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
----- Original Message -----
From: Clyde Barcus<mailto:barcusc@comcast.net>
To: zenith-list@matronics.com<mailto:zenith-list@matronics.com>
Sent: Monday, November 24, 2008 3:21 PM
Subject: Re: Spreading fear about the XL
<barcusc@comcast.net<mailto:barcusc@comcast.net>>
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
----- Original Message -----
From: "Juan Vega"
<amyvega2005@earthlink.net<mailto:amyvega2005@earthlink.net>>
To: <zenith-list@matronics.com<mailto:zenith-list@matronics.com>>;
<zenith-list@matronics.com<mailto:zenith-list@matronics.com>>
Sent: Monday, November 24, 2008 3:19 PM
Subject: Re: Spreading fear about the XL
<amyvega2005@earthlink.net<mailto:amyvega2005@earthlink.net>>
>
> 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
>
> -----Original Message-----
>>From: Dirk Zahtilla
<ideaz1@sbcglobal.net<mailto:ideaz1@sbcglobal.net>>
>>Sent: Nov 24, 2008 10:56 AM
>>To: zenith-list@matronics.com<mailto:zenith-list@matronics.com>
>>Subject: Re: Spreading fear about the XL
>>
>>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
>> ----- Original Message -----
>> From: jaybannist@cs.com<mailto:jaybannist@cs.com>
>> To: zenith-list@matronics.com<mailto:zenith-list@matronics.com>
>> Sent: Monday, November 24, 2008 5:11 AM
>> Subject: Re: 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@sunflower.com<mailto:hills@sunflower.com>>
>> To: zenith-list@matronics.com<mailto:zenith-list@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@matronics.com<mailto:owner-zenith-list-server@ma
tronics.com>
>> [mailto:owner-zenith-list-server@matronics.com] On Behalf Of Jeff
>> Sent: Sunday, November 23, 2008 11:13 AM
>> To: zenith-list@matronics.com<mailto:zenith-list@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
>> Is!
> sue, 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
>>
>>
>>
>>
http://www.matronics.com/contribution
on>< pre>
>>
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