190-01639-00
GSU 75 ADAHRS Installation Manual
Rev. 6
Page 5-7
12. Repeat the turn-and-stop process until the PFD instructs the operator that a successful calibration
is complete.
13. Press the ENTER key on the PFD to conclude this procedure.
NOTE
A magnetometer calibration failure is indicated by a “Calibration Error” message. In the
event of a failure, verify that the installation passes the Magnetometer Interference Test
(
), verify the relative orientation of the GSU 75 relative to the GMU 44 (
), and (if needed) move the aircraft to a different location and attempt the magnetic
calibration again.
5.6 Calibration Procedure C: Heading Offset Compensation
NOTE
Calibration Procedures A and B must have been successfully completed before
Calibration Procedure C can be performed. This procedure is strongly recommended only
if the GMU 44 is not installed to within 0.5° of the aircraft forward longitudinal direction.
This procedure is strongly recommended only when the GMU 44 Magnetometer has not been installed to
within 0.5° of the aircraft forward longitudinal direction. 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 GSU/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°.
NOTE
A tolerance of
0.5° can be used if
0.25° is not achievable.
3. Maneuver the aircraft with the longitudinal axis aligned with the desired heading line of the
compass rose.
4. The operator must confirm each aircraft heading. Press the ENTER key to confirm. The
CONFIRM HEADING field stops blinking.
5. The PFD informs the operator of the calibration results. Press the ENTER key on the PFD to
conclude this procedure.
340095
The document reference is online, please check the correspondence between the online documentation and the printed version.
