The helicopter was at approximately 400 feet above the ground on a normal straight-in landing to a paved runway. At an airspeed of 45 miles per hour the pilot heard a snap and the helicopter began to spin. The pilot entered an autorotation and said he was concentrating on just “trying to keep the helicopter as flat as possible”. The helicopter struck the trees in a nose down attitude. There was no fuel spill and no post crash fire. The helicopter was substantially damaged and the pilot, who was the only occupant, sustained minor injuries. The Texas State Trooper that responded to the accident scene said the tail rotor gear box was missing from the area of the main wreckage. By the next day residents in the area had found a single tail rotor blade and several hundred feet away they found the other tail rotor blade still attached to the tail rotor hub and tail rotor gearbox. Photographs of the separated tail rotor blade show that the skin had ripped away from all three blade grip bolt holes. A post-crash examination of the helicopter failed to reveal why the tail rotor blades and gearbox separated from the aircraft.