What happened
While cruising at approximately 2,500 feet above the ground, the pilot of the helicopter heard a popping sound and experienced a rightward yaw. The engine began to lose power, prompting the pilot to lower the collective and initiate a partial autorotation. Despite attempts to accelerate the engine, the pilot continued to hear sputtering and popping sounds as power loss persisted.
The pilot decided to execute a full autorotational landing in a clearing within a heavily wooded area. Although the aircraft touched down with very low forward speed, the landing site consisted of a wet and muddy bog. Upon touchdown, one of the skids sank into the mud, causing the aircraft to roll onto its side. There were no injuries reported following the incident.
The investigation
An inspection of the engine and fuel system was conducted by an FAA Airworthiness Inspector and maintenance personnel from a fixed base operator. This examination revealed no evidence of any anomaly that could have caused the loss of power. Following the initial inspection, the engine was placed on a stand and operated at various speeds for approximately eight minutes. During this test run, the engine started easily and functioned smoothly at all tested speeds, reaching a maximum of 3,100 rpm.