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This 912 ULS with 363hrs and a history.  It powers a SeaRey amphibious airplane and after only being flown a few hundred hours sat unused for 4 years.  We have no idea how or if the engine went through any preservation process.  The engine has had several oil changes with careful filter exams and nothing unusual has been found in the filter.  It came time for its first mag plug inspection, since the new owners bought her, and we found not just metal fuzz but big chunks of metal.  

Has anyone else experienced something like this?  Does anyone recognize where the bits might have come from?  As their mechanic, I am very concerned about a possible catastrophic engine failure during a critical phase of flight.   

8037_1_N312AC Mag plug pieces.jpg (You do not have access to download this file.)
8037_1_N312AC Mag plug pieces 2.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: Big parts on Mag Plug

    by » 6 weeks ago


    Based on the location of the Magnetic Plug, I would be looking in the Prop Gear box First.

    I do not understand why they placed the mag plug in the top of the engine.

    In the sump, near the return hoses, would make more sense to me.

    If the plug has chunks, you can assume that it misses a lot more of them.

    I would open the Oil filter for sure.

    The other logical places that gravity would take them would be the bottom of the Oil Tank and the Engine Oil Sump itself.

    Pull the oil return Banjo.

    There is also an alternate Oil return on the sump for use when the engine is mounted pointing the other direction.  Tractor/Pusher.

    This plug may reveal something.

    - - -

    An Oil Analysis my be in order if you have at least a few hours on the oil.

    Blackstone Labs is reported to do quality Aircraft oil analysis for ~$30.

    - - -

    Hopefully someone will recognize the casting marks on that big chip.

     


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


    Thank you said by: Jeffrey Fritts, RotaxOwner Admin

  • Re: Big parts on Mag Plug

    by » 6 weeks ago


    Agreed Bill.  Doesn't make sense to me I guess it is better to have a mag plug somewhere in the engine than not.  I looked back at the engine logbooks and the engine has had three oil changes since the aircraft came here.  Oil filters are always cut open and inspected but no evidence was found.  Unless this fault just happened since the last oil change.  The aircraft is owned by four partners and one of the partners said someone mentioned to him that metal parts no larger than 1/8" were okay.  I don't agree especially if there are multiple ones like in this case.  Anyway, the biggest piece is over .125" (1/8") so that takes care of that theory.  Where do these people get these ideas, certainly not from the manufacture?  

     

    26540_2_N312AC mag plug biggest piece.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: Big parts on Mag Plug

    by » 6 weeks ago


    This amount of particle collection is excessive and would warrant further investigation for a possible cause. In this instance, judging by the external condition of the magnetic plug however, it looks as though it hasn't been cleaned, removed or inspected since the engine was first commissioned or 100 hrs maintenance carried out.


    Thank you said by: Jeffrey Fritts

  • Re: Big parts on Mag Plug

    by » 6 weeks ago


    xing,

    You are correct.  Rotax maintenance schedules in the Maintenance Manual Line require the magnetic plug to be inspected every 100hrs or annually.   Service bulletin SB-912-051UL describes the process in detail and talks of further investigation if the plug exhibits more the 3mm of metal.  The primary function of the plug is to catch metal filings from the gearbox and warn of any excessive wear or damage.  In this case, we did not have more than 3mm of metal filings but instead had actual large metal pieces.  So large in fact we could see them with the naked eye.  And if you look closely there are marks on the parts where they were machined.  At my recommendation, the owners of the aircraft will have me remove the gearbox for inspection. 


    Jeffrey Fritts, USAF (ret.)

    www.flywwlsa.com

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


  • Re: Big parts on Mag Plug

    by » 6 weeks ago


    Okay I'm back and the story of my demise was greatly exaggerated.😂

    It was Bill had my evil twin lock me up, but I've escaped 🤣

    Just kidding Bill. How have you been? Safe I hope.

     

    That chunk is from the gearbox and it absolutely needs to come off and should be inspected by a Rotax Service center. Now begs the question. What caused it? My guess is either severe vibration from not balancing carbs, bad prop balance or misalignment ( i just had one like this $3K to fix. Mechanic caused), broken plastic thrust washer. Maybe a contributing factor if wrong oil was used, but maybe the oil wasn't a factor. More aircraft history is needed.

    Before you put a newly refurbished gearbox back on fix what caused it.

    I agree with Bill :) that the oil should be checked for metal and the oil filter and take an oil sample for a lab.

    A better way to check the oil filter for particles than just cutting it open and looking is;

    Get a jar about the size of a pickle jar. Pour in about 1" of gasoline. Cut the filer medium out of the filer and place it in the jar with a lid. Shake, but no to crazy. We are just going to wash the filter. After about 30 seconds take the filter out and leave the gas in the jar. Examine the filter and since it was washed I doubt you'll see anything. Now place a white paper-towel over another can / jar and pour all the fuel and remnants in the gas jar over the paper-towel. The fuel will drain away and you will be left with anything that might have been in the filer. Even the tiniest specs show up like a flag. If you see black flakes or dust take a magnet and see if they are metal or just a few specs of carbon. 

     

    p.s.

    You can drain the oil when it comes out of the oil tank over 1-2 strong magnets. If there is any metal there it will stick to the magnet.

     

    Okay now I have to make sure my evil twin can't get to me any more. LOL


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-574-1080 Home (TRY HOME FIRST)
    520-349-7056 Cell


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