Leak Check on all the Bleed Air Ducts [IAE]

TASK 75-21-00-790-801-A
Leak Check on all the Bleed Air Ducts

WARNING: BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS.

1. Reason for the Job
This procedure gives the general description of the leak check on all the bleed air ducts.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	FOIL - ALUMINUM
No specific	AR	WATER - DISTILLED
No specific	AR	WATER - SOAPY SOLUTION
08STHEB	1	SURFACE TEMPERATURE INDICATOR

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.14QEB1)	Wire-Locking Dia: 0.6 mm CRES Nickel Alloy -
(Material No.14SBA1)	Textile-Lint free Cotton -

C. Referenced Information

REFERENCE	DESIGNATION
TASK 71-00-00-710-012-B	Test No.3 : Idle Leak Check
Typical Installation of Indicator Strip-Temp Self Adhesive

3. Job Set-up
Subtask 75-21-00-860-050-A ** ON A/C NOT FOR ALL

WARNING: WHEN THE THRUST REVERSER COWLS AND FAN COWLS ARE OPEN AND SAFETIED WITH THE HOLD-OPEN RODS, DO NOT OPERATE THE ENGINE AT POWER HIGHER THAN IDLE. IF YOU DO NOT OBEY THIS INSTRUCTION, INJURY TO PERSONS AND/OR DAMAGE TO EQUIPMENT CAN OCCUR.

A. Aircraft Maintenance Configuration

NOTE: Some tubes/ducts can only be pressurized while the engine is running

(1) To do a leak check, you can use three potential air sources:

Air source from the APU
Air source from a ground air-supply unit.
Engine Air

(2) For leak checks that require engine air refer to (Ref. AMM TASK 71-00-00-710-012) for the set-up and engine run procedures (only). It is not necessary to follow the fluid leak check procedures included in that task.

4. Procedure
Subtask 75-21-00-790-050-A ** ON A/C NOT FOR ALL

A. Leak Check on all the Bleed Air Ducts

NOTE: There are three methods to do a leak check at the connections of the bleed air ducts (duct joint, flexible connections).

(1) Soap solution method.

NOTE: Leaks are permitted if the WATER - SOAPY SOLUTION stays on the joint line with a continuous series of bubbles. This shows that the leaks are not important.
Leaks are not permitted if the air pressure (from the air source) blows the soap solution off the joint line and prevents a continuous series of bubbles.

(2) Aluminum foil method.

NOTE: This method is recommended when you do a leak check with hot air.

(a) Wind the FOIL - ALUMINUM on the joint once.
(b) Twist tight the seam of the foil wrap.
(c) Make the foil wrap as tight as possible on the tube but do not rip the wrap.
(d) Attach the foil wrap at the two sides of the pneumatic joint with lockwire 14QEB1Wire-Locking Dia: 0.6 mm CRES Nickel Alloy -.
(e) Do a leak check:
1 If there is a leak, the foil installed on the duct breaks or becomes too hot.
(3) Indicator strip-temp self adhesive method.

NOTE: This procedure is recommended when you do a leak check with hot air and if you found no leak with the aluminum foil procedure.

NOTE: The indicators strip-temp self adhesive monitor the temperature in range of approximately 158 deg.F (70.00 deg.C) to 230 deg.F (110.00 deg.C).

(a) Wrap the 08STHEB SURFACE TEMPERATURE INDICATOR around the overheat sensing element in the applicable area.
(b) Do a check of the indicators strip-temp self adhesive after an engine or APU operation with bleed air system in operation, or after the subsequent flight.
1 There is a leak in the area if the temperature is more than 230 deg.F (110.00 deg.C).

5. Close-up
Subtask 75-21-00-860-051-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Use WATER - DISTILLED to remove all the soap solution from the ducts, and dry with Textile-Lint free Cotton - (Material No.14SBA1) or remove materials used to do the leak test.
(2) For leak checks that required engine air, follow the engine "close-up" shown in the task as follows: (Ref. AMM TASK 71-00-00-710-012).

[Rev.10 from 2021] 2026.04.01 03:11:05 UTC