Nimbus 4DT accident 31 July 2000 in Spain.

Stefan writes
Wrong. Neither of the two would have done any damage. They broke the
glider by doing both things at the same time.

No. With the Spanish tragedy the pilots didn't open the airbrakes but
the P1 broke the wings by pulling back too hard. Presumably it wasn't
necessarily Vne that broke the wings but excessive load (pulling back
too hard in a panic) once past maximum maneuvouring speed? Given the
P1's self-confessed lack of currency in spin-training (paraphrased from
memory; "did it once twenty years ago and swore never again") is it fair
to say that without the panic from an unpractised situation the spin and
resulting dive recovery might not have broken the wings? Limiting your
spin recovery to just pulling back hard is going to have unfortunate
consequences which ever way it turns out. That said, it was a terrible
thing to happen and my heart really does go out to the pilot and his
family.

The Minden tragedy involved opened airbrakes which in turn contributed
to breaking the wing. Still from pulling back too hard, but in quite
different circumstances where "too hard" might not have been so apparent
because of the reduction in wing area and thus perceived wing-loading.
But had the airbrakes not been out the wing might have sustained the
load. Though Vne may then have been passed.

So it would seem the answer is to not open the airbrakes but respect the
yellow band on your ASI when loading the aircraft with g. Even if this
means passing through Vne?

Or, if you do open the airbrakes in a last ditch attempt to avoid
breaching Vne be even more respectful with the loading when pulling out
of the dive. But, between the devil and the deep blue sea you're better
off not having stepped out onto the gunwale in the first place


--
Bill Gribble
http://www.scapegoatsanon.demon.co.uk
- Learn from the mistakes of others.
- You won't live long enough to make all of them yourself.

At 15:12 24 June 2005, Stefan wrote:
HL Falbaum wrote:

Further in the report it is indicated that the N4DM
was certified by JAR
with exceptions for stall/spin behavior.

How so? You cannot get a glider certificated without
adhering to all JAR
22 requirements.

So, in summary, one pilot pulled the stick and broke
the aircraft, and one
pilot pulled the spoilers and broke the aircraft.

Wrong. Neither of the two would have done any damage.
They broke the
glider by doing both things at the same time.

Stefan

No, in the accident in Spain which started this thread,
all evidence points to the brakes not being deployed,
at all.

Andrew Warbrick wrote:

No, in the accident in Spain which started this thread,
all evidence points to the brakes not being deployed,
at all.

Please read the thread before commenting. HLF, to whom I was responding,
was explicitely referring to the Minden accident.

Stefan

Bill Gribble wrote:

But, between the devil and the deep blue sea you're better

JAR 22 requires that a glider can be recovered from a spin of at least 5
full turns (or the number at which the spin transfers to a spiral, if
that number is smaller) by applying the "standard procedure" and without
exceeding the load limits. Last I've heard there are a couple of Nimbi
4DT registered in Germany and other European countries. Which means they
are JAR certificated, hence...

Stefan

I think it's misleading to say that modern aircraft "must be 'helped'
into the spin". There are some circumstances when a spin entry can be
made without any "odd" control inputs at all.

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.

My understanding is that although everything looks fine, in fact you are
flying below 1G stall speed (possible because of the reduced G resulting
from the pushover, which is why BGA training requires you to push over
beyond the normal attitude after a cable break, monitor the airspeed and
not turn until a safe speed is regained). When 1G is restored the wings
stall, but because you're already in a turn the down wing stalls earlier
and autorotation ensues.

If you think about it, an aggressive pull up into a thermal coupled with
turning a little later than normal might produce similar effects.

I believe there are a number of other modes of spin entry without
unusual control movements, though you would need a far more experienced
pilot than me to explain them.

This is not to say that a glider in normal flight will depart into a
spin without abuse of the controls, but I think it important to
recognise that co-ordinated flight is not an *absolute* protection and
to understand when extra precautions are required (and what those
precautions are).

wrote:
Most important is recognition of prestall and initial departure. Since
the spin is a product of yaw moment at departure, you can prevent a
spin with coordinated controls alone. IE, modern aircraft must be
"helped" into the spin. (Put another way, the vertical stabilizer
creates enough yaw dampening to prevent autorotaion at stall so long no
pro spin control imputs are made. Since there are two yaw controls,
that would mean pro rudder or anti stick.) Thus, any prestall or
initial departure that is met with a release of back pressure and use
of coordinated controls to level the wings will produce the desired
effect before a spin or spiral dive can develop. Even if you choose not
to release back pressure, you shouldn't spin. Instead, you might find
yourself in a secondary stall. The longer it takes to apply these
simple actions, the less likely that it will produce an immediate
remedy, as the aircraft will continue into either a spin or spiral dive.

I agrre with most of this except the exceed VNe bit.
The damger from exceeding VNe is flutter and flutter
WILL break the aircraft. I think the last paragraph
is the only option.

The only time a pilot (test pilots excepted) is likely
to experience a spin in a big wing aeroplane is if
it happens accidentally. Non aerobatic means no deliberate
spinning (in the UK anyway) which means there is no
opportunity to practice. Makes prevention and early
recognition even more vital.

At 16:00 24 June 2005, Bill Gribble wrote:
Stefan writes
Wrong. Neither of the two would have done any damage.
They broke the
glider by doing both things at the same time.

No. With the Spanish tragedy the pilots didn't open
the airbrakes but
the P1 broke the wings by pulling back too hard. Presumably
it wasn't
necessarily Vne that broke the wings but excessive
load (pulling back
too hard in a panic) once past maximum maneuvouring
speed? Given the
P1's self-confessed lack of currency in spin-training
(paraphrased from
memory; 'did it once twenty years ago and swore never
again') is it fair
to say that without the panic from an unpractised situation
the spin and
resulting dive recovery might not have broken the wings?
Limiting your
spin recovery to just pulling back hard is going to
have unfortunate
consequences which ever way it turns out. That said,
it was a terrible
thing to happen and my heart really does go out to
the pilot and his
family.

The Minden tragedy involved opened airbrakes which
in turn contributed
to breaking the wing. Still from pulling back too hard,
but in quite
different circumstances where 'too hard' might not
have been so apparent
because of the reduction in wing area and thus perceived
wing-loading.
But had the airbrakes not been out the wing might have
sustained the
load. Though Vne may then have been passed.

So it would seem the answer is to not open the airbrakes
but respect the
yellow band on your ASI when loading the aircraft with
g. Even if this
means passing through Vne?

Or, if you do open the airbrakes in a last ditch attempt
to avoid
breaching Vne be even more respectful with the loading
when pulling out
of the dive. But, between the devil and the deep blue
sea you're better
off not having stepped out onto the gunwale in the
first place


--
Bill Gribble
http://www.scapegoatsanon.demon.co.uk
- Learn from the mistakes of others.
- You won't live long enough to make all of them yourself.

Interesting set of circumstances. I'll try it, before I comment at
length. However, I will not recover to see if it really is a spin. I
suspect I'll see it become a spiral dive based on previous flight
testing in this regime. But experimentation will tell.

By the way, I do this often, though not in quite the order you state or
for the same reason. I enjoy pointing the nose up 60 degrees or so,
then letting it park. The stall and pitch through is typically well
past vertical. Great fun, and completely self recovering after the
stall break. And much, much more exciting than a wing over.



Chris Reed wrote:
I think it's misleading to say that modern aircraft "must be 'helped'
into the spin". There are some circumstances when a spin entry can be
made without any "odd" control inputs at all.

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.

My understanding is that although everything looks fine, in fact you are
flying below 1G stall speed (possible because of the reduced G resulting
from the pushover, which is why BGA training requires you to push over
beyond the normal attitude after a cable break, monitor the airspeed and
not turn until a safe speed is regained). When 1G is restored the wings
stall, but because you're already in a turn the down wing stalls earlier
and autorotation ensues.

If you think about it, an aggressive pull up into a thermal coupled with
turning a little later than normal might produce similar effects.

I believe there are a number of other modes of spin entry without
unusual control movements, though you would need a far more experienced
pilot than me to explain them.

This is not to say that a glider in normal flight will depart into a
spin without abuse of the controls, but I think it important to
recognise that co-ordinated flight is not an *absolute* protection and
to understand when extra precautions are required (and what those
precautions are).

wrote:
Most important is recognition of prestall and initial departure. Since
the spin is a product of yaw moment at departure, you can prevent a
spin with coordinated controls alone. IE, modern aircraft must be
"helped" into the spin. (Put another way, the vertical stabilizer
creates enough yaw dampening to prevent autorotaion at stall so long no
pro spin control imputs are made. Since there are two yaw controls,
that would mean pro rudder or anti stick.) Thus, any prestall or
initial departure that is met with a release of back pressure and use
of coordinated controls to level the wings will produce the desired
effect before a spin or spiral dive can develop. Even if you choose not
to release back pressure, you shouldn't spin. Instead, you might find
yourself in a secondary stall. The longer it takes to apply these
simple actions, the less likely that it will produce an immediate
remedy, as the aircraft will continue into either a spin or spiral dive.

At 18:12 24 June 2005, Stefan wrote:
Andrew Warbrick wrote:

No, in the accident in Spain which started this thread,
all evidence points to the brakes not being deployed,
at all.

Please read the thread before commenting. HLF, to whom
I was responding,
was explicitely referring to the Minden accident.

Stefan

I'll let that pass with the suggestion that you read
the thread more carefully before flaming people. Enough
said.

A little consideration before I go try this in the air. First, it is
possible to stall a glider while coordinated. No epiphany there. If you
stall in a bank, you are likely to have the low wing drop, for the
reasons Chris gave. This, however, should not result in a spin.
UNLESS... given the variables Chris has introduced, we have a glider
that is potentially flying well below its 1G stall speed. This means
that the force available to the vertical stabilizer to dampen a yawing
motion is significantly diminished. So then is the power of the rudder.
Adverse yaw of the ailerons is increased at the stall. Harmonization
(ie, required pilot control inputs to maintain coordinated flight)
changes as the horizontal stab is now operating at less than design
speeds. Interesting. There would seem to be a crossover in this regime,
where even if the contols are harmonized (given the relative torques
available to VS and ailerons), there simply may not be enough
weathervaning potential in the VS to prevent autorotation if a stall
develops at the wingtip.

Is it safe to say that winch launching is an aerobatic maneuver, and
therefore requires very specific training techniques since the glider
is likely to be flown outside its design limits? Also, it seems the key
to avoiding this situation is to avoid the stall, which means no sudden
snatching back of the stick (even to neutral) once a "normal" attitude
is achieved. Since this situation is likely to occur near the ground,
where the horizon is not a particularly useful airspeed indicator, do
you teach close monitoring of airspeed throughout the recovery? And a
complicating factor... if there is already a bank during the recovery,
how do you address it? You've noted that AOA differential is enough to
snap the glider into a spin. Attempting to level the wings would seem
to only aggrevate any impending tip stall.

I'm not unfamiliar with this regime. Though I typically don't turn at
the top of a hard pull into a thermal (I generally start the turn
during the pull, if I'm going to turn at all), I do on occasion decide
that I've misjudged the thermal's size and its worth a turn. However,
the glider's roll is typically so slow, I find myself moving the stick
well forward (and sometimes dumping flaps) to increase the roll rate...
a normal reaction to sluggish controls near the stall. So again, I'm
wondering that the pilot isn't introducing an aggrevating factor
(misuse of the elevator), though admittedly, I hadn't considered this
narrow flight band when addressing the first, best recovery to an
unaticipated loss of control.




Chris Reed wrote:
I think it's misleading to say that modern aircraft "must be 'helped'
into the spin". There are some circumstances when a spin entry can be
made without any "odd" control inputs at all.

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.

My understanding is that although everything looks fine, in fact you are
flying below 1G stall speed (possible because of the reduced G resulting
from the pushover, which is why BGA training requires you to push over
beyond the normal attitude after a cable break, monitor the airspeed and
not turn until a safe speed is regained). When 1G is restored the wings
stall, but because you're already in a turn the down wing stalls earlier
and autorotation ensues.

If you think about it, an aggressive pull up into a thermal coupled with
turning a little later than normal might produce similar effects.

I believe there are a number of other modes of spin entry without
unusual control movements, though you would need a far more experienced
pilot than me to explain them.

This is not to say that a glider in normal flight will depart into a
spin without abuse of the controls, but I think it important to
recognise that co-ordinated flight is not an *absolute* protection and
to understand when extra precautions are required (and what those
precautions are).

wrote:
Most important is recognition of prestall and initial departure. Since
the spin is a product of yaw moment at departure, you can prevent a
spin with coordinated controls alone. IE, modern aircraft must be
"helped" into the spin. (Put another way, the vertical stabilizer
creates enough yaw dampening to prevent autorotaion at stall so long no
pro spin control imputs are made. Since there are two yaw controls,
that would mean pro rudder or anti stick.) Thus, any prestall or
initial departure that is met with a release of back pressure and use
of coordinated controls to level the wings will produce the desired
effect before a spin or spiral dive can develop. Even if you choose not
to release back pressure, you shouldn't spin. Instead, you might find
yourself in a secondary stall. The longer it takes to apply these
simple actions, the less likely that it will produce an immediate
remedy, as the aircraft will continue into either a spin or spiral dive.

wrote in message
ups.com...

Is it safe to say that winch launching is an aerobatic maneuver, and
therefore requires very specific training techniques since the glider
is likely to be flown outside its design limits?

Absolutely not true. Winch launch and the associated maneuvers are well
within the design limits of any modern glider. Winch launch is not an
aerobatic maneuver.



Chris Reed wrote:
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.

One of my favorites too but it needs to be understood that, in Chris Reed's
example, the glider is at a very high AOA and deeply stalled, or will be as
soon as 1G is re-established. The ASI will only be indicating 10 - 15
knots. Initiating a turn while in a deep stall will cause a wing drop and a
spin entry - no surprise here. This 'feels' normal only because of the
normal glide attitude. It is a variant of an accelerated stall.

This maneuver is for instructors so they can anticipate the results if a
student botches a wire break recovery. I've sometimes used it with student
to demonstrate WHY the nose needs to be well down and the airspeed seen to
be above best L/D and increasing before initiating a turn. In all cases,
this practice maneuver is done at a safe altitude.

To further explain, if a wire break occurs during the nose high part of a
winch launch, it's very likely that the best landing option is straight
ahead. When the glider is high enough that a turn is needed, the nose
attitude will be lower and the height AGL will be much greater.

Bill Daniels