Re: Explosive decompression - how fast?

Brian Davis <brdavis@[EMAIL PROTECTED]
> wrote:
>> Here is a direct quote from the NTSB report:
>>
>> "This was a survivable accident; the fatality was the result of the
>> explosive nature of the decompression. The flight attendant was swept
>> violently from the airplane and passed through an opening of jagged
>> metal."
> 
> Thank you for the direct quote (and the source - you're right, I
> hadn't found that). I don't think the NTSB "got it wrong", as much as
> "it didn't matter". They did not say, for instance, if it was
> internally-produced turbulence, or shock-front acceleration, or non-
> compressible fluid flow resulting from the pressure differential set
> up due to the difference in pressure between the uniform internal
> atmosphere and the external pressure. And those are the sort of
> differences we're discussing here. They simply say "was swept" - not
> what did the sweeping, or what the proposed forces and accelerations
> were.

They directly state that the loss of the flight attendant was due to the 
explosiveness of the decompression. If they thought it had been caused by 
outside air then it wouldn't matter if it had happened over a millisecond 
or over ten seconds. You're right that it doesn't matter, so it's possible

they didn't put much analysis into it. The NTSB statement above may simply

be based on an assumption that it was the decompression rather than any 
analysis, or the analysis may be wrong. But that is what it says.

> *Especially* since the original example explicitly postulated an
> external environment that is at a vacuum.

A vacuum should be substantially worse, because the outside pressure is so

much lower

>> As for the bit about being thrown to the floor, humans tend to fall
down
>> when experiencing significant unexpected lateral accelerations.
> 
> My point was that in a single sentence you mentioned one being sucked
> up and one being thrown down... and then used this as a starting point
> to assume the airflow due to the pressure differential was
> responsible. That construction immediately calls into question how the
> second person "fell down", if explosive decompression was so critical.

The flight attendent who died was not sucked up, she was sucked out the 
left side of the plane. One who fell down was knocked down by flying 
debris. The other one was knocked down by the decompression, but avoided 
the fate of the first one because she was well inside the intact portion 
of the aircraft body.

Wandering a bit, this discussion makes me wonder about the possibilities 
for unpressurized passenger aircraft. Pressurization is dangerous (lots of

accidents due to explosive decompression which didn't involve individuals 
being pulled outside the plane directly by the decompression) and adds 
substantial weight, complexity, and cost to the aircraft.

The obvious solution would be to give everybody oxygen masks. They do that

anyway, but these would be for regular use. These would be uncomfortable, 
but the flying populace has shown themselves willing to put up with almost

anything to save money. A somewhat larger problem would be an inability to

go very far from your seat.

Would it make sense to have an aircraft cabin that's fairly well sealed 
but not pressurized, such that it could be filled with pure oxygen at 
altitude? The experience in such a plane would be much like an airliner of

today, except with a lot more ear popping during the ascent and descent.

-- 
Michael Ash
Rogue Amoeba Software