Safety, CRM, QA & Emergency Response Planning A wide ranging forum for issues facing Aviation Professionals and Academics

Asiana Crash Investigation

Old 4th Aug 2013, 19:01
  #41 (permalink)  
 
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,350
Likes: 0
Received 0 Likes on 0 Posts
@EEngr

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.
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'.
Ian W is offline  
Old 5th Aug 2013, 08:22
  #42 (permalink)  
 
Join Date: Dec 2001
Location: what U.S. calls ´old Europe´
Posts: 941
Likes: 0
Received 0 Likes on 0 Posts
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.
Calculations and simulations are not done for a variety of crash szenarios. It is the overengineering which produces the margins for unplanned loading of the airframes.
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.
Volume is offline  
Old 5th Aug 2013, 15:39
  #43 (permalink)  
 
Join Date: Jan 2011
Location: Seattle
Posts: 715
Likes: 0
Received 1 Like on 1 Post
Problems.
--Anchor points for shoulder straps
Solvable with some smart engineering. Particularly with the new seat designs with rigid backs that 'recline' by sliding the seat bottom forward.

--Getting pax to put shoulder straps on when they moan at lap belts
Make the shoulder strap independent from the lap section so it doesn't have to be worn for other then take-offs and landings. That will obviate the need for pre-tensioners. These are used in autos where the lap/shoulder belts are slack (spring-loaded winders in most cases) and need to be pulled into place in the event of an accident. A shoulder belt only needs to be snug for a few minutes so its not too much to expect them to be worn correctly. Passengers don't like it? Take the bus cross country the next trip. No belts required.

--Getting the beancounters to accept the extra weight/cost of shoulder straps and tensioners.
Tough. And until they start charging overweight passengers, I think they can live with a few extra pounds per.

--Issues with escape when pax are secured by lap and shoulder straps.
Same as for lap only belts. A one handle release should be easy to design.
EEngr is offline  
Old 5th Aug 2013, 16:46
  #44 (permalink)  
 
Join Date: Jan 2010
Location: London
Age: 85
Posts: 23
Likes: 0
Received 0 Likes on 0 Posts
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?
ttodd is offline  
Old 5th Aug 2013, 17:46
  #45 (permalink)  
 
Join Date: Jul 2002
Location: UK
Posts: 3,093
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Uplinker
Dozy; the Comet 1 failures were a very unfortunate disaster, but calling it a "fiasco" is too harsh - and you might want to rephrase that. Facts about structural science and design that we now take for granted were simply not known back then.
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.
DozyWannabe is offline  
Old 7th Aug 2013, 22:27
  #46 (permalink)  
 
Join Date: Jan 2008
Location: Hertfordshire
Posts: 6
Likes: 0
Received 0 Likes on 0 Posts
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.
MYvol is offline  
Old 8th Aug 2013, 08:15
  #47 (permalink)  
 
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,350
Likes: 0
Received 0 Likes on 0 Posts
@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.
Ian W is offline  
Old 8th Aug 2013, 23:53
  #48 (permalink)  
 
Join Date: Oct 2010
Location: In the back of a bus
Posts: 1,023
Received 1 Like on 1 Post
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...
givemewings is offline  
Old 9th Aug 2013, 17:46
  #49 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 4,569
Likes: 0
Received 1 Like on 1 Post
Only a change in type approval to mandate better seats and seat restraints will change the current system.
You forgot about type approval for the passengers as well.

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.
lomapaseo is offline  
Old 10th Aug 2013, 09:50
  #50 (permalink)  
 
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,350
Likes: 0
Received 0 Likes on 0 Posts
@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.
Ian W is offline  
Old 11th Aug 2013, 02:34
  #51 (permalink)  
 
Join Date: Nov 2003
Location: UK/OZ
Posts: 1,886
Received 7 Likes on 4 Posts
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...
An inflight magazine will do a good job against sharp objects.

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.
mickjoebill is offline  
Old 11th Aug 2013, 04:38
  #52 (permalink)  
 
Join Date: Feb 2001
Location: UK
Posts: 647
Likes: 0
Received 0 Likes on 0 Posts
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.

Last edited by chrisN; 11th Aug 2013 at 04:41.
chrisN is offline  
Old 11th Aug 2013, 06:48
  #53 (permalink)  

Plastic PPRuNer
 
Join Date: Sep 2000
Location: Cape Town
Posts: 1,898
Received 0 Likes on 0 Posts
"..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.

Last edited by Mac the Knife; 11th Aug 2013 at 06:50.
Mac the Knife is offline  
Old 11th Aug 2013, 10:53
  #54 (permalink)  
 
Join Date: Apr 2007
Location: Bristol
Age: 77
Posts: 132
Received 9 Likes on 4 Posts
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.
SRMman is offline  
Old 11th Aug 2013, 11:27
  #55 (permalink)  
 
Join Date: Jul 2007
Location: UK
Posts: 140
Likes: 0
Received 0 Likes on 0 Posts
Modern rocket seat do not have a cushion. They only have a thin "wipe clean" covering!
windytoo is offline  
Old 11th Aug 2013, 20:07
  #56 (permalink)  

Plastic PPRuNer
 
Join Date: Sep 2000
Location: Cape Town
Posts: 1,898
Received 0 Likes on 0 Posts
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

Last edited by Mac the Knife; 11th Aug 2013 at 20:22.
Mac the Knife is offline  
Old 12th Aug 2013, 14:32
  #57 (permalink)  
 
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,350
Likes: 0
Received 0 Likes on 0 Posts
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
Ian W is offline  
Old 12th Aug 2013, 16:22
  #58 (permalink)  
 
Join Date: Jul 2013
Location: Alternative Universe
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
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?

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.
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.
Standard Toaster is offline  
Old 13th Aug 2013, 08:28
  #59 (permalink)  
 
Join Date: Jan 2008
Location: The Smaller Antipode
Age: 89
Posts: 31
Received 13 Likes on 8 Posts
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.

Last edited by ExSp33db1rd; 13th Aug 2013 at 08:29.
ExSp33db1rd is offline  
Old 13th Aug 2013, 11:25
  #60 (permalink)  
 
Join Date: Apr 1999
Location: Manchester, UK
Posts: 1,958
Likes: 0
Received 0 Likes on 0 Posts
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.
ShotOne is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.