Wing skin crack

[Fred Eisert]

My airplane partner found a crack in the left wing upper surface last night. I am looking for options to repair.
1. Replace the section skin--lots of work, maybe overkill
2. Stop drill and patch--ugly, in the laminar flow part of the wing
3. Stop drill

The service manual nor AC43-13 provides no guidance on the maximum crack size permitted before a patch plate is required. The wing skin is 2024-T3 0.040".

I was supposed to fly to NY tomorrow morning, but decided that it is better to leave the airplane in the hangar at this time.

[9089P]

Hi Fred,

This a common occurrence on comanche wings generally occurring at or about the 3000 airframe hour mark. I have one on each of my wings. It is not a problem. I would remove that ugly bit of tape and fly the plane.

The cracks are not uniform but are generally small. Once they occur it is believed stress is relived. Mine have not changed size in the last 25 years.

Maurice Taylor did a study of these cracks and recommended doing nothing.

Have a good flight.

Don

[Kristin Winter]

I would second Don's advice. That crack is a nothing-burger. Fly the plane.

If I had to repair cracks in a Comanche wing, I would ignore the diamond shaped patch in 43.13-2A and get a field approval or DER to allow me to use an elliptical patch that picked up the existing rivets and then bonded with structural adhesive. Then some filler blended out some 5-6 inches from the edge of the patch. Repaint the panel, and presto, you won't even know that there is a patch there.

[Don Nelson]

I agree with Don D. and Kristin.
My last 250 had a similar crack on each wing when I bought it. After 12 years and 1700 hours the cracks had not changed.

One can't help but watch such a crack, but needn't worry about it.

Best, Don N.

PS,
BTW, My twin has the diamond patches on each wing - Ugly!
Dn

[Pat Donovan]

Do you suppose these cracks are the resulting of wing flex due to turbulence? I've got over 4K hours with no cracks. Am I just lucky?

PatD

[David Pyle]

Always an advocate of neat and tidy...I suggest if you take the 'leave be' advice of Kristin, Pat, and Don(s) that you cover the crack(s) with a smidgin of epoxy, sand and dab on a tad of matching paint. That way you hide the embarrassment .

[Tom Veatch]

4000+ hours on a 250 and there is a spot on each wing at about the same spanwise location. Looks much the same except only the paint is chipped. I look at them each preflight, but, so far, there are no obvious cracks. I understand, from what I've heard here and been told elsewhere, which I can neither confirm nor deny, it's fairly common to see such evidence of flexure at about the midspan of Comanche wings.

[SLIMDREDGER]

I am well over 6500 hrs on my 1964 PA 30 C/R with no cracks on the top of the wing. My only crack on the airplane is one 1/4" long on the bottom of the left wing that was stop drilled 30 years ago and has not changed since. The airplane has seen lots of grass strip and no pavement landings as well as winter time rough air.

I added the Robertson STOL wing cuff at about 1000 hours on the airplane and wonder of the extra added structure might have helped prevent the usual top wing cracks. My intuition says extra stiffness in the leading edge would not do much to prevent a crack half way back on the wing, but it might help ???

I have a friend who thinks tip tanks add to the chances of having the top wing cracks, but no figures to support his position. I can't agree or disagree

Al Powers ICS 2978

[Zach Grant L1011jock]

Notice in the picture of the wing the pucker in the skin along the rivet line. Most singles suffer from this pucker and it is my belief that if you have this pucker, you will also have the associated rivet radial cracking that is being discussed here at one of the adjacent rivets. This is a stress relieving crack and is different from the cracks that develop on the twins. The only issue is if the skin gets loose around the rivet and starts to work, at which time you will need to do something. The chances of the crack expanding from what it presents now is not likely under any circumstances, as long as present stresses and structure remain intact. I have one on my left wing and have chosen to leave it be, as the fix, short of reskinning, would be worse than the illness IMHO.

-Zach

[Alan Cheak]

Leave it alone. My Comanche 250 has had one for 18 years.

Alan

[Matt Bogard]

I have one in the same spot as well. We learned in the Comanche Pilot Proficiency Program (excellent program!) that it's pretty common across the fleet.

[Fred Eisert]

Many thanks for all your inputs. I had no idea that wing cracks were such a common problem! I did speak with Webco and they also said it was a common problem and just to leave it alone. They did say one option is to patch the skin, which means deskinning a major portion of that section. As Zach said, the cure is worse than the problem. One of my concerns is that as an A&P/IA signing off the aircraft as airworthy with an obvious defect. Structurally such a small crack on one rivet is pretty insignificant I suppose.
Fred

[9089P]

Hi Fred,

My IA did question the cracks and that is what occasioned the call to Maurice Taylor. There is a letter in the records somewhere between Maurice and the FAA on the subject the gist of which is the FAA agrees the cracks are well enough left alone. Webco might have a copy or there might be one on this site.

Good luck, Don