Nicopress fitting failure report

[Chad Jensen]

This is a report that was submitted to us by an NTSB investigator who needs to remain anonymous as an impartial investigator. Pictures and words are not mine so I can't offer any answers to questions. This is simply a passing of information to anyone using nicopress fittings to use the proper tools.

Thankfully, this was a known-circumstance, no-injury accident, and we were hoping to share the lessons learned from it with an interested audience. Your members are likely to be involved in the building of flight control systems, or the re-rigging of those systems in antique aircraft, and that’s why we sought you out.

The NTSB Accident Number is ERA11CA375. You can go to our website and read the Factual Report as well as the Board’s finding of probable cause. The public docket which contains the documents and photographs used to support the investigation can also be found there. I have attached a number of those items for your convenience.

Because my position requires that I be an impartial investigator, I am reluctant to self-publish on a website or discussion forum. It am not, however, precluded from sharing the facts and circumstances with you and your members. From there, you can draw your own conclusions, or start a discussion or debate as the situation dictates.

[Mike Switzer]

Did the fitting fail or did the cable break? I can't tell from the pictures. We use similar crimp sleeves for fencing & vineyard wire splices, and if you use the wrong tool it will not crimp properly & the wire will pull out under load.

[Chad Jensen]

Fitting failed, cable slid through. That's all I know though...

[Bill Berson]

Ultralights often use two copper sleeves instead of one.

But in his ultralight book, Lack Lambie said using two sleeves will weaken the cable slightly.
I never understood this. Anybody have the facts on using two sleeves?

[Frank Giger]

I can't really tell, but it looks like he didn't crimp them properly, and didn't use a go/no go gauge to ensure they were tight enough.

[dewi8095]

I can't really tell, but it looks like he didn't crimp them properly, and didn't use a go/no go gauge to ensure they were tight enough.

What is a go/no go guage and how does it work?

Don

[Neil]

Don't know in this particular case but I see this type of failure from time to time when a builder tries to make up cables with the "Econo Swagers" that get all their clamp force from a couple of bolts. There is no good substitute for the proper lever type swaging tool.

[Dana]

I don't think there is a problem with the clamp bolt swagers if used properly.

Some years ago Quicksilver had a problem with a lot of improperly swaged wing cables at the factory. Seems 1/8" cables had been swaged with a 5/32" tool; the swage looked OK but wouldn't pass a go/no go check.