Borescope Inspection of the Low Pressure Turbine (LPT) Blades [CFML]

TASK 72-00-00-290-822-A
Borescope Inspection of the Low Pressure Turbine (LPT) Blades

WARNING: BE CAREFUL WHEN YOU DO WORK ON THE ENGINE PARTS AFTER THE ENGINE SHUTDOWN. USE APPLICABLE THERMAL GLOVES. THE ENGINE PARTS CAN STAY HOT FOR ONE HOUR AFTER SHUTDOWN AND CAN BURN YOU.

WARNING: BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS.

ZONE: 210
ZONE: 400

1. Reason for the Job
This procedure gives the criteria for the borescope inspection of the Low Pressure Turbine (LPT) blades.

NOTE: You can use equivalent alternatives for standard tools, equipment and consumable materials.

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	AR	WARNING NOTICE(S)
No specific	Torque wrench: range to between 55 and 50 lbf.in (0.62 and 0.57 m.daN )

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.CP2619)	Never Seez-Pure Nickel, Special

C. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
210	CKPT,FWD COMPT BHD TO FLT COMPT BULKHEAD
400	POWER PLANT, NACELLES AND PYLONS
FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENGINE 1)
437AL, 438AR, 451AL, 452AR
FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENGINE 2)
447AL, 448AR, 461AL, 462AR

D. Referenced Information

REFERENCE	DESIGNATION
TASK 71-13-00-010-803-A	Opening of the Fan Cowl Doors
TASK 71-13-00-410-803-A	Closing of the Fan Cowl Doors
TASK 72-00-00-220-803-A	Check of the Axial Preload of the Low Pressure Turbine (LPT) Stage 7 Blades
TASK 72-00-00-290-812-A	Engine Borescope Examination Preparation
TASK 72-00-00-290-822-A	Borescope Inspection of the Low Pressure Turbine (LPT) Blades
TASK 72-58-00-300-801-A	Leading and Trailing Edges Low Pressure Turbine (LPT) Blades Boro-Blending (Stage 3 to 7)
TASK 78-30-00-040-809-A	Deactivation of the Thrust Reverser System for Ground Maintenance
TASK 78-30-00-440-809-A	Reactivation of the Thrust Reverser System after Ground Maintenance
TASK 78-36-00-010-806-A	Opening of the Thrust Reverser Cowl Doors
TASK 78-36-00-410-806-A	Closing of the Thrust Reverser Cowl Doors
Visual Inspection of Low Pressure Turbine (LPT) Blade Areas
Visual Inspection of Blade Root Platform
Visual Inspection of Tip Shroud
Visual Inspection of Seal Teeth
Low Pressure Turbine (LPT) Blade
Visual Inspection of the Retainer Ring Stage

3. Job Set-up
Subtask 72-00-00-941-249-A

A. Safety Precautions
(1) On the center pedestal, on ENG panel 115VU:
(a) Make sure that the ENG/MODE selector switch is in the NORM position.
(b) Make sure that the ENG/MASTER 1(2) control switch was in the OFF position not less than five minutes before you do this procedure.
(c) Put the WARNING NOTICE(S) in position to tell persons not to operate:

The ENG/MODE selector switch
The ENG/MASTER 1(2) control switch.

(2) On the ENG section of maintenance panel 50VU:
(a) Make sure that the ON legend of the FADEC GND PWR/1(2) pushbutton switch is off.
(b) Put the WARNING NOTICE(S) in position to tell persons not to energize FADEC 1(2).

Subtask 72-00-00-010-339-A

B. Get Access
(1) Open the fan cowl doors (Ref. AMM TASK 71-13-00-010-803):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENGINE 1)
437AL, 438AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENGINE 2)
447AL, 448AR.
(2) Put the ACCESS PLATFORM 1M(3 FT) in position.

Subtask 72-00-00-040-163-A

C. Deactivation of the Thrust Reverser System 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 ground maintenance (Ref. AMM TASK 78-30-00-040-809).

Subtask 72-00-00-010-340-A

D. Get Access
(1) Open the thrust reverser cowl-doors (Ref. AMM TASK 78-36-00-010-806):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENGINE 1)
451AL, 452AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENGINE 2)
461AL, 462AR.

4. Procedure
Subtask 72-00-00-010-353-A

A. Removal of the Borescope Plugs
(1) Remove the borescope plugs (Ref. AMM TASK 72-00-00-290-812).

Subtask 72-00-00-480-089-A

B. Assemble the Borescope Inspection Tools
(1) Assemble the borescope inspection tools (Ref. AMM TASK 72-00-00-290-812).

Subtask 72-00-00-290-144-A

C. Visual Inspection of the LPT Stage 1 to 7 Blades

NOTE: For LPT stages 3 to 7 blades boro-blending repair and associated serviceable limits (Ref. AMM TASK 72-58-00-300-801).

INSPECT/CHECK	MAXIMUM SERVICEABLE LIMITS	REMARKS
1.Visual inspection of all the areas: Visual Inspection of Low Pressure Turbine (LPT) Blade Areas
A.Temperature discoloration of the airfoil	All blades: Any amount.
B.Distortion	All blades: Not serviceable.
C.Corrosion	Blades 1 (1), 2 (2), 3 (3), 4 (4), 5 (5) and 6 (6): Any amount acceptable for 3200 cycles if no missing material Blade 7 (7): Not Serviceable.	NOTE: This continue-in-service limit is a repeat inspection.
D.Peeling of particles	Blades 1 (1), 2 (2), 3 (3), 4 (4), 5 (5), 6 (6) and 7 (7): Any amount in the airfoil, blade root platform and tip shroud platform, if the airfoils are not bowed or melted. NOTE: Not to be confused with metal deposit.
E.Metal deposit	Blades 1 (1), 2 (2), 3 (3), 4 (4), 5 (5), 6 (6) and 7 (7): Any amount with a maximum size/dimension of 0.047 in. (1.19 mm).
2.Visual inspection of the airfoil leading edge:
A.Cracks	All blades: Not serviceable.	For airfoil blend limits (Ref. AMM TASK 72-58-00-300-801).
B.Nick, dents	Blade 1 (1): Any number if not more than 0.0098 in. (0.25 mm) in depth in areas A and D. Blade 2 (2): Any number if not more than 0.015 in. (0.38 mm) in depth in area A Any number if not more than 0.0098 in. (0.25 mm) in depth in area D. Blades 3 (3), 4 (4), 5 (5) and 6 (6): Any number if not more than 0.015 in. (0.38 mm) in depth in area A Not serviceable in area D. Blade 7 (7): Any number if not more than 0.02 in. (0.51 mm) in depth in area A Any number if not more than 0.015 in. (0.38 mm) in depth in area D Any number if not more than 0.0118 in. (0.30 mm) in depth in area E.	For airfoil blend limits (Ref. AMM TASK 72-58-00-300-801). Blades 1 to 6: The continue-in-service limit of 5 cycles is permitted with the criteria: Any amount of nicks and/or dents is allowed provided there is no missing material or cracks in areas A and D. Blade 7: The continue-in-service limit of 100 cycles is permitted with the criteria: Not more than 0.0394 in. (1 mm) in depth of nicks and/or dents is allowed provided there is no missing material or cracks in area E Not more than 0.0787 in. (2 mm) in depth of nicks and/or dents is allowed provided there is no missing material or cracks in areas A and D.
3.Visual inspection of the airfoil trailing edge:
A.Cracks	All blades: Not serviceable.	For airfoil blend limits (Ref. AMM TASK 72-58-00-300-801).
B.Nicks, dents	Blade 1 (1): Any number if not more than 0.015 in. (0.38 mm) in depth in area C Any number if not more than 0.0098 in. (0.25 mm) in depth in area F. Blades 2 (2), 3 (3), 4 (4), 5 (5) and 6 (6): Any number if not more than 0.015 in. (0.38 mm) in depth in area C. Blade 7 (7): Any number if not more than 0.015 in. (0.38 mm) in depth in areas C and J Any number if not more than 0.0118 in. (0.30 mm) in depth in area G.	For airfoil blend limits (Ref. AMM TASK 72-58-00-300-801). Blade 1: The continue-in-service limit of 5 cycles is permitted with the criteria: Any amount of nicks and/or dents is allowed provided there is no missing material or cracks in areas C and F. Blades 2 to 6: The continue-in-service limit of 5 cycles is permitted with the criteria: Any amount of nicks and/or dents is allowed provided there is no missing material or cracks in area C.
C.Bent
	LPT blades stage 1:	Smooth, no sharp edges.
	Any number if not more than 0.15 mm (0.01 in.) in depth with L/D > 20 in areas C and F.	Any number of blades.
	LPT blades stage 2:	Smooth, no sharp edges.
	Any number if not more than 0.25 mm (0.01 in.) in depth with L/D > 20 in area C.	Any number of blades.
	LPT blades stages 3 to 6:	Smooth, no sharp edges.
	Max 0.15 mm (0.01 in.) in depth with L/D > 20 in area C.	Any number of blades.
	Max 1.20 mm (0.05 in.) in depth with L/D > 4 in area C.	No more than 5 blades per stage, one bent max per blade.
D.Rub mark from LPT stage 3 nozzles in the middle of trailing edge (area C)	Blade 2 (2): Not serviceable.	Blade 2 (2): The continue-in-service limit of 1300 cycles is permitted with the criteria: If no more than 0.0008 in. (0.02 mm) length and provided there is no missing material or cracks.
4.Visual inspection of the concave and convex airfoil surfaces:
A.Cracks	All blades: Not serviceable.
B.Nicks, dents	Blades 1 (1) and 2 (2): Any number if not more than 0.0098 in. (0.25 mm) in depth in area B Not serviceable in area E. Blades 3 (3), 4 (4), 5 (5) and 6 (6): Any number if not more than 0.0098 in. (0.25 mm) in depth in area B. Blade 7 (7): Any number if not more than 0.015 in. (0.38 mm) in depth in areas B and H Any number if not more than 0.0118 in. (0.30 mm) in depth in area F.	Blades 4 to 6: The continue-in-service limit of 5 cycles is permitted with the criteria: Any amount of nicks and/or dents is allowed provided there is no missing material or cracks in area B.
C.Negative casting line on an airfoil	Blades 5 (5) and 6 (6): Serviceable up to 0.0019 in. (0.05 mm) depth, length any amount.
D.Polish aspect	Blades 3 (3), 4 (4), 5 (5) and 6 (6): Any amount.
5.Visual inspection of leading edge (area E) borescope inspection of the LPT stage 7 blades:
A.Wear	Blade 7 (7): Any number if not more than 0.0118 in. (0.30 mm) in depth in area E provided there is no cracks.
6.Visual inspection of the blade root platform: Visual Inspection of Blade Root Platform
A.Cracks	All blades: Not serviceable.
B.Rub marks on platform side faces	Blade 1 (1): Any amount if not more than 0.004 in. (0.10 mm) in depth in area S. Blade 2 (2): Any amount if not more than 0.004 in. (0.10 mm) in depth in area T. Blades 3 (3) and 6 (6): Any amount if not more than 0.004 in. (0.10 mm) in depth in area K. Blades 4 (4) and 5 (5): Any amount if not more than 0.016 in. (0.41 mm) in depth in area K.
C.Out-of-flush	Blades 1 (1), 2 (2), 3 (3), 4 (4), 6 (6) and 7 (7): Not more than 0.03902 in. (0.99 mm). Blade 5 (5): Not more than 0.02720 in. (0.69 mm).
D.Gaps between two platforms	All blades: Any amount if no wear evidence.
E.Corrosion, pitting	LPT blades stages 1 and 2: Any amount if no missing material.
7.Visual inspection of the tip shroud: Visual Inspection of Tip Shroud
A.Cracks	All blades: Not serviceable.
B.Interlock gap	PRE SB 72-0412 Blade 1 (1): Permitted if no wear is detectable on hard face at the interlock loss. Perform a 360 degree borescope inspection of the LPT stage 1 retainer ring. Visual Inspection of Tip Shroud Visual Inspection of the Retainer Ring Stage END PRE SB 72-0412 POST SB 72-0412 Blade 1 (1): Not serviceable. END POST SB 72-0412 Blades 2 (2): Permitted if: Gaps between two forward tip shrouds (leading edge side) is less than 0.108 in. (2.74 mm) No more than 7 interlock gaps No consecutive interlock gaps No wear is detectable on hard face at the interlock loss. Blades 3 (3) to 6 (6): Not serviceable. Blade 7 (7): (Ref. AMM TASK 72-00-00-220-803).
C.Gaps between two tip shrouds	Blades 1 (1) to 7 (7): Any amount if interlock gap serviceable.
D.Wear in interlocks	All blades: Any amount if: Visual Inspection of Tip Shroud Interlock gap serviceable.
E.Shingled, unlatched	All blades: Not serviceable.
F.Out-of-flush	Blades 1 (1), 2 (2), 3 (3), 4 (4) and 6 (6): Serviceable if not more than 0.05083 in. (1.29 mm). Blades 5 (5) and 7 (7): Serviceable if not more than 0.03902 in. (0.99 mm).
G.Polish aspect	Blades 5 (5) and 6 (6): Any amount in area Y.
8.Visual inspection of the seal teeth: Visual Inspection of Seal Teeth
A.Radial cracks	All blades: Not serviceable.
B.Flaking on the hardened seal teeth	All blades: Any amount.

INSPECT/CHECK	MAXIMUM SERVICEABLE LIMITS	REMARKS
1.360 degree visual inspection of the stage 1 retainer ring (only for PRE SB 72-0412): Visual Inspection of the Retainer Ring Stage
A.Cracks Visual Inspection of the Retainer Ring Stage	Findings	LEAP-1A23, -1A24, -1A24E1, -1A26, -1A26E1	LEAP-1A26CJ, -1A29, -1A29CJ, -1A30, -1A32, -1A33, -1A33B2, -1A35A	When the engine rating is changed contact CFM for disposition.
0 crack	1600 FC	1600 FC
1 crack	800 FC if the number of blade hooks between cracks is equal or more than 5 and the maximum crack width is less than half a blade slot.	500 FC if the number of blade hooks between cracks is equal or more than 5 and the maximum crack width is less than half a blade slot.
2 cracks	600 FC if the number of blade hooks between cracks is equal or more than 5 and the maximum crack width is less than half a blade slot.	A continue-in-service limit of 150 FC is permitted before CFM disposition if the number of blade hooks between cracks is equal or more than 5 and the maximum crack width is less than half a blade slot. Please provide to CFM: Number of cracks, number of blade hooks between cracks, engine rating (for quicker and accurate recommendation pictures are welcome).
3-9 cracks	400 FC if the number of blade hooks between cracks is equal or more than 5 and the maximum crack width is less than half a blade slot.	A continue-in-service limit of 100 FC is permitted before CFM disposition if the number of blade hooks between cracks is equal or more than 5 and the maximum crack width is less than half a blade slot. Please provide to CFM: Number of cracks, number of blade hooks between cracks, engine rating (for quicker and accurate recommendation pictures are welcome).
≥10 cracks	A continue-in-service limit of 50 FC is permitted before CFM disposition. Please provide to CFM: Number of cracks, number of blade hooks between cracks, engine rating (for quicker and accurate recommendation pictures are welcome).
Number of blade hooks between cracks ≤ 1	A continue-in-service limit of 10 FC is permitted before CFM disposition. Please provide to CFM: Number of cracks, number of blade hooks between cracks, engine rating (for quicker and accurate recommendation pictures are welcome).
1 < Number of blade hooks between cracks < 5	A continue-in-service limit of 50 FC is permitted before CFM disposition. Please provide to CFM: Number of cracks, number of blade hooks between cracks, engine rating (for quicker and accurate recommendation pictures are welcome).
Maximum crack width > 1/2 blade slot	A continue-in-service limit of 50 FC is permitted before CFM disposition. Please provide to CFM: Number of cracks, number of blade hooks between cracks, engine rating (for quicker and accurate recommendation pictures are welcome).
B.Anti-rotation pin bent Visual Inspection of the Retainer Ring Stage	A 500-cycles inspection interval is permitted if the anti-rotation pin is bent less than 18 percent (0.08 in. (2.03 mm)). Visual Inspection of the Retainer Ring Stage A 50 cycles inspection interval is permitted if the anti-rotation pin is bent more than 18 percent (0.08 in. (2.03 mm)).
C.Anti-rotation pin missing (only for PRE SB 72-0176) Visual Inspection of the Retainer Ring Stage	Findings	Disposition for all Ratings
Bent length ≤ 25%	500 FC
Bent length ≤ 50%	250 FC
Bent length > 50%	Inspect every 50 FC until anti-rotation pin liberation, then do an inspection of the LPT stage 1 to stage 7 blades. If the LPT flow path is serviceable per (Ref. AMM TASK 72-00-00-290-822) re-apply SB LEAP-1A-72-00-0151-01A-930A-D within 1600 FC.
Anti-rotation pin missing	Do an inspection of the LPT stage 1 to stage 7 blades. If the LPT flow path is serviceable per (Ref. AMM TASK 72-00-00-290-822) re-apply SB LEAP-1A-72-00-0151-01A-930A-D within 1600 FC.
LPT blade hook missing	Maximum one blade hook missing Do an inspection of the LPT stage 1 to stage 7 blades. If the LPT flow path is serviceable per (Ref. AMM TASK 72-00-00-290-822) re-apply SB LEAP-1A-72-00-0151-01A-930A-D within 1600 FC.
D.LPT stage 1 blade hook missing	One blade hook missing maximum permitted. Do an inspection of the LPT flow path (LPT stage 1-7 blades). If the LPT flow path is serviceable as per this AMM task, re-inspect within 1600 cycles.
E.Other findings	Not serviceable.	A continue-in-service limit of 10 cycles is permitted before CFM disposition except if the junction opening of the retainer ring is greater than one blade slot.

Subtask 72-00-00-080-080-A

D. Removal of the Borescope

CAUTION: BEFORE YOU CONTINUE THE WORK, MAKE SURE THAT ALL BORESCOPE TOOLS ARE REMOVED. IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE ENGINE CAN OCCUR.

(1) Remove all borescope tools.

Subtask 72-00-00-410-305-A

E. Installation of the Borescope Plugs

CAUTION: WHEN YOU INSTALL THE BORESCOPE PLUGS, MAKE SURE THAT:

THE LOCKING FEATURE IS IN ONE OF THE TWO GROOVES ON THE BORESCOPE BOSS, AND
THERE IS NO GAP BETWEEN THE BORESCOPE BOSS AND PLUGS IN THE END.

IF YOU DO NOT OBEY THESE CONDITIONS, THE BORESCOPE PLUGS WILL NOT BE CORRECTLY INSTALLED.

(1) Apply CP2619Never Seez-Pure Nickel, Special to the threads of the borescope plugs and install on the LPT case.
(2) TORQUE plugs to between 55 and 50 lbf.in (0.62 and 0.57 m.daN )

5. Close-up
Subtask 72-00-00-410-295-A

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 78-36-00-410-806):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENGINE 1)
451AL, 452AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENGINE 2)
461AL, 462AR.

Subtask 72-00-00-440-155-A

B. Do the reactivation of the thrust reverser system after ground maintenance (Ref. AMM TASK 78-30-00-440-809).

Subtask 72-00-00-410-296-A

C. Close Access
(1) Close the fan cowl doors (Ref. AMM TASK 71-13-00-410-803):
(a) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENGINE 1)
437AL, 438AR.
(b) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENGINE 2)
447AL, 448AR.
(2) Remove the access platform(s).
(3) Remove the WARNING NOTICE(S).

[Rev.10 from 2021] 2026.04.01 13:03:41 UTC