# What is the capacity of the vent surge tank in an A320?

If the wing tanks of an A320 are fully filled and the fuel expands due to high temperatures then the fuel overflows into the vent tank. My question is, does the fuel get stored in the vent tank? If yes, how much? If not, does all of the fuel just spill on the ramp?

## 1 Answer

From Airbus flight crew operating manual (FCOM):

The expansion tanks above the center tank allow the center tank to be filled to the maximum. Tanks capacity is 23,858 liters.

The FCOM says the fuel can expand up to 2 % without spillage in the vent/surge tanks. That's about 239 liters per surge tank.

The volumetric expansion of the fuel is about 0.095% per °C. 2% allows for a 21°C temperature increase.

The vent/surge tank communicates with the outer tank on the same side, and fuel can flow back by gravity, when conditions permit.

• Note that this is not unique to the a320 or Airbus in general. Most large planes have similar features in this respect. The actual numbers may vary of course, but the principle remains the same. (Note: I'm not a pilot or aircraft mechanic, but I helped write training software for simulating exactly this system on a few models of larger military planes.) – Darrel Hoffman Apr 27 '16 at 13:39