System Maintenance Manual

Page 7-34 G1000/GFC700 System Maintenance Manual – C90A/C90GT/C90GTi King Air
Revision F 190-00682-01
5. 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 associated numeric values
are displayed on the PFD.
NOTE
Should a failure occur, the technician may perform the Engine Run-up test up to 3 times successively
before corrective action must be taken. If the test does not pass after three attempts, then the installation
should not be considered reliable until the source of the vibration problem is identified and remedied. In
the event of repeated failure of the engine run-up test, 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) Vibration motion of GRS77 and/or GMU44 caused by neighboring equipment and/or
supports.
b) Mounting screws and other hardware for GRS77 and/or GMU44 not firmly attached.
c) GRS77 connector not firmly attached to unit.
d) Cabling leading to GRS77 or GMU44 not firmly secured to supporting structure.
e) An engine / propeller that is significantly out of balance.
6. Press the ENT key on the PFD to conclude this procedure
7. Repeats steps 1 through 6 for GRS 77 #2 and proceed to Section 7.7.6.
7.7.6 GRS/GMU Test
The aircraft can now be taxied back and the engine can be shut down for final testing. Restart the
displays in normal mode to conduct final system checks. When the PFDs power up in normal mode, the
AHRS attitude and heading information displayed should become valid within 1 minute of power-up, as
shown in Figure 7-8 (provided both GPS receivers have a valid position; if GPS is unavailable, AHRS
initialization may take as long as 2 minutes).