Spin recovery vs tail design

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

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.

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

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

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

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

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

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"

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

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.