"Andreas Maurer" wrote in message
...
Hi Bill,

On Fri, 30 Mar 2007 09:49:23 -0600, "Bill Daniels"
bildan@comcast-dot-net wrote:

The winch should be constructed such that it is not be possible for the
airspeed to increase as a result of raising the glider's nose. Otherwise,
the winch should be regarded as dangerous.

Is it such a problem to teach the pilot to pull the release if his
airspeed exceeds the desired prameters?



Bye
Andreas


Overspeeds shouldn't be a safety problem for a well trained pilot but if it
happens frequently, it will reduce confidence in the winch/driver. For not
quite so well trained pilots, it may become a safety issue. Pilot
confidence in the system is strongly related to the consistency of the
launches. If pilots lose confidence in the winch launch system, they'll go
elsewhere.

The advantages of automatic tension control are so large that there's every
reason to adopt it. Since the tension can't exceed the breaking strength of
the weak link and certainly not the cable, these things become extremely
rare. Automatic tension controlled launches are extremely consistent
regardless of external variables - or winch driver skill.

A collateral problem related to adoption of lightweight 'plastic' winch rope
is that the winch driver can no longer see the rope sag. With heavy steel
cable, winch drivers used cable sag as a gauge of tension. And, absent
airspeed telemetry, the winch driver has no information about the gliders
airspeed. This absence of feedback leads to inconsistent launches.

To deal with lack of feedback and the possibility of overspeeds, winch
drivers just reduce power to increase margins which results in lower
launches. Highly accurate automatic tension control allows the power to be
increased while maintaining launch consistency. Higher power means higher
launches.

Bill Daniels