New 29 Palms Winchfest Video

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

Even better, buy a Skylaunch 2 Winch with adjustable
throttle stops for glider type and wind direction.
It isn't even fitted with a RPM meter, because it doesn't
need one. We had one demonstrated at Lasham recently,
and it was very easy to drive and gave great launches:
See the following video:

http://www.youtube.com/watch?v=0qc3U_7_4FY

I wrote a report on the demo day for our club newsgroup,
which I reproduce below:-

Hi,

Mike Groves and the Skylaunch team brought along one
of their latest main winches for a demonstration day
at Lasham on 12th December to coincide with the 'Winter
Wednesdays' flying group, which is a very active and
pro-active instructional team, so there was plenty
of launching to be done. It was a beautiful Winter's
day, with lots of sunshine and a very light South-Easterly
wind. We set up on the Easterly run (semi-crosswind)
with our normal retrieve winch in action, as the grass
was rather too wet, soft and slippery for too much
vehicle retrieving after a period of prolonged rain.

This was the first time I had seen a Skylaunch with
the trim tab throttle setting system, although I have
flown many launches at the Long Mynd on their original
prototype winch, which is not so fitted. With this
system there are two setting tabs, one for glider typerunning
from A+ for DG1000s down to F for vintage gliders,
and a headwind component tab (which we set to 5 knots).
In the cab was a booklet with most glider types listed
with the appropriate settings

After watching a few launches, I was allowed to drive
this winch
under the supervision of their pro winch driver. Compared
with our Tosts it was ridiculously simple, without
all the fiddly bits. The controls are a drum selection
lever on the left, a gearbox drive selector, a console
with the throttle lever and tabs, and just one instrument
(interestingly no rev counter) plus a few warning lights,
and a brake lever on the right.

To launch you select the drum, engage 'drive', and
select the
appropriate throttle tab setting for the type of glider
being
launched (you have to be informed by radio what it
is, particularly as we were launching over a hump so
couldn't quite see the launch point). Then a little
touch on the throttle lever for 'take up slack' and
then push the lever up to the preset and hold it there
for the first 2/3rds of the launch (no need to back
off during rotation),after which you have to start
backing off a bit as normal. You can overide the preset
if you consider this necessary. As the glider gets
nearly overhead, you reduce the throttle to indicate
that the launch is over, and as soon as the glider
releases apply a short burst of power to pull the cable
straight. After that select neutral and allow the retrieve
winch to pull the cable back to the launch point. There
is a automatic tow-out brake, controlled by gas struts,
so no need to wrestle with the handbrake levers as
with the Tost. You just rest your hand on the brake
lever and apply a litle bit of brake as the cable(s)
slows down as the other end reaches the launch point
to prevent the drum over-running.

My first launch was a 'Baby Grob' G102, which we launched
on the Grob Astir setting. This produced a bit of initial
tail wagging (signal for too fast) so I had to back
the power off a touch, after which the rest of the
launch went smoothly. Peter the winch driver said he
had never launched one of these before, and suspected
that it was a bit slower and lighter than the Astir
(which it is) and that we should have used the next
lowest setting down. This probably shows how accurate
the system is!
Then I launched a heavy Grob 2 seater and then a K13
which seemed to be having a very good launch until
the instructor pulled a simulated cable break on his
student. No problem, I just closed the throttle and
let the cable drop and waited until the glider landed.
Then after liasing with the retrieve winch by radio
I pulled a little bit of cable in to straighten things
up, and then the cable was retrieved as normal. I did
a couple more launches which went smoothly with no
signalling from the glider.

Although I am not a current winch driver, I found this
winch very
little more difficult to drive than our retrieve winch.
It was just
winch driving by numbers. Mike pointed out that this
winch is
designed specifically to be driven by ordinary gliding
club members, as opposed to skilled professional drivers.
Compared with the Tost, it is very quiet,comfortable
and user friendly

Later on I a tried a solo launch in a K21 on this winch.
The ground run acceleration was a little bit faster
than we normally get and the glider rotated into an
ideal 65 knots climb. I tried pulling back a bit harder
and it slowed down to 60 knots and then eased forward
and it speeded up to 70 knots. So with this system
you can control the speed. Despite this messing around
I still got a 1400ft launch off a short run (1080 metres)
in a crosswind using steel cables, which is about 100ft
or so higher than I would have expected on the Tost.
Members generally
reported 1300-1400ft launches.

A few interesting points. Mike Groves said that some
clubs with
shorter runs are using rope rather than dyneema, which
is a fraction of the cost, but still much lighter than
steel cables, although somewhat thicker so you can't
get so much onto a drum. No good for really long runs.

He will also re-engineer old Tost winches to modern
standards, which includes turning the axle over so
it is the right way up and properly lubricated, throwing
away the small diameter drums and level wind gear and
fitting Skylaunch narrow large diameter bottom feeding
drums. If you have an old Tost with a decent engine
and gearbox, this could be very cost effective and
will reduce maintenance requirements.

Derek Copeland



At 01:06 19 December 2007, Andreas Maurer wrote:
On Tue, 18 Dec 2007 10:14:05 -0700, 'Bill Daniels'
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

On 19 Dec 2007 22:04:13 GMT, Del C
wrote:

Even better, buy a Skylaunch 2 Winch with adjustable
throttle stops for glider type and wind direction.

Hi Derek,

sound pretty good - and as close to the KISS principle as it gets.


Just one annotation:
I regard 70 kts for an ASK-21 as a little on the too-fast side (it
will break the weak link if you pull back too much at this speed) - do
you always tow that fast?

Bye
Andreas

I agree with Andreas Maurer that 70 knots is a bit
too fast for winch launching a K21. However flying
a normal launch profile, where the stick is just back
from centre for the full climb,gave a perfect 65 knots
launch on the Skylaunch. I tried pulling back harder
and then easing forward just to see what would happen,
as some people in the winching world seem to believe
that the airspeed should be controlled by the pilot
changing the pitch angle. I found you could vary the
speed by about 5 knots either way, but I can't really
see the point of doing this, as it only gives you poorer
launches than flying at the optimum speed!

BTW, everyone I have spoken to has been very impressed
by the Skylaunch 2 Winch.

Del Copeland

At 23:42 19 December 2007, Andreas Maurer wrote:
On 19 Dec 2007 22:04:13 GMT, Del C
wrote:

Even better, buy a Skylaunch 2 Winch with adjustable
throttle stops for glider type and wind direction.

Hi Derek,

sound pretty good - and as close to the KISS principle
as it gets.


Just one annotation:
I regard 70 kts for an ASK-21 as a little on the too-fast
side (it
will break the weak link if you pull back too much
at this speed) - do
you always tow that fast?

Bye
Andreas

On Dec 20, 1:32 pm, Del C
wrote:
I tried pulling back harder
and then easing forward just to see what would happen,
as some people in the winching world seem to believe
that the airspeed should be controlled by the pilot
changing the pitch angle. I found you could vary the
speed by about 5 knots either way

Just out of interest - when pulling back was the 5 knot change one of
increasing or decreasing speed?


Dan

Dan

Can I refer you back to my report on this winch!

For the record, pulling back harder reduced the airspeed
and easing forward increased it.

Cheers and Happy Xmas
Del C

At 18:00 20 December 2007, Dan G wrote:
On Dec 20, 1:32 pm, Del C
wrote:
I tried pulling back harder
and then easing forward just to see what would happen,
as some people in the winching world seem to believe
that the airspeed should be controlled by the pilot
changing the pitch angle. I found you could vary the
speed by about 5 knots either way

Just out of interest - when pulling back was the 5
knot change one of
increasing or decreasing speed?


Dan

Pilot controlling speed on Winch Launch:
- Another thing that speaks against pulling to slow down is this that
if the winch driver does nothing when you pull, the speed can only be
slowed temporarily by pulling.

So you may slow down on certain set ups and aircraft, by you have to
ease off on the extra pull over normal pretty soon, at which point
you'll speed up again. So what's the point? You're just slowing down
temporarily only to speed up again, or release prematurely by breaking
the weak link or having the back release release earlier.

Pushing over when to slow should be done anyway, for safety reasons.
So no argument there. But unless the winch driver changes power
settings, nothing will change. He's in charge.

I also am more inclined to believe that oscillating by the pilot to
influence airspeed, the way Bill Daniels advocates, will result in
lower release altitudes than using the KISS method.

On Dec 20, 6:54 pm, Del C
wrote:
Dan

Can I refer you back to my report on this winch!

For the record, pulling back harder reduced the airspeed
and easing forward increased it.

Cheers and Happy Xmas
Del C

Sorry, a goldfish brain moment on my part. Your experience with the
speed is the same as mine on a V8 LPG winch.

I think of the winch launch as a little bit like horse-riding - there
are two brains involved in controlling what happens next.... Both
pilot and winch driver control the speed to some degree, with the
winch driver having the ability to induce bigger speed excursions from
the optimum.


Dan