What happened
Following takeoff, the pilot observed that the aircraft engine was running roughly. He continued to fly the traffic pattern, but the engine's performance steadily deteriorated. During the final approach phase, the pilot reported that the engine could not generate sufficient power to reach the runway. Consequently, he executed a forced landing in a marsh located short of the runway.
The investigation
Examination of the engine after recovery revealed that the right magneto was worn. This defect prevented the ignition system from producing full power, resulting in the loss of engine performance observed during flight.
Findings
The mechanical failure of the right magneto was the primary factor in this incident. The worn component caused the engine to run rough and eventually lose power, leading to the forced landing. No injuries were reported among the occupants.