DOC AIRBUS | AMM A320FAPU FUEL PUMP SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The APU fuel pump system supplies the necessary fuel to operate the APU in all operation conditions.
The APU fuel supply is tapped from the engine feed line. The fuel pressure for the APU comes from either the engine fuel pumps or the APU fuel pump.
To prevent draining the cross feed line when you remove the APU fuel pump, the pump is mounted in a cannister.
** ON A/C NOT FOR ALL The APU fuel pump system supplies the necessary fuel to operate the APU in all operation conditions.
The APU fuel supply is tapped from the engine feed line. The fuel pressure for the APU comes from either the engine fuel pumps or the APU fuel pump.
To prevent draining the cross feed line when you remove the APU fuel pump, the pump is mounted in a cannister.
2. Component Location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 4QC | PUMP-APU FUEL | 141 | 28-22-51 | ||
| 7QC | PRESS SWITCH-APU FUEL PRESSURE | 141 | 28-22-15 | ||
| 8QC | P/BSW-VENT APU FUEL LINE | 313 | 28-22-00 | ||
| 9QM | CANISTER - APU FUEL PUMP | 141 | 28-22-52 | ||
| ** ON A/C NOT FOR ALL | |||||
| 5030QM | SWITCH-APU FUEL LP | 315AL | 315 | 28-22-14 | |
| 5040QM | VALVE - VENT AND DRAIN | 315AL | 315 | 28-22-43 | |
| ** ON A/C NOT FOR ALL | |||||
| 5030QM | SWITCH-APU FUEL LP | 315 | 28-22-14 | ||
| 5040QM | VALVE - VENT AND DRAIN | 315 | 28-22-43 | ||
3. System Description
The APU usually takes its fuel supply from the LH engine-feed line, but when the cross-feed valve is open, the RH engine-feed line can also supply the APU with fuel.
Normally, the necessary fuel pressure is achieved by the main-engine fuel pumps. The fuel pressure is monitored by the APU fuel-pressure switch 7QC. If the fuel pressure in the APU fuel line drops below 1.5 bar (22 PSI), the APU fuel pressure switch energizes the APU fuel pump to ensure a stable fuel supply to the APU.
To purge the APU fuel line, it is possible to operate the APU fuel pump by the APU Fuel-Line Vent-Pushbutton 8QC, installed on the APU compartment firewall. The APU fuel pump operates as long as the pushbutton is pushed.
** ON A/C NOT FOR ALL The APU usually takes its fuel supply from the LH engine-feed line, but when the cross-feed valve is open, the RH engine-feed line can also supply the APU with fuel.
APU Fuel Pump - Block DiagramNormally, the necessary fuel pressure is achieved by the main-engine fuel pumps. The fuel pressure is monitored by the APU fuel-pressure switch 7QC. If the fuel pressure in the APU fuel line drops below 1.5 bar (22 PSI), the APU fuel pressure switch energizes the APU fuel pump to ensure a stable fuel supply to the APU.
To purge the APU fuel line, it is possible to operate the APU fuel pump by the APU Fuel-Line Vent-Pushbutton 8QC, installed on the APU compartment firewall. The APU fuel pump operates as long as the pushbutton is pushed.
4. Power Supply
For normal operation, the essential busbar 801XP (115V AC) supplies the pump motor. When the busbar is not energized, the static inverter busbar 901XP (115V AC) supplies the pump motor. The APU fuel pump supply relay 9QC (on panel 103VU) monitors the essential busbar and performs the busbar to switch. The pushbutton switch 8QC operates the APU pump on the ground to purge the fuel line. The APU fuel-line vent relay (6QC) is supplied with 28V DC from the DC Busbar 1 (103PP).
** ON A/C NOT FOR ALL For normal operation, the essential busbar 801XP (115V AC) supplies the pump motor. When the busbar is not energized, the static inverter busbar 901XP (115V AC) supplies the pump motor. The APU fuel pump supply relay 9QC (on panel 103VU) monitors the essential busbar and performs the busbar to switch. The pushbutton switch 8QC operates the APU pump on the ground to purge the fuel line. The APU fuel-line vent relay (6QC) is supplied with 28V DC from the DC Busbar 1 (103PP).
5. Interfaces
The APU fuel pump system has interfaces with:
** ON A/C NOT FOR ALL The APU fuel pump system has interfaces with:
- the APU fire-extinguishing system (Ref. AMM D/O 26-22-00-00),
- the main fuel pump system (Ref. AMM D/O 28-21-00-00),
- the APU LP fuel shut-off system (Ref. AMM D/O 28-29-00-00),
- the APU fuel distribution system (Ref. AMM D/O 49-31-00-00),
- the APU control and monitoring system (Ref. AMM D/O 49-61-00-00),
- the APU emergency shutdown (Ref. AMM D/O 49-62-00-00).
A. Description of the Pump Element FIN: 4-QC
(1) The pump element (4QC) is a centrifugal type impeller which is driven by a 3 phase electric motor, supplied with single phase 115 V AC at 400HZ. The fuel that circulates through the unit, cools and lubricates the pump element. A thermal fuse, set at 175DEG.C (347DEG.F), protects the motor from an overheat condition.
B. Description of the Pump Canister (P/N C49AA0221)
(1) The pump canister (9QM) contains the pump and is attached to the wing-box rear spar. A drain gutter collects any fuel leakage and drains it away from the installation area. The engine fuel crossfeed and the APU fuel lines are bolted to the canister within the tank.
C. Description of the Pump Canister (P/N C49AA0222)
(1) The pump canister (9QM) contains the pump and is attached to the wing-box rear spar. The engine fuel crossfeed and the APU fuel lines are bolted to the canister within the tank.
D. Description of the Pressure Switch
(1) The pressure switch (7QC) has a cylindrical chamber with a banjo type head. A bolt secures it to a check valve on the rear spar. The fuel pressure in the crossfeed line goes through the check valve and the banjo head to operate a microswitch in the chamber.
(2) When the fuel pressure drops below 1.5 bar (22 PSI) the microswitch closes and transmits 28VDC to APU fuel pump relay, to energize the APU fuel pump.
E. Description of the VENT APU FUEL LINE Pushbutton-Switch
(1) The VENT APU FUEL LINE pushbutton-switch (8QC) permits the APU fuel pump to operate on the ground. You press and hold the pushbutton-switch to purge the fuel line during ground maintenance. This energizes the APU fuel line vent relay (6QC) to start the pump. The pump is supplied with 115V AC from the essential busbar 801XP. The pump stops when the pushbutton is released.
F. Description of the APU Inlet Low Pressure Switch
(1) The APU inlet low pressure switch (5030QM) is installed in the APU compartment at the fuel inlet connection to the FCU. It operates on fuel absolute pressure in the APU fuel-feed line at the inlet to the FCU. When it operates, it transmits a signal to the Electronic Control Box (ECB) 59KD.
(2) The switch closes when the inlet pressure decreases to 1.09 +-0.06 bar or -+0.06 bar (15.8091 +-0.8702 psi or -+0.8702 psi). The switch opens when the inlet pressure increases to 1.19 +-0.06 bar or -+0.06 bar (17.2595 +-0.8702 psi or -+0.8702 psi).
G. Description of the Drain and Vent Valve
(1) The fuel drain and vent valve (5040QM) is installed in the APU compartment at the fuel inlet connection to the FCU. It permits the APU fuel-feed line to be drained of fuel and bled of air during maintenance of the system.
(1) The APU fuel-feed line connects the engine fuel-feed line with the APU fuel distribution system. The APU fuel-feed line installation includes:
- a aluminium-alloy tube, installed from the crossfeed line to the top of the wing center tank (immediately forward of FR42),
- a double-walled vented hose, installed from FR42 to FR80,
- high-pressure Teflon flexible hose which incorporates spacing rings to support and locate the hose in its tube,
- a fire sleeve from FR80 to the APU fuel inlet connection,
- a drain tube, which connects to the vented shroud, at its lowest point (top of the wing center-box, immediately forward of FR42) with the drain mast,
- a drain mast at FR47, which connects to the drain tube. It permits the fuel to drain overboard if a fuel leak occurs in the hose.
7. Operation/Control and Indicating
When the APU MASTER SW is set to on, the Electronic Control Box (ECB) 59KD energizes the APU MAIN RELAY 4KD. This causes the APU Fuel Low-Pressure Actuator 3QF to open the APU Fuel Low-Pressure Valve 9QM. The APU fuel-feed line is now connected to the main-engine fuel-feed line.
The necessary fuel pressure is achieved either by at least one of the main-engine fuel pumps or by the APU Fuel Pump 4QC.
As long as one of the main-engine fuel pumps is operating and the fuel pressure in the APU fuel feed line is higher than 1.5 bar (22 PSI), monitored by the APU Fuel-Pressure Switch 7QC, the APU Fuel Pump 4QC is in standby mode (not operating).
As soon the main-engine fuel pump stops and/or the fuel pressure in APU fuel-feed line drops below 1.5 bar (22 PSI), the APU fuel pump, energized by the APU Fuel-Pressure Switch, takes over/supports the fuel supply of the APU.
If an APU shutdown occurs, either manual or automatic (APU failure), the ECB de-energizes the APU MAIN RELAY 4KD. This causes:
If an emergency shutdown of the APU occurs (e.g. due to fire) the FIRE EMER RELAYS 5WF and 6WF immediately causes the APU Fuel Low-Pressure Valve-Actuator to close the APU Fuel-Low Pressure Valve and they de-energize the APU Fuel Pump, if it was operating.
To purge the APU fuel-feed line during ground maintenance, it is possible to energize the APU fuel pump with the APU-Fuel Vent-Line Pushbutton 8QC. When the pushbutton 8QC is pushed the APU FUEL VENT LINE RELAY 6QC energizes. This causes:
When the APU MASTER SW is set to on, the Electronic Control Box (ECB) 59KD energizes the APU MAIN RELAY 4KD. This causes the APU Fuel Low-Pressure Actuator 3QF to open the APU Fuel Low-Pressure Valve 9QM. The APU fuel-feed line is now connected to the main-engine fuel-feed line.
The necessary fuel pressure is achieved either by at least one of the main-engine fuel pumps or by the APU Fuel Pump 4QC.
As long as one of the main-engine fuel pumps is operating and the fuel pressure in the APU fuel feed line is higher than 1.5 bar (22 PSI), monitored by the APU Fuel-Pressure Switch 7QC, the APU Fuel Pump 4QC is in standby mode (not operating).
As soon the main-engine fuel pump stops and/or the fuel pressure in APU fuel-feed line drops below 1.5 bar (22 PSI), the APU fuel pump, energized by the APU Fuel-Pressure Switch, takes over/supports the fuel supply of the APU.
If an APU shutdown occurs, either manual or automatic (APU failure), the ECB de-energizes the APU MAIN RELAY 4KD. This causes:
- the APU Fuel Low-Pressure Valve Actuator to close the APU Fuel Low-Pressure Valve. The APU fuel feed line is now disconnected from the main-engine fuel feed line;
and - the APU Fuel Pump to be de-energized, if it was operating.
If an emergency shutdown of the APU occurs (e.g. due to fire) the FIRE EMER RELAYS 5WF and 6WF immediately causes the APU Fuel Low-Pressure Valve-Actuator to close the APU Fuel-Low Pressure Valve and they de-energize the APU Fuel Pump, if it was operating.
To purge the APU fuel-feed line during ground maintenance, it is possible to energize the APU fuel pump with the APU-Fuel Vent-Line Pushbutton 8QC. When the pushbutton 8QC is pushed the APU FUEL VENT LINE RELAY 6QC energizes. This causes:
- the APU Fuel Low-Pressure Valve Actuator to open the APU Fuel Low-Pressure Valve. The APU fuel feed line is now connected to the main-engine fuel feed line;
and - the APU Fuel Pump to be energized.