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Old January 26th 05, 02:38 PM
jls
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" jls" wrote in message
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"Corky Scott" wrote in message
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On Tue, 25 Jan 2005 08:13:09 -0800, Ed Sullivan
wrote:

I'm not sure why you have a header tank unless it is for inverted
flight. On my Jungster the wing tank feeds into the fuel valve as does
the fuselage tank. I can then select either the wing or fuselage tank,
but not both otherwise the wing tank could overflow the fuselage tank.
I have both upright and inverted vents on the fuselage tank and
inverted tank. On the wing tank I just use a vented cap.

Ed Sullivan


Really? You can't just plumb the wing tanks into the header tank?
Thought that was done all the time. Is it necessary to vent the
header tank if the wing tanks are properly vented?

Thanks, Corky Scott


Well, maybe, but wing tanks on a Taylorcraft are vented with ram-air tubes
on the caps and so is the header tank. In flight those tubes make

positive
pressure on the 6-gallon wing tanks and the 12-gallon header tank.

I've seen a few times, too, that the wing tank gets balky emptying into

the
header tank during flight, despite the ram-air tubes.


Let me elaborate on this rather uncomplicated fuel vent system on the
Taylorcraft. The 12-gallon header tank is fixed to 4130 fuselage tubes and
sits behind the firewall and in front of the panel. Its vent --which is
merely an acute angle cut facing forward in a vertical tube rising from the
filler cap on the boot cowl just forward of the windscreen -- is also the
hole through which the fuel gauge wire moves up and down according to the
quantity of fuel in the header tank.

Obviously the positive pressure supplied by this vent tube is slightly less
than the pressure provided by either of the ram-air tubes on the wing tank
caps. Otherwise, wing tank flow into the header tank might not occur. And
I've seen that happen with Taylorcrafts other than mine.

Some people install glorified ram air tubes on their wing tank caps. They
braze onto the caps longer tubes pointed into the slipstream and bellmouth
them. The apparent fix gives them a better pressure differential to push
wing tank fuel down into the already pressurized fuselage tank. Of course,
with the valves on the wing tanks closed, the fuselage tank must have some
way of its own to maintain positive pressure to feed gasoline through the
gascolator and into the carburetor bowl, especially in a climb where
sometimes gravity alone is not enough.

C. G. Taylor, also the designer of the Cub, must have been thinking about
those steep climbs in a Taylorcraft when he designed the ram-air tubes on
the wing tanks because they are bent more than 90 degrees downward so they
face directly into the slipstream during a steep climb.

On the subject of a small header tank in addition to a fuselage tank, that
sure does sound a little like Rube Goldberg to me. It must a device to cure
a history of fuel starvation, something I have never heard of in a simple
system like the Taylorcraft's. OTOH,maybe there's a good reason for it.

I have flown a Taylorcraft since the eighties and never had it give trouble
feeding from the wing tank to the fuselage tank, with one or two exceptions.
And never ever had a fuel starvation problem. Here are the exceptions:
You know those socks you put over a 172's pitot tube to keep bugs out while
you're sitting on the ramp? Well, those bugs, angry at the socks on 172's,
will seek out and set up housekeeping in your ram-air tubes. So you just
take a length of .016 safety wire and punch the little *******s out. When
you get one in your 172's pitot because like me you were too slack to put on
the sock, the cure is not so easy.