Garmin G1000 Maintenance Manual page 145

_________________________________________________________________
Typically, a compass rose is an acceptable location to perform the magnetometer
calibration procedure.
maintained, even an existing compass rose should be regularly evaluated using
the method described here to determine if it is free of magnetic disturbances. If
evaluation of an existing compass rose indicates that magnetic disturbances are
present, then an alternative location must be found to perform the Magnetometer
Calibration Procedure.
The G1000 system can be used to evaluate a candidate site for magnetic disturbances and
determine whether or not it is a suitable location to perform the magnetometer calibration
procedure. The magnetometer calibration procedure itself contains the logic to simultaneously
survey the location for magnetic cleanliness while it is computing the magnetometer calibration
parameters. The Garmin equipped aircraft used to evaluate the site must have already
completed the pitch/roll offset compensation procedure (Procedure A). However, prior
completion of the Magnetometer Calibration Procedure (Procedure B) is not required.
In order to evaluate a candidate site, the Magnetometer Calibration Procedure must be
performed twice: once turning clockwise around the site, and once turning counter-clockwise.
Both times, the procedure should be conducted with the exception of the direction of turns
around the site.
Although the Magnetometer Calibration Procedure should be performed by
making a series of clockwise turns around the site, the procedure can also be
performed by making counter-clockwise turns for the purpose of evaluating the
site for magnetic disturbances.
If, upon completion of the Magnetometer Calibration Procedure in each clockwise and counter-
clockwise direction, the PFD displays the "CALIBRATION SUCCESSFUL / SITE IS CLEAN"
message, then the candidate site is sufficiently free of magnetic disturbances and is acceptable
for performing the Magnetometer Calibration Procedure. It is important to obtain successful
result in both the clockwise and counter-clockwise directions to ensure that the magnetometer
sweeps over a large enough area at the candidate site.
If, upon completion of the Magnetometer Calibration Procedure in either of the two directions,
the PFD displays either the "MAG FIELD AT SITE NOT UNIFORM", or "MAG FIELD AT SITE
DIFFERS FROM IGRF MODEL" message, then the site contains magnetic disturbances that
are too large and can not be used for Magnetometer Calibrations.
With the aircraft stationary, initiate the GRS 77 AHRS magnetometer calibration procedure as
follows:
1. Start both displays in normal mode.
2. Start the aircraft engine following the procedures in the POH.
3. After aircraft engine startup, taxi the aircraft to a properly calibrated compass rose or
magnetically clean location determined in section above.
G1000 System Maintenance Manual
190-00907-00
NOTE
However, because not all compass roses are well
NOTE
Page 7-19
Rev. B