FUEL IDG COOLING SYSTEM PRESENTATION
FUEL IDG COOLING SYSTEM PRESENTATION (3)
PRINCIPLE
The Integrated Drive Generator (IDG) oil is cooled by fuel; a recirculation system is installed. Some fuel supplying the engines is used to cool the IDG oil. A return valve allows the hot fuel to be returned to the outer cell. The return valve opens at low engine fuel flow if the engine oil temperature is above 93°C (199°F). The return valve mixes the hot fuel with cold fuel from the LP pump to maintain the temperature of the returned fuel below 100°C (212°F). Fuel Level Sensing Control Unit (FLSCU) 1 and Electronic Control Unit (ECU) 1 control the recirculation system in the left wing. FLSCU 2 and ECU 2 control the right wing system.
FUEL RETURN
The re-circulated fuel is sent to the outer cell through a check valve and a pressure holding valve in order to prevent the fuel from boiling. The pressure holding valve maintains a pressure of 15.5 psi in the return line; if the pressure increases, fuel bleeds through the valve into the outer cell. The check valve prevents fuel flow from the wing tank to the engine when the recirculation system is not in operation.
NOTE:Note: When the outer cell is full, the fuel overflows into the inner cell through a spill pipe.
PUMP LOGIC
As long as fuel is being delivered from the center tank, the wing tanks are still full and will tend to overfill, as the returned fuel is delivered to the wings tanks. In this case the center tank pump stops when the inner cell reaches the FULL level. The wing tank pumps will operate until approximately 1100 lbs (500 kg) of fuel have been used i.e.: under full sensors reached. The logic circuit then restarts the center tank pump.FRV CLOSURE
LOW LEVEL
The Fuel Return Valve (FRV) closes when the fuel level in the inner cell drops to the low level sensors (IDG shut-off sensor 38QT) at 280 Kg.
NOTE:Note: The low level sensor i.e. IDG shut-off sensor signals the return valve to close at 620 lbs (280 kg).
Note: Closing the return valve will reduce the amount of
unusable fuel.
INNER CELL HIGH TEMPERATURE
The FRV closes if the fuel temperature is too high in the inner cell
i.e. 52.5°C (126.5°F). As the returned fuel is hot, the FLSCU prevents
temperature limitation exceedance. In this case, the FLSCU sends an inhibition signal to the Full Authority Digital Engine Control (FADEC) for FRV closure.
OUTER CELL HIGH TEMPERATURE
The FRV closes if the fuel temperature is too high in the outer cell
i.e. 55°C (131°F). This prevents a large volume of high temperature
fuel from entering the inner cell, in the event of intercell valve opening.
This also keeps the fuel temperature at an acceptable level should a tank rupture occur.
PUMP PRESSURE LOSS
The FRV closes if a LP is signaled by all pumps of one wing supplying the related engine and crossfeed valve closed, or if a LP is signaled by all pumps of both wings with crossfeed valve opened. This is to reduce fuel flow and allow maximum available pressure for fuel burn during gravity feeding. LP is sensed by the pump LP switch and
signaled to the FLSCU.
OVERFLOW
The FRV closes if the center tank pump fails to respond to the logic signals of the full sensors, causing the wing tank to overflow into the vent surge tank.
PRINCIPLE ... FRV CLOSURE
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W ATER DRAIN V ALVE OPERATION (2) GENERAL
Water which collects beneath the fuel in the lowest parts of the wing tanks is drained away through small bore pipes connected to manually operated water drain valves. To drain remaining fuel and water:
W ARNING:DO NOT GET AIRCRAFT FUEL:
- IN YOUR MOUTH,
- IN YOUR EYES,
- ON YOUR SKIN FOR A LONG TIME.
AIRCRAFT FUEL IS POISONOUS.
DO NOT GET YOUR CLOTHES SOAKED WITH FUEL.
BEFORE Y OUR REFUEL OR DEFUEL THE AIRCRAFT
YOU MUST MAKE THE AREA AROUND IT SAFE. IN
THE SAFETY AREA DO NOT:
- SMOKE,
- MAKE SPARKS OR FIRE,
- USE ANY EQUIPMENT WHICH IS NOT APPROVED
FOR REFUEL/DEFUEL PROCEDURES.
AIRCRAFT FUEL IS FLAMMABLE.
GENERAL
W ATER DRAIN V ALVE OPERATION (2)
JOB SET-UP
A - Follow the safety precautions.
B - Put the access platform below the applicable water drain valve.
C - Put the container below the applicable water drain valve.
D - Put "NO SMOKING" warning notices at the limit of the safety area.
E - On the TEST EQUIPMENT JET PUMP fully retract the nut (4), the screw (3) and the plunger (1) assembly.
F - Install the TEST EQUIPMENT JET PUMP:
- (a) Put the hexagonal end of the bush (2) into the base plate of the drain valve,
- (b) Turn the bush (2) through 30 deg,
- (c) Turn the nut (4) until it touches and seals against the bottom skin, - (d) Put the end of the hose into the container.
JOB SET-UP
W ATER DRAIN V ALVE OPERATION (2)
DRAIN PROCEDURE
A - Hold the bush (2) and turn the screw (3) to the end of its travel. This causes the plunger (1) to open the drain valve and the fuel to flow.
DRAIN PROCEDURE
W ATER DRAIN V ALVE OPERATION (2) CLOSE-UP
A - When the fuel flow stops, remove the TEST EQUIPMENT JET JUMP.
B - Remove all the ground support equipment, the maintenance equipment, the standard and special tools and all other items.
C - Make sure that the work area is clean and clear of tools and other items.
CLOSE-UP
ENGINE FEED SYSTEM D/O (3)
GENERAL
The main fuel pump system supplies fuel from the fuel tanks to the engines. Each tank has two centrifugal booster pumps. Fuel is first supplied by the center tank pumps and then by the wing tank pumps when the center tank is empty. The crossfeed valve divides the engine fuel feed system into two independent feed systems.
MAIN PUMPS
The main pumps, driven by a 3-phase 115/200 V AC motor, have different power supplies. When it is in operation, each main pump supplies fuel to:
- its related engine,
- the fuel recirculation cooling system,
- the crossfeed system,
- the refuel/defuel system.
Each wing tank collector has:
- two fuel pumps contained in their related canisters,
- two fuel strainers,
- a suction valve,
- two check valves.
CANISTER CHECK V ALVES
The canister lets you replace the fuel pump without draining fuel. The wing fuel pump element is located in a canister attached to the wing bottom skin, with an inlet connected to a fuel strainer. The canister has three outlets:
- one upper outlet is connected to the engine feed line and contains an internal flap-type check valve,
- the other upper outlet is connected to a sequence valve,
- a smaller outlet is connected to the scavenge jet pumps and the fuel pump pressure switch.CENTER FUEL PUMP CANISTER CHECK V ALVE
When a fuel pump is not in operation, the two check valves prevent any reverse flow of fuel through the pump. The center fuel pump element is located in a canister attached to the center tank bottom skin, with a lower inlet connected to a fuel strainer. The canister has two outlets:
- an upper outlet is connected to the engine feed line and contains an internal flap-type check valve,
- a smaller outlet is connected to the scavenge jet pumps and the fuel pump pressure switch.
PRESSURE SWITCHES
The pressure switches monitor the output of the pumps through a pressure pipe. If the pressure from the main pump decreases to less than 6 psi (0.41 bars) the pressure switch sends a warning signal to the ECAM system.
BY-PASS SUCTION V ALVE
A by-pass suction valve is installed on the engine feed line, downstream of the main pumps. If there is complete main pump failure, the by-pass suction valve lets fuel be sucked from the tank by the Engine Driven Pumps (EDP) and thus supply the engine by "gravity".
AIR RELEASE V ALVE
The air release valve releases air trapped in the engine fuel feed line. The air release valve is installed at the high point between the pump and the LP valve.
LP V ALVES
The LP valve is installed on the wing tank front spar, in the feed line to the engine. Each LP valve has an actuator with 2 electric motors. Each
one of them is supplied by different 28 V DC power sources. The LP valve isolates the engine fuel feed supply at shutdown, i.e. normal procedure, or in case of emergency, i.e. engine fire procedure.
JET PUMPS
Center tank scavenge jet pumps move fuel and water caught in the tank to the related main pump inlet. Outer cell scavenge jet pumps move the surge tank fuel to the rear intercell transfer valves. Check valves, in the line between the surge tank, combined with these jet pumps, make sure that fuel cannot enter the surge tank via the pump if the main pumps are off.
CROSSFEED V ALVE
The crossfeed valve in the center tank, i.e. transfer tank, is usually in the closed position. In this position, it divides the main fuel pump system into two parts, one part for each engine. When the crossfeed valve is open, either tank can supply fuel to either engine.
SEQUENCE V ALVE
The wing tank pumps are equipped with a sequence valve to make sure that the center tank is emptied first.
INTERCELL TRANSFER V ALVE
The intercell transfer valves let the outer cell fuel flow into the inner cell when the inner cell low level sensors are dry.
FUEL SUPPLY LOGIC
When all the tanks contain fuel, the center tank is emptied first. Keeping a fuel mass in the wings as long as possible reduces the bending stresses at the wing roots. When the center tank fuel has been used, engines are supplied by fuel from the inner cells. The outer cell fuel flows to the inner cell by gravity through the transfer valves, which open when the inner cell fuel quantity decreases to a given value.
GENERAL ... FUEL SUPPLY LOGIC
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APU FEED SYSTEM D/O (3)
GENERAL
The APU fuel supply system comprises a fuel pump, a Low Pressure (LP) fuel valve and an actuator on the rear wall of the center tank. The fuel supply to the APU is normally from the Left Hand (LH) crossfeed line. The APU LP fuel shut-off system has a LP fuel valve that controls the supply of fuel to the APU. If an APU fire occurs on ground, the APU emergency shutdown system closes the LP fuel valve to stop the flow of fuel. When the crossfeed valve is open, either engine feed line, left or right, can supply fuel to the APU.
APU PUMP
The fuel pressure for the APU comes from either the engine fuel pumps or the APU fuel pump. For normal operation, the essential bus bar 801XP (115V AC) supplies the pump motor. When the bus bar is not energized, the static inverter bus bar 901XP (115V AC) supplies the pump motor.
CANISTERS
The canister permits pump replacement even with fuel in the tanks or in the APU fuel line. When a pump is removed, the fuel pressure closes the canister inlet and outlet.
PRESSURE SWITCH
The pressure switch controls pump operation. The pressure in the left crossfeed line goes through the check valve to operate a micro switch. The APU fuel pump stops if the crossfeed line pressure reaches 23.3 psi absolute (1.6 bar) and restarts at 21.7 psi (1.5 bar).
APU LP SHUT-OFF V ALVE
The APU LP fuel shut-off valve is used to isolate the APU fuel supply line from the left engine feed line, when the APU does not operate. The two DC motors in the actuator are supplied from different 28V DC sources.
V ALVE OPEN
The valve opens when:
- the APU MASTER SWitch is set to ON,
- the FUEL VENTilation P/BSW in the APU compartment is pressed and held.
The FUEL VENT P/BSW is used to purge the system during ground maintenance.
V ALVE CLOSE
The valve closes when:
- the APU MASTER SW is set to OFF,
- the FUEL VENT P/BSW is released,
- the APU FIRE P/BSW on the overhead panel is pressed,
- the APU FIRE SHUT-OFF switch on the panel FWD of the Nose Landing Gear (NLG) bay is operated,
- the fire detection system operates on the ground. CROSSFEED OPERATION
When the crossfeed valve is open, the Right Hand (RH) engine feed line can also supply the APU fuel supply line.
FUEL VENT P/B
When the A/C is on ground, it is possible to operate the APU fuel pump (single phase 115V AC) to purge the fuel line. The P/BSW HOLD on frame (FR) 80 in the APU compartment is used to operate the pump and to open the LP fuel valve.
APU MASTER SWITCH
If the APU MASTER SW P/BSW is pressed ON, the APU pump will operate if the pump inlet pressure is below 21.7 psi (1.5 bar) absolute. This is initiated automatically through the pressure switch.
LINE SHROUD AND DRAIN MAST
To prevent that a leakage is spilled into the area of the fuselage (AFT Cargo Compartment, Bilge area, THS Compartment), the APU fuel supply line is shrouded. The shroud is connected to a Drain Mast which is located AFT of the MLG Doors.
GENERAL ... LINE SHROUD AND DRAIN MAST
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