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I recently noticed my RV-12iS (about 40 hrs TT) exhibit RPM fluctuations with engine at idle (app. 2,000 RPM)

This happens during descent with throttle at idle or taxiing back to the hangar after the flight.

The RPMs will fluctuate in a consistent and regular cycle from 1,900 to 2,100.  It will climb to 2,100, drop to 1,900 and then continually repeat.

Is this normal?

  • Re: RV-12iS Idle RPM Fluctuation

    by » 8 months ago


    What is your propeller type? On my CTLSi, i do experience the same due to the use of an eprop (very light prop) according to FD, this is normal.


  • Re: RV-12iS Idle RPM Fluctuation

    by » 8 months ago


    It isn't normal and sounds like a fuel delivery issue. Props don't know a consistent and regular cycle. The prop shouldn't be affecting this. Does the fuel pressure or fuel flow change with this? 

    Since the plane sounds new you may have collected some extra debris from Mfg to assembly and have some in the fuel filter. Does it change with one pump or the other or both running?


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


  • Re: RV-12iS Idle RPM Fluctuation

    by » 8 months ago


    I've recently changed the fuel filter and the screen inside the fuel tank during the conditional.  I haven't really paid attention to this issue as I've either grown accustomed to it or been told it's normal.  

    What is bothering is a drop in fuel pressure during high altitude climb, especially after a long climb with the throttle full open.  Retarding the throttle back to 5,200 RPM restores fuel pressure.


  • Re: RV-12iS Idle RPM Fluctuation

    by » 8 months ago


    Do you have a Differential Fuel Pressure sender?   Or is your Fuel display properly configured?
    What pressure are you displaying and how much is it varying?  Numbers, Please! 


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


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