What happened
The incident occurred while a helicopter was engaged in external load aerial spraying operations over a lake. After completing an application, the aircraft experienced a partial loss of power accompanied by a decaying rotor revolutions per minute (RPM). The pilot recognized the mechanical failure and maneuvered the aircraft toward the shoreline to execute an autorotation. However, the helicopter was at an altitude of approximately 150 feet above ground level (AGL) when the maneuver began. This altitude proved insufficient for the pilot to successfully negotiate the terrain near the shore, resulting in a crash.
The investigation
Following the accident, investigators examined the wreckage of the aircraft. The physical inspection revealed significant mechanical issues within the propulsion system. Specifically, the examination disclosed that the fuel control unit contained contaminants. These foreign materials within the fuel control unit were identified as the primary mechanical anomaly associated with the power loss.
Findings
The investigation determined that the partial loss of power was directly linked to the condition of the fuel system components. The presence of contaminants in the fuel control unit prevented proper operation, leading to the decaying rotor RPM. The pilot's decision to attempt an autorotation was a standard emergency procedure; however, the low altitude at the onset of the failure left no margin for error. The inability to clear the shoreline was a direct consequence of the sudden power degradation at low height.