OK, so the theory as described by Dave and Graviman is that the R22 blades do not flap about the coning hinges individually, they flap as a unit about the teeter hinge as any other Bell two blade would. So the coning hinges would act as flapping hinges only if the teeter hinge was welded firm, but as long as the rotor is free to pivot on the teeter hinge the coning hinges are held tight.
Phil,
The 206 has fixed undersling of course, but at low Rrpm with a heavy load the 2.5 degree undersling would be less than needed. It is my understanding that for this case the blade is made extra strong to absorb the additional lead/lag load.
Therefore, the R22 would have some lead /lag strain also when the coning angle is higher than the fixed design undersling. But the R22 blade does'nt look very strong to me in the lead/lag plane as compared with a Bell. And some of the blades have failed at the root fitting attachment.
The coning hinges relieve the blade bending strain, but I think the design has some problems with with in-plane lead/lag fatigue loads.
The tri-hinge design does have some appeal, I wonder if others will use it now that the patent has expired.
Thanks for your help.