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Fuel lines for a 912 ?

in 912 / 914 Technical Questions 12 years ago
Hi , I would like to know what make of fuel lines you are using on a 912 or 912ULS non-certified engine setup, firewall forward. What are you using for connections or fuel blocks, specifically to branch to the carbs coming from the gearbox fuel pump ?

Kevin

  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Kevin,

    My uls still has the fuel lines that came with the engine but I've seen many uncertified modified installations that seem to work quite well. The better installations used automotive type 30R6 or 30R7 alcohol resistant line, Preferably the fuel injection line, which is a little stiffer and thicker walled. Slide a fire sleeve over it and you are in business.

    Bill.
      
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  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Hi Kevin,

    The fuel line and rubber replacement has been a big debate and learning experience on a couple of forums. The ctflier.com has been a very good place to learn and see some of the research that has transpired. I started out using fuel injected hose as many did a couple of years back. This hose doesn't have any give in the rubber with its extra reinforcement when trying to fit it over barbed fittings. So many people cause some mechanical damage and small flecks break off and travel downstream. Then too many people over crimp fittings which also causes mechanical damage and those flakes travel downstream. If you damage the inner liner of the fuel hose and it gets up into the hose that wasn't designed for the fuel it can cause some degradation over time to occur and those flakes travel down stream.You can change all your fuel fittings to be smooth shank with a flared end which would be better, but most of our aircraft has some barbed fittings.

    I know you know what is down stream. CARB BOWLS
    Now here's the thing. Some people, but not all have fuel filters and them some have a gascolator with a 100 micron mesh screen and then the fuel pump has a fine mesh screen. So you say how does all this debris get to the carb bowls. Many don't have all the filters above. The one slightly saving grace is the fuel pump has a fine filter so any debris may stop there, but the pressure side out off the bottom of the pump usually has no filter in line and any small debris can go right to the carbs. It only takes a few pin head sized pieces to get sucked up and you have a big reduced power in flight situation.

    This rarely shows up on the ground during a run up after a hose change. There hasn't been enough time to get to the bowl and even when there is enough time it still doesn't usually show up. Sitting on the ground the plane is still and sitting flat. The fuel and floats aren't bouncing around so all the debris sits on the bottom of the bowl, UNTIL you take off and change the angle of the plane, get the fuel and floats bouncing around slightly and bring this debris off the bowl bottom and up into the fuel stream being sucked up into the jet. The only saving grace is this tiny debris doesn't usually cause a total engine failure and just a severe reduced power issue. It is usually only one carb being affected and it is not a full obstruction. That said never say never.

    I have done a little over 30 some hose changes and have seen this as I have had two of those issues early on. I have seen it all through the Rotax community.

    What have many done to stop this issue. We have gotten away from fuel injection hose. Standard carburetor fuel hose has an operating pressure of 50 psi with a burst pressure of 250 psi. That is well within the 2-6 psi that we use. The standard carb fuel hose goes easily over all fittings where the fuel injection has no give and when forced over barbed fitting will usually cause mechanical damage just waiting to head downstream. Most of us that have done a lot of the hose changes have gone to Gates Barricade standard carburetor hose. This has 4 liners and is setup to handle our more corrosive fuels. We don't over crimp our hoses and last, but not least it is important to use something that gives a very clean cut edge. I use Sear's Utility Cutters. It has a 4" straight edge that is scalpel sharp and gives a a perfect cut. If you use something that is dull or has a serrated edge it will leave those tiny little pin head size pieces that head downstream.
    When pushing hose through fire sleeve make sure that hose gets blown out for any debris that gets pushed into the end of the hose.






    Watch this video to see the cutters.

    http://www.youtube.com/watch?feature=player_embedded&v=QwNP_szsPj8



    I hope this helps, I wore my fingers to a nub. ;) :)
    Fuelpumpfilter.jpg (You do not have access to download this file.)
    gascolatordebris.jpg (You do not have access to download this file.)
    carbbowl1.jpg (You do not have access to download this file.)

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Thanks Bill and Roger.

    I should of mentioned , I am changeing the old lines because of the 5 yr rotax recommendation, not for any other reason.

    I tried to find what my plane had on it locally, Aeroquip FC-332 socketless hose 1/4 ", with no success. The supply line from firewall to the rotax fuel pump was 5/16" milspec 6000, and was replaced with such.

    I picked up some goodyear fuel injection line 30R9 , it has a blue inside lining, which when slid over a barb does damage very easily like Rodger mentioned . I did not like that , so I went all milspec 6000. I then posted my question on this site :unsure:

    Any reason not to use milspec 6000 ?

    Good tip on blowing the lines out after firesleeve is applied over top, I applied the firesleeve over the hose in direct sunlight and watched the fiberglass fibres float in the air as I was putting the firesleeve on. I blew out the lines, then I went as far as to run the electric fuel pump to flush the lines before hooking to the carb hook ups.

    I am concerned about messing with the fuel lines and cause an engine out or the worst case scenario a fuel fire , it's in the back of my mind. ( that's the firefighter in me coming out).

    It's ironic that this preventative maintenance makes me feel that way :(
      
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  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Hi Kevin,

    I'm a retired 30 yr. firefighter. So I'm with you on preventive maint. and that safe feeling. We have certainly seen our share of preventable and foolish acts in our jobs.
    I wish I had a dime for every person that said "Well that never happened before". :woohoo:

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Hi Roger,

    Thanks for your advice to buy the Craftsman Handi Cutter 3-7/8 in. I have installed a bypass for the electrical fuel pump should it fail.
    I have cut the fuel lines but the cuts were not clean so I shall check the bowls before the next flight.

    BR Jan
      
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