[SkyPuncher]

You could absolutely design a system that could detect a leak. I’m guessing that it’s just not common enough, or at least catastrophically common enough, to warrant.

At its simplest you measure estimated volume delivered to the engines against estimated volume remaining in the tank. Both are things that should be digitally measurable.

The problem seems to be that the only case it really matters is in a catastrophic accident where such measurements are going to be broken anyways.

[stevepeg]

It’s a good idea, some aircraft have quite complex fuel systems though so it would have to account for fuel moving between tanks.

E.g. the A330 has an inner tank in each wing (which itself can be split into two compartments if damaged), an outer tank in each wing and fuel in the horizontal stabiliser which is used for CG control in the cruise. All of that plumbing can leak too. You’d be adding significant weight and complexity implementing leak detection across all that.

Regardless of all of this, the aircraft is still fully controllable even with a total asymmetry (one side empty the other full) so balancing the tanks isn’t a massive priority.

[SkyPuncher]

All of that only adds complexity in the calculation, not the measurement.

The engines have predictable fuel consumption patterns. Even if fuel move across a bunch of tanks, you can still calculate total onboard fuels and detect a leak.

[stevepeg]

That’s what it already does though. We get a total fuel figure in the flight deck (FOB) and a figure for how much the engines have used (FU - measures flow in the pylons). Add the two together and if the resulting number isn’t what the flight started with then there’s a leak.

The challenge is knowing where the leak is.