-
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,
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APU Fuel Line Figure 009
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-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 Indication________________________________ (Ref. Fig. 004) 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.
The APU Fuel Low-Pressure Valve is open and the APU Fuel Pump is operating
as long as the pushbutton 8QC is pushed.
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APU FUEL PUMP SYSTEM - ADJUSTMENT/TEST
______________________________________ TASK 28-22-00-710-001 Operational Test of the APU Fuel-Pump System on Ground to Purge the Fuel Line WARNING : OBEY THE FUEL SAFETY PROCEDURES.
_______
1.
Reason for the Job
__________________
Self Explanatory
2.
Job Set-up Information
______________________
A. Fixtures, Tools, Test and Support Equipment
-------------------------------------------------------------------------------REFERENCE QTY DESIGNATION -------------------------------------------------------------------------------
No specific access platform 3.5 m (11 ft. 6 in.) No specific container 5.0 l (1.3208 USgal) 98A28007570000 1 ADAPTER - VENT AND DRAIN VALVE, APU
B. Referenced Information
-------------------------------------------------------------------------------REFERENCE DESIGNATION -------------------------------------------------------------------------------
24-41-00-861-002 Energize the Aircraft Electrical Circuits from the External Power 24-41-00-862-002 De-energize the Aircraft Electrical Circuits Supplied
from the External Power 52-41-00-010-001 Open the APU Doors for Access 52-41-00-410-001 Close the APU Doors after Access
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