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but they are out of date.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.


"mm" wrote:


Yes, as a matter of fact I am qualified to say he is mistaken. I can
guarantee you that I know MUCH more about ground resonance than you or your
source. I challenge you to find a single reputable reference (text book,
technical paper, certification documentation, FAA training material, etc.)
that relates ground resonance directly to tip Mach number. Your source may
be the worlds ultimate helicopter pilot, but I don't think that this is much
of credential with respect to rotor aeromechanics and structural dynamics.

The original analysis of helicopter ground resonance was by Coleman and
Fiengold, NACA TN 3844. Read it, and will not find any mention of tip Mach
number.

Your tuning fork and marching soldiers examples are essentially meaningless
in this context.





Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
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