Bob Darrah wrote:

Bob Darrah wrote:

Paul wrote:

Snip.

If it feeds into a vented tank, you have the same problem, except when
 you switch tanks, you can get the air out of the header tank.

Not exactly the same Bob. The engine does not stop right away.
It must deplete the fuel in the vented header tank. That is why
I said; "if you see your header tank going down then is the time
to land".

Everything in an airplane is a compromise.  If , on the ground, you have
 problems with the feed to a small header tank, it will quit on run-up, while
 a large header will get you to 300 feet on take-off.

I think the transfer pump would cavitate long before the wing collapsed.
It would be a good thing to check before you flew your airplane.

I'll give you this one, but I was planning on using a EFI pump here.  Was
it Tracy that wrote that while testing his system, he forgot to open the vent in
a 1 gallon can and the pump collapsed the can?

Use a float switch if necessary to control the wing tank pump
to maintain the fuel  level in the header tank.

If you need an additional fuel pump and float switch to keep the engine
running that is another failure source.

True. But then you have the safety of knowing exactly how much fuel
is in the header tank when you are low on gas. Nothing like
the big surprise you get when the engine stops because your high
pressure pump(s) is/are in the main wing tank(s) and you ran both wing

 tanks dry.

That is a NO-NO!  You have already violated the law if that happens!

BTW Old VW bugs had what amounted to a header tank and it worked great.
You ran out of gas on the main tank and switched to the aux tank. You
then knew you had to find a gas station quick.

It didn't work so good on the old BT-13!  They would run out of gas on T/O
and hit the ground before the pilot could switch to the aux tank.

There is nothing stopping you from running both vent lines out the
same hole in the airplane or using a manometer to check both
pressures.

Or internally venting all three tanks together.  That gives you the
 advantage of if one vent is plugged, you can still feed from both tanks.

I would then have a back up mechanical wobble pump
to fill the header tank if necessary. This too will extend
your alternator-out flying range.

A BRS would be nice, too, but  risk management is  influenced by money
 and weight.

IMHO!!!! again

Bob Darrah

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