On Thursday, February 28, 2019 at 12:45:49 AM UTC-5, Surge wrote:
On Monday, 25 February 2019 15:28:09 UTC+2, Tango Eight wrote:
Chris Rollings:
Being in low-tow when that happens
simple makes the sunsequent event take about half a second longer - not
enough extra time to greatly increase the chance of releasing before the
critical point."

So low tow does offer more time to react to a tug upset.
From the info at hand it appears that a tug upset occurs over a duration of about 3 to 4 seconds. An additional 0.5 seconds on 4 seconds is a 12.5% increase.
Why throw a free 12.5% additional safety margin away?

I think we have two distinct types of events to consider, that differ in their causes, effects and kinetics.

In the case of "kiting" accidents, what does the towplane in is the *pitch of the glider*, not the pitch of the tow rope. It's the acceleration of the glider that produces the dangerous deceleration of the tow plane. We think that beyond a critical (glider) pitch of about 30 degrees, the situation is not recoverable. I don't think low tow buys you much in this scenario.

In "distraction" events, the glider remains below the critical pitch, the situation remains recoverable much longer, the problem is caused when the glider drifts so far out of position that the angle of the rope becomes a problem for the tug. Or it may turn into a kiting event.

Here's the order of priorities for prevention of both types of problems:

1. PIC that maintains situational awareness and positive control, all the time.
2. Rope of reasonable length. We find that 200 - 225' works well. Longer gets to be a problem for recovery at our airport.
3. Tow position probably improves margin in distraction scenario.

I have reservations about using low tow at our club because a PTT below 200' means something is going to get bent with high probability (it's roughly a ten second window of time between able to land straight ahead and able to make a safe 180). On a 225' rope, low tow is about 30 feet lower than high tow, why throw away 15%? :-)

best,
Evan