AAAvnC did not demonstrate or discuss vortex ring state in 1968. CFS Tern Hill did not include it in the QHI Course in 70/71. However I do recall the "high altitude (10,000ft)" sortie, with parachute and the only instructional outcome being 'more left pedal required at altitude.'
As a civilian instructor for the last eighteen years, with around 10.000 instructional hours, I regularly demonstrate vortex ring state - requirements, symptoms, entry and recovery, in a variety of heli including R22, R44, AS350, H500, BK117 ....... Buggered if I can consistently demonstrate it in a B47 or B206 tho'! Dammed if I know why? Been put in it three times (inadvertantly) in these types by folks doing base and line checks. Opened my eyes.....
The subject has been well covered in PPRune in the past. Rates of descent vary on the same machine on different days. However, in my experience, the standard recovery technique works every time!
Surely the instructor should ensure the student understands the requirements to get into it and the symptoms - both incipient and developed. We then need to be shown and practise the standard recovery (and the variations.)The idea being to avoid the "nasty." However, if Bloggs manages to achieve the undesirable, he needs the tools to avoid spoiling his day by a heavy impact with terra firma!