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Thread: counter balance spring

  1. #1

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    counter balance spring

    Just starting a smith cub. I notice on this kit it uses 1 spring on the elevator counter balance but in the old PA-18 book it shows 2 springs. What are you guy doing out there 1 or 2?

  2. #2
    Ruidoso Ron's Avatar
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    Kevin,
    Most SC's use only one spring also. Two, if for seaplane.

  3. #3
    Steve Pierce's Avatar
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    Kevin, Like Ron said most are only using one spring. There is a Piper Service Bulletin on it's removal in the Piper Service Bulletin, Memos and Instructions book that Univair sells. I think it was originally installed to meet a criteria for the military.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  4. #4
    Ruidoso Ron's Avatar
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    Quote Originally Posted by Steve Pierce
    Kevin, Like Ron said most are only using one spring. There is a Piper Service Bulletin on it's removal in the Piper Service Bulletin, Memos and Instructions book that Univair sells. I think it was originally installed to meet a criteria for the military.
    yeah, that's what I meant.

  5. #5
    Cajun Joe's Avatar
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    Ron/Steve,
    Seriously now, why two springs on a seaplane?

    Jl

  6. #6
    Ruidoso Ron's Avatar
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    Quote Originally Posted by Cajun Joe
    Ron/Steve,
    Seriously now, why two springs on a seaplane?

    Jl
    Because most of them are so seriously over gross and out of CG that it takes another spring to help move the controls.

    Actually, Steve tells me that it had to do with pitch dampening during the certification process. Not sure why some required it, and some didn't.

  7. #7
    Steve Pierce's Avatar
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    Well I looked it up. Parts manual calls out the lower bungee for PA18-105 only and Piper Service Letter No. 150 allowed it to be removed. It also states that it was originally designed for to meet adverse load requirements of Military Aircraft for the United States Airforce and it was carried over to the Commercial airplanes in production. There were complaints of the stiff elevator and Piper's engineering dept. approved the removal.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  8. #8

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    counter balance spring

    I am building a Sport Trainer , PA-11 style and I am still wandering if the elevator spring is required. The engine is a C-90
    Thanks

  9. #9
    Steve Pierce's Avatar
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    I would leave it out if it were me. I have never seen the springs in a J-3 or a PA11.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    counter balance spring

    Thank you Steve for your quick reply.

  11. #11
    T.J.'s Avatar
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    Woops,
    gotta disagree with my old buddy Steve.
    My PA-11 broke a bungee spring a couple years ago. I couldn't throw enough crap in the rear baggage compartment to make it fly level. Trim full nose up, and the dang nose still wanted to go down.
    I would guess that just the weight of the elevators pulling down, makes the nose want to go up?
    Anyway, I replaced the bungee spring and the old 11 flew fine.

  12. #12
    Steve Pierce's Avatar
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    Interesting. I have only worked on two PA11s and they didn't have the springs. I took it out of the L18 and couldn't tell a difference. From what I can tell the bungee pulls the elevator up when you trim nose up. I know a couple of PA18s who don't run it and don't see any adverse effects. You got me wundering now TJ. I gotta go find that post Kase made on the subject a while back.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  13. #13
    Steve Pierce's Avatar
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    Here is the old thread with some good information.

    http://www.supercub.org/phpBB2/viewt...=14227&start=0
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  14. #14
    mvivion's Avatar
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    For what its worth, the CC-18-180 has some skukum springs and/or bungees attached to the elevator. Feels like a Husky, stick force-wise.

    I'm guessing the 2300 GW required that.

    MTV

  15. #15
    T.J.'s Avatar
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    Checked my PA-11 parts book......The elevator balance bungee is installed.
    I'm not sure I understand all that I know about this.
    I've also seen a couple Cubs without the bungee. The owners didn't notice anything.
    My 11 is basically stock, weights 750# or there abouts. With nothing in the rearseat/baggage area, it would definitely be a job to fly the thing without the bungee.

  16. #16
    JP's Avatar
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    Quote Originally Posted by Steve Pierce
    Interesting. I have only worked on two PA11s and they didn't have the springs. I took it out of the L18 and couldn't tell a difference. From what I can tell the bungee pulls the elevator up when you trim nose up. I know a couple of PA18s who don't run it and don't see any adverse effects. You got me wundering now TJ. I gotta go find that post Kase made on the subject a while back.
    I'll have to go that post to refresh my memory, too. I put the spring in during the rebuild and the elevator is more or less neutral, moving as trim is cranked in...stick pressure does increase, though, as I pull back. It does trim easily, though.
    JP Russell--The Cub Therapist
    1947 PA-11 Cub Special
    www.bloomerrussellbeaupain.com

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