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Cruise rpm in 912 motor

in 912 / 914 Technical Questions 9 years ago

  • Re: Cruise rpm in 912 motor

    by » 9 years ago

    A 914 is totally different than the 912 Roger was discussing.
    at full throttle a 914 is making 40 inhg of manifold pressure and technically should not be below 5700-5800rpm.
    Yaa, I know that is not the real world application.
    My only experience is with a constant speed 914 so maybe others can chime in with some practical advise for a 914, fixed-pitch STOL aircraft?
      
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  • Re: Cruise rpm in 912 motor

    by » 9 years ago

    Hi Rob,

    I know it is far better to have a 914 with an inflight adjustable prop. If locked into a ground adjustable prop what do you think of a pitch setting to get 5700+ rpm @ WOT flat and level then throttle back for extended cruise time?

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

      
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  • Re: Cruise rpm in 912 motor

    by » 9 years ago

    sounds Ok but like I said, I'm not all that familiar with the fixed pitch 914. I think its a crime to put a fixed pitch of this engine and waste all that potential. All my customers have constant speed props. Cadillac baby!
      
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  • Re: Cruise rpm in 912 motor

    by » 9 years ago

    I agree with you on the prop choice, but here in the US we only get ground adjustable in many cases and aren't allowed inflight adjustable in many applications.

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

      
    Report

  • Re: Cruise rpm in 912 motor

    by » 9 years ago

    sounds Ok but like I said, I'm not all that familiar with the fixed pitch 914. I think its a crime to put a fixed pitch of this engine and waste all that potential. All my customers have constant speed props. Cadillac baby!


    If the reason for having the turbo is to go fast in thin air then one would want a CS prop. But if the airplane's mission is STOL and the reason for the turbo is to maintain horsepower for STOL operations at altitude, then it seems to me that a fixed prop pitched for maximum takeoff and climb is a superior choice to a CS prop. STOL operations can continue as normal all the way up to 8000 feet. Like most things aeronautical, there is a tradeoff. Cruise speed will suffer, but on the plus side we get better takeoff, better climb, lower weight, lower mechanical complexity, lower pilot workload and lower acquisition cost. Seems like a fair trade to me.
      
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