Hi,

Attached is my idea of a simple fuel system for my Vision low wing aircraft.
Will this work or am I overlooking something?

Regards,

Pierre Swanepoel

Not a bad idea. Looks like it is worth a try. Monitor the tank
quantities when testing to see what happens. I assume there is a bit
of dihedral in the wings.

Paul Lamar


I think you will find that you will end up dumping fuel out of one or the
other tanks through the vent.

From my experience, it will be very difficult to get exactly equal pressure
drop in the two 3/8" return lines, one may be slightly longer than the
other -- or have a slightly different bend in it causing a different
pressure drop. Net result, the flow will not be equal thru the return lines.
You are relying on the difference in head pressure to move the unequal flow
back to the other tank, and it is a small number compared to the pressure
drop in the return lines.

Bill Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed

Depends on the vent configuration. Never point the vent opening
directly into the air stream. This would act as a pito tube.
However I have seen it done. The C182 has the vent line
mounted just behind the wing strut pointing dead ahead.
I am not sure it feeds both wing tanks but it probably
does.

At 200 MPH dynamic pressure is 100 pounds per square foot or
0.7 psi. Fuel weighs 49 pounds per cubic foot. So one foot of fuel
is .34 psi. Two feet of fuel is .68 psi. However static pressures
in the return line or in the tank are unlikely to be in this ball park.

The RV4 vents have a  2 foot high loops that the fuel must go up and over.
These are in the cockpit and the aft facing vents are in the bottom skin.
An even better place would be in the vertical tail.

Mike set up the RV4 with one pumps near each tank with separate switches
for each pump. If the left tank switch is on the fuel returns to
the left tank. In theory that is OK as more fuel goes out than comes
back.

If the left switch tank is off the fuel returns to the right tank
as it assumes that is the feed tank. That is done by an electric
selector valve.

Preflight allows both pumps to be checked.

For take off both pumps should be on in case one pump fails however
the quantity of fuel used remains the same so in theory some fuel
could be forced out of the left tank. Of course some fuel is used
in taxing  and run up. Only the left tank should be used during
that time.  Both tanks for take off.

In flight only one pump should be on.

How have you configured your system Bill?

Paul Lamar



Paul,
Mine is very straight forward. I have an Andair duplex valve (R-L-Off)
located on the center console, where it cannot be bumped or inadvertently
changed. It feeds into a Facet boost pump, which is only used to prime the
main pumps if necessary -- turned out it was not needed, but is 'insurance'.
The fuel then goes to two high pressure pumps in parallel, each pump outputs
to its own FI filter, then the flow rejoins and goes to the fuel rails,
pressure regulator, and back to the tank it came from.



Bill Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed