Fuel tank fittings, tubing, etc.

Bartman

Bartman

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Trying to get my fuel tanks organized as the rest of the spar installation steps are wrapping up. My 13 gal 7ECA fuel tanks have three bungs each for forward and rear vents and engine fuel feed. The tanks were plumbed with a combination of AN and brass fittings. The bungs in the tank are pipe threads, the AN fittings are 37 degree flare fittings. I say all of this because the next person along might get a jump on things by reading it, I'm kind of figuring it out as I go and my IA is vacationing at the moment so I'm trying not to disturb him. :)

So far it looks like each bung will need to be transitioned from pipe threads to a flare fitting using an AN816 nipple
https://aircraftproducts.wicksaircraft.com/viewitems/an-ms-fittings/an816-nipple-fitting

And it looks like for each tubing connection I'll need an MS20819 Sleeve and AN818 Nut
https://aircraftproducts.wicksaircraft.com/viewitems/an-ms-fittings/ms20819-sleeve-fitting
https://aircraftproducts.wicksaircraft.com/viewitems/an-ms-fittings/an818-nut

Adapters, extensions, etc. all seem to stick with the pipe thread fittings until there's a tubing to connect at which point they transition to the flare fitting

Here's my dilemma though, is it ok to come out of the tank with a single compression to flare adapter and then connect a tube with a 90 degree bend just a few inches from the fitting or are bends close to the tank better done with a combination of fittings that end with a pipe-to-flare 90 degree elbow like this?
https://aircraftproducts.wicksaircraft.com/viewitems/an-ms-fittings/ms20822-elbow-fitting

I'd prefer to minimize the number of fittings and take advantage of my handy tubing bender for a much cleaner and simpler installation but what is considered standard in aviation?

I'm not sure which of these two options would have been factory original back in 1968.

Edit: Looking in my parts manual, it looks like a single pipe-to-pipe nipple is installed in the tank bung with a pipe-to-flare elbow and the tubing attached directly to that. In the photo I attached to the post below you can see there is a male nipple in each bung, with a female adapter and then a pipe-to-flare elbow, probably to extend the fittings out of the wing root. Anyone else have the same or something different?

Thanks!
Bart
 
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I had a mishmash of everything when the tanks came out.

If you look at that top right fitting in the photo, the tubing passes through it and it somehow compresses onto the tubing to seal it. It's for the upper vent that tucks into the lip of the filler neck. Having trouble identifying that fitting.

IMG_20180815_153908885.webp
 
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WagAero to the rescue

There's a ferrule that slides onto the tube before the nut goes on and that is where the sealing occurs.
https://www.wagaero.com/aeronca-male-connector-68f3-8x1-4.html

68f0604.png
 
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Just ordered everything to reinstall the fuel and vent lines. Used Aircraft Spruce and WagAero although I think Aircraft Spruce also had the pass through fitting.
 
Here was my setup with the tank fittings. The vent line was cut and then a piece of tubing to connect it for easy removal of the tank without messing with the filler neck. The other two fittings were simply a piece of pipe with pipe threads on both sides and then to a 90 degree fitting with a flare.
 

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thanks Cliff. I was thinking about the fittings that face inward through the root rib. They would probably be impossible to get tight enough if they were a length of tubing with a 90 degree bend right out of the tank. The stack of fittings probably allows a wrench to get in there when installing or removing the lines for whatever reason. I'm basically putting everything back in the way that I found it, just with all new parts.
 
Hi Bart!
We have the 13 gal. tanks in our Champ. The main feeds on our tanks look like what Clifford has shown in his pics. Even though his tanks look bigger. Hope this helps!

MA
 
Another interesting thing that the welder who is repairing our tanks mentioned is fittings that have a screen in them!? I had never heard of that. Has anyone else heard of this? He says it would be better than just the screen in the gascolater. Thoughts?
 
Not an expert but I wouldn't go there. Is the welder an airplane guy or a local general purpose welder?

Mine are the 13 gallon tanks also. The parts diagram shows fewer parts but if we went that route there wouldn't be enough clearance to have the lines protrude from behind the root ribs. I tried to find aircraft grade 1/4" PT x 3" nipples but had no luck so I'm not comfortable putting one back in that I can't identify as an aircraft part. Would love to simplify as much as possible but it's got to be traceable back to an aircraft grade part/spec.
 
JimParker256 said:
In reference to post #9 above:

The fuel bungs for my Bearhawk Patrol kit have screens that screw into the bung, and extend into the tank. They look like this: https://www.aircraftspruce.com/catalog/appages/fingstrainers.php?clickkey=6952 Very simple, and easy to replace if necessary.
Click to expand...
I see what you meen now! Cool! My Dad and I will discuss about them.
On a side note our Champ is in “owner mantenence” class. Though we are very concient of and try to follow aviation standards, we don’t have to get an approuvale/signature from an AME. Btw, we do consult one and follow his good advice though.
 
Bartman said:
Not an expert but I wouldn't go there. Is the welder an airplane guy or a local general purpose welder?

Mine are the 13 gallon tanks also. The parts diagram shows fewer parts but if we went that route there wouldn't be enough clearance to have the lines protrude from behind the root ribs. I tried to find aircraft grade 1/4" PT x 3" nipples but had no luck so I'm not comfortable putting one back in that I can't identify as an aircraft part. Would love to simplify as much as possible but it's got to be traceable back to an aircraft grade part/spec.
Click to expand...
He says he has been a certified welder for a renown aircraft repair shop in southern Ontario welding fuselages and fuel tanks. He’s also a pilot. Whatever truth there is to that, I’m not sure. He was refered to us by an aircraft salvage place. Hoping for the best on this one! Lol!
 
Bartman said:
Not an expert but I wouldn't go there. Is the welder an airplane guy or a local general purpose welder?

Mine are the 13 gallon tanks also. The parts diagram shows fewer parts but if we went that route there wouldn't be enough clearance to have the lines protrude from behind the root ribs. I tried to find aircraft grade 1/4" PT x 3" nipples but had no luck so I'm not comfortable putting one back in that I can't identify as an aircraft part. Would love to simplify as much as possible but it's got to be traceable back to an aircraft grade part/spec.
Click to expand...

Can you find an aircraft grade piece of pipe? You could cut your length and put your threads on. Brass is easy enough with a cheap tap and die kit. Your call obviously but I’d rather match the parts diagram and every connection opens up the possibility of a leak
 
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