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Revision A5
HXr Installation Manual GRT Avionics
9. If calibration is successful, the AHRS will re-start itself automatically, and begin using the
corrections. While re-starting, the AHRS will not provide data. This will result in the AHRS data
disappearing from the display unit for about 10 seconds.
10. If calibration is unsuccessful, one of two things will happen. In either case, the calibration
procedure must be repeated.
a. If the airplane is rotated too rapidly, the calibration will not end after the airplane has been
rotated 380 degrees.
b. It will exit calibration mode, and will show “Calibration INVALID - Maximum correction
exceeded” if a correction of greater than 127 degrees is required. (Invalid - OVERLIMIT will
be displayed on the AHRS maintenance page next to the Magnetometer Calibration field.)
A correction of greater than 127 degrees can be caused by incorrect mounting of the
magnetometer, or location of the magnetometer too close to ferrous metal in the aircraft,
or starting with the airplane not pointed toward magnetic north or magnetometer wiring
errors.
The accuracy of the magnetometer calibration can now be verified.
11. Point the airplane toward magnetic north.
12. Turn ON the AHRS (if already ON, turn it OFF, and then back ON).
13. Verify the AHRS (on AHRS Maintenance page) shows a heading close to north. (Small errors
are likely to be a result of not positioning the airplane to the exact heading used during
magnetometer calibration.)
14. Select the Magnetometer Calibration page. (Do not activate the calibration this time.)
15. Rotate the airplane through 360 degrees, and inspect the Calculated Error graph (the red line)
drawn on the screen.
The magnetic heading errors should be less than 5 degrees, and can typically be reduced to about
2 degrees. Accurate magnetic heading is required for the AHRS to display accurate heading data,
and to allow accurate wind speed/direction calculations.
The graph will also show the correction stored in the AHRS as a green line. The green line will be
within the +/- 30 degree range if the magnetometer was mounted in a good location, and was
mounted accurately with respect to the AHRS.
The status of the magnetometer correction data is indicated by the field next to the Magnetometer
Calibration setting on the AHRS Maintenance page. If the field has the message “Change to open
page,” then no valid data is stored within the AHRS and it must be recalibrated. If the field says
“Valid,” it means that the data is present. Keep in mind that the accuracy of this data is not assured
