Leak Test of the APU

TASK 49-00-00-790-002-A
Leak Test of the APU

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

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	FLASHLIGHT
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
No specific	1	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
314AR, 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 49-00-00-100-002-A	Cleaning of the APU Compartment with installed APU (APS 3200)
TASK 49-00-00-100-804-A	Cleaning of the APU Compartment without the APU Installed
TASK 49-00-00-710-008-A	Operational Test of the APU
TASK 49-00-00-790-805-A	Check of the APU Compartment and the Air Intake Duct for Oil Contamination or Oil Leakage after Oil Smell in the Cabin (APS 3200)
TASK 49-16-00-100-006-A	Cleaning of the APU Air Intake (APS 3200)
TASK 49-21-00-000-001-A	Removal of the Oil Transfer Tubes (APS 3200)
TASK 49-21-00-400-001-A	Installation of the Oil Transfer Tubes (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
TASK 52-41-23-010-801-A	Opening of Access Door 314AR
TASK 52-41-23-410-801-A	Closing of Access Door 314AR

3. Job Set-up
Subtask 49-00-00-860-071-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).

4. Procedure
Subtask 49-00-00-790-051-A ** ON A/C NOT FOR ALL

A. Test the APU for Oil/Fuel Leaks
(1) Start and operate the APU for five minutes in the ECS mode (Ref. AMM TASK 49-00-00-710-008).
(2) During the operation of the APU:

Do a check for oil smell in the passenger compartment. We recommend that you use an air-quality measuring device to get an accurate estimate.
Do a 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 49-00-00-710-008).

Subtask 49-00-00-860-231-A ** ON A/C NOT FOR ALL

B. Aircraft Maintenance Configuration
(1) On the overhead panel 25VU, make sure that the APU MASTER SW pushbutton switch is released (ON legend is off).
(2) Make sure that the hydraulic systems are depressurized
(Ref. AMM TASK 29-00-00-864-001).
(3) On the APU section of overhead panel 25VU, put a WARNING NOTICE(S) to tell persons not to start the APU.

Subtask 49-00-00-865-092-A ** ON A/C NOT FOR ALL

C. 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 49-00-00-010-063-A ** ON A/C NOT FOR ALL

D. 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 a safety harness before you start work in the work area
(2) Put the ACCESS PLATFORM 4M (13 FT)-ADJUSTABLE in position below the APU access doors 315AL and 316AR.
(3) Open the APU access doors 315AL and 316AR (Ref. AMM TASK 52-41-00-010-001).
(4) Set the light switch 11LJ to the ON position.
(5) Open access door 314AR and safety it in the open position.
(Ref. AMM TASK 52-41-23-010-801).
(6) If necessary, use a FLASHLIGHT.

Subtask 49-00-00-210-061-A ** ON A/C NOT FOR ALL

E. Visually Inspect the APU for Oil/Fuel Leaks.
(1) Do an inspection of the oil scavenge (6 o'clock position) transfer tube for oil leaks.

If you find leaks, replace the oil-scavenge transfer tube (Ref. AMM TASK 49-21-00-000-001), (Ref. AMM TASK 49-21-00-400-001).

(2) Do an inspection of the oil supply (11 o'clock position) transfer tube for oil leaks.

If you find leaks, replace the oil-supply transfer tube (Ref. AMM TASK 49-21-00-000-001), (Ref. AMM TASK 49-21-00-400-001).

(3) Do an inspection of the oil vent (1 o'clock position) transfer tube for oil leaks.

If you find leaks, replace the oil-vent transfer tube (Ref. AMM TASK 49-21-00-000-001), (Ref. AMM TASK 49-21-00-400-001).

(4) Do a check for oil at the forward bearing seal-drain (Ref. AMM TASK 49-00-00-790-805).
(5) Make sure that adjacent area to the replaced part(s) is inspected for oil leak(s)/presence and cleaned if necessary.
(6) 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 externally .
(c) Clean the APU compartment (Ref. AMM TASK 49-00-00-100-002) or (Ref. AMM TASK 49-00-00-100-804).
(d) Clean the APU access doors internally and externally (Ref. AMM TASK 49-00-00-100-804).
(e) Clean the APU air intake flap internally/externally as necessary (Ref. AMM TASK 49-16-00-100-006).
(7) 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 49-16-00-100-006).

5. Close-up
Subtask 49-00-00-410-067-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 access door 314AR (Ref. AMM TASK 52-41-23-410-801).
(3) Set the light switch 11LJ to the OFF position.
(4) Close the APU access doors 315AL and 316AR (Ref. AMM TASK 52-41-00-410-001).
(5) Remove the access platform(s).
(6) Remove the WARNING NOTICE(S).

Subtask 49-00-00-865-093-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 49-00-00-860-072-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).

[Rev.10 from 2021] 2026.04.01 01:25:52 UTC