Yowee these valves are expensive.  But, this is a seriously important
item, so good quality is important.  I assume the '6-port' means you will
route the return fuel back to the same tank?  If so, this makes fuel mgmt
pretty simple.  Is this a manual valve or electically operated?  A/C or
auto?  ( I assume A/C).  Sounds like a good solution if I understand this
correctly.

Bill
Long EZ builder & pilot
mechanical engineer

Bill,

  The discussion on fuel system design is starting to make me a little
nervous about my planned system. My planned design evolved following
previous discussions here about fuel systems. The airplane is a low wing
(RV4) with 1 tank per wing and EFI. It is different from the norm (and
unproven) and relies on automotive style electric selectors. This has been
discussed before but I would like to revisit it just to get a warm fuzzy
feeling about it.

  The plan is to use one hi press pump per tank located as close as
possible to the tank pickup. I have been told by a knowledgeable mechanic
who works on EFI systems that the typical pumps used arent designed to draw
fuel when mounted any appreciable distance from the tank and as a result
should be as close to the tank as possible. Ive seen the same
recommendation in the installation instructions for the 2 aftermarket EFI
systems Ive installed in cars so this seems to be a wise choice. I am
planning to "T" the outlets of the pumps together and allow the built in
pump check valves to prevent cross feeding from 1 tank to the other. From
the "T" the fuel goes thru the fuel rail and then to an automotive style
electric selector valve for return to the proper tank. Tank selection is
accomplished by a single switch which turns on the selected pump and
properly positions the selector valve.

  An alternative to this would be to use a ganged selector (electric or
manual) rather than relying on the check valves. An electric valve has been
identified here previously and there is a good manual valve available from
Andair (in the ridiculous price range mentioned previously).

  I will need to have an additional line between tanks to allow for
crossfeed in case of pump or selector failure.

  Going with all electric valves in such a system makes it possible to keep
all fuel system components out of the cockpit which to me would seem to be
a worthwhile goal. I know of 2 fatalities in 2 seperate incidents in the RV
community in the past year or so that were due to fire in the cockpit. It
also makes it possible to automate fuel management (using a simple micro
controller) at some future date to reduce pilot workload.

  A more conventional system would bring both tanks together through the
Andair selector, then to 2 paralleled hi press pumps (for redundancy) then
on to the fuel rail, back through the selector and to the selected tank. Of
course this forces the pumps quite a ways downstream of the tank and makes
it impossible to keep the fuel system components out of the cockpit. This
would seem to be my fall back design if some one can point out a
significant flaw in the system described above.

  So what is your opinion on this? All opinions welcome.

Mike Wills

Mike, Do you have any details about those RV cockpit fires?
Thousands of Cessna's and other GA airplanes  have fuel selector valves 
in the cockpit with rarely a cockpit fire caused by the fuel system. I read the
NTSB reports on a regular basis and I have never read about such
an event. I can't help but think there was something seriously wrong
with those RV fuel systems.

Don't get me wrong. I like the idea of a remote switching valve where it
simplifies the plumping. The question I have is about
their reliability over a simple mechanical valve. 

You are very right about placing those high fuel pressure pumps in the
fuel tanks.

Paul Lamar

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