ERA20LA071

During the flight to observe feral swine invading farm fields, the pilot noted a loss of engine power and rotor rpm. He maneuvered the helicopter away from trees for an autorotation to an open, plowed cornfield. During the landing on rough terrain, the helicopter nosed forward and the main rotor blades contacted the ground, resulting in substantial damage to the helicopter. A postaccident examination of the flight controls, drive train, fuel system, main rotor system, and tail rotor system did not reveal evidence of a preexisting mechanical malfunction or anomaly. The engine was removed and placed on a test stand; it ran normally for about 2 minutes before the run was concluded. A laboratory test of a fuel sample was unremarkable. The reason for the loss of engine power could not be determined.

On January 8, 2020, about 1339 eastern standard time, a Hughes OH-6A, N6186U, was substantially damaged when it was involved in an accident near Preston, Georgia. The commercial pilot and one crewmember sustained minor injuries. The helicopter was registered to the U.S. Department of Agriculture and was operated as a public aerial observation flight. The pilot reported that the purpose of the flight was to conduct aerial wildlife damage management operations. A feral swine was located and the pilot informed the ground crew via radio of its location. Shortly thereafter, the pilot noted a loss of engine power and rotor rpm. The pilot maneuvered the helicopter away from trees for an autorotation to an open, plowed cornfield. During the landing on rough terrain, the helicopter nosed forward and the main rotor blades contacted the ground. The engine appeared to be running at the time of impact. A Federal Aviation Administration inspector responded to the accident site and examined the wreckage. The tail boom was separated from the helicopter and three of the four main rotor blades were separated from the hub. The fuselage sustained structural damage. The operator reported that the N2 (power turbine) governor was changed before the flight due to a problem on a previous flight. The wreckage was retained for further examination, and examination of the flight control system, drive train, main rotor system, and tail rotor system did not reveal evidence of a preexisting mechanical malfunction or anomaly. The engine was removed from the airframe and sent to a factory-authorized overhaul facility for further examination. Continuity was established for the N1 (gas producer turbine) and N2 rotors. The rotors moved freely without binding or noise. Control continuity was confirmed from the collective twist grip to the fuel control unit. The control linkage to the power turbine governor was fractured at the engine firewall due to impact forces. The engine was installed on a test stand and prepared for a test run. The engine performed satisfactorily at takeoff power for 2 minutes as well as two lower power test points over a test period totaling about 20 minutes. Following the test run, the power turbine governor, fuel control unit, fuel nozzle, and fuel pump were bench-tested. The power turbine governor that was removed and replaced before the accident flight was also tested. All units tested satisfactorily and within the manufacturers' specifications. Examination of the fuel system revealed no anomalies, and the fuel lines and filters were free of contamination and obstructions. A fuel sample was tested in a laboratory with normal results.