(3)  
AMM 72-31-01/401, Inlet Cone

 (4)  
AMM 78-11-02/401, Turbine Exhaust Plug

 (5)  
AMM 72-31-00/501, Fan Trim Balance (Three Shot Plot Procedure)

 (6)  
AMM 71-00-00/501, Vibration Survey

 E.
Access

 (1)  
Location Zone
 117 Electrical and Electronics Compartment - Left
 118 Electrical and Electronics Compartment - Right
 211 Flight Compartment - Left
 212 Flight Compartment - Right
 412 Engine No. 1
 422 Engine No. 2
 432 Engine No. 3
 442 Engine No. 4

 F.
Prepare for the Trim Balance Procedure.

 S 845-105-N00
 (1)  
This trim balance procedure uses the imbalance data recorded and calculated by the AVM during one of the last six flights or engine ground runs from the No. 1 bearing vibration sensor.

 S 845-106-N00

 (2)
You can get this data from the front panel display of the AVM:

 (a)  
The current imbalance data.

 (b)  
The results of a calculation of a 1-plane balance (fan only).

 S 915-107-N00
 (3)  
This procedure is not to be used for an engine if the alternate accelerometer location on the No. 1 bearing is used.

 S 945-110-N00

 (4)  
Make sure that this circuit breaker is closed:

 (a)  
Circuit Breaker Panel, P6-2:
 1) H26, VIBAMP ENG 1 AND 2

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
S 945-111-N00
 (5)  
Open the Electronic Equipment Access Door, 117A.

 G.  
Trim Balance Procedure

 S 945-112-N00
 (1)  
Follow these steps to get to the fan balancing menu on the AVM front panel:

 (a)  
Push and release one of the four buttons to show SELF TEST? on the front panel display.

 NOTE: The front panel display will turn off if the buttons are
____ not pushed for five minutes or if an engine starts running.
 (b)  
Push and release the NO button 3 times until the BALANCE? option shows.

 (c)  
Push and release the YES button to go to the balance menu. This causes the BALANCE ENGINE 1? screen to show.

 (d)  
To get the balance data for engine 1, push and release the YES button. This causes the IMBAL DATA READ? screen to show.

 (e)  
To get the balance data for engine 2, do these steps: 1) Push and release the NO button. This causes the BAL ENGINE 2? screen to show.

 2)  Push and release the YES button. This causes the IMBAL DATA READ? screen to show.

 (f)  
To get the balance data for engine 3, do these steps: 1) Push and release the NO button 2 times. This causes the BAL ENGINE 3? screen to show.

 2)  Push and release the YES button. This causes the IMBAL DATA READ? screen to show.

 (g)  
To get the balance data for engine 4, do these steps: 1) Push and release the NO button 3 times. This causes the BAL ENGINE 4? screen to show.

 2)  Push and release the YES button. This causes the IMBAL DATA READ? screen to show.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
S 835-113-N00
 (2)  It is recommended to look at the imbalance data for other flights or trim balance runs. Do these steps to go into the IMBAL DATA READ? menu to read the balance data:
 NOTE: The AVM gathers data from six N1% speed ranges for each
____ engine and stores this data from the previous six flights or engine ground runs. A balance calculation can be performed on the data from or all of these six flights or engine ground runs. This calculation can be performed as long as the flight or ground run has imbalance data recorded in one or more of the N1% speed ranges. Better balances are obtained when the flight or ground run has captured data in several N1% speed ranges, and when the data has been obtained in flight rather than a ground run.
　
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