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#31
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Spin recovery vs tail design
Thanks to all who have contributed to answering my original question. I
am especially interested in the comments about the ASK-21, especially in reference to changes in how it behaves as the spin continues through more than one or two turns. The short answer is: With all legal loading it recovers by the book from as many turns as your or your student's wallet allows. The somewhat longer answer is that usually it recovers in less than half a turn, but in certain special circumstances recovery may take up to two turns. This will frighten you if you aren't prepared, but the ASK *will* eventually recover. Some people will tell you that the ASK may bite you; actually, it will not, but probably those people have experienced a longer than expected recovery delay. (Or more probably have been told the story from somebody who knows somebody who knows somebody...) The longest answer is that a long time ago there has been a spin accident with a cadet of the USAF academy. Subsequently the USAF topk the ASK 21 through a thorough spin test program, in which they found what I wrote above. Schleicher will probably send you a copy of the 120 page report if you kindly ask them. One more thing: Outward ailerons will flatten the spin considerably which doesn't help on recovery. I've never tried whether it will recover at all from that flat attitude. |
#32
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Spin recovery vs tail design
"One more thing: Outward ailerons will flatten the spin considerably which
doesn't help on recovery." What does that mean? At 07:44 12 May 2009, John Smith wrote: Thanks to all who have contributed to answering my original question. I am especially interested in the comments about the ASK-21, especially in reference to changes in how it behaves as the spin continues through more than one or two turns. The short answer is: With all legal loading it recovers by the book from as many turns as your or your student's wallet allows. The somewhat longer answer is that usually it recovers in less than half a turn, but in certain special circumstances recovery may take up to two turns. This will frighten you if you aren't prepared, but the ASK *will* eventually recover. Some people will tell you that the ASK may bite you; actually, it will not, but probably those people have experienced a longer than expected recovery delay. (Or more probably have been told the story from somebody who knows somebody who knows somebody...) The longest answer is that a long time ago there has been a spin accident with a cadet of the USAF academy. Subsequently the USAF topk the ASK 21 through a thorough spin test program, in which they found what I wrote above. Schleicher will probably send you a copy of the 120 page report if you kindly ask them. One more thing: Outward ailerons will flatten the spin considerably which doesn't help on recovery. I've never tried whether it will recover at all from that flat attitude. |
#33
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Spin recovery vs tail design
Nyal Williams wrote:
"One more thing: Outward ailerons will flatten the spin considerably which doesn't help on recovery." What does that mean? First it probably means bad terminology. Second, it means that the pitch attitude of the ASK in the spin depends on aileron position. Play enough with the ailerons and you will find yourself in something like a flat spin which may be reluctant to recovery. But you can always continue to play with the ailerons until you'll find yourself in a normal spin again. |
#34
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Spin recovery vs tail design
I've never tried this, but I have wondered whether adding downward
deflected aileron on the outside wing during a spin might 1) add drag that would slow the rotation, stall that wing and further reduce the asymmetric lift, and thus aid in stopping the spin. Comments, anyone? At 12:25 12 May 2009, John Smith wrote: Nyal Williams wrote: "One more thing: Outward ailerons will flatten the spin considerably which doesn't help on recovery." What does that mean? First it probably means bad terminology. Second, it means that the pitch attitude of the ASK in the spin depends on aileron position. Play enough with the ailerons and you will find yourself in something like a flat spin which may be reluctant to recovery. But you can always continue to play with the ailerons until you'll find yourself in a normal spin again. |
#35
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Spin recovery vs tail design
Nyal Williams wrote:
I've never tried this, but I have wondered whether adding downward deflected aileron on the outside wing during a spin might 1) add drag that would slow the rotation, stall that wing and further reduce the asymmetric lift, and thus aid in stopping the spin. Spins are aerodynamically extremely complex and each aircraft type reacts differently. |
#36
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Spin recovery vs tail design
At 13:56 12 May 2009, John Smith wrote:
Nyal Williams wrote: I've never tried this, but I have wondered whether adding downward deflected aileron on the outside wing during a spin might 1) add drag that would slow the rotation, stall that wing and further reduce the asymmetric lift, and thus aid in stopping the spin. Spins are aerodynamically extremely complex and each aircraft type reacts differently. No question; that's why it's important to read the POH. |
#37
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Spin recovery vs tail design
To answer your question: Outside aileron often flattens the spin because
it increases the drag on the inner wing, this accelerates the rotation, which increases the centrifugal forces and therefore flattens the spin. The consequence is twofold: The angular momentum increases while the rudder becomes less effective to the point that the rotation cannot be stopped anymore. |
#38
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Spin recovery vs tail design
John Smith wrote:
To answer your question: Outside aileron often flattens the spin because it increases the drag on the inner wing, this accelerates the rotation, which increases the centrifugal forces and therefore flattens the spin. The consequence is twofold: The angular momentum increases while the rudder becomes less effective to the point that the rotation cannot be stopped anymore. By "outside aileron", I assume you mean "the aileron motion achieved by moving the stick towards the outside of the turn/spin". Sometimes that is called "top aileron", as when you are in a turn, and the outside wing is the high wing. -- Eric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * Sections on Mode S, TPAS, ADS-B, Flarm, more * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#39
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Spin recovery vs tail design
John Smith wrote:
Spins are aerodynamically extremely complex and each aircraft type reacts differently. "Spins are a normal mode of flight, unsuitable for landing". Unknown British aerodynamicist (sp?). Tony V. |
#40
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Spin recovery vs tail design
At 13:56 12 May 2009, John Smith wrote:
Spins are aerodynamically extremely complex and each aircraft type reacts differently. One too many words in that statement, delete the word type. |
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