Chase Thread Repair of Borescope Boss on the Outer Diffuser Case Assembly [PW11]

TASK 72-41-01-300-802-A
Chase Thread Repair of Borescope Boss on the Outer Diffuser Case Assembly

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.

ZONE: 400

1. Reason for the Job
Use this procedure to chase the damaged borescope boss threads on the outer diffuser case assembly.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE
No specific	1	VACUUM CLEANER
PWA26657	1	TAP CHASING DIFFUSER CASE SPARK IGNITER THREAD

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
400	POWER PLANT, NACELLES AND PYLONS
FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
437AL, 438AR, 451AL, 452AR
FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
447AL, 448AR, 461AL, 462AR

C. Referenced Information

REFERENCE	DESIGNATION
TASK 70-27-00-910-804-A	SPOP 208 - Degreasing of Parts by Solvent Wiping
TASK 71-00-00-860-833-A	Procedure to Prevent Engine Motoring
TASK 71-13-00-010-802-A	Opening of the Fan Cowl Doors
TASK 71-13-00-410-802-A	Closing of the Fan Cowl Doors
TASK 72-00-00-000-804-A	Removal of the Borescope Plugs
TASK 72-00-00-400-804-A	Installation of the Borescope Plugs
TASK 78-30-00-040-805-A	Deactivation of the Thrust Reverser System for Ground Maintenance
TASK 78-30-00-440-805-A	Reactivation of the Thrust Reverser System after Ground Maintenance
TASK 78-36-00-010-802-A	Opening of the Thrust Reverser Cowl-Doors
TASK 78-36-00-410-802-A	Closing of the Thrust Reverser Cowl-Doors
Chase Thread Repair of Borescope Boss on the Outer Diffuser Case Assembly

3. Job Set-up
Subtask 72-41-01-941-055-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 72-41-01-010-060-A ** ON A/C NOT FOR ALL

B. Get Access
(1) Open the fan cowl doors (Ref. AMM TASK 71-13-00-010-802):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
437AL, 438AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
447AL, 448AR.
(2) Put an ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE in position.

Subtask 72-41-01-040-055-A ** ON A/C NOT FOR ALL

C. Deactivation of the Thrust Reverser for Maintenance

WARNING: YOU MUST DEACTIVATE THE THRUST REVERSER BEFORE YOU DO WORK ON OR AROUND IT. IF YOU DO NOT, THE THRUST REVERSER CAN OPERATE ACCIDENTALLY AND CAUSE AN INJURY AND/OR DAMAGE.

(1) Do the deactivation of the thrust reverser system for maintenance (Ref. AMM TASK 78-30-00-040-805).

Subtask 72-41-01-010-061-A ** ON A/C NOT FOR ALL

D. Get Access
(1) Open the thrust reverser cowl-doors (Ref. AMM TASK 78-36-00-010-802):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
451AL, 452AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
461AL, 462AR.

4. Procedure

CAUTION: WIPE CLEAN ALL PARTS AND TOOLS AS NECESSARY TO REMOVE UNWANTED DEBRIS AND PREVENT DAMAGE TO THE ENGINE.

Subtask 72-41-01-350-051-A ** ON A/C NOT FOR ALL

A. Chase Thread Repair of Borescope Boss on the Outer Diffuser Case Assembly

NOTE: Minor thread damage can be repaired by chasing threads. If threads cannot be repaired by chasing, the part cannot be repaired by this procedure. A VACUUM CLEANER must be used to keep debris out the engine during thread chasing.

(1) Remove the borescope plugs (Ref. AMM TASK 72-00-00-000-804).
(2) Chase the borescope boss threads at location K with the PWA26657 TAP CHASING DIFFUSER CASE SPARK IGNITER THREAD or a thread cutting tap (0.375-24 UNJF-3B). See the sheets 1 and 2 of the figure:

Chase Thread Repair of Borescope Boss on the Outer Diffuser Case Assembly ** ON A/C NOT FOR ALL

(3) Chase the borescope boss threads at locations J and L with a PWA26657 TAP CHASING DIFFUSER CASE SPARK IGNITER THREAD or a thread cutting tap (0.375-24 UNJF-3B). See the sheets 1, 3 and 4 of the figure:

Chase Thread Repair of Borescope Boss on the Outer Diffuser Case Assembly ** ON A/C NOT FOR ALL

(4) Clean the repaired areas by SPOP 208 (Ref. AMM TASK 70-27-00-910-804).
(5) Do an inspection of the threads with a certified go/no go thread gage. If a thread hole fails the gage inspection, the part cannot be repaired with this procedure.
(6) Install the borescope plugs (Ref. AMM TASK 72-00-00-400-804).
(7) Examine the assembly for foreign objects, damage and correct assembly.

5. Close-up
Subtask 72-41-01-410-060-A ** ON A/C NOT FOR ALL

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the thrust reverser cowl-doors (Ref. AMM TASK 78-36-00-410-802):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
451AL, 452AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
461AL, 462AR.

Subtask 72-41-01-440-055-A ** ON A/C NOT FOR ALL

B. Do the reactivation of the thrust reverser system after maintenance (Ref. AMM TASK 78-30-00-440-805).

Subtask 72-41-01-410-061-A ** ON A/C NOT FOR ALL

C. Close Access
(1) Remove the access platform(s).
(2) Close the fan cowl doors (Ref. AMM TASK 71-13-00-410-802):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
437AL, 438AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
447AL, 448AR.
(3) Remove the WARNING NOTICE(S).

[Rev.10 from 2021] 2026.04.01 02:49:35 UTC