System Maintenance Manual

G1000/GFC700 System Maintenance Manual – C90A/C90GT/C90GTi King Air Page 7-31
190-00682-01 Revision F
7.7.4 Procedure B: GRS 77/GMU 44 Magnetic Calibration
NOTE
Procedure A-1 (Section 7.7.2) must first be successfully accomplished before performing
Procedure B, only for situations where the GRS 77 was replaced with a new unit.
Calibration Procedure B must be carried out on a compass rose in order to guarantee measurements free
of environmental magnetic disturbances. Attempting to carry out this maneuver on a typical ramp area
may not yield a successful calibration. The accuracy of the AHRS cannot be guaranteed if this calibration
is not performed on a magnetically clean compass rose. If the compass rose condition is not known, it is
recommended that the technician follow the guidance in Section 7.7.3.
1. Start the aircraft engine following the procedures referenced in the appropriate King Air AFM or
AFMS as listed in Table 1-2.
2. After aircraft engine startup, taxi the aircraft to a properly calibrated compass rose.
3. At the compass rose, align the aircraft to a heading of magnetic north (±5°).
CAUTION
CALIBRATION PROCEDURE B MUST BE CARRIED OUT ON A COMPASS ROSE IN
ORDER TO GUARANTEE MEASUREMENTS FREE OF ENVIRONMENTAL MAGNETIC
DISTURBANCES. ATTEMPTING TO CARRY OUT THIS MANEUVER ON A TYPICAL
RAMP AREA MAY NOT YIELD A SUCCESSFUL CALIBRATION. THE ACCURACY OF
THE AHRS CANNOT BE GUARANTEED IF THIS CALIBRATION IS NOT PERFORMED
ON A MAGNETICALLY CLEAN COMPASS ROSE OR EQUIVALENT.
NOTE
This procedure provides instructions for calibrating both GRS 77 magnetometers separately. It is
acceptable to calibrate both GRS 77 magnetometers simultaneously by putting both PFD 1 and
PFD 2 in configuration mode and following the procedure below, using PFD 1 to calibrate GRS
#1 and PFD 2 to calibrate GRS #2.
4. Restart the PFD and MFD in configuration mode.
5. Go to the GRS Page Group on the PFD.
6. Select the GRS/GMU Calibration page and enter the following softkey password:
a) 9
b) 10
c) 11
d) 12 (far right softkey)
7. Press the FMS small knob to highlight GRS 77 #1. The FMS small knob can now be turned to
select either GRS 77 #1 or GRS 77 #2 for calibration. Press the ENT key after selecting the
desired GRS 77 unit to calibrate. The SELECT PROCEDURE field is not blinking.
8. Using the FMS small knob, select MAGNETOMETER. Press the ENT button.
9. Use the cursor to highlight the BEFORE CALIBRATION window.
10. Follow the checklist items displayed on the PFD and press the ENT key as each one is completed
or confirmed. When the CALIBRATE field is blinking, press the ENT key to begin the
procedure.