REFLECTOR: Accident report - SQ2000

Jim Sower canarder at frontiernet.net
Fri Sep 23 23:26:52 CDT 2005


<... Here is a link (oregonaero) for you ...>

Long ago in another life, I was heavily involved in ejection seats.  The 
major players at the time were Martin-Baker and RAPEC.  M-B used more or 
less a cannon shell in a telescoping tube to get maybe a 15' - 20' 
stroke.  Paralysis wasn't assured, but significant spinal injury pretty 
much was - particularly if you weighed more than 160 lb).  The "seat 
cushion" was WOOD.  Anything softer would allow the seat to build up a 
good head of steam before it hit your ass and assure paralysis.  RAPEC 
OTOH incorporated a rocket with maybe a 100' - 150' stroke.  It was 8-10 
Gs compared to M-B's 20 Gs or more.  Interestingly, RAPEC could use soft 
seat cushions and still out perform M-B (you could eject successfully in 
the chocks while with M-B you needed 80 - 100 kts forward motion).  M-B 
was experimenting with the precursor to memory foam, but filling it with 
liquid.  It would slowly migrate to fit your butt comfortably, but be as 
incompressible as wood when you ejected.

The lesson here is clearly stroke length.  M-B had 15', RAPEC had 150'.  
Which was more comfortable (you only get one guess :-)?  Crushable 
structure in the airframe buys us a longer stroke than a rigid 
structure.  Seat cushions don't add anything consequential to the stroke 
length.

I'm not aware of anyone successfully designing a crushable structure 
(like in race cars) that would work in an airplane.  Go for your 
lastafoam seat.  Compared to me in my cheap-ass bench, you'll be much 
more comfortable when we both die in similar crashes.

If you think it enhances your survival chances, great - go for it - be 
happy ... Jim S.


Terry Miles wrote:

>Jim,
>Here is a link for you
>http://www.oregonaero.com/p4243_2001.html
>If you ask, Oregon Aero, they will tell you that the buy the foam from
>Hi-Tech foam.  Same way that Spruce buys their Scroth seatbelts from
>Karas Engineering who has the exclusive N.Am franchise.  My info on this
>differs significantly from yours.  I've been told it does protect you.
>
>Terry
>
>-----Original Message-----
>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>Behalf Of Jim Sower
>Sent: Friday, September 23, 2005 5:18 PM
>To: Velocity Aircraft Owners and Builders list
>Subject: Re: REFLECTOR: Accident report - SQ2000
>
>
><... 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
>>
>>-----Original Message-----
>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>>    
>>
>
>  
>
>>Behalf Of Scott Derrick
>>Sent: Thursday, September 22, 2005 7:21 PM
>>To: Velocity Aircraft Owners and Builders list
>>Subject: Re: REFLECTOR: Accident report - SQ2000
>>
>>There are seats for race cars available that are very light and 
>>designed
>>for high speed car crashes. 
>>
>>I ave an 97 Std. and the seats are part of the air frame.  I can't see
>>them coming apart, but I also can't seem them offering any crush to 
>>lessen thr impact.
>>
>>Scott
>>
>>Chuck Jensen wrote:
>>
>> 
>>
>>    
>>
>>>The solution that was put into my plane was seats out of a Corvette.  
>>>They are low profile (to enable the low-slung Vette look) and seem to 
>>>be substantial, yet don't seem to weight much.  Semi-reclining type 
>>>auto seats may be worth a look.
>>>
>>>Chuck
>>>
>>>-----Original Message-----
>>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] 
>>>On Behalf Of Tom Martino
>>>Sent: Thursday, September 22, 2005 12:37 PM
>>>To: Velocity Aircraft Owners and Builders list
>>>Subject: RE: REFLECTOR: Accident report - SQ2000 
>>>
>>>This comes at the exact time that I pulled my seats because I decided 
>>>they are flimsy.  One day while flying in chop ... I felt my self 
>>>being bounced a couple of times up against the seat back ... and I did
>>>      
>>>
>
>  
>
>>>not like the feeling.  The seat back seems weak.
>>>
>>>
>>>I am molding buckets that attach to the floor directly.  The "buckets"
>>>      
>>>
>
>  
>
>>>will be lined with a system of shock absorbing material (like in a 
>>>helmet) with memory foam on top.
>>>
>>>The bucket is one piece bottom and back, with some flex ... but no 
>>>"joints".  It will cradle my body somewhat like a clam-shell.  I call 
>>>it a seat helmet or "pod".
>>>
>>>I totally agree with many accident findings that forced landings and 
>>>rapid descents often turn fatal due to inadequate restraint, shock 
>>>absorption and seat structure.  I hope to overcome these weaknesses.
>>>
>>>Tom Martino
>>>
>>>-----Original Message-----
>>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] 
>>>On Behalf Of Jim Sower
>>>Sent: Thursday, September 22, 2005 10:10 AM
>>>To: Velocity Aircraft Owners and Builders list
>>>Subject: Re: REFLECTOR: Accident report - SQ2000 [heur]
>>>
>>>I seem to recall that Paul bought his seats from Velocity - along with
>>>some other things. I never liked the seat structure but accepted that,
>>>      
>>>
>
>  
>
>>>like spam cans, the seat has little or nothing to do with restraint - 
>>>the harness being bolted to the airframe. I further assumed that the 
>>>seat structure would crush on vertical impact and therefore be of some
>>>      
>>>
>
>  
>
>>>benefit in absorbing energy. I'm skeptical about the plane springing 
>>>backwards as I am about intimations that he was flying out of limits
>>>      
>>>
>aft CG.
>  
>
>>>I assumed that the Velocity restraint structure had been tested
>>>satisfactorily ... Jim S.
>>>
>>>Al Gietzen wrote:
>>>
>>>
>>>
>>>   
>>>
>>>      
>>>
>>>>Some of you may have seen this on other venues. This is not happy
>>>>reading but I post it here because of one factor that relates to our 
>>>>airplanes - the seats.
>>>>
>>>>You can skip the rest of the report, but note that the lack of
>>>>seatback support is cited as a cause in the pilots death. The seat is
>>>>        
>>>>
>
>  
>
>>>>essentially the same as the Velocity. From the first time I saw the 
>>>>Velocity seats I was very concerned that is provides very little 
>>>>support against strong forces vertically or from the rear. Once the 
>>>>back support breaks there is no longer a restraint system.
>>>>
>>>>And speaking of restraint system, I also pressed the factory years 
>>>>ago
>>>>for some test of the 5/16" bolt threaded into ¼" aluminum block as an
>>>>        
>>>>
>
>  
>
>>>>adequate seat belt attachment; particularly for the inboard side of 
>>>>the front seat.
>>>>
>>>>The analysis of the 4 canardians who examined the wreckage of Paul
>>>>Conner's aircraft is now available at:
>>>>
>>>>     
>>>>
>>>>        
>>>>
>>http://www.cozybuilders.org/N2992_Accident_Eval/
>>
>> 
>>
>>    
>>
>>>>Al
>>>>
>>>>---------------------------------------------------------------------
>>>>---
>>>>
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>>>>  
>>>>
>>>>     
>>>>
>>>>        
>>>>
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>>    
>>
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