Almost perfect payout winch launch.

One of the most important things we teach all glider pilots is that it is there responsibility to keep themselves safe at all times, no matter what happens with the launch vehicle, be it winch, or aerotow. At no time should the pilot put himself in a position that he can't recover from in the event of a launch failure. That means you don't climb until you have sufficient airspeed, you limit the climb angle below 200', you abort the tow with enough runway to land straight ahead if you aren't climbing. No matter what happens to the launch vehicle, it is up to the glider pilot to keep himself in a safe place at all times, with safe options. Maybe you guys train differently? Even if my truck blew up, it just means the glider doesn't get as high as he would have. If the brake fails, it just means the glider doesn't get as high as he might. If my truck fails to get up to speed, the truck goes to the left and the glider lands straight ahead. Our payout system has been very dependable, but we train for launch failures just the same. Contrary to your assumptions, our operation is innovative, simple, safe, and really fun, and it doesn't cost a boat load of money.

Boggs

At 14:55 10 May 2013, Bill D wrote:
On Friday, May 10, 2013 8:42:39 AM UTC-6, Peter F wrote:
Don is right in thinking that there should be one person in charge of
the=
launch.

Unfortunately the person he thinks should be in charge is at the wrong
en=
d of the cable.

You are correct, it's much better to have the pilot control airspeed with
p=
itch. However, for this to happen, the winch has to control rope tension
a=
ccurately as a percentage of glider weight. Control is divided where
pilot=
controls airspeed and winch controls tension. This means Gary is right
to=
control rope tension with his payout winch.

No, I said there should be one person with total control of the winch, just
the same as the number of people in command of a glider. Would you fly an
airplane where one pilot had control of the stick pulling back and another
pilot was in control of pushing it forwards? The person in charge of the
launch is always the pilot of the glider who has absolute control of the
airspeed at all times via the stick and yellow knob.

From a 2500' run we get 1000 ft winch launches in still air. We are cleared
and capable of winching to 3000ft but seldom do, using a standard Skylaunch
winch.
Average winch launch at our site using the standard runs is 1500ft.

On Friday, May 10, 2013 8:59:22 AM UTC-6, Waveguru wrote:
One of the most important things we teach all glider pilots is that it is there responsibility to keep themselves safe at all times, no matter what happens with the launch vehicle, be it winch, or aerotow. At no time should the pilot put himself in a position that he can't recover from in the event of a launch failure. That means you don't climb until you have sufficient airspeed, you limit the climb angle below 200', you abort the tow with enough runway to land straight ahead if you aren't climbing. No matter what happens to the launch vehicle, it is up to the glider pilot to keep himself in a safe place at all times, with safe options. Maybe you guys train differently? Even if my truck blew up, it just means the glider doesn't get as high as he would have. If the brake fails, it just means the glider doesn't get as high as he might. If my truck fails to get up to speed, the truck goes to the left and the glider lands straight ahead. Our payout system has been very dependable, but we train for launch failures just the same. Contrary to your assumptions, our operation is innovative, simple, safe, and really fun, and it doesn't cost a boat load of money.



Boggs

I have no doubt Gary is a highly responsible pilot and instructor who trains pilots to the best of his ability. He is absolutely correct in describing the pilot's responsibility for his own safety.

That said, I think it may be instructive to examine some of the German DAeC Technical Commission's requirements for winches. (I have a copy translated for me by Ulrich Newmann and I can provide a copy to anyone who requested it.) It's a satisfyingly practical document clearly developed from their vast experience and the results show in their absolutely stellar safety record.

Lets start with power,tension and rope speeds where the DAeC sets minimums.


"In dead calm air, the glider has to be controllable around it's longitudinal axis after less than 15 meters and must reach it's takeoff speed after a maximum of 45 meters."

I think Gary's payout winch can meet this requirement since it only depends on how fast the drum brake is engaged.

Now, here's a tough one - minimum rope speed. This is important because a glider launched in thermic conditions can encounter unexpected tailwind gusts or tailwind layers aloft.

"The drum speed (RPM) has to be chosen such that using the drum core diameter and the power to accelerate the glider according to (above), a rope speed of no less than 1.2 x Va is achievable."

Va on many gliders is in excess of 100 knots so let's say 1.2 x Vw which is typically 70% - 75% of Va but this still may require rope speeds near 100 knots. In the case of a payout winch, one has to add whatever the payout speed is to get the truck speed. I think Gary's pickup truck may have some difficulty with this one since it could mean tow vehicle speeds in excess of 100mph.

Here's a crucial one - minimum release height.

"The power of the winch has to be such that at MTOW in dead calm air, a glider launched at maximum permissible (Vw) airspeed for winch launching can achieve a release altitude of at least 25% of the initial rope length. This must assure safe execution of a normal pattern."

While it's possible Gary's payout winch could achieve this, there may be issues with tow vehicle traction when launching the heaviest gliders. Rope tensions up to a ton may be required at tow speeds.

There are a lot more requirements in the DAeC technical documents on winch design which make good reading.

On Friday, May 10, 2013 11:01:53 AM UTC-5, Bill D wrote:
On Friday, May 10, 2013 8:59:22 AM UTC-6, Waveguru wrote: One of the most important things we teach all glider pilots is that it is there responsibility to keep themselves safe at all times, no matter what happens with the launch vehicle, be it winch, or aerotow. At no time should the pilot put himself in a position that he can't recover from in the event of a launch failure. That means you don't climb until you have sufficient airspeed, you limit the climb angle below 200', you abort the tow with enough runway to land straight ahead if you aren't climbing. No matter what happens to the launch vehicle, it is up to the glider pilot to keep himself in a safe place at all times, with safe options. Maybe you guys train differently? Even if my truck blew up, it just means the glider doesn't get as high as he would have. If the brake fails, it just means the glider doesn't get as high as he might. If my truck fails to get up to speed, the truck goes to the left and the glider lands straight ahead. Our payout system has been very dependable, but we train for launch failures just the same. Contrary to your assumptions, our operation is innovative, simple, safe, and really fun, and it doesn't cost a boat load of money. Boggs I have no doubt Gary is a highly responsible pilot and instructor who trains pilots to the best of his ability. He is absolutely correct in describing the pilot's responsibility for his own safety. That said, I think it may be instructive to examine some of the German DAeC Technical Commission's requirements for winches. (I have a copy translated for me by Ulrich Newmann and I can provide a copy to anyone who requested it.) It's a satisfyingly practical document clearly developed from their vast experience and the results show in their absolutely stellar safety record. Lets start with power,tension and rope speeds where the DAeC sets minimums. "In dead calm air, the glider has to be controllable around it's longitudinal axis after less than 15 meters and must reach it's takeoff speed after a maximum of 45 meters." I think Gary's payout winch can meet this requirement since it only depends on how fast the drum brake is engaged. Now, here's a tough one - minimum rope speed. This is important because a glider launched in thermic conditions can encounter unexpected tailwind gusts or tailwind layers aloft. "The drum speed (RPM) has to be chosen such that using the drum core diameter and the power to accelerate the glider according to (above), a rope speed of no less than 1.2 x Va is achievable." Va on many gliders is in excess of 100 knots so let's say 1.2 x Vw which is typically 70% - 75% of Va but this still may require rope speeds near 100 knots. In the case of a payout winch, one has to add whatever the payout speed is to get the truck speed. I think Gary's pickup truck may have some difficulty with this one since it could mean tow vehicle speeds in excess of 100mph. Here's a crucial one - minimum release height. "The power of the winch has to be such that at MTOW in dead calm air, a glider launched at maximum permissible (Vw) airspeed for winch launching can achieve a release altitude of at least 25% of the initial rope length. This must assure safe execution of a normal pattern." While it's possible Gary's payout winch could achieve this, there may be issues with tow vehicle traction when launching the heaviest gliders. Rope tensions up to a ton may be required at tow speeds. There are a lot more requirements in the DAeC technical documents on winch design which make good reading.

if a 100 knot rope speed was required, any auto tow, payout or not, would be impossible.

On Friday, May 10, 2013 9:36:02 AM UTC-6, Don Johnstone wrote:
At 14:55 10 May 2013, Bill D wrote:

On Friday, May 10, 2013 8:42:39 AM UTC-6, Peter F wrote:

Don is right in thinking that there should be one person in charge of

the=

launch.



Unfortunately the person he thinks should be in charge is at the wrong

en=

d of the cable.



You are correct, it's much better to have the pilot control airspeed with

p=

itch. However, for this to happen, the winch has to control rope tension

a=

ccurately as a percentage of glider weight. Control is divided where

pilot=

controls airspeed and winch controls tension. This means Gary is right

to=

control rope tension with his payout winch.



No, I said there should be one person with total control of the winch, just

the same as the number of people in command of a glider. Would you fly an

airplane where one pilot had control of the stick pulling back and another

pilot was in control of pushing it forwards? The person in charge of the

launch is always the pilot of the glider who has absolute control of the

airspeed at all times via the stick and yellow knob.



From a 2500' run we get 1000 ft winch launches in still air. We are cleared

and capable of winching to 3000ft but seldom do, using a standard Skylaunch

winch.

Average winch launch at our site using the standard runs is 1500ft.


That's a fuzzy analogy. A better analogy is an airplane with a flight engineer controlling the power of the engines. The engineer (think winch operator) applies whatever power the pilot asks for. The pilot then takes that power and controls airspeed with pitch attitude.

Please describe to us a winch accident that would be the fault of the winch and not the pilot.

Boggs

On Friday, May 10, 2013 10:08:48 AM UTC-6, Tony wrote:

if a 100 knot rope speed was required, any auto tow, payout or not, would be impossible.

Not impossible, just not as safe as it could be. Those are German DAeC rules and you simply can't argue with their safety record.

On Friday, May 10, 2013 10:25:24 AM UTC-6, Waveguru wrote:
Please describe to us a winch accident that would be the fault of the winch and not the pilot.



Boggs

First, Gary, let me say again I agree with your position on pilot responsibility and I would be perfectly willing to take a tow behind your payout winch. However, here's a couple of scenarios where a powerful winch can be safer than auto tow.

On a calm but strongly thermic day, a tailwind gust is encountered just as the glider begins rotation into the climb. If the winch has substantial reserve power, and is controlling rope tension, it will instantly add power to help the glider maintain a safe margin over stall in the critical rotation phase. In this case, the pilot has less control over his fate than the winch. If the winch or tow car power is marginal, the glider may stall in this situation.

This is why the DAeC Technical Committee guidelines set minimum power and rope speed requirements.

Another scenario is a winch which balks just after the glider is airborne leaving the glider momentarily gliding at minimum controllable airspeed. The winch then "catches" and applies full power. Without the runway surface supporting the tail wheel, and if the glider's CG is well above its hook, the inertial couple effect may cause a dangerous uncommanded pitch-up.

This is why the DAeC Technical Committee, in another paragraph, requires absolute smoothness in winch power without any tension oscillations or spikes in rope tension.

On Friday, May 10, 2013 11:50:21 AM UTC-5, Bill D wrote:
On Friday, May 10, 2013 10:08:48 AM UTC-6, Tony wrote: if a 100 knot rope speed was required, any auto tow, payout or not, would be impossible. Not impossible, just not as safe as it could be. Those are German DAeC rules and you simply can't argue with their safety record.

sure but there are differences between auto and winch tow. notably that the rope is not getting shorter. any idea how the auto tow accident rate compares to winch? i don't recall ever reading about an auto tow accident but that is probably because its not very common.

On May 10, 10:17*am, Tony wrote:
i don't recall ever reading about an auto tow accident but that is probably because its not very common.

The "Cadillac commercial" accident comes to mind. That, of course, was
hardly a typical auto tow.

Bart