I contacted my friend who used to fly 747s. He said that 6000 fpm is no problem (he even gave me the checklist for this). But starting from 38,000’, there’s likely to be problems for folks without supplemental oxygen.
Ooh, ooh, my two cents:
When I last did the altitude chamber and we prepared for rapid decompression, we did pre-breathe 100% oxygen for a half-hour - the reasoning being that we were told that we were subject to getting the bends. So, I’m inclined to go with Broomstick on that one. Here’s my problem with the parachutes - it takes a trained person a half-minute to don a chute. You gotta wrap straps around your legs, buckle stuff, adjust and tighten straps, etc. I don’t see a reasonable situation where the flight attendants can possibly get everyone suited up rapidly in such a confined space. Plus the added weight. So, ejection seats? Well, Martin-Baker says they weigh about 125-150Lb per seat (check out some of their other cool stuff!). Multiplied by the number of passengers, that cuts even more into useful load and profits. AND, I’ll tell you they aren’t too comfortable - imagine something worse than coach (which is all I know outside the cockpit), where you’re constantly strapped in and can’t recline.
I have been on flights that if there had been selective ejection seating, I do believe it would have been used by for some passengers regardless of an emergency with the actual aircraft. 
OK, I think that’s how mssmith537’s coding was supposed to work…
Look, the point is not “Can Xema go to 32,000 feet with supplemental oxygen without passing out?”, it’s what happens to folks across a spectrum of humanity. In the average planeload of passengers some will be able to tolerate high altitude than others, it’s that simple.
About footage of bomber crews - know something else you never see? NASA astronauts vomiting. But 2/3 of them do exactly that for their first 3-7 days in space. It’s always happy-happy-joy-joy on the video. Likewise you don’t see hypothermic bomber crews passing out at their stations, only heroic men doing their patriotic duty. But men did become hypothermic, they did occassionally pass out, there were cases of frostbite… in early testing with high-altitude chambers men sometimes died because the effects weren’t well understood and neither were the risk factors. Now we’re aware of some of these factors, which is why Caligynephobia did some pre-breathing before entering one, because why take the risk of the bends when you don’t have to? Does that mean if the pre-breathing hadn’t been done Caligynephobia would have had the bends? Dunno. Maybe, maybe not. How would your grandmother do? I dunno - and neither do you. We don’t do high-altitude testing on senior citizens, people with heart disease, the morbidly obese, people with headcolds, or drunken tourists returning from Puerto Rico but it’s a fair bet they’d fair worse, to one degree or another, than your average person shuffled into such a chamber because ill/weakened/at high risk people are not put into such situations delibrately.
In the case of Everest - no one is simply dropped off at Base Camp in a helicoptor. You are dropped off at a much lower airstrip and walk the rest of the way up, giving your body a chance to adapt. These adaptations take days or even weeks or months to engage. There won’t be time for them to kick in if your plane suddenly despressurizes. Above Everest base camp, even the most well-conditioned body starts a slow (and sometimes not so slow) deterioration, becoming progessing more dehydrated, less able to keep warm, and unable to heal injuries, even minor ones. Nowhere on Earth are there permanent human habitations above 14,000 feet - that’s only half the height of Everest - because long-term we don’t do well at those altitudes. Even the Sherpas and Tibetans struggle on Everest, it really is at the very limit of human endurance. People do die on Everest from the effects of altitude, even very fit people. That’s another thing you never seen in those nature films of the great, icy vistas of Everest - the dead bodies along the trails. They stay there, because at that altitude no one has the strength to drag them down or bury them.
My personal opinion is that if you did have this hypothetical emergency at 30,000 feet a good dozen or so folks would never get their oxygen masks on and would quickly pass out. I don’t know how you’d get 100+ people into a parachute harness who have never had one on before - some of them won’t strap in properly. Later on, this may be fatal. Good luck keeping order among these folks while evacuating - diminished oxygen supply + fear will result in folks amenable to reason and more prone to panic. Add in some alcohol for more fun. Someone is going to get hurt going out the door, probably a couple of them. Worst case - you get a crowd jam, like the E2 nightclub in Chicago, or what happened in the Rhode Island Station with the Great White concert - folks form a jam in the exit and no one gets out after that, and some are crushed to death outright. Some folks may pass out on during the trip down - maybe their mask gets dislodged, maybe they hyperventilate, if they have cardiac problems they may just have a heart attack The parachutes had better be pretty foolproof, both in opening up and in remaining functional - that is, the lines don’t tangle, they don’t require steering, etc. Then, when you get to landing, you have hazards like powerlines, trees, water, and ground obstacles that provide all that footage you see on those TV shows purporting to be funny - guys slamming into someone’s Ford or Dodge or house roof as they land. You’re going to get at least a few sprained ankles, probably some fractures as well.
In other words, the evacuation process is going to kill at least a couple people, and injure a bunch more.
OK, people seem to be getting a little too wrapped around the axle here.
The question was whether parachutes would be feasible on an airliner. I think we’ve established that for the “dangerous” operations (ie takeoff and landing) a parachute would be useless. The only time that a parachute would even begin to be feasible would be at cruise (and then we have to consider all of Broomstick’s very valid points about the dangers involved.)
So, let’s say you’re cruising along in coach at 35,000 ft. Suddenly something goes wrong. Unless it involves the structural integrity of the airplane and you lose pressurization the doors are NOT coming open until you are too low for parachutes to be useful.
As an example, let’s use the smallest door - an overwing exit. And lets use a very small pressure differential - say 1.0 PSID, something that you’d see at about 2,000 feet AGL. An overwing exit door has to be big enough to let everyone out - let’s call it 3 feet tall and 2 feet wide. So, 36 in tall by 24 in wide = 864 sq inches on that door. At ONE PSI differential there is 864 lbs of pressure forcing that door into the seal. Good luck getting it open. Suffice it to say that NO door is coming open while the airplane is pressurized.
So, our emergency at 35,000 feet has depressurized the airplane. Everyone on board the airplane will go from 8,000 feet cabin altitude to 35,000 feet actual altitude. Regardless of the very real danger of the bends, everyone will be fighting the Time of Useful Consciousness battle. The more rapid the decompression, the lower the TUC. Times vary, but for an average person a decompression to 35K will result in a TUC of about 30 seconds. Go here for a well-done illustration of the problem.
Now, what happens when the airplane depressurizes? I can assure you that the pilots up front will be quicker on the mask than you are. In fact, I am required to wear the mask above 25K when the other pilot gets out of the seat. Even with both of us in the seat, we have “quick-don” masks that we test before every flight and are intimately familiar with. We practice flying approaches with these things on (including the smoke goggles) just in case something like this happens. When the airplane depressurizes we will immediately begin an emergency descent down to a habitable altitude (10,000 ft depending on terrain). We will max perform the aircraft during the descent - meaning the descent rate and airspeed will be as high as we can get them (barring known structural damage).
So, the airplane depressurizes - if you can stay conscious long enough to don your parachute, get to a door and then open it you will be contending with extremely high airspeeds, virtually ensuring broken limbs on the exit from airstream impact alone. Then you must contend with the external factors - temperatures, landing area, future survival, etc.
Someone asked earlier about people bailing out affecting an airliner’s CG. If the airplane is controllable enough to allow a bailout, this should not be a problem. IF (notice the capital IF) we set up the airplane for a bailout it would be much like a military airdrop - slow speed (say 150 knots), and medium altitude. At this speed the longitudinal control from trim and elevator control is more then enough to compensate for CG shifts due to passengers exiting the aircraft. So, no problem.
But here’s the big question: if we can control the aircraft that well, why in the world would you want to jump out of it? If we can slow it down and control it, we can land the thing.
So we come down to a parachute being considered in the following situation: At cruise an airliner loses pressurization, the pilots become incapacitated but the airframe itself is not damaged and the airplane continues to cruise at 35,000 feet (if it descends the pilots will regain consciousness at a lower altitude). Some passengers are able to remain functional long enough to don their parachutes, make their way to a door and then open the door (all within 30 seconds). They then jump out over (take your pick: the North Atlantic, the Pacific, Northern Canada, etc. The area of the Earth that is populated is surpisingly small) what is most likely very hostile terrain. They then attempt to survive with literally what they have on their backs. My words to you: Good luck. Buy a lottery ticket when you get back to civilization.
How often has something like this occurred? The crash of a Learjet with golfer Payne Stewart aboard was due to a pressurization malfunction - but at 37,000 feet it incapacitated everyone on board. I cannot find a single instance of a pressurization problem that incapacitated the pilots but left the passengers conscious.
In short, don’t sweat the lack of parachutes and enjoy the flight!
Good jobs, Pilot141, Broomstick.
One thing to add. The doors could be disigned to open at any altitude.
Maybe explosives that would blow off the hinges that keep the door in place. Or some battery backup electronic solenoid device that could be enabled in an emergency.
From all the previous post I think we can agree that bailing out the passengers of a commercial is restricted to a freak situation, which AFAIK has never happpened; on the other hand installing explosive devises to blow open large panels on the fuselage yield a greater source of potential problems than the prospect of succesful parachute evacuation could offset. IMO,YMMV and all that…
I agree. Very informative thread. It’s also a somewhat common thing to wonder about, so I’m thinking that with a little bit of editing, the longer, more detailed posts above could be smushed together to make a very nice Mailbag article.
Bullshit. Using a parachute does not take training. Anyone can pull a ripcord - and you don’t even need to do that if you’re on a static line drop. The difficult part is landing. I almost broke my elbow learning PLFs.
Also, didn’t the French prove in Vietnam that the casualty rates from drops were the same whether the users were trained or not?
In the SF novel One Milluion Tomorrows by Bob Shaw, the passenger jets are equipped with seats that, in the event of an unrecoverable emergency, would automatically manouevre themselves out of the door in orderly fashion, on a rail system; the descent was made safe by means of a force-field parachute, which is about as workable a concept as the whole.
Disclaimer: while I work in a relevant industry, I’m not an aeronautical engineer or scientist.
There’s another possibility which might bear consideration: the plane disintegrating, likely due to a bomb (q.v. Lockerbie). So the shell of the plane is disintegrating. You’re still strapped to your seat and the parachute pack is with the lifejacket under the seat or it might be in the seat-back, designed as a tearaway. So it’s falling with you. Maybe there’s an oxygen supply in the seat as well. As others have said, at cruising altitude you’ve got maybe 30 seconds without oxygen before brain damage hits. If the parachute is under the seat, you’re going to need all that time to get the d*mn thing on. And mind you don’t lose it in the wind. But let’s suppose it’s built into the seat and a quick-fit device, so it takes very little time. And you’ve got the oxygen so the clock doesn’t start counting until you exit the seat. Most people will pull the ripcord immediately upon exiting and thereby doom themselves as it will take a long time to get to a low enough altitude to survive. Sure your body will get down safely, but your brain won’t. The more educated person will realise that he needs to get lower ASAP and not deploy his chute until later, but how does he determine the altitude? How does he determine the correct altitude at which to deploy?
Basically, you’re stuffed. If the plane is still flying, trust the pilots and maybe go forward to check on them. Otherwise enjoy the ride down. You might as well.
So… who gets to do the editing?
Er… if a bomb goes off you’ll likely be unconcious from the concussion effects. There’s also the matter of flaming jet fuel (hot enough to melt steel) and flying shrapnel in the vicinity. Things are not looking good for Our Hero from the onset…
Couple questions: if the parachute is on the back of the seat, and you’re strapped into the front, how are you going to reach it? Or am I misunderstanding what you’re saying here? Or do you plan to unbelt, hang onto the seat, and somehow manipulate it and yourself around to access the relevant equipment? In 30 seconds or less?
Keep in mind, also, that the “time of useful conciousness” is not 30 seconds of clear thinking followed by >boom< - out go the lights. It’s useful conciousness, not clear conciousness. During that brief interval your vision will be dimming and narrowing from the normal field of view to a small dot of light. Your judgement and coordination will be impaired. And you will be colder than you have ever been in your life. Ever try to untie your shoelaces with numb fingers? It will be worse than that.
That is why Pilot141 and his co-workers are required to actually WEAR an oxygen mask when above 25,000 feet and the other pilot leaves his duty station. That interval of conciousness is too small and fragile to garauntee that even an experienced, trained, and practiced pilot can get a quick-donning oxygen mask in place and working.
For your scenario you’d almost be better off with a robot that automatically slaps a mask over your face and straps you into a parachute - except we don’t have those. Any equipment you proprose for use in such an emergency has to be amazingly easy to use and blindingly obvious in how to use it even to the Average Drunken Tourist
By the way, anyone taking a nap in their seat at the time this happens is doomed.
Actually, it just might - the extremely low temperatures will lower your metabolic rate (if they don’t kill you) which might buy the brain additional time. As they say in the winter time here in the Midwest when they drag a corpsicle into the ER, you aren’t dead until you’re warm and dead.
As someone who flies frequently in small planes, I’m a pretty fair judge of altitude and, if sufficiently motivated, could probably judge 1000 or 2000 foot above ground level by eyeball - but that took considerable experience and practice to learn. I’m pretty educated and reasonably at ease in the sky, but I honestly don’t know if I’d have the willpower to hold off from pulling the ripcord before that. I also know that most 'chutes need at least 400 feet to open (curtesy of my skydiving friends) so I’m guessing a pull anywhere between 1000-5000 feet would be acceptable. So, just watch me and when you see my 'chute open pull your ripcord.
Really, though, anything likely to make the plane totally unflyable will probably kill the passengers, too. Airplanes can fly even with massive structural damage - that flight out of Hawaii where the skin of the fuselage peeled off over a large section of the passenger cabin was still flyable and landed safely (aside from the folks who fell out in the initial problem). The Sioux City, Iowa crash involved an airplane that was almost unsteerable yet 2/3 of the folks aboard survived. You really are better off sticking with the airplane barring an extreme freak of an accident. Systems like ejection seats, explosive bolts for doors, and the like are far more likely to malfunction and cause a problem than to be utilized in an emergency.
Interesting mental excercise, though.
Not to mention that the extra weight of all that hardware comes at the cost of carrying fewer passengers or less baggage; this is one area where small changes can very quikly eat away at the airline’s competitive margin.
Well I think this question has been very comprehensively answered. I’d just like to say that if something fairly disastrous happened at altitude, but the aircraft was still more or less intact, I would be inclined to have faith in the aircrew’s ability to get it down safely. After all, they have quite a vested interest in landing it 
I don’t know if anyone remembers this 10-15 years ago.
“From 11,470 metres, the 747 became an enormous glider as the crew repeatedly tried to restart the engines. During the first check the plane fell as much as 930 metres; the crew ran through the restart procedures at least twenty times after that. At 4,030 metres altitude, one engine was restarted and another started about 90 seconds later, and 20 seconds after that the remaining two engines came on with an enormous roar. But the number two engine was surging badly, causing the plane to lurch from side to side, so Captain Moody ordered it shut down.”
Imagine what a rush for the exits there would have been if everyone had been sitting there with their parachutes on when this happened.