Incident Overview
During a fish-spotting flight, the pilot reported hearing an abnormal engine sound 35 minutes into the flight. He turned the helicopter toward his ship and initiated a precautionary approach to the water. Engine performance continued to deteriorate during the descent.
Engine Failure and Autorotation
At an altitude between 350 and 400 feet and an airspeed of 50 to 60 knots, the engine failed completely. The pilot executed an autorotation, turning left into the wind. Approximately 30 seconds after the first indication of an engine problem, the helicopter contacted the water in a hard landing.
Pilot's Observations
The pilot stated that the hard landing resulted from high density altitude conditions and the absence of wind, combined with the low altitude at which the engine failed and quit. Additionally, the sun's reflection on the water created illusions that made it difficult to visually judge distance from the water, speed, and rate of descent.
Engine Investigation
The nature of the underlying engine problem was not reported by the operator.