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Spreading fear about the XL
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jeffrey_davidson(at)earth
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PostPosted: Sun Nov 23, 2008 9:13 am    Post subject: Spreading fear about the XL Reply with quote

Friends, neighbors, and fellow Zenith Enthusiasts,

I have received multiple off-list communications about the unexplained XL crashes. We now have folks not part of the Zenith community spreading "information" about the accidents. As I reported on this list then, a group of LSA competitors advanced negative information about the XL in person at the September 2007 Zenith Gathering in Winchester, Virginia. For my part, I have not heard anything conclusive from the entities looking at the design, including the Zenith Builder's Analysis Group, Zenith, the NTSB, and European Governments, with two exceptions. One is the cable tension advisory and the other is the European action. Neither tells us what is happening unless you believe that insufficient cable tension is the proper explanation. Others have failed to find any design problem despite an extensive review. ZAC conducted a second static load test with acceptable results. But the impact of all the discussion is becoming clear. In the Second November Issue, 2008 of Trade-A-Plane, there are three kits for sale and a completed aircraft. See page 87. Some advertisements have appeared on this list. Locally, some builders are making the decision to stop work on their projects. While all losses of human life are mourned without reservation, especially losses that need not occur, I believe that we all seek a rational explanation for these events if one exists, not speculation about what the facts we know might mean.

So let me call on ZAC, the NTSB, the ZBAG, and all other investigators with the standing to make valid conclusions, to report whatever they have found or not found at this time in order to limit the fear of the 601 XL that is currently spreading through the community. They must speak up now before more damage based on fear is done to our community.

Please correct me if anyone with standing has provided a full explanation of the events that are causing these concerns about the XL.

Jeff Davidson



[quote][b]


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notsew_evets(at)frontiern
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PostPosted: Sun Nov 23, 2008 9:28 am    Post subject: Spreading fear about the XL Reply with quote

Jeff

Excellent response.

Im about to fly my 601XL and have concerns.


Steve W.
N 9554 Z
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kmccune



Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

PostPosted: Sun Nov 23, 2008 3:38 pm    Post subject: Re: Spreading fear about the XL Reply with quote

The same guy has posted the following to 4 websites that I frequent. I posted some comments about waiting for the out come and not jumping to conclusions, how many hours that have been flown on this aircraft ect...

Here is the post.

" The CH601 XL apparently sports a failure mode that has caused one of its wings to 'fold up' on at least seven occasions.
After such a case transpired in The Netherlands as well - killing both
occupants - the local authorities grounded all CH601 XL aircraft until
further notice."

It sound nice and it begins and ends with concern, but the exact same verb-age was used in all the posts that I saw. Sounds a little fishy to me.

You most all, know that I'm not a 601 guy, but bad/misleading info just burns my A$$.

I would fly in a Ch601 without any more care then getting in my truck... well depending on the pilot. ;^)

In my opinion, that does not count for much in the big picture, the CH601 is an excellent design and as safe as any. My gut tells me that the incidents were caused by pilot error or extenuating circumstances, or both.

OK... back off my soap box. And just go fly your 601!
I'm still building my 701 so the jokes on me, anyway :^)

Kevin


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_________________
“Always do what you are afraid to do.”
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"Life is a good deal...it's worth it" Feb 1969
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hills(at)sunflower.com
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PostPosted: Sun Nov 23, 2008 6:52 pm    Post subject: Spreading fear about the XL Reply with quote

Howdy all;

My A&P was looking over my 601HDS and commented that the ailerons were not counterbalanced. He said this can lead to aileron flutter. My Sonerai had
balanced ailerons, can someone comment on if the 601XL has balanced ailerons and if not, could this result in wing flutter?

Roger




From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Jeff
Sent: Sunday, November 23, 2008 11:13 AM
To: zenith-list(at)matronics.com
Subject: Spreading fear about the XL


Friends, neighbors, and fellow Zenith Enthusiasts,

I have received multiple off-list communications about the unexplained XL crashes. We now have folks not part of the Zenith community spreading "information" about the accidents. As I reported on this list then, a group of LSA competitors advanced negative information about the XL in person at the September 2007 Zenith Gathering in Winchester, Virginia. For my part, I have not heard anything conclusive from the entities looking at the design, including the Zenith Builder's Analysis Group, Zenith, the NTSB, and European Governments, with two exceptions. One is the cable tension advisory and the other is the European action. Neither tells us what is happening unless you believe that insufficient cable tension is the proper explanation. Others have failed to find any design problem despite an extensive review. ZAC conducted a second static load test with acceptable results. But the impact of all the discussion is becoming clear. In the Second November Issue, 2008 of Trade-A-Plane, there are three kits for sale and a completed aircraft. See page 87. Some advertisements have appeared on this list. Locally, some builders are making the decision to stop work on their projects. While all losses of human life are mourned without reservation, especially losses that need not occur, I believe that we all seek a rational explanation for these events if one exists, not speculation about what the facts we know might mean.

So let me call on ZAC, the NTSB, the ZBAG, and all other investigators with the standing to make valid conclusions, to report whatever they have found or not found at this time in order to limit the fear of the 601 XL that is currently spreading through the community. They must speak up now before more damage based on fear is done to our community.

Please correct me if anyone with standing has provided a full explanation of the events that are causing these concerns about the XL.

Jeff Davidson


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bryanmmartin



Joined: 10 Jan 2006
Posts: 1018

PostPosted: Sun Nov 23, 2008 7:32 pm    Post subject: Spreading fear about the XL Reply with quote

The 601XL does not have balanced ailerons. If the control cables are
tensioned properly, this is not a problem. If the cables are way too
loose, there is a risk of flutter.

On Nov 23, 2008, at 9:50 PM, Roger & Lina Hill wrote:

Quote:
Howdy all;

My A&P was looking over my 601HDS and commented that the ailerons
were not counterbalanced. He said this can lead to aileron
flutter. My Sonerai had
balanced ailerons, can someone comment on if the 601XL has balanced
ailerons and if not, could this result in wing flutter?



--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.


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Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.
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hills(at)sunflower.com
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PostPosted: Sun Nov 23, 2008 8:41 pm    Post subject: Spreading fear about the XL Reply with quote

Well, why not just add a counterbalance to the 601XL and get rid of the
flutter questions?

My sonerai had a simple method, it just had a weight ahead of the aileron
hinge at the wing tip. Though, this would mean having making a modification
to the wing tip. On the sonerai, it was a fiber glass wing tip so it was no
Problem adding it.

Roger
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jaybannist(at)cs.com
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PostPosted: Mon Nov 24, 2008 5:12 am    Post subject: Spreading fear about the XL Reply with quote

Roger.

Your A&P did not design the 601HDS. How could he possibly know that "this could lead to aileron flutter"? Chris Heintz designed the CH200, CH601, CH601HD, CH601HDS, CH601XL, CH701, CH801 and CH750, all without aileron balance. The rudder and elevators are not balanced either. Control surface flutter is a MAJOR concern of all aircraft designers. If he thought his control surface designs could lead to flutter, don't you think he would have included some sort of balance?

Exactly how many of these designs (PROPERLY constructed, flown and maintained) has experienced VERIFIED aileron flutter?

If you don't trust Chris Heintz, stay away from Chris Heinz designed airplanes. Otherwise, COOL IT!

Jay in Dallas
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hills(at)sunflower.com
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PostPosted: Mon Nov 24, 2008 6:12 am    Post subject: Spreading fear about the XL Reply with quote

Jay;

To be more exact, I believe his point was that ANY unbalanced aileron, regardless of make and model, would be more likely to flutter and that balancing them could reduce or even avoid the possibility of flutter. As for not designing the 601, I don’t think it is necessary to design something in order to understand it. My A&P is about 70 years old, his dad was an A&P as well, so I think he could know through a combination of training and experience. He is also a homebuilder and so was his father, who unfortunately died when his homebuilt wing failed in flight a few years ago.

Roger




From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of jaybannist(at)cs.com
Sent: Monday, November 24, 2008 7:11 AM
To: zenith-list(at)matronics.com
Subject: Re: Zenith-List: Spreading fear about the XL


Roger.

Your A&P did not design the 601HDS. How could he possibly know that "this could lead to aileron flutter"? Chris Heintz designed the CH200, CH601, CH601HD, CH601HDS, CH601XL, CH701, CH801 and CH750, all without aileron balance. The rudder and elevators are not balanced either. Control surface flutter is a MAJOR concern of all aircraft designers. If he thought his control surface designs could lead to flutter, don't you think he would have included some sort of balance?

Exactly how many of these designs (PROPERLY constructed, flown and maintained) has experienced VERIFIED aileron flutter?

If you don't trust Chris Heintz, stay away from Chris Heinz designed airplanes. Otherwise, COOL IT!

Jay in Dallas
Do not archive





-----Original Message-----
From: Roger & Lina Hill <hills(at)sunflower.com>
To: zenith-list(at)matronics.com
Sent: Sun, 23 Nov 2008 8:50 pm
Subject: RE: Spreading fear about the XL
Howdy all;



My A&P was looking over my 601HDS and commented that the ailerons were not counterbalanced. He said this can lead to aileron flutter. My Sonerai had

balanced ailerons, can someone comment on if the 601XL has balanced ailerons and if not, could this result in wing flutter?



Roger








From: owner-zenith-list-server(at)matronics.com (owner-zenith-list-server(at)matronics.com) [mailto:owner-zenith-list-server(at)matronics.com ([email]owner-zenith-list-server(at)matronics.com?[/email])] On Behalf Of Jeff
Sent: Sunday, November 23, 2008 11:13 AM
To: zenith-list(at)matronics.com (zenith-list(at)matronics.com)
Subject: Spreading fear about the XL




Friends, neighbors, and fellow Zenith Enthusiasts,



I have received multiple off-list communications about the unexplained XL crashes. We now have folks not part of the Zenith community spreading "information" about the accidents. As I reported on this list then, a group of LSA competitors advanced negative information about the XL in person at the September 2007 Zenith Gathering in Winchester, Virginia. For my part, I have not heard anything conclusive from the entities looking at the design, including the Zenith Builder's Analysis Group, Zenith, the NTSB, and European Governments, with two exceptions. One is the cable tension advisory and the other is the European action. Neither tells us what is happening unless you believe that insufficient cable tension is the proper explanation. Others have failed to find any design problem despite an extensive review. ZAC conducted a second static load test with acceptable results. But the impact of all the discussion is becoming clear. In the Second November Issue, 2008 of Trade-A-Plane, there are three kits for sale and a completed aircraft. See page 87. Some advertisements have appeared on this list. Locally, some builders are making the decision to stop work on their projects. While all losses of human life are mourned without reservation, especially losses that need not occur, I believe that we all seek a rational explanation for these events if one exists, not speculation about what the facts we know might mean.



So let me call on ZAC, the NTSB, the ZBAG, and all other investigators with the standing to make valid conclusions, to report whatever they have found or not found at this time in order to limit the fear of the 601 XL that is currently spreading through the community. They must speak up now before more damage based on fear is done to our community.



Please correct me if anyone with standing has provided a full explanation of the events that are causing these concerns about the XL.



Jeff Davidson






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larry(at)macsmachine.com
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PostPosted: Mon Nov 24, 2008 6:22 am    Post subject: Spreading fear about the XL Reply with quote

Hi Roger,
The HDS ailerons are not counterbalanced because the aircraft is not a
fast aircraft and the ailerons would have too low a frequency for flutter
unless you were in a high speed dive etc. I've no recollection that
anyone has reported flutter in the HDS 23-ft short thick wing.
I don't think cable tension or lack of it would affect the Zenith 601
series either.

Larry McFarland 601HDS at www.macsmachine.com

Roger & Lina Hill wrote:
Quote:

Howdy all;



My A&P was looking over my 601HDS and commented that the ailerons were
not counterbalanced. He said this can lead to aileron flutter. My
Sonerai had

balanced ailerons, can someone comment on if the 601XL has balanced
ailerons and if not, could this result in wing flutter?



Roger





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notsew_evets(at)frontiern
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PostPosted: Mon Nov 24, 2008 6:57 am    Post subject: Spreading fear about the XL Reply with quote

Piper J-3s, Piper Super Cubs never had counter balance weights. Built from
1938 til 1959 and now made by "other" names still dont use weights. Go
figure.....

SW
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frankroskind(at)HOTMAIL.C
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PostPosted: Mon Nov 24, 2008 7:13 am    Post subject: Spreading fear about the XL Reply with quote

While I have trouble coming up with a slimier tactic than a competitor trashing Zenith over the difficulties C I also think that some people have ideas which might be relevant to safety C not only of the XL C but even other manufacturers' designs C whether or not they are XL builders. For all we know some of the competitors' designs have the same potential flaws as the XL C but just don't have enough exposure (they can't sell as many planes) to have experienced an in-flight failure. In fact C if you go to earlier posts in this thread C you will read that the 70 year old A&P's father died in a wing failure accident C which almost certainly did not involve a 601 XL. I would guess that anyone who lost his father in a wing failure accident would take a very keen interest in the ways in which wings might fail C and would have some valuable contributions to make to the discussion. I doubt that silencing opinions would havea beneficial effect C or would lead to an end to XL wing failures. I think that balancing ailerons could not hurt C nor could maintaining cable tension. Flutter might not be teh accident cause C but it doesn't hurt to reduce the likelihood of flutter. I also think that doing a good job of reaming holes on wing attach bolts could not hurt either. I don't think that a wide range of thoughts on the likey causes of the wing failures is harmful C as long as the discussion does not blind us to other issues.

To: zenith-list(at)matronics.com
Subject: Re: Spreading fear about the XL
Date: Mon C 24 Nov 2008 08:11:09 -0500
From: jaybannist(at)cs.com

Roger.

Your A&P did not design the 601HDS. How could he possibly know that "this could lead to aileron flutter"? Chris Heintz designed the CH200 C CH601 C CH601HD C CH601HDS C CH601XL C CH701 C CH801 and CH750 C all without aileron balance. The rudder and elevators are not balanced either. Control surface flutter is a MAJOR concern of all aircraft designers. If he thought his control surface designs could lead to flutter C don't you think he would have included some sort of balance?

Exactly how many of these designs (PROPERLY constructed C flown and maintained) has experienced VERIFIED aileron flutter?

If you don't trust Chris Heintz C stay away from Chris Heinz designed airplanes. Otherwise C COOL IT!

Jay in Dallas
Do not archive





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jaybannist(at)cs.com
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PostPosted: Mon Nov 24, 2008 7:44 am    Post subject: Spreading fear about the XL Reply with quote

Roger,

Not to be argumentative, but I am 74 years old and I practiced architecture for more than 45 years. So I know a LOT about building design. That does not qualify me to judge the functional or structural integrity of another architect's design without knowing the details of the criteria, the specific goals for the design, and the logic of the design solution. I have plenty of prejudices when it comes to the practice of architecture; but I recognize them a such and refrain from publicly condemning others who do not share my philosophy.

Stating that "ANY unbalanced aileron, regardless of make and model, would be more likely to flutter and that balancing them could reduce or even avoid the possibility of flutter" is a prejudiced statement and it is simply not true. Flutter potential of any control surface is determined by the totality of the design: size, shape, weight, weight distribution, pivot location, control system, design speed and so forth and so on. If the designer makes the right choices (which might compromise other parts of the design) he can provide a control surface that will not flutter, period. However, many examples prove that most designers are not willing to compromise other parts of the airframe to provide a flutter-free control surface. The fallback is to provide a20design work-around in the form of balance weights or aerodynamic balancing surfaces. That is not to criticize the use of balancing. It is simply a matter of choice. Chris Heintz chose to provide control surfaces that do not need balancing when operated within the stated operating limits. If you exceed those limits, you are on your own and in dangerous territory - "outside the envelope". That is true of any aircraft and it is where failures occur, including control surface flutter, wing failure and who knows what.

I'll say it again: If you don't trust the designer, don't fly the airplanes he has designed. And don't try to "tweek" his design when you don't know why and how it was designed the way it is.

'Nuff said - Jay in Dallas
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PostPosted: Mon Nov 24, 2008 7:57 am    Post subject: Spreading fear about the XL Reply with quote

You forgot the 640 which also has unbalanced ailerons HOWEVER... it has push-pull tubes instead of cables and boxed wing spars (more related to the load carying capacity).The margin between cruise and VNE is much closer than the XL design. Maybe we need to look at this!? As I look at the designs, they become capable of increasingly high cruise speeds and with builders putting more h.p. in it becomes very easy to reach VNE very quickly by entering even a very shallow dive. (also the rudder on the 6,7,&8 series ARE balanced, note the portion of the rudder ahead of the hinge points...this is aerodynamic balance as opposed to weight balance).

I think that what we are seeing is two groups of builders here: one group who builds and fly's well within the specs of the design, and one group that wants to achieve everything to the edge of the envelope and perhaps a bit beyond. One group is made of builder/flyers, and one group is made of experimenter builders/test pilots. This latter group will always push aircraft design firms to re-examine their designs and hopefully this will benefit the first group who will end up flying increasingly safe and more capable aircraft.

I'm sure that no-one on this list means to offend the builder/flyer group, I know I don't. We are just part of the group that reaches out to extend our potential.

I am building a 601XL (which I may re-designate as 601XLA(airobat)orM(modified) just to make it clear that it is not totally to plans) As I have said before I will use push-pull tubes for the ailerons and elevator and balance both as well. The ailerons will move the hingepoint rearward and the elevator will use weights in the tips which will be attached to the elevator instead of the horizontal stab. I will also use a boxed spar in the wing that meets at the center instead of bolting on at the outer part of the fuselage.

Dirk Z
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PostPosted: Mon Nov 24, 2008 8:16 am    Post subject: Spreading fear about the XL Reply with quote

Just another comment. Sorry Jay, I truly mean no offense. It is not our guess or an A/Ps opinion that balancing control surfaces reduces the possibility of flutter. It's a proven condition of aerodynamics. If not, I'm sure NOBODY would put lead weights in their ailerons' leading edges. While I build I also own and fly a Cessna 150 with weight balanced ailerons. It's cruise speed is just a bit more than some older designs at about 105mph without balance weights but the VNE is 160mph. This is a Much larger ratio than the 601 and I don't think it would meet the certification requirements at that speed without balanced surfaces(the elevator is balanced as well and also the rudder).
Dirk

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PostPosted: Mon Nov 24, 2008 9:47 am    Post subject: Spreading fear about the XL Reply with quote

In this latest discussion, we're all operating on the speculation that the cause of the handful of wing fold accidents in the 601 have their initial cause in aileron flutter (a believable hypothesis, given the current lack of any other concrete data). Flutter at high speeds can destroy an airframe structure in seconds, and it's pretty easy to imagine a fluttering aileron might overstress the rear spar/fuselage attach point to failure, allowing the wing to twist until the lower main spar attachment surrenders, and the wind folds up and over. Not a pretty scenario.

Some have suggested that balancing the ailerons is the cure. And I remember a recent YouTube video showing exactly this modification to some Brazilian 601 airframes, which also sported some other significant modifications. Push pull tubes would also firm up the play in the aileron control system. That's the beauty of an experimental aircraft. As the manufacturer of record, we can do these things legally. But legal isn't always safe, and any departures from what the kit manufacturer has designed should be done with extreme care and be thoroughly tested. To Zenith's credit, they've been very approachable when submitting concepts for improvements or changes.

But the fact remains that the flight control surfaces are not going to flutter if the cable tensions are anywhere near proper specification. We can add weight and complexity as added insurance (and to make ourselves feel better), but I think it's good idea every now and then to take a deep breath and consider how we fly the airplane as well.

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. Sure, I'd like to hear more from Zenith about what's been found in their collaboration with the NTSB so far, but I also understand the restrictions in divulging information prematurely that they must adhere to.

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).

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PostPosted: Mon Nov 24, 2008 10:08 am    Post subject: Spreading fear about the XL Reply with quote

Jay, what you say makes good sense. Course, I may be the only XL builder and flyer that has had aileron flutter and got out of it without the wings coming off. It's like having a rev'ed up chain saw drop in your lap while flying. Something I don't ever want to have again. I really like my XL, it does what I want and has from when I bought the kit and built it. Still, I also saw the Challenger blow up so my faith that a designer, any designer, or team of experts could miss something is not absolute. I'm going to modify my XL over the holidays by removing the cables and installing push/pull rods similar to the ones I built for my RV-8a. I hope that reduces the potential for flutter. At least it will increase my piece of mind. Never the less, I will continue flying my XL, not in some blind faith that CH designed a perfect plane, but that I built and maintain a safe plane. Trust is foolish if blind. Best regards, Bill of Georgia


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jaybannist(at)cs.com
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PostPosted: Mon Nov 24, 2008 10:33 am    Post subject: Spreading fear about the XL Reply with quote

Dirk,

I don't mean to offend either, but since you didn't read and understand what I wrote, I will not respond.


Jay io Dallas
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notsew_evets(at)frontiern
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PostPosted: Mon Nov 24, 2008 11:37 am    Post subject: Spreading fear about the XL Reply with quote

Bill, you had flutter. I assume after the incident the control cables were checked on your aircraft? If so, what did you find ????
In your specific case, were the cables tensioned as per plans at 30 + - pounds ??

SW
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amyvega2005(at)earthlink.
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PostPosted: Mon Nov 24, 2008 12:21 pm    Post subject: Spreading fear about the XL Reply with quote

Dirk,
pull up the archives, i brought up the issue of VNE and Max manauvering speeds over one year ago, but the back room engineers ignored it.

Fly it and follow the specs. My guess is the guys flying and that augered in ignored the flight envelope of the aircraft. BUILD IT TO PLANS AND FLY IT TO SPECS.

Time to move on folks,

Juan

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barcusc(at)comcast.net
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PostPosted: Mon Nov 24, 2008 1:26 pm    Post subject: Spreading fear about the XL Reply with quote

Juan

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. That
should eliminate one possible problem and if I should ever "auger in" you
can bet it will not be loose cables or exceeding design limits, you can take
that to the bank. Without the recent discussions I would have probably
twanged the cables and let it go at that, obviously I have changed my mind.

To Bill of Georgia: Thanks!

Regards:

Clyde Barcus
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