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Possible Rudder Airworthiness Directive

I guess I can open my mouth now. Two engineers working for the Vintage division of EAA came to my hangar and we went over this rudder issue. I showed them my fix and they were skeptical as was the FAA engineer I suggested it to. However when I handed them a 7/8"x .035" wall tube and a 3/4"x .035" wall tube they were pleasantly surprised at how tight they fit together. Last conversation I had with them was the possibility of doing some flight tests on my Super Cub and another one I maintain on floats with some instrumentation to see what the forces actually are. Also discussed a simple fixture and pull test with a fish scale or torque wrench as a pre-flight measure. Sharp guys and a lot of experience in aircraft structures. I talked to Steve Caruthers from the Short Wing Piper Club last Sunday as well and it sounds like the FAA has a full plate from engineers, a lawyer and lots of us maintainers and pilots.
Steve, if two identical cubs show up and one opts for a new 4130 rudder and the other goes with your AMOC, what is the dollar difference? I assume it would come down to the cost of fabric repair, but I honestly don't know. I do appreciate your work. We need more GA and classic mechanics.

I've already pulled my trigger. If I could do it all over, I'd probably wait and see, but my wife likes the idea of a new rudder. I guess I should have kept my mouth shut, but that's nothing new.
Keep in mind that until there is an actual AD there is no AMOC. Everyone involved hope the NPRM will be rescinded based on inaccurate info that FAA used. Failing that, we hope for an inspection criteria applying a load at the top of the rudder. Now that the comment period is closed it will take time for FAA to review the submitted comments, disposition those comments and then either rescind, modify the NPRM or issue the AD.
From AOPA:
"A chorus of aviators, aviation mechanics, and groups including AOPA called for the FAA to rescind a proposed airworthiness directive that would affect nearly 31,000 vintage Piper aircraft, citing a lack of evidence of risk, unjustifiably broad scope, and a broken process."
Regardless of outcome, one of the issues remains....abrasive surface cleaning of the rudder and any potentially delayed effects also due to surface pitting. The NTSB Dockets on materials discovered and reported that alteration to the base metal. The effect of that impingement on tubing strength? Remains to be seen apparently.

One materials example below. There's others in the two Dockets.



  • 21-068-Rel.pdf
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I don’t think anyone questions the possible safety issues, just the overly broad scope and lack of alternatives to replacing or major surgery on the rudder. The fact remains that the FAA process was broken and not followed. If our regulators can’t follow the process they need to go back to square 1 and start over!
If you want to replace your rudder that is fine but when you crunch the numbers and there are two zeros behind the decimal point I am not getting real excited. I will do my die diligence but don't circumvent the system and expect me to go along with it. I have sat in way too many Aging Aircraft meetings with the FAA with the good ones who reach out and we respect one another and then there are the "Cram it down your throat cause we are the FAA". You want to feel good, do a pull test. Dirt simple, cheap and effective.