wrote in
:

I'm not sure what the actual tip speed is, but I know that a lot of
modern fully articulated systems run at tip speeds just under the
speed of sound in order to significantly reduce the chances of ground
resonance.

Do you mean at a hover? I don't think that's the case. If the tip speed
is just below supersonic at a hover, then at a very low forward airspeed
they'd go supersonic, & all kinds of bad things would happen, not the least
being huge amounts of noise, which is already the bane of helicopters.
Rotors have to be far below supersonic at a hover so the leading blade
doesn't go supersonic in fast cruise. Even the UH1 blades can approach
supersonic near Vne, and the tailrotor blades are close all the time.

--
Regards,

Stan