Yaw String in a Spin

John Galloway wrote:
It means exactly the same rudder direction you apply
in any other, non spinning, yawed condition (how could
it be otherwise as the string doesn't change its mode
of action in a spin?). The front end of a yaw string
is stuck to the canopy and if the loose end is pointing
left in a spin you apply apply right rudder.


Are you sure? Imagine a flat spin. If the loose end is pointing to the
left, doesn't that mean yoiu are spinning to the right? So don't you
want left rudder?

Yikes...
This thread is well on its way to the top for adding
confusion to a topic!!

I don't even think of yaw string in terms of 'pointing'...

for me it solely reflects how air is passing over it,
the string always stays aligned to this airflow...and
most all of the time I want to keep my ship aligned
pointy end first into that same airflow. My contribution
to the confusion.


At 04:00 17 January 2005, Greg Arnold wrote:
John Galloway wrote:
It means exactly the same rudder direction you apply
in any other, non spinning, yawed condition (how could
it be otherwise as the string doesn't change its mode
of action in a spin?). The front end of a yaw string
is stuck to the canopy and if the loose end is pointing
left in a spin you apply apply right rudder.


Are you sure? Imagine a flat spin. If the loose end
is pointing to the
left, doesn't that mean yoiu are spinning to the right?
So don't you
want left rudder?

At 04:00 17 January 2005, Greg Arnold wrote:
Are you sure? Imagine a flat spin. If the loose end
is pointing to the
left, doesn't that mean yoiu are spinning to the right?
So don't you
want left rudder?

You better sort that out in your head quick!

Think. Start straight level and slow. Feed in full
left rudder. The glider rotates (yaws) left but continues
initially on the track it was going. The airflow is
now coming more from the right and blows the yaw string
out to the left (the slip ball, which is free to move
in its tube, goes out to the right sharply because
the airflow is decelerating the whole aircraft apart
from it).

The left wing reaches the stall, the wing drops and
the angle of attack increases even further. The increase
in drag on the wing causes the glider to continue rotating
to the left.
The glider is now sinking rapidly with the left wing
more badly stalled than the right due to the rotation.
This means that the glider continues to yaw and roll
left.

Looking from above the glider is now following a circular
anti-clockwise path with the nose pointing into the
circle and the tail out. The airflow is still coming
more from the right (over the whole aircraft and not
just forward of the centre of gravity) and the yaw
string is being blown out to the left whether the nose
pitches down or up into a flat attitude or not. The
slip ball (and you) are trying to continue in a straight
line and feel a force throwing you to the right. This
is a left hand spin!

The anti-spin action at this point is to reduce the
yaw to the left with full right rudder; pull the string,
push the ball or step on the head of the snake (sounds
like a position in the Kama Sutra) as your personal
mantra dictates and then move the stick forward from
its central position (where I hope you placed it as
the spin developed) until the wing unstalls. Now centralise
the rudder before loading the wing up on the pull out
or you'll be off the other way.

Thanks Z. Couldn't have put it better myself - in
fact I didn't!



It is interesting that I have had various feed back
from pilots who have applied the wrong rudder or found
it difficult to instantly decide which way they were
rotating in a sudden unexpected spin or knew about
someone else who had reported this experience.

To refocus, and taking into consideration the fact
that my use the word 'opposite' has created confusion
that I really didn't expect, my new improved (?) wording
is:

1)The string acts laterally in the same sense in a
spin as at all other times and the rudder correction
for a given direction of yaw string deviation is exactly
the same direction as in level flight.

2)Deciding how to correct yaw by use of a yaw string
is a task that glider pilots do almost continually
during flight but deciding which way the glider is
rotating in a spin is a very occasional task - and
one that is survival critical

3)Use the yaw string as the primary reference to decide
the correct rudder to apply in the event of an unexpected
spin

4)All sailplanes should have yaw strings.

John Galloway

At 06:00 17 January 2005, Z Goudie wrote:
At 04:00 17 January 2005, Greg Arnold wrote:
Are you sure? Imagine a flat spin. If the loose end
is pointing to the
left, doesn't that mean yoiu are spinning to the right?
So don't you
want left rudder?

You better sort that out in your head quick!

Think. Start straight level and slow. Feed in full
left rudder. The glider rotates (yaws) left but continues
initially on the track it was going. The airflow is
now coming more from the right and blows the yaw string
out to the left (the slip ball, which is free to move
in its tube, goes out to the right sharply because
the airflow is decelerating the whole aircraft apart
from it).

The left wing reaches the stall, the wing drops and
the angle of attack increases even further. The increase
in drag on the wing causes the glider to continue rotating
to the left.
The glider is now sinking rapidly with the left wing
more badly stalled than the right due to the rotation.
This means that the glider continues to yaw and roll
left.

Looking from above the glider is now following a circular
anti-clockwise path with the nose pointing into the
circle and the tail out. The airflow is still coming
more from the right (over the whole aircraft and not
just forward of the centre of gravity) and the yaw
string is being blown out to the left whether the nose
pitches down or up into a flat attitude or not. The
slip ball (and you) are trying to continue in a straight
line and feel a force throwing you to the right. This
is a left hand spin!

The anti-spin action at this point is to reduce the
yaw to the left with full right rudder; pull the string,
push the ball or step on the head of the snake (sounds
like a position in the Kama Sutra) as your personal
mantra dictates and then move the stick forward from
its central position (where I hope you placed it as
the spin developed) until the wing unstalls. Now centralise
the rudder before loading the wing up on the pull out
or you'll be off the other way.

4)All sailplanes should have yaw strings.


While watching 'Top Gun' on the boob-tube the other
day...I noticed the Navy puts them on the F-14. Didn't
do Maverick any good though

So what is the logic for no yaw string?...I had the
occasion to fly in a private two seater once, that
did not have one. Some logic I did not understand
about using the T+B ball instead.

At 06:00 17 January 2005, Z Goudie wrote:
At 04:00 17 January 2005, Greg Arnold wrote:
Are you sure? Imagine a flat spin. If the loose end
is pointing to the
left, doesn't that mean yoiu are spinning to the right?
So don't you
want left rudder?

You better sort that out in your head quick!

Yep! We had better do some spins and observe the yawstring
while it develops; I'll confess that I have never paid
attention to the string while spinning. (Further comments
in body of post)


Think. Start straight level and slow. Feed in full
left rudder. The glider rotates (yaws) left but continues
initially on the track it was going. The airflow is
now coming more from the right and blows the yaw string
out to the left (the slip ball, which is free to move
in its tube, goes out to the right sharply because
the airflow is decelerating the whole aircraft apart
from it).

The left wing reaches the stall, the wing drops and
the angle of attack increases even further. The increase
in drag on the wing causes the glider to continue rotating
to the left.
The glider is now sinking rapidly with the left wing
more badly stalled than the right due to the rotation.
This means that the glider continues to yaw and roll
left.


I think everyone agrees to this point. Error in thought
takes place once the spin starts.


Looking from above the glider is now following a circular
anti-clockwise path with the nose pointing into the
circle and the tail out. The airflow is still coming
more from the right (over the whole aircraft and not
just forward of the centre of gravity) and the yaw
string is being blown out to the left whether the nose
pitches down or up into a flat attitude or not. The
slip ball (and you) are trying to continue in a straight
line and feel a force throwing you to the right. This
is a left hand spin!
(Here is another indicator; if you feel a force throwing
you to the right you need to add right rudder)

This is where the confusion begins; it is tempting
to think that the glider is simply rotating about its
CG without sideways movement; (it almost looks that
way above 3000ft. agl). If that were the case the
yaw string would switch sides because the airflow would
now be from the left ahead of the CG and from the right
aft of the CG.

In truth, the whole glider is still sliding through
the air to the right side in this left-hand spin, so
the yaw string should still be to the left side.


The anti-spin action at this point is to reduce the
yaw to the left with full right rudder; pull the string,
push the ball or step on the head of the snake (sounds
like a position in the Kama Sutra) as your personal
mantra dictates and then move the stick forward from
its central position (where I hope you placed it as
the spin developed) until the wing unstalls. Now centralise
the rudder before loading the wing up on the pull out
or you'll be off the other way.

This mental error in not recognizing the sideways component
of the spin is what accounts for stall/spin accidents
on turn to final; down low the sideways movement is
dramatically noticeable in a way that it is not at
altitude. This is the reason pilots do not recognize
a spin down low. We should emphasize this continuing
sideways component in all spins and call attention
to it by the behavior of the yaw string. I would like
to believe that focussing on this sideways movement
might prevent some future accidents.

I am convinced. Keeping the rule as simple as possible: "Do the same
thing to straighten the yaw string in a spin as you would do at any
other time."


John Galloway wrote:
Thanks Z. Couldn't have put it better myself - in
fact I didn't!



It is interesting that I have had various feed back
from pilots who have applied the wrong rudder or found
it difficult to instantly decide which way they were
rotating in a sudden unexpected spin or knew about
someone else who had reported this experience.

To refocus, and taking into consideration the fact
that my use the word 'opposite' has created confusion
that I really didn't expect, my new improved (?) wording
is:

1)The string acts laterally in the same sense in a
spin as at all other times and the rudder correction
for a given direction of yaw string deviation is exactly
the same direction as in level flight.

2)Deciding how to correct yaw by use of a yaw string
is a task that glider pilots do almost continually
during flight but deciding which way the glider is
rotating in a spin is a very occasional task - and
one that is survival critical

3)Use the yaw string as the primary reference to decide
the correct rudder to apply in the event of an unexpected
spin

4)All sailplanes should have yaw strings.

John Galloway

At 06:00 17 January 2005, Z Goudie wrote:

At 04:00 17 January 2005, Greg Arnold wrote:

Are you sure? Imagine a flat spin. If the loose end
is pointing to the
left, doesn't that mean yoiu are spinning to the right?
So don't you
want left rudder?

You better sort that out in your head quick!

Think. Start straight level and slow. Feed in full
left rudder. The glider rotates (yaws) left but continues
initially on the track it was going. The airflow is
now coming more from the right and blows the yaw string
out to the left (the slip ball, which is free to move
in its tube, goes out to the right sharply because
the airflow is decelerating the whole aircraft apart

from it).

The left wing reaches the stall, the wing drops and
the angle of attack increases even further. The increase
in drag on the wing causes the glider to continue rotating
to the left.
The glider is now sinking rapidly with the left wing
more badly stalled than the right due to the rotation.
This means that the glider continues to yaw and roll
left.

Looking from above the glider is now following a circular
anti-clockwise path with the nose pointing into the
circle and the tail out. The airflow is still coming
more from the right (over the whole aircraft and not
just forward of the centre of gravity) and the yaw
string is being blown out to the left whether the nose
pitches down or up into a flat attitude or not. The
slip ball (and you) are trying to continue in a straight
line and feel a force throwing you to the right. This
is a left hand spin!

The anti-spin action at this point is to reduce the
yaw to the left with full right rudder; pull the string,
push the ball or step on the head of the snake (sounds
like a position in the Kama Sutra) as your personal
mantra dictates and then move the stick forward from
its central position (where I hope you placed it as
the spin developed) until the wing unstalls. Now centralise
the rudder before loading the wing up on the pull out
or you'll be off the other way.

Duane Eisenbeiss wrote:

The above post was incomplete. Over sensitive Send button.

View the string as a pointer. The forward end (the point) points at the
required rudder pedal to continue the turn or stop yaw.

It is impossible for the forward end to "point" at anything,
since it is fixed in place by tape. The string pivots
around its stationary forward end.

Any "pointing" is of course done by the free aft end
of the string, away from the pivotal point.

Same thing as the hands of a clock. The minute hand
points "right", not left, at five past twelve.

If you give left rudder you will slip to the right
and the string will point left.

Cheers CV

"Stewart Kissel" wrote in
message ...
So what is the logic for no yaw string?...

Flawed.
That was easy, next?!

Brent

CV wrote:
Duane Eisenbeiss wrote:


The above post was incomplete. Over sensitive Send button.

View the string as a pointer. The forward end (the point) points at the
required rudder pedal to continue the turn or stop yaw.


It is impossible for the forward end to "point" at anything,
since it is fixed in place by tape. The string pivots
around its stationary forward end.

Any "pointing" is of course done by the free aft end
of the string, away from the pivotal point.

Same thing as the hands of a clock. The minute hand
points "right", not left, at five past twelve.

If you give left rudder you will slip to the right
and the string will point left.

So do you tell students that the wind sock points to where the wind is
going?
Impossible or not, by using my *imagination* early in my flying career,
I was able to simply and quickly make sense of what the yaw string was
indicating without having to think about where the relative wind was
coming from, or which pedal to push.
Jeez.

Shawn