On Wednesday, May 20, 2020 at 4:30:05 AM UTC-7, Sci Fi wrote:

It is true that increasing tow rope angle precedes a towplane upset, it
is
=
not exclusive to upsets. That is why I suggested putting a load cell on
the=
tow release to measure the force on the tow rope which is a better
indicat=
or of a kiting event.

Tom

Tom, if you made the load cell rupture when it sensed an overload would be
good... Don't we have them now.. they are called Weak-Links. All you
need to do is correctly calculate the maximum tension that you could allow.


As a starting point.. A 350kg Glider with a 35:1 L/D ratio just requires
10kg of pull to keep it flying. So factor in a safety margin to allow for
turbulence, of say 10x, and what you need is a 150kg Weak-Link. This is
much less than the lowest (White.) Link made so far. But as you know
those links are designed for Winch (Kiting.) Launches. Our Link needs to
be made for safe aero-tow.

I simplified the criteria in the spirit of understandability: the decision would not be based on a static load level, it would be based on the input of several sensors using a technique called state estimation. An upset state or event is characterized by a rapidly increasing load on the tow rope, a rapidly increasing pitch down attitude of the towplane, and a decreasing towplane airspeed. Note: a weak link is not a sensor.

Tom