How to get maximum height on a winch launch?

Derek Copeland wrote:

The exact position to hold the stick during a winch
launch is very type dependent. Gliders with way back
c of g hooks, such as the K21, K8 and Pirat will require
the stick to be held neutral or even forward of neutral
during the full climb.

My Pirat will fly a very nice winch launch which is almost completely
independent of anything the pilot chooses to do with the stick! It's
not so much the fore-and-aft position of the hook, I think, as the
vertical one: since it is at the bottom of a deep fuselage there is a
considerable nose up pitching moment during the ground run. As soon as
it takes off, therefore, it does a lovely rotation into full climb all
by itself: full forward stick has no effect at all.

Gliders with single 'compromise' hooks such as
the Slingsby Skylark and the Bocian will need the stick
to be held on the back stop if they are to climb at
all steeply.

All the Bocians I have ever flown had C of G and nose hooks. The Pirat
manual specifically permits winching on the nose hook: using full back
stick and forward trim from the "All Out", and warning that it will
only give 60% of normal release height. I have never tried this, for
several reasons, one being that I rather like having the back release
there ...

Ian

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

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

Ian wrote:
Martin Gregorie wrote:
Dan G wrote:

and for K21s
winch drivers are briefed to give full throttle the whole way up (winch
is c.300bhp).

That sounds excessive to me. The only glider that gets full power all
the way is an ASH-25.

It shouldn't, since an ASH-25 is a brown weak link, not a black one.
Many clubs, pilots and winch drivers ignore this, but at their peril.
When I am driving I will refuse to launch an ASH-25 unless someone I
trust will confirm to me that it has the right link in place. 60:1 does
not bring immortality.

Fair comment - I've never been in the winch or at that end when one was
launched, but it certainly seemed to need a lot of grunt to get it
moving and rotated into full climb.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Martin Gregorie wrote:
Ian wrote:

It shouldn't, since an ASH-25 is a brown weak link, not a black one.
Many clubs, pilots and winch drivers ignore this, but at their peril.
When I am driving I will refuse to launch an ASH-25 unless someone I
trust will confirm to me that it has the right link in place. 60:1 does
not bring immortality.

Fair comment - I've never been in the winch or at that end when one was
launched, but it certainly seemed to need a lot of grunt to get it
moving and rotated into full climb.

Thanks. Yes, they are heavy (about 1600lbs max AUW, iirc) but the
designers have specified a brown link and I respect that. It's not as
if the damn things need to get high anyway!

Ian

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

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