On Tuesday, June 2, 2020 at 5:11:34 PM UTC-7, Neal Alders wrote:
To answer the Australia Low Tow question, as seen in the The Gliding Federation of Australia Inc Aerotowing Manual

Go to page 44 in this PDF, As well as see PDF Page 53 for tow plane upset..

http://doc.glidingaustralia.org/inde...als&Itemid=101

If you cannot or do not want to open the link, here is the text.

10.1.12.High-tow and Low-tow An aircraft in flight generates a “slipstream” behind it.This is a region of turbulent air, originating mainly from large vortices streaming from the wingtips, with small amounts of mechanical turbulence such as propeller wash thrown in for good measure. A glider pilot may choose to fly either above or below this turbulent slipstream(Refer 10.1.10).Australia tends to favour the “low-tow” position.Other countries prefer “high-tow”.
10.1.12.1.Low-tow With a glider in low-tow, below the slipstream, the combination tends to be less pitch sensitive and tow pilots have less difficulty in maintaining attitude for a constant air speed and a stable platform for the glider pilot to follow.
10.1.12.2.High-tow In high-tow, above the slipstream, the combination feels a little more pitch sensitive and tow pilots need to work harder to maintain a constant climb attitude and air speed.The difference is not large and tow pilots should have no difficulty in maintaining a stable platform whichever position the glider pilot chooses.WARNING: HIGH-TOW IS, BY DEFINITION, ABOVE THE SLIPSTREAM, NOT ABOVE THE TOW PLANE. There is one important difference between low-tow and high-tow and this becomes apparent if a glider gets out of position vertically(i.e. too high). In low-tow a glider can get very low and still not cause significant difficulty for the tow pilot in controlling his aircraft.Furthermore, out-of-trim forces tend to change at a slow enough pace that the tow pilot has ample time to release the glider if there is any fear that the limits of elevator control might be reached. In high-tow, things happen more rapidly and the tow pilot will have less time to react to a glider going too high.If a glider that is out of station in high tow(i.e. too high)is not released immediately, there is a risk of the tow plane being pulled out of control.See Section 10.3“The tow plane upset”. Tow pilots need to be trained to tow gliders in both high and low-tow and to experience a glider transitioning between the two positions.To avoid subjective judgements about high-tow and low-tow, the reference for the glider pilot establishing the towing position is always the slipstream.


Regarding the safety difference between high and low tow, I'm not sure that the relatively small vertical difference between high and low tow (about 50ft max?) is very important for tow safety. In my experience, getting unusually high from the high-tow position (eg in preparation for demonstrating a slack rope) causes no difficulty for the towplane, provided one moves high slowly (and always keep the towplane in sight). It does not affect the towplane much because the tension in the rope (glider drag is probably only about 50lbs during normal tow) probably changes very little during this maneuver, and the angle of the rope changes little too (50ft in 200ft would be about 15 degrees). The problem of kiting occurs when the glider moves high QUICKLY, causing the tension in the rope to increase rapidly. Probably a similar downward kiting effect could occur if the glider was in low tow, and dived quickly.