Families of two pilots have taken a lawsuit against Robinson helicopters. Two pilots died in 2016 when their R66 Turbine helicopter had catastrophic in-flight breakup in the middle of the desert due to mast bumping. The Law suit states that the helicopters, 'specially the R66 , “are especially susceptible to catastrophic mast bumping events due to, among other things, the design of the rotor head and main rotor blade system.”
NTSB reports weather conditions had strong thermals along with strong winds according to witnesses.
This will be interesting to see play out.