Removal of the Mixer Unit

TASK 21-21-43-000-001-A
Removal of the Mixer Unit

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 PNEUMATIC SYSTEM IS DEPRESSURIZED BEFORE YOU START WORK. PRESSURIZED AIR CAN CAUSE INJURY TO PERSONNEL.

WARNING: DO NOT TOUCH THE COMPONENT UNTIL IT IS SUFFICIENTLY COOL TO PREVENT BURNS.

CAUTION: DO NOT PUT YOUR WEIGHT ON THE DUCTS. IT IS VERY EASY TO BREAK THEM.

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.

ZONE: 130

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 2M (6 FT)
No specific	AR	CAP - BLANKING
No specific	AR	PLUG - BLANKING
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
No specific	AR	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
130	FWD CARGO COMPT AFT BULKHEAD OF AVNCS COMPT TO FWD PRESSURE BULKHEAD OF WING CENTER BOX
191CB, 191DB, 825

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 25-54-12-000-001-A	Removal of the Forward Cargo-Compartment Partition
TASK 52-30-00-860-001-A	Open the FWD or Aft Cargo-Compartment Door with the Yellow Electric Pump
TASK 06-41-53-00	FUSELAGE-DESCRIPTION AND OPERATION
Mixer Unit ** ON A/C NOT FOR ALL
Mixer Unit ** ON A/C NOT FOR ALL

3. Job Set-up
Subtask 21-21-43-860-050-A

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

Subtask 21-21-43-865-050-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	AIR COND/TEMP CTL/SYS 1 CHAN B/28VDC	52HH	D08
** ON A/C NOT FOR ALL
122VU	AIR COND/FLOW/MIXER/FLAP	3HB	V22
122VU	AIR COND/ZONE TEMP CTL/28VDC/SYS2	4HK	V20
122VU	AIR COND/ZONE TEMP CTL/28VDC/SYS1	3HK	V19
122VU	AIR COND/ZONE TEMP CTL/115VAC/SYS2	2HK	V18
122VU	AIR COND/ZONE TEMP CTL/115VAC/SYS1	1HK	V17
** ON A/C ALL
122VU	AIR COND/RECIRC FAN/R/CTL	11HG	W20
122VU	AIR COND/RECIRC FAN/R/SPLY	3HG	W18
122VU	AIR COND/RECIRC FAN/L/CTL	2HG	X20
122VU	AIR COND/RECIRC FAN/L/SPLY	1HG	X18
** 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 1/CHAN A/115VAC	49HH	X22
122VU	AIR COND/TEMP CTL SYS 1/CHAN A/28VDC	51HH	X21
122VU	AIR COND/TEMP CTL SYS 2/CHAN B/28VDC	56HH	Y21
122VU	AIR COND/TEMP CTL SYS 2/CHAN B/115VAC	54HH	Y20
122VU	AIR COND/TEMP CTL SYS 1/CHAN B/115VAC	50HH	Y18

Subtask 21-21-43-941-051-A

C. Safety Precautions
(1) On the overhead panel, on panel 30VU:
(a) Make sure that the APU BLEED pushbutton switch is in the off position (the ON legend is off).
(b) Make sure that the ENG 1 BLEED and the ENG 2 BLEED pushbutton switches are in the off position (the OFF legends are on).
(c) Make sure that the PACK 1 and the PACK 2 pushbutton switches are in the off position (the OFF legends are on).
(d) Make sure that the HOT AIR pushbutton switch is in the off position (the OFF legend is on).
(e) Put WARNING NOTICE(S) in position to tell persons not to operate these pushbutton switches.
(2) At access door 191DB, on the HP ground connector, put a warning notice in position to tell persons not to pressurize the pneumatic system.
(3) At access door 191CB, on the LP ground connector, put a warning notice in position to tell persons not to pressurize the air conditioning system.

Subtask 21-21-43-010-050-A

D. Get Access
(1) Put the ACCESS PLATFORM 2M (6 FT) in position below the forward cargo-compartment door (door 825).
(2) Open the forward cargo-compartment door (Ref. AMM TASK 52-30-00-860-001).
(3) Remove the access panels at partition FR34 (Ref. AMM D/O 06-41-53-00), (Ref. AMM TASK 25-54-12-000-001).

4. Procedure
Subtask 21-21-43-020-050-A

A. Removal of the Mixer Unit
(1) Disconnect the electrical connectors (14), (19) and (22).
(2) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.
(3) Remove the clamp (4) and disconnect the sleeve (3).
(4) Remove and discard the tie wraps (43).
(5) Remove the insulations (41) and (42).
(6) Remove the clamps (40).
(7) Move the sleeves (46) onto the supply ducts (44) and (45).
(8) Remove the clamps (2), (11) and (13) and disconnect the sleeves (1), (10) and (12).
(9) Remove the nut (35), the washer (36), the bolt (38) and the washer (37).
(10) Disconnect the tie rod (34) from the mixer unit (18).
(11) Hold the mixer unit (18) and remove the bolts (17) and the washers (16).
(12) Remove the mixer unit (18).
(13) Remove the sleeves (46) and the O-rings (39).

WARNING: USE GOGGLES AND GLOVES WHEN YOU REMOVE OR INSTALL LOCKWIRE. EACH TIME YOU CUT LOCKWIRE, REMOVE AND DISCARD IT IMMEDIATELY. LOOSE LOCKWIRE CAN CUT YOU OR MAKE YOU BLIND, AND/OR CAN CAUSE DAMAGE.

(14) Cut and discard the lockwires of the sensors (15) and (20).
(15) Remove the sensors (15) and (20) and the O-rings (21) from the mixer unit (18).
(16) Remove the nuts (9), the washers (8), the seal (7) and the flap assembly (5) from the mixer unit (18).
(17) Remove the nut (28) and the washer (29).
(18) Remove the screws (32), the washers (33), the supply duct (23) and the flange gasket (24) from the mixer unit (18).
(19) Remove the nut (31) and the washer (30).
(20) Remove the screws (27), the washers (26), the supply duct (25) and the flange gasket (24) from the mixer unit (18).
(21) Put the PLUG-BLANKING in each disconnected line end.

[Rev.10 from 2021] 2026.04.02 06:10:54 UTC