Incident Overview
During a sightseeing flight, the pilot heard a series of pops and observed illumination of the oil pressure and oil temperature warning lights. In response, the pilot initiated an autorotation to an open field. During the landing maneuver, the tail rotor separated from the aircraft.
Engine Inspection
An inspection of the engine revealed that the number 4 connecting rod shank was broken into three pieces. A metallurgical examination of the connecting rod assembly indicated that one connecting rod bolt displayed a fracture characteristic of a tensile overstress separation. The other connecting rod bolt was not located.
Findings
The examination of the connecting rod assembly did not identify the cause of the tensile overstress separation. The missing connecting rod bolt was not recovered, and its condition could not be determined.