Mark/Ed,
What's a Jet pump?
George ( down under)
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.