Something came up during inspection: Is it a crack or scratch?

[taylormarc]

This is what I have ion the lower LH of the wing near the most LH inspection panel closest to the ailerons. The IA said he isn't sure how to diagnose this given the limited amount of experience he has regarding wood construction. As for me this looks like a scratch. But is there a formal way to analyze this? i.e x-ray or ultrasound. The area is hard to reach and those were the pics taken with a borescope.

2.jpg

[mike lutz]

Looks to me like the nail hole protrusion on the flange of the rib scratched the varnish when they assembled the wing. I had a couple just like that on my spars at assembly, and I made sure the rest of the rib flanges were flat and no old nail holes protruding where they were nailed prier to disassembly. I have the same pattern which is from walking the rib on the spar at assembly. The spacing looks about like mine also. I took a permeant marker and made a notation on the spar by the mark as to what it was, for future inspection explanation to whoever the IA might be during future annuals. Put your finger on the mark and have someone at the tip of the wing pull up and down and see if you feel any movement and squeaking from that area. I Have never seen a cracked spar look like that. Usually they are a straighter line .

[Robert Lees]

I agree with the above. If were a crack it would follow the wood grain.

[Hank Jarrett]

I have several spar pieces from wrecked wings that have these marks that originate at the rib nail holes. Careful removal of the spar finish usually shows it does NOT go into the wood and when it does the mark doesn't follow the grain Not that you couldn't have a spar crack but a rib nail wouldn't originate it. If you see a mark like that coming from a drilled hole like where the root fittings are attached THAT would be a problem.

Hank

[N96337]

Scratch. For what it's worth from 40 years of working on wood spars.
JH

[tagflyer]

I disassembled a wing and created scratches on removing the 1st couple ribs. I bent up a couple “L” shaped pieces of sheet aluminum the width equal to the height of the spars, slid them underneath the rib flange next to the spars, then able to slide them off without scratching. Then was able to take some hand seamers to flatten the nail dimples.