"J R (Bob) Gowing" wrote:
>
> I saw Bob Harrison's message on headrests but has there been any comment or
> action on the important issue of lifting the direction of the straps over
> the shoulders to avoid compressing the spine in a crash please?
This is not intended as criticism of any modification to prevent the
injury, but I reviewed the detailed NTSB accident data, and it appears
that the odds that it would make much difference are long, from some
scratch math I did. This is mostly due to the odd fact that only
about 10% of accidents result in serious injury, by NTSB definition
anything beyond cuts and bruises. That's right; 90% are either fatal
or no big deal. So when you do the math within any reasonable
(guesstimate) subset of that narrow 10% -- the apparent Europa design
defect were it a factor in all accidents -- and apply it to overall
accident odds, they come out really long, like a million/1 or more for
an assumed one-hour flight. The injury would occur only with rapid
forward deceleration, which usually results from stall-spin or terrain
impact due to IMC conditions, which are generally either not
survivable or will result in serious injury for reasons beyond a poor
restraint system (e.g., crushing of structure). The remaining
collision data in NTSB stats do not mostly suggest significant frontal
impact (ground loop, hard landing, wing hitting things, etc.).
OTOH, if one does redesign the belt attachment, it appears that U.S.
FAA regs require attachment strength of 2,573 pounds, so make it
beefy. Any failure in an accident could possibly involve much greater
odds of resulting in an avoidable fatality than that of the spinal
compression phenomenon in a nonfatal accident one seeks to avoid.
Them darn statistics again.
Anyway, snowing like hell here _again_, so just playing with the math
and maybe even correctly. Old 15-Leema didn't go nowhere today,
'cause I'm beyond the day when it seemed rational to shoot approaches
in 600/2 for the fun of it, and Europa N3EchoYou needs much warmer
temps for the next steps in the build.
Regards,
Fred F., A063, N3EU
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