Helicopter Accident During Low-Altitude Flight Following Creek Bed (N575PF)

Sequence of Events

Prior to the accident, the helicopter was flying on an easterly heading in level flight at approximately 20 knots while making shallow turns following a creek bed. The pilot reported that the helicopter lost all of its lift and power and started descending toward the trees. The pilot added that the anti-torque pedals were ineffective and the helicopter was spinning to the right prior to impact with the trees.

Post-Accident Examination

Minor repairs were made to the engine in order to run the engine on the helicopter. The engine was started and operated twice within the 1300 to 2500 RPM range for 18 minutes. A representative of the engine manufacturer reported that "no pre-existing engine deficiencies were noted and the investigation did not produce any evidence that the engine was not capable of operating and producing power at the time of the accident."

Environmental Conditions

The conditions at the time of the accident were found to be conducive to the formation of a tail rotor vortex ring state.