Yaw String in a Spin

[John Galloway]

In another thread Ian Strachan wrote:

'>The standard recovery procedure once a full spin has
>>developed that
>works for most aircraft is,

>1. Full rudder opposite to the spin direction (make
>sure it >really is
>opposite to the rotation, I for one have applied the
>wrong >rudder in a
>spinning jet when I was caught by a surprise departure).'
=======================================

I have long surmised that application of the wrong
rudder in a panic situation might be a cause of failure
to recover from a spin. If it can happen to a military
test pilot of Ian's calibre then it can certainly happen
to me.

The yaw string *always* points to the inside of a spin
(according the Reichmann and others) and modifying
the teaching to 'apply full rudder opposite to the
direction of the yaw string' would be a more certain
way of choosing the life rudder pedal rather than the
death one at low altitude

Slip balls do not, apparently, invariably point to
the outside of spins so they are not as certain a guide.

'Every saiplane should have a yaw string' - said Helmut
Reichmann for this reason.

John Galloway

[[email protected]]

John,

interesting thoughts. Even with strong visual cues, the more nose down
a spin, the more difficult it might be to surmise its direction. Thus,
a quick reference to the yaw string is in order. Isn't the Pooch known
for its nose down attitude while spinning?

Yet another reason to put the emphasis on stall avoidance and prompt
recovery from prestall conditions. A suprise stall and autorotation at
low altitude presents a great a risk, even for well trained, heads-up
pilots.

[Papa3]

I agree that this is an interesting point. Even experienced, current pilots
can be caught off guard, and perhaps a better training/recognition method
might be in order. Maybe the yaw string can/should be a more integral
part of the program in terms of spin recovery training?

For what it's worth, I have had a couple of unintentional spin entries over
the last 20 years. One in particular sticks in my mind. A guy at the
local gliderport is an experienced aerobatics competitor; he owns a two
place Fox aerobatic glider. He asked me to go up with him one day, since
he was having some trouble getting the Fox to climb. He figured thermals
were a lot cheaper than 5,000 foot aerotows.

We got into a moderate thermal, and I took the controls to show him how we
"real" soaring pilots thermal. I cranked us over to 40 degrees of bank to
core the thermal. "Now, watch how I slow us up to really tighten the
circle..." I said. The owner mentioned that I ought to "be a little
careful [since] stall speed at this..." He never finished the sentence.

Departure was instantaneous. Rotation was spectacular. I recall at first
doing everything wrong. It took me at least one full revolution to realise
that the glider was spinning, and I think it was a couple of seconds more
before I figured out the direction. Fortunately, we were at least 4,000
AGL at the time, and the owner just sat back and let me figure things out.

This flight came on a day when I had been the duty instructor in the club.
I had probably done 4 or 5 incipient spin lessons earlier in the day, and I
probably had 40 hours flying in the preceeding 90 days. So, I was current
and reasonably on top of my game.

This experience just reinforced the fact that the ability to recognize a
spin, especially an unplanned one, is probably not an easy thing to teach.
The normal training mode is thoroughly unnatural, as the student is primed
and ready. The reality is a lot different, and I'm wondering if any of us
emphasize the recognition aspects of the immediate post-departure moments
enough?

Erik Mann (P3)

> wrote in message
oups.com...
> John,
>
> interesting thoughts. Even with strong visual cues, the more nose down
> a spin, the more difficult it might be to surmise its direction. Thus,
> a quick reference to the yaw string is in order. Isn't the Pooch known
> for its nose down attitude while spinning?
>
> Yet another reason to put the emphasis on stall avoidance and prompt
> recovery from prestall conditions. A suprise stall and autorotation at
> low altitude presents a great a risk, even for well trained, heads-up
> pilots.
>

[John Galloway]

Since my original post today I mentioned the subject
to 2 instructors round the table at our club. One
had himself applied the wrong rudder in a spin and
he had also experienced a pupil doing the same.

When I was first taught spinning (aged 17 in 1969)
it was not immediately intuitively obvious to me which
way I was rotating without thinking back to what direction
the glider had been circling before departure - or
which wing had dropped if the instructor had started
the spin from a level stall. I confess that during
spin training, as the instructor started the spin
entry procedure, I made sure that I mentally rehearsed
in advance which rudder to apply - which rather defeated
the point I guess.

John Galloway


At 16:30 16 January 2005, Papa3 wrote:
>I agree that this is an interesting point. Even experienced,
>current pilots
>can be caught off guard, and perhaps a better training/recognition
>> method
>might be in order. Maybe the yaw string can/should
>be a more integral
>part of the program in terms of spin recovery training?
>
>For what it's worth, I have had a couple of unintentional
>spin entries over
>the last 20 years. One in particular sticks in my
>mind. A guy at the
>local gliderport is an experienced aerobatics competitor;
>he owns a two
>place Fox aerobatic glider. He asked me to go up
>with him one day, since
>he was having some trouble getting the Fox to climb.
> He figured thermals
>were a lot cheaper than 5,000 foot aerotows.
>
>We got into a moderate thermal, and I took the controls
>to show him how we
>'real' soaring pilots thermal. I cranked us over
>to 40 degrees of bank to
>core the thermal. 'Now, watch how I slow us up to
>really tighten the
>circle...' I said. The owner mentioned that I ought
>to 'be a little
>careful [since] stall speed at this...' He never finished
>the sentence.
>
>Departure was instantaneous. Rotation was spectacular.
> I recall at first
>doing everything wrong. It took me at least one full
>revolution to realise
>that the glider was spinning, and I think it was a
>couple of seconds more
>before I figured out the direction. Fortunately,
>we were at least 4,000
>AGL at the time, and the owner just sat back and let
>me figure things out.
>
>This flight came on a day when I had been the duty
>instructor in the club.
>I had probably done 4 or 5 incipient spin lessons earlier
>in the day, and I
>probably had 40 hours flying in the preceeding 90 days.
> So, I was current
>and reasonably on top of my game.
>
>This experience just reinforced the fact that the ability
>to recognize a
>spin, especially an unplanned one, is probably not
>an easy thing to teach.
>The normal training mode is thoroughly unnatural, as
>the student is primed
>and ready. The reality is a lot different, and I'm
>wondering if any of us
>emphasize the recognition aspects of the immediate
>post-departure moments
>enough?
>
>Erik Mann (P3)
>
> wrote in message
oups.com...
>> John,
>>
>> interesting thoughts. Even with strong visual cues,
>>the more nose down
>> a spin, the more difficult it might be to surmise
>>its direction. Thus,
>> a quick reference to the yaw string is in order. Isn't
>>the Pooch known
>> for its nose down attitude while spinning?
>>
>> Yet another reason to put the emphasis on stall avoidance
>>and prompt
>> recovery from prestall conditions. A suprise stall
>>and autorotation at
>> low altitude presents a great a risk, even for well
>>trained, heads-up
>> pilots.
>>
>
>
>

[Tony Verhulst]

Since several experienced pilots have said that they have had trouble
determining the direction of the spin, I accept that it happens - and
that it can happen to me. I do not understand why. Most glider spins
happen when turning and, in the hunderds of intentional spins that I've
done (I have only one unintentional spin), the glider spins in the
direction of the turn. What am I missing? I do like the yaw string idea.

Tony V.

[Stewart Kissel]

The first time I went over-the-top into a spin...it
definitely took a minute to figure out the rotation...others
experience may vary.


I was thinking about this topic and came up with this
observation....

1.) Training spin fatalities seem to happen from a
distance above earth that involves several rotations
before impact...for whatever reason, the spin developed
and could not be stopped.

2.) Inadvertant spin fatalities seem to almost always
occur so low (base to final)...that once the spin has
started, proper recovery probably would not save the
pilot.

So IMHO...are we really training for what is occuring?



At 18:00 16 January 2005, Tony Verhulst wrote:
>
>Since several experienced pilots have said that they
>have had trouble
>determining the direction of the spin, I accept that
>it happens - and
>that it can happen to me. I do not understand why.
>Most glider spins
>happen when turning and, in the hunderds of intentional
>spins that I've
>done (I have only one unintentional spin), the glider
>spins in the
>direction of the turn. What am I missing? I do like
>the yaw string idea.
>
>Tony V.
>

[Nyal Williams]

At 12:00 16 January 2005, John Galloway wrote:
>In another thread Ian Strachan wrote:
>
>'>The standard recovery procedure once a full spin has
>>>developed that
>>works for most aircraft is,
>
>>1. Full rudder opposite to the spin direction (make
>>sure it >really is
>>opposite to the rotation, I for one have applied the
>>wrong >rudder in a
>>spinning jet when I was caught by a surprise departure).'
>=======================================
>
>I have long surmised that application of the wrong
>rudder in a panic situation might be a cause of failure
>to recover from a spin. If it can happen to a military
>test pilot of Ian's calibre then it can certainly happen
>to me.
>
>The yaw string *always* points to the inside of a spin
>(according the Reichmann and others) and modifying
>the teaching to 'apply full rudder opposite to the
>direction of the yaw string' would be a more certain
>way of choosing the life rudder pedal rather than the
>death one at low altitude
>
>Slip balls do not, apparently, invariably point to
>the outside of spins so they are not as certain a guide.
>
>'Every saiplane should have a yaw string' - said Helmut
>Reichmann for this reason.
>
>John Galloway



Good post, but I must point out a trap. I learned
from a student that it is easy to misunderstand which
end of the string is doing the pointing.

I always taught students to 'step on the head of the
snake.' One student could never get it right (never
been around snakes) and he was stepping on the tail
-- the aft, unattached end. I found that other students
had figured out their own way of bringing the string
into line and just ignored my comments.

We should have a conversation with students specifically
about which end of the yaw string is the pointer/tail/indicator,
etc. and which foot does what to that end of the string
under discussion.

On the other hand, perhaps my analogies are just weird.

[Ken Kochanski (KK)]

I had a two turn spin in my 20 a couple of years ago at a Mifflin
contest. The ship was in a coordinated right 45 degree bank, nose on
the horizon, and I was making my third searching circle attempting to
center the strong core of a good thermal. I was stable and coordinated
in the turn when the tail pitched up violently and the ship rolled
inverted to the right. My first thought was that I got hit by another
glider ... but since my searching couldn't locate another ship, I then
thought something broke. (It's amazing how time slows down in these
situations...) Entering the second rotation, I figured I was high
enough (4000')to jump, but continued to scan outside and inside and I
happened to look at my hand ... which was holding the stick just aft of
center. What, could this be a stall/spin? Opposite rudder, stick
forward, flaps to negative ... yep, recovery ... and immediately
climbing in the thermal again. I hit the tail dump switch and made a
promise to see if I could duplicate the situation when I got home ...
which I did.

Looking back, I suspect my left outside wing went through the tight
strong thermal core, which pushed the wing up, I instinctively applied
left aileron, and of course, the inside wing stalled, and the
combination of forces kinda 'snap-rolled' the ship to the right. The
spin entry from level flight and relatively violent forces disguised
the situation and delayed my recovery ... which of course is deadly at
lower altitude. So, stall/spins don't happen the way you practice them
.... although the recovery inputs taught are correct ... you just have
to execute immediately.

I now have a rule ... or mindset ... to execute stall/spin recovery
first in any situation like this. It won't help if you do indeed have
a structural or control problem ... but it is imperative avoid an
intellectual exercise if you are really in a stall/spin. As soon as
you hear yourself saying, "What the F___" ... you should be executing
stall/spin recovery.

KK


Papa3 wrote:
> I agree that this is an interesting point. Even experienced, current
pilots
> can be caught off guard, and perhaps a better training/recognition
method
> might be in order. Maybe the yaw string can/should be a more
integral
> part of the program in terms of spin recovery training?
>
> For what it's worth, I have had a couple of unintentional spin
entries over
> the last 20 years. One in particular sticks in my mind. A guy at
the
> local gliderport is an experienced aerobatics competitor; he owns a
two
> place Fox aerobatic glider. He asked me to go up with him one day,
since
> he was having some trouble getting the Fox to climb. He figured
thermals
> were a lot cheaper than 5,000 foot aerotows.
>
> We got into a moderate thermal, and I took the controls to show him
how we
> "real" soaring pilots thermal. I cranked us over to 40 degrees of
bank to
> core the thermal. "Now, watch how I slow us up to really tighten
the
> circle..." I said. The owner mentioned that I ought to "be a little
> careful [since] stall speed at this..." He never finished the
sentence.
>
> Departure was instantaneous. Rotation was spectacular. I recall at
first
> doing everything wrong. It took me at least one full revolution to
realise
> that the glider was spinning, and I think it was a couple of seconds
more
> before I figured out the direction. Fortunately, we were at least
4,000
> AGL at the time, and the owner just sat back and let me figure things
out.
>
> This flight came on a day when I had been the duty instructor in the
club.
> I had probably done 4 or 5 incipient spin lessons earlier in the day,
and I
> probably had 40 hours flying in the preceeding 90 days. So, I was
current
> and reasonably on top of my game.
>
> This experience just reinforced the fact that the ability to
recognize a
> spin, especially an unplanned one, is probably not an easy thing to
teach.
> The normal training mode is thoroughly unnatural, as the student is
primed
> and ready. The reality is a lot different, and I'm wondering if any
of us
> emphasize the recognition aspects of the immediate post-departure
moments
> enough?
>
> Erik Mann (P3)
>
> > wrote in message
> oups.com...
> > John,
> >
> > interesting thoughts. Even with strong visual cues, the more nose
down
> > a spin, the more difficult it might be to surmise its direction.
Thus,
> > a quick reference to the yaw string is in order. Isn't the Pooch
known
> > for its nose down attitude while spinning?
> >
> > Yet another reason to put the emphasis on stall avoidance and
prompt
> > recovery from prestall conditions. A suprise stall and autorotation
at
> > low altitude presents a great a risk, even for well trained,
heads-up
> > pilots.
> >

[Greg Arnold]

"Apply full rudder opposite to the direction of the yaw string" -- what
does that mean? What is the direction of the yaw string? If the loose
end of the yaw string is on the right side of the canopy, is the
direction of the yaw string to the right, or is it to the left?

I think you mean that if the loose end of the yaw string is on the right
side of canopy, you apply right rudder? Or the opposite of the normal rule?




> The yaw string *always* points to the inside of a spin
> (according the Reichmann and others) and modifying
> the teaching to 'apply full rudder opposite to the
> direction of the yaw string' would be a more certain
> way of choosing the life rudder pedal rather than the
> death one at low altitude
>

[Don Johnstone]

At 18:30 16 January 2005, Nyal Williams wrote:
>Good post, but I must point out a trap. I learned
>from a student that it is easy to misunderstand which
>end of the string is doing the pointing.
>
>I always taught students to 'step on the head of the
>snake.' One student could never get it right (never
>been around snakes) and he was stepping on the tail
>-- the aft, unattached end. I found that other students
>had figured out their own way of bringing the string
>into line and just ignored my comments.
>
>We should have a conversation with students specifically
>about which end of the yaw string is the pointer/tail/indicator,
>etc. and which foot does what to that end of the string
>under discussion.
>
>On the other hand, perhaps my analogies are just weird.


I don't think they are weird, mine were 'kick the ball'
and 'draw the string'. Of course these days I never
have to use them that is why I remember them so well.
Isn't stepping on snakes a bit dangerous? :-)
>
>
>
>

[Jackal]

In a classic left turn traffic pattern stall spin that is caused be a
cross control attempt to rudder a turn to align the ship to final after
it breaks over the top which way is it spining and what is the proper
recovery? In a steep left turn coring a strong thermal at low altitude
the outside or high wing enters the surrounding down and the spin over
the top happens, which way is the glider spinning and what is the
proper spin recovery? No time to think correct answer please your life
depends on it.

[Andy Blackburn]

At 19:00 16 January 2005, Greg Arnold wrote:
>'Apply full rudder opposite to the direction of the
>yaw string' -- what
>does that mean? What is the direction of the yaw string?
> If the loose
>end of the yaw string is on the right side of the canopy,
>is the
>direction of the yaw string to the right, or is it
>to the left?

Seems like there is some potentially confusing terminology
being used here that I've never heard before. I've
always been taught that the the 'direction' of the
yaw string is the side of the glider it leans to, and
so you correct by pressing the rudder on the opposite
side.

Here I think people are saying that if the yaw string
is displaced to the right side of the glider it is
'pointing' left. While I can understand how you might
naturally want the front end to be the tip of the 'pointer',
I think it's confusing to refer to 'pointing' at all
because of this left/right confusion. I prefer to
say the yaw string is 'to the left' or 'to the right'
as position is less ambiguous that the 'pointing' direction.

To be honest, I've never looked at the yaw string in
a spin as it has never been ambiguous to me which way
the world was turning - if the world is going round
and round counter-clockwise how can this not be spinning
to the right? I guess I presumed that for a spin to
persist the glider would have to stay skidding, but
in a fully established spin you might wonder, if the
yaw string was far enough forward (say in a two-seater),
whether the rotation overcomes the skid in terms of
the local flow across the canopy - apparently not given
the comments here. Boy I'd hate for that to be wrong
though.

Years ago when I was flying a Ventus A 16.6 (easy to
spin unintentionally in my experience) I taught myself
that if the inside wing in a turn ever dropped, to
push the stick forward and into the turn and to hit
top rudder. You try to make it as instinctive as possibe,
but it takes practice. The top rudder is the easiest
part - the stick movement is against most people's
instincts.

9B

[John Galloway]

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.

I have never heard of anyone referring to the front
end of the yaw string being the way that it is pointing.
If they do that in the States the wording could
be changed. However, since pilots have ingrained into
thenm the wording 'full opposite rudder' for spin recovery,
I would strongly suggest retaining the word 'opposite'
and referring to the loose end of the yaw string as
the way it points.

There is nothing new to learn in what I suggest - I
just picked it up from Reichmann's book. The change
in emphasisis just that the attention is directed to
the yaw string in any case of doubt rather than to
watching the houses whirling about.

John Galloway


At 19:00 16 January 2005, Greg Arnold wrote:
>'Apply full rudder opposite to the direction of the
>yaw string' -- what
>does that mean? What is the direction of the yaw string?
> If the loose
>end of the yaw string is on the right side of the canopy,
>is the
>direction of the yaw string to the right, or is it
>to the left?
>
>I think you mean that if the loose end of the yaw string
>is on the right
>side of canopy, you apply right rudder? Or the opposite
>of the normal rule?
>
>
>
>
>> The yaw string *always* points to the inside of a
>>spin
>> (according the Reichmann and others) and modifying
>> the teaching to 'apply full rudder opposite to the
>> direction of the yaw string' would be a more certain
>> way of choosing the life rudder pedal rather than
>>the
>> death one at low altitude
>>
>

[Mike the Strike]

On the same topic, I entered an unintentional stall spin for the first
time last year. I have about 1,000 hours in gliders and 450 hours in
my ASW 20. I was flying fully ballasted in a cross-country contest
task on a typical Arizona summer day with strong, turbulent thermals.
Entering a thermal, I eased into a left bank, slowing down and applying
flaps as I've done thousands of times. However, I overshot my normal
fully-ballasted zero flap setting and went to plus 1 instead.

Suddenly, I was aware that something was wrong. The air went quiet,
the controls went sloppy and suddenly the yaw string pointed left and
slightly away from me. For a moment or two, I didn't have a clue as to
what was happening. The glider then fell sideways out of the thermal.

Following the clue of the yawstring, I centered the stick, applied full
right rudder and full negative flap. The glider recovered immediately,
but lost a few hundred feet in the ensuing dive out as I recovered
airspeed. I never got any sense of rotation.

>From my log file, it looks as if I overshot the center of the thermal
and entered severe outflow windshear. With the airspeed gone, aided by
a tad too much positive flap, the glider momentarily quit flying and
dropped sideways.

The yaw string was my only clue as to what was happening.

I agree with others that the experience was totally different from spin
training, in which the spin entry is expected. The problem is
recognizing what is happening and you don't have time to scan
instruments. The yaw string is the most responsive and most effective
inidicator of unusual airflow.

Mike

ASW 20 WA

[Shawn]

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.
>
> I have never heard of anyone referring to the front
> end of the yaw string being the way that it is pointing.

Really? I picked it up somewhere in my instruction. Something to the
effect of "Think of the yaw string as an arrow with the head attached to
the canopy. It points to the the rudder pedal you need to push to
coordinate."
Seemed very natural and simple to me.

Shawn

[John Galloway]

At 23:00 16 January 2005, Shawn 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.
>>
>> I have never heard of anyone referring to the front
>> end of the yaw string being the way that it is pointing.
>
>Really? I picked it up somewhere in my instruction.
> Something to the
>effect of 'Think of the yaw string as an arrow with
>the head attached to
>the canopy. It points to the the rudder pedal you
>need to push to
>coordinate.'
>Seemed very natural and simple to me.
>
>Shawn

So that's the pedal you'll want to press in a spin.
Use your way of thinking about it. No dispute between
us. See Mike the Strike's posting.

John Galloway

[Tony Verhulst]

> Really? I picked it up somewhere in my instruction. Something to the
> effect of "Think of the yaw string as an arrow with the head attached to
> the canopy. It points to the the rudder pedal you need to push to
> coordinate." Seemed very natural and simple to me.

Yes. I use this most often with transitioning power pilots who are
taught to "step on the ball" of the inclinometer ("step on the head of
the arrow"). With ab initio glider pilots I start with telling them to
add rudder on the opposite side of where the tail of the string is
pointing. If that doesn't work, I switch to the above.

Tony V.

[Nyal Williams]

At 23:00 16 January 2005, Shawn 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.
>>
>> I have never heard of anyone referring to the front
>> end of the yaw string being the way that it is pointing.
>
>Really? I picked it up somewhere in my instruction.
> Something to the
>effect of 'Think of the yaw string as an arrow with
>the head attached to
>the canopy. It points to the the rudder pedal you
>need to push to
>coordinate.'
>Seemed very natural and simple to me.

Yes, it is pointing into the relative wind; point the
glider toward that.
>
>Shawn
>

[Duane Eisenbeiss]

"Nyal Williams" > wrote in message
...
> >
> We should have a conversation with students specifically
> about which end of the yaw string is the pointer/tail/indicator,
> etc. and which foot does what to that end of the string
> under discussion.
>
View the string as a pointer. The forward end (the point) points at the
required rudder pedal.

Duane

[Duane Eisenbeiss]

"Duane Eisenbeiss" > wrote in message
...
>
> "Nyal Williams" > wrote in
message
> ...
> > >
> > We should have a conversation with students specifically
> > about which end of the yaw string is the pointer/tail/indicator,
> > etc. and which foot does what to that end of the string
> > under discussion.
> >
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. Therefore opposite
rudder in a spin would be the other rudder pedal or the top of the string.

Duane

[Greg Arnold]

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?

[Stewart Kissel]

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?
>
>
>

[Z Goudie]

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.

[John Galloway]

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.
>
>
>

[Stewart Kissel]

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.

[Nyal Williams]

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.

[Greg Arnold]

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.
>>
>>
>>
>
>
>

[CV]

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

[For Example John Smith]

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

Flawed.
That was easy, next?!

Brent

[Shawn]

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

[John Galloway]

At 18:31 17 January 2005, Greg Arnold wrote:
>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.'
>
>
Greg,

Getting close to an agreement here but the fullness
of the rudder - not just to straighten the string -
needs to be emphasised. How about:

'Full yaw corrective rudder (in the usual sense as
commanded by the yaw string)' ?

The rudder affects the yaw aspect of a spin and not
(except by secondary effect ) the rolliing/autorotating
aspect so for us to have, all these years, decided
on which sense to move the yaw control by looking at
the roll axis direction has been workable but illogical.

John Galloway

[Duane Eisenbeiss]

There have been many comments about using the yaw string to determine the
direction of a spin. Most of us will admit that we do not look at the yaw
string while in a spin. One honest pilot even admitted it in print.

Several U.S. pilots have seen the video of the U S Air Force flight tests of
the spin charecteristics of an ASK-21. During a fully developed spins the
yaw string could be seen moving left then right then up and even forward.
The real conclusion to this discussion should be that the yaw string is not
*always* a reliable indication of spin direction.

What is most important is "situational awarness". A pilot must learn to
know where he is and how he got there.

Duane

[Greg Arnold]

John Galloway wrote:
> At 18:31 17 January 2005, Greg Arnold wrote:
>
>>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.'
>>
>>
>
> Greg,
>
> Getting close to an agreement here but the fullness
> of the rudder - not just to straighten the string -
> needs to be emphasised. How about:
>
> 'Full yaw corrective rudder (in the usual sense as
> commanded by the yaw string)' ?


Sounds good to me.

>
> The rudder affects the yaw aspect of a spin and not
> (except by secondary effect ) the rolliing/autorotating
> aspect so for us to have, all these years, decided
> on which sense to move the yaw control by looking at
> the roll axis direction has been workable but illogical.
>
> John Galloway
>
>

[Z Goudie]

At 01:25 18 January 2005, Duane Eisenbeiss wrote:
>Several U.S. pilots have seen the video of the U S
>Air Force flight tests of
>the spin charecteristics of an ASK-21. During a fully
>developed spins the
>yaw string could be seen moving left then right then
>up and even forward.

Well they must have had the balls for it then......

[Michel Talon]

Duane Eisenbeiss > wrote:
> There have been many comments about using the yaw string to determine the
> direction of a spin. Most of us will admit that we do not look at the yaw
> string while in a spin. One honest pilot even admitted it in print.
>
> Several U.S. pilots have seen the video of the U S Air Force flight tests of
> the spin charecteristics of an ASK-21. During a fully developed spins the
> yaw string could be seen moving left then right then up and even forward.
> The real conclusion to this discussion should be that the yaw string is not
> *always* a reliable indication of spin direction.

The yaw string position is always (*) a reliable indication of the relative direction
of the air flow and the glider at the level of the cockpit. Except in case
there is such turbulence that the air flow has a completely different
direction at the cockpit level and the wings level, this implies that to
unstall the glider you want to align the airflow and the glider, and reduce
angle of attack. Hence you have to center the yaw string, whatever
considerations you may introduce about the spin direction.

(*) by definition. I would be curious to hear arguments to the opposite.


--

Michel TALON

[[email protected]]

Tony,

If the spin is unintentional, you may not have the presence of mind to
recall, at the moment of recognition, which way you were turning. The
brain is very efficient at dumping extraneous information to focus
entirely on the situation at hand. Unfortunately, this isn't always a
good thing. The whole spin training regimen is flawed, since it
presumes that you know you are entering a spin. It teaches you the
muscle memory to enter a spin, and a reflexive response once you've
entered, based almost entirely on the process of entry. As we become
more aware of the necessary steps to recognize and properly react to a
surprise spin, I think we're likely to become more interested in
improving our skill at avoiding them altogether.

Consider panic stops in an automobile as an anology. If you are on a
test track, you know exactly when you must apply the brakes on a
measured course to determine brake efficiency. A stopping distance of
100 to 140 feet from 60 mph is typical. But on the road we don't know
when we'll need to react. Response time must be added. This increases
stopping distance to over 300 feet.

In the glider we need to recognize that something is wrong, establish
what the problem is, then react properly. Intentionally entering the
spin is like taking a test with a textbook at your side, conveniently
opened to the appropriate page. But a surprise departure and
autorotation is going to require some flipping through the pages. And
getting it wrong could be devastating.

[COLIN LAMB]

"What is most important is "situational awarness". A pilot must learn to
know where he is and how he got there."

The last part of that statemenht may not always be true. I have read
reports from test pilots who intentionally place the aircraft in
out-of-control positions in order to determine a recovery procedure. A
common response is that they ride the aircraft until they are in a position
they recognize and as soon as that happens they can recover. How they got
there was irrelevant.

Although few airplanes use yaw strings (the pilots are still behind the
curve a bit), they are normally used on helicopters. Although the pedals
are used to counteract the torque of the tail rotor, we operate them the
same way - keep the yarn centered.

Colin N12HS


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[[email protected]]

Agreed. And even better, the pilot should know where he is and how to
avoid going where he doesn't want to be. We need to be trained in how
to recognize a spin and recover, but even more, we need to be able to
discern the preamble to departure and correct it. Remember, there is an
altitude from which a spin is unrecoverable.

Should we change the way we fly at and below that altitude, or practice
that caution as the rule and be aware when we choose to fly differently?

[[email protected]]

Good thread, John. Thanks for bringing it up.

[Don Johnstone]

I think that the test pilots concerned knew exactly
how they got there but it may not have helped them
much. I re-call seeing a very good video of a Jaguar
that had departed and was tumbling end over end with
fuel being forced out of the jet intakes. I think the
pilot took about 20000ft to find a point where he could
break into the sequence and return to controlled flight.
As a result the action to be taken if a Jaguar departs
is seize the handle between your legs and pull hard.

At 14:31 18 January 2005, Colin Lamb wrote:
>'What is most important is 'situational awarness'.
> A pilot must learn to
>know where he is and how he got there.'
>
>The last part of that statemenht may not always be
>true. I have read
>reports from test pilots who intentionally place the
>aircraft in
>out-of-control positions in order to determine a recovery
>procedure. A
>common response is that they ride the aircraft until
>they are in a position
>they recognize and as soon as that happens they can
>recover. How they got
>there was irrelevant.
>
>Although few airplanes use yaw strings (the pilots
>are still behind the
>curve a bit), they are normally used on helicopters.
> Although the pedals
>are used to counteract the torque of the tail rotor,
>we operate them the
>same way - keep the yarn centered.
>
>Colin N12HS
>
>
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>Checked by AVG anti-virus system (http://www.grisoft.com).
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>10/25/04
>
>
>

[John Galloway]

At 15:00 18 January 2005, Don Johnstone wrote:
>I think that the test pilots concerned knew exactly
>how they got there but it may not have helped them
>much. I re-call seeing a very good video of a Jaguar
>that had departed and was tumbling end over end with
>fuel being forced out of the jet intakes. I think the
>pilot took about 20000ft to find a point where he could
>break into the sequence and return to controlled flight.
>As a result the action to be taken if a Jaguar departs
>is seize the handle between your legs and pull hard.
>
Well, Don, its a good enough way of passing one's last
few moments but I would try ejecting rather than....
and the next part of the line is just so obvious I
can't even bring myself to finish.....damn - done it
again.

Sorry.

John

[Shawn]

John Galloway wrote:
> At 15:00 18 January 2005, Don Johnstone wrote:
>
>>I think that the test pilots concerned knew exactly
>>how they got there but it may not have helped them
>>much. I re-call seeing a very good video of a Jaguar
>>that had departed and was tumbling end over end with
>>fuel being forced out of the jet intakes. I think the
>>pilot took about 20000ft to find a point where he could
>>break into the sequence and return to controlled flight.
>>As a result the action to be taken if a Jaguar departs
>>is seize the handle between your legs and pull hard.
>>
>
> Well, Don, its a good enough way of passing one's last
> few moments but I would try ejecting rather than....
> and the next part of the line is just so obvious I
> can't even bring myself to finish.....damn - done it
> again.

Now how would the NTSB address *that* in the accident report.
Delicately, I'd hope.

Shawn

[Nyal Williams]

At 14:31 18 January 2005, Colin Lamb wrote:
>'What is most important is 'situational awarness'.
> A pilot must learn to
>know where he is and how he got there.'
>
>The last part of that statemenht may not always be
>true. I have read
>reports from test pilots who intentionally place the
>aircraft in
>out-of-control positions in order to determine a recovery
>procedure. A
>common response is that they ride the aircraft until
>they are in a position
>they recognize and as soon as that happens they can
>recover. How they got
>there was irrelevant.
>
>Although few airplanes use yaw strings (the pilots
>are still behind the
>curve a bit), they are normally used on helicopters.
> Although the pedals
>are used to counteract the torque of the tail rotor,
>we operate them the
>same way - keep the yarn centered.
>
>Colin N12HS
>
Wha-a-t?

How can you use a yaw string in a helicopter? Doesn't
the rotor wash it around? Educate me.

(I had one helicopter ride in an H-13 in 1954; didn't
see no stinkin' yaw string.)

[COLIN LAMB]

"How can you use a yaw string in a helicopter? Doesn't
the rotor wash it around? Educate me.

(I had one helicopter ride in an H-13 in 1954; didn't
see no stinkin' yaw string.)"

Helicopter pilots have learned a lot since 1954. I fly helicopters (just
Schweizers). Perhaps the production crew kept putting them on from
sailplane days, but they work just like any other yaw string. And, they are
brightly colored yarn, too. Only one of the helicopters I have flown has a
turn and bank indicator - and all have the yarn.

When you are hovering, the yarn is meaningless - but you are not going
anywhere, either. As soon as you move to forward flight, the relative wind
goes from the front of the helicopter to the back, just like any other
aircraft.

At best glide ratio, I get just over 3:1, but with a headwind the glide
angle approaches that of an elevator.

Colin N12HS



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[[email protected]]

Andy,

Remember my spin entry tests in the V2b a year and a half ago. One of
the departures was so violent, I lost reference, and even though I knew
which way I entered, I can see how a surprise stall with the same sort
of departure could cause disorientation and application of pro spin
rudder. At low altitudes (during a save, for instance), the delay in
recovery could be very bad news.

As for spin dynamics, it might be interesting to look at airfoil tufts
throughout to see what's going on. Anyone have a link? I think most of
us envision a spin as a straight line down, the aircraft rotating about
this axis. That seems too simple. At any rate, the yaw string should
always be displaced into the direction of spin (or average there if
oscillating). Staying in the spin requires that the inside wing be
producing higher drag (as a result of AOA), and thus the pro-rotation
displacement.

I won't be able to fly until April, but maybe one of you southwestern
types could provide some video of the yaw string through 2 or three
full rotations. We can discuss this ad nauseum, but a few pictures
would make the discussion much more interesting and possibly fruitfull.
Andy, you up for it?

[Nyal Williams]

At 17:00 19 January 2005, wrote:
>Andy,
>
>Remember my spin entry tests in the V2b a year and
>a half ago. One of
>the departures was so violent, I lost reference, and
>even though I knew
>which way I entered, I can see how a surprise stall
>with the same sort
>of departure could cause disorientation and application
>of pro spin
>rudder. At low altitudes (during a save, for instance),
>the delay in
>recovery could be very bad news.
>
>As for spin dynamics, it might be interesting to look
>at airfoil tufts
>throughout to see what's going on. Anyone have a link?
>I think most of
>us envision a spin as a straight line down, the aircraft
>rotating about
>this axis.

This vision was the basis for my remarks about not
recognizing a spin on turn to final. We need to re-think
the teaching of spin recognition to include a better
vision of what the aircraft movement really is -- a
circular skid path, to point that out and impress it
on students and ourselves. Successive spins at lower
and lower altitudes will demonstrate that the lower
one is the more obvious the sidewise motion will be.
But no demonstrations in the pattern, please!




>That seems too simple. At any rate, the yaw string
>should
>always be displaced into the direction of spin (or
>average there if
>oscillating). Staying in the spin requires that the
>inside wing be
>producing higher drag (as a result of AOA), and thus
>the pro-rotation
>displacement.
>
>I won't be able to fly until April, but maybe one of
>you southwestern
>types could provide some video of the yaw string through
>2 or three
>full rotations. We can discuss this ad nauseum, but
>a few pictures
>would make the discussion much more interesting and
>possibly fruitfull.
>Andy, you up for it?
>
>

[John Galloway]

Some very interesting thoughts there - especially about
whether or not the glider spins about an axis in a
vertically downwards line. The airflows - and especially
the behaviour of the yaw string - are very much easier
to understand if the glider c of g is thought of descending
in a spiral and the centre of the whole spin rotation
is inside the rotation circle of the yaw string.

From the pilot/glider frame of reference in a steep
spin the nearest point on the central axis of rotation
of the spin may be a short distance above the pilot's
head - or looking down the nose the point of interception
of the central axis may be a long way in front of the
nose (the first view being like looking down a radius
to the centre of an inverted verically descending cone
cone and the second being like looking down a side
of the cone to the vertically descending point)


There is a natural tendency to imagine the spinning
glider as rotating a point somewhere near its C of
G with the yaw string on the opposite side of the axis
of rotation from the tail. But, if the tail and the
yaw string were both to turn out to be on the same
side of the central axis of rotation of the spin, as
described above, then the loose end of the string would,
very obviously to everyone, be pointing to the inside
spin/downgoing wing side of the canopy - irrespective
of the other factors causing the same deviation of
the string to the inside that have been described previously
in this thread.

John Galloway

At 17:00 19 January 2005, wrote:
>Andy,
>
>Remember my spin entry tests in the V2b a year and
>a half ago. One of
>the departures was so violent, I lost reference, and
>even though I knew
>which way I entered, I can see how a surprise stall
>with the same sort
>of departure could cause disorientation and application
>of pro spin
>rudder. At low altitudes (during a save, for instance),
>the delay in
>recovery could be very bad news.
>
>As for spin dynamics, it might be interesting to look
>at airfoil tufts
>throughout to see what's going on. Anyone have a link?
>I think most of
>us envision a spin as a straight line down, the aircraft
>rotating about
>this axis. That seems too simple. At any rate, the
>yaw string should
>always be displaced into the direction of spin (or
>average there if
>oscillating). Staying in the spin requires that the
>inside wing be
>producing higher drag (as a result of AOA), and thus
>the pro-rotation
>displacement.
>
>I won't be able to fly until April, but maybe one of
>you southwestern
>types could provide some video of the yaw string through
>2 or three
>full rotations. We can discuss this ad nauseum, but
>a few pictures
>would make the discussion much more interesting and
>possibly fruitfull.
>Andy, you up for it?
>
>

[Edward Lockhart]

>I won't be able to fly until April, but maybe one of
>you southwestern
>types could provide some video of the yaw string through
>2 or three
>full rotations. We can discuss this ad nauseum, but
>a few pictures
>would make the discussion much more interesting and
>possibly fruitfull.
>Andy, you up for it?
>
>
Good idea.

I've just looked at some video I took in 2003 which
includes a 1 turn spin in each direction.

Initially, as the nose drops, the yaw string points
inside the spin, i.e. a spin to the right, the string
says use more right rudder. Once the glider starts
rotating, the string points outside the spin, i.e.
spinning right, string says use left rudder.

Can't post it, nowhere to put it.

Ed.
(Pilatus)

[Jackal]

The yaw string just indicates the direction of the flow in the boundary
layer at that point. I have seen in a stabilized spin in a 2-32 the yaw
string point in the direction of the turn, straight forward, straight
aft and in a direction opposite the direction of the rotation. This was
an induced spin with the CG almost at the max allowable aft position. I
have heard reports of an ASK-21 doing similar things but have not
experienced it.

[Jackal]

Possibly looking through the string and just observing the direction
the world is moving and inputting rudder in the direction counter to
the direction of motion might have merit?

[Bert Willing]

No. Too low tech.

--
Bert Willing

ASW20 "TW"


"Jackal" > a écrit dans le message de news:
. com...
> Possibly looking through the string and just observing the direction
> the world is moving and inputting rudder in the direction counter to
> the direction of motion might have merit?
>

[John Galloway]

At 11:30 21 January 2005, Jackal wrote:
>Possibly looking through the string and just observing
>the direction
>the world is moving and inputting rudder in the direction
>counter to
>the direction of motion might have merit?
>


Yes - I think there is no choice.

I started the thread because that is apparently not
always as easy to do in an unexpected spin as in a
practice or training spin - and was prompted by the
posting from a professional test pilot that even he
had once used the wrong rudder in a spin recovery in
a jet.

The suggestion about considering using the string was
based on Helmut Reichmann's comment in Cross Country
Soaring (P147 Revised Edition) that 'the string always
points to the inside in a spin'.

Two interesting things have come out of the feedback
within the thread and directly:

1) Confirmation that even experienced pilots and instructors
can get disorientated about rotational direction an
unexpected spin.

2) Reichmann's assertion has been undermined and consequently
the behaviour of the string can't be said to be reliable
enough to advocate as the primary reference for which
rudder to use in a fully developed spin.

John Galloway

[jimk]

"Stewart Kissel" > wrote in
message ...
> 4)All sailplanes should have yaw strings.
> >
> 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.

What's the logic?
You mean besides the fact that the string will just jump around randomly all
the time?

Unless, of course, you mount it on the INSIDE of the windscreen.
Then, if you had a weight on it, would work pretty good as a heads up yaw
indicator. But, of course, it would work opposite from a string mounted on
the outside of a glider...

And, on the third hand, it would work on the outside if you were flying a
big daddy twin (excluding the Cessna Skymaster, of course). But since most
of they guys that fly big daddy twins mostly started out in single engine
spam cans, their bad habits are pretty much ingrained.

Eh?

jimk