If I understand the difference in idiom, the British term "flick roll"
is equivalent to the US term "snap roll". If that's correct, stalling
the vertical fin will not cause a snap roll which is a spin in the
horizontal plane. And, as we all know, a spin requires a stall with
yaw. In the case of a snap roll, it is an accelerated stall and I don't
see any change in AoA of the wing to cause that stall. But then I'm
just a poor victim if US military flight training... Or I could be
wrong on the term "flick roll". Or the BGA manual could be (horrors) wrong!

On 4/30/2015 8:33 AM, son_of_flubber wrote:
On Thursday, April 30, 2015 at 10:16:16 AM UTC-4, wrote:

There is nothing fundamentally dangerous about the technique when properly done.

The BGA reference (page 30) says that pulling the tug laterally has the potential to abruptly stall the vertical stabilizer of the tug, inducing a flick roll of the tug and a possible midair collision. It goes on to say "The highest risk of a lateral upset is during the
'glider cannot release' signal demonstration".


See Section 42 of the BGA Aerotowing Guidance Notes (LATERAL
TUG UPSETS):

https://www.gliding.co.uk/bgainfo/cl.../documents/aer
otownotes.pdf

--
Dan Marotta