DOC AIRBUS | AMM A320FSequencing of the Fan Blades with PWBAL [PW11]
TASK 72-11-03-710-801-A
Sequencing of the Fan Blades with PWBAL
Determine Fan Blade sequence with PWBAL. Use this procedure to perform a balance of the fan blade set when replaced with one or more fan blades.
PWBAL is a blade sequence optimization tool for installing fan blades. It works with moment weight measurements of each blade. It does not use any inputs from an engine run. It is not trim balance software.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment
B. Work Zones and Access Panels
C. Referenced Information
3. Job Set-up
Subtask 72-11-03-941-065-A ** ON A/C NOT FOR ALL
Subtask 72-11-03-710-052-A ** ON A/C NOT FOR ALL
Subtask 72-11-03-420-052-A ** ON A/C NOT FOR ALL Subtask 72-11-03-860-057-A ** ON A/C NOT FOR ALL
[Rev.10 from 2021]
2026.04.01 02:47:46 UTC
Sequencing of the Fan Blades with PWBAL
WARNING:
BE CAREFUL WHEN YOU DO WORK ON THE ENGINE AFTER SHUTDOWN. THE ENGINE CAN STAY HOT FOR A LONG TIME. IF YOU DO NOT OBEY THIS INSTRUCTION, INJURY CAN OCCUR.
WARNING:
BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS.
1. Reason for the JobDetermine Fan Blade sequence with PWBAL. Use this procedure to perform a balance of the fan blade set when replaced with one or more fan blades.
PWBAL is a blade sequence optimization tool for installing fan blades. It works with moment weight measurements of each blade. It does not use any inputs from an engine run. It is not trim balance software.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment
| REFERENCE | QTY | DESIGNATION |
|---|---|---|
| PWA101032 | 1 | SOFTWARE, DISTRIBUTION ASSEMBLY - FAN BLADE |
| PWA211565 | 1 | CONTAINER, SHIPPING |
| PWA211707 | 1 | PROGRAM PWBAL OPTIONS |
| ZONE/ACCESS | ZONE DESCRIPTION |
|---|---|
| 430 | ENG 1 AIR INTAKE, FAN AND ACCESS GEARBOX |
| 440 | ENG 2 AIR INTAKE, FAN AND ACCESS GEARBOX |
| REFERENCE | DESIGNATION |
|---|---|
| TASK 71-00-00-860-833-A | Procedure to Prevent Engine Motoring |
| TASK 72-11-01-000-801-A | Removal of the Inlet Cone |
| TASK 72-11-01-400-801-A | Installation of the Inlet Cone |
| TASK 72-11-03-000-801-A | Removal of the Fan Blades |
| TASK 72-11-03-400-801-A | Installation of the Fan Blades |
Sequencing of the Fan Blades with PWBALSubtask 72-11-03-941-065-A ** ON A/C NOT FOR ALL
A. Safety Precautions
(1) Do the procedure to prevent engine motoring
(Ref. AMM TASK 71-00-00-860-833).
Subtask 72-11-03-020-052-A ** ON A/C NOT FOR ALL Subtask 72-11-03-940-051-A ** ON A/C NOT FOR ALL (1) Do the procedure to prevent engine motoring
(Ref. AMM TASK 71-00-00-860-833).
C. General
(1) If replacement fan blades are necessary:
(3) Refer to the operating instructions contained in the PWBAL USER Manual for detailed instructions.
(4) Prepare the fan blade set with replacement blades. Use the installation by PWA101032 SOFTWARE, DISTRIBUTION ASSEMBLY - FAN BLADE and PWA211707 PROGRAM PWBAL OPTIONS stage file.
4. Procedure(1) If replacement fan blades are necessary:
NOTE: Relative to the engine acceptance test at production or overhaul, you can replace a maximum of four fan blades in an engine set without requirements to adjust the N1 modifiers that are stored in the Data Storage Unit or to calibrate the engine in a test cell. Operator records must track the number of blades replaced between test cell runs. The number of fan blades replaced since the engine acceptance test is the number of new blade serial numbers in the current installation that were not in the original installation for the original engine acceptance test. Example: If Blade A was replaced by Blade B, then Blade B was replaced by Blade C and no other blade changes occurred, this counts as one blade replacement, for the purposes of N1 modifier updates. Refer to (Ref. AMM TASK 72-11-03-400-801).
(2) When you select replacement blades, attempts must be made to select blades that match the RAD and TAN moment weights as closely as possible to the blades being replaced. See step 4.B.(2). (3) Refer to the operating instructions contained in the PWBAL USER Manual for detailed instructions.
(4) Prepare the fan blade set with replacement blades. Use the installation by PWA101032 SOFTWARE, DISTRIBUTION ASSEMBLY - FAN BLADE and PWA211707 PROGRAM PWBAL OPTIONS stage file.
NOTE: It is recommended to add the word "new" or "replaced" to the comments field in the PWBAL data file or another fan blade file to track new fan blades since the last test cell run. Remove the comment after a test cell run.
(5) PWBAL is a computer program sold by Pratt & Whitney. The PWBAL program must be run with PWBAL Stage files (.esf). Before you use PWBAL, you must make a record of all fan blade hub locations (No. 1 - 20), part numbers, serial number, and radial (RAD)/axial (AX)/tangential (TAN) moment weights and A-angle at removal and the same information for all replacement fan blades (other than hub locations). There is a Pratt & Whitney data file of the "As Delivered Configuration" for the fan blade locations, part numbers, serial numbers, weight, and A-angles. Operators get this data for each of their engines with the engine delivery records. Always check this data file and your installed configuration before you use PWBAL. When you use PWBAL, you can use the "Balance for Fewest Swaps" (Procedure 2) or the "Assembly Balance" (Procedure 3) program. The "Assembly Balance" program will result in a new sequence of the fan blades. Subtask 72-11-03-710-052-A ** ON A/C NOT FOR ALL
A. Procedures
(1) Procedure 1 - Individual blade replacement without the use of PWBAL:
(a) Use this procedure when you will replace only one fan blade. This procedure lets you replace a fan blade if the RAD and TAN moment weights of the new blade are equivalent to that of the old blade. If the Root Sum Squared (RSS) value (refer to Step 4.B.(2)) is 10 oz-in (7200 g-mm) or less, the use of PWBAL is not necessary. To make sure of configuration accuracy for fan blade changes done at a later time, the PWBAL data file must be updated with fan blade change information. If a single blade replacement with an RSS value of 10 oz-in (7200 g-mm) or less is not available, do Step 4.A.(2).
(2) Procedure 2 - Fan blade replacement (six blades or less). Use PWBAL "Balance for Fewest Swaps" option:
(a) Use this procedure to interchange minimal fan blades. When you use this procedure, some fan blades can change location (more than just the replacement fan blades) to get a rotor unbalance of less than 40 oz-in (28803 g-mm).
(b) When you use this procedure, PWBAL gives you a fan blade sequence chart which has symbols to show how to move the fan blades to the new locations.
(d) If the PWBAL results show the unbalance after fan blade replacements that is more than 15 oz-in (10801 g-mm) and not more than 21 oz-in (15121 g-mm), add counterweight P/N 51A597-01CL1 180 degrees from the heavy angle (identified by PWBAL as Static Angle) to balance the fan in 10 oz-in (7200 g-mm) before the fan trim balance.
(e) If the PWBAL results show the unbalance after fan blade replacements that is more than 21 oz-in (15121 g-mm), try to select a blade that gives a lower RSS value. Refer to Step 4.B.(2) or go to Step 4.A.(3).
(3) Procedure 3 - Fan blade replacement (seven blades or more) or when PWBAL "Balance for Fewest Swaps" cannot result in a permitted unbalance solution.
(a) Use this procedure if a new fan blade sequence is necessary to get the lowest quantity of rotor unbalance (frequently less than 5 oz-in (3600 g-mm)). When you use this procedure, all the fan blades can change location. This procedure uses the "Assembly Balance" option in the PWBAL program.
(c) If the PWBAL results show the unbalance after fan blade replacements that is more than 10 oz-in (7200 g-mm), the installation of counterweights to balance the fan in 10 oz-in (7200 g-mm) is necessary before the fan trim balance. The counterweight is to be added to the fan hub opposite the heavy angle identified by PWBAL. Refer to Step 4.B.(4)(d) for counterweight instructions.
Subtask 72-11-03-710-053-A ** ON A/C NOT FOR ALL (1) Procedure 1 - Individual blade replacement without the use of PWBAL:
(a) Use this procedure when you will replace only one fan blade. This procedure lets you replace a fan blade if the RAD and TAN moment weights of the new blade are equivalent to that of the old blade. If the Root Sum Squared (RSS) value (refer to Step 4.B.(2)) is 10 oz-in (7200 g-mm) or less, the use of PWBAL is not necessary. To make sure of configuration accuracy for fan blade changes done at a later time, the PWBAL data file must be updated with fan blade change information. If a single blade replacement with an RSS value of 10 oz-in (7200 g-mm) or less is not available, do Step 4.A.(2).
(2) Procedure 2 - Fan blade replacement (six blades or less). Use PWBAL "Balance for Fewest Swaps" option:
(a) Use this procedure to interchange minimal fan blades. When you use this procedure, some fan blades can change location (more than just the replacement fan blades) to get a rotor unbalance of less than 40 oz-in (28803 g-mm).
(b) When you use this procedure, PWBAL gives you a fan blade sequence chart which has symbols to show how to move the fan blades to the new locations.
NOTE: Do not remove the existing fan balance counterweights when using the "Balance for Fewest Swap". The existing fan balance counterweights are usually only required to be removed when the "Assembly Balance" option is used.
(c) If the PWBAL results show the unbalance after fan blade replacements that is more than 10 oz-in (7200 g-mm) and not more than 15 oz-in (10801 g-mm), add counterweight P/N 51A592-01CL3 180 degrees from the heavy angle (identified by PWBAL as Static Angle) to balance the fan in 10 oz-in (7200 g-mm) before the fan trim balance. (d) If the PWBAL results show the unbalance after fan blade replacements that is more than 15 oz-in (10801 g-mm) and not more than 21 oz-in (15121 g-mm), add counterweight P/N 51A597-01CL1 180 degrees from the heavy angle (identified by PWBAL as Static Angle) to balance the fan in 10 oz-in (7200 g-mm) before the fan trim balance.
(e) If the PWBAL results show the unbalance after fan blade replacements that is more than 21 oz-in (15121 g-mm), try to select a blade that gives a lower RSS value. Refer to Step 4.B.(2) or go to Step 4.A.(3).
(3) Procedure 3 - Fan blade replacement (seven blades or more) or when PWBAL "Balance for Fewest Swaps" cannot result in a permitted unbalance solution.
(a) Use this procedure if a new fan blade sequence is necessary to get the lowest quantity of rotor unbalance (frequently less than 5 oz-in (3600 g-mm)). When you use this procedure, all the fan blades can change location. This procedure uses the "Assembly Balance" option in the PWBAL program.
CAUTION:
DO NOT REMOVE COUNTERWEIGHTS WHICH HAVE THE "HUB" INDICATION. IF YOU DO, YOU CAN CAUSE INCREASED FAN VIBRATIONS.
(b) When you use this procedure, PWBAL gives you a fan blade sequence chart which shows how to sequence all 20 fan blades. When using the PWBAL "Assembly Balance" option, you must remove all trim balance clip-on spring counterweights and riveted counterweights marked with "FAN" or "TB" that were installed before this procedure. Before you save the PWBAL sequence, make sure that the blade numbers are indexed again to agree with the slot numbers to prevent errors during the blade set installation. A trim balance is necessary after all the PWBAL assembly balance procedures and/or fan blade replacements. (c) If the PWBAL results show the unbalance after fan blade replacements that is more than 10 oz-in (7200 g-mm), the installation of counterweights to balance the fan in 10 oz-in (7200 g-mm) is necessary before the fan trim balance. The counterweight is to be added to the fan hub opposite the heavy angle identified by PWBAL. Refer to Step 4.B.(4)(d) for counterweight instructions.
B. Prepare the Fan Blades
(1) Fan blade selection - It is recommended to select a replacement fan blade with the equivalent moment weight to minimize fan unbalance during the post the fan blade replacement trim balance procedure.
(2) Use the RSS calculation (Root Sum Squared of radial and tangential moment weight deltas) that follows to select the replacement fan blade with almost the same or equivalent moment weights. The calculation uses the RAD and TAN moment weights from each blade. The AX moment weight is not used in this calculation:
(3) PWBAL procedure:
(a) Follow the requirements of the applicable PWBAL option listed in step 4.A.
(b) Print the PWBAL sequence.
(4) Replace or reposition the fan blades as necessary, refer to PWA 101032 PWBAL sequence:
(a) Remove the fan blades to be replaced or repositioned (Ref. AMM TASK 72-11-03-000-801).
(b) Store the removed fan blades in the PWA211565 CONTAINER, SHIPPING or equivalent safe storage container/area.
(c) Install the necessary blades defined in the PWBAL sequence (Ref. AMM TASK 72-11-03-400-801).
(d) If necessary, after step 4.A.(2) and the PWBAL sequence, install counterweights to the ten tabs of the fan hub as follows:
2 Release the pin and the spring to engage the end of the pin through the hole of the tab.
3 Pull each counterweight (1) and (2) body inward to make sure the pin is engaged correctly.
5. Close-up(1) Fan blade selection - It is recommended to select a replacement fan blade with the equivalent moment weight to minimize fan unbalance during the post the fan blade replacement trim balance procedure.
(2) Use the RSS calculation (Root Sum Squared of radial and tangential moment weight deltas) that follows to select the replacement fan blade with almost the same or equivalent moment weights. The calculation uses the RAD and TAN moment weights from each blade. The AX moment weight is not used in this calculation:
NOTE: RAD1 and TAN1 are moment weights from the damaged fan blade that must be removed.
NOTE: RAD2 and TAN2 are moment weights from the blade that will possibly replace the damaged blade.
NOTE: RSS = [(RAD2-RAD1)squared + (TAN2-TAN1)squared]square root.
(a) It is necessary to select the replacement blade that results in the lowest RSS value. (3) PWBAL procedure:
(a) Follow the requirements of the applicable PWBAL option listed in step 4.A.
(b) Print the PWBAL sequence.
(4) Replace or reposition the fan blades as necessary, refer to PWA 101032 PWBAL sequence:
(a) Remove the fan blades to be replaced or repositioned (Ref. AMM TASK 72-11-03-000-801).
(b) Store the removed fan blades in the PWA211565 CONTAINER, SHIPPING or equivalent safe storage container/area.
(c) Install the necessary blades defined in the PWBAL sequence (Ref. AMM TASK 72-11-03-400-801).
(d) If necessary, after step 4.A.(2) and the PWBAL sequence, install counterweights to the ten tabs of the fan hub as follows:
NOTE: Clip-on counterweights are installed on the tab outer holes only.
NOTE: Rivet counterweights are installed on the tab center holes only.
1 Push out the pin and the spring on the front side of the counterweights (1) and (2) and install on the balance flange tab. 2 Release the pin and the spring to engage the end of the pin through the hole of the tab.
3 Pull each counterweight (1) and (2) body inward to make sure the pin is engaged correctly.
Subtask 72-11-03-420-052-A ** ON A/C NOT FOR ALL Subtask 72-11-03-860-057-A ** ON A/C NOT FOR ALL
B. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Remove the warning notice installed in Prevent Engine Motoring.
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Remove the warning notice installed in Prevent Engine Motoring.