Fuel Tank Sender probe "off"?

[GraemeSmith]

Ho Hum - trust but verify.......

Gallon at a time

I had no reason to think there was a problem. The fuel tank gauge was "correct" and I always put in the expected amount of fuel to top it off. The builder had provided a calibration sheet from the build too.
And then two weeks ago I landed after a longish X-Country. I thought I had 4 galls in the tank, which matched my anticipated fuel burn and what the gauge said. And that matched all my fuel logging. And I was good on my personal minimum of an hour of VFR on landing. So 12 Galls to go in the tank.....

14 Galls later..............

So I was legal VFR minimums with 30 mins fuel. But not legal personal minimums. And if I had had to stretch it for any reason - I might have been one of THOSE statistics who thought they had more fuel than they had.

So today - drain tank - plane in level flight attitude and a gallon at a time while calibrating the tank probe.

So the tank actually holds 16.6 galls level flight and 17 galls tail down and I have the EFIS screen recalibrated.

Anyone know if the probes change characteristic with age? This one now has about 390 hours on it.

[DCASonex]

If the sender you are using is of the capacities type such as from Princeton (GRT) it will give very different readings for 100LL vs mogas. And if it is one of those, it is very easy to re-calibrate for the fuel you are using.

David A.