Coordinated turning stall and spins

Thanks for your responses. My reason for posing the
final question is not so much speed as deceleration.
I once saw a tiger moth hit the ground spinning, both
pilots survived albeit one is now a paraplegic. It
is not just forward speed but a matter of what strikes
the ground first, a matter of pure chance I agree.
What is certain is that in a dive the most likely thing
to reach the scene of the accident first is the nose
of the glider where the soft part sits. This may indeed
happen in a spin but forward speed is not the main
factor, it is the rate of descent and will this be
less in a spin than in a dived and accelerating condition?
It's not speed that kills you it's stopping. I really
don't know and I am not eager to find out either :-)
Whatever the answer the best solution is to avoid the
spin in the first place but sadly it is not a perfect
world.
The only difference between a fatal and non-fatal accident
is the dead body and that can also be a matter of pure
blind chance.

At 17:06 12 November 2003, Chris Ocallaghan wrote:
Snip
One final question, if a spin is entered at 300 feet
should recovery even be attempted? Are the chances
of survival greater if the glider hits the ground
spinning
than if it is part recovered and 'tent pegged'? Interesting
what?


That's a tough one to answer. I see your point: better
to hit the
ground at 70 knots than 100 knots. In either case I
suspect the
results will be the same. I suppose it a matter of
whether you expire
at the scene or several hours later in an ICU. To that
end, I'd always
try to recover -- your chances of survival going from
miniscule to
maybe.



At 00:00 12 November 2003, Chris Ocallaghan wrote:
Posted this to the discussion on spinning Blaniks
from
a coordinated turning stall.

November 9, 2003
Turning Stalls and Insipient Spins

As promised, apropos to this discussion on spin entry
from coordinated
turning stalls, I took a tow this morning to 5000
feet
agl and
performed a series of coordinated and cross control
turning stalls.

The aircraft used was a Ventus 2bx, delivered this
year. I have
approximately 75 hours in this aircraft and about
525
hours total in
the model. I flew the glider at approximately 70%
of
the aft cg limit.
Wing loading was 7.8 lbs per square foot. All stalls
were entered in
the first positive flap position.

My intention was as follows: to perform a series of
turning stalls,
both coordinated and cross controlled, to determine
the departure and
post departure characteristics of a modern fiberglass
sailplane.
Stalls were entered gently and in a shallow bank (lower
wingtip on
horizon). Whether coordinated or cross controlled,
I fixed the
controls in the pre-departure position for three full
seconds after
departure (that is, no attempt was made to recover
immediately after
the stall break).

Once off tow I completed two clearing turns, then
stalled
the glider
wings level twice to establish attitude. I then entered
a coordinated
shallow left turn and gently eased back on the stick.
The stall broke
cleanly. The glider initially yawed about 30 degrees
to the left,
dropped its nose through the horizon, then began to
increase its bank
angle and gain speed. G forces accumulated and I recovered
from the
spiral dive at about 80 knots and roughly 70 degrees
of bank. (As
noted above, the elevator was held firmly aft and
aileron
and rudder
neutral until recovery was initiated.

I repeated the same maneuver to the right. The stall
break was less
clean (more mushy). Development of the ensuing spiral
dive was slower,
but airspeed and bank angle both accumulated until
I released the
controls and initiated a recovery.

I repeated this sequence with like results.

I then entered a shallow bank turning stall (left)
while skidding
slightly. As the low wing began to drop, I applied
about ½ stick
travel to the right, ostensibly to raise the dropping
wing. Entry into
the spin was immediate and dramatic. The glider yawed
approximately
ninety degrees while dropping it nose to about 60
degrees
below the
horizon. I left the controls in this position for
a
count of three
(one one thousand, two one thousand?) The glider completed
approximately 1.25 rotations before I initiated a
recovery
(stick
forward, ailerons neutral, opposite rudder, pull up
from dive).

I repeated this process to the right. However, this
time, I gently
accelerated the stall (achieving a slightly higher
nose attitude
before departure). Once again, I skidded the turn
(10
to 20 degrees),
and tried to pick up the low wing as it stalled, this
time with full
deflection of the aileron. The ensuing spin entry
was
even more
dramatic. I was unable to measure rotation rate (even
roughly) because
the glider's nose went immediately past vertical.
As
I lost the
horizon I became disoriented, until I looked out at
the wingtip and
found the horizon again. I nonetheless fixed the controls
for a count
of three. There was no noticeable g build up until
I initiated a spin
recovery. Max speed during the dive was just above
120 knots, about 20
knots more than I typically see for a recovery from
a fully developed
spin.

It should be noted that my glider has a flap redline
of 80 knots. In
all cases, if airspeed exceeded 80 knots, I moved
the
flap handle to
the first negative position.

My interpretation: while the glider exhibited a yawing
motion during
the coordinated turning stall, it did not auto rotate,
nor did it show
any such propensity. Some pilots may find the dropping
wing, yaw
motion, and reduced g force of a coordinated turning
stall
disquieting, but when compared in sequence to an actual
autorotation
leading to a fully developed spin, the prior is patently
docile.
Height loss after an immediate recovery from a coordinated
turning
stall using a release of back pressure and coordinated
ailerons and
rudder could be measured in 10s of feet. The spin,
however, from entry
to the bottom of the dive recovery was measured in
hundreds. Loss of
height for the first spin, from entry, through development,
to the
bottom of the recovery dive was 475 feet. The second:
750 feet.

Conclusions: draw your own.

Don,

I underestand completely your concerns. It's a subject that's troubled
me for a long time, and I seem prone to flip flopping. The problem
isn't so much a question of energy... you'll have less in the spin
than in the ensuing dive after recovery (both of which are nose down),
but having a "procedure" that you can apply without thinking. When
close to the ground, you simply don't have time to observe and react
to more than a few inputs. For example, if I were to cross-control the
aircraft into a stall below 300 feet, if I were over trees, I might
just lock up the controls, close my eyes, and get ready for the hurt.
But to do this I would have to overcome my rote training... that is,
if I sense a departure, I recover immediately. I'm not sure that type
of switch would be valuable. The lesson I've taken away from this
discussion is that in the pattern, the yaw string stays bolt straight.
An unexpected stall can be handled if the aircraft is coordinated. If
not, the bottom falls out quickly.

If you accept as axiomatic that a stall can happen at any speed and at
any attitude, then I have to place priority on coordination fist,
airspeed second, though both are clearly primary concerns in the
pattern.

It is a virtue, or perhaps a nuissance, of our sport, that when near
the ground, the envelope narrows significantly. Between 1000 agl and
10 agl is like climbing solo. Falling is not an option, and we need to
attune ourselves to that.

OK, I agree with what you say and I suspect that if
the glider departed at 300ft I would be straight into
recovery as well. I suppose the point I am trying to
make is that departure from flight with insufficient
distance between the glider and the ground is going
to hurt whatever we do. We spend an awful lot of time
teaching spin recovery, and rightly so. We seem to
me, to spend less time emphasising the signs and symtons
of approaching stalls/spins and this I feel needs to
be put right. The cpncentration on keeping balanced
flight when near the ground indicates that the problem
has been thought about and recognised. How many glider
pilots have thought that deeply and really understand
that lighting fast recovery techniques will not help
when close to the ground? How many are able to recognise
the onset of disaster and take recovery action before
it happens? The people who have been posting on this
thread almost certainly have but what of the silent
ones?
The final turn stall/spin claims many every year. Are
we really approaching the problem in the right way?
As an aside it is not just glider pilots who get it
wrong. I recall reading an accident report of an airliner
which had taken off from Heathrow back in the 60's
or 70's. The aircraft stalled at about 3000ft and hit
the ground in a stalled condition. There were 3 qualified
ATPL pilots in the cockpit, two of them qualified as
captain on type. None of them it would appear recognised
that the airplane was stalled.
What chance have we mere mortals got if the gods get
it wrong?


At 15:06 13 November 2003, Chris Ocallaghan wrote:
Don,

I underestand completely your concerns. It's a subject
that's troubled
me for a long time, and I seem prone to flip flopping.
The problem
isn't so much a question of energy... you'll have less
in the spin
than in the ensuing dive after recovery (both of which
are nose down),
but having a 'procedure' that you can apply without
thinking. When
close to the ground, you simply don't have time to
observe and react
to more than a few inputs. For example, if I were to
cross-control the
aircraft into a stall below 300 feet, if I were over
trees, I might
just lock up the controls, close my eyes, and get ready
for the hurt.
But to do this I would have to overcome my rote training...
that is,
if I sense a departure, I recover immediately. I'm
not sure that type
of switch would be valuable. The lesson I've taken
away from this
discussion is that in the pattern, the yaw string stays
bolt straight.
An unexpected stall can be handled if the aircraft
is coordinated. If
not, the bottom falls out quickly.

If you accept as axiomatic that a stall can happen
at any speed and at
any attitude, then I have to place priority on coordination
fist,
airspeed second, though both are clearly primary concerns
in the
pattern.

It is a virtue, or perhaps a nuissance, of our sport,
that when near
the ground, the envelope narrows significantly. Between
1000 agl and
10 agl is like climbing solo. Falling is not an option,
and we need to
attune ourselves to that.

Don Johnstone wrote:

OK, I agree with what you say and I suspect that if
the glider departed at 300ft I would be straight into
recovery as well. I suppose the point I am trying to
make is that departure from flight with insufficient
distance between the glider and the ground is going
to hurt whatever we do. We spend an awful lot of time
teaching spin recovery, and rightly so. We seem to
me, to spend less time emphasising the signs and symtons
of approaching stalls/spins and this I feel needs to
be put right. The cpncentration on keeping balanced
flight when near the ground indicates that the problem
has been thought about and recognised. How many glider
pilots have thought that deeply and really understand
that lighting fast recovery techniques will not help
when close to the ground? How many are able to recognise
the onset of disaster and take recovery action before
it happens? The people who have been posting on this
thread almost certainly have but what of the silent
ones?
The final turn stall/spin claims many every year. Are
we really approaching the problem in the right way?
As an aside it is not just glider pilots who get it
wrong. I recall reading an accident report of an airliner
which had taken off from Heathrow back in the 60's
or 70's. The aircraft stalled at about 3000ft and hit
the ground in a stalled condition. There were 3 qualified
ATPL pilots in the cockpit, two of them qualified as
captain on type. None of them it would appear recognised
that the airplane was stalled.
What chance have we mere mortals got if the gods get
it wrong?


I completely agree on the point that training should more
focus on early detection and correction of incipient stall/spin
than on recovery of fully developed ones. As my previous favorite
sport was windsurfing, I developed a feeling for recognizing this
situation, because in this case, if you don't react immediately,
you can't avoid falling in water on the upwind side. I had a discussion
with a German pilot who did the same and feels the same thing.
Anyway, each time before I turn to final, I recite in my mind: "Watch your
speed and symmetry, here is the place where people kill themselves",
and I think I am going to say the same thing to my students.

When a stall/spin happens or nearly happens, it is only if the pilot has the
correct reflexes that the stall is prevented, or recovery is made with
minimum loss of height. But it is less likely to go wrong if there is also
good understanding.

There are three dangers from a stall/spin:

1. You hit something before recovery to normal flight.

2. You overstress the glider before recovery to normal flight.

3. After recovery you are not able to make a normal landing, because of
the height you have lost, or the direction you are now pointing.

It is essential to judge all these circumstances to know when a stall/spin
must not be risked.

There are four stages of an inadvertent stall/spin.

1. Avoid altogether.

2. Recognise that a stall/spin is close.

3. Recognise that the glider has stalled / is starting to spin.

4. Recover.

Too many people think that to avoid a stall/spin altogether what you need is
to be expert and quick at recognising that you are nearly stalled. The
real problem is that the glider can depart into a steep stall/spin without
any prior warning so far as the pilot is concerned; this is not because the
pilot failed to notice symptoms that the stall was close, but because there
weren't any. This is more likely to happen to a type known to readily spin
(Puchacz, IS28) but it can happen to any type (K21, Discus).

What matters is the angle of attack:

a. Angle of attack higher than the critical angle, you are stalled and
likely to have lateral instability (spin entry).

b. Angle of attack at the critical angle, you are stalling.

c. Angle of attack below the critical angle but close, you are at risk
from stalling in any gust wind gradient or shear, or due to inaccurate
flying.

If speed is low you are more likely to stall other things being equal, but
it is possible to stall at high speed, and possible to be at a very low
speed and not be stalled; what is critical is the angle of attack and not
the speed.

Inaccurate flying of itself will only stall you if you are already at a high
angle of attack, nearly stalled; the inaccuracy may tip you into the stall,
and the actual departure may be more violent and more complete. At a low
angle of attack whatever you do with ailerons and rudder will not stall you
(but it may cause a lot of extra drag, which may lead to a higher angle of
attack).

Inaccurate flying makes it more difficult to hold the desired angle of
attack, and to know if the angle of attack is increasing because it
disguises symptoms of high angle of attack. It will also increase drag
perhaps when you do not want any unnecessary loss of energy.

To avoid stalling keep the angle of attack well below the stalling angle.

How?

If you want to increase the angle of attack, you move the stick back (and
the elevator up).

If you want to reduce the angle of attack, you move the stick forward (and
the elevator down), this is why the recovery from a stall or from nearly
stalled always includes moving the stick forward.

If you are moving the stick back you are calling for a higher angle of
attack, whatever you reason for moving it back.

If you are moving the stick forward you are calling for a lower angle of
attack, again whatever your reason for moving it forward.

Therefore to be sure of avoiding an inadvertent stall/spin, part of our
flying must include monitoring stick movement and position. This is more
important than monitoring speed and change of speed (which is also
essential).

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Don Johnstone" wrote in
message ...

snip

We spend an awful lot of time teaching spin recovery, and rightly so. We
seem to me, to spend less time emphasising the signs and symptoms of
approaching stalls/spins and this I feel needs to be put right. The
concentration on keeping balanced flight when near the ground indicates
that the problem has been thought about and recognised. How many glider
pilots have thought that deeply and really understand that lighting fast
recovery techniques will not help when close to the ground? How many are
able to recognise the onset of disaster and take recovery action before it
happens? The people who have been posting on this thread almost
certainly have but what of the silent ones?

The final turn stall/spin claims many every year. Are we really
approaching the problem in the right way?

snip

The final turn stall/spin claims many every year. Are
we really approaching the problem in the right way?
As an aside it is not just glider pilots who get it
wrong. I recall reading an accident report of an airliner
which had taken off from Heathrow back in the 60's
or 70's. The aircraft stalled at about 3000ft and hit
the ground in a stalled condition. There were 3 qualified
ATPL pilots in the cockpit, two of them qualified as
captain on type. None of them it would appear recognised
that the airplane was stalled.
What chance have we mere mortals got if the gods get
it wrong?


Its something to with having 3 pilots. Too many cooks...
But if you are referring to the accident I think you are, didn't the
enquiry find that the two younger pilots were terrified of saying
anything to the very senior captain, who was probably having a heart
attack at the time?

At least we don't get that in gliders, thank goodness.

--
Mike Lindsay

If anyone wishes to read the full account of the investigation into this
accident (Trident 1 G-ARPI near Staines on 18th June 1972), it is now
available on-line.

BGA Website, Info for Clubs & Members, Safety, Links -
http://www.gliding.co.uk/bgainfo/safety/links.htm .
Air Accidents Investigation branch (AAIB) - http://www.aaib.gov.uk/ ,
Formal reports, Full reports, a.. No:4/73 - Trident I, G-ARPI, near Staines
http://www.dft.gov.uk/stellent/group...cst?n=5250&l=4 .

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Mike Lindsay" wrote in message
...

The final turn stall/spin claims many every year. Are
we really approaching the problem in the right way?
As an aside it is not just glider pilots who get it
wrong. I recall reading an accident report of an airliner
which had taken off from Heathrow back in the 60's
or 70's. The aircraft stalled at about 3000ft and hit
the ground in a stalled condition. There were 3 qualified
ATPL pilots in the cockpit, two of them qualified as
captain on type. None of them it would appear recognised
that the airplane was stalled.
What chance have we mere mortals got if the gods get
it wrong?


Its something to with having 3 pilots. Too many cooks...
But if you are referring to the accident I think you are, didn't the
enquiry find that the two younger pilots were terrified of saying
anything to the very senior captain, who was probably having a heart
attack at the time?

At least we don't get that in gliders, thank goodness.

Mike Lindsay

In this particular case, they all recognised the airliner was stalled. The
airliner was a Trident, with a 'T'-tail configuration. This particular
design (Ibeleiev in common with other T-tail designs) was able to get into a
stabe deep-stall configration where the nose rises so high that the
elevators descend into the wing wake and no longer have the authority to
lower the nose and the aircarft just pancakes down. Give enough height, I
think it is is possible to use the undercarriage and flaps to create enough
drag to correct the situation. These poor people didn't have the height
required.

"Mike Lindsay" wrote in message
...
The final turn stall/spin claims many every year. Are
we really approaching the problem in the right way?
As an aside it is not just glider pilots who get it
wrong. I recall reading an accident report of an airliner
which had taken off from Heathrow back in the 60's
or 70's. The aircraft stalled at about 3000ft and hit
the ground in a stalled condition. There were 3 qualified
ATPL pilots in the cockpit, two of them qualified as
captain on type. None of them it would appear recognised
that the airplane was stalled.
What chance have we mere mortals got if the gods get
it wrong?


Its something to with having 3 pilots. Too many cooks...
But if you are referring to the accident I think you are, didn't the
enquiry find that the two younger pilots were terrified of saying
anything to the very senior captain, who was probably having a heart
attack at the time?

At least we don't get that in gliders, thank goodness.

--
Mike Lindsay

"Don Johnstone" wrote in
message ...
the ground in a stalled condition. There were 3 qualified
ATPL pilots in the cockpit, two of them qualified as
captain on type. None of them it would appear recognised
that the airplane was stalled.
What chance have we mere mortals got if the gods get
it wrong?
No need to put ATPL's on a pedestal. At one of our club meetings, we had a
speaker whose business is teaching unusual attitude recovery to ATPLs. To
get his presentation going he gave us a number of scenarios and asked how
we'd respond. After giving us half a dozen of these and having the group
respond in unison with the right answer to each of them, he said "you know
more about this subject than any group of airline pilots I've ever trained".

Most of us glider pilots have a gut reaction in bad situations to unload the
wings first. Many professional pilots apparently don't.

That said, I don't mean to congratulate us all into any reduction in stall
avoidance and recovery training.

Simon,
Your explanation sounds plausible but bears no relation
to the accident investigation report. As far as I
know, the nose never got high - they would have realised
this, but it did get into the wrong configuration.
They could have recovered if they had (a) realised
the droop was retracted and put it down again, (b)
let the system do it's job (stick shaker warned them
and stick push tried to correct it but they dumped
it) or (c) initiated a normal stall recovery - lower
the nose - gain speed.
They were too slow at every stage of the flight and
somehow got into the wrong configuration, all of which
was 'probably' due to the Captain's partial incapacity
due to a heart attack and the crew not realising the
Captain's problem.
I suspect you were recalling a different incident in
a similar aircraft?
Rob
At 16:06 16 November 2003, Simon Waddell wrote:
In this particular case, they all recognised the airliner
was stalled. The
airliner was a Trident, with a 'T'-tail configuration.
This particular
design (Ibeleiev in common with other T-tail designs)
was able to get into a
stabe deep-stall configration where the nose rises
so high that the
elevators descend into the wing wake and no longer
have the authority to
lower the nose and the aircarft just pancakes down.
Give enough height, I
think it is is possible to use the undercarriage and
flaps to create enough
drag to correct the situation. These poor people didn't
have the height
required.

'Mike Lindsay' wrote in message
...
The final turn stall/spin claims many every year.
Are
we really approaching the problem in the right way?
As an aside it is not just glider pilots who get it
wrong. I recall reading an accident report of an airliner
which had taken off from Heathrow back in the 60's
or 70's. The aircraft stalled at about 3000ft and
hit
the ground in a stalled condition. There were 3 qualified
ATPL pilots in the cockpit, two of them qualified
as
captain on type. None of them it would appear recognised
that the airplane was stalled.
What chance have we mere mortals got if the gods get
it wrong?


Its something to with having 3 pilots. Too many cooks...
But if you are referring to the accident I think you
are, didn't the
enquiry find that the two younger pilots were terrified
of saying
anything to the very senior captain, who was probably
having a heart
attack at the time?

At least we don't get that in gliders, thank goodness.

--
Mike Lindsay