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New Zenith Statement
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Gig Giacona

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

Posted: Sat Apr 25, 2009 6:26 am Post subject: New Zenith Statement

April 22, 2009



Zenair met with FAA officials on April 22, 2009.  The meeting was productive, with FAA officials confirming that they have no plans to ground the fleet of Zodiac CH-601XL aircraft.



In response to the NTSB Safety Recommendation letter (dated April 14, 2009), the FAA officials stated that they will commence their own thorough review of the Zodiac design, and has given this review high priority.  Zenair will cooperate fully in assisting the FAA.



Zenair also continues with the ongoing design analysis of the Zodiac CH-601XL, including wing flutter analysis. The independent consulting team from Germany has released preliminary findings.  These preliminary findings confirm that the aircraft, with properly tensioned control cables, is not prone to flutter.  The team is continuing its analysis, including the recommendations set forth in the NTSB's letter, such as mass balanced ailerons.



Zenair wants to remind builders, owners and pilots to verify that all control surfaces are properly fastened and secured, and free of play, and that control stops are present and properly installed, and that the control systems are not loose.  Pilots are reminded to operate the aircraft within its design limitations.



///

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

tigerrick(at)mindspring.c
Guest

Posted: Sat Apr 25, 2009 9:23 am Post subject: New Zenith Statement

Hi, Gig. Kinda confirms what's been stated all along, doesn't it?



(sigh)



Rick Lindstrom

Zenvair N42KP



--

craig(at)craigandjean.com
Guest

Posted: Sat Apr 25, 2009 10:08 am Post subject: New Zenith Statement

Here is what I see in my crystal ball: Zenith and other organizations will carefully analyze the XL and find no design flaws. But we will be left with the fact that (as a percentage of the flying fleet) XL's crash more often for unknown reasons than comparable aircraft. It is the distance between those two realities that gives everyone pause.



-- Craig



--

tigerrick(at)mindspring.c
Guest

Posted: Sat Apr 25, 2009 1:24 pm Post subject: New Zenith Statement

Hi, Craig.



Since my crystal ball is in the shop, here's what I'm waiting for...



How many of the crashed aircraft had loose or slack aileron cables?

How many of the crashed aircraft had loose or improper wing attachments?

How many of the crashed aircraft were overstressed from intentional or unintentional control inputs?

How many of the crashed aircraft were built or maintained outside of design specification?



Once I have that number, and subtract it from 6, I'll have a much better idea if the risk of flying my airplane is excessive, or not.



Rick Lindstrom

Zenvair N42KP

--

craig(at)craigandjean.com
Guest

Posted: Sat Apr 25, 2009 1:48 pm Post subject: New Zenith Statement

But why should the items on your list be different for the XL when compared to other aircraft types? Do you disagree that the XL has had a disproportionate number of unexplained crashes when compared to other types? 



-- Craig



--

tigerrick(at)mindspring.c
Guest

Posted: Sat Apr 25, 2009 2:19 pm Post subject: New Zenith Statement

Hi, Craig.



Yes, I do disagree that the crash numbers are disproportionate when compared to other kits.



The 601XL is an extremely easy to build kit, demanding little skill, and perfect for first time  builders. (Like me.) It's inexpensive to acquire, and very easy to fly.



However, it does have a very effective elevator, it is NOT stressed beyond the standard category, and it WILL easily go faster than it was originally designed to do.



These things are not detriments, unless abused. Which, given the date we've seen, is likely for at least some of the crashes.



RVs, by comparison, generally require more skill to build, and attract a different kind of pilot. I'm not saying that Zenith pilots are less skilled, just that the airplanes are more "entry level". Of course, there are a whole bunch of Zenith pilots who have zillions of hours and aeronautical experience, but still love the airplane's simplicity and flight characteristics. And I know that several of crashes involved pilots with oodles of experience, which makes me suspect maintenance or turbulence issues in these cases.



But this is all just speculation without hard data. That's why I won't simply say "It crashes more than others do" without bona fide evidence.



Just my opinion.



Rick Lindstrom

N42KP



--

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sat Apr 25, 2009 3:01 pm Post subject: Re: New Zenith Statement

 	  Gig Giacona wrote: 	
		  April 22, 2009



 These preliminary findings confirm that the aircraft, with properly tensioned control cables, is not prone to flutter.  



	




Who wants to fly an airplane that is going to come apart in mid air as soon as the aileron cables are not perfectly tensioned.  Cables become loose, if an airplane design is so bad that it requires perfection to fly safely, then the design should be fixed.



Obviously, having perfectly tensioned cables all the time is unrealistic in the real world of airplanes, as evidenced by a lot of recent crashes.   I know many will talk a big talk to defend a company they bought an airplane from, but I wonder how many here would send up their Kids, or their wife in a Zodiac CH-601XL airplane today ???



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

craig(at)craigandjean.com
Guest

Posted: Sat Apr 25, 2009 3:03 pm Post subject: New Zenith Statement

If you want to restrict the comparison to low-wing, all metal LSA then what about Sonex, the 601HD or HDS? If we can throw in high-wing rag-and-tube then there is Kitfox, Rans, etc. Or the 701, Flight Design CTSW and CTLS, etc.



The point of my original post is that I doubt that the current investigation will turn up a smoking gun. Which means that we will be back to where we were before ZBAG and the NTSB indicted flutter.



It is the nature of accident investigations that we are not going to get hard answers to the specific questions on your list. But if the mix of pilots building and flying XLs is similar to those flying other LSA then significant differences in the accident rates point to the aircraft. It may be that adding the stops to restrict elevator travel will make planes with that change safer. But this is an experiment that will take a long time to yield results.



-- Craig



--

craig(at)craigandjean.com
Guest

Posted: Sat Apr 25, 2009 3:18 pm Post subject: New Zenith Statement

 	  Quote: 	
		   I  wonder how many here would send up their Kids, or their wife in a

Zodiac CH-601XL airplane today ???
	




Well, Chris Heintz for one.



-- Craig

--

bootless(at)earthlink.net
Guest

Posted: Sat Apr 25, 2009 3:24 pm Post subject: New Zenith Statement

Mike,

 

 Who would send up their kids (or their wife) in a Zodiac CH-601XL, you ask? Well, Chris Heinz does. 

 

 And if that's not sufficient, I find it hard to believe that all but a truly suicidal pilot would climb into an airplane without ensuring that it's properly maintained and in airworthy condition.

 

 And you ask, "Who wants to fly an airplane that is going to come apart in mid air as soon as the aileron cables are not perfectly tensioned. Cables become loose, if an airplane design is so bad that it requires perfection to fly safely, then the design should be fixed." 

 

 Sounds like a straw man argument to me. Any airplane you fly requires rigorous preflight inspection and proper (and regular) maintenance. There's a difference between perfection and appropriate maintenance, and I believe you know that.

 

 Cory

 [quote]    	  Quote: 	
		  

Obviously, having perfectly tensioned cables is not always going to happen, as evidenced by a lot of recent crashes.   I know many will talk a big talk to defend a company they bought an airplane from, but I wonder how many here would send uptheirr Kids, or their wife in a Zodiac CH-601XL airplane today ???



Mike



--------

&quot;NO FEAR&quot; -  If you have no fear you did not go as fast as you could have !!!



Kolb MK-III Xtra, 912-S





Read this topic online here:



[url=http://forums.matronics.com/viewtopic.php?p 41252#241252]http://forums.matronics.com/viewtopic.php?p 41252#241252[/url]



  	
 [b]

tigerrick(at)mindspring.c
Guest

Posted: Sat Apr 25, 2009 3:40 pm Post subject: New Zenith Statement

Mike:



You've made two statements that you might want to consider retracting:



 	  Quote: 	
		  Who wants to fly an airplane that is going to come apart in mid air as soon as the aileron cables are not perfectly tensioned.  Cables become loose, if an airplane design is so bad that it requires perfection to fly safely, then the design should be fixed.<


	


Are you speaking of the 601XL? Seems to me that they fly just fine, even with cable tensions well under specification. My own airplane flew with no flutter, at speeds as high as 125 IAS with a 12 pound aileron cable tension. But I did acquire a tensiometer, confirmed the calibration, and raised the tension to 20 pounds when Zenith issued the bulletin. Your statement of "come apart in mid air...not perfectly tensioned" is incendiary and inappropriate.



 	  Quote: 	
		  Obviously, having perfectly tensioned cables is not always going to happen, as evidenced by a lot of recent crashes.   I know many will talk a big talk to defend a company they bought an airplane from, but I wonder how many here would send uptheirr Kids, or their wife in a Zodiac CH-601XL airplane today ???<


	


A LOT of recent crashes? ALL due to imperfect cable tensions? A couple in the last two years, maybe, from pretty slack aileron cables. Do you KNOW something that the rest of us don't, or are you just throwing gasoline on the fire? Again?



Sheesh.



Rick

tigerrick(at)mindspring.c
Guest

Posted: Sat Apr 25, 2009 3:48 pm Post subject: New Zenith Statement

Well, I installed the elevator stops on my plane after raising the aileron cable tension. I have no desire to exceed 4 negative Gs under any condition, including having a pax accidentally whack the stick forward while in cruise.



I have no idea exactly what the forensic analysis, should there be one, of the 601 crashes will turn up. And you may well be right, that we'll be right back where we started in some regards.



So I'll find it interesting if there will be any more wing failure related crashes of 601 that are flown within design limits, have proper maintenance, and have limited down elevator.



And I intend to keep logging hours until the jury comes back in.



Rick



--

jmaynard

Joined: 27 Feb 2008
Posts: 394
Location: Fairmont, MN (FRM)

Posted: Sat Apr 25, 2009 4:32 pm Post subject: New Zenith Statement

On Sat, Apr 25, 2009 at 04:01:13PM -0700, JetPilot wrote:

 	  Quote: 	
		   Who wants to fly an airplane that is going to come apart in mid air as

 soon as the aileron cables are not perfectly tensioned.  Cables become

 loose, if an airplane design is so bad that it requires perfection to fly

 safely, then the design should be fixed.


	


This is significantly overstating the case. Lots of Zodiacs have flown lots

of hours with cables looser than spec. Mine did. It doesn't any more.



It's pretty obvious to most folks who actually bother to think about the

situation that it takes much more than just loose aileron cables to cause a

problem.



 	  Quote: 	
		   Obviously, having perfectly tensioned cables is not always going to

 happen, as evidenced by a lot of recent crashes.  I know many will talk a

 big talk to defend a company they bought an airplane from, but I wonder

 how many here would send uptheirr Kids, or their wife in a Zodiac CH-601XL

 airplane today ???


	


I would take anyone up in mine, in a heartbeat, without restriction or

reservation.

-- 

Jay Maynard, K5ZC, PP-ASEL, AGI      http://www.conmicro.com

http://jmaynard.livejournal.com       http://www.tronguy.net

Fairmont, MN (KFRM)                        (Yes, that's me!)

AMD Zodiac CH601XLi N55ZC http://www.tronguy.net/N55ZC.shtml

_________________
Jay Maynard, K5ZC
AMD Zodiac XLi N55ZC

rsteele(at)rjsit.com
Guest

Posted: Sat Apr 25, 2009 5:17 pm Post subject: New Zenith Statement

What the ground vibration testing actually found, according to  

statements made in Avweb Interview, was that while flutter could occur  

with loose cables, it was recoverable and not a threat to the  

airframe.  This seems to be in direct conflict with your statement  

below.  Of course it's impossible to completely model what happens in  

the air while on the ground, it sure looks like you are overstating  

things, by a lot.





On Apr 25, 2009, at 7:01 PM, JetPilot wrote:



 	  Quote: 	
		   --> Who wants to fly an airplane that is going to come apart in mid  

 air as soon as the aileron cables are not perfectly tensioned.   

 Cables become loose, if an airplane design is so bad that it  

 requires perfection to fly safely, then the design should be fixed.

 Mike



 --------

 &quot;NO FEAR&quot; -  If you have no fear you did not go as fast as  

 you could have !!!



 Kolb MK-III Xtra, 912-S

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Mon Apr 27, 2009 6:00 am Post subject: Re: New Zenith Statement

The best theory so far is flutter, and yes its just a theory at this point.   Bottom line is these accidents are HAPPENING the accidents are not theory they are reality.  It wont matter what the cause is if you are in the airplane that breaks up in flight.  How many of those dead guys do you think will say, its OK, because it might not have been flutter, or its OK, because Zenith Air released a statement...



No matter how you sugar coat it, or try to reason it away, for whatever reason Zodiac CH-601XL are having a large number of structural failures, and coming apart in flight.  This is not acceptable for any design.



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

tonyplane(at)bellsouth.ne
Guest

Posted: Mon Apr 27, 2009 6:18 am Post subject: New Zenith Statement

In my "opinion" FWIW, the "best theory" is improper stick input for the 

flight condition, causing excessive g loading.  If the wings and horiz stab 

are well designed, it is a toss up as to which fails first in overload, 

assuming speed above Va.



Tony Graziano

XL/Jab; N493TG; 487 hrs

---

tigerrick(at)mindspring.c
Guest

Posted: Mon Apr 27, 2009 6:43 am Post subject: New Zenith Statement

Excuse me, Mike, but I have to ask.



Do you have ANY personal experience with this design, or the airplane itself?



You've posted some really outrageous statements, such as saying the airplane will disintegrate in mid-air if your cable tensions aren't perfect. Based on what evidence?



And now you're painting a picture that these crashes are endemic ("Bottom line is these accidents are HAPPENING, if wont matter what the cause is if you are in the airplane that breaks up in flight.") in spite of hard data to contrary. There have been six crashes over two years, with 10 fatalities, with a small variety of contributing factors suspected so far. You ignore the tens of thousands of successful flight hours racked up by the XL in its history, that debunk your claim of "...having a large number of structural failures, and coming apart in flight."



And now you're insinuating that we don't care about "the dead guys." What nerve. Those of us who have built and fly the 601 are a family, after all, and we do care about each other. And like most families, we aren't shy about disagreements. How dare you insult the group like this? Are you one us, or just someone wading into the discussion from the outside just to stir up some crap?



What exactly are your motives here?



Rick



--

jmaynard

Joined: 27 Feb 2008
Posts: 394
Location: Fairmont, MN (FRM)

Posted: Mon Apr 27, 2009 6:43 am Post subject: New Zenith Statement

On Mon, Apr 27, 2009 at 09:17:58AM -0500, T. Graziano wrote:

 	  Quote: 	
		   In my "opinion" FWIW, the "best theory" is improper stick input for the 

 flight condition, causing excessive g loading.  If the wings and horiz stab 

 are well designed, it is a toss up as to which fails first in overload, 

 assuming speed above Va.


	


I don't buy this explanation, at least in the case of N158MD. An

experienced, 79-year-old pilot with several owned airplanes and many hours

of flight under his belt, taking his wife for her first flight in their new

airplane, is not going to make the kinds of control inputs that would tear

the wings off from straight and level flight. Something else happened first.



I don't know where Mathieu Heintz got his statement in the AVweb podcast

citing a -7G (-8G? Something like that) force as the start of the accident

sequence, but the NTSB didn't say that in their report.

-- 

Jay Maynard, K5ZC, PP-ASEL, AGI      http://www.conmicro.com

http://jmaynard.livejournal.com       http://www.tronguy.net

Fairmont, MN (KFRM)                        (Yes, that's me!)

AMD Zodiac CH601XLi N55ZC http://www.tronguy.net/N55ZC.shtml

_________________
Jay Maynard, K5ZC
AMD Zodiac XLi N55ZC

tigerrick(at)mindspring.c
Guest

Posted: Mon Apr 27, 2009 7:05 am Post subject: New Zenith Statement

Sudden incapacitation comes to mind.



Rick



--

Gig Giacona

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

Posted: Mon Apr 27, 2009 7:16 am Post subject: Re: New Zenith Statement

 	  tigerrick(at)mindspring.c wrote: 	
		  Sudden incapacitation comes to mind.



Rick



-- 	




That's the first thing that came to mind for me as well. There is also the chance of all sorts of other accidental control inputs.

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

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