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Fuel Line Connections at Wing

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  • Fuel Line Connections at Wing

    Looking for some input on the pros/cons of using AN fitting connections for fuel lines at the wing root to fuselage versus flexible rubber fuel hose to make those connections. Having had a C182, I know that Cessna uses the flexible hose to make the connections. I've also experienced the flexible line deteriorating and cracking/leaking in my 182 but only after many years. Thanks.
    Larry Driver
    Bearhawk 4-Place Quickbuild N22LD
    Mogollon Airpark, Overgaard AZ

  • #2
    I think you understand the issues Larry. If you use a AeroQuip or high quality aircraft rubber line to connect the wing to the fuselage aluminum lines - eventually it will deteriorate. But last many years. My worst luck was with auto racing "high quality" rubber line. It lasted maybe 3-4 years. Much better luck with aircraft line. Mark

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    • #3
      I used solid aluminum lines all the way from the tank to the firewall, and so fat no problems.

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      • #4
        I put male AN adapters in the fuel tank outlets and made aluminum tubes to connect the tank to the tubes in the fuselage. Very easy to do. I swear it's easier than attaching hose to the nipple fittings.
        I got to be friends with the IA who did the annual inspections of my previous (certified) plane. Nick wanted to replace hoses at 5 years in service. "I know they're good for 5 yrs. Probably 7, but maybe not 10. At what point, past 5 yrs, are you still comfortable?" Nick asked. Excess caution? Yep! When Nick signed the inspection, you could bet the bank that the plane was safe for flight!
        I just didn't feel like changing those wing root hoses in 5 years. Ya never know when Nick might drop in and look around...

        Bill

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        • #5
          Thanks, everyone, for the input. Actually, Jared, it was your 360 video that you posted that got me thinking about this. (Yes, I "snooped around" in your plane.<g>)

          Bill, your IA was smart. I came out to go fly in my 182 one day and smelled fuel. Then all of a sudden saw blue stains running down the door posts. I'm not talking a small leak. It was more like a complete failure. Ended up draining tanks quickly. Glad I wasn't in air. I didn't know to check these and the IA doing my annuals obviously didn't check them. I don't have an issue with high-quality hose, as Mark suggests, but you do need plan on them being part of a maintenance cycle.
          Larry Driver
          Bearhawk 4-Place Quickbuild N22LD
          Mogollon Airpark, Overgaard AZ

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          • #6
            And this is probably a "duh" for most folks, but... Make sure when you replace the rubber part of the lines, you're replacing it with "fresh" tubing, not stuff that's been sitting around the shop for 5 years... (I know - I know - but SOMEBODY will do it one of these days...)
            Jim Parker
            Farmersville, TX (NE of Dallas)
            RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)

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            • Bdflies
              Bdflies commented
              Editing a comment
              I'd probably be the one to do that.....

              Bill

          • #7

            I don't understand the issue, so my default setting is build IAW the plans. But now I am curious. What is the intent of the specified rubber hose? Why did Cessna specify Rubber hose?

            Brooks Cone
            Southeast Michigan
            Patrol #303, Kit build

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            • #8
              Possibly to give you some wiggle room to make that last connection - much (?) easier than getting two rigid lines to fit up just right.

              On that note, how might you get those two lines to meet exactly if you build the fuselage and wing lines separately? Mock up a wing root?

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              • jaredyates
                jaredyates commented
                Editing a comment
                Just plan to wait until the wings are on. Run the line up into space, or plan on a union fitting. Once the wings were on, it was really a non-event to get the bend right.

            • #9
              I made up short stubs of Versatube with AN fittings at the tank side that extend through the wing root rib. They were made long and will have to be trimmed and bent to mate up with the fuselage tubes. Still not sure which is going to be easier... rubber connecting hoses or AN fittings with a nipple coupler. It's a tight space.
              Larry Driver
              Bearhawk 4-Place Quickbuild N22LD
              Mogollon Airpark, Overgaard AZ

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              • #10
                I left that plumbing until the "final assembly" stage. For easier access. make the fuel hookups before installing the windshield

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                • #11
                  Would steel braided line last any longer?

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                  • #12
                    Originally posted by davzLSA View Post
                    Would steel braided line last any longer?
                    I would add to the question, would Teflon tubing last longer than neoprene or what every the "rubber" material is?

                    I did rear in the Aeroquip catalogue that there can be an issue with "oxidized fuel that is found in EFI system return lines.

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                    • #13
                      I finally got around to making some fittings that I have been thinking about. I really wanted to use flexible fuel line from the tanks to the hard lines at the wing root. I didn't like the fuel line I bought from one of the vendors. It was not very flexible, and was on the roll so long it was already partially collapsed in on itself. I bought some Aeroquip Startlite hose. Very light, thinner, and flexible (3" min bend radius). Not the SS covered stuff. Nomex/kevlar cover. It seems to be very dimensionally stable. it doesn't tend to collapse when bent.

                      I wanted to try making a curved hard tube and use that as a fitting to run the fuel line through. 5/8" 3003 Versatube was a perfect, snug fit for the fuel line. I couldn't figure out how to bend it as tight as I needed. So I made up some 2 inch pieces, bent as much as I could, and brazed them into an elongated hole (step drill at an angle) of .040 al at about a 20 degree angle. The Versatube is flared on both sides so it won't chafe. These will be screwed to the wing root rib. fitting.jpgfitting2.jpg

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                      • #14
                        Playing devil's advocate here... If/when that fuel line needs to be replaced, how will you remove it and install a new one? Looks like only the hose will fit through the fitting, not the end fittings... Or will you just attach the fitting you showed with a screw instead of riveting or bonding it in place?

                        I'm channeling my mechanic, who – when he learned I was building a plane – told me "Always think about how you will maintain what you're building. If you can't R&R it easily, you're creating a lot more work for yourself somewhere down the road – and likely when you're far from home and all your tools..." (The fact that he was doing an annual inspection on a Mooney gave him the opportunity to show me a whole host of "bad design for maintenance" issues. The most egregious was lubing the autopilot servo, which required removal of BOTH the aileron and flap on one wing, and the subsequent re-rigging of said flaps and ailerons... It was his cussin' over that particular task that caused me co come over and talk to him. (I was visiting the avionics shop with whom he shares a hangar.)
                        Jim Parker
                        Farmersville, TX (NE of Dallas)
                        RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)

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                        • svyolo
                          svyolo commented
                          Editing a comment
                          My way of thinking as well. The inner "fitting" is a flared tube fitting to the tank, and the hose goes over that with hose clamps (2 each). In theory it can be removed. In practice it can be a giant PITA to get a hose off a fitting after a few years. I can either cut the hose, or cut the tube fitting, and replace it if I can't get the hose off.

                          The aluminum bushing/fitting will be secured with 2 screws and nylocs.

                        • jaredyates
                          jaredyates commented
                          Editing a comment
                          It seems like a lot of doing just to end up with an end result less desirable than hard aluminum lines.

                        • Bdflies
                          Bdflies commented
                          Editing a comment
                          ^^What Jared said.
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