Garmin GFC 600H Maintenance Manual page 136

GMC 605H
Compass rose or a calibrated magnetic sight compass should be used to calibrate the magnetometer. Ensure
the rotorcraft and compass are located away from magnetic buildings and other structures. The accuracy of
the AHRS cannot be guaranteed if the calibration is performed in an area that is not free of ferrous
structure or objects (i.e., magnetically clean location). The calibration site should be free of nearby
magnetic materials and other vehicles/aircraft should be a minimum of 40 feet away from the rotorcraft
under test. Refer to the guidance in Section 7.7.6.
NOTE
If either the GMC 605H or GRS 79H / GSU 75H require pitch/roll calibration, then both the
GMC 605H and GRS 79H / GSU 75H must calibrate the magnetometer with GMU 44( ) at
the same time.
1. Start the rotorcraft engine per the RFM.
2. With all the rotorcraft systems powered and operating normally, position the rotorcraft on a
compass rose at a heading of 360° ±5° (Magnetic North), or select a level, magnetically clean
location and use a calibrated sight compass.
a. The rotorcraft must be positioned to enable clockwise turning around the compass rose. It is
best to position the aircraft in the center of the compass rose as depicted below.
3. If not already done, power the GMC 605H on in Configuration mode in accordance with
Section 3.3. Press the HDG button when "CONT" is displayed on the GMC 605H.
4. Navigate to the GFC ' CALIBRATE → MAG (MAGNETOMETER) page.
5. Scroll through each of the magnetometer calibration pages (1 through 11), following the
instructions on each page to ensure that the system is ready for calibration.
6. Select START TEST to start the calibration process. The GMC 605H display will advise the
operator when to turn the aircraft, when to stop/hold, and when to turn again.
7. Upon instruction to turn, lift the aircraft off the ground and maintain a level orientation.
a. While the aircraft is hovering, make a heading change of approximately 30° to the right (i.e.,
clockwise).
b. After turning by approximately 30°, the aircraft should be set back down on the ground.
190-02081-03
Rev. 3
Figure 7-1 Rotorcraft Position Example
GFC 600H HFCS Part 27 STC Maintenance Manual
Page 7-15