NTSB Factual Report

On October 14, 2010, at 1517 Pacific daylight time, a Bell 206B, N2763M, rolled onto its side following an autorotation at the base of Auburn Dam, Auburn, California. Whirl Wide, Inc. dba TGR Helicopters, was operating the helicopter as a repositioning flight under the provisions of 14 Code of Federal Regulations Part 91. The commercial pilot and one passenger were not injured. The helicopter was substantially damaged. Visual meteorological conditions prevailed and no flight plan was filed. The flight departed from PG & E Auburn Service Center Heliport, Auburn, about 1515, and was being repositioned to Mother Lode Service Center Heliport, Angels Camp, California.

The pilot reported that he was transitioning along the west canyon wall of American River Canyon to reposition the helicopter when it experienced a violent vertical vibration at 150 feet. The pilot entered an autorotation and landed on a downsloping dirt road. The helicopter rolled over and came to rest on its right side. The pilot and passenger did not see any transmission lines along their route of flight. The pilot reported no mechanical anomalies with the helicopter prior to the vertical vibration.

California State Parks personnel indicated that the helicopter came to rest on a road below the Auburn, California dam. The helicopter came to rest on its right side, facing southeast and the tail section was separated. Additional investigation revealed that there was a downed power line owned by Placer County Water Agency (PCWA). The unmarked line was a power supply for a temporary pumping station that was used during the construction of the PCWA Pump Station that began in 2003. The line spanned an 800-foot gap across a small divide from a fenced electric substation to a power pole on a high outcropping to the east. The line was removed following the accident.

NTSB Probable Cause

The pilot's failure to maintain clearance from a transmission line during flight.