Shoulder Belt/Brace Position
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Shoulder Belt/Brace Position
Hello there! Since many of you are high-speed safety experts I was curious if any of you had any insight to this.
Numerous carriers and corporate aircraft have chosen to incorporate a shoulder belt as part of the restraint system. Examples include the Dornier 328, Cathay Pacific's newly designed Economy and Business class seats, and numerous business aircraft. Recommended brace positions for these seats typically are to sit straight up, but to lower the head to the neck. (Bow to the cockpit, so to speak.) Hands should be palms up underneath the legs.
But what should happen to these shoulder-belted passengers if they attempted to take the traditional lap-belt only brace position (grabbing their ankles, heads down position) during a crash? Would anything "bad" (i.e. worse than usual) happen to them? (It could happen, especially is pax don't pay attention to the safety briefing!)
I haven't found any convincing evidence that anything WORSE will happen to these pax if they adopt the "wrong" brace position, but I was curious if any of you knew.
Thanks!
Numerous carriers and corporate aircraft have chosen to incorporate a shoulder belt as part of the restraint system. Examples include the Dornier 328, Cathay Pacific's newly designed Economy and Business class seats, and numerous business aircraft. Recommended brace positions for these seats typically are to sit straight up, but to lower the head to the neck. (Bow to the cockpit, so to speak.) Hands should be palms up underneath the legs.
But what should happen to these shoulder-belted passengers if they attempted to take the traditional lap-belt only brace position (grabbing their ankles, heads down position) during a crash? Would anything "bad" (i.e. worse than usual) happen to them? (It could happen, especially is pax don't pay attention to the safety briefing!)
I haven't found any convincing evidence that anything WORSE will happen to these pax if they adopt the "wrong" brace position, but I was curious if any of you knew.
Thanks!
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Consider the normal crash dynamics (I haven't had a look but CAMI may have a video or two of sled tests on the net somewhere). Also run a search on "hic" and "crash dynamics" or similar to find lots of interesting stuff to read ...
(a) if the occupant is sitting normally in a lap belt only restraint, the initial crash load moves the body (in the sitting attitude) forward until the lap belt becomes effective in restricting further movement. The body then jack-knifes about the lap belt. In the typical environment, one expects significant head and lower leg impacts on the structures in front. The dummy test recordings indicate that limb flailing is a significant problem ..
(b) with upper body restraint (sash part of lap sash, or full harness), the upper body restraint slows the torso in its rotation .. with the generally accepted rule of thumb that head impact speed is reduced to around half of the unrestrained value.
(c) (you really need to see some sled test recordings to appreciate this comment) the idea of lowering the head probably reduces the likelihood of significant whiplash style injuries during the impact sequence.
.. me, I'd stick with the head forward, arms tucked into the side ...
(a) if the occupant is sitting normally in a lap belt only restraint, the initial crash load moves the body (in the sitting attitude) forward until the lap belt becomes effective in restricting further movement. The body then jack-knifes about the lap belt. In the typical environment, one expects significant head and lower leg impacts on the structures in front. The dummy test recordings indicate that limb flailing is a significant problem ..
(b) with upper body restraint (sash part of lap sash, or full harness), the upper body restraint slows the torso in its rotation .. with the generally accepted rule of thumb that head impact speed is reduced to around half of the unrestrained value.
(c) (you really need to see some sled test recordings to appreciate this comment) the idea of lowering the head probably reduces the likelihood of significant whiplash style injuries during the impact sequence.
.. me, I'd stick with the head forward, arms tucked into the side ...
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I'm 6'4" and with carriers like easyJ and their tiny distance between each seat, I have no chance of adopting the brace position. Can I assume in a real life situation of a crash that my seat will come adrift from its mountings and a general concertina of seats takes place. In which case it doesn't really matter which position I adopt. Does it?
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Gannet Fan,
I'm 6'4"...
that presents a problem with the anthropometrics as seating is not designed for the ends of the distribution curve.
I have no chance of adopting the brace position
if the seat in front is unoccupied, there is time, and it has a break forward feature ... push the back down and then use the normal crash position. If that is not applicable, I suggest one would opt for maximum tightening of the seat belt assembly and still adopt the normal position. The seat back in front will have some degree of delethalisation padding and, for modern aircraft using dynamic standards seats, the HIC will have considered head impact on the seat during the certification program. Main thing is to have the belt tight and rely on the upper body restraint keeping the head impact impact velocity down.
Can I assume in a real life situation of a crash that my seat will come adrift from its mountings
For older designs this is a problem. The seat and seat/track design is based on static loads and any seat track disruption can precipitate separation .. so, the answer for such aircraft is that it all depends .. especially on the dynamics of the crash.
For newer designs certificated to the dynamic standards, the situation is far better with both seat and seat/track design so the risks reduce.
CAMI did some interesting tests in the early days of dynamic certification and demonstrated that a given seat performs dramatically better the larger the size of the aircraft .. largely due to the increased crush volumes underneath and in front of the seat ..
Rule of thumb ? Fly widebodies, not helos (which have the worst impact environments), fly dynamic certificated seats, preferably in aircraft of compatible certification. Another consideration is that the history stats suggest that the aft seats in the cabin generally have a better outcome in accidents.
... and, if that doesn't give you comfort, take note that the comparative transport mode accident stats still put scheduled aircraft above most other modes for outcomes. It always amused me that rail came out very well represented in the stats ...
... give me a good sleeper carriage or Mr P&O ...
I'm 6'4"...
that presents a problem with the anthropometrics as seating is not designed for the ends of the distribution curve.
I have no chance of adopting the brace position
if the seat in front is unoccupied, there is time, and it has a break forward feature ... push the back down and then use the normal crash position. If that is not applicable, I suggest one would opt for maximum tightening of the seat belt assembly and still adopt the normal position. The seat back in front will have some degree of delethalisation padding and, for modern aircraft using dynamic standards seats, the HIC will have considered head impact on the seat during the certification program. Main thing is to have the belt tight and rely on the upper body restraint keeping the head impact impact velocity down.
Can I assume in a real life situation of a crash that my seat will come adrift from its mountings
For older designs this is a problem. The seat and seat/track design is based on static loads and any seat track disruption can precipitate separation .. so, the answer for such aircraft is that it all depends .. especially on the dynamics of the crash.
For newer designs certificated to the dynamic standards, the situation is far better with both seat and seat/track design so the risks reduce.
CAMI did some interesting tests in the early days of dynamic certification and demonstrated that a given seat performs dramatically better the larger the size of the aircraft .. largely due to the increased crush volumes underneath and in front of the seat ..
Rule of thumb ? Fly widebodies, not helos (which have the worst impact environments), fly dynamic certificated seats, preferably in aircraft of compatible certification. Another consideration is that the history stats suggest that the aft seats in the cabin generally have a better outcome in accidents.
... and, if that doesn't give you comfort, take note that the comparative transport mode accident stats still put scheduled aircraft above most other modes for outcomes. It always amused me that rail came out very well represented in the stats ...
... give me a good sleeper carriage or Mr P&O ...
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Also, just to add to the above, when adopting a brace position, the following is usually desirable. There are many variations of brace positions (the FAA and UK CAA recommend slightly different positions, to name one difference), but there is some commonality in all brace positions.
1) Pre-position your head, if possible, on the object you are most likely to strike with your head. (Usually this is the seat-back in front of you.)
2) Avoid leg flailing by adopting a "feet back" position. (Feet flat on the floor, slightly behind the knees)
3) Lean over to some degree. If you can only lean over and rest your head on the seat back, that's fine. If you can lean all the way over and grab your ankles, that's fine too.
4) Prevent arm flailing. The UK CAA recommends hands on top of another (not interlocked) and placed around the head. The US FAA recommends either wrapping your arms around your legs, or, resting your forehead on crossed arms, with the arms against the seat back.
Things to avoid:
-Having your head to one side
-Having any part of your limbs outstretched and locked against an object
-Being in an upright position UNLESS your aircraft seat is equipped with a seat-belt mounted airbag. (Found of Virgin Atlantic, Air Canada, Singapore Airlines and Air New Zealand premium aircraft seating, to name a few) or you are wearing a shoulder belt or harness.
1) Pre-position your head, if possible, on the object you are most likely to strike with your head. (Usually this is the seat-back in front of you.)
2) Avoid leg flailing by adopting a "feet back" position. (Feet flat on the floor, slightly behind the knees)
3) Lean over to some degree. If you can only lean over and rest your head on the seat back, that's fine. If you can lean all the way over and grab your ankles, that's fine too.
4) Prevent arm flailing. The UK CAA recommends hands on top of another (not interlocked) and placed around the head. The US FAA recommends either wrapping your arms around your legs, or, resting your forehead on crossed arms, with the arms against the seat back.
Things to avoid:
-Having your head to one side
-Having any part of your limbs outstretched and locked against an object
-Being in an upright position UNLESS your aircraft seat is equipped with a seat-belt mounted airbag. (Found of Virgin Atlantic, Air Canada, Singapore Airlines and Air New Zealand premium aircraft seating, to name a few) or you are wearing a shoulder belt or harness.
Tabs please !
I have always suspected that the function of the brace position is to protect the dental evidence that will be used to identify your remains.
If safety was the top concern, all seats would face rearwards as (so I am told) they do in the military.
If safety was the top concern, all seats would face rearwards as (so I am told) they do in the military.
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Not just a matter of turning the seats around .. the back structure then has to be able to take the crash loads without excess deformation ... ie the great god dollar generally wins out.
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Let's get real: Seat belts are to keep you from falling out of your seat during turbulence. The airframe is like an eggshell, in case of a crash it will buckle and crumble, the seat tracks will come unglued and the overhead bins will collapse. At most, you'll be found somewhere in the debris field with the seat still strapped to you.
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Not the case .. with dynamic test aircraft/seat combinations, the performance is significantly better than with older static designs.
However, at the end of the day, if the impact load spectrum is moderately in excess of the Design Standard requirements .. then you are probably going to come out with injuries ranging up to fatalities .. much the same as with motor vehicles ..
However, at the end of the day, if the impact load spectrum is moderately in excess of the Design Standard requirements .. then you are probably going to come out with injuries ranging up to fatalities .. much the same as with motor vehicles ..
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I don't believe I have read up on that accident .. but I presume it was pretty bad in the overall scheme of things.
Doesn't matter whether we are talking cars or aircraft... if the crash loads are high enough (or it just wasn't your day and the occupant volume is broached in a low energy impact) then the outcome is fatal.
The aim is to push up the low and survivable injury envelope as far as practicable .. hence no belts ... lap belts ... three point ... full harness ... dynamic seats ... etc., etc.... and, if you are serious about it ... helmets.
However, at the end of the day, Lady Luck plays a part whether we like it or not.
Doesn't matter whether we are talking cars or aircraft... if the crash loads are high enough (or it just wasn't your day and the occupant volume is broached in a low energy impact) then the outcome is fatal.
The aim is to push up the low and survivable injury envelope as far as practicable .. hence no belts ... lap belts ... three point ... full harness ... dynamic seats ... etc., etc.... and, if you are serious about it ... helmets.
However, at the end of the day, Lady Luck plays a part whether we like it or not.
