Today's Message Index:
----------------------
1. 06:44 AM - Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 (Sabrina)
2. 11:59 AM - Re: Landing Gear Shock Cords (Jim Weston)
3. 03:09 PM - Re: Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 (Juan Vega)
4. 03:09 PM - Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 (Zenair_Mathieu)
5. 05:18 PM - Re: Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 (Warning - Long Message!) (Paul Mulwitz)
6. 06:59 PM - Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 (Sabrina)
Message 1
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| Subject: | Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 |
Wait for the other shoe to drop (NTSB)?
By the way, Thank You to the NTSB 601XL teams as well.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287800#287800
Message 2
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| Subject: | Landing Gear Shock Cords |
Thanks Larry....That's interesting info. I'm ashamed to admit it, but mine
are the original shock cords from 1998. They are still working ok, but are
starting to look a bit frayed. I guess that I'm not flying my plane enough.
Anyway, the gear has always been stiff. Mine has never protruded out the
top of the wing. I can tell from the scuff marks that the gear has traveled
as much as an inch, but no more. I've even flown it from the somewhat rough
grass strip behind my house a few times. The stiffness is why I'm
considering changing to standard 1080s. I also have the nylon inserts.
Those shock cords seemed overdone when I originally installed them. I'm
starting to wonder if they were mislabeled.
Thanks...Jim Weston 601HDS
-----Original Message-----
From: owner-zenith-list-server@matronics.com
[mailto:owner-zenith-list-server@matronics.com] On Behalf Of Larry McFarland
Sent: Friday, February 19, 2010 9:46 AM
Subject: Re: Zenith-List: Landing Gear Shock Cords
Hi Jim,
I've also got the 1080HD cords and the strut caps stick up about 3/8ths
inch with me in the plane, 1/4 inch without.
My mains are responsive in a bumped landing to the tune of about 2
inches max and seem easy to move during taxi.
My 601HDS has nylon guides in the top and bottom of the wings. Just
changed out the main shock cords after 2 years
because I'd slightly damaged them during disassembly for paint.
I think the main spring gear on the XLs is much heavier than the strut
type HD series and imposes adverse shock loads into
the fuselage.
Larry McFarland 601HDS at www.macsmachine.com
Jim Weston wrote:
>
> I have the CH601HDS with tri-gear, and am getting ready to replace the
shock
> cords on the main gear. The gear has always been very stiff; particularly
> noticeable on a grass runway. The kit came with 1080HD shock cords, which
> is what I installed. Has anyone tried the standard 1080, rather than the
> 1080HD? If so, how did it work out? Any other options? No, I'm not
going
> to change to the spring landing gear. Wish I had it, too much work to
> change.
>
> Thanks Folks,
> Jim Weston
> CH601HDS, with Stratus Subaru
>
>
>
Message 3
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| Subject: | Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 |
I would not lose sleep over any of the aircraft. Now you have an over built, over
analyzed experimental built by You, the manufacturer, and you, Paul, as well
as Sabrina and all of us, no are the one to determine its flyable. If you
built it, and are confident, quit making excuses and go fly it. I am working
on my mods, and once done, will commence using it every day as I did before
all this started. I built a good plane, fly it within specs, am in the process
of finishing the mods, and will commence to fly it when done. Frankly I consider
this a good time to do the mod and look at it as an extensive annual. Found
a few things that needed upgrades and am doing those as well. I rang the
plane through the ringer, 130 hours per year for a total of 263 hours. So this
is all good.
Juan
-----Original Message-----
>From: Paul Mulwitz <psm@att.net>
>Sent: Feb 23, 2010 2:48 AM
>To: zenith-list@matronics.com
>Subject: RE: Zenith-List: Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650
>
>
>Hi Sabrina,
>
>I share your sentiments, but your applause for the need for extra testing
>leaves me with a huge question.
>
>Does this mean that even after installing the upgrade we still need to lose
>sleep over the design of the XL?
>
>How should we proceed now?
>
>Paul
>XL upgrade kit in transit
>
>-----Original Message-----
>From: owner-zenith-list-server@matronics.com
>[mailto:owner-zenith-list-server@matronics.com] On Behalf Of Sabrina
>Sent: Monday, February 22, 2010 10:59 PM
>To: zenith-list@matronics.com
>Subject: Zenith-List: Re: Q&A FAA Special Review Team Report - Zodiac
>601XL/650
>
>
>"Please note that I will only be answering on www.zenith.aero"
>
>Wishful thinking.
>
>First off, THANK YOU to the FAA Team reviewing the 601XL design.
>
>A wonderful, comprehensive report that requires further testing of the XL
>upgrades both on the ground and in the air.
>
>Christmas in February for those of us that started with the original 601XL
>kit.
>
>
Message 4
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| Subject: | Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 |
Paul,
Good question. Please post your question at www.zenith.aero so that I can answer it and everyone can view it.
Thanks
Mathieu Heintz
Zenair
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287891#287891
Message 5
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| Subject: | Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 |
(Warning - Long Message!)
Ok, Mathieu.
You inspired me to really think about this whole situation. I posted a long
comment on Zenith.aero, and here is a copy for anyone who doesn't use that
web site.
Best regards,
Paul
===============================
Mathieu,
First let me say I appreciate the openness of this whole discussion. I am
hopeful we will eventually reach a level of comfort with the Zodiac design
that has been sorely lacking for years.
After reading the FAA report (at least the parts I could understand) and
reading the comments on this Q&A I'm afraid we are almost back where we
started last year when the NTSB letter came out. It seems you are saying all
is well and the government is saying there is need for major further effort
and potential changes. The FAA report calls for many additional tests and
you are saying the stuff submitted months before the report was written
takes care of all the needs.
I realize there are a lot of expensive things under discussion. These are
not only expensive for Zenair/Zenith/AMD they are also expensive for every
builder/owner of this design. The government has a significant interest in
seeing this question reach a happy conclusion. I suspect there are many
owners who feel like I do that the costs involved in further testing and
analysis should not prevent having them take place. We are all in this
together.
As an owner, I stand to lose the investment I have already made in this
plane. However, I would rather scrap it than take undue risk flying it when
it needs further evaluation and possible improvement. Unfortunately, I don't
have the knowledge or resources to take the further steps by myself. I would
certainly consider contributing a share of the funds needed to get this
design to the level needed for all of us to sleep well at night
I think the next step should be an open discussion with all the parties to
this fiasco present. This should include representatives from the NTSB, FAA,
Zenith/Zenair/AMD (particularly Mathieu and Sebastian Heintz) and builders
and owners of these planes. Perhaps Sun n Fun could provide a suitable venue
for this big meeting. I would expect the meeting to take at least several
hours and possibly several days.
My goals for such a meeting are:
1. A clear understanding by all major parties that answers the question: Is
the current set of changes sufficient to be comfortable with this design or
is further testing and possible design change needed?
2. A plan for conducting any further tests that are needed including who
will conduct the tests and where the funding will come from. This requires
several phases- first define the needs, then estimate the costs, finally
come up with a funding plan. Furthermore, we should examine the availability
of government engineers to aid in the design and evaluation of any further
testing that is required. Clearly, the FAA and NTSB have more engineering
manpower than either the builders or Zenair/Zenith/AMD.
3. Since the NTSB letter really started this public discussion of the Zodiac
problems, I suggest the NTSB provide a chairman to lead this discussion. If
that choice doesn't work, then I suggest the FAA provide a chairman.
4. I hope any further engineering analysis can be done as an open and public
event rather than the secretive style used so far in this situation. That
way we should all be able to reach the same general conclusions about the
engineering judgments that are currently under significant dispute.
If such a meeting is scheduled, I will personally attend it (after traveling
3,000 miles) and I will also consider contributing funds toward the costs of
further testing.
I hope we can eventually reach a point where we all can sleep well while
flying and selling our Zodiacs.
Paul Mulwitz
Camas, WA
-----Original Message-----
From: owner-zenith-list-server@matronics.com
[mailto:owner-zenith-list-server@matronics.com] On Behalf Of Zenair_Mathieu
Sent: Tuesday, February 23, 2010 3:10 PM
Subject: Zenith-List: Re: Q&A FAA Special Review Team Report - Zodiac
601XL/650
Paul,
Good question. Please post your question at www.zenith.aero so that I can
answer it and everyone can view it.
Thanks
Mathieu Heintz
Zenair
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287891#287891
Message 6
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| Subject: | Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 |
Dearest Juan,
If, after digesting the report, you still think the aircraft is over-designed and
the math was over analyzed by Zenith, you must sleep much better than many
of us.
SPARS
FAA: analysis estimated that the wing design loads were 20 to 25 percent too low...
The spar chords do not have structural flanges that are usually present
on most typical spar designs. Such flanges work to resist buckling, which has
been noted in static load tests on the CH 601 XL, and is present in accident photos...
Zenith upgraded the spars but tested them to less than 100% load. Similar tests
were performed by the manufacturer in Canada in September 2009 on a modified
structure to the 1,320 lb weight LSA version of this aircraft. During these tests,
buckling was noted in the wing structure below ultimate load, so the tests
were halted and the wing structure was modified. (again?)
FAA: The manufacturer needs to perform additional structural testing (If it has
been performed since the report was written, the NTSB should have the new data.)
FLUTTER
The upgrade changed the structure so reliance upon testing on an unmodified airframe
does not satisfy the FAA: FAA has requested the manufacturer perform additional
analysis and testing on the revised structure to verify flutter concerns
have been mitigated... This should include a complete flutter investigation
(ground vibration test (GVT), flutter analysis, and flight test) accomplished
by a noted flutter expert. So too, the testing in Germany was a linear evaluation,
non-linear techniques of the flutter characteristics since the frequency
and mode shapes may be affected by post buckling effects on wing skin structural
stiffness... may be needed.
THE MATH BEHIND THE 601XL
The FAA identified several significant issues with the manufacturers structural
loads analysis. These issues included...
Our estimated wing bending and torsion loads are significantly higher than those
computed by the manufacturer, as shown in figure 1...
The manufacturers analysis assumes the wing planform covered by the fuselage is
as effective in producing lift as an adjacent portion of exposed wing planform.
This assumption may not be conservative and may be noncompliant with the ASTM
F 2245 5.1.1.2 requirement...
The manufacturers analysis used an assumption that the lift distribution has a
purely elliptical shape. This assumption is often used in academic evaluations,
but is incorrect for compliance to ASTM F 2245 5.1.1.2...
The manufacturer appears to have computed the wing loads assuming a 15 gallon fuel
tank in each wing. However, the manufacturers drawings and advertising materials
clearly show that a 12 gallon tank is standard equipment on the CH 601
XL. This small discrepancy in fuel tank capacity underestimates the wing design
bending loads by about four percent. This could lead to the structure being
designed to a lower capacity than needed....
The manufacturers analysis defines the MZFW as the maximum takeoff weight (MTOW)
minus full fuel. This definition is incorrect...
The manufacturers analysis was based on estimates of the airfoil pitching moment
characteristics obtained from the airfoil designer. The manufacturer then assumed
a reduction in the magnitude of the airfoil pitching moment without providing
substantiating test data to support it. This assumption could impact the
torsional loads used to design the wing structure, possibly leading to a reduction
in stiffness and damping characteristics of the wing, which could impact
flutter....
The manufacturers analysis assumes that the intent of this standard is to multiply
both torsion and wing bending loads by 75%. The manufacturers interpretation
is incorrect...
The manufacturer determined VA to be 90 knots (103) mph based on a stall speed,
VS, of 44 knots (51 mph). However, the manufacturers flight test report documents
a measured stall speed of 43 knots (49 mph). In addition, the flight test
report did not appear to contain proper temperature corrections to convert the
measured data to standard atmospheric conditions...
The manufacturer should consider higher values for the MZFW, given the empty weights
of the existing fleets, owners preference for installed equipment including
ballistic recovery systems, owners preference for allowable baggage, and the
weight of any structural modifications...
The manufacturer should establish limitations for VO, VNO, and VNE...
The manufacturers flight test report was reviewed. It appears the airspeed calibration
data presented was only calibrating indicated airspeed to true airspeed...
However, to be valid both the airspeed and altitude must be constant while
the data is collected. From the data reviewed, it appears there are numerous
data points collected above VH, which implies that the aircraft must have been
in a dive to reach those speeds. This potentially invalidates the GPS reverse
course method.... The FAA suggests the manufacturer work with a qualified technical
source to develop a revised calibration method...
With these criteria in mind, the manufacturers original calibration did not meet
14 CFR Part 23 23.1323 until after correcting for standard day temperature
conditions. For comparison, neither CZAW nor the UK LAAs data meets 14 CFR Part
23 23.1323, though they are not required to do so. However it is unusual for
a low speed aircraft like the CH 601 XL to need a -24 knot static source error
correction, indicating a potential error in the calibration methods used...
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287919#287919
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