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Take off rpm in a high altitude airport.

in 912 / 914 Technical Questions 13 years ago
I am having 5300 rpm during take off at WOT in my 912UL engine, the airport altitude is 3200 ft, normal ambient temperature is 77F. so the density altitude is close to 5000ft.
Does anybody have an idea if this is normal or does this required to adjust the propeller blade angle?
Airplane is a Quicksilver GT500, engine is a ROTAX 912UL 297 TTSN, propeller is a Warp Drive 3 blade ground adjustable, and even with this T/O RPM, the take off at gross weight is pretty normal.
I just don't want to overload the engine.
Thanks.

  • Re: Take off rpm in a high altitude airport.

    by » 13 years ago

    Hi Mynor,

    Actually with your ground adjustable prop it is a little too flat a pitch. Take off rpm is not as telling as some other setting because you can have a flat or steep climb and or a no flap or with flaps take off and they all affect rpm. The best place to set up your rpm is at 5500-5550 rpm at WOT flat and level at your normal cruise altitude. Everything else from idle to this will then take care of itself. Set your idle rpm at 1750-1800 for the 912ULS for vibration, gearbox and the rest of the engine's sake.

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

      
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  • Re: Take off rpm in a high altitude airport.

    by » 13 years ago

    Thanks Roger Lee,

    I just check my prop pitch this morning and it is set at 15deg in relation to the prop hub, I also checked the prop track and is within limits, so no problem there.
    At 5500 ft, level flight, cruise, WOT, I am having 5500 to 5600 RPM, which according to your thinking is fine. So I am probably fine with the way the prop is set right now.
    I will go to a sea level runway this weekend and see what RPM I have there. I will keep you posted.
      
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  • Re: Take off rpm in a high altitude airport.

    by » 13 years ago

    Hello Roger Lee,

    This is just to update what I have done, first I toke the prop pitch from 15deg to 17deg and what I had was: 5000RPM at takeoff and 5200RPM at cruise and the airspeed at 5100RPM was just at VNE. So I changed the prop pitch to 16deg and what I have is: 5200RPM at takeoff run, 5300RPM in climbout, 5550RPM at cruise WOT and 98MPH airspeed. this is the way I want it, so 16deg prop pitch, works fine for me with a: Quicksilver GT500 with a Rotax 912UL Engine and a 3 blade warp Drive prop.
    I hope this will help somebody else with the same issue.

    Mynor.
      
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  • Re: Take off rpm in a high altitude airport.

    by » 13 years ago

    What is WOT ???
      
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  • Re: Take off rpm in a high altitude airport.

    by » 13 years ago

    WOT = Wide Open Throttle.
      
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