Garmin GFC 600H Maintenance Manual page 137

NOTE
Due to the difficulties in executing smooth, accurate turns, the GMC 605H display may
incorrectly interpret a station and instruct to "HOLD AIRCRAFT FOR n SECONDS"
prior to full completion of a 30° turn. If this scenario is encountered, it is best to ignore the
command and instead use outside references to complete the approximate 30° of turn.
Instead of using the GMC 605H display instruction to turn as a real-time indication of
when to turn, simply judge the 30° (±5°) turn increments of the aircraft by using the
compass rose radials. Dwelling at these 30° increments for the time recommended by the
GMC 605H display should result in successful calibration.
8. The GMC 605H display guides the operator to hold at multiple headings around a complete circle.
NOTE
Due to high winds or excessive airframe vibration, the GMC 605H display may restart the
18-second countdown without full completion of the previous countdown. A turn to the
next station (approximately 30°) should commence if this happens more than once for a
given station. A minimum of two (2) successful stations per quadrant is required, where a
successful station is a full 18 second countdown followed by instruction to move. Ensure
that if stations are skipped, at least a minimum of two (2) stations per quadrant are
completed. Thus, it may be required to hold at a station after a countdown restart. A
maximum of twenty (20) stations is allowed for the entire calibration procedure. If too
many countdown restarts are encountered, the calibration will fail with the message
"TEST FAILED: TOO MANY STATIONS AROUND COMPASS ROSE". Refer to Garmin
P/N 190-02081-03 for troubleshooting.
9. Repeat the turn and hold procedures until the GMC 605H display instructs the operator that a
successful calibration is complete.
10. Press the ENTER key on the GMC 605H display to conclude this procedure.
NOTE
A magnetometer calibration failure is indicated by a "TEST FAILED: <specific failure>"
message (Refer to Garmin P/N 190-02081-03 for detailed message and troubleshoot
steps). In the event of a failure, verify that the GMU 44( ) installation passes the
Magnetometer Interference Test in accordance with Section 7.7.2, and (if needed) move
the aircraft to a different location and attempt the magnetic calibration again.
190-02081-03
Rev. 3
GFC 600H HFCS Part 27 STC Maintenance Manual
Page 7-16