What was found
OPERATING FLIGHT 1821 ALB TO MSS RETURNED TO ALB IMMEDIATELY AFTER TAKEOFF & LANDED SAFELY WITH 3 PAX ON BOARD. PILOT NOTED DECREASING LT ENG OIL PRESS & HEARD A LOUD BANG FROM LT ENG AFTER ROTATION. LT ENG MAGNETO SEPARATED FROM ACCESSORY DRIVE & CONNECTING ROD PENETRATING CASE. SIGNIFICANT DAMAGE TO UPPER LT ENG COWLING. CORRECTIVE ACTION WILL BE TO REPLACE ENGINE ASSEMBLY, REPLACE ALL ENG DRIVEN ACCESSORIES, REPLACE PROPELLER, FLUSH & INSPECT ALL FLUID CARRYING LINES & HOSES PRIOR TO RELEASE. ENG ASSEMBLY WILL BE ROUTED TO OEM ANALYTICAL DEPARTMENT FOR COMPLETE TEARDOWN INSPECTION, REPORT OF FINDINGS & WARRANTY CONSIDERATION. PROPELLER WILL BE SHIPPED TO PROPELLER REPAIR STATION FOR DISASSEMBLY & INSPECTION AS A PRECAUTION FOR POSSIBLE METAL CONTAMINATION. AFFECTED ACCESSORIES WILL BE ROUTED TO APPROPRIATE VENDORS FOR DISASSEMBLY & INSPECTION AS A PRECAUTION FOR POTENTIAL METAL CONTAMINATION. LT NACELLE UPPER COWLING WILL BE REPLACED.