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New SB out

Good info. http://cubcrafters.com/c/publications/
Got one in for inspection today and had not checked the Cub Crafters site yet. I thought this was a weird failure on that fitting on a ground looped FX3 I have here. This is the rear fitting. Sheared the domes off the factory head.



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that is the dimple in a brazier head rivet with the sides of the head sheared off. I thought it was strange because I usually see the head shear off.
My drawings call out a AN470AD4-6. I have never seen a rivet fail like that. I would think that the rivets would have to be complete tension as the hole in the spar acts as the shearing force.
All the other rivets in the wing look perfect. The only thing I can think is that when the wing hit the ground it kind of pried the fitting off rather than sheared it.
I am ready to cover the wings on my EX-3 build. I would like to fix this problem first of course. I talked to an FX-3 owner who found the fittings to be loose on his preflight, who may have precipitated the SB.

Steve, with the understanding that this was an extraordinary event, was there other damage besides the sheared rivets? Was the spar damaged or deformed by the forces? Will the simple upgrade of rivets help? The fittings themselves seem very stout.

Thanks, John
It was a bad ground loop. Had lunch with Jon Delamarter yesterday, former customer service/builder assist at Cub Crafters and now our airport manager. He said the AD rivets don't have the shear strength that the Cherry rivet has and that they have only had an issue with the front jury strut fitting shearing the rivets. My picture was of the rear and definetley because of the groundloop.


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