Detailed Visual Inspection (DVI) of the Buffer Air Heat Exchanger [PW11]

TASK 75-26-01-200-801-A
Detailed Visual Inspection (DVI) of the Buffer Air Heat Exchanger

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.

1. Reason for the Job
A. Use this procedure to do a Detailed Visual Inspection (DVI) of the buffer air heat exchanger. If you see damage, this procedure will reference you to a more DVI for limits and dispositions.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 1M(3 FT)
No specific	1	FLASHLIGHT

B. Work Zones and Access Panels

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

C. Referenced Information

REFERENCE	DESIGNATION
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 72-21-08-000-801-A	Removal of the Fan Exit Liner Segments
TASK 75-26-01-000-801-A	Removal of the Buffer Air Heat Exchanger
TASK 75-26-01-400-801-A	Installation of the Buffer Air Heat Exchanger
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
Detailed Visual Inspection (DVI) of the Buffer Air Heat Exchanger

3. Job Set-up
Subtask 75-26-01-941-052-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 75-26-01-010-054-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

Subtask 75-26-01-040-052-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 75-26-01-010-055-A ** ON A/C NOT FOR ALL

D. Get Access
(1) Open the left thrust reverser cowl-doors (Ref. AMM TASK 78-36-00-010-802):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
451AL
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
461AL
(2) Put an ACCESS PLATFORM 1M(3 FT) in position.

4. Procedure
Subtask 75-26-01-210-050-A ** ON A/C NOT FOR ALL

A. Detailed Visual Inspection (DVI) of the Buffer Air Heat Exchanger
(1) Do a detailed visual inspection of the buffer air heat exchanger as follows:
(a) Remove the fan exit liner segment at the 12 o'clock position (Ref. AMM TASK 72-21-08-000-801).
(b) Perform a visual inspection of the buffer air heat exchanger with a FLASHLIGHT for cracks and damage. Pay special attention to the areas around the tube bosses and inlet areas.
1 Table 1 Buffer Air Heat Exchanger - Inspection Criteria

EXAMINE	DAMAGE	DISPOSITION
Cracks	Any amount	Not permitted. Replace the buffer air heat exchanger (Ref. AMM TASK 75-26-01-000-801) and (Ref. AMM TASK 75-26-01-400-801).
Round bottom dents	A maximum of 0.050 in. (1.27 mm) depth	Permitted
	More than 0.050 in. (1.27 mm) depth	Not permitted. Replace the buffer air heat exchanger (Ref. AMM TASK 75-26-01-000-801) and (Ref. AMM TASK 75-26-01-400-801).
Nicks, gouges or scratches	A maximum of 0.030 in. (0.76 mm) depth	Permitted
	More than 0.030 in. (0.76 mm) depth	Not permitted. Replace the buffer air heat exchanger (Ref. AMM TASK 75-26-01-000-801) and (Ref. AMM TASK 75-26-01-400-801).
Pitting and corrosion	A maximum of 0.020 in. (0.51 mm) depth	Permitted
	More than 0.020 in. (0.51 mm) depth	Not permitted. Replace the buffer air heat exchanger (Ref. AMM TASK 75-26-01-000-801) and (Ref. AMM TASK 75-26-01-400-801).

5. Close-up
Subtask 75-26-01-410-052-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
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
461AL

Subtask 75-26-01-440-051-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 75-26-01-410-053-A ** ON A/C NOT FOR ALL

C. Close Access
(1) 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
(2) Remove the access platform(s).
(3) Remove the WARNING NOTICE(S).

[Rev.10 from 2021] 2026.04.01 03:13:14 UTC