Magnetometer Interference Test - Garmin GI 275 Installation Manual

The following are potential causes for a failure of the engine run-up check:
• Vibration motion of AHRS and/or GMU 11/44B caused by neighboring equipment and/or
supports
• Mounting screws and other hardware for AHRS and/or GMU 11/44B are not firmly attached
• AHRS connector is not firmly attached to unit
• Wiring connected to the remotely mounted AHRS or GMU 11/44B is not firmly secured to
supporting structure
• An engine/propeller is significantly out of balance
• GI 275 does not have up-to-date software
• A connector is inadequately torqued (loose connectors can affect the Acceleration and Gyro data
very easily)
• Harnesses are inadequately secured (if there is a 'pre-load' from the harness or P/S lines, this can
cause a specific axis to fail)
• Batteries are not properly installed with dampers
• Mounting hole and screws are not properly torqued (verify the seating of the GI 275)
• The panel mounting provisions are inadequate:
◦ The panel thickness is inadequate
◦ Adjacent instrumentation insecurely mounted (any external mounted items, such as an iPad
attached to the panel, can result in issues)
◦ Pull the power to any other instrument on the panel that might have a gyro, such as the Turn
Coordinator
After the AHRS calibration is complete, the AHRS attitude and heading information displayed will
become valid within 1 minute of power-up in Normal mode.
6.4.4

Magnetometer Interference Test

For dual AHRS installations, the following procedure must be performed on each AHRS through the
display it is directly wired to. The test can be done simultaneously on each display. Follow the display
prompts.
1. Power on the display(s) in Configuration mode.
2. Navigate to the test page (Calibration/Test → Attitude/Heading → Interference Test).
3. Complete the Before Calibration steps listed on the display; touch Next after completing each step
to move to the next step.
NOTE
The second item on the checklist instructs the operator to "prepare a detailed test
sequence". An example sequence is listed in Section 4.6.1.1 and Garmin document AHRS/
Magnetometer Installation Considerations (P/N 190-01051-00).
4. Touch Start to start the procedure.
5. Perform each action on the Test Sequence List at its specified elapsed time and duration. This will
help ensure correct identification of magnetic field deviation sources after the survey is complete.
The Magnetometer Interference Test must be run for a duration of at least 25 seconds to properly
complete.
6. Monitor the magnetic field deviation percentage throughout the survey. If deviation levels exceed
thresholds, mark the survey sequence exercises during which these deviations occurred.
190-02246-10
Rev. 11
GI 275 Part 23 AML STC Installation Manual
Page 6-26