Installation of the Avionics Equipment Blowing-Duct

TASK 21-26-42-400-802-A
Installation of the Avionics Equipment Blowing-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.

ZONE: 120
ZONE: 130

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
120	AVIONICS COMPARTMENT
130	FWD CARGO COMPT AFT BULKHEAD OF AVNCS COMPT TO FWD PRESSURE BULKHEAD OF WING CENTER BOX
131CW, 131DW, 131GW, 131HW

B. Referenced Information

REFERENCE	DESIGNATION
TASK 21-26-00-710-001-A	Operational Check of the Avionics Equipment Ventilation-System via MCDU
TASK 21-26-00-710-001-A-01	Operational Check of the Avionics Equipment Ventilation (without the CFDS)
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 25-54-11-000-001-A	Removal of the Forward Cargo-Compartment Partition FR24A
TASK 25-54-11-400-001-A	Installation of the Forward Cargo-Compartment Partition FR24A
TASK 25-54-12-000-003-A	Removal of the Sidewall Panels in the Forward Cargo Compartment
TASK 25-54-12-400-003-A	Installation of the Sidewall Panels in the Forward Cargo Compartment
TASK 52-30-00-860-001-A	Open the FWD or Aft Cargo-Compartment Door with the Yellow Electric Pump
Avionics Equipment Blowing-Duct

3. Job Set-up
Subtask 21-26-42-860-060-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 AIR COND panel 30VU:
(a) Make sure that the APU BLEED, all ENG BLEED and PACK 1(2) pushbutton switches are released.
(b) Make sure that the WARNING NOTICE(S) is(are) in position to tell persons not to operate these pushbutton switches.
(3) On the HP and the LP ground connectors, make sure that the WARNING NOTICE(S) is(are) in position to tell persons not to supply the ground air sources.

Subtask 21-26-42-865-063-A

B. Make sure that this(these) circuit breaker(s) is(are) open, safetied and tagged:

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 21-26-42-010-066-A

C. Get Access
(1) Make sure that the ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE is in position below the forward cargo-compartment door.
(2) Make sure that the forward cargo-compartment door is open (Ref. AMM TASK 52-30-00-860-001).
(3) Make sure that forward cargo-compartment partition-panels 131CW and 131DW are removed (Ref. AMM TASK 25-54-11-000-001).
(4) Make sure that forward cargo-compartment sidewall-panels 131GW and 131HW are removed (Ref. AMM TASK 25-54-12-000-003).

4. Procedure
Subtask 21-26-42-420-060-A

A. Installation of the Avionics Equipment Blowing-Duct
(1) Make sure that the parts retained from the removed component are clean and in the correct condition.
(2) Make sure that the clamps (3), (5) and (7), the flexible sleeves (6) and the ducts (1), (2) and (4) are in the correct condition.
(3) Remove the PLUG-BLANKING from each disconnected line end.
(4) Install the flexible sleeves (6) on the ducts (1) and (4).
(5) Put the duct (2) is in position into the flexible sleeves (6).
(6) Make sure that the flexible sleeves (6) are in position between the two red markings.
(7) Install the clamps (5) and (7) on the sleeves (6).
(8) Install the clamp (3) that attach the duct (2) to the structure.
(9) Make sure that the distance between the two red markings of the ducts (1), (2) and (4) is 90 +5 mm or -5 mm (3.5433 +0.1969 in. or -0.1969 in.).
(10) Tighten the clamps (3), (5) and (7).

Subtask 21-26-42-865-064-A

B. Remove the safety clip(s) and the tag(s) and close 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 21-26-42-710-050-A

C. Operational Test
(1) Do an operational test of the avionics equipment ventilation-system (Ref. AMM TASK 21-26-00-710-001):
(a) By hand make sure there is no leak on the connection you install.

NOTE: Leaks are not permitted.

(b) Stop the operational test.

5. Close-up
Subtask 21-26-42-410-062-A

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Install the forward cargo-compartment sidewall-panels 131HW and 131GW (Ref. AMM TASK 25-54-12-400-003).
(3) Install forward cargo-compartment partition-panels 131DW and 131CW (Ref. AMM TASK 25-54-11-400-001).
(4) Close the forward cargo-compartment door (Ref. AMM TASK 52-30-00-860-001).
(5) Remove the access platform(s).

Subtask 21-26-42-862-061-A

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

[Rev.10 from 2021] 2026.04.02 06:11:05 UTC