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Thread: Weight and balance issue - experts check in

  1. #1

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    Default Weight and balance issue - experts check in

    I am going through the W/B for 6125D as I recently swapped from 31" ABW to 26" Goodyears and am now in the process of putting on a baby bushwheel tailwheel. That being said, I have been using the file one of the members here created and it seems to mathematically work, however, I have some questions as it relates to different arms.

    I have seen different things with the datum being either the WLE or the axle on the mains - the one I have from Steve Pierce on this airplane appears to use the WLE, however, the excel file I have appears to show that the WLE and axle are in the same place and have an arm of "0". Tried calling Steve earlier to ask but I figured someone on here might know. Steve used an arm of +16" for the mains. If I can verify that, I can measure to the tail post for the tailwheel installation, however, I am thinking the mains ought to be -16.

    Anyone know the right answer?

    Datum Sheet.jpgSide.jpg

  2. #2

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    Default Re: Weight and balance issue - experts check in

    The axles were zero inches from the WLE on the PA-20 I had. It was that way on the original Piper paperwork too. Since yours is a conversion I think I would level it and check it.

    Would the mains on a Tri-Pacer be +16 inches from the WLE?
    Last edited by Jeff J; 10-11-2017 at 02:41 PM.
    "Good judgement comes from experience, and experience comes from bad judgement." - Fred Brooks

  3. #3
    Pacerfgoe's Avatar
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    Default Re: Weight and balance issue - experts check in

    I had this discussion with some forum members a while back, and it helped me sort it out. Pay attention to posts #4,19,20,26,27, and look at Gilberts plane when he had it level.....the tail is way way up in the air. Thanks to Photobucket some of the pics are missing, but the info is there....pay attention to the link in post #4 that Brian made. If you look at the side view of the plane, and read the notes below it very closely it says the datum and the c/l of the main gear are all even with the wing leading edge.....I missed these notes on my '52 weight and balance, but they were there, they might be on yours too.

    http://www.shortwingpipers.org/forum...lance-Question
    Last edited by Pacerfgoe; 10-11-2017 at 05:40 PM.
    Forrest Miller

  4. #4

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    Default Re: Weight and balance issue - experts check in

    Ok, I tried the search on my phone maybe that's why I didn't come across that thread. I did weigh it and put the tail up, line plumb to punch mark on seat frame. It was more of a check to see how accurate the books were. Well, they aren't! The scales were not certified so I can't use it but I am trying to at least have a "legal" copy I can use for AROW purposes.

    Book weight of 1,138 and weighed at 1,173 last week.

  5. #5

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    Default Re: Weight and balance issue - experts check in

    From the PA-20 Type Certificate, page 8, the arm for the mains is 0. The arm for the Scott 3200 is +178. Datum is Wing Leading Edge.

  6. #6

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    Default Re: Weight and balance issue - experts check in

    Still trying to figure out the arm of 16 though, sent the picture to Steve so hopefully he can square me away.

  7. #7

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    Default Re: Weight and balance issue - experts check in

    Quote Originally Posted by Jeff J View Post
    Would the mains on a Tri-Pacer be +16 inches from the WLE?
    Nevermind....+31.5 according to the Type Certificate
    "Good judgement comes from experience, and experience comes from bad judgement." - Fred Brooks

  8. #8

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    Default Re: Weight and balance issue - experts check in

    Quote Originally Posted by TxAgfisher View Post
    Still trying to figure out the arm of 16 though, sent the picture to Steve so hopefully he can square me away.

    Could be using the firewall as the datum in that spreadsheet. Might check the arm of something like the oil which is -29 if the WLE is used. If it's -13 or thereabouts then likely the firewall is the datum in the spreadsheet. Just a thought.

  9. #9

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    Default Re: Weight and balance issue - experts check in

    Found out the datum is in fact the firewall in the original calculations but that throws all of the other arms off. Trying to find the flight supplement with the firewall as the datum - anyone have it?

  10. #10
    Steve Pierce's Avatar
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    Default Re: Weight and balance issue - experts check in

    Here is the weight and balance from the conversion. Need the Light lane Components Flight Manual Supplement to verify datum, arms and CG limit IAW the approved data of the STC. I will have to dig a copy out as I do not have a digital copy.

    VanMeter.jpg

    VanMeter PA.jpg

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