Wjcandee From United States of America, joined Jun 2000, 5515 posts, RR: 22 Posted (9 years 9 months 2 weeks 4 days 10 hours ago) and read 4080 times:
I am starting a new thread to suggest a specific take on the Cypriot aircraft accident. I am intrigued that all the discussion on here and in the media assumes a rapid decompression entirely on the aircraft's own accord, followed by the crew's failure to descend, or a "slow leak" that nobody noticed. Neither of these sit well with me, although I note Jim Hall's comment that it was likely a major malfunction of the crew O2 or a training issue. "Training issue" is a broad phrase, and I'm thinking that he's suggesting politely that some human activity may have compounded the problem.
A few things that I think I know are worthy of exploring here.
First, why haven't we discussed what human actions could have caused/compounded this situation? Let's start with an understanding of what an explosive decompression is like at cruise altitude. It's not like the safety demonstration where the masks drop and people go "Oh, I guess I need some oxygen", and happily reach up for their mask. Nor is it just like holding your breath. It's more like getting punched really, really hard in the stomach, and smacked in the back of the head simultaneously, knocking the wind out of you, while you feel like your ears have exploded. It is apparently disorienting as hell, and one has to immediately recognize it for what it is and react properly by grabbing for the mask before you pass out. And it's quite possible that one can react improperly in such a state.
That said, I never bought the "text message" story, and I'm a little dubious about the assertion that the crew reported "air conditioning problems" to ATC. Who would do that? "Uh, Center, [Callsign] 732, uh, it's kind of cold in the airplane." Doesn't sound right. Maybe they called Company maint to report that or for some help troubleshooting. And there is where I think it could get interesting. Wasn't there an ATA flight a few years ago where they started having some pressurization issues and the Captain stood behind the FE and reached over and either rotated or almost rotated the cabin outflow valve improperly, leading to or almost leading to a serious problem? Troubleshooting at altitude sometimes compounds a problem. I don't know much about the pressurization controls available to the flight crew on the 737, but it's conceivable that some action by the crew had an unexpected result, either due to their error or because the system didn't respond as it should have, and that might make an interesting topic of discussion for those in the know. I wonder if such folks could weigh in a little on that.
All the best,
PS A few other thoughts: I wouldn't extrapolate too much about the captain not being visible, as he simply could have slumped sideways. I don't think the "slow leak" would likely lead to hypoxia of the flight crew without their knowing about it, because the cabin altitude is monitored, displayed, and the subject of an audible warning. Finally, I'm dubious about the utility of the voice recorder, given the long period that the aircraft flew before impact; wouldn't it have recorded over some portion of the incident sequence by the time it lost power from the impact?
HZ747300 From Hong Kong, joined Mar 2004, 1817 posts, RR: 1
Reply 1, posted (9 years 9 months 2 weeks 4 days 10 hours ago) and read 4052 times:
Quoting Wjcandee (Thread starter): That said, I never bought the "text message" story, and I'm a little dubious about the assertion that the crew reported "air conditioning problems" to ATC. Who would do that? "Uh, Center, [Callsign] 732, uh, it's kind of cold in the airplane." Doesn't sound right. Maybe they called Company maint to report that or for some help troubleshooting.
That's true - how could the problem occur so quickly that the pilots could not radio anything, but passengers could type messages on cellphones? If they radio'd in a problem regarding the air conditioning my guess is that the problem with the air was to the point that it was interfering with the flight--not to complain about the cabin climate.
DFORCE1 From Canada, joined Jul 2005, 505 posts, RR: 0
Reply 3, posted (9 years 9 months 2 weeks 4 days 8 hours ago) and read 3908 times:
Quoting HZ747300 (Reply 1): That's true - how could the problem occur so quickly that the pilots could not radio anything, but passengers could type messages on cellphones?
It was already reported by news agencies that the text message from the passenger sent from the plane to his cousin was a hoax. In fact, his cousin was not even on board and the man is now facing charges.
Jeb94 From United States of America, joined Oct 2004, 621 posts, RR: 4
Reply 5, posted (9 years 9 months 2 weeks 4 days 7 hours ago) and read 3784 times:
If I recall correctly, the oxygen generators are designed to provide 45 minutes of breathable oxygen. They would've survived that long. There are portable o2 bottles for medical problems. It all depends on how big a bottle the airline uses as to how long that lasts. The crew have a seperate, large o2 bottle that is connected to their masks. Its a very different system to the one the passengers use. If the bottle was not turned on for some reason or had a faulty gauge indicating full when the bottle was actually empty, the crew might not notice quickly enough to get an alternate source of o2. They only had a very few seconds. Perhaps this is why the captain didn't appear to be in his seat? Its also possible he was removed from his seat by an F/A that was seen trying to fly the plane.
Spacecadet From United States of America, joined Sep 2001, 3836 posts, RR: 11
Reply 6, posted (9 years 9 months 2 weeks 4 days 1 hour ago) and read 3649 times:
It's more like getting punched really, really hard in the stomach, and smacked in the back of the head simultaneously, knocking the wind out of you, while you feel like your ears have exploded. It is apparently disorienting as hell, and one has to immediately recognize it for what it is and react properly by grabbing for the mask before you pass out. And it's quite possible that one can react improperly in such a state.
Yet many people have lived through explosive decompressions at high altitudes and come out fine. The cockpit and cabin crews are all trained in how to deal with this situation and will help passengers put on masks if needed. All the pilot has to do is reach for his own mask and pull it over his head - this is what he gets paid for, it's part of his job to react properly in an emergency.
People act like this is the first time decompression has ever happened. The media is treating it that way as well, quoting "aviation experts" who talk about how difficult it is to operate after a decompression, how little time there is, and assuming that the decompression alone knocked everybody out. That isn't the way it works, or at least it shouldn't be. There have been literally dozens of explosive decompressions over the years and not one of them has in itself caused a crash. Not one of them, to my knowledge, resulted in the incapacitation of the crew either. It just shouldn't happen - I want to say it *can't* happen but I guess you never really know. It is always possible that a crew will react in a way contrary to their training.
Anyway, I don't really believe explosive decompression occured. There was no visible damage to the airplane, and you know those F-16 pilots were looking for it. It's been proven time and again that you need a sizable hole to explosively decompress an airplane, one that would be easily visible externally.
(Manufacturers do this testing themselves, but the US TV show Mythbusters showed this on national TV here a while back, pressurizing a DC-9 on the ground to 35,000 feet and then doing various things to it to try to get an explosive decompression. The results of their tests showed that a small hole in an airplane - such as a bullet hole, which they tested - would not cause explosive decompression. They had to blow out an entire window pane before explosive decompression occured.)
Even if the damage was to an interior bulkhead, it would have caused secondary visible exterior damage, as happened to JAL flight 123.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
Wjcandee From United States of America, joined Jun 2000, 5515 posts, RR: 22
Reply 9, posted (9 years 9 months 2 weeks 3 days 18 hours ago) and read 3343 times:
Quoting Spacecadet (Reply 6): There have been literally dozens of explosive decompressions over the years and not one of them has in itself caused a crash. Not one of them, to my knowledge, resulted in the incapacitation of the crew either. It just shouldn't happen - I want to say it *can't* happen but I guess you never really know. It is always possible that a crew will react in a way contrary to their training.
I am afraid that you are far too cavalier about this.
Read this: http://www.ntsb.gov/ntsb/brief2.asp?...208X05709&ntsbno=CHI96IA157&akey=1 This WOULD CERTAINLY have been a fatal crash along the lines of the Helios accident if the FO, who had only 10 hours TT in the a/c, hadn't put on his mask at the first sign of a pressurization issue. The incredibly-experienced captain and the F/E and the F/A all ignored their training and experience and damn near paid for it with their lives. This was as close as anyone would have wanted to come to a real friggin' tragedy, and they were saved only because the rookie did the right thing. There's a much more critical analysis of this somewhere else on the web.
Wjcandee From United States of America, joined Jun 2000, 5515 posts, RR: 22
Reply 11, posted (9 years 9 months 2 weeks 3 days 18 hours ago) and read 3276 times:
One other thing on the ATA incident. By their own accounts, the Captain saw a cabin altitude of 14,000 feet and the f/e saw an altitude of 16,000 feet, and yet neither thought to don their masks. Indeed, after the cabin altitude warning lights illuminated, the captain, still with his mask off, told the f/a to go see if the cabin masks had dropped. She passed out upon returning to the flight deck to report that they had. The masks had dropped for the pax but the captain and f/e hadn't donned theirs.
I guess we can assume that "well trained crews" don't always follow their training. (Vis. the dead Pinnacle guys).
Again, according the NTSB report, only because the rookie donned his mask immediately upon hearing the cabin altitude warning horn did these guys live. Unreal.
AS739X From United States of America, joined Apr 2003, 6266 posts, RR: 24
Reply 12, posted (9 years 9 months 2 weeks 3 days 18 hours ago) and read 3244 times:
Wasn't the plane flying at 35,000 feet? If they had a pack out then they would have been flying lower then that. We fly our planes at 24 or 25 when operating on one pack. So them already having a A/C problem and reporting it tells me that if thats true, then they didn't take corrective action right then and there.
"Some pilots avoid storm cells and some play connect the dots!"
RobertS975 From United States of America, joined Aug 2005, 961 posts, RR: 0
Reply 13, posted (9 years 9 months 2 weeks 3 days 18 hours ago) and read 3184 times:
Quoting Geoffm (Reply 8): Payne Stewart, believed cause of accident (as far as I know from Googling) stemmed from explosive decompression.
The Ler 35 with Payne Stewart aboard did not suffer explosive decompression. There was apparent depressurization with incapitation of the crew and passengers. The plane flew on autopilot for hours, finally running out of fuel and crashing into a South Dakota field. There have been several other cases of unconscious crews presumably caused by hypoxia at altitude.
Connector4you From Canada, joined May 2001, 936 posts, RR: 2
Reply 14, posted (9 years 9 months 2 weeks 3 days 16 hours ago) and read 3074 times:
I tend to believe that either the flight crew was not properly trained for this particular emergency situation or they failed to properly and timely recognize the severity of it.
To support my belief, I have chosen a suggestive quote from the first article pointed to us here by Wjcandee.
Quote: While climbing out of 32,000' for 33,000' the cabin altitude warning horn sounded. The captain told the flight engineer to silence the horn. The flight engineer had trouble locating the silencer button and the captain pointed it out to him. While the captain was doing this he noticed the right pack was selected to the off position. The captain stated he tried to get the flight engineer to reinstate the pack. The cabin altitude continued to climb through 14,000' at which time the cabin altitude warning lights illuminated.
The lead flight attendant was in the cockpit serving meals and the captain asked her to look back in the cabin and see if the oxygen masks had dropped. She stated she looked in the back and the masks were in fact down. She returned to the cockpit and informed the captain that the masks were down. She then leaned against the cockpit door, became unconscious, and slumped to the floor.
The captain stated he recalled the flight engineer selecting "something" on the panel after the cabin altitude warning light illuminated. The flight engineer stated he turned the right pack on, selected manual AC, closed the outflow valve and checked the temperatures. He stated he recalled seeing the cabin pressure at 16,000' when he switched the pack on. He stated the cargo heat outflow valve was in the "normal" position and he did not think of closing it. It was at this time the captain recalled feeling an "air surge" at which time he reached for his mask. He recalled pulling the mask away from the strap but not putting it over his face.
The first officer stated he donned his oxygen mask when the cabin altitude warning horn sounded. He stated he then felt a "tremendous rush of air" and he switched to emergency oxygen flow for his mask. He stated that at this time they had lost most of if not all of their cabin pressure. He also stated that from the time the horn sounded until he felt the rush of air was less than a minute.