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Paul,
Do you know the temp of the fuel in the sump tank
when you had the bad day?
Consider the following -- you ran the engine and
got every thing hot. You are circulating the fuel back to the sump, but the fuel
is getting warmer and warmer, particularly after the 'hot soak' while you
changed props. Now you go out with the second prop, everything is warm, if you
get some boiling after the pressure regulator (hot line, warm fuel), the vapor
bubbles could go into the sump tank, and get sucked into the pump inlet for
return to the engine. The pump would then lose pressure capability because
of sucking in some bubbles, pressure out would drop, and you would be fuel
starved.
Bill Schertz
KIS Cruiser # 4045
Hi, John....No fun pumping
perfectly good fuel overboard. In my system, the unused fuel is pumped
back into the aluminum sump tank. If the sump tank is already full, then
less fuel would be drawn from the main tank, (I presume), or it would
slowly just push the fuel into the sump tank and back up the main supply
line back into the selected tank. ( I have an Andair fuel tank selector,
and can select left, right or both). Of course this system only has
approximately 9.5 flight hours and maybe 10 initial ground/taxi hours, so
it is not entirely proven, of course. I shamelessly copied Ed
Anderson's aluminum sump tank, with the exception that my tank is slightly
larger, and is located on the cool side of the firewall instead of the
engine side of the firewall like Ed's. Paul Conner
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