Last year 2001, I was with a very experienced Ex mil Cfi who showed me what can happen in a very fast descentVRS(Heli was R22) we went very high(5000ft) and he showed me a rate of decent to 3500 fpm, recovery was achieved by simply completely closing the collective, after recovery to height again it was my turn, and the same sort of recovery was made, It was very fast, very intimidating but after the event I feel able to cope with this problem( if it arises) in the future, brilliant for the old ticker!!
Regards Peter RB