W DOC AIRBUS | AMM A320F

Borescope Inspection of High Pressure Turbine [CFML]

TASK 72-52-00-290-803-A
Borescope Inspection of High Pressure Turbine

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
Refer to the MPD TASK: 725000-L1
BORESCOPE INSPECTION OF HIGH PRESSURE TURBINE.
This procedure gives instructions to do the inspection of the High Pressure Turbine (HPT) blades and the visible nozzles and shrouds with a rigid borescope.
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
BORESCOPE SET
No specific
AR
WARNING NOTICE(S)
No specific
1
WRENCH - STANDARD
 B. Consumable Materials
REFERENCE
DESIGNATION
(Material No.CP2619)
Never Seez-Pure Nickel, Special
(Material No.CP2691)
penetrant
(Material No.CP2961)
tiodize T8E-H grease
 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 72-00-00-290-812-A
Engine Borescope Examination Preparation
TASK 72-00-00-290-814-A
Borescope Inspection of the Stage 1 High Pressure Turbine (HPT) Nozzle Guide Vanes
TASK 72-00-00-290-815-A
Borescope Inspection of the Stage 2 High Pressure Turbine (HPT) Nozzle Guide Vanes (NGVs)
TASK 72-00-00-820-802-A
Find the Zero Index Mark of the High Pressure Compressor (HPC) Rotor
TASK 72-00-00-820-803-A
Turning of the N2 Rotor
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
F HPT Section Nozzles, Shroud Segments and Turbine Blade
F HPT Borescope Plugs - PRE and POST SB 72-0249
F Borescope Port Data
3. Job Set-up
Subtask 72-52-00-941-058-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 72-52-00-010-064-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 72-52-00-040-057-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 maintenance (Ref. AMM TASK 78-30-00-040-809).
Subtask 72-52-00-010-065-A
D. Open the thrust reverser cowl-doors (Ref. AMM TASK 78-36-00-010-806):
   (1) FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENGINE 1)
451AL 452AR.
   (2) FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENGINE 2)
461AL 462AR.
4. Procedure
Subtask 72-52-00-290-057-A
A. Do the borescope examination preparation (Ref. AMM TASK 72-00-00-290-812).
Subtask 72-52-00-820-051-A
B. Manually or electrically motor the HPC rotor (Ref. AMM TASK 72-00-00-820-803).
Subtask 72-52-00-820-050-A
C. Do the N2 rotor find the zero index mark (Ref. AMM TASK 72-00-00-820-802).
Subtask 72-52-00-020-050-A
D. Continue preparation as follows:
   (1) Remove the borescope plugs from ports R, S and T, which are necessary for inspection:
F HPT Section Nozzles, Shroud Segments and Turbine Blade
     (a) Spray penetrant (Material No.CP2691) on the ratcheting mechanism.
     (b) Let the penetrating oil soak.
     (c) Apply break torque with the WRENCH - STANDARD to remove the borescope plug from the case.
     (d) Spray penetrant (Material No.CP2691) to lubricate the borescope plug thread if necessary.
     (e) Remove the borescope plug.
     (f) For the borescope plugs which you did not remove, do the check that follows:
       1 Do a visual check to make sure that the anti-rotation tab of the locking ring is fully engaged with one of the two slots on the borescope boss on the borescope inspection port.
       2 Make sure that the borescope plug is fully installed against the case.
       3 If you have no direct visual access to the borescope plugs, use the BORESCOPE SET to do a check of their condition.
       4 Apply hand pressure to the borescope plug in the removal direction to make sure that it is not loose.
       5 If the borescope plug is loose, tighten it to the correct torque value again.
     (g) Put an identification tag on each borescope plug.
   (2) Insert the BORESCOPE SET (dia 0.23 in. (6 mm) or smaller) into position for the inspection.
NOTE: Inspection is applicable only to what you can see with the rigid borescope.
Subtask 72-52-00-290-058-A
E. HPT Section Inspection
   (1) Table 1 identifies how many HPT blades are there in the HPT stage 1 and HPT stage 2 rotors:
COMPONENT
QUANTITY OF BLADES
Stage 1 HPT blades
60
Stage 2 HPT blades
68
   (2) Do an inspection of:
INSPECTION/CHECK
MAXIMUM SERVICEABLE LIMITS
REMARKS
1.Concave surfaces of the HPT stage 1 nozzle segment as follows:
See sheets 1 and 2 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Radial cracks that extend from the gill holes
Any amount permitted if no material is missing.

B.Other cracks, not in the gill hole rows
Any amount permitted if no material is missing.

C.Burns
Any amount permitted if no material is missing and the burns are not fully through.

D.Cracks in the fillet area adjacent to the inner and outer platforms
Any amount permitted if no material is missing.

E.The over-serviceable limit extension for the concave surfaces of the HPT stage 1 nozzle segment
A maximum of 0.175 in.2 (112.90 mm2) of missing material on each airfoil, because of cracks or burn-through, is permitted for a maximum of 25 cycles.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
2.Examine the convex surfaces of the HPT stage 1 nozzle segment as follows:
See sheets 1, 4 and 5 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Radial cracks
Any amount permitted if no material is missing.

B.Axial cracks
Any amount permitted if no material is missing.

C.Burns
Any amount permitted if no material is missing and burns are not fully through.

D.Cracks in the fillet area adjacent to the inner and outer platforms
Any amount permitted if no material is missing.

E.The over-serviceable limit extension for the convex surface of the HPT stage 1 nozzle segment
A maximum of 0.175 in.2 (112.90 mm2) of missing material on each airfoil, because of cracks or burn-through, is permitted for a maximum of 25 cycles.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
3.Examine the Trailing Edge (TE) of the HPT stage 1 nozzle segment airfoils as follows:
See sheets 1, 4 and 5 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Axial cracks that start at the slots adjacent to the TE
Any amount permitted.

B.Buckling or bowing
Any amount permitted.
C.Material that is missing
The area of missing material must not exceed 0.525 in.2 (338.71 mm2) for each airfoil.

D.The over-serviceable limit extension for TEs of the HPT stage 1 nozzle segment
A maximum area of 0.875 in.2 (564.52 mm2) of missing material on each airfoil is permitted for a maximum of 25 cycles.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
4.Examine all the areas of the HPT stage 1 nozzle segment airfoil as follows:
See sheets 1 and 2 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Craze cracks
Any amount permitted.

B.Nicks, scores, scratches and dents
Any amount permitted.

C.Metal splatter
Any amount permitted.

D.Missing thermal barrier coating
Any amount permitted.

5.Examine the inner and outer platforms of the HPT stage 1 nozzle segment as follows:
See sheets 1 and 2 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Missing thermal barrier coating
Any amount permitted.

B.Cracks in the parent material
Any amount permitted if no material is missing.

C.Nicks, scores, scratches and dents on the platform surface
Any amount permitted.

D.Burns
Any amount permitted if no material is missing and the burns are not fully through.

E.Bulges or bows
Bulges or bows are not permitted.

F.The HPT stage 1 nozzle segment inner platform spline seal protruding or missing
Any amount permitted.

G.The over-serviceable limit extension for the inner and outer platforms of the HPT stage one nozzle segment
Bulges or bows are permitted for a maximum of 25 cycles.
This over-serviceable limit extension is for a reduced interval, repeat inspection.

A maximum area of 0.070 in.2 (45.16 mm2) of missing material, on each airfoil, because of cracks or burn-through, is permitted for a maximum of 25 cycles.

6.Examine the HPT stage 1 shroud segment as follows:
See sheets 1 and 3 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade

NOTE: The inspection applies to both the shroud segment Leading Edge (LE) and the TE.
A.Blade rub
There is no limit to the amount of blade rub.

B.Cracks in shroud base material
Any amount, 0.60 in. (15.24 mm) in length maximum.

C.Cracks in flow path coating
Max serviceable limit - in the area 0.50 in. (12.70 mm) from the TE, cracks in the coating 1.50 in. (38.10 mm) in length maximum are permitted. All other areas, any amount, 0.60 in. (15.24 mm) in length maximum.

D.Missing flow path coating
In the areas 0.10 in. (2.54 mm) from the LEs and TEs, any amount of missing coating and exposed base material is permitted.


For remaining areas of the shroud segments, up to 0.250 in.2 (161.29 mm2) per shroud segment of missing coating is acceptable.


Exposed base material (where the coating is completely missing, is not permitted in these areas).
Refer to H. Over serviceable limit extension for missing coating.
E.Chipping of the shroud segment base material along the LE
It is permissible to have up to two instances per shroud segment, max. Major dimension is to be less than 0.050 in. (1.27 mm).

F.Chipping of the shroud segment base material along the circumferential split line
Up to 1.0 in. (25.4 mm) axial length is permitted on up to 10 shroud segments, each end.

G.Missing spline seals
Up to 18 missing or partially missing discourager spline seals and up to 10 missing or partially missing primary spline seal for each engine is permitted.

H.The over-serviceable limit extension for missing coating on the shroud flow path surface
PRE SB LEAP-1A-72-00-0119-01A-930A-D

Check the engine data plate for thrust rating 1A23, 1A24, 1A24E1, 1A26, 1A26E1.

A 500-cycle inspection interval is permitted with these conditions:
  • Any amount of missing coating on the shroud segment, provided there is no oxidation on the adjacent stage 2 nozzle outer platform LE.

A 200-cycle inspection interval is permitted with these conditions:
  • Any amount of missing coating on the shroud segment, oxidation on the adjacent stage 2 nozzle outer platform LE is permitted.

Check engine data plate for thrust rating 1A30, 1A32, 1A33, 1A33B2, 1A35A.

A 200-cycle inspection interval is permitted with these conditions:
  • Any amount of missing coating on the shroud segment, provided there is no oxidation on the adjacent stage 2 nozzle outer platform LE.

A 100-cycle inspection interval is permitted with these conditions:
  • Any amount of missing coating on the shroud segment, oxidation on the adjacent stage 2 nozzle outer platform LE is permitted.

END OF PRE SB LEAP-1A-72-00-0119-01A-930A-D
POST SB LEAP-1A-72-00-0119-01A-930A-D

A 1600-cycle inspection interval is permitted with these conditions:
  • In the areas between 0.1 in. (2.54 mm) and 0.3 in. (7.62 mm) from the TE, any amount of missing coating is permitted, if the base material is not exposed.
  • In the area between 0.66 in. (16.8 mm) from the TE and 0.4 in. (10.2 mm) from the circumferential split line, any amount of missing coating and exposed based material is permitted.

A 600-cycle inspection interval is permitted with these conditions:
  • Any amount of missing coating on the shroud segment.

END OF POST SB LEAP-1A-72-00-0119-01A-930A-D


POST SB LEAP-1A-72-00-0213-01A-930A-D

A 1600-cycle inspection interval is permitted with these conditions:
  • Any amount of missing coating on the shroud segment.

END OF POST SB LEAP-1A-72-00-0213-01A-930A-D

Remove the engine in 10 cycles or less with these conditions:
  • If a hole through the shroud segment is found.
Refer to K. Spline seals you can see for missing material at circumferential ends.
J.The over-serviceable limit extension for chipping of the shroud segment base material along the LE and TE

A 800-cycle inspection interval is permitted with these conditions:
  • Chipping of the shroud base material up to 0.25 in. (6.3 mm) from the LE and up to 0.15 in. (3.8 mm) from the TE.

A 100-cycle inspection interval is permitted with these conditions:
  • Chipping of the shroud base material up to 0.35 in. (8.9 mm) from the LE and up to 0.25 in. (6.3 mm) from the TE.
The over-serviceable limit extension is for a reduced interval, repeat inspection.
K.The over-serviceable limit extension for chipping of the shroud segment base material along the circumferential split line
A 200-cycle inspection interval is permitted with these conditions:
  • A maximum axial length of 1.0 in. (25.40 mm) is permitted on each shroud segment.
The over-serviceable limit extension is for a reduced interval, repeat inspection.
7.Examine the surface coating of the HPT rotor stage 1 blades:
See sheets 1, 4, 5, 6 and 7 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade
Any amount of missing surface coating is permitted with metal oxidation (green or black discoloration of the material) if there are no holes or cracks in the blade.

8.Examine the LEs of the HPT rotor stage 1 blades as follows:
See sheets 1, 2, 4 and 5 of the figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Axial and radial cracks in Area A
Any number of cracks permitted in these conditions:
  • A crack does not connect more than three holes.
  • Axial cracks do not extend past the cooling air holes in row 2 or row 6.

B.The over-serviceable limit extension for axial and radial cracks in Area A of the HPT rotor stage 1 blade LE
A 650-cycle inspection interval is permitted in these conditions:
  • Cracks can connect any number of holes, if there is no missing material.
  • Remove the engine in 25 cycles or less if the axial crack extends past the cooling air holes in row 2 or row 6.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
C.Radial cracks that go out of Area B LE holes
Any number of cracks permitted in these conditions:
  • A crack does not connect more than two holes.
  • There are no radial cracks that turn in an axial direction.

D.The over-serviceable limit extension for radial cracks in Area B of the HPT stage 1 blade LE
A 250-cycle inspection interval is permitted in these conditions:
  • Cracks can connect any number of holes, if there is no missing material.
  • Remove the engine in 25 cycles or less if the radial cracks turn in an axial direction and extend past the cooling air holes in row 2 or row 6.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
E.Axial cracks in Area B
Axial cracks in Area B are not permitted.

F.The over-serviceable limit extension for axial cracks in Area B of the HPT stage 1 blade LE
A 250-cycle inspection interval is permitted in these conditions:
  • Cracks can connect any number of holes, if there is no missing material.
  • Cracks do not extend past the cooling air holes in row 2 or row 6.
  • Remove the engine in 25 cycles or less if a crack extends past the cooling air holes in row 2 or row 6.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
G.Nicks and dents in Area A
Any number of nicks and dents permitted in these conditions:
  • The nick, dent or any related crack does not extend farther than the nose holes.
  • The nick, dent or any related crack does not extend farther than the cooling air holes in row 2.

H.Nicks and dents in Area B
Any number of nicks and dents permitted in these conditions:
  • The nick, dent or any related crack does not extend farther than the nose holes.
  • The nick, dent or any related crack does not extend farther than the cooling air holes in row 2.
  • No related tears or material that is missing.

J.Material that is missing in Area A
Material that is missing is not permitted.
NOTE: The squealer tip area is not part of Area A.
K.The over-serviceable limit extensions for material that is missing from Area A of the HPT stage 1 blade LE
A 650-cycle inspection interval is permitted in these conditions:
  • Any amount is permitted if it does not extend farther than the first internal rib. The first internal rib would be forward from row 2 on the convex side and aligned with row 6 on the concave side.
  • Any related axial cracks do not extend farther than the nose holes.
  • Any related axial cracks do not extend farther than the cooling air holes in row 2.
  • Remove the engine in 25 cycles or less if the related axial cracks extend farther than the cooling air holes in row 2 or row 6.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
L.The over-serviceable limit extensions for material that is missing from Area A of the HPT stage 1 blade LE that extends farther than the first internal rib
A 125-cycle inspection interval is permitted in these conditions:
  • Any amount is permitted.
  • Any related axial cracks do not extend farther than the nose holes.
  • Any related axial cracks do not extend farther than the convex surface gill holes.
  • Remove the engine in 25 cycles or less if any related axial cracks extend farther than the cooling air holes in row 2 or row 6.
  • Remove the engine in 15 cycles or less if the metal that is missing, extends farther than the second internal rib (Missing material into or beyond row 1 on the convex side and farther aft of row 6 on the concave side).
This over-serviceable limit extension is for a reduced interval, repeat inspection.
M.Material that is missing in Area B
Material that is missing is not permitted.

N.The over-serviceable limit extensions for material that is missing from Area B of the HPT stage 1 blade LE
A 250-cycle inspection interval is permitted in these conditions:
  • Any amount is permitted if it does not extend farther than the first internal rib.
  • Any related axial cracks are not permitted.
  • Any related radial cracks are not permitted.
  • Remove the engine in 5 cycles or less if missing material extends farther than the first rib.
  • Remove the engine in 25 cycles or less if related axial or radial cracks are present.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
P.Blocked nose holes
One blocked cooling hole (rows 1 - 6) permitted in Area B.
No blocked cooling holes (rows 1 - 6) permitted in Area A.

9.Examine the TEs of the HPT rotor stage 1 blade as follows:
See sheets 1, 4, 5, 6 and 7 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade

The TE is defined as the area that includes the TE slots.
A.Axial cracks in Area A
Any number of cracks permitted that are less than 0.200 in. (5.08 mm) from the TE.

B.The over-serviceable limit extensions for axial cracks in Area A of the HPT stage 1 blade TE
A 650-cycle interval is permitted in these conditions:
  • The cracks are less than 0.275 in. (6.98 mm) in length.
  • Remove the engine in 25 cycles or less if the cracks are more than 0.275 in. (6.98 mm) in length.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
C.Axial cracks in Area B, that do not include the TE root fillet radius
Not permitted.

D.The over-serviceable limit extensions for axial cracks in Area B of the HPT stage 1 blade TE, but not in the TE root fillet radius
A 250-cycle inspection interval is permitted in these conditions:
  • The cracks are less than 0.275 in. (6.98 mm) in length.
  • Remove the engine in 15 cycles or less if the cracks are more than 0.275 in. (6.98 mm) in length.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
E.Axial cracks in the TE root radius
Any number of cracks permitted that are less than 0.135 in. (3.43 mm) in length and do not turn radially.

F.The over-serviceable limit extensions for axial cracks in the TE root radius
A 125-cycle inspection interval is permitted in these conditions:
  • The cracks are less than 0.275 in. (6.98 mm) in length and do not turn radially.
  • Remove the engine in 25 cycles or less if the cracks are longer than 0.275 in. (6.98 mm) in length or turn in a radial direction.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
G.Nicks in Area A
Any number of nicks permitted if there is no related missing or torn material or cracks.

H.The over-serviceable limit extensions for nicks in Area A with related missing or torn material or cracks
A 650-cycle inspection interval is permitted in these conditions:
  • No internal cavities can be seen.
  • Inspect the TE every 125 cycles if internal cavities can be seen.
  • There are no cracks more than 0.275 in. (6.98 mm) in length, remove the engine in 25 cycles or less.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
J.Nicks in Area B
Any number of nicks permitted in Area B in these conditions:
  • There is no related torn material or cracks.
  • There are no nicks in the root fillet radius.

K.The over-serviceable limit extensions for nicks in Area B
A 650-cycle inspection interval is permitted in this condition:
  • Nicks in the root fillet radius are less than 0.275 in. (6.98 mm) and there is no torn material or cracks.
This over-serviceable limit extension is for a reduced interval, repeat inspection.

A 250-cycle inspection interval is permitted in these condition:
  • There is no torn metal or cracks.


A 125-cycle inspection interval is permitted in these conditions:
  • Internal cavities can be seen.


Remove the engine in 25 cycles or less if torn metal or cracks are more than 0.275 in. (6.98 mm).

L.Dents in Area A
Any number of dents permitted in Area A in these conditions:
  • The length or diameter of the dent is not more than the length of one TE slot 0.11 in. (2.79 mm).
  • The depth of the dent is not more than 0.03 in. (0.76 mm).
  • No metal extrusion from the dent into the TE slot is permitted.

M.The over-serviceable limit extensions for dents in Area A that have an extrusion into the TE slot
A 650-cycle inspection interval is permitted in this condition:
  • There are no related cracks.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
N.Dents in Area B
Any number of dents permitted in Area B in these conditions:
  • The length or diameter of the dent is not more than the length of one TE slot 0.11 in. (2.79 mm).
  • The depth of the dent is not more than 0.03 in. (0.76 mm).
  • No metal extrusion from the dent into the TE slot is permitted.

P.The over-serviceable limit extensions for the stage 1 blade with TE dents in Area B that have an extrusion into the TE slot
A 250-cycle inspection interval is permitted in this condition:
  • There is no cracking.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
Q.Tears in Area A
Tears in Area A are not permitted.

R.The over-serviceable limit extensions for tears in Area A
A 650-cycle inspection interval is permitted in these conditions:
  • The tear is farther than 0.275 in. (6.98 mm) from the TE.
  • Any axial cracks from the tears are less than 0.07 in. (1.78 mm) in length.
  • Radial cracks in the direction of the tip from tears are permitted.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
S.Tears in Area B
Tears in Area B are not permitted.

T.The over-serviceable limit extensions for stage 1 tears in Area B
A 250-cycle inspection interval is permitted in these conditions:
  • The tear is farther than 0.275 in. (6.98 mm) from the TE.
  • Any axial cracks from the tears are less than 0.07 in. (1.78 mm) in length.
  • Radial cracks in the direction of the tip from tears are permitted.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
U.Oxidation in the root radius
Oxidation in the root fillet radius is not permitted.

V.The over-serviceable limit extensions for oxidation in the stage 1 blade TE root radius
A 125-cycle inspection interval is permitted in these conditions:
  • Internal cavities cannot be seen.
  • Remove the engine in 10 cycles or less if you can see internal cavities.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
W.Metal that is missing from the stage 1 blade TE in Area A
It is permitted to have metal that is missing if you do not see the internal cavities of the blade.

X.The over-serviceable limit extensions for metal that is missing from the stage 1 blade TE in Area A where internal cavities can be seen
A 650-cycle inspection interval is permitted in these conditions:
  • Axial cracks are permitted if they are not more than 0.07 in. (1.78 mm) in length.
  • Radial cracks are permitted if they are not more than 0.14 in. (3.56 mm) in length.
  • Missing metal is not more than 0.07 in. (1.78 mm) in diameter or equivalent area.

A 250-cycle inspection interval is permitted in these conditions:
  • Axial cracks are permitted if they are not more than 0.07 in. (1.78 mm) in length.
  • Radial cracks are permitted if they are not more than 0.14 in. (3.56 mm) in length.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
Y.Metal that is missing from the stage 1 blade TE in Area B or in the root radius
Metal that is missing is not allowed.
  • If metal is missing, see the over-serviceable limit extensions that follow:

Z.The over-serviceable limit extensions for metal that is missing from the stage 1 blade TE in Area B or in the root fillet radius, with no cracks
Remove the engine in 10 cycles or less.
NOTE: This over-serviceable limit is for one time use.
AA.There is no over-serviceable limit extensions for metal that is missing from the stage 1 blade TE in Area B or in the root fillet radius, with axial or radial cracks
Axial and radial cracks are not permitted.
Remove the engine before the next flight.
10.Examine the HPT rotor stage 1 blade concave and convex surfaces as follows:
See sheets 1, 4 and 5 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Radial cracks at the cooling air holes
Any number permitted above cooling air hole 9 in row 2 with this condition:
  • Any radial cracks connecting a maximum of two holes and not running in an axial direction.

No cracks are permitted at the row 7 cooling air holes.
  • See the over-serviceable limit extensions.

B.The over-serviceable limit extensions for stage 1 blade concave surface radial cracks at the cooling air holes
Remove the engine in 10 cycles or less if there are cracks in any row 7 cooling air holes.
NOTE: This over-serviceable limit extension is for one-time use.
C.Radial cracks in Area A other than at the cooling air holes
Radial cracks in Area A other than at the film or gill holes are permitted in these conditions:
  • There is a maximum of one crack on the concave surface and it is no longer than 0.30 in. (7.62 mm).
  • The crack does not turn in an axial direction.
  • The internal cavity of the blade cannot be seen.

D.The over-serviceable limit extensions for radial cracks in Area A other than at the cooling air holes
A 650-cycle inspection interval is permitted in these conditions:
  • There is a maximum of one crack on the concave surface and is no longer than 0.56 in. (14.22 mm) and less than 0.07 in. (1.78 mm) in width.
  • The internal cavity of the blade cannot be seen.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
E.The over-serviceable limit extensions for radial cracks in Area A other than at the cooling air holes
A 250-cycle inspection interval is permitted in these conditions:
  • There is a maximum of one crack on the concave surface and it is no longer than 0.69 in. (17.53 mm) and less than 0.14 in. (3.56 mm) in width.
  • The internal cavity of the blade cannot be seen.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
F.Radial cracks in Area B other than at the cooling air holes
Radial cracks in Area B other than at the cooling air holes are permitted in these conditions:
  • There is a maximum of one crack and the crack is no longer than 0.3 in. (7.62 mm).
  • The crack does not turn in an axial direction.
  • The internal cavity of the blade cannot be seen.

G.The over-serviceable limit extensions for radial cracks in Area B other than at the cooling air holes
A 250-cycle inspection interval is permitted in these conditions:
  • The internal cavity of the blade cannot be seen.
This over-serviceable limit extension is for a reduced interval, repeat inspection.

  • There is a maximum of one crack on the concave surface and it is no more than 0.42 in. (10.67 mm) in length.
  • Remove the engine in 25 cycles or less if the crack is more than 0.42 in. (10.67 mm) in length.


  • The crack does not go in an axial direction.
  • Remove the engine in 10 cycles or less if the crack is in an axial direction.
NOTE: This over-serviceable limit extension is for a one-time use.
H.Radial cracks that go out of the tips of the cooling air holes
Three cracks are permitted in these conditions:
  • The cracks do not go into the next cooling air hole.
  • The cracks do not go in the direction of the blade platform from the bottom hole.
  • The cracks do not go in an axial direction.

J.The over-serviceable limit extensions for radial cracks that go out of the tip of the cooling air holes
A 250-cycle inspection interval is permitted in these conditions:
  • The cracks do not connect more than two cooling air holes.
  • The cracks do not go in the direction of the platform from the bottom hole.
  • The cracks do not turn in an axial direction.
  • Remove the engine in 10 cycles or less if the crack turns axial or if it goes in the direction of the platform from the bottom hole.
This over-serviceable limit extension is for a reduced interval, repeat inspection.

A 25-cycle inspection interval is permitted in these conditions:
  • The cracks connect a maximum of three cooling air holes.
  • The cracks do not go in the direction of the platform from the bottom hole.
  • The cracks do not turn in an axial direction.
  • Remove the engine in 10 cycles or less if the crack connects more than three cooling air holes or turn in an axial direction.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
K.Nicks and dents in Area A concave and convex surfaces
Any number of nicks and dents in Area A in this condition:
  • There are no tears, cracks or holes that go through the surface metal.

L.Nicks and dents in Area B concave and convex surfaces
Any number of nicks and dents permitted in the Area B concave surface in this condition:
  • The diameter of the nick or dent is not more than 0.07 in. (1.78 mm).

Any number of nicks and dents permitted in the Area B convex surface in this condition:
  • There are no tears, cracks or holes through the surface metal.

No nicks or dents are permitted in the root area.

M.Twisted, bent, burnt or melted airfoil surfaces
Twisted, bent, burnt or melted airfoil surfaces are not permitted.

N.Axial cracks in Areas A and B
Axial cracks are not permitted. See the over-serviceable limit extensions that follow:

P.The over-serviceable limit extensions for axial cracks on the concave and convex surface Areas A and B
A 250-cycle inspection interval is permitted in these conditions:
  • There is a maximum of one crack that is less than 0.07 in. (1.78 mm) in length.
  • The crack does not turn in a radial direction.

A 125-cycle inspection interval is permitted in these conditions:
  • There is a maximum of one crack that is less than 0.14 in. (3.56 mm) in length.
  • The crack does not turn in a radial direction.
  • Remove the engine in 10 cycles or less if the crack is more than 0.14 in. (3.56 mm) in length or if the crack turns in a radial direction.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
11.Examine the HPT rotor stage 1 blade for radial cracks on the pressure (concave) airfoil between, but not related to, row 7 and 8 cooling air holes as follows:
See sheets 1, 4, 5, 6 and 7 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Radial cracks on the HPT rotor stage 1 blade on the pressure (concave) airfoil between, but not related to row 7 and 8 cooling air holes
Not permitted.

B.The over-serviceable limit extensions for radial cracks on the HPT rotor stage 1 blade on the pressure (concave) airfoil between, but not related to row 7 and 8 cooling air holes
A 1300-cycle inspection interval is permitted in these conditions:
  • There is a maximum of one crack in Region A (Region A is different than Area A) and it is not more than 0.19 in. (4.83 mm).

A 650-cycle inspection interval is permitted in these conditions:
  • There is a maximum of one radial crack that extends farther than Region A and into Regions B or C and the crack is no more than 0.48 in. (12.19 mm).
  • There is a maximum of one radial crack that goes through upper Region C to the tip that is no more than 0.48 in. (12.19 mm).
  • Remove the engine in 25 cycles or less if there is a radial crack on the pressure surface that extends farther than Regions B or C.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
12.Examine the HPT rotor stage 1 blade tip as follows:
See sheets 1, 4, 5, 6 and 7 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade

The blade tip is defined as the area within 0.16 in. (4.06 mm) of the end of the blade.
A.Radial cracks that begin at the end of the blade (the crack could open up at the tip and make a 'V' notch)


(1)Concave side of the blade
It is permitted to have a crack in the 'V' notch if you do not see the internal cavity.

It is permitted for cracks to intersect the top cooling holes in a concave film row.

Any number of cracks are permitted if they do not go farther than 0.20 in. (5.08 mm) from the end of the blade.

(2)The over-serviceable limit extensions for radial cracks on the concave side of the blade
  • An 800-cycle inspection interval is permitted, if the radial tip cracks are between 0.20 in. (5.08 mm) and 0.25 in. (6.35 mm) and the internal cavity cannot be seen.
  • A 400-cycle inspection interval is permitted, if the radial tip cracks are between 0.25 in. (6.35 mm) and 0.30 in. (7.62 mm) and the internal cavity cannot be seen.
  • Remove the engine in 10 cycles or less, if the radial cracks are longer than 0.30 in. (7.62 mm) or if the internal cavity can be seen.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
(3)Convex side of the blade
It is permitted to have a crack in the 'V' notch if you do not see the internal cavity.

Any number of cracks are permitted if they do not go farther than 0.20 in. (5.08 mm) from the end of the blade.

(4)The over-serviceable limit extensions for radial cracks on the convex side of the blade
  • An 800-cycle inspection interval is permitted, if the radial tip cracks are between 0.20 in. (5.08 mm) and 0.25 in. (6.35 mm) and the internal cavity cannot be seen.
  • A 400-cycle inspection interval is permitted, if the radial tip cracks are between 0.25 in. (6.35 mm) and 0.30 in. (7.62 mm) and the internal cavity cannot be seen.
  • Remove the engine in 10 cycles or less if the radial cracks are longer than 0.30 in. (7.62 mm) or if the internal cavity can be seen.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
B.Axial cracks
Any number of axial cracks permitted.

C.Bent or curled blade tips
Any amount permitted if the bent or curled tips do not go below the most outboard trail edge slot and the internal cavity cannot be seen.

D.Metal that is missing from the blade squealer tip
Any amount permitted if the missing material does not go below the most outboard TE slot and the internal cavity cannot be seen.

E.The over-serviceable limit extensions for metal that is missing from the blade squealer tip
Remove the engine in 10 cycles or less if the internal cavity can be seen.
This over-serviceable limit extension is for a one-time use.
F.Metal that is missing from the tip on the TE
Metal that is missing from the tip on the TE is permitted in these conditions:
  • Damage does not go below the first TE slot.
  • The internal cavity cannot be seen.

G.The over-serviceable limit extensions for metal that is missing from the tip on the TE
A 125-cycle inspection interval is permitted in these conditions:
  • The damage goes below the first TE slot, but does not go farther than 0.20 in. (5.08 mm).
  • The internal cavity cannot be seen.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
13.Examine cracks in Area B on the concave side of the airfoil surface that go out of row 12 cooling holes toward row 9 cooling holes:
See sheets 1, 4, 5, 6 and 7 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Cracks that go out of row 12 cooling holes toward row 9 cooling holes
Not permitted.

B.The over-serviceable limit extensions for cracks that go out of row 12 cooling holes toward row 9 cooling holes
250-cycle inspection interval is permitted in these conditions:
  • Cracks from the bottom hole do not reach the blade platform.
  • Cracks are not within 0.10 in. (2.54 mm) of row 9 cooling holes.

Remove the engine in 10 cycles or less if the crack from the bottom hole reaches the blade platform or is within 0.10 in. (2.54 mm) of row 12 cooling holes.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
14.Examine the HPT stage 1 rotor blade tips for build-up of first stage shroud material as follows:
See sheets 1, 4, 5, 6 and 7 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Shroud material build-up on the blade tips
Permitted.

15.Examine the HPT rotor stage 1 blade platform as follows:
See sheets 1, 4, 5, 6 and 7 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Cracks on the pressure side of the platform
Cracks less than 0.2 in. (5.080 mm) in length.
  • Any amount allowed.
Cracks less than 0.2 in. (5.080 mm) in length.
  • Any amount permitted.
    Post SB 72-0216
  • One crack permitted from row 14 hole 1, any length permitted. A crack from this location is not permitted to connect with any other cracks or extend beyond to the forward edge of the platform (platform LE). Lifting of material is not permitted.
END OF Post SB 72-0216
B.Cracks on the TE of the platform
Pre SB 72-0072
No more than three cracks are permitted from the platform edge.
Cracks are permitted that extend from the platform TE to the platform cooling holes.
Cracks are not permitted between the platform cooling holes.
Cracks are not permitted between the platform cooling holes and the airfoil root radius.
Lifting material between cracks is not permitted.
END OF Pre SB 72-0072
Post SB 72-0072
No more than three cracks are permitted from the platform edge.
Cracks are not permitted at the airfoil root radius.
Lifting material between cracks is not permitted.
END OF Post SB 72-0072
C.The over-serviceable limit extensions for cracks on the HPT rotor Stage 1 blade convex platform
Pre SB 72-0072
A 650-cycle inspection interval is permitted in this condition:
  • The blade platform cracks are between the platform cooling holes on the convex side of the platform.
A 250-cycle inspection interval is permitted in this condition:
  • The blade platform cracks are between the platform cooling holes and the convex airfoil root radius.
Remove the engine in 25 cycles or less if the blade platform crack is at the convex airfoil root radius.
Remove the engine in 25 cycles or less if there is lifting material between cracks.
END OF Pre SB 72-0072
Post SB 72-0072 and Post SB 72-0216
A 250-cycle inspection interval is permitted in this condition:
  • The blade platform cracks are between the platform and the convex airfoil root radius.
Remove the engine in 25 cycles or less if the blade platform crack is at the convex airfoil root radius.
Remove the engine in 25 cycles or less if there is lifting material between cracks.
END OF Post SB 72-0072 and Post SB 72-0216
This over-serviceable limit extension is for a reduced interval, repeat inspection.
D.The over-serviceable limit extensions for cracks on the HPT rotor stage 1 blade concave platform
A 600-cycle inspection interval is permitted in this condition:
  • Cracks on the concave platform less than 0.3 in. (7.62 mm), but greater than 0.2 in. (5.08 mm).

A 350-cycle inspection interval is permitted in this condition:
  • Cracks on the concave platform less than 0.35 in. (8.89 mm), but greater than 0.3 in. (7.62 mm) and no lifted material.

A 100-cycle inspection interval is permitted in this condition:
  • Cracks on the concave platform less than 0.4 in. (10.16 mm), but greater than 0.35 in. (8.89 mm) with no lifted material.

Remove the engine in 5 cycles or less if there are cracks greater than 0.4 in. (10.16 mm) in length and/or any lifted material is observed on the concave platform.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
16.Examine the vane airfoils of the HPT stage 2 nozzle segment as follows:
See sheets 1 and 8 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade

The inspection is only of the HPT stage 2 nozzle segment that is adjacent to the borescope port.
A.Axial cracks in the vane TEs that are more than 0.25 in. (6.35 mm) from the inner platform.
Any amount of axial cracks permitted in the vane TEs if they are not more than 0.06 in. (1.52 mm) in length.

It is permitted to have two cracks for each vane if they are not more than 0.35 in. (8.89 mm) in length and they are separated from each other by a minimum of 0.25 in. (6.35 mm).

B.All types of cracks in the vane TEs that are less than 0.25 in. (6.35 mm) from the inner platform
Any amount of cracks permitted if they do not extend more than 0.35 in. (8.89 mm) from the TE.

C.Axial cracks in the vane LEs
It is permitted to have one axial crack if it is 0.20 in. (5.08 mm) or less in length.

No cracks are permitted in Area C if they are parallel to the outer platform.

Any amount of cracks permitted in the vane LEs if there are no separation cracks in the surface coating.

D.Cracks in the vane concave surfaces
It is permitted to have two cracks for each vane concave surface if they are 0.50 in. (12.70 mm) or less in length.

E.Cracks in the convex side of the vane to the outer platform fillet area
Not permitted.

F.Nicks, scores, scratches and dents
Any amount permitted if they are not more than 0.17 in. (4.32 mm) in diameter and 0.02 in. (0.51 mm) in depth.

G.Oxidation or missing material in the concave and convex surfaces
It is permitted to have an area that is 0.5 in.2 (322.58 mm2) or less.
It is not permitted to have holes that are through the surface material.

H.Oxidation or missing material in the LE
It is permitted to have a total area that is 0.50 in. (12.70 mm) or less in length and 0.3 in. (7.62 mm) or less in width.
If the adjacent stage 1 HPT stator shroud segment EBC is spalled, this additional criterion applies:
It is permitted to have a total area 0.1 in.2 (64.5 mm2) or less in Area A.
It is not permitted to have a hole through the parent metal, regardless of stage 1 HPT stator shroud EBC condition.
The adjacent stage 1 HPT stator shroud EBC is spalled if the shroud segment is missing complete circumferential EBC in or less than 0.100 in. (2.54 mm) of the TE.
J.The over-serviceable limit extension for oxidation or missing material in the LE
A 200-cycle inspection interval is permitted for any amount of oxidation or missing material if there is no hole through the parent metal.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
K.Coating that is missing from the airfoil surfaces
Any amount of missing coating permitted if the adjacent stage 1 HPT stator shroud EBC is not spalled.
It is permitted to have a total area 0.5 in.2 (322.6 mm2) or less in Area A if the adjacent stage 1 HPT stator shroud segment EBC is spalled. Any amount of missing coating is permitted outside Area A.
The adjacent stage 1 HPT stator shroud EBC is spalled if the shroud segment is missing complete circumferential EBC in or less than 0.100 in. (2.54 mm) of the TE.
L.The over-serviceable limit extension for missing coating in Area A with EBC spall of the adjacent stage 1 HPT stator shroud
An 800-cycle inspection interval is permitted for any amount of missing coating.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
M.Material that is missing from the TE
It is permitted to have an area 0.18 in. (4.57 mm) or less in axial direction by 0.35 in. (8.89 mm) or less in radial direction.

N.Cracks in the vane convex surfaces
It is permitted to have a maximum of two cracks on each vane in these conditions:
  • The cracks are 0.35 in. (8.89 mm) or less in length.
  • The cracks are separated from the inner and outer platform by 0.35 in. (8.89 mm) or more.

17.Examine the inner and outer platform of the HPT stage 2 nozzle segment as follows:
See sheets 1 and 8 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade

The inspection is limited to the HPT stage 2 nozzle segment that is adjacent to the borescope port.
A.Cracks
Any amount of cracks permitted that are 0.35 in. (8.89 mm) or less in length.

B.Nicks, scores, scratches and dents in the inner and outer platform surfaces
Any amount of nicks, scores, scratches and dents permitted that are 0.02 in. (0.51 mm) or less in depth.

Nicks, scores, scratches and dents that are more than 0.02 in. (0.51 mm) in depth are not permitted.

C.Craze cracks
Any amount permitted.

D.Cracks in the outer platform TE
Any amount permitted that are 0.30 in. (7.62 mm) or less in length if the cracks do not go into the vane fillet radius.

E.Coating that is missing
Any amount of missing coating permitted if the adjacent stage 1 HPT stator shroud EBC is not spalled.
It is permitted to have a total area 0.5 in.2 (322.6 mm2) or less in Area B if the adjacent stage 1 HPT stator shroud segment EBC is spalled. Any amount of missing coating is permitted outside Area B.
The adjacent stage 1 HPT stator shroud EBC is spalled if the shroud segment is missing complete circumferential EBC in or less than 0.100 in. (2.54 mm) of the TE.
F.The over-serviceable limit extension for missing coating in Area B with EBC spall of the adjacent stage 1 HPT stator shroud
An 800-cycle inspection interval is permitted for any amount of missing coating.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
G.Heat distress or oxidation on the inner platform
Not permitted to heat distress or burns on the inner platform.

H.Heat distress or oxidation on the outer platform
Any amount permitted if the adjacent stage 1 HPT stator shroud EBC is not spalled.
It is permitted to have a total area 0.1 in.2 (64.5 mm2) or less in Area B if the adjacent stage 1 HPT stator shroud segment EBC is spalled. Any amount of heat distress or oxidation is permitted outside Area B.
It is not permitted to have holes that are through the parent metal, regardless of stage 1 HPT shroud EBC condition.
The adjacent stage 1 HPT stator shroud EBC is spalled if the shroud segment is missing complete circumferential EBC in or less than 0.100 in. (2.54 mm) of the TE.
J.The over-serviceable limit extension for the stage 2 nozzle outer platform cracking
A 1600-cycle inspection interval is permitted with these conditions:
  • Any amount of cracking if there is no hole through the parent metal.

K.The over-serviceable limit extension for the stage 2 nozzle outer platform oxidation
If the adjacent stage 1 HPT stator shroud segment EBC is spalled, a 200-cycle inspection interval is permitted for any amount of oxidation or missing material in Area B.
This over-serviceable limit extension is for a reduced interval, repeat inspection.

Remove the engine in 10 cycles or less if there is a hole through the parent metal, regardless of stage 1 HPT shroud EBC condition.
This over-serviceable limit is for a one-time use.
18.Examine the HPT stage 2 shroud segment as follows:


A.Blade rub
Any amount is permitted.

B.Cracks
Not permitted.

C.Surface corrosion/oxidation
Any amount is permitted, as long as no burn through is present on flow path surface of the shroud.

D.A hole through the shroud flow path surface
Not permitted.

E.Missing material from split line
Any amount allowed in the split line region up to 0.075 in. (1.90 mm) from the end face.


A 500 cycles interval is permitted in these conditions:
  • Any number, if more than 0.075 in. (1.90 mm) up to 0.110 in. (2.79 mm) of missing material from split line.
The over-serviceable limit extensions are at decreased interval, inspection must be done again after not more than 500 engine cycles.

More than 0.110 in. (2.79 mm) of missing material from split line not permitted.

19.Examine the HPT rotor second stage blade LE as follows:
See sheets 1, 13 and 14 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Cracks
There is no limit to the number permitted in Area A if they are not related to a dent.

Cracks are not permitted in Area B.

B.Nicks and dents in Area A
There is no limit to the number of nicks and dents permitted.

C.Dents in Area B (includes the root radius)
1. Three dents out of contour and 0.025 in. (0.63 mm) apart are permitted.
NOTE: Surface distortion other than the dent is not permitted.
D.Nicks in Area B
1. Four nicks 0.020 in. (0.51 mm) in length and 0.125 in. (3.17 mm) apart are permitted.
2. One nick 0.040 in. (1.02 mm) in length on the LE only is permitted.
E.Metal that is missing in Area A
Not permitted.

F.The over-serviceable limit extensions for the HPT stage 2 blade LE metal that is missing in Area A
A 250-cycle inspection interval is permitted in these conditions:
  • Any amount less than 0.004 in.2 (2.58 mm2) that does not go farther than the first internal rib.
  • Axial cracks that do not go farther than the first internal rib (or 0.164 in. (4.17 mm) in length from the LE).
  • Remove the engine in 25 cycles or less if the missing material is more than 0.004 in.2 (2.58 mm2) or goes farther than the first rib.
  • Remove the engine in 15 cycles or less if the cracks go farther than the internal rib.
This over-serviceable limit extension is for a reduced interval, repeat inspection.
G.Metal that is missing in Area B
Not permitted.

H.The over-serviceable limit extensions for HPT stage 2 blade LE metal that is missing in Area B
Remove before the next flight if metal that is missing goes farther than the first internal rib.

Remove the engine in five cycles if metal that is missing does not go beyond the first rib.

J.Metal splatter
There is no limit to the amount of metal splatter in these conditions:

20.Examine the HPT rotor second stage blade TE as follows:
See sheets 1, 13 and 14 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Cracks
Not permitted.

B.Nicks and dents
There is no limit to the number of nicks and dents permitted if they are not within 0.35 in. (8.89 mm) of the inner and outer platforms.

C.Metal that is missing and tears
Not permitted.

21.Examine the HPT rotor second stage blade concave and convex surfaces as follows:
See sheets 1, 13 and 14 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Cracks
Not permitted.

B.Nicks and dents
There is no limit to the number of nicks and dents in these conditions:
  • The diameter is less than 0.18 in. (4.57 mm).
  • There is no torn metal.
  • They are not within 0.35 in. (8.89 mm) of the blade platform.

C.Positive braze material
Positive braze material is permitted in these conditions:
  • The material is in Area D of the concave and convex surfaces.
  • The material extends not more than 0.003 in. (0.08 mm) above a concave or convex surface.

D.Blade surface coating
There is no limit to the amount of missing surface coating, with metal oxidation (green or black discoloration of the material), if there are no holes or cracks in the blade.

22.Examine the HPT rotor second stage blade as follows:
See sheets 1, 13 and 14 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Pits
Four pits are permitted on the concave or convex surface in these conditions:
  • Each pit is less than 0.02 in. (0.51 mm) in length.
  • Each pit is less than 0.005 in. (0.13 mm) in depth.
  • Each pit is more than 0.088 in. (2.24 mm) from an adjacent pit.

There is no limit to the number of pits that are permitted on the concave or convex surface in these conditions:
  • Each pit is less than 0.011 in. (0.28 mm) in length.
  • Each pit is less than 0.005 in. (0.13 mm) in depth.
  • There is a clear separation between each pit and an adjacent pit.

One pit is permitted on the concave and convex surfaces in these conditions:
  • The pit is not more than 0.035 in. (0.89 mm) in length.
  • The pit is not more than 0.010 in. (0.25 mm) depth.

23.Examine the HPT rotor second stage blade tip area as follows:
See sheets 1, 13 and 14 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Radial cracks
Two radial cracks for concave or convex sides are permitted in these conditions:
  • They are less than 0.07 in. (1.78 mm) below the tip.
  • You do not see the internal cavity of the blade.

B.Axial cracks
There is no limit to the number of axial cracks permitted if they are not more than 0.35 in. (8.89 mm).

C.The over-serviceable limit extensions for the stage 2 blade tip area
There is no limit to the length of axial cracks permitted above the tip cap for no more than 10 cycles.
The over-serviceable limit extension is for a one-time use.
D.Bent or curled blade tip
There is no limit to the number permitted.

E.Metal that is missing and tears
There is no limit to the number permitted in these conditions:
  • You do not see the tip cavity shelf because part of or all of the tip cap is missing.
  • The opposite cavity wall is not missing.
  • There is only one area on each cavity wall that has damage 0.21 in. (5.33 mm) in length.

F.Build-up of second stage shroud material
It is permitted to have shroud material build-up on the blade tips.

24.Examine the HPT rotor second stage blades thermal barrier coating as follows:
See sheets 1, 13 and 14 of figure:
F HPT Section Nozzles, Shroud Segments and Turbine Blade


A.Thermal barrier coating
There is no limit to the amount of missing thermal barrier coating if there are no holes or cracks in the blade.

Subtask 72-52-00-080-052-A
F. When the inspection is completed, remove the BORESCOPE SET.
Subtask 72-52-00-420-050-A
G. Install the borescope plugs in ports R, S and T as follows:
F HPT Borescope Plugs - PRE and POST SB 72-0249
   (1) Do a visual inspection of the borescope plugs and the borescope ports (Ref. AMM TASK 72-00-00-290-812).
   (2) Remove the identification tags from the borescope plugs R, S and T before you install each borescope plug.
   (3) Apply layer of tiodize T8E-H grease (Material No.CP2961) to the threads, mating surfaces and ratcheting mechanism of the borescope plugs R and S.
NOTE: You can use CP2619Never Seez-Pure Nickel, Special as an alternative.
   (4) Apply layer of CP2619Never Seez-Pure Nickel, Special to the threads and ratcheting mechanism of borescope plug T.
   (5) Install the borescope plugs in the borescope ports R, S and T:
     (a) Before you fully tighten the borescope plug, make sure that the anti-rotation sleeve or sleeves are correctly engaged with the slots on the borescope boss.
F HPT Borescope Plugs - PRE and POST SB 72-0249
     (b) You can spray penetrant (Material No.CP2691) into the ratcheting mechanism to release it. You must do this before the replacement of the borescope plug.
   (6) TORQUE the borescope plugs (Ref. AMM TASK 72-00-00-290-812).
F Borescope Port Data
   (7) After the borescope plug is installed, do a check of the borescope plug:
     (a) Do a visual inspection of the borescope plug and make sure that the anti-rotation tab of the locking ring is fully engaged with the one or two slots on the borescope boss.
     (b) Make sure that the head of the borescope plug is fully installed against the borescope boss.
     (c) If one or two of these conditions do not occur, the ratcheting mechanism of the borescope plug can be seized or locked. Do the steps that follow:
       1 Apply penetrant (Material No.CP2691) directly in between the locking ring and the head of the borescope plug.
       2 Apply torque to the plug again until the plug starts to turn freely.
       3 TORQUE the borescope plugs (Ref. AMM TASK 72-00-00-290-812).
F Borescope Port Data
     (d) Do a second check of the borescope plug:
       1 Do a visual inspection of the borescope plug and make sure that the anti-rotation tab of the locking ring is fully engaged with the one or two slots on the borescope boss.
       2 Make sure that the head of the borescope plug is fully installed against the borescope boss.
     (e) If one or two of these conditions do not occur, replace the borescope plug.
     (f) If you have no direct visual access to the borescope plugs, use a BORESCOPE SET to do a check of their condition.
Subtask 72-52-00-080-053-A
H. Remove the motoring tool (Ref. AMM TASK 72-00-00-820-803).
5. Close-up
Subtask 72-52-00-410-064-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 72-52-00-440-057-A
B. Do the reactivation of the thrust reverser after maintenance (Ref. AMM TASK 78-30-00-440-809).
Subtask 72-52-00-410-065-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 02:53:49 UTC
"Aviabrain" 2025