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#51
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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 |
#52
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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) |
#53
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"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 |
#55
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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 |
#56
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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 |
#57
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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 |
#58
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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 |
#59
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"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. |
#60
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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 |
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