Catastrophic Decompression; Small Place Solo

During the explosive decompression portion of my Air Force altitude chamber
training, we sat in a small chamber adjacent to the larger main chamber with
our masks off. The airtight door between the two chambers was closed. The
large chamber was evacuated to 50,000 feet, or so. We were at about 10,000
feet and had our masks off.

Without warning, the hatch between the chambers was suddenly opened. There
was a loud bang, and the pressure in the two chambers very quickly equalized
to about 30,000 feet. The whole chamber filled with thick fog. I felt for my
mask and put it on.

Ever after, I have been amused at the flight attendant's briefing, "In the
unlikely event of a sudden loss of cabin pressure, the oxygen masks in front
of you will automatically deploy. Simply put the mask over your mouth and
nose and breath normally. Etc. etc."

Yeah, right! First there's a loud bang and everyone thinks a bomb has gone
off. Then the cabin fills with super cold thick fog. The pilot puts the
plane in a dive to get to breathable air and the masks are hanging a couple
feet in front of you. I think it would be absolute chaos.

Have any of you experienced an actual explosive decompression while in
flight?

Jon

Cub Driver wrote in message . ..
Don't believe ANYTHING you see on TV or in the movies about aviation

In my case, the warning about explosive decompression came from a
BRITISH AIRLINE SECURITY CONSULTANT, speaking on an NPR station. So
clearly the myth extends far beyond Hollywood. This man was presented
as making a living from his special knowledge!


Was that in reference to a stray bullet causing the decompression?
If so, I'd have to agree that he's full of it. Explosive
decompression caused by a larger hole in the pressure vessel (i.e.
small bomb or failure of the structure) can be quite serious.
Remember that 747 that had a big chunk of the skin blow out enroute to
Australia? As I recall, 2 or 3 people were sucked out along with
their seats. Also, at 35K ft. the amount of time until loss of
conciousness is measured in seconds.

I was once enroute on a long X-C near the AZ/NM border when I heard
a TWA flight tell Center that they were in an emergency descent due to
a sudden decompression of the cabin. A few minutes later I watched
the 727 come down to 12K ft. (a few thousand ft. over the mountain
tops) and start a turn east towards Albuquerque. Very strange to see
something that large down at unpressurized GA altitudes.

John Galban=====N4BQ (PA28-180)

"Bob Gardner" wrote
No way. You start off at sea level, of course, and they pump the chamber
pressure down to 25000 feet with masks on...then they do some experiments
with a few of the pilots taking their masks off, just to show how severely
their abilities are affected. Then comes the explosive decompression, which
takes the chamber from 25K back down to sea level in a second or two.

Bob, what you have described is "explosive compression" not "decompression".

I would reccommend this web site to clear-up the confusion:

http://www.wvi.com/~lelandh/Alt_Chamber.htm

Bob Moore

(John Galban) wrote:

Was that in reference to a stray bullet causing the decompression?
If so, I'd have to agree that he's full of it. Explosive
decompression caused by a larger hole in the pressure vessel (i.e.
small bomb or failure of the structure) can be quite serious.
Remember that 747 that had a big chunk of the skin blow out enroute to
Australia? As I recall, 2 or 3 people were sucked out along with
their seats. Also, at 35K ft. the amount of time until loss of
conciousness is measured in seconds.

About 22,000 feet, and 9 pax were sucked out. Better than the loss of
all 356 people on board, though.

Date: February 24, 1989
Type: 747-122
Registration: N4713U
Operator: United Airlines
Whe Honolulu, Hawaii
Report No. NTSB-AAR-90-01
Report Date: April 16, 1990 Pages: 68

Executive Summary:

On February 24, 1989, United Airlines (UAL), flight 811, a Boeing
747-122 (B-747), N4713U, was being operated as a regularly scheduled
flight from Los Angeles, California (LAX) to Sydney, Australia (SYD)
with intermediate stops in Honolulu, Hawaii (HNL) and Aukland, New
Zealand (AKL). There were 3 flightcrew, 15 flight attendants, and 337
passengers aboard the airplane.

The flightcrew reported the airplane's operation to be normal during
the takeoff from Honolulu, and during the initial and intermediate
segments of the climb. The flightcrew observed en route thunderstorms
both visually and on the airplane's weather radar, so they requested
and received clearance for a deviation to the left of course from the
HNL Combined Center Radar Approach Control (CERAP). The captain
elected to leave the passenger seat belt sign "on."

The flightcrew stated that the first indication of a problem occurred
while the airplane was climbing between 22,000 and 23,000 feet at an
indicated airspeed (IAS) of 300 knots. They heard a sound, described
as a "thump," which shook the airplane. They said that this sound was
followed immediately by a "tremendous explosion." The airplane had
experienced an explosive decompression. They said that they donned
their respective oxygen masks but found no oxygen available. Engines
No. 3 and 4 were shutdown because of damage from foreign object
ingestion.

The airplane made a successful emergency landing at HNL and the
occupants evacuated the airplane. Examination of the airplane revealed
that the forward lower lobe cargo door had separated in flight and had
caused extensive damage to the fuselage and cabin structure adjacent to
the door. Nine of the passengers had been ejected from the airplane
and lost at sea.

The issues in this investigation centered around the design and
certification of the B-747 cargo doors, and the operation and
maintenance to assure the continuing airworthiness of the doors.

The National Transportation Safety Board determines that the probable
cause of this accident was the sudden opening of the improperly latched
forward lower lobe cargo door in flight and the subsequent explosive
decompression. Contributing to the cause of the accident was a
deficiency in the design of the cargo door locking mechanisms, which
made them susceptible to inservice damage, and which allowed the door
to be unlatched, yet to show a properly latched and locked position.
Also contributing to the accident was the lack of proper maintenance
and inspection of the cargo door by United Airlines, and a lack of
timely corrective actions by Boeing and the FAA following the 1987
cargo door opening incident on a Pan Am B-747.

The Safety Board issued three safety recommendations as a result of
this investigation that addressed measures to improve the airworthiness
of the B-747 cargo doors and other non-plug doors on pressurized
transport category airplanes. It also issued recommendations affecting
cabin safety.

http://dnausers.d-n-a.net/dnetGOjg/240289.htm

--
Scott M. Kozel Highway and Transportation History Websites
Virginia/Maryland/Washington, D.C. http://www.roadstothefuture.com
Philadelphia and Delaware Valley http://www.pennways.com

On Tue, 30 Dec 2003 23:05:40 GMT, Martin Hotze
wrote:

On Tue, 30 Dec 2003 17:32:44 -0500, Ron Natalie wrote:

I think this is a good guess. It sort of looks like the top of a can of
parmesan cheese.

A _*can*_ of cheese? Hu?

Cheese has to be 'fresh', and parmesan is made at the table from the piece.

You *can't* have spent enough time in the U.S. if you've never seen a
green can of Kraft grated parmesan cheese.

And there's no such thing as "fresh cheese".

Rob

Then you've never been around Oshkosh at dawn after a couple of six-packs and a
few cans of bean dip the night before.

Jim

-
-And there's no such thing as "fresh cheese".
-
-Rob


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Wouldn't it be nice if all participants in the aviation newsgroups
subscribed to...what was that name again?...oh yes, the Summit Aviation
CD-ROM. Then they could research this stuff themselves.

(Couldn't live without it, Jon)

Bob Gardner

"Jon Woellhaf" wrote in message
news:jvFIb.85543$VB2.191432@attbi_s51...
During the explosive decompression portion of my Air Force altitude
chamber
training, we sat in a small chamber adjacent to the larger main chamber
with
our masks off. The airtight door between the two chambers was closed. The
large chamber was evacuated to 50,000 feet, or so. We were at about 10,000
feet and had our masks off.

Without warning, the hatch between the chambers was suddenly opened. There
was a loud bang, and the pressure in the two chambers very quickly
equalized
to about 30,000 feet. The whole chamber filled with thick fog. I felt for
my
mask and put it on.

Ever after, I have been amused at the flight attendant's briefing, "In the
unlikely event of a sudden loss of cabin pressure, the oxygen masks in
front
of you will automatically deploy. Simply put the mask over your mouth and
nose and breath normally. Etc. etc."

Yeah, right! First there's a loud bang and everyone thinks a bomb has gone
off. Then the cabin fills with super cold thick fog. The pilot puts the
plane in a dive to get to breathable air and the masks are hanging a
couple
feet in front of you. I think it would be absolute chaos.

Have any of you experienced an actual explosive decompression while in
flight?

Jon

Thank you, everyone, for providing lots of helpful answers and info.

Even with slightly inaccurate info (2-seater; 6-seater), I guess
the second Q was easy:
Is the simplified movie solo flight completely
bogus or could it happen that way?

The basic answer is "more or less".

The answers to the first Q, being more tecnically compicated, leave
me asking for a few clarifications. That was about what REALLY happens
when a large pressurized aircraft, e.g., a 747, explosively or
catastrophically decompresses at high (25000+ feet) altitude.

Ron Natalie ) wrote:
On the one hand, passengers need to get denser air to breathe
but large aircraft have oxygen masks that drop down.

The pilots initiate the dive for the reasons you suggest. While
supplemental oxygen helps, it's still better to get down to a reasonable altitude. They presmably notify ATC while they are doing
this that there is an emergency in progress.

So, other than alarms or other signals, there is NOTHING AUTOMATIC
that puts the aircraft into rapid descent. Pilots have to respond
to the signals (explosion, screams from the cabin, meters in their
cockpit, their own ears popping, flashing lights, bells and whistles,
etc.) and initiate the dive MANUALLY. For well trained pilots this
would take, what, only a few seconds at most? Do they put their oxygen
masks on FIRST or start the dive first?

In some movies, the pilots are often unconscious, slumped over the
controls (wedging the 'steering wheel' / joystick full forward) as
the hero struggles to pull them out of the way and get out of the
dive. It sounds like a pilot, if not alert or in good health, could
actually lose consciousness from hypoxia under these conditions, so
maybe those kinds of movie scenes are ALMOST believable?

(This assumes worst case total decompression. It was pointed out
by Mike Rapoport ) that the cabin might
not even go to ambient pressure if the hole isn't too big and the
outflow valves close down and the engines keep pumping air into the
cabin.)

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. 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?

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.

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. Apparently, some people posting have
done this during training in hyperbaric chambers.

Once again, THANK YOU for your answers. Even tho' I'm annoyed
or perplexed by a lot of Hollywood pseudoscience, I get extra
value from these usenet discussions.

Have a Happy New Year.






--
Sent by xanadoof from yahoo included in com
This is a spam protected message. Please answer with reference header.
Posted via http://www.usenet-replayer.com

"Bob Gardner" wrote in message news:bgFIb.16418$I07.44872@attbi_s53...
Well, it's been awhile, John, and I can hardly remember things that happened
last week, much less things that happened in the 70s. However, I do not
recall anything odd happening to my body during the ascent to 25000 but do
recall my lips doing the blub-blub-blub thing during the decompression. As
the pressure in the chamber rapidly increased, it kinda pushed the trapped
gas out.
It's the other parts of your body doing the blub-blub-blub thing that's problematic.

Basically the Hollywood depicts what would happen if the cabin was
preasurized to 400PSI.

Mike
MU-2

"Aviation" wrote in message
u...
Thank you, everyone, for providing lots of helpful answers and info.

Even with slightly inaccurate info (2-seater; 6-seater), I guess
the second Q was easy:
Is the simplified movie solo flight completely
bogus or could it happen that way?

The basic answer is "more or less".

The answers to the first Q, being more tecnically compicated, leave
me asking for a few clarifications. That was about what REALLY happens
when a large pressurized aircraft, e.g., a 747, explosively or
catastrophically decompresses at high (25000+ feet) altitude.

Ron Natalie ) wrote:
On the one hand, passengers need to get denser air to breathe
but large aircraft have oxygen masks that drop down.

The pilots initiate the dive for the reasons you suggest. While
supplemental oxygen helps, it's still better to get down to a reasonable
altitude. They presmably notify ATC while they are doing
this that there is an emergency in progress.

So, other than alarms or other signals, there is NOTHING AUTOMATIC
that puts the aircraft into rapid descent. Pilots have to respond
to the signals (explosion, screams from the cabin, meters in their
cockpit, their own ears popping, flashing lights, bells and whistles,
etc.) and initiate the dive MANUALLY. For well trained pilots this
would take, what, only a few seconds at most? Do they put their oxygen
masks on FIRST or start the dive first?

In some movies, the pilots are often unconscious, slumped over the
controls (wedging the 'steering wheel' / joystick full forward) as
the hero struggles to pull them out of the way and get out of the
dive. It sounds like a pilot, if not alert or in good health, could
actually lose consciousness from hypoxia under these conditions, so
maybe those kinds of movie scenes are ALMOST believable?

(This assumes worst case total decompression. It was pointed out
by Mike Rapoport ) that the cabin might
not even go to ambient pressure if the hole isn't too big and the
outflow valves close down and the engines keep pumping air into the
cabin.)

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. 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?

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.

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. Apparently, some people posting have
done this during training in hyperbaric chambers.

Once again, THANK YOU for your answers. Even tho' I'm annoyed
or perplexed by a lot of Hollywood pseudoscience, I get extra
value from these usenet discussions.

Have a Happy New Year.






--
Sent by xanadoof from yahoo included in com
This is a spam protected message. Please answer with reference header.
Posted via http://www.usenet-replayer.com