What was found
(CAN) AIRCRAFT DEPARTED, JUST AFTER TAKEOFF, THE PILOT NOTICED OIL ON THE WINDSHIELD. AFTER CHECKING ENGINE INSTRUMENTS, OIL TEMP NORMAL, OIL PRESSURE NORMAL. CYLINDER HEAD TEMP 240 (OAT FOR THE DAY WAS ABOUT 30 DEGREES CELSIUS). PILOT DECIDED TO CONTINUE THE FLIGHT TO MAIN BASE ABOUT 16 MILES AWAY. ABOUT 8 MILES FROM BASE, THE OIL LEAK STARTED TO WORSEN AND ENGINE STARTED RUNNING ROUGH. PILOT DECIDED TO LAND. THE PLANE LANDED WITHOUT INCIDENT. ON INVESTIGATION OF THE ENGINE, NR 9 PISTON DISCOVERED BROKEN AND MISSING 2 TOP RINGS WHICH CAUSED THE CASE TO PRESSURIZE AND BLOW OIL OUT THE NOSE CASE. NR 9 CYLINDER WAS CHANGED AND ENGINE INSPECTED FOR ANY OTHER DAMAGE. AIRCRAFT WAS RETURNED TO SERVICE.