DOC AIRBUS | AMM A320FFUEL DISTRIBUTION - 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
1. General
A. Fuel Distribution
Incoming fuel from the A/C fuel system is received by the FCU. The FCU diverts some of the fuel into a hydraulic circuit to operate the IGV-actuator and the SCV. Returned fuel is routed back into the FCU.
The FCU also pressurizes and meters the fuel for APU operation. The fuel is passed through the flow divider assy to the primary and/or secondary fuel manifold. These deliver the fuel to the 10 dual-orifice fuel nozzles, located around the circumference of the combustion chamber. There the fuel is atomized.
Incoming fuel from the A/C fuel system is received by the FCU. The FCU diverts some of the fuel into a hydraulic circuit to operate the IGV-actuator and the SCV. Returned fuel is routed back into the FCU.
The FCU also pressurizes and meters the fuel for APU operation. The fuel is passed through the flow divider assy to the primary and/or secondary fuel manifold. These deliver the fuel to the 10 dual-orifice fuel nozzles, located around the circumference of the combustion chamber. There the fuel is atomized.
2. Component Location
** ON A/C NOT FOR ALL 
Fuel Distribution - Component Location| ------------------------------------------------------------------------------- |
| FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA |
| | | | | DOOR | REF. |
| ------------------------------------------------------------------------------- |
| 8020KM MANIFOLD - PRIMARY FUEL 315/ 315AL/ 49-31-43 |
| 316 316AR |
| 8021KM MANIFOLD - SECONDARY FUEL 315/ 315AL/ 49-31-44 |
| 316 316AR |
A. Fuel Atomizers and Manifolds
(1) The APU has 10 dual orifice fuel-nozzles. They are installed in equal distances around the outer case of the combustion chamber. This makes sure that the temperature in the combustion chamber is equally divided.
Each fuel nozzle has a primary and a secondary fuel orifice. The primary orifices give accurate fuel atomization at low fuel quantity and pressure. They get a controlled fuel supply from the FCU through the flow divider assy. This is controlled by the ECB 59KD logics, during start, operation and shutdown. The secondary orifices get the fuel when the primary nozzle pressure is greater than 120psig. They provide accurate fuel atomization at high fuel consumption.
Each fuel nozzle has a primary and a secondary fuel orifice. The primary orifices give accurate fuel atomization at low fuel quantity and pressure. They get a controlled fuel supply from the FCU through the flow divider assy. This is controlled by the ECB 59KD logics, during start, operation and shutdown. The secondary orifices get the fuel when the primary nozzle pressure is greater than 120psig. They provide accurate fuel atomization at high fuel consumption.
4. Interface
The fuel distribution system has interfaces with:
** ON A/C NOT FOR ALL The fuel distribution system has interfaces with:
- the APU drain system (Ref. AMM D/O 49-17-00-00),
- the APU fuel control (Ref. AMM D/O 49-32-00-00),
- the APU fuel pump system (Ref. AMM D/O 28-22-00-00),
- the APU LP fuel shutoff system (Ref. AMM D/O 28-29-00-00).
- the IGV actuator (49-23-00).
- the Surge Control Valve (49-51-00)-
5. Component Description
A. Flow Divider Assy
The flow divider assy is installed between the FCU and the APU primary and secondary fuel nozzle manifolds.
The assy consists of a check valve and a normally open fuel solenoid.
The flow divider assy is installed between the FCU and the APU primary and secondary fuel nozzle manifolds.
The assy consists of a check valve and a normally open fuel solenoid.
B. Primary and Secondary Fuel Nozzle and Manifolds
(1) The primary and the secondary fuel manifolds are insulated, flexible lines. The fittings connect the manifolds to the flow divider assy and to the fuel nozzles.
(a) The flexible lines are made from teflon tubes and a single layer of steel braid makes them stronger. The fuel-tight steel fittings have conical contact faces. Rubber sheaths protect the braids.
(2) The fuel nozzles have two flow paths. The orifices of the primary and the secondary flow paths are concentric.
(a) The connectors to the fittings of the manifold are of different diameters. Filters are installed in the flow paths. The nozzle housing goes into the air shroud. The air shroud guides the air to the nozzle tip to pre-mix the fuel with air, and to sweep the nozzle tip to prevent carbon formation.
6. Operation/Control and Indicating
At the start of the APU the fuel flow from the FCU is routed by the flow divider assy to the primary fuel manifold. The primary fuel manifold then distributes the fuel to the primary inlet port of the fuel nozzles
When the fuel pressure is greater than 125 psid (8.618 bar) at the primary fuel nozzles due to increased fuel flow, the check valve within the flow divider assy opens and the fuel also flows to the secondary fuel manifold. The secondary fuel manifold than distributes the fuel to the secondary inlet port of the fuel nozzles.
The check valve operation can be disabled by by the fuel solenoid, also part of the flow divider assy. The fuel solenoid is normally open (de-energized) but during cold start and high altitude operation the ECB energizes the solenoid valve to close during the first 25% speed of the APU. The fuel is then forced through the primary manifold only to achieve a better engine acceleration.
At the start of the APU the fuel flow from the FCU is routed by the flow divider assy to the primary fuel manifold. The primary fuel manifold then distributes the fuel to the primary inlet port of the fuel nozzles
When the fuel pressure is greater than 125 psid (8.618 bar) at the primary fuel nozzles due to increased fuel flow, the check valve within the flow divider assy opens and the fuel also flows to the secondary fuel manifold. The secondary fuel manifold than distributes the fuel to the secondary inlet port of the fuel nozzles.
The check valve operation can be disabled by by the fuel solenoid, also part of the flow divider assy. The fuel solenoid is normally open (de-energized) but during cold start and high altitude operation the ECB energizes the solenoid valve to close during the first 25% speed of the APU. The fuel is then forced through the primary manifold only to achieve a better engine acceleration.