Installation of the Avionics Equipment Ventilation-Duct

TASK 21-26-42-400-001-A
Installation of the Avionics Equipment Ventilation-Duct

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.

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) - ADJUSTABLE
No specific	AR	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
824

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-42-00-861-001-A	Energize the Ground Service Network from the External Power
TASK 24-42-00-862-001-A	De-energize the Ground Service Network Supplied from the External Power
TASK 52-41-00-010-002-A	Open the Avionics Compartment Doors for Access
TASK 52-41-00-410-002-A	Close the Avionics Compartment Doors after Access
Avionics Equipment Ventilation-Duct

3. Job Set-up
Subtask 21-26-42-860-050-A

A. Aircraft Maintenance Configuration
(1) Make sure that the ground service network is energized (Ref. AMM TASK 24-42-00-861-001).
(2) On the AIR COND panel 30VU:
(a) Make sure that the APU BLEED, all ENG BLEED and the PACK 1(2) pushbutton switches are released.
(b) Make sure that a WARNING NOTICE(S) in position to tell persons not to operate these pushbutton switches.
(3) On the HP and LP ground connectors, make sure that a WARNING NOTICE(S) is in position to tell persons not to supply the ground air sources.

Subtask 21-26-42-010-051-A

B. Get Access
(1) Make sure that the ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE is in position at the access door 824.
(2) Make sure that the access door 824 is open (Ref. AMM TASK 52-41-00-010-002).

4. Procedure
Subtask 21-26-42-420-050-B

A. Installation of the Avionics Equipment Ventilation-Duct
(1) Clean the component interfaces and the adjacent area.
(2) Make sure that the clamps, the flexible sleeves and the duct are in the correct condition.
(3) Remove the PLUG-BLANKING from each disconnected line end.
(4) Install the clamp (8) on the bracket (7) and the duct (9). Do not tighten at this time.
(5) Put the flexible sleeves (11) in position on ducts (1) and (5).
(6) Install the duct (2).
(7) Make sure that the flexible sleeves (11) are in position between the two red markings.
(8) Install the clamps (10). Use the clamps (10) kept during the removal procedure.
(9) Make sure that the distance between the two red markings of the ducts is 90 -5 mm or +5 mm (3.543 -0.197 in. or +0.197 in.).
(10) Tighten the clamps (10).
(11) Install the clamp (6) and tighten it.
(12) Tighten the clamp (8).
(13) Connect the flexible hose (4).
(14) Install the clamp (3) and tighten it.

5. Close-up
Subtask 21-26-42-410-050-A

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the access door 824 (Ref. AMM TASK 52-41-00-410-002).
(3) Remove the access platform(s).

Subtask 21-26-42-862-051-A

B. De-energize the ground service network (Ref. AMM TASK 24-42-00-862-001).

[Rev.10 from 2021] 2026.04.01 12:30:37 UTC