Refuelling Cut off Valve

[Danial9874]

Hi
I am curious how the refuelling valve auto cut off when the fuel is fully filled in the fuel tank
Example : If now the aircraft fuel tank contain 20 degree celcius of fuel inside the tank
The fuel bouser refill a fuel of 40 degree celcius into the fuel tank
Hence fuel expanded in volume
but how the refuelling valve auto cut off when fuel is full
how does it know when is it full

thank you

[Dave Therhino]

Any airplane with a pressure fueling system is going to have a volume based cutoff at the maximum allowed fuel volume for each tank (leaving the required expansion space). This feature is required by FAR/CS 25.979(b). On some airplanes it's float switch driven, and on others it's capacitive probe driven. Boeing uses the term volumetric top off, or VTO, for their feature in their literature. I don't know if Airbus uses the same name.