I assembled my fuselage several years ago. I recently had a follow up tech counselor visit, and they said they were surprised that I didn’t place large (1”+) washers on the bolts next to the rod end bearings. Allegedly the bearings can fail, and with no washer, the rod can slip over the nut, resulting in Bad Things. 

The plans make no mention of this situation or mitigation. How many have used the washers?


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Your tech counselor is exactly correct to tell you that this is best practice.  Zenith apparently did not deem it necessary based on the expected wear and the fact that you should catch the ball wear during inspections long before it opens up enough for the ball to slip out.  My choice, since I won't have my plane on floats and I don't live near a salt water environment where corrosion could increase the rate of wear, was to follow the Zenith plans.  If there was more stress on these control ends I might take a different view.  Just my approach to the question.  My DAR did not raise it as a concern during the inspection. 

Yes, my TC noted it, and was surprised, but he deferred to the Zenith standards and plans. I'm in DFW, so no salt environment within a few hunnert miles, and I'm not going to be yankin' and bankin' on it, so similar thoughts to yours.

Interesting. The Zenith Construction Standards document by Chris Heinz indicates they're not required (it shows a diagram of the installed rod end with no washer) and in Are Your Nuts Tight: Guide to Identifying Problems on Your Amateur-Built Aircraft, by Vic Syracuse (A&P/IA, DAR, EAA technical advisor), he repeatedly stresses the need for jam nuts on the rod ends but doesn't mention washers at all. Most of the pictures in that book do show washers, but not all. Tony Bingelis does recommend using them: https://www.eaa.org/eaa/aircraft-building/builderresources/while-yo...

Since there isn't a consensus, it might be one of those failures that is technically possible but highly unlikely.

If the bolt is long enough to fit a washer with threads to spare then why not add a washer? 1"+ diameter seems excessive though... as long as the washer is wider than the bearing then it can't fit through the housing - wider than that is just extra weight. That's my $0.02

Interesting view on inconsistency! Some of my nuts are pretty close to not having the 1-2 threads showing, so I was concerned about the washer thickness. The diameter was related to the bolt size - AN3 vs AN4 vs AN5 etc.

I put the washers at all rod ends on my build. Example in photo. Some washers had to be bent cone shaped to not interfere at travel limits. Also some had to be thinned in the middle for proper nut engagement. Used garden variety fender washers.


I don’t have any on my airplane because they weren’t on the drawing.  They are not on the Zenith drawings because there is no basis for the requirement for a safety washer on a rod end ball joint, to include no mention of them in AC 43.13-1b. If they make you feel safer, by all means install them.

Good point about AC 43.13-1b!

After just reading the Bingellis article and getting ready for final inspection, I was thinking I had to install these washers. Having read this thread, I think I will opt for not and monitor. Thanks for the timely discussion.

I have. Makes perfect sense. A 2 minute job for significant added safety. 

As maintenance test pilot, I've had a rod end fail. The Air Force required safety washers for this very reason. I was able to recover the aircraft. So when built this 750, I increased the bolt length on every bolt on the push pull tube that has a rod end bearing. You can buy them at any speed shop or online. Double check with flaps fully extended that vertical flaperon lower rods are not binding on the bellcrank

Egads!! Glad you recovered and can relate your experience! Thanks for sharing; good case for including them. 

The bellcrank binding can be resolved by adding a few millimeters to the spacers/bushings...


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