CFM56-7B TRAINING MANUAL ENGINE FAN TRIM BALANCE (3 SHOT PLOT)

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71-00-00 Aug 99
CFM56-7B TRAINING MANUAL
ENGINE FAN TRIM BALANCE (3 SHOT PLOT)
Objectives:
Given an Objective Exercise, the student will:
- identify the conditions where fan trim balance must be performed on the CFM56-7engine. (1.A.a.)
- state the purpose of the engine fan trim balance. (2.B.a.)
- identify the methods used for balancing the engine. (1.B.a.)
- Perform the maintenance practice calculations for the 3 shot plot procedure. (3.E.a.)
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CFM56-7B TRAINING MANUAL
FAN TRIM BALANCE
Introduction
Why is fan trim balance necessary for the CFM56-7B
engine?
Purpose (2.B.a.)
The purpose of the engine fan trim balance is to bring
back the engine vibration level to a satisfactory level.
This ensures that:
- The engine reliability will not be affected by
abnormal vibration,
- Engine performance level is maintained for all
operational phases,
- Cabin noise is maintained to a satisfactory level.
The trim balance procedure should limit vibration levels
measured on fan and Low Pressure Turbine to 1.5 AVM
units during all engine ground runs.
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CFM56-7B TRAINING MANUAL
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FAN TRIM BALANCE
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CFM56-7B TRAINING MANUAL
FAN TRIM BALANCE
Identification (1.A.a)
These are the conditions where Fan Trim balance
procedure is performed on the CFM56-7B to reduce
engine vibration levels:
- Fan or/and LPT vibrations are equal or more
than 3 AVM units or 6 mils Double Amplitude.
- After the replacement of 1or more fan blades
and the correction weight installed on the spinner
cone is more than 3.36 pound inches or 600 cm.g.
- After the repair of 1or more fan blades
and the correction weight installed on the spinner
cone is more than 3.36 pound inches or 600 cm.g.
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CFM56-7B TRAINING MANUAL
REASONS TO PERFORM A FAN TRIM BALANCE
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CFM56-7B TRAINING MANUAL
FAN TRIM BALANCE
Maintenance Practice (3.E.a)
These are the two different maintenance practice
procedures available to perform fan trim balance:
- Airborne Vibration Monitoring Unit (AVM) Method
-The 3 Shot Plot Method
Airborne Vibration Monitoring Unit (AVM)
The procedure using the Boeing on board optional
equipment installed in the airplane electronic bay on the
E3-2 shelf. This procedure is uses the vibration data for
phase angle and vibration levels collected during the last
32 flight legs and when necessary during engine ground
runs.
The AVM uses these signal inputs to calculate vibration
levels:
-Vibration sensor from N1 bearing
-Vibration sensor from the FFCCV
-N1 Speed Sensor
-N2 Speed Sensor
The AVM signal conditioner continuously calculates
vibration data for several areas of each engine.
-Fan and LP compressor
-HPC Compressor
-HPT Turbine
-LPT turbine
The highest vibration level is displayed on the CDS, on
the vibration indicator.
The four possible vibration monitoring units are the
(Endevco -203, -213 and Vibrometer -103, -113). These
units calculate the amount and location of weight
necessary to balance the engine back to a normal level.
The PO weight is selected and then needs to be installed
in the engine rear cone by the technician.
(Refer to the AMM 71-00-00 for more information.)
The 3 Shot Plot Method
In case your aircraft is not equipped with such optional
vibration monitoring units, you still have one way to get
your engine balanced using the alternate manual
procedure called "the 3 shot plot."
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CFM56-7B TRAINING MANUAL
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CFM56-7B TRAINING MANUAL
FAN TRIM BALANCE
General (3.E.a)
The 3 shot plot procedure philosophy
This method is used when no equipment is available to
find out the phase angle of the engine unbalance.
To find out the location and amount of weight to install on
the engine rear spinner cone, engine runs must be
performed.
A minimum of 5 runs are necessary.
Initial run
The actual engine unbalanced condition is recorded
through different engine speeds.
First run
Balance weights are installed on the spinner cone, and
engine is operating at the same speeds that during the
initial run and vibration levels are recorded. Obviously,
the vibration amplitudes change and are more or less
important that the one recorded during the initial run.
Second run
Balance weights installed for the engine first run are
removed and installed in different position 120° apart) ,
Engine is run again at the same speeds that the earlier
runs, and vibration levels are recorded.
Once again, Vibration amplitudes change, and are more
or less important that previous engine runs.
Third run
Balance weights installed for the engine second run are
removed and installed in a different position (120° apart)
from the second run. Engine is run again at the same
speeds, and vibration levels are recorded.
Once again, Vibration amplitudes change, and are more
or less important that amplitudes recorded during
previous engine runs depending on the position of
unbalance.
Engine runs analysis
From the engine runs recorded data, a manual vectorial
construction is performed to determine the amount of
balance weight to install, and the position to install the
weight. This is calculated using the different forms
available within the Boeing Maintenance Manual.
Weight is then installed on the engine rear spinner cone
according to the analysis calculation.
Final run
The engine is operated to record the engine vibration
amplitude, and to verify that the level is within limits.
NOTE: If during engine run with test weights installed the
vibration level is measured within limits, the fan trim
balance procedure is finished.
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CFM56-7B TRAINING MANUAL
3 SHOT PLOT PHILOSOPHY
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Aircraft and engine preparation is to be performed prior
to operation of the engine.
To read vibration in mils, vibration equipment is to be
installed. The vibration indicator in the flight compartment
reads in units and is not possible to read vibration in mils.
If the aircraft is not equipped with unbalance phase angle
recording features, it is not possible to know if vibration is
generated by the N°1 bearing vibration sensor or the
FFCCV sensor. It isn't possible to read vibration in mils
either.
To obtain more information, install a selector switch
which isolates the signals coming from the vibration
sensors, and install the breakout cable. Disconnect the
AVM signal conditioner from its support (Refer to the
AMM 77-31-00), and connect the breakout cable to the
electronic shelf connector. Route the breakout cable up
to the flight compartment area and connect it with the
selector switch.
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CFM56-7B TRAINING MANUAL
PREPARATION
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Initial run
Prior to start the engine, a careful record of the actual
balanced screws installed on the rear spinner cone must
be performed. Record the configuration on the Balance
screw location chart.
Then start the engine, and bring it to stabilized thermal
condition if the engine was shut down for more than 6
hours. The stabilized engine thermal condition is
obtained running the engine at 80% N1 for at least 5
minutes.
If the engine was not shut down the last 6 hours, stabilize
the engine in idle for 3 minutes, and then slowly
accelerate the engine until the takeoff N1 target of the
day is reached.
Important: Stop engine acceleration if the vibration level
equals 4 units on the vibration gage or 8 mils scale on
the indicator overlay.
Stabilize the engine at the T/O N1 target (if you can
reach this RPM) and record the vibration amplitude for
both N°1 bearing sensor and FFCCV sensor. Selection
of sensors output is selected through the selector
switch.
Decrease the engine speed to the next lower N1 speed
target defined in the AMM, (now 93,7%) and record the
vibration levels red from the N°1 bearing sensor and
FFCCV sensor.
Important: Wait engine EGT and N1 parameters to
stabilize prior to record those data.
Follow the same exact procedure to record vibration
levels for the next lower speeds. (85%, 81%, 66%, and
54%).
Shut down the engine, and prepare balance weights for
the next run called engine first run.
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CFM56-7B TRAINING MANUAL
ENGINE INITIAL RUN
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
First run
Install three balance screws P05 instead of P07 balance
screws installed on the rear spinner cone.
You can now start the engine, stabilize it in idle. The
engine warm up procedure (stabilization at 80% N1) is
not needed.
Repeat exactly the same running procedure that the
initial run to record vibration amplitudes for both N°1
bearing sensor and FFCCV sensor.
Record the vibration amplitudes into the second column
of the three shot plot worksheet form.
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CFM56-7B TRAINING MANUAL
ENGINE FIRST RUN
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Second run
Remove the three P05 screws which have been installed
during the last run, and replace them with P07 screws.
120° apart from their latest position, install the three
balance screws P05 instead of P07 balance screws .
You can now start the engine, stabilize it in idle. The
engine warm up procedure (stabilization at 80% N1) is
not needed.
Repeat exactly the same running procedure that the last
run to record vibration amplitudes for both N°1 bearing
sensor and FFCCV sensor.
Record the vibration amplitudes into the third column of
the three shot plot worksheet form.
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CFM56-7B TRAINING MANUAL
ENGINE SECOND RUN
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Third run
Remove the three P05 screws which have been installed
during the second run, and replace them with P07
screws. Next install 120° from P05 second run position,
install the next three balance PO5 screws after removing
the P07 balance screws.
Now start the engine, stabilize it in idle. The engine warm
up procedure (stabilization at 80% N1) is not needed.
Repeat exactly the same running procedure that the last
run to record vibration amplitudes for both N°1 bearing
sensor and FFCCV sensor.
Record the vibration amplitudes into the fourth column of
the three shot plot worksheet form.
Shut down the engine and proceed to the next step.
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CFM56-7B TRAINING MANUAL
ENGINE THIRD RUN
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
Once all data have been accurately recorded,
determinate the location and amount of weight to install
on the rear spinner cone to correct the engine unbalance.
Note: To facilitate the calculation, select only the speeds
where the three highest vibration amplitudes from each
sensor have been recorded in the initial run.
Give an identification letter to each one of the recorded
vibration amplitude;
- A = highest vibration level
- B = second highest vibration level
- C = third highest vibration level
for N°1 bearing sensor.
- D = highest vibration level
- E = second highest vibration level
- F = third highest vibration level
for the FFCCV sensor.
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CFM56-7B TRAINING MANUAL
3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
Represent the initial unbalance on a polar graph. Choose
a correct scale size that will fit on the polar graph.
Represent each of the 6 points A-B-C and D-E-F on a
different polar graph to get accurate representation.
For each point, draw one circle from the center of the
polar graph. The radius of the circle you draw is equal to
the vibration amplitude that was recorded for the point
selected.
Note: For training purposes, only one point (A)
construction will be demonstrated in detail, the other
points will be shown later.
For the point A, the vibration amplitude equals to 6.5
mils. First define a scale which suits the amplitudes for
point A, and then draw a circle of radius 6.5 from the
center of the polar graph.
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
Represent the First engine run vibration behavior with
the set of PO5 balance weights installed.
To represent it, draw a circle which has the radius of the
vibration level for the selected point (A), using the
identical scale used the step earlier.
For this example, the vibration level recorded for the
point A was 4 mils, so, draw a circle with the radius
taken from the scale.
Its center is located at the intersection of the initial
unbalanced condition circle and the radius passing from
the center of the graph to the central balance screw
position (here position 35).
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
Represent the second engine run vibration behavior with
the set of PO5 balance weights installed.
To represent it, you must draw a circle which has the
radius of the Vibration level for the selected point (A),
using the identical scale you used the step earlier.
For this example, the vibration level recorded for the
point A was 8.6 mils.
Its center is located at the intersection of the initial
unbalanced condition circle and the radius passing from
the center of the graph to the central balance screw
position (here position 23).
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
Represent the third engine run vibration behavior with
the set of PO5 balance weights installed.
To represent it, you must draw a circle which has the
radius of the balance level recorded at the third run for
the selected point for the (A).
For this example, the vibration level recorded for the
point A was 7.8 mils, so, with the scale, it is represented
with a 47 mm radius circle.
Its center is located at the intersection of the initial
unbalanced condition circle and the radius passing from
the center of the graph to the central balance screw
position (here position 11).
The scale used is: 6 mm for 1 mils of vibration.
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CFM56-7B TRAINING MANUAL
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
The resultant R for the point (A) is the vector which is
drawn from the center of the polar graph, and the
intersection of the 3 circles drawn for each run.
NOTE: If during your construction, the 3 circles do not
cross in one point, draw the vector from the center of
the polar graph to the center of the common area of
those 3 circles.
For this point (A), according to the scale we used, the
amplitude in mils equals 2.7 mils.
The angle of this vector has to be measured from the
vertical axis, so for this point (A), the angle equals 5
degrees.
Calculate the balance weight W6 corresponding to
the point (A) using the formula.
W6 = 831.8 x U0 (initial unbalance)
R1 (calculated resultant for
point A)
For point (A), this is 831.8 x 6.5 = 2002 cm.g
2.7
The final calculation for the point (A) concerns the
sensitivity. It represents how the additional weights
PO5 added to the engine in 3 different positions (120 °
apart) affect the balance condition of the engine for this
particular speed.
Sensitivity = 831.8 = 831.8 = 308
R1 2.7
Calculate and fill in the information for all the remaining
points onto the corresponding form .
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
The angle of this vector has to be measured from the
vertical axis, so for this point (A), the angle equals 5
degrees.
You must also calculate the balance weight W6
corresponding to the point (A) using the formula The
angle of this vector has to be measured from the vertical
axis, so for this point (A), the angle equals 5 degrees.
Calculate the balance weight W6 corresponding to the
point (A) using the formula
The next step is to represent graphically each calculated
balance weight W6 for all the different points A, B, C, D,
E, F onto one polar graph.
Note: You must select a scale which permits you to draw
each point onto the polar graph.
For this example a scale of 1 cm for 500 cm.g is
selected.
Report each balance weight point at the correct angle
onto the polargraph.
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
Using the last polar graph fill out the form to calculate the
maximum amplitude for each vector.
To calculate it, you must graphically joint each point
which is mentioned in the form, starting by AB, then AC,
then AD, up to EF.
Note: Once you measure the distance in between a and
B, A and C, don't forget to transform this distance into
moment weight using the same scale as used earlier 1
cm corresponding to 500 cm.g.
For vector AB:
To fill out the first Sensitivity P1 column, get the
information (point A) from the chart . To fill out the
second Sensitivity P1, get the information (point B) from
the chart.
You just need to make the addition of those two columns
to fill out the SP1+SP2 column.
To calculate the amplitude (U), use the formula provided
into the form which corresponds to the distance of the
considered vector (AB) divided by the sum of the
sensitivity you calculated in column SP1+SP2.
Do the same for all the remaining vectors AC, AD, etc.
Once all amplitudes (U) have been calculated, select the
highest one to calculate the distance from P1.
In this example, the selected one is corresponding to the
vector AD, where the amplitude equals 2.623.
Using the formula which is the amplitude multiplied by
the sensitivity of the point A, we will find the distance
from point A.
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
On the polar graph you used earlier and using the same
scale, report the distance you calculated onto the form,
starting at the point A.
Draw the vector from the center of the graph to this point,
and measure it.
Transform this distance into balance weight using the
scale, and measure the angle from the vertical axis.
Record this value on the form, this is what you need to
balance the engine.
In this example, the result is 1550 cm.g at 26°.
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CFM56-7B TRAINING MANUAL
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
In this example, the result is 1550 cm.g at 26°.
Going to the balancing weight location form, find out the
physical location of balancing weight position.
In this example, the measured angle is 26°, so the
calculated angle selection is the one in between 23 and
27 degrees.
The balancing weight must be centered into 2 screws
positioned in 34 and 35.
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Balancing weights calculation process
Using the PO weight chart, find the balancing weight
required centered into two screws in figure 514.
Find on the right hand side column, the closest balance
weight corresponding to the calculated balance weight
needed.
For this example, 1527cm.g is the closest to the 1550
cm.g needed.
Balance screws selection is mentioned on the horizontal
line corresponding to the 1527 cm.g.
For this example, 6 screws are needed, and they are:
- 2 P06 screws
- 4 P04 screws.
To install them, number the screws from the horizontal
centerline in counterclockwise direction, corresponding to
the balance screws position Aft Looking Forward.
In this example, install P06 screws in position 34 and 35,
and P04 screws in position 32, 33, and 36 and 1.
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL
THE 3 SHOT PLOT EXERCISE
Maintenance Practice (3.E.a)
Last Engine Run
Remove the old balance screws and install the new
balance screws at the correct position in the rear spinner
cone.
Start the engine and operate it at the same speeds as
before on the run sheets.
Record the vibration levels at the determined speeds and
record them onto the vibration recording form.
Check that all vibration levels are below the limits found
in the AMM 71-00-00.
This concludes the fan trim balance "3 shot plot"
procedure.
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3 SHOT PLOT EXERCISE
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CFM56-7B TRAINING MANUAL ENGINE FAN TRIM BALANCE (3 SHOT PLOT)

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f214216709

7B的资料哦  非常不错的

titanium

啦啦啦啦啦