On October 7, 2011, about 1430 central daylight time, a Eurocopter AS350 B2, sustained substantial damage to the section during an engine start on the off-shore oil platform (South Pass 93A), Gulf of Mexico. The commercial pilot and the two passengers were not injured. The helicopter was registered to and operated by ERA Helicopters under the provisions of 14 Code of Federal Regulations Part 135 as an on-demand air taxi. Visual meteorological conditions prevailed for the flight, which operated on a company visual flight rules flight plan. The flight was originating at the time of the accident. According to a statement provided by the pilot, the helicopter’s nose was facing towards the wind that was measured by a velometer to be about 23 knots. The pilot centered and locked the controls prior to engine start in accordance with the helicopter’s checklist. About 22 Ng and three full main rotor rotations, the pilot felt chatter/vibrations from the helicopter. The pilot shut down the engine and found damage consistent with a main rotor blade strike to. The helicopter's tail rotor drive shaft had been distorted and damaged. The helicopter’s helipad was elevated from the main platform with a generator room west (downwind) of the helipad. The pilot reported that when the wind was from the east, the wind contacts the generator room and can cause occasional updrafts on the helideck. In the helicopter's flight manual's checklist for the "Checks Before Starting the Engine", the helicopter's cyclic is to be in the neutral position and the cyclic stick friction lock adjusted. Note 1 of the "Starting" checklist states, "In strong wind, apply a little forward cyclic and accelerate the engine, up to approx. 320 rpm, as fast as in compatible with t4 limitations, then follow normal procedure." An examination of the helicopter did not discover any preexisting anomalies with the helicopter which would have precluded normal operation of the helicopter. It could not be determined if the controls had been locked improperly or if winds displaced the main rotor blades during the engine start. A review of accidents involving AS350 helicopters by the Bureau d'Enquêtes et d'Analyses (BEA), revealed that in all recorded tail boom strikes by main rotor blades during start two conditions needed to be present: cyclic not centered and air turbulence pushing strongly on the main rotor blades.