Removal of the Trim-Air Check Valves

TASK 21-63-42-000-001-A
Removal of the Trim-Air Check Valves

WARNING: MAKE SURE THAT AIR IS NOT SUPPLIED TO THE AIR CONDITIONING SYSTEM FROM THE MAIN ENGINE, THE APU OR A GROUND SOURCE. HOT COMPRESSED AIR CAN CAUSE INJURY TO PERSONNEL.

WARNING: MAKE SURE THAT THE COMPONENTS OF THE BLEED AIR SYSTEM ARE COOL. HOT COMPONENTS WILL BURN YOU.

CAUTION: BE VERY CAREFUL WHEN YOU DO WORK ON OR NEAR THE AIR-CONDITIONING DUCTS. THE DUCTS ARE MADE OF THIN MATERIAL AND YOU CAN EASILY BREAK THEM.

FIN: 18HM
FIN: 19HM

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	SAFETY CLIP - CIRCUIT BREAKER
No specific	1	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
191BB, 191CB, 191DB

C. Referenced Information

REFERENCE	DESIGNATION
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
Trim-Air Check Valve

3. Job Set-up
Subtask 21-63-42-861-051-A

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

Subtask 21-63-42-865-050-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
FOR FIN: 18HM (P1 CHECK VALVE TRIM AIR)
49VU	AIR COND/TEMP CTL/SYS 1 CHAN B/28VDC	52HH	D08
** ON A/C NOT FOR ALL
122VU	AIR COND/PACK TEMP/CTL SYS1/1/115VAC	1HH	X22
122VU	AIR COND/PACK TEMP/CTL SYS1/1/28VDC	3HH	X21
122VU	AIR COND/PACK TEMP CTL SYS2/1/28VDC	4HH	Y19
122VU	AIR COND/PACK TEMP CTL SYS2/1/115VAC	2HH	Y18
** ON A/C NOT FOR ALL
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
** ON A/C NOT FOR ALL
FOR FIN: 19HM (P2 CHECK VALVE TRIM AIR)
122VU	AIR COND/PACK TEMP/CTL SYS1/2/115VAC	21HH	W22
122VU	AIR COND/PACK TEMP/CTL SYS1/2/28VDC	23HH	W21
122VU	AIR COND/PACK TEMP CTL SYS2/2/28VDC	24HH	Y21
122VU	AIR COND/PACK TEMP CTL SYS2/2/115VAC	22HH	Y20
** ON A/C NOT FOR ALL
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 21-63-42-941-050-A

C. Safety Precautions
(1) In the cockpit, on AIR COND panel 30VU:
(a) Make sure that the APU BLEED pushbutton switch is released (the OFF legend is on).
(b) Make sure that the ENG 1 BLEED and the ENG 2 BLEED pushbutton switches are released (the OFF legends are on).
(c) Make sure that the PACK 1 and the PACK 2 pushbutton switches are released (the OFF legends are on).
(d) Make sure that the HOT AIR pushbutton switch is released (the OFF legend is on).
(e) Put the WARNING NOTICE(S) in position to tell persons not to operate these pushbutton switches.
(2) At access doors 191CB and 191DB:
(a) On the LP and the HP ground connectors, put the WARNING NOTICE(S) in position to tell persons not to supply the ground air.

Subtask 21-63-42-010-050-A

D. Get Access
(1) Open the access panel (Ref. AMM TASK 53-35-13-000-002), 191BB.

4. Procedure
Subtask 21-63-42-020-050-A

A. Removal of the Trim-Air Check Valve
(1) FOR [18HM] (P1 CHECK VALVE TRIM AIR)
(a) Remove the nut (6), the washer (5) the bolt (13) and disconnect the bonding strap (3).
(b) Remove the nut (20), the washer (21), the bolt (23) and disconnect the bonding strap (22).
(c) Move the sleeve (25) as far to the clamp (24) as it will go.

NOTE: Turn the sleeve when you move it.
This will help to prevent damage to the seals in the sleeve.

(d) Remove the nuts (7), the washers (8) and the bolts (10).
(e) Hold the duct (1) and remove the nuts (32), the washers (31) and the bolts (29).
(f) Carefully remove the duct (1) from the sleeve (25) and the support rods (28) and (30).

NOTE: Turn the sleeve (25) when you remove the duct (1).
This will help to prevent damage to the seals in the sleeve
When you remove the duct (1) you must take care that the trim-air check valve (9) does not fall and become damaged.

(g) Remove the trim-air check valve (9) and discard the packings (4) and (12).
(h) Remove and discard the seal (27) from the sleeve (25).
(i) Put protective covers on the open ends of the ducts (1) and (14), the duct spigot (26) and the sleeve (25).
(2) FOR [19HM] (P2 CHECK VALVE TRIM AIR)
(a) Remove the nut (6), the washer (5) the bolt (13) and disconnect the bonding strap (3).
(b) Remove the nut (20), the washer (21), the bolt (23) and disconnect the bonding strap (22).
(c) Move the sleeve (25) as far to the clamp (24) as it will go.

NOTE: Turn the sleeve when you move it.
This will help to prevent damage to the seals in the sleeve.

(d) Remove the nuts (7), the washers (8) and the bolts (10).
(e) Hold the duct (2) and remove the nuts (32), the washers (31) and the bolts (29).
(f) Carefully remove the duct (2) from the sleeve (25) and the support rods (28) and (30).

NOTE: Turn the sleeve (25) when you remove the duct (2).
This will help to prevent damage to the seals in the sleeve.
When you remove the duct (2) you must take care that the trim-air check valve (9) does not fall and become damaged.

[Rev.10 from 2021] 2026.04.02 06:11:44 UTC