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My Rotax engine is 914 F2 and it's critical flying altitude for Continuous performance is metioned in operator's manual as 16000 ft above sea level and at this stated critical altitude the respective Manifold pressure is available 

Is it feasible for me to fly above 16000 ft as my aircraft manufacturer claims max ceiling of 23000 ft with max take off weight between 1300 to 1350 kg?

 How will this affect overall performance of engine over the period of time? 

  • Re: Max continuous performance

    by » one month ago


    Just for reference

    This Cessna C150 was equipped with a Rotax 914 and flew to 24,000 feet hundreds of times during testing of the engine in the early 90s. As you increase in altitude the performance of the engine will diminish and manifold temperatures will increase. Keeping your parameters within limitations will dictate the max altitude you will be able to operate at. 

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  • Re: Max continuous performance

    by » one month ago


    I would love to know in which aircraft you are flying to that altitude with a 914.  Pressurized cabin?


  • Re: Max continuous performance

    by » one month ago


    Critical altitude is usually defined as the point above which the turbocharger can no longer maintain maximum rated manifold pressure.  I would suspect you will not get 40" of manifold if you try a max power climb (for 5 minutes or less) above 16,000 feet.

    As far as impacting the engine, I can only speculate.  Typically engines have difficulty shedding heat as they fly higher.  I'd expect Rotax is not much different.  That extra heat impacts thing like rubber parts, and engine mounts.  CHT may hit limits, and the induction air may also hit limits since it is much hotter.   Also I'm not sure how Rotax ignition modules handle the altitude, but typical magnetos can arc more at higher altitudes due to the lower air densisty.   Another limit you may hit is the max RPM (and well below 16,000 feet).  Presumably you have a variable pitch / constant speed prop?

    Another issue you might face is excessive engine cooling if you "chop the throttle" and glide down from 24,000 feet.  Power on descents will solve this problem and let you make up that speed for the slow climb up to the flight levels.   --And yes, you start planning descents 45 minutes out. (100 miles out.)


    Thank you said by: Pilot Joe

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