Winch Launching

bildan wrote:

- limited in height and distance, i.e. you can't tow to that thermal 10 miles away if there's none nearby

The practical reality is that you rarely actually know there is a
thermal 10 miles away. If there's lift around, you can find it with a
2000'AGL winch launch - if there's no lift around, why consider an
aero tow?

This depends on the location. At our site, we seldom can reach a thermal
from the winch, and even on those rare days not reliably. So as much as
we'd like to use it for cross country launches (heck, it *is* cheaper
and more fun!), winch launches are pretty much limited to student
instruction.

On the other hand, we often *do* know that there's that thermal 10 miles
away. First, because it is always there, and second, because of the
forming cumulus. But between our site and that thermal, there are 10
miles of sink. Agreed, on most days there eventually will grow thermals
near the airfield, but only at noon, when those pilots who did a aerotow
have already 2 hours under their belt and are 100 miles away. Agreed,
you can fill that gap with a sustainer, but then, you can as well
aerotow. Most airports weren't planned by glider pilots!

I wonder if one of the new generation winches like the Hydrowinch with
a 4000ft launch would make a difference. Most winch operations I have
read about all end with a 2K+ launch which does not give you a lot of
time before starting a landing pattern. Just imagine a 4K launch
without any lift, it still ends up being a perfect training flight of
15-25 minutes. I really want to go out to Colorado and test out the
new prototype and see if it is for real. Too bad they cost so much $$$
$$.

flyingmr2 wrote:
I wonder if one of the new generation winches like the Hydrowinch with
a 4000ft launch would make a difference.

The limiting factor is not the winch, but the rope length which in turn
is related to the available runway length. A rough estimate is that the
height with no wind is about half the rope length.

Here's what you can do with a perfectly conventional tost winch and 3000
meters of spectra rope: http://www.youtube.com/watch?v=-VlRd9-wxQI (note
that the altimeter is in meters and the vario im m/s)

The limiting factor is not the winch, but the rope length which in turn
is related to the available runway length. A rough estimate is that the
height with no wind is about half the rope length.

Super cool video with an awesome launch. The hydrowinch site says
they have enough room on the spool for 10K of Spectra rope. I guess
if you have a 10k runway available,. you could get launched into
space! Well, not quite, but it would sure seem high compared to a
regular 2k launch.

flyingmr2 wrote:

if you have a 10k runway available,. you could get launched into
space! Well, not quite, but it would sure seem high compared to a
regular 2k launch.

Just be sure to publish a NOTAM. Nobody expects a winch rope above, say,
3000 feet AGL.

On Jan 5, 9:11 am, John Smith wrote:
flyingmr2 wrote:
if you have a 10k runway available,. you could get launched into
space! Well, not quite, but it would sure seem high compared to a
regular 2k launch.

Just be sure to publish a NOTAM. Nobody expects a winch rope above, say,
3000 feet AGL.

Lets say, just for argument, that a rope below 1500' AGL would not
deserve a NOTAM but that over 1500' it would. So how long would the
rope be above 1500' on a 3000' launch? My educated guess is that
would be 15 - 20 seconds.

Would a rope the the 1500 - 3000 foot band for 20 seconds every 10
minutes warrant a NOTAM? A typical light plane at cruise travels
about 4000 feet in 20 seconds. Couldn't you just scan the airspace
visually out to three miles before starting the launch? It's really
quiet at a winch start line so you would probably hear an approaching
aircraft. The thing is that winch ropes just aren't in the sky very
long.

Obviously, there are situations that would require a NOTAM but that's
not the case everywhere.

bildan wrote:

Lets say, just for argument, that a rope below 1500' AGL would not
deserve a NOTAM but that over 1500' it would. So how long would the
rope be above 1500' on a 3000' launch? My educated guess is that
would be 15 - 20 seconds.

15 to 20 seconds are plenty enough for disaster. But I didn't mean it
literally. (Albeit, the 5000 feet launch in the linked YouTube clip did
require a NOTAM.) Anyway, I didn't mean it literally, but just wanted to
point out that a long rope will interfere with power traffic. This is
solvable, of course, if you have a plan and everybody cooperates. But
you definitely do need a plan.

On Jan 5, 8:46 am, flyingmr2 wrote:
The limiting factor is not the winch, but the rope length which in turn
is related to the available runway length. A rough estimate is that the
height with no wind is about half the rope length.

Super cool video with an awesome launch. The hydrowinch site says
they have enough room on the spool for 10K of Spectra rope. I guess
if you have a 10k runway available,. you could get launched into
space! Well, not quite, but it would sure seem high compared to a
regular 2k launch.

The question of just how high a winch launch could go has come up
several times. There is a small group of extreme kite flyers who have
flown L/D ~4 kites up to 30,000 feet using the same Spectra rope used
by glider winches. That suggests that launching a glider to the floor
of Class A airspace would be possible given enough runway and wind. I
expect that someone will do that fairly soon.

If the glider can be launched into a 50 knot wind layer, a tension
controlled winch would automatically reverse the drum rotation
direction and pay out rope - the glider would in effect be a high L/D
kite. The possible release height would then depend on the length of
the rope, not the length of the runway.