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Thread: Seat belt mounting........

  1. #1

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    Seat belt mounting........

    I need some help........ My wife says I need a lot of help but thats another story.

    The mounting point for my shoulder belt is located all the way back by my tail wheel, she is a taildragger. My bird goes into the shop in a few days and I believe this should be changed. I worry, again I worry alot, about an incident where I might break my fuse in half and then I am hooked to the tail of the bird by my shoulder straps.

    The way we do it on the dragster is the shoulder belt should not go down but is mounted even with your shoulders, so no down pressure in the event of a crash, you will not compress the spin.

    I would think it does not matter what the belt system is in but it should be mounted this way.


    Am I correct for thinking this.

    H.A.S.

  2. #2

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    The shoulder mount is connected to a cable and this cable runs to the tail of my bird. I know this can not be good, I could be wrong........

  3. #3

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    You worry too much.

    There are a number of airplanes that anchor the shoulder harness that way. The shoulder harness' job is to keep your face from slamming into the instrument panel. That said, it will not guarantee that your face will not contact the instrument panel. If you impact so hard that your tail section deforms, when the tail is the last part of the airplane to the scene of the accident, your cockpit has already deformed in an manner that is likely not survivable. At lease in the most common accident situation which is a straight on impact. If you manage to have a landing accident that cartwheels the airplane, typically the wings and engine area take the most abuse. The tail section is pretty light and the mechanics of that sort of crash appear to involve more repeated impact of the heavier parts of the airplane (I hope I formulated that right).

    So the shoulder harness mounting is intended to do its job in a survivable accident. Your job is to have an accident that stays within its design parameters.

    Best of luck,

    Wes
    N78PS

  4. #4

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    If the shoulder harness is anchored aft like yours, up to a 5 degree downward slope to the anchor point is acceptable. It won't compress your spine. All in all, it sounds like the shoulder harness is installed IAW AC 43.13-2B. Not sure I would try to "improve" it.
    Last edited by martymayes; 01-06-2013 at 06:55 PM.

  5. #5

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    I will leave it as is. Thanks for the info.

  6. #6
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    f you impact so hard that your tail section deforms, when the tail is the last part of the airplane to the scene of the accident, your cockpit has already deformed in an manner that is likely not survivable. At lease in the most common accident situation which is a straight on impact.
    Except that the tail frequently bends or the attachments are prone to failure at forces well below the human

    All in all, it sounds like the shoulder harness is installed IAW AC 43.13-2B. Not sure I would try to "improve" it.
    The problem with AC 43.13-2B is that it leaves much to be desired with regard to crash survivability. It's in dire need of a revision based on science from the last 30-50 years.

    up to a 5 degree downward slope to the anchor point is acceptable.
    Just for the sake of thoroughness, a 5-10 degree upward slope is better.


    I worry, again I worry alot, about an incident where I might break my fuse in half and then I am hooked to the tail of the bird by my shoulder straps.
    You would be more likely to be left with no shoulder protection (the attachments would fail if it is designed anything like your "standard"/AC 43.13-2B arrangement) and would allow you to be thrown forward striking your face or chest on the instrument panel or control stick. Having the shoulder harness attach directly to an intertial reel which is directly bolted to a substantial part of the airframe is more ideal.

    Feel free to PM me if you'd like to discuss this further. I am always happy to help with occupant protection issues.
    Unfortunately in science what you believe is irrelevant.

    "I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.



  7. #7

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    The problem with AC 43.13-2B is that it leaves much to be desired with regard to crash survivability. It's in dire need of a revision based on science from the last 30-50 years.

    AC 43.13-2B was revised 3/3/08.

    Signing off on a non-STC'd seatbelt installation, probably best to use data in the AC vs. SGOTI.

  8. #8
    steveinindy's Avatar
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    AC 43.13-2B was revised 3/3/08.


    But it still uses largely the same assumptions about human tolerances that the previous version did. The FAA is very hesitant to increase the standards most likely because of pressure from the certificated industry.

    Signing off on a non-STC'd seatbelt installation, probably best to use data in the AC vs. SGOTI.
    This is another case where an STC simply means someone did some paperwork that allows them to charge more for something than it is worth.

    Personally, I'd go with the US Army's crash survival design guide standards. It is probably one of the single best scientifically based sources of information available and has a large role to play in why I believe what I do. The AC is a better than nothing but it is far from being ideal or anything I would want to rely upon if it were my butt on the line. We have the ability as homebuilders to exceed the basic standards created by some bureaucrats in DC so why should we settle for the minimum especially when it is something that is directly connected to our safety (literally and figuratively)?
    Unfortunately in science what you believe is irrelevant.

    "I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.



  9. #9

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    Everything in aviation is a trade-off. The Army can apply $$ and horsepower to the problem. An installation appropriate to an AH-64 is not practical in an ultralight. And the military sends aircraft places where the expectation is for a higher crash rate. Most civilian aviators are much less likely to have an uncontrolled contact with the ground than any military aviator. So the trade-offs are different.

    The safest airplane is one that never leaves the ground. But they aren't any fun either.

    Best of luck,

    Wes
    N78PS

  10. #10

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    me 014.jpg

    My little bird......Fisher Avenger....Not an UL...Should be...but not.....If you ask me...if you wiegh half what your plane weighs....Its an UL....But we all know the story....so she is a EAB...

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