NTSB Identification: LAX02FA114.
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Accident occurred Thursday, March 21, 2002 in Susanville, CA
Probable Cause Approval Date: 04/28/2004
Aircraft: Eurocopter AS-350B, registration: N1184H
Injuries: 1 Fatal,2 Serious.
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 collided with the surface of a glassy smooth lake while in cruise flight at low altitude. The purpose of the flight was to reposition the helicopter to the operator's base, after a patient delivery to a regional medical center. The approximate 10-miles in diameter lake is a shallow non-perennial body of water located about 11 miles east of the operators base. The wreckage was located about 2.5 miles from the east shore line and about 3.5 miles from the west shore. The lake is on a normal routing from the hospital to the operator's base. The flight nurse said he was sitting directly behind the pilot in a forward facing seat. He said that usually they crossed the lake about 500 feet above the surface, but this time they were much lower. He estimated that they had descended to within 20 to 50 feet of the lake surface, and, as they flew further out over the water they seemed to get lower and lower. He looked over the pilot's shoulder, and to the right, and noted how glassy smooth the water was. He stated that it was like a mirror and reflected the clouds and the sky perfectly, and was "kind of mesmerizing and disorienting" to see clouds both above and below with no distinct horizon. Just before they hit the water the pilot said on the intercom, "Boy, it's disorienting when the lake is this smooth." The nurse looked out the right side window at the distant shoreline and thought to himself that the flight seemed very, very low. The helicopter then hit the water. The flight nurse and paramedic medical crew members stated that there were no apparent mechanical malfunctions or failures with the helicopter prior to the collision with the lake surface. Examination of the extensively fragmented helicopter disclosed that all control system torque and push/pull tubes, and their associated rod end fittings, were accounted for. Scoring and other rotational evidence was noted on all drive system components.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Failure of the pilot to maintain sufficient altitude/clearance above the water while performing a low altitude flight. Factors relating to the accident were the glassy water condition, and a lack of visual cues concerning perception of altitude. Full narrative available
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