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#21
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Aeronca 11AC Chief Project FS
"Jim Logajan" wrote in message .. . I found it notable for the simple fact that it is the only CH-801 fatal accident I could find in the NTSB database. Yes, but I recall that it is difficult to rely on the NTSB database for homebuilt model statistics because model designations for like aircraft are not reliably the same. For example: somebody's CH-801 could be a "Smith 801 Rocket" or whatever. Vaughn |
#22
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Aeronca 11AC Chief Project FS
On 2008-06-23, Victor Bravo wrote:
You can walk up to a CH601 and move the tip of the horizontal stabilizer fore and aft a very disturbing amount (I have on three separate aircraft). What do you consider a "very disturbing amount"? I want to try it on my Zodiac. -- Jay Maynard, K5ZC http://www.conmicro.com http://jmaynard.livejournal.com http://www.tronguy.net Fairmont, MN (FRM) (Yes, that's me!) AMD Zodiac CH601XLi N55ZC (got it!) |
#23
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Aeronca 11AC Chief Project FS
In article ,
Jay Maynard wrote: On 2008-06-23, Victor Bravo wrote: You can walk up to a CH601 and move the tip of the horizontal stabilizer fore and aft a very disturbing amount (I have on three separate aircraft). Several years ago that was discovered on the Cherokee Six that I fly. The airplane was immediately grounded and put into maintenance to have the bushings replaced. |
#24
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Aeronca 11AC Chief Project FS
On Mon, 23 Jun 2008 22:19:42 GMT, "Vaughn Simon"
wrote: "Jim Logajan" wrote in message .. . I found it notable for the simple fact that it is the only CH-801 fatal accident I could find in the NTSB database. Yes, but I recall that it is difficult to rely on the NTSB database for homebuilt model statistics because model designations for like aircraft are not reliably the same. For example: somebody's CH-801 could be a "Smith 801 Rocket" or whatever. I looked in my 1998-2006 database and found five CH-801 accidents, of which this one was the only fatal. The five planes were registered as: Zenith 801 CH-801 STOL CH 801 Zenith CH801 CH801 "*801*" as a search team would have picked these up. I ran "*801*" against the total FAA registration database (Jan 4 2008 edition) and got 53 hits. Only three planes didn't have either "CH", "Zenair", or "Zenith" as part of their model name, and just one was obviously not a Zenith 801 (certification date in mid-80s). Ron Wanttaja |
#25
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Aeronca 11AC Chief Project FS
On Tue, 24 Jun 2008 00:55:06 GMT, Jay Maynard
wrote: On 2008-06-23, Victor Bravo wrote: You can walk up to a CH601 and move the tip of the horizontal stabilizer fore and aft a very disturbing amount (I have on three separate aircraft). What do you consider a "very disturbing amount"? I want to try it on my Zodiac. All considered, there is NOT a safer plane design flying than the Zenair Zodiac 601. PERIOD. For the number sold and flying, the fatalities have been minimal - and none have been attributed to the design of the plane. ** Posted from http://www.teranews.com ** |
#26
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Aeronca 11AC Chief Project FS
On Jun 23, 5:55 pm, Jay Maynard
wrote: What do you consider a "very disturbing amount"? I want to try it on my Zodiac. Jay, I moved the tip of the stabilizer fore and aft about three inches, which resulted in the four main stabilizer mounting tabs moving in a twisting/shearing motion relative to each other. I first did this on a 601XL which was built by one of our local EAA chapter members. I thought for sure that the guy had forgotten a piece of metal someplace. But one of our other EAA chapter members is an engineer, he read the plans, and determined the tail attach had been built per plans. Then I tried to duplicate this fore-aft movement on a CH 701, which uses a similar mounting, and was able to move it some amount as well. Then I tried it on another 601XL which was built by the factory (QSP in Cloverdale, CA) and was able to move the stabilizer fore and aft an inch or two, again with the twisting/shearing motion on the stabilizer mounting tabs. I am definitely NOT an engineer, and cannot run any numbers or make any authoritative statements about the structure. Chris Heintz IS an engineer, and supposedly a very good one. But I will say that if/when I build my 701 I will research and add some more aluminum back there to stiffen and reinforce the structure so you can't move the stab tips fore and aft. There are probably little or no assymetrical NORMAL FLIGHT LOADS on it, but small movements back and forth caused by air buffeting and vibration over some period of time can easily cause the metal to become brittle and/or crack. Speaking as an AMATEUR mechanic, I believe the problem is that the stabilizer mounting tabs are not supported against bending or movement in one or two directions, and the tabs stick up too far above the upper longeron for the off-axis loads to be totally absorbed by the thickness of the metal. Real engineers are more than welcome to correct me, disagree, or tell me the problem is valid but far too small to cause a problem. Call me a dinosaur, but I don't think you should be able to move the stabilizer on an airplane that far fore and aft while watching the fuselage structure twist from medium force hand movements. And in response to what someone else posted, the 601 is not the best or safest airplane by any stretch. The DC-3 / C-47 has a 70+ year record of flying without ever one single structural failure. |
#27
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Aeronca 11AC Chief Project FS
Jay Maynard wrote:
On 2008-06-23, Victor Bravo wrote: You can walk up to a CH601 and move the tip of the horizontal stabilizer fore and aft a very disturbing amount (I have on three separate aircraft). What do you consider a "very disturbing amount"? I want to try it on my Zodiac. Jay, he's full of crap. The Horz Stab has four attach points. It doesn't move at all unless you count the fact that the entire airplane moves when you move it. |
#28
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Aeronca 11AC Chief Project FS
On 2008-06-24, Victor Bravo wrote:
On Jun 23, 5:55 pm, Jay Maynard wrote: What do you consider a "very disturbing amount"? I want to try it on my Zodiac. Jay, I moved the tip of the stabilizer fore and aft about three inches, which resulted in the four main stabilizer mounting tabs moving in a twisting/shearing motion relative to each other. I was not able to move mine more than a half inch at most. -- Jay Maynard, K5ZC http://www.conmicro.com http://jmaynard.livejournal.com http://www.tronguy.net Fairmont, MN (FRM) (Yes, that's me!) AMD Zodiac CH601XLi N55ZC (got it!) |
#29
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Aeronca 11AC Chief Project FS
On 2008-06-24, Gig 601Xl Builder wrote:
Jay Maynard wrote: On 2008-06-23, Victor Bravo wrote: You can walk up to a CH601 and move the tip of the horizontal stabilizer fore and aft a very disturbing amount (I have on three separate aircraft). What do you consider a "very disturbing amount"? I want to try it on my Zodiac. Jay, he's full of crap. The Horz Stab has four attach points. It doesn't move at all unless you count the fact that the entire airplane moves when you move it. Actually, mine did move a little bit, but not the three inches he said he saw. -- Jay Maynard, K5ZC http://www.conmicro.com http://jmaynard.livejournal.com http://www.tronguy.net Fairmont, MN (FRM) (Yes, that's me!) AMD Zodiac CH601XLi N55ZC (got it!) |
#30
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Aeronca 11AC Chief Project FS
On Jun 24, 6:32 am, Gig 601Xl Builder
wrote: Jay, he's full of crap. The Horz Stab has four attach points. It doesn't move at all unless you count the fact that the entire airplane moves when you move it. I am indeed full of crap sometimes, but not this time. The four attach points that Dr. Einstein here was referring to are the exact parts that moved slightly when I pulled on the stabilizer tip. Here's a graphic visual example for the mechanically challenged: Imagine that the four stabilizer mounting tabs on top of the fuselage were all 12 inches tall, instead of the one or two inches tall that they actually are... So the horizontal tail would be mounted a foot above the top of the fuselage. Under this example, when you tried to move one stabilizer tip forward and the other one aft, it would move easily, and the four foot-long imaginary mounting tabs would all move back and forth a little as you twist the tail left and right (looking from above). In order to prevent this type of movement, you would have to rivet sheets of aluminum between these tall stabilizer supports to make the system "torsionally stable". You would be riveting "shear webs" between the stab supports, to oppose the shearing (and then twisting) relative motion. Now of course the mounting tabs are not a foot tall, so you cannot swing the stabilizer tip fore and aft with one finger like you could if it was a foot tall. But the stabilizer mounting tabs ARE an inch or two above the fuselage, and this distance is NOT braced in shear or twisting. So you CAN move it fore and aft a little, and when you do this you CAN see the mounting tabs move relative to each other a little. Ladies and Gentlemen, you CANNOT move the stabilizer back and forth this way on an undamaged Cessna, Taylorcraft, Champ, or Beech. You cannot do it on a Luscombe, you cannot do it on an undamaged Piper Cherokee, and you cannot do it on a Maule and you cannot do it on a Grumman Yankee. I can go on if I have not made the point clearly enough. The stabilizer mounting system on the 601 and possibly the 701 is in my opinion not rigid enough. The tabs are not braced against shearing or twisting. There is no reason you should be able to move the stabilizer back and forth on a standard configuration light aircraft like that. When you move it like this, you are slightly bending the stabilizer mounting tabs (and the attach structure on the fuselage) back and forth a little bit each time. |
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