fuel tank plumbing

My apologies to the group if this has been covered recently.

I bought a Smith Miniplane DSA-1 off eBay recently which has a 10gal aux
fuel tank in the upper wing center section which is not plumbed into the
fuel system yet. I would like some input from the RAH gallery as to how this
could be accomplished; all practical ideas would be most welcome, with
emphasis on simplicity. The fuel system in operation to feed the O-200
presently is a 12gal fuselage tank directly behind the firewall with about a
2gal header tank underneath.

Thanks,
Monty

On Tue, 25 Jan 2005 08:46:25 -0600, "pwm" wrote:

My apologies to the group if this has been covered recently.

I bought a Smith Miniplane DSA-1 off eBay recently which has a 10gal aux
fuel tank in the upper wing center section which is not plumbed into the
fuel system yet. I would like some input from the RAH gallery as to how this
could be accomplished; all practical ideas would be most welcome, with
emphasis on simplicity. The fuel system in operation to feed the O-200
presently is a 12gal fuselage tank directly behind the firewall with about a
2gal header tank underneath.

Thanks,
Monty


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

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

"Corky Scott" wrote in message
...
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.

On Tue, 25 Jan 2005 13:14:41 -0500, " jls"
wrote:

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.

Well if the header tank is below the wing tanks, and the header tank
is vented, what's preventing the wing tanks from overfilling the
header tank as Ed Sullivan suggested?

Does the header tank vent have a checkvalve?

I was picturing the header tank being downstream of the wing tanks and
not being vented. In effect, the header tank is simply a distorted
downstream fuel line.

Thanks, Corky Scott

"Corky Scott" wrote in message
...
On Tue, 25 Jan 2005 13:14:41 -0500, " jls"
wrote:

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.

Well if the header tank is below the wing tanks, and the header tank
is vented, what's preventing the wing tanks from overfilling the
header tank as Ed Sullivan suggested?

I never saw Ed's post, but I can tell you from my own experience that if you
haven't run at least six gallons out of the header tank before you open the
valve on a wing tank, you're going to get overflowing gas sprayed from the
vent tube all over the windshield.

Does the header tank vent have a checkvalve?

No. I've never heard of one. Taylorcrafts are made to fly, not to be
overly complicated.

I was picturing the header tank being downstream of the wing tanks and
not being vented. In effect, the header tank is simply a distorted
downstream fuel line.

That very well may work, Corky, but I think I'd want the header tank vented.

Thanks, Corky Scott


Thanks to you too.

This thread reminds me of the two guys flying a Taylorcraft cross-country
from East to West Tennessee. They stopped near Knoxville to refuel and had
the lineboy fill the wing tanks. As they flew along enjoying themselves,
counting cows in the green pastures below, the wire gauge dropped and they
decided to refill the header by dumping the contents of a wing tank. The
trusty copilot opened a valve and no gas. He opened another valve and no
gas. They began to look for a landing strip to put down, but the engine
quit they landed and nosed over in a muddy cow pasture. The lineboy had
screwed the lids on the wing tanks with the ram air tubes backwards. Low
pressure caused all the gas to be sucked out and emptied the tanks.

Corky Scott wrote:

On Tue, 25 Jan 2005 13:14:41 -0500, " jls"
wrote:

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.

Well if the header tank is below the wing tanks, and the header tank
is vented, what's preventing the wing tanks from overfilling the
header tank as Ed Sullivan suggested?

Does the header tank vent have a checkvalve?

I was picturing the header tank being downstream of the wing tanks and
not being vented. In effect, the header tank is simply a distorted
downstream fuel line.

Thanks, Corky Scott


The header tank could have a vent the sme height as the wing tanks,

it would fill completely, bleed to the open air,

I would perhaps vent the header tank to the wing tank/s, not open air,
at any level
--


Mark Smith
Tri-State Kite Sales
1121 N Locust St
Mt Vernon, IN 47620
1-812-838-6351

http://www.trikite.com

On Tue, 25 Jan 2005 12:16:41 -0500, Corky Scott
wrote:

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

Corky, I don't know why you need a header tank with a fuselage tank. I
have an inverted tank at the bottom of my fuselage tank which is
separate from the main tank, but has a 1" tube running to the bottom
of it to feed the inverted tank. Both it and the main tank are vented
for upright flight and a second vent runs from the inverted tank for
inverted flight. The fuel is fed to the fuel valve through an
aerobatic flop tube. When I am on the wing tank I switch the valve and
the fuel gavity feeds to the gascolator. I haven't looked at it in a
long time, but the location of the vents is pretty critical.

Ed Sullivan

So far, I am down to two concepts:

1) feed header tank from either main fuselage tank or upper wing tank with a
main/aux selector valve

2) feed header tank from only the main fuselage tank; fill main fuselage
tank (only until sight gauge shows full) from the upper wing tank via a
shutoff valve

Any other suggestions? (keep 'em simple)

Monty

Don't use a header tank with a separate vent, no matter what
the height of the vent. There have been homebuilt crashes resulting
from unbalanced venting of tanks, and certified aircraft having
interconnected tanks (a "both" position) MUST have a common vent
system. The Cessna 172, for example, has a single vent unde the left
wing that is plumbed into the left tank, and a line from the top of
that tank to the top of the right tank. This maintains equal pressure
in both tanks, and therefore equal head on the fuel.
I recall a homebuilt that suffered engine failure because the
guy had installed a header tank under the panel fed by the wing tanks.
The header had its own vent plumbed up to the wing root, and due to
aerodynamic considerations had a slightly higher pressure than the wing
tanks. (It can easily happen when the wing tank caps are vented;
remember that the zone above the wing has a rather low pressure.) The
wing tanks would not drain into the header and the engine quit at a
really bad time after takeoff. The header should have been vented into
the top of the wing tanks.
Another case: the Glastar had (might still have) two wing tanks
plumbed into a single on-off valve in the cockpit. The tank vents were
run from each tank out to the tip of each wing, where they stuck down
into the slipstream and were cut on a 45 degree angle facing forward.
Besides scratching the head of anyone passing under the tip, they
provided uneven pressure to the tanks and one tank would run dry before
the other. If the pressure differential was large enough, the full tank
would not feed at all. We fixed that by running another line between
the inboard ends of the tanks. There were fittings conveniently welded
into the tanks at the right spot for this. The other drawback of tip
vents: Parked on a bit of a sideslope, the full tanks will send fuel
out the low vent, and the fuel from the high tank runs through the
plumbing (even with the valve off) and into the low tank, and you come
to work to find 15 gallons of fuel on the floor waiting to ignite.
We disconnected the tip vents and put ram tubes on the filler
caps. Stuck them up high enough to get out of the lowest pressure.
Gee, I'm talkative tonight. But I wish there was a website or a
book published for homebuilders with all the "Don't Do This" stuff in
it to keep us from making the same mistakes our predecessors made. It's
dumb to die twice for the same error.

Dan