Bad Week for Airbus

"Mxsmanic" wrote in message
...
I'm capable of understanding that if Mommy and Daddy don't put on their
masks
first

And I'm capable of flying a REAL airplane.

Neither statement is germane to the issue at hand.

Judah wrote:

If you've ever flown JetBlue or Song, where they generally mock the
seatbelt briefing, and even the "water landing" part, they generally
don't leave out this important tidbit or even joke about of it...

"... put on your own mask first before assisting children or adults behaving
like children..."

regards,
Friedrich

Stefan wrote:
george schrieb:

Point out to me where I am wrong...

Your mistake is, that the quantity of gas which can be solved in water
is proportional to pressure. So you mustn't think in absolute
quantities, but in relative.

what I was thinking, but better explained, thanks.

regards,
Friedrich

It is actually true that to first order the amount of gas dissolved in
blood (with the exception of oxygen since it's subject to the
hemoglobin dissociation curve -- sort of an s shaped curve) is
proportional to the absolute pressure of the gas. The size of the
bubble that results from the serum's outgassing would depend first on
the difference in absolute pressure (that would tell you the mass of
gas that might no longer be in solution) and then on the ambient
pressure, since if the pressure was lower the bubble would expand
according to the gas laws (inversely proportional to pressure,
temperature is pretty fixed in the body. So, going from 34 feet deep
to the surface in water is a change of about one atmosphere. Going
from ground level to 18000 feet is a change of about a half an
atmosphere. The diver coming up from 34 feet would have twice the
potential mass of gas coming out of solution as would someone who went
from 0 to 18000 feet as suddenly.

It would, instead be like a diver coming up quickly after being at
17 feet deep. 0 to 18000 feet would be more or less the same as going
from a 7000 foot cabin pressure to one at 34000 feet. The pressure in
atmospheres is something like e^(-.034 A) where A is the altitude in
thousands of feet.

All of this is back of the envelope stuff done during a coffee break
so it could be very wrong. If 'feels' reasonable, though. I think
people die from explosive decompresssion because they don't get
oxygen, not from the bends.


. EURO On Nov 26, 1:09 pm, "Friedrich Ostertag"
wrote:
Stefan wrote:
george schrieb:

Point out to me where I am wrong...

Your mistake is, that the quantity of gas which can be solved in water
is proportional to pressure. So you mustn't think in absolute
quantities, but in relative.

what I was thinking, but better explained, thanks.

regards,
Friedrich

On Nov 26, 11:31 pm, Stefan wrote:
george schrieb:

Point out to me where I am wrong...

Your mistake is, that the quantity of gas which can be solved in water
is proportional to pressure. So you mustn't think in absolute
quantities, but in relative.

Going from a short exposure of low pressure to a longer period of
exposure to a higher presure will have no effect on soluble gases in
the bloos stream.
The only time that becomes a factor is if the subject has been SCUBA
diving and using decompression time.


Example: At flightlevel 360 (give or take a few) the atmospheric
pressure has dropped to roughly a quarter. So, solutionwise, climbing
from sea level to FL360 has roughly the same effect as a diver which
climbs from a water depth of 100ft to the surface (at sea level). Now if
you're saturated at 100ft (and we are saturated!), and then suddenly go
up to the surface, you *will* encounter serious decompression disease. I
would expect the same in a sudden pressure loss at FL360.

The pressure at 100 feet (to use your figures) is approx 4 atmospheres
= 56 psi
The barometric pressure at sea level is 14.7 psi.
A change of pressure of 44 psi. or about 4048 mb

Decompression at altitude is covered in the Regs that specify the
longest permitted time before descent has to be initiated.

The pressure difference between Fl30 and Fl10 is about 30 mb.

Of course the two situations are not exactly the same, because in
aviation there is a much smaller quantity of gas involved. (Besides that
the cabin pressure is usually not equal to sea level but to something
like 7000ft.) I would expect some air forces to have seriously studied
this, and plenty of literature to be available, because the climb rate
of fighter jets allow for such critical pressure changes. But frankly, I
don't know anything about it, except that your reasoning was wrong. But
then, at the climb rate my glider gives me, I guess that I needn't to
worry anyway, even in strong wave.

The Diamond height is yet to come eh :-)

"Friedrich Ostertag" wrote in
:

Judah wrote:

If you've ever flown JetBlue or Song, where they generally mock the
seatbelt briefing, and even the "water landing" part, they generally
don't leave out this important tidbit or even joke about of it...

"... put on your own mask first before assisting children or adults
behaving like children..."

Oh, yes. I forgot. I don't fly jetblue enough I guess...

Admittedly, this doesn't eradicate the message (in fact it rather elucidats
it). I was on a flight once where the announcement went something like, "If
anyone has not existed on this planet for the last 100 years and doesn't know
how to buckle and unbuckle their seatbelt, please raise your hand."

On Mon, 26 Nov 2007 19:06:26 +0100, "Friedrich Ostertag"
wrote:

Judah wrote:

If you've ever flown JetBlue or Song, where they generally mock the
seatbelt briefing, and even the "water landing" part, they generally
don't leave out this important tidbit or even joke about of it...

"... put on your own mask first before assisting children or adults behaving
like children..."

"And if you're flying with more than one child, please pick which one
you love more now."

Peter Clark writes:

"And if you're flying with more than one child, please pick which one
you love more now."

Why would you have to do that? If you put your mask on first, the children
will all survive.

Tina writes:

I think people die from explosive decompresssion because they don't get
oxygen, not from the bends.

Explosive decompression is very rare (and very different from rapid
decompression), but when it occurs, many deaths occur due to direct physical
trauma from differences in air pressure. Ruptured hearts and lungs are not
unusual. This was seen in the early accidents with the Comet, which actually
did explosively decompress on several occasions when defects in its
construction yielded at altitude.

george writes:

Going from a short exposure of low pressure to a longer period of
exposure to a higher presure will have no effect on soluble gases in
the bloos stream.

It will, however, add a bit more gas in solution to the blood and body
tissues.