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5.7
Calibration Procedure D: Engine Run-Up Vibration Test
Calibration Procedure D is required for all installations to validate the
vibration characteristics of the installation. Calibration Procedures A-1
through C are not required prior to this procedure.
1. Initiate the AHRS engine run-up vibration test procedure by performing the following steps:
a) If the PFD is not displaying the GRS/GMU CALIBRATION configuration page, follow steps
from calibration procedure A-1 listed previously.
b) The FMS small knob can now be used to select which calibration/validation procedure to run.
Select ENGINE RUN-UP TEST and press the ENTER key. If the ENGINE RUN-UP TEST
selection is still blinking, press the ENTER key again.
c) Follow the checklist items displayed on the PFD, and press the ENTER key as each one is
completed or confirmed. When the CALIBRATE field is blinking, press the ENTER key to
begin the procedure.
2. The PFD display instructs the operator to gradually increase power from idle to full throttle and
back to idle over the course of a couple of minutes.
3. When the operator has completed the engine run-up and the engine is back to an idle setting,
press the ENTER key to indicate that the process is complete. When this is done, the TEST
COMPLETE field stops blinking.
4. The PFD informs the operator if the installation has passed or failed the vibration test. If the test
fails, the specific measurements causing the failure are identified and numeric values are
displayed on the PFD. Use the FMS small knob to scroll through and view the entire list of failed
measurements.
If failures are indicated, the engine run-up test may be repeated up to three times. If the test does
not pass after three attempts, then the installation should be considered unreliable until the source
of the vibration problem is identified and remedied.
When the engine run-up test fails repeatedly, record the values that are reported to be out of range
for future reference.
The following are potential causes for failure of the engine run-up test:
a) Excessive flexibility of GRS 77 and/or GMU 44 mechanical mounting with respect to
airframe (See Section 2.6 entitled "Aircraft Mounting Requirements for GRS 77/GMU 44").
b) Vibrational motion of GRS 77 and/or GMU 44 caused by neighboring equipment and/or
supports.
c) Mounting of GRS 77 at a location that is subject to severe vibrations (example; close to an
engine mount.)
GRS 77/GMU 44 Installation Manual
190-00303-10
NOTE
Page 5-11
Revision L
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