Puchaz Spinning thread that might be of interest in light of the recent accident.

The behaviour described in a previous message as an "insipient spin" with
the ASH-25 seems to be a very simple early part of a stall.
If ailerons are used close to the Stall AOA, they might seem to work in
reverse, which is consistent with the description given in that message.
This is due to the fact that in the pre-stall, you're already close to the
Stall AOA.
The lowering Aileron (to pick up the low wing) will produce an increase in
the AOA in that part of the low wing, thus exceeding the Stall AOA and
essencially stalling that part (where the aileron is) of the low wing.
In other words : Pre-stall, left wing is low (for instance), right aileron
will stall the left wing tip thus increasing the bank angle and going to a
spiral, an apparent control reversal, easily corrected by :
The correct control input, which is to apply right rudder to pick it up, and
move the stick forward enough the reduce AOA.

This is the reason why instructors teach all students to pick up a low wing
during pre-stall by using Rudder (opposite rudder, for that matter), and not
by using coordinated controls as it is suggested, because the aileron will
work against the intended recovery.
Even if the glider wing was designed with some twist to lower the AOI at the
wingtips, they will still suffer from this reverse effect when in a
pre-stall condition.

All existing airplane and glider literature clearly recomends picking up a
low wing with opposite rudder during pre-stall, along with lowering the
nose.
I have never seen a manual suggesting to pick up a low wing at the pre-stall
with "coordinated controls", it would surprise me very much if the ASH-25
suggested something like that.

What it may be suggesting is that you always use coordinated controls (the
correct use) while thermalling, and if you sense the glider in a pre-stall
condition, lower the nose slightly and use coordinated controls to continue
the turn.

I wrote about this before : While thermalling, if you feel an inpending
stall, it may not be necessary to "dive like mad" to recover.
It may be a simple case of lowering the nose only slightly and maybe
applying some opposite rudder for a few seconds.
If you do it calmly, other gliders in the same thermal won't even notice
that you were about to stall.
Again, any experienced instructor can demonstrate this.

Happy flying.


"Chris OCallaghan" wrote in message
om...
I've noted that many 25s have wing extended wing tips, some factory,
some home built. The vertical stab was designed to some theoritical
maximum... This would be yet another aggrevating factor.

What fascinates me about these reports is the effect in the real world
of the designer's tradeoff between stability and controlability.
Bigger vertical stabs would reduce the likelihood of a spin, but at
the cost of much drag. Less drag is better, but you don't want a
sailplane so unstable that moderate turbulence can flick it into a
spin from a low speed turn. So if you want to give it a good low speed
roll rate, you have to depend on the pilot's proper use of the
powerful rudder he'll need to counteract adverse yaw. But pilots are
people, and we all make mistakes. So the conscientious designer must
needs put enough surface area back there to prevent autorotation so
long as the pilot neutralizes the controls at the first indication of
an insipient stall. Even if the stall progesses, so long as the
controls aren't crossed, it shouldn't lead to a spin.

Little modern gliders seem to reflect this philosophy. As bigger
gliders become more popular among lower time pilots, shouldn't we be
examining their characteristics more carefully? While manuals give
very precise instructions on how to recover from a fully developed
spin, they recommend coordinated use of ailerons and rudder
(accompanied by a forward motion of the stick) to pick up a dropping
wing during the initial phase of a stall, straight ahead or turning.
In other words, the designer is recommending picking up the low wing
so long as it is accompanied by a "firm easing of the control stick
forward." This procedure is recommended because it results in the
minimum loss of height. We were all taught, thouigh, that if the wing
begins drop during a stall, we neutralize the ailerons, ease the stick
forward, and kick opposite rudder. Given the number (I counted 4) of
over the top spin entries noted in another thread, I wonder if we
haven't been to aggressive in preventing the "insipient spin" with
spin recovery control motions.

And as a result, misinterpret any yawing of the nose during a stall to
be the preamble to a spin. I'm splitting hairs. And it's certainly not
the stuff for students to be pondering. They need a one size fits all
recovery. But I'm genuinely interested in just what is going on at the
stall and immediately after, and if our perceptions haven't been
altered by the necessity of the shortcuts we take during training to
get us quickly to the point where we can go teach urselves.
Robert Ehrlich wrote in message
...
Chris OCallaghan wrote:

This is an interesting case. I haven't really thought this through
since stalling is difficult in most properly balanced sailplanes at
high angles of bank. A long wingspan adds yet another aggrevator. But
your speed is higher in a steep turn, thus the vertical stabilizer is
more efficient. And right off hand I can think of several outcomes
that would look like spins, but are, in fact, something else. Think of
a wing over, for example. If you shot the initial 90 degrees of turn
after apex, it would look very much like a spin entry.

Nonetheless, I haven't tried a stall from a coordinated steep turn,
with controls crossed and the yaw string straight. And I won't have a
chance for another month or so...

Perhaps, for the time being, I need to ammend my position to say that
a spin is unlikely in most sailplanes if the ailerons and rudder are
neutralized.

In the meantime, if you have a chance to repeat, see if the instructor
will let the "spin" develop. I'm interested to see if it is really a
spin (I think the chances are good, though, if the controls stay
crossed). Try it again, but at entry, center the ailerons and rudder,
but leave the stick back. That is, add no further aggrevation after
the stall break and see what it does. By the way, how rapid was the
autorotation at stall break? How much change in direction did you
experience before rolling back to level? How much altitude did you
lose, if you took notice? And was there anything unusual about this
particular 25?


There was nothing unusual about this 25, only about myself. It was my
first flight in the ship, I had a very low experience at this time (
100
hours) and had only flown ASK21 and ASK23. This happened twice in the
day
at a low bank angle. There was almost no autorotation or change in
direction. It was rather the feeling that increasing outside stick could
no more counter the overbanking tendancy, but rather increased it,
that made me realize that the inner wing was stalled and the I had to
quickly release back pressure to avoid some mess, so nothing wrong
happened before immediate recovery. My propension to low speed flight
came from my familiarity with the ASK23 whose wing loading is much
lower,
and from the fact that it was a weak day where low speed rather than
high bank angles helps to remain close to the core of thermals, at least
in the ASK23 I was usually flying. It was my first attempt to make a
flight
longer than 5 hours, I felt it was better to try it first with an
instructor
behind me and in a glider in which this may be achieved even in
unfavorable
weather. This last point turned out to be true, all other gliders were
in the hangars when we landed at the end of the day and the duration was
effectively over 5 hours. However I had to wait another season before
getting my silver duration, but this is another story.

BTW I cannot try what you suggest since this 25 is no more in my club,
nor any other club 25 (but 2 private ones) and the instructor in such
a repeat attempt would probably be myself as I got this rating during
last September.

At 09:48 31 January 2004, Arnold Pieper wrote:

The correct control input, which is to apply right
rudder to pick it up, move stick forward enough the
reduce AOA.

Sorry to pull one part of your story out for comment.

Some years ago the British Gliding Association dropped
the term incipient spin and called this 'Stall With
With Wing Drop'.

Most older instructors and pilots were taught as you
decribed to pick up the dropping wing with rudder.


The current BGA instructors manual states:-)

'When a wing drops at the stall it is essential to
unstall the glider before attempting to level the wings.
Once the glider is unstalled, level the wings with
coordinated ailerons and rudder.' Section 18 page 2

In the demonstration and practice section page 18.4.
The instructor is told

'Emphasise

the wings are levelled with coordinated use of ailerons
and rudder, BUT ONLY AFTER the glider is unstalled.'

Spinning is merely the natural consequence of failure
to understand and/or recognise the onset of the problems
caused by flying at or close to the stalling speed.
It is for this reason that students should be taught
both in theory and practice the stall symptoms and
the BGA further stalling exercises. Together with the
dangers of flying at of close to the stall speed in
any phase of their flight.

I agree that in many cases merely relaxing the back
pressure on the stick to regain flying speed can prevent
the onset of stalling the wing and it consequences.


Dave

U=BFytkownik Bill Daniels w wiadomooci do grup =
dyskusyjnych ...
=20
It does make one wonder. I seem to recall something on r.a.s. to the =
effect
that an inspection of a Puch in the USA turned up a metal plate that =
was
adrift somewhere in the rudder control curcuit. This loose plate, it =
was
said, could prevent the rudder from moving back from the fully =
deflected
position. I seem to recall that it was suspected that some of the =
spin-in
accidents might be due to this.

One day I was told about a Puchacz accident at Bielsko in southern =
Poland, many years ago. The trim handle (a small green ball made of =
fabric) went loose and disappeared. The student replaced it with another =
one, but didn't check where's the one which got lost, and then took off =
for a spin training...
The ball has been left inside, and it managed to get into controls, and =
in the moment they were in spin and tried to move stick forward to get =
out of the spin, it locked itself preventing the stick from moving =
forward. The student with instructor kept on pushing the stick, and =
finally hit the ground killing themselves.
Finally it became clear that if they had moved stick back for a second, =
they could survive, because thic could loosen the ball...

I just wonder how the student stupid had to be to not check the glider =
throughly after noticing that the handle has gone.

Regards,


--=20
Janusz Kesik

visit www.leszno.pl - home of the www.css-leszno.it.pl

U=BFytkownik Chris OCallaghan w wiadomooci do =
grup dyskusyjnych =
gle.com...

My understanding is that the Puchaz became popular only for its spin
characteristics.=20

Not only, it's just a very good trainer.

It's easy to put into a spin throughout its cg range.

Because it was designed for that.


--=20
Janusz Kesik

visit www.leszno.pl - home of the www.css-leszno.it.pl

"Janusz Kesik" wrote in message
...

I just wonder how the student stupid had to be to not check the glider
throughly after noticing that the handle has gone.

Three thoughts:
1) I find it courious that the student was doing maintence work on the
glider. and...

2) In exactly the same situation, I wonder if I would have been sufficiently
courious to check all of the deep-dark spaces in the belly of the glider.
Frankly, I am afraid of the answer. Perhaps that is why we let A&P's do
that sort of thing? and...

3) In many gliders it is very difficult to inspect under the floorboards and
back in the tailcone, yet you never really know what may be lurking there,
tools, lost cellphones, critters, etc. I once saw a good-sized snake bail
out of a glider just as it was landing and then slink off quickly,
apparently none the worse for the experience. It was not the first flight
of the day for that ship.

Regards,
Vaughn





--
Janusz Kesik

visit www.leszno.pl - home of the www.css-leszno.it.pl

I see Dave.

I'm courious now :
When you're teaching Stalls and a wing is low just before the stall, you
don't pick it up until AFTER the stall ?

This is not the way it's done in both countries where I fly.


"Dave Martin" wrote in message
...
At 09:48 31 January 2004, Arnold Pieper wrote:

The correct control input, which is to apply right
rudder to pick it up, move stick forward enough the
reduce AOA.

Sorry to pull one part of your story out for comment.

Some years ago the British Gliding Association dropped
the term incipient spin and called this 'Stall With
With Wing Drop'.

Most older instructors and pilots were taught as you
decribed to pick up the dropping wing with rudder.


The current BGA instructors manual states:-)

'When a wing drops at the stall it is essential to
unstall the glider before attempting to level the wings.
Once the glider is unstalled, level the wings with
coordinated ailerons and rudder.' Section 18 page 2

In the demonstration and practice section page 18.4.
The instructor is told

'Emphasise

the wings are levelled with coordinated use of ailerons
and rudder, BUT ONLY AFTER the glider is unstalled.'

Spinning is merely the natural consequence of failure
to understand and/or recognise the onset of the problems
caused by flying at or close to the stalling speed.
It is for this reason that students should be taught
both in theory and practice the stall symptoms and
the BGA further stalling exercises. Together with the
dangers of flying at of close to the stall speed in
any phase of their flight.

I agree that in many cases merely relaxing the back
pressure on the stick to regain flying speed can prevent
the onset of stalling the wing and it consequences.


Dave

On Thu, 29 Jan 2004 00:07:35 UTC, Eric Greenwell
wrote:

: Ian Johnston wrote:


: Personally, I think the tail ends of single seaters sticking out of
: fields and hill sides makes a pretty good attack on that position.
:
: Do these accidents show an inability to: 1) recover from full spins, 2)
: from incipient spins, 3) detect the signs of an impending (but not yet
: incipient) spin, 4) avoid spin precursors entirely?

5) Take spins seriously as a threat.

Ian

On Sat, 31 Jan 2004 14:46:10 +0100, "Janusz Kesik"
wrote:

I just wonder how the student stupid had to be to not check the glider throughly after noticing that the handle has gone.

I wonder if he thought to tell anybody else about the missing knob.


--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

At 19:00 31 January 2004, Arnold Pieper wrote:
I see Dave.

I'm courious now :
When you're teaching Stalls and a wing is low just
before the stall, you
don't pick it up until AFTER the stall ?

This is not the way it's done in both countries where
I fly.


Arnold

Effectively Yes, and it works.

Rather than me try to explain my thoughts and experience
the manual explains the logic quite neatly (18.6)

'Whilst use of the rudder to prevent yaw in the direction
of the down-going wing is a counsel of perfection,
it must be realised that the pilot caused the inadvertent
stall in the first place by inappropriate use of the
controls. He is unlikely to start making skilful or
precise movements now. Do not attempt to use the secondary
effect of the rudder to restore the wings to the level
position. This would introduce yaw which could result
in the glider spinning. The priority must be to unstall
the glider by moving the stick forward.'

There are further spinning exercises including a demonstration
of the changing effect of the rudder at the stall to
emphases this point.

Dave

U=BFytkownik Martin Gregorie w wiadomooci =
do grup dyskusyjnych =
om...

I wonder if he thought to tell anybody else about the missing knob.

Could be...

JK