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The breakups

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paulrod36(at)msn.com
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Posted: Fri Apr 24, 2009 10:58 am Post subject: The breakups

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> I'm OK with various people having various interpretations and differing  viewpoints, but in all I have read, I am still waiting for the following  data:  In each crash, has anybody identified the individual piece that  failed?  I seem to recall that one crash summary stated that the main spar  had failed, and been twisted, but there seems to be a dearth of information on  this.  as in: if the rear spar tore loose from the carry-through, for  instance, I'd look at either a thicker attach point plate, or two attach point  plates, on either side of the carry-through and the spar. If it's flutter, then  it seems reasonable to either pre-load the ailerons a couple of degrees down, or  use push-pull tubes insttead of cables. If we're looking at excessive G,  (positive or negative) then maybe more stringent elevator stops would be called  for.  If we're looking at excessive positive G, could that point to pilot  error? I have a hard time believing that somebody could not know when he's  pulling 4 or more G, no matter how light the stick force is. Since, I'm sure,  the FAA and NTSB have a set of plans, I'd love to see a call-out of the part  numbers that either failed or are broken, and are not attributable to ground  impact.  Until somebody comes up with that information, I guess I'll keep  building, albeit at a slower pace. 

  

 Paul Rodriguez

   [quote][b]

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Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Fri Apr 24, 2009 12:20 pm Post subject: Re: The breakups

It sounds like the accident you are referring to is the Yuba City crash. It looks like you have a firm grasp of what is in the report. 



The problem isn't what part broke. I have not seen and the NTSB did not refer to any data, that any part on the 601XL fails to hold up to the G forces called out in the design with the exception of one report that the design might not quite make the +6G ultimate load number. Hence, my suggestion in a previous post to take your plans and mark out +6G and replace it with +5G.



The meat of the NTSB position is that something is happening that is causing the aircraft to exceed the design load limit. They believe it is flutter and that the only way to fix that is with mass balancing.



The designer feels that proper tension of the control cables is enough protection.





 	  paulrod36(at)msn.com wrote: 	
		  <xml><xml><endif> I'm OK with various people having various interpretations and differing  viewpoints, but in all I have read, I am still waiting for the following  data:  In each crash, has anybody identified the individual piece that  failed?  I seem to recall that one crash summary stated that the main spar  had failed, and been twisted, but there seems to be a dearth of information on  this.  as in: if the rear spar tore loose from the carry-through, for  instance, I'd look at either a thicker attach point plate, or two attach point  plates, on either side of the carry-through and the spar. If it's flutter, then  it seems reasonable to either pre-load the ailerons a couple of degrees down, or  use push-pull tubes insttead of cables. If we're looking at excessive G,  (positive or negative) then maybe more stringent elevator stops would be called  for.  If we're looking at excessive positive G, could that point to pilot  error? I have a hard time believing that somebody could not know when he's  pulling 4 or more G, no matter how light the stick force is. Since, I'm sure,  the FAA and NTSB have a set of plans, I'd love to see a call-out of the part  numbers that either failed or are broken, and are not attributable to ground  impact.  Until somebody comes up with that information, I guess I'll keep  building, albeit at a slower pace. 

  

 Paul Rodriguez

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_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR

d.goddard(at)ns.sympatico
Guest

Posted: Fri Apr 24, 2009 12:20 pm Post subject: The breakups

Hi Paul, NO! to my (limited) knowledge nobody knows if  there is a problem, much less what it is. But there have been incidents of  failures, and there is no proof of those pilots flying outside of the  envelope or abusing the airframe either. It's a big question mark. Nobody knows,  but now it looks like they are trying to find out. Keep building. 

 [quote]   ---

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