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1. 04:05 AM - Re: Engine out..deadstick landing required..question on header t (rawheels)
2. 04:51 AM - Re: Re: Engine out..deadstick landing required..question on header t (Walter O'Neal)
3. 09:40 AM - Re: Re: Engine out..deadstick landing required..question on header t (Guy Buchanan)
4. 03:47 PM - Re: Engine out..deadstick landing required..question on header (mikeperkins)
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| Subject: | Re: Engine out..deadstick landing required..question on header |
t
Kitfox Service Bulletin #29 says to get rid of the fuel selectors, because they can contribute to fuel starvation: http://www.kitfoxaircraft.com/support/service_bulletins/sb29.htm
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=376622#376622
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| Subject: | Re: Engine out..deadstick landing required..question |
on header t
amen!
Walter O'Neal
Director of Technical Services
Tideland E.M.C.
252-944-2409 Dir.
252-943-8265 Cel
1-800-637-1079
-----Original Message-----
From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of rawheels
Sent: Tuesday, June 26, 2012 7:05 AM
Subject: Kitfox-List: Re: Engine out..deadstick landing required..question on header
t
Kitfox Service Bulletin #29 says to get rid of the fuel selectors, because they can contribute to fuel starvation: http://www.kitfoxaircraft.com/support/service_bulletins/sb29.htm
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=376622#376622
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| Subject: | Re: Engine out..deadstick landing required..question |
on header t
On 6/26/2012 4:04 AM, rawheels wrote:
> Kitfox Service Bulletin #29 says to get rid of the fuel selectors, because they can contribute to fuel starvation:http://www.kitfoxaircraft.com/support/service_bulletins/sb29.htm
>
Hmmm. Wonder how they do that? After all, we know that "Valves don't
kill people. People kill people." ;-)
Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 912-S / Warp 3cs / 500 hrs. and grounded
Now a glider pilot, too.
Message 4
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| Subject: | Re: Engine out..deadstick landing required..question on header |
Sorry to hear about the outcome of your glider experience. Not fun, and expensive.
A power loss associated with switching tanks would only occur if the header tank
contained mostly air. That could happen if the header vent line were obstructed.
True that the head pressure comes from the fuel tanks, not the header tank. But
wing tank head pressure is not always reliable. A lot of high-wing aircraft do
not have a header tank.
In a Kitfox, the purpose of the header tank is to provide fuel when both wing tanks
are unported (during slips and negative pitch with low fuel, etc.). Also,
without a header tank with two ports, a T would be necessary. However, T's are
notorious for creating vapor lock (a bubble lock) when located where head pressure
is very low, and so the header tank eliminates the need for a T. In any
case, the intent of the header tank behind the seat is not in itself to supply
head pressure.
The folding-wing design contributes to the tendency for the hoses to have a rise
near the wing hinges which are prone to vapor locking. And thus the header tank
also provides insurance against temporary vapor locking in those humps and
gets rid of the need for a T.
Being a Model I builder, before Service Bulletin #29 was written I became aware
that some builders were mounting their fuel valves conveniently to the fuselage
structure adjacent to the wing tanks, nearly level with the fuel tank outlet,
and in some cases even above the outlets. With practically zero head pressure
here, we eventually concluded there was the possibility for air to be trapped
in the valve innards as well as in a hose hump.
Since fuel is notorious for not liking to be pulled by a pump and for not overcoming
vapor locks, aka ever-expanding fuel bubbles (because of its characteristically-high
vapor pressure), the pump engine pump was not able to draw fuel.
So if both valves or both fuel hose humps were vapor-locked, no fuel would get
to the engine. (This is one of several reasons the EAA and FAA had to prove
back in the 80s that auto fuel would work in certificated aircraft and why there
are not mogas STCs for all aircraft. But all gasoline, including 100LL, has
some vapor pressure - it's just that mogas comes equipped with more of it.)
The answer for the Kitfox fuel flow problems was to put the valves down much lower
and to prevent any rises in the hoses and fuel lines prior to the header tank.
It was discovered after SB #29 was written that this was ok to do, but the
SB remained in effect, probably for liability reasons.
My wing tank valves for 400 hours have been about 3 above the seat-backs, no fuel
problems. It is not convenient for in-flight operation; the intention was mostly
for fueling and de-fueling purposes anyway. This location reduces the possibility
for vapor lock because there is a 20 drop from the wing tanks fuel outlet
before reaching the valve. And care was taken to avoid fuel hose humps in
the hinge area. For flight-emergency purposes, I installed a master fuel valve
on the floorboard under the left door near the carry-through truss.
Running a gravity fuel supply test is always good idea, but it does not account
for vapor lock caused by combinations of flight conditions, differences in the
gasoline used, and high temperatures, etc.
It is best to put fuel pumps near the tanks so that fuel is pushed, rather than
pulled, using perhaps a pair of Facet pumps. Low wing aircraft would do best
this way, obviously not a Kitfox issue, but something worth mentioning.
If the selector valves are up high, they should be relocated lower, but it is ok
to have them as long as there is a significant fuel-system drop before them.
And the vent line should be checked for blockage. Obviously filters and fuel
lines in general should be checked. A mud dauber when the lines are apart for
maintenance can cause havoc. Also, a filler cap vent blow-test should be a checklist
item. A pair of Facet pumps hear the tanks would also overcome a variety
of fuel-system sins.
Hope this helps.
--------
Mike Perkins
EAA TC/FA
Havana, Illinois
Model I, 532, B gearbox, GSC prop
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=376681#376681
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