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Fuel System Musings, comments encouraged



 
 
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  #21  
Old October 21st 08, 08:29 PM posted to rec.aviation.homebuilt
[email protected]
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Posts: 23
Default Fuel System Musings, comments encouraged

On Oct 20, 10:55*pm, flybynightkarmarepair wrote:
(snip)
I recall a LONG argument on this forum *(or maybe it was on a Zenith
601 forum - LOTS of that design fly with a system VERY much like
you're advocating) about unporting a tank at low fuel levels and
sucking air, that I don't want to rehash, but I'll just note that I'm
firmly in the LEFT/RIGHT/OFF fuel selector camp for low wing planes
with wing tanks.


Just one more word on the subject and I'll go back to lurk around.

Since the Ercoupe design feeds the engine from the header tank,
unporting of a wing tank may momentarily interrupt the replenishment
of the header tank - but will not interrupt fuel flow to the engine.
Indeed, when the wing tank(s) are empty, the fuel pump is just suckin'
air. No harm, no foul.

I remember when I was young and stupid (as opposed to now being old
and senile), I left Buchanan Field - Concord, CA just North of S.F.
and headed south in a '46 Ercoupe. It took 30 minutes to climb to 9.5K
as I remember and we had a nice north tailwind. As we neared Los
Angeles the cork float gauge on the header tank was on it's way down.
I had a sectional on my lap and was going to fly the freeways down to
Fullerton airport. Should make it easy. Hah! We hit the smog and
horizontal visibility went to zilch. I could see straight down, so I
followed the concrete. Then we came to an interchange. Do you know how
many frippin' freeways there are in L.A.!!! I was so lost I couldn't
find my butt with both hands.

After 10 - 15 minutes of screwing around, I called L.A. Approach and
confessed. Note: This was way before transponders were common in civil
aircraft. They came right back with no help at all. Advised me to fly
west until I saw water IIRC. All of a sudden, there it was.
Disneyland! I turned the map around until it was right and decided the
nearest airport was only a couple of miles in front of me. Trouble
being, it was a Naval Air Station. I told LAX I was going to land
there and they advised me that I would never take off again. They were
able to give me vectors to Fullerton and I turned that way. The float
gauge was no longer bobbing - it just sat still. I figured the engine
could quit any second.

In less the five minutes it seemed, we were approaching Fullerton. I
called the tower, advised low fuel, was told to enter downwind and I
was #15 to land. "Did I want to declare an emergency?" Thinking of the
reams of paperwork sure to follow, I gulped, "Not at this time." We
finally kissed the pavement and even taxiied off to the FBO. Fueling
up, I paid for just 1/10th gallon less than the usable capacity of the
three tanks. I never let the fuel get nearly that low again. Later in
that same trip, we flew North into the Grand Canyon and then couldn't
climb back up and out over the North Rim. But that's another story.

Rich S.

  #22  
Old October 21st 08, 08:55 PM posted to rec.aviation.homebuilt
jerry wass
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Posts: 180
Default Fuel System Musings, comments encouraged

wrote:
On Oct 20, 11:55 pm, flybynightkarmarepair wrote:

Anybody have anything to say about the fittings? That was my initial
interest. Should I ditch the pumps I have and just bite the bullet
and go with AN fittings per the exemplar? Do all those unions make
sense?(heavy little suckers! Think of a ball of solid brass the
diameter of a quarter for the 1/8" NPT size, and the diameter of a
Susan B. Anthony dollar for the 1/4" NPT size, and they lighten the
wallet to the tune of $13-20 per at the same time they increase empty
weight) - given that NPT fittings don't seal anyway metal-to-metal,
and you can "clock" them with SOME degree of freedom as long as
they're at least slightly more than finger tight, relying on Loctite
Pipe Sealant to keep them leak free?


AN fittings are available in aluminum. They weigh almost
nothing. Look for the blue fittings. But watch when you thjread an
aluminum pipe thread into another aluminum fitting or tank boss;
they'll grab and gall and tear the threads apart if you don't use some
decent sealant. We use Seal-Lube, Permatex Aviation Form-A-Gasket,
sometimes Loctite hydraulic sealant. Stay away from teflon tape.

Dan

And why not teflon tape???BECAUSE-it has a tendency to extrude from the
threads in a FORWARD direction,Into the fitting, depositing the stringy
little pieces in the first Carb float needle valve or metering jet they
come to..Jerry
  #23  
Old October 22nd 08, 01:22 AM posted to rec.aviation.homebuilt
flybynightkarmarepair
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Posts: 106
Default Fuel System Musings, comments encouraged

On Oct 21, 12:29*pm, wrote:
On Oct 20, 10:55*pm, flybynightkarmarepair wrote:

(snip)
I recall a LONG argument on this forum *(or maybe it was on a Zenith
601 forum - LOTS of that design fly with a system VERY much like
you're advocating) about unporting a tank at low fuel levels and
sucking air, that I don't want to rehash, but I'll just note that I'm
firmly in the LEFT/RIGHT/OFF fuel selector camp for low wing planes
with wing tanks.


Just one more word on the subject and I'll go back to lurk around.

Since the Ercoupe design feeds the engine from the header tank,
unporting of a wing tank may momentarily interrupt the replenishment
of the header tank - but will not interrupt fuel flow to the engine.
Indeed, when the wing tank(s) are empty, the fuel pump is just suckin'
air. No harm, no foul.


Really good point.

You and Veeduber may have convinced me to try a Header Tank solution,
and FIND room for it. My gripe then will be No Pressurized Fuel in
the Cockpit, but I think I can work my way around that by having the
header tank VERY close to the firewall (maybe even in front of it...),
with the pump, the gasolator, and most of the fittings ahead of the
firewall. The next question becomes, how small can I reasonable go in
the header tank? I'm thinking that for an engine that burns, at most,
4 gallons per hour, a gallon USABLE might be enough.

I remember when I was young and stupid (as opposed to now being old
and senile),


Great story, I particularly enjoyed it as I know both areas well.

Later in
that same trip, we flew North into the Grand Canyon and then couldn't
climb back up and out over the North Rim. But that's another story.


Oh do tell! Either give it to us here, or e-mail it to me and I'll
post it on my blog or on my website.

Rich S.


My sincere thanks for all the comments thusfar, yours, Dan's,
Veeduber's, all y'all.

 




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