New 29 Palms Winchfest Video

Andeas:


Andreas

p.s.:
I think it's usually the response of the winch driver that results in
an airspeed increase: If the winch driver notices a sudden
pitch-decrease (or an abnormal low pitch) of the gilder, he assumes
that the gider is too slow and adds power.
We don't have (and don't need) a voice communication between glider
and winch.

Bye
Andreas

Despite the danger that Bill Daniels calling me dangerous or some
other unsubstantiated claim, I post here to agree with you 100%.
Playing around with the airspeed should not be the focus of the
launch. It is the winch driver who controls this to the greatest
degree.

Safety and minimizing risk should be the main focus of the pilot.

The incidents mentioned here, are indicative of an increase in risks
during winch launches when trying to influence airspeed as discussed
in this thread. Weak links breaking as you're pulling back to put
strain on the winch or the premature back releases of the cable as
you're pulling are certainly not desirable nor add to safety.

I am with Andreas that from the pilot's point of view, it should be a
simple matter. The winch driver will also get a clue as to what's
happening by observing the glider. However, by pushing and pulling as
discussed here, the winch driver may not be able to figure out what's
going on and perhaps not respond at all or respond in a way that makes
thing worse.

Since the winch driver is the one who has the most control over speed,
you really don't want to confuse him or her.

On Mon, 17 Dec 2007 16:40:49 -0800 (PST), tommytoyz
wrote:


from the pilot's point of view, it should be a
simple matter.

I think that's the main point.

@Bill:
I really love the fact that you are trying to promote winch launching
in the US - but (please correct me if I'm wrong) from the comments
here in this newsgroup I get the impression that you US guys regard
the winch launch as something pretty hazardous that needs a lot of
technology to be safe.
Consequently, your approach to a US winch design looks a little
over-engineered to me, I have to admit. Complex and expensive to
build, hard to set up correctly. Possibly prone to mechanical
problems.

Us European guys seem to see things in a more relaxed way - we tend to
advocate training instead of technological devices to achieve safe
winch operations.

Considering the number of accident-free winch launches per year on my
side of the pond, don't you think that it might be useful to stick
more closely to the KISS-principle ("keep it simple, stupid"), forget
all that high-tech stuff and concentrate on correct training?

Nearly all the winches here are basically very simple.
Anything a winch needs is a strong diesel engine, two drums, 3.500 ft
of cable (be it steel or plastic). No rocket science involved.




Bye
Andreas

"Andreas Maurer" wrote in message
...
On Mon, 17 Dec 2007 16:40:49 -0800 (PST), tommytoyz
wrote:


from the pilot's point of view, it should be a
simple matter.

I think that's the main point.

@Bill:
I really love the fact that you are trying to promote winch launching
in the US - but (please correct me if I'm wrong) from the comments
here in this newsgroup I get the impression that you US guys regard
the winch launch as something pretty hazardous that needs a lot of
technology to be safe.
Consequently, your approach to a US winch design looks a little
over-engineered to me, I have to admit. Complex and expensive to
build, hard to set up correctly. Possibly prone to mechanical
problems.

Us European guys seem to see things in a more relaxed way - we tend to
advocate training instead of technological devices to achieve safe
winch operations.

Considering the number of accident-free winch launches per year on my
side of the pond, don't you think that it might be useful to stick
more closely to the KISS-principle ("keep it simple, stupid"), forget
all that high-tech stuff and concentrate on correct training?

Nearly all the winches here are basically very simple.
Anything a winch needs is a strong diesel engine, two drums, 3.500 ft
of cable (be it steel or plastic). No rocket science involved.




Bye
Andreas

Andreas, I have great respect for the long experience you have on that side
of the pond. I have spent years researching just what you do over there.
That's where I got my ideas.

But, there are problems with the very basic KISS principle. If you ask the
winch driver to control the glider's airspeed, you have to give him a way to
to judge how well he does that. If the pilot has an airspeed indicator with
which he judges the quality of a launch but the winch driver has nothing but
"feel", that's unfair to the winch driver since the pilot has MUCH more
information than he does. It's interesting to see that a German company is
now selling an inexpensive airspeed telemetry unit to address this.

If you ask the winch driver to control tension instead of airspeed, he has
several things to help him do that - things like cable sag (if using steel)
throttle setting and the sound and feel of the winch. It's even simpler for
him if there is a tensiometer. It's still better if you can link the
instantaneous cable tension to a throttle control loop so the winch does it
automatically.

The critical point is that neither the pilot or winch driver can control
both airspeed AND tension at the same time. If you tell the pilot to just
"go along for the ride" and task the winch driver with controling both, you
are giving the winch driver an impossible task.

If the winch driver controls only tension, the pilot now has to step up and
control his own airspeed. Once I realized I could do this, launches assumed
a high level of smoothness and consistency. This REALLY works SWEET. The
math shows it works right up to the cable tension that would break the weak
link so winch engine potential power or torque has nothing to do with it.

However, this is a hard concept to teach someone who has been trained
otherwise. I've had people who were jumping up and down with indignation
since they "knew" that pulling harder would make the glider speed up. "Show
me", I said. They lost the bet - every time.

A good analogy is old cars with drum brakes. When they got wet, braking
action vanished until they dried out. There is an almost overpowering
sensation that the car actually speeds up when you step hard on the brakes
and nothing happens.

I'm sure this is what is confusing glider pilots on a winch. As the nose
rises during the rotation, the glider is still accelerating and, since the
airspeed doesn't drop when they pull, they assume pulling on the stick makes
the glider speed up - or at least that they have no control over airspeed.

Once the glider has stabilized in the climb, the old pitch/airspeed
relationship is restored and you can control airspeed. Pitch up to slow and
down to speed up. As the glider nears the top of the launch, the ability to
reduce airspeed is much reduced but releasing back pressure will definitely
make the glider speed up.

There are things that make this hard to see. For one thing, the airspeed
response is not instantaneous - it takes a little time for a pitch input to
result in an airspeed change. For another, if the glider is loaded with the
CG at or even beyond the forward limit, you will likely not have enough up
elevator authority to slow the glider. This is a W&B problem - not a winch
problem. It's is the "two 200+ pounders in a glider with a 380 pound
maximum cockpit load" problem.

So, is this approach unnecessarily complicated? I don't think so. All I am
saying is to give the winch driver the ability to control tension extremely
accurately no matter what. Any driver, any wind, any glider or pilot and
the tension is always exactly right. What's not to like about that?

All you ask of the pilot is to control airspeed with pitch exactly like it
is done in all other flight situations. In other words, "Just fly the
glider". What's complicated about that?

An AOA indicator helps the pilot because his wings are loaded to the
equivalent of 3.5 G's so the "loaded stall airspeed" is much higher than in
1G flight. Glider's have stalled while on the wire with disastrous results.
A safe AOA indication is an absolute guarantee that you won't stall - no ASI
indication gives that level of assurance.


Bill Daniels

Bill,

accidents don't happen because somebody is missing a gadget.

Accidents happen because people are not aware about the situation they are
in. On a winch launch, and more so during free flight, you have lots of
indications about what is going on (speed, attitude, feel, sound).

Whenever somebody lacks situational awareness, he is an accident waiting to
happen, and the lack of awareness is the main cause of accidents. It's not
the missing AoA which is fatal..

Somebody who doesn't pay attention to what is going on will not benefit from
an AoA because he obviously doesn't care about all the information he
already gets.

I am a profound believer that you can increase safety only by training (both
mental and on the stick), and by increasing situational awareness. Adding
gadgets is an engineering approach to something which can't be solved by an
engineering approach. Somebody who doesn't get the fact that he is about to
stall will find another way to die, once you've added the AoA (and he cares
to look).

Bert

"Bill Daniels" bildan@comcast-dot-net wrote in message A safe AOA
indication is an absolute guarantee that you won't stall - no ASI
indication gives that level of assurance.


Bill Daniels

On Tue, 18 Dec 2007 10:14:05 -0700, "Bill Daniels"
bildan@comcast-dot-net wrote:


But, there are problems with the very basic KISS principle. If you ask the
winch driver to control the glider's airspeed, you have to give him a way to
to judge how well he does that.

Yup.
Here in Germany we call this training.

A new winch driver needs 100 winch launches on 10 different days
(read: different weather situations) to acquire his winch driver
license.
Any winch driver student is able to drive the winch safely after a
dozen launches using his feeling, an RPM meter and a look at the cable
sag.
Driving a winch is pretty simple if you ask me.


If you ask the winch driver to control tension instead of airspeed, he has
several things to help him do that - things like cable sag (if using steel)
throttle setting and the sound and feel of the winch. It's even simpler for
him if there is a tensiometer. It's still better if you can link the
instantaneous cable tension to a throttle control loop so the winch does it
automatically.

Nice to have... but we use a much simpler way: We have an RPM meter.

Winch driver accelerates to a certain RPM (depending on glider type).
This RPM is modified according to the wind condition. Once the glider
goes through 45 degrees "winch driver head up", RPM is slowly
decreased.
Works like a charm 99.99 percent of the time.


The critical point is that neither the pilot or winch driver can control
both airspeed AND tension at the same time. If you tell the pilot to just
"go along for the ride" and task the winch driver with controling both, you
are giving the winch driver an impossible task.

I think you are wrong here. The fact alone that nearly all winches in
Europe operate the way I described above means that this task is easy
to handle, don't you agree?


If the winch driver controls only tension, the pilot now has to step up and
control his own airspeed. Once I realized I could do this, launches assumed
a high level of smoothness and consistency. This REALLY works SWEET. The
math shows it works right up to the cable tension that would break the weak
link so winch engine potential power or torque has nothing to do with it.

Who cares?
I can assure you that with the KISS principle we reach the same
altitudes as you do.


However, this is a hard concept to teach someone who has been trained
otherwise. I've had people who were jumping up and down with indignation
since they "knew" that pulling harder would make the glider speed up. "Show
me", I said. They lost the bet - every time.

LOL... here comes the urban legend "pilot controls airspeed" again...


I'm sure this is what is confusing glider pilots on a winch. As the nose
rises during the rotation, the glider is still accelerating and, since the
airspeed doesn't drop when they pull, they assume pulling on the stick makes
the glider speed up - or at least that they have no control over airspeed.

I don't think so.
Being able to control the airspeed safely by pulling on the stick has
been an urban legend for ages. We sometimes talk about it, have a good
laugh, and return to the standard technique.


There are things that make this hard to see. For one thing, the airspeed
response is not instantaneous - it takes a little time for a pitch input to
result in an airspeed change. For another, if the glider is loaded with the
CG at or even beyond the forward limit, you will likely not have enough up
elevator authority to slow the glider. This is a W&B problem - not a winch
problem. It's is the "two 200+ pounders in a glider with a 380 pound
maximum cockpit load" problem.

I can ssure you - even a very tail-heavy DG-505 (the glider that can
break *any* weak-link) is unable to slow a winch with halfways
sufficient power down, although its elevator authority is sufficient
to stall it in any phase of the winch launch.
Fly one if you get the chance - it's interesting to see the loss of
aileron authority when you approach the stall during the winch
launch...


So, is this approach unnecessarily complicated? I don't think so. All I am
saying is to give the winch driver the ability to control tension extremely
accurately no matter what. Any driver, any wind, any glider or pilot and
the tension is always exactly right. What's not to like about that?

The complexity.
The fact that extremely few winch operators feel the need to build a
winch according to yxour ideas points out that there might be other
priorities.


All you ask of the pilot is to control airspeed with pitch exactly like it
is done in all other flight situations. In other words, "Just fly the
glider". What's complicated about that?

It's not how it's done.
Taking the example of the 505 - if I tried to reduce airspeed by
pulling at more than 115 kph, I'd break the strongest weak link *any
time*.

An AOA indicator helps the pilot because his wings are loaded to the
equivalent of 3.5 G's so the "loaded stall airspeed" is much higher than in
1G flight. Glider's have stalled while on the wire with disastrous results.
A safe AOA indication is an absolute guarantee that you won't stall - no ASI
indication gives that level of assurance.

I disagree completely.

Take a closer look at causes for winch accidents:

Most accidents happen due to ground loops (just look at the video that
started this thread if you want to see some close cases) and badly
executed rope-break procedures.

There's hardly any case (I know of none) where the glider stalled at
an altitude of more than 200 ft. Nearly all stall related accidents
happen due to a too-sudden transition into full climb, followed by an
immediate highspeed stall and cartwheel or spin.
It's extremely simple to avoid this kind of accident: Keep the stick
in the recommended position for their first 150 ft of the winch launch
before pulling back smooooothly to enter the full climb angle.

Usually such a stall occurs extremely quickly - it's nearly impossible
to recover before impact.

These pilots were not able to hold the stick halfways in the correct
position, nor were they able to detect the very sudden transition into
a steep nose-up attitude. Nor, obvously, were they able to perform the
very simple corrective measu Push the stick forward immediately.

I strongly doubt that these pilots had been able to watch, interpret
and act according to an AoA meter.




Bye
Andreas