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joe(at)kfiz.com
Guest

Posted: Fri May 11, 2007 11:10 am Post subject: accident

I agree with Jerry. Does anyone know if a representitive from ZENITH ever 

travels to inspect the wreckage from these various accidents? I think it 

would make prudent business sense to have the designer travel to look at the 

wreckage and report back to the builders! I'm not too concerned yet because 

the accident rate for 601's in comparison to the number flying is very low. 

I do like the idea of thickening the doubler plate and adding a bigger bolt. 

If Zenith isn't interested in the idea, I wouldn't be against pooling some 

money into a engineering review of the wing spar attachments. It may not be 

needed, but it may make us feel more secure.



I'm sure the people at Zenith read these postings. Can we have someone from 

the Company chime in here with answers to some of these postings?



Joe in Oshkosh

601 XL

admin(at)arachnidrobotics
Guest

Posted: Fri May 11, 2007 1:10 pm Post subject: accident

Guys, if you re-read all the accident reports, you'll find that it appears the aircraft operating limitations were exceeded in nearly every case (speculation yes, but based on preliminary reports).  I hate to break it to you, but if you yank back on a fully loaded C150, something's going to break.  

    This discussion is starting to sound a lot like the US media treats any shocking incident.  If a kid shoots up a classroom, it's the gunmakers fault.  Smokers are dying like flies, and it's the cigarrette companies fault.  I don't really like guns or cigarrettes myself, but it's the idiot on the other end of them that is to blame for any problems they create.  When did we stop thinking for ourselves in this country?

    If an aircraft comes down because the pilot did something the designer said not to do (pull high G's at high gross weight), it's the pilot's fault and problem.  The poor  aircraft company shouldn't even be brought into it.  (See discussions earlier this week regarding frivolous law suits, etc.)



    DO NOT ARCHIVE



Joe <joe(at)kfiz.com> wrote:[quote] --> Zenith-List message posted by: "Joe" 



I agree with Jerry. Does anyone know if a representitive from ZENITH ever 

travels to inspect the wreckage from these various accidents? I think it 

would make prudent business sense to have the designer travel to look at the 

wreckage and report back to the builders! I'm not too concerned yet because 

the accident rate for 601's in comparison to the number flying is very low. 

I do like the idea of thickening the doubler plate and adding a bigger bolt. 

If Zenith isn't interested in the idea, I wouldn't be against pooling some 

money into a engineering [quote][b]

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Fri May 11, 2007 1:19 pm Post subject: Re: accident

These incidents are probably akin to a newly wed couple wearing out their bedsprings; a little too much enthusiasm.



Still it would be nice to see a video of a CH601 being stressed tested to failure with some metrics.

p.mulwitz(at)worldnet.att
Guest

Posted: Fri May 11, 2007 2:53 pm Post subject: accident

Hi Tom,



In general, I agree with you on this point.  If people are indeed 

exceeding the limits of these airplanes then failures are the 

expected result.



Unfortunately, we don't know if the design limits were exceeded or 

not.  What we do know is that a lot of planes are disintegrating in 

flight.  Furthermore, they all seem to be Zodiac XLs.  I haven't 

heard any reports of similar failures in any other model of 

LSA.  Maybe they have been occurring and I just haven't heard about 

them.  That is part of the reason I wrote to the experts at EAA to 

ask if these accidents seem to be out of the ordinary.  They haven't 

responded to me yet.



This situation reminds me of a similar experience with V-tail 

Bonanzas.  Those planes had a long history of in-flight structural 

failures.  For decades, Beechcraft and others said it was simply a 

case of poor pilots exceeding the Vne of the plane and pulling up too 

hard causing the tail to fall off.  The pilots in question couldn't 

defend their skills since they were all dead.  Then after decades of 

this same failure occurring again and again they came out with a 

design change reinforcing the tail section of these planes.  After 

that the break-ups came to an abrupt end.  To my knowledge there has 

not been another one since.



I don't know how to proceed with this whole situation.  I know I am 

alarmed and facing flight testing of my XL which will probably be 

completed within a few months.  I don't want to bring any lawyers 

into this or have any lawsuits.  I just want to know if there is a 

design flaw and how it can be fixed if there is one.



I don't like all the speculation.  I don't like people thinking there 

is a fatal design flaw in my airplane.  Similarly, I don't like all 

the accident reports and I really don't like speculation that it is 

all the fault of the dead pilots.  I wish there was a practical way 

to find out the real truth of this matter.



Paul

XL fuselage

At 02:09 PM 5/11/2007, you wrote:

 	  Quote: 	
		      Guys, if you re-read all the accident reports, you'll find that 

 it appears the aircraft operating limitations were exceeded in 

 nearly every case (speculation yes, but based on preliminary 

 reports).  I hate to break it to you, but if you yank back on a 

 fully loaded C150, something's going to break.

     This discussion is starting to sound a lot like the US media 

 treats any shocking incident.  If a kid shoots up a classroom, it's 

 the gunmakers fault.  Smokers are dying like flies, and it's the 

 cigarrette companies fault.  I don't really like guns or 

 cigarrettes myself, but it's the idiot on the other end of them 

 that is to blame for any problems they create.  When did we stop 

 thinking for ourselves in this country?

     If an aircraft comes down because the pilot did something the 

 designer said not to do (pull high G's at high gross weight), it's 

 the pilot's fault and problem.  The poor aircraft company shouldn't 

 even be brought into it.  (See discussions earlier this week 

 regarding frivolous law suits, etc.)

ihab.awad(at)gmail.com
Guest

Posted: Fri May 11, 2007 3:18 pm Post subject: accident

On 5/11/07, Paul Mulwitz <p.mulwitz(at)worldnet.att.net> wrote:

 	  Quote: 	
		   I wish there was a practical way

 to find out the real truth of this matter.


	


Here's an off-the-wall idea --



Perhaps a radio controlled version of the aircraft could be built. It

could be instrumented with video cameras and some basic telemetry,

loaded with sandbags but minimal fuel to minimize the risk of

post-crash fire that would destroy the evidence, then progressively

tested to failure over the desert somewhere, with inspections between

each loading condition.



Given the whacky RC stuff some folks are doing, what with giant scale,

turbojet engines, retracts, flaps, spoilers and on-board video

cameras, it's really not much of a stretch to imagine doing this with

equipment off the shelf.



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

chris Sinfield

Joined: 28 Nov 2006
Posts: 270
Location: Sydney Australia

Posted: Fri May 11, 2007 3:38 pm Post subject: Re: accident

If you look at the british crash report

it shows it was an 601 UL factory built NOT an XL and and also the old wing design..

Plese keep to the facts.. and it does make a good read so download the report and dont up load your wings..



Chris..

 Do not archive

Gig Giacona

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

Posted: Fri May 11, 2007 3:43 pm Post subject: Re: accident

Paul, your definition of "a lot" seems to be different than mine or you know about some accidents that I don't.



I know of only 2 XLs that have failed in this way. The California crash that has been mentioned today and this most recent accident in Texas.



Can you point me towards info on any others?

 	  p.mulwitz(at)worldnet.att wrote: 	
		  



SNIP



 What we do know is that a lot of planes are disintegrating in 

flight.  Furthermore, they all seem to be Zodiac XLs.  	




SNIP

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

Kurt.Schumacher(at)schumi
Guest

Posted: Fri May 11, 2007 3:45 pm Post subject: accident

 	  Quote: 	
		   I wish there was a practical way to find out the real truth of this

matter.
	




Start with that:



Make your kit/aircraft supplier showing non-misleading specifications:

http://www.zenithair.com/zodiac/xl/specification.html



LOAD FACTOR (G) limit    +/- 4 

(DESIGN LOAD FACTOR (G) ultimate +/- 6)



Or better follow CZAW, e.g. on http://www.czaw.cz/sportcruiser.htm#airframe



"G" limit load factor +4 / -2



Everything else - including what ZAC actually shows for the XL - must be

considered misleading. I am just an engineer, and not a lawyer.



Because _if_ your XL is heavy and _if_ you fly beyond the limit load factor

- for a very short time - life might become short as troubles are coming up

very fast.



Good Luck!



-kurt.



--

planes_by_ken(at)bellsout
Guest

Posted: Fri May 11, 2007 3:59 pm Post subject: accident

Did we not learn about maneuvering speed, load factors, stall speeds, turbulence and weight and balance in ground school?

 We can't complain if the thing comes apart if we ignore the rules.

 Ken Lilja

 

 Kurt A. Schumacher wrote: [quote]    	  Quote: 	
		  --> Zenith-List message posted by: "Kurt A. Schumacher" <Kurt.Schumacher(at)schumi.ch> (Kurt.Schumacher(at)schumi.ch)



        	  Quote: 	
		  I wish there was a practical way to find out the real truth of this

    	
   matter.



Start with that:



Make your kit/aircraft supplier showing non-misleading specifications:

http://www.zenithair.com/zodiac/xl/specification.html



LOAD FACTOR (G) limit    +/- 4 

(DESIGN LOAD FACTOR (G) ultimate +/- 6)



Or better follow CZAW, e.g. on http://www.czaw.cz/sportcruiser.htm#airframe



"G" limit load factor +4 / -2



Everything else - including what ZAC actually shows for the XL - must be

considered misleading. I am just an engineer, and not a lawyer.



Because _if_ your XL is heavy and _if_ you fly beyond the limit load factor

- for a very short time - life might become short as troubles are coming up

very fast.



Good Luck!



-kurt.



  	
 [b]

Kurt.Schumacher(at)schumi
Guest

Posted: Fri May 11, 2007 4:53 pm Post subject: accident

 	  Quote: 	
		   We can't complain if the thing comes apart if we ignore the rules.


	


Cannot agree more! 



Anyway, I like to point out again, that the +/-6 G shown by ZAC >>>are<<<

misleading! For example, compare with an Extra EA-300 where the specs sheet

says "FAA Certified Load Factor +/- 10 Gs" - numbers I assume you can fly

safely 6.6 Gs - or really 10 Gs, aside all the other issues coming up then. 



..making use of the ZAC listed +/-6 will lead to structural deformations or

worst case a failure. Not because of any specific design flaws - just due to

having a nice marketing number.



-Kurt.



---



From: owner-zenith-list-server(at)matronics.com

[mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Ken Lilja

Sent: Saturday, May 12, 2007 2:01 AM

To: zenith-list(at)matronics.com

Subject: Re: accident



Did we not learn about maneuvering speed, load factors, stall speeds,

turbulence and weight and balance in ground school?

We can't complain if the thing comes apart if we ignore the rules.

Ken Lilja

<snip>

barcusc(at)comcast.net
Guest

Posted: Fri May 11, 2007 5:23 pm Post subject: accident

Chris



I read the post again, you are partially right, it is listed as a 601 UL, 

but it also states it was kit built.

Clyde Barcus

601 XL, Continental Powered

Wings, Tail & Engine Complete

Working on Fuselage



Do Not Archive



---

p.mulwitz(at)worldnet.att
Guest

Posted: Fri May 11, 2007 6:37 pm Post subject: accident

Hi Gig,



I thought I have heard of 4 breakups in the last year or so, but when 

I went searching for details I ran into computer problems.  (The NTSB 

search page is still loading after an hour of SLOW data transfer).  I 

did find 3 references in old emails I had on my PC.



N105RH 2/08/2006 Oakdale,CA Traffic pattern inflight breakup 

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



N158MD 11/4/2006 Yuba City, CA  in flight breakup (explosion?)

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



N10028 5/2/2007 Canadien, TX  in flight breakup (IMC?)

http://www.ntsb.gov/ntsb/brief.asp?ev_id 070509X00539&key=1



I intend to keep looking once the computer starts cooperating a 

little better.  I will post anything interesting I find.



Paul

XL fuselage



At 04:43 PM 5/11/2007, you wrote:

 	  Quote: 	
		  



Paul, your definition of "a lot" seems to be different than mine or 

you know about some accidents that I don't.



I know of only 2 XLs that have failed in this way. The California 

crash that has been mentioned today and this most recent accident in Texas.



Can you point me towards info on any others?

NamesChangedTo...

Joined: 29 Dec 2006
Posts: 2

Posted: Fri May 11, 2007 7:12 pm Post subject: Re: accident

Jay-ZUZ Friggin!!  Can I bother you girls with some facts?  

My apologies to any actual women out there.



Yes, Chris did respond to the California accident where the wings folded - http://www.zenithair.com/zodiac/xl/data/cheintz-ntsb-lax06la105.pdf 

Here's the NTSB report - http://ntsb.gov/ntsb/brief2.asp?ev_id=20060217X00209&ntsbno=LAX06LA105&akey=1

The rear channel pulled through the fuse support.

In short, there was no problem with the stabilizer section.



The Mitchell 801 accident can be found at - http://ntsb.gov/ntsb/brief2.asp?ev_id=20030312X00321&ntsbno=LAX03FA102&akey=1

I hate to trouble with you with more facts but the Mitchel 801 used a LOM engine which exceeded the max engine weight.  Chris derated max G's and reduced V(a) on that aircraft.

Art Mitchell sold the machine to the crash pilot.  And yes, there was THC in both the pilot and passengers bloodstreams.



A pothead pulled some stunts and overstressed the attachments.  I dare anyone to prove there has been even 1 more instance when the stabilizer fell off a Zenith aircraft.

And with regards to Zenith not saying anything, why would anyone put make a statement that might be contradicted by an official conclusion?  And if you're not familiar with a forensic tear down, they are often attended by a representative of both the airframe and engine companies.  Just because the company doesn't say something, it doesn't mean they aren't actively involved in and concerned with an the investigation.



Since we're experimental, you can beef up any parts you want.  Before you do, you should have a thorough understanding of materials and stress analysis.  The most common effect is that you simply shift the stress to a different area that wasn't designed to handle it.

Care for an example?  Consider lightening holes.  A novice might consider eliminating them to make the wing rib stronger.  But they would really be making it weaker.

Ok, what if a novice knew this and decided to make the lightening hole bigger?  This is a bad idea because it makes the rib weaker.



Sometimes things are the way they are for a good reason.  Before you go making a serious adjustment, such as in the stabilizer attachment, could you at least run run it past an engineering student?  And while you're at it, ask if they would bet their entire families life on their opinion.

Facts can only hurt you if you profit from the fallacy.

skyguynca

Joined: 05 Jun 2006
Posts: 128

Posted: Fri May 11, 2007 7:32 pm Post subject: accident

I thought there were 3 in a very short period and 14 months is really short. 

Maybe it is something to look into.



David Mikesell

23597 N. Hwy 99

Acampo, CA 95220

209-224-4485

skyguynca(at)skyguynca.com

www.skyguynca.com

---

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Fri May 11, 2007 8:19 pm Post subject: Re: accident

Yes, those 3 and then this most recent one. That's 4. Even though it could be totally the pilots fault, I'd still be more comfortable with soe new testing.



There's tons of 1975 Cessna 150s that have been beat to shit by student pilots over the years that are still flying without shedding a wing. What's the difference between them and thes new by comparison 601s. The 601 is rated for +-6G. A 150, something like +3.8 and -1.8 G.



 	  p.mulwitz(at)worldnet.att wrote: 	
		  Hi Gig,



I thought I have heard of 4 breakups in the last year or so, but when 

I went searching for details I ran into computer problems.  (The NTSB 

search page is still loading after an hour of SLOW data transfer).  I 

did find 3 references in old emails I had on my PC.



N105RH 2/08/2006 Oakdale,CA Traffic pattern inflight breakup 

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



N158MD 11/4/2006 Yuba City, CA  in flight breakup (explosion?)

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



N10028 5/2/2007 Canadien, TX  in flight breakup (IMC?)

http://www.ntsb.gov/ntsb/brief.asp?ev_id 070509X00539&key=1



I intend to keep looking once the computer starts cooperating a 

little better.  I will post anything interesting I find.



Paul

XL fuselage



At 04:43 PM 5/11/2007, you wrote:

 	  Quote: 	
		  



Paul, your definition of "a lot" seems to be different than mine or 

you know about some accidents that I don't.



I know of only 2 XLs that have failed in this way. The California 

crash that has been mentioned today and this most recent accident in Texas.



Can you point me towards info on any others?

stshuck(at)comcast.net
Guest

Posted: Fri May 11, 2007 8:24 pm Post subject: accident

I find it interesting how Zodie Rocket has been so quiet during all this 

discussion.

---

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri May 11, 2007 8:47 pm Post subject: accident

You are comparing apples to oranges. The published load factor for the 

Cessna 150 is the FLIGHT load factor, the published load factor for the 

CH601 is the DESIGN load factor. The design load factor is 1.5 times the 

flight load factor so the FLIGHT load factor of the 601 is +-4 G NOT +- 

6G. The C-150 is certificated in the utility category so it's flight 

load factor is +4.4 -2.2 G, so it's actually a bit stronger in positive 

G loading. It also has much more drag so it's harder to build up enough 

speed to put you at high risk of structural damage during abrupt maneuvers.



ashontz wrote:

 	  Quote: 	
		   

 

 Yes, those 3 and then this most recent one. That's 4. Even though it could be totally the pilots fault, I'd still be more comfortable with soe new testing.

 

 There's tons of 1975 Cessna 150s that have been beat to shit by student pilots over the years that are still flying without shedding a wing. What's the difference between them and thes new by comparison 601s. The 601 is rated for +-6G. A 150, something like +3.8 and -1.8 G.

 

 


	




-- 

Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

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

msherman95632(at)yahoo.co
Guest

Posted: Fri May 11, 2007 10:00 pm Post subject: accident

Mr. No Name.

 

I read the NTSB report you listed and the nice letter from Chris H.  I don't see where either says the rear channel pulled through.  If I missed it, please point it out to me.  The final NTSB report said the wing failed with both main and rear attach points secure.  I must be missing something.

 

Mark S. ( not scared to post my name)

701/912ULS

---

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Sat May 12, 2007 4:42 am Post subject: Re: accident

I agree. I read the whole thing and the only thing that I remember hearing was that the main attach points were still secure, implying (because that's all you get) that the wing structure itself failed. Now whether it failed due to over stressing or something structurally/design wrong with it, we don't know. It's good to know that those attach points are strong though.



Whether it was overstressed about it's rated load factor or broke below that load factor, what we're seeing is that the wings weakness lies in all probability from rib 4 out to about rib 6. The NTSB noted S-shaped deformities in this area. I would put extra ribs between 4 and 5 and 5 and 6 for starters. I would have also designed it with a 1.5" x 1.5" x 1/8" extrusion for an upper spar cap angle. Considering the wing spar is forward inclined 9 degrees and the lift component is not only not straight up but back maybe 10 degrees, this means that the lift component in relation to the main spar is roughyl 19 degrees. That sounds like an excellent starting point for distortion of the main spar. The main spar is strong as hell in the upright position, flat it's weak as shit. Any vector other than zero starts to put more shear force on the rivets to keep the spar inline. Why they didn't design it with the spar at least perpendicular (no less 9 degrees forward inclined) to the centerline of the plane is beyond me. As far as I'm concerned, that a designed in/built in Achille's Heel.



If we use the 9 degree forward inclined spar and a 10 degree back lift component (lift plus drag) we get the wing being only 94% as strong as listed. Not only that, but we also get 32% of the lift force gets translated in rivet shear. Let's say the plane weighs 1300. At 4 Gs that 5200lbs, 32% of that is shear through the rivets trying to hold the skin on, or about 1664 lbs collectively, 832 lbs per wing. Considering the cantilever design of the wing, that force gets concentrated into the inboard 1/3 of the wing. Yeah, only 4 rivets should be able to hold 800 lbs, but then we have other torsional effects. And it's still 800lbs trying to snap the main spar flat. Me and I my neighbor applied about 300 lbs of force to bend a 6 foot piece of .040 for spar cap angles. Just something to think about.



 	  msherman95632(at)yahoo.co wrote: 	
		  Mr. No Name.

 

I read the NTSB report you listed and the nice letter from Chris H.  I don't see where either says the rear channel pulled through.  If I missed it, please point it out to me.  The final NTSB report said the wing failed with both main and rear attach points secure.  I must be missing something.

 

Mark S. ( not scared to post my name)

701/912ULS

---

Last edited by ashontz on Sat May 12, 2007 5:10 am; edited 2 times in total

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Sat May 12, 2007 4:44 am Post subject: Re: accident

I realize this. That's what I'm saying. So basically when we take away the 'happy talk' selling points and compare them apples to apples and TRUE flight load factor to flight load factor, the Cessna 150 is actually a bit beefier.



 	  bryanmmartin wrote: 	
		  You are comparing apples to oranges. The published load factor for the 

Cessna 150 is the FLIGHT load factor, the published load factor for the 

CH601 is the DESIGN load factor. The design load factor is 1.5 times the 

flight load factor so the FLIGHT load factor of the 601 is +-4 G NOT +- 

6G. The C-150 is certificated in the utility category so it's flight 

load factor is +4.4 -2.2 G, so it's actually a bit stronger in positive 

G loading. It also has much more drag so it's harder to build up enough 

speed to put you at high risk of structural damage during abrupt maneuvers.



ashontz wrote:

 	  Quote: 	
		   

 

 Yes, those 3 and then this most recent one. That's 4. Even though it could be totally the pilots fault, I'd still be more comfortable with soe new testing.

 

 There's tons of 1975 Cessna 150s that have been beat to shit by student pilots over the years that are still flying without shedding a wing. What's the difference between them and thes new by comparison 601s. The 601 is rated for +-6G. A 150, something like +3.8 and -1.8 G.

 

 



	




-- 

Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

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