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Thread: Wipaire Gross Weight Increase

  1. #1
    Amy's Avatar
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    Wipaire Gross Weight Increase

    I mentioned I would post in this in a different thread that is no longer available. This is the text from the Wipaire 2,000 lb. kit installation drawing. There are a few STCs that are specifically called out as compatible, but also a fair bit of latitude for the installing mechanic to establish compatibility with other modifications. SA292AL is likely the most interesting to you as it is what takes the older, lighter PA-18s up to PA-18-150 gross weights. (link here: https://rgl.faa.gov/Regulatory_and_G...ent&Highlight= sa292al) I do not have a copy of SA292AL showing more detailed requirements, though, so you would want to check it to see how the two play together.

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    Interesting reading, Amy. Typical FAA where they make things clear as mud! In one case the list the PA-18-150 as the model eligible for installation while your installation drawing notes indicate all PA-18 serial 18-3771 and later (PA-18-150), and any PA-18 previously modified to a gross weight of 1750.


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    I know of at least one PA-18-95 converted to 150 with the 2000lb kit. Installed and signed by Cub Crafters.

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    Amy's Avatar
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    Quote Originally Posted by dgapilot View Post
    Interesting reading, Amy. Typical FAA where they make things clear as mud! In one case the list the PA-18-150 as the model eligible for installation while your installation drawing notes indicate all PA-18 serial 18-3771 and later (PA-18-150), and any PA-18 previously modified to a gross weight of 1750.


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    As the STC holder, we bear some of the responsibility for that—as it’s been told to me (and I wasn’t around when this modification was developed and certified, so take this with a grain of salt), we started with the PA-18-150 series and then the question came up about airplanes rebuilt essentially from dataplates, using components that made them structurally equivalent to PA-18-150 aircraft. That’s probably where the note about “modified equivalent” came from, and then it gets FAA muddy because the STC only lists the PA-18-150.

    The goal of updating this STC is to make it more clear that the 2,000 lb. gross weight is applicable to PA-18-150s and equivalent other models but it is never quite so simple when updating the paperwork. I look forward to when that is finalized, though there will always be the question of the installing mechanic establishing compatibility with the hundreds of Super Cub mods available.

    —Amy


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  5. #5
    BC12D-4-85's Avatar
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    Does the fuel tank filler cap placard still apply? "100/130 only"

    Gary

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    Quote Originally Posted by BC12D-4-85 View Post
    Does the fuel tank filler cap placard still apply? "100/130 only"

    Gary
    That only applies to 160 HP by the note.


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    Quote Originally Posted by Amy View Post
    As the STC holder, we bear some of the responsibility for that—as it’s been told to me (and I wasn’t around when this modification was developed and certified, so take this with a grain of salt), we started with the PA-18-150 series and then the question came up about airplanes rebuilt essentially from dataplates, using components that made them structurally equivalent to PA-18-150 aircraft. That’s probably where the note about “modified equivalent” came from, and then it gets FAA muddy because the STC only lists the PA-18-150.

    The goal of updating this STC is to make it more clear that the 2,000 lb. gross weight is applicable to PA-18-150s and equivalent other models but it is never quite so simple when updating the paperwork. I look forward to when that is finalized, though there will always be the question of the installing mechanic establishing compatibility with the hundreds of Super Cub mods available.

    —Amy


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    I sympathize with you guys doing STCs. I currently own two and have an application in for a third. The Aircraft Certification guys don’t have a clue about old airplanes! Every time I get a new advisor, I have to educate them about the CARs. It’s always challenging.


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    BC12D-4-85's Avatar
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    Quote Originally Posted by dgapilot View Post
    That only applies to 160 HP by the note
    We haven't seen 100/130 since about the Last Century in these parts.

    Gary

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    Quote Originally Posted by BC12D-4-85 View Post
    We haven't seen 100/130 since about the Last Century in these parts.

    Gary
    Haven’t seen 80/87 in longer time, but it is still the required limitation placard on lots of airplanes.


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  10. #10
    BC12D-4-85's Avatar
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    Can I assume as long as the fuel meets ASTM D910-21 equivalency of 100 or 100/130 it's ok? 100LL does.

    Gary

  11. #11

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    Wipaire Gross Weight Increase

    All the limitations are specified octane avgas or greater.


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