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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
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