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Yuba City Probable cause released

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dougsire

Joined: 10 Jan 2006
Posts: 37

Posted: Mon Dec 29, 2008 2:07 pm Post subject: Yuba City Probable cause released

NTSB released the probable cause for the 11/06 AMD accident in Yuba City.   The smoking gun is....In-flight structural failure of the horizontal stabilizer and wings for undetermined reasons.



Doug Sire

Billings, MT

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Doug Sire 601XL
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Gig Giacona

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

Posted: Mon Dec 29, 2008 2:50 pm Post subject: Re: Yuba City Probable cause released

That makes things clear as mud. The one useful bit of info i gout out of it was this. "no oscillatory loading of the control surfaces was apparent." That would seem to be NTSB speak that rules out flutter.



That and they didn't rule out abrupt control input. Just that they couldn't see it on radar.

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

Jeyoung65(at)aol.com
Guest

Posted: Mon Dec 29, 2008 4:29 pm Post subject: Yuba City Probable cause released

Giacona, why do you said "no oscillatory loading of the control surfaces  was apparent"? Did I miss something in the post? I would think "In-flight  structural failure of the horizontal stabilizer and wings for undetermined  reasons." indicates they DO NOT KNOW why they failed!  Jerry of  Ga   DO NOT ARCHIVE



  

  In a message dated 12/29/2008 5:51:22 P.M. Eastern Standard Time,  wrgiacona(at)gmail.com writes:

  	  Quote: 	
		  -->    Zenith601-List message posted by: "Gig Giacona"    <wrgiacona(at)gmail.com>



That makes things clear as mud. The one    useful bit of info i gout out of it was this. "no oscillatory loading of the    control surfaces was apparent." That would seem to be NTSB speak that rules    out flutter.

	




click here for the latest news that will have people talking.

  [quote][b]

Gig Giacona

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

Posted: Mon Dec 29, 2008 4:44 pm Post subject: Re: Yuba City Probable cause released

I said "no oscillatory loading of the control surfaces  was apparent" and put it in quotes because it is a direct quote from the report. I may be wrong but I would think that the phrase "oscillatory loading of the control surfaces" would be NTSB speak for flutter. If I'm wrong I'd like to know what it does mean.

[quote="Jeyoung65(at)aol.com"]Giacona, why do you said "no oscillatory loading of the control surfaces  was apparent"? Did I miss something in the post? I would think "In-flight  structural failure of the horizontal stabilizer and wings for undetermined  reasons." indicates they DO NOT KNOW why they failed!  Jerry of  Ga   DO NOT ARCHIVE



  

  In a message dated 12/29/2008 5:51:22 P.M. Eastern Standard Time,  wrgiacona(at)gmail.com writes:

  	  Quote: 	
		  -->    Zenith601-List message posted by: "Gig Giacona"    <wrgiacona>



That makes things clear as mud. The one    useful bit of info i gout out of it was this. "no oscillatory loading of the    control surfaces was apparent." That would seem to be NTSB speak that rules    out flutter.

	




click here for the latest news that will have people talking.

   	  Quote: 	
		  [b]

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

tonyplane(at)bellsouth.ne
Guest

Posted: Mon Dec 29, 2008 4:58 pm Post subject: Yuba City Probable cause released

The separation of the wings and horizontal stabilizer was in a downward 

direction

..the possibility of an abrupt control input cannot be excluded. This 

airplane is very responsive in pitch control. One of the handling quality 

characteristics designed by the



airplane's manufacturer is that movement of the control stick produces large 

and rapid changes in pitch attitude."



FWIW. I believe abrupt up elevator input caused horizontal stab downward 

failure.  Causes extreme nose down pitch and extreme neg gs on wing 

resulting in wing failure in downward



direction.  Saw this on a T-28A at the Crash Lab at March AFB many years ago 

during aircraft accident investigation course.



Tony Graziano



601XL; N493TG; 454 hours



---

jaybannist(at)cs.com
Guest

Posted: Mon Dec 29, 2008 4:59 pm Post subject: Yuba City Probable cause released

Yes, you must have missed it.  Quote from the report: "All observed fracture surfaces were overload, and no oscillatory loading of the control surfaces was apparent."

 

 Another part of the report said that the failure was from static overload, not dynamic.

 

 Jay in Dallas

 Do not archive

   

   

 

   

 

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jaybannist(at)cs.com
Guest

Posted: Mon Dec 29, 2008 5:18 pm Post subject: Yuba City Probable cause released

I guess I still don't understand the difference between static and dynamic loads.  The report said that all the overloads were static, not dynamic. ZAC tested the 601XL wings for static loads twice and they passed with flying colors. So the static loads seen by the failed wings and horizontal stabilizer must have been greater than they were designed for.

 

 Jay in Dallas

 Do not archive

 

   

 

   

 

 --

tonyplane(at)bellsouth.ne
Guest

Posted: Mon Dec 29, 2008 5:41 pm Post subject: Yuba City Probable cause released

That is why the stick is sometimes referred to a  wing remover - you can remove the wings with ONE abrupt  full deflection pull or push, with airspeed above Va.

  

 Tony Graziano

 [quote]   ---

planecrazydld(at)yahoo.co
Guest

Posted: Mon Dec 29, 2008 7:16 pm Post subject: Yuba City Probable cause released

Jay, you understand perfectly. Static overload can still happen if controls are used too suddenly or even in extreme wind shear. The other this is that low cycle fatigue/iterative static overload is accumulative. Each load past yield deforms the structure and particularly attach points. I also agree that this is a nice nail in the flutter coffin for this case at least.



David L. Downey

  Harleysville (SE) PA, USA



  

--- On Mon, 12/29/08, jaybannist(at)cs.com <jaybannist(at)cs.com> wrote:

[quote]From: jaybannist(at)cs.com <jaybannist(at)cs.com>

Subject: Re: Re: Yuba City Probable cause released

To: zenith601-list(at)matronics.com

Date: Monday, December 29, 2008, 8:15 PM



  I guess I still don't understand the difference between static and dynamic loads.  The report said that all the overloads were static, not dynamic. ZAC tested the 601XL wings for static loads twice and they passed with flying colors. So the static loads seen by the failed wings and horizontal stabilizer must have been greater than they were designed for.

 

 Jay in Dallas

 Do not archive

 

   

 

   

 

 --

leinad

Joined: 19 Sep 2006
Posts: 283
Location: Central Virginia

Posted: Tue Dec 30, 2008 10:20 am Post subject: Re: Yuba City Probable cause released

I just checked the NTSB database and didn't see the report.  Where are you guys reading this?  Could someone post a link?



 	  dougsire wrote: 	
		  NTSB released the probable cause for the 11/06 AMD accident in Yuba City.   The smoking gun is....In-flight structural failure of the horizontal stabilizer and wings for undetermined reasons.



Doug Sire

Billings, MT

_________________
Scratch building XL with Corvair Engine

Iberplanes

Joined: 10 Dec 2007
Posts: 174
Location: Igualada - Barcelona - Spain

Posted: Tue Dec 30, 2008 10:37 am Post subject: Yuba City Probable cause released

[url=http://www.ntsb.gov/ntsb/brief.asp?ev_id 061115X01677&key=1]http://www.ntsb.gov/ntsb/brief.asp?ev_id 061115X01677&key=1[/url]



[url=http://www.ntsb.gov/ntsb/brief2.asp?ev_id 061115X01677&ntsbno=LAX07FA026&akey=1]http://www.ntsb.gov/ntsb/brief2.asp?ev_id 061115X01677&ntsbno=LAX07FA026&akey=1[/url]

 



Alberto Martin

www.iberplanes.es

Igualada - Barcelona - Spain



----------------------------------------------

Zodiac 601 XL Builder

Serial: 6-7011



Tail Kit: Finished

 Wings: Not Started

Fuselage: Ordered

Engine: Jabiru 3300

  [quote][b]

_________________
Alberto Martin
601 XL - Jabiru 3300
http://www.iberplanes.es
Igualada - Barcelona - Spain

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Tue Dec 30, 2008 7:04 pm Post subject: Re: Yuba City Probable cause released

I found it here:



http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX07FA026&rpt=fi



and the most interesting thing is at the end.



REASON FOR OCCURRENCE UNDETERMINED



Let's try to keep that in mind.

_________________
Ron Lendon
WW Corvair with Roy's Garage 5th bearing
CH 601 XLB
N601LT - Flying
http://www.mykitlog.com/rlendon
Corvair Engine Prints:
https://sites.google.com/site/corvairenginedata/

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Thu Jan 01, 2009 10:38 am Post subject: Re: Yuba City Probable cause released

I do not recall that ZAC ever did a negative G static test on this aircraft.



 	  jaybannist(at)cs.com wrote: 	
		  I guess I still don't understand the difference between static and dynamic loads.  The report said that all the overloads were static, not dynamic. ZAC tested the 601XL wings for static loads twice and they passed with flying colors. So the static loads seen by the failed wings and horizontal stabilizer must have been greater than they were designed for.

 

 Jay in Dallas

 Do not archive

 

   

 

   

 

 --

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Jan 01, 2009 11:05 am Post subject: Yuba City Probable cause released

See: http://www.zenithair.com/zodiac/6-photo-testing.html



The pictures shown near the top of the page show negative G static  

load testing. Positive G load testing would be done with the airframe  

upside down with the sandbags stacked on the bottom of the wings.  

Positive G load testing is shown in some of the photos in the lower  

part of the page.



On Jan 1, 2009, at 1:38 PM, David X wrote:



 	  Quote: 	
		   



 I do not recall that ZAC ever did a negative G static test on this  

 aircraft.




	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

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Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
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jaybannist(at)cs.com
Guest

Posted: Thu Jan 01, 2009 11:24 am Post subject: Yuba City Probable cause released

Go to the Zenithair.com site, click on 601 series, go clear to the bottom of the page and search 601 wing load test.  You will find two separate series of test photos, both negative and positive.

 

 Jay in Dallas

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