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Only 5200 RPM at takeoff (Roger Lee topic)

in 912iS Technical Questions 8 years ago

  • Re: Only 5200 RPM at takeoff (Roger Lee topic)

    by » 8 years ago

    Thanks a lot Roger!

    I would like to know what is your personal preference for prop.
    2, 3, 4- blades and manufacture?

    Also wondering if you agreed with my cold starting procedure. Essentially spinning engine with starter and looking for oil pressure, versus spinning by hand and listening to oil tank.

    Thanks again.
      
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  • Re: Only 5200 RPM at takeoff (Roger Lee topic)

    by » 8 years ago

    This is a personal preference issue. You rarely see 4 blades on light aircraft. I personally prefer 3 blade just because I think they are smoother running. 2 blades perform just fine, but it seems like they have more vibration than a 3 blade.
    All prop Mfg's will tell you they have the best prop since sliced bread. Just ask them and most perform just fine as attested to by the many different types out there..

    This is kind of like Chevy and Ford's. You tend to like one, but not the other, but they both get you to where you're going.

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

      
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  • Re: Only 5200 RPM at takeoff (Roger Lee topic)

    by » 8 years ago

    Roger,

    Went for 0°F flight this morning. With both radiators completely taped with duck tape on front side. Oil temperatures got to 185 degrees and coolant about 140. I do have oil and coolant T-stats installed. Very happy with my hydronic heater in the cockpit.

    On the takeoff however with WOT Engine couldn't get above 4750 rpm. At 3000 ft on the straight and level flight Engine barely makes above 5000 RPM. My best guess that outside temperature was about 6° below.

    On 50° day my engine was spinning almost 5600 RPM. Does temperature has such dramatic effect?????

    If so, then we really need in-flight adjustable propellers !!!!!
    Or we need to I just our propellers every three months with weather changes???

    I can't wait to hear your explanation.

    Eugene
      
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  • Re: Only 5200 RPM at takeoff (Roger Lee topic)

    by » 8 years ago

    Going from a 95F day to a 6F day makes a difference. 50F to -6F not as much. The cold air is much denser. It will give you better engine and prop performance. That said it shouldn't be 600 rpm. I would think only around 75 and maybe up to 100 rpm. This may be the cold air affecting the engine itself i.e. the carbs and fuel delivery. Maybe someone who flies in the zero degree range can chime in with their experiences. I don't live in that type of climate. My OAT's in Tucson, AZ yesterday was 75F and the low was 45F. :)
    What is the spark plug gap? In cold weather you want the gaps closer than in warm weather. Try down around .022 -.023 in that single digit OAT.
    I would fly it again and see if it is the same. You can adjust the prop again. Just rule out plugs and fuel.

    Just an odd thought. If you have carb heat give it a try and see if the rpm drops or rises.

    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: Only 5200 RPM at takeoff (Roger Lee topic)

    by » 8 years ago

    Roger,
    Looks like I found explanation for my cold wether low RPM problem.
    Wether was much warmer today +4F. Preheater was plugged in overnight. Oil temp. was 82F and engine started right up! Engine RPM however stock at 1800 RPM and didn't go up with lever all the way forward!!!
    Turns out my cables in cold wether have enough friction, and didn't move at all!!!

    Maybe I need to wait for warmer days :-)
      
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