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Thread: Check your Tach

  1. #1

    Join Date
    May 2010
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    Default Check your Tach

    I have been playing with props on multiple planes and charting the differences. Static RPM, take off time, climb rate, cruise speed, max RPM straight and level, max speed etc.

    I have been starting with the metal prop and charting the numbers then swap to the sensenich ground adjustable prop and run the tests again at various pitch settings.

    After the 4th airplane we did this on and comparing numbers it was beginning to look like I had the worlds strongest 160 HP 0320 or the guys with 180 HP engines were "sick". I ordered the trutach optical tach and checked it out. Turns out the tach in the plane was reading almost 250 RPM low on the high end so when I thought I was cruising at 2450 I was much closer to 2200. I thought I was turning 2700 on take off but was much closer to 2450 (with the borer prop). It also explains why it felt like I was cruising slow and had to fly tail low to maintain altitude.

    At RPMs under 1100 the mechanical tach is dead on with the optical tach but it rapidly goes astray at higher RPM.

    I am going to run all the tests again and see what I get turning "rated" RPM.

  2. #2
    tnowak's Avatar
    Join Date
    Dec 2007
    Location
    Hampshire, England
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    719
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    Default Re: Check your Tach

    Did you buy the TruTach II, as available from Aircraft Spruce?
    I have tried other models without too much success or with me needing to be really close to the prop.
    I would really like to be able to use a device like this from inside the cockpit.
    I assume this is how you used your optical tach?
    TonyN

  3. #3

    Join Date
    Nov 2019
    Location
    White bear lake , mn
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    3
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    Default Re: Check your Tach

    I've used the simple RC prop tach from inside the cockpit and it works great. Really cheap, $27.

    Hangar 9 Micro Digital Tachometer, HAN156 on Amazon

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

  4. #4
    andya's Avatar
    Join Date
    Dec 2007
    Location
    UT47
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    1,711
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    Default Re: Check your Tach

    Have used similar device from ACS (don't recall the brand name).
    worked better when I put some reflective tape on back of one blade and
    flew with sun behind me. they work fine
    "Progress is our most important problem"

  5. #5
    tnowak's Avatar
    Join Date
    Dec 2007
    Location
    Hampshire, England
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    719
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    Default Re: Check your Tach

    Thanks for your replies. Will get one of these.

    TonyN

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