Accident Details
A certificated commercial helicopter pilot was conducting a salmon survey for the State of Alaska, Department of Fish & Game. The operation required hovering the helicopter over a stream while the passenger, a wildlife biologist employed by the State of Alaska, noted the number of fish.
Pilot Actions
The pilot reported feeling a slight vibration followed by a partial loss of engine power while in a hover above the stream. While hover taxiing the helicopter to a suitable landing area, the engine continued to lose power, forcing the pilot to make a downwind autorotation.
Damage and Postaccident Inspection
As the helicopter touched down, the main rotor blades flexed downward and struck the tail boom. The tail boom and tail rotor gearbox sustained substantial damage. During a postaccident inspection of the engine, a fractured intake manifold flange was discovered on the number three cylinder assembly.