Incident Overview
Shortly after takeoff while established on the downwind leg, the pilot reported that the engine began to run roughly. Unable to maintain altitude, he landed the airplane on the airport property.
Inspection Findings
An inspection of the engine after the accident revealed that the left magneto was incorrectly timed. Additionally, both magnetos were observed breaking down during a test run. The pilot, who was also the mechanic of the airplane, reported that the magneto drop on the left magneto was 500 RPM prior to takeoff. He elected to fly the airplane as a test hop to troubleshoot the problem.
Additional Details
When a witness secured the airplane following the accident, he noted that the magneto switch was loose and fell out of the instrument panel when he tried to turn the key. The pilot had not accomplished a biennial flight review in over five years.