Fuel Flashcards
What are the suction valves?
Are they available in fuel center tank?
Allow gravity feeding through suction when loss of fuel pump pressure prevents the valves from being held closed.
Not in fuel center tank so no gravity feeding from center tank
What is the Tank Vent Surge function and when will it operate?
The vent surge tanks are outboard of the outer tanks and are a protection system that expels the fuel overboard should the inner and outer tanks become overfilled, this could be through fuel expansion or IDG cooling return fuel
When the aircraft has been filled to maximum capacity, how much can the fuel expand by before spilling to vent tank?
2% equal to a 20deg temperature rise
What fuel side supplies the APU & how is fuel supplied to the APU for starting when the system is not pressurised?
The APU is supplied by fuel from engine 1 side.
A special pump powered by the batteries will pressurise the APU fuel feed line to enable starting and running when fuel feed pressure is low due to loss of tank pumps or loss of normal AC electrical supply. The pump normally runs off AC ESS SHED but runs off the AC STAT INV BUS from the batteries if the AC ESS SHED fails or is not powered.
Describe the fuel recirculating system
Fuel from the HP fuel line is diverted prior to entering the burners through the IDG heat exchanger.
Heat from IDG oil is absorbed by the fuel and that fuel is then returned to the outer tank via the fuel return valves
How is centre tank fuel prioritised over the inner tanks on traditional A320 system?
Centre tank pumps deliver fuel at a higher pressure than the inner wing tank pumps so when centre pumps are switched on fuel from the centre tank will drain over fuel in the inner tanks
Why is centre tank fuel prohibited for takeoff?
So fuel not being supplied from common source
Assuming full fuel, what is the fuel feed sequence of a traditional A320 fuel system?
After engine start centre tanks deliver fuel for 2 mins or until slats extended. Then switch off until 500kg has burned from each inner tank to make room for IDG return fuel. Centre tanks then switch back on and supply fuel until it is drained. The inner tanks then supply fuel for the remainder of flight, once the fuel level in one inner tank reaches 750kg, transfer valves open and allow fuel from outer tank to drain into inner tank.
Assuming full fuel, what is the fuel feeding sequence on a modern A320/321 NEO?
On modern aircraft, fuel jet pumps suck the centre tank fuel into the inner tank when required. With full fuel, fuel is burned from the inner tank until 500kg (250kg on 321) has been used. The centre tank jet pumps then activate and suck fuel from centre tank into inner tank until it is full and then they switch off. This process repeats until the centre tank is empty. Fuel is then burned from the inner tanks until 750kg is left, transfer valves then open and outer tank fuel drains into inner tank.
Can you refuel on batteries only?
Yes, switch on fuel panel enables this
What are Jet pumps and how many are there?
1 Jet pump in each inner tank. They suck fuel from the centre tank into the inner tank. Become active when 500kg of inner tank fuel have been used and switch off again when inner tank is full.
Explain the Fuel Quantity Indication (FQI) system
Has two channels to performs fuel computations, channel 2 takes over it channel 1 fails
Responsible for displaying fuel quantities on ECAM fuel page
Explain the Fuel Level Sensing Control Unit (FLSCU)
Seperate to the FQI comprises of fuel level sensors in the tanks to sense high and low fuel levels for appropriate switching functions
Also has a fuel temperature sensor to control IDG cooling recirculating
When one wing tank goes below 750kg the low level sensor triggers the LO LVL warning on ECAM
How does automatic refuelling sequence?
Outer tanks first that then spills over into inner tanks.
If fuel selected exceeds the amount for inner tanks only, centre tank is simultaneously refuelled
What is the Centre tank fuel inerting system?
To prevent fire risk in the centre tank, as fuel is burned, it is replaced by air from the bleed system which has passed through the fuel inerting system which removes oxygen from the air and replaces it with nitrogen. The result is air that is depleted of oxygen and therefore a lot less flammable.
