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crash B.S.
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chapred(at)free.fr
Guest

Posted: Sat Mar 07, 2009 12:55 am Post subject: crash B.S.

Hello all of you over the Atlantic ocean !



 



I react to Paul Mulwitz post. because he is speaking of what is happening in

Europe and I’m living in France with my 601xl built from a 100% kit .



I already introduced myself to you last year.



 



It’ is right Dutch authorities decided ( maybe too quickly)to stop flights

with 601;



In the same time, German people did the same , a few weeks ago ! they have

considered, exactly as you said, that.



 



Design sounds good and number of 601 flying world wide a kind of proof.

However, they said that dynamic tests were not run  and that is not correct

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psm(at)att.net
Guest

Posted: Sat Mar 07, 2009 4:36 am Post subject: crash B.S.

Bon jour Francois,



 Thank you for writing to announce the dynamic testing in Germany.  Also, I thought Michael Heintz was in California and Nicholas and Chris were in Europe.  Those guys move around very quickly.



 My understanding of dynamic testing is different from your description.  As I understand it, vibrations are introduced into various parts of the airframe.  The hope is to find a particular vibration frequency and location that becomes resonant.  This makes the amplitude of the vibration much larger and can lead, very quickly, to structural failure.



 The problem with this type of test is the number of different vibration frequencies and locations for introducing the vibrations is nearly infinite.  That makes this kind of testing very difficult and expensive.  It is done (required?) for many certified aircraft, but not usually done for experimental ones.



 I am not familiar with the wind tunnel testing you described.  It sounds like a good idea, but I have no idea what sort of issues it examines.  Perhaps this is a way to look at the possibility of control flutter.



 I believe the sand bag loading test is called static testing.  This kind of test has been performed at least twice on the American version of the Zodiac XL.  I don't know if it has been done on the European version at all.



 I am glad to learn there are competent people still looking for true explanations for the problems with the XL.  I will be flying mine very soon (a month or two?) and don't expect to have any problem.  Still, I am concerned that there might be a very small chance for a very big problem.



 Best regards,



 Paul

 XL getting close



 

 At 12:51 AM 3/7/2009, you wrote:



 [quote]Hello all of you over the Atlantic ocean !



  



 I react to Paul Mulwitz post. because he is speaking of what is happening in Europe and I’m living in France with my 601xl built from a 100% kit .



 I already introduced myself to you last year.



  



 It’ is right Dutch authorities decided ( maybe too quickly)to stop flights with 601;



 In the same time, German people did the same , a few weeks ago ! they have considered, exactly as you said, that.



  



 Design sounds good and number of 601 flying world wide a kind of proof. However, they said that dynamic tests were not run  and that is not correct .



  



 So you must know that last week , ZENAIR FRANCE (Michael Heintz) sent a 601XL to a private laboratory in HAMBOURG (Germany) to have dynamic examination in an artificial speed room ( blowers)



 They also asked ZENAIR to have a dynamic “g” test by loading wings , both sides, (intrados and extrados) with a charge of sand sacks .



  



 So you see that tests that were never ran in the past are going to be done!  All buzz will stop that day !



  



 Be sure that ZENAIR EUROP will communicate the very results if they are positive



 Be sure German authorities will communicate the very results if they are negative !



  



 Yours,



  



 François Chapperon



  



 [img]width[/img][b]

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daveaustin2(at)primus.ca
Guest

Posted: Sat Mar 07, 2009 5:48 am Post subject: crash B.S.

Could we give this subject a rest, please.   And don't forget the do not archive, because we won't want to go searching this  stuff anytime.

 Dave Austin  601HDS -  912

    [quote][b]

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Afterfxllc(at)aol.com
Guest

Posted: Sat Mar 07, 2009 12:20 pm Post subject: crash B.S.

Take me with you this is getting old.

  	  Quote: 	
		  Oh, boy.    Here we go again. I'm going out flying to get away from all this.  

	


 

  

 A Good Credit Score is 7001325337/aol?redir=http:%2F%2Fwww.freecreditreport.com%2Fpm%2Fdefault.aspx%3Fsc%3D668072%26hmpgID%3D62%26bcd%3DfebemailfooterNO62"> See yours in just 2 easy steps!

  [quote][b]

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paulrod36(at)msn.com
Guest

Posted: Sat Mar 07, 2009 12:22 pm Post subject: crash B.S.

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Rhino, they may have something there. The fact that there were tire marks  on one wing suggests that the wing may have folded down in flight. The only way  I can think to explain that one is that the plane may have experienced a violent  updraft, followed by one hellacious downdraft. My thinking is that at the top of  the updraft, and at the moment of entering the downdraft, the inertia of the  fuselage would have been to continue up, while the downdraft was acting on the  wings. Just a thought.  I seem to remember something similar happened to  some T-28s a long time ago.

  

 Paul Rodriguez

 DO NOT ARCHIVE

 [quote]   ---

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larry(at)macsmachine.com
Guest

Posted: Sat Mar 07, 2009 12:56 pm Post subject: crash B.S.

Exactly right Andrew,



The discussion of this problem is painful for most posters XL builders 

and owners, but it will run on until statistic or proofs resolve the issue.



I built a revision 4 HDS that was much heavier than the first edition 

HDS that first flew with a Rotax 583 at a 580 lb empty wt. The HDS has 

been progressively upgraded and strengthened by thicker materials to use 

larger engines, presumably to fly faster, but as a drawing set, revision 

4 HDS is still a very light aircraft by comparison to RV and others.

The newer XL at first glance with a reduction of wing thickness and 

flaps assured a way to fly faster and land slower. The concept seemed 

improved. Bolting a simpler bent-leaf-gear to the bottom of the fuselage 

was easier to design, package and build. Wings cantilevered from the 

fuselage required a center spar shortened to fuselage width. Repackaging 

601HD and HDS from a more complex construct to a much simpler aircraft 

allows it to compete with all LSA. The same passenger, pilot, baggage 

and fuel are unchanged. The shorter center spar and longer wings 

refocused and magnified stresses within the fuselage across a much 

shorter and reduced section spar. It is this reduced spar section and 

length that increases material stress within the spar and fuselage 

attach points. Discussion seems focused on wings that “fail and fold”. I 

don’t believe an XL wing has ever failed unless it was damaged 

externally. The center spar is, in design-terms, capable of doing its 

job when the aircraft is constructed correctly, not overloaded, and has 

properly torqued wing bolts. The safety margins in stress on the XL 

cannot be as forgiving as those found in the HD and HDS series because 

higher stresses are focused to a shorter lesser cross-section 

center-spar material. This newer canted angle spar design still meets 

the requirements and is thought to be statistically safe as demonstrated 

by a history of many older and actively flying XL. It is the margin of 

safety that needs to be addressed to preclude continuation of “the 

problem”, whether it is better builder-flyer adherence to loading, 

construction, etc or the introduction of a thicker section spar and 

better integration of spar connections with the fuselage. This kind of 

assumption would say that post-accident investigation would be unlikely 

to find anything that relates to cause until there are lots more broken 

parts and witnesses for comparing data. Early Bensen Gyrocopters went 

through a more frequent kind of the same pain until improvements were 

made much later when Bensens were no longer available. Even though a few 

Bensons are still flying, 601XLs are still way safer!



Do fly safe guys,



Larry McFarland 601HDS at www.macsmachine.com



rans6andrew wrote:

 	  Quote: 	
		   



 Juan, have you read the following, which I posted in December?  Nobody has criticised it so I guess it is reasonable, level headed stuff.



 I had been thinking along the same lines as Scotsman (who is from South Africa, apparently) and then I came around to comparing accident types and rates with other Zenair(ith) designs.



 I don't know how many 601XLs there are out there or indeed how many 601HDs there are or 601ULs there are. In the UK we currently have 20 XLs on the register, 28 ULs , 17 HD and 10 HDS models. So less than 30 % of the fleet is XL types.



 Is this typical of the ratio in the world as a whole?



 If it is, assuming that the same sort of people buy/build ULs, HDs, HDSs and XL varients, assuming that the same spread of pilot abilities, the same ratio of aerobatic wannabees buy each model and the same spread of builder competences we should be hearing about 3 times as many in flight break ups of the non XL types as XL types.



 We don't.



 Where are the others?



 This line of thinking tells me that either I have missed something significant or that there is something peculiar to the XL.

 Please correct me if there is a fatal flaw in my reasoning.



 Oh, and feel free to flame me 'cos it seems to be par for the course if you post from the UK!

 Andrew - in the UK and building a 601UL.

 I'm going to run the engine for the first time this weekend.



 --------

 A good way through building a 601UL with 912UL.

 Still flying Rans S6 with 503.

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d.goddard(at)ns.sympatico
Guest

Posted: Sat Mar 07, 2009 1:06 pm Post subject: crash B.S.

It's strange for an outsider to watch this three sided argument, on the one 

hand we have those (with money invested, not a neutral stance) who have 

absolute belief and faith in the XL. There IS not a problem and if the wings 

fell off in the driveway they would deny it. The opposing side who assumes 

there IS a problem and until it is proven that nothing can possibly ever go 

wrong will condemn the design. And the third (condemned by both preceding 

sides) who looks at what appears to be happening and wonders why that might 

be the case.

Me? I have an idea and no expertise and no proof, so I wait and watch.  I DO 

have an idea how this will play out that I am happy to share though. The XL 

will go down in history with a lot of other aircraft as a design that for 

some reason or other developed an undesirable history. Zenith will quietly 

retire the design and move on (CH-650). Those who have 601XL's will have 

either positive experiences and crow about the aircraft, others may have 

less  positive experiences and will say nothing, but others will either 

blame or commiserate  with them and post endlessly about it. For history ( 

and hysteria) look up the Beech (Doctor Killer) Bonanza or the Cirrus and 

there are others out there.  Look folks, sometimes bad things happen, all 

designs should be endlessly suspect with an eye to making things better.

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