Garmin G1000 Nxi System Maintenance Manual page 324

Compass Rose Evaluation of Magnetic Disturbances for Magnetometer
Calibration Procedure (Optional)
The Magnetometer Calibration Procedure that follows in Section 7.10.3
(Calibration Procedure B) must be carried out at a site that is
determined to be free of magnetic disturbances. If it is unsure whether
the site is 'clean', the technician should verify that the site is 'clean' by
following the guidance provided in Section 7.10.2. The technician may
skip Section 7.10.2 if the site condition is acceptable.
Typically, a compass rose is an acceptable location to perform the
magnetometer calibration procedure.
compass roses are well 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.
A G1000-equipped airplane that has completed the pitch/roll offset compensation procedure
(Procedure A-1, Section 7.10.1) can be used to evaluate a candidate site for magnetic
disturbances and determine whether 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.
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 as described in Section 7.10.3 of this
document, with the exception of the direction of turns around the site.
Although Section 7.10.3 indicates that 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 the PFD displays the "CALIBRATION SUCCESSFUL / SITE IS CLEAN" message upon
completion of the Magnetometer Calibration Procedure in each clockwise and counter-
clockwise direction, 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 the PFD displays either the "MAG FIELD AT SITE NOT UNIFORM" or "MAG FIELD AT SITE
DIFFERS FROM IGRF MODEL" message upon completion of the Magnetometer Calibration
Procedure in either of the two directions, then the site contains magnetic disturbances that are
too large.
G1000 NXi System Maintenance Manual
King Air 300 Series
190-00716-N1
NOTE
However, because not all
NOTE
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