Nimbus 4DT accident 31 July 2000 in Spain.

wrote in message
ps.com...
Bill,

In fact, at least according to US regs, a winch launch IS an aerobatic
manuever.

I believe you are referring to the +-30 degrees pitch and +-45 degrees bank
definition of aerobatics. I believe there is an exclusion for aircraft for
which these are normal maneuvers. Gliders routinely exceed these values
thus they are not considered aerobatic for gliders.

But that wasn't my point. If normal recovery from a normal
operation places the pilot on the ragged edge of a deep stall, then I
think it best to characterize the operation as "ab"normal., requiring
reactions unique to that environment. And thus my toying with the term
aerobatic.

Normal winch operation does not place the glider on the ragged edge of a
stall. A normal launch places the max AOA very near that for best L/D. A
wire break handled properly with a prompt pushover is flown at a still lower
AOA with the airspeed not dropping below 1.3 x Vs or so. The margin is even
greater when you consider that the pushover is at less than one G so the
stall airspeed is lower.

The wire break training maneuver described by Chris is to show an instructor
candidate what can happen if the student is allowed to mis-handle the wire
break and is WAY outside normal operation.

The whole point is to drum into the instructors who will then insist that
his students learn that the nose must be promptly lowered well below normal
glide and the airspeed seen to be at a safe value and increasing before any
thought is given to a turn. This is to establish and maintain a large
safety margin. In many cases no turn is necessary and the glider lands on
the remaining runway.


BTW, have you demonstrated this maneuver without recovery? IE, have you
left the controls in place to let the spin fully develop?

Yes, It is a normal spin with a normal recovery at least with the trainers
in common use.

The wire break recovery being discussed here is safer and less dramatic than
the equivalent airtow maneuver consisting of a 200 foot AGL release on
departure and a turn back to the runway.

Bill Daniels

Silly me, playing too loosely with terms.

What interests me is that recovery from a cable break, if misapplied,
appears to place the pilot in a very unusual situation. This flight
condition was presented to put into question the abolutism of some
simple control movements that should keep pilots out of danger of loss
of control. So my question becomes one of instructional emphasis. Since
some problems evolve so quickly that thoughtful consideration isn't
always a best first course, some absolutes are needed. But if you are
flying outside normal flight conditions (IE, aerobatics or cable break
recoveries), those absolutes might not apply. Yanking the stick back to
neutral to fix the horizon on the canopy at the top of a cable break
recovery qualifies as departing from normal flight conditions. But I
certainly see the problem you face. We train pilots to take note of a
stick well aft as one sign of an imminent stall. They might not so
quickly recognize that the glider can be stalled with the stick at
neutral under these conditions. Nor might they realize that
coordination of ailerons and rudder has changed at extremely low
airpseed. Thus the opportunity to enter a wing low stall with your
hands and feet in a position that should normally signal safe flight.

All that said, I spent about 15 minutes on Sunday afternoon
experimenting with this maneuver. The results weren't as previously
published, so I'll need to take some time to write up the results. I'll
start this as a new thread.

Bill Daniels wrote:
wrote in message
ps.com...
Bill,

In fact, at least according to US regs, a winch launch IS an aerobatic
manuever.

I believe you are referring to the +-30 degrees pitch and +-45 degrees bank
definition of aerobatics. I believe there is an exclusion for aircraft for
which these are normal maneuvers. Gliders routinely exceed these values
thus they are not considered aerobatic for gliders.

But that wasn't my point. If normal recovery from a normal
operation places the pilot on the ragged edge of a deep stall, then I
think it best to characterize the operation as "ab"normal., requiring
reactions unique to that environment. And thus my toying with the term
aerobatic.

Normal winch operation does not place the glider on the ragged edge of a
stall. A normal launch places the max AOA very near that for best L/D. A
wire break handled properly with a prompt pushover is flown at a still lower
AOA with the airspeed not dropping below 1.3 x Vs or so. The margin is even
greater when you consider that the pushover is at less than one G so the
stall airspeed is lower.

The wire break training maneuver described by Chris is to show an instructor
candidate what can happen if the student is allowed to mis-handle the wire
break and is WAY outside normal operation.

The whole point is to drum into the instructors who will then insist that
his students learn that the nose must be promptly lowered well below normal
glide and the airspeed seen to be at a safe value and increasing before any
thought is given to a turn. This is to establish and maintain a large
safety margin. In many cases no turn is necessary and the glider lands on
the remaining runway.


BTW, have you demonstrated this maneuver without recovery? IE, have you
left the controls in place to let the spin fully develop?

Yes, It is a normal spin with a normal recovery at least with the trainers
in common use.

The wire break recovery being discussed here is safer and less dramatic than
the equivalent airtow maneuver consisting of a 200 foot AGL release on
departure and a turn back to the runway.

Bill Daniels

wrote:

But if you are
flying outside normal flight conditions (IE, aerobatics or cable break
recoveries),

A cable brake during a winch launch is a perfectly normal flight
condition, and as such, is regulariliy trained. Maybe I'm wrong, but it
seems you didn't do many winch launches, did you?

Stefan

No. Several dozen.

BTW,

For the purposes of this section, aerobatic flight means an intentional
maneuver involving an abrupt change in an aircraft's attitude, an
abnormal attitude, or abnormal acceleration, not necessary for normal
flight. This is from the US FARs. While we can discuss ad nauseum
whether a winch launch is an aerobatic maneuver... (and really it
isn't), it clearly requries control motions that constitute aerobatic
flight, and as such represent a "special" set of circumstances.

Note that Chris introduced me to a manuever which can be accurately
described as outside the parameters of normal flight (IE, abrupt change
in aircraft attitude). In preparing to defend the efficacy of winch
launching, you're missing my point. There is a disconnect between the
control actions required for safe recovery from a cable break and the
correction of a stall and/or dropping wing during normal flight. My
point is that the cable break recovery is a special case and needs to
be discussed in depth, and differentiated from the "normal" control
movements to establish and maintain controlled flight. But I digress.
This is the subject of new thread.

BTW, I learned to winch launch under the tutelage of a BGA instructor
in Britain. This concern of the snap spin was never discussed. Recovery
of airspeed, certainly, but no warning against starting a turn.

Per the particulars of earlier notes in this thread, I'll offer some
opinions at length based on what I experienced in my glider yesterday,
but it'll be a few days before I can take the time to document them.

Stefan wrote:
wrote:

But if you are
flying outside normal flight conditions (IE, aerobatics or cable break
recoveries),

A cable brake during a winch launch is a perfectly normal flight
condition, and as such, is regulariliy trained. Maybe I'm wrong, but it
seems you didn't do many winch launches, did you?

Stefan

wrote in message
oups.com...
Yanking the stick back to
neutral to fix the horizon on the canopy at the top of a cable break
recovery qualifies as departing from normal flight conditions.

We agree. This is the reason for the training scenario which teaches
avoidance of this situation.

But I certainly see the problem you face. We train pilots to take note of
a
stick well aft as one sign of an imminent stall. They might not so
quickly recognize that the glider can be stalled with the stick at
neutral under these conditions.

To stop the nose at the normal gliding attitude after a wire break requires
a powerful elevator and full back stick. This is definitely a pilot induced
stall resulting from a mis-use of the elevator. However, accident records
show that this has occasionally been the cause of a spin accident so the
training scenario was added. To repeat what I wrote earlier, this is merely
a slight variant of an accelerated stall. If the stick were held neutral,
the nose would fall through to a steep nose down attitude. This is not the
best technique but it wouldn't result in a deep stall.

Bill Daniels

I found it difficult, in practice, to pull the stick back far enough to
park the nose on the horizon. Very couterintuitive (for me, at least),
though I can see how any pilot at low altitude might let a canopy full
of terrain misinform his better judgement.

BTW, throughout a dozen or more of these maneuvers, the glider never
spun. I'll give details. And remember, the point of the exercise wasn't
to show how misapplied controls might cause a sudden spin (this was
more than clear throughout the maneuver), but what would happen if I
paid accute attention to coordination.

I missed your last paragraph. As I noted to Andreas, it's all a matter
of what you are used to. A 200 foot rope break in the absence of
strong winds or turbulence is completely benign, at least for me,
having done hundreds of them.

What I'm finding interesting is the need to make fairly dramatic
motions of the controls as part of a cable break recovery. So again,
I'll flirt with the term aerobatic, not as a maneveur designed to
thrill and excite and audience or a passenger, but as a way to
differentiate use of the controls given these circumstances.

Even if you fail to observe the moment the rope breaks on aerotow, and
only become aware of it as you fail to maintain position behind the tow
plane, use of the controls is not nearly so dramatic as post cable
break. Nor, apparently, quite as critical. Though I think we can both
agree that they each represent real emergencies demanding preplanned
action.

wrote:

What I'm finding interesting is the need to make fairly dramatic
motions of the controls as part of a cable break recovery. So again,
I'll flirt with the term aerobatic,

Last weekend I flew in the mountains. Conditions were rough and I had to
make fairly dramatic motions of the controls to keep the blue side up.
I'll log it as an aerobatic flight, then.

Even if you fail to observe the moment the rope breaks on aerotow, and
only become aware of it as you fail to maintain position behind the tow
plane,

Awareness and prompt reaction are indispensable to survive which
launches. A winch launch *is* dangerous, in the way as there is a very
small margin for errors and it asks for your full focus.

Stefan

On Mon, 27 Jun 2005 15:48:07 UTC, Stefan
wrote:

: Last weekend I flew in the mountains. Conditions were rough and I had to
: make fairly dramatic motions of the controls to keep the blue side up.
: I'll log it as an aerobatic flight, then.

All this seems to hinge on what's meant by "aerobatic". Frankly, it
seems like a pretty pointless term to me, since it seems to depend on
the intention of the pilot rather on the manoevres flown. Why, for
example, is a loop aerobatic yet a tight thermalling turn, involving
similar stresses on the glider, is not?

To me, it makes more sense to categorize manoevres as high load / low
load and high risk / low risk, where "load" relates to forces on the
glider and "risk" relates to the speed with which things will go wrong
if the pilot misreacts.

That gives four permutations:

1) low load / low risk (normal flight)
2) low load / high risk (inverted flight)
3) high load / low risk (loop, tight thermalling)
4) high load / high risk (spin or spiral dive recovery)

This is off the top of my head, and I am sure we could argue about the
categories (should there be a "medium" in each case?) and
categorisations (how hard is a loop) for ages.

However, I think I would put many display aerobatic manoevres and
winch launching together in the high load / high risk category: it's
not that winch launching is aerobatic (whatever that means) but it is
also a time when the glider is being flown with higher than normal
structural loadings and when pilot error can cause things to go very
nasty very quickly.

I'd put mountain flying, from the little I have done, in the low load
/ high risk category at the very least, and probably high / high on
rough days.

Ian


--

Ian,

I like your train of thought. As well as decoupling from a term that
has such strong connotations.

Ian Johnston wrote:
On Mon, 27 Jun 2005 15:48:07 UTC, Stefan
wrote:

: Last weekend I flew in the mountains. Conditions were rough and I had to
: make fairly dramatic motions of the controls to keep the blue side up.
: I'll log it as an aerobatic flight, then.

All this seems to hinge on what's meant by "aerobatic". Frankly, it
seems like a pretty pointless term to me, since it seems to depend on
the intention of the pilot rather on the manoevres flown. Why, for
example, is a loop aerobatic yet a tight thermalling turn, involving
similar stresses on the glider, is not?

To me, it makes more sense to categorize manoevres as high load / low
load and high risk / low risk, where "load" relates to forces on the
glider and "risk" relates to the speed with which things will go wrong
if the pilot misreacts.

That gives four permutations:

1) low load / low risk (normal flight)
2) low load / high risk (inverted flight)
3) high load / low risk (loop, tight thermalling)
4) high load / high risk (spin or spiral dive recovery)

This is off the top of my head, and I am sure we could argue about the
categories (should there be a "medium" in each case?) and
categorisations (how hard is a loop) for ages.

However, I think I would put many display aerobatic manoevres and
winch launching together in the high load / high risk category: it's
not that winch launching is aerobatic (whatever that means) but it is
also a time when the glider is being flown with higher than normal
structural loadings and when pilot error can cause things to go very
nasty very quickly.

I'd put mountain flying, from the little I have done, in the low load
/ high risk category at the very least, and probably high / high on
rough days.

Ian


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