I've got a question along these lines...
What restricts the VNE from being higher on a Bell 212 when 230s with teetering rotors have maximum speeds upwards of 25-30 knots faster than the 212? While I'm not completley sure of the main rotor RPM difference between the two I don't see it being enough to threaten the 212 with RBS and not the 230s... the 212 has a good bit of power too, especially on a light weight flight. Is the fuselage unaerodynamc enough to limit the airspeed so heavily?
The 206L seems to share the 212's low speed as well, while the 206B is more towards the 230 end of the spectrum.
Is the 230 vastly different in some way to the other teetering rotor helicopters?
Mike