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5.6
Calibration Procedure C: Heading Offset Compensation
Calibration Procedures A and B must have been successfully completed
before Calibration Procedure C can be carried out. This procedure is
required only if the GMU 44 is not installed facing forward, aligned to
within 0.5° of the aircraft longitudinal axis.
This procedure is required only when the GMU 44 Magnetometer has not been installed facing forward
and parallel to within 0.5° 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. Initiate the AHRS heading offset calibration mode by performing the following steps:
a) If the PFD is not displaying the GRS/GMU CALIBRATION configuration page, follow steps
from calibration procedure A-1 listed previously.
b) The FMS small knob can now be used to select which calibration/validation procedure to run.
Select HEADING OFFSET, then press the ENTER key. If the HEADING OFFSET selection
is still blinking, press the ENTER key again.
c) Follow the checklist items displayed on the PFD and press the ENTER key as each one is
completed or confirmed. When the CALIBRATE field is blinking press the ENTER key to
begin the procedure.
2. The PFD display advises the operator when to turn the aircraft to a cardinal heading, when to
stop, and when to turn to another heading. During the procedure, the operator turns to magnetic
headings of 360, 090, 180, and 270 degrees, within a tolerance of ±0.25°.
A tolerance of ±0.5° can be used if ±0.25° is not achievable.
Maneuver the aircraft with the longitudinal axis aligned with the desired heading line of the
compass rose.
3. The operator must confirm each aircraft heading. Press the ENTER key to confirm. The
CONFIRM HEADING field stops blinking.
4. The PFD informs the operator of the calibration results. Press the ENTER key on the PFD to
conclude this procedure.
Page 5-10
Revision L
NOTE
NOTE
GRS 77/GMU 44 Installation Manual
190-00303-10
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