Flight Details
The accident occurred during an aeromedical evacuation (EMS-MEDEVAC) flight conducted at night over mountainous terrain. The pilot interrupted a normal position report and broadcast "MAYDAY" three times to a company dispatcher, providing his position but not stating the nature of the emergency. No further communications were recorded.
Witness Observations
Witnesses in a southbound automobile observed the helicopter flying toward them from the south. They reported that the helicopter's fuselage began rotating counter-clockwise. The aircraft then veered to the west, went out of sight, and subsequently crashed.
Wreckage Examination
All major components of the helicopter were located except for approximately 33 inches of the tail rotor drive shaft and its No. 5 bearing. The tail boom was found in three sections. Rotational and longitudinal scoring damage was noted on the tail boom in the vicinity of the No. 3 and No. 5 bearing supports. A laboratory report stated that the rotational damage occurred before the gross deformation of the tail boom and subsequent in-flight breakup of the helicopter.