Table of Contents
Advertisement
5.9
Site Evaluation of Magnetic Disturbances for Magnetometer
Calibration Procedure
As mentioned in Section 5.5, the Magnetometer Calibration Procedure (Calibration Procedure B) must be
carried out at a site that is determined to be free of magnetic disturbances.
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 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 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 (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 5.5 of this document, with the exception of the direction of
turns around the site.
Although Section 5.5 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 both the clockwise and counter-
clockwise directions, 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 perform the procedure 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.
GRS 77/GMU 44 Installation Manual
190-00303-10
NOTE
NOTE
Page 5-17
Revision L
Advertisement
Table of Contents
