Proposed Piper rudder AD

[tnowak]

The FAA is currently drafting an AD that will mandate the replacement of nearly all rudders on fabric covered Piper aircraft.
This is as a result of the failure of the rudder posts on two (note TWO aircraft ONLY) Alaska-based aircraft which were float-planes and equipped with non-STC’d anti-collision beacons of circular cross-section which were mounted atop the rudder posts.
On the failed rudder posts there was evidence of fatigue cracking at the points of failure - immediately above the upper rudder hinges.

The view of many owners in the USA is that those anti-collision beacons, given their circular cross-sections, would have always produced lateral oscillatory forces within the rudder posts during flight - that’s just fundamental aerodynamics - and these forces being concentrated at the point of maximum bending i.e. just above the upper rudder hinges.

It is, therefore, no small wonder that fatigue cracking and, ultimately, failure of those rudder posts occurred. Therefore, many consider that for the FAA to possibly mandate imposing such a blanket AD, which would affect nearly ALL fabric-covered Piper aircraft, is inappropriate; it should be aimed at those machines with the non-standard and non-STC’d anti-collision beacons.

If you are the owner of a fabric covered Piper aircraft you can submit your own comments regarding the proposed AD.
However, you only have approximately 50 days left to submit comments…

FAA website:
https://www.regulations.gov/document/FAA-2023-1893-0001

US Government Comments website:
https://www.regulations.gov/commenton/F ... -1893-0001

I think it will greatly benefit owners of LAA administered Piper aircraft to make comments regarding the current wording of the proposed AD.

Tony

[coxargus]

I have carried out Piper Service Bulletin 1379 (downloadable) to confirm my rudder is contructed of 4130 steel.

The major problem is obtaining/finding someone with the 70% nitric acid as it is a highly controlled substance (ie making explosives). I was lucky to find an engineer in the SW who had jumped through all the beaurocratic hoops to obtain some and did the 30 second test for me - however he was not permitted by one of those hoops to 'dispense, said acid to enable a DIY test. .

Also my rudder was uncovered as I am doing a complete rebuild of my PA18-150

Frank