Everyone knows all 2 blade systems can experience mast bumping. Nothing new there.
But the R series has more than double the amount of others.
This was determined by an exhaustive study by NTSB and a high level aviation university
It was a true apple to apple comparison , nothing to do with number of machines sold or pilot experience.
NTSB nomenclature call it "loss of rotor control" or "blade incursion into cabin or boom"
And of course all of them also show mast bumping and broken droop tusks.
But my question has always been ..... what caused the initial loss of rotor control which caused all the other bumping-incursion damage ???
We all know about Zero-G ..... strong gusts ... updrafts ..... downdrafts ... equally applicable to all 2 blade systems .... with some advantage to heavy blades .... but can we blame the R failures on light blades alone ??? .... personally I dont think so.
I have always been suspicious of the 3 hinge points in the R system . It works as advertised and is a clever way to eliminate stress and bending at the blade roots. And at overhaul time mechanics will see wear at the main teeter pin and bushings (normal) and no wear at the coning hinge pins (good)
This indicates the coning hinges will only compensate for coning and pretty well remain fixed (no continuous movement-flapping in flight.) .... just as it was designed to do.
But what is to say that a rare aerodynamic situation could not occur that causes one blade to flap up on its coning hinge .... it would put the rotor system out of balance , plus without a lead-lag hinge a lot of stress on the (un-reinforced) blade root.
Other 2 blade rotor systems have a rigid head and are stiff and reinforced at the first few feet of each blade , thus the disturbance would be dampened and partly transferred to the other blade.
The R system is like a limp noodle by comparison with those 3 hinge points. And yes .... I realize centrifugal force tries to keep the coning hinges "stiff" but maybe a split second disturbance could alter that
I could be creating a monster that does not exist .... just trying to reason out why the R rotor experiences almost double the rotor incursions of other 2-bladers when all other circumstances are equal. (apples to apples )