NTSB Identification: SEA95FA214.
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Accident occurred Monday, September 11, 1995 in WINSLOW, WA
Probable Cause Approval Date: 04/29/1997
Aircraft: Agusta A109A II, registration: N1WC
Injuries: 3 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The helicopter pilot took off at night on a positioning flight for an emergency medical service (EMS) operation. There were reports of a low overcast layer varying from 1,000 feet above ground level to the surface. The majority of the witnesses reported that the helicopter was flying low as it traveled over the ground and continued over water toward a nearby island. Subsequently, the helicopter collided with the water and sank. Several of the witnesses reported that the engine sounded normal until the helicopter crashed. Some witnesses reported a 'popping' sound or a 'laboring' sound from the engines; however, after the engines were recovered at a later date, no evidence of a preimpact mechanical failure or malfunction was found. Local residents reported that the water condition at the time of the accident was 'calm' or 'glassy.' Several small pieces of the fuselage and main rotor blades were found floating on the surface of the water. Examination revealed that 3 of the main rotor blades had separated approximately three feet out from the attach points. The fourth blade separated approximately seven feet out from the attach point; however, the blade was bent and cracked chordwise approximately three feet out from the attach point. Using side scan sonar, wreckage was found over a distance of approximately 600 feet. The landing gear was found in the extended position, and the engine power levers were found in the flight position. Also, torsional evidence was found on the tail rotor driveshaft.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the pilot failed to maintain sufficient altitude/clearance above the surface of water, while flying over calm water conditions at night. Factors relating to the accident were: darkness, low ceiling, fog, glassy (calm) water conditions, and the lack of visual cues for visual perception of altitude.

Full narrative available

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