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Date: Mon, 30 May 2005 16:08:45 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: will EFI pumps pump air
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Agreed; that's why I said that it's not my favorite choice. :-)  One 
possible way around that is to just use the selector valve as a roll 
trim device & never remove your hand unless it is pointed at the main 
tank. Ultimate emptying of the aux tank(s) could/should be done while at 
cruise altitude & within gliding distance of a landing zone, anyway, 
because you've just eliminated any 'plan B'. My personal preference is 
to have 2 options late in the flight if I have plenty of fuel & to have 
it all in one tank if (due to no fault of my own, of course...) fuel 
quantity is marginal as I approach my destination.

Of course, *any* tank switching/transfer method has it's downsides. 
Tracy's method (which I think is fine, overall) has the downside of no 
plan B if there's a problem with blockage, contamination etc with the 
primary supply tank.

Anyone care to start a spreadsheet with various fuel system 
architectures & their upsides, downsides, failure modes, etc? This would 
be an ideal thing to put on Bob's wiki. That way it can be updated as we 
see fit & we can each evaluate the risks & benefits & 'pick our poison'.

Charlie


William wrote:

> Be careful with the system of pumping from one tank and returning to 
> the other. With the flow rates that an EFI pump returns to the tank, 
> it would require very active tank managment to avoid sucking the one 
> tank dry. this caused an engine out/off field landing for the 
> prototype Pulsar 100 a few years back.
>  
> Bill Schertz
> KIS Cruiser # 4045
>
>     ----- Original Message -----
>     From: Russell Duffy <mailto:13brv3@bellsouth.net>
>     To: Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
>     Sent: Monday, May 30, 2005 2:45 PM
>     Subject: [FlyRotary] Re: will EFI pumps pump air
>
>     One thing I'm considering is to just use the regular pumps to transfer
>     fuel. If you plumb the tanks to a fuel selector, then when you select
>     the aux side the excess flow will end up in what's now your primary
>     tank.
>
>     This is probably a step better than having one pump per tank.  The
>     only negative I see is not being able to run the tank out without
>     killing the engine.  With all the tanks you're talking about
>     having, that's probably not a big deal, but the RV-3 only has two
>     15 gallon tanks, so using every last gallon is useful (if I ever
>     went anywhere).
>
>     I've seen the 1st idea work in certified planes; the 2nd idea is wild
>     speculation.
>
>     Thanks, but I have enough wild speculation of my own :-)
>
>     Charlie
>     (Wish you could have made it up here this weekend; if you get bored &
>     need a place to fly come on up for lunch sometime.)
>
>     Roger.  It might happen some day. 
>
>     Rusty
>
>      
>