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Prop pitch for pusher ULS

in General Tech Discussion 6 years ago
I will be getting my new 3- blade 70" prop from Powerfin for my high wing pusher Skyboy with ULS engine.

Any idea were I should start with my pitch? Is 15° sounds like good number?

Old 5-blade 60" was set at 17.5° for 5650 WOT

  • Re: Prop pitch for pusher ULS

    by » 6 years ago

    Your 5600 - 5650 is a good balance for the new prop to. Since it is a different prop may may have to set static on the ground for approximately 4600 - 4700 and then go fly. Then tweak the final pitch to get your in flight rpm you desire.
    I never care about what the actual pitch number is because it can change depending on how a person does it and where he does it.
    15 - 16 is as good a place to start as any then do a static run and then your flight if all seems good. When I did my prop research project years ago each prop was a little different. All you really care about is the final result.

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

    Thank you said by: Eugene Klimenko
      
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  • Re: Prop pitch for pusher ULS

    by » 6 years ago

    Ok, I did 16° and went for short flight this morning. Didn't had time to do anything more. At full power airplane was climbing at 4700 RPM. So, I landed right away.

    So, next time I should try with 15 1/2°, or 15°?

    Target is about 5200-5400 on climb? And 5600 WOT in level cruise. Correct?
      
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  • Re: Prop pitch for pusher ULS

    by » 6 years ago

    Found my answer! Thank you!
    - "A prop getting 5200 on take seems a little under pitched and would get upwards of 5800 at WOT in level flight. Nothing really wrong with that. That gives you a good climb prop, but you would lose some speed and fuel economy. In other words you'll have to give it more throttle and rpm to do a decent cruise speed which in turn would eat up more fuel. Most guys are around 4950-5000 rpm at takeoff and that usually puts them in the 5600 range, Adding a little pitch back into the prop will also increase temps a small amount. Probably not much in your case." -
      
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  • Re: Prop pitch for pusher ULS

    by » 6 years ago

    Did little video test to see airflow in to my new propeller. Doesn't look very good, for sure!

    https://drive.google.com/open?id=18mSCARsph_s0xgMjd1GxvgVFlrccX7pl
    Thank you said by: Garrett Wysocki
      
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  • Re: Prop pitch for pusher ULS

    by » 6 years ago

    Set prop for 14° this morning, went flying, but still can only get 5420 WOT in level flight.

    70" prop vs 60" prop for sure big difference on pitch setting, but so far I am going slower at 5000 RPM by about 8 MPH.

    Less vibration this time = must be prop related problem.

    I will try with 13° next time.
      
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