McDonnell Douglas MD-369FF, Haena, Hawaii, March 11, 2007–The Inter-Island Helicopters MD-369 was destroyed and a passenger was killed when the helicopter crashed into trees during a sightseeing tour. In cruise, the tail-rotor output shaft and the tail-rotor blades separated from the tail-rotor gearbox and fell into the ocean. The pilot autorotated to a campground near the beach.
The pilot, who was not injured, said he thoroughly inspected the helicopter before his first flight. After two flights to a waterfall, he conducted a post-flight inspection “as we always do.” During both flights, the helicopter operated normally and the pilot noted no unusual vibrations.
He told investigators that during the third flight, the accident flight, he felt no abnormal vibrations in the controls. Flying over Tunnel Beach, about 50 yards from the shoreline, at 1,000 feet agl and 80 to 85 knots, he heard two loud “bangs” and he “felt it” in his seat and pedals. The nose of the helicopter pitched down and the helicopter yawed to the right. The yaw developed into a tight spin. He realized that he had “lost his tail rotor.”
After the helicopter hit, he checked on the passengers’ condition and, after exiting, saw that the tail-rotor blades and output shaft had separated from the tail-rotor gearbox.
The NTSB Materials Laboratory’s initial inspection of the tail-rotor gearbox showed that all the fractures were typical of overstress failure.