---------------------------------------------------------- Zenith601-List Digest Archive --- Total Messages Posted Sat 04/18/09: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:22 AM - Trigger for NTSB letter (David Johnson) 2. 05:56 AM - HD/HDS cable specs (Jeff) 3. 07:01 AM - Re: Thoughts regarding Flutter (jaybannist@cs.com) 4. 08:40 AM - Re: Trigger for NTSB letter (Bryan Martin) 5. 09:10 AM - Re: Thoughts regarding Flutter (Bryan Martin) 6. 11:23 AM - Re: Thoughts regarding Flutter (NYTerminat@aol.com) 7. 12:03 PM - Re: Thoughts regarding Flutter (Craig Payne) 8. 04:23 PM - Re: Thoughts regarding Flutter (T. Graziano) 9. 08:11 PM - Cable tensions for the HDS (LarryMcFarland) ________________________________ Message 1 _____________________________________ Time: 02:22:04 AM PST US From: "David Johnson" Subject: Zenith601-List: Trigger for NTSB letter There seems to be an awful lot of speculation (and anger) about who got the NTSB interested in the 601XL. Most of it seems to be directed at the ZBAG group. No-one seems to have mentioned the letter that the Dutch authorities sent to all civil aviation authorities around the world, basically saying that the 601XL is not fit to fly. Whether this went to the NTSB or the FAA (if the latter, then I would expect them to pass it on to the NTSB for comment), it is not something that any bureaucrat could or would ignore. I don't have the content of the letter, but notification of it was published on the Zenair Europe website. http://www.zenairulm.com/News/index_files/Page972.htm They have published their response, but I believe that it was only sent to European authorities. Dave Johnson Ready to test fly - grounded - in limbo (and NOT HAPPY!!) do not archive ________________________________ Message 2 _____________________________________ Time: 05:56:11 AM PST US From: "Jeff " Subject: Zenith601-List: HD/HDS cable specs Roger, Edition 3 dated Jan. 1995 of the CH 601 (HD) Construction Manual gives the cables tension as "30 to 40 lbs." on page 29. Since the HDS plans were an addendum to this manual, I presume the same tension applies to the HDS. As far as I know, the cable runs were exactly the same for the HDS as for the HD. Jeff Davidson Howdy all; I have my annual inspection on Saturday, and for the life of me I can't find the 601 HDS cable tension specs. Does anyone know what the elevator and rudder cables should be tension to on a 601 hds? Thanks Roger ________________________________ Message 3 _____________________________________ Time: 07:01:25 AM PST US Subject: Re: Zenith601-List: Thoughts regarding Flutter From: jaybannist@cs.com Tony, I happen to agree with you.? I also think that the elevator is a more likely source of trouble than the ailerons.? Even though the XL that I flew didn't seem to me to have an overly sensitive elevator, I have read and heard comments that indicates that it is troublesome to others. The NTSB letter goes into some detail about the elevator being progressively effective.? It is fairly well accepted that excessive elevator input can overstress an airframe. In the case of the XL accidents, a gross elevator movement could very well have overstressed the wings and made them fail.? The NTSB accident report of the Yuba accident speculated that the first thing to fail was the horizontal stabilizer, in a downward direction.? It seems to me that a max down elevator could have caused that. I did not see any mention of whether the Heintz recommended elevator stop had been added to this airplane. This makes me wonder if adding progressive resistance to fore and aft movement of the stick might make sense to defeat the progressive effectiveness of the elevator, ie: bungees or springs. what do you think? Jay Bannister -----Original Message----- From: T. Graziano Sent: Fri, 17 Apr 2009 11:32 pm Subject: Re: Zenith601-List: Thoughts regarding Flutter ? Additional thoughts, Scott? ? Sounds reasonable.? I thought about replacing cables with push rods, but then thought that the natural freq of a rod would probably be lower than a tensioned cable and more likely to resonate. ? Today as I was up enjoying the sky in my XL, I crossed mid-field and broke to down wind and it reminded my of another reconstructed crash at the crash lab at March AFB during a course I took in Aircraft Accident Investigation at USC thirty years ago. It was an AeroCommander Twin that shed its wings.? ? The physical investigator?instructor, (who was also my undergraduate instructor in Rotary Wing Aerodynamics years prior) related that he was requested to investigate the wing failure of another Twin Commander, I believe that occurred in Co.? If I recall correctly, the Commander made a mid-field crossing and broke to down wind and had a wing structural failure which was attributed to pilot error causing the overload.? The instructor related that there were also other Commanders?that?had had the same failure. ? What he discovered (and I have the plot somewhere in my class notes, buried ?) was that the stick forces per?G went NEGATIVE at about 4 Gs.? Imagine the yoke coming back in your lap?and the wing fails due to overload, if above Va. (There was an AD issued to require a weight in the control system to pull the stick under G loading?(bob weights?have been ?used?in many aircraft control systems). ? The reason I bring this up is that I still believe the XL light stick forces can easily result excessive G loading and are quite possibly the?REAL reason for the wing failures.? Not that light stick forces are bad, but one has to not be ham fisted above Va. (I previously related giving an older pilot a ride in my XL during a pretty turbulent day and he pushed the stick rapidly nose down?such that I would have gone through the canopy without a seat belt.? This happened during climb out? at about 80 - 90kts and the gusty conditions had caused a pitch up.(still can not believe another pilot would have done that, but possibly his Tomahawk had a much different elevator response).? ? Somehow, some people jumped on the flutter bandwagon, and as another matronics "inputer" stated - "and so it was" ? What really concerns me is that the NTSB might wish to make a "Science Project" (Note)?over additional flutter testing of the XL. They evidently do not wish to accept the successful flutter tests already done by Zenith (see page 6 of the NTSB report).??????????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????? Note: ????????????? A Science Project is where you spend all of your?resources but never come up with a result that is acceptable to the government because additional tests or analytical parameters are ALWAYS?required. ("You only tested (or modeled)?down to -40F.? We?require additional testing at -65F .......and on ....and on ..and ..............").? ? Tony Graziano Buchanan, Tn XL/Jab; N493TG; 483 really great hours in?my XL ? ? ________________________________________________________________________ Email message sent from CompuServe - visit us today at http://www.cs.com ________________________________ Message 4 _____________________________________ Time: 08:40:25 AM PST US From: Bryan Martin Subject: Re: Zenith601-List: Trigger for NTSB letter Unfortunately, the Dutch report that started that grounding was seriously flawed. For instance, one of the accidents cited in that report (in England) didn't even involve a 601XL but rather a 601UL that was obviously the result of the pilot mishandling the aircraft. That report was released before any significant investigation into the Dutch accident had been done. It's almost like the author of that report simply did some cursory research into the design and came across all the rumor, innuendo and ignorant speculation circulating around the net at that time, and based his report on that information. And now, aviation authorities in several other countries are taking action based in part on that flawed Dutch report. Has anybody ever heard the term "garbage in, garbage out"? One of the three greatest lies in history: "I'm from the government, I'm here to help you." On Apr 18, 2009, at 5:19 AM, David Johnson wrote: > There seems to be an awful lot of speculation (and anger) about who > got the NTSB interested in the 601XL. Most of it seems to be > directed at the ZBAG group. > > No-one seems to have mentioned the letter that the Dutch authorities > sent to all civil aviation authorities around the world, basically > saying that the 601XL is not fit to fly. > > Whether this went to the NTSB or the FAA (if the latter, then I > would expect them to pass it on to the NTSB for comment), it is not > something that any bureaucrat could or would ignore. > > I don't have the content of the letter, but notification of it was > published on the Zenair Europe website. > > http://www.zenairulm.com/News/index_files/Page972.htm > > They have published their response, but I believe that it was only > sent to European authorities. > > Dave Johnson > > Ready to test fly - grounded - in limbo (and NOT HAPPY!!) > -- Bryan Martin N61BM, CH 601 XL, RAM Subaru, Stratus redrive. do not archive. ________________________________ Message 5 _____________________________________ Time: 09:10:15 AM PST US From: Bryan Martin Subject: Re: Zenith601-List: Thoughts regarding Flutter Another thing to consider is that the CG of the 601XL shifts rearward as you burn off fuel. So If you make a long cross country flight in a heavily loaded XL, you may discover that the pitch sensitivity has increased significantly when it comes time to land. I have had this experience myself. I was a little surprised when the plane started to porpoise on short final. I realized what was happening and got it settled down fairly quickly, but it did get my attention. I sure am glad I spent the extra money for the confor-foam seats cushions. I can spend four hours in the plane without getting greatly fatigued. I added a bungee cord to the elevator controls to assist with nose up trim. One of these days, I'm going to link it to the flap torque tube to provide some automatic trim adjustment with flap deployment. On Apr 18, 2009, at 9:58 AM, jaybannist@cs.com wrote: > Tony, > > I happen to agree with you. I also think that the elevator is a > more likely source of trouble than the ailerons. Even though the XL > that I flew didn't seem to me to have an overly sensitive elevator, > I have read and heard comments that indicates that it is troublesome > to others. The NTSB letter goes into some detail about the elevator > being progressively effective. It is fairly well accepted that > excessive elevator input can overstress an airframe. In the case of > the XL accidents, a gross elevator movement could very well have > overstressed the wings and made them fail. The NTSB accident report > of the Yuba accident speculated that the first thing to fail was the > horizontal stabilizer, in a downward direction. It seems to me that > a max down elevator could have caused that. I did not see any > mention of whether the Heintz recommended elevator stop had been > added to this airplane. > > This makes me wonder if adding progressive resistance to fore and > aft movement of the stick might make sense to defeat the progressive > effectiveness of the elevator, ie: bungees or springs. what do you > think? > -- Bryan Martin N61BM, CH 601 XL, RAM Subaru, Stratus redrive. do not archive. ________________________________ Message 6 _____________________________________ Time: 11:23:50 AM PST US From: NYTerminat@aol.com Subject: Re: Zenith601-List: Thoughts regarding Flutter But weren't some of these accidents straight and level? Bob Spudis In a message dated 4/18/2009 12:10:49 P.M. Eastern Daylight Time, bryanmmartin@comcast.net writes: --> Zenith601-List message posted by: Bryan Martin Another thing to consider is that the CG of the 601XL shifts rearward as you burn off fuel. So If you make a long cross country flight in a heavily loaded XL, you may discover that the pitch sensitivity has increased significantly when it comes time to land. I have had this experience myself. I was a little surprised when the plane started to porpoise on short final. I realized what was happening and got it settled down fairly quickly, but it did get my attention. I sure am glad I spent the extra money for the confor-foam seats cushions. I can spend four hours in the plane without getting greatly fatigued. I added a bungee cord to the elevator controls to assist with nose up trim. One of these days, I'm going to link it to the flap torque tube to provide some automatic trim adjustment with flap deployment. On Apr 18, 2009, at 9:58 AM, jaybannist@cs.com wrote: > Tony, > > I happen to agree with you. I also think that the elevator is a > more likely source of trouble than the ailerons. Even though the XL > that I flew didn't seem to me to have an overly sensitive elevator, > I have read and heard comments that indicates that it is troublesome > to others. The NTSB letter goes into some detail about the elevator > being progressively effective. It is fairly well accepted that > excessive elevator input can overstress an airframe. In the case of > the XL accidents, a gross elevator movement could very well have > overstressed the wings and made them fail. The NTSB accident report > of the Yuba accident speculated that the first thing to fail was the > horizontal stabilizer, in a downward direction. It seems to me that > a max down elevator could have caused that. I did not see any > mention of whether the Heintz recommended elevator stop had been > added to this airplane. > > This makes me wonder if adding progressive resistance to fore and > aft movement of the stick might make sense to defeat the progressive > effectiveness of the elevator, ie: bungees or springs. what do you > think? > -- Bryan Martin N61BM, CH 601 XL, RAM Subaru, Stratus redrive. do not archive. **************Access 350+ FREE radio stations anytime from anywhere on the web. Get the Radio Toolbar! (http://toolbar.aol.com/aolradio/download.html?ncid=emlcntusdown00000003) ________________________________ Message 7 _____________________________________ Time: 12:03:32 PM PST US From: "Craig Payne" Subject: RE: Zenith601-List: Thoughts regarding Flutter > One of these days, I'm going to link it to the flap torque tube to provide some automatic trim adjustment with flap deployment. There is a little box that does this (although you might consider it overkill): http://www.aircraftextras.com/ -- Craig ________________________________ Message 8 _____________________________________ Time: 04:23:26 PM PST US From: "T. Graziano" Subject: Re: Zenith601-List: Thoughts regarding Flutter Jay, What commonly has been done is to add a mass to the bottom of the stick assembly, usually Tungsten or depleted Uranium to save space. As you change the angle of the stick, the mass tends to pull the stick relatively straight neutral and the more G loads the more force exerted by the mass to center the stick relatively neutral, ---- the more Gs pulled, the more force it takes to hold back the stick; stick forces per G goes up. I don't know if the geometry of the XLs "stick configuration" would permit a mass addition. The Yuba City with the stab failure in a down direction indicates UP elevator. Once the stab fails, the nose pitches violently down, and the wing fails in a relatively down direction - excessive negative Gs. In a good design, it would be a toss up as to what fails first under excessive G loading, the stab or the wing. I believe the Yuba City wing failure speaks volumes about an overstress condition caused by stick input Tony. ----- Original Message ----- From: jaybannist@cs.com To: zenith601-list@matronics.com Sent: Saturday, April 18, 2009 8:58 AM Subject: Re: Zenith601-List: Thoughts regarding Flutter Tony, I happen to agree with you. I also think that the elevator is a more likely source of trouble than the ailerons. Even though the XL that I flew didn't seem to me to have an overly sensitive elevator, I have read and heard comments that indicates that it is troublesome to others. The NTSB letter goes into some detail about the elevator being progressively effective. It is fairly well accepted that excessive elevator input can overstress an airframe. In the case of the XL accidents, a gross elevator movement could very well have overstressed the wings and made them fail. The NTSB accident report of the Yuba accident speculated that the first thing to fail was the horizontal stabilizer, in a downward direction. It seems to me that a max down elevator could have caused that. I did not see any mention of whether the Heintz recommended elevator stop had been added to this airplane. This makes me wonder if adding progressive resistance to fore and aft movement of the stick might make sense to defeat the progressive effectiveness of the elevator, ie: bungees or springs. what do you think? Jay Bannister -----Original Message----- From: T. Graziano To: zenith601-list@matronics.com Sent: Fri, 17 Apr 2009 11:32 pm Subject: Re: Zenith601-List: Thoughts regarding Flutter Additional thoughts, Scott Sounds reasonable. I thought about replacing cables with push rods, but then thought that the natural freq of a rod would probably be lower than a tensioned cable and more likely to resonate. Today as I was up enjoying the sky in my XL, I crossed mid-field and broke to down wind and it reminded my of another reconstructed crash at the crash lab at March AFB during a course I took in Aircraft Accident Investigation at USC thirty years ago. It was an AeroCommander Twin that shed its wings. The physical investigator instructor, (who was also my undergraduate instructor in Rotary Wing Aerodynamics years prior) related that he was requested to investigate the wing failure of another Twin Commander, I believe that occurred in Co. If I recall correctly, the Commander made a mid-field crossing and broke to down wind and had a wing structural failure which was attributed to pilot error causing the overload. The instructor related that there were also other Commanders that had had the same failure. What he discovered (and I have the plot somewhere in my class notes, buried ?) was that the stick forces per G went NEGATIVE at about 4 Gs. Imagine the yoke coming back in your lap and the wing fails due to overload, if above Va. (There was an AD issued to require a weight in the control system to pull the stick under G loading (bob weights have been used in many aircraft control systems). The reason I bring this up is that I still believe the XL light stick forces can easily result excessive G loading and are quite possibly the REAL reason for the wing failures. Not that light stick forces are bad, but one has to not be ham fisted above Va. (I previously related giving an older pilot a ride in my XL during a pretty turbulent day and he pushed the stick rapidly nose down such that I would have gone through the canopy without a seat belt. This happened during climb out at about 80 - 90kts and the gusty conditions had caused a pitch up.(still can not believe another pilot would have done that, but possibly his Tomahawk had a much different elevator response). Somehow, some people jumped on the flutter bandwagon, and as another matronics "inputer" stated - "and so it was" What really concerns me is that the NTSB might wish to make a "Science Project" (Note) over additional flutter testing of the XL. They evidently do not wish to accept the successful flutter tests already done by Zenith (see page 6 of the NTSB report). Note: A Science Project is where you spend all of your resources but never come up with a result that is acceptable to the government because additional tests or analytical parameters are ALWAYS required. ("You only tested (or modeled) down to -40F. We require additional testing at -65F .......and on ....and on ..and .............."). Tony Graziano Buchanan, Tn XL/Jab; N493TG; 483 really great hours in my XL ------------------------------------------------------------------------- ----- Email message sent from CompuServe - visit us today at http://www.cs.com ________________________________ Message 9 _____________________________________ Time: 08:11:22 PM PST US From: LarryMcFarland Subject: Zenith601-List: Cable tensions for the HDS Jeff, Within the Construction Manual for the Zodiac Ch 601, the required cable tension is stated "cable tension 30 - 40 lbs." Larry McFarland 601HDS at www.macsmachine.com ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message zenith601-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Zenith601-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/zenith601-list Browse Digests http://www.matronics.com/digest/zenith601-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.