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Advice needed - prop governor locking nuts

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  • Advice needed - prop governor locking nuts

    I’m after some advice.

    Regarding the nuts that hold the prop governor onto the studs, what is the preferred way of securing them ? Should they be drilled and lock wired ? Or use a castellated nut ? Or a self locking nut ? A split washer ?

    They same question applies to attaching the fuel servo body to the engine studs. This is something I have discussed with my mentor……but for my own reasons I’d also like to see what others are doing.

    The usual places….AC43, Lycoming engine manual etc aren’t shedding the light on it that I’d hoped so I’m guessing that it’s probably something so fundamentally obvious that I’m expected to know it.

    Thanks in advance.

    95100DD2-FE61-4808-A28A-59852AFE3FDF.jpeg

    6083556D-A4EC-4831-935E-7B38C4D29AB9.jpeg
    Nev Bailey
    Christchurch, NZ

    BearhawkBlog.com - Safety & Maintenance Notes
    YouTube - Build and flying channel
    Builders Log - We build planes

  • #2
    I have a 250 Comanche with an O-540. I believe the carburetor and prop governor both have a flat washer, star washer and plain nut. I'll be at the hangar tomorrow and can verify.
    Last edited by Chris Werner; 06-13-2021, 07:03 PM. Reason: spelling error
    Model B quick build started 2021

    Comment


    • Nev
      Nev commented
      Editing a comment
      Thanks, appreciate that.

    • Chris Werner
      Chris Werner commented
      Editing a comment
      Confirmed, the O-540 in my Comanche has a flat washer, star washer with internal teeth and a nut on the carburetor, propeller governor, magnetos, and exhaust flanges. I also looked in my Lycoming parts manual and found they call out for a flat washer, plain nut and a pal nut. In the last 62 years the star washer method hasn't failed on my airplane.

  • #3
    The way you have it is the standard. When I installed my prop governor on my RV-8, I went a little farther and installed Nordlock washers, but it wasn't necessary. A MS35333 star locking washer against the usual AN washer is standard

    Comment


    • Nev
      Nev commented
      Editing a comment
      Many thanks Mark.

  • #4
    Agreed. The Lycoming parts catalog I have for the IO-540 says plain washer, internal star washer, then the nut.

    Comment


    • #5
      I can't tell, have you got a star crush washer under there? That's all you need. Of course, torqued to the right value.

      Comment


      • #6
        Thanks guys, exactly what I was after.
        Nev Bailey
        Christchurch, NZ

        BearhawkBlog.com - Safety & Maintenance Notes
        YouTube - Build and flying channel
        Builders Log - We build planes

        Comment


        • #7
          Is there a "convention" for where to use the star washers? All metal lock nuts?

          Comment


          • noema
            noema commented
            Editing a comment
            I always found the NASA Fastener Design Manual helpful when faces with design decisions. It's a pretty easy read.

            This manual was written for design engineers to enable them to choose appropriate fasteners for their designs. Subject matter includes fastener material selection, platings, lubricants, corrosion, locking methods, washers, inserts, thread types and classes, fatigue loading, and fastener torque. A section on design criteria covers the derivation of torque formulas, loads on a fastener group, combining simultaneous shear and tension loads, pullout load for tapped holes, grip length, head styles, and fastener strengths. The second half of this manual presents general guidelines and selection criteria for rivets and lockbolts.


            For star lock washers it says. "[...] Although this washer provides some locking action, it damages the mating surfaces. These scratches can cause crack formation in highly stressed fasteners, in mating parts, or both, as well as increased corrosion susceptibility."

            In short, this manual includes many things not immediately obvious while giving solid general advise.
            Last edited by noema; 06-14-2021, 01:10 AM.

          • Bcone1381
            Bcone1381 commented
            Editing a comment
            The Lycoming parts manual calls for a plane washer under the star washer like Nev did in post #1. The teeth grip the nut and the plane washer avoiding damage to the mating parts.
            Last edited by Bcone1381; 06-14-2021, 07:01 AM.
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