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Parachutes in commercial aircraft.

by matthyaouw
Tags: aircraft, commercial, parachutes
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matthyaouw
#1
Aug19-05, 02:57 PM
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I've been told that commercial aircraft don't provide parachutes due to the fact that depressurising the aircraft suddenly to let everyone jump out would kill them. This doesn't add up... If the plane is at 40,000ft, then fair enough, you can't really blow the doors, but if the plane is in trouble then it's not going to stay at that altitude very long, so as it decends there must be a point where the doors can be safely blown (perhaps the cabin could be decompressed slowly as it decends?)
Anyway, surely the problems caused by decompression must be less than those caused by sudden, flaming "supercompression"?
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Entropy
#2
Aug19-05, 02:59 PM
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No it wouldn't kill you. They probably don't put parachutes on because it would be to hard to teach everyone on board how to use them properly.
wolram
#3
Aug19-05, 03:05 PM
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Knowing a little about the industry, i would say airlines would give all sorts of
reasons why they do not have them, but saving weight would be the last thing
they would say.

hitssquad
#4
Aug19-05, 03:08 PM
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Parachutes in commercial aircraft.

Even if it were technically feasible, why would you put parachutes in a commercial aircraft?
outsider
#5
Aug19-05, 03:16 PM
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they lose cargo revenue due to weight restrictions, plus they would have to pay for the parachutes, and will also need to pay to train staff (it's not cheap and there are a lot of staff, some of whom would not want to skydive for training)...

and then there is the actuarial calculation based on deaths to justify their use... remember that the parachute is not a guarantee of life...

and imagine 300 parachutes coming down all around you... is that war or a plane coming down?
Moonbear
#6
Aug19-05, 03:20 PM
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Quote Quote by Entropy
No it wouldn't kill you. They probably don't put parachutes on because it would be to hard to teach everyone on board how to use them properly.
I agree that they aren't terribly useful if you don't know how to use it properly, when to open it, etc. Not to mention somehow avoiding sucking the passengers through the jet engines as they are jumping out of an erratically descending plane that may or may not still have power to some engines (I don't know if that would be part of the problem, but that's because I'm one of those people who would have no idea when to open a 'chute or how to land, or how to steer it away from someone's swimming pool or the high tension power lines or the 4-lane highway. ) I'd rather take my chances with the pilot managing to get the plane back under control or landing with a plane still between me and the ground with emergency crews ready and waiting.
hitssquad
#7
Aug19-05, 03:27 PM
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They would exit out a back door (back doors would have to be designed into all planes)so they wouldn't hit the wings and engines. But 200-600 novice jumpers all trying to get out of a plane at the same time would never work. 90% would freeze up in the doorway. And no one else would be able to get out. There would be panic and riots. It would be basically a holocaust.

Most commercial jet crashes occur on take-off or landing. You can't jump out of an airplane that close to the ground, and if you could, could you get 600 people to get strapped into parachutes and out one door in 5 seconds?
Moonbear
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Aug19-05, 03:36 PM
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Quote Quote by hitssquad
But 200-600 novice jumpers all trying to get out of a plane at the same time would never work. 90% would freeze up in the doorway. And no one else would be able to get out.
I'm not sure that would be the biggest issue. Afterall, the other 199 people behind them would probably just shove them through the door whether they wanted to go or not. I would think the bigger problem would be once they were shoved out of the plane, all those who balked at the door are going to completely freeze up in panic with the sensation of free-fall, possibly even black out, as they plummet to the ground and will forget to pull the cord or be unable to do so.

Most commercial jet crashes occur on take-off or landing.
Technically, don't they all occur on landing? A really bad, perhaps unexpected, sudden landing, even if it occurs only moments after the initial take-off? Well, with the exception of the rare mid-air collision I suppose.
hitssquad
#9
Aug19-05, 03:57 PM
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Quote Quote by Moonbear
the other 199 people behind them would probably just shove them through the door whether they wanted to go or not.
I was thinking of Fluffy the Cat and a bathtub full of water. Besides, it has been demonstrated numerous times in burning buildings that a pile of people trying to get out one door will just create a pile. Fluffy the Cat in front won't help matters.



as they plummet to the ground and will forget to pull the cord or be unable to do so.
Commercial jump companies use a system for novice jumpers that automatically pulls the rip cord as the jumper exits the plane. (You clip your ripcord to a cable strung along the inside of the fuselage at about head height.) Naturally, commercial jets would use the same system.



Technically, don't they all occur on landing?
Good point. But seriously, on takeoff if one of the engines conks out, the plane crashes. Also, an unusual temperature inversion situation where the air near the airport is rushing downward causes some plane crashes on takeoff. For the former, we can make more reliable engines and stiffer maintenance requirements, but nothing can be done about the latter.
Moonbear
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Aug19-05, 04:22 PM
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Quote Quote by hitssquad
I was thinking of Fluffy the Cat and a bathtub full of water. Besides, it has been demonstrated numerous times in burning buildings that a pile of people trying to get out one door will just create a pile. Fluffy the Cat in front won't help matters.
The problem/difference with escaping a burning building is that if you try to shove the person ahead of you out of the way, they trip and fall in front of you creating an obstacle to everyone behind them. Someone else trips, starts creating a pile-up, people get trampled, and it's all quite mess. With jumping out of a plane, if you shove the person in front of you out the door, there's nothing there, so they don't continue to be an obstacle.

However, there would be the complication of trying to get everyone into their 'chutes, people still putting them on as they get to the door, the person in the front of the plane who gets theirs on quickly and tries to climb over the people in the aisle still trying to sort out the clasps, etc. I'm certainly not disagreeing there would be major logistic issues that would make it a far worse option than just staying buckled into your seat while the pilot does his/her best to regain control of the aircraft. If you're still at high enough altitute to jump when a problem is discovered, I would think you'd have a lot more chance that the pilot could land the aircraft...dump fuel, try to glide in, have runways cleared and coated with foam if necessary, etc.

Commercial jump companies use a system for novice jumpers that automatically pulls the rip cord as the jumper exits the plane. (You clip your ripcord to a cable strung along the inside of the fuselage at about head height.) Naturally, commercial jets would use the same system.
Hmm..I didn't know that. I always assumed that's why people did tandem jumps when first jumping, so you would be with someone more experienced until you learned how to do it yourself.


Good point. But seriously, on takeoff if one of the engines conks out, the plane crashes. Also, an unusual temperature inversion situation where the air near the airport is rushing downward causes some plane crashes on takeoff. For the former, we can make more reliable engines and stiffer maintenance requirements, but nothing can be done about the latter.
Yeah, I was only joking about them all happening on landing. I understood what you meant about crashes at take-off.

The cost issue that has been raised is also not insignificant. For that one flight every 10 years where it might help to have jumped mid-air rather than crash-landing, it just doesn't make financial sense. Airlines are already struggling with rising fuel costs. If you add more weight and take up space that could have been used to earn revenue with cargo, all the airlines will be going bankrupt because it'll be too expensive for most people to buy a plane ticket.
Evo
#11
Aug19-05, 04:24 PM
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Quote Quote by Moonbear
However, there would be the complication of trying to get everyone into their 'chutes, people still putting them on as they get to the door, the person in the front of the plane who gets theirs on quickly and tries to climb over the people in the aisle still trying to sort out the clasps, etc.
Then there would be the morons trying to get their luggage out of the overhead bins.
Moonbear
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Aug19-05, 04:36 PM
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Quote Quote by Evo
Then there would be the morons trying to get their luggage out of the overhead bins.
There's always one of them! I was on a flight with a medical emergency on board (okay, several medical emergencies...half the flight crew came down with food poisoning, or something with similar symptoms about mid-way between Britain and the US). We were instructed to stay in our seats, clear of the aisles and to NOT open the overhead bins until the EMTs were done and had assisted the sick crew members off the plane. And of course there was one moron who got up to get his bag the moment the plane came to a stop and was in the way as the EMTs were trying to get down the aisle.
Ivan Seeking
#13
Aug19-05, 05:34 PM
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One idea that people are toying with is that of parachutes for the airplane itself. This is now done for some small planes, and the technology already pretty much exists to do it for jets - from the space program. The questions are whether or not it would do much good and of course the cost.



Previous thread.
http://www.physicsforums.com/showthr...ight=parachute

This system has already saved lives.
moose
#14
Aug19-05, 05:35 PM
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When does everyone think "OK we have to jump now, we wont make it" and actually have time to jump out and get everyone out? Most of the time you wouldn't know you are definitely going to crash, and once you do, well, you wouldn't have time for parachutes. Plus, the added weight would make airplane tickets cost more because of more fuel usage. Why make something safe only slightly safer, yet uneconomically? I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air????????????????
Grogs
#15
Aug19-05, 07:00 PM
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Quote Quote by moose
When does everyone think "OK we have to jump now, we wont make it" and actually have time to jump out and get everyone out? Most of the time you wouldn't know you are definitely going to crash, and once you do, well, you wouldn't have time for parachutes. Plus, the added weight would make airplane tickets cost more because of more fuel usage. Why make something safe only slightly safer, yet uneconomically? I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air????????????????
It's not only that. The FAA requires that reserve parachutes get repacked every 90 days, whether they're used or not. This has to be performed by an FAA Master Rigger and the going rate, on a civilian drop zone is about $50 per repack. Multiply $50 by 300 by 4 times per year, and you're looking at an additional $60,000 per year per plane. You'd also have to store the parachutes somewhere that the passengers couldn't get too them during a routine flight, otherwise they'd have to be inspected after every flight to make sure they hadn't been tampered with.

As bad as the financial problems are, they wouldn't be anything compared to the technical problems. You have 300 people scared out of their minds trying to don a piece of gear they are completely unfamiliar with, move to the rear of the plane, and jump out.

Assuming that's no problem, when 300 people run to the rear of the plane, the Center of Gravity will shift beyond the Aft CG limit and the plane will stall, the people will be pinned to the ceiling until the pilot recovers from the stall (if he can,) then slung to the floor. The plane probably isn't in very good condition in any case (everyone's jumping out after all) so this problem is more likely.

Next you've got exit speed. A commercial airplane cruises at about 400-500 knots. Standard parachutes are made to open at speeds more along 110 knots. No parachute I know of is designed to open at 4-500 kts. It would either rip the fabric of the canopy to shreds, break most of the lines on the chute, or rip the harness out from between your legs (maybe taking them along.) The only way to slow down to the proper speed would be to jump out and freefall for a while until you reached a slower speed, then deploy. Obviously, this isn't possible with a static line system, and even if you did give the passengers a manually deployed chute, how many of them are going to wait more than a nanosecond before they pull the ripcord or throw out the pilot chute.

Back when I jumped every weekend, I carried my rig on a commercial airliner a couple of times. I thought about every conceivable scenario, and the only time I could see using it was if the plane disentigrated around me and I was able to don it before I passed out from hypoxia. I ended up just putting it in the overhead bin.
Pengwuino
#16
Aug19-05, 07:11 PM
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Quote Quote by moose
When does everyone think "OK we have to jump now, we wont make it" and actually have time to jump out and get everyone out? Most of the time you wouldn't know you are definitely going to crash, and once you do, well, you wouldn't have time for parachutes. Plus, the added weight would make airplane tickets cost more because of more fuel usage. Why make something safe only slightly safer, yet uneconomically? I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air????????????????
Yah! In what situation are you really going to have the pilot thinking that this is an unsurvivable situation yet be level enough and high enough to start parachuting people out? All i can think of is having a fuel leak occur in the middle of the ocean.
hitssquad
#17
Aug19-05, 07:23 PM
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Quote Quote by Pengwuino
All i can think of is having a fuel leak occur in the middle of the ocean.
No one would survive a parachute jump into the ocean. Oceans are great for ditching planes, though.

Pengwuino
#18
Aug19-05, 07:40 PM
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Oh yah good point...

Those peopel look awefully happy for having their aircraft bail into the ocean.


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