Originally Posted by
paco
You don't automatically get GR with more rotor blades, it's whether they have drag dampers or not. Actually, the teetering head is the most susceptible to ground resonance as a design.
this is not correct. Below is a reasonable layman’s explanation of why 2 bladed teetering hubs are not susceptible to GR.
Cant post the direct link but Google this site and read the explanation.
spinningwing
/helicopter/ground-resonance