Fuel System

Question 1

What are the suction valves?

Answer 1

Closed by pumps pressure in normal operation, they allow engines to be fed by gravity if the inner tank pumps fail.

Question 2

What is the Tank Vent Surge function and when will it operate?

Answer 2

Vent surge tank outboard of each wing tank.
When a/c fuelled to capacity fuel can expand by 2% (20C temp rise) without spilling.
Overpressure protector in each vent, outer and inner tank (vent, wing A321) and between the centre and left inner (left wing A321) tank.

Question 3

What side supplies the APU?

Answer 3

APU supplied by fuel from eng 1 side (left side).

Question 4

How is fuel pressure supplied to the APU for starting when the system is not pressurised?

Answer 4

A special fuel pump supplies fuel for APU startup when fuel feed pressure is low (loss of tank pumps or norm AC supply). Pump normally runs of AC ESS SHED, but runs off AC STAT INV BUS if AC BUS SHED fails.

Question 5

Describe the fuel recirculating system.

Answer 5

Some of the fuel supplied to each engine goes from the high-pressure fuel line in that engine, through the IDG heat exchanger, to the fuel return valve and back to the outer fuel tank.

Question 6

How is the center tank fuel prioritised over the inner tanks on a traditional A320 fuel system?

Answer 6

CT fuel pumps deliver fuel at a higher pressure than the inner tank fuel pumps. So, when CT pumps are on the CT fuel will drain before inner tanks.

Question 7

Assuming full fuel what is the fuel feed sequence of a traditional A320?

Answer 7

1. After engine start, CT for 2 mins (or slats extended)
2. CT pumps off, Inner tanks until 500kg burned
3. CT pumps back on, CT until empty
4. Inner tanks for remainder of flight.
5. When fuel in one inner tank = 750kg, outer tank xfr valves open so outer fuel can drain into inner

Question 8

Why is CT fuel prohibited for takeoff?

Answer 8

Prohibited due regulation against feeding both engines from same fuel source during takeoff.

Question 9

How is the fuel system different on a modern A320 fuel system compared to traditional style, and what is the fuel feed sequence assuming full fuel?

Answer 9

Fuel feeds from inner tanks only, CT fuel drains into inner tanks via tank xfr valves, and fuel jet pumps.

Assuming fuel full:
1. Inner tanks until 250kg burned in a tank
2. CT xfr valves open & jet pump activates
3. When fuel reaches high level sensor jet pumps off & xfr valves close.
4. process repeats
5. When fuel in one inner tank = 750kg, outer tank xfr valves open

Question 10

What are jet pumps and how many are there?

Answer 10

1 jet pump in each inner tank. Fuel from inner tank pumps flows through jet pump and creates a suction in it which moves fuel from the centre tank to the related inner tank.

Question 11

What is the CT fuel inserting system?

Answer 11

Center tanks have a high flammability exposure.
To reduce flammability, Fuel Tank Inerting System produces a conditioned o2 depleted air using bleed air that replaces the ambient air in centre tank.

Question 12

Trip fuel modifications?

Answer 12

Increase trip fuel by 5kg for each mile increase
Reduce trip fuel by 4kg for each mile reduction

Question 13

Fuel system procedures including de-fueling, gravity fueling, refuelling with an engine running, can be found where?

Answer 13

FCOM/PROC/NORM/SUPP/FUEL

Question 14

Which procedures for the fuel system are located in the QRH?

Answer 14

Fuel Imbalance - confirm no fuel leak first
Fuel Leak
Gravity Fuel Feeding
Fuel Overread

Question 15

What advisory conditions are in the QRH related to fuel, and what corrective actions can be taken?

Answer 15

1. Fuel Imbalance > 1500kg : Fuel leak/imbalance proc
2. Fuel inner cell > 45C, outer > 55C : Galley OFF
3. Fuel inner/outer < -40C : Descend or increase TAT