Borescope Inspection of the APU Power Plant (APS 3200)

TASK 49-20-00-290-001-A
Borescope Inspection of the APU Power Plant (APS 3200)

WARNING: DO NOT TOUCH THE APU UNTIL IT IS SUFFICIENTLY COOL TO PREVENT BURNS WHEN YOU DO THE MAINTENANCE TASK(S).

WARNING: DISCONNECT THE LOW-TENSION ELECTRICAL SUPPLY 6 MINUTES BEFORE YOU START WORK ON THE IGNITION SYSTEM. THE HIGH CURRENT AND VOLTAGE WHICH ARE USED IN THE IGNITION SYSTEM CAN KILL YOU.

FIN: 4005KM ** ON A/C NOT FOR ALL

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 4M (13 FT)-ADJUSTABLE
No specific	1	BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR
No specific	1	BORESCOPE - RIGID
No specific	1	BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE
No specific	1	BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
No specific	1	WARNING NOTICE(S)
98L12003001000	AR	HARNESS,SAFETY
TB3043G002	1	TOOL FOR ENDOSCOPIC INSPECTION

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
315AL, 316AR

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 24-41-00-862-002-A	De-energize the Aircraft Electrical Circuits Supplied from the External Power
TASK 24-41-00-862-002-A-01	De-energize the Aircraft Electrical Circuits Supplied from the APU
TASK 24-41-00-862-002-A-02	De-energize the Aircraft Electrical Circuits Supplied from the Engine 1(2)
TASK 29-00-00-864-001-A	Put the Related Hydraulic System in the Depressurized Configuration before Maintenance Action
TASK 49-00-00-710-008-A	Operational Test of the APU
TASK 49-11-11-000-003-A	Removal of the Power Plant (APU) (APS 3200)
TASK 49-11-11-400-003-A	Installation of the Power Plant (APU) (APS 3200)
TASK 49-16-48-210-001-A	Detailed Inspection of the acoustic bulkhead pins (APS 3200)
TASK 49-41-41-000-003-A	Removal of the Igniter Plug(s) (APS 3200)
TASK 49-41-41-400-002-A	Installation of the Igniter Plug(s) (APS 3200)
TASK 49-52-53-000-001-A	Removal of the Permanent Magnet Generator (PMG) and Cooling Fan Assembly (APS 3200)
TASK 49-52-53-400-001-A	Installation of the Permanent Magnet Generator (PMG) and Cooling Fan Assembly (APS 3200)
TASK 49-72-15-000-001-A	Removal of the Thermocouple (APS 3200)
TASK 49-72-15-400-002-A	Installation of the Thermocouple (APS 3200)
TASK 52-41-00-010-001-A	Open the APU Doors for Access
TASK 52-41-00-410-001-A	Close the APU Doors after Access
APU Power Plant - Borescope Inspection
Power Compressor and Load Compressor Impeller-Blades
IGVs
APU Borescope Inspection
Nozzle Guide Vanes and Turbine Blades
Diffuser Vanes

3. Job Set-up
Subtask 49-20-00-860-055-A ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration
(1) Energize the aircraft electrical circuits
(Ref. AMM TASK 24-41-00-861-002).
(2) On overhead panel 25VU, make sure that the APU MASTER SW pushbutton switch is released (the ON legend is off).
(3) On the APU section of overhead panel 25VU, make sure that the WARNING NOTICE(S) is in position to tell persons not to start the APU.
(4) Make sure that the hydraulic systems are depressurized
(Ref. AMM TASK 29-00-00-864-001).

Subtask 49-20-00-865-070-A ** ON A/C NOT FOR ALL

B. Open, safety and tag this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
121VU	APU/APU/CTL	2KD	L42
121VU	APU/ECB/SPLY	1KD	L41

Subtask 49-20-00-010-059-A ** ON A/C NOT FOR ALL

C. Get Access

WARNING: BEFORE YOU START WORK, YOU MUST PUT ON A SAFETY HARNESS AND ATTACH IT TO THE ACCESS PLATFORM. WITHOUT A SAFETY HARNESS, YOU CAN FALL. THIS CAN KILL YOU OR CAUSE YOU INJURY.

(1) Put on and attach the HARNESS, SAFETY before you start work in the work area.
(2) Put an ACCESS PLATFORM 4M (13 FT)-ADJUSTABLE in position below APU access doors 315AL and 316AR.
(3) Open APU access doors 315AL and 316AR (Ref. AMM TASK 52-41-00-010-001).
(4) Set the light switch 11LJ to the ON position.

4. Procedure
Subtask 49-20-00-020-057-A ** ON A/C NOT FOR ALL

A. Preparation for the Inspection
(1) Remove the cooling-fan inlet duct. To do this, refer to step 4.A.(1).(f) of (Ref. AMM TASK 49-52-53-000-001).
(2) Remove the two igniter plugs (Ref. AMM TASK 49-41-41-000-003).
(3) Remove the left thermocouple probe (Ref. AMM TASK 49-72-15-000-001).
(4) The borescope inspection kit has the components that follow:

The BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE
The BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE
The TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION
The BORESCOPE - RIGID
The borescope battery
The cable adapter
The liquid light guide-cable
The eye-piece adapter
The BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR.

NOTE: If borescopes with the recommended diameters are not available, you can use alternative borescopes with smaller diameters.
If you use borescopes with smaller diameters than those of the recommended tools, the field of vision will be smaller and the inspection time will be longer.

Subtask 49-20-00-290-059-A ** ON A/C NOT FOR ALL

CAUTION: BEFORE YOU PUT THE BORESCOPE TOOL(S) INTO THE APU, MAKE SURE THAT THE APU INTERNAL TEMPERATURE IS NOT MORE THAN 66 DEG.C (150.80 DEG.F). HEAT CAN CAUSE DAMAGE TO THE BORESCOPE TOOL(S).

B. Inspection

APU Power Plant - Borescope Inspection ** ON A/C NOT FOR ALL

(1) Inspection of the load compressor and the Inlet Guide Vanes (IGV):
(a) Connect the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE to the BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR with the liquid light guide-cable. Adjust the light intensity to the necessary brightness.
(b) Put the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE into the front half of the air inlet plenum (1).
(c) Do an inspection of the IGVs:

IGVs ** ON A/C NOT FOR ALL

1 Cracks are not permitted.
2 Bent vanes are not permitted.
3 Erosion is permitted.
(d) If the IGVs are not in the correct condition, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003).
(e) Put the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE through an IGV that has holes (1).
(f) Inspection of the impeller Leading Edge (LE) blades of the load compressor:
1 Put the applicable ratchet handle, extension and socket in position on the retaining nut of the cooling-fan center shaft.

CAUTION: BEFORE YOU TURN THE ENGINE, MAKE SURE THAT THE BORESCOPE OPTICAL HEAD IS AWAY FROM THE ROTATING ASSEMBLY PARTS. IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE BORESCOPE AND THE ROTATING ASSEMBLY CAN OCCUR.

2 Turn the rotor slowly.
3 Do an inspection of the impeller LE blades of the load compressor:

Power Compressor and Load Compressor Impeller-Blades ** ON A/C NOT FOR ALL

a Cracks are not permitted.
b One bend of no more than 30 degrees with no signs of cracks is permitted on each blade.
c Dents, nicks or cracks are not permitted in the blade root area.

NOTE: The length of the blade root area is one quarter of the length of the blade LE from the root.

d Erosion and dents are permitted in the identified area on the blade LE tip.
e Blade cropping is permitted if it is the result of a repair.
(g) If the load-compressor impeller LE-blades are not in the correct condition, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003).
(h) Remove the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE from the air inlet plenum (1).
(2) Inspection of the power section compressor:
(a) Connect the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE to the BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR with the liquid light guide-cable. Adjust the light intensity to the necessary brightness.
(b) Put the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE into the rear half of the air inlet plenum (2).
1 If you find signs of damage, do an inspection of the condition of the air inlet plenum (2) (Ref. AMM TASK 49-16-48-210-001).
(c) Inspection of the impeller LE blades of the power compressor:
1 Put the applicable ratchet handle, extension and socket in position on the retaining nut of the cooling-fan center shaft.

2 Turn the rotor slowly.
3 Do an inspection of the impeller LE blades of the power compressor:

Power Compressor and Load Compressor Impeller-Blades ** ON A/C NOT FOR ALL

a Cracks are not permitted.
b Bends are not permitted.
c Dents, nicks or cracks are not permitted in the blade root area.

NOTE: The length of the blade root area is one quarter of the length of the blade LE from the root.

d Erosion, dents or nicks are permitted on the blade LE tip, if there are no cracks in the identified area.
e Blade cropping is not permitted.
(d) If the power-compressor impeller LE-blades are not in the correct condition, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003).
(e) Put the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE between the impeller blades until you can see a diffuser vane.
(f) Do an inspection of the Trailing Edge (TE) blades. To do this, move the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE between each blade and make sure that there are no missing tips at the long TE blades.
1 If one or more tips are missing, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003).
(g) Turn the rotor assembly very slowly and examine the diffuser vanes at the fan impeller. Do this in four different locations through the inlet screen and the lower plenum:

NOTE: You can only see a small area of the diffuser circumference. You can only examine the lower part of the diffuser circumference.

Diffuser Vanes ** ON A/C NOT FOR ALL

1 Cracks are not permitted.
2 Erosion, dents and missing parts are permitted in the identified areas.
(h) If the diffuser vanes are not in the correct condition, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003).
(i) Remove the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE from the air inlet plenum (2).
(3) Inspection of the combustor exhaust and lining:

For the damage limits,
APU Borescope Inspection ** ON A/C NOT FOR ALL

(a) Inspection of the combustor exhaust area:
1 Connect the BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE to the BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR with the liquid light guide-cable. Adjust the light intensity to the necessary brightness.
2 Put the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION into the combustor through the plug mounting boss of the right igniter (3).
3 Engage the BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE through the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION.
4 Do an inspection of the combustor exhaust area as far as possible:
a For the damage limits and the subsequent corrective actions, refer to step 4.B.(3)(c).
5 Remove the BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE and the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION from the combustor.
6 Put the BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE and the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION through the plug mounting boss of the left igniter (3).
7 Do steps 3, 4 and 5 again.
(b) Inspection of the combustor liner:
1 Connect the BORESCOPE - RIGID to the BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR with the liquid light guide-cable. Adjust the light intensity to the necessary brightness.
2 Put the BORESCOPE - RIGID into the combustor through the plug mounting boss of the right igniter (3).
3 Do an inspection of the combustor liner as far as possible:
a For the damage limits and the subsequent corrective actions, refer to step 4.B.(3)(c).
4 Remove the BORESCOPE - RIGID from the combustor.
5 Put the BORESCOPE - RIGID into the combustor through the plug mounting boss of the left igniter (3).
6 Do steps 3 and 4 again.
(c) If you find cracks, holes, erosion, distortion or burns that are not in the limits that follow, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003):
1 Cracks are permitted in the combustor liner circumference if there is no intersection with other cracks that can cause the material to break.
2 Cracks are permitted in the internal cooling strips to a maximum of:

One quarter of the strip width, or
One quarter of the strip length.

3 Burn spots are permitted if there is no burn-through.
4 Circumference cracks in the exhaust bend assembly are permitted to a maximum of one half of the circumference if the crack does not cause the material to break.
a More than one crack is permitted if the total length of these cracks is less than one half of the circumference.

NOTE: The total circumference length is equivalent to 16 cooling plates (one half of the circumference is equivalent to eight cooling plates).

(4) Inspection of the first stage turbine:
(a) Connect the BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE to the BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR with the liquid light guide-cable. Adjust the light intensity to the necessary brightness.
(b) Put the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION into the combustor through the plug mounting boss of the left igniter (3).
(c) Engage the BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE through the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION.
(d) Do an inspection of the first-stage nozzle guide-vane:

Nozzle Guide Vanes and Turbine Blades ** ON A/C NOT FOR ALL

1 Broken blades are not permitted.
2 Holes across the vanes on the leading edge are not permitted.
3 Erosion and cracks on the leading edge are permitted, refer to the limits given in the figure.
4 Cracks on the trailing edge are permitted, refer to the limits given in the figure.
5 Particles of thermal barrier coating on the trailing edge are permitted.
(e) If the first-stage nozzle guide-vane is not in the correct condition, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003).
(f) Inspection of the first stage turbine-blades:
1 Put the applicable ratchet handle, extension and socket in position on the retaining nut of the cooling-fan center shaft.

2 Turn the rotor slowly.
3 Do an inspection of the first stage turbine-blades:

Nozzle Guide Vanes and Turbine Blades ** ON A/C NOT FOR ALL

a Cracks are not permitted.
b Bends are not permitted.
c Dents, erosion, burns or nicks are permitted, if there are no cracks in the identified area.
d Damage in the platform/airfoil link radius is not permitted.
(g) If the first stage turbine-blades are not in the correct condition, replace the APU (Ref. AMM TASK 49-11-11-000-003) and (Ref. AMM TASK 49-11-11-400-003).
(h) Remove the BORESCOPE DIA 5.0 MM (7/32 IN) - FLEXIBLE and the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION from the combustor.
(5) Inspection of the second stage turbine:
(a) Connect the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE to the BORESCOPE - HIGH INTENSITY LIGHT PROJECTOR with the liquid light guide-cable. Adjust the light intensity to the necessary brightness.
(b) Put the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION into the thermocouple mount boss (4).
(c) Engage the BORESCOPE DIA 8.0 MM (5/16 IN) - FLEXIBLE through the TB3043G002 TOOL FOR ENDOSCOPIC INSPECTION.
(d) Inspection of the second stage turbine-blades:
1 Put the applicable ratchet handle, extension and socket in position on the retaining nut of the cooling-fan center shaft.

2 Turn the rotor slowly.
3 Do an inspection of the second stage turbine-blades:

NOTE: You can only see the trailing edge. You cannot see the leading edge with the borescope tools.

Nozzle Guide Vanes and Turbine Blades ** ON A/C NOT FOR ALL

Subtask 49-20-00-420-053-A ** ON A/C NOT FOR ALL

C. Installation
(1) Install the two igniter plugs (Ref. AMM TASK 49-41-41-400-002).
(2) Install the LH thermocouple (Ref. AMM TASK 49-72-15-400-002).
(3) Install the cooling-fan inlet duct (Ref. AMM TASK 49-52-53-400-001).

5. Close-up
Subtask 49-20-00-410-061-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) Set the light switch 11LJ to the OFF position.
(3) Close APU access doors 315AL and 316AR (Ref. AMM TASK 52-41-00-410-001).
(4) Remove the access platform(s).
(5) Remove the 98L12003001000 HARNESS,SAFETY.

Subtask 49-20-00-865-071-A ** ON A/C NOT FOR ALL

B. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
121VU	APU/APU/CTL	2KD	L42
121VU	APU/ECB/SPLY	1KD	L41

Subtask 49-20-00-710-065-A ** ON A/C NOT FOR ALL

C. Do the operational test of the APU (Ref. AMM TASK 49-00-00-710-008)

Subtask 49-20-00-860-051-A ** ON A/C NOT FOR ALL

D. Aircraft Maintenance Configuration
(1) Pressurize the aircraft hydraulic systems
(Ref. AMM TASK 29-00-00-864-001).
(2) Remove the WARNING NOTICE(S).
(3) De-energize the aircraft electrical circuits
(Ref. AMM TASK 24-41-00-862-002).

[Rev.10 from 2021] 2026.04.01 01:28:40 UTC