Warbird Information Exchange

I decided to start a new thread on the same topic. This is a very serious issue and it is important that we all do this right the first time. If a wing separation happens again any time in the next decade, we will all be grounded for sure. Lets not take any chances, we have to do the inspection correctly and pay attention corrosion and cracks that could potentially kill us as well as affect everyone else.

Here is a picture of the wing attach points on the plane as seen from the front.

This is a picture of attach angles that have been removed from the stress panels. I have put red marks where you should pay special attention to when you are inspecting.

_________________
Live to fly, Fly to live.....

Thanks Chuck!

It's very sad it happened. Anyway, It looks easy enough to check that area.

You wrote:



What makes you say this? Several have occured on T-34s, and tail flutter on V-tail Bonanzas. history repeats itself, and the FAA should deal with it the same way they have in the past. I'd say your advise is conservative, and sets a good standard.

Hi Chuck,

As the AD states the area around the spot faces, as you have marked in red, should be inspected closely for cracks. Any airplane that has had these angles replace may be especially succeptable to cracks due to improper spot facing. The cutter used to spot face around the holes should have a small radius on the O.D. so that it does not cut a sharp corner around the O.D. of the spot face causing a stress riser that may result in a crack. You might want to be careful to use the proper cutter when spot facing those new angles in the picture! Most piloted counterbores come with sharp corners and should be re-ground with a radius before use, although radiused counterbores are available.

Glenn

Hi Glenn:

Another aircraft rebuilder and I were looking over my attach angles today, and he made that same comment about stress concentrations where the bolt areas are faced. I'd think there are stress concentrations in well faced components as well. Perhaps, the one that failed had an stress concentration imperfection near the bend in the angle.

Thanks Chuck, for showing us clearly with a photograph what the AD was trying to describe. We'll pay close attention when doing the inspection to this area.

This folks, is why I put up with all the bullsh*t on WIX. Ever so often, you find a diamond amongst all the clutter.

Hey Steve!

Really, I just thought you were a glutton for punishment, but hey I guess that means you can handle more g's during aerobatics.

Glenn is EXACTLY correct. A radius on the OD spot face would help reduce opportunities for cracks.
Tooling marks where the bolts attach have an arc where wrenches and sockets score into the metal a little and dont tend to lead to straight line cracks.

_________________
Live to fly, Fly to live.....

Chuck, first of all thanks for the pics, they really do help a lot understanding better. Do u guys have the wing attach fairings installed? I've heard and seen several T-6/Harvard/SNJ without them and I wonder why. I guess that they placed it there not only an estethycal thing, even if maybe the fairings might cause water condensation and of course they visually cover all the bolts. A daily visual inspection is more difficult (even if it's not difficult to remove them, but it takes two ppl and it's a pain in the ar$e), but I guess they are more protected in general.. What do u guys think about it?

Alex

according to the area u've put in evidence, the crack started from the main wing spar area, isnt it? And I thought that was one of the most resistent parts of the T-6..

Alex

It seems like it would be an easy enough item to machine in quantity anyway, in case a replacement is needed. I can think of far worse parts (spars, etc) that would be harder to access, and far more difficult to handle in regard to inspection and possible replacement. Looks like the only trick in the design is the slight front-to-back curvature in what otherwise looks like a piece of common bar stock material.

_________________
Rob Mears
'Surviving Corsairs' Historian
robcmears@yahoo.com
http://www.robmears.com

The fairings are probably necessary for drag reduction. Without them your cruise speed and range may be affected. Also, the fairings protect the wing joint from getting water inside the joint. Any condensation should drain out at the trailing edge.

uhm, drag reduction of course (eventually that's what a fairing is meant for! )
The fairings have a rubber seal running around the edge, so drain can only occurr thru drain holes, but I dont remember if there are any. There's a locking lever on top though..

Alex

Rob Wrote:



I asked someone w/ blueprints about this about 1 yr ago. Actually if I remember right, the originals were soft pliable (w/ doughlike consistency) T-0 AL. This was formed over a mold and then heat treated and quenched to, I believe, T-3 hardness.

Using barstock may not be good, because when it is milled the surface is work hardened, and this could cause a stress concentration.

Actually, on the other hand if the mat'l had a higher strength; tensile, compressive, and shear you may be able to accept the workhardened surface. A titanium attach angle would be awesome! Possibly Titanium could be riveted directly to Aluminum w/o dissimilar metals corrosion.

In addition, it might be nice if an improved angle with more material on it for incresed strength. However, you'd need to get it STC'd. I know a guy who sucesfully STC'd a camshaft, and another who sucessfully STC'd an aircraft air conditioner.

I dont think it's possible to change a component of a certified plane like that pal..
I guess there's no sense to "have more material on it for incresed strength", the structural design is supposed to resist to higher than given G loads, it's just a matter of having a part in pristine conditions, without any sort of damage/corrosion. U can have it in titanium, aluminium or kryptonite, but if it's rotten it's the same...

Alex

Hi Alex, do you know what an STC is?



Well Alex, you might want to read what I said more carefully again, I can tell from the above comment that you didn't read it.