REFLECTOR: Accident report - SQ2000

[Brian Michalk]

I think a much better place to expend engineering brain cells would be 
the structure that holds up the seats.

Rather than two foam cores set vertical, some sort of collapsing 
arrangement would be better.

At the Texas DOT I have witnessed several laboratory crashes.  The last 
one I saw, we were testing a new safety barrier.

This one was very interesting.  The object was to make a cushion that 
could be replaced/reset in under an hour, and be able to safely 
decelerate large trucks and light cars.
Of course a single opposing force for this task would not work.  The 
force to safely decelerate a heavy truck would kill anyone in a light car.

Picture something like a railroad track.  On this track rides a cart. 
This cart has a built-in shear that cuts a plate of metal of pushed hard 
enough.  Between the track and the cart, sheets of metal are bolted to 
the track.  At maximum extension, only a single plate of metal is 
sheared by the cart.  As the cart moves along the track, more plates are 
placed such that the thickness of plates increases as the cart travels 
along the track.  This sort of arrangement, provided the occupants are 
healthy (not geriatric), and wearing their seatbelt is usually 
survivable when the car/truck is traveling 50 MPH.

I think it would be in our grasp to devise something that would involve 
ripping two layers of glass apart, or something like that.  The only 
problem is as amateurs we would not be able to build something that 
would deliver repeatable safe deceleration within some known error.

Having said all that, our greatest injury is a broken back or neck.  Our 
spines are not meant to be placed under compression and it takes 
surprisingly little to get messed up.  I know a person that slipped on a 
flatbed truck, and bounced his ass on the edge of the bed as he fell. 
It compressed his spine, (did some medical terms I don't recall) and 
he's been on disability ever since.

We don't have much room at all for this deceleration.  Six inches maybe? 
If we pancake it down vertical, say with landing gear retracted, I think 
most people would break their back at anything more than 10 miles per hour.

Jim Sower wrote:
> <... At some G-loading it's the body that would break anyway and not the 
> seat...>
> Actually, I think the rigidly anchored, form fitting, temper/memory foam 
> covered seats that have been discussed will kill you quicker than the 
> factory seats.  Crash survivability turns on structure crushing/breaking 
> and absorbing energy.  The factory seats have [a little of] that.  
> Temper foam (or any other cushion for that matter) is comfortable, but 
> useless for absorbing impact energy. A good 4-point restraint is as good 
> as you can do IMO, but I haven't seen one in a Velocity.  Cozys and EZs 
> have them, but they have rigid, structural seats, so there's no impact 
> energy absorption.
> 
> Composite planes are just too damn strong to be crash worthy ... Jim S.
> 
> 
> Carruth, Joel L wrote:
> 
>> I agree that the seats are a somewhat flimsy. However, correct me if I 
>> missed something here, but from the last picture (100-3047) of the 
>> cockpit, it appears that the hinges are still intact - at least not 
>> broken. It looks more like the #10 screws were either sheared off or 
>> pulled from the aluminum hard point.
>> Assuming you stay with the factory seat (less $), it seems that the 
>> following would be necessary:
>> 1) Instead of #10s, use some AN-3s. With a doubler+nutplate on the 
>> inside.
>> 2) Extra glass (3 BID??, UNI?) moving up the sides covering the 
>> aluminum attach point and doubler.  Perhaps some UNI going from 
>> side-to-side at shoulder blade height.
>> Probably not as good as an engineered seat, but it will definitely 
>> help. At some G-loading it's the body that would break anyway and not 
>> the seat.
>> Any other reinforcement ideas?
>>
>> Joel Carruth
>> Lockheed Martin JSF - Pilot System Software
>> W: (817) 763-4337
>> Fax: (817) 777-8378
>> joel.l.carruth at lmco.com