Incident Overview
Approximately 10 seconds after takeoff from an offshore platform, the pilot, who had accumulated 3,299 flight hours, heard a loud bang and the engine lost partial power. The pilot initiated an autorotation toward the water, during which a subsequent bang was heard.
Float Deployment
Prior to touchdown, the pilot attempted to inflate the helicopter's floats; however, the floats did not inflate. The pilot executed a flare and "pulled in pitch," noting that the helicopter "still had power." The helicopter entered a hover before the pilot reported that it "seemed to still be pulling in power when the [helicopter] touched the water then rolled and the blades hit [the water]."
Engine Inspection
Inspection of the engine revealed minor damage to the compressor diffuser vane and the impeller, as well as foreign object damage (FOD) in the combustion chamber. It was not determined whether the FOD occurred prior to impact with the water. The reason for the partial loss of engine power was not determined.