Removal of the Air Inlet Check Valve

TASK 21-26-56-000-001-A
Removal of the Air Inlet Check Valve

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	ACCESS PLATFORM 2M (6 FT)
No specific	AR	PLUG - BLANKING
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
824

C. Referenced Information

REFERENCE	DESIGNATION
TASK 21-26-43-000-003-A	Removal of the Filter Assembly
TASK 21-26-43-000-006-A	Removal of the Filter Assembly
TASK 24-42-00-861-001-A	Energize the Ground Service Network from the External Power
TASK 52-41-00-010-002-A	Open the Avionics Compartment Doors for Access
Air Inlet Check-Valve

3. Job Set-up

CAUTION: USE ONLY THE GROUND SERVICE NETWORK TO SUPPLY ELECTRICITY BECAUSE THE AVIONICS VENTILATION SYSTEM IS NOT SERVICEABLE. IF YOU ENERGIZE THE AIRCRAFT ELECTRICAL CIRCUITS WITHOUT THE VENTILATION SYSTEM YOU WILL CAUSE DAMAGE TO ELECTRICAL EQUIPMENT.

Subtask 21-26-56-861-050-A

A. Energize the ground service network (Ref. AMM TASK 24-42-00-861-001).

Subtask 21-26-56-865-050-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	AIR COND/AVNCS VENT/CTL	6HQ	D06
49VU	AIR COND/AVNCS VENT/CTL	5HQ	D05
122VU	AIR COND/AVNCS/VENT/MONG	3HQ	Y17
** ON A/C NOT FOR ALL
123VU	AVNCS VENT/EXTC/FAN	2HQ	AE02
** ON A/C ALL
123VU	AVNCS VENT/BLOWER/FAN	1HQ	AD10
** ON A/C NOT FOR ALL
123VU	AVNCS VENT/EXTC/FAN	2HQ	AC04

Subtask 21-26-56-010-050-A

C. Get Access
(1) Put the ACCESS PLATFORM 2M (6 FT) in position below access door 824.
(2) Open access door 824 (Ref. AMM TASK 52-41-00-010-002).

4. Procedure
Subtask 21-26-56-020-050-C

A. Removal of the Air Inlet Check-Valve
(1) Remove the clamp (3).
(2) Remove the filter assembly (1) (Ref. AMM TASK 21-26-43-000-006) or (Ref. AMM TASK 21-26-43-000-003).
(3) Remove and discard the O-ring (2).
(4) Remove the screws (6) and the washers (5).
(5) Remove the check valve (4).
(6) Put the PLUG - BLANKING on the disconnected line ends.

[Rev.10 from 2021] 2026.04.02 06:11:09 UTC