Fuselage Tank fuel sender wonky?

[Chester Fitchett]

Has anyone seen very non-linear behavior in the fuel sender?  This seems to be a new problem.

Actual Fuel -> Indicated Fuel

14L -> 14L

12L -> 14L

10L -> 13L

8L -> 12L

6L -> 11L

4L -> 10L

2L -> 9L

1L -> 5L

0L -> 0L

Also, if I don't have the wing tanks attached, there doesn't seem to be any overflow outlet from the main tank, it just pressures up and eventually opens up the big connections that normally snap to the wing tanks, and sprays fuel around in the cockpit.  I'm pretty sure that should overflow into the overflow tank instead?

Chester

[ronald...@gmail.com]

I have seen some strange behavior - but we have awful fuel smell in the cockpit....

[Chester Fitchett]

I also have a crack on the top of the fuel tank, the mechanic patched this with a few coats of some special epoxy.  Looking forward to removing the tank and having it welded.

Sounds like you have a fuel leak.  I normally don't have any fuel smell in the cockpit.  You can get cheap USB endoscope cameras, next time you derig I recommend taking the time to hunt down the fuel leak.

Chester

[Mark Zivley]

Greetings,

For the fuel tank over pressure, be sure the outlet at the bottom of the fuse isn't plugged.    Next, you might check if there is flow between the tank and overflow by carefully pulling the tube off the small overflow tank above the spar and using a hand vacuum pump to see if that line is obstructed.   If not, then it's probably the line to the exit.  Don't apply pressure or you risk blowing a line off the tank...

There have been a couple issues where there are leaks in the fuel system.   I had a leak in my fuel filling line because it became pinched by the airbrake arm.  This was left side, down low.   Another pilot had a line split back near the fuel filters as the hose was too small, but during assembly, someone forced it onto the connection and it subsequently split.

It is possible to re-calibrate the tank sender, but if the sender has gone bad, that may be a repetitive process.  There are instructions in the maint manual on tank calibration if I remember correctly.

Mark

[Mark B]

How much non-usable fuel do others have in the wing bags? I think it is supposed to be half a litre a side, but I have experienced draining 3 litres when draining with a wing up and the drain pipe attached (which I do before derigging).