Sender: "Marvin Kaye" <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Tue, 21 Dec 2004 22:17:20 -0500
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From: "Joseph Trepicone" <joe.t@trepicone.com>
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Subject: pressure tank (air/fuel separator)
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Hi Group,

After several months of study, and input from many people much more
knowledgeable than I, we've decided to make some modifications to the
Lancair 35 gallon tank fuel system.  First let me say that I / we are
not suggesting that the system, as it is currently designed by Lancair,
is anything less than adequate.  The modifications we've made are
intended to give a little additional insurance that air will not find
its way into the engine.  It's been said that the only time you have too
much fuel on board an aircraft is when you're on fire... I'd add to a
much lesser degree "when the fuel is unusable".  We feel the issues
dealing with picking up fuel in a relatively flat bottom, long,
centerline fuel tank are unique.  (There is an unconfirmed story of a
turbine Legend - NOT a Lancair - that ran out of fuel a few months ago
with 30 gallons of fuel in its belly tank.  Maybe someone has additional
information on this.)  Slosh bays, slosh bay doors, low-fuel aircraft
maneuvering limitations certainly all will help but it comes down to a
couple issues:  How much fuel can we consider as useable?  How much fuel
can we consider our reserve and will that reserve be there if and when
we need it?  Or will air some how find its way into the fuel system and,
in the case of a turbine, cause a flame out?

The approach we took is this:  The fuel pick-up tube WILL eventually
suck some air.  It's inevitable.  At some point, some attitude, some
flight condition, some fuel level, at some moment in time, an air bubble
will find its way into the fuel pick up tube and into the fuel system.
How can we increase our chances that the engine will not flame out?  

We're proposing this:  We are adding a +/- 3.5 gallon, pressurized
aluminum fuel header tank, to the system.  We are relocating the
continuous duty, electric fuel pump currently supplied by Lancair to a
location between the fuel tank (where fuel is being picked up) and this
pressure tank so the fuel is pumped (pushed) through the pressure tank
at about 32 psi to create what is essentially a fuel/air separator.  The
pressure tank is vented at the very top, and can be equipped with an
optical fuel sensor or fuel probe.  Fuel is picked up at the very
bottom.  If the continuous use electric pump fails it fails in the open
position and the system allows the engine driven pump to continue
supplying fuel to the engine giving time to land - just like it does in
the previous design.  Explaining the system further is beyond the scope
of this post.  I've had the tank engineered by a company that
specializes in pressure tanks and it's designed to withstand 4 times the
maximum pressure possible.  We received delivery of the first three
tanks today and of course until one of us is flying the system is
unproven.  At 6 pounds the weight of the tank and fittings is a little
heavier than I would have liked however I'm told fuel system components
should be designed to 4 times the maximum pressure possible.  

I have no desire to market, sell or profit from the tank or the system.
My motivation was to get one for myself. Chris Skoppe of Turbine
Solutions Group will be selling the system as a kit.  For more
information please contact me directly.  

Thanks to all the people who helped design the system.  Several of you
are members of this group.
Regards and Happy Holidays to all,
Joe Trepicone