Long-EZ Winglet/Wing Joint Failure Analysis

[Marc Zeitlin]

Folks:

 

As many of you may be aware, Tim Sullivan suffered a winglet/wing joint failure on his Long-EZ on a flight in June. He was able to land the plane safely, but due to an unrelated brake failure on landing sustained substantial damage to the aircraft. Neither he nor anyone else was injured in the landing.

 

Tim asked me to evaluate and analyze the failed structure with the intent of learning how a 22 year old Long-EZ that had been flying safely could suddenly have a major structural issue with no warning whatsoever.

 

A couple of weekends ago, I was able to get a hold of the structure in question and perform a forensic analysis. I've posted the results of that analysis at:

 

http://www.cozybuilders.org/N7999H_Accident_Eval/

 

This is, at this point, somewhat preliminary. I am open to any comments, corrections, feedback, or questions and will modify the report with whatever useful information is provided.

 

In order not to have a discussion on this topic going on in four different places, I'll only be responding to comments or questions in public on the canard-aviators and COZY mailing lists.

 

Thanks.

[Kent Ashton]

Very informative write-up Marc.

 

In addition to your comments on the incident, it does not look like Layup #1 extended a full 2" into the wing/winglet and the corner was left very sharp there.

 

You prompted me to review my pics of Layup #1 from my current Long-EZ project (which I'll post here FWIW). Wish I had some from my Cozy IV build. BTW, The wedges here are blue styrofoam, epoxy is EZ-Poxy.

[planecrazy]

Hey Marc Z thanks for that info- by the way thanks for all you and a few other guys write here.Also is there any info on blending of the wing and winglets as you were speaking of ?( just asking)Thanks again.

[TMann]

Marc, did anyone check/verify the AOA of the winglet?

[fnordmorph]

This analysis brings up the question, is there any way the prospective buyer of a partially completed kit can tell anything about the quality and appropriateness of the layups on partially constructed (not filled/painted) parts? The airframe I'm considering doesn't have winglets attached yet, so those particular problems would be left for me, but anything for the inexperienced to look at in other parts of the airframe?

 

--Dan

[TMann]

This analysis brings up the question, is there any way the prospective buyer of a partially completed kit can tell anything about the quality and appropriateness of the layups on partially constructed (not filled/painted) parts?

The information you have available will be whatever documentation the builder has done. i.e. photos, logs, etc.

 

Other than that .... no guarantee

[goatherder]

All the more reason for my decicion not to buy somebody else's project.

[Kent Ashton]

is there any way the prospective buyer of a partially completed kit can tell anything about the quality and appropriateness of the layups on partially constructed (not filled/painted) parts?

If you can visit a few projects going together you'll get a pretty good idea what good construction looks like. This website also has a lot of pictures.

http://www.maddyhome.com/canardpages/main

 

I have seen an EZ I wouldn't fly in and the poor workmanship was obvious: heavy, lots of filler used, big bump on the wing where the spar caps were overfilled with UNI (later smoothed with filler), did I say heavy? Most builders do a good job though.

[Wayne Hicks]

I've been on the canard lists for about 12 years now. Most projects that come up for sale are in the Chapter 7 through Chapter 10 stage. These are easy to inspect since the plane isn't covered in micro. Plus, there's little that can go wrong with construction if the builder followed the plans and has good workmanship. This is easy to verify if you know what you are looking for.

 

I wouldn't hesitate to buy one of these projects. You can acquire them for pennies on the dollar.