Cable break recovery spin entry... as previously discussed

Pilots depend on simple, quickly applied remedies to any loss of
control. Since we are not always afforded the luxury of examination,
analysis, and consideration of options as a preamble to action, any
flight condition where these simple rules of recovery do not work
demands closer examination and appropriate training to recognize
symptoms and take appropriate actions.

Modern aircraft are designed to meet well-defined controllability
requirements. For example, in the United States, the recommended
recovery (generic) for any impending or developed stall is to move the
control column forward while applying coordinated aileron and rudder to
halt an un-commanded roll. The Flight Manual for my S-H Ventus 2bx
states on page 3.4:

--On stalling whilst flying straight ahead or in a banked turn, normal
flying attitude is regained by firmly easing the control stick forward
and, if necessary, applying opposite rudder and aileron.--

Page 3.5 (Spin Recovery) continues...

--Note: Spinning may be safely avoided by following the actions given
in section 3.4 "Stall Recovery"-

During the past several years, I have made it a point to experiment
with various applications of controls throughout the stall break (and
in a variety of makes and models). In all cases where I maintained
coordination, either paying attention to the yaw string or through
application of equal amounts of aileron and rudder, the aircraft did
not spin, even if I held the stick firmly against the rear stop.
Instead, it would transition from stall to spiral dive.

In a recent RAS thread (Nimbus 4DT accident 31 July 2000 in Spain), I
was introduced to a maneuver practiced by BGA instructors to
demonstrate that a quick transition from coordinated flight into a spin
can take place while recovering from a winch launch cable break. This
was pointed out to refute my comment in that thread that modern gliders
need to be "helped" into a spin (by either intentional or
inadvertent abuse of the controls).

Chris Reed described the following:

--One of my favourite exercises for my annual checkouts as a UK Basic
Instructor is the spin off a simulated winch launch (only try this at
height with an appropriate instructor with you!). Simulate a winch
launch by diving to 90 kt and then pulling up at 45 degrees. As the
speed drops to about 60 kt cry "BANG - cable break", and push over into

the normal flying attitude. The moment normal attitude is reached,
begin
a co-ordinated turn.
All will be fine for a second or so, as you are flying at reduced G.
However, once the G comes back on many gliders will roll smoothly (no
buffeting) into a spin so fast that there is little you can do about it

(though the purpose of the exercise is to show the spin entry and then
a
recovery, so I've not tried reducing back pressure as the wing drops).
The Puchacz is excellent for this.--

For me, this raised an immediate alarm. It indicates that there are
flight regimes (whether experienced during a cable break recovery,
during an aggressive thermal entry, or as a result of turbulence) where
normal control movements may result in an immediate and unannounced
spin entry.
Since such matters are best examined in the air, I put together an
informal flight test plan to measure just how sudden the spin entry is
and whether there might be mitigating factors.

To prepare for the test, I set up the following limits:

First, I would at no time during the maneuver bring the stick back all
the way to the stop. We must assume that all pilots meet a base level
of competency, and under no circumstance would any competent pilot
resort to full up elevator to maintain attitude during a cable break
recovery. I would consider such control usage an abuse of the controls.

Second, I would remain coordinated (as indicated by my yaw string)
throughout the maneuver per the instructions of my flight manual.

Third, at stall break, I would hold the controls firm and visually
verify their positions, then wait for the sailplane to assume its new
state (either spin or spiral dive) then clearly identify that state
before making an appropriate recovery.

I began the test sequence with a series of four dives and recoveries
just as Chris described, but without introducing a bank. At 60 knots, I
called out "Bang - cable break - recover!" I pushed the stick
firmly forward. Three out of the four, I briefly suspended loose dirt
in the cockpit. As soon as the nose passed through the horizon into a
normal flying attitude, I moved the stick quickly back to its normal
position for that attitude. Of course, this did not entirely halt the
downward pitch of the nose. However, it was clearly apparent through
the feel of the controls that the sailplane was either stalled or on
the edge of a stall as a result of my quick application of stick from
well forward to neutral. It was very clear that bringing the stick
straight back to the stop would result in a full stall.

I began the dives in flap position -1, moving the flaps to position +1
as I slowed through 70 knots, as I might if I were entering a thermal,
though my recovery (pitch over) was much more aggressive than any I
would use during cross-country flight. Once I was comfortable with my
ability to keep myself from making an immediate recovery from any
stall, I stopped to thermal, then found a clear patch of sky and warned
off others away, as I fully expected to spin the sailplane.

In order to force an immediate turn, I imagined that there was an
obstruction preventing a straight ahead landing. As soon as the nose
came down, I determined that I would have to make an immediate turn to
the right, which I did, without adverse results. The sailplane rolled
sluggishly and felt on the edge of stall, but there was no loss of
control, and certainly no sudden yaw and entry into a spin. I thought
perhaps I had waited too long to initiate the turn, so with the next
pull and recovery, I made the decision, before the nose came fully
over, that I would land to the left in an adjoining field. I rolled to
about 30 degrees, then as the nose reached normal flying attitude, I
brought the stick right back to neutral... and braced myself against
making an immediate recovery.

As before, there was a sense of mushing through the air, but no
tendency for the glider to yaw itself into a spin. For the next pull
and recovery, I delayed saying "Bang - cable break - recover!"
until 50 knots. Given the additional delay, I was much more aggressive
with the stick, both moving it forward and returning it to neutral once
I reach normal flying attitude. And once again, the sailplane
demonstrated a sluggish, heavy feel as the g force came back on, but
without any tendency to "fall" into the direction of the turn.

It was clear to me that I could have easily induced a spin during this
maneuver. A little too much rudder or stick against the turn coupled
with bringing the stick full aft would have tipped the sailplane right
over. But my intent was to produce an unanticipated spin, even though I
was, ostensibly, doing everything right.

I repeated this maneuver several more times, making slight adjustments
to angle of bank, but without adverse effects.

My conclusions:

This is an interesting flight regime. I suspect that it would prove
useful for producing spins in typically resistant aircraft, and require
significantly less control abuse among those gliders that are inclined
to spin. However, for my make and model (which can be easily coaxed to
incipiency), normal attention to stall warning signs and application of
coordinated aileron and rudder are adequate. There does not appear to
be any tendency for the glider to spin suddenly or unpredictably,
though I would caution that if the stick is used to catch a dropping
wing without appropriate application of rudder, the spin entry could be
significantly accelerated.

The greater the span, the more pronounced the effects of a tip stall
would be, but greater span is usually compensated for by a longer tail
boom and larger vertical stabilizer. Some designs may choose to
underpower the vertical stabilizer to increase glide performance, but
hopefully these would include appropriate warnings and recovery
procedures in their respective flight manuals.

As far as thermal entry is concerned, I would give the same warning: if
you delay your pushover on thermal entry to the point where G and
airspeed are significantly reduced below the norms (generally not the
most efficient way to enter a thermal), extra attention should be paid
to coordination. I wouldn't expect the glider to snap into a spin,
but it is entirely possible that the now underpowered vertical
stabilizer may not adequately compensate if you have any tendency
towards sloppiness.

I intend to experiment with this maneuver some more over the coming
weeks. As I discover anything interesting, I'll add my comments to
the thread. Also, I uploaded my FR trace to the OLC, but my sampling
was 4 seconds, hardly adequate for analysis. However, just in case you
are tempted to make an armchair assay, be my guest!

http://www2.onlinecontest.org/olcphp...823e438ec30ed8

The test run began at 1454 ET (UTC-4) and ended at 1503 ET.

It is not obvious to me, why, in a cable break scenario, you would be close
to stalling when you push the nose down to a normal attitude while you
maintain 60 knot airspeed. This sounds like you are flying significantly
above stall speed. Could you elaborate?

Thanks,
Mike Schumann

wrote in message
oups.com...
Pilots depend on simple, quickly applied remedies to any loss of
control. Since we are not always afforded the luxury of examination,
analysis, and consideration of options as a preamble to action, any
flight condition where these simple rules of recovery do not work
demands closer examination and appropriate training to recognize
symptoms and take appropriate actions.

Modern aircraft are designed to meet well-defined controllability
requirements. For example, in the United States, the recommended
recovery (generic) for any impending or developed stall is to move the
control column forward while applying coordinated aileron and rudder to
halt an un-commanded roll. The Flight Manual for my S-H Ventus 2bx
states on page 3.4:

--On stalling whilst flying straight ahead or in a banked turn, normal
flying attitude is regained by firmly easing the control stick forward
and, if necessary, applying opposite rudder and aileron.--

Page 3.5 (Spin Recovery) continues...

--Note: Spinning may be safely avoided by following the actions given
in section 3.4 "Stall Recovery"-

During the past several years, I have made it a point to experiment
with various applications of controls throughout the stall break (and
in a variety of makes and models). In all cases where I maintained
coordination, either paying attention to the yaw string or through
application of equal amounts of aileron and rudder, the aircraft did
not spin, even if I held the stick firmly against the rear stop.
Instead, it would transition from stall to spiral dive.

In a recent RAS thread (Nimbus 4DT accident 31 July 2000 in Spain), I
was introduced to a maneuver practiced by BGA instructors to
demonstrate that a quick transition from coordinated flight into a spin
can take place while recovering from a winch launch cable break. This
was pointed out to refute my comment in that thread that modern gliders
need to be "helped" into a spin (by either intentional or
inadvertent abuse of the controls).

Chris Reed described the following:

--One of my favourite exercises for my annual checkouts as a UK Basic
Instructor is the spin off a simulated winch launch (only try this at
height with an appropriate instructor with you!). Simulate a winch
launch by diving to 90 kt and then pulling up at 45 degrees. As the
speed drops to about 60 kt cry "BANG - cable break", and push over into

the normal flying attitude. The moment normal attitude is reached,
begin
a co-ordinated turn.
All will be fine for a second or so, as you are flying at reduced G.
However, once the G comes back on many gliders will roll smoothly (no
buffeting) into a spin so fast that there is little you can do about it

(though the purpose of the exercise is to show the spin entry and then
a
recovery, so I've not tried reducing back pressure as the wing drops).
The Puchacz is excellent for this.--

For me, this raised an immediate alarm. It indicates that there are
flight regimes (whether experienced during a cable break recovery,
during an aggressive thermal entry, or as a result of turbulence) where
normal control movements may result in an immediate and unannounced
spin entry.
Since such matters are best examined in the air, I put together an
informal flight test plan to measure just how sudden the spin entry is
and whether there might be mitigating factors.

To prepare for the test, I set up the following limits:

First, I would at no time during the maneuver bring the stick back all
the way to the stop. We must assume that all pilots meet a base level
of competency, and under no circumstance would any competent pilot
resort to full up elevator to maintain attitude during a cable break
recovery. I would consider such control usage an abuse of the controls.

Second, I would remain coordinated (as indicated by my yaw string)
throughout the maneuver per the instructions of my flight manual.

Third, at stall break, I would hold the controls firm and visually
verify their positions, then wait for the sailplane to assume its new
state (either spin or spiral dive) then clearly identify that state
before making an appropriate recovery.

I began the test sequence with a series of four dives and recoveries
just as Chris described, but without introducing a bank. At 60 knots, I
called out "Bang - cable break - recover!" I pushed the stick
firmly forward. Three out of the four, I briefly suspended loose dirt
in the cockpit. As soon as the nose passed through the horizon into a
normal flying attitude, I moved the stick quickly back to its normal
position for that attitude. Of course, this did not entirely halt the
downward pitch of the nose. However, it was clearly apparent through
the feel of the controls that the sailplane was either stalled or on
the edge of a stall as a result of my quick application of stick from
well forward to neutral. It was very clear that bringing the stick
straight back to the stop would result in a full stall.

I began the dives in flap position -1, moving the flaps to position +1
as I slowed through 70 knots, as I might if I were entering a thermal,
though my recovery (pitch over) was much more aggressive than any I
would use during cross-country flight. Once I was comfortable with my
ability to keep myself from making an immediate recovery from any
stall, I stopped to thermal, then found a clear patch of sky and warned
off others away, as I fully expected to spin the sailplane.

In order to force an immediate turn, I imagined that there was an
obstruction preventing a straight ahead landing. As soon as the nose
came down, I determined that I would have to make an immediate turn to
the right, which I did, without adverse results. The sailplane rolled
sluggishly and felt on the edge of stall, but there was no loss of
control, and certainly no sudden yaw and entry into a spin. I thought
perhaps I had waited too long to initiate the turn, so with the next
pull and recovery, I made the decision, before the nose came fully
over, that I would land to the left in an adjoining field. I rolled to
about 30 degrees, then as the nose reached normal flying attitude, I
brought the stick right back to neutral... and braced myself against
making an immediate recovery.

As before, there was a sense of mushing through the air, but no
tendency for the glider to yaw itself into a spin. For the next pull
and recovery, I delayed saying "Bang - cable break - recover!"
until 50 knots. Given the additional delay, I was much more aggressive
with the stick, both moving it forward and returning it to neutral once
I reach normal flying attitude. And once again, the sailplane
demonstrated a sluggish, heavy feel as the g force came back on, but
without any tendency to "fall" into the direction of the turn.

It was clear to me that I could have easily induced a spin during this
maneuver. A little too much rudder or stick against the turn coupled
with bringing the stick full aft would have tipped the sailplane right
over. But my intent was to produce an unanticipated spin, even though I
was, ostensibly, doing everything right.

I repeated this maneuver several more times, making slight adjustments
to angle of bank, but without adverse effects.

My conclusions:

This is an interesting flight regime. I suspect that it would prove
useful for producing spins in typically resistant aircraft, and require
significantly less control abuse among those gliders that are inclined
to spin. However, for my make and model (which can be easily coaxed to
incipiency), normal attention to stall warning signs and application of
coordinated aileron and rudder are adequate. There does not appear to
be any tendency for the glider to spin suddenly or unpredictably,
though I would caution that if the stick is used to catch a dropping
wing without appropriate application of rudder, the spin entry could be
significantly accelerated.

The greater the span, the more pronounced the effects of a tip stall
would be, but greater span is usually compensated for by a longer tail
boom and larger vertical stabilizer. Some designs may choose to
underpower the vertical stabilizer to increase glide performance, but
hopefully these would include appropriate warnings and recovery
procedures in their respective flight manuals.

As far as thermal entry is concerned, I would give the same warning: if
you delay your pushover on thermal entry to the point where G and
airspeed are significantly reduced below the norms (generally not the
most efficient way to enter a thermal), extra attention should be paid
to coordination. I wouldn't expect the glider to snap into a spin,
but it is entirely possible that the now underpowered vertical
stabilizer may not adequately compensate if you have any tendency
towards sloppiness.

I intend to experiment with this maneuver some more over the coming
weeks. As I discover anything interesting, I'll add my comments to
the thread. Also, I uploaded my FR trace to the OLC, but my sampling
was 4 seconds, hardly adequate for analysis. However, just in case you
are tempted to make an armchair assay, be my guest!

http://www2.onlinecontest.org/olcphp...823e438ec30ed8

The test run began at 1454 ET (UTC-4) and ended at 1503 ET.

Mike Schumann wrote:
It is not obvious to me, why, in a cable break scenario, you would be close
to stalling when you push the nose down to a normal attitude while you
maintain 60 knot airspeed. This sounds like you are flying significantly
above stall speed. Could you elaborate?

Thanks,
Mike Schumann

Mike;
I don't think Chris means he maintain 60 knots.
Starts at 60 knots, but with the nose up speed decays.....
Push the nose over to an *attitude* that in normal flight would give
around 60 knots and the trap is set....

Real speed is ~ Vs (say 40k) but attitude is good and she IS flying
(as G 1)

once the G reverts to 1 you either have a good angle of attack/speed
and you are flying
or you don't and you arent.

thats my take - Vs increases in a tight turn as g1.
so... when G1 (bunt/top of loop etc.) Vs *reduces*


;-) Jonny.

And I should add that I was explaining the exercise from memory and may
have got the speeds wrong. 90 kts is definitely over the top for
starting - pull up from 65 or 70 into a 45 degree climb so as not to
throw more height away at the outset.

In the case of a real cable break, climbing at 45 at 60 kt you *will*
take a second or two before you begin the pushover (and if you have
quick reactions pretend to be an out of practice, early solo pilot).
Then it will take the aircraft another second or two to complete the
pushover, which will mean the speed decays further. Performing this
exercise, I'd expect to see the normal gliding attitude with a speed of
perhaps 30kt or even as low as 20kt, but you're still flying because of
reduced G. Mike is quite right that the controls don't feel quite right,
but you're concerned to make the turn as early as possible because
you're just at that awkward height where you can't get in ahead but are
low for an abbreviated circuit (say 450ft at my airfield) so you turn,
the G comes back on, and the wing drops.

Whether you enter a spin will depend on the aircraft - our K21 won't
spin, even in this exercise, so falls out into a spiral dive. The
Puchacz rolls smoothly into the spin without any buffeting or other
warning, and I suspect most Polish gliders would do the same. Our K13
used to do the same, though in a more stately fashion, but since
re-covering seems more reluctant.

My point was not that a spin is inevitable, but that many gliders will
spin from this even though you are flying co-ordinated.

jonnyboy wrote:
Mike Schumann wrote:

It is not obvious to me, why, in a cable break scenario, you would be close
to stalling when you push the nose down to a normal attitude while you
maintain 60 knot airspeed. This sounds like you are flying significantly
above stall speed. Could you elaborate?

Thanks,
Mike Schumann


Mike;
I don't think Chris means he maintain 60 knots.
Starts at 60 knots, but with the nose up speed decays.....
Push the nose over to an *attitude* that in normal flight would give
around 60 knots and the trap is set....

Real speed is ~ Vs (say 40k) but attitude is good and she IS flying
(as G 1)

once the G reverts to 1 you either have a good angle of attack/speed
and you are flying
or you don't and you arent.

thats my take - Vs increases in a tight turn as g1.
so... when G1 (bunt/top of loop etc.) Vs *reduces*


;-) Jonny.

Chris Reed wrote:

And I should add that I was explaining the exercise from memory and may
have got the speeds wrong. 90 kts is definitely over the top for

Watch the limits: The LS 4 for example is limited to 77 knots on the winch.

In the case of a real cable break, climbing at 45 at 60 kt you *will*
take a second or two before you begin the pushover (and if you have

Two seconds? Never! If it takes you two seconds to react on the winch,
then you are not winch worthy. Hanging at the winch is not the place to
be dozing.

quick reactions pretend to be an out of practice, early solo pilot).

An out of practice, early solo pilot isn't sent solo at the winch.
Never. In our club, even the most experienced pilots are required to do
the first winch launch of the year with an instructor. (Club rule. And
yes, before you ask, for the instructors it's a catch 22 situation. It
works for us.)

reduced G. Mike is quite right that the controls don't feel quite right,
but you're concerned to make the turn as early as possible because
you're just at that awkward height where you can't get in ahead but are
low for an abbreviated circuit (say 450ft at my airfield) so you turn,

Nothing awkward with this height: There's plenty of time for a safe
downwind landing. In fact, you *must* take your time for that downwind
landing. Turn too early, and you'll find yourself with the (now in fact
awkward) problem of 200 ft height over the runway with possibly a tailwind.

Stefan

If you imagine that you are climbing at 55kts no probs
and the cable breaks. The glider starts to decelerate
so the immediate action is to push the stick forward
to pitch the nose down. The glider flies a parabolic
arc and while it's mass remains the same the weight
that the wing has to support is dramatically reduced
at the top of the arc. So the glider can be at 45kts
or less and the wing has not stalled, the AoA is still
below the stalling angle and the airspeed is sufficient
with the reduced G to keep the glider flying. The harder
the push the greater the reduction in G and effective
weight the wing has to support. Because of inertia
the glider will take time to accelerate to sufficient
speed to generate the lift necessary to support the
glider as the G increases to 1. If aileron is applied
to turn before this acceleration takes place the increasing
G can mean that in effect the wing is stalled and application
of aileron could initiate the spin. It is important
to remember that it is the attitude of the glider to
the relative airflow that determines the angle of attack,
not the relationship of the glider to the horizon.
The picture the pilot sees in these circumstances could
well be one where the nose is well below the horizon
(approach attitude) but acceleration has not taken
place and the wing is stalled. Once the glider accelerates
it is then safe to use the ailerons as normal. It is
a reversal of the situation where high G increases
the stalling speed, the further stalling exercise.
I have seen as little as 20 kts at the top of a push
over with no ill effect provided the ailerons remain
central. Try it sometime at a safe height, this will
be a far better way of seeing the problem than my explanation.

At 14:36 30 June 2005, Mike Schumann wrote:
It is not obvious to me, why, in a cable break scenario,
you would be close
to stalling when you push the nose down to a normal
attitude while you
maintain 60 knot airspeed. This sounds like you are
flying significantly
above stall speed. Could you elaborate?

Thanks,
Mike Schumann

wrote in message
roups.com...
Pilots depend on simple, quickly applied remedies
to any loss of
control. Since we are not always afforded the luxury
of examination,
analysis, and consideration of options as a preamble
to action, any
flight condition where these simple rules of recovery
do not work
demands closer examination and appropriate training
to recognize
symptoms and take appropriate actions.

Modern aircraft are designed to meet well-defined
controllability
requirements. For example, in the United States, the
recommended
recovery (generic) for any impending or developed
stall is to move the
control column forward while applying coordinated
aileron and rudder to
halt an un-commanded roll. The Flight Manual for my
S-H Ventus 2bx
states on page 3.4:

--On stalling whilst flying straight ahead or in a
banked turn, normal
flying attitude is regained by firmly easing the control
stick forward
and, if necessary, applying opposite rudder and aileron.--

Page 3.5 (Spin Recovery) continues...

--Note: Spinning may be safely avoided by following
the actions given
in section 3.4 'Stall Recovery'-

During the past several years, I have made it a point
to experiment
with various applications of controls throughout the
stall break (and
in a variety of makes and models). In all cases where
I maintained
coordination, either paying attention to the yaw string
or through
application of equal amounts of aileron and rudder,
the aircraft did
not spin, even if I held the stick firmly against
the rear stop.
Instead, it would transition from stall to spiral
dive.

In a recent RAS thread (Nimbus 4DT accident 31 July
2000 in Spain), I
was introduced to a maneuver practiced by BGA instructors
to
demonstrate that a quick transition from coordinated
flight into a spin
can take place while recovering from a winch launch
cable break. This
was pointed out to refute my comment in that thread
that modern gliders
need to be 'helped' into a spin (by either intentional
or
inadvertent abuse of the controls).

Chris Reed described the following:

--One of my favourite exercises for my annual checkouts
as a UK Basic
Instructor is the spin off a simulated winch launch
(only try this at
height with an appropriate instructor with you!).
Simulate a winch
launch by diving to 90 kt and then pulling up at 45
degrees. As the
speed drops to about 60 kt cry 'BANG - cable break',
and push over into

the normal flying attitude. The moment normal attitude
is reached,
begin
a co-ordinated turn.
All will be fine for a second or so, as you are flying
at reduced G.
However, once the G comes back on many gliders will
roll smoothly (no
buffeting) into a spin so fast that there is little
you can do about it

(though the purpose of the exercise is to show the
spin entry and then
a
recovery, so I've not tried reducing back pressure
as the wing drops).
The Puchacz is excellent for this.--

For me, this raised an immediate alarm. It indicates
that there are
flight regimes (whether experienced during a cable
break recovery,
during an aggressive thermal entry, or as a result
of turbulence) where
normal control movements may result in an immediate
and unannounced
spin entry.
Since such matters are best examined in the air, I
put together an
informal flight test plan to measure just how sudden
the spin entry is
and whether there might be mitigating factors.

To prepare for the test, I set up the following limits:

First, I would at no time during the maneuver bring
the stick back all
the way to the stop. We must assume that all pilots
meet a base level
of competency, and under no circumstance would any
competent pilot
resort to full up elevator to maintain attitude during
a cable break
recovery. I would consider such control usage an abuse
of the controls.

Second, I would remain coordinated (as indicated by
my yaw string)
throughout the maneuver per the instructions of my
flight manual.

Third, at stall break, I would hold the controls firm
and visually
verify their positions, then wait for the sailplane
to assume its new
state (either spin or spiral dive) then clearly identify
that state
before making an appropriate recovery.

I began the test sequence with a series of four dives
and recoveries
just as Chris described, but without introducing a
bank. At 60 knots, I
called out 'Bang - cable break - recover!' I pushed
the stick
firmly forward. Three out of the four, I briefly suspended
loose dirt
in the cockpit. As soon as the nose passed through
the horizon into a
normal flying attitude, I moved the stick quickly
back to its normal
position for that attitude. Of course, this did not
entirely halt the
downward pitch of the nose. However, it was clearly
apparent through
the feel of the controls that the sailplane was either
stalled or on
the edge of a stall as a result of my quick application
of stick from
well forward to neutral. It was very clear that bringing
the stick
straight back to the stop would result in a full stall.

I began the dives in flap position -1, moving the
flaps to position +1
as I slowed through 70 knots, as I might if I were
entering a thermal,
though my recovery (pitch over) was much more aggressive
than any I
would use during cross-country flight. Once I was
comfortable with my
ability to keep myself from making an immediate recovery
from any
stall, I stopped to thermal, then found a clear patch
of sky and warned
off others away, as I fully expected to spin the sailplane.

In order to force an immediate turn, I imagined that
there was an
obstruction preventing a straight ahead landing. As
soon as the nose
came down, I determined that I would have to make
an immediate turn to
the right, which I did, without adverse results. The
sailplane rolled
sluggishly and felt on the edge of stall, but there
was no loss of
control, and certainly no sudden yaw and entry into
a spin. I thought
perhaps I had waited too long to initiate the turn,
so with the next
pull and recovery, I made the decision, before the
nose came fully
over, that I would land to the left in an adjoining
field. I rolled to
about 30 degrees, then as the nose reached normal
flying attitude, I
brought the stick right back to neutral... and braced
myself against
making an immediate recovery.

As before, there was a sense of mushing through the
air, but no
tendency for the glider to yaw itself into a spin.
For the next pull
and recovery, I delayed saying 'Bang - cable break
- recover!'
until 50 knots. Given the additional delay, I was
much more aggressive
with the stick, both moving it forward and returning
it to neutral once
I reach normal flying attitude. And once again, the
sailplane
demonstrated a sluggish, heavy feel as the g force
came back on, but
without any tendency to 'fall' into the direction
of the turn.

It was clear to me that I could have easily induced
a spin during this
maneuver. A little too much rudder or stick against
the turn coupled
with bringing the stick full aft would have tipped
the sailplane right
over. But my intent was to produce an unanticipated
spin, even though I
was, ostensibly, doing everything right.

I repeated this maneuver several more times, making
slight adjustments
to angle of bank, but without adverse effects.

My conclusions:

This is an interesting flight regime. I suspect that
it would prove
useful for producing spins in typically resistant
aircraft, and require
significantly less control abuse among those gliders
that are inclined
to spin. However, for my make and model (which can
be easily coaxed to
incipiency), normal attention to stall warning signs
and application of
coordinated aileron and rudder are adequate. There
does not appear to
be any tendency for the glider to spin suddenly or
unpredictably,
though I would caution that if the stick is used to
catch a dropping
wing without appropriate application of rudder, the
spin entry could be
significantly accelerated.

The greater the span, the more pronounced the effects
of a tip stall
would be, but greater span is usually compensated
for by a longer tail
boom and larger vertical stabilizer. Some designs
may choose to
underpower the vertical stabilizer to increase glide
performance, but
hopefully these would include appropriate warnings
and recovery
procedures in their respective flight manuals.

As far as thermal entry is concerned, I would give
the same warning: if
you delay your pushover on thermal entry to the point
where G and
airspeed are significantly reduced below the norms
(generally not the
most efficient way to enter a thermal), extra attention
should be paid
to coordination. I wouldn't expect the glider to snap
into a spin,
but it is entirely possible that the now underpowered
vertical
stabilizer may not adequately compensate if you have
any tendency
towards sloppiness.

I intend to experiment with this maneuver some more
over the coming
weeks. As I discover anything interesting, I'll add
my comments to
the thread. Also, I uploaded my FR trace to the OLC,
but my sampling
was 4 seconds, hardly adequate for analysis. However,
just in case you
are tempted to make an armchair assay, be my guest!

http://www2.onlinecontest.org/olcphp...info.php?ref3=
197828&ueb=N&olc=olc-usa&spr=en&dclp=c9701de37223903b6f823e438ec30
ed8

The test run began at 1454 ET (UTC-4) and ended at
1503 ET.

Someone taught me a pretty effective way to put almost "all" the
gliders in a spin. It consist in just flying straight at a speed just a
little over the stall speed. Then use the ailerons only to slightly
bank the wings, say ten or fifteen degrees. At that moment if you push
the rudder on the side of the low wing you _will_ enter a spin.

I remember that during instruction we had to use the ASK13 for the
spins, because the Grob Twin Astir was not really spinning. Years after
I have then tried the Twin with this system, and geez down it goes...

At 20:54 30 June 2005, Stefan wrote:
Chris Reed wrote:

And I should add that I was explaining the exercise
from memory and may
have got the speeds wrong. 90 kts is definitely over
the top for

Watch the limits: The LS 4 for example is limited to
77 knots on the winch.

As you are fond of pointing out, read the thread.

What Chris is describing is an upper air excercise
(no winch involved), Va and Vne are relevant, the max
winch speed is of no concern (personally I favour 70-75kts
as an entry speed, 60 isn't quite enough to get the
glider into the winch launch attitude, push over and
then stop the nose dropping on the horizon, 90 would
work but you'd be wasting height).

To simulate the situation which kills people (namely
spinning as a result of commencing a turn before flying
speed is regained after a cable break) you dive to
acquire speed, pull up into the winch launch attitude
then, at the appropriate moment, shout 'bang' and recover,
but check the pitch down at the normal gliding attitude
for 60kts, then immediately start a co-ordinated turn.
A Puchacz will immediately spin off this if you get
it right (the speeds are quite critical), too slow
you can't hold the nose up, too fast and it gets 'untidy'.
Trying to do this demo off a real winch launch would
hurt.

"Andrew Warbrick" wrote in message
...
At 20:54 30 June 2005, Stefan wrote:
Chris Reed wrote:

And I should add that I was explaining the exercise
from memory and may
have got the speeds wrong. 90 kts is definitely over
the top for

Watch the limits: The LS 4 for example is limited to
77 knots on the winch.

As you are fond of pointing out, read the thread.

What Chris is describing is an upper air excercise
(no winch involved), Va and Vne are relevant, the max
winch speed is of no concern (personally I favour 70-75kts
as an entry speed, 60 isn't quite enough to get the
glider into the winch launch attitude, push over and
then stop the nose dropping on the horizon, 90 would
work but you'd be wasting height).

To simulate the situation which kills people (namely
spinning as a result of commencing a turn before flying
speed is regained after a cable break) you dive to
acquire speed, pull up into the winch launch attitude
then, at the appropriate moment, shout 'bang' and recover,
but check the pitch down at the normal gliding attitude
for 60kts, then immediately start a co-ordinated turn.
A Puchacz will immediately spin off this if you get
it right (the speeds are quite critical), too slow
you can't hold the nose up, too fast and it gets 'untidy'.
Trying to do this demo off a real winch launch would
hurt.

You guys do this a little bit more subtly than I did it. I just asked the
student to deliberately botch the simulated wire break by doing nothing at
first. Just leave the glider pointed at the sky until it runs out of energy
and the nose falls through on it own and THEN, just as the nose falls
through the horizon, yank hard back on the stick while attempting a turn.
Almost any spinable glider will spin with enthusiasm under those conditions.
Of course, I'm talking about doing this at a safe altitude.

Fiveniner's point that this is abnormal use of controls is a fact but a
rusty or inexperienced pilot already unnerved by a wire break and now seeing
the nose fall toward the earth may just do it this way if not for this sort
of explicit training. It would appear that there are several cases in the
BGA accident database where this might have happened.

Just in case there are lurkers reading this who are getting the impression
that this is a sort of trap for the unwary should carefully read fiveniner's
flight test report. It DOES require the pilot to use very abnormal, in fact
illogical, control inputs. The training just reinforces the very basic idea
that the pilot must see a safe airspeed for the glider being flown before
establishing a normal glide or attempting a turn. No rocket science here,
just mind your airspeed and use smooth, logical control inputs.

Bill Daniels

At 00:48 01 July 2005, Bill Daniels wrote: (snip)
Just in case there are lurkers reading this who are
getting the impression
that this is a sort of trap for the unwary should carefully
read fiveniner's
flight test report. It DOES require the pilot to use
very abnormal, in fact
illogical, control inputs. The training just reinforces
the very basic idea
that the pilot must see a safe airspeed for the glider
being flown before
establishing a normal glide or attempting a turn.
No rocket science here,
just mind your airspeed and use smooth, logical control
inputs.

Unfortunately Bill that is just what it is, a trap
for the unwary. You can be in a situation where everything
looks normal, the nose is down in the approach attitude
you put in aileron and rudder and voila, spin/spiral
dive.

I have always taught that the decision whether to land
ahead or turn should never be made until both conditions
are met, attitude and airspeed. You cannot rely on
attitude in the same way as we do for 'normal' flying.
It is a trap easily avoided by thinking rather than
acting instictively. It's a bit like the turn on finals
- open the airbrake syndrome, people do it until it
bites.