DOC AIRBUS | AMM A320FDISTRIBUTION - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The engine fuel supply distribution system mainly consists of:
** ON A/C NOT FOR ALL The engine fuel supply distribution system mainly consists of:
Engine Fuel System - Schematic- a fuel supply line
- an engine two-stage pump and filter assembly
- an engine oil/fuel heat exchanger (Ref. AMM D/O 79-20-00-00)
- a servo fuel heater
- a hydromechanical unit (Ref. AMM D/O 73-20-00-00)
- an IDG oil cooler
- a fuel return valve system
- a fuel manifold
- 20 fuel nozzles (16 standard and 4 pilot nozzles)
2. Plumbing
A. Fuel Supply Line
The fuel supply line is connected to the hydraulic junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the pump. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
The fuel supply line is connected to the hydraulic junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the pump. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
B. Fuel Return Line
The fuel return line is connected to the fluid junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the fuel return valve. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
The fuel return line is connected to the fluid junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the fuel return valve. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
3. Fuel Pump and Filter Assembly
A. General
(1) The fuel pump pressurizes and circulates the fuel in the fuel system.
The tank fuel pumps deliver the fuel supply up to the engine fuel pump inlet. The fuel then enters the low pressure (LP) stage of the fuel pump. After initial pressurization, the fuel is delivered to the main oil/fuel heat exchanger. There it cools the engine oil.
The tank fuel pumps deliver the fuel supply up to the engine fuel pump inlet. The fuel then enters the low pressure (LP) stage of the fuel pump. After initial pressurization, the fuel is delivered to the main oil/fuel heat exchanger. There it cools the engine oil.
(2) On discharge from the heat exchanger, the fuel flows back to the pump.
It passes through a disposable filter before undergoing a second pressure increase in the high pressure (HP) stage of the pump. The fuel then enters the wash filter where it is divided into a filtered and unfiltered flow. The unfiltered flow bypasses the filter and enters the hydromechanical fuel unit (HMU). The filtered flow goes through the servo fuel heater and then into the HMU. This flow is sufficiently hot to prevent jamming of the HMU servo-mechanisms due to ice particles.
It passes through a disposable filter before undergoing a second pressure increase in the high pressure (HP) stage of the pump. The fuel then enters the wash filter where it is divided into a filtered and unfiltered flow. The unfiltered flow bypasses the filter and enters the hydromechanical fuel unit (HMU). The filtered flow goes through the servo fuel heater and then into the HMU. This flow is sufficiently hot to prevent jamming of the HMU servo-mechanisms due to ice particles.
(3) The returning fuel bypassed from the HMU is tapped to feed the Integrated Drive Generator (IDG) oil cooler. There it cools the oil coming from the engine IDG. The fuel returns then to the pump upstream of the filter, between the LP and HP fuel pump stages. The fuel returns via a port located on the oil/fuel heat exchanger.
(4) If the filters or heat exchanger become clogged:
- a number of bypass valves are provided to prevent excessive pressure build-ups.
(5) The fuel pump and HMU are mounted as a unit. This unit is located on the accessory gearbox (AGB) (aft face on the left side of the horizontal drive shaft housing, aft looking forward).
B. Functional Description
(1) Fuel pump drive system
The fuel pump drive system consists of the following:
The fuel pump drive system consists of the following:
(a) A main drive shaft, driven by the AGB which, in turn, drives the HP stage drive spur gear. The main drive shaft has a shear neck to protect the AGB from any excessive torque in the fuel pump drive.
(b) A LP stage drive shaft, driven by the HP stage drive spur gear, providing drive for:
1 The LP stage via a hollow shaft.
2 The HMU via the HMU drive shaft. The LP pump drive shaft has a shear neck:
- to protect the HMU from LP stage failures
- to maintain proper engine operation even in case of total failure (seizing) of the LP stage.
(2) Fuel pump LP stage
(a) General
The LP stage of the fuel pump is of the centrifugal type. It delivers a boost pressure to the HP stage to avoid pump cavitation. The LP stage general characteristics at takeoff power are as follows :
The LP stage of the fuel pump is of the centrifugal type. It delivers a boost pressure to the HP stage to avoid pump cavitation. The LP stage general characteristics at takeoff power are as follows :
1 Boost (LP) stage pressure rise: 165 psid (1138 kPa) (minimum).
2 Speed rating: 6250 RPM.
1 The fuel pump LP stage consists of:
- an impeller supported by 2 plain bearings provided with swirl ramps,
- an inducer having helical grooves and a scroll.
2 The fuel discharged from the boost pumps:
- enters the fuel pump LP stage,
- leaves the pump under pressure,
- flows to the main oil/fuel heat exchanger
- and controls the fuel return valve.
(c) LP stage lubrication system
The fuel tapped from the scroll at the discharge of the LP stage lubricate the LP stage rotating parts. The lubricated elements are :
The fuel tapped from the scroll at the discharge of the LP stage lubricate the LP stage rotating parts. The lubricated elements are :
- the front and rear bearings
- the LP pump drive shaft splines
- the HMU drive shaft splines
(3) Fuel pump HP stage
(a) General
1 The fuel pump HP stage converts mechanical energy into hydraulic power required to supply:
- the fuel nozzles
- the HMU servos
- the variable bleed valve (VBV) and variable stator vane (VSV) hydromechanical systems.
2 The HP stage hydraulic power is supplied by a positive displacement (gear-type) pump. For a given number of revolutions, the pump delivers a constant fuel flow regardless of the discharge pressure.
A pressure relief valve connected in parallel with the HP pump protects the pump.
A pressure relief valve connected in parallel with the HP pump protects the pump.
3 The HP stage general characteristics at takeoff power are as follows:
PRE SB 72-032
PRE SB 72-032
- discharge pressure: 1000 psig (6895 kPa gage) (maximum)
- speed rating: 6250 RPM
- Fuel Flow (maximum): 59 USgal.mm (223 l.min).
POST SB 72-032 - discharge pressure: 1145 psig (7895 kPa gage) (maximum)
- speed rating: 6250 RPM
- Fuel Flow (maximum): 68 USgal.mm (257 l.min).
(b) Functional Description
The HP fuel pump consists of 2 gearshafts. Each gearshaft is supported by 2 plain bearings ; one is stationary and the other self-aligning.
The filtered fuel enters the HP stage and, after pressurization, is delivered to the HMU. Should an overpressure occur (discharge pressure higher or equal to 1050 psi (7240 kPa), a valve bypasses the fuel toward the HP stage inlet.
The HP fuel pump consists of 2 gearshafts. Each gearshaft is supported by 2 plain bearings ; one is stationary and the other self-aligning.
The filtered fuel enters the HP stage and, after pressurization, is delivered to the HMU. Should an overpressure occur (discharge pressure higher or equal to 1050 psi (7240 kPa), a valve bypasses the fuel toward the HP stage inlet.
(c) HP stage lubrication system
The fuel used to lubricate the LP stage items, lubricates also the HP stage rotating parts.
The lubricated elements are:
The fuel used to lubricate the LP stage items, lubricates also the HP stage rotating parts.
The lubricated elements are:
- the HP stage bearings, and
- the thrust ring.
(4) Fuel filter
(a) General
This fuel filter is located between the main oil/fuel heat exchanger and fuel pump HP stage. It protects the HMU from particles in suspension in the fuel. The filter disposable cartridge is designed to retain foreign material. The cartridge is periodically replaced and removed. The cartridge is discarded.
This fuel filter is located between the main oil/fuel heat exchanger and fuel pump HP stage. It protects the HMU from particles in suspension in the fuel. The filter disposable cartridge is designed to retain foreign material. The cartridge is periodically replaced and removed. The cartridge is discarded.
(b) Functional description
The fuel filter consists of a filter cartridge and a pressure relief valve. The filter cartridge is installed in a cavity on the pump body.
The fuel circulates from the outside to the inside of the filter cartridge. The cartridge has a filtering capability of 32 microns absolute (PRE SB 72-032) or 38 microns absolute (POST SB 72-032). In case of a clogged filter, a pressure relief valve bypasses the fuel to the HP stage.
Tappings on pump housing enable transmission of the differential pressure across the fuel filter to the fuel differential pressure switch. This pressure switch supplies a clogging indication to the cockpit (Ref. AMM D/O 73-30-00-00).
The fuel filter consists of a filter cartridge and a pressure relief valve. The filter cartridge is installed in a cavity on the pump body.
The fuel circulates from the outside to the inside of the filter cartridge. The cartridge has a filtering capability of 32 microns absolute (PRE SB 72-032) or 38 microns absolute (POST SB 72-032). In case of a clogged filter, a pressure relief valve bypasses the fuel to the HP stage.
Tappings on pump housing enable transmission of the differential pressure across the fuel filter to the fuel differential pressure switch. This pressure switch supplies a clogging indication to the cockpit (Ref. AMM D/O 73-30-00-00).
(5) Wash flow filter
(a) General
The wash flow filter is located at the HP stage discharge. It catches the particles in suspension remaining in the fuel supplying the HMU servos.
Foreign materials retained by the filter are removed by the fuel flow supplying the HMU metering system.
The wash flow filter is located at the HP stage discharge. It catches the particles in suspension remaining in the fuel supplying the HMU servos.
Foreign materials retained by the filter are removed by the fuel flow supplying the HMU metering system.
(b) Functional description
The wash flow filter is incorporated with the pump housing. It consists of a filtering element and a pressure relief valve. Should the filter clog, a pressure relief valve bypasses the fuel to the HMU servos fuel supply. The wash flow filter has a filtering capability of 65 microns absolute.
The wash flow filter is incorporated with the pump housing. It consists of a filtering element and a pressure relief valve. Should the filter clog, a pressure relief valve bypasses the fuel to the HMU servos fuel supply. The wash flow filter has a filtering capability of 65 microns absolute.
4. Servo Fuel Heater
(1) The servo fuel heater raises the temperature. This prevents ice from entering the control servos inside the hydromechanical fuel unit (HMU).
(2) The servo fuel heater is mounted on the aft section of the main oil/fuel heat exchanger located on the accessory gearbox (AGB) aft face, between the oil tank and the fuel pump/HMU package.
B. Description and Operation
The servo fuel heater consists of :
The oil :
Heat exchange between oil and fuel occurs by conduction and convection inside the unit. The 2 fluids circulate in the servo fuel heater through separate flowpaths.
The oil initially lubricates and cools the engine sumps.
Then it enters the servo fuel heater, giving off heat to the fuel from the wash filter. The heated fuel then flows to the internal HMU servos.
The servo fuel heater consists of :
- a housing with a heat exchanger core inside
- a cover.
The oil :
- enters the heater through one flange of the housing
- circulates around the core tubes, and
- leaves through the opposite flange of the housing.
- one corresponding to the normal circuit
- the other is used if clogging of the main oil/fuel heat exchanger restricts oil circulation beyond acceptable limits.
Heat exchange between oil and fuel occurs by conduction and convection inside the unit. The 2 fluids circulate in the servo fuel heater through separate flowpaths.
The oil initially lubricates and cools the engine sumps.
Then it enters the servo fuel heater, giving off heat to the fuel from the wash filter. The heated fuel then flows to the internal HMU servos.
NOTE: There is no fuel anti-clogging valve in the servo fuel heater system.
5. IDG Oil Cooler Assembly
(1) The purpose of the cooler assembly is to cool oil coming from the Integrated Drive Generator (IDG). The heat generated is transferred to the fuel coming from the HMU and returning to the oil/fuel heat exchanger.
The IDG oil cooler is located approximately at the 9:00 o'clock position, left-hand side of the fan inlet case and between Flanges E and F (above the oil tank).
The IDG oil cooler is located approximately at the 9:00 o'clock position, left-hand side of the fan inlet case and between Flanges E and F (above the oil tank).
B. Description
The IDG oil cooler has a cylindrical shape. It is composed of an oil housing, a fuel housing and a matrix.
The IDG oil cooler has a cylindrical shape. It is composed of an oil housing, a fuel housing and a matrix.
(1) The oil housing has:
- One OIL-IN port and one OIL-OUT port.
- One oil DRAIN port.
- Two mounting lugs
(2) The fuel housing has:
- One FUEL-IN port.
- One FUEL-OUT port.
- One fuel pressure-relief valve connected in parallel with the fuel inlet and outlet ports. If the matrix is clogged, the pressure relief valve opens and bypasses the fuel flow to the fuel tank, via the FRV.
(3) The matrix
It contains a tubeplate, 7 baffles and aluminium alloy fuel tubes (U-shaped). The fuel tubes are attached to the plate. The matrix permits 8 oil flow paths and 2 fuel flow paths.
It contains a tubeplate, 7 baffles and aluminium alloy fuel tubes (U-shaped). The fuel tubes are attached to the plate. The matrix permits 8 oil flow paths and 2 fuel flow paths.
(1) Oil flow path
The oil flows through the tube bundle where, by thermal conduction, it releases its calories to the fuel tubes. The temperature range at the oil outlet is -40 deg.F (-40 deg.C) to 367 deg.F (186 deg.C).
The oil flows through the tube bundle where, by thermal conduction, it releases its calories to the fuel tubes. The temperature range at the oil outlet is -40 deg.F (-40 deg.C) to 367 deg.F (186 deg.C).
(2) Fuel flow path.
- The fuel flows inside the fuel tubes and takes away the heat released by the oil.
If the differential pressure between the inlet and the outlet of the matrix is more than 14.5 psi (100 kPa): - the pressure relief valve opens,
- the fuel flow bypasses the matrix and returns to the fuel tank via the FRV.
6. Fuel Return Valve Assembly
(1) The purpose of the fuel return valve is to return fuel back to the tank.
It mixes hot fuel flowing from the IDG fuel/oil heat exchanger and cold fuel from the LP fuel pump.
It is controlled by the ECU based on engine oil temperature which is correlated with the IDG oil temperature.
It provides a stop function for the recirculated fuel, when no recirculation is commanded by the ECU or when the engine is shut down through HMU hydraulic signal.
END OF PRE SB CFM 73-0096
POST SB CFM 73-0096
It mixes hot fuel flowing from the IDG fuel/oil heat exchanger and cold fuel from the LP fuel pump.
It is controlled by the ECU based on engine oil temperature which is correlated with the IDG oil temperature.
It provides a stop function for the recirculated fuel, when no recirculation is commanded by the ECU or when the engine is shut down through HMU hydraulic signal.
END OF PRE SB CFM 73-0096
POST SB CFM 73-0096
(2) The purpose of the fuel return valve is to return fuel back to the tank.
It mixes hot fuel flowing from the IDG fuel/oil heat exchanger and cold fuel from the LP fuel pump.
It is controlled by the ECU based on engine oil temperature which is correlated with the IDG oil temperature.
It provides a stop function for the recirculated fuel, when no recirculation is commanded by the ECU.
END OF SB CFM 73-0096
It mixes hot fuel flowing from the IDG fuel/oil heat exchanger and cold fuel from the LP fuel pump.
It is controlled by the ECU based on engine oil temperature which is correlated with the IDG oil temperature.
It provides a stop function for the recirculated fuel, when no recirculation is commanded by the ECU.
END OF SB CFM 73-0096
(3) The fuel return valve is located on the left-hand side of the fan inlet case, at the 10:00 o'clock position and between flanges E and F (above the IDG oil cooler).
(1) The rectangular-shaped FRV (starting from top and clockwise) has 6 fuel nipples for connection with the tubing which follows:
- Fuel return line to the fuel tank (WRT)
PRE SB CFM 73-0096 - Shut-off signal line from the HMU (P Stop)
END OF PRE SB CFM 73-0096
POST SB CFM 73-0096 - Bypass line to the fuel pump LP stage (CLP)
END OF SB CFM 73-0096 - Line from the fuel pump HP stage (PSF)
- Cold fuel line from the fuel pump LP stage (CLP)
- Hot fuel line from the IDG oil cooler (HLP)
- Fuel drain line.
(2) The FRV has also 2 electrical receptacles for connection with the channels A and B of the ECU.
(1) The fuel return valve controls 2 flow levels :
(a) The first level recirculates 500 kg.h (1100 lb.h) including 300 kg.h (726 lb.h) of hot fuel and 200 kg.h (440 lb.h) of cold fuel.
(b) The second level recirculates 1000 kg.h (2203 lb.h) including 600 kg.h (1320 lb.h) of hot fuel and 400 kg.h (881 lb.h) of cold fuel.
(2) The mixing of the recirculated fuel is such that its temperature is maintained below 100 deg.C (212 deg.F) continuously and 110 deg.C (230 deg.F) transiently. Both levels of the fuel return valve are controlled by the ECU based on the engine oil temperature value:
- On ground:
Only the first level is selected when engine oil temperature (TEO) is greater or equal to 90 deg.C (194 deg.F) - In flight
The first level is selected when TEO is greater or equal to 90 deg.C (194 deg.F)
The second level is selected when TEO is greater or equal to 95 deg.C (203 deg.F)
PRE SB CFM 73-0096
(3) The fuel is not recirculated when the FRV receives an HMU hydraulic signal at the engine shutdown or when the ECU does not command first or second level of recirculated fuel if any of the following conditions is met:
- N2 less than 50 percent
- measured fuel flow greater than 5520 lb.h (2504 kg.h)
- when the ECU receives the inhibition signal to shut off the FRV
END OF PRE SB CFM 73-0096
POST SB CFM 73-0096
(4) The fuel is not recirculated when the ECU does not command first or second level of recirculated fuel if any of the following conditions is met:
- N2 less than 50 percent
- measured fuel flow greater than 5520 lb.h (2504 kg.h)
- when the ECU receives the inhibition signal to shut off the FRV
END OF SB CFM 73-0096
(5) The shut off piston of the valve is equipped with a dual position switch to provide closed/not closed indication. These position switch indications are processed by the ECU.
7. Burner Staging Valve
A. General
Not applicable
Not applicable
8. Fuel Manifold
A. General
The fuel manifold supplies metered fuel to the twenty fuel nozzles and drains any fuel that may leak from the fuel supply connection lines.
The fuel manifold supplies metered fuel to the twenty fuel nozzles and drains any fuel that may leak from the fuel supply connection lines.
B. Description and Operation
The fuel manifold consists of a manifold supplying fuel to ten fuel nozzles, a staged manifold that always supplies fuel to the remaining ten fuel nozzles when the engine is in operation, and a drain manifold. Fuel nozzles on the two fuel manifolds are located in an alternating pattern. Each manifold is divided into two segments joined by connecting nuts at the 6 and 12 o'clock positions.
The fuel supply manifold halves are connected to supply lines. Each of the connections has individual drain lines. This fuel supply splitting limits fuel pressure drop across lines and facilitates removal/installation operations.
A drain function is performed at each fuel nozzle connection by a shroud sealed by two o-rings. The shrouds are connected to the main drain manifold by fifteen integral and five removable drain lines. The five removable drain tubes are to facilitate access to borescope ports. A drain line connected to the aircraft drain mast is attached to the drain manifold at the 7 o'clock position.
The fuel manifold consists of a manifold supplying fuel to ten fuel nozzles, a staged manifold that always supplies fuel to the remaining ten fuel nozzles when the engine is in operation, and a drain manifold. Fuel nozzles on the two fuel manifolds are located in an alternating pattern. Each manifold is divided into two segments joined by connecting nuts at the 6 and 12 o'clock positions.
The fuel supply manifold halves are connected to supply lines. Each of the connections has individual drain lines. This fuel supply splitting limits fuel pressure drop across lines and facilitates removal/installation operations.
A drain function is performed at each fuel nozzle connection by a shroud sealed by two o-rings. The shrouds are connected to the main drain manifold by fifteen integral and five removable drain lines. The five removable drain tubes are to facilitate access to borescope ports. A drain line connected to the aircraft drain mast is attached to the drain manifold at the 7 o'clock position.
9. Fuel Nozzle
A. General
The fuel nozzles are installed into the combustion case assembly. They are connected to the fuel manifold assembly. The 20 fuel nozzles deliver fuel into the combustor in a spray pattern. This provides good light-off and efficient burning at high power.
Four of the 20 fuel nozzles (position 7, 8, 14 and 15) have a wider primary spray pattern to provide enhanced altitude relight reliability.
The fuel nozzles are installed into the combustion case assembly. They are connected to the fuel manifold assembly. The 20 fuel nozzles deliver fuel into the combustor in a spray pattern. This provides good light-off and efficient burning at high power.
Four of the 20 fuel nozzles (position 7, 8, 14 and 15) have a wider primary spray pattern to provide enhanced altitude relight reliability.
B. Operation
The fuel nozzles contain both primary and secondary fuel flow passages.
As the engine is started :
This fuel passes through the secondary passage of the nozzle tube and tip.
Then it enters the combustion chamber as an uniform density, cone shaped spray. The cone of the secondary spray is wider than that of the primary, therefore, surrounding the primary spray pattern.
The fuel nozzles contain both primary and secondary fuel flow passages.
As the engine is started :
- the fuel passes through the inlet, and
- accumulates in the portion of nozzle that houses the valves.
- is directed through the check valve
- passes through the primary passage of the nozzle tube and tip,
- enters the combustion chamber as an uniform density spray
This fuel passes through the secondary passage of the nozzle tube and tip.
Then it enters the combustion chamber as an uniform density, cone shaped spray. The cone of the secondary spray is wider than that of the primary, therefore, surrounding the primary spray pattern.
10. Fuel Nozzle Filter
A. General
The fuel nozzle filter is located just before the injectors. It protects the injectors from particles in suspension in the fuel.
The fuel nozzle filter is located just before the injectors. It protects the injectors from particles in suspension in the fuel.
B. Functional Description
The fuel nozzle filter consists of a filter element and a by-pass valve. The filter element has a filtering capability of 300 microns absolute.
In case of a clogged filter element, the valve by-passes the fuel to the injectors.
The fuel nozzle filter consists of a filter element and a by-pass valve. The filter element has a filtering capability of 300 microns absolute.
In case of a clogged filter element, the valve by-passes the fuel to the injectors.