On August 10, 1999, at 1407 central daylight time, a Messerschmitt-Boelkow-Blohm (Mbb) BO-105S helicopter, N2785R, was substantially damaged during takeoff when it collided with a parked helicopter on the Vermilion 250 helipad, located offshore in the Gulf of Mexico. The instrument rated commercial pilot and the three passengers were not injured. The helicopter was registered to Offshore Logistics, L.L.C., of Lafayette, Louisiana, and operated by Air Logistics, L.L.C., of New Iberia, Louisiana. Visual meteorological conditions prevailed for the 14 Code of Federal Regulations Part 135 on-demand air taxi flight and a company VFR flight plan was filed. The flight was originating at the time of the accident and was destined for Cameron, Louisiana. According to the pilot, the helicopter was positioned at the southwest corner of the helipad on a westerly heading, and he was preparing for takeoff. An unmanned, Bell 206L-3 helicopter, N367AL, was parked on the northeast corner of the same helipad. The pilot "advanced the throttles to 100%," and then as he reached to adjust the volume of the radios, the helicopter began "spinning to the left and sliding backwards." The collective was in the "DOWN" position (not locked) and the anti-torque pedals were in the "NEUTRAL" position when the helicopter began to spin and move backwards. The pilot stated that he applied "right pedal and forward cyclic" in an attempt to terminate the spinning. The helicopter contacted the parked Bell 206L-3 and completed one 360 degree revolution. The helicopter continued to spin to the left and contacted the Bell 206L-3 a second time; consequently, the Bell 206L-3 was knocked off of the platform and fell into the Gulf of Mexico. The helicopter completed a second revolution before coming to rest upright, in the "safety wire" at the edge of the platform. The pilot reported that at the time of the accident the winds were from the south, southwest at 30 knots. The pilot and two mechanics reported that the tailboom of the BO-105S was bent. They added that one of its main rotor blades was destroyed, and the remaining three main rotor blades were fractured approximately 3 feet inboard from the blade tips. An FAA inspector, a representative from American Eurocopter and a representative from Air Logistics L.L.C., examined the helicopter on August 16, 1999, at the Air Logistics facilities located in New Iberia, Louisiana. Anti-torque control continuity was established from the tail rotor blades through the tailboom to the anti-torque control pedals in the cockpit. Control continuity was established from the cyclic and collective cockpit controls to the main rotor blades. No mechanical anomalies were observed during the examination.