NTSB Identification: LAX01LA304.
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Accident occurred Saturday, September 22, 2001 in Chico, CA
Probable Cause Approval Date: 06/08/2005
Aircraft: Aerospatiale AS350BA, registration: N911NT
Injuries: 1 Fatal,1 Serious,1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

During a steep approach to a confined landing zone, the helicopter encountered a brown out condition due to dust and dirt clouds formed by the rotor downwash, and the helicopter collided with trees during an attempted go-around. After circling the landing area twice the pilot approached the landing zone from the west to the east. Ground witnesses and the onboard flight nurses said the approach was completely normal until the helicopter neared the ground. About 30 feet above the ground there was a dirt/dust condition created from the helicopter's rotor blades and the witnesses lost sight of the helicopter. One flight nurse, who was using night vision goggles to assist the pilot with ensuring that the landing zone was clear, told investigators that as the dust cloud formed their outside vision was completely obscured. The flight nurse asked the pilot if he could see anything, but the pilot did not respond. The medical crew estimated that the pilot started to go around about 15 feet above the ground, and during the go-around the helicopter drifted about 90 feet to the south and impacted trees. Witnesses recalled hearing the engine power up and then heard the helicopter impact trees. During the engine power up and go-around, no problems were heard with the engine. The on board medical crew said that they did not perceive any mechanical difficulties with the helicopter.

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

the pilot's inadequate in-flight decision and delay in initiating a go-around during an encounter with brown out conditions, which led to his failure to maintain alignment of the helicopter with the intended go-around flight path and a resulting collision with trees.


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