Optional Visual Inspection of the Stage 4 Blades from the Rear of the Engine [CFMB]

TASK 72-54-00-210-004-A
Optional Visual Inspection of the Stage 4 Blades from the Rear of the Engine

FIN: 1000EM1 ** ON A/C NOT FOR ALL
FIN: 1000EM2 ** ON A/C NOT FOR ALL

1. Reason for the Job
To do a direct, hands-on, visual inspection of the stage 4 LPT blades.
During the borescope inspection of this blade stage (Ref. TASK 72-54-00-290-00600), on some rare occasions, you may see blades with their tip shroud shingled or unlatched, or with radial mismatches/out-of-flush defects or with gaps at their interlocks.
This inspection is not mandatory since the Limit Extensions (Ref. TASK 72-00-00-200-02500) referred to in the borescope inspection of the stage 4 blades give the specific time/cycles of operation with these defects.
However, it makes sense to prevent a further deterioration of the turbine stage, before the expiration of the permitted limit extensions. Therefore, a visual inspection is recommended as soon as possible after the finding of these defects, if the aircraft maintenance schedule permits.
The benefits of this visual inspection are that you can:

put back some blades that are shingled/unlatched in the correct interlock positions
make a more accurate measurement of the mismatch (at the blade tip shrouds) than the estimate you can make from the borescope inspection
better see gaps, or areas of the blade interlocks that do not touch each other (the gaps are the result of the deterioration of the blade pretwist (angle) characteristic)
make an evaluation of the correct blade pretwist characteristic through a simple manual method.

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
FOR [1000EM1] (ENGINE-1)
437AL, 438AR, 451AL, 452AR
FOR [1000EM2] (ENGINE-2)
447AL, 448AR, 461AL, 462AR

C. Referenced Information

REFERENCE	DESIGNATION
TASK 71-13-00-010-040-B	Opening of the Fan Cowl Doors
TASK 71-13-00-410-040-B	Closing of the Fan Cowl Doors
TASK 78-11-11-000-041-A	Removal of the Core Nozzle Assembly
TASK 78-11-11-400-041-A	Installation of the Core Nozzle Assembly
TASK 78-11-12-000-041-A	Removal of the Centerbody
TASK 78-11-12-400-041-A	Installation of the Centerbody
TASK 78-30-00-081-041-B	Make the Thrust Reverser Serviceable after Maintenance
TASK 78-30-00-481-041-B	Make the Thrust Reverser Unserviceable for Maintenance
TASK 78-36-00-010-040-B	Opening of the Thrust Reverser Doors
TASK 78-36-00-410-040-B	Closing of the Thrust Reverser Doors
Visual Inspection of the Stage 4 Blades

3. Job Set-up
Subtask 72-54-00-941-063-A ** ON A/C NOT FOR ALL

A. Safety Precautions
(1) On the center pedestal, on the ENG panel 115VU:
(a) Put a WARNING NOTICE(S) to tell persons not to start the engine.
(2) Make sure that the engine 1(2) shutdown occurred not less than 5 minutes before you do this procedure.
(3) On the overhead maintenance panel 50VU:
(a) Make sure that the ON legend of the ENG/FADEC GND PWR/1(2) pushbutton switch is off.
(b) Put a WARNING NOTICE(S) to tell persons not to energize the FADEC 1(2).

Subtask 72-54-00-010-085-A ** ON A/C NOT FOR ALL

B. Open the fan cowl doors (Ref. AMM TASK 71-13-00-010-040):
(1) FOR [1000EM1] (ENGINE-1)
437AL 438AR
(2) FOR [1000EM2] (ENGINE-2)
447AL 448AR

Subtask 72-54-00-040-063-A ** ON A/C NOT FOR ALL

C. Make the thrust reverser unserviceable (Ref. AMM TASK 78-30-00-481-041).

Subtask 72-54-00-010-086-A ** ON A/C NOT FOR ALL

D. Get Access
(1) Open the thrust reverser doors (Ref. AMM TASK 78-36-00-010-040):
(2) FOR [1000EM1] (ENGINE-1)
451AL 452AR
(3) FOR [1000EM2] (ENGINE-2)
461AL 462AR
(4) Let the temperature of parts decrease to ambient temperature.

4. Procedure
Subtask 72-54-00-010-087-A ** ON A/C NOT FOR ALL

A. Removal for Access to the Inspection Area
(1) Remove the core nozzle assembly (Ref. AMM TASK 78-11-11-000-041).
(2) Remove the centerbody (Ref. AMM TASK 78-11-12-000-041).

NOTE: The removal of these nacelle hot exhaust components is necessary in order to get an unrestricted access to the turbine last stage, through the rear of the engine. Besides, this inspection necessitates some checks and corrective actions you can do only by hand.

Subtask 72-54-00-210-055-A ** ON A/C NOT FOR ALL

B. Inspection of Defects Found during the Borescope Inspection
(1) Shingling/Unlatching

CAUTION: DO NOT HIT THE BLADES WITH A DRIFT AND A HAMMER TO PUT THEM BACK IN THEIR CORRECT INTERBLOCKS. FURTHER DAMAGE TO THE BLADES COULD RESULT. IF NECESSARY, USE ONLY SHAPED TOOLS MADE OF HARDWOOD OR HARD PLASTICS MATERIAL AS PRYING OR PUSHING TOOLS.

(a) Past experience has shown that it is possible to put back shingled/unlatched blades in their correct interlocking position. To do this, apply hand force as show in sheet 2.

Visual Inspection of the Stage 4 Blades ** ON A/C NOT FOR ALL

(b) If you can not remove the shingling/unlatching of two blades (or more) do no try further. Let expire the applicable limit extensions. Beyond these, it is up to the airline management to take the necessary hardware actions.
(2) Hard-facing wear on the blade interlock surfaces.

NOTE: A worn hard-facing may be at the origin of the shingling and unlatching defects. This condition results in radial and axial mismatches at the blade tip shrouds which are no longer in the same alignment (radial out-of-flush, for example).

(a) You can measure the interlock wear by the quantity of the aft mismatch of the blade tip shroud.
(b) Use the honeycomb cells in the outer stationary air seal as a scale to measure the quantity of mismatch.
One honeycomb cell is 0.06 in. (1.52 mm) in the largest dimension. If you are not sure, use modeling clay to get an imprint. Then, measure and record the value of the mismatch.
The mismatch at the aft edge of the blade tip shroud must not be more than 0.059 in. (1.50 mm).
(3) Blade pretwist check.

CAUTION: DO NOT USE PLIERS IN ORDER TO CLOSE THE GAPS AND GET BACK THEIR PRETWIST ANGLE. IT IS IMPOSSIBLE TO CORRECT THIS CONDITION.

(a) An incorrect pretwist is shown by gaps and some mismatch at the blade tip shrouds (sheet 3).

Visual Inspection of the Stage 4 Blades ** ON A/C NOT FOR ALL

Result: the adjacent interlock surfaces do not touch each other as they should. This condition is not serviceable.

if you see that kind of defects, let expire the applicable limit extensions. Beyond these, let the airline management take the necessary hardware actions
if not, you may want to take the opportunity of full access to the stage 4 blades and do the manual check shown in sheet 1.
Visual Inspection of the Stage 4 Blades ** ON A/C NOT FOR ALL
Do the check on at least 2 blades in each quadrant to make a good evaluation of the pretwist characteristic.

Subtask 72-54-00-410-086-A ** ON A/C NOT FOR ALL

C. Install the Exhaust Components Removed for Access to the Inspection Area
(1) Install the centerbody (Ref. AMM TASK 78-11-12-400-041).
(2) Install the core nozzle assembly (Ref. AMM TASK 78-11-11-400-041).

5. Close-up
Subtask 72-54-00-410-087-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 doors (Ref. AMM TASK 78-36-00-410-040):
(a) FOR [1000EM1] (ENGINE-1)
451AL 452AR
(b) FOR [1000EM2] (ENGINE-2)
461AL 462AR

Subtask 72-54-00-440-063-A ** ON A/C NOT FOR ALL

B. Make the thrust reverser serviceable (Ref. AMM TASK 78-30-00-081-041).

Subtask 72-54-00-410-088-A ** ON A/C NOT FOR ALL

C. Close Access
(1) Close the fan cowl doors (Ref. AMM TASK 71-13-00-410-040):
(a) FOR [1000EM1] (ENGINE-1)
437AL 438AR
(b) FOR [1000EM2] (ENGINE-2)
447AL 448AR
(2) Remove the WARNING NOTICE(S).

[Rev.10 from 2021] 2026.04.01 02:43:10 UTC