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Power settings

in General Tech Discussion 8 years ago

  • Re: Power settings

    by » 8 years ago

    Unless you have a turbocharged engine, if you use reasonable settings, you will not get into trouble.

    At max power 5800rpm and WOT at sea level you will make ~27.5" MAP at best. This is OK for 5 minutes.

    At climb power, 5500 rmp and WOT at >500ft ASL you will make ~27" MAP. This is OK Continuously.

    Unless your full power climb is <100ft/min., you will be good for both of the above.

    At cruisePower,4800<>5200 RPM and slightly reduced power, a MAP of <26" is OK.
    If you are >3000ft MSL you might not make 26" at WOT.

    At 55% Power, 4300 RPM, you are good for 24" MAP.
    Unless you intentionally pitch the prop up to the limits. It will be difficult to slow the rpm down without backing off the power below 24".

    In general, if you stay above 5200 RPM you can set the MAP to anything you want and not get into trouble as long as you don't fly below sea level. ;)

    See your Operators Manual for details.

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

    Thank you said by: Andrew Dunning
      
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  • Re: Power settings

    by » 8 years ago

    Your naturally aspirated engine will always be at least 1 to 1.5" below atmospheric. You dont want to lug and over stress the engine components.

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

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  • Re: Power settings

    by » 8 years ago

    Hi Roger
    Reference again to RPM. Do these Rotax figures just relate to a standard 2 blade prop ?
    IMG_9106.PNG (You do not have access to download this file.)
      
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  • Re: Power settings

    by » 8 years ago

    The chart is just for reference. Your real time numbers will be different. They may show numbers down in the 4K rpm, but that doesn't mean to fly there.

    It will depend on factors like: variable vs ground adjustable prop, prop pitch setup, field elevation, altitude and DA.

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

      
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  • Re: Power settings

    by » 8 years ago

    D Mack
    Until 12months ago I had a Sportcruiser which I built and owned for 6years. It had a Woodcomp 3blade prop with a Woodcomp Kremen controller not the Smart controller you have.

    Firstly I would stop the MAP gauge fluctating by fitting a restrictor into the line vacuum line.This will give a rock steady reading.

    I used to fly my S/C at 4800 and 26inches MAP giving me 104kts cruise and 18litres per hour fuel consumption as per the Rotax manual. At this setting the engine just felt 'right'. I don't think you will like the Sportcruiser cockpit at 5200 rpm!
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