Aviation wrote:

Do they put their oxygen masks on FIRST or start the dive first?

Masks go on first. After the Payne Weber incident, there was some discussion about
instituting a policy whereby at least one of the flight crew is wearing a mask at all
times above a certain altitude. I don't know if that was emplemented. Crews would set
the autopilot to perform the descent even if they lose consciousness.

Someone also pointed out my goof about "holding" your breath
upon going from cabin (8000 ft pressure) to ambient (25-35,000
ft pressure). In estimating how much time the average civilian
passenger could go without TAKING a breath of good air (14,000
ft or below), I used the HOLD your breath estimate. Assuming
there is 3-5 minutes of mask-oxygen and one minute of "holding"
the last breath, they've got 3-6 minutes to get down to breathable
(14,000 ft?) air and then below.

Once again. You cannot hold the last breath for 1 minute. You can't hold it for five
seconds. The air will rush out of your lungs as rapidly as it rushes out of the
plane,
and there isn't a single thing you can do about it. As soon as the pressure gets
below
about 10 psi, the oxygen will start to leave your bloodstream. You have perhaps 45
seconds before you turn into a babbling idiot - probably much less. If they don't get
you down to a decent altitude in less than about 4 minutes, you may stay a babbling
idiot for the rest of your life. A few more minutes, and you will probably die.

For the movie Executive Decision,
they were cruising at 39,000 ft. so they'd have to dive 25,000 ft
to 14,000 ft in 5 minutes, 5,000 ft/minute, average. Doable?

Mike Rappaport posted that his aircraft can descend at 10,000 fpm. He also posted
the opinion that many jets can do better than that.

I found some rate of ASCENT data of about 3850 ft/min at
http://www.altairva-fs.com/fleet/poh...0747%20POH.htm
but descent data isn't clear to me but it looks like 2500 ft/min
from cruise altitude down to 10,000 ft is the recommended ROD.

Recommended descent rate goes out the window in an emergency. Think on it a little.
Most jet airliners top out between 400 and 500 mph. Idle the engines and point the
nose down, you should be able to get a rate of descent in excess of 25,000 fpm. Hit
500 knots straight down, and you're talking 50,000 fpm, but the pullout would
probably
pull the wings off.

The discussion of the ear problem seems unsettled. Upon going
from 8000 ft cabin pressure to 25000+ ft pressure in a couple
of seconds (if loss of pressure is total), some rapid swallowing
should equilibrate your ears to low pressure. Descending from
25,000+ (39,000) ft at 5,000 ft/min could result in reversible
or IRREVERSIBLE damage depending on a person's ability to
equilibrate REALLY fast.

If you have the presence of mind to do the exercises necessary to save your ears
when the pressure drops, perhaps you'd have the presence of mind to hold your
nose and blow into your ears on the way down? Even if you don't, it beats dying.

George Patterson
Great discoveries are not announced with "Eureka!". What's usually said is
"Hummmmm... That's interesting...."