LAX93LA071

During cruise the pilot detected a buffeting in the airframe followed by a left yaw. The engine gages indicated decreasing power output with a high turbine outlet temperature, and, the engine chip and failure lights illuminated. The pilot executed an auto rotation and had to stretch the glide slightly to reach the only suitable area which involved a down wind landing. The main rotor sliced off the tail boom as the helicopter slid to a stop. Review of the operators daily flight sheets for the accident helicopter revealed that a engine chip light had illuminated on the flight prior to this one. The corrective action taken was to clean the chip plug and reinstall it. No test flight and further check of the plug was done as required in the maintenance manuals. Disassembly of the engine revealed that the number 1 and 2 bearings in the compressor module had failed. Review of maintenance records revealed that the compressor module was formerly installed in an engine which was involved in a helicopter accident in may of 1992. The compressor module was not disassembled for inspection as required in the overhaul and maintenance manual, and was not signed off for return to service. It was installed by the operator in the accident helicopter engine on November 21, 1992.