Introduction
On October 14, 2010, at 1517 Pacific daylight time, a Bell 206B helicopter, registration N2763M, came to rest on its right side following an autorotation at the base of Auburn Dam in Auburn, California. The helicopter was operated by Whirl Wide, Inc. dba TGR Helicopters as a repositioning flight under 14 Code of Federal Regulations Part 91. The commercial pilot and one passenger were not injured. The helicopter sustained substantial damage. Visual meteorological conditions prevailed and no flight plan was filed.
Flight Details
The flight departed from PG&E Auburn Service Center Heliport in Auburn at about 1515, destined for Mother Lode Service Center Heliport in Angels Camp, California. The pilot reported that he was transitioning along the west canyon wall of the American River Canyon to reposition the helicopter.
Accident Sequence
At an altitude of approximately 150 feet, the helicopter experienced a violent vertical vibration. The pilot initiated an autorotation and landed on a downsloping dirt road. During the landing, the helicopter rolled over and came to rest on its right side. The pilot and passenger did not observe any transmission lines along their route of flight. The pilot reported no mechanical anomalies prior to the vertical vibration.
Post-Accident Findings
California State Parks personnel indicated that the helicopter came to rest on a road below the Auburn dam, facing southeast with the tail section separated. Additional investigation revealed a downed power line owned by the Placer County Water Agency (PCWA). The unmarked line was a power supply for a temporary pumping station used during construction of the PCWA Pump Station, which began in 2003. The line spanned an 800-foot gap from a fenced electric substation to a power pole on a high outcropping to the east. The line was removed following the accident.