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CTC-201-126-01
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ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03

CFMI PROPRIETARY INFORMATION
CFM56-5B TRAINING MANUAL
EFG
FUEL RETURN VALVE
Recirculation to the tank is inhibited, (FRV closed), in any of the following cases:
-
When N2 speed is below 50% during engine start.

-
When the metered fuel flow is greater than 5520 pph.
(T/O power).

-With engine shut-down.
-When the aircraft management system sends an
inhibit signal (fuel temp high + fuel tank full).

-When flight / ground status is not available. The FRV is opened to the second level (HIGH):
- During a FADEC ground motoring test.

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CTC-201-127-02
EFFECTIVITY
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ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03

CFMI PROPRIETARY INFORMATION
CFM56-5B TRAINING MANUAL
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EFG
VARIABLE GEOMETRY CONTROL SYSTEM

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
VARIABLE GEOMETRY CONTROL SYSTEM
The variable geometry control system is designed to maintain satisfactory compressor performance over a wide range of operation conditions.
The system consists of:
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 A Variable Bleed Valve (VBV) system, located downstream from the booster.

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 A Variable Stator Vane (VSV) system, located within the first stages of the HPC.

The compressor control system is commanded by the ECU and operated through HMU hydraulic signals.
At low speed, the LP compressor supplies a flow of air greater than the HP compressor can accept.
To establish a more suitable air flow, VBV’s are installed on the contour of the primary airflow stream, between the booster and the HPC.
At low speed, they are fully open and reject part of the booster discharge air into the secondary airflow, preventing the LPC from stalling.
At high speed, the VBV’s are closed.
The HPC is equipped with one Inlet Guide Vane (IGV) stage and three VSV stages.
An actuation system changes the orientation of the vanes to provide the correct angle of incidence to the air stream at the blades leading edge, improving HPC stall margins.

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CTC-201-142-01
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
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EFG
VARIABLE BLEED VALVE

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