SAFE Winch Launching

On Jul 11, 11:45*am, Berry wrote:
In article
,



*bildan wrote:
On Jul 11, 2:00*am, Derek Copeland wrote:

At my club we typically get about 1600ft in no wind and
2000ft launching into a 10 knot headwind. Our standard aerotows are 2000ft,
but you can go as high as you like, depending on your needs and the depth
of your wallet.

This week we were getting as high as 1900' from 3900 feet of rope at
9000 feet density altitude with little wind with the Hydrowinch. *With
no gear shifting at all, the Hydrowinch is MUCH smoother than any
winch with an automatic transmission.

Skylaunches are just like old Gerhleins with new paint - they use
exactly the same components. *They are not particularly well
controlled since they use road vehicle torque converters and automatic
transmissions free to shift gears when they please. *The old junk
Gerhleins around most US clubs are probably the only winches in the
world worse than a Skylaunch - but they are a LOT cheaper.

BTW, notice how Derek has to reply to himself to get any conversation
at all?

My club used to have a very good winch. It was a one-off called the
"Eagle Winch" and was designed and built by one of our members. He got
his initial glider training in Germany and had knowledge of quality
winches. That winch is now with the Philadelphia Glider Council, I
believe. We were forced to let go of it because we moved to a municipal
airport that was incompatible with winch operations (crossing runways).

The Eagle winch has an automatic transmission. However, in our operation
it was locked into 2nd gear for normal conditions. In strong wind, we
used 1st gear. No gear changes necessary. It was very easy to operate
and became even more so after the steel cable was swapped our for plasma
rope by the second owners at the Memphis club. At our original field,
with 4000 feet of cable out, we could easily launch our single seaters
to 2000 feet if we had any headwind.

Germany is a good place to learn about winches. Plasma rope is like
night and day compared to steel. Steel cable is evil stuff. If you
have a winch actually designed for Plasma - unlike the Skylaunch and
Gerhlein - it will outlast steel by as much as 5x making it actually
cheaper in the long run.

Did you actually lock your transmission in 2nd or just place the gear
selector in 2nd? It's an important question since a standard tranny
will still make the 1-2 upshift causing a power oscillation. We see
a lot of tension traces showing tension oscillations from these
winches.

Anyone considering an automatic transmission for a gilder winch really
needs to understand how they work. Automatics are highly developed
for road vehicles whose requirements are diametrically opposed to
those of a glider winch. If a road vehicle encounters an increasing
load, such as a hill, it is designed to help the driver maintain speed
by increasing torque to the wheels to meet the higher load, doing what
it can to reduce the loss of speed. Cresting the hill and starting
down, it reduces torque and tends toward coasting. Both actions
increase vehicle performance and minimize fuel consumption.

If a glider encounters a thermal during a launch, the rope tension
will increase which the automatic transmission will see as a "hill"
causing it to increase torque to the drum. This increases rope
tension still more as it tries to pull the glider down through the
thermal. If the glider hits sink, the automatic transmission will
slack off the torque just when the glider needs more power. A good
winch operator can overcome these to a degree with constant throttle
adjustments - if he can tell what is going on in the glider but it's
hard, skilled work. It's definitely not "set and forget".

A tension controlled winch will do the opposite - decreasing power in
thermals letting lift do the work and increasing it in sink leaving
the pilot to control speed with pitch. The pilot sees a very smooth
launch regardless of wind or thermals. The winch operator doesn't
need to do anything at all.

It's wonderful to never need speed signals again.