On May 3, 2011, sometime between 0130 and 0355 eastern daylight time, an Aerospatiale AS350B2, N916AM, operated by Air Methods Corp., was substantially damaged while maneuvering at Woodward Field, Camden, South Carolina. The two certificated airline transport pilots were not injured. Night visual meteorological conditions prevailed and no flight plan was filed for the local flight. The training flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. According to a Federal Aviation Administration (FAA) inspector and the Operator, the helicopter was being utilized for night vision goggle training. Two training flights were conducted between 2130 on May 2, and 0355 on May 3, 2011. According to the instructor pilot, both training flights comprised of similar maneuvers and profiles, which included rapid decelerations, standard autorotations, hovering autorotations, autorotations with turns, sloping ground landings, and simulated hydraulic failures. The instructor pilot stated that the helicopter was inspected prior to the second training flight, which began about 0130, and no discrepancies were noted. He further stated: "…At no time during both training flights did any maneuver feel nor indicate either a heavy landing, or contact between the tail fin stinger and the ground. No abnormal vibrations were experienced throughout the evening training events…." Subsequent inspection of the helicopter by an FAA inspector and a company mechanic revealed that the tail boom was buckled about 42-inches in front of the horizontal stabilizer. In addition, the tail rotor gearbox input seal was excessively leaking oil, and the tail fin stinger, which is reference by Eurocopter as the lower fin tail guard, contained fresh ground contact marks. The mechanic noted that no damage was present during an inspection he performed about 1900 on May 2, 2011. In addition, the mechanic reported that a postaccident landing gear "spread check" was within manufacturer specifications; however, there were no previous measurements taken on the accident helicopter that could be used for comparison purposes.