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

[countertroll]

Ian,

the point of my link was to show that you will not spin from
coordinated flight. If you want to spin, at some point you'll need to
make a yaw movement, either with rudder or aileron, and for most
gliders, some of each. If the yaw string stays straight throughout the
stall break, there isn't enough yaw motion to achieve autorotation.

I suspect those who think they can enter a spin from balanced flight
have one of two things happening:

1. They are misusing the controls at the moment of the stall break,
creating yaw through aileron drag by instinctively trying to lift the
dropping wing, or by feeding in rudder. In either case, these are very
bad habits if done unconsciously.

2. They are entering spiral dives and misidentifying them as insipient
spins. Since the insipient phase looks much the same this isn't
surprising, and one can recover early in the spiral dive with the same
control inputs used for spin recovery; however, recognition and
appropriate response will save many feet of altitude loss.

This is worth thinking through. If a sailplane can spin from
coordinated flight, then at any given moment you are at risk of losing
500 to 1000 feet in a matter of seconds. This is based on the notion
that you have absolutely no control over the process save recognition
and recovery. But your use of the controls are of paramount importance
during an unexpected stall, the result of turbulence or distraction.
If your instinctive reaction is to nuetralize the controls, you've
removed the aggrevation that will take an aircraft past its "tipping"
point into autorotation. This is the classic compromise between
stability and controlability.

If we flew aircraft so unstable they could enter a spin without
control inputs, we'd all be hard pressed to justify the risks we would
face while flying.

"Ian Johnston" wrote in message news:cCUlhtvFIYkV-pn2-O04tsSrmcyTw@localhost...
On Mon, 26 Jan 2004 16:59:56 UTC, (Chris
OCallaghan) wrote:

: To review the importance of coordination in spin avoidance

Personally I rather like the spin entries from balanced flight. Very
thrilling.

Ian

--

On Tue, 27 Jan 2004 12:35:43 UTC, (Chris
OCallaghan) wrote:

: the point of my link was to show that you will not spin from
: coordinated flight.

Tight turn. Slow speed. String in the middle. Pull up sharply as if
another glider has just cut into the thermal. Whoops. Well, it works
in a Bocian, anyway.

Ian
--

Ian Johnston wrote:

On Tue, 27 Jan 2004 12:35:43 UTC, (Chris
OCallaghan) wrote:

: the point of my link was to show that you will not spin from
: coordinated flight.

Tight turn. Slow speed. String in the middle. Pull up sharply as if
another glider has just cut into the thermal. Whoops. Well, it works
in a Bocian, anyway.

Ian
--

Another way I experienced it during my 1st flight in an ASH25 (with
an instructor in the back seat of course). Circling in a thermal, with
just to much aft stick than approriate. Speed slowly decayed (slowly
beacause the hight weight and inertia of the glider), induced roll
and yaw slowly increased, needing more and more inside rudder and
outside stick, up to the point where a incipent spin started, immediateley
stopped by releasing back pressure and centralizing ailerons and rudder.
At the time of departure, stick and rudder were strongly crossed,
but the flight was coordinated and the yaw string in the middle.

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?

Robert Ehrlich wrote in message ...
Ian Johnston wrote:

On Tue, 27 Jan 2004 12:35:43 UTC, (Chris
OCallaghan) wrote:

: the point of my link was to show that you will not spin from
: coordinated flight.

Tight turn. Slow speed. String in the middle. Pull up sharply as if
another glider has just cut into the thermal. Whoops. Well, it works
in a Bocian, anyway.

Ian
--

Another way I experienced it during my 1st flight in an ASH25 (with
an instructor in the back seat of course). Circling in a thermal, with
just to much aft stick than approriate. Speed slowly decayed (slowly
beacause the hight weight and inertia of the glider), induced roll
and yaw slowly increased, needing more and more inside rudder and
outside stick, up to the point where a incipent spin started, immediateley
stopped by releasing back pressure and centralizing ailerons and rudder.
At the time of departure, stick and rudder were strongly crossed,
but the flight was coordinated and the yaw string in the middle.

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.

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.

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.

I'll take your word for it... stalling from a tight turn is difficult
unless the elevator is powerful or the cg well back. However, the next
time you do this, keep the stick back, ailerons and rudder neutral. If
it spins you should be able to let it go through 3 or 4 full rotations
without building up speed. Count them, and let me know if that's the
case. I'll want to find one an fly it.

I suspect there are sailplanes out there without adequate vertical
stabilizers, or, conversely, appropriate washout in the wing. But I
hope not many, and it would serve us all to know which ones they are.

"Ian Johnston" wrote in message news:cCUlhtvFIYkV-pn2-FWmHH7udlJdT@localhost...
On Tue, 27 Jan 2004 12:35:43 UTC, (Chris
OCallaghan) wrote:

: the point of my link was to show that you will not spin from
: coordinated flight.

Tight turn. Slow speed. String in the middle. Pull up sharply as if
another glider has just cut into the thermal. Whoops. Well, it works
in a Bocian, anyway.

Ian
--