What was found
(CAN) UPON FIRST GROUND RUN OF M412 DURING MANUFACTURING FTP`S (WITHOUT M/R BLADES INSTALLED), A NOISE (BANG) WAS HEARD TWICE AND HYDR PRESSURE RAISED TO +1300 PSI ON THE GAGE. PILOT SHUTDOWN THE HYDR SYSTEM AND ABORTED GROUND RUN FOR INVESTIGATION. FURTHER INVESTIGATION REVEALED THAT A SWIRL OF COPPER METAL (CHIPS) JAMMED THE HYDRAULIC CHECK VALVE IN AN OPEN POSITION WHICH ALLOWED REVERSED FLOW AND AN HYDR LOCK BY PRESSURIZING THE PUMP CASE DRAIN, FOLLOWED BY A TEMPERATURE RISE. HYDRAULIC COMPONENTS REPLACED AND AIRCRAFT RETURNED TO SERVICE. FURTHER LAB TESTING WERE ABLE TO REPRODUCE THE PROBLEM AND TEMPERATURE WAS TWICE THE NORMAL RANGE WITHIN 4 MIN. OF OPERATION. THE SOURCE OF THE DEBRIS WAS NOT FOUND COULD