before replacing either unit.
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G3X/G3X Touch Installation Manual - Troubleshooting
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