Naming no names but it's quite a hard pull off soft grass (aka Sod) for a
K21 with two
large people and a Pawnee! And surely the device should be "Kiting Off
Upwards
Automatic release System"?
- KOUGARS.


At 15:45 20 May 2020, Sci Fi wrote:
At 15:11 20 May 2020, 2G wrote:
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
=3D
not exclusive to upsets. That is why I suggested putting a load cel
on
the=3D
tow release to measure the force on the tow rope which is a better
indicat=3D
or of a kiting event.

Tom

Tom, if you made the load cell rupture when it sensed an overload
would
b=
e
good... Don't we have them now.. they are called Weak-Links. Al
you
need to do is correctly calculate the maximum tension that you could
allo=
w.
=20
=20
As a starting point.. A 350kg Glider with a 35:1 L/D ratio jus
requires
10kg of pull to keep it flying. So factor in a safety margin to allow
fo=
r
turbulence, of say 10x, and what you need is a 150kg Weak-Link. Thi
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
t=
o
be made for safe aero-tow.

I simplified the criteria in the spirit of understandability: th
decision
=
would not be based on a static load level, it would be based on the
input
o=
f 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
to=
wplane airspeed. Note: a weak link is not a sensor.

Tom

Sorry Tom, but I was brought up in the Horse-drawn era, where some ver
elegant and simple solutions were found for problems. We engineere
systems in the most uncomplicated ways, because there were no 'Apps' o
'Actuators' or Hydraulics to make things complicated.
What could be simpler than a 'Weak-Link' of 150 kg breaking strain..?
Maybe the BGA needs to amend the rules to state that for aero-tows th
weak-link needs to be 1/3 the breaking strain of that used for winc
launches.
Glider owners would then need to have two lead ropes, one for winching
wit
a white or blue link. and the other with a green Tost link.