Incident Overview
During a hover operation involving the slinging of an external load over rough terrain, the engine chip light illuminated. The pilot immediately maneuvered the aircraft to release the load. Shortly thereafter, the engine began emitting a whining noise. Several seconds later, all engine power was lost.
Emergency Landing
The pilot performed an autorotation, resulting in a firm landing. Upon touchdown, the main rotor blades flexed downward and severed the tail boom.
Examination Findings
An examination of the engine's turbine components revealed the presence of a sludge material in the scavenge oil line from the No. 8 bearing. Additionally, a heavy buildup of carbon was found on the engine rotor 'peashooter' drive shaft. The accumulated material caused shaft rub and failure of the power turbine's inner shaft.
Operator's Statement
The operator reported that an early inspection of the N1/N2 drive shaft area could have detected the problem and prevented the accident.