28 Fuel Flashcards
What is the fuel feed sequence of a traditional A320?
Centre tanks for 2 mins or until slats extended
Inner tanks until 500kg used
CT until empty (may turn off if recirc fuel puts it up above 500kg limit)
Inner tanks to 750kg
Outer tanks to inner tanks
How is Centre Tank fuel prioritised in the traditional A320 system
CT fuel pumps deliver fuel at higher pressure than inner tanks. As a result the CT pumps drain fuel before the inner tanks
Describe the fuel feed sequence on newer A320’s.
Centre tank first unless the inner is full. 250kgs used from inner before centre tanks TFR’s open. The centre till empty.
If the inner tanks fuel then the jet pump switches off and the valves close. The process is repeated until CT is empty.
Inner tank empties down to 750kg
Outer tank fuel transfers into inner tank
(A321NEO has no outer tank)
Describe fuel recirculating system
Fuel from HP fuel line is diverted through the heat exchanger of the IDG. Heat from the oil is radiated away by the fuel in the exchanger.
It is then sent either to the HP fuel line or sent back to the outer tanks
Why is CT fuel prohibited for TO?
Wing tanks fill before CTs. If fed from CT during TO then recirculated fuel would go into full wing tanks and cause the surge vent to spill excess overboard
What happens to the fuel from the fuel return valve (used for IDG cooling) if the inner tank is already full?
If the FUEL MODE SEL pb is in AUTO, and the centre tank pumps are feeding, the system selects CTR TK PUMPs off, and wing tanks pumps will automatically feed each engine until around 500kg has been used in each wing.
If the FUEL MODE SEL pb is in MAN, the CTR TK PUMPs will not be automatically switched off, which could lead to over flow of the wing tanks.
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Where is the vent surge fuel tank located?
Outboard of the outer tank in each wing
When the fuel is filled to maximum capacity, how much can the fuel expand by without spilling?
2%
What is the total usable fuel on the A320 family approx?
Between 18.5 and 19 tonnes
How many fuel pumps are there on newer A320s and the A321?
Four (two in each wing), the centre “pumps” are jet pumps with transfer valves
How many fuel pumps are there on A319 and older A320 aircraft?
Six (two in each wing, and two in centre tank)
How many transfer valves are located in each wing?
Two
Which electrical system supplies the APU fuel pump if the fuel feed pressure is low (due to loss of tank pumps or normal AC supply)?
The AC ESS SHED
If this fails, it runs off the AC STAT INV BUS
What does the fuel system cool?
The Integrated Drive Generator
The fuel passes through the IDG heat exchanger (which absorbs heat), then to the fuel return valve and back to the outer fuel tank.
This ensure IDG cooling when oil temperature is high or at low engine power.
What happens to the fuel from the fuel return valve (used for IDG cooling) if the outer tank is already full?
The fuel overflows to the inner tank through a spill pipe
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How long does it take to refuel all tanks (around 19T)?
20 minutes (around 1T per minute)
What causes a fluctuation in the inner tank fuel quantity indications after take off? How long does it take to return to normal?
For low fuel quantities below 7T, acceleration and high pitch angles causes the fuel to move in the tank. This can see the FOB reduce for 2 minutes after take off, then increase to accurate values about 6 minutes later during the climb. Maximum fluctuations can be up to 400kg (300kg in the go-around).
For higher fuel loads, a FOB increase up to 1000kg may occur after takeoff, this returns to accurate within a maximum of 6 minutes.
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What does the Fuel Tank Inerting System do? And how does it do it?
Reduces flammability in the fuel tanks which have a high flammability exposure (only the centre tank).
The system produces oxygen-depleted air that goes in the centre tank to replace the ambient air (around 12% oxygen level rather than 21% normally).
This isn’t installed on all aircraft, only later MSNs ( MSN 5019-9171).
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How long do the centre tank pumps run for if the low level is reached?
5 minutes
Which valve is displayed on the FUEL SD page immediately below the F.USED quantity at the top of the screen?
Engine LP valve
When does a fuel imbalance advisory appear?
When the difference in the two wings is greater than 1500kg
Which fuel type do we usually use?
Jet A1
What is the minimum fuel temperature?
-43degC
What is the maximum fuel temperature?
54degC (55degC for NEO)
