2-Bladed Rotor Ground Resonance
All:
I have a fair amount of career experience in helicopter dynamics and yet I'm stumped. This is in the weeds, but I'm hoping some of you can point out what I might be missing.
Helicopters with articulated rotors (usually 3+ blades) can be susceptible to ground resonance and therefore have damping elements at the rotor (lag dampers) and in the airframe (oleo dampers, etc). 2-bladed rotors are usually teetering and therefore are not susceptible to GR. However, many RC helicopters have 2-bladed articulated rotors with lead lag hinges but no dedicated blade lag dampers or skid/airframe dampers as far as I can tell, and yet GR events are rare to non-existent. Does anyone know why this may be the case?
GR should be possible on an articulated 2-blade rotor, even if the fuselage and rotor frequencies are well separated. It is surprising to me this seems not to be the case even with no dampers present. Any insight would be much appreciated!
Thanks,
Chris