Removal of the Hydromechanical Unit (HMU) [CFMB]

TASK 73-21-10-000-002-A
Removal of the Hydromechanical Unit (HMU)

ZONE: 400
FIN: 4000KC1 ** ON A/C NOT FOR ALL
FIN: 4000KC2 ** 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	ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE
No specific	AR	BOLT - 250-28UNF-2A X 0.50IN.
No specific	AR	CAP - BLANKING
No specific	AR	CONTAINER 5 L (1.32 USGAL)
No specific	AR	COVER - BLANKING
No specific	AR	PLIERS - NOSE, SOFT, LONG
No specific	AR	PLUG - BLANKING
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
No specific	AR	WARNING NOTICE(S)
856A1336	1	ADAPTOR SET, TORQUE - MEC FASTENERS
856A1469	1	WRENCH SET, RUN ON OFF - MEC FUEL PUMP NUTS
856A1494	1	FIXTURE,HANDLING-HMU

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
400	POWER PLANT, NACELLES AND PYLONS
FOR [1000EM1] (ENGINE-1)
437AL, 438AR, 451AL, 452AR
FOR [1000EM2] (ENGINE-2)
447AL, 448AR, 461AL, 462AR

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 70-21-00-918-002-A	Seals (Preformed Packings and O-rings) and Gaskets
TASK 71-13-00-010-040-B	Opening of the Fan Cowl Doors
TASK 73-11-45-000-001-A	Removal of the Fuel Nozzle Filter (Downstream Fuel Filter)
TASK 73-21-10-600-002-A	Preservation of the Hydromechanical Unit (HMU)
TASK 73-31-10-000-002-A	Removal of the Fuel Flow Transmitter
TASK 78-30-00-481-041-B	Make the Thrust Reverser Unserviceable for Maintenance
TASK 78-36-00-010-040-B	Opening of the Thrust Reverser Doors
Hydromechanical Unit

3. Job Set-up
Subtask 73-21-10-941-051-A ** ON A/C NOT FOR ALL

A. Safety Precautions
(1) On the center pedestal, on the ENG panel 115VU:
(a) Put a WARNING NOTICE(S) to tell persons not to start the engine.
(2) Make sure that the engine 1(2) shutdown occurred not less than 5 minutes before you do this procedure.
(3) On the overhead maintenance panel 50VU:
(a) Make sure that the ON legend of the ENG/FADEC GND PWR/1(2) pushbutton switch is off.
(b) Put a WARNING NOTICE(S) to tell persons not to energize the FADEC 1(2).

Subtask 73-21-10-861-053-A ** ON A/C NOT FOR ALL

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

Subtask 73-21-10-865-052-A ** ON A/C NOT FOR ALL

WARNING: OPEN CIRCUIT BREAKERS 1QG (2QG) AND 3QG (4QG) BEFORE YOU OPEN CIRCUIT BREAKER 1KC1 (2). IF NOT, THE LP FUEL VALVE WILL OPEN AND THERE IS A RISK THAT FUEL WILL FLOW OUT.

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
FOR FIN: 1000EM1 (ENGINE1)
49VU	FUEL/LP VALVE/MOT1/ENG1	1QG	A08
49VU	ENGINE/1/HP FUEL SOV	1KC1	A01
121VU	FUEL/LP VALVE/MOT2/ENG1	3QG	M25
FOR FIN: 1000EM2 (ENGINE2)
49VU	FUEL/LP VALVE/MOT1/ENG2	2QG	A09
49VU	ENGINE/2/HP FUEL SOV	1KC2	A02
121VU	FUEL/LP VALVE/MOT2/ENG2	4QG	M26

Subtask 73-21-10-010-053-A ** ON A/C NOT FOR ALL

D. Get Access
(1) Open the fan cowl doors: (Ref. AMM TASK 71-13-00-010-040)
(a) FOR [1000EM1] (ENGINE-1)
437AL 438AR
(b) FOR [1000EM2] (ENGINE-2)
447AL 448AR
(2) Put the ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE in position.

Subtask 73-21-10-040-052-A ** ON A/C NOT FOR ALL

E. Make the thrust reverser unserviceable (Ref. AMM TASK 78-30-00-481-041).

Subtask 73-21-10-010-054-A ** ON A/C NOT FOR ALL

F. Open the thrust reverser doors: (Ref. AMM TASK 78-36-00-010-040)
(1) FOR [1000EM1] (ENGINE-1)
451AL 452AR
(2) FOR [1000EM2] (ENGINE-2)
461AL 462AR

4. Procedure
Subtask 73-21-10-020-053-A ** ON A/C NOT FOR ALL

WARNING: BE CAREFUL NOT TO GET AIRCRAFT FUEL IN YOUR MOUTH OR IN YOUR EYES. IF YOU GET FUEL ON YOUR SKIN OR ON YOUR CLOTHES, FLUSH IT IMMEDIATELY WITH WATER. IF NECESSARY, GET MEDICAL HELP. AIRCRAFT FUEL IS POISONOUS.

A. Prepare the HMU for removal

NOTE: Put a CONTAINER 5 L (1.32 USGAL) under the HMU to catch fuel released when fuel lines are disconnected.

(1) Disconnect the electrical connector (50) from the fuel flow transmitter. If necessary, use PLIERS - NOSE, SOFT, LONG.
(2) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.
(3) Remove the bolt (20) and nut (40) from the loop clamp (30) that attaches the electrical connector (50) to the support bracket. Remove the loop clamp (30).
(4) Remove the bolts (100) to remove the fuel supply tube from the discharge port of the Hydromechanical Unit (HMU).
(5) Disconnect the fuel supply hose from the union (10) of the fuel injection supply tube.
(6) Remove the bolts (80) and washers (90) that attach the inlet bracket to the HMU.
(7) Remove the bolts (60) and washers (70) that attach the discharge bracket to the HMU.
(8) Remove the assembled fuel flow transmitter, fuel supply tube, inlet bracket, discharge bracket, and fuel supply hose from the HMU (Ref. AMM TASK 73-31-10-000-002).

POST CFMI SB 73-0071

(9) Remove the downstream fuel filter (Ref. AMM TASK 73-11-45-000-001).

END of POST CFMI SB 73-0071

(10) Install PLUG - BLANKING on the open discharge port of the HMU and on the open ends of the fuel supply tube.
(11) Install PLUG - BLANKING on the fuel supply hose and the union (10) of the fuel injection supply tube.
(12) Remove and discard the gasket (110) from the discharge port of the HMU.
(13) Disconnect the electrical connector, Channel A (120) and Channel B (210), from the HMU. If necessary, use soft nose pliers.
(14) Disconnect the electrical connector (170) from the latching solenoid. If necessary, use soft nose pliers.
(15) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.
(16) Disconnect the flex-hoses from the HMU nipples that follow:

CAUTION: USE TWO WRENCHES TO REMOVE OR INSTALL THE TUBE COUPLING NUTS:

ONE WRENCH TO HOLD THE UNION, AND
ONE TO LOOSEN OR TIGHTEN THE COUPLING NUT.

THIS PREVENTS DAMAGE TO THE PARTS.

(a) VBV open hose (240) from nipple (220).
(b) RACSB hose (400) from nipple (410).

NOTE: Only applicable for non /P engines.

NOTE: Only applicable for /P engines.

(d) VBV closed hose (310) from nipple (320).
(e) PCR hose (280) from nipple (290).
(f) HPTACC hose (460) from nipple (470).
(g) LPTACC hose (430) from nipple (440).

PRE CFMI SB 73-0096

(h) SOV hose (570) from nipple (580).

NOTE: Only applicable for SAC engines.

PRE CFMI SB 73-0114

(i) BSV hose (270) from nipple (250).

NOTE: Only applicable for DAC engines.

(j) VSV head hose (370) from nipple (380).
(k) VSV rod hose (340) from nipple (350).
(l) OVBD drain tube (600) from nipple (490).

NOTE: If necessary, loosen the first union of each flex-hose from the HMU. This will permit the flex-hose to move so that you can easily remove the HMU.

(17) Install PLUG - BLANKING on the disconnected flex-hose ends.
(18) Disconnect the servo heater return hose (530) coupling nut connection at the servo fuel heater.
(19) Remove the bolts (520) and the washers (525) to remove the servo heater-return hose (530) from the servo port on the HMU.
(20) Remove the gasket (510) between the servo heater-return hose (530) and the servo port on the HMU.
(21) Install COVER - BLANKING on the open end of the servo heater-return hose (530).
(22) Remove the bolts (550) to remove the IDG supply tube (540) from the IDG port on the HMU.
(23) Remove the gasket (560) between the IDG supply tube (540) and the IDG port of the HMU.
(24) Install COVER - BLANKING on the open end of the IDG supply tube (540).
(25) Install the 856A1494 FIXTURE,HANDLING-HMU (856A1494G01) to the HMU. Use four BOLT - 250-28UNF-2A X 0.50IN.
(26) Remove the HMU:

CAUTION: HOLD THE HMU LEVEL DURING THE REMOVAL/INSTALLATION. MAKE SURE THAT THE WEIGHT OF THE HMU IS NOT AGAINST THE FUEL-PUMP DRIVE SHAFT AND THAT THE HMU DOES NOT HIT THE FUEL-PUMP MATING FLANGE. IF YOU DO NOT OBEY THESE INSTRUCTIONS, DAMAGE TO THE FUEL-PUMP DRIVE SHAFT, MATING FLANGE OR HMU CAN OCCUR.

CAUTION: DO NOT HOLD OR MOVE THE HYDROMECHANICAL UNIT BY THE TORQUE MOTORS. CHANGES TO THE CALIBRATION OF THE HYDROMECHANICAL UNIT CAN OCCUR.

(a) Break the torque of the nuts (190) that attach the HMU to the fuel pump. Use the 856A1336 ADAPTOR SET, TORQUE - MEC FASTENERS (856A1336G02).
(b) Remove the nuts (190) and washers (200) that attach the HMU to the fuel pump. Use the 856A1469 WRENCH SET, RUN ON OFF - MEC FUEL PUMP NUTS (856A1469G01) to remove the nuts that are difficult to reach.
(c) Remove the HMU from the fuel pump, with the 856A1494 FIXTURE,HANDLING-HMU (856A1494G01).

Pull the HMU lightly and carefully to let the fuel flow in the container.

Remove the HMU from the fuel pump.

(27) Remove and inspect the gasket (180) (Ref. AMM TASK 70-21-00-918-002) between the HMU and the fuel pump.
(28) Install the COVER - BLANKING on the HMU mounting pad on the fuel pump.
(29) Remove the nipples and plugs and discard the O-rings as follows:
(a) VBV open nipple (220) and O-ring (230).
(b) RACSB nipple (410) and O-ring (420).

NOTE: Only applicable for non /P engines.

NOTE: Only applicable for /P and /3 engines.

(d) VBV closed nipple (320) and O-ring (330).
(e) PCR nipple (290) and O-ring (300).
(f) HPTACC nipple (470) and O-ring (480).
(g) LPTACC nipple (440) and O-ring (450).

PRE CFMI SB 73-0096

(h) SOV nipple (580) and O-ring (590).

NOTE: Only applicable for SAC engines.

PRE CFMI SB 73-0114

(i) BSV nipple (250) and O-ring (260).

NOTE: Only applicable for DAC engines.

(j) VSV head nipple (380) and O-ring (390).
(k) VSV rod nipple (350) and O-ring (360).
(l) Cut and remove the lockwire and remove the PB plug (130) and O-ring (140).
(m) Cut and remove the lockwire and remove the PS plug (150) and O-ring (160).
(n) OVBD drain nipple (490) and O-ring (500).
(30) Install PLUG - BLANKING, caps and covers on all open ports of the HMU to prevent contamination.

Subtask 73-21-10-620-055-A ** ON A/C NOT FOR ALL

B. Do a HMU preservation procedure (Ref. AMM TASK 73-21-10-600-002)

[Rev.10 from 2021] 2026.04.01 12:55:25 UTC