What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
This flight was a post annual inspection test flight. Pilot stated that all pre-departure checks and engine run up checks were performed and checked in limits. After departure from lhd, on the tudor overpass transition the pilot experienced a rough running engine and turned back towards anc. The pilot called ATC and asked for priority handling due to a rough running engine and thought he might not make the airport. ATC gave instructions to land on runway 32 at anc. Landing was uneventful. After landing pilot taxied to maintenance hangar. Maintenance run after shutdown found no negative indications. Further investigation discovered both spark plugs in the number one cylinder damaged. Borescope of cylinder found damage to the piston and cylinder head. A small round metal object was removed from the exhaust system. Foreign object and engine sent to Lycoming for inspection and reporting.
As the FAA filed it
THIS FLIGHT WAS A POST ANNUAL INSPECTION TEST FLIGHT. PILOT STATED THAT ALL PRE-DEPARTURE CHECKS AND ENGINE RUN UP CHECKS WERE PERFORMED AND CHECKED IN LIMITS. AFTER DEPARTURE FROM LHD, ON THE TUDOR OVERPASS TRANSITION THE PILOT EXPERIENCED A ROUGH RUNNING ENGINE AND TURNED BACK TOWARDS ANC. THE PILOT CALLED ATC AND ASKED FOR PRIORITY HANDLING DUE TO A ROUGH RUNNING ENGINE AND THOUGHT HE MIGHT NOT MAKE THE AIRPORT. ATC GAVE INSTRUCTIONS TO LAND ON RUNWAY 32 AT ANC. LANDING WAS UNEVENTFUL. AFTER LANDING PILOT TAXIED TO MAINTENANCE HANGAR. MAINTENANCE RUN AFTER SHUTDOWN FOUND NO NEGATIVE INDICATIONS. FURTHER INVESTIGATION DISCOVERED BOTH SPARK PLUGS IN THE NUMBER ONE CYLINDER DAMAGED. BORESCOPE OF CYLINDER FOUND DAMAGE TO THE PISTON AND CYLINDER HEAD. A SMALL ROUND METAL OBJECT WAS REMOVED FROM THE EXHAUST SYSTEM. FOREIGN OBJECT AND ENGINE SENT TO LYCOMING FOR INSPECTION AND REPORTING.