Spin recovery vs tail design

On Tue, 12 May 2009 01:25:24 +0200, John Smith
wrote:


It may quicken up the recovery, but JAR-22 requires a sailplane to
recover with any flap setting.

Indeed - but many gliders who are still popular were designed before
JAR-22.
I'm always amazed about how much easier the ASW-27 handles in this
regard compared to a, say, ASW-20.

Bye
Andreas

At 23:54 11 May 2009, Andreas Maurer wrote:
On Tue, 12 May 2009 01:25:24 +0200, John Smith
wrote:


It may quicken up the recovery, but JAR-22 requires a sailplane to
recover with any flap setting.

Indeed - but many gliders who are still popular were designed before
JAR-22.
I'm always amazed about how much easier the ASW-27 handles in this
regard compared to a, say, ASW-20.

Bye
Andreas

Andreas is correct, the ASW17 was extremely reluctant to recover from a
spin in anything above 0 flap and if it did recover the flap speed would
be exceeded in the recovery a loose loose situation. I suspect for this
reason the spin recovery action was:

1 Flaps to a non positive setting
2 Full opposite rudder
3 Pause
4 Stick progressively forward until the spinning stops
5 Recover

I have never flown a Nimbus but I am told it is much the same.

The pause between the application of rudder and moving the stick forward
is frequently ommitted in modern teaching but there are valid reasons for
it's inclusion. Having said that in most gliders, Puchaz excepted, as
soon as the back pressure is released the glider stops spinning.
The only glider I have ever flown that spun properly was the Slingsby
Swallow which would wang round like a good un until the full recovery
action was taken.

At 23:54 11 May 2009, Andreas Maurer wrote:
On Tue, 12 May 2009 01:25:24 +0200, John Smith
wrote:


It may quicken up the recovery, but JAR-22 requires a sailplane to
recover with any flap setting.

Indeed - but many gliders who are still popular were designed before
JAR-22.
I'm always amazed about how much easier the ASW-27 handles in this
regard compared to a, say, ASW-20.

Bye
Andreas
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. My club has one with the spin kit and we look
forward to practicing but it is better to do so fully prepared with
knowledge of the experiences others have had. Thanks!

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.

"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.

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.

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.

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.