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deaphen
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Are Planes Too Fragile?

Thu May 04, 2006 2:08 am

Hi,
I am sure as all of you are aware, in most opinions, a plane crash means total fatality. Well in a majority of the cases, it does mean that all the passengers and crew on board perish. An example is the Armenian plane crash which everyone has been shocked over.

We over here are all aviation lovers and hence whether a plane goes down in the USA or in India or Russia, it hurts us. Mainly because of the loss of life which causes so much distress to families but also its like one of US has gone down. I dont know why, its just a sinking feeling when any aircraft is lost.

Anyways, back to my question. Why are most plane crashes concieved to be so fatal? I mean are they made of very fargile material? Couldnt there be a way that the main fuselage of an aircraft could survive even on an impact at about 250-300 kmph? I agree that at cruise and other times when the speed is extremely high, the chances of the fuselage sustaining totaly damage is great, but what about the Armenian crash. How fast would they have been going when they hit the water?

Is this scenario in any way avoidable? I mean when you stand there are look at a plane all you can think about is how strong it looks (physically), but when it comes to an accident, they seem so fragile.

Can anyone answer my question and perhaps give your own comments. I have always wondered if anyone else has felt this way.

thanks
nitin
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Ralgha
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:16 am

One word: Fire.
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longhauler
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:17 am

While it is feasible to make an aircraft with a "crash cage" construction, much like Volvo or Mercedes Benz automobiles, there is no way the human body can withstand deceleration forces like that. Even if strapped into a secure seat, every internal organ in one's body would let go, and you would be dead before the aircraft stopped.
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OPNLguy
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:19 am

Quoting Deaphen (Thread starter):
Couldnt there be a way that the main fuselage of an aircraft could survive even on an impact at about 250-300 kmph?

Most simply stated, one could engineer an aircraft to better withstand such impact forces, but the resultant aircraft would weigh so much that there would be little (if any) payload carrying capability, thus rendering the aircraft economically unviable. It's the same thing with automobiles--one could make them more crashworthy, but at what cost weight-wise, fuel economy-wise, and acquisition price-wise?

I'm not an engineer, mind you, but like just about anything else in life, there's a risk-versus-reward equation at work here.
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GQfluffy
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:21 am

Aircraft, for as heavy as they are...are as strong as they can be while still being able to fly...AND turn a profit for an airline. Could they be stonger? Sure...but at what weight? And at what cost? And think about this for a second...or three... Would it actually be feasible?
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United787
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:22 am

Because they have to be lightweight. If you made it like a car so that it could survive impact, then it wouldn't fly. The skin of an airplane is only as thick as needs to be to fly.
 
cincinnaticj
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:30 am

I isn't the speed that's the problem - it's the sudden stop. Even if it was made of the same stuff as the "black box" (which happens to be dayglow orange) the bodies inside wouldn't survive, in most cases.
 
MrMcCoy
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:43 am

We've all heard the joke "Why can't they build aircraft out of the same stuff they use to make the black box?" Err.. the aircraft would weigh as much as a locomotive perhaps? Big grin
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deaphen
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:45 am

Hey guys,
Thank you for your replies, yea the reasons are quite the same as i thought of.
It just seems a shame though, but i suppose flying would be extremely more expensive and unviable incase such aircraft were flown!
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cincinnaticj
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:50 am

Deaphen, do you worry as much about automobiles? They are a gillion times more dangerous than commercial airliners............
 
deaphen
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:02 am

Quoting Cincinnaticj (Reply 9):
Deaphen, do you worry as much about automobiles? They are a gillion times more dangerous than commercial airliners............

haha... no i am not worried about automobiles.. lol. I am not worried about planes either. the only thing is that planes carry far more passengers than any automobile.

And i know i know the statistics say plans are much much safer.. and i agree with that too. But i was specifically referring to the near 100% fatality in plane crashes.
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deltadc9
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:20 am

Unlike cars, they seem to design Airliners to fly 100% of the time and never crash. Is crash performance even a consideration for certification?

NASA tried a fuel addative to prevent such large blazes during and after a crash, but it failed in a very famous test. Since they were going to crash an airliner in the test they installed crash test dummies and cameras. They did a belly landing and the results were not hopeful for much progress at this time. The forces at play are very powerful.
Dont take life too seriously because you will never get out of it alive - Bugs Bunny
 
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litz
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:25 am

Quoting MrMcCoy (Reply 7):
We've all heard the joke "Why can't they build aircraft out of the same stuff they use to make the black box?" Err.. the aircraft would weigh as much as a locomotive perhaps? {Big grin}

It's actually not unheard of for an aircraft to weigh as much as a locomotive (small ones are around 225,000 lbs, big ones 450-500,000 lbs) ... the big difference is, locomotives don't fly.

And - if you've ever seen a high speed train wreck, it can be just as messy as an airplane crash.

http://64.246.11.82/images/d/DSC_1029.JPG.86935.jpg

ANY time you take a half million pounds and stop it suddenly, the kinetic energy is NEVER going to be in your favor.

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Gary2880
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:26 am

Quoting Cincinnaticj (Reply 9):
do you worry as much about automobiles? They are a gillion times more dangerous than commercial airliners............

i am also more worryed about flying than i am about a car crash.

reason is in a car crash you have an instant crash and dont have to fall 36,000ft first to get the same result.
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TIA
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:40 am

The safety factor in airplane structures is lower (only 1.5) than almost in any other engineering design. The reason is simple:

Quoting OPNLguy (Reply 3):
thus rendering the aircraft economically unviable.
 
JayinKitsap
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:48 am

The WTC was a very strong & redundant structure. Besides for 4" thick concrete filled metal decking floors, there were beam at about 8 foot centers. The exterior columns at the impact floor were also at about 8 feet on center and were I shaped with a depth of 16" and width of 10 inches. The metal thicknesses were on the order of 3/4" for the flange, 3/8" for the web.

The plane cut thru like a dozen of the columns, was cut apart on the floor slab, and still went partially out the other side. To armor nuclear reactors it takes a concrete dome or cylinder like 7 foot thick concrete with a mind bending amount of steel. That was to stop an accidental accident with a 727 or 737 sized airliner at around 200 knots.

Basically the physics makes it not possible. It is better to improve the reliability and capabilities of the aircraft rather than to try and harden the plane.
 
Glareskin
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:57 am

Thank you Deaphen for bringing such a nice and different topic! But I have to say that I disagree with a lot of the reactions above. Yes, the comparison with cars comes to mind. But I don't want to compare the aircraft structure with a regular automobile (not even a Volvo or a fancy German car..) because usually fatal aviation accidents are not caused by two planes crashing. But I'd like to make the comparison with Formula 1. These cars have a so called 'monocoque' which is especially designed to withstand the incredibly forces of a high speed impact. If you see a car crashing into a hard obstacle, all the parts fall off but the cocoon stays intact. The monococque remains intact and due to a special security system the driver mostly sustains minor injuries. This monocoque is some kind of carbon fibre based composite. So my real question is if modern aircraft like the 787 are more rigid in the way that they better keep intact after a 250 mph with water (like today's crash). Anyone having thoughts about that?
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Aither
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RE: Are Planes Too Fragile?

Thu May 04, 2006 4:19 am

Around the formula one composite monocoque cockpit you have like shock absorbers (especially the front nose and on the sides). If the car was too strong around the composite structure the pilot would die because of the deceleration. Composite is a poor shock absorber and when it breaks it breaks completely.

A well known example by the Americans is the death of Dale Earnhart. The car was not very damaged but the pilot inside was killed.

[Edited 2006-05-03 21:19:33]
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LY4XELD
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RE: Are Planes Too Fragile?

Thu May 04, 2006 4:45 am

Quoting DeltaDC9 (Reply 11):
Unlike cars, they seem to design Airliners to fly 100% of the time and never crash. Is crash performance even a consideration for certification?

Wrong. Airplanes ARE designed to "crash" and be surviveable. How do you explain escape slides, emergency doors, etc.? Obviously, the idea is that something COULD happen, so there are ways to evacuate. Other airplane systems are designed to survive certain G loads, etc. on a crash that is not catastrophic to the overall aircraft.
 
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sebolino
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RE: Are Planes Too Fragile?

Thu May 04, 2006 4:50 am

Quoting Deaphen (Thread starter):
Anyways, back to my question. Why are most plane crashes concieved to be so fatal? I mean are they made of very fargile material? Couldnt there be a way that the main fuselage of an aircraft could survive even on an impact at about 250-300 kmph?

In a crash (plane or car), people usually don't die because they are ejected, but because they suffer a great desceleration. You can have ten meters of metal + concrete to protect you, it won't change anything.
 
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litz
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RE: Are Planes Too Fragile?

Thu May 04, 2006 11:05 am

Quoting LY4XELD (Reply 18):
Wrong. Airplanes ARE designed to "crash" and be surviveable. How do you explain escape slides, emergency doors, etc.? Obviously, the idea is that something COULD happen, so there are ways to evacuate. Other airplane systems are designed to survive certain G loads, etc. on a crash that is not catastrophic to the overall aircraft.

And if you don't believe this, just look at the Air France A340 in Toronto.

The plane broke. The plane burned.

Everyone got out. everyone survived.

Why? Because of the precise engineering innovations described above.

(and a couple hundred cool cucumbers for passengers)

- litz
 
lincoln
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RE: Are Planes Too Fragile?

Thu May 04, 2006 11:44 am

Quoting United787 (Reply 5):
Because they have to be lightweight. If you made it like a car so that it could survive impact, then it wouldn't fly. The skin of an airplane is only as thick as needs to be to fly.

As an illustartion of this point... my dad is in management for an aviation supplier (customers include Boeing, Sikorsky, and if I remember correctly, Airbus as well, among many others). One of the things done at the site where his office is located is forming fuselage panels for various aircraft, from flat sheetstock to the time it's curved, has window holes cut in it, and loaded on a truck/train/boat to be delivered to the customer.

One of the steps in this process is taking what is already relatively thin metal, and milling approximately half the thickness out of the majority of the panel (what's left resembles a grid -- full thckness at the edges, as thin as possible in the middle of each cell).

All this just to eliminate some unnecessary weight...

Lincoln
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bayareapilot
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RE: Are Planes Too Fragile?

Thu May 04, 2006 12:02 pm

Quoting Deaphen (Reply 10):
But i was specifically referring to the near 100% fatality in plane crashes.

What near 100% fatality rate? There are thousands of examples of non-fatal plane crashes. Go to http://www.ntsb.gov/ntsb/query.asp and see for yourself. As long as the plane impacts the ground in a relatively upright attitude and minimal vertical speed the chances for survival are good. That's why even if the plane is going down the pilots do whatever they can to keep it right side up and fly it all the way to the ground.
 
radelow
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:00 pm

Let's not forget the human body cannot take the G-forces that would be created by a so-called "crash-proof" airplane slamming into the ground at 350mph.
 
jetdeltamsy
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:04 pm

Quoting Deaphen (Thread starter):
a plane crash means total fatality.

Incorrect. The vast majority people involved in aircraft accidents survive the impact.

It's usually fire that kills people.
Tired of airline bankruptcies....EA/PA/TW and finally DL.
 
khobar
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:35 pm

Quoting Litz (Reply 20):
And if you don't believe this, just look at the Air France A340 in Toronto.

The plane broke. The plane burned.

Everyone got out. everyone survived.

Was the plane going 250-300mph at the time?

Quoting Bayareapilot (Reply 22):
What near 100% fatality rate? There are thousands of examples of non-fatal plane crashes. Go to http://www.ntsb.gov/ntsb/query.asp and see for yourself. As long as the plane impacts the ground in a relatively upright attitude and minimal vertical speed the chances for survival are good. That's why even if the plane is going down the pilots do whatever they can to keep it right side up and fly it all the way to the ground.

How many non-fatal plane crashes when the plane is going 250-300mph, the speed the original poster mentioned?
 
Ilovenz
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RE: Are Planes Too Fragile?

Thu May 04, 2006 2:36 pm

I've always wondered what the structural requirements are for commercial airliners these days in terms of the maximum force different parts have to be able to endure? And then, how much greater is this than anything an airliner would experience in typical severe turbulence? These are questions I have serious concerns about.

Sam
 
Scrappy74
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:16 pm

I wasn't particularly good at calculus in high school and it sounds simplistic but if you consider the sheer number of pax and a/c's over the number of times there is any kind of incident (particularly total hull loss), we're pretty safe up there.

Even with resulting fires miracles can happen...I was reminded of UA232 (Sioux City, Iowa in 1989) by a video clip on MSNBC this evening. Check out the story if you don't know it already.
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deaphen
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RE: Are Planes Too Fragile?

Thu May 04, 2006 3:56 pm

This is a very interesting topic once you start to think about it.
Though a die hard aviation guy, i honestly have to tell you that most of the times i feel safer in a car than on a plane. I dont know why, i guess i feel that in a car i have more control. Mind you that i feel that way only when i am driving. When someone else is driving i would rather fly. It is definately a "control" issue.

I guess all of us witness car crashes often, and thats why it has become more a part of life for us, but a airliner crash seems so much graver than that. IMHO, when a plane crashes landing on its tires in the same way as landing, the chances of survival are much more. As compared to a plane slamming into the ground wing first or nose first. I feel that even if the body cannot withstand the impact of deaccelaration, it should atleast be equipped with that. I mean i would be happier thinking that i WONT die because of slamming into the ground, but because of some other reason.

Again, we can see that fear of flying is all mental, and the major fear is attributed to a passengers mind thinking "WHAT IF".

Another thing i have never understood is that on board, in the safety card, they have such a nice cartoon of a plane floating on the water and the slides deployed and everyone sliding out. I wanna ask.. how possible is it for a plane to crash land like that? I mean if i remember correctly, this has never been done before. I may be wrong, but i remember reading a post in some forum saying that even though they are prepared for an emergency like that, none has ever happened.

All the videos i have seen of airliners crashign into water is wing first and then once the wing touches the water, the whole fuselage disintegrates.

Another thing i want to know is when a plane is heading for the ground, isnt it possible for the pilot to slow it down to a great extend so as to decrease the magnitute of impact? Is there any example of a controlled crash landing where the pilot has totally hit the ground, but in a controlled manner and hence less fatalities? And i dont men emergency landings where the plane has been out of control but the pilot has managed to land it safely.

Thanks
I want every single airport and airplane in India to be on A.net!
 
Fly2HMO
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RE: Are Planes Too Fragile?

Thu May 04, 2006 4:17 pm

Quoting DeltaDC9 (Reply 11):
NASA tried a fuel addative to prevent such large blazes during and after a crash, but it failed in a very famous test.

So many lives would have been saved if somebody wold've had the balls to repeat that test again, it was such a good project, but to bad the dude flying the R/C 707 didn't think about doing a practice pass... DUH!!!             

[Edited 2006-05-04 09:18:15]
 
BAtriple7
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RE: Are Planes Too Fragile?

Thu May 04, 2006 6:43 pm

Quoting DeltaDC9 (Reply 11):
NASA tried a fuel addative to prevent such large blazes during and after a crash

I was reading about this regarding the use of explosive suppressant and fire suppressant fuel additives - the military gives it serious thought, so why couldn't it be turned into a civilian application and added to avgas used on pax planes?

See http://www.military-aerospace-techno...gy.com/print_article.cfm?DocID=367

I realise cost is always an issue, but if all airlines used such fuel, there would be economies of scale to reduce cost per gallon...
 
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jetfuel
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RE: Are Planes Too Fragile?

Thu May 04, 2006 7:51 pm

Quoting Deaphen (Reply 28):
i honestly have to tell you that most of the times i feel safer in a car than on a plane

I am unsure if you are a pilot, however I think most pilots will agree they feel safe when they are flying. Sitting down the back of a plane I always feel so helpless and that I dont know who has control of my life. Sitting in the back of a car I feel the same way.

Staistically you are still far more at risk in a car
Where's the passion gone out of the airline industry? The smell of jetfuel and the romance of taking a flight....
 
tockeyhockey
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RE: Are Planes Too Fragile?

Thu May 04, 2006 9:30 pm

Quoting Deaphen (Thread starter):
Anyways, back to my question. Why are most plane crashes concieved to be so fatal? I mean are they made of very fargile material? Couldnt there be a way that the main fuselage of an aircraft could survive even on an impact at about 250-300 kmph?

this is simply physics my friend -- it doesn't matter if the airplane fuselage can withstand a 500 kt crash; you cannot.

when the jet goes from 500 kt to 0 kt in less than a second, your body is smashed against the interior of the plane at forces that will kill you instantly.

even in a more gentle water landing, where you go from, say, 150 kt to 0 in a few seconds, the forces are very great and will most likely kill you. then, good luck getting out.

now, if we could just find a way to make jets out of Nerf, we might have something.
 
deltadc9
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RE: Are Planes Too Fragile?

Thu May 04, 2006 9:56 pm

Quoting LY4XELD (Reply 18):
Wrong. Airplanes ARE designed to "crash" and be surviveable. How do you explain escape slides, emergency doors, etc.? Obviously, the idea is that something COULD happen, so there are ways to evacuate. Other airplane systems are designed to survive certain G loads, etc. on a crash that is not catastrophic to the overall aircraft.

I am not referring to the safety systems, and I don't believer the original poster is either. The airframe itself is not designed to crash like a car is. Cars have crumple zones, safety cages, bumpers, safety glass, padded dashes, and many other things designed into the structure specifically intended for the event of a crash. Airbags and seat-belts are not the same thing even in a car.

Same for a plane if a plane does crash, certain tings are provided like slides, but the airframe itself, I do not believe is designed with crash performance as a factor. Also, if what you said was true, then crash performance would be a part of certification.

I may be wrong, but nothing here so far leads me to believe I am.
Dont take life too seriously because you will never get out of it alive - Bugs Bunny
 
Goldenshield
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RE: Are Planes Too Fragile?

Thu May 04, 2006 10:07 pm

The ASA EMB-120 accident in Carrollton, GA, proves that you could survive a high speed crash from a nearly-uncontrollable descent. Everyone in the cabin, as well as the first officer, lived through the crash; the only fatality was the PIC from blunt force traume (I assume from not having his shoulder straps on—it's not said in the report.) while doing all he could to save his ship and it's occupants from disaster.
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HiFi
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RE: Are Planes Too Fragile?

Thu May 04, 2006 10:19 pm

Quoting Ilovenz (Reply 26):
I've always wondered what the structural requirements are for commercial airliners these days in terms of the maximum force different parts have to be able to endure? And then, how much greater is this than anything an airliner would experience in typical severe turbulence? These are questions I have serious concerns about.

Sam

Feel free to find out: http://ecfr.gpoaccess.gov/cgi/t/text...ew=text&node=14:1.0.1.3.11&idno=14  Big grin

Commercial aviation must be safe AND economically viable.
Aircraft are designed to endure all loads to which they are submitted during take-off, flight and landing for their entire operational life, including turbulence. Turbulence does not take an aircraft down to the ground, trust me.

Quoting Glareskin (Reply 16):
Thank you Deaphen for bringing such a nice and different topic! But I have to say that I disagree with a lot of the reactions above. Yes, the comparison with cars comes to mind. But I don't want to compare the aircraft structure with a regular automobile (not even a Volvo or a fancy German car..) because usually fatal aviation accidents are not caused by two planes crashing. But I'd like to make the comparison with Formula 1. These cars have a so called 'monocoque' which is especially designed to withstand the incredibly forces of a high speed impact. If you see a car crashing into a hard obstacle, all the parts fall off but the cocoon stays intact. The monococque remains intact and due to a special security system the driver mostly sustains minor injuries. This monocoque is some kind of carbon fibre based composite. So my real question is if modern aircraft like the 787 are more rigid in the way that they better keep intact after a 250 mph with water (like today's crash). Anyone having thoughts about that?

Please don't compare commercial aviation and Formula 1. You're comparing protection for 100-500 persons to protection for 1 person.
Besides, assuming the possibility of implementing a flying cocoon for 200 passangers, it would not be enough. The Formula 1 pilot survives because the impact is in great part absorbed by the outer structure of the car (and maybe some tires on the wall) before reaching the cocoon. Still, when the collision is straight frontal and direclty on a wall, chances are not very good (Ayrton Senna in Imola comes to mind). Then, try to get a ride on a Formula 1 car and check out how much it would cost you..  Wink
As to composites, some of them may have great properties, but be very careful in using them because they ususally behave very differently in case of failure and can be very hard maintenance.

Quoting Deaphen (Reply 28):
Mind you that i feel that way only when i am driving.

Irrational. The pilot flying the plane has had a LOT better training than you driving your car..  Wink
no commercial potential
 
deltadc9
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RE: Are Planes Too Fragile?

Thu May 04, 2006 10:25 pm

Quoting HiFi (Reply 35):
Irrational. The pilot flying the plane has had a LOT better training than you driving your car..

I dont know about that! The Indiana court ordered defensive driving class is pretty good, especially when you have taken it half a dozen times!  sarcastic 
Dont take life too seriously because you will never get out of it alive - Bugs Bunny
 
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breiz
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RE: Are Planes Too Fragile?

Thu May 04, 2006 10:35 pm

As expressed in several replies, the human body is the limiting factor about how much protection can be provided.
Depending on the speed at impact and the angle with which the plane touch the ground, the deceleration force will or will allow people to survive.
In addition to g-forces, there are the objects flying in the cabin on impact which are also lethal.
And finally, as already said, smoke and fire take also their toll.

Possible improvement in safety would be to have seats turned to face the back of the plane. On impact, people would be better maintained and the g-force would be spread on a bigger body surface.
Hand-carried objects could also be forbidden to avoid that they are getting loose and kill people.
But who (airlines and passengers) would accept such measures?
 
darkblue
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RE: Are Planes Too Fragile?

Thu May 04, 2006 10:47 pm

Many people have already stated something similar but the simplest answer to your question is:

No, planes are not too fragile. People are.
 
ozguy
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RE: Are Planes Too Fragile?

Thu May 04, 2006 11:04 pm

Quoting Deaphen (Reply 10):
But i was specifically referring to the near 100% fatality in plane crashes.

I don't know how accurate that figure is. I don't mean to bash your topic but accident statistics seem to prove that, with the exception of the most horrific accidents such as TWA 800 and JAL 123, most accidents are survivable for the majority of people on board.

"Commercial accidents are survivable, contrary to popular belief. The facts may come as a surprise. Ninety percent of all aircraft accidents worldwide are survivable, according to the European Transport Safety Council (ESTC). Even more striking, the NTSB recently published their analysis: For all accidents involving U.S. air carriers between 1983 - 2000, 95.7% of passengers survived. And in more than 46% of the most serious accidents - those involving fire, serious injury, and substantial or total damage to the aircraft - more than 80% of passengers survived" (MacPherson, Malcolm, 2002, 'On a Wing and a Prayer', Harper Perennial, New York)
 
deaphen
Topic Author
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RE: Are Planes Too Fragile?

Thu May 04, 2006 11:15 pm

This is in reference to my reply 28:

Can anyone tell me more about the water crash landings and in what situation would an aircraft land in water the way shown in the safety cards onboard?

IIRC, there was a post once saying that just the engines touching the water is enough for them to tear off the wings and cause disaster. So then in what situation would a pilot land his commercial aircraft on water.

Secondly, all facts apart about whether flying is safe or not. Do you personally think companies can do more and invest more in safety than they already do? They may or may not impliment them, but i am talking from the investing more money point of view.

Thirdly, why are planes equipped only with seat belts which encircle the lower part of the human body. What would be the pro and cons of having shoulder straps like pilots do? Are they more expensive and is this move just a cost cutting gesture?

sorry for all the questions!

thanks
nitin
I want every single airport and airplane in India to be on A.net!
 
khobar
Posts: 1336
Joined: Fri Mar 17, 2006 4:12 am

RE: Are Planes Too Fragile?

Fri May 05, 2006 12:11 am

Quoting Goldenshield (Reply 34):
The ASA EMB-120 accident in Carrollton, GA, proves that you could survive a high speed crash from a nearly-uncontrollable descent. Everyone in the cabin, as well as the first officer, lived through the crash; the only fatality was the PIC from blunt force traume (I assume from not having his shoulder straps on—it's not said in the report.) while doing all he could to save his ship and it's occupants from disaster.

If you are referring to ASA Flight 529, an EMB-120 that crashed in Carrollton, GA in 1995, there were 9 fatalities, and the aircraft impacted trees at 120 knots IAS before crashing into a field.

Still, it's not a bad example - certainly qualifies as a real crash.

Quoting Deaphen (Reply 40):
Can anyone tell me more about the water crash landings and in what situation would an aircraft land in water the way shown in the safety cards onboard?

Ditching is dangerous. Hitting water at speed is a lot different than jumping into a pool, and if you've ever done a bellyflop you can begin to appreciate some of what happens.

Quote:
IIRC, there was a post once saying that just the engines touching the water is enough for them to tear off the wings and cause disaster. So then in what situation would a pilot land his commercial aircraft on water.

Hijacking (fuel starvation, no choice): http://www.cnn.com/WORLD/9611/26/com...crash/crash.really.large.14sec.mov

"The aircraft initially dragged the left wing tip in the water, followed by the left engine. The left engine apparently broke up, and the increased drag caused the aircraft to swing to the left. The right wing and engine stayed out of the water as the aircraft continued to swing to the left. The fuselage broke somewhere aft of the wing, causing a number of objects to be ejected forward as the remains of the aircraft came to rest."

The engines are designed to detach from the wing - take a look at http://www.airdisaster.com/photos/st-apy/photo.shtml.

There are other cases of ditching, some with really good results (Aeroflot Tu124, Oct. 1963, ditched in Neva River where aircraft remained floating for two days. All 52 souls survived. Plane was subsequently towed out and was probably returned to service  Wink )
 
Goldenshield
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RE: Are Planes Too Fragile?

Fri May 05, 2006 12:35 am

Quoting Khobar (Reply 41):
there were 9 fatalities

Nine were killed, yes, but they survived the crash. It was the post-crash fire that killed them.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
OPNLguy
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Joined: Tue Jun 15, 1999 11:29 am

RE: Are Planes Too Fragile?

Fri May 05, 2006 12:42 am

Quoting OzGuy (Reply 39):
I don't know how accurate that figure is. I don't mean to bash your topic but accident statistics seem to prove that, with the exception of the most horrific accidents such as TWA 800 and JAL 123, most accidents are survivable for the majority of people on board.

I've read and re-read your statement a few times, and perhaps I'm mis-reading your intent, but JAL123 did, in fact, have some survivors. Not many, mind you, but some (4). Maybe it was your using JAL123 in the same sentence as TWA800 that suggested that both accidents were 100% fatal.

A minor quibble.. Carry on...

JAL123
Crew: Fatalities: 15 / Occupants: 15
Passengers: Fatalities: 505 / Occupants: 509
Total: Fatalities: 520 / Occupants: 524
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
Jamie757
Posts: 838
Joined: Wed Apr 27, 2005 8:33 pm

RE: Are Planes Too Fragile?

Fri May 05, 2006 1:20 am

Quoting HiFi (Reply 35):
Turbulence does not take an aircraft down to the ground, trust me.

Just to nitpick, turbulence has brought aircraft down in the past, see here.

Back to the topic, the limiting factor here is the human body and as has been said before, it simply cannot withstand a deceleration like the kind experienced when an airliner makes contact with the ground (generally speaking).

Rgds.
"I feel like a turkey who's just caught Bernard Matthews grinning at him!"
 
planespotting
Posts: 3026
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RE: Are Planes Too Fragile?

Fri May 05, 2006 1:52 am

Impact forces are the cause of most fatal injuries in high-speed accidents. Fire is the cause of death of most fatal injuries in low speed accidents.

Drowning was probably the cause of death for the Armenien accident.
Do you like movies about gladiators?
 
aer lingus
Posts: 367
Joined: Sun Mar 25, 2001 6:40 pm

RE: Are Planes Too Fragile?

Fri May 05, 2006 1:57 am

I think they should install something that inflates under the aircraft when the aircraft is about to hit water. As it hits the water it deflates so it would lower the impact force like the airbags that we have on cars.

I think this could ba an good idea apart from the extra weight.

Your opinions.
Split Scimitar or Sharklets?
 
Tod
Posts: 1716
Joined: Sat Aug 28, 2004 6:51 am

RE: Are Planes Too Fragile?

Fri May 05, 2006 2:20 am

Quoting Deaphen (Reply 40):
Thirdly, why are planes equipped only with seat belts which encircle the lower part of the human body. What would be the pro and cons of having shoulder straps like pilots do? Are they more expensive and is this move just a cost cutting gesture?

Aside from the small cost of the belts and the inconvienence of the pax, the biggest issue would be the redesign of the seats. Pax seats are currently not designed to take any of the pax restraint load through the seat back.

Tod
 
mustang304
Posts: 70
Joined: Thu Aug 04, 2005 1:35 am

RE: Are Planes Too Fragile?

Fri May 05, 2006 2:57 am

I have an engineering background, however, I am not a structures guy- that being said-

The issue at hand relates to Kinetic energy and Potential Energy. When a crash occurs you transform all of the energy from these two into deformation of the vehicle, heat and noise.

Basically commerical aircraft have some mass, and travel fairly fast. It is really, really difficult to design a light structure that can handle a rapid deceleration without catastrophic results. Engineering is always a matter of trade offs, weight, strength, costs, etc. So the engineers do their best to make a crash survivable-- including the use of flammable resistant materials, removal of sharp edges on surfaces, soft impact surfaces for people's bodies, etc.

Cars can not handle high speed crashes. A crash over 50 mph has substantially worse results than a crash at 25. In car design, the design is usually around 30-35 mph impact- worst case. The assumption is that driver will hit the brakes before impact (and in most cases does). If you look at accident data from a 50 mph impact vs a 25 mph impact, the car in the 50 mph case fairs much worse-- and so do the passengers.

In general, automobile and aviation industries do their best to make a crash survivable.

If you look at automotive engineering, cars in the 50's had metal dash boards, solid frames, and lap belts were options. As the industry has learned, we have airbags, soft dashes (vinyl), frames that crumple and three point harnesses.

In aviation, a DC-3 had steel frames, wooden interiors, a seat belt, but there was little if any consideration to impact surfaces. The newer aircraft have no (or should not have) sharp edges that someone could fall into or hit, the seats are totally covered (the frame is hidden in padding), and the aircraft has a substantial amount of fire resistance inside.

As the industry advances technically, I'd expect we will see more safety improvements and the chances of catastrophic failure will continue to decrease.

For the amount of service time, training, engineering and redundancy, I'd fly any day over driving. Even if I'm not in control, I trust the system much more than I do the other drivers.

Len
 
LY4XELD
Posts: 659
Joined: Tue Mar 21, 2000 5:14 am

RE: Are Planes Too Fragile?

Fri May 05, 2006 3:06 am

Quoting DeltaDC9 (Reply 33):
Also, if what you said was true, then crash performance would be a part of certification.

I may be wrong, but nothing here so far leads me to believe I am.

Again, you are wrong! They obviously don't crash test airplanes...they test sections, they prove the design can handle a crash by analysis, and when I say design, I mean the fuselage. #1 Priority is safety of passengers and crew. And OF COURSE this is part of certification!!!! The FAA won't let something that is NOT designed to crash fly! My employer's history can prove it to you!

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