The flight was scheduled as recurrent training in helicopters; the foreign rated pilot was accompanied by a flight instructor, and an interpreter and observer who were seated in the back seats. After a series of maneuvers, the foreign pilot conducted a hovering autorotation, following directions from the flight instructor which were translated by the interpreter. During the autorotation, the helicopter yawed slightly right and settled to the ground. The instructor and observer noted that the landing did not feel that hard, but more like a firm or rough landing. The training flight continued with several other autorotations. During a post flight inspection of the helicopter, several wrinkles were found in the tail boom of the helicopter. Further examination of the helicopter revealed that the tail boom had sustained substantial damage.