Replacement of Fan Rotor Blades in Pairs [CFMI]

TASK 72-21-00-300-026-A
Replacement of Fan Rotor Blades in Pairs

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 1M (3 FT)-ADJUSTABLE
No specific	1	MAT - PROTECTIVE
No specific	AR	WARNING NOTICE(S)
No specific	Torque wrench: range to between 75 and 65 lbf.in (0.85 and 0.73 m.daN )
856A3770	1	CFMI SOFTWARE FOR BLADE MAPPING

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.CP1039)	acetone
(Material No.CP1041)	isopropyl alcohol
(Material No.CP2011)	stoddard solvent
(Material No.CP2101)	graphite grease
(Material No.CP2559)	ardrox 552
(Material No.CP2560)	turco ind 79
(Material No.CP2566)	mag-chem teksol
(Material No.CP2584)	degreasol 99 R
(Material No.CP2656)	mag-chem skysol
(Material No.CP5061)	temporary marking

C. Referenced Information

REFERENCE	DESIGNATION
TASK 71-00-00-710-009-A	Vibration Check
TASK 71-00-00-750-001-A	Fan Trim Balance - 1 Sensor 3 Speed
TASK 71-00-00-750-001-A-01	Fan Trim Balance - 1 Sensor 1 Speed
TASK 72-21-00-000-001-A	Removal of the Spinner Front Cone
TASK 72-21-00-000-002-A	Removal of the Spinner Rear Cone
TASK 72-21-00-000-003-A	Removal of the Fan Rotor Blades
TASK 72-21-00-300-006-A	Correction of the Static Imbalance.
TASK 72-21-00-400-001-A	Installation of the Spinner Front Cone
TASK 72-21-00-400-002-A	Installation of the Spinner Rear Cone
TASK 72-21-00-400-003-A	Installation of the Fan Rotor Blades
Fan Blade Replacement
Replacement of Several Pairs of Fan Blades
Fan Blades, Balance Screw Location Chart and Vectorial Diagram
Various Balance Screw Arrangements for Given Moment Weights
Various Balance Screw Arrangements for Given Moment Weights
Diagram for Fan Blade Change
Balance Screws

3. Job Set-up
Subtask 72-21-00-941-083-A ** ON A/C NOT FOR ALL

A. Safety Precautions
(1) On the center pedestal, on the ENG panel 115VU:
(a) Put a WARNING NOTICE(S) to tell persons not to start the engine.
(2) Make sure that the engine 1(2) shutdown occurred not less than 5 minutes before you do this procedure.
(3) On the overhead maintenance panel 50VU:
(a) Make sure that the ON legend of the ENG/FADEC GND PWR/1(2) pushbutton switch is off.
(b) Put a WARNING NOTICE(S) to tell persons not to energize the FADEC 1(2).
(4) Put an ACCESS PLATFORM 1M (3 FT)-ADJUSTABLE in position.
(5) Install MAT - PROTECTIVE in the lower half of the inlet cowl.

4. Procedure
Subtask 72-21-00-869-076-B ** ON A/C NOT FOR ALL

CAUTION: BE CAREFUL WHEN YOU REPLACE FAN BLADES IN PAIRS, DO NOT MIX OLD FAN BLADES AND NEW RECAMBERED FAN BLADES ON A SAME FAN DISK (FAN BLADES PRE CFM56 SB 72-0123 AND FAN BLADES POST CFM56 SB 72-0123), BECAUSE THEY HAVE DIFFERENT BLADE ANGLES.

A. Remove the fan blades before recording the moment weight.

NOTE: The spare blades are grouped in pairs so that the difference between the moment weights is not more than 80 in.g (200 cm.g). However, you must do the checks and corrections described below before and after blade installation to make sure the engine imbalance is not more than the limits. This will also optimize the engine operation. Three conditions can exist, refer to the logic diagram and Para. B.

Diagram for Fan Blade Change ** ON A/C NOT FOR ALL

NOTE: If you replace more than three pairs of fan blades and for individual fan blade replacement, a vibration survey must be performed (Ref. AMM TASK 71-00-00-710-009). Results from the vibration survey will determine if a trim balance is necessary. In this last case, do a trim balance operation (Ref. AMM TASK 71-00-00-750-001) if the aircraft is at the main base or as soon as the aircraft returns to the base.

(1) Put a rubber mat in the air intake cowl.
(2) Use a temporary marking (Material No.CP5061) and identify the fan blades with numbers.
(3) Remove the spinner front cone (Ref. AMM TASK 72-21-00-000-001).
(4) Remove the spinner rear cone (Ref. AMM TASK 72-21-00-000-002).
(5) Remove and record the location of the balance screws.
(6) Record location of each blade to be replaced and of each blade opposite.
(7) Remove fan blades:

CAUTION: BE CAREFUL IF THESE MARKS ARE SHOWN ON THE HUB OF THE REWORKED FAN DISK: "SHIMS REQUIRED" AND "DISK REPAIRED". DAMAGE CAN OCCUR IF YOU DO NOT FOLLOW CORRECT PROCEDURES FOR ENGINES POST CFM56 SB 72-0621.

CAUTION: FOR ENGINES POST CFM56 SB 72-0621, BE CAREFUL WHEN YOU HANDLE THE SHIMS. THEY ARE THIN AND ARE EASILY DAMAGED. DO NOT USE TOO MUCH FORCE WHEN YOU REMOVE THE SHIMS FROM THE FAN BLADE ROOTS. THE COATING ON THE FAN BLADES AND THE SHIMS IS EASILY DAMAGED. OBEY THESE INSTRUCTIONS OR YOU WILL CAUSE DAMAGE TO THE EQUIPMENT.

(a) Remove fan blades (Ref. AMM TASK 72-21-00-000-003).
(8) Record the moment weight of the blades that you removed using a temporary marking (Material No.CP5061) .

Fan Blade Replacement ** ON A/C NOT FOR ALL

NOTE: For engine POST CFM56 SB 72-0621, you must write also moment weight of the shim installed on the root of the removed fan blade.

NOTE: Grease deposits can mask the moment weight indication. If necessary, clean blade base with isopropyl alcohol (Material No.CP1041) or acetone (Material No.CP1039) or stoddard solvent (Material No.CP2011) or ardrox 552 (Material No.CP2559) or turco ind 79 (Material No.CP2560) or mag-chem teksol (Material No.CP2566) or degreasol 99 R (Material No.CP2584) or mag-chem skysol (Material No.CP2656) .

Subtask 72-21-00-420-079-A ** ON A/C NOT FOR ALL

B. Record the moment weight of the spare blades and install the spare blades.

CAUTION: FOR EACH PAIR OF FAN BLADES, INSTALL THE HEAVIER SPARE BLADE AT THE POSITION OF THE HEAVIER BLADE TO BE REMOVED.

(1) Record the moment weight of the spare blades.
(2) Do a check of the quantity of replaced fan blade pairs.

(a) If the quantity of pairs is less than or equal to three and in the limits of the 200 cm.g (80 in.g) pair criteria, do as follows:
1 Install the spare blades (Ref. AMM TASK 72-21-00-400-003).
2 A vibration survey is not necessary.
(b) If the quantity of pairs is less than or equal to three but more than the 200 cm.g (80 in.g) pair criteria, do as follows:
1 Do a static correction procedure (refer to Para. C.) or do a blade mapping with 856A3770 CFMI SOFTWARE FOR BLADE MAPPING.
2 Install the spare blades (Ref. AMM TASK 72-21-00-400-003).
3 Go to Para. D.
(c) If the quantity of pairs is more than three, do as follows:
1 Do a static correction procedure (refer to Para. C.) or do a blade mapping with the 856A3770 CFMI SOFTWARE FOR BLADE MAPPING.
2 Install the spare blades (Ref. AMM TASK 72-21-00-400-003).
3 Go to Para. D.

NOTE: Static correction has to be limited to four blade pairs.

NOTE: If the CFMI SOFTWARE FOR BLADE MAPPING (856A3770) plotting is not satisfactory, do a static correction procedure (refer to Para. C.) to reduce the blade set unbalance.

NOTE: For engine POST CFM56 SB 72-0621, you must write also moment weight of the shim installed on the root of the fan blade to be installed.

Subtask 72-21-00-820-052-A ** ON A/C NOT FOR ALL

C. Static correction procedure. Determine the balance screws to be installed.
(1) Determine the resultant vector length and direction, then select balance screws to provide a correction returning the fan to its initial balance condition as follows.

NOTE: It is advisable to limit the number of balance screws on the spinner due the complexity and the risk of confusion when performing further corrections, and to install only one set of balance screws. This requires the construction of a vector diagram for determining the sum of the corrections. An example is given in (Ref. AMM TASK 72-21-00-300-006).

(a) Assume the following blades with the moment weights indicated are to be removed:
No. 01: 164832 cm.g (64895 in.g)
No. 36: 163245 cm.g (64270 in.g)
No. 03: 162510 cm.g (63980 in.g)
No. 35: 164185 cm.g (64640 in.g)
(b) Assume the moment weights of the opposite blades are as follows:
No. 19: 164647 cm.g (64822 in.g)
No. 18: 163405 cm.g (64333 in.g)
No. 21: 162650 cm.g (64035 in.g)
No. 17: 164160 cm.g (64630 in.g)
(c) Calculate differences between moment weights as below:
D1: (No. 01/19) = 164832 - 164647 = 185 cm.g (73 in.g)
D2: (No. 18/36) = 163405 - 163245 = 160 cm.g (63 in.g)
D3: (No. 21/03) = 162650 - 162510 = 140 cm.g (55 in.g)
D4: (No. 35/17) = 164185 - 164160 = 025 cm.g (10 in.g)
(d) Calculate moment weight differences corresponding to spare fan blades as below:
D'1: (No. 01/19) = 162905 - 162730 = 175 cm.g (69 in.g)
D'2: (No. 18/36) = 161205 - 161185 = 020 cm.g (08 in.g)
D'3: (No. 21/03) = 164570 - 164545 = 025 cm.g (10 in.g)
D'4: (No. 35/17) = 163825 - 163630 = 195 cm.g (77 in.g)
(e) Calculate differences between removed blades and spare blades as below:
D1 - D'1 = 185 - 175 = 010 cm.g (04 in.g) = F1
D2 - D'2 = 160 - 020 = 140 cm.g (55 in.g) = F2
D3 - D'3 = 140 - 025 = 115 cm.g (45 in.g) = F3
D'4 - D4 = 195 - 025 = 170 cm.g (67 in.g) = F4
(f) Determine the direction of corrections as follows:

NOTE: When D is greater than D', the balance weight should be added close to the heavier blade. When D is lighter than D', the balance weight should be added close to the lighter blade.

1 For blades No. 1 and 19, D1 is greater than D'1 and the balance weight should thus be added close to the heavier blade: No. 1.
2 For blades No. 18 and 36, D2 is greater than D'2 and the balance weight should thus be added close to the heavier blade: No. 18.
3 For blades No. 21 and 3, D3 is greater than D'3 and the balance weight should thus be added close to the heavier blade: No. 21.
4 For blades No. 35 and 17, D4 is less than D'4 and the balance weight should thus be added close to the lighter blade: No. 17.
(g) Construct vectorial diagram as follows:

Replacement of Several Pairs of Fan Blades ** ON A/C NOT FOR ALL

Fan Blades, Balance Screw Location Chart and Vectorial Diagram ** ON A/C NOT FOR ALL

1 On a polar diagram, draw vectors corresponding to moment weight difference calculated in (e) and orientated as in (f).

Fan Blades, Balance Screw Location Chart and Vectorial Diagram ** ON A/C NOT FOR ALL

2 Draw the resultant FR representing the correction required from F1, F2, F3 and F4.

NOTE: In this example, FR is approximately 405 cm.g (159 in.g) and orientated close to the balance screw No. 18.

NOTE: When resultant imbalance direction is between 2 holes, the screw must be placed in the nearest hole.

(h) Select balance screws as follows:

Balance Screws ** ON A/C NOT FOR ALL

Various Balance Screw Arrangements for Given Moment Weights ** ON A/C NOT FOR ALL

1 Find in the tables the value of the resultant FR calculated in paragraph (g). This indicates which balance screws must be installed. The screw in the fifth column of the table must be installed at location calculated in paragraph (g).

NOTE: In this example, for a resultant FR of 405 cm.g (159 in.g), one centered screw P01 installed in hole No. 18 and two lateral screws P02 installed in holes No. 17 and No. 19 provide a correction returning the fan to its initial balance condition.

NOTE: Balance screws are identified by a number corresponding to their moment weight (P01-P02-P03-P04-P05-P06-P07) engraved on screw head. As it may be difficult to read the numbers due to erosion and pollution, the relationship between the screw reference and screw length is shown in.

Balance Screws ** ON A/C NOT FOR ALL

Subtask 72-21-00-420-088-A ** ON A/C NOT FOR ALL

D. Vibration Survey
(1) Install the spinner rear cone (Ref. AMM TASK 72-21-00-400-002).
(2) Install the balance screws, lightly coated with graphite grease (Material No.CP2101) .
(3) TORQUE the screws to between 75 and 65 lbf.in (0.85 and 0.73 m.daN )

.
(4) In case of blade mapping with the 856A3770 CFMI SOFTWARE FOR BLADE MAPPING, install a complete set of balance screws P07 lightly coated with graphite grease (Material No.CP2101) on the spinner rear cone.
(5) Install the spinner front cone (Ref. AMM TASK 72-21-00-400-001).
(6) Remove the rubber mat from the air intake cowl.
(7) Do a vibration check (Ref. AMM TASK 71-00-00-710-009) if:
(a) You installed a new fan blade mapping.
(b) You did the static correction for replacement of more than three blade pairs.
(8) If the vibration level is out of the limits, do a trim balance (Ref. AMM TASK 71-00-00-750-001).

5. Close-up
Subtask 72-21-00-869-077-A ** ON A/C NOT FOR ALL

A. Make sure that the work area is clean and clear of tools and other items.

Subtask 72-21-00-942-076-A ** ON A/C NOT FOR ALL

B. Close Access
(1) Remove the WARNING NOTICE(S).
(2) Remove the MAT - PROTECTIVE from the inlet cowl.
(3) Remove the access platform(s).

[Rev.10 from 2021] 2026.04.02 06:33:39 UTC