190-01639-00
GSU 75 ADAHRS Installation Manual
Rev. 6
Page 5-6
5. The GSU/GMU Calibration page is protected and requires a keystroke password to perform the
calibration. Press the following softkeys in sequence:
a) softkey 9
b) softkey 10
c) softkey 11
d) softkey 12
6. Press the FMS small knob to highlight GSU 75 #1. The FMS small knob can now be turned to
select either GSU 75 #1 or GSU 75 #2 for calibration. Press the ENTER key after selecting the
desired GSU 75 unit to calibrate. The SELECT PROCEDURE field is now blinking.
7. Using the FMS small knob, select MAGNETOMETER and press the ENTER key. If the
MAGNETOMETER selection continues to blinking, press the ENTER key again.
8. 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.
9. The PFD advises the operator when to turn the aircraft, when to stop, and when to turn again.
10. FOR FIXED-WING AIRCRAFT - Upon instruction to turn, taxi the aircraft in a right turn. After
approximately 30° of turn from the last heading the PFD instructs the operator to stop the aircraft.
FOR HELICOPTER - Upon instruction to turn, lift the aircraft off the ground and maintain a level
orientation. While the aircraft is hovering, make a heading change of approximately 30° to the
right (i.e., clockwise). After turning by approximately 30°, the aircraft should be set back down on
the ground.
NOTE
Due to the difficulties in executing smooth, accurate turns the PFD may incorrectly
interpret a station and instruct to “HOLD POSITION” prior to full completion of a 30
turn. If this scenario is encountered, it is best for the operator to ignore the “HOLD
POSITION” command and instead use outside references to complete the approximate
30
of turn. Instead of using the PFD 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 PFD
should result in successful calibration.
11. The PFD guides the operator to dwell at multiple headings around a complete circle.
NOTE
Due to high winds or excessive airframe vibration, the operator may encounter a
condition where the PFD restarts the 18-second countdown without full completion of the
previous countdown. If this is encountered more than once for a given station, the
operator should begin turning to the next station (approximately 30
). A minimum of 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 2 stations per quadrant are completed. Thus, it may sometimes be required to
dwell at a station after a countdown restart. A maximum of 30 stations is allowed for the
entire calibration procedure. If too many countdown restarts are encountered, the
calibration will fail with the message, “TOO MANY STATIONS.”
340095
The document reference is online, please check the correspondence between the online documentation and the printed version.
