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Thread: Aileron woes

  1. #1
    Kodiakmack's Avatar
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    Aileron woes

    Looking for some advice about rigging ailerons on the -12. We weren’t getting correct throw, and the rod end/bearings were corroded badly. So we replaced the rod ends and are trying to get rigged but are struggling.

    We’ve read everything we can find, and the erection manual seems way too easy. We’ve rigged the down 25 degrees with the rod/bearings, but to get the ailerons to be at trail or slightly low, and still get full throw (31 up 25 down correct?), we only have a couple threads in each side of the barrel on the balance cable, and the control cables on both sides are as tight as they will go. We don’t dare keep so many threads showing on the balance cable but can’t think of anything else to do. High praise to whoever is willing to call and explain or explain here.
    HAVE FUN. DON'T DIE.

  2. #2

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    Is it a new fuselage or an original?

  3. #3

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    Are the stops on the control torque tube set correctly to allow enough throw side to side?

  4. #4
    Kodiakmack's Avatar
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    Yes. I opened them wide open so that they aren’t interfering at all.
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  5. #5
    WhiskeyMike's Avatar
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    Quote Originally Posted by Kodiakmack View Post
    Looking for some advice about rigging ailerons on the -12. We weren’t getting correct throw, and the rod end/bearings were corroded badly. So we replaced the rod ends and are trying to get rigged but are struggling.

    We’ve read everything we can find, and the erection manual seems way too easy. We’ve rigged the down 25 degrees with the rod/bearings, but to get the ailerons to be at trail or slightly low, and still get full throw (31 up 25 down correct?), we only have a couple threads in each side of the barrel on the balance cable, and the control cables on both sides are as tight as they will go. We don’t dare keep so many threads showing on the balance cable but can’t think of anything else to do. High praise to whoever is willing to call and explain or explain here.
    are you sure about 25. I thought it was more like 15 down.

  6. #6
    Kodiakmack's Avatar
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    Click image for larger version. 

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  7. #7

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    Did you check the travel before you started working on it. Might have been off before you started. Start from scratch and right the wings then controls, may need new cables.
    DENNY

  8. #8
    Kodiakmack's Avatar
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    They were under to begin with. Control cables are an absolute last resort. Currently removing a link at the control horn and fabricating new slightly longer link.
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  9. #9
    skywagon8a's Avatar
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    Check that the bellcranks in the wing are in the neutral position before you start. Adjust the length of the pushrods so that the ailerons are in neutral. Set the travel stops last.

    If the bellcranks are not in the correct position in relation to the surfaces, the surfaces will not be in their correct position. You should not need to be modifying the airplane by changing the link.

    I haven't rigged a PA-12, this would be a standard procedure for any airplane with this type of system. If the bellcranks are not correct in neutral, you will tear your hair out wondering why!
    N1PA
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  10. #10
    Gordon Misch's Avatar
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    On my -12 the bottom of the stick where the aileron cables attach is extended by an inch or so. It's a bolt-on piece, and operates to give more cable travel for a given stick deflection. I don't recall offhand if that's factory, but the stick geometry is different between -12 and -18, presumably due to the greater control surface travels on a -12.
    Gordon

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  11. #11
    Kodiakmack's Avatar
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    Thanks for the advice. As for starting my with the horns centered, I feel like that’s essentially what one does by putting the horn at the physical stop with the aileron at it’s down spec, in this case 25 degrees. Much more accurate than trying to eyeball or measure ‘centered’. The ideal thing would be correct length cables. IA and Dad-Chanic both are on board with slight modification to make it work.
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  12. #12
    Bearhawk Builder's Avatar
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    Here's 3/4" per shackle.

  13. #13
    skywagon8a's Avatar
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    Quote Originally Posted by Kodiakmack View Post
    Thanks for the advice. As for starting my with the horns centered, I feel like that’s essentially what one does by putting the horn at the physical stop with the aileron at it’s down spec, in this case 25 degrees. Much more accurate than trying to eyeball or measure ‘centered’. The ideal thing would be correct length cables. IA and Dad-Chanic both are on board with slight modification to make it work.
    Not true. As the bellcrank rotates, the amount the aileron moves varies. It will only be correct when the stick, the ailerons and the bellcrank are all in the neutral position. This is adjusted by varying the length of the push rod from the bellcrank to the aileron.

    If the aileron is in neutral and the bellcrank is not, you will be forever messing with it. They must both be in neutral, then you adjust the stick to neutral. Then you set the stop limits.
    N1PA

  14. #14
    Kodiakmack's Avatar
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    Are the limits you’re talking about the stops in the wing the bell crank hits or the internal moveable stops?
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  15. #15
    skywagon8a's Avatar
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    If you have two sets of adjustable stops. The ones in the wing are set to the limits specified 31 & 25. The ones at the stick are set so that they are loose when the wing stops are met. This is to ensure you have full travel with the air loads on the ailerons. The cables "stretch" slightly against the air loads so the wing stops are the actual limits.
    N1PA

  16. #16
    behindpropellers's Avatar
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    Post a picture of the connection at the bottom of your torque tube.
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  17. #17
    cubpilot2's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    On my -12 the bottom of the stick where the aileron cables attach is extended by an inch or so. It's a bolt-on piece, and operates to give more cable travel for a given stick deflection. I don't recall offhand if that's factory, but the stick geometry is different between -12 and -18, presumably due to the greater control surface travels on a -12.
    ive seen a couple of PA12s converted to the 18 torque tube assembly to which they had overlooked adding the extension back on. It will change the travel.
    Ed
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  18. #18
    Kodiakmack's Avatar
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    We got it : ) and I can now see what you meant by ‘centering the horn’. Both our methods achieve the same thing, I just think we had a language separation.

    anyways...

    we put our new link in and tensioned/rigged until we got ailerons centered at stick centered with 31 up and 25 down +\- 0.4 degrees or so.

    happy days!
    HAVE FUN. DON'T DIE.
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    Whew
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  20. #20

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    While doing a ground up restoration there are literally hundreds of those “whew” moments, especially if it’s a 12. Scariest ones are cutting the last few new holes in an almost finished instrument panel, cutting down the windshield to fit the frame, and the biggest “whew” comes after weighing it and finding it’s 50 pounds lighter than you hoped for and the CG is right where you needed it to be.

    You made the right decision to post your questions here before you went off on your own. It tells you’ll do just fine
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  21. #21
    Kodiakmack's Avatar
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    I’m very glad we’re not doing a ground up. MT12 did that for me in 2012 ; ) but it was one of a few whew moments we’ve had doing this deep annual. That new panel is getting a few last holes next week and then we’ll be flying shortly after : ) I’m lucky to have my a&p as a dad with over 50 years in this world. He’s saved my back. And taught me so much this winter.
    HAVE FUN. DON'T DIE.
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