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Thread: Not getting up to speed

  1. #1
    Senior Member Maverick's Avatar
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    Default Not getting up to speed

    I have a 912 ULS on a KF5 with a 72" IvoProp and cockpit adjustable propeller. I've been told I should run the engine up to 5,800 rpm and set the prop to 5,600 to fly. I tried this and could only get the engine rpms up to 4,800. I've flattened the prop as much as I can. I've read other threads that suggest that this might be a prop length issue. Does anyone have any experience with this problem? What was your solution?

    Maverick

  2. #2
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    Default Re: Not getting up to speed

    I'm running a 72" IVO ultralight prop on my 912 80 HP engine, and have it set for about 5000 static rpm. Seems to be working good for me. With 20 more HP, you should be able to spin that prop pretty good... JImChuk

  3. #3
    Senior Member PapuaPilot's Avatar
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    Default Re: Not getting up to speed

    Are you 100% sure you tachometer is correct?
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  4. #4
    Senior Member Maverick's Avatar
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    Default Re: Not getting up to speed

    Turns out that the circuit breaker for the adjustable prop was popped and I wasn't flattening the prop. Once I figured that out I was able to get up to over 5800 rpm. All is good.
    Thanks.
    EAA, AOPA
    KF5 (N49FK & N36KJ)
    Phoenix, AZ

  5. #5
    Senior Member Slyfox's Avatar
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    Default Re: Not getting up to speed

    Quote Originally Posted by Maverick View Post
    Turns out that the circuit breaker for the adjustable prop was popped and I wasn't flattening the prop. Once I figured that out I was able to get up to over 5800 rpm. All is good.
    Thanks.
    now that's funny. not always do I flatten until the circuit breaker pops, but that's how the system was designed. you flatten the prop, the breaker pops and your ready to land. at least that's what I do, flatten until no more rpm change and stop. well a couple flights ago I checked my prop before getting in the plane, works all the time even with the main off, and I didn't hear the prop. I thought crap, motor problems, than I looked on the panel and saw the breaker was popped. reset and all was ok.
    steve
    slyfox
    model IV 1200-flying
    912uls
    IVO medium in-flight
    RV7A-flying
    IO-360
    constant speed prop

  6. #6
    Senior Member Slyfox's Avatar
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    Default Re: Not getting up to speed

    one more thing on the prop breaker, there is a bunch of wire that gets wound up and put under the panel. that wound up wire is actually the resistor for the breaker to work right. if you cut that extra wire out, ends up being a super amount of wire, the breaker will blow with the slightest use of the prop motor.
    steve
    slyfox
    model IV 1200-flying
    912uls
    IVO medium in-flight
    RV7A-flying
    IO-360
    constant speed prop

  7. #7
    Senior Member Eric Page's Avatar
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    Default Re: Not getting up to speed

    Some time ago there was a lengthy discussion of the Ivoprop circuit breaker issues on the AeroElectric-List forum, and the forum moderator, Bob Nuckolls, designed a circuit that gently stops the motor without tripping a circuit breaker or requiring manual reset by the pilot. It was reported by at least a couple of forum members to work well. You'll find a link to the circuit schematic and Bob's description of how it works, here.

    If you want to read the discussion that led to this design, you can, but it's a bit of a mission:

    • Start at this search link.
    • Enter "IVO" in the [Search for Keywords:] box
    • Select 'AeroElectric-List' from the [Forum:] dropdown menu
    • Click the [Search] button

    Because of the way the Matronics forums work (as a hybrid of online forum and email list server), the results are a disorganized mess, but it's all there.

    There was a later design that I was briefly involved in developing that used a PIC microcontroller. I don't believe that it went any further than a prototype, and I don't recall that it was ever installed in an aircraft. Anyway, getting ahold of the firmware to run it could be difficult.
    Eric Page
    Building: Kitfox 5 Safari | Rotax 912iS | Dynon HDX
    Member: EAA Lifetime, AOPA, ALPA
    ATP: AMEL | Comm: ASEL, Glider | ATCS: CTO
    Map of Landings

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