G1000/GFC 700 Post Installation Checkout Procedure – Hawker / Beechcraft King Air C90
Page 5-3
190-00682-00
Revision 5
5.3
Final GRS 77/GMU 44 Calibration Procedures
The Magnetometer Calibration Procedure (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 5.3.1. The technician
may skip Section 5.3.1 if the site condition is known to be acceptable.
5.3.1
Site Evaluation of Magnetic Disturbances for Magnetometer Calibration Procedure
(Optional)
Typically, a compass rose is an acceptable location to perform the
magnetometer 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
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 C90 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-equipped C90 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 as described in Section 5.3.2 of this document, with the exception of the direction of
turns around the site.
Although Section 5.3.2 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, upon completion of the Magnetometer Calibration Procedure in each clockwise and counter-clockwise
direction, the “CALIBRATION SUCCESSFUL / SITE IS CLEAN” message is displayed, 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, either the
“MAG FIELD AT SITE NOT UNIFORM”, or “MAG FIELD AT SITE DIFFERS FROM IGRF MODEL”
message is displayed, then the site contains magnetic disturbances that are too large.
NOTE
NOTE
