On 2/9/2010 8:10 AM, pilotmac818 wrote: > All the fuel in the header tank has siphoned to the wing tanks leaving the > header dry. Is this normal? > Do you know for sure it is going back into the wings? The way the fuel system is designed, it should not be possible for any fuel to return to the wing tanks when the engine is not running. This is true even if the check valves in the pump fail (there are two, and both would have to fail). The fuel inlet is higher than the return standpipe, so it should not be submerged.
I have seen cases where the inlet and outlet are switched. this allows some fuel to flow back (if the check valves fail) but not much as it stops when it gets to the level of the overflow standpipe (same level as when all is working correctly.) As others have stated, the most likely cause is leakage at the carburetor which drains the tank. Depending on the tank design (there are several) you might have a crack in the standpipe, near the bottom of the tank, which allows fuel to leak back into the standpipe and then back to the wings. If so, get it fixed before further flight as if it breaks clean off there will be no fuel for the engine since the return capacity exceeds the pump output. Another reason to address it immediately is this means you can have fuel flowing to the engine side of the firewall that you cannot control with a shut off valve. The fire concerns should be self apparent. Bottom line, figure out what's going on before your next flight. John
