Accident Sequence
The pilot landed the helicopter on a gravel bar located in a river with high banks. The wind was variable during the approach and landing. After landing, the pilot lifted the helicopter back into a hover to reposition on the same gravel bar. Shortly after becoming airborne, the helicopter began to turn to the right. The pilot applied left pedal input, felt a response, but was unable to arrest the rotation. During the turn, the helicopter descended and struck the water. Following the impact, all occupants exited the helicopter. Subsequently, the helicopter rolled over and sank in the river.
Background Information
The purpose of the flight was fish guiding. According to information from the manufacturer and the Federal Aviation Administration (FAA), when a helicopter is operating at or near its maximum gross weight, tail rotor control may become marginal depending on wind conditions. Hovering with a tailwind may cause a temporary loss of tail rotor effectiveness, allowing the helicopter to rotate about its vertical axis.