SASless:
For you BO and BK drivers....ever try to fly the aircraft using collective movements to control roll? In cruise flight....roll attitude can be controlled by use of the collective if you are patient and catch on to which way the aircraft reacts to those collective movements. That will demonstrate much of what Crab is saying about cyclic/collective roll coupling.
"...In cruise flight." Heh. Not in a Boelkow, old boy. Cruise flight in a 105 (around 120 knots) is denoted by a healthy 8 - 10 degree nose-down pitch attitude. At such an attitude, leaving the cyclic unattended for any length of time results in the a/c trying to turn itself inverted.......regardless of what you do with that lever next to the seat. I've flown a lot of different 105's (including some that their regular pilots proclaimed to be "very stable"), and NONE of them would stand more than about 9 or 10 seconds of hand-off-the-cyclic before departing S/L flight no matter how well-trimmed I could get it.
At 60-70 knots however, it is fun to fly the BO by using the collective alone. At those speeds it is "relatively" stable, although I laugh at the very thought of using the words "stable" and "Boelkow" in the same sentence.
I had an amusing conversation with a Boelkow pilot once. It enlightened me as to how fiercely loyal and unobjective pilots can be about their aircraft. This guy was going on and on about how wonderfully stable the 105 was. I was chuckling to myself and shaking my head. When he finally stopped to take a breath, I managed to interject my little discovery about how they'll start to go upside down in an average of seven seconds if you take your hands off the cyclic. He immediately replied, "Yeah, they do that."
This man obviously had no earthly idea what constituted "stability" as it applies to helicopter flight.
His "solution" was novel. "What power-setting do you fly at?" he asked. I said, "120 knots, and whatever it takes to get me there." He then said, "Well that's your problem! You're cruising too fast. Slow it down to 100 knots and it's VERY stable."
He was dead serious too, as far as I could tell. I think he was trying to get me to believe that when he flew the 105, he drove around at 100 knots watching everything from Astars to 407's blow by him. Sorry chaps, but I've spent my life in 70 knot Bell 47's, 90 knot 206B's and 104 knot 206L's. I'm not about to reign in a ship that can "scoot" at 120. And I don't think most other 105 pilots do either.
And for the record, the 105 isn't all that much more stable at 100 knots than 120. It's better......but that's not saying much.