Jeff Spitzer wrote:

At 07:26 AM 6/2/99 -0700, you wrote:

Wrathall Mark wrote:

If you vent this tank you will lose this vacuum fuel transfer. In one of
the messages someone suggested this vent would be a good idea, could
that person please elaborate. As I see it, those using fuel injection
will have to have Hi Px pumps anyway, so one may as well use the
advantage of this vacuum transfer. The only concern I can see is priming
this tank if you empty it in flight by running a wing tank dry.

If you have a float switch in the header turn on a warning light and the
Lo Px transfer pump, what is the alternate operating mode? In the RNZAF
we had an A-4k Skyhawk crash because the float switch which initiated
fuel transfer failed simultaneously with the low fuel warning light
system failure. Bad day.
                    Mark Wrathall
                  Lauda Air
                   Production, Planning and Control
                GE90 Powerplant Engineer
             * + 43 1 7000-75320
           Fax +43 1 7000-75315

"Sucking" with fuel pumps is a bad idea, period.  Gas has a very low vapor
pressure and is prone to cavitation.  This is especially true if you get
"winter" MOGAS.  They actually modify the vapor pressure considerably by
region and altitude to try to improve mixture formation.  If you take
"winter, sea level" gas to altitude you have very little cavitation margin.
(vapor pressure of 100LL is fixed) You should try to have a positive head
on the pump inlet at best or slight negative at worst.  This means don't
suck through a paper filter...use a sock filter to keep the rocks out of
the pump and *push* through the paper filter.

Jeff Spitzer

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