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Thread: Strut Failure, Fatal Crash

  1. #1
    Steve Pierce's Avatar
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    Strut Failure, Fatal Crash

    I just punch tested a set of Tri-Pacer struts and installed freshly tested forks. Huge PITA. From the pictures of the strut in this accident I doubt it was ever treated.
    https://www.tbnewswatch.com/local-ne...photos-1639172


    OTTAWA, Ont. — The Transportation Safety Board of Canada has issued a safety advisory following its investigation of a fatal plane crash north of Kenora in March.
    The pilot of a ski-equipped single-engine aircraft died after it went out of control and struck the frozen surface of Snowshoe Lake, where he owned a hunting and fishing lodge.
    According to the TSB, the crash occurred while the pilot was making a low pass over the lake to advise lodge guests of his arrival.
    An employee who was a passenger in the plane died in hospital six days later from injuries suffered in the collision.

    Investigators inspected the airframe at the site and discovered a separation in the strut assembly caused by excessive corrosion.
    The U.S. Federal Aviation Administration had issued a directive in 2015 requiring the inspection of potentially corroded strut assemblies on several different models of Piper aircraft.
    The TSB said it could find no record such an inspection was conducted on the plane that crashed at Snowshoe Lake.
    However, it discovered during its own lab tests that one of the methods prescribed by the FAA for checking for corrosion—a "punch test" followed by an inspection for any resulting dents—produces inconclusive results.
    The TSB is now recommending that Transport Canada review the testing procedures that are currently prescribed to ensure their reliability.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  3. #3
    Steve Pierce's Avatar
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    Here is how they concluded the punch test was not a good indicator of internal corrosion. I am and always have been a fan of sealed struts.
    http://www.bst-tsb.gc.ca/eng/securit...026-D1-A1.html
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  4. #4
    cubdriver2's Avatar
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    We punched struts 20 years ago after the AD came out. It was almost impossible to not do damage to the strust. Damage that would encourage future corrosion. Never did it again. Local IA took the small bulb from a minimag flashlight and soldered it onto small speaker wire and both fit up into the hole in the strut when the fork was removed. In a darkened hangar you could see what was inside the strut. I know the AD says to punch them but never understood how punching on the outside was going to show corrosion starting on the inside? Not to mention that your probably work hardening the strut with every push?
    Cub Club recommend the light test over punching a long time ago. Tough decision, test legal or smart?

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  5. #5
    RaisedByWolves's Avatar
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    Seems to me that the couple grand in parts is money well spent


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  6. #6
    www.SkupTech.com mike mcs repair's Avatar
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    Never was a fan of punch test either. But who runs old style struts anymore?? The cost of X-ray and labor adds up.... obviously those weren’t xrayed


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  7. #7
    WhiskeyMike's Avatar
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    Decades ago, this weak point was known after several failures. An early fix was the STC'd Bradley Safety straps, made by Ben Bradley. It involved drilling, and welding bushings into the struts and bolting on external straps. Worked well. This was before the new struts. Back in the late 1980's I advised a good friend about this but they rebuild a stock J-3, not wanting to modify the looks, and he lost his life in it. My 2 cents is, if it doesn't have sealed struts - don't fly it.

    I'm also constantly on the look out for people standing or leaning heavily on the struts. 200 lbs. sideways against the threads isn't a great idea and stressing metal repeatedly over the years can't have a happy ending. There's no emergency procedure for wing loss other than a parachute. There's a simple solution. What's your life worth?
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    cubdriver2's Avatar
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    The ones on my J4 are over 50 years old. I beadblasted them and inspected the inside and they looked almost new inside. Painted and oiled. I have some original 1940 J4 struts that hard been bent and replaced that came with a set of wings I bought for parts. Struts had sat on the dirt floor of a shed for years. Outside of struts were badly rusted. I cut them open and the inside had almost no corrosion.
    I think the important thing is to at least look inside the struts every couple years

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  9. #9
    cubdriver2's Avatar
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    I notice that Carbon Cubs are still built with 7/16" forks. Different strut design but still small forks

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  10. #10

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    Piper wing struts and Beechcraft wing bolts. Never skimp.

  11. #11
    40m's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    I notice that Carbon Cubs are still built with 7/16" forks. Different strut design but still small forks

    Glenn
    Yah but they're carbon fiber

    From Genesis: "And God promised men that good and obedient wives would be
    found in all corners of the earth."

    Then he made the earth round... and He laughed and laughed and laughed!
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  12. #12
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by WhiskeyMike View Post
    .

    I'm also constantly on the look out for people standing or leaning heavily on the struts. 200 lbs. sideways against the threads isn't a great idea and stressing metal repeatedly over the years can't have a happy ending.
    They use to haul 55 gallon drums on the strut with a piece of plywood against fuselage and maybe under drum too?


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  13. #13

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    I believe Carbon cub struts are aluminum. If carbon fiber, I'm not riding in one! End broke off my carbon fiber fly rod when I just shook it!

  14. #14
    mvivion's Avatar
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    Goes to prove the old saw: “The cheapest thing in an airplane? The pilot.”

    MTV

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    cubdriver2's Avatar
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    Quote Originally Posted by mvivion View Post
    Goes to prove the old saw: “The cheapest thing in an airplane? The pilot.”

    MTV
    Yup, that would be me, and I'm quite proud of it. I never made more then 35k a year but have managed to own 5 airplanes over the last 25 years, 2 at the moment. 4300+ Cub hours, 1100+ of that on floats. 600+ on skis. I don't eat lunch most days so I have a couple bucks for gas. I wouldn't change a thing, anybody can fly with money.

    Glenn
    Last edited by cubdriver2; 08-16-2019 at 10:20 PM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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    algonquin's Avatar
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    I’m afraid I’m bad about this but I won’t sign off any pipers with the old struts. The only reason is the liability involved should a old style strut fail. It’s truly a shame we have gotten to this point, but one much protect there families also.
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  17. #17
    skywagon8a's Avatar
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    Quote Originally Posted by algonquin View Post
    I’m afraid I’m bad about this but I won’t sign off any pipers with the old struts. The only reason is the liability involved should a old style strut fail. It’s truly a shame we have gotten to this point, but one much protect there families also.
    Yup, It is a wonder that all who have sat through a talk by the FAA's legal department at an IA meeting haven't just turned in their IA tickets on the table and walked out.
    N1PA
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  18. #18
    RaisedByWolves's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Yup, It is a wonder that all who have sat through a talk by the FAA's legal department at an IA meeting haven't just turned in their IA tickets on the table and walked out.
    I have considered it. But I’m to stubborn. But hey, they are “promoting safety”


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  19. #19

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    Promoting safety and legal liability are not really related. If you don't have some form of liability insurance you are hanging it out no matter how careful you are. They will sue you if the crash was pilot error, and you will win, but the legal fees may cost you your business.

    If you don't sign airplanes with legal struts to avoid liability, just remember how many Cubs crash, and what percentage of that is in flight strut failure. Not including this one, which may have been a result, not a cause, we think there has been maybe four?
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  20. #20
    Steve Pierce's Avatar
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    I shoulda got my **** together sooner and been an airline pilot and then a mechanic so I could have something to be sued for.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    txpacer's Avatar
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    Then you could've rubbed down with unguent and called yourself the "Salvey Aviator"
    Quote Originally Posted by Steve Pierce View Post
    I shoulda got my **** together sooner and been an airline pilot and then a mechanic so I could have something to be sued for.
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