
G1000 System Maintenance Manual – Diamond DA40/40F Page 7-27
190-00545-01 Revision G
GRS 77 Output Validity
System software for certain aircraft allows valid outputs from the AHRS prior to completion of the AHRS
and magnetometer calibration procedures, as long as the GRS 77 can definitively determine that the
aircraft is not moving. This gives a technician the ability to perform functional tests during aircraft
assembly that require valid AHRS outputs. Additionally, a “CALIBRATE AHRS/MAG” message will
be displayed on the PFD until a successful calibration has been completed.
The criteria used by the AHRS to determine the aircraft is moving are as follows:
1. If valid GPS data is available and each component of 3D GPS velocity is less than 4 knots, the
aircraft is considered “not moving” and attitude/heading will become valid.
2. If valid 3D GPS data is not available, but valid true airspeed is less than 30 knots, the aircraft is
considered “not moving” and attitude/heading will become valid.
3. If both 3D GPS and true airspeed are unavailable, attitude/heading will not become valid.
Recalibration Procedures
There are six calibration procedures available for the GRS 77 and GMU 44 listed below. Those not
applicable to DA40 are noted as ‘NOT PROVIDED’. Do not attempt to use those procedures or the
GRS/GMU will need to be recalibrated.
• Pitch/Roll Offset: (Procedure A1, PROVIDED IN SECTION 7.7.2.1)
• Pitch/Roll Offset, Manual Entry: (Procedure A2, NOT PROVIDED)
• Magnetometer Calibration: (Procedure B, PROVIDED IN SECTION 7.7.2.3)
• Heading Offset Compensation: (Procedure C, NOT PROVIDED)
• Engine Run-Up Vibration Test: (Procedure D, PROVIDED IN SECTION 7.7.2.4)
• Magnetometer Interference Test: (Procedure E, PROVIDED IN SECTION 7.7.2.5)
NOTE
Procedures A2 and C are not required and should not be performed on DA 40 aircraft.
When ready to perform the procedures, shut the PFD and MFD off by pulling the PFD and MFD circuit
breakers. Restart both displays in configuration mode. Follow the steps given for each procedure on-
screen at the GRS/GMU CALIBRATION page. Note that the CALIBRATE command cannot be selected
and activated until the technician acknowledges all required steps have been carried out by pressing the
ENT key on each step.
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