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Thread: SA0009 Release

  1. #21
    Junior Member MJD's Avatar
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    Default Re: SA0009 Release

    I hope so.



    Sent from my iPhone using Tapatalk
    Michael D
    N606RJ
    #3

  2. #22
    Senior Member carlconti's Avatar
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    Default Re: SA0009 Release

    Jim, Randy,

    I applaud your safety emphasis and your current efforts.

    As a physicist, Carbon Cub driver and engineer I am very curious about a few things.
    1. What are the flight modes that induce oscillation?
    2. How does the PA18 design differ from the CC11 design?
    3. What are the designs being tested?

    Pictures would be much appreciated.

    Carl

  3. #23
    Senior Member randylervold's Avatar
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    Default Re: SA0009 Release

    Quote Originally Posted by carlconti View Post
    Jim, Randy,

    I applaud your safety emphasis and your current efforts.

    As a physicist, Carbon Cub driver and engineer I am very curious about a few things.
    1. What are the flight modes that induce oscillation?
    2. How does the PA18 design differ from the CC11 design?
    3. What are the designs being tested?

    Pictures would be much appreciated.

    Carl
    Carl,

    I believe Eric Leaver, our Director of Engineering, will post shortly with answers to your questions.
    Randy Lervold

  4. #24
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    Default Re: SA0009 Release

    Thanks for asking Carl.
    I have the same questions.
    Bill

  5. #25
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    Default Re: SA0009 Release

    Some of you have asked for an explanation of the failure of the wires. We apologize that we have not responded immediately but we have focused out attention on finding a solution and making certain that parts can be shipped as soon as possible. Also, it is difficult to condense all the work that has been done into a few paragraphs.

    We initially suspected that the wires oscillated during certain phases of flight. Therefore, a flight test program was initiated with carefully instrumented wires. It included among other things 2g turns, stalls and dives to VFE and VNE. Tests were repeated with the wires set at different tensions. Tests were carried out on a CC11-100, a CC11-160, a CC11-160 EX that had a CC18 tail and a CC18. The latter was included because there is ample service history with the Piper PA-18 style of wire attachments that is used on the CC18 and it provided a baseline for the tests. The tests were carried out by an FAA DER that specializes in fatigue. A DER that specializes in flutter was also consulted.

    It was found that as the stabilizers deflect, they tend to bend the wires, putting stresses on the exposed threads. On the CC18, the design of the attachments of the wires to the stabilizers is different and deflections in the stabilizers are not as likely to produce bending and compression stresses in the wires. The new design that will be retrofitted in the fleet will be similar to the CC18’s- in fact there will be several parts in common.

    The phase of flight where the problem was most prevalent was during takeoff, immediately after the aircraft came out of ground effect.

    Our aim with the new design is to ensure that the cyclical stresses in the wires are comparable to the stresses experienced by the CC18’s wires.

    Finally, it is worth adding that during the investigations, the failed wires, wires taken at random from production aircraft, new wires from the stock room and wires removed from a Piper PA-18 were subject to laboratory analyses. The analyses included examination under a stereomicroscope, scanning electron microscope, energy dispersive spectrometric analysis and hardness testing. Observations of the threaded portions of all wires revealed no significant differences.

  6. #26
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    Default Re: SA0009 Release - Sport Cub

    Mr. Richard

    Yes, your airplane will have the retrofit completed at CubCrafters prior to delivery.

    Regards

    Jeff Glab
    Customer Support Manager

    Quote Originally Posted by deano View Post
    Can I assume that my plane #295 will be assembled with the fix in place. If not I will patiently await notification of the process.

  7. #27
    Senior Member carlconti's Avatar
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    Default Re: SA0009 Release

    Quote Originally Posted by eric.leaver View Post
    Some of you have asked for an explanation of the failure of the wires. We apologize that we have not responded immediately but we have focused out attention on finding a solution and making certain that parts can be shipped as soon as possible. Also, it is difficult to condense all the work that has been done into a few paragraphs.

    We initially suspected that the wires oscillated during certain phases of flight. Therefore, a flight test program was initiated with carefully instrumented wires. It included among other things 2g turns, stalls and dives to VFE and VNE. Tests were repeated with the wires set at different tensions. Tests were carried out on a CC11-100, a CC11-160, a CC11-160 EX that had a CC18 tail and a CC18. The latter was included because there is ample service history with the Piper PA-18 style of wire attachments that is used on the CC18 and it provided a baseline for the tests. The tests were carried out by an FAA DER that specializes in fatigue. A DER that specializes in flutter was also consulted.

    It was found that as the stabilizers deflect, they tend to bend the wires, putting stresses on the exposed threads. On the CC18, the design of the attachments of the wires to the stabilizers is different and deflections in the stabilizers are not as likely to produce bending and compression stresses in the wires. The new design that will be retrofitted in the fleet will be similar to the CC18’s- in fact there will be several parts in common.

    The phase of flight where the problem was most prevalent was during takeoff, immediately after the aircraft came out of ground effect.

    Our aim with the new design is to ensure that the cyclical stresses in the wires are comparable to the stresses experienced by the CC18’s wires.

    Finally, it is worth adding that during the investigations, the failed wires, wires taken at random from production aircraft, new wires from the stock room and wires removed from a Piper PA-18 were subject to laboratory analyses. The analyses included examination under a stereomicroscope, scanning electron microscope, energy dispersive spectrometric analysis and hardness testing. Observations of the threaded portions of all wires revealed no significant differences.
    Thank you. Have you concluded, subject to further testing, that the solution will be to eliminate the bending moment with a swiveling attachment such as on the PA18?

  8. #28
    Senior Member randylervold's Avatar
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    Default Re: SA0009 Release

    Quote Originally Posted by carlconti View Post
    Thank you. Have you concluded, subject to further testing, that the solution will be to eliminate the bending moment with a swiveling attachment such as on the PA18?
    Eric may want to elaborate, but in essence yes. Verification though is why there will be an additional round of testing next week. We want this issue resolved permanently.
    Randy Lervold

  9. #29
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    Default Re: SA0009 Release








    • Just thinking, looking at this photo above, the hinge line for the elevator is just aft or off center of the rear spar for the stablizer. And the rear spar is the center line hinge point when the stab goes up and down when you trim. So as you trim the stab up the rear spar rotates CCW and the wire/elevator pin goes down pulling harder on the top wire and vise versa when the stab goes down.





      All the airplanes designs from the 1920s, 30s and 40s that had an adjustable tail for trim had the load attach point for the wires on the center of the stabilizer rear spar, which is the center hinge line for the stab. So that when the front of the stab is going up and down with trim changes it does not move the location of the wire attach point. The Carbon Cub moved the wire attach point to the stab/elevator hinge pin. That looked like a simple solution when I first looked at it but now I think it's going to be a problem area thats going to have to be redesigned by CC. I'm no engineer, what do you think?



      Glenn
    Last edited by Cubdriver2; 11-26-2013 at 03:11 PM.

  10. #30
    Senior Member cityrancher's Avatar
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    Default Re: SA0009 Release

    Quote Originally Posted by Cubdriver2 View Post







    • Just thinking, looking at this photo above, the hinge line for the elevator is just aft or off center of the rear spar for the stablizer. And the rear spar is the center line hinge point when the stab goes up and down when you trim. So as you trim the stab up the rear spar rotates CCW and the wire/elevator pin goes down pulling harder on the top wire and vise versa when the stab goes down.





      All the airplanes designs from the 1920s, 30s and 40s that had an adjustable tail for trim had the load attach point for the wires on the center of the stabilizer rear spar, which is the center hinge line for the stab. So that when the front of the stab is going up and down with trim changes it does not move the location of the wire attach point. The Carbon Cub moved the wire attach point to the stab/elevator hinge pin. That looked like a simple solution when I first looked at it but now I think it's going to be a problem area thats going to have to be redesigned by CC. I'm no engineer, what do you think?



      Glenn
    This makes more sense than any other post so far. Thanks for taking the time to put it together. I can see the "fix" as fairly complicated. Would the factory care to comment on these ideas.

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