Leak Test of the APU

TASK 49-00-00-790-003-A
Leak Test of the APU

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	AR	SAFETY CLIP - CIRCUIT BREAKER

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 49-00-00-710-010-A	Operational Test of the APU
TASK 49-00-00-860-008-A	APU Start by External Power
TASK 49-00-00-860-008-A-01	APU Start by Batteries
TASK 49-00-00-860-009-A	APU Shutdown by External Power (131-9(A))
TASK 49-00-00-860-009-A-01	APU Shutdown by Batteries (131-9(A))
TASK 49-11-11-000-004-A	Removal of the Power Plant (APU) (131-9(A))
TASK 49-11-11-400-004-A	Installation of the Power Plant (APU) (131-9(A))
TASK 49-16-00-100-005-A	Cleaning of the APU Air Intake (131-9(A))
TASK 49-23-51-000-004-A	Removal of the Inlet Guide Vane - Actuator (131-9(A))
TASK 49-23-51-400-004-A	Installation of the Inlet Guide Vane - Actuator (131-9(A))
TASK 49-32-11-000-003-A	Removal of the Fuel Control Unit (FCU) (131-9(A))
TASK 49-32-11-400-003-A	Installation of the Fuel Control Unit (FCU) (131-9(A))
TASK 49-51-52-000-003-A	Removal of the Surge Control Valve (131-9(A))
TASK 49-51-52-400-003-A	Installation of the Surge Control Valve (131-9(A))
TASK 49-91-45-000-003-A	Removal of Oil Lube Module (131-9(A))
TASK 49-91-45-400-003-A	Installation of Oil Lube Module (131-9(A))
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
TASK 49-20-00-00-16	ENGINE - DESCRIPTION AND OPERATION

3. Job Set-up
Subtask 49-00-00-860-098-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 the panel 25VU, make sure that the APU MASTER SW p/bsw is OFF.
(3) Make sure that the hydraulic systems are depressurized
(Ref. AMM TASK 29-00-00-864-001).

4. Procedure
Subtask 49-00-00-790-052-A ** ON A/C NOT FOR ALL

A. Test the APU for Oil/Fuel Leaks
(1) Start and operate the APU in the ECS mode (Ref. AMM TASK 49-00-00-710-010).
(2) During APU operation:

check for oil smell in the passenger compartment.
check for smoke from the APU exhaust.

NOTE: Oil smell in the passenger compartment is an indication of internal oil leakage or ingestion of external oil leakage. Smoke from the APU exhaust is an indication of internal oil leakage.

(3) Stop the APU (Ref. AMM TASK 49-00-00-860-009).
(4) Put a warning notice in the cockpit to tell persons not to start the APU.

Subtask 49-00-00-865-105-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 49-00-00-010-066-A ** ON A/C NOT FOR ALL

C. Get Access

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

(1) Put the access platform in position below the APU access doors 315AL and 316AR.
(2) Open the APU access doors 315AL and 316AR (Ref. AMM TASK 52-41-00-010-001).
(3) Set the LIGHT control SW 11LJ to the ON position.

Subtask 49-00-00-790-063-A ** ON A/C NOT FOR ALL

D. Test of the APU Drain Lines for Oil/Fuel Leaks
(1) Do a check of the APU drain mast for oil and/or fuel leaks.
(2) If you find leaks on the APU drain mast, to find the source of the leakage, do a check of the drain lines of:

The Fuel Control Unit (FCU)/lube module
The surge control valve
The Inlet Guide Vane (IGV) actuator
The load-compressor cavity drain.

(a) Refer to the table in ATA (Ref. AMM D/O 49-20-00-00) for the oil and fuel leakage limits.
(3) If the source of the leakage is the FCU/lube module:
(a) Measure the leakage rate.
(b) If the leakage rate is more than the maximum permitted value, replace the packing between the FCU and the lube module (Ref. AMM TASK 49-32-11-000-003) and (Ref. AMM TASK 49-32-11-400-003).
(c) Clean the drain line of the FCU/lube module.
(d) Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
(e) Make sure that there are no more leaks.
(f) If you find leaks on the drain line of the FCU/lube module again, measure the leakage rate.
1 If the leakage rate is more than the maximum permitted value, find the type of the leakage.
a If you find fuel leaks:

Replace the FCU (Ref. AMM TASK 49-32-11-000-003) and (Ref. AMM TASK 49-32-11-400-003).
Clean the drain line of the FCU/lube module.
Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
Make sure that there are no more leaks.

b If you find oil leaks:

Replace the FCU (Ref. AMM TASK 49-32-11-000-003) and (Ref. AMM TASK 49-32-11-400-003).
Clean the drain line of the FCU/lube module.
Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
Make sure that there are no more leaks.

c If you cannot find the type of the leakage:

Replace the FCU (Ref. AMM TASK 49-32-11-000-003) and (Ref. AMM TASK 49-32-11-400-003).
Clean the drain line of the FCU/lube module.
Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
Make sure that there are no more leaks.
If you find leaks again and if the leakage rate is more than the maximum permitted value, replace the oil lube module (Ref. AMM TASK 49-91-45-000-003) and (Ref. AMM TASK 49-91-45-400-003).
Clean the drain line of the FCU/lube module.
Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
Make sure that there are no more leaks.

d If the leakage is not fuel or oil:

Replace the FCU and the oil lube module (Ref. AMM TASK 49-32-11-000-003), (Ref. AMM TASK 49-32-11-400-003), (Ref. AMM TASK 49-91-45-000-003) and (Ref. AMM TASK 49-91-45-400-003).
Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
Make sure that there are no more leaks.

(4) If the source of the leakage is the surge control valve:
(a) Measure the leakage rate.
(b) If the leakage rate is more than the maximum permitted value, replace the packings of the surge control valve (Ref. AMM TASK 49-51-52-000-003) and (Ref. AMM TASK 49-51-52-400-003).
(c) Clean the drain line of the surge control valve.
(d) Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
(e) Make sure that there are no more leaks.
(f) If you find leaks on the drain line of the surge control valve again, measure the leakage rate.
(g) If the leakage rate is more than the maximum permitted value, replace the surge control valve (Ref. AMM TASK 49-51-52-000-003) and (Ref. AMM TASK 49-51-52-400-003).
(h) Clean the drain line of the surge control valve.
(i) Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
(j) Make sure that there are no more leaks.
(5) If the source of the leakage is the IGV actuator:
(a) Measure the leakage rate.
(b) If the leakage rate is more than the maximum permitted value, replace the packings of the IGV actuator (Ref. AMM TASK 49-23-51-000-004) and (Ref. AMM TASK 49-23-51-400-004).
(c) Clean the drain line of the IGV actuator.
(d) Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
(e) Make sure that there are no more leaks.
(f) If you find leaks on the drain line of the IGV actuator again, measure the leakage rate.
(g) If the leakage rate is more than the maximum permitted value, replace the IGV actuator (Ref. AMM TASK 49-23-51-000-004) and (Ref. AMM TASK 49-23-51-400-004).
(h) Clean the drain line of the IGV actuator.
(i) Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
(j) Make sure that there are no more leaks.
(6) Do a check of the cavity drain of the load compressor on the drain mast.
(a) If you find oil leaks on the cavity drain of the load compressor, replace the APU (Ref. AMM TASK 49-11-11-000-004) and (Ref. AMM TASK 49-11-11-400-004).
(b) Clean the drain line of the IGV actuator.
(c) Operate the APU for five minutes (Ref. AMM TASK 49-00-00-860-008) and (Ref. AMM TASK 49-00-00-860-009).
(d) Make sure that there are no more leaks.

Subtask 49-00-00-210-066-A ** ON A/C NOT FOR ALL

E. Visually Inspect the APU for Oil/Fuel Leaks.
(1) Inspect the APU and plumbing for oil/fuel leaks. If leak(s) are apparent:
(a) Locate and repair all oil/fuel leaks.
(b) Clean the APU compartment.
(c) Clean the APU access doors internally and externally.
(d) Clean the APU air intake flap internally/externally as necessary.
(2) Check for oil/fuel migration externally/internally into the APU air intake duct. If the air intake and air intake duct are found to be contaminated, clean the air intake duct (Ref. AMM TASK 49-16-00-100-005).

5. Close-up
Subtask 49-00-00-410-070-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 control SW 11LJ to the OFF position.
(3) Close the APU access doors 316AR 315AL (Ref. AMM TASK 52-41-00-410-001).
(4) Remove the access platform(s).

Subtask 49-00-00-865-106-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 49-00-00-860-099-A ** ON A/C NOT FOR ALL

C. Aircraft Maintenance Configuration
(1) Put the related hydraulic system in the pressurized configuration (Ref. AMM TASK 29-00-00-864-001).
(2) De-energize the aircraft electrical circuits
(Ref. AMM TASK 24-41-00-862-002).
(3) Remove the WARNING NOTICE(S).

[Rev.10 from 2021] 2026.04.01 01:26:01 UTC