• 3400 rpm (99.1%).
NOTE: Use Figure 504 to convert from vibration units (on the EICAS display) to mils.
(b) If the amplitude is less than 10 mils, let the engine become stable at 3400 rpm (99.1%).
SUBTASK 72-31-00-975-011-G00
(3) Make a record with marker, STD-7049 on the log sheet of this information:
vibration amplitude (Ux), phase angle (Ax), and the N1 speed setting (rpm) (Figure 502).
SUBTASK 72-31-00-865-012-G00
(4) Use the Power Plant Operation (Normal) procedure to do the engine shut-down
(PAGEBLOCK 71-00-00/201).
H. Balance Weight (W1) Selection
SUBTASK 72-31-00-975-013-G00
(1) Do the steps that follow to find the balance weight (W1) that is necessary to balance the
engine:
(a) Use the trim balance matrix (Figure 503) to find the spinner hole location where the
balance weight will be installed.
(b) Find the balance weight quantity (W1) in grams at the intersection of the amplitude (Uo)
and RPM columns of trim balance matrix.
SUBTASK 72-31-00-975-014-G00
(2) Do the steps that follow for the selection of the balance screws:
(a) Make a map of the balance weights (screw part numbers) that are now in the spinner
(Figure 505).
(b) Make a mark marker, STD-7049 on the weight map where the balance screw or screws
are to be installed.
NOTE: All 38 spinner holes must have a balance screw. To prevent too much balance
weight in the spinner it is possible to replace certain screws with a screw of less
weight. This would be an alternative to the normal procedure.
1) Look at the weight of the screw that is opposite from the screw that you plan to
replace.
2) If the opposite screw weighs more than 6.44 grams (P07), you can replace it with a
lighter screw.
3) Calculate the difference quantity.
NOTE: This is the weight of the screw you removed minus the weight of the lighter
screw that will replace it.
4) Subtract this difference quantity from the balance weight quantity (W1) that was
found in Figure 503.
5) You now have a new balance weight quantity (W1).
SUBTASK 72-31-00-975-015-G00
(3) Use the table of balance screw weights (Figure 505) to make a selection of the necessary
screw or screws.
(a) Example of balance screw selection:
1) From the log sheet example (Figure 502).
Ao = 280°~
Uo = 8.0 MIL
767
AIRCRAFT MAINTENANCE MANUAL
CF6-80A SERIES ENGINES
72-31-00
NoC
Page 504
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ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details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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