TASK 72-31-00-705-042-G00
3. Alternate Trim Balance Procedure - (Uses a Three Try Plot)
A. General
(1) The alternate trim balance procedure uses the aircraft vibration monitoring system that is
shown on the EICAS display in the flight compartment. This procedure makes three engine
runs with a known balance weight (Wt). The results are put on polar graph paper, and a
balance correction weight (WF) is calculated and installed on the spinner cone.
(2) The terms and symbols used in this procedure are specified as follows:
(a) Vibration Amplitude (U) - The engine imbalance (in units) as shown on the EICAS display
in the flight compartment.
(b) Phase angle (X) - The phase angle of the engine imbalance in units of degrees.
(c) Weight (W) - The balance correction weight in units of grams. It is a balance screw (or
screws) which are installed on the spinner cone.
(d) R - The resultant imbalance in units of mils.
B. References
Reference Title
71-00-00 P/B 201 POWER PLANT (OPERATING PROCEDURES) -
MAINTENANCE PRACTICES
72-52-00 P/B 501 LOW PRESSURE TURBINE (LPT) SECTION -
ADJUSTMENT/TEST
C. Tools/Equipment
Reference Description
STD-6378
Protective Mat - Rubber, Manufacturers Association, Grade SC43,
neoprene sponge, 1 inch thick, approximately 3 x 4 feet with warning
streamer attached
STD-7049
Marker
D. Location Zones
Zone Area
410 Left Powerplant
420 Right Powerplant
E. Operate the Engine
SUBTASK 72-31-00-865-010-G00
WARNING
USE AMM 71-00-00/201 TO OPERATE THE POWER PLANT. IF YOU DO NOT
USE THIS PROCEDURE, YOU CAN CAUSE DAMAGE TO EQUIPMENT AND
INJURY TO PERSONS.
(1) Use the Power Plant Operation (Normal) procedure to start the engine
(PAGEBLOCK 71-00-00/201).
767
AIRCRAFT MAINTENANCE MANUAL
CF6-80A SERIES ENGINES
72-31-00
NoC
Page 520
D633T1B7 Aug 22/2017
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
EFFECTIVITY
ABX 001-007, 011, 012, 016-019, 021, 022, 025, 101,
109, 114, 115, 314-999
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