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CTC-201-021-02
EFFECTIVITY
73-21-18 Page 9
ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03
CFMI PROPRIETARY INFORMATION
CFM56-5B TRAINING MANUAL
EFG
HYDROMECHANICAL UNIT
The general schematic shows all the components that make up the HMU FMV section.
The main items are :
-The pressure regulators.
- The FMV.
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The delta P valve.
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The by-pass valve.
- The overspeed governor.
-The pressurizing and shut-off valve.
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CTC-201-261-01 .
EFFECTIVITY
73-21-18 Page 11
ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03
CFMI PROPRIETARY INFORMATION
CFM56-5B TRAINING MANUAL
EFG
HYDROMECHANICAL UNIT
The HMU is supplied by two fuel pressures, Ps and Psf, that come from the fuel pump HP stage discharge.
Under certain operating conditions, some of the fuel pressure may be by-passed, and is known as Pb.
Ps pressure.
From HP pump discharge stage to the FMV system :
This is the fuel for the combustor.
Max Ps = 1250 psig.
Psf pressure.
From HP pump discharge stage to the HMU servo
application, through the servo fuel heater :
This is used to generate the working pressures for the
actuators .
Max Psf = 1250 psig.
Pb pressure.
By-passed fuel flow is excess fuel not used in combustion
and the servo mechanisms :
It is returned to the main oil/fuel heat exchanger, through
the IDG oil cooler.
Max Pb = 235 psig.
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CTC-201-023-02
EFFECTIVITY
73-21-18 Page 13
ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03
CFMI PROPRIETARY INFORMATION
CFM56-5B TRAINING MANUAL
EFG
HYDROMECHANICAL UNIT
Pc: Control pressure.
(Pc = Pb + 300 psi.)
Pc pressure is regulated at a constant value of 300 psi above Pb.
The regulator controls the Psf supply in order to maintain a constant pressure differential throughout the range of flows required downstream. It also compensates for varying Pb pressures.
A spring in the pressure regulator provides a pre-loaded force that is calibrated to 300 psid.
EFG
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CTC-201-024-02
EFFECTIVITY
73-21-18 Page 15
ALL CFM56-5B ENGINES FOR A319-A320-A321
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