Removal of the Air Duct upstream of the Flow Control Unit

TASK 21-51-51-000-002-B
Removal of the Air Duct upstream of the Flow Control Unit

FIN: 23HB ** ON A/C NOT FOR ALL
FIN: 24HB ** ON A/C NOT FOR ALL

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	COVER - PROTECTION
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
FOR [23HB] (FLOW CTL UNIT - PACK 1)
191BB, 191KB
FOR [24HB] (FLOW CTL UNIT - PACK 2)
192FB, 192KB

C. Referenced Information

REFERENCE	DESIGNATION
TASK 21-51-51-200-002-A	Attachment Components (In-Service Wear Limits) - Air Duct
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 53-35-13-000-002-A	Removal of the Quick-Release Access Panels from the Belly Fairing Structure
Attachment Components - Air Duct
Attachment Components - Air Duct

3. Job Set-up
Subtask 21-51-51-861-055-A ** ON A/C NOT FOR ALL

A. Energize the aircraft electrical circuits (Ref. AMM TASK 24-41-00-861-002).

Subtask 21-51-51-865-066-A ** ON A/C NOT FOR ALL

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
FOR FIN: 23HB (FLOW CTL UNIT PACK 1)
49VU	AIR COND/TEMP CTL/SYS 1 CHAN B/28VDC	52HH	D08
122VU	AIR COND/TEMP CTL SYS 1/CHAN A/115VAC	49HH	X22
122VU	AIR COND/TEMP CTL SYS 1/CHAN A/28VDC	51HH	X21
122VU	AIR COND/TEMP CTL SYS 1/CHAN B/115VAC	50HH	Y18
FOR FIN: 24HB (FLOW CTL UNIT PACK 2)
122VU	AIR COND/TEMP CTL SYS 2/CHAN A/115VAC	53HH	W22
122VU	AIR COND/TEMP CTL SYS 2/CHAN A/28VDC	55HH	W21
122VU	AIR COND/TEMP CTL SYS 2/CHAN B/28VDC	56HH	Y21
122VU	AIR COND/TEMP CTL SYS 2/CHAN B/115VAC	54HH	Y20

Subtask 21-51-51-941-054-A ** ON A/C NOT FOR ALL

C. Safety Precautions
(1) On the panel 30VU:
(a) Make sure that:

the APU BLEED pushbutton switch is in the off position (the ON legend is off) and,
the ENG 1 BLEED and the ENG 2 BLEED pushbutton switches are in the off position (the OFF legends are on).

(b) Put a warning notice in position to tell persons not to operate these pushbutton switches.
(2) On the HP ground connector put a warning notice in position to tell persons not to supply the ground air.

Subtask 21-51-51-010-062-A ** ON A/C NOT FOR ALL

D. Get Access
(1) Remove the access panels (Ref. AMM TASK 53-35-13-000-002):
(a) FOR [23HB] (FLOW CTL UNIT - PACK 1)

191KB and
191BB.

(b) FOR [24HB] (FLOW CTL UNIT - PACK 2)

192KB and
192FB.

4. Procedure
Subtask 21-51-51-020-069-A ** ON A/C NOT FOR ALL

A. Removal of the Air Duct Assembly

Attachment Components - Air Duct ** ON A/C NOT FOR ALL

(1) Remove the nut (1), the washer (2), the screw (3) and disconnect the bonding strap (4).
(2) Remove the nuts (10), the washers (9) and the bolts (7) from the support rods (5).
(3) Remove the v-clamps (12) and (13).
(4) Remove the air duct assembly.
(5) Remove and discard the o-ring (11).
(6) Put COVER - PROTECTION on the open duct ends.

Subtask 21-51-51-020-070-A ** ON A/C NOT FOR ALL

B. Removal of the Support Rods

Attachment Components - Air Duct ** ON A/C NOT FOR ALL

(1) Remove the nuts (24), the washers (23), the bolts (20), the bushings (21) and the support rods (5) from the attachment brackets (22).
(2) Do the inspection of the components for in-service wear (Ref. AMM TASK 21-51-51-200-002).

[Rev.9 from 2019] 2026.04.02 06:11:23 UTC