---------------------------------------------------------- Zenith-List Digest Archive --- Total Messages Posted Tue 02/23/10: 6 ---------------------------------------------------------- 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 _____________________________________ Time: 06:44:50 AM PST US Subject: Zenith-List: Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 From: "Sabrina" 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 _____________________________________ Time: 11:59:10 AM PST US From: "Jim Weston" Subject: RE: Zenith-List: 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 _____________________________________ Time: 03:09:55 PM PST US From: Juan Vega Subject: RE: Zenith-List: 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 >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 _____________________________________ Time: 03:09:55 PM PST US Subject: Zenith-List: Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 From: "Zenair_Mathieu" 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 _____________________________________ Time: 05:18:53 PM PST US From: "Paul Mulwitz" Subject: RE: Zenith-List: 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 _____________________________________ Time: 06:59:38 PM PST US Subject: Zenith-List: Re: Q&A FAA Special Review Team Report - Zodiac 601XL/650 From: "Sabrina" 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 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message zenith-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Zenith-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/zenith-list Browse Digests http://www.matronics.com/digest/zenith-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.