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A student and CFI experienced a strong fuel odor and brought the aircraft back for an immediate landing. A quick inspection of this Tecnam P2004 Bravo with a 912 ULS showed fuel pouring out of the bottom of the left carb float bowl. A detailed up close view found fuel pouring from a hole in the bottom of the float bowl. I removed the float bowl and found the inboard float guide pin had come out of its press fit hole. Bing drills these holes all the way through the bottom of the float bowl instead of having a blind hole. We put the pin back in place, checked the other pin and checked the other carb and sent them back out to finish their training flight.

Has anyone else had this happen? You can see how far the guide pins are pressed through from the bottom of the float bowl. Are they supposed to be flush with the bottom of the casting or is it acceptable for them to be slightly recessed?
Bing64LeftFloatBowlShowingFloatGuidePin.jpg (You do not have access to download this file.)

Jeffrey Fritts, USAF (ret.)

www.flywwlsa.com

"In aircraft maintenance, good enough is not good enough."

  • Re: Loose float guide pin

    by » 6 years ago


    Yep - Had this conversation about 6 weeks ago and it had happened to 3 of us on this forum before.
    I think that makes you number 4.
    My experience was the fuel being forced directly onto the exhaust muffler of a gyrocopter in outback Australia.
    We flew another 5 NM before landing.

    Regards.......Chook.

    Thank you said by: Jeffrey Fritts

  • Re: Loose float guide pin

    by » 6 years ago


    The new bowl pin holes don't go all the way through if memory serves.
    I'm sure Rotax would like people to replace the bowl if this happens.

    If all you did was push the pin back in it may come out again. I've used Loctite 648 and others I know have used it and so far had 100% success with keeping it in place, but it also must be fully seated and press fitted back in the hole and not just pushed in with your fingers. I have seen a few put a spot of JB Weld or epoxy on the outside bottom of the hole to help seal it just in case.

    Rob or Bill can you weigh in on this some?

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


    Thank you said by: Jeffrey Fritts

  • Re: Loose float guide pin

    by » 6 years ago


    Good thing the problem was recognized by Bing and new float bowls designed. The student and CFI were questioned at length about engine performance and said they didn't notice any performance issues even though one of the floats was floating around loose in the carb. Probably desperately wanting to be back on the ground to notice. I can only imagine what might have happened if the other guide pin in that carb had decided to let go at the same time. The leakage was somewhat contained by the drip pan installed beneath the carb and sent overboard beneath the aircraft.
    Thanks for the tip about using some Loctite 648. The loose pin was pressed back in place with some not so gentle persuasion of a small hammer and was fully seated so it was flush with the bottom of the float bowl. I'll be adding this to my inspections from now on, now that I know this is not just a one-off.
    Thanks for the words of wisdom, guys.

    Jeffrey Fritts, USAF (ret.)

    www.flywwlsa.com

    "In aircraft maintenance, good enough is not good enough."


    Thank you said by: Capt. Siva,

  • Re: Loose float guide pin

    by » 6 years ago


    The Loctite is a good idea.

    JB Weld is just Epoxy with a filler.
    Most Epoxies are Not fuel proof and will soften and fall off in time.
    I have used Epoxy to try to repair small holes in portable gas containers.
    It works well initially but seems to fail within a year or so.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.


    Thank you said by: Jeffrey Fritts

  • Re: Loose float guide pin

    by » 6 years ago


    Bill,
    Once the pin was fit back into the float bowl the fuel leakage stopped, so no further repair was required. I did give some thought to sealing the bottom of the holes that these float guide pins fit into, but I decided not to. My thought process goes something like this...when I do an inspection I can look at the bottom of the float bowl and see how far the pins are inserted into the holes. Right now the pins have been driven deep enough that they are flush with the casting. If I see that one of them is backing out and showing a recess in the hole, then it is time to remove the float bowl and investigate further. I have two concerns about all of this. One is, of course, the fire danger leaking fuel could cause and two a malfunctioning carburetor that could cause a rough engine or loss of power during a critical phase of flight.
    BTW are you retired Air Force?

    Jeffrey Fritts, USAF (ret.)

    www.flywwlsa.com

    "In aircraft maintenance, good enough is not good enough."


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