You still want to be careful even with 2 pumps in the tanks. If, as stated
the 2 lines only connect at the fuel rail(s), it is still possible that the
pump that runs dry first, starts to pump air into the rail.....

Thomas J.


----- Original Message -----
From: "Perry Mick" <pjmick@mail.viclink.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, May 29, 2005 7:12 PM
Subject: [FlyRotary] Re: Fuel Tank Selection


> Dale:
>
> With a BOTH function and such a low gravity head, the tanks may not feed
> equally, or worse, the engine quits while there is still fuel in one of
> the tanks, the same problem that Jim S. has described having with his
> Velocity sump.
> If you have an EFI pump in each tank and both pumps are providing fuel
> to the EFI fuel rail at the same time, that would not be the same
> situation, there is no gravity feed from separate tanks to a common
> point in that design.
>
> I'm doubtful that this BOTH function was the cause of Paul's accident,
> but I still think you want to avoid a BOTH function in a LEZ or other
> low-wing fuel system.
>
> Perry
>
> Bill,
>
>    Thank you for that clarification. When I read Perry's
> comments, I was wondering "why?" - because the system I'm
> building has the functions: Left, Right, Both, None.
>
>    Now I'm not so worried, because each high pressure fuel
> pump draws from it's own tank and the only point of inter-
> connection is where the lines join at the fuel rail(s).
>
>    I borrowed the basis of my setup from Marc and Nadine
> Parmalee's COZY:
>
> http://www.marcnadine.com/fuelvalve.html
>
> Dale R.
>
>  > From: "BillDube@killacycle.com" <billdube@killacycle.com>
>  > Date: 2005/05/29 Sun AM 02:03:31 EDT
>  > To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>  > Subject: [FlyRotary] Re: Paul's Fuel System Error
>  >
>  > About a year ago I did a little "Google" research on the John
>  > Denver fatal crash. The bottom line appeared to be that one tank was
> empty,
>  > and the fuel selector was not fully turned to the other tank. (It was
> in a
>  > very awkward position to reach, and this may have also caused the
> pilot to
>  > auger in while attempting to reach it.) Thus, it was in the
> equivalent of a
>  > "both" position. This caused air to be drawn in to the fuel supply line
>  > from the dry tank. This, in turn, caused the pump to lose its prime and
>  > stop pumping fuel to the engine.
>  >
>  > As Perry mentions in his post, only a gravity feed fuel system can
>  > have a "both" type fuel selector. Low-wing aircraft that have negative
>  > pressure in the fuel lines from the tanks must NOT have a "both"
> position
>  > on the fuel selector, otherwise the pump (or the sump) will suck air
> if one
>  > tank runs dry (or if there is a leak in a fuel line.)
>  >
>  > This kind of makes you want to put a pump in each tank.
>  >
>  >
>
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