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Message-ID: <002401c51320$ce115210$3f571fd3@george>
From: "George Lendich" <lendich@optusnet.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-729084@logan.com>
Subject: Re: [FlyRotary] Re: Fuel System Design - Jet Pump
Date: Tue, 15 Feb 2005 15:40:05 +1000
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Mark,
Thanks!
George ( down under)
George,
It is a little venturi type pump that was mentioned in the article Ed
referenced earlier today.  It operates off of some bypass fuel from the main
fuel pump.  It is used to transfer fuel from one sump to another in Ford
cars/trucks.

I'm at home now so I don't have the URL handy.  If you can't find it, let me
know and I'll post it again tomorrow, if Ed doesn't beat me to it.

Mark S.


-----Original Message-----
From: Rotary motors in aircraft on behalf of George Lendich
Sent: Mon 2/14/2005 8:01 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Fuel System Design - Jet Pump


  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 -----
    From: Mark R Steitle
    To: Rotary motors in aircraft
    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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