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Date: Tue, 03 Oct 2006 22:30:41 -0400
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From: Guy Buchanan <bnn@nethere.com>
Subject: Re: Shudda gone down when the buzzard went up
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At 03:06 AM 10/3/2006, you wrote:
>Looks like the leading edge was forced back to the spar by the initial 
>impact, flexing and tearing the skin as it deformed. A large flap of skin 
>folded back, forced up to vertical by the airflow, formed a very effective 
>spoiler in front of the aileron. It took full stick and lots of rudder to 
>keep the blue side up.
>
>Where does one begin a repair like this?

First you have to find all of the pieces of the buzzard. Then you lay them 
out on a big floor. Next, starting with the beak, if you can find it...

Oh you mean YOUR plane! (Sorry. Gallows humor.)

You begin by determining the scope of damage. There are a couple of ways of 
doing this. The "simple" way is to start removing material until you reach 
undamaged hardware. I say simple because it takes diligence and sometimes 
expertise to recognize damaged versus undamaged material. And sometimes 
damage occurs in odd places, away from the obvious damage. (You'd be amazed 
at what that wing probably looked like just before the leading edge 
failed.) Unfortunately, even if you remove all the obvious damage you will 
probably want to invoke the more "complex" assessment methods, which is to 
use non destructive testing (NDT). With cored structures it is entirely 
possible that the shock of the impact and/or amount of deformation prior to 
failure has precipitated core failure far beyond the region of obvious damage.

Since you have cored structure you can have some success with thermal 
imaging. In the solid regions you might be able to use ultrasonics. Suffice 
to say these methods require extensive expertise well beyond the 
capabilities of the average builder. You'll have to bring in an NDT 
consultant to do the work, and it will be expensive, and not conclusive.

Once you determine the scope of the damage you determine the type and scope 
of the repair. It is certainly possible to affect a local repair, even one 
this extensive. You'll gain a little weight, which you'll have to balance 
in the other wing, but it can be structurally and cosmetically sound. I can 
help with the design, and I'm guessing Dan Newland would be willing to help 
as well. There may be other composites experts on the list I don't know about.

My recommendation, on the face of what I saw in your pictures, is to 
seriously consider replacing the wing. It's not that I lack confidence in a 
repair, but it may take you longer to do the repair than to build and 
install a new wing. (Or find a replacement somewhere.) You'll have to try 
to assess the time it would take to replace the wing, but I can tell you it 
will be a big job to do the repair right. (It's somewhat quicker to do it 
"the fast way", but it will be heavy, and probably visible.)

Oh yes. Congratulations on your recovery. We have a lot of large bird 
activity here in Ramona and I often wonder what happens when you hit one.

Feel free to contact me off-line.


Guy Buchanan
Principal
Buchanan & Newcomer
16718 Peace Valley Lane
Ramona, CA  92065-7046
USA
1-760-789-4482
1-760-809-6145: Cell
bnn@nethere.com  
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At 03:06 AM 10/3/2006, you wrote:<br>
<blockquote type=cite class=cite cite="">Looks like the leading edge was
forced back to the spar by the initial impact, flexing and tearing the
skin as it deformed. A large flap of skin folded back, forced up to
vertical by the airflow, formed a very effective spoiler in front of the
aileron. It took full stick and lots of rudder to keep the blue side up.
<br>
&nbsp;<br>
Where does one begin a repair like this? </blockquote><br>
First you have to find all of the pieces of the buzzard. Then you lay
them out on a big floor. Next, starting with the beak, if you can find
it...<br><br>
Oh you mean YOUR plane! (Sorry. Gallows humor.)<br><br>
You begin by determining the scope of damage. There are a couple of ways
of doing this. The &quot;simple&quot; way is to start removing material
until you reach undamaged hardware. I say simple because it takes
diligence and sometimes expertise to recognize damaged versus undamaged
material. And sometimes damage occurs in odd places, away from the
obvious damage. (You'd be amazed at what that wing probably looked like
just before the leading edge failed.) Unfortunately, even if you remove
all the obvious damage you will probably want to invoke the more
&quot;complex&quot; assessment methods, which is to use non destructive
testing (NDT). With cored structures it is entirely possible that the
shock of the impact and/or amount of deformation prior to failure has
precipitated core failure far beyond the region of obvious damage.
<br><br>
Since you have cored structure you can have some success with thermal
imaging. In the solid regions you might be able to use ultrasonics.
Suffice to say these methods require extensive expertise well beyond the
capabilities of the average builder. You'll have to bring in an NDT
consultant to do the work, and it will be expensive, and not
conclusive.<br><br>
Once you determine the scope of the damage you determine the type and
scope of the repair. It is certainly possible to affect a local repair,
even one this extensive. You'll gain a little weight, which you'll have
to balance in the other wing, but it can be structurally and cosmetically
sound. I can help with the design, and I'm guessing Dan Newland would be
willing to help as well. There may be other composites experts on the
list I don't know about.<br><br>
My recommendation, on the face of what I saw in your pictures, is to
seriously consider replacing the wing. It's not that I lack confidence in
a repair, but it may take you longer to do the repair than to build and
install a new wing. (Or find a replacement somewhere.) You'll have to try
to assess the time it would take to replace the wing, but I can tell you
it will be a big job to do the repair right. (It's somewhat quicker to do
it &quot;the fast way&quot;, but it will be heavy, and probably
visible.)<br><br>
Oh yes. Congratulations on your recovery. We have a lot of large bird
activity here in Ramona and I often wonder what happens when you hit
one.<br><br>
Feel free to contact me off-line.<br><br>
<x-sigsep><p></x-sigsep>
<b><u>Guy Buchanan<br>
</u></b>Principal<br>
Buchanan &amp; Newcomer<br>
16718 Peace Valley Lane<br>
Ramona, CA&nbsp; 92065-7046<br>
USA<br>
1-760-789-4482<br>
1-760-809-6145: Cell<br>
bnn@nethere.com </body>
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