What happened
During a coyote eradication flight, the aircraft experienced a partial loss of engine power. While the pilot was maneuvering at low altitude and low airspeed, a vibration was felt throughout the airframe. Following this vibration, the engine and main rotor RPM began to decrease, causing the instrument needles to split.
The pilot attempted to apply full power; however, the engine would only develop 2,000 RPM. As the pilot maneuvered the aircraft toward a clear area, the main rotor blades struck trees. This caused the aircraft to roll to the right and impact the ground. There were no fatalities reported in this accident.
The investigation
Following the accident, the engine was subjected to a test run within the airframe, which revealed that the engine was running rough. The subsequent investigation determined that the engine camshaft lobes were worn beyond allowable limits. Additionally, the #4 exhaust valve showed signs of heat discoloration and evidence of sticking.