G1000 Supplemental Maintenance Manual Page 7-37Textron Nav III Series Revision 3190-02128-04Procedure B: GSU 75 or GRS 77 and GMU 44 Magnetic CalibrationNOTESProcedure A-1 (Section 7.10.1) must first be successfully accomplished beforeperforming Procedure B, only for situations where the GSU/GRS was replacedwith a new unit.On the calibration pages, “GRS” refers to whichever GRS or GSU unit isinstalled.1. Start the aircraft engine following the procedures referenced in the appropriate CessnaNav III AFM as listed in Table 1-1.2. 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°).CAUTIONCalibration Procedure B must be carried out on a compass rose in order toguarantee measurements free of environmental magnetic disturbances.Attempting to carry out this maneuver on a typical ramp area may not yield asuccessful calibration. The accuracy of the AHRS/ADAHRS cannot beguaranteed if this calibration is not performed on a magnetically clean compassrose or equivalent. If the compass rose condition is not known, it isrecommended that the technician follow the guidance in Section 7.10.2.4. Restart the PFD 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:• 9• 10• 11• 12 (far right softkey)7. Use the FMS small knob to highlight GRS/GSU for calibration and press the ENT key.8. Using the FMS small knob, select MAGNETOMETER. Press the ENT button.9. Use the cursor to highlight the first step in the BEFORE CALIBRATION window.10. Follow the checklist items displayed on the PFD and press the ENT key as each one iscompleted or confirmed. When the CALIBRATE field is blinking, press the ENT key tobegin the procedure.11. The PFD display advises the operator when to turn the aircraft, when to stop, and whento turn again.12. Upon instruction to turn, taxi the aircraft in a right turn. After approximately 25° to 30° ofturn from the last heading, the PFD display advises the operator to stop the aircraft.NOTEDue to the difficulties in executing smooth, accurate turns the PFD mayincorrectly interpret a station and instruct to “HOLD POSITION” prior to full
