Spin recovery vs tail design

[Ron Ogden]

I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.

[Andreas Maurer]

On 11 May 2009 16:00:06 GMT, Ron Ogden > wrote:

>I would like to solicit comments on the question: Compared to a standard
>tail configuration such as a 2-33 or Blanik L-13, does the initiation and
>recovery from a spin vary substantially in T-tail (ASK-21 type),
>all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
>to reading and learning.

No significant differences - stick neutral, rudder against direction
of the pin.

Some V-tail gliders require the stick to be pushed fully forward (to
achieve sufficient deflection of the V-tail).

Bye
Andreas

[Wayne Paul]

"Andreas Maurer" > wrote in message ...
> On 11 May 2009 16:00:06 GMT, Ron Ogden > wrote:
>
>>I would like to solicit comments on the question: Compared to a standard
>>tail configuration such as a 2-33 or Blanik L-13, does the initiation and
>>recovery from a spin vary substantially in T-tail (ASK-21 type),
>>all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
>>to reading and learning.
>
> No significant differences - stick neutral, rudder against direction
> of the pin.
>
> Some V-tail gliders require the stick to be pushed fully forward (to
> achieve sufficient deflection of the V-tail).
>

Ron,

Like Andreas, I find no significant dirrerences. My "V" tail HP-14 doesn't require any special technique.

Wayne
HP-14 "6F"
http://www.soaridaho.com/Schreder

[bildan]

On May 11, 10:24*am, "Wayne Paul" > wrote:
> "Andreas Maurer" > wrote in messagenews:3jjg05hpl4e6hth12gegpo24l4718kv571@4ax .com...
> > On 11 May 2009 16:00:06 GMT, Ron Ogden > wrote:
>
> >>I would like to solicit comments on the question: Compared to a standard
> >>tail configuration such as a 2-33 or Blanik L-13, does the initiation and
> >>recovery from a spin vary substantially in *T-tail (ASK-21 type),
> >>all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
> >>to reading and learning.
>
> > No significant differences - stick neutral, rudder against direction
> > of the pin.
>
> > Some V-tail gliders require the stick to be pushed fully forward (to
> > achieve sufficient deflection of the V-tail).
>
> Ron,
>
> Like Andreas, I find no significant dirrerences. *My "V" tail HP-14 doesn't require any special technique.
>
> Wayne
> HP-14 "6F"http://www.soaridaho.com/Schreder

[Nyal Williams[_2_]]

Read the manual for the glider; the spin characteristics were worked out by
a professional test pilo, and the best advice you can get will be in the
operating handbook.

tAt 16:13 11 May 2009, Andreas Maurer wrote:
>On 11 May 2009 16:00:06 GMT, Ron Ogden wrote:
>
>>I would like to solicit comments on the question: Compared to a
standard
>>tail configuration such as a 2-33 or Blanik L-13, does the initiation
and
>>recovery from a spin vary substantially in T-tail (ASK-21 type),
>>all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look
>forward
>>to reading and learning.
>
>No significant differences - stick neutral, rudder against direction
>of the pin.
>
>Some V-tail gliders require the stick to be pushed fully forward (to
>achieve sufficient deflection of the V-tail).
>
>Bye
>Andreas
>

[bildan]

On May 11, 10:24*am, "Wayne Paul" > wrote:
> "Andreas Maurer" > wrote in messagenews:3jjg05hpl4e6hth12gegpo24l4718kv571@4ax .com...
> > On 11 May 2009 16:00:06 GMT, Ron Ogden > wrote:
>
> >>I would like to solicit comments on the question: Compared to a standard
> >>tail configuration such as a 2-33 or Blanik L-13, does the initiation and
> >>recovery from a spin vary substantially in *T-tail (ASK-21 type),
> >>all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
> >>to reading and learning.
>
> > No significant differences - stick neutral, rudder against direction
> > of the pin.
>
> > Some V-tail gliders require the stick to be pushed fully forward (to
> > achieve sufficient deflection of the V-tail).
>
> Ron,
>
> Like Andreas, I find no significant dirrerences. *My "V" tail HP-14 doesn't require any special technique.
>
> Wayne
> HP-14 "6F"http://www.soaridaho.com/Schreder

I would disagree.

Studies done on exactly this in the early 1960's by NASA at Edwards
AFB did show an effect. To understand the finding, consider how the
airflow moves over the tail at a very high angle of attack as in a
well developed spin.

The flow tends to parallel the swept rudder hinge line on a 2-32 or
2-33. The low mounted tail disrupts or blanks some of the air flowing
toward the rudder. The result is a measurable reduction in rudder
effectiveness which manifests itself in a delayed spin recovery.

Swept tails are undesirable at any airspeed below transonic and are
used merely for styling.

A "T" tail with a vertical rudder hinge is a good solution since the
rudder sees clean airflow and the horizontal acts as an end plate on
the fin and rudder. The one caveat is that the "T" tail shouldn't be
in the wings turbulent wake at any achievable angle of attack - else
you risk a "deep stall" phenomenon.

The second best configuration is a low stab/elevator mounted ahead of
the fin as seen in a BG-12 or K-13 so the free flow has unobstructed
access to the rudder at high angles of attack.

Finally, a separate stabilizer and elevator produces more nose down
moment than an all moving "slab" tail which can stall in it's full-
down position. A stab/elevator can also stall but will nonetheless
produce enough nose down moment to break the stall/spin.

This led to the NACA standard spin recovery technique which called for
anti-spin rudder while holding full up elevator until the auto-
rotation slowed and only then applying down elevator. The reasoning
was that full up elevator exposed more of the rudder to high energy
flow.

[sisu1a]

> Read the manual for the glider; the spin characteristics were worked out by
> a professional test pilot, and the best advice you can get will be in the
> operating handbook.

Great advice, although with my Sisu 1a no such manual exists... that
said, it had a very well designed V tail that required no special
considerations for initiating or recovering from spins, and there were
no other indications in flight that would indicate it's unconventional
configuration. Spin recovery was quicker with the flaps retracted
though, so that too was a consideration, although probably not one
specific to V tails.

I personally enjoy spinning ships, and like to do what I call 'spot
spinning', meaning coming out on predetermined headings after a
predetermined number of revolutions... WEEE great fun!! Haven't got
into inverted spins yet though...

-Paul

[Chris Reed[_2_]]

Ron Ogden wrote:
> I would like to solicit comments on the question: Compared to a standard
> tail configuration such as a 2-33 or Blanik L-13, does the initiation and
> recovery from a spin vary substantially in T-tail (ASK-21 type),
> all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
> to reading and learning.
>

The main difference, to the extent that there is any generic difference,
might be that T-tails tend to end up rather more nose down after you've
stopped the spin. However, this may not be true for a particular model
of glider. Also, your timing of the spin recovery will alter this, and
other matters.

Of those I've spun:

K13 (low tail) - quite gentle, recovers into a dive but not a
particularly steep one.

K6cr (low tail) - ditto, though it all happen quicker than a K13.

Puchacz (mid tail) - recovery may be into a dive beyond the vertical and
substantial height loss per turn, but it does exactly what the manuals
say if you perform the recovery properly.

Astir CS (Grob 103, T-tail) - quite gentle, recovers into a steeper dive
than the K13

IS28 (T-tail) - like the Astir, but a bit slower all round.

Open Cirrus (mid tail) - fairly gentle, dive after recovery about as
steep as the Astir. However, you do need FULL rudder to stop the spin
(and the last inch requires a hard push; it feels like you're on the
stop but you're not).

I've read that some V-tails need full forward stick before they recover,
but haven't had the pleasure of flying any.

Of my list I'd say the most "extreme" attitudes on recovery are from the
Puchacz, so from my limited experience the difference in tail
configuration is not the most important factor.

[John Smith]

Primary answer: Use the spin recovery technique which is described in
the AFM.

Secondary answer: All certificated modern gliders will recover with the
"standad procedure", it's a requirement for certification.

That said: Eric Müller was a, no, probably *the* spin expert. He
described the ins and outs of spins in detail in his book "flight
unlimited". According to him, most "conventional" tail designs recover
best when you keep holding the stick back until the rotation stops,
because pushing it forward will blank the rudder. With T-tails it's
exactly the other way: Pushing the stick generates more airflow on the
rudder to stop the rotation. V-Tails are a story by themselves. There
has been at least one fatal accident with a salto which spun into the
ground. Eric was the accident investigator for this case and examined
the spin behaviour of another salto. He found that the salto would only
recover with the stick pushed *fully* forward.

But again, this is the theory, in practice, do whatever the AFM recommends.

[Cats]

On May 11, 5:00*pm, Ron Ogden > wrote:
> I would like to solicit comments on the question: Compared to a standard
> tail configuration such as a 2-33 or Blanik L-13, does the initiation and
> recovery from a spin vary substantially in *T-tail (ASK-21 type),
> all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
> to reading and learning.

If your glider is JAR 22 certified then it will respond to the
standard spin recovery - reverse rudder, stick centrally forwards
(e.g. ailerons neutral) until the spin stop, centralise the rudder and
pull out of the dive. Exactly how it responds depends on the type of
glider and probably the spin itself.

There are also several ways of getting a glider to spin, but AFAIK the
recover is the same for all. For check flights I slowly ease back on
the stick until the nose drops (or it mushes) and kick in with the
rudder. The wing drops, and I have to hold it in to start the spin
proper. I have heard of one club where three ways of getting a glider
(K13) to spin have to be demonstrated.

But, as someone else said, read the manual and talk to instructors.
And if you can get an ASK-21 to spin I suggest you check the cockpit
weights - I don't know anyone who has without the use of tail ballast.

[sisu1a]

> I would like to solicit comments on the question: Compared to a standard
> tail configuration such as a 2-33 or Blanik L-13, does the initiation and
> recovery from a spin vary substantially in *T-tail (ASK-21 type),
> all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
> to reading and learning.

Center of Gravity is critically important when considering spin
characteristics. The same 'docile' ship with a forward CofG can bite
your head off quite easily with an aft CofG, regardless of tail
type... which in my book this is the single most important reason to
fully understand and fully respect the G/G specs for whatever ship you
are in.

Now up to $0.04 on the subject,
-Paul

[John Smith]

sisu1a schrieb:

> Center of Gravity is critically important when considering spin
> characteristics. The same 'docile' ship with a forward CofG can bite

C of G ist critical for spin entry, but for recovering from a sustained
spin, mass distribution is far more important. (The rudder force must
overcome the angular momentum.)

Of course, C of G and mass distribution are somehow related.

[Andreas Maurer[_1_]]

On Mon, 11 May 2009 21:53:53 +0200, John Smith
> wrote:


>Eric was the accident investigator for this case and examined
>the spin behaviour of another salto. He found that the salto would only
>recover with the stick pushed *fully* forward.

I've been doing some spins in the alto myself - the cause for this is
the poor (doenwards) deflection of the outside tail surface, the inner
having sufficient deflection but being blocked by the outer tail
surface.

>But again, this is the theory, in practice, do whatever the AFM recommends.

Always a good advice.
By the way, it's pretty amazing how spin manners change with CG.



Bye
Andreas

[Andreas Maurer[_1_]]

On Mon, 11 May 2009 12:59:17 -0700 (PDT), Cats >
wrote:

>And if you can get an ASK-21 to spin I suggest you check the cockpit
>weights - I don't know anyone who has without the use of tail ballast.

<Raises his hand and yells "Here">

The 21 won't stay in the spin (will enter a spiral dive after 1.5
turns), but even enters a spin with pretty forward CG (up to 30%).

How to reproduce this:
- Start turn in a 15 degrees bank at 130 kp/h
- raise nose 10 degrees over the horizon and keep this attitude. Speed
is going to bleed off
- at 80-82 kph IAS enter full rudder into the direction of the turn
and start to pull back the stick fully to raise pitch attitude slowly
- once the 21 starts to rotate, apply full adverse aileron
- Keep full rudder, adverse aileron and full elevator

Voila - the 21 starts to spin immediately.
You'll find your self in a genuine spin and can practice recovery
techniques. After 1.5 turns it will recover itself into a very steep
spiral dive. Neutralizing the controls will end the spin immediately.





Bye
Andreas

[Andreas Maurer[_1_]]

On Mon, 11 May 2009 23:19:26 +0200, John Smith
> wrote:

>C of G ist critical for spin entry, but for recovering from a sustained
>spin, mass distribution is far more important. (The rudder force must
>overcome the angular momentum.)

Interesting noone has mentiond flap setting yet - setting the flaps to
negative is by far the best way to quicken up the spin recovery.

I guess pretty many pilots here have flown the ASW-20 - recovering it
with setting 4 (zhermal setting) with a medium to rearward CG ca take
up to 2 turns, but with flaps 1 (fully negative) recovery takes at
maximum 0.75 turns.


Bye
Andreas

[Darryl Ramm]

On May 11, 3:19*pm, Andreas Maurer > wrote:
> On Mon, 11 May 2009 23:19:26 +0200, John Smith
>
> > wrote:
> >C of G ist critical for spin entry, but for recovering from a sustained
> >spin, mass distribution is far more important. (The rudder force must
> >overcome the angular momentum.)
>
> Interesting noone has mentiond flap setting yet - setting the flaps to
> negative is by far the best way to quicken up the spin recovery.
>
> I guess pretty many pilots here have flown the ASW-20 - recovering it
> with setting 4 (zhermal setting) with a medium to rearward CG ca take
> up to 2 turns, but with flaps 1 (fully negative) recovery takes at
> maximum 0.75 turns.
>
> Bye
> Andreas

Not surprising at all - it would surprise me if anybody really wants
to teach this. Lets see -

- A desire to teach a standardized recovery
- Don't distract people with grabbing for a handle while under stress
(or if not stress just physically being thrown around a little)
- Likelyhood of grabbing the wrong handle (esp. if transitioning from
another ship) and just moving it (i.e. opening full spoilers)
- With full negative flap what happens to increased likelihood of
entering another/reverse spin if the pilot recovers too "hard"?

Darryl

[Andreas Maurer[_1_]]

On Mon, 11 May 2009 09:53:56 -0700 (PDT), bildan >
wrote:


>This led to the NACA standard spin recovery technique which called for
>anti-spin rudder while holding full up elevator until the auto-
>rotation slowed and only then applying down elevator. The reasoning
>was that full up elevator exposed more of the rudder to high energy
>flow.

Trying this method in nearly any glider is a very safe way to get
killed.

I am pretty sure that most glasss gliders of the least 40 years will
not recover from a spin if the elevator is held fully up during the
recovery attempt - they simply are not going to stop rotation quickly
enough.









Bye
Andreas

[bildan]

On May 11, 4:30*pm, Andreas Maurer > wrote:
> On Mon, 11 May 2009 09:53:56 -0700 (PDT), bildan >
> wrote:
>
> >This led to the NACA standard spin recovery technique which called for
> >anti-spin rudder while holding full up elevator until the auto-
> >rotation slowed and only then applying down elevator. *The reasoning
> >was that full up elevator exposed more of the rudder to high energy
> >flow.
>
> Trying this method in nearly any glider is a very safe way to get
> killed.
>
> I am pretty sure that most glasss gliders of the least 40 years will
> not recover from a spin if the elevator is held fully up during the
> recovery attempt - they simply are not going to stop rotation quickly
> enough.
>
> Bye
> Andreas

Read more carefully. I didn't write anything about trying a recovery
with full up elevator. I wrote "until the auto-rotation slowed and
only then applying down elevator"

[sisu1a]

> Interesting noone has mentiond flap setting yet - setting the flaps
to
> negative is by far the best way to quicken up the spin recovery.

Actually flap settings are touched on in my first $0.02 I pitched in 9
posts ago... although I make no mention of negative flaps I simply
state that retracting them hastens the recovery process in it, and
that it was probably not specific to V tails... The Fowler flaps on my
Sisu had 0-20 deg, but no neg... but- flap setting as a concept was at
least mentioned :)

Feeling like I only pitched in $0.04 (OK, maybe $0.05), but for an
actual price of $0.06,
-Paul

[John Smith]

Andreas Maurer wrote:

> Interesting noone has mentiond flap setting yet - setting the flaps to
> negative is by far the best way to quicken up the spin recovery.

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

[John Smith]

Andreas Maurer wrote:

> Not to mention that a significant forward elevator is going to induce
> some serious negative G once the glider snapped out of the spin.

With the ASK-21 you can find yourself in a sudden inverted spin if you
push the stick fully forward.

[Andreas Maurer[_1_]]

On Mon, 11 May 2009 15:51:27 -0700 (PDT), bildan >
wrote:

>Read more carefully. I didn't write anything about trying a recovery
>with full up elevator. I wrote "until the auto-rotation slowed and
>only then applying down elevator"

I know - what i wanted to say is that the rotation isn't going to slow
down significantly in many gliders if you keep the elevator pulled up.

Not to mention that a significant forward elevator is going to induce
some serious negative G once the glider snapped out of the spin.

Bye
Andreas

[Andreas Maurer[_1_]]

On Mon, 11 May 2009 15:28:18 -0700 (PDT), Darryl Ramm
> wrote:

>Not surprising at all - it would surprise me if anybody really wants
>to teach this. Lets see -
>
>- A desire to teach a standardized recovery
>- Don't distract people with grabbing for a handle while under stress
>(or if not stress just physically being thrown around a little)
>- Likelyhood of grabbing the wrong handle (esp. if transitioning from
>another ship) and just moving it (i.e. opening full spoilers)
>- With full negative flap what happens to increased likelihood of
>entering another/reverse spin if the pilot recovers too "hard"?

All of your points are right on the spot.
However, I really teach this.

The command is simple: "Push the flap lever forward".
The other levers on the left side of the cockpit (gear and airbrakes)
cannot be pushed forward, so no harm can be done by grabbing the wrong
lever.

Apart from the quicker recovery in negative flaps, there's one much
more important point why it's absolutely necessary (in my opinion!) to
move the flap lever forward as standard part of the spin recovery
procedure:

In nost gliders (certainly all Schleicher ones), it is nearly
impossible with positive flaps NOT to exceed the Vne for this flap
setting during the recovery.

And pulling significant G with too-positive flap setting is the best
way to induce extremely high torsional load on the wing... with all
its consequences.

At the speeds during the recovery even the most negative flap setting
won't lead to a secondary stall.




Bye
Andreas

[Andreas Maurer[_1_]]

On Mon, 11 May 2009 16:07:29 -0700 (PDT), sisu1a
> wrote:

>Actually flap settings are touched on in my first $0.02 I pitched in 9
>posts ago...

Hey... here in Europe we only move flaps positive and flaps negative,
we don't retract them... we don't even know these fowler type things
(apart from the ones on this Blanik thing)... ;)


> although I make no mention of negative flaps I simply
>state that retracting them hastens the recovery process in it, and
>that it was probably not specific to V tails... The Fowler flaps on my
>Sisu had 0-20 deg, but no neg... but- flap setting as a concept was at
>least mentioned :)

:)

Let's wait tll the first one points out to retract the Schempp-Hirth
type airbrakes due to structural reasons...

Bye
Andreas

[Andreas Maurer[_1_]]

On Tue, 12 May 2009 01:27:30 +0200, John Smith
> wrote:


>With the ASK-21 you can find yourself in a sudden inverted spin if you
>push the stick fully forward.

So far I didn't dare to try this... :)


Bye
Andreas

[Andreas Maurer[_1_]]

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

[Don Johnstone[_4_]]

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.

[Eric Greenwell]

Darryl Ramm wrote:
> On May 11, 3:19 pm, Andreas Maurer > wrote:

>> I guess pretty many pilots here have flown the ASW-20 - recovering it
>> with setting 4 (zhermal setting) with a medium to rearward CG ca take
>> up to 2 turns, but with flaps 1 (fully negative) recovery takes at
>> maximum 0.75 turns.
>>
>> Bye
>> Andreas
>
> Not surprising at all - it would surprise me if anybody really wants
> to teach this. Lets see -
>
> - A desire to teach a standardized recovery
> - Don't distract people with grabbing for a handle while under stress
> (or if not stress just physically being thrown around a little)
> - Likelyhood of grabbing the wrong handle (esp. if transitioning from
> another ship) and just moving it (i.e. opening full spoilers)
> - With full negative flap what happens to increased likelihood of
> entering another/reverse spin if the pilot recovers too "hard"?

Wouldn't the chance of another/reverse spin be even greater in a
positive flap setting if the pilot recovers too "hard"? What I noticed
in my ASW 20 and my ASH 26 E is going to negative flap immediately
stopped the spin and there is nothing to "recover" from except a "mild"
nose down attitude. I haven't tried waiting more than a half turn;
perhaps waiting a full turn or more might be different, but I'm only
concerned about immediate recovery attempts.

--
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

[Ron Ogden]

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!

[Surfer!]

In message >, Andreas Maurer
> writes
>On Mon, 11 May 2009 09:53:56 -0700 (PDT), bildan >
>wrote:
>
>
>>This led to the NACA standard spin recovery technique which called for
>>anti-spin rudder while holding full up elevator until the auto-
>>rotation slowed and only then applying down elevator. The reasoning
>>was that full up elevator exposed more of the rudder to high energy
>>flow.
>
>Trying this method in nearly any glider is a very safe way to get
>killed.
>
>I am pretty sure that most glasss gliders of the least 40 years will
>not recover from a spin if the elevator is held fully up during the
>recovery attempt - they simply are not going to stop rotation quickly
>enough.

I heard about some folks spinning a K21 with the weights kit, and they
nearly ended up bailing out. Later the instructor concluded that they
hadn't been pushing the stick far enough forwards during the
unsuccessful attempts.

--
Surfer!
Email to: ramwater at uk2 dot net

[John Smith]

> 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[_2_]]

"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.
>

[John Smith]

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[_2_]]

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.
>

[John Smith]

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.

[Nyal Williams[_2_]]

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.

[John Smith]

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.

[Eric Greenwell]

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

[TonyV[_2_]]

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.

[Don Johnstone[_4_]]

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.