Incident Overview
Shortly after departure, the airplane's engine experienced a partial loss of power. The private pilot, who had accumulated 604 flight hours, decided to execute an emergency landing on a road. During the landing roll, the rotating beacon collided with an unmarked static transmission line, and the left wing tip struck a mailbox.
Engine Examination
Following the incident, an examination of the engine revealed that the right magneto had sustained an internal failure, resulting in misfiring. The magneto had been installed eight years prior and had accumulated approximately 469 hours of operation since its last rebuild.
Maintenance History
A service bulletin previously issued by the magneto manufacturer stated that the magneto must be overhauled or replaced at the expiration of five years from the date of original manufacture or last overhaul, without regard to accumulated operating hours.