Removal of the Sensing Elements

TASK 26-13-15-000-001-A
Removal of the Sensing Elements

FIN: 21WG
FIN: 22WG

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	AR	CAP - BLANKING
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 24-42-00-861-001-A	Energize the Ground Service Network from the External Power
TASK 29-00-00-864-001-A	Put the Related Hydraulic System in the Depressurized Configuration before Maintenance Action
TASK 52-41-00-010-001-A	Open the APU Doors for Access
TASK 52-41-23-010-801-A	Opening of Access Door 314AR
Sensing Elements of the APU Fire Detector
Sensing Elements - Installation

3. Job Set-up
Subtask 26-13-15-861-050-A

A. Aircraft Maintenance Configuration
(1) Put a warning notice on the panel 25VU to tell persons not to start the APU.
(2) Energize the ground service network
(Ref. AMM TASK 24-42-00-861-001).
(3) De-pressurize the hydraulic systems (Ref. AMM TASK 29-00-00-864-001).

Subtask 26-13-15-865-050-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	APU/FIRE AND OVHT/DET/LOOP B	2WG	L44
121VU	APU/FIRE AND OVHT/DET/LOOP A	1WG	L43
121VU	APU/APU/CTL	2KD	L42
121VU	APU/ECB/SPLY	1KD	L41
121VU	APU/FIRE/EXTIG/SQUIB/B	2WF	L39
121VU	APU/FIRE/EXTIG/SQUIB/A	1WF	L38
121VU	APU/FIRE/LP VALVE/NORM	4WF	M42
121VU	APU/FIRE/LP VALVE/STBY	3WF	M41

Subtask 26-13-15-010-050-A

C. Get Access
(1) Put the ACCESS PLATFORM 4M (13 FT)-ADJUSTABLE in position below the APU compartment.
(2) Open access door 314AR and safety it in the open position.
(Ref. AMM TASK 52-41-23-010-801).
(3) Open the APU access doors 315AL and 316AR (Ref. AMM TASK 52-41-00-010-001)
(4) Set the LIGHT control switch 11LJ to the ON position.

4. Procedure
Subtask 26-13-15-020-050-A

A. Removal of the APU Fire Sensors

NOTE: The procedure is the same for the APU fire sensors 21WG and 22WG.

(1) Turn the screws (2) and open the dual clamps (3).
(2) Keep the support bushes (1).
(3) Disconnect the electrical connector 21WG(22WG)-A (9).
(4) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.
(5) Remove the screws (6) and the washers (5).
(6) Disconnect the fire/overheat detector 21WG(22WG) (7) with the sensing element.
(7) Remove and discard the O-rings (4).
(8) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.

[Rev.10 from 2021] 2026.04.05 10:34:55 UTC