Spin recovery vs tail design

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.

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

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
procedu

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

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

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

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.

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

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!

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