How to get maximum height on a winch launch?

Dan G wrote:

With a K21, which winch drivers here (which includes me) are told to
give "full power all the way up" from our Oldsmobile V8.

Then with all due respect, I think your club needs to think about its
training policy for winch drivers. "Give full power all the way up" is
a recipe for disaster - it should be "Give enough power all the way up,
and don't assume that means full throttle". A good winch driver knows
how much welly to give it by the bow in the cable, the speed of the
drums and the appearance of the glider. Whacking in full throttle
without a care is as bad as giving full back stick from the start of
the launch.

If your club is training winch drivers to think about throttle position
without considering effects and training pilots to think about stick
position without considering effects, it may have to do some
fundamental thinking about flying and training. In both cases the
principle should be "Know what effect you want and use the right amount
of control to achieve it, monitoring the situation and varying inputs
as required." I would be very cautious about an organisation which
taught crude open-loop control in two separate safety-critical areas.

Please don't take this personally, because it's not so intended.

Ian

Ian,

winch launching my Calif over 8 years on a 280 hp winch was exactly "full
power until release", and that was the only way to go.
So, in some cases this type of instructions actually does work.

Bert

"Ian" wrote in message
ps.com...

Dan G wrote:

With a K21, which winch drivers here (which includes me) are told to
give "full power all the way up" from our Oldsmobile V8.

Then with all due respect, I think your club needs to think about its
training policy for winch drivers. "Give full power all the way up" is
a recipe for disaster - it should be "Give enough power all the way up,
and don't assume that means full throttle". A good winch driver knows
how much welly to give it by the bow in the cable, the speed of the
drums and the appearance of the glider. Whacking in full throttle
without a care is as bad as giving full back stick from the start of
the launch.

If your club is training winch drivers to think about throttle position
without considering effects and training pilots to think about stick
position without considering effects, it may have to do some
fundamental thinking about flying and training. In both cases the
principle should be "Know what effect you want and use the right amount
of control to achieve it, monitoring the situation and varying inputs
as required." I would be very cautious about an organisation which
taught crude open-loop control in two separate safety-critical areas.

Please don't take this personally, because it's not so intended.

Ian

"Bert Willing" wrote in message
...
Ian,

winch launching my Calif over 8 years on a 280 hp winch was exactly "full
power until release", and that was the only way to go.
So, in some cases this type of instructions actually does work.

Bert

Full power for the whole launch works when the winch is severely
underpowered. As more powerful winches are introduced, you will find there
are points in the launch where the driver must reduce power to maintain
constant tension.

Bill Daniels

Bill Daniels wrote:

Full power for the whole launch works when the winch is severely
underpowered. As more powerful winches are introduced, you will find there
are points in the launch where the driver must reduce power to maintain
constant tension.

It's the inflexibility of "full power all the way" which worries me.
I've lobbed K21's off at Sutton Bank on windless days which needed full
throttle, windy days on which a whisker over idle was quite enough and
days when things changed from calm to windy half way up the launch. A
driver who thinks "K21 - right, full power" is ... I was going to right
"get himself into trouble oneday" but that isn't quite right. He's
going to get two other people into trouble one day.

Ian

Should say that it's "full power all the way up" the main climb, of
course we back off at the top. But there was some suprise at the launch
point recently when a K21 waved off... the common thought was "K21s
should be able to handle it". Maybe it could if it was no wind, but
with a good headwind they just can't.

So far the sole answer to my original question has been "look at the
wingtips during the launch and find what stick position
will hold them at about 45 degrees to the horizon AND
give a safe speed. If you have a low powered winch
you may have to adopt a lesser angle" from Derek.

Does everyone agree with this?


Dan

Dan G wrote:
Should say that it's "full power all the way up" the main climb, of
course we back off at the top. But there was some suprise at the launch
point recently when a K21 waved off... the common thought was "K21s
should be able to handle it". Maybe it could if it was no wind, but
with a good headwind they just can't.

Headwind makes a big difference. Our underpowered winch can overspeed
the twins easily if the wind gets above about 15knots. If indicated
airspeed is above 60knots, you're getting diminishing returns from the
launch.

Frank Whiteley

Dan G wrote:
Should say that it's "full power all the way up" the main climb, of
course we back off at the top. But there was some suprise at the launch
point recently when a K21 waved off... the common thought was "K21s
should be able to handle it". Maybe it could if it was no wind, but
with a good headwind they just can't.

And that was a surprise? Find yourself another club, man, because if
headwinds on a winch launch are unexpected your current lot are going
to damage someone one day.

So far the sole answer to my original question has been "look at the
wingtips during the launch and find what stick position
will hold them at about 45 degrees to the horizon AND
give a safe speed. If you have a low powered winch
you may have to adopt a lesser angle" from Derek.

Does everyone agree with this?

No. I think it's bad advice. Yes, you should aim to have a proper climb
angle and air speed, but the stick position is irrelevant. Just use
enough to do what's needed.

How many inches of rudder movement would you use to balance a 20 degree
per second roll into a turn? Or would you just aim to us enough to keep
the string straight?

Ian

Ian wrote:

Dan G wrote:
Should say that it's "full power all the way up" the main climb, of
course we back off at the top. But there was some suprise at the launch
point recently when a K21 waved off... the common thought was "K21s
should be able to handle it". Maybe it could if it was no wind, but
with a good headwind they just can't.

And that was a surprise? Find yourself another club, man, because if
headwinds on a winch launch are unexpected your current lot are going
to damage someone one day.

Easy now, my club has a long safety record any would be proud of. AFAIK
there's never been a winch launch accident. In that particular example
there was a very strong wind gradient. I was using as an illustration
of the belief that K21s can take everything the winch gives.

So far the sole answer to my original question has been "look at the
wingtips during the launch and find what stick position
will hold them at about 45 degrees to the horizon AND
give a safe speed. If you have a low powered winch
you may have to adopt a lesser angle" from Derek.

Does everyone agree with this?

No. I think it's bad advice. Yes, you should aim to have a proper climb
angle and air speed, but the stick position is irrelevant. Just use
enough to do what's needed.

Well, "find what stick position will hold them at about 45 degrees to
the horizon AND give a safe speed" and "you should aim to have a proper
climb angle and air speed" seems to be the same thing...


Dan

Dan G wrote:
Ian wrote:

And that was a surprise? Find yourself another club, man, because if
headwinds on a winch launch are unexpected your current lot are going
to damage someone one day.

Easy now, my club has a long safety record any would be proud of. AFAIK
there's never been a winch launch accident. In that particular example
there was a very strong wind gradient. I was using as an illustration
of the belief that K21s can take everything the winch gives.

I am glad to hear about the safety record. I only hope they can keep
it.

No. I think it's bad advice. Yes, you should aim to have a proper climb
angle and air speed, but the stick position is irrelevant. Just use
enough to do what's needed.

Well, "find what stick position will hold them at about 45 degrees to
the horizon AND give a safe speed" and "you should aim to have a proper
climb angle and air speed" seems to be the same thing...

No, they are completely different. Stick position is irrelevant. All
that matters is whether you need to move it.

Let me give a simple example. The exact position of the temperature
lever on a shower doesn't matter, does it? If it's too hot you move it
"cold" a bit and if it's too cold you move it "hot" a bit. You don't
say "I'll have a position 5 shower, no matter how hot that is".

Same with the stick.

Ian