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From: Dale Rogers <dale.r@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Fuel System Design - Jet Pump
Date: Wed, 16 Feb 2005 17:10:14 -0500
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Ooh!  That suggests something actually useable on my 
system.  A circuit that measures the differential between 
the fuel level sensors in my two tanks, and when it exceeds 
a certain value triggers an annunciator: "Dale, it's time 
to switch tanks."

Dale R.
COZY MkIV #1254

 
> From: "Mark R Steitle" <mark.steitle@austin.utexas.edu>
> Date: 2005/02/16 Wed AM 09:17:06 EST
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Re: Fuel System Design - Jet Pump
> 
> Jim,
> 
> What I was envisioning is a simple electrical solenoid controlling fuel
> transfer.  Forget all the lines from bottom of A to top of B, etc.  Some
> sort of fuel level sensor could tell the solenoid when to open and
> close.  (Some of you electronic whizzes will have to step in here.)
> This would free up the pilot to do other things, like watch for traffic.
> 
> 
>  
> 
> Mark S.
> 
>  
> 
>  
> 
>  
> 
> <... you'd want two lines.  One from the bottom of B to the jet pump.
> Another from the mid level of A to the top of B ... A full B empty... B
> full A empty ... A & B half full ... A & B full ... parked on a hill ...
> >
> Sounds a lot like a ten-cent tail wagging a forty-dollar dog here.
> Didn't we set out to simplify something?  How about just ONE line from B
> to A with a Facet pump.  To get fancy, you could have a momentary ON for
> the pump that would cause it to pump for 2 or 3 min or something and
> then turn itself off.  
> 
> Just trying to stay on message ... Jim S.
> 
> PS  Has anyone actually seen the two-line-jet-pump and watched it
> actually WORK ??
> (the devil made me say that )
> 
> 
> Ernest Christley wrote:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Thoughts on the jet pump: 
> <> 
> 
> 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 
> 
> 
> Looking over the diagram in the PDF that Ed sent.  The jet pump works
> all the time, constantly pumping fuel from the bottom of B into A, where
> the main pump can pick it up.  An important element to this is that
> there is a large return path for fuel to go from A to B.  If the tank is
> half full or more, all the fuel moved by the jet pump just flows back
> over. 
> 
> In the airplane transfer, you'd want two lines.  One from the bottom of
> B to the jet pump.  Another from the mid level of A to the top of B.
> The lines need to stay below the tanks.  At no point will the the sides
> ever be more than 1/2 a tank different.  Consider: 
> 
> A is full, B is empty 
>    Fuel will flow from A to B via the return line, until A is half
> empty. 
> B is full, A is empty 
>    Fuel will flow to A via the jet pump, until B is empty. 
> A and B are both half full 
>    Fuel will flow to A.  If A gets more than half full, fuel will flow
> back to B. 
> A and B are both full, and you park sideways on a hill. 
>    Fuel will flow to the ground until the high tank is empty. Doh!! 
> 
> 
> 
> 
> 
> 	 Homepage:  http://www.flyrotary.com/ 
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> 
>  
> 
> 
>