71Zulu From United States of America, joined Aug 2006, 2333 posts, RR: 1 Reply 3, posted (2 years 7 months 4 days 10 hours ago) and read 3316 times:
I think that is the cabin altitude alert but the crew had no idea what it meant in their condition. Amazing how they came back to normal so quickly after the descent, man they were lucky the controllers figured out what was going on and got them down.
Jawed From United States of America, joined Sep 2006, 477 posts, RR: 0 Reply 4, posted (2 years 7 months 4 days 10 hours ago) and read 3308 times:
The voices at the end sound so different, I can't actually tell where the crew goes from really drunk on oxygen deprivation to normal. Around what time does that change take place in the audio?
71Zulu From United States of America, joined Aug 2006, 2333 posts, RR: 1 Reply 5, posted (2 years 7 months 4 days 9 hours ago) and read 3286 times:
About 3:30-3:40, after he clears them to descend to 26,000 and talking about the precip you can hear a slight difference. The next time he talks he has been already cleared to 11,000 and not sure exactly what altitude he is at, but you can hear a big improvement. The co-pilot is first heard at 3:47, the captain comes back at 4:10 and you can now hear how he normally should sound and what a difference from the beginning. This 4.5 minute tape is condensed from about 30 minutes real time.
Pilotpip From United States of America, joined Sep 2003, 3014 posts, RR: 13 Reply 6, posted (2 years 7 months 4 days 9 hours ago) and read 3283 times:
Hypoxia is no joke. I saw a student of mine go totally unconscious at 10,000 feet in a 182 a few years back. I wasn't keen on his plan and told him the number of reasons for my objections but elected to let him find out why. I thought I'd be demonstrating that stronger winds aloft more than offset the increase in TAS but I didn't have the chance. I told ATC I was descending to 4,000 and he came to around 7,000 but really wasn't aware of how bad it was until he put on the portable O2 that I put on as we were climbing through 9,000.
I would highly encourage any of our pilots here to take the time to visit an altitude chamber. I usually start to really conk out at around 15,000 but prolonged time above 7,000 feet and I'll start to get a headache and get really thirsty. It's not unusual for me to grab a quick shot of O2 out of the mask and that will keep me sharp on our longer legs (4 hours). Watching the video after the fact was amazing as every one of us had very different reactions. Some acted drunk, some had blue lips, some got belligerent, and some just had very degraded motor skills. Knowing your symptoms could save your life.
FlybaurLAX From United States of America, joined Oct 2008, 619 posts, RR: 0 Reply 7, posted (2 years 7 months 4 days 8 hours ago) and read 3275 times:
That's just really crazy. I'm glad everything came out ok, and I'm impressed with how well the controller handled the situation, and other pilots helping out, too.
Moose135 From United States of America, joined Oct 2004, 1834 posts, RR: 14 Reply 8, posted (2 years 7 months 3 days 20 hours ago) and read 3162 times:
Do commercial/airline pilots undergo any sort of hypoxia training? In the Air Force, we were required to go through altitude chamber training, both during initial pilot training, and again every few years as refresher training. In addition to classroom training on the causes and effects of hypoxia, they take you for a couple of rides up in the chamber, so you can experience the effects of it - as Pilotpip said, different people react differently to hypoxia, and it's important to recognize your specific symptoms so you can react in time.
PJFlysFast From United States of America, joined May 2006, 463 posts, RR: 1 Reply 9, posted (2 years 7 months 3 days 17 hours ago) and read 3113 times:
We are trained to recognize the affects and symptoms of hypoxia but it is still unbelievable to actually hear it through that recording and how it can happen to anyone. I don't know if that incident could have been avoided if the pilots saw that there cabin pressure was decreasing or what but I will say that those guys are extremely lucky to be alive today because as we all know that could have had a very tragic ending.
Rwessel From United States of America, joined Jan 2007, 1614 posts, RR: 2 Reply 10, posted (2 years 7 months 3 days 17 hours ago) and read 3102 times:
Quoting PJFlysFast (Reply 9): We are trained to recognize the affects and symptoms of hypoxia but it is still unbelievable to actually hear it through that recording and how it can happen to anyone.
The altitude chamber session I did had some fixed video cameras and a guy with a camcorder. Fairly shocking footage, even though I was expecting it.
Tb727 From United States of America, joined Jun 2005, 1140 posts, RR: 4 Reply 11, posted (2 years 7 months 3 days 15 hours ago) and read 3079 times:
Quoting Jawed (Reply 2): Is that an alarm sounding in the background?
That was the cabin altitude sound alarm going off. In training it is drilled into our heads to listen to each alarm on pre-flight so you know what each one sounds like and means.
I am not going to go into specifics since I fly for that company and have flown that airplane. It was only moments away from becoming another Payne Stewart type incident if it wasn't for ATC descending the airplane.
Tdscanuck From Canada, joined Jan 2006, 11028 posts, RR: 72 Reply 12, posted (2 years 7 months 3 days 11 hours ago) and read 3045 times:
Quoting Moose135 (Reply 8): Do commercial/airline pilots undergo any sort of hypoxia training?
The Air Force altitude chamber training is available, for an extremely small fee, to anyone with an FAA medical cert. I'm not sure that there's any FAR requiring it of commercial pilots, but it's certainly a good idea. For the ~$75 it costs, I think you'd be a fool to fly an airplane without it, or something equivalent.
PJFlysFast From United States of America, joined May 2006, 463 posts, RR: 1 Reply 13, posted (2 years 7 months 2 days 21 hours ago) and read 2976 times:
Quoting Tdscanuck (Reply 12): The Air Force altitude chamber training is available, for an extremely small fee, to anyone with an FAA medical cert. I'm not sure that there's any FAR requiring it of commercial pilots, but it's certainly a good idea. For the ~$75 it costs, I think you'd be a fool to fly an airplane without it, or something equivalent.
Where can you find these chambers?
Also I looked further into this incident and by talking to both pilots and maintenance professionals who used to fly Learjet's they said that they leaked supplemental oxygen on the ground so bad that some crews would turn it off and the only way to do that is from the outside near the nose and one in the back of the aircraft so if you forgot to reopen these valves before your flight and you had a decompression then you were out of luck when you put on your masks.
Tb727 From United States of America, joined Jun 2005, 1140 posts, RR: 4 Reply 14, posted (2 years 7 months 2 days 21 hours ago) and read 2968 times:
Quoting PJFlysFast (Reply 13):
Also I looked further into this incident and by talking to both pilots and maintenance professionals who used to fly Learjet's they said that they leaked supplemental oxygen on the ground so bad that some crews would turn it off and the only way to do that is from the outside near the nose and one in the back of the aircraft so if you forgot to reopen these valves before your flight and you had a decompression then you were out of luck when you put on your masks.
That may happen but that wasn't the case in this flight.
PJFlysFast From United States of America, joined May 2006, 463 posts, RR: 1 Reply 16, posted (2 years 7 months 2 days 18 hours ago) and read 2933 times:
Quoting 2H4 (Reply 15): There's one at the Wright-Patterson base in Dayton. Here's an article about one in Florida:
Njxc500 From United States of America, joined Dec 2007, 185 posts, RR: 0 Reply 18, posted (2 years 7 months 2 days 8 hours ago) and read 2842 times:
One of my instructors was in the air force, and we were on a cross country on a clear day and he put on a mask and took me to 17,500 in a 182. My reaction was minimal over 15 minutes, but I was definitely slow, and I'm sure it could have gotten really bad. I agree with all the comments, and I think instructors should cover this to some extent.
How many GA aircraft actually carry masks on board. I had 2 masks in my 182, and I used them on occasion, especially at night over 5,000 feet. It is amazing how much difference it can make and surprising how low it can make a difference.
I happen to use Fairchild AFB in Spokane, but the link Rwessel provided gives you the whole list. *Very* worthwhile training, in my opinion, for any flight crew, private or commercial.
DocLightning From United States of America, joined Nov 2005, 14022 posts, RR: 55 Reply 20, posted (2 years 6 months 4 weeks 12 hours ago) and read 2590 times:
Quoting 71Zulu (Reply 3): Amazing how they came back to normal so quickly after the descent, man they were lucky the controllers figured out what was going on and got them down.
So this is explainable by the molecular structure of hemoglobin. OK, put your geek hats on.
Hemoglobin is a "tetramer," which means that it is a combination of four subunits. Two alpha chains and two other chains (Beta chains in normal adults, gamma chains in fetuses and newborns, etc.). If you start with hemoglobin in its completely deoxygenated state, it has zero molecuoes of O2 attached. When one of those subunits binds a molecule of O2, it undergoes a change in shape that is transmitted to the other subunits making it easier for them to bind oxygen. With each binding of oxygen, the barrier to more binding gets lower. The flip-side is that if you have fully oxygenated hemoglobin, having one oxygen molecule unbind makes it more likely that another one will unbind, etc.
The result of this is that the percent saturation of hemoglobin in the blood increases from very low at low oxygen pressures to very high at higher pressures in a very sharp, S-shaped curve. This is important because it basically means that when hemoglobin is in an oxygen-rich environment, like the lungs, it will grab all the oxygen it can get, but in an oxygen-poor environment, like the innards of a working brain, it will readily dump all the oxygen it has (in reality, the venous oxygen saturation in even a vigorously exercising human is never less than about 40-50%).
However, this system evolved under elevations of sea level to about 14,000 feet. Higher than that and the partial pressure of oxygen in the atmosphere drops so low that you start to drop the oxygen-binding affinity of hemoglobin, even in the lungs. So for a very small decrease in pressure, you drop WAY down the saturation curve.
Once the aircraft descends, you drop way UP the saturation curve just as quickly and then it's simply a matter of waiting for the blood to get to the brain (a process of no more than a couple minutes).
KELPkid From United States of America, joined Nov 2005, 5609 posts, RR: 5 Reply 22, posted (2 years 6 months 3 weeks 16 hours ago) and read 2334 times:
Quoting DocLightning (Reply 20): So this is explainable by the molecular structure of hemoglobin. OK, put your geek hats on.
Hemoglobin is a "tetramer," which means that it is a combination of four subunits. Two alpha chains and two other chains (Beta chains in normal adults, gamma chains in fetuses and newborns, etc.). If you start with hemoglobin in its completely deoxygenated state, it has zero molecuoes of O2 attached. When one of those subunits binds a molecule of O2, it undergoes a change in shape that is transmitted to the other subunits making it easier for them to bind oxygen. With each binding of oxygen, the barrier to more binding gets lower. The flip-side is that if you have fully oxygenated hemoglobin, having one oxygen molecule unbind makes it more likely that another one will unbind, etc.
The result of this is that the percent saturation of hemoglobin in the blood increases from very low at low oxygen pressures to very high at higher pressures in a very sharp, S-shaped curve. This is important because it basically means that when hemoglobin is in an oxygen-rich environment, like the lungs, it will grab all the oxygen it can get, but in an oxygen-poor environment, like the innards of a working brain, it will readily dump all the oxygen it has (in reality, the venous oxygen saturation in even a vigorously exercising human is never less than about 40-50%).
However, this system evolved under elevations of sea level to about 14,000 feet. Higher than that and the partial pressure of oxygen in the atmosphere drops so low that you start to drop the oxygen-binding affinity of hemoglobin, even in the lungs. So for a very small decrease in pressure, you drop WAY down the saturation curve.
Once the aircraft descends, you drop way UP the saturation curve just as quickly and then it's simply a matter of waiting for the blood to get to the brain (a process of no more than a couple minutes).
Any idea what this curve looks like for other animals? I once flew with a friend, and the friend had a litter of bunnies (and a momma rabbit) in a cardboard box in the baggage area. It was a spring day, over New Mexico, so we cruised at 10,500 feet (initially...), until my friend noticed that the little rabbit kits (that's what you call a baby rabbit) appeared to be passed out...so I went lower (8,500) and threaded around the mountain peaks, rather than fly above them.
The bunnies appeared to be okay upon arrival, just a little woozy...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
DocLightning From United States of America, joined Nov 2005, 14022 posts, RR: 55 Reply 23, posted (2 years 6 months 3 weeks 12 hours ago) and read 2308 times:
Quoting KELPkid (Reply 22):
Any idea what this curve looks like for other animals?
Well, it's always an S-shaped curve, but obviously different species will have different hemoglobin molecules and different levels of modifying factors.
For your bunnies, I don't know about rabbit hemoglobin, but I do know that baby humans (and presumably all placental mammals) have a hemoglobin that has a higher oxygen affinity than adult hemoglobin. This is so that the fetal hemoglobin can grab oxygen from the maternal hemoglobin. However, at high altitude, it's more reluctant to give up its oxygen in the tissues, so that's why babies tend to tolerate high altitudes more poorly than adults.
DocLightning From United States of America, joined Nov 2005, 14022 posts, RR: 55 Reply 24, posted (2 years 6 months 3 weeks 8 hours ago) and read 2281 times:
Oh, another thought on the rabbits. I know that after humans are born, they have hemoglobin levels that can be higher than a grown man's. But very quickly, within a few weeks, those levels drop quite low.
I would assume that this process occurs in rabbits (but I don't know; any vets around?), and maybe that's why the kits were more affected.
Maverick623 From United States of America, joined Nov 2006, 3807 posts, RR: 4 Reply 25, posted (2 years 6 months 2 weeks 6 days 16 hours ago) and read 2209 times:
Quoting Rcair1 (Reply 21):
Sorry - couldn't resist - my house is above 7000ft.
And yes - people who are not acclimated to elevation can have problems here.
When I was 12, I went up to visit some family in Wyoming. We had to leave two days early because I was so sick I couldn't eat anything.
It was strange, because as soon as we hit 4000 feet I perked up, garbled down a ton of food, and I've never had trouble with altitude sickness since...
Quoting Rcair1 (Reply 21):
but prolonged time above 7,000 feet and I'll start to get a headache and get really thirsty.
That's actually plain dehydration, as at higher altitudes water evaporates from the lungs at a faster rate.
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