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Possible Rudder Airworthiness Directive

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As to cleaning a four foot tube, why not a shotgun bore cleaner? Or a bottle brush on the end of a long shaft? I no longer have weapons, but I think I still have the bore cleaning kit - and the 4130 insert is due today, for a trial fit.

PRC - does it inhibit corrosion?
 
Got the 4 ft 4130 tube today. It slides in to roughly 1" past the top cluster, where the forward part starts. I did not force it further, but I probably could hammer it in. It is not loose in there, but there is plenty of room for adhesive.

I think if one has to force the inner sleeve past a weld cluster, some care would be in order. It has to go far enough in to be on both sides of the upper hinge area, and it has to terminate inside the original tube far enough in so the tailwheel steering arm still fits.
 
3/4" abrasive flapper wheel on a long drill stem extension. Make sure the wheel is tight in the extension, or. Then some non-oil based bore cleaner and air for removing dislodged debris. Repeat until it fits past the weld.

Gary
 
No - I think rudders with sagging weld beads inside that tube might not be amenable to the insert idea. There may be a way to insert a cutter to clean out minor sags, but I am guessing that most rudders will accept the tube. Tomorrow I will check a Cub without tail light - maybe its owner would be up for a check - four cotter pins and two bolts - two hours, at my speed these days.
 
In post 10 I installed the tube in a gas welded rudder and also did so in a Tig welded rudder. 2 people to do it but it went and I was able to remove although it is snug.
 
I have successfully tested one, and in the next month or so I will test two more. We have two J3s on the field with no wiring or tail light, so it is easy - just time consuming.

I should add that this morning I submitted my comment for the new 90 day comment period. It looks a lot like the one I posted for the first comment period, but has corrections and computations for nested tubes. I copied it on the J3 Cub forum.
 
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I checked my logbooks and found that STC SA00151DE (ROCKY MOUNTAIN AIRFRAME, INC. RUDDER) was installed when it was rebuilt in 1996. I'm going to confirm this week but am hoping to be exempt.
 
Hello everyone. A little confused regarding what year models this applies to - is it only aircraft manufactured up until 1976 or does this also apply to a 1990 Super Cub? From what I understand, all Super Cubs from 1977 and on have rudder posts constructed with 4130 steel? Or am I getting this wrong?
 
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The above screenshot is from the SB. Check your serial number, but 3 June 1974 should have been the 4130N start date.
 
Thanks for the clarification, much appreciated. So, in other words, from 1974 and on, the Super Cub rudder posts can either be made from 4130 or 1025 steel. Has anyone used an XRF analyzer instead of the acid test to find out?
 
I'm thankful for the supercub.org email that made me aware of this rudder business. These crosswind landings in North Dakota wouldn't be any fun at all if my rudder folded over! My PA-12 had PA-18 tail surfaces installed in 1989 using STC SA5-39. Trouble is, no details in the log book about whether new or used parts were installed. (Is that not mandatory?) I see mentioned that the Dakota Cub part can be ID'd by a "square hole" on control arm. (Thanks for that) Otherwise, is "acid" or "Brunell method" testing the only way to discover which metal type the rudder post is..?

Thx-Duncan
 
Duncan, not sure what you mean by the “Brunell method”, but it states in the Piper Service Bulletin (1379A) that “As an alternative to the acid test method described in this service bulletin, a portable X-ray Fluorescence (XRF) analyzer may be used to determine the alloy used in the rudder post. Follow device manufacturer’s instructions.” I am currently looking into that, will let you know if I make any progress.
 
You would have, according to the draft AD (which is not law) two years minimum to replace your rudder. I understand the desire for safety, and the desire to get ahead of a mandatory AD that could ground your airplane.

But consider: if the FAA mandates replacement, possibly two or three fabricators could get PMAs and set up assembly lines, possibly dropping the cost by a significant amount. And we really don’t know what the outcome will be - suppose they mandate .049 wall in that tube? Or allow us to glue in an inner sleeve in our old rudder?
 
I read through a lot of the comments on this proposed AD. https://www.regulations.gov/docket/FAA-2023-1893/comments

You can Comment here. Deadline is Tuesday 2-20-2024 https://www.regulations.gov/document/FAA-2023-1893-0165/comment

Afterwards I submitted my comment:

I am an A&P/IA who has specialized in the maintenance, repair and restoration of tube and fabric Piper aircraft for almost 30 years. Having worked with the FAA, ACO and the Small Aircraft Directorate on issues effecting Aging Aircraft in the past I have to say that I have been very disappointed in the communication with the type clubs on this rudder issue. When you eat, sleep and breath these aircraft and spend lots of time insuring that they are flown, maintained and restored in the safest possible condition you hope you would be contacted when these type of issues come up as I personally have in the past. Some of these previous correspondences have resulted in SAIB, AD revisions and others were just general knowledge. It proved to me personally that this was not “us against them”. Nothing to do with this issue has made me feel that way.

Piper built in excess of 50k airplanes with this rudder. I have read the ACS dated 9-4-2020, NTSB AIR-22-02and the NTSB Aviation Investigation Final Reports for the aircraft listed in the preceding documents. Having maintained, repaired and rebuilt fabric covered aircraft for almost 30 years I have discovered there are lots of causes of failures. I am curious as to the history of the aircraft involved, modifications, history of repairs, etc. Way more questions than answers in the data provided.

Since this issue came up almost 4 years ago I have investigated several ways to both verify the integrity of the rudder and to reinforce it. A simple fixture can be fabricated to fit over the top of the rudder to attach a fish scale to or even a torque wrench to allow a pull test to a minimum standard. Also I have installed a 3/4”x.035” wall 4130 steel tube into several rudders to verify that it is both doable and to check the tightness of fit. It is doable and tight. Could even be held to the outside tube via Cherry rivets.

I would be curious to know the load on the rudder on any given model. Is a J3 with a 65 hp engine even close to the load put on the rudder of a PA12 with 180 hp, on floats with no ventral fin? Again, more questions than answers.

This proposed AD will take years to comply with given the availability of rudders and experienced personnel to do the cover work. I would hope that the FAA takes all things into account and realizes that 2 or 3 incidence in a fleet of at least 30,000 aircraft is a probability of .0001 to .000066.
 
I just sent in my comment.
The website Steve listed shows all previous listed comments. I see Short Wing Piper but nothing from SC.org.......maybe they are not
all posted yet.
 
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In Post #54 are links to two Docket with some load tests the NTSB reported. They were done I believe for rudders common to PA-12-18, and not necessarily other Pipers. Steve's question above re potential loads on various rudder P/N's is a good one.

Gary
 
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I worked closely with the Short Wing Piper Club on their response in coordination with legal counsel for their responses and my own. If you have not yet submitted a response please do so. The NPRM is based on flawed data and should be either withdrawn or changed based on the additional date provided by multiple sources. The only way to get that done is by the Public (that means you) getting involved. If you dont feel comfortable writing feel free to plagiarize comments from others but inserting your information. The more comments there are the better the chance of this not becoming an AD.
 
The latest from EAA

 
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