On September 24, 1993, at 1600 mountain daylight time, the main rotor blades on an Aerospatiale, SA 315B Lama, N351RM, struck a tree stump while standing on a narrow landing pad near Avery, Idaho. The pilot was unable to maintain control of the helicopter as it pitched over and rolled down the steep hill. Visual meteorological conditions prevailed at the time and no flight plan was filed. The helicopter was substantially damaged and the certificated commercial pilot was seriously injured. The two passengers received minor injuries. The operator reported that the helicopter had been conducting logging operations throughout the day. At the end of the day, the helicopter landed on the narrow pad to pick up and transport personnel from the logging site. As the helicopter was standing with the engine running, one passenger was strapped into her seat, the other passenger was just boarding, when a loud bang was heard. The helicopter suddenly started to spin around and the one boarding passenger was thrown out of the helicopter. The pilot was unable to maintain control, and the helicopter travelled over the edge of the pad and rolled down the hill. It was later found that the main rotor blade struck a tree stump that was in close proximity to the pad and approximately five feet, two inches above the skids.