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601XL main spar question
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sdthatcher

Joined: 13 Mar 2008
Posts: 91
Location: Port Saint Lucie

Posted: Thu Apr 15, 2010 6:49 am Post subject: Re: 601XL main spar question

I've still got mine... from some 40 years ago!  



 	  Sabrina wrote: 	
		  P.S.  Dear John... a better book than CH's is Bruhn's Analysis & Design of Flight Vehicle Structures...  a little bit more expensive at $100 used (original cost new was $17 back in the day) but well worth it...

_________________
Scott Thatcher, Port Saint Lucie, FL
601XL with Corvair, Registered as E-LSA
N601EL, EAA203 140 hours and not flying currently.

sdthatcher

Joined: 13 Mar 2008
Posts: 91
Location: Port Saint Lucie

Posted: Thu Apr 15, 2010 6:58 am Post subject: Re: 601XL main spar question

Sabrina... Is your comment below the reason you felt uneasy about the upgrade?  



"Do you think, in a flutter scenario you suggest, the wing fails first in negative gs?"

_________________
Scott Thatcher, Port Saint Lucie, FL
601XL with Corvair, Registered as E-LSA
N601EL, EAA203 140 hours and not flying currently.

sabrina

Joined: 15 Jun 2009
Posts: 170

Posted: Thu Apr 15, 2010 10:20 am Post subject: Re: 601XL main spar question

Do Not Archive

Last edited by sabrina on Fri Jun 25, 2010 9:26 pm; edited 1 time in total

grs-pms(at)comcast.net
Guest

Posted: Thu Apr 15, 2010 10:50 am Post subject: 601XL main spar question

Sabrina:



Just a thought here from  an old aero engineer:  Have you considered that, 

if flutter is the problem, the failure mode is quite likely torsion, rather 

than bending?



George

---

psm(at)att.net
Guest

Posted: Thu Apr 15, 2010 11:03 am Post subject: 601XL main spar question

Hi Sabrina,



I'm afraid nobody knows the answer to your question.  If they did then the

cause of the accidents would not be "Unknown".



All we know for sure is that the airframe seems to always fail in the same

place - the joint between the wings and fuselage.  You could get more

detailed description of the failure to include exact part numbers, but the

result is the same.



The upgrade blessed by the FAA, Chris, and apparently everyone who has

installed it merely beefs up the whole wing structure.  It also balances the

ailerons (as originally demanded by the NTSB).  It does nothing to fix the

control sensitivity gradient that the NTSB also asked for.



Any guesses as to the actual failure scenario would be just that -- guesses.

I truly hope you reexamine your decision to design your own fix for this

totally unknown problem.  I would sleep a lot better if you either installed

the approved upgrade or just scrapped your plane.  I am currently installing

the upgrade in mine, but I will not take it out of phase I testing until a

significant amount of time (perhaps a year) has gone by with no more

structure failures.



I have no doubt that you are very smart and probably the best educated

person on this list.  Still, I don't think that is enough to know what is

wrong with the Zodiac XL design and how to fix it.



Best regards,



Paul

Installing XL upgrade

--

sabrina

Joined: 15 Jun 2009
Posts: 170

Posted: Thu Apr 15, 2010 11:25 am Post subject: Re: 601XL main spar question

Do Not Archive

Last edited by sabrina on Fri Jun 25, 2010 9:26 pm; edited 1 time in total

PatrickW

Joined: 27 Oct 2006
Posts: 380
Location: Fort Worth, Texas

Posted: Thu Apr 15, 2010 1:39 pm Post subject: Re: 601XL main spar question

 	  Sabrina wrote: 	
		  I would like to poll the members... 	


Torsion.



Take a cardboard shoe box.  Tape it up nice and tight.  You can stand on it.



Take that same cardboard shoe box.  Tape it up nice and tight, but with a 9 degree tilt to it.  Then try to stand on it.  Not nearly as strong.



The question is, "do the upgrades make the wing strong enough...?"  It appears that as far as Zenith and the FAA is concerned, the answer is "yes".



Time will tell as more of us complete the upgrades and return to the air.



Patrick

XL/Corvair/BRS

rtdin

Joined: 16 Mar 2008
Posts: 46
Location: Florida panhandle

Posted: Thu Apr 15, 2010 2:51 pm Post subject: 601XL main spar question

A poll? Nobody here kicked tin at the various accident sites. I would sooner rely on the investigating agencies and not the "experts" who were not there.

 

 "Tearing our wings off ?" Just about all of the wing failures happened in cruise flight. Several in the traffic pattern. One purely weather related case.

 

 "Horizontal stabilizer?" NTSB says that in only one case, the fwd stabilizer brackets collapsed first, followed by total break up. I was asked to look at a project in the area and found the rear bracket cracked. Zero flight time. A more detailed exam revealed cracks left and right side. I posted pictures in ZBAG "photos." I am still tying to get my hands on this part. Any questions, contact me at MaxNr(at)aol.com. 

 

 Questions about flutter are not adequately covered in a few posts on a user group. Many people "believe" or "don't believe" only as matter of faith. As for me, I depend on advice from a retired aerodynamicist in my area who worked on USAF flutter projects. Bingelis has archived lots of flutter stuff on the EAA website. Barnaby Wainfan recently wrote columns on flutter in Kitplanes. I also listen a lot to an A.I. who is still a senior inspector at the carrier that I retired from.

 

 I so wanted to stay out of this, but couldn't resist.

 

 Bob Dingley 

 601XL Plans 6-6791 Jab 3300 (Formerly a Lyc)

 Picking away at the recently arrived upgrade.

   [quote][b]

sabrina

Joined: 15 Jun 2009
Posts: 170

Posted: Thu Apr 15, 2010 4:09 pm Post subject: Re: 601XL main spar question

Do Not Archive

Last edited by sabrina on Fri Jun 25, 2010 9:27 pm; edited 1 time in total

JohnDRead(at)aol.com
Guest

Posted: Thu Apr 15, 2010 8:35 pm Post subject: 601XL main spar question

Pilot error!

  

 Regards,  John



CH701 - Colorado - Jabiru 3300



Cell: 719-494-4567

Home:  303-648-3261   

  In a message dated 4/15/2010 6:27:53 P.M. Mountain Daylight Time,  chicago2paris(at)msn.com writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: "Sabrina"    <chicago2paris(at)msn.com>



Bob,



You are exactly the person to    pull into the discussion...  what do your experts think is being    addressed by the factory mods... in other words which failure mode is being    addressed the most with the upgrade according to your    sources...



although we each know very little on our own, we all have an    expert of two giving us advice...





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=294371#294371===============================================

_-=    the  ties  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================

JohnDRead(at)aol.com
Guest

Posted: Thu Apr 15, 2010 8:36 pm Post subject: 601XL main spar question

Thanks Bob, there is some sanity out there!

  

 Regards,  John



CH701 - Colorado - Jabiru 3300



Cell: 719-494-4567

Home:  303-648-3261   

  In a message dated 4/15/2010 4:52:12 P.M. Mountain Daylight Time,  MaxNr(at)aol.com writes:

  	  Quote: 	
		  A poll? Nobody here kicked tin at the various accident sites. I    would sooner rely on the investigating agencies and not the "experts" who were    not there.



"Tearing our wings off ?" Just about all of the wing    failures happened in cruise flight. Several in the traffic pattern. One purely    weather related case.



"Horizontal stabilizer?" NTSB says that in only    one case, the fwd stabilizer brackets collapsed first, followed by total break    up. I was asked to look at a project in the area and found the rear bracket    cracked. Zero flight time. A more detailed exam revealed cracks left and right    side. I posted pictures in ZBAG "photos." I am still tying to get my hands on    this part. Any questions, contact me at MaxNr(at)aol.com. 



Questions about    flutter are not adequately covered in a few posts on a user group. Many people    "believe" or "don't believe" only as matter of faith. As for me, I depend on    advice from a retired aerodynamicist in my area who worked on USAF flutter    projects. Bingelis has archived lots of flutter stuff on the EAA website.    Barnaby Wainfan recently wrote columns on flutter in Kitplanes. I also listen    a lot to an A.I. who is still a senior inspector at the carrier that I retired    from.



I so wanted to stay out of this, but couldn't resist.



Bob    Dingley 

601XL Plans 6-6791 Jab 3300 (Formerly a Lyc)

Picking away at    the recently arrived upgrade.

 	  Quote: 	
		  



====================================

 href="http://www.matronics.com/Navigator?Zenith-List">http://www.matron====================================

ms.matronics.com/">http://forums.matronics.com

====================================

tp://www.matronics.com/contribution">http://www.matronics.com/contribution

====================================

JohnDRead(at)aol.com
Guest

Posted: Thu Apr 15, 2010 8:42 pm Post subject: 601XL main spar question

None of you seem to understand what a monocoque structure is and how it  resists both bending and torsion. As I suggested in a recent post - buy a copy  of Chris Heintz book and you will understand. There are other books about  airframe structure design but none written about the Zenith series of aircraft  by the designer.

  

 Regards,  John



CH701 - Colorado - Jabiru 3300



Cell: 719-494-4567

Home:  303-648-3261   

  In a message dated 4/15/2010 3:40:50 P.M. Mountain Daylight Time,  pwhoyt(at)yahoo.com writes:

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

Sabrina wrote:

 	  Quote: 	
		   I would like to    poll the members... 


	


Torsion.



Take a cardboard shoe box.     Tape it up nice and tight.  You can stand on it.



Take that same    cardboard shoe box.  Tape it up nice and tight, but with a 9 degree tilt    to it.  Then try to stand on it.  Not nearly as strong.



The    question is, "do the upgrades make the wing strong enough...?"  It    appears that as far as Zenith and the FAA is concerned, the answer is    "yes".



Time will tell as more of us complete the upgrades and return to    the air.



Patrick

XL/Corvair/BRS





Read this topic    online    here:



http://forums.matronics.com/viewtopic.php?p=294356#294356===============================================

_-=    the  ties  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================

n801bh(at)netzero.com
Guest

Posted: Fri Apr 16, 2010 5:43 am Post subject: 601XL main spar question

Yeah... The Yube City fatal crash has pilot error written all over it..... Couple in their 70's, straight and level, below VA, all documented by radar returns....... 

from straight and level to massive destruction left scattered all over an orchard in about 40 seconds.  Maybe the elderly gentleman was showing his wife how he was going to fly in the Red Bull challange and broke the plane with her in it for her first ride in it....  FAT CHANCE. 

Sure looks like pilot error to me.

Ben Haas

N801BH

www.haaspowerair.com



--------

ken Buchmann

Joined: 18 Feb 2008
Posts: 6
Location: New Haven,MO

Posted: Fri Apr 16, 2010 6:51 am Post subject: Re: 601XL main spar question

Dear Everyone:



I always enjoy these learned discussions pertaining to wings.  As a retired farm practice veterinarian, I am now enjoying a life long desire to experience traveling through the air like the birds do, but only in a flying machine.



I have owned a Cessna 172A, CH801, CH701 and now am building a CH750.  I have never seen a low winged bird in my entire veterinary experience and what is good enough for God is good enough for me.  Also, where wise men disagree, fools step in.



And now at 80 years of age I am considering building a wooden (God's Composite) open cockpit (white scarf and goggles) Biplane (Wright number of wings for mankind)



Ken 



do not archive

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri Apr 16, 2010 8:02 am Post subject: 601XL main spar question

The Yuba city crash did NOT happen in straight and level flight. The radar track clearly shows maneuvering flight just before the break-up. The radar showed a climb followed by a fairly rapid descent just before the break-up. The accident report shows a failure in negative G loading. Maybe the pilot pushed the nose over suddenly to avoid a bird strike. Or maybe he had a sudden medical problem. We'll never know for sure.



Why do you keep denying the possibility of pilot error in these accidents? It's a fact that pilot error is a factor in more accidents than all other causes combined. It is an especially prevalent problem for low time pilots with low time in type. Low time in type seems to be about the only common thread in these accidents, along with low time on the airframe.



On Apr 16, 2010, at 9:37 AM, n801bh(at)netzero.com wrote:



 	  Quote: 	
		   Yeah... The Yube City fatal crash has pilot error written all over it..... Couple in their 70's, straight and level, below VA, all documented by radar returns.......

 

 from straight and level to massive destruction left scattered all over an orchard in about 40 seconds.  Maybe the elderly gentleman was showing his wife how he was going to fly in the Red Bull challange and broke the plane with her in it for her first ride in it....  FAT CHANCE.

 

 Sure looks like pilot error to me.

 


	




-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

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

Terry Phillips

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

Posted: Fri Apr 16, 2010 8:05 am Post subject: 601XL main spar question

Thank you, Ken



At last someone is spreading some real wisdom on these issues.



You post has made my day!



Terry (still a low wing building fool--not even 70 yet--hope I'll have 

finished my 601XL and be building something else when I'm 80)

At 07:51 AM 4/16/2010 -0700, you wrote:

 	  Quote: 	
		  Dear Everyone:



I always enjoy these learned discussions pertaining to wings.  As a 

retired farm practice veterinarian, I am now enjoying a life long desire 

to experience traveling through the air like the birds do, but only in a 

flying machine.



I have owned a Cessna 172A, CH801, CH701 and now am building a CH750.  I 

have never seen a low winged bird in my entire veterinary experience and 

what is good enough for God is good enough for me.  Also, where wise men 

disagree, fools step in.



And now at 80 years of age I am considering building a wooden (God's 

Composite) open cockpit (white scarf and goggles) Biplane (Wright number 

of wings for mankind)



Ken



do not archive


	




Terry Phillips

ttp44~at~rkymtn.net

Corvallis MT

ZU-601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail & flaps are done;

Upgrading wings & ailerons per the AMD Safety Directive

http://www.mykitlog.com/N47TP/

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

psm(at)att.net
Guest

Posted: Fri Apr 16, 2010 8:47 am Post subject: 601XL main spar question

Hi Bryan,



I believe you are correct when you refuse to rule out pilot error as cause

for all the XL breakups.  Indeed, there has never been a determination, by

the accident investigation experts, of any probable cause for these

accidents.



The problem I have with blaming all this on pilot error is:



1.  It is too convenient.  The pilots are all dead and unable to defend

themselves or their actions.  This makes them easy targets for those who

prefer to stay "In Denial" that there is actually a design problem with the

XL.

2.  It doesn't make sense for me that only Zodiac XLs attract pilots prone

to errors that remove the wings from their planes.  The Zodiac XL is the

only design that has experienced multiple accidents of this, or any, type

among LSA in the last few years.  Out of hundreds of designs flying today

only this one has experienced unexplained in-flight structure failures.

Indeed the failures all amounted to the wings coming off at the root.

3.  It doesn't provide any useful solutions to the problem.  If the whole

cause for these accidents is pilot error then the only remedial action that

would help would be to find better pilots to fly Zodiac XLs.  Perhaps a

special pilot's license is called for?

4.  I find it odd, perhaps incredible, that the agencies that nearly always

find pilot error as the cause for any accident they investigate have never

found pilot error to be even a consideration in all these accidents.  Only

the designer and companies that make their living from selling these planes

has taken a public position that pilot error, or maintenance problems, are

behind all the deaths.



So, while I agree with you that we cannot eliminate pilot error from the

cause of any of the XL accidents I think blaming the whole problem on

unfortunate pilot actions is nothing short of absurd "Denial".



Paul

XL installing upgrade

--

sabrina

Joined: 15 Jun 2009
Posts: 170

Posted: Fri Apr 16, 2010 9:17 am Post subject: Re: 601XL main spar question

Do Not Archive

Last edited by sabrina on Fri Jun 25, 2010 9:29 pm; edited 3 times in total

grs-pms(at)comcast.net
Guest

Posted: Fri Apr 16, 2010 9:34 am Post subject: 601XL main spar question

Hi Ken:



You make an interesting point about God's design choices, but don't carry it 

too far.  There are no recorded sightings of a bird with wing struts, or one 

on wheels, floats or even skis.  And they do tend to land in trees, so be 

careful.



George

---

pchap(at)primus.ca
Guest

Posted: Fri Apr 16, 2010 9:53 am Post subject: 601XL main spar question

At 13:17 16-04-10, you wrote:

 	  Quote: 	
		  Check out this picture of the Zenith load testing... notice the 

additional cuff bonded/riveted between the wing and 

fuselage...  (this really bothers my mentors) would the wing have 

failed the load test without that reinforcement?   (I know some will 

say it is just for aerodynamics, but why test in that configuration?)


	


Hi Sabrina,



Hope this helps:



It kind of looks like the same heavy plastic sheeting or whatever it 

is, that is laid along the wing, under the wood (?) ontop of which 

the weights sit.

The sheeting looks a bit like a reflection at first but one can see 

it extend a little past the wing tip at the nav light.



A good interpolated zoom of the photo, eg by control - mouse scroll 

wheel in Firefox, helps to see it more clearly.



Peter Chapman

Toronto, ON

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