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Message-ID: <000a01c513a5$3fbfe780$2402a8c0@edward2>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-740498@logan.com>
Subject: Re: [FlyRotary] Re: Fuel System Design - Jet Pump
Date: Tue, 15 Feb 2005 16:28:08 -0500
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Ernest,

One thing that you might want to consider ref the "jet" pump is the effect
that high altitude might have on the operation of the pump.  I have not
looked into it but wonder whether the lesser air density would affect the
amount of pressure differential produced.  Whether there might be a  point
where the jet just ceases to pump.

Ed A


> 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!!
>
>
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