I don't mean to further yet another moronic discussion about yet
another pie in the sky (lol) rotorcraft, but MM, regardless of
who he is, is correct. Ground resonance has nothing to do with
rotor tip speed. Its mainly germane to helicopters which have
shock-struts as the main rotor rotational rate crosses the
resonant frequency(ies) of the struts. It tends to be exaggerated
and more dangerous in machines with four struts and three blades.
Nothing has ever caused my Jetranger to enter the onset of
ground resonance. Know why?; Two blades, No struts....Hmmm.

Mach number my eye, and who the heck cares about ground resonance
in a discussion on increasing Vmax?

Bart

wrote:
I never said anything about tip mach number. I said "rotor speed".
The two are similar, but not the same. I'm not going to sit here and
argue with an anonymous person who thinks a "diskCopter" is practical.
Your facts about ground resonance may have been accurate 50 years ago,
but they are out of date.

Dennis.