Tracy,
I believe the Jet Pump works off fuel rerouted from the main pump, not the return fuel. You may need a higher gpm pump in order to provide enough flow for WOT operations though. If you controlled the transfer process with a couple of sensors in the main tank, one for upper limit and another for low limit, it could be a fully automatic system.
Mark S.
-----Original Message-----
From: Rotary motors in aircraft on behalf of Tracy Crook
Sent: Mon 2/14/2005 7:17 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Fuel System Design - Jet Pump
Thoughts on the jet pump:
Jet pump requires a restriction (jet) in the return line. ANY pressure in the return line adds to the regulated fuel pressure which means your regulator doesn't regulate accurately any more. Remember that return flow will change with power setting.
Fuel tank levels needs to be controlled in order to eliminate a 'heavy wing' which is very fatiguing on a long cross country. Aileron trim can do it but that adds drag. A valve can be used but that adds to the complexity again.
Tracy
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 sa
nity check.
Mark S.
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