Accident Overview
A private pilot was performing a test flight following the replacement of the number three cylinder. During the initial climb, the engine began to vibrate, backfire, and lose power. The aircraft subsequently crashed on a highway median located approximately one mile from the airport center.
Post-Crash Findings
Examination of the engine after the crash revealed a piece of exhaust valve lodged in the number one piston head. Another valve fragment was found inside the muffler. The pilot reported that the number three cylinder change was necessitated by a previously failed exhaust valve on that cylinder, which had caused internal damage. An assumption was made that the fragments from the failed valve had exited the engine via the exhaust system.
Maintenance History
A local mechanic changed the cylinder but did not complete the repair due to a lack of time. The pilot then finished the repair, conducted a test run of the engine, and proceeded to fly the aircraft on the accident flight. The engine was not certified airworthy prior to the flight.