I received these from the chief scientist at the NTSB responsible for investigating recent 601XL crashes and flutter incidents.

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more bull, fi chicken little claims long enough and loud enough, it may really fall. Un subscribe me from yet another list of chicken littles.
The NTSB is not known for crying wolf. There's something there. Whether Zenair's recommendation to deal with the problem with aileron cable tension is adequate is open to debate, and it doesn't look like the FAA is going to ground the fleet immediately. Still, too many experts have said there's a problem there to ignore it.
Get a grip Art.... Jay, Dave X and Doug are right on the money. Let's take a scientific approach to this problem and not start pointing fingers at other pilots, you think are "Chicken Littles".
Art, if you have something specific issues/concerns, by all means bring it to the attention of the investigating scientist (contact details below). He has been very responsive to all my questions and concerns. He has also told me that he has seen a partially assembled 601XL and he liked the aircraft a lot ... that it was something he'd enjoy flying. That hardly seems like a "chicken little" to me. I think you should take the report seriously.

clarkj@ntsb.gov
John Clark
Chief Scientist
Office of Aviation Safety
National Transportation Safety Board
490 L'enfant Plaza SW
Washington, DC 20594
Cell 202-257-0121
Office 202-314-6300
www.ntsb.gov
I have read both of the letters. As a lawyer and law professor I see some flaws in the quality of the evidence and the connections (reasoning) from proposition to conclusions. Also, there are several Zodiac XL's out there with over 400 hours of flying and no flutter, or signs of problems. HOWEVER, the primary issue is safety for an inherently dangerous activity, and I agree that the issue must be addressed and solved. The factory has responsibility here as the design originated there. If mass balancing, or rods to replace cables, are practical and effective solutions, I would like to see the factory start working on a proper study and develop a retro-kit to do this. This should reduce the risk immediately. In the mean time, pilots need to get a tensionometer and get those cables to spec. It will be worth the 300 bucks to save a life. It only takes about 15 minutes to check the cables during the preflight inspection. Also, stay within the performance envelope and slow down to appropriate speeds for the flying conditions.
I also would like to see a factory retro-fit of a push rod solution to this potential problem. The cost of turnbuckles etc. actually would cost more than rod ends and bell crank bearings, and be a lot simpler to fabricate and maintain.
Ater having read the recommendation Letter, I am now more convinced than ever that installing aileron pushrods in my CH601XL was the correct thing to do. Installing pushrods is very easy as an aftermarket item. I believe that it can be safely done without removing the wings. The hardest item to complete the installation is the hole thru the fuselage allowing the pushrod access to the aileron bellcrank out on the wing. everything else is straight forward. Personally, i would recommend aileron pushrods be installed in all CH601XLs. I am now looking at pushrods for the elevator to do at my next 'Condition Inspection' in June. Rudder cables will stay. Let us see what Zenith has to say about al of this. i hope they respond in a timely fashion.
One thing that caught my eye on the NTSB investigation was the eyewitness accounts of actually seeing / hearing wing vibration. How's that possible?? I am not doubting that there's a flutter problem, but I've never heard anyone say anything about a wing vibration as witnessed from the ground. You ever stand outside and say to someone.. "see that wing vibrate?" David, as far as Zenith responding in a timely fashion, they've come out with their standard form letter, on their website, stating "We continue to believe wing flutter will not occur if the control cables are adjusted properly. Nonetheless, we are carefully considering the points raised in the memo, including whether the Zodiac CH-601XL is susceptible to wing flutter. Each accident discussed in the NTSB memo occurred under different circumstances". The thing is, I trust Zenith, and I trust the NTSB. It might take a fleet grounding to get this resolved. I hope not, but safety first.
David

Please describe the materials you used for your aileron push rod system and the approximate cost. I think all would be surprise at how simple and inexpensive the refit would be. A list of materials and photos would be much appreciated.
Hi Dave, Great looking plane (dvd #171) I really think that push rods are the answer-like the Mooney I had. My first wing is ready to rivit top skin- bottom skin is rivited. To install push rods-must I do it before riviting or can it be done later? Did you use supplied aileron bell crank? What guides did you use? Would appreciate all info you can give me.

Thanks, Frederick Schutt

David I have been looking for pushrods installations instead of cables.

 

Could you guide me to a site where this info could be obtained?

 

Please answer to my email address.

 

Thanks in advance for your help;

 

 

 

 

 

Alfonso Lebron-Berges

 

alebron@bellsouth.net

 

ZODIAC 601-XL

 

Rudder, elevator and flaps completed.

 

.

 

I just bought a used 601 XL and must say I feel like the stupidest person on the planet. I knew about the issues with the plane from my research but believed the cable tensioning was the fix. The plane has 346 hours and has been flow by multiple pilots without incident. The cables were inspected and tightened before purchase.

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