Mike Wills wrote:

At 10:19 AM 6/2/99 -0700, you wrote:

Bob Darrah wrote:

With the specific intent of stirring up controversy, I will present the
Darrah
Theory (untried, unproven) on header tanks.  Also keep in mind, I have
never learned anything from someone with whom I agreed!

1. A header tank that is unvented is unneeded.

2. Using an engine that requires an electric fuel pump to be operating
continusly in order to run does not need a vented  header tank.

Now that ought to stir up some of you.

Bob Darrah

 I will address a couple of your points for my RV-4 installation. I dont
think my unvented header tank really qualifies as a tank at all. It
probably holds about a quart of fuel. Think of it as a sump or an
accumulator or simply a wide spot in the fuel line. What it does is provide
a convenient place to seperate the low pressure and high pressure sections
of the fuel system. My fuel system is stock RV (wing tanks, selector, boost
pump, filter/gascolator) upstream of the header tank and standard EFI (with
parallel redundant high pressure pumps) downstream of the header tank. The
header tank is really just an easy place to make all the connections required.
 I installed a fuel level switch in the header tank. I suspect that the
only time the fuel level in the header will drop is if the main tank vent
gets plugged (or if I run the main tank dry!). If the light ever comes on
my assumption will be a plugged main tank vent and response will be to
immediately switch tanks. I thought about a clear tube to visually verify
the header tank quantity but decided against that because I thought it was
to fragile for a fuselage installed fuel tank.
 I was originally planning to build a totally high pressure system with
return lines to both tanks and using an electric ganged selector from a
dual tanked truck to switch supply and return lines. After last years
Oshkosh winning EZ went down when the electric selector failed and I heard
from a couple of other folks who had problems with electric selectors I
scrapped that idea.

 Again this is all untested (by me) theorizing on my part.

Mike Wills

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