Re the preliminary report:
One obvious hypothesis arises from the report along these lines; loss of one tail rotor blade, a huge resultant one per tail vibration which in turn results in the tail rotor, tail rotor head and associated structure separating from the aircraft. CG shifts forward, perhaps beyond the capability of the available cyclic range to correct etc etc. One side possibility here would be the pilot instinctively applying full aft stick rapidly, perhaps slicing into and separating the tail cone ( this is suggested by the report statement about separate tail cone pieces ). Something like this would preclude any radio calls. The weakness of this hypothesis is that I have no info or feel for the CG range, control rigging, control moment capability and the like for the subject aircraft. My guess is that by now the NTSB will have looked at this possibility, and probably others, and may have a good idea of what happened.