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Thread: Rudder service bulletin 1379 2nd December 2022

  1. #1

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    Rudder service bulletin 1379 2nd December 2022

    What do we think of this? Basically mandates replacement if pre 1974 or otherwise found to be of 1025 steel. Have there been failures to cause this?


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  2. #2
    jrussl's Avatar
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    This looks like complete BS. A few PA-12’s with rudder mounted beacons break their rudders and now all fabric Pipers have to replace their rudders. What an overreaction. What do all the experienced folks that have been wrenching on these birds for most of their lives have to say about this? How many cracked rudders are you seeing?

  3. #3
    Gordon Misch's Avatar
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    I don't see PA-12 listed in the models affected portion of the SB. Maybe because Piper no longer owns the PA-12 type certificate.
    Last edited by Gordon Misch; 12-06-2022 at 12:23 AM.
    Gordon

    N4328M KTDO

  4. #4
    nanook's Avatar
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    The PA-12s had PA-18 rudders, if you have a 60 - 70 year old rudder…you might want to replace it…
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  5. #5
    aktango58's Avatar
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    Metal fatigue? Never happens! If it did, it would give you lots of warning...

    NOT!
    I don't know where you've been me lad, but I see you won first Prize!
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  6. #6
    BC12D-4-85's Avatar
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    Piper's just protecting their interests and TCDS via a SB for commercial ops. In the meantime is the FAA in NPRM mode yet? The tech data I read for the examined tubes indicated compromised metal was present, not factory new 1025. If it were mine under Part 91 ops I'd look at the rudder tube area above the upper hinge for reduced thickness and potential loss of strength.

    Gary
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  7. #7
    cubdriver2's Avatar
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    Blasted and recovered my 82 year old J4 rudder a few years ago. Looked perfect

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  8. #8

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    Steve Pierce, what do you think?

  9. #9

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    It doesn't show yet on the Piper website. Anyone knows where to find the document?
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  10. #10
    skywagon8a's Avatar
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    If the rudder is the original, it IS 1025 steel.

    Drawing 40622
    Attachment 63841Attachment 63840http://www.supercubproject.com/drawings/pdfs/A3310113.pdf
    The rudder post is the -3 part. the description of materiel is 7/8 X .035 X 53-5/16 #1025 steel tube
    N1PA

  11. #11
    Steve Pierce's Avatar
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    https://www.supercub.org/forum/showt...SB-Notice-2252

    Somewhere is a thread on this. Saw one of the rudders at Oshkosh in the NTSB booth. I believe all the failures had rudder mounted beacons
    Steve Pierce

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  12. #12

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    You know this is a BS CYA SB when even the non balanced non electrical equipped J-3 rudder is listed.

    is this coming from the PA-12 on floats a couple of years ago with the rudder bent over with the light on top?

    Not many J-3’s with a light attached to the top of the post either.
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  13. #13
    BC12D-4-85's Avatar
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    A local shop is paying particular attention to that tube and rudder hinge bushings. Side pressure is applied to the rudder top to see if it's weakend. Loose bushings indicating unusual wear are replaced. Not sure of the eventual outcome.

    Gary

  14. #14
    cubpilot2's Avatar
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    https://www.supercub.org/forum/showt...ht=Rudder+post

    This links to lots of earlier discussion. The first post has a link to the FAA investigation with photos of rudder failures.

    I know the guy that had the failure on his PA 14. Scary experience!

    I put an internal 4130 sleeve in mine during the rebuild.
    Ed

  15. #15

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    It’s a service bulletin, not an AD. That sounds like lawyers advised Piper to cover themselves given the known failures. These planes have lasted longer than they were designed for. Another point, similar to Cessna’s SID, this bulletin isn’t required for the majority of the affected airplanes. It simply establishes that the manufacturer has acknowledged a problem and recommended a solution.
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  16. #16
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    Quote Originally Posted by stewartb View Post
    It’s a service bulletin, not an AD. That sounds like lawyers advised Piper to cover themselves given the known failures. These planes have lasted longer than they were designed for. Another point, similar to Cessna’s SID, this bulletin isn’t required for the majority of the affected airplanes. It simply establishes that the manufacturer has acknowledged a problem and recommended a solution.
    ”these planes have lasted longer than they were designed for “, a simple statement to justify a 4130 powder coated new rudder. Especially if yours is not original and has been changed with a tube to support beacon or whatever light attachment. That’s the common denominator for failures. Cost should not be a factor as well.
    IMO,
    JK

  17. #17
    Steve Pierce's Avatar
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    Interesting that I cannot find this service bulletin anywhere but here. Not on Piper's website. Where did you get it?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  18. #18
    Gordon Misch's Avatar
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    Quote Originally Posted by nanook View Post
    The PA-12s had PA-18 rudders, if you have a 60 - 70 year old rudder…you might want to replace it…
    Yes, maybe, subject to IRAN. Mine was carefully inspected a couple years ago. It's never had a beacon on top. I agree with the concern.
    Gordon

    N4328M KTDO

  19. #19
    BC12D-4-85's Avatar
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    Those potentially affected by this might want to read the NTSB's Docket regarding the failed PA-12 rudders. Pay particular attention to those developed by the Materials Lab and Structures Group. My take is there's not much strength reserve with 1025 tubing compared to 4130, especially when compromised by surface corrosion or vigorous media blasting.

    Gary
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  20. #20

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    Quote Originally Posted by Steve Pierce View Post
    Interesting that I cannot find this service bulletin anywhere but here. Not on Piper's website. Where did you get it?
    My engineer in Australia found it. I'll ask him.

  21. #21
    Waldo M's Avatar
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    Received this SB from Piper today via e-mail. I'm not aware of any issues with J-3 and PA-11 rudders and none are mentioned in SAIBs for the type certificate [A-691]. The rudder on my airplane was bead blasted, epoxy primed, and inspected before covering in 2013. I won't be complying with this service bulletin.

    I wonder if new rudders for J-3s and PA-11s made by Univair and others use 4130 steel. My guess is that to comply with manufacturer specs for a PMA approved part, they are made from 1025 steel, but I emphasize that is a guess.

  22. #22
    BC12D-4-85's Avatar
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    Here's why the NTSB in their rudder loads study concluded 4130 steel is preferred over 1025 for this application. Ftu mentioned below is the ultimate tensile strength of the material. Estimated propeller effects on rudder post fatigue were minimal and worse at idle. Both steels work...one is more resistant to surface contamination and bending stress:

    "9.0 Conclusions
    1. The material properties of AISI 1025 and AISI 4130 steel show that AISI 4130 has, in some cases, somewhat better corrosion resistance.
    2. The ultimate tensile strength and endurance limit of AISI 4130 steel is 64% higher than AISI 1025 steel.
    3. The tensile yield strength of AISI 4130 steel is 94% higher than AISI 1025 steel.
    4. The calculated bending stress in the rudder post due to the certification maneuvering loads are 28% of Ftu on average for 1025 steel and 17% of Ftu on average for 4130N steel representing a 50% increase in the margin of safety for 4130N steel with respect to the endurance limit.
    5. The calculated bending stress in the rudder post due to the certification gust loads are 33% of Ftu on average for 1025 steel and 20% of Ftu on average for 4130N steel representing a 76% increase in the margin of safety for 4130N steel with respect to the endurance limit.
    6. The effect of a stress concentration due to a corrosion pit is more critical for 1025 steel increasing the bending stress in the rudder post above the endurance limit for much smaller pit sizes.
    7. The propeller blade pass frequency is significantly higher than the natural frequency of the upper rudder post."

    Gary
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  23. #23

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    Posted this at the SWP site thought I should share:



    I think some interested parties shoos work up an AMOC (alternate means of compliance)


    -incorporating a sleeve of 4230 tubing inserted through the top and extending past the upper hinge 8”


    -chaise”the rudder post with an aproropret tool to get clean and smooth the inside of the bore so the nesting tube will clear without excesse force.


    -fish mouth lower end of doubler tube 3” to remove localized stress concentration.


    -swab the interior with epoxy primer


    - insert doubler tubing with 2226 structural adhesive or equivalent.


    Something like this.


    couple of observations both the pa12 and pa14 that failed or what 1948-ish aircraft? What are the odds both have original rudders, I would have to say vary slim but…


    Both aircraft were on floats during failure and float ops rattle the **** out of the empanage.




    Rocket
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  24. #24

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    I’ve never seen an issue with a 65 HP J-3 Cub. If this is the case, then might as well replace the whole airframe, since the sky is falling.

  25. #25
    BC12D-4-85's Avatar
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    Float ops require use of rudder, maybe more than other landing gears? They can be directionally or longitudinally unstable when on them in my experience (they can create adverse yaw from float surface area in front of CG). Often additional fins or fillets are installed to help, as well as wing dihedral or the lack thereof being critical. My PA-12 would go play on its own unless constantly corrected. Other float aircraft felt neutral to positive stability. Perhaps the rudder on some planes or some gears gets more of a workout which eventually fatigues the metal?

    Gary

  26. #26
    skywagon8a's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    My PA-12 would go play on its own unless constantly corrected.

    Gary
    Did your PA-12 have the required ventral fin installed? This is called for on the TC.
    N1PA

  27. #27
    BC12D-4-85's Avatar
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    No fin until the end of ownership. We discussed this some privately...I had those useless springs on the lift handles cables to the rudder. I did try a borrowed ventral fin and it helped but sold the plane before much more trial. The NTSB seems to be fishing in #22 for an explanation of the rudder failures. Corrosion, surface imperfections, top beacons, 1025 strength margins vs 4130, material fatigue, etc.

    I'm not a materials engineer, but as a former owner of several Piper 1025 rudders I'd now ask how about doing (or estimating) some dynamic stress testing to failure for the components (versus only the static loads CAR 3 required). Figure out what loads rudders experience (they hint at that via their rudder area affected and area centroid vs rudder post spacing discussion). Test them to failure using the various metal conditions noted plus additional loads from beacons. There's something to be learned here if someone really gives a ****. It's easier just to SB or AD the problem away.

    Gary
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  28. #28

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    When the NPRM gets posted, be sure to comment. As with the Champ spar AD, there is a chance that lower horsepower aircraft may be subjected to less rigorous scrutiny.

  29. #29

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    Anyone purchased 70% nitric acid for the Piper Service Bulletin 1025/4130 determination test?

  30. #30

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    Mine is 4130, tested with 70% nitric (which was a hassle to get) today. The drop of nitric is actually on the tube in the pictureClick image for larger version. 

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  31. #31
    Steve Pierce's Avatar
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    Quote Originally Posted by BritishCubBloke View Post
    Mine is 4130, tested with 70% nitric (which was a hassle to get) today. The drop of nitric is actually on the tube in the pictureClick image for larger version. 

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    What year is your Super Cub? Any history of rudder replacement? Accidents?
    Steve Pierce

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    Will Rogers

  32. #32

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    Can you give details on your internal sleeve installation? Tube O.D. X wall thickness? How installed, etc.
    Thanks

  33. #33
    Steve Pierce's Avatar
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    The original rudder post is 7/8" OD x .035" wall 1025 mild steel. If you clean up some of the weld slag on the inside of the rudder tube you can slide a 3/4" OD 4130N tube inside all the way to the top. I would think that .035" wall thickness would suffice more than adequately. NTSB Report With Data
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  34. #34

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    Regarding rudder post liner tube

    Steve,
    Thank you for that information. Wonder why Piper and NTSB did not propose that solution. If a 7/8” 4130 tube has that much safety margin, surely a 3/4” 4130 liner tube will get you home if the 1025 tube fails.
    Don

  35. #35
    BC12D-4-85's Avatar
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    If available be sure to suggest that sleeve method as an alternative means of compliance if a NPRM is developed for Part 91.

    Gary

  36. #36
    Waldo M's Avatar
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    I wonder if new rudders for J-3s and PA-11s made by Univair and others use 4130 steel. My guess is that to comply with manufacturer specs for a PMA approved part, they are made from 1025 steel, but I emphasize that is a guess.[/QUOTE]

    My guess was wrong. I just spoke with Jason at Univair. He stated that all Cub rudders made by Univair have used 4130 chromemoly steel since the mid 1970s.

  37. #37

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    Yes, Univair states that they use 4130 tubing on their website. Has anyone found a source for small quantities of 70% nitric acid?
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