Asiana Crash Investigation
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@EEngr
and those shoulder belts (which have no anchor points) would need to be equipped with pre-tensioners that pull the pax into the correct position for a vertical impact just having shoulder straps would not do it as many ejectees have found to their cost.
Problems.
--Anchor points for shoulder straps
--Getting pax to put shoulder straps on when they moan at lap belts
--Getting the beancounters to accept the extra weight/cost of shoulder straps and tensioners.
--Issues with escape when pax are secured by lap and shoulder straps.
There are a lot of 'sound bite' good ideas, until you sit down with an engineer who has to make the 'good idea' a 'functional idea'.
Quote:
Although safety experts say assuming the crash position would have limited jolting to the spine, passengers appear to have received little or no warning of the impact.
No warning might be the case in many more crashes. So perhaps its time to forget about a crash position and equip all seats with shoulder belts.
Although safety experts say assuming the crash position would have limited jolting to the spine, passengers appear to have received little or no warning of the impact.
No warning might be the case in many more crashes. So perhaps its time to forget about a crash position and equip all seats with shoulder belts.
Problems.
--Anchor points for shoulder straps
--Getting pax to put shoulder straps on when they moan at lap belts
--Getting the beancounters to accept the extra weight/cost of shoulder straps and tensioners.
--Issues with escape when pax are secured by lap and shoulder straps.
There are a lot of 'sound bite' good ideas, until you sit down with an engineer who has to make the 'good idea' a 'functional idea'.
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With all due respect, that's rubbish. Modern airframe designs tend to make greater use of lightweight materials and technology, but with advances in CAD and engineering tools load calculations can be simulated far more accurately than was once the case, meaning that the need for overengineering is reduced.
I agree that the 737 is not the best example of a robust airframe... But there have always been crashes where most passengers walked away because the aiframe stood strong. Some Fokker 100 (Austrian, Air France), MD11 (Mandarin), DC-10 (Iberia, Garuda) come to mind.
Nevertheless, the 777 fuselage indeed demonstrated excellent structural crashworthiness behavior.
Problems.
--Anchor points for shoulder straps
--Anchor points for shoulder straps
--Getting pax to put shoulder straps on when they moan at lap belts
--Getting the beancounters to accept the extra weight/cost of shoulder straps and tensioners.
--Issues with escape when pax are secured by lap and shoulder straps.
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What about pillows?
It has always seemed obvious to me to place the pillow supplied in front of my face if we ever have to brace.
There must be a good reason why they aren't advised or used apart from their getting in the way on egress?
But they'll be scattered all over the cabin anyway, surely?
There must be a good reason why they aren't advised or used apart from their getting in the way on egress?
But they'll be scattered all over the cabin anyway, surely?
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Regarding use of the term "fiasco" - I wasn't talking about the design of the aircraft itself, as much as the political pressure to keep the aircraft flying when the fact that there was an unknown structural issue became apparent. This led to more accidents, rendered the Comet's reputation unrecoverable and had a severe knock-on effect to confidence within the UK's civil aviation industry.
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Seat belts
It is interesting to note that in the Ford BMax the front seat belts top mountings are on the seats. And car seat belts automatically adjust, unlike aircraft seats. Would a better, more ergonomic belt system be more acceptable to most passengers than the present, frankly cumbersome, aircraft belts.
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@EEngr and MYvol
The seat belts on aircraft are the simplest money can buy that will meet the type certification tests. Car manufacturers would not dream of using such basic restraint systems indeed they would be illegal, yet their collisions are far less severe. It would appear that the specification for aircraft seat belts is more to stop people being thrown out of the seat in turbulence than for safety in a crash.
I would imagine that pretensioned seat belts as found in cars would have pulled the pax into an upright position with heads back against the seats and there may well have been less spinal and facial injuries.
If seat belts were designed for safety they would be inertia reel seat belts with pretensioners and as a minimum lap and diagonal or with a full harness design. However, as I pointed out above, in the beancounters' calculatons the weight penalty and subsequent fuel cost exceed the safety benefit.
Only a change in type approval to mandate better seats and seat restraints will change the current system.
The seat belts on aircraft are the simplest money can buy that will meet the type certification tests. Car manufacturers would not dream of using such basic restraint systems indeed they would be illegal, yet their collisions are far less severe. It would appear that the specification for aircraft seat belts is more to stop people being thrown out of the seat in turbulence than for safety in a crash.
I would imagine that pretensioned seat belts as found in cars would have pulled the pax into an upright position with heads back against the seats and there may well have been less spinal and facial injuries.
If seat belts were designed for safety they would be inertia reel seat belts with pretensioners and as a minimum lap and diagonal or with a full harness design. However, as I pointed out above, in the beancounters' calculatons the weight penalty and subsequent fuel cost exceed the safety benefit.
Only a change in type approval to mandate better seats and seat restraints will change the current system.
And again, back to the issue of the pax actually wearing them. As flight crew we are trained in how to wear our seatbelts properly... pax are not. Even when you tell them it must be worn "low and tight" they still don't wear them properly (if at all) I would hazard a guess that at least some of the Asiana injuries would have been from seatbelts worn too loosely.
Then the other problem you have with a harness (even for takeoff and landing) is wearing it properly. It has to sit over your hip bones with the buckle in the correct position or you risk causing more damage than its worth. Given that half the crew I fly with don't even wear it properly (and this has applied at every airline I've worked at) then hoping for pax to do it is probably too much to ask....
Pillows will end up everywhere (you see a few in the photos) personally I have mine on my lap ready when a pax, just in case... not sure it would help much in fact you'd need to be careful that it's not going to change the angle of your neck too much but could be helpful to cushion the back of your head against flying debris...
Then the other problem you have with a harness (even for takeoff and landing) is wearing it properly. It has to sit over your hip bones with the buckle in the correct position or you risk causing more damage than its worth. Given that half the crew I fly with don't even wear it properly (and this has applied at every airline I've worked at) then hoping for pax to do it is probably too much to ask....
Pillows will end up everywhere (you see a few in the photos) personally I have mine on my lap ready when a pax, just in case... not sure it would help much in fact you'd need to be careful that it's not going to change the angle of your neck too much but could be helpful to cushion the back of your head against flying debris...
Only a change in type approval to mandate better seats and seat restraints will change the current system.
I use my belt just enough that I won't kill my fellow passenger and think the best when I fly.
You can influence the non-flying public, but you can not influence all passengers to the same extent.
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@omapaseo
And of course the marketeers would also say that having more capable seat belts would be seen as an admission that the airline is less safe.
Nevertheless, with inertial reel lap and diagonal seat belts with pretensioners a lot of issues of incorrectly worn belts would be solved.
And of course the marketeers would also say that having more capable seat belts would be seen as an admission that the airline is less safe.
Nevertheless, with inertial reel lap and diagonal seat belts with pretensioners a lot of issues of incorrectly worn belts would be solved.
not sure it would help much in fact you'd need to be careful that it's not going to change the angle of your neck too much but could be helpful to cushion the back of your head against flying debris...
The average seat cushion does little to absorb energy in a serious accident.
In fact I'm told by an aviation engineer that a soft cushion isolates the body from the initial deceleration when the aircraft frame distorts at the initial impact. This is a bad idea.
It is only for a fraction of a second but it counts. So instead of the passengers body continues to travel at near the original speed. What happens next is the initial millisecond deceleration is over but the body is travelling faster than the airframe so then hits the seat bottom with greater impact than if there were no cushion.
His rather blunt advice is unless you have a purpose designed "hard", energy absorbing seat it is better to remove the cushion, put it on your head and bolt your spine to the airframe.
Last edited by mickjoebill; 11th Aug 2013 at 05:21.
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What Mickjoebill said. This has been known in gliding circles (among others?) for years. From the BGA:
Safety Cushions 11th July 2012
BGA RP38 recommends that all glider cockpits should be equipped with cushions containing energy absorbing materials. These cushions are widely used in club gliders but less so in privately owned ones. The BGA has published a booklet explaining how safety cushions work and how they can reduce injury - not just in a crash but also in heavy landings. You can download the booklet here [ http://www.gliding.co.uk/bgainfo/saf...safetyfoam.pdf ] - if you do not already fly with a safety cushion, we hope that it will encourage you to do so.
The originally recommended safety cushions were rather hard, though there was a “pudgee” version with some compliance in it, but there is now an alternative similar to the “Tempur mattress” deformable material which conforms to one’s shape. All these (at current retail prices) are quite expensive.
Safety Cushions 11th July 2012
BGA RP38 recommends that all glider cockpits should be equipped with cushions containing energy absorbing materials. These cushions are widely used in club gliders but less so in privately owned ones. The BGA has published a booklet explaining how safety cushions work and how they can reduce injury - not just in a crash but also in heavy landings. You can download the booklet here [ http://www.gliding.co.uk/bgainfo/saf...safetyfoam.pdf ] - if you do not already fly with a safety cushion, we hope that it will encourage you to do so.
The originally recommended safety cushions were rather hard, though there was a “pudgee” version with some compliance in it, but there is now an alternative similar to the “Tempur mattress” deformable material which conforms to one’s shape. All these (at current retail prices) are quite expensive.
Last edited by chrisN; 11th Aug 2013 at 04:41.
Plastic PPRuNer
"..contravenes the laws of physics..."
No. Think of an ejection seat.
With no (or a hard) cushion, the initial upwards acceleration of the seat is instantly (or almost instantly) transferred to the ischial tuberosities and thence to the spine and rest of body.
With a soft or air cushion, the seat starts accelerating upwards but the cushion compresses, delaying the transmission of force to the bum.
By the time the cushion is fully compressed and can transmit it's impulse to the bum, the ejection seat has already had time to accelerate quite a bit and when it finally transmits it's impulse to the bum, it is travelling a lot faster.
Much bigger shock load then, as the pioneers of ejection seat technology Like John Paul Stapp) found out to their discomfort.
No. Think of an ejection seat.
With no (or a hard) cushion, the initial upwards acceleration of the seat is instantly (or almost instantly) transferred to the ischial tuberosities and thence to the spine and rest of body.
With a soft or air cushion, the seat starts accelerating upwards but the cushion compresses, delaying the transmission of force to the bum.
By the time the cushion is fully compressed and can transmit it's impulse to the bum, the ejection seat has already had time to accelerate quite a bit and when it finally transmits it's impulse to the bum, it is travelling a lot faster.
Much bigger shock load then, as the pioneers of ejection seat technology Like John Paul Stapp) found out to their discomfort.
Last edited by Mac the Knife; 11th Aug 2013 at 06:50.
Mac the Knife,
I think you're thinking about the old 'bang seats'; today the rocket ejection seats spread the acceleration over a longer period thus reducing the instantaneous acceleration to a much smaller figure.
I think you're thinking about the old 'bang seats'; today the rocket ejection seats spread the acceleration over a longer period thus reducing the instantaneous acceleration to a much smaller figure.
Plastic PPRuNer
Sorta kinda think that "....longer period..." is a bit relative.
From the available videos and the two people I've met who survived ejections (one with lumbar fractures and the other with a broken arm) it seems to be a pretty violent event
Suspect it beats impacting terra firma with the aircraft though...
John Stapp, Jim Hall, Joe Kittinger, Yeager and all the other early guys at Muroc, Holloman and all those friendly desert places are the real heroes. Not forgetting Doddy Hay and the rest of them outside the US either.
See Badass of the Week: John Paul Stapp
From the available videos and the two people I've met who survived ejections (one with lumbar fractures and the other with a broken arm) it seems to be a pretty violent event
Suspect it beats impacting terra firma with the aircraft though...
John Stapp, Jim Hall, Joe Kittinger, Yeager and all the other early guys at Muroc, Holloman and all those friendly desert places are the real heroes. Not forgetting Doddy Hay and the rest of them outside the US either.
See Badass of the Week: John Paul Stapp
Last edited by Mac the Knife; 11th Aug 2013 at 20:22.
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I always remember a report on research into high speed ejection prior to the use of leg-restraints - with the quote: " The pilot experienced leg flailing after ejection"
Shows the bravery of the next guy to go.
Having ridden in the ejection seat training rigs where a half charge fires you up a retarding slide about 40-50 ft long the ::BANG:: of the ejection seat charges appeared coincident with the click-click-click of the ratchet stopping the seat sliding back. Exciting times
Shows the bravery of the next guy to go.
Having ridden in the ejection seat training rigs where a half charge fires you up a retarding slide about 40-50 ft long the ::BANG:: of the ejection seat charges appeared coincident with the click-click-click of the ratchet stopping the seat sliding back. Exciting times
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Shoulder straps? Seriously?
How are you going to certify that? How much is it going to cost? Specially retrofitting costs?
What about children? What about babies? What about overweight people? What about obese people? What about very tall people? What about handicapped people? Is it going to be adjustable? Is has to be.... If so, what's the added weight and volume of that solution? What about added maintenance? What's the cost of that added maintenance? What's the time lost with that maintenance? If the pre-tensioners fails, I'm sure it has to be immediately repaired, because regulators would never allow a seat that has a defective seat-belt to be occupied...
After certification, the usage surely would not be mandatory to all passengers because of several reasons (height, weight, special physical conditions and so on). If so, how are airlines going to train their crews so they can "force" the passengers that are eligible to use the shoulder straps to actually use it?... What's the criteria? How much time will it be lost on each flight because of it?
They wouldn't dream? Of course they would, because they already did... The only reason they presently don't is because of changed public perception towards safety, partially due to some publications like Unsafe at Any Speed and others, and now safety is a selling point.
And when you state that aviation collisions are far more severe than car collisions, that's simply not true... The survivable aviation crashes are far less severe than your average serious car accident, that calls for the 3-point seat belts, airbags and all those additional safety features. For instance, this Asiana crash everyone is talking about... All passengers survived and were able to walk from the airplane by themselves or with a little help (and this was a serious survivable airplane accident)... In a serious survivable car accident, you wouldn't even be able to move...
And finally, how many accidents have there been that justify the enormous cost? How many passengers would have been saved? How many serious injuries would have been avoided? Would the design, certification, implementation, training, lost revenue due to time lost on forcing the passenger to use it, maintenance and so on justify the investment vs the insurance premium airlines already pay to cover those said costs? I reallyyyyyy don't think so.
Regards.
How are you going to certify that? How much is it going to cost? Specially retrofitting costs?
What about children? What about babies? What about overweight people? What about obese people? What about very tall people? What about handicapped people? Is it going to be adjustable? Is has to be.... If so, what's the added weight and volume of that solution? What about added maintenance? What's the cost of that added maintenance? What's the time lost with that maintenance? If the pre-tensioners fails, I'm sure it has to be immediately repaired, because regulators would never allow a seat that has a defective seat-belt to be occupied...
After certification, the usage surely would not be mandatory to all passengers because of several reasons (height, weight, special physical conditions and so on). If so, how are airlines going to train their crews so they can "force" the passengers that are eligible to use the shoulder straps to actually use it?... What's the criteria? How much time will it be lost on each flight because of it?
Originally Posted by Ian W
Car manufacturers would not dream of using such basic restraint systems indeed they would be illegal, yet their collisions are far less severe.
And when you state that aviation collisions are far more severe than car collisions, that's simply not true... The survivable aviation crashes are far less severe than your average serious car accident, that calls for the 3-point seat belts, airbags and all those additional safety features. For instance, this Asiana crash everyone is talking about... All passengers survived and were able to walk from the airplane by themselves or with a little help (and this was a serious survivable airplane accident)... In a serious survivable car accident, you wouldn't even be able to move...
And finally, how many accidents have there been that justify the enormous cost? How many passengers would have been saved? How many serious injuries would have been avoided? Would the design, certification, implementation, training, lost revenue due to time lost on forcing the passenger to use it, maintenance and so on justify the investment vs the insurance premium airlines already pay to cover those said costs? I reallyyyyyy don't think so.
Regards.
Following a serious motor accident when seat belts in cars were but a twinkle in Henry Fords' eye, and never provided, I researched and located a car harness from the GQ parachute people, one that was in fact a full harness, i.e. lap and two shoulder type, and was not of the present 'inertia' style, so once adjusted there was no possibility of even reaching the radio - and fitted it to my replacement car.
It was monstrous, and my passengers laughed at me and refused to wear theirs, and eventually I gave it up and bought one of the first lap and diagonal inertia reel models, but I do wonder if I mightn't twist sideways out of it in the event of another head-on, as my accident was ?
In fact a simple lap-strap would have saved my thigh, which was snapped against the base of the steering wheel as I rose vertically in my seat.
It was monstrous, and my passengers laughed at me and refused to wear theirs, and eventually I gave it up and bought one of the first lap and diagonal inertia reel models, but I do wonder if I mightn't twist sideways out of it in the event of another head-on, as my accident was ?
In fact a simple lap-strap would have saved my thigh, which was snapped against the base of the steering wheel as I rose vertically in my seat.
Last edited by ExSp33db1rd; 13th Aug 2013 at 08:29.
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Why are the majority of these posts so negative? Almost all passengers survived what could easily have been a total calamity despite the massive impact(s) and extensive structural damage.