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INSPECTION HOLES AND WORK THROUGH HOLES
by Evan McCombs, Technical Advisor

Now, there is a boring subject, you say. Yes, I agree. However, it is not so boring when you are laying on your back trying to figure out where to cut a hole in the bottom of your newly completed and freshly painted airplane.

During the building or rebuilding phase is the time to install any needed inspection holes. The basic rule is: any part that is added to, bolted on, screwed on, or any part that moves, needs inspection holes to be able to see it or work on it. Inspection holes can be any size as long as you can get a small flashlight and mirror into it to see. A work through hole must be big enough to get at least one hand through and work—usually a 4-inch diameter hole minimum. However, sometimes the hole needs to be big enough to get both arms, your head and shoulders through!

Advisory circular 43.13-1B shows how to install inspection holes in sheet metal, wood, and fabric covered structures. This book shows basic guidelines and approved methods.

Spend some time and look at any airplane sitting around and count how many inspection holes you will see. You will be surprised by the number, size, and where they are.

As always, anyone who reads this newsletter may give me a call about this subject or anything else that I be of service to you. I can be reached at my business, Evan’s Aircraft Body Shop, 719-683-2382, M-F, 9-5.