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SZD 36 COBRA C-15

WARNING ON WING CONNECTION

An unofficial Advisory

 

To Whom it may concern,

I am the brother of the pilot who was killed in Sylacauga, Alabama on March 31, 2007 flying a SZD 36a cobra 15 #813. I also flew the airplane in question as much as he did. The number one thing I want to tell you is, do not assume anything. We assumed that because we could see the top bushing or pin seat all the up, than the bottom one was doing the same thing. In our case this was not so. If you don't do anything else to your glider make sure you provide a hole to visually confirm that the bushing or pin (whatever you want to call it) that rides the jack screw and pins your wing anchor points are fully in place. I am not going to tell you where to drill holes in any airplane but it may be possible to put a 1" or so hole in the partition of the turtle deck, so that you can see directly what is going on at the lower anchor point. Please consult a skilled A&P to help evaluate the situation. Just make sure you can see that both of your main wing anchor points are properly secure and than you should be safe.

 
I have include some photos below of the damaged wing connection to help you see what happen. You will notice in photo, located top row 2nd from left, that the upper tab that is suppose to keep the center flange centered is worn away. That wear allowed the whole assembly to ride up a 1/4" or so and that in my opinion in only part of the problem. The lower pin failed to penetrate about 3/4".   What we really missed is that if on screwing the pins out to a fully seated connected position, if those anchor points where not perfectly aligned, than the lower pin would  bite like a pair of vice grips on top of the opposite wing's anchor point but, not pin the connection. The upper pin would than continue to travel up showing us a connected & fully seated top pin. On the damaged assembly you could hold with your fingers or block with a stick the lower pin entry and the upper pin would continue up and the lower pin would wedge only on the obstruction. It is unfortunate that the manufacturer did not provide a way to visual confirm connection or that we did not think to provide it for ourselves.  In hindsight it seems so simple now but, we did not have the benefit of someone else's experience in this regard. I am assuming, there is that word again, that this is the first time it has happen to anyone. I find that a little hard to believe but, it is what it is.
 
What you cannot see in the photos is that the lower pin or bushing had about 1/8" to 1/4" (cannot really tell exactly how much) of it's bottom end sheared off, which must have been partly penetrating the hole of the left wing anchor point and was sheared as the wings lifted up and away. This seems to me to be a bit of a contradiction, in that, if the pin was partly penetrating the left wing anchor point hole instead biting down on top of it, than it should have continued thru and pinned the connection but , the obstruction just stopped the travel of the pin. I really don't know exactly what the mechanics are as I had limited time to inspect the damaged connection but, you had better be confirming that, in fact, visually the connection is correct.
 
The official investigation should release some advisory directives thru the SSA & EAA in a few weeks, I was told. However, there has been nothing done and it is now 2012. Please contact me with any questions that you may have and I will help as much as possible. I am open to any comments or thoughts that anyone may have, as well. Please anyone reading this information, have any other owner that you may know, or come across, of this type of sailplane or a similar connection design, get a hold of me immediately or at lease direct them to this site. If I cannot bring my brother back, which I cannot, than I want to at least keep someone else from being the victim of the same problem.

Post Scripts:

4-28-07 - I have been made aware that at least one other SZD 36A Cobra has been found, in Great Britain, with a wore away tab or lug that serves to keep the jack screw collar centered. Also, that Foka (SZD24C) sailplanes have a very similar wing connection and that this notice should be extended to pilots and owners of the Foka SZD24C.

 
Sincerely,
 
Steve Wallace

swallace500@aol.com

 

cell 205-365-0646

 

PLEASE NOTE WHEN VIEWING THESE PHOTOS THE PIN OR BUSHING HAD BEEN RUN UP & DOWN THE SCREW BY SEVERAL PEOPLE SINCE THE ACCIDENT, SO THEY COULD GET AN IDEA OF HOW IT WORKED, AND IT IS NOT IN THE POSITION IT WAS FOUND IN AFTER THE ACCIDENT.

LEFT WING, UPPER ANCHOR POINT SNAPPED OFF

RIGHT WING, NOTE THE SNAPPED OFF ANCHOR POINT FROM THE OPPOSITE WING IS BENT UP AND REMAINS WITH THE JACK SCREW ASSEMBLY.

TOP VIEW OF LEFT WING

TOP VIEW OF RIGHT WING

SIDE VIEW OF RIGHT WING FROM TRAILING EDGE

RIGHT WING, THE PIN POSITION IS NOT IN THE AS FOUND POSITION.

ANOTHER VIEW OF LEFT WING