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Good Idea, Mark
I think that people get pretty hung up and adamant
about certain things - even though they may indeed work. While all fuel
systems clearly require careful design and construction attention, some appear
to require even more scrutiny. What I think sometimes gets folks in
trouble is they "copy" a design they have seen/hear works. However, they
seldom ever copy the design faithfully either due to space/configuration
constraints - or they have an "improvement" to it. The bottom line is the
system has changed, "Yes, Virginia, it may really matter as to whether the
pickup is at the top vs the bottom, etc. ".
Even Tracy's system can byte you if you are not
careful. You must pay attention to fuel transfer or you can end up
with the return fuel pushing out the vent of the return tank. So
while I do believe his design eliminates (or certainly diminishes the chance of
vapor lock) - you now must carefully monitor how much fuel is in the return
tank. I believe Tracy uses a facet pump to move fuel from one tank to
the other - which even though unlikely, could fail leaving fuel
unavailable. I would have to agree though that scenario certainly would
leave you a bit more time to consider your options - than a faltering engine on
take off.
But, yes, it would appear that the "jet pump"
might indeed be a replacement for the facet pump. Interesting
concept.
Ed A
----- Original Message -----
Sent: Monday, February 14, 2005 4:40
PM
Subject: [FlyRotary] Fuel System Design -
Jet Pump
Ed,
Thanks for that excellent article
on fuel system design. In reading through it, on page 5, I came to the
description of the jet pump and had a thought (that alone is a scary
thing). I was thinking that this could be used to eliminate the need for
the facet pump in a design such as Tracy’s which would simplify things even
more than Tracy’s system already does. Of course, as in Tracy’s design, this
would eliminate the need for the fuel selector valve too. As it was
designed to do, the Jet Pump would be powered by excess fuel from the main
fuel pump located in the left tank. Fuel from the other (right) wing
tank would be drawn into the main (left) tank by the Jet Pump. To
prevent overfilling the main tank, transfer could be controlled by a small
solenoid valve. Since you would be drawing fuel from the right tank
pretty much all the time, it may be possible to route the return fuel to the
right tank. I guess this idea could also be used with a sump tank.
Time for a sanity check.
Mark S.
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