Accident Description
During takeoff, the helicopter experienced a loss of power and subsequently landed hard. The event was investigated post-flight.
Examination Findings
Postaccident examination of the engine revealed that the No. 2 cylinder intake valve rocker shaft had migrated out of the shaft bosses of the cylinder head. The shaft, cover, and nuts were located during the examination; however, the washers were not found. The owner/pilot reported that there were internal star washer imprints on the cover plate, which are commonly caused by torque or tightening of the nut.
Maintenance History
The helicopter had accrued a total of 61.5 hours since new. It had received one 50-hour inspection since delivery to the owner/pilot. The owner/pilot changed the oil and oil filter just prior to that inspection.