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Thread: Tri Pacer elevator rigging

  1. #1

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    Default Tri Pacer elevator rigging

    Are the specs for rigging the elevators on the Tri Pacer to be measured with full trim in either direction? Is it measured from the horizontal stab or level?

  2. #2

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    With trim "zeroed", but there are travels required on the stab, too. After leveling the a/c per the TCDS, you place a bubble level across the forward and rear stabilizer tubes. Note that "Stab level, or zero" is referenced to the CENTERLINES of those tubes...AND they are different diameters. Shimming the aft tube one-half the difference in diameter difference (under the spirit level) is required. This gives you the "zero angle" for the stab, and the travels are measured from this "zero" and must be within spec. If this is not obtainable, then the chances are that the trim jackscrew yoke is installed upside down. This DRASTICALLY affects slow speed operation because of not being able to trim the stab enough, and MUST BE corrected.

    After this is done, reset the stab to zero for the elevator swing. The fact is that the elevator WILL HAVE the correct throws IF the elev horns contact the hard stops inside the tail both nose up and nose down. The nose up stop is a rearward extending tab on the lower cable, that hits a short piece of steel welded across the upper longerons. The horns shall contact the hard stops in the tail JUST BEFORE the yoke contacts the secondary stops under the panel (on the little square tube that guides the yoke swing). Ninety five percent of shortwings are flying around after recover/cable replacement incorrectly rigged. That's a crying shame... getting the cable rigging RIGHT can be a bit frustrating for the first timer to the task, and too many people have a "ta hell with it, that's good enough" attitude this deep into the project. That's no excuse. Most of the complaints that "there isn't enough elevator in these airplanes" are pure bunk! The rigging is incorrect! These are WONDERFUL flying airplanes when rigged correctly, and are one of the best landing airplanes ever built, when correctly rigged.

  3. #3

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    Got it, Thanks. If you rig at the up and down stops everything else comes out right.

  4. #4

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    Uhhh, You are grossly compacting my description, and the way you have put it is indeed concise...but the way you are putting it leaves much to be desired. No, your summation -in it's brevity- is incomplete and incorrect.

    I'm sayin'...you have to rig the stab first. If and when you have those throws, you re-zero the stabilizer, make sure your "zero" is correct on that, and then you check your elevator travels off that zero (which MUST be set up with the aircraft correct "leveled"; you can't do this with a fancy digital level and the tail sitting any old place. You get the airplane leveled and THEN you check the swing of the elevators "off" the zero stab setting.). The elevator is "zeroed" when it is in perfect trail with a properly zeroed stabilizer. You don't simply ensure you are hitting the stops and call it "a job". Someone MAY HAVE left out the appropriate part number part that hits the nose down stop, or any other of numerous "unexpected" issues. "Correcting" any out of limit inaccuracies may go WELL beyond simply turning a turnbuckle barrel a few times. You MORE THAN LIKELY will have to get into the adjustable fork up front, between the MLGs (above the belly panel) forward of where the cables attach to their forward bellcrank, and there is even the possibility that the elevator cables (which -contrary to popular misconception- are NOT the same length!) will be found to be switched. Not a definite, but this IS a very common mistake.

    Sorry, but do not try to oversimplify. My description may appear a tad bit verbose, but it is COMPLETE in what you HAVE TO do, while you "consolidation" quite easily can come off without doing any of the things that you are checking for!. Just "making the elevator hit the stops and everything else comes out right" is definitely NOT what you are looking to accomplish. Saying that misquotes my seemingly verbose description and makes it effete, whereas what I wrote is how you have to proceed. That would be EXACTLY why most shortwings are not rigged correctly when it comes to control surface deflections...someone misinterprets the instructions and cuts all the way across the most important details thinking that it is "that simple". That is precisely why rigging requires a Certified Mechanic and a logbook statement for the work performed... because it isn't quite the simple statement that you have reduced it to. Fourteen words does NOT tell the whole story.

    MAYBE I have insulted you with an unfortunate wrong read. That isn't my intention, and if my "take" was wrong, I apologize (nonetheless, there is more to it than your statement implies). There are always REASONS why a long explanation may be warranted (over and above a perceived "need on my part" to listen to myself talk). My interest here is to make sure you, as the Owner, are fully understanding of what is required. After all, it IS the Owner's responsibility to ensure his aircraft is getting "fitting and proper" maintenance performed on it. An informed Owner is a smarter AND safer Owner. But simplifying the task does not always cover the intended content. So... simply making the elevator hits both PRIMARY stops is not the full answer (the stops under the instrument panel are SECONDARY stops, and if you don't fully understand the difference, ask your IA to explain it to you). Even if you "know all this" before you ever asked the question, SOMEONE reading this might mistake your "consolidation" to be the "only thing you have to do" to correctly rig the empennage. I wouldn't feel right if that were to happen. So, my "answers" may sometime resemble "a warm wind, blowing". I don't care who thinks that...so long as ONE PERSON learns something from it that makes them understand more about their airplane.

    I HAVE, by the way, found filed stops, missing stops, and "modified stops", incorrect cable installations, rigs that hit the secondary stops but not the primary stops, and twenty or so other "maladies". There is indeed a possibility that simply "making the elevators hit the stops" is WRONG, and that is why you need to walk the whole mile rather than cutting off a few corners. The correct statement would actually be "If everything is the way Piper designed and built the airplane, then when the elevator travels are correct, both elevator stops inside the aft fuselage will be hit at the end of their travel(s). However, the converse is NOT able to be automatically assumed to be true and correct.
    Last edited by JohnW; 08-25-2011 at 07:33 PM.

  5. #5

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    Default Need help adjusting elevator travel.

    As Some of you know, I purchased a PA 22/20 a couple of months ago and am working on getting some things corrected... I recently discovered that my elevator does not have enough "up" travel. When fully extended (pulled back) the control yoke hits the secondary stop inside the cockpit while the primary stop (rear of airplane) has about a 1/2 in gap and not touching the stop. When pushed into the down position, the control makes contact with the primary down stop. From what I can ascertain, I am getting 12 - 14 degrees of down elevator and about this same amount of up elevator. Needing 24 degrees of up! So, the question is, how does one adjust this throw to be correct? I know yokes secondary stop should not be making contact when pulled back and the primary (at rear of plane) should be....
    Thanks folks, I always appreciate your input and help! Gary.

  6. #6
    Gilbert Pierce's Avatar
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    Default Re: Need help adjusting elevator travel.

    Seen two of these lately.
    In the tail tighten the top cable turn buckle and loosen the bottom cable turn buckle the same amount until the up elevator is against the stop in the tail.
    At that point you will probably be about 1/4" off the up elevator stop under the panel.

    The above assumes both cables are the proper length and have not been reversed. The top cable is shorter than the bottom cable.

    The one I fixed just needed adjusted. The one Steve fixed the top cable was not the proper length.
    Last edited by Gilbert Pierce; 05-01-2016 at 09:20 AM.

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    Default Re: Need help adjusting elevator travel.

    One more question. Should the tension on the cables be checked with the elevator spring removed or still in place?

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    Gilbert Pierce's Avatar
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    Default Re: Need help adjusting elevator travel.

    Quote Originally Posted by GaryV View Post
    One more question. Should the tension on the cables be checked with the elevator spring removed or still in place?
    In place with the elevator static. I would not disconnect the springs. Just remove the turnbuckle safety wire on both cables.
    Loosen the bottom by same amount you tighten the top until you have the elevator against the hard stop in the tail with yoke full back.
    If the tension was good before it will still be good.

  9. #9
    Administrator Steve Pierce's Avatar
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    Default Re: Need help adjusting elevator travel.

    Hopefully someone didn't replace your cables with some of a different length. We fought to rig one recently that had been flying with shorter cables and only about 12 degrees of up elevator. Not a fun job.

  10. #10

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    Default Tri-Pacer Elevator Rigging

    Greetings all,
    First post here & also first time checking the elevator rigging on a Tri-Pacer.
    Leveled the aircraft & set the horizontal stab/trim to zero angle per the manual & other recommendations on here. Spec for elevator travel is 24 up & 12 down. With the aircraft I'm working on, elevator travel is 23.7 up (does not contact the stop in the tail) but only 9.0 down (which does make contact with the stop in the tail). The control yoke is making contact with its stops in both fore/aft up front. Looking for recommendations on how to proceed further & correct the issue.
    Thanks.

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