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Page 8-14 G3X Installation Manual – Post Installation Checkout and Calibration Procedures
Revision A 190-01115-01
8.3.4 Calibration Procedure D: Heading Offset Compensation
NOTE
Calibration Procedures B and C must have been successfully completed before
Calibration Procedure D can be performed.
This procedure is optional, and generally not recommended as it is difficult to orient the entire aircraft
with an absolute accuracy of less than a few degrees. This procedure is required only when the GMU 44
Magnetometer has not been installed facing forward and parallel to within 0.5º of the aircraft longitudinal
axis. For calibration accuracy, maneuver the aircraft with assistance from outside the cockpit to precisely
align the aircraft to cardinal compass heading reference lines on the compass rose.
In order to accomplish the necessary degree of accuracy in heading alignment, it is generally required that
the aircraft be physically towed by hand. Towing tugs should not be used as they distort the magnetic
field in their vicinity.
1. Enter configuration mode by holding down the left-hand softkey while powering on the GDU
37X (if needed).
2. Use the FMS Joystick to select the GSU Page (if needed).
3. Unlock the GSU Page by pressing softkeys 2, 3, 4 in order (if needed).
4. On the GSU Status Page, use the FMS Joystick to select HEADING OFFSET.
5. Ensure that all the required status boxes are checked (Tables 8-2 and 8-3). The GMU 44 and
GSU 73 units must be communicating with the GDU 37X, and the GPS antenna must have a
clear view of the sky or a GPS repeater to produce positive status indications.