Site Evaluation Of Magnetic Disturbances For Magnetometer Calibration - Garmin G1000 Line Maintenance Manual

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interference test fails, record the three magnetometer maximum deviation values
and their corresponding timestamps. Any maximum deviation value greater than
2.5 milligauss indicates a problem that must be resolved. Compare the
corresponding timestamps with the prepared test sequence to identify which
action produced the problem. Contact Garmin for assistance in resolving the
problem.
NOTE
Two common reasons for a failed magnetometer interference test are: 1)
new equipment is installed near the GMU 44 magnetometer (i.e. HID light
ballasts), and 2) an existing or new electronic device has become
grounded through the aircraft structure instead of using the proper ground
wire in a twisted shielded pair (i.e. NAV lights).
6. Press the ENT key on the PFD to conclude this procedure.

7.6.7 Site Evaluation of Magnetic Disturbances for Magnetometer Calibration

As mentioned earlier in this section, the Magnetometer Calibration Procedure
(Calibration Procedure B) must be carried out at a site that is determined to be free of
magnetic disturbances.
NOTE
Typically, a compass rose is an acceptable location to perform the magne-
tometer calibration procedure. However, because not all compass roses
are well maintained, even an existing compass rose should be regularly
evaluated using the method described here to find out if it is free of mag-
netic 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 NXi system equipped airplane 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.
The G1000 NXi system equipped airplane installation used to evaluate the site must
have already completed the pitch/roll offset compensation procedure (Procedure A-1).
However, prior completion of the Magnetometer Calibration (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
counterclockwise. Both times, the procedure should be conducted, with the exception of
the direction of turns around the site.
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190-02102-00 Rev.4