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  • IVO prop

    Just wondering if anyone has ever done a comparison thrust test with IVO inflight adjustable props and other fixed pitch props?
    I am finding my IVO prop not quite as good as the old fixed pitch for getting airborne.
    Once airborne and pitch set though it goes extremely well.

  • #2
    Consider that the climb rate is a factor of Power.
    RPM is an indication of Power but is not the same thing. POWER is King!
    The IVO Prop allows you to adjust the load on the engine to achieve maximum Power only if set properly.

    Assuming that your engine makes maximum power at 5800 RPM at Wide Open Throttle (WOT), Any RPM less than 5800 and/or any throttle setting less than WOT means that you are not producing maximum Power.

    If you typically set the prop to Full FINE before taking off, you will find the prop trying to over-rev in the climb.
    If you reduce the throttle, you reduce Power.
    5800 rpm means little unless the throttle is Wide Open at the same time.
    The correct response would be to increase pitch.
    Now, understanding that adjust the pitch during the takeoff roll is too much of a work load to add to all the other activities that demand your attention, it is understandable that pulling off a little throttle is a quicker/simpler solution.

    The trick is to set the proper pitch before the takeoff roll.

    On your next flight, establish a Vy climb at WOT and adjust the prop pitch to achieve the recommended RPM for your specific engine.
    Now, without changing the Pitch, Land the plane.
    With the plane stopped and the brakes set, throttle up to WOT and record what the RPM is. This is your Static RPM Target.

    The next time you go flying, before taking the runway, set WOT and adjust the pitch to achieve the Static RMP that you now know will produce maximum power in the climb.
    It might be 400-600 rpm low while stopped on the ground but will increase to the ideal rpm once you get moving.

    Food for thought:
    A 500lb plane, climbing at 1000 ft/min, uses 500,000 lb·ft/min = ~15 HP for the climb.
    All the remaining engine power is being used just to maintain level flight.
    If you were to lose just 10 HP because of a misadjusted Prop, you will lose 2/3rds of your climb rate. 1000 ft/min becomes 330 ft/min.
    Lose just another 5 hp and you'll start to descend.

    Most of the engine's power is used just to maintain level flight, therefore even a small change in power has a major effect on the climb.

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    • #3
      What great advice Willie!!!
      Last edited by All_In; 01-21-2017, 12:17 AM.
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      • #4
        Yes, food for thought.

        That's why I'm considering a ground ajustable IVO prop, 60" dia., 3 blades, for my Rotax SCSI 503.

        So sooner or later, I'll be able to find the best thrust compromise for both takeoff and cruise.

        Cheers
        Erik
        Last edited by rcflier; 06-18-2017, 12:17 AM.

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