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Scott,
Thank for the very thoughful response.
I have a 235 with a 320 engine and constant speed
propeller and big battery in the tail. The fuel
reconfig is for CG purposes. I am in pretty good shape
but I often fly alone with 15 or so gallons. In that
config I am on the front edge of the envelope. I would
rather have a near empty header and pull from the
wings which would put me in middle of the envelope.
Thanks again...
Randy.
--- Sky2high@aol.com wrote:
>
> In a message dated 12/31/2007 1:39:57 P.M. Central
> Standard Time,
> randylsnarr@yahoo.com writes:
>
> I am looking for feedback from those who pull fuel
> directly from their wings
> that do not have slosh boxes installed. My fuel
> pickups are in the typical
> place (BL 50 about 2/3 of the way back between the
> front and rear spar).
> I am contemplating changing the fuel system with a
> 3 way valve to pull from
> Left Main and Right tanks.
> I would be very interested to know if you ever
> unport the fuel and under
> which conditions it happens if ever.
>
>
>
> Randy,
>
> I can only answer your question theoretically. I
> believe in the simple
> system pretty much as designed for the wee Lancairs.
> As such, the wings can be
> completely emptied into the header tank while in
> level flight (down to the
> last cupful), thus maximizing the available fuel
> onboard.
>
> Drawing directly from a wing without a slosh chamber
> means that at some
> lesser fuel level, the wing feeding the engine can
> unport via a slip, skid,
> uncoordinated flight, high pitch angle (extended
> climb or descent) or a spin. The
> fuel level may be different for each of the
> conditions listed and it is
> doubtful if any were tested whilst the wings were
> off the airplane when it is
> easy to check at certain pitch angles. Let's see,
> how about a Vx, Vy or missed
> approach climb out with a standard rate turn
> (albeit slightly uncoordinated)
> away from the 1/4 filled wing? Does this mean the
> checklists for takeoffs,
> landings and approaches contains a check off to
> switch to the wing with a 1/2
> or better fuel quantity? So many bad possibilities
> are extant.
>
> Some planes that have 3-way selectors and pumps that
> are utilized to keep
> the header full, where the header is used for
> takeoff and landing or reserve
> only. The selector valve is considered a backup in
> case a pump (or the
> complete electrical system) should fail.
>
> Of course, others (like myself) keep the header tank
> full (>8 gal) at all
> times (engine sole fuel source) and have pre-made
> the decision that should they
> note a pump failure, the "nearest airport" GPS
> function is activated. The
> safest way to reach your destination is with
> everything working - even if it
> takes a day or two longer. We look at the header
> as the main fuel tank and
> the wings merely as aux tanks.
>
> Scott Krueger AKA Grayhawk
> Lancair N92EX IO320 SB 89/96
> Aurora, IL (KARR)
>
> Darwinian culling phrase: Watch This!
>
>
>
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