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Accident in Spain was a Zodiac 601XL and there is a pictur

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psm(at)att.net
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Posted: Tue Mar 11, 2008 8:15 am Post subject: Accident in Spain was a Zodiac 601XL and there is a pictur

Hi Andy,



This is a good question - what could cause an explosion.  Indeed, I 

remember another report of an explosion that seemed to just precede a 

structural failure.  I also remember a report of an engine revving 

irregularly just before the explosion.  Perhaps I am mixing and 

matching different incidents, but I remember both reports.



I would guess the most likely ingredient for an accidental explosion 

would be loose fuel in the cabin.  There really isn't a way you could 

get a lot of loose fuel in the wing structure since the fuel is 

stored on the front side of the mostly solid wing spar.



I can envision a fuel leak combined with a wing mounted fuel pump 

that forces a lot of fuel into the cabin.  This isn't as likely if 

the normal fuel pump arrangement is used because a leak would give 

the pump in the engine compartment just air to suck on rather than 

fuel.  A cabin full of fuel vapor and air combined with a spark of 

some sort might give a big fuel-air explosion.



Please note that the theoretical explosion described above has no 

basis at all in a structural design or construction issue.  It is 

based on a simple failure in the fuel system combined with an 

ill-advised arrangement of fuel pumps.



As far as I know, there has been no proven wing design problem.  I 

don't know where that idea came from.  There have been wing 

separations, but I can't remember any confirmed explanation as to why 

that separation occurred.   Since Chris Heintz has reexamined and 

retested the wing structure since the first few structural failures I 

think it would be foolish to make a major wing design change with the 

hope of solving a problem.  Any major change, like adding ribs, would 

be just as likely to cause new problems as to solve any old ones.



I personally feel there is no point in trying to come up with some 

mathematical explanation of the accidents with the hope of computing 

odds of failure of any new plane.  This might help you sleep at 

night, but I don't think it is a valid analysis technique for this 

kind of problem.  There have been several airplane designs in the 

past that had horrible accident records and structural 

failures.  None of these were random in nature.  They were 

expressions of latent design problems that were eventually identified 

and fixed.  The planes I am thinking of for this point are the V-tail 

Bonanza and the Lockheed Electra.



As for personal decisions, I think everyone considering flying a 

Zodiac XL (like me) should come to terms with the notion that this is 

a dangerous activity that could end in disaster.  If you can't live 

with that then you shouldn't be flying this or any other experimental 

airplane.  To pretend that experimental airplanes are anything other 

than dangerous is just kidding yourself.



Paul

XL fuselage



At 08:16 AM 3/11/2008, you wrote:

 	  Quote: 	
		  What would cause an explosion, leaking fuel tank into the wing 

structure? Empty tank that for some reason exploded?

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skyguynca

Joined: 05 Jun 2006
Posts: 128

Posted: Tue Mar 11, 2008 8:53 am Post subject: Accident in Spain was a Zodiac 601XL and there is a pictur

While the loud bang was heard and a falling twisting mass was see does not 

necessarily mean something exploded. Has anyone here see a wing tested to 

failure? I have see a 747, 727, Cessna 310, 210 and 150 wing tested to 

failure......when they finaly failed, it was a very surpisingly loud bang. 

What the witnesses heard could have just been the structual failure......The 

one thing I never saw in the reports were evidence of a fire in the air or 

witnesses seeing a smoke trail to the ground.



David Mikesell

Cloverdale, CA 95425



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