Flight and Accident
The helicopter was conducting cruise flight at 500 feet MSL when the pilot perceived a "thud." The aircraft then yawed left and lost engine power, prompting the pilot to enter an autorotation aimed at a water landing. During the descent, the pilot executed a right turn into the wind. According to the pilot, before the turn was completed, the hydraulic system ceased functioning.
Landing and Post-Accident Conditions
The helicopter impacted the water with significant force and subsequently rolled inverted. The pilot informed the operator that he had deployed the emergency floats; however, post-accident inspection determined the floats were still stowed. All three fuel cells were found empty, but each sustained damage that compromised its integrity.
Fuel System Examination
Examination of the fuel system revealed that the fire-shield-to-fuel-nozzle supply line contained no fuel. A sample from the fuel filter was tested and found to consist of 10 percent fuel and 90 percent sea water. The presence of sea water in the fuel system suggests contamination.
Airframe and Engine Inspection
A representative from the helicopter manufacturer examined the main rotor hub and blades. The observed damage was described as consistent with the impact of a slow-turning rotor. The airframe and engine underwent detailed inspection, revealing no structural or mechanical anomalies that would have prevented normal operation prior to the accident.