Incident Overview
During a routine flight, a helicopter initiated an approach to an offshore platform, heading into the wind. The pilot reported that the helicopter made an "uncontrolled, un-induced yaw to the right." In response, the pilot attempted to turn right to counteract the yaw and maneuver away from the platform. As power was increased, the aircraft "went into an uncontrollable and rapid spin to the right."
Pilot Actions and Impact
The pilot then closed the throttle and reduced power, which "slowed but did not stop the spin." Just as the pilot pulled the collective control, the aircraft impacted the water. Following impact, the helicopter rolled over and sank.
Post-Recovery Examination
After the helicopter was recovered from the water, flight control continuity checks were performed. No anomalies were found within the tail rotor drive or flight control systems that could not be attributed to impact or recovery damage.