Helicopter Rolls Over After Hard Landing Following Engine Power Loss (N9184F)

Incident

While executing a turn at the end of a swath run, the pilot heard a distinct bang and subsequently noticed a loss of engine power. The pilot entered an autorotative landing from a low altitude at a low airspeed. The helicopter then landed hard and rolled over onto its right side.

Investigation

An investigation into the incident revealed that the spur adapter gearshaft had failed due to fatigue. The fatigue crack originated on the loaded side of a spline tooth at an area of heavy wear. The total flight time accumulated on the failed part was 3491 hours. The spur adapter gearshaft serves to couple the compressor to the N1 turbine.

Findings

The failure of the spur adapter gearshaft led to the loss of engine power. The subsequent autorotative landing from a low altitude and low airspeed resulted in a hard landing and rollover. No other factors were identified in the investigation.