72-31-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
H. Check Run.
S 975-100-N00
(1)
Do a Check Run:
(a)
Thermally stabilize the engine with the steps given earlier in this task.
(b)
To do the trim balance survey, stop at the same N1 speeds used during the As-Is Trim Balance Survey and make a record of the data.
(c)
Do a slow decel (90-120 seconds) to IDLE.
NOTE: Trim balance data is only taken during the accel
____
vibration survey.
(d)
Operate the engine at IDLE for five minutes to let the engine become cool.
(e)
Use the Power Plant Operation (Normal) procedure to do the engine shutdown (AMM 71-00-00/201).
(f)
If the vibration levels are satisfactory, do these steps:
1) Return the airplane to service with the steps given later in this task.
(g)
If the vibration levels are not satisfactory, do the steps that follow: 1) Input the trim balance data from Figure 507 to a trim
balance computer program.
NOTE: The PBS-4100 computer can be used if software
____ 2.25 and higher is installed. This software allows the manual input of the trim balance data.
2) Calculate the quantity and location of the counterweight for each speed and find the quantity and location that will decrease the vibration to satisfactory levels.
3) If there are no satisfactory balance solutions, remove the engine (AMM 71-00-02/401).
I. Re-Balance (Repeat Shot).
S 975-101-N00
(1)
Do the Re-Balance (Repeat Shot) as follows:
(a)
Remove the inlet cone (AMM 72-31-01/401).
(b)
With the "BALANCE WGTS" feature of the PBS-4100, find which weights to remove and to install.
(c)
Temporarily install the correction weights in the fan with the cotter pins.
(d)
Obey the computer instructions to make sure the weights you installed are the same as the solution. 1) If you installed weights that are different from the
balance solution, make sure you change the data in the computer.
(e)
Install the inlet cone (AMM 72-31-01/401).
(f)
Do a Check Run with the steps given earlier in this task.
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72-31-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
J. Return the Airplane to Service.
S 825-102-N00
(1)
Remove the trial balance weights and install the permanent counterweight(s).
(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.
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