A320 Fuel System

Question 1

How many fuel tanks do most of our aircraft have?

Answer 1

5. A center tank, 2 inner wing tanks, and 2 outer wing tanks.

Question 2

How is the IDG for each engine cooled?

Answer 2

It’s cooled through a heat exchanger where the hot IDG is cooled using fuel from the outer wing tank. After it cools the IDG its returned to the outer wing tank. This can cause the fuel to overheat during long delays on the ground during hot summer days.

Question 3

Which fuel tank provides the fuel used for cooling the IDG?

Answer 3

The outer wing tank

Question 4

When the aircraft is fueled, in what order is the fuel added?

Answer 4

To the inner wing tanks first, then to the center tanks, and finally to the outer wing tanks.

Question 5

Where are the vent surge tanks and what do they do?

Answer 5

The vent surge tanks our located outboard of each outer wing tank. They are there to provide temporary fuel storage during thermal expansion of fuel and during aircraft movement.

Question 6

What system allows the fuel tanks to stay at ambient pressure?

Answer 6

The Aircraft Fuel Ventilation system

Question 7

Does fuel from the center tanks directly fuel the engines in the NEO aircraft?

Answer 7

No, it is simply moved from the center tank to the inner wings tanks via jet pumps

Question 8

Which aircraft have only 1 wing tanks instead of an inner and outer wing tank?

Answer 8

The A321 aircraft only have an outer wing tanks instead of, instead of an inner and outer wing tanks. All A320 aircraft have both inner and outer wing tanks.

Question 9

Which are the only tail numbers that have center tank pumps that allow direct feeding of fuel from the center tank to the engines?

Answer 9

N228FR, and N229FR. I believe both of these aircraft have been returned so we no longer have any aircraft in our fleet that have these pumps.

Question 10

Which fuel tank does the APU usually draw from?

Answer 10

The left wing tank. This could possibly be changed by opening the X-feed valve, or atleast allow draw from both tanks.

Question 11

How could you correct a wing tank fuel imbalance?

Answer 11

Open the X-feed valve, and turn off the fuel pumps from the low side. This would force both engines to run off fuel from the high side.

Question 12

Why does the APU needs its own fuel pump?

Answer 12

With engines running there should already be enough fuel pressure to send fuel to the APU. If no engines are running however, the APU fuel pump allows flow of fuel to the APU.

Question 13

What allows the engines to gravity feed fuel in the event that the fuel pumps fail?

Answer 13

Suctions valves in each wing tank

Question 14

What normally inhibits the suction valves from allowing the engines to gravity feed?

Answer 14

Fuel pressure from the fuel pumps closes the suctions valves.

Question 15

Is gravity feeding from the center tanks possible?

Answer 15

No. There are no suction valves in the center tank. Gravity feeding can only be accomplished from the wing tanks. Therefore if all fuel pumps fail or are unpowered, you will end up with the center tank fuel being unusable.

Question 16

What 2 items control the engine low pressure fuel valves?

Answer 16

The engine master levers and the engine fire pushbuttons

Question 17

Which fuel tank receives very low oxygen air from the fuel inserting system?

Answer 17

The center tank only

Question 18

What controls the transfer of fuel from the center tank to the wings tanks in AUTO mode?

Answer 18

The FLSCU or Fuel Level Sensor Control Unit

Question 19

What is the order in which fuel is used and transferred in auto mode?

Answer 19

1.) Fuel is used from the wing tanks until a total between both wings tanks of 1100lbs is used
2.) When the FLSCU senses that 1100 lbs has been used, the jet pumps activate to transfer fuel from the center tank to the wings tanks
3.) When the wing tanks are full, the jet pumps turn off
4.) This process continues until the center tank is empty
5.) When the wing tanks get below 1650lbs each or 3300lbs total, the outer wing tank valves open and allow the outer tank fuel to enter the inner wing tanks.
6.) All of the fuel is now in the inner wings tanks and the engines will draw from them until they’re out of fuel

Question 20

What does a FAULT light on a L/R TK PUMP pushbutton indicate?

Answer 20

Low fuel pump delivery pressure

Question 21

What does a FAULT light on a CTR TK L/R XFR pushbutton indicate?

Answer 21

A L/R inner wings tank overflow

Question 22

What would happen if you pressed the MODE SEL pushbutton on the FUEL pane and did nothing else?

Answer 22

You would put the CTR TK XFR valves into manual operation and the fuel would begin to flow from the center to the wing tanks. This could potentially cause the wing tanks to overflow. Care must be used.

Question 23

What does the FAULT light in the MODE SEL pushbutton indicate?

Answer 23

That more than 550lbs remains in the center tank, and either wing tank contains less than 11,000lbs of fuel. This indicates a failure of the auto mode of fuel transfer.

Question 24

What does it mean of the FOB is half-boxed in amber?

Answer 24

-The CTR TK XFR valves for or are switched off, or
-Both outer wing transfer valves fail to open when the inner tank as at low level

Note: Both these conditions imply that unless something is done, you have unusable fuel on the aircraft.

Question 25

When will the center tank transfer valves close, following the complete emptying of the center tank?

Answer 25

5 minutes after the center tank is empty

Question 26

What is the purpose of the A320 having both inner and outer wing tanks, instead of a single wing tank?

Answer 26

The purpose is to keep the fuel in the outer tank as long as possible to minimize wing bending and provide flutter relief

Question 27

When do the outer wing tank transfer valves close after allowing their fuel to enter the inner tank?

Answer 27

Not until the next refueling

Question 28

Can the outer wing tank transfer valves open with more than 1650lbs in each inner wing tank?

Answer 28

Yes. The transfer valves are told to open when a low level sensor senses low fuel in the inner wing tanks. This sensor is calibrated such that it will detect low fuel with around 1650lbs of fuel remaining, but this is only in unaccelerated flight. During steep turns or accelerations the sensor may detect low fuel at a higher actual fuel quantity and trigger the transfer valves to open.

Question 29

How does the plane ensure that both outer tank transfer valves open at the same time?

Answer 29

Each inner tank has its own low fuel level sensor. Each outer wing tank has two transfer valves. In order to ensure that both outer tanks begin pouring into the inner tanks at the same time, each fuel sensor controls 2 transfer valves, one in each outer tank. Thus, when either inner wing tank detects low fuel, at least one transfer valve in each outer wing tank should open.

Question 30

What is the purpose of the spills pipes?

Answer 30

Fuel from the outer tank goes through a heat exchanger to cool the IDG. That fuel is then returned to the outer wing tanks. If the outer wing tank is full and fuel is trying to get in from the IDG het exchanger, the fuel will automatically go through the spill pipes and into the inner tank.