rtdin
Joined: 16 Mar 2008
Posts: 46
Location: Florida panhandle
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 Posted: Fri Mar 13, 2009 7:25 pm Post subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 |
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I prefer to deal in facts rather than insults, but its not as much fun. This is serious business. Look at several in flight breakups. Oakdale CA two years ago, Yuba City, CA Nov 06 and Polk City, FL last year.
It has been alleged that they were caused by improper control inputs. Oakdale happened in the traffic pattern with a 17,000+ hour CFI. Polk City was as the pilot was about to join the published arrival route for Sun N Fun (100KTS and 1200 feet). Yuba City happened in ideal weather as a mature, experienced pilot was giving his wife her first ride in a new airplane. The story goes, if you believe the allegations that while in straight and level cruise, this pilot impulsively made an excessive and abrupt control input that caused the tail to break off. The NTSB's Probable Cause is rich in data but a bit vague.
Aileron flutter has never been proven by the NTSB. It seems to be an area worthy of investigation. The design has never been tested for this to my knowledge. Why do I think that flutter is a possibility?
1. ZBAG (Terry Phillips did the leg work) has compiled first person flutter reports. They are available at http://groups.yahoo.com/group/ZBAG/files/ click on "601XL Flutter Compendium." Flutter has occurred in the ailerons.
2. Examination of my plans by a retired Aerodynamicist that I know. He tells me that a control surface with its entire mass aft of the hinge is prone to flutter. I told him that proper cable tension was required. No, I will not tell you how to reach Ron, he's retired and he will not submit to cross examination. He does have an awesome C.V. and I take his word as the truth. In fact, he made a flat statement that "If the CG of the surface is ahead of the hinge, flutter cannot happen!" He did like the design.
3. Sonex and Thorp T-18 have almost identical ailerons. Except that they are balanced. They have never had issues despite their higher speeds.
It is welcomed news that a French airframe is to be tested in a wind tunnel. A first. It could lead to redesigned ailerons. I also want to see what breaks when it is load tested. Perhaps using CH's approved material substitutions can somewhat fix things if needed. (Zenair News #129 Mar/Apr 2002) I wish them good luck.
Bob Dingley
601XL/Lyc starting wings
Do not archive
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A Good Credit Score is 700 or Above. Se39616x1201372437/aol?redir=http:%2F%2Fwww.freecreditreport.com%2Fpm%2Fdefault.aspx%3Fsc%3D668072%26hmpgID%3D62%26bcd%3DfebemailfooterNO62) [quote][b]
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