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Thread: Ahars interference

  1. #1

    Join Date
    Nov 2011
    Posts
    6

    Ahars interference

    I recently purchased a Van's RV-6. The builder installed the control box for the Wheelan strobes in the baggage compartment. I want to relocate it to the aft fuselage. Aircraft is equipped with a Dynon D100. The AHARS unit is installed in the upper aft fuselage behind the baggage bulkhead. Do I need to be concerned about EMI if I relocate the box to the lower fuselage? Thanks!

  2. #2

    Join Date
    Nov 2011
    Location
    Camas, WA
    Posts
    10
    I'm going to guess the unit you see is not indeed an attitude box but rather a magnetic sensor. The Dynon magnetic pickup is an aluminum box perhaps 3" x 2" x 1" and has (I think) a DB-9 connector and cable running to the EFIS-D100. If this is the unit you are considering moving you should check the new location for magnetic interference from cables and other stuff like electrical wires. You can do this with a cheap whiskey compass.

    Good luck,

    Paul
    Camas, WA

  3. #3
    MPerkins's Avatar
    Join Date
    Nov 2011
    Location
    Central Illinois (Havana)
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    6
    I have a couple recommendations for you (as an electronic engineer and aircraft builder). Modern Whelan strobes are designed to work in close proximity to other aircraft systems, even radios, in that they don't produce much EMI to begin with. Second, if you are able to route the strobe's cabling say more than 6-12" from the AHRS unit, things should be fine. At the same time, however, it would be good to check the before-and-after performance of your AHRS very carefully to make sure something unintended didn't creep in with the change. Maybe before you relocate the strobe unit using rivets and screws, you could run a little "Larry Lightbulb" experiment - extend the strobe to the intended location using a connectored-cable and see how things work during a ground test. If you place your cable for this test twice as close to the AHRS unit as it will be in the final installation and the AHRS still works as before, you can pretty well be assured of success (because any interference would be four times as great). . . . By the way, the use of a whiskey compass (or a map compass) is a good idea but it will only reveal the presence of a DC magnetic field; AC electromagnetic interference would only be revealed by other test equipment. . . . I also presume the weight and balance change will not be a problem for your aircraft. - Mike Perkins TC/FA.

  4. #4

    Join Date
    Nov 2011
    Posts
    6
    Thanks for the input. I will try that.

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