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Rotax 912ULS Cruising RPM !!!!

in General Tech Discussion 8 years ago

  • Re: Rotax 912ULS Cruising RPM !!!!

    by » 8 years ago

    Hi Michael,

    I would still set any of my ground adjustable props to see approximately 5600-5650 in level flight at my average altitude. Static on the ground is just a good place to start the process and get in the ballpark. I have found that some props like 2 blades vs 3 blades and length can have very different static rpms on the ground, but the same rpm in flight. I wouldn't worry about your MAP on the UL or ULS engine. If the rpm is set well then MAP is what it is. You shouldn't care what the MAP is around 4400-4500 because you should not be cruising at those rpms. You aren't developing proper torque or HP to constantly fly there and the engine wasn't designed for that. Set the prop up for the 5600-5650 and cruise between 5100-5300 and see what you think. You can always change back.

    Setting a prop is easy to change and any setting isn't written in stone.


    Every prop MFG will tell you their prop is the best thing since sliced bread just ask them. :)
    When I did my research project rpm was the main determining factor and no prop really outshined the other to make me want one over the other. The only exception was the Warp Drive prop. It's climb profile was noticeably less than all the others. I'm sure it's because of the flat blade style that looks like a wing profile. I have experience with that because I had a 3 blade 66" Warp on my plane for 2 years.
    The Warp is heavier and could be a good choice for flying onto dirt strips where rocks are a big concern. It can take more abuse and still get you home and it easy to repair. That said it also transmits more energy into the gearbox and engine if you have a major prop strike.

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

      
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  • Re: Rotax 912ULS Cruising RPM !!!!

    by » 8 years ago

    Hi, Roger

    Thanks for the information very informative.

    I will wait for the new DUC Flash prop and will do as said above.

    Regards
      
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  • Re: Rotax 912ULS Cruising RPM !!!!

    by » 8 years ago

    The nice thing about ground adjustable props is you can try something and if you don't like it it takes about 40 minutes to change it.

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

      
    Report

  • Re: Rotax 912ULS Cruising RPM !!!!

    by » 8 years ago

    Hi Mike, I cruise all day at 5000rpm
    with a Kiev 3 blade prop. Lower than
    5k listen to Rogers advise. I returned from Florida recently to New England and
    Cruised the entire trip at high cruise at
    5400 to make up for headwind. Absolutely no problems. FF difference is
    Minimal.



    Bob
    N854K
      
    Report

  • Re: Rotax 912ULS Cruising RPM !!!!

    by » 8 years ago

    Hi
    Roger

    I am under the impression I should operate my 912ULS with a constant speed prop as per the table in the operators manual on page 5-6 which says for a constant speed prop "Run the engine in accordance with the following table"
    At 55% power the rpm is 4300 at a MAP of 24inches for example, 65% power is 4800rpm at 26inches MAP
    In addition, SL-912-016 states that a MAP guage must be fitted where a variable pitch or constant speed prop is fitted.
    I presume your comments re cruise RPM only apply to fixed pitch prop installs?

    Doug
      
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