On March 26, 2026, about 1539 Hawaii standard time, a Hughes 369D helicopter, N715KV, was substantially damaged when it was involved in an accident near Haena, Hawaii. The pilot and one passenger sustained serious injuries, and three passengers were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 135 revenue sightseeing flight. The helicopter departed Lihue Airport (LIH), Lihue, Hawaii, about 1512 for a local sightseeing tour. It was scheduled for the sixth and final flight of the day. The flight was uneventful until it reached the northern shore of the island, near Haena about 20 miles northeast of LIH. According to the pilot, upon reaching Kalalau beach, he accomplished a left turn away from the shoreline as part of the normal flight profile. Upon entering the turn, the pilot experienced a high frequency vibration throughout the helicopter that came in waves and became stronger each time. Subsequently, the helicopter started an un-commanded right yaw that could not be corrected with input from the left anti-torque pedal. The helicopter quickly began to rotate clockwise, completing about 2 rotations, and the pilot entered the helicopter into an autorotation. He rolled the throttle to idle and attempted to increase the airspeed for better directional control. The pilot noted that the spinning had stopped during the autorotation and he made a mayday radio call. Unable to make the beach, the helicopter impacted the water and rolled onto its right side about 75 yards from the shoreline and shortly afterwards became partially submerged. A witness, who was flying near the accident site, observed the helicopter impact the water. The helicopter came to rest upright and tilted slightly to the right, facing towards the east. Another witness reported that the helicopter appeared to be intact before it impacted the water and broke up. The surviving passenger on the flight said that she heard a change in the sound and the helicopter slowed down. She then observed the helicopter rotating towards the water. Subsequently, the helicopter nosedived into the water. Postaccident examination revealed that the helicopter’s fuselage and main rotor blades sustained substantial damage. The helicopter was recovered to a secure facility and retained for further examination.