Wayne Throop <throopw@[EMAIL PROTECTED]
> wrote:
> : Michael Ash <mike@[EMAIL PROTECTED]
>
> : he image of everything that's not nailed down flying out the door may
be
> : inaccurate, but the earlier estimate of 0.3m/s would appear to be
> : inaccurate as well. Perhaps the most famous explosive decompression
> : incident is Aloha Airlines 243 which suddenly lost a large section of
skin
> : but managed to land safely. One flight attendant was thrown to the
floor
> : and another one was thrown out of the plane altogether, never to be
seen
> : again.
>
> Sure, but that's what being exposed to 300+mph winds will get you.
> Just the decompression, not so much. It's the fact that so much
> of the hull was peeled away.'
But that 300mph wind should mostly stay outside the aircraft. The missing
skin was all on the sides, so it should continue past. There will surely
be a great deal of turbulence in the cabin but it's not going to be 300mph
in the aisle. I'm doubtful that it's going to be enough to pull anyone
out, but I could be wrong.
While poking at this accident I found some information about an alternate
theory involving a "fluid hammer". In this theory, a relatively small
piece of skin detached first. The unfortunate flight attendent was then
sucked into this hole, blocking it, which then caused the massive failure
seen in all the amazing pictures. I'm not sure how plausible this whole
thing really is, but in any of the things I read which disagreed with it,
none of them mentioned the implausibility of getting sucked into the hole
by the decompression.
A bit of BOTE calculations to back it up. The wind should be roughly the
speed of sound. The terminal velocity of a human at the lower reaches of
the atmosphere oriented parallel to the ground is roughly 120mph, implying
that aerodynamic forces are 1 gee at this speed. Aerodynamic drag scales
as the square of the speed. The speed of sound is about 6 times greater
than this, implying a force on the human of around 36 gees. At 700mph the
air will take about 1/10sec to exit a 100 foot aircraft body, and 36 gees
over 1/10sec is about 80mph, plenty sufficient to toss an unsecured person
outside. Of course this whole analysis is ridiculously simplistic.
A perhaps more convincing example is British Airways 5390. A pane of the
windshield was improperly installed and blew out at 17,000ft. This very
nearly ejected the pilot from the aircraft. As it was he wedged halfway
and spent the rest of the flight with his upper body outside the plane.
While the high speed outside air certainly contributed to the inability to
retrieve him, it didn't seem to pull on the people who had remained inside
the flight deck. It would appear that an explosive decompression can
indeed pull people outside the plane in the right circumstances.
> The mythbusters bit (iirc) was concerned with two aspects of a fairly
> small hole. First, will it suck everything inside towards it, and
> second, will it rip the hull open and expose the interior to the
airstream
> (that is, will any small break in the skin necessarily spread very far).
> And they concluded, no and no. Of course, they were talking about
> a bullethole (again iirc). But I doubt things would be much different
> for anybody at a reasonable distance from, say, a hatch-sized hole.
> An upper-half-of-the-hull-peels-away-in-a-section-tens-of-feet-long
> sized hole is another matter entirely, and I doubt anybody will
> notice the decompression, given the brisk breeze outside.
A significant factor is the size of the hole compared to the size of the
aircraft. (Or more correctly, I suppose, the cross section of the
aircraft.) Air will exit through the whole at the same speed no matter how
big the plane is, but a bigger plane will have more air to move around, so
it will move slower when at a distance from the hole. But the hole in the
case of the British Airways flight was not that big, although the pilot
was pretty close to it.
In the post which started the thread, the hole was assumed to be somewhat
small compared to the cross section of the airlock, but looking at the
media which prompted the post I don't see this shown anywhere. If the door
opens approximately instantaneously it seems that the victim will indeed
get blown out.
--
Michael Ash
Rogue Amoeba Software
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