On February 1, 1999, at 1056 central standard time, a Bell 206L-3 helicopter, N6603X, was substantially damaged upon impact with a wind sock during final approach at the West Delta 105B offshore platform in the Gulf of Mexico. The commercial pilot, who was the sole occupant of the helicopter, was not injured. The helicopter was registered to and operated by Petroleum Helicopters, Inc., of Lafayette, Louisiana. Visual meteorological conditions prevailed and a company flight plan was filed for the Title 14 CFR Part 91 positioning flight which originated from the South Pass 25 offshore platform at 0915. The pilot was positioning the helicopter to the West Delta 105B offshore platform when, according to the pilot's written statement, he heard a "buzzing sound followed by a right yaw." The pilot then executed a hovering autorotation to the platform. The pilot stated that he suspected that the tail rotor blades contacted the wind sock during the approach. The wind sock's internal frame showed evidence of a tail rotor blade strike. Maintenance personnel reported that one of the tail rotor blades was missing approximately the outboard four inches. The tail rotor gear box was torn from its mounting and the tail boom had sustained structural damage. According to company flight records, the pilot had accumulated 3,893 hours total flight time, of which 2,517 hours were in the Bell 206L-3.