VR:
I said it has less to do with disc loading and more to do with lock number which is derived using the dimensions of the blade itself and the load put on it. That is why the B blades are more susceptable to it. As far as disc loading the B and B2 have the same disc loading at 4300 lbs but you take your B to 10 grand on a windy day and try to cruise at max cont. hang on. Plus at higher altitudes the pitch on blades is higher for same torque setting thus imposing a greater load to the hydraulic system which is why it is more easily encountered at altitude.
There is a blurb in the book "the art and science of flying a helicopter" on lock number, makes it easier for us simple folk.
CTD:
I have towed a bird in the rocks with BA and never got close to ST, yes you are doing hard manuevers but at lower airspeeds(80 kts and less) and thus the blades/hyd aren't overloaded. Have done lots of high altitude slinging and production skiiing but the most have encountered ST is sightseeing in level flight at max continuous power in gusty wind conditions. Why sightseeing, well we would climb up to 12000 feet to go and sometimes enroute it got windy. Heliskiing doesn't normally have you trekking across the sky in level flight as often.
I also encountered it while pulling out of high speed descent as used to from Gazelle days and woke me up.
SB;
We used to train the same way but I feel that since you have to put the a/c through a relatively high load with only two people in it to encounter ST that was not getting the message to the pilots. What we did was to brief the pilot on the maneuver and while flying at 80 kts turn off the hydraulics on collectve, wait for the pilot to lower collective slightly then turn them back on. Would work up to 100 kt doing same manueaver, and was an good way to show the feedback associated to ST.
It is also referred to as jack stall, and there has been much written about it in the US.
It is a bit hard to get some pilots head around the fact that you don't have to be pulling any G's to get into ST it is just that most a/c will be flown at lower altitudes and probably encounter ST more by being flown overly aggressive. The reassuring thing about ST in turbulence is that once the blades are unloaded slightly it goes away, many times before I could even lower the collective. But a few months in the rockies or coastal range will be enough experience to enlighten most.
In my experience the bigger blades on BA,1,2 are much better and would assume the same with B3, although wonder about being over 6000 lbs with external load in windy day.
Magseal, imagine your hand out the window doing 40 kmhr and feeling the aerodynamic forces then go to 120 kmhr and do the same. No G force difference only higher load on arm, g force would be felt by body being flung out on road when door opens. Ha, ha.
I need hockey fix aaaaaaaaaaaaaaah. GO FLAMES GO.
Thats better.
sc
