NTSB final report
Probable cause:
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot's failure to anticipate and correct for conditions (high gross weight, low indicated airspeed, and a right downwind turn) conducive to loss of tail rotor effectiveness (LTE), which resulted in LTE and an uncontrolled spin. Contributing to the accident was the pilot’s inadequate preflight planning, which resulted in the helicopter being in excess of its maximum allowable gross weight at takeoff.