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Thread: Tailwheel Shimmy and Spring Arch

  1. #21
    Administrator Steve Pierce's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    Yes but you will need some longer AN4-15A bolts for the bracket, AN7-21A spring to tailwheel and AN6-26A spring to fuselage. Your lengths may vary slightly.

  2. #22
    McDaver63's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    I purchased and installed the ABW PA-18 tail springs and and bracket on my PA-20/22 and had no problems. I did have to use different bolts for the FWD and bracket attach bolts. Not sure the size but Steve is probably right on. They so far have been working great.


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  3. #23
    andya's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    Link errored out for me
    "Progress is our most important problem"

  4. #24
    Jim Hann's Avatar
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    Default Recommended Tailwheel Spring for PA-22/20

    From another tail spring thread:
    Quote Originally Posted by Steve Pierce View Post
    The Husky spring has a different arch and requires a shim at the tailpost. We used the Husky spring until they came out with the PA18 spring. It is 3 leaves that are individually thicker than the 4 leaves that Piper used. They are 1 3/4" wide and come with a different attach bracket to do away with the original "U" shaped bracket. The spring is now approved on the PA18 and using AC23-27 substitution of parts on Vintage aircraft should be simple.
    Steve, which spring from ABI? I don't see any approvals listed for the PA-18 single hole spring. I'll ask my IA about the 23-27 substitution.

    I've been looking at my saggy tail wheel spring while I've been working on the wings and I'm ready to deal with it once I've got the paint on the fabric.

    Thanks!
    Last edited by Jim Hann; 09-11-2014 at 12:48 AM.
    1957 PA-22/20 "Super Pacer" based 1H0
    Lifetime EAA member
    Vintage Aircraft Association member
    Lifetime EAA Chapter 32 member


  5. #25
    Administrator Steve Pierce's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    Call them and ask for Jason. I intalled them before they were approved for the PA18 as a owner produced part. Taken off too may springs that have lost their arch and too many wrecks where it was a huge contributing factor,

  6. #26
    Jetfever's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    Quote Originally Posted by Steve Pierce View Post
    Call them and ask for Jason. I intalled them before they were approved for the PA18 as a owner produced part. Taken off too may springs that have lost their arch and too many wrecks where it was a huge contributing factor,
    Steve! This is the first I have ever heard about this!!!

    How does a lost arch/ sagging T/W spring contribute to a wreck?

    Thanks, Steve M.

  7. #27
    Jim Hann's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    Steve,

    The springs aren't approved. Isreal (sp?) explained it just like you did. I'll check with my IA on his feelings on the owner produced part, I know STL FSDO can be a PITA. If we can't do it I'll get mine re-arched for now and plan a trip to Graham! Thanks for the information!

    Jim
    1957 PA-22/20 "Super Pacer" based 1H0
    Lifetime EAA member
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    Lifetime EAA Chapter 32 member


  8. #28
    JrBirdman's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    Here's how I think the tailspring arch and caster angle can contribute to a wreck as Steve P. pointed out. On my way out to Calif in June maybe 300 lbs under gross weight I landed in Spanish Fork UT on a 100 degree day and 4500 foot elev. Higher touchdown speed then my tailwheel was used to and much heavier weight also. It immediately went into a VIOLENT TW shimmy. So bad I thought at first I had a flat main tire or worse. It broke a steering chain and threw a steering spring out in the weeds. Luckily the plane tracked straight with light differential braking.
    I was using the Univair 1 1/4 inch leaf springs that had been re-arched 12 years ago. Age, weight, bad-landings, spring relaxing all contributed to the caster angle going past the magic level with the ground point.
    I rebuilt the tailwheel : it looked like not having the swivel bolt tight enough allowed the bottom thrust washer to jump the dowel pin and also all the pins on the thrust plate were sheared, and it was over greased in the head portion where the thrust plate and phenolic washer live. A no-no as Steve at Steve’s aircraft pointed out. I tightened all the bolts, and took the play out of the leaf adapter plate. I also made a temporary shim to get the caster angle back close to level when loaded.
    It worked OK for about 12 more landings, but on the way back to Georgia again heavily loaded I landed for fuel in South Dakota on a black top runway and at about 35 MPH the tailwheel jammed at an angle and even with full opposite brake (read skid) the old girl headed into the grass. But luckily it was low-speed enough no damage. I kept going thinking I would just wheel land and then brake hard when the tail came down. That worked OK on the next landing but that evening at Lee’s Summit MO it happened again. One second I was tracking down the centerline the next second the old girl was headed for the weeds. Again full opposite rudder and brake had minimal effect. It was like the tailwheel had jammed sideways. This time it was at a higher speed and I was really thrown sideways and took out a runway light in the process. I was very lucky not to fold a gear leg or drag a wing tip.
    They are a great bunch there at Lee’s Summit. They loaned me a Scott TW off a wrecked Citabria, I put some washers under the leafspring shim, threw out half my survival and camping gear and other stuff to lighten the load and made it home in 2 more landings. Wheel landings with firm braking.
    The moral is like many have posted here over the years…that Scott TW is a nice unit but it better be maintained right and that caster angle has to be aggressive, especially if you are loaded down. Once you’ve entered the VIOLENT SHIMMY regime it can tear up the innards of the TW, and you can be in for an ugly ground loop.
    Last edited by JrBirdman; 09-17-2014 at 06:21 PM.

  9. #29
    Administrator Steve Pierce's Avatar
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    It is also harder to steer when the angle is negative.

  10. #30
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    Default Re: Recommended Tailwheel Spring for PA-22/20

    Quote Originally Posted by Steve Pierce View Post
    It is also harder to steer when the angle is negative.
    Or discover you can't steer on an asphalt runway....did that last year in Palmer. Had to use power, elevator full down-up-down to try to bounce the tail) 60 pound bag of sand in the back) and brake. Once off the asphalt onto the ice....nada. Had to shut down and walk the tail around. Flew up to Willow...Eddie installed a Pawnee tail spring with a stack of shims to get the correct angle... Steered great after.
    Mark M.


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