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My engine has 1170 hrs on it.  Attached is the most recent oil analysis which indicates high level of iron. At last oil change Magnetic Plug showed very little and oil filter has one very small magnetic sliver. Attached is Blackstone oil analysis and picture of plug.  Gear box was disassembled and inspected by Leading Edge Air Foils at 689 hrs. I would appreciate any recommendation or guidance.

9502_1_MagPlug9162022.jpg (You do not have access to download this file.)
9502_1_N116SC-220919-1.pdf (You do not have access to download this file.)
  • Re: Iron in Oil

    by » 4 months ago


    The gearbox is the most likely source of Iron.
    Yours was last checked 480 hours ago.
    If the Gear teeth are wearing excessively, the Gear backlash will be increasing.
    It is easy enough to do an external check of the Gear Backlash.

    Measured at the Propeller Tip;
    A new Gearset will have ~ 0.002" of backlash per Prop Blade length.
    The wear limit is 0.004" of backlash per Prop Blade length.

    Assuming a 72" Prop will have 36" blades.
    A new gearbox will show about 0.002 * 36 = 0.072" (~1/16") of backlash at the prop tip.
    A badly worn Gearbox would show 0.004 * 36 = 0.144" (>1/8") of backlash at the prop tip.

    Ref.
    912is Heavy Maintenance Manual, Chapter 72-10-00, Page 22, Gearset Backlash.


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


  • Re: Iron in Oil

    by » 4 months ago


    I checked the backlash at the tip of prop and measured about 1/16”. I compared my prop backlash with three other SportCruisers in the hangar and found them about the same. 


  • Re: Iron in Oil

    by » 4 months ago


    When was the last gearbox inspection / overhaul? I have seen specs like this quite often and has never manifested itself into any issue. It's within specs. If you didn't get the gearbox done at 1000 hrs. I'd do it and if you did at 600 hrs. you may be due again. On a new overhauled box you may see minute specs from the initial run and break in from new parts. Sitting and idling at low rpm too often could cause some of this. I wouldn't panic and just do another oil change and mag plug check in 25 hours.

    Oil analysis can have elevated levels in some areas over the life time. It can be caused by several factors including how you caught your sample. 

    Are you using Aero Shell Sport Plus 4?

     

    When it looks like the picture then worry.

    34207_2_magnetic plug top view.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


  • Re: Iron in Oil

    by » 4 months ago


    The gear box was last inspected 480 hrs ago. Thanks for your response I will continue to look for metal on plug or in the oil filter. 


  • Re: Iron in Oil

    by » 4 months ago


    Hi Richard

    Perhaps your worry is premature.  To check that build-up of material you need to understand what is happening.  During running the metal spring washers, the gear dog and the gearset all shed small bits of metal.  They are so small that it passes harmlessly into the system and is picked up in the filter.  In the oil volume passes by the magnetic chip detector...the key thing to remember here is it is a "chip" detector and not important when magnetic dust is picked up on the magnet.  To determine the difference you need to take the material in your fingers and pull it off so you can look for "chips".  If when you pull this fuzzy stuff off the magnet it simply turns to a grease then don't worry, that is normal.  If you indeed find a chip of any substantial size it would call for full gearbox inspection of the gears and other parts.  The longer you leave it between checks (should be done at each annual or 100 hour) the worse it will appear.  When you reach the point of needed reshim of the gearbox I always recommend replacement of the disk springs as they give up the most metal with the wear on the edges.  That wear produces the magnetic fuzz you see.  It is normal in my view.  See the page from the Rotax MML current edition 

     

    Cheer

    34341_2_chip detector inspection 2021 MML.jpg (You do not have access to download this file.)

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