Winch Launch Extreme 5200 ft

Neils, this is really VERY, VERY clever. Actually it's elegant.

We have now heard of 300+ launches a day with one winch and launches to 5200
feet AGL with another.

Lets say your only tug is doing 4 - 5 launches an hour at $75 each and
you're #6 in the aero tow queue. The winch across the field is making a
2500 foot launch every 3 minutes for $10. (You're #6 because you failed to
notice a solo student catch a thermal off a winch launch at 10:30 so
everybody else got in front of you.) The tug will need a fuel stop every 5
or so launches but the winch will run all day on one tank. It's going to be
2PM before you get an aero tow. What do you do?

What's not to like about winches.?

Bill Daniels


"Niels Erik Danielsen" wrote in message
...

"Marc Ramsey" wrote in message
...
Niels Erik Danielsen wrote:
In our Club in Herning Denmark we have a 25 year old Diesel Electrical
winch, controled by an industrial controller.

http://www.herningsvaeveflyveklub.dk/jordmateriel.shtml

Prior to launch the maximum wire tension is preset according to aircraft
type, and the rest of the launch is basically automatic.

It looks to be quite an interesting design. Does the generator drive AC
traction motors directly through the controller, or are there batteries
or some other form of buffer in the system?

There is no buffer, all power is generated by the generator when needed.

The frame consist of a late 60' SCANIA VARBIS tractor trailer,
combined with two traction motors (used as winch motors)and generator from
a diesel DC
electric locomotive.

The engine has been replaced with a newer more powerful turbo
charged SCANIA engine. (This engine is used for both road driving, and
winch.)

The generator is mounted as a part of the drive shaft between the
gearbox and the differential.(Rotating when in gear)
The differential had two gears controlled by air pressure, one for
normal road speed and another for reduced speed.
As the pinion for the 'normal road speed' has been removed, it has
become a `neural' allowing the generator to run without driving (moving)
the
winch.
When the winch is moved the generator is still rotating, but not
magnetized.

The winch drums are mounted directly on the traction motors drive
shafts.

The first 'computer' was analog, and consists of a custom made
circuit board filled with operational amplifiers, and passive
components.

This computer controls:
Parking brake/Differential interlocking
Throttle actuator for engine.
Contactors for drum selection.
Contactor for wire retrieve-braking dump load.
Torque by excitation of the windings in the generator

The systems measures:
Engine RPM
Engine Actuator position
Generator speed.
Wire speed.
Torque derived from DC current, no tensiometer needed.
DC Voltage.
Wind speed.
Wind direction component.
Position of spring loaded torque/speed command handle.
Calculation of power based on Current and Voltage.

In the late 90' the analog controller was replaced with an
industrial micro controller, but the functions as seen from the
operator is essentially unchanged.
Except for the possibility of connecting a PC via. a serial cable,
and record a time track of the launch parameters.

The max speed and max force is set on two dials.
For an ASK21 the force is set at 550daN, and max speed is set to 125
km/h,

Max. force is approx the weight of the glider, and max. speed is a
speed approx. halfway between normal launch speed and max speed
allowed in winch launch for type of glider.
Then one of the drums are selected by pressing the Left or Right
push button, this starts excitation of the generator and set the
engine in high idle (ca. 1200 RPM)

The spring loaded command handle has a manual control range for
taking up the slack and at the end of launch bring down the chute.
When the handle is full forward against it's stop a 'kick-down button'
is activating the automatic sequence.

During the launch the diesel engine RPM is controlled to ensure
enough power (Max RPM used is about 1800 RPM)

The set point for the speed/torque servo is ramped up (Ramp time
approx 2 sec.) to the values given by the dials. (Power peaks at
about 160KW for a heavy two seater)

After acceleration, during the initial climb the speed set point is
automatic ramped down to
approx 70% since the glider now have a speed composant tangential to
the winch.
The decision on when to start speed ramp down is based on time
calculated from the wind composant in launch direction. (My feeling
is rampdown is done 4 to 10 secs into the launch)

Later during the launch the max force (torque) is also ramped down,
this is also based on time.

When the glider is at an angle of approx. 75° the command handle is
eased a little backward and the glider hook back releases.

Andy wrote:
Graeme Cant wrote:

I must have only flown off traditional winches. My experience is the
same as Bill Daniels. What over-powered monster do you fly off?

I have flown off winches at 5 UK sites and 5 US sites (9 different
winches). I don't think any of them were over-powered monsters but
most had enough power to see this effect.

Please refer to "Gliding" by Derek Piggott, which was the standard UK
text when I started flying gliders. Page 80 of fourth edition -
"Unless the winch is seriously underpowered, steepening the climb will
result in an increase in launching speed".

Andy

Well, I speak only from my experience, not from a book, no matter how
eminent the author, and ... it's not MY experience. Clearly it's also
not Bill Daniels' and several others. I note what you say about your
experience and I'll learn from it.

As for Derek Piggott's experience, I recommend the 7th Edition where he
has modified his teaching somewhat and simply says (p.106, K&G edition)

"Steepening the climb MAY result in an increase in launch speed..." (my
emphasis).

Earlier on that page, however, he also says

"If the launch is too fast, for example, the glider pilot pulls back
more..." He seems to have revised his views between the 4th and 7th
Editions. That's the problem with citing authorities - they change
their mind without telling you!

My experience of winches (also on two continents - Snap!) tells me that
European winches are generally more serious and powerful than the ones
I'm used to. Nobody on this continent could afford a Skylaunch for
example and nothing like it exists in my area. Not many exist in the US
either judging by the fact that, like us, they appear to find the cost
of a European winch is about the same as a brace of good Pawnees.

Perhaps that explains why I said that "traditional winch" and "adequate
power" didn't go together. I also used the words "overpowered monster"
lightheartedly...

GC

Graeme Cant wrote:

Well, I speak only from my experience, not from a book, no matter how
eminent the author, and ... it's not MY experience. Clearly it's also
not Bill Daniels' and several others. I note what you say about your
experience and I'll learn from it.

I suspect that our experience of pitch effect on speed is not really
that different. Neither of us has defined the conditions in sufficient
detail. I think it's true to say that for any winch that is capable of
maintaining constant tow line speed, pitching the glider up will result
in an increase in airspeed. It is also true to say that continuous
pitch up will not result in a continuous increase in airspeed. Either
the winch has insufficient power to maintain line speed, or the tension
limiter reduces line speed, or the glider weak link breaks. So I
believe there is a cross over point for underpowered or tension
controlled winches. For pitch/speed below the cross over point,
increasing pitch results in increasing speed. Above the cross over
point the reverse is true. For a tension and speed controlled winch I
suspect that the cross over point is early in the launch and before the
glider has established normal climb attitude.

Thanks for the update on "Gliding". You are right, he didn't tell me
he'd changed the text


Andy

I personally don't think that a constant force regulation results in an
ideal winch tows. I have observed a number of tows in which the glider
was initially accelerated to quickly so that the pilot reacted by
maintaining a low climb angle. This low angle results in lower force
measured by the winch and leads to a further increase of power. In a
Ka8 nearing Vne the only possible action is to abort the tow.

At our airfield we use a system which transmits the airspeed of the
glider to the winch operator. Pared with a good winch operator and a
powerful winch, this results in very good winch tows.

Interesting. What sort of telemetry equipment are you using? I had
proposed this several years ago but the consensus was that it would be too
expensive to equip each glider with a telemetry transmitter. Constant
tension puts all the sensors at the winch and requires no extra equipment in
the glider.

George Moore has written a series of excellent papers on automatic control
of winch launches. George favors the constant tension approach but with
cable speed regulation in the ground roll and rotation phases to prevent
overspeeding the glider. These papers are available for download from the
files section of the Yahoo group "winchdesign".

Bill Daniels


"alex8735" wrote in message
oups.com...
I personally don't think that a constant force regulation results in an
ideal winch tows. I have observed a number of tows in which the glider
was initially accelerated to quickly so that the pilot reacted by
maintaining a low climb angle. This low angle results in lower force
measured by the winch and leads to a further increase of power. In a
Ka8 nearing Vne the only possible action is to abort the tow.

At our airfield we use a system which transmits the airspeed of the
glider to the winch operator. Pared with a good winch operator and a
powerful winch, this results in very good winch tows.

You can't just control for constant force. You also need to limit the
maximum winch speed to address this exact issue.

Mike Schumann

"alex8735" wrote in message
oups.com...
I personally don't think that a constant force regulation results in an
ideal winch tows. I have observed a number of tows in which the glider
was initially accelerated to quickly so that the pilot reacted by
maintaining a low climb angle. This low angle results in lower force
measured by the winch and leads to a further increase of power. In a
Ka8 nearing Vne the only possible action is to abort the tow.

At our airfield we use a system which transmits the airspeed of the
glider to the winch operator. Pared with a good winch operator and a
powerful winch, this results in very good winch tows.

Eric,

the forces are all the same.

there is no difference in forces strengths launching to 1000ft or to 5000ft
the applying forces just last longer thats all.

I did hundreds of take offs on the winch.
I wish we would have good winches in Australia.
Here we only have historical rubbish standing around.

Chris



"Eric Greenwell" wrote in message
news:GBu1h.4529$WB4.3254@trndny04...
Gerhard Wesp wrote:
That sounds a bit frightening - 3500 fpm! What are the stresses on the
glider to get that kind of climb rate? How far away is disaster if the
pilot twitches a bit on the controls or hits some wind shear or a
thermal?

Hmmm, if they are using weak links, I don't see a problem.

Stress (=force) is related to acceleration, not to speed. You can go
straight up at 1000000 fpm with the same force as at 10 fpm. Just takes
you a bit longer to reach the speed.

Of course, the net force on the glider is zero, otherwise it would
accelerate, but the individual forces are much greater and vary during
the launch. We've all seen the wings curve up and stay that way as the
pilot rotates into the climb on a winch launch, indicating much more
lift is being generated to counteract the pull of the cable.

Surely the cable tension must be greater to provide a 3500 fpm launch
instead of a 1000 fpm launch? I'm curious about the amount of tension
needed to provide a 1000 pound glider that 3500 fpm climb.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

news wrote:
Eric,

the forces are all the same.

there is no difference in forces strengths launching to 1000ft or to 5000ft
the applying forces just last longer thats all.

I agree with that, but what I asked about was the rate of climb (fpm =
feet per minute):

Surely the cable tension must be greater to provide a 3500 fpm launch
instead of a 1000 fpm launch?

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

"Eric Greenwell" wrote in message
news:ei5ch.74$R_1.4@trndny08...
news wrote:
Eric,

the forces are all the same.

there is no difference in forces strengths launching to 1000ft or to
5000ft
the applying forces just last longer thats all.

I agree with that, but what I asked about was the rate of climb (fpm =
feet per minute):

Surely the cable tension must be greater to provide a 3500 fpm launch
instead of a 1000 fpm launch?

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Not surprising.

A typical launch will have the glider climbing at a 45 degree angle and 60
knots. That works out to a little over 42 knots vertical speed. Of course,
that the peak climb rate. The average on a high launch can be around 35
knots. The stresses are about the same as mild aerobatics.

There are a number of GPS logs on the web that show rates of climb about the
same as these figures.

If you want to work out the stress for yourself, the peak cable tension will
roughly equal the flying weight of the glider. The cable pull vector will
start horizontal and swing down to 70 degrees during the launch. At
approximately 70 degrees, the CG hook will automatically "back-release" the
cable.

Serious fun.

Bill Daniels

I suspect that is not quite true, as the glider's wings
in the 5000ft winch launch have to lift a longer and
therefore heavier length of cable into the air. However
the weak link remains the same and still protects the
glider. What allowed these very high launches to be
achieved was the combination of a very long (3000 metre)
winch run and the advent of modern lightweight synthetic
UHMWPE cable.

Derek Copeland


At 02:42 01 December 2006, News wrote:
Eric,

the forces are all the same.

there is no difference in forces strengths launching
to 1000ft or to 5000ft
the applying forces just last longer thats all.

I did hundreds of take offs on the winch.
I wish we would have good winches in Australia.
Here we only have historical rubbish standing around.

Chris



'Eric Greenwell' wrote in message
news:GBu1h.4529$WB4.3254@trndny04...
Gerhard Wesp wrote:
That sounds a bit frightening - 3500 fpm! What are
the stresses on the
glider to get that kind of climb rate? How far away
is disaster if the
pilot twitches a bit on the controls or hits some
wind shear or a
thermal?

Hmmm, if they are using weak links, I don't see a
problem.

Stress (=force) is related to acceleration, not to
speed. You can go
straight up at 1000000 fpm with the same force as
at 10 fpm. Just takes
you a bit longer to reach the speed.

Of course, the net force on the glider is zero, otherwise
it would
accelerate, but the individual forces are much greater
and vary during
the launch. We've all seen the wings curve up and
stay that way as the
pilot rotates into the climb on a winch launch, indicating
much more
lift is being generated to counteract the pull of
the cable.

Surely the cable tension must be greater to provide
a 3500 fpm launch
instead of a 1000 fpm launch? I'm curious about the
amount of tension
needed to provide a 1000 pound glider that 3500 fpm
climb.

--
Eric Greenwell - Washington State, USA
Change 'netto' to 'net' to email me directly

'Transponders in Sailplanes' on the Soaring Safety
Foundation website
www.soaringsafety.org/prevention/articles.html

'A Guide to Self-launching Sailplane Operation' at
www.motorglider.org