> If you draw from both tanks at once what happens if for any reason one
tank
> loses its fuel before the other?  Think loose cap, leaking fuel line, leak
> in tank for some reason. .  At this point one of your suctions is
uncovered
> and your pump will only suck air, which the engine will not burn.  Sound
of
> silence ensues and high pucker up factor is felt.

Ian, with a header tank, this is not a factor. The wings pump independently
into the header. If one starts pumping air...so what, it's just pumping air
into the top of the header tank. You're using fuel from the bottom of the
header tank via gravity.


> I know you have a header tank Bob but it could dramatically shorten your
> radius of operation if you lose the ability to tap your wing tanks.  Guess
> what, Murphy says it will only happen when you need to top up your header
> tank in heavy IFR.

Possible, but very unlikely if you design your system against single point
failures. For instance, I have two transfer pumps. Left pump pumps fuel from
the left wing to the header and right pump pumps right. Either pump can be
powered from either of the two electrical systems via independent wiring and
circuits. Opening a simple crossfeed valve at the low point in the system
allows EITHER pump to pump from BOTH wings at the same time (wing dihedral
and gravity). In order to not be able to use ALL of my fuel, I'd have to
loose BOTH pumps or BOTH electrical systems. Certainly possible, but the
probability is very low.

>
> I hope that Bob Smiley and anyone else who can have both tanks on line
also
> has the capability to isolate one tank if needs be.  That is has a left,
> right and both position on the fuel cock.

With a header, there is no fuel cock. Only fuel transfer pump switches.

>
> I may be wrong but I believe there are authorities who forbid the plumbing
> of a plane to include a permanently connected "BOTH" set up.

Yep, in a direct, wing to engine system. With a header, it's not a factor.

I don't mean to sound like I've got all of the answers. Header tanks are not
necessarily the answer to everyones needs. However, the system is so
dependable and relatively foolproof that I believe that the advantages far
outweigh the disadvantages. I also put in a automatic fill system ($25 in
parts from Radio Shack) that has a bunch of self tests and failure warnings
and can be easily bypassed. With all of this, I feel very confident planning
long trips and knowing that the probability of having ALL of the fuel aboard
available to the engine is extremely high.

Let me know if you'd like any more details on the systems.


Bill
harrelson@erols.com
N5ZQ    LNC2    O-320
Planning a trip to Cranfield England next summer.