Thursday, August 4, 2011

Safety wiring for dummies

I posted this picture on Facebook the other day. It's the safety wiring of the bolts that hold the filtered air box top plate to the fuel servo. Pretty, eh?

When I was doing this, I was referring to AC 43.13, the so-called "bible" of building and maintaining an airplane (order yours today!), specifically this page.

In fact, I was holding the page up to the plate as I figured out how to properly secure it. Compare:

The problem is: I'm not seeing much of a difference there.

I mention this because one of my RV-building buds sent me a note on Facebook.

Take a look at for some great examples of what it should look like.

It is definitely an art to figure out how to safety stuff properly. It shouldn't take you very long to redo those 4 bolts since they are extremely accessible. I learned from a local builder showing me the tricks to safetying. It sure was a lot easier to get some tips and tricks from him rather than my method of trial and mostly error!

I know he's probably right because he's highly regarded as a good builder, but I'm not seeing what it is that's different in the photos above and I presume he hasn't been on Facebook lately to see my return query.

So I am missing something really important here. But what is it?

Update 8/10/11 It should've looked like this. Many thanks for all of the advice.


  1. Just guessing here, but shouldn't the safety wire go into the bottom bolt at least sixty degrees CCW from where you have it? That way the wire will prevent the bolt from turning at all.

    The way you have it the bolt can turn CCW quite a ways before being constrained by the safety wire.

    Please don't take my word for it: I'd never fly in a plane that I built.

  2. I guess that's what confuses me. The wire is going through the holes that are available. I see that bottom bolt turning CCW, and forcing the top bolt to turn CW.

  3. I am definitely not a professional, however I have seen quite a few safety's while flying UH-60s and have seen many crew chiefs struggle with the same thing.

    It seems like most of the safety's that I have seen aren't placed through the nearest hole, but the next one available CCW. In addition, the twisting is usually more consistent throughout and ending as close to the bolt head as possible.

    Again, I have never placed a safety on before, but these are just some of my observations. Thanks for posting some great articles.

  4. When you affix this bolt, can you hold the bolt steady (with the hole at the correct orientation for wiring) and spin only the nut? If not, back the nut off until the bolt and nut can both be turned CCW together, then hold the nut steady and re-tighten the bolt.

    Forgive me if I'm being Captain Obvious again. I'm as ignorant as the next internet user, but as a complete layman that's what I'd try.

  5. No, there's no nut. It's a threaded hole in the base of the fuel servo.

  6. Wow. Do they orient the hole to the thread in the same way? Would a different bolt (which I'm sure are really cheap) make any difference?

  7. This is incorrect. I am a Collateral Duty Inspector in the Navy and that bottom bolt should have had the safe wire entering from the left side of the bolt, basically anywhere from 7 to 11 on the clock dial. Then half moon the other side of the safety wire around twist it off CCW. The integrety of the Safety Wire above shown has about 45 degrees of movement if torque were placed on it in either direction.

  8. Awesome! Can't get more authoritative than that!

  9. i was a us navy AD (engine mechanic) and honestly in the updated picture they look fine to long as your safety wire is in a tightening manner, as it looks, it should be fine. what vibration is going to put torque onto any of these bolts? yes you can make it look prettier but that is unnecessary for function. your 43.13 should tell you a certain twists per inch which i don't know off hand(i can usually eyeball it and feel the tension on the wire for that). in your first pic it looks to be in the correct orientation but the final twists looked sloppy and loose and the initial back wrap on the upper bolt could have been tighter as well. you don't need 60 degrees of wrap on a bolt. in my personal opinion 45 degrees of ccw wrap pulling in a cw manner is good, only go more if you have to and you can even go as low as 0 degrees as long as its not in a loosening manner(preferably on a low stress bolt)if you absolutely have to. even at zero degrees wrap the bolt will be held in place and not be pulled in a loosening manner as long as where its tied to isn't in an angle that will cause loosening. a trick i used to figure out the way i needed to wrap my safety tie (even if i couldn't see the bolt and it was facing reversed and away from me) would be to point my ringers toward the bolt head and snap my fingers, and the rotating motion of snapping my fingers would indicate a tightening manner. hope that makes sense and helps with future safety wiring