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I am searching for a nice motorglider, but a big issue with Rotax engines allways comes, that is there are many motorgliders 10 to 15 years old and with almost no time engines 100 to 500 hours. BUT you need a 10 year overhaul to be airworthy and the price goes from U$ 20,000 and up? Maybe 25% or more of the airplane value.
Why? I think a good inspection would be more than enough in engines less than 300 hours of use. And save maybe 80% of the overhaul cost.
  • Re: Engine Time Overhaul

    by » 11 years ago


    Honestly it is not a big problem with the Rotax as they use nicasil, nitrating and other methods to avoid internal corrosion BUT it can happen. An engine that has only 300 hrs in 12 years is a bigger potential problem than a 5 year old engine with 2500+ hours. Corrosion and rubber deterioration is the reason. A piston engine produces acid and water during normal operation. If it is allowed to sit it will cause corrosion eventually. Fortunately the Rotax 912/914 series have nicasil coated aluminum cylinders so we don’t have the same cylinder corrosion issues as Lyc and TCM.
    You can’t inspect the inside of the bearings/journals with the engine together so how do you be sure it is OK? Oil analysis is great but with a 50hr oil change interval and low utilization it could be too late before you caught a problem.
    From a manufactures perspective they need to place a limit as the utilization and storage conditions are unknown. TCM recommends a 12 year limit and Lycoming has a low utilization SL to address this problem.
    If you are sure the engine has been operated/maintained/stored properly to prevent corrosion you should check to see if your aviation authority enforces “hard time” for private aircraft or if they have an on-condition program. Canada has an Airworthiness Notice to address this and it works very well for flight schools (see attached). However the intent is exceeding the time in service TBO (high utilization), not calendar time.
    See the attached example of an 11 year engine that has serious problems inside due to corrosion and seal breakdown.
    BO41Ed4onconditionrequirments.pdf (You do not have access to download this file.)

  • Re: Engine Time Overhaul

    by » 11 years ago


    file size too large.... here they are in seperate pages
    11yrOldEng1.pdf (You do not have access to download this file.)
    11yrOldEng2.pdf (You do not have access to download this file.)
    11yrOldEng3.pdf (You do not have access to download this file.)

  • Re: Engine Time Overhaul

    by » 11 years ago


    Very interesting point about corrosIon. Thanks!

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