The helicopter was operating at a remote, unimproved landing zone (LZ) with a ground crew consisting of firefighters. They were conducting aerial firefighting training with an external load consisting of a 50 ft longline and a water bucket. The LZ consisted of about 2.5 ft tall prairie grass, with the tail of the helicopter going up slope. During the landing to the LZ, the tail rotor impacted a backpack on the ground. The helicopter landed upright and the pilot shutdown the helicopter. The pilot performed a self-assessment of the damage sustained to the tail rotor blades and then flew the helicopter back to the airtanker base with the ground crew onboard. The helicopter sustained substantial damage to both tail rotor blades and the tail rotor hub. The pilot reported there were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation. The pilot was in radio contact with the ground crew during the training. However, during the landing, there was no communication between the ground crew and the pilot either via radio or hand signal. The orange-colored backpack was owned and was used by the ground crew. According to the operator, the pilot and the ground crew had worked together previously conducting aerial firefighting operations and the pilot had landed to the LZ several times in the past.