NTSB Identification: WPR10FA055
14 CFR Part 91: General Aviation
Accident occurred Saturday, November 14, 2009 in Doyle, CA
Probable Cause Approval Date: 08/29/2013
Aircraft: AEROSPATIALE AS350BA, registration: N5793P
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.

Ten minutes after dropping off a patient at the local hospital and while returning to home base in dark night conditions, the flight crew made a routine position report. About 8 minutes later, the flight crew transmitted that the helicopter was going down.

Radar data indicated that after departure from the hospital, the helicopter initiated a climb from about 4,500 feet mean sea level (msl) and established a northwesterly course. In the vicinity of the accident site, the target indicated a climbing turn to the northeast followed by a turn to the southwest, and then a climbing turn back to the northeast. The last two targets indicated a turn to the right. The last recorded altitude was at 10,200 feet msl.

On-site documentation of the wreckage suggested that the helicopter was in a nose-low attitude and about a 90-degree bank angle when it contacted the ground.

A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

A study of the weather conditions in the vicinity of the accident site indicated clouds were present with tops reaching about 13,000 feet msl. Light clear icing was present with the potential for moderate clear icing in or near clouds. Visibility was at or greater than 10 statute miles.

Given the helicopter’s flight path shortly before the accident, it is likely that the pilot was maneuvering to avoid clouds and became disorientated in the dark night conditions, which resulted in a loss of helicopter control.

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

The pilot became spatially disoriented while maneuvering on a dark night, which resulted in a loss of helicopter control.

Full narrative available

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