Dent Repair in Horiz Stabilizer

[aviationinfo]

Hi All:

Was off having a great time in Idaho visiting strips when I noticed a nice dent in my horizontal stab, apparently from a rock thrown by one of the tires.

The dent is a bit smaller than the size of a quarter, indented nearly 1/4" at it's deepest point. The fabric was torn (right through the protective tape on the leading edge).

I had my IA look at it. We cleaned off the fabric to allow a good look---there is no cracking of the 4130 anywhere. He feels the dent isn't worth anything more than a cosmetic repair, certainly not replacing the leading edge of the stab.

A friend looked up dent repair in AC 43.13 and discovered that if the dent in a tubular structure is larger in size than 10% of the diameter of the tube, you're supposed to splice in a new piece. So are we to believe basically that something smaller than a BB-sized impingement on something like that requires a splice? That seems silly to me. My understanding of 43.13 is that it is not regulatory in nature but of course someday the plane will be sold and obviously the repair should make sense.

I need advice on the dent. It seems ridiculous to replace the leading edge of the stab over a dent, UNLESS of course it's compromising the safety/integrity of the structure. I cannot believe you folks landing on gravel bars don't have any dented stabs, or haven't repaired same. How do I handle this?

Thanks in advance for your thoughts.

 

[citabrickr]

The dent is a bit smaller than the size of a quarter, indented nearly 1/4" at it's deepest point. The fabric was torn (right through the protective tape on the leading edge).

I had my IA look at it. We cleaned off the fabric to allow a good look---there is no cracking of the 4130 anywhere. He feels the dent isn't worth anything more than a cosmetic repair, certainly not replacing the leading edge of the stab.

A friend looked up dent repair in AC 43.13 and discovered that if the dent in a tubular structure is larger in size than 10% of the diameter of the tube, you're supposed to splice in a new piece. So are we to believe basically that something smaller than a BB-sized impingement on something like that requires a splice? That seems silly to me.

Maybe your friend should be an IA instead...he's right, your IA is wrong. You can weld a patch plate over the dent instead of splicing the tubing if you look closer, much easier to do.

My understanding of 43.13 is that it is not regulatory in nature but of course someday the plane will be sold and obviously the repair should make sense.
I need advice on the dent. It seems ridiculous to replace the leading edge of the stab over a dent, UNLESS of course it's compromising the safety/integrity of the structure. I cannot believe you folks landing on gravel bars don't have any dented stabs, or haven't repaired same. How do I handle this?

43.13 repairs listed are the recommended repairs and the guideline for making such standard repairs. Your answer is right in there as you have already found.

 

[bob turner]

Of course that repair procedure applies to the most highly stressed tubes as well as those with absolutely no stress on them at all. When you look at it that way, your IA is using common sense. Your lawyer friends are also telling you the correct thing is to follow 43-13.

If you put the weld patch on there, you will not be improving the strength of the leading edge, but you will be legal. You cannot grind the weld smooth, so you will always see it.

If you bondo it and then sell it you have a duty to disclose - just tell the seller what is under there, and offer to buy him or her a new stab at a slightly additional cost, and let them make the decision.

That is all opinion. Not a recommendation.

 

[slowmover]

I had a similar-sounding dent in the leading edge of my horizontal stab and flew it like that for several years. When I moved to the lower 48, my A&P welded a diamond-shaped plate over it as described. I've had annuals from 3 different IAs since then and nobody has mentioned it even though the patch is clearly visible.

 

[aviationinfo]

May thanks for your input.

I wonder, having never seen one of these stabs without covering, what part does that leading edge play in the structural integrity of the thing? If I can weld a patch on there and it doesn't increase the strength, I'm thinking the leading edge is strong enough without it. Obviously the odd perfect dent will weaken it but I'm curious.

Thanks again.

 

[bob turner]

You could practically saw it in two and still fly it. The weak point is no doubt those wires and ferrules. However, a dent like that in a lower longeron right behind the rear gear leg could cause problems.

 

[cubunltd]

Email me at jswalt@comcast.net and I'll tell you how to fix it without welding a patch over it.

 

[aviationinfo]

Just sent you an email ----thanks.

 

[S2D]

Ball Bearing

 

[aviationinfo]

I just pm'd you - thx.

 

[bob turner]

What a neat idea - but how do you get the ball bearing back out of there?

Somebody please tell us how severely stressed that giant leading edge tube is - it must be holding thousands of pounds of tension, trying to keep the trailing edge straight. It's a wonder those AN-3 bolts just don't shear right off . . .

Just joking.

 

[NimpoCub]

What a neat idea - but how do you get the ball bearing back out of there?

I'd guess the same way you got it IN there...
It hast'a be welded on a long rod of some sort to drive it past the ding, right?
So, when you're finished beating your rod to get into da ding, you just pull your rod until it comes out'a da ding.

Kinda like resizing rifle brass. (What were YOU thinking?)

 

[bob turner]

I guess I was mentally just driving the bearing in there. That sounds like a great idea!

 

[Charlie Longley]

I am the "friend" and I am actually an IA. I stand by my recommendation.

 

[S2D]

http://www.youtube.com/watch?v=quAbyTTPUtc

 

[bob turner]

Two very different things going on here. One is simply regulatory - you are obliged to follow them. The other is - what is the downside of not following them. An in-flight structural failure of a stab leading edge could surely be catastrophic. Let's hear the probability of such a failure?

 

[jay cross]

You can buy and weld in a new leading edge tube. Airframes has them.