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A pre-loaded spring.
- Two position switches.
Under normal operation, Pcr, or Pc pressure, combined with a pre-loaded spring force, is applied to the pressurization valve rod compartment.
The pre-loaded spring force guarantees enough Psf to operate the Pc, Pcr and Delta P regulator systems, and provides adequate force margins for all pistons and actuators.
EFFECTIVITY ALL CFM56-5B ENGINES FOR A319-A320-A321
CFMI PROPRIETARY INFORMATION
FMV downstream pressure is applied on the top of the piston.
A minimum FMV downstream pressure is required to displace the valve piston far enough to open a port.
Under engine shut-down conditions, the shut-off system exchanges Pcr, or Pc, for Psf pressure, resulting in a closed valve position. The fuel supply to the nozzles is stopped, and the engine shuts down.
The pressurizing valve is provided with switches, which inform the ECU that the valve is in the shut-off position.
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EFFECTIVITY
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ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03
CFMI PROPRIETARY INFORMATION
CFM56-5B TRAINING MANUAL
EFG
HYDROMECHANICAL UNIT
Fuel shut-off system. FMV shut-off shuttle valve.
The fuel shut-off system ensures engine shut-down and According to its position, the FMV shut-off shuttle valve fuel pump unloading. routes either Pb, or Psf pressure to the A/C shut-off solenoid valve, in order to hydraulically reset the solenoid The system is composed of : and also generate an SOV signal to shut down the engine.
-An FMV shut-off shuttle valve.
-The A/C shut-off solenoid. A/C shut-off solenoid.
-A shut-off shuttle valve.
-The pressurizing and shut-off valve. The A/C shut-off solenoid is a magnetic latching solenoid,
which provides an independent path through which the During a shut-down order, the ECU control logic engine can be shut down, by actuating the Master Lever. generates a hydraulic Shut-Off Valve (SOV) signal. The output of the A/C shut-off solenoid forms the SOV
signal. The SOV signal activates a shut-off shuttle valve which :
Shut-off shuttle valve.
-Closes the pressurizing and shut-off valve to stop fuel nozzles supply. The shut-off shuttle valve is a non-rotating spool valve,
-Opens a by-pass valve to avoid fuel pump loading actuated by the SOV hydraulic signal. It controls the and prevent over-pressure inside the HMU. porting of pressure to the pressurizing and shut-off valve
and to the by-pass valve, through the OSG and the The pilot is able to generate a shut-down order, through Delta P regulator system. the Master Lever in the cockpit.
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