ERA24LA166 · Robinson Helicopter R44

About 20 minutes after departure on the over-water flight, the pilot of the helicopter felt two “jerks,” although there were no caution/warning illuminations or aural warnings and the engine gauges were all “in the green.” He turned toward land and descended to 500 ft above the water. The pilot applied carburetor heat, then felt a “shake” and noted that he was having to add power as the helicopter was decelerating. While maneuvering the helicopter as close to land as possible, the low main rotor rpm horn sounded and the pilot described that the engine had lost a significant amount of power. The pilot selected an unoccupied area in the water for an autorotative landing, during which the tailboom separated. He exited the helicopter and was rescued shortly afterward. Postaccident examination of the airframe and engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation of the helicopter or its engine. Additionally, the engine governor control box was tested and it passed all testing parameters. Significant saltwater and sediment contamination prevented the determination of any non-mechanical pre-impact anomalies that may have impacted normal engine operation. Although weather conditions were favorable for carburetor icing at glide power, the pilot stated that he applied carburetor heat during his descent, so carburetor ice was not a likely reason for the loss of engine power.

Verbatim NTSB analysis and probable cause from the NTSB dataset