(a)  
Install the permanent fan weights as follows: 1) Remove the front segment of the inlet cone (AMM 72-31-01/401). 2) Vibro peen the letters "TB" on the inner diameter face of all the trim balance counterweight(s). 3) Install each permanent fan weight with a rivet. a) Use the riveter to make a 0.125 inch (3.175 mm) diameter head on the rivet.

 4)  Install the front segment of the inlet cone (AMM 72-31-01/401).

 (b)  
Operate the engine with the counterweights installed to make sure that the engine vibration is within limits.

 (2)  
Remove the trim balance equipment as follows:

 S 085-089-N00
 WARNING: DO THE THRUST REVERSER DEACTIVATION PROCEDURE TO PREVENT
_______ THE OPERATION OF THE THRUST REVERSER. ACCIDENTAL OPERATION OF THE THRUST REVERSER CAN CAUSE INJURIES TO PERSON AND DAMAGE TO EQUIPMENT.
 (a)  Do the deactivation procedure for the thrust reverser for ground maintenance (AMM 78-31-00/201).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
(b)  
Open the right fan cowl panel (AMM71-11-04/201).

 (c)  
Open the core cowl panels (AMM 71-11-06/201).

 (d)  
After you disconnect the N1 Sensor Pickup Jumper, connect the flight N1 sensor harness to the N1 sensor.

 (e)  
Remove the PWA 85774 bracket and the PWA 85703 accelerometer assembly from Flange P at the 9 o'clock position.

 (f)  
After you disconnect the N1 Sensor Pickup Jumper, connect the flight N1 sensor harness to the N1 sensor.

 (g)  
Close the core cowl panels (AMM 71-11-06/201).

 (h)  
Close the right fan cowl panel (AMM 71-11-04/201).

 (i)  
Do the activation procedure for the thrust reversers (AMM 78-31-00/201).

 (j)  
Make sure all equipment that was installed for the trim balance procedure was removed.

 TASK 72-31-00-725-090-N00
 3. Balance the Front Balance Plane (Trim Balance - Airborne Vibration
__________________________________________________________________
 Monitoring (AVM) Procedure

__________________________
 A. General
 (1)  
It is recommended that this trim balance procedure be done by personnel that are trained in the use and operation of the PBS-4100 portable trim balancing system and have experience with engine trim balance.

 (2)  
This trim balance procedure uses engine vibration data that is generated by the aircraft AVM system. You can manually get the engine vibration data through the AVM balancing screen of the EICAS system. This method is used to lower fan ("A" flange) vibration levels only. This procedure should not be used to correct cabin noise problems.

 (3)  
A fan plane balance will affect the low rotor vibration levels on both the fan ("A" flange) and turbine ("P" flange) cases. Because the AVM only has vibration pickups on the fan case, the affect of a fan plane balance on the turbine case will not be known. Therefore, this procedure has a limit on the qunatity of weight that you can install to the fan balance flange. A turbine plane balance cannot be done with this procedure.

 (4)  
The weights for the engine trim balance are installed on the compressor (front balance plane). The trim balance procedure can be done on the engine while it is on the airplane.

 (5)  
Trim balance is only used to correct stable low rotor related (1EL) vibration.

 (6)  
The total vector sum of the trim balance weights and the weights installed for component (LPC) balance must not be more than the limits that follow:

 Fan Plane: 20 oz-inches (14,400 g.mm)
 NOTE: If it is necessary to add more correction weight than
____ permitted, you must examine the engine for incorrect assembly and part damage.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
　
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