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I recently replaced a woodcomp prop on my stingsport that had a crack in the hub to the new DUC swirl 3, It has definitely increased my knots about 5 to 8 in Cruise ( from 105-110 to 110-120) still trying to dial it in with wide open throttle RPM settings at first it was too flat and constantly over exceeding 5650-5750 at wide open throttle cruise 3500 feet, and jumped off the runway, been back and forth, now it’s producing about 5250@ 3500-5500’ft, I had a mechanic tell me that the Rotax 912uls wants to be closer to 5450 right under 5500 continuous for the Rotax engines was wanting to know if this is the better setting I’m concerned that the engine is not spinning fast enough and the lower RPM setting is laboring the engine in the long run ?
  • Re: DUC Prop pitch

    by » 6 years ago


    Your mechanic's kind of off base. Since we have a ground adjustable prop we need to find a balance between climb, cruise, fuel economy and engine temps. During a big research project I found this to be 5600-5650 rpm at WOT at your AVERAGE altitude. It's a good balance between all our needs for the average flier. Average altitude because sometimes we fly higher and sometimes lower. If you pitch to get under 5500 rpm WOT then you throw the things away mentioned above. There are ZERO redeeming qualities with an over pitched prop.
    If you need a slightly better climb prop then the 5700-5750 RPM may be a bit better. This would be better for regular short field take offs, regular high DA take offs, heavily weighted all the time, float flying, ect...

    At 5250 WOT reduce pitch approx. 1.75 degrees and that should get you close to your target.

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


  • Re: DUC Prop pitch

    by » 6 years ago


    Thanks Roger I’ll head back in that direction with it , thanks

  • Re: DUC Prop pitch

    by » 6 weeks ago


    I just got a duc flash installed and I am not impressed.  To get 5500 wot cruise I get 5700 static.  5300 static drops to 5300 wot cruise and I lost 7 mph from my nr.

    It is an edge performance mod engine so tried a 1 inch logger  prop.

    Anyone want to buy it? Or any ideas?

     


  • Re: DUC Prop pitch

    by » 6 weeks ago


    Hi Fred,

    Something not right with your statement.

    Ask Roger but I think that STATIC (aircraft stationary) rpm at WOT should be lower than DYNAMIC (aircraft moving) rpm at WOT


  • Re: DUC Prop pitch

    by » 5 weeks ago


    No that is the problem.  I flew it this morning to test a setting.  Static tied down is 5670 and wot cruise is 5470. I have tried it in both directions and this is the best.


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