Witness Holes

[Phil]

I have a question for those of you who are putting witness holes in the ends of your push tubes. I'm curious to know 3 things.

1) What size is the hole?

2) How do you check it? Visually or with a probe that's poked through the hole? - Is there enough light to actually see something in there?

3) What was your criteria for locating them?

I think witness holes are a great thing and I wish I had thought of putting them in earlier. Now I've got a few to pull out of the airframe if I want to check all of them.

Thanks,
Phil

[pierre smith]

On my Air Tractor and other certified airplanes, the witness holes will accomodate a piece of safety wire, making it easy to check.

An easy way to ensure that your threads are deep enough is to apply some torque seal or finger nail polish...even a Sharpie marker to the threads before you screw in the end and simply run it down to the painted area.

Best,

[swisseagle]

Hello Pierre and Phil

Interesting thread!

I would also know how much the thread engagement should be (so you can position the witness hole). I heard once 1,5x the thread diameter, but with the Vans design, the tubes are on the short side and the threads are less then 1.5x engaged. Look also here what I like to know: http://www.vansairforce.com/communit...t=aileron+tube

Hopefully someone can help.

Happy new year!

Regards, Dominik