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upgrade decisions

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z601a(at)anemicaardvark.c
Guest

Posted: Thu Nov 12, 2009 12:03 pm Post subject: upgrade decisions

I haven't had a lot of free time the last few days, but what time I have had, 

I've spent trying to decide which of these modifications are useful, and 

which are not. Do I really want to do any of them, all of them, or some of 

them? Somehow, I needed to get my ideas down, and think through my decisions.



To this end, I have created a decision tree in Open Office calc. I'm trying to 

trade off possible risks against benefits. What is worth doing? Anything? 

Everything? Nothing? My mind is by no means made up on things, but in the 

interest of exchanging ideas, I have posted the tree here for downloading:



http://www.anemicaardvark.com/Z601XL/XLUpgrade.xls



(this site is case sensitive)



Please understand that the entries reflect my thoughts at the moment. I may 

very well change some of them before I do anything. 



I am not suggesting that you necessarily agree with my assessments, but 

rather, that it may be useful to evaluate how you feel about things on your 

own aircraft, using this as a starting point. By all means, if you wish to 

use this as a starting point, adjust things to reflect what you think about 

your aircraft.

-- 

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

                Do not archive.

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

                Jim B Belcher

    BS, MS Physics, Math, Computer Science

                  A&P/IA

     Retired aerospace technical manager



     Mathematics and alcohol do not mix.

         Do not drink and derive.

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

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craig(at)craigandjean.com
Guest

Posted: Thu Nov 12, 2009 12:21 pm Post subject: upgrade decisions

A list of reasonable assessments but we still have to deal with the big picture. Our ability to pick and choose the various changes is compromised by some external factors:



- the latest ZAC load test was against an aircraft with all the spar mods. We would have to guess which mods made the plane stronger in those tests and which didn't.



- insurance: I believe that when the dust settles the insurance companies will have one question: have you done the mod *package* or not - the WHOLE package.



-- Craig



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z601a(at)anemicaardvark.c
Guest

Posted: Thu Nov 12, 2009 12:39 pm Post subject: upgrade decisions

It sounds like your defacto decision is to do all the mods. Obviously, what I 

am suggesting is that some of us may not choose to do this. 



Other reasons for doing everything would be in the hope it satisifies the FAA, 

or that it makes the builder more comfortable. But to each his/her own: 

that's the beauty of an experimental aircraft!



On Thursday 12 November 2009 14:20, Craig Payne wrote:

 	  Quote: 	
		   



 A list of reasonable assessments but we still have to deal with the big

 picture. Our ability to pick and choose the various changes is compromised

 by some external factors:



 - the latest ZAC load test was against an aircraft with all the spar mods.

 We would have to guess which mods made the plane stronger in those tests

 and which didn't.



 - insurance: I believe that when the dust settles the insurance companies

 will have one question: have you done the mod *package* or not - the WHOLE

 package.


	


-- 

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

                Do not archive.

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

                Jim B Belcher

    BS, MS Physics, Math, Computer Science

                  A&P/IA

     Retired aerospace technical manager



     Mathematics and alcohol do not mix.

         Do not drink and derive.

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

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jaybannist(at)cs.com
Guest

Posted: Thu Nov 12, 2009 12:42 pm Post subject: upgrade decisions

Jim,

 

 While I agree with Chris that these mods are not really necessary, we now have them on the table.  That makes them more or less mandatory, not necessarily from an engineering standpoint, but certainly from a regulatory, insurance and liability standpoint.

  

 The original airframe was designed as a whole.  You wouldn't have considered leaving out some of the rivets, because they somehow looked redundant, would you ?  These mods have also been designed as a whole.  I personally would not try to second guess the designer nor the reason for each separate part of the mods.  I would instead guess that they are all a part of a structural system, not individual "area" upgrades, assignable to a particular questionable area.  

 

 Just my quarters worth (formerly two  cents).

 

 Jay Bannister. 

 

   

 

   

 

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z601a(at)anemicaardvark.c
Guest

Posted: Thu Nov 12, 2009 12:59 pm Post subject: upgrade decisions

On Thursday 12 November 2009 14:41, jaybannist(at)cs.com wrote:

 	  Quote: 	
		    Jim,



 While I agree with Chris that these mods are not really necessary, we now

 have them on the table.  That makes them more or less mandatory, not

 necessarily from an engineering standpoint, but certainly from a

 regulatory, insurance and liability standpoint.



 The original airframe was designed as a whole.  You wouldn't have

 considered leaving out some of the rivets, because they somehow looked

 redundant, would you ?  These mods have also been designed as a whole.  I

 personally would not try to second guess the designer nor the reason for

 each separate part of the mods.  I would instead guess that they are all a

 part of a structural system, not individual "area" upgrades, assignable to

 a particular questionable area.


	


I think some of them are, and some of them aren't. I doubt the mass balance in 

the ailerons, for example, has anything to do with the stiffners under the 

seat. 



The beefed up rear spar attach has not much to do with anything, according to 

Zenith. I communicated with them on this subject several weeks, and was 

assured the forces on this are minimal. That matches what I know from the 

design of the rear spar attach on other aircraft.



..and so on. Once again, this is an experimental aircraft. I'm not saying I 

will leave any of these out, just that I consider the whole thing open for 

individual decision. I'm still deciding.

-- 

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

                Do not archive.

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

                Jim B Belcher

    BS, MS Physics, Math, Computer Science

                  A&P/IA

     Retired aerospace technical manager



     Mathematics and alcohol do not mix.

         Do not drink and derive.

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

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tigerrick(at)mindspring.c
Guest

Posted: Thu Nov 12, 2009 2:27 pm Post subject: Upgrade Decisions

I was thinking along the very same lines, Jim, until I had a long conversation with Mathieu Heintz at Zenair this morning. Frankly, I didn't see the need to add aileron counterweights either, as long as the rest of the mods were installed. But Mathieu says he's really tired of visiting crash sites with the NTSB (he's been to all in North America), and sees the whole package as just increasing the 601 safety margins as much as possible. Who can argue with that?



He strongly feels that overloading the airframe is what has caused the majority of these in-flight breakups, and it's not that hard to do with high airspeeds, partial fuel, a single occupant, an aft CG, especially when compounded by neglected maintenance or an inadequate preflight inspection. Once the wing has been overstressed and possibly deformed, it's very likely that the aileron cables could go slack, setting up an airframe harmonic vibration or flutter that quickly destroys the wing.



We talked about what happens when some really big guy gets in, sharply moves the stick to the side and accidently overstresses the aileron control system and slackens the cables (it only takes 40 pounds of pressure). Or when the airplane is tied down and encounters sharp gusts on its control surfaces, which can also wreck the bellcrank system if left to flap around in the wind. (I recall seeing some dramatic pictures of 601 gust damage online not too long ago.)



My 601XL has always lived in a hangar, I'm the only who flies it (in good weather and gently), and I'm pretty anal when it comes to maintenance. So I could probably fly the airplane without any modifications until the cows came home without any problem. But you can't always forecast severe vertical gusts or just plain passenger stupidity, so you have to design with these things in mind. Mathieu also shared that Chris was aghast at how some of the 601s were being flown, modified, or neglected, and we openly wondered if our society had been dumbed down to the point of eliminating our ability to properly assess personal risk.



But that's a whole different discussion, and the best solution set that Zenith has developed over the last year addresses every possible way the airplane could come apart in the air, and is included in the upgrade package. In the mean time, they recommended flying slower and with less weight to be on the safe side. Admittedly, beefing up the airframe AND installing aileron mass balance is a real "belt and suspenders" approach to eliminating any possible flutter scenario, but it could happen where a chain of events result in totally slack cables. So they're including it. And I'll put it in my own airplane.



I can easily foresee insurance agencies and even the FAA making things sticky in the future unless the whole package is used. I'm sure my favorite A&P/AI would insist upon the whole enchilada during the next condition inspection. And even if it's overkill for my particular flying, I'll still do it to avoid any future degradation of aircraft value or insurance difficulties or just if I happen to miss something during a preflight.



Hey, it couldn't hurt.



Rick Lindstrom

ZenVair 601XL N42KP



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Doug.Norman(at)sportaviat
Guest

Posted: Thu Nov 12, 2009 3:04 pm Post subject: Upgrade Decisions

Well stated. Thank you.

Doug Norman

N601DN



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Larry Webber

Joined: 05 Jun 2008
Posts: 63
Location: West Kingston Rhode Island

Posted: Thu Nov 12, 2009 3:56 pm Post subject: Upgrade Decisions

Rick i also C will do the whole enchilada and your right !   like chicken soup " it couldnt hurt"



 Larry Webber601xl/rhode island/corvair chugger



  



[quote] Date: Thu C 12 Nov 2009 17:26:26 -0500

 From: tigerrick(at)mindspring.com

 To: zenith-list(at)matronics.com

 Subject: Re: Upgrade Decisions

 

 --> Zenith-List message posted by: Rick Lindstrom <tigerrick(at)mindspring.com>

 

 I was thinking along the very same lines C Jim C until I had a long conversation with Mathieu Heintz at Zenair this morning. Frankly C I didn't see the need to add aileron counterweights either C as long as the rest of the mods were installed. But Mathieu says he's really tired of visiting crash sites with the NTSB (he's been to all in North America) C and sees the whole package as just increasing the 601 safety margins as much as possible. Who can argue with that?

 

 He strongly feels that overloading the airframe is what has caused the majority of these in-flight breakups C and it's not that hard to do with high airspeeds C partial fuel C a single occupant C an aft CG C especially when compounded by neglected maintenance or an inadequate preflight inspection. Once the wing has been overstressed and possibly deformed C it's very likely that the aileron cables could go slack C setting up an airframe harmonic vibration or flutter that quickly destroys the wing.

 

 We talked about what happens when some really big guy gets in C sharply moves the stick to the side and accidently overstresses the aileron control system and slackens the cables (it only takes 40 pounds of pressure). Or when the airplane is tied down and encounters sharp gusts on its control surfaces C which can also wreck the bellcrank system if left to flap around in the wind. (I recall seeing some dramatic pictures of 601 gust damage online not too long ago.)

 

 My 601XL has always lived in a hangar C I'm the only who flies it (in good weather and gently) C and I'm pretty anal when it comes to maintenance. So I could probably fly the airplane without any modifications until the cows came home without any problem. But you can't always forecast severe vertical gusts or just plain passenger stupidity C so you have to design with these things in mind. Mathieu also shared that Chris was aghast at how some of the 601s were being flown C modified C or neglected C and we openly wondered if our society had been dumbed down to the point of eliminating our ability to properly assess personal risk.

 

 But that's a whole different discussion C and the best solution set that Zenith has developed over the last year addresses every possible way the airplane could come apart in the air C and is included in the upgrade package. In the mean time C they recommended flying slower and with less weight to be on the safe side. Admittedly C beefing up the airframe AND installing aileron mass balance is a real "belt and suspenders" approach to eliminating any possible flutter scenario C but it could happen where a chain of events result in totally slack cables. So they're including it. And I'll put it in my own airplane.

 

 I can easily foresee insurance agencies and even the FAA making things sticky in the future unless the whole package is used. I'm sure my favorite A&P/AI would insist upon the whole enchilada during the next condition inspection. And even if it's overkill for my particular flying C I'll still do it to avoid any future degradation of aircraft value or insurance difficulties or just if I happen to miss something during a preflight.

 

 Hey C it couldn't hurt.

 

 Rick Lindstrom

 ZenVair 601XL N42KP

 

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