The helicopter pilot was approaching the airport for landing about 350 feet above ground level when a fixed-wing airplane taxied in front of his intended landing spot and stopped. He slowed the helicopter to avoid blowing the airplane and the helicopter subsequently lost tail rotor effectiveness. The helicopter then rapidly descended to the ground and came to rest in a drainage depression. The helicopter sustained substantial damage to the fuselage and tail boom during the accident sequence and the pilot was not injured. The airport elevation was 6,572 feet mean sea level (msl) and the calculated density altitude at the time of the accident was about 9,300 feet msl. The pilot reported no mechanical malfunctions or failures with the helicopter and further stated that he could have prevented the accident by avoiding slow speeds at high density altitudes.