Matronics Email Lists :: View topic - NTSB Final Report Available

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

NTSB Final Report Available

Matronics Email Lists Forum Index -> Zenith-List

View previous topic :: View next topic

Author Message

moorecomp

Joined: 14 Aug 2006
Posts: 32

Posted: Thu Mar 29, 2007 4:49 am Post subject: NTSB Final Report Available

All,



The NTSB released the final report on the crash from last February in Modesto, CA that killed 2 people.



http://www.ntsb.gov/ntsb/brief.asp?ev_id=20060217X00209&key=1



"The National Transportation Safety Board determines the probable 

cause(s) of this accident as follows: 



The structural failure of the wings for undetermined reasons."



Comments?



Craig Moore A&P

Northern MI

701 builder wannabe

p.mulwitz(at)worldnet.att
Guest

Posted: Thu Mar 29, 2007 5:28 am Post subject: NTSB Final Report Available

We pay zillions of tax dollars for this?



Perhaps they should have said the plane crashed because it hit the ground.



Paul

XL fuselage

do not archive



At 04:49 AM 3/29/2007, you wrote:

 	  Quote: 	
		  



All,



The NTSB released the final report on the crash from last February 

in Modesto, CA that killed 2 people.



http://www.ntsb.gov/ntsb/brief.asp?ev_id 060217X00209&key=1



"The National Transportation Safety Board determines the probable

cause(s) of this accident as follows:



The structural failure of the wings for undetermined reasons."



Comments?



Craig Moore A&P

Northern MI

701 builder wannabe


	


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

Paul Mulwitz

32013 NE Dial Road

Camas, WA 98607

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

Gig Giacona

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

Posted: Thu Mar 29, 2007 5:31 am Post subject: Re: NTSB Final Report Available

One key sentence was, "The main wing aft attach points remained secured to the fuselage in the normal manner." Because, if I remember correctly, there was some talk at the time of the accident that the bolt in the rear spar was missing or loose.



Do we know if this was Zenith built spar or a scratch built?

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

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Mar 29, 2007 6:15 am Post subject: NTSB Final Report Available

It still isn't very clear whether or not the rear wing attach bolts  

were installed. The reports states: "The main wing aft attach points  

remained secured to the fuselage in the normal manner." and: "The aft  

spar attach point was intact." But makes no mention of the rear bolts  

themselves. It's almost like the investigators are hinting at a  

possible couse but can't make a definite determination due to the  

extent of the fire damage.



It seems to me that if those bolts were installed they would have had  

to have been pulled out when the wings folded as described. In that  

case, the attach points would have shown extensive damage due to the  

bolts pulling out. The only way they could remain intact is if the  

bolts were either not installed or fell out before the accident.  

Maybe they were inserted into the holes but the nuts were left off.



Of course, this is all conjecture on my part since I had nothing to  

do with the investigation. But with the long safety record of the 601  

series and my engineering background, I can't think of a more  

plausible explanation for this kind of accident.

On Mar 29, 2007, at 8:49 AM, moorecomp wrote:



 	  Quote: 	
		   The NTSB released the final report on the crash from last February  

 in Modesto, CA that killed 2 people.



 http://www.ntsb.gov/ntsb/brief.asp?ev_id 060217X00209&key=1



 "The National Transportation Safety Board determines the probable

 cause(s) of this accident as follows:



 The structural failure of the wings for undetermined reasons."


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

Gig Giacona

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

Posted: Thu Mar 29, 2007 6:26 am Post subject: Re: NTSB Final Report Available

I can't imagine considering all the other things they say, especially in the full narrative, that they would mention that the rear spar was not attached if, in fact, it wasn't.

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

Terry Phillips

Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT

Posted: Thu Mar 29, 2007 7:30 am Post subject: NTSB Final Report Available

Lots of things of interest here.



  1st, the probable cause, structural failure of the wings for undetermined reasons, is troubling. But, the fire damage to the aluminum structure destroyed any evidence that might have told why the collapse occurred.  
2nd, with an estimated takeoff weight of 1326 lbs, the aircraft was 26 lbs over the stated gross of 1300 lbs. The gross currently listed for 601XL's on the Zenith website is 1320 lbs.  
3rd, this may have been the first flight of the airplane with two persons on board. If so, the extra 200 lb load may have been enough to collapse the wings.  
4th, it is not clear whether the builder, Mr. Hooker, flew the airplane beyond the 40 hr. requirement. The total hours on the airframe is not given.  
5th, while it is not explicitly stated, it appears that this aircraft was built from a kit, not from plans. That should remove the possibility that the wing spars were poorly constructed by the builder. It does not preclude damage to the spars during or prior to construction.  
6th, I find no mention in the report of the use of "hardware store" bolts in the spars which has been suggested in some posts to this group or of loose bolts.  
7th, the empty weight of the aircraft is given as 754.5 lbs which is about 60 lbs greater than the 695 lbs listed for the 601/Jab 3300 on the Zenith website. It would be enlightening to know where the 60 lbs comes from. The dual brakes are one item. My conclusion is that we should be very rigorous in evaluating the weight/benefit ratio of anything we add to the basic airframe. I'm curious what empty weights others builders have ended up with. 
8th, the reports gives the unusable fuel as 3 gal. I know I've seen that number before, but I cannot seem to find it in the information I have. A useful fuel load of 21 gal vs. 24 gal makes me wish I had opted for the 30 gal tanks.  
9th, the elongated rivet holes probably resulted from the forces of impact. However, if they were a construction defect, is it possible that they could have weakened the wing structure?  In summary, lots of information here, but it would have been great if they had identified the cause of the wing failure. Then we could make sure that, at least, we try to correct any obvious shortcomings in the design.



 Terry



  



 At 05:49 AM 3/29/2007 -0700, you wrote:

  	  Quote: 	
		  --> Zenith-List message posted by: "moorecomp" <moorecomp(at)yahoo.com>



 All,



 The NTSB released the final report on the crash from last February in Modesto, CA that killed 2 people.



 [url=http://www.ntsb.gov/ntsb/brief.asp?ev_id 060217X00209&key=1]http://www.ntsb.gov/ntsb/brief.asp?ev_id 060217X00209&key=1[/url]



 "The National Transportation Safety Board determines the probable 

 cause(s) of this accident as follows: 



 The structural failure of the wings for undetermined reasons."



 Comments?



 Craig Moore A&P

 Northern MI

 701 builder wannabe

 	
 

 ttp44~at~rkymtn.net

 Corvallis MT

 Just starting a 601 kit     [quote][b]

_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings.

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Thu Mar 29, 2007 10:46 am Post subject: Re: NTSB Final Report Available

 	  p.mulwitz(at)worldnet.att wrote: 	
		  



We pay zillions of tax dollars for this?



Perhaps they should have said the plane crashed because it hit the ground.



	




Nothing wrong with the report, they could not determine why it failed,

likely because fire consumed all the important evidence of the failure.

People who seek answers to every question, some times end up

dissapointed.

larry(at)macsmachine.com
Guest

Posted: Thu Mar 29, 2007 12:17 pm Post subject: NTSB Final Report Available

Terry,

The thing I see so often and would question, is whether the cap angles 

were of the correct material.  Too often people ask if the spar cap angles

can be bought from local sources like Farm & Fleet.  The fact that the 

wing is considerably thinner and that so many have questioned the

material for this particular part of construction suggests that perhaps 

the builder(s) may have made a seriously bad assumption.  I'd doubt FAA

investigators would even check material type and strength.



Simple adherence to material and bolt call outs would not get you to 

failure of a spar structure with any of the excess weights below.



Larry McFarland  601HDS at www.macsmachine.com

do not archive

 

Terry Phillips wrote:

 	  Quote: 	
		   Lots of things of interest here.



     * 1st, the probable cause, structural failure of the wings for

       undetermined reasons, is troubling. But, the fire damage to the

       aluminum structure destroyed any evidence that might have told

       why the collapse occurred.

     * 2nd, with an estimated takeoff weight of 1326 lbs, the aircraft

       was 26 lbs over the stated gross of 1300 lbs. The gross

       currently listed for 601XL's on the Zenith website is 1320 lbs.

     * 3rd, this may have been the first flight of the airplane with

       two persons on board. If so, the extra 200 lb load may have been

       enough to collapse the wings.

     * 4th, it is not clear whether the builder, Mr. Hooker, flew the

       airplane beyond the 40 hr. requirement. The total hours on the

       airframe is not given.

     * 5th, while it is not explicitly stated, it appears that this

       aircraft was built from a kit, not from plans. That should

       remove the possibility that the wing spars were poorly

       constructed by the builder. It does not preclude damage to the

       spars during or prior to construction.

     * 6th, I find no mention in the report of the use of "hardware

       store" bolts in the spars which has been suggested in some posts

       to this group or of loose bolts.

     * 7th, the empty weight of the aircraft is given as 754.5 lbs

       which is about 60 lbs greater than the 695 lbs listed for the

       601/Jab 3300 on the Zenith website. It would be enlightening to

       know where the 60 lbs comes from. The dual brakes are one item.

       My conclusion is that we should be very rigorous in evaluating

       the weight/benefit ratio of anything we add to the basic

       airframe. I'm curious what empty weights others builders have

       ended up with.

     * 8th, the reports gives the unusable fuel as 3 gal. I know I've

       seen that number before, but I cannot seem to find it in the

       information I have. A useful fuel load of 21 gal vs. 24 gal

       makes me wish I had opted for the 30 gal tanks.

     * 9th, the elongated rivet holes probably resulted from the forces

       of impact. However, if they were a construction defect, is it

       possible that they could have weakened the wing structure?



 In summary, lots of information here, but it would have been great if 

 they had identified the cause of the wing failure. Then we could make 

 sure that, at least, we try to correct any obvious shortcomings in the 

 design.



 Terry

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Fri Mar 30, 2007 8:08 pm Post subject: Re: NTSB Final Report Available

This is plausible. The only problem here is that this was built from a kit, correct, unless the builder replaced something.



I was watching a video the other day of the stress test of a 777s wings. They had it up to 1.5 times design max load before the rivets along the top of the wing ripped out. The engineers said this was the expected mode of failure and were glad it reach 1.5 times max design. Possibly the rivets pulled out of the spar caps for some reason. If it was a kit though, the spar would have been built by Zenith. Maybe this guy had one of those pre-drilled skins, and the skin didn't match up with the ribs correctly and consequently his edge distances sucked, but he went ahead with it anyway and the wing failed due to poor construction practices due to going ahead with misaligned pre-drilled holes and rib center lines? That's the most likely explanation if it was build from a kit. That or he used Home Depot pop-rivets instead of aircraft grade pulled rivets.



Sitting here rolling up my EAA Sport Pilot mag into the shape of a wing, it's pretty stiff, even so, it's easy to 'warp the wing' Wright brothers style with minimal lateral play in what the rivets would be holding in shear, (ie a small amount of movement shear-wise in the rivets results in a large twist or warp of the wing. Could elongated holes contributed to the wing initially warping, causing them to flutter and then flutter out of control to the point of shearing the rivets and ultimate failure of the wing? It'd be nice if the NTSB actually provided pictures, because their description sucks. Following it word by word, they actually contradict themselves. If you had to draw what they're describing, their instructions would suck about as bad as an IKEA entertainment center assembly manual that was first translated from Swedish to Japanese, then to Engrish.



 	  larry(at)macsmachine.com wrote: 	
		  Terry,

The thing I see so often and would question, is whether the cap angles 

were of the correct material.  Too often people ask if the spar cap angles

can be bought from local sources like Farm & Fleet.  The fact that the 

wing is considerably thinner and that so many have questioned the

material for this particular part of construction suggests that perhaps 

the builder(s) may have made a seriously bad assumption.  I'd doubt FAA

investigators would even check material type and strength.



Simple adherence to material and bolt call outs would not get you to 

failure of a spar structure with any of the excess weights below.



Larry McFarland  601HDS at www.macsmachine.com

do not archive

 

Terry Phillips wrote:

 	  Quote: 	
		   Lots of things of interest here.



     * 1st, the probable cause, structural failure of the wings for

       undetermined reasons, is troubling. But, the fire damage to the

       aluminum structure destroyed any evidence that might have told

       why the collapse occurred.

     * 2nd, with an estimated takeoff weight of 1326 lbs, the aircraft

       was 26 lbs over the stated gross of 1300 lbs. The gross

       currently listed for 601XL's on the Zenith website is 1320 lbs.

     * 3rd, this may have been the first flight of the airplane with

       two persons on board. If so, the extra 200 lb load may have been

       enough to collapse the wings.

     * 4th, it is not clear whether the builder, Mr. Hooker, flew the

       airplane beyond the 40 hr. requirement. The total hours on the

       airframe is not given.

     * 5th, while it is not explicitly stated, it appears that this

       aircraft was built from a kit, not from plans. That should

       remove the possibility that the wing spars were poorly

       constructed by the builder. It does not preclude damage to the

       spars during or prior to construction.

     * 6th, I find no mention in the report of the use of "hardware

       store" bolts in the spars which has been suggested in some posts

       to this group or of loose bolts.

     * 7th, the empty weight of the aircraft is given as 754.5 lbs

       which is about 60 lbs greater than the 695 lbs listed for the

       601/Jab 3300 on the Zenith website. It would be enlightening to

       know where the 60 lbs comes from. The dual brakes are one item.

       My conclusion is that we should be very rigorous in evaluating

       the weight/benefit ratio of anything we add to the basic

       airframe. I'm curious what empty weights others builders have

       ended up with.

     * 8th, the reports gives the unusable fuel as 3 gal. I know I've

       seen that number before, but I cannot seem to find it in the

       information I have. A useful fuel load of 21 gal vs. 24 gal

       makes me wish I had opted for the 30 gal tanks.

     * 9th, the elongated rivet holes probably resulted from the forces

       of impact. However, if they were a construction defect, is it

       possible that they could have weakened the wing structure?



 In summary, lots of information here, but it would have been great if 

 they had identified the cause of the wing failure. Then we could make 

 sure that, at least, we try to correct any obvious shortcomings in the 

 design.



 Terry

stshuck(at)comcast.net
Guest

Posted: Fri Mar 30, 2007 9:51 pm Post subject: NTSB Final Report Available

Here is Mark Townsend's comment of the accident back in Oct. He had me 

convinced back then that there was a bolt missing on the rear spar. However 

the NTSB reports says nothing of this.



Yes there has been some speculation as to that crash and the fact that bolts 

were purchased just before the flight from Home depot ( not confirmed). What 

is confirmed is that the owner neglected to install nuts on the rear spar 

bolts(confirmed) The bolts were thought to have departed the spar well into 

the flight and the adding of flaps was what folded the wing . It is as we 

suspected and talked about. Is there a lesson to be learned from this, No 

you already should have learned to pre-flight your plane and if you remove 

any structure you double check everything then have someone else check it. I 

feel bad for the pilot and families sometimes it is hard to calm the 

eagerness before a flight.



Mark Townsend



Can-Zac Aviation Ltd.



president(at)can-zacaviation.com



www.can-zacaviation.com





---

planecrazydld(at)yahoo.co
Guest

Posted: Sat Mar 31, 2007 4:28 am Post subject: NTSB Final Report Available

the thing that has bothered me all along since reading that the holes in the separated components were elongated is that those A4s are unlikely to have that effect on the structure before the heads pop off. Look at the bearing vs shear for the parts and it looks to me like (some of) the structure was possibly double drilled? That would have the dreaded "zipper effect" in teh event of the right overload.

  Also Andy, the 787 wing failed right on the money just above the 1.5 - that is hwere it MUST fail for the certification. On the other hand, when the A380 wing failed at 1.38 and they decided they could implement a design fix into the certified plane without repeating the wing testing - now that is where my shorts pucker up.

  do not archive

ashontz <ashontz(at)nbme.org> wrote:

  [quote]--> Zenith-List message posted by: "ashontz" 

This is plausible. The only problem here is that this was built from a kit, correct, unless the builder replaced something.

I was watching a video the other day of the stress test of a 777s wings. They had it up to 1.5 times design max load before the rivets along the top of the wing ripped out. The engineers said this was the expected mode of failure and were glad it reach 1.5 times max design. Possibly the rivets pulled out of the spar caps for some reason. If it was a kit though, the spar would have been built by Zenith. Maybe this guy had one of those pre-drilled skins, and the skin didn't match up with the ribs correctly and consequently his edge distances sucked, but he went ahead with it anyway and the wing failed due to poor construction practices due to going ahead with misaligned pre-drilled holes and rib center lines? That's the most likely explanation if it was build from a  kit. That or he used Home Depot pop-rivets instead of aircraft grade pulled rivets.

larry(at)macsmachine.com wrote:

 	  Quote: 	
		   Terry,

 The thing I see so often and would question, is whether the cap angles 

 were of the correct material. Too often people ask if the spar cap angles

 can be bought from local sources like Farm & Fleet. The fact that the 

 wing is considerably thinner and that so many have questioned the

 material for this particular part of construction suggests that perhaps 

 the builder(s) may have made a seriously bad assumption. I'd doubt FAA

 investigators would even check material type and strength.

 Simple adherence to material and bolt call outs would not get you to 

 failure of a spar structure with any of the excess weights below.

 Larry McFarland 601HDS at www.macsmachine.com

 do not archive

 Terry Phillips wrote:

 > Lots of things of interest here.

 > 

 > * 1st, the probable cause, structural failure of the wings for

 > undetermined reasons, is troubling. But, the fire damage to the

 > aluminum structure destroyed any evidence that might have told

 > why the collapse occurred.

 > * 2nd, with an estimated takeoff weight of 1326 lbs, the aircraft

 > was 26 lbs over the stated gross of 1300 lbs. The gross

 > currently listed for 601XL's on the Zenith website is 1320 lbs.

 > * 3rd, this may have been the first flight of the airplane with

 > two persons on board. If so, the extra 200 lb load may have been

 > enough to collapse the wings.

 > * 4th, it is not clear whether the builder, Mr. Hooker, flew the

 > airplane beyond the 40 hr. requirement. The total hours on the

 > airframe is not given.

 > * 5th, while it is not  explicitly stated, it appears that this

 > aircraft was built from a kit, not from plans. That should

 > remove the possibility that the wing spars were poorly

 > constructed by the builder. It does not preclude damage to the

 > spars during or prior to construction.

 > * 6th, I find no mention in the report of the use of "hardware

 > store" bolts in the spars which has been suggested in some posts

 > to this group or of loose bolts.

 > * 7th, the empty weight of the aircraft is given as 754.5 lbs

 > which is about 60 lbs greater than the 695 lbs listed for the

 > 601/Jab 3300 on the Zenith website. It would be enlightening to

 > know where the 60 lbs comes from. The dual brakes are one item.

 > My conclusion is that we should be very rigorous in evaluating

 > the weight/benefit ratio of anything we add to the basic

 > airframe. I'm  curious what empty weights others builders have

 > ended up with.

 > * 8th, the reports gives the unusable fuel as 3 gal. I know I've

 > seen that number before, but I cannot seem to find it in the

 > information I have. A useful fuel load of 21 gal vs. 24 gal

 > makes me wish I had opted for the 30 gal tanks.

 > * 9th, the elongated rivet holes probably resulted from the forces

 > of impact. However, if they were a construction defect, is it

 > possible that they could have weakened the wing structure?

 > 

 > In summary, lots of information here, but it would have been great if 

 > they had identified the cause of the wing failure. Then we could make 

 > sure that, at least, we try to correct any obvious shortcomings in the 

 > design.

 > 

 > Terry

 > 

 > 

--------

Andy  601XL/Corvair?

   TV dinner still cooling?

[url=http://us.rd.yahoo.com/evt=49979/*http://tv.yahoo.com/]Check out "Tonight's Picks"[/url] on Yahoo! TV. [quote][b]

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Sat Mar 31, 2007 5:21 am Post subject: Re: NTSB Final Report Available

You saw that video too then.

What do you mean by double drilled? Twice as many rivets installed?

[quote="planecrazydld(at)yahoo.co"]the thing that has bothered me all along since reading that the holes in the separated components were elongated is that those A4s are unlikely to have that effect on the structure before the heads pop off. Look at the bearing vs shear for the parts and it looks to me like (some of) the structure was possibly double drilled? That would have the dreaded "zipper effect" in teh event of the right overload.

  Also Andy, the 787 wing failed right on the money just above the 1.5 - that is hwere it MUST fail for the certification. On the other hand, when the A380 wing failed at 1.38 and they decided they could implement a design fix into the certified plane without repeating the wing testing - now that is where my shorts pucker up.

  do not archive

ashontz <ashontz> wrote:

  [quote]--> Zenith-List message posted by: "ashontz" 

This is plausible. The only problem here is that this was built from a kit, correct, unless the builder replaced something.

I was watching a video the other day of the stress test of a 777s wings. They had it up to 1.5 times design max load before the rivets along the top of the wing ripped out. The engineers said this was the expected mode of failure and were glad it reach 1.5 times max design. Possibly the rivets pulled out of the spar caps for some reason. If it was a kit though, the spar would have been built by Zenith. Maybe this guy had one of those pre-drilled skins, and the skin didn't match up with the ribs correctly and consequently his edge distances sucked, but he went ahead with it anyway and the wing failed due to poor construction practices due to going ahead with misaligned pre-drilled holes and rib center lines? That's the most likely explanation if it was build from a  kit. That or he used Home Depot pop-rivets instead of aircraft grade pulled rivets.

larry(at)macsmachine.com wrote:

 	  Quote: 	
		   Terry,

 The thing I see so often and would question, is whether the cap angles 

 were of the correct material. Too often people ask if the spar cap angles

 can be bought from local sources like Farm & Fleet. The fact that the 

 wing is considerably thinner and that so many have questioned the

 material for this particular part of construction suggests that perhaps 

 the builder(s) may have made a seriously bad assumption. I'd doubt FAA

 investigators would even check material type and strength.

 Simple adherence to material and bolt call outs would not get you to 

 failure of a spar structure with any of the excess weights below.

 Larry McFarland 601HDS at www.macsmachine.com

 do not archive

 Terry Phillips wrote:

 > Lots of things of interest here.

 > 

 > * 1st, the probable cause, structural failure of the wings for

 > undetermined reasons, is troubling. But, the fire damage to the

 > aluminum structure destroyed any evidence that might have told

 > why the collapse occurred.

 > * 2nd, with an estimated takeoff weight of 1326 lbs, the aircraft

 > was 26 lbs over the stated gross of 1300 lbs. The gross

 > currently listed for 601XL's on the Zenith website is 1320 lbs.

 > * 3rd, this may have been the first flight of the airplane with

 > two persons on board. If so, the extra 200 lb load may have been

 > enough to collapse the wings.

 > * 4th, it is not clear whether the builder, Mr. Hooker, flew the

 > airplane beyond the 40 hr. requirement. The total hours on the

 > airframe is not given.

 > * 5th, while it is not  explicitly stated, it appears that this

 > aircraft was built from a kit, not from plans. That should

 > remove the possibility that the wing spars were poorly

 > constructed by the builder. It does not preclude damage to the

 > spars during or prior to construction.

 > * 6th, I find no mention in the report of the use of "hardware

 > store" bolts in the spars which has been suggested in some posts

 > to this group or of loose bolts.

 > * 7th, the empty weight of the aircraft is given as 754.5 lbs

 > which is about 60 lbs greater than the 695 lbs listed for the

 > 601/Jab 3300 on the Zenith website. It would be enlightening to

 > know where the 60 lbs comes from. The dual brakes are one item.

 > My conclusion is that we should be very rigorous in evaluating

 > the weight/benefit ratio of anything we add to the basic

 > airframe. I'm  curious what empty weights others builders have

 > ended up with.

 > * 8th, the reports gives the unusable fuel as 3 gal. I know I've

 > seen that number before, but I cannot seem to find it in the

 > information I have. A useful fuel load of 21 gal vs. 24 gal

 > makes me wish I had opted for the 30 gal tanks.

 > * 9th, the elongated rivet holes probably resulted from the forces

 > of impact. However, if they were a construction defect, is it

 > possible that they could have weakened the wing structure?

 > 

 > In summary, lots of information here, but it would have been great if 

 > they had identified the cause of the wing failure. Then we could make 

 > sure that, at least, we try to correct any obvious shortcomings in the 

 > design.

 > 

 > Terry

 > 

 > 

--------

Andy  601XL/Corvair?

   TV dinner still cooling?

[url=http://us.rd.yahoo.com/evt=49979/*http://tv.yahoo.com/]Check out "Tonight's Picks"[/url] on Yahoo! TV.  	  Quote: 	
		  [b]

planecrazydld(at)yahoo.co
Guest

Posted: Sat Mar 31, 2007 6:27 am Post subject: NTSB Final Report Available

I see all those videos - since I have worked for Boeing for 20+ years in the Materials Engineering department.

  The usual source of elongated or double drilled holes in structure is a mis-rig during the skin drill out. When the rigging is restored to the correct twist or lack of twist, the holes end up mis aligned between the structure and overlying skin(s). In the case where adequate edge distance is still available for a larger fastener, the error is usually corrected by correcting the rigging and re-drillign the same holes such that the new larger diameter picks up the full diameter of the mis-aligned holes. This leaves circular, properly sized holes through the stack that can be fastened by the appropriate oversized fastener. In the even that there is adequate edge distance for the larger fastener, at some point the failure mode will shift to a tear out or "bearing failure" along the fastener row - the "zipper effect". As long as the  fastener edge distance is OK the loads at fail will be greater than the original mode unles the original mode was bearing failure to start with.

  When they say that the holes were elongated, I hear "not completely cleaned out to the larger diameter in all components" - a recipe for a low failure.

  do not archive

ashontz <ashontz(at)nbme.org> wrote:

  [quote]--> Zenith-List message posted by: "ashontz" 

You saw that video too then.

What do you mean by double drilled? Twice as many rivets installed?

[quote="planecrazydld(at)yahoo.co"]the thing that has bothered me all along since reading that the holes in the separated components were elongated is that those A4s are unlikely to have that effect on the structure before the heads pop off. Look at the bearing vs  shear for the parts and it looks to me like (some of) the structure was possibly double drilled? That would have the dreaded "zipper effect" in teh event of the right overload.

Also Andy, the 787 wing failed right on the money just above the 1.5 - that is hwere it MUST fail for the certification. On the other hand, when the A380 wing failed at 1.38 and they decided they could implement a design fix into the certified plane without repeating the wing testing - now that is where my shorts pucker up.

do not archive

ashontz wrote:

[quote]--> Zenith-List message posted by: "ashontz" 

This is plausible. The only problem here is that this was built from a kit, correct, unless the builder replaced something.

I was watching a video the other day of the stress test of a 777s wings. They had it up to 1.5 times design max load before the rivets along the top of the wing ripped out. The engineers said this was the expected mode of failure and  were glad it reach 1.5 times max design. Possibly the rivets pulled out of the spar caps for some reason. If it was a kit though, the spar would have been built by Zenith. Maybe this guy had one of those pre-drilled skins, and the skin didn't match up with the ribs correctly and consequently his edge distances sucked, but he went ahead with it anyway and the wing failed due to poor construction practices due to going ahead with misaligned pre-drilled holes and rib center lines? That's the most likely explanation if it was build from a kit. That or he used Home Depot pop-rivets instead of aircraft grade pulled rivets.

larry(at)macsmachine.com wrote:

 	  Quote: 	
		   Terry,

 The thing I see so often and would question, is whether the cap angles 

 were of the correct material. Too often people ask if the spar cap angles

 can be bought from local sources like Farm & Fleet. The fact that the 

 wing is considerably thinner and that so many  have questioned the

 material for this particular part of construction suggests that perhaps 

 the builder(s) may have made a seriously bad assumption. I'd doubt FAA

 investigators would even check material type and strength.

 Simple adherence to material and bolt call outs would not get you to 

 failure of a spar structure with any of the excess weights below.

 Larry McFarland 601HDS at www.macsmachine.com

 do not archive

 Terry Phillips wrote:

 > Lots of things of interest here.

 > 

 > * 1st, the probable cause, structural failure of the wings for

 > undetermined reasons, is troubling. But, the fire damage to the

 > aluminum structure destroyed any evidence that might have told

 > why the collapse occurred.

 > * 2nd, with an estimated takeoff weight of 1326 lbs, the aircraft

 > was 26 lbs over the  stated gross of 1300 lbs. The gross

 > currently listed for 601XL's on the Zenith website is 1320 lbs.

 > * 3rd, this may have been the first flight of the airplane with

 > two persons on board. If so, the extra 200 lb load may have been

 > enough to collapse the wings.

 > * 4th, it is not clear whether the builder, Mr. Hooker, flew the

 > airplane beyond the 40 hr. requirement. The total hours on the

 > airframe is not given.

 > * 5th, while it is not explicitly stated, it appears that this

 > aircraft was built from a kit, not from plans. That should

 > remove the possibility that the wing spars were poorly

 > constructed by the builder. It does not preclude damage to the

 > spars during or prior to construction.

 > * 6th, I find no mention in the report of the use of "hardware

 > store" bolts in the spars which has been suggested in  some posts

 > to this group or of loose bolts.

 > * 7th, the empty weight of the aircraft is given as 754.5 lbs

 > which is about 60 lbs greater than the 695 lbs listed for the

 > 601/Jab 3300 on the Zenith website. It would be enlightening to

 > know where the 60 lbs comes from. The dual brakes are one item.

 > My conclusion is that we should be very rigorous in evaluating

 > the weight/benefit ratio of anything we add to the basic

 > airframe. I'm curious what empty weights others builders have

 > ended up with.

 > * 8th, the reports gives the unusable fuel as 3 gal. I know I've

 > seen that number before, but I cannot seem to find it in the

 > information I have. A useful fuel load of 21 gal vs. 24 gal

 > makes me wish I had opted for the 30 gal tanks.

 > * 9th, the elongated rivet holes probably resulted from the forces

  > of impact. However, if they were a construction defect, is it

 > possible that they could have weakened the wing structure?

 > 

 > In summary, lots of information here, but it would have been great if 

 > they had identified the cause of the wing failure. Then we could make 

 > sure that, at least, we try to correct any obvious shortcomings in the 

 > design.

 > 

 > Terry

 > 

 > 

--------

Andy 601XL/Corvair?

TV dinner still cooling?

Check out "Tonight's Picks" (http://us.rd.yahoo.com/evt=49979/*http://tv.yahoo.com/) on Yahoo! TV. 

 	  Quote: 	
		   [b]

--------

Andy Shontz

CH601XL - Corvair

www.mykitlog.com/ashontz

Read this topic online  [quote][b]

Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Sat Mar 31, 2007 10:21 am Post subject: Re: NTSB Final Report Available

I wonder if Mark has any more light to shed on this.....  that said, when I took the rudder class from Mark and David at CanZac, Mark told me that the XL uses three times the number of rivets required to meet the design strength.  One would think you would have to do a lousy job of installing the majority of rivets to create conditions for a failure so catastrophic.  I would think there would have been plenty of clues visable on a walk around like weeping or protruding rivets.  Like everyone else, I would like to know whether the rear spar bolts were indeed installed and tight when all this happened.   



As to the LE separation - if the fuel tanks contained enough gas their weight against the inside of the skin would likely tear the LE off on impact.   I saw a stinson flip on it's back during landing once and both wing tanks ripped out and went bouncing down the runway.



Tim

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

Display posts from previous:

	Matronics Email Lists Forum Index -> Zenith-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum