What was found
(CAN) AFTER TAKEOFF, CREW NOTICED THE LT ENG STARTED RUNNING ROUGH & FOLLOWED BY A PARTIAL POWER LOSS. RETURNED TO AIRFIELD & LANDED WITHOUT FURTHER INCIDENT, TOWER NOTED SMOKE COMING FROM LT ENGINE. AFTER LANDING, OIL WAS DRIPPING FROM EXHAUST STACK & GEAR COVERED IN OIL. MX REMOVED EXHAUST PIPE FROM TURBOCHARGER & FOUND OIL INSIDE TURBO. TURBINE BLADES HAD HIT HOUSING, SHAFT BENT & VERY SLOPPY. BEARING FAILURE SUSPECTED. OIL FILTER & SUCTION SCREEN INSPECTED FOR METAL CONTAMINATION & TRACES FOUND BUT NOT SIGNIFICANT. NEW FILTER INSTALLED. COMPRESSION CHECKED ON ALL CYLINDERS AS PRECAUTION, ALL SERVICEABLE. FAULTY TURBOCHARGER REPLACED WITH AN OVERHAULED TURBO. ACFT GROUND RUN FOR FUNCTION CHECK & LEAK CHECK, & RELEASED PENDING A SATISFACTORY FLT TEST. ACFT FLOWN BACK TO MAIN BASE WHERE OIL WAS DRAINED & FILTERED, SUCTION SCREEN & OIL FILTER INSPECTED FOR CONTAMINATION. NO CONTAMINATES FOUND. NEW FILTER INSTALLED & OIL REPLENISHED WITH NEW. ACFT RETURNED TO SERVICE.