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Spreading fear about the XL
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jmaynard

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

Posted: Mon Nov 24, 2008 4:04 pm Post subject: Spreading fear about the XL

On Mon, Nov 24, 2008 at 09:46:48AM -0800, Rick Lindstrom wrote:

 	  Quote: 	
		   Unless we need to stress the airframe for aerobatics, or are given to

 rapid control inputs, or plan on significantly higher cruise airspeeds

 beyond what the airframe was designed for, I think we can have some level

 of confidence in the design as it is when flown and maintained as

 specified by Zenith.


	


This is pretty much my take on the matter, as well...though the one

AMD-built aircraft does give me pause. Until we find a smoking gun, I'm

going to be vigilant about maintaining my airplane to all manufacturer's

specifications and making sure never to subject it to maneuvers or speeds

that have any risk of departing the recommended and designed flight

envelope.



 	  Quote: 	
		   Overall, I think these kinds of discussion are generally positive, as long

 as we don't succumb to wild speculation and give in to the temptation to

 "fix" something that may not even be a factor. Like everyone else, I look

 forward to the day when we can positively identify the smoking gun (if

 there even is one).


	


I'm confident one will be found, if not as quickly as we would like. I'm not

going to let it get in the way of me enjoying my airplane.

-- 

Jay Maynard, K5ZC, PP-ASEL           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

JAPhillipsGA(at)aol.com
Guest

Posted: Mon Nov 24, 2008 4:46 pm Post subject: Spreading fear about the XL

The incident happened at 103 hours, but prior to the first annual. Before the first flight, as a courtesy, the AMD fellows flew up from Eastman, inspected the plane, tested the cables, W&B, control travel, etc., and looked over the whole thing for a couple hours. Proclaimed it was safe and the AMD test pilot, John Begonias (sp) flew it first. I expect the cables were correct before he flew because I saw them test them. I did not test them between first flight and the incident simply because I did not know I should. After the incident I inspected every rivet, bolt and joint and tightened the cables, but I did not have a tensionometer and in fact I don't remember if I knew then what the correct setting should have been. When I checked the tension last week after reading the AMD letter and buying a tenisonometer the aileron cables were at 17 pounds. They are set correctly now. Best regards, Bill

**************

One site has it all. Your email accounts, your social networks, and the thingid=aolcom40vanity%26ncid=emlcntaolcom00000001)  [quote][b]

hills(at)sunflower.com
Guest

Posted: Mon Nov 24, 2008 5:56 pm Post subject: Spreading fear about the XL

Howdy all;



Gee, it looks like I took a smoke in a fireworks factory!!!



I too am an engineer, but just not an aircraft engineer, still I do know a

thing or two about harmonic oscillations, almost enough to be dangerous!!! I

also studied flight control designs in grad school, but never put it to good

use.



I should clear up a couple of thing, my 601 HDS does have push rods to the

ailerons, so the design does differ from the newer 601XL.  I note this

because apparently the older models have not had any flutter issues, well

none that I know about anyway.



Also, my A&Ps father died flying his Michel flying wing, something he built

25 years earlier.  This plane was registered experimental, and had a wood

structure. Over the years, fuel leaked from the tanks and weakened the glue

holding the wing D-box structure together.  This caused it to fail at 200

feet AGL, right in the pattern at the airport. Worse, it was right in front

of his buddies. Of course, we don't have to worry about this with our

planes, one less worry.  Inspecting the D-box was out of the question

without special tools, this section was covered by fabric and ply wood.



I once had my aileron push rod detach on my RC plane, if that matters. It

buzzed in the wind, but perhaps because of the low cruise speed of the

aircraft, it had no other detrimental effects other than to add drag to one

wing. I think the airspeed, oscillation frequency and magnitude of the

oscillations when the flutter occurs has a direct relationship to the damage

potential to the wing. Some flutter at low speeds seem to be completely

tolerable as in my experience, but I suspect that as airspeeds increase, so

does the damage potential if flutter does occur.



Roger





--

tigerrick(at)mindspring.c
Guest

Posted: Mon Nov 24, 2008 6:58 pm Post subject: Spreading fear about the XL

Hi, Roger.



I don't think anyone here thinks you're "smoking in a fireworks factory", it's just that all the conjecture and speculation on this issue has created a rather large sore spot among those of us who own and fly the 601XL. There have been a ton of posts with headers like "601 Wing Failure" and "Another Zenith 601 Crash" that have only served to fan the flames of fear of the design and impugn the company behind it. So far, the efforts of the NTSB, Zenith Aircraft, and even the ZBAG group have turned up little in terms of a common causal factor in these crashes. The only thing that we all share is frustration, those who have lost loved ones are understandably angry that such a thing could happen, and those of us who continue to fly the 601 series want to have confidence that there will be no more human tragedies.



I'm fortunate not to have encountered flutter personally in my 4,500+ PIC hours so far, but I've recently seen in-flight video of elevator flutter in action on a Piper that scared the hell out of me. I didn't know a tail structure could take that sort of abuse and still hold together. And I think of that video every time I go flying.



Fortunately, there are many factors that we can control - cable tensions, rigging, airspeeds, and ongoing airframe integrity. This doesn't replace knowing the exact cause of the wing fold crashes, but it does give me enough peace of mind to not live in fear and continue to enjoy the airplane.



Rick



--

mcjon77

Joined: 17 May 2008
Posts: 55
Location: Chicago

Posted: Tue Nov 25, 2008 12:18 am Post subject: Re: Spreading fear about the XL

 	  hills(at)sunflower.com wrote: 	
		  ..I should clear up a couple of thing, my 601 HDS does have push rods to the

ailerons, so the design does differ from the newer 601XL.  I note this

because apparently the older models have not had any flutter issues, well

none that I know about anyway.

-- 	




Just so I can get some clarification, was the switch from pushrods to cables something that happened with the introduction of the XL model?  Did both the 601 HDS and 601 HD have pushrods instead?

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Tue Nov 25, 2008 5:20 am Post subject: Re: Spreading fear about the XL

Just to correct what someone said in an earlier post; the CH640 uses cables, not pushrods on all controls. The 640 rudder and stabilator are balanced, the ailerons are not.

leo(at)zuehlfield.com
Guest

Posted: Tue Nov 25, 2008 7:16 am Post subject: Spreading fear about the XL

My 601HDS has cables, built to 2001 plans.

-- 

Leo Gates

N601Z - CH601HDS TDO

Rotax 912UL

mcjon77 wrote:

 	  Quote: 	

 hills(at)sunflower.com wrote:

> ..I should clear up a couple of thing, my 601 HDS does have push rods to the

> ailerons, so the design does differ from the newer 601XL.  I note this

> because apparently the older models have not had any flutter issues, well

> none that I know about anyway.

> --

>     

 Just so I can get some clarification, was the switch from pushrods to cables something that happened with the introduction of the XL model?  Did both the 601 HDS and 601 HD have pushrods instead?

ideaz1(at)sbcglobal.net
Guest

Posted: Tue Nov 25, 2008 7:20 am Post subject: Spreading fear about the XL

OOPs,

I misread the following from the 640 aileron control description. "They are 

connected to push/pull rods which are connected to a simple bellcrank in the 

wing." I failed to read the last half "Control cables are connected between 

the bellcrank and the fuselage torque tube"



Dirk Z

---

Gig Giacona

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

Posted: Tue Nov 25, 2008 12:02 pm Post subject: Re: Spreading fear about the XL

Bill your quote below concerns me. I've been doing quite a bit of research on this in several places and can't find for the life of me any place what shows that cables such as the ones we use should be able to stretch this much.



Are you certain that there isn't something bent in that wing?

 	  JAPhillipsGA(at)aol.com wrote: 	
		  [SNIP] When I checked the tension last week after reading the AMD letter and buying a tenisonometer the aileron cables were at 17 pounds. They are set correctly now. Best regards, Bill

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

Gig Giacona

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

Posted: Tue Nov 25, 2008 12:29 pm Post subject: Re: Spreading fear about the XL

Roger,



Did you build your HDS or purchase it? I ask because I'm pretty sure the cables were always used on all versions of the 601. Though push rods have been added by some builders.

 	  hills(at)sunflower.com wrote: 	
		  

I should clear up a couple of thing, my 601 HDS does have push rods to the

ailerons, so the design does differ from the newer 601XL.  I note this

because apparently the older models have not had any flutter issues, well

none that I know about anyway.

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

wjones(at)brazoriainet.co
Guest

Posted: Tue Nov 25, 2008 1:07 pm Post subject: Spreading fear about the XL

I think you are correct Gig , IMHO it would take much more pressure than we 

are capable of using our hands only to  stretch these 1/8" 2000# cables . 

Tony Bingelis (one of my heroes) also shares the theory that cables do not 

stretch , in our planes the fairleads can become worn and may need to be 

tensioned from time to time .

Wade  Jones  South Texas

601XL Franklin 0-235

---

amyvega2005(at)earthlink.
Guest

Posted: Tue Nov 25, 2008 1:53 pm Post subject: Spreading fear about the XL

Gig, cables do stretch all the time, then they set.  quite trying to extrapolate some solution,  just check them, i do it on piper cubs, on cessnas, and keep in mind maunuvering speed is differnt than Max cruise relative to gross weight.



--

japhillipsga(at)aol.com
Guest

Posted: Tue Nov 25, 2008 1:54 pm Post subject: Spreading fear about the XL

Gig, the great probability is that other than when first set by the AMD guy they never have been correct or even anywhere near correct. I had a landing 2 years ago next March in a 20 knot + crosswind landing that ballooned up even with full aileron pitch down on the wing and to save it I fought the stick and bumped the throttle and got it down. I know I stretched the cables then because I also bent some stuff I had to replace. When I reattached the cables and reset the tension, but it was without a meter. If you set the cables you will find that about one turn of the turnbuckle is 10-15 pounds and I don't believe anybody can tell much difference between 20 and 30 pounds by touch. Best regards, Bill. 

 

 

 --

hills(at)sunflower.com
Guest

Posted: Tue Nov 25, 2008 4:53 pm Post subject: Spreading fear about the XL

Howdy all;



I bought my 601HDS from the original builder, then changed the engine to a

100 HP water cooled head VW engine. Looking at the wing bell crank, it does

indeed have a single push rod. The bell crank has a place for cables to

attached, but no cables.Hummm,,,

Works good though, I also have hinged alerions and turning them down a bit

gives me a stall speed of 50mph.



Roger



--

paulrod36(at)msn.com
Guest

Posted: Wed Nov 26, 2008 3:50 pm Post subject: Spreading fear about the XL

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  At our last meeting of EAA Chapter 91, we had an aerodynamics instructor  from Missouri Central University (the old CMSU) who gave a presentation on  "Seven Ways an Aircraft Can Contact The Ground" (long story there), and who  discussed flutter. There being more than a few 601'ers there, he had a very  attentive audience. After the meeting I asked him THE  question.One of the things he said was possibly to do like Cessna  does, and rig the ailerons with 2-3 degrees down at neutral stick. He said that  each aileron would be in tension against the other, causing a constant load on  each control surface. He said you give up a little airspeed, but you reduce the  possibility of flutter. I also asked him about putting weights on the aileron  pushrods inside the wing, and, after thinking about it, he felt it was worth  trying, but cautioned me to check a metals nobility chart first to assure I  wasn't trading one benefit for a risk, that of corrosion. Now that I think  of it, I do recall that my 172's ailerons didn't match the wingtips.

  

 Paul Rodriguez

 501XL/Corvair

 [quote]   ---

jeffrey_davidson(at)earth
Guest

Posted: Thu Nov 27, 2008 1:05 am Post subject: Spreading fear about the XL

Clyde wrote:  

   

"That is all it is, a guess, some of us want to know as much as   

possible to avoid mistakes and to build a good solid plane. I think there has been   

some good conversation on the subject of properly tensioning control cables   

to avoid the "possibility" of flutter. I agree with building it to plans   

and flying within the design limitations but coming to the conclusion that   

all of them augured because of exceeding VNE and maneuvering speeds is a   

little over the top. From Bill's account, he experienced flutter, and he   

wasn't busting any design limits and later found his cables were not   

tensioned to spec. This is great information and something we can all learn from,   

in my opinion, that is exactly what this list is for, knowledge. I know I   

will buy the tool to check tension and it will be part of my frequent check   

list until I determine there is no need to check it quite as frequently."  

   

My real purpose for this post and the resulting thread was to try to prompt an authority we builders could depend on to make a statement identifying the problem we are experiencing, if a single one actually exists.  So far, there has been no response, including from the NTSB whom I know is monitoring this list for now.  I guess they are just shy guys and girls afraid to talk out loud, but their silence creates an environment that encourages whisper campaigns.  On a practical level as aircraft manufacturers and owners, and since we are without any other input, Clyde has given us a pretty good summary for this thread.  So our attention to cable tension has been re-established.   As has been said a couple times, let's move on, but only after checking our cables.  At least we will make the tool makers happy!  

   

Jeff Davidson  

   

   

       [quote][b]

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