Winch Launch Safety Study

On Mar 17, 11:12*pm, wrote:
The article says that the older gasoline powered winches with
automatic transmissions are tension controlled types, or at least
allow themselves to be controlled that way. I'm not familiar with
transmissions to know either way, just citing what the article says.

They go on to recommend that the existing electric ones and the
Diesels commonly used at least install a tension meter. Further, the
older Hercules winches should be abandoned as they are not up to par,
break down often and are not of the highest standard. These are mainly
from eastern Europe.

To take away, besides maintaining the equipment, is to realize that an
avoidable danger is in accelerating too fast in the first few seconds,
because this can (emphasis on "can") cause an unavoidable pitch up
movement that can not be compensated for with the available elevator
authority - resulting in either a high speed and nose high stall at
low altitude due to an excessive angle of attack or a rope break (weak
link). the former is almost always fatal. The latter not, but can be
if the pilot does not react properly and can contribute to
accidents.

The pleasing part is that the new German statistics show winch launch
actually safer than air tow. I've always felt that this should be the
case if the equipment was well maintained and the pilots were trained
to the same level as is common with air tow.

However there seems to be a lot of technical confusion in the article.

"Tension Controlled" means that rope tension is continuously monitored
and controlled through an automatic feedback loop. There are very few
winches that do this. Two American built super winches are both
tension controlled with feedback systems.

Automatic transmissions are designed to help a vehicle driver maintain
highway speed on varying road grades - that's speed control and the
exact opposite of tension control. There is no torque regulation in
an automatic transmission and there is no way to modify one to provide
it. To refer to them as "tension controlled is plain wrong.
Automatic transmissions taken from road vehicles simply don't belong
in glider winches.

Electric winches could easily be tension controlled by just monitoring
the current flowing to the motor as could hydrostatic winches by
monitoring hydraulic pressure although a running line tensiometer
would be a better solution. My understanding is that the ESW-2B is
tension controlled. I know for a fact that both American super
winches under development ARE tension controlled.

Specific attacks on electric winches show a complete lack of
understanding of electric power. The innate characteristics of
electric motors make them ideal for torque control.

"Older gasoline powered winches" most likely mean underpowered winches
that are actually "tension limited" such that the glider pilot can
control airspeed with pitch. To refer to these as tension controlled
is unwarranted and will confuse the issue. These are not "tension
controlled".

The hysterics about initial acceleration needs hard data not theory or
speculation to back it up. The experiments I have done with "pitch
strings" used as an angle of attack indicator suggest that the AOA is
nowhere near stall regardless of initial acceleration. In fact,
greater acceleration actually reduces peak AOA.

The preceding paragraph needs to be qualified by saying there are a
small number of types with well deserved reputations for
uncontrollable pitch-up under hard acceleration. There are relatively
few of these and they are .