What happened
Shortly after takeoff, the Cessna (type not specified in source) experienced a partial loss of engine power. The pilot, who had 604 hours of flight experience, elected to perform an emergency landing on a nearby road. During the landing sequence, the aircraft's rotating beacon struck an unmarked static transmission line, and the left wing tip collided with a mailbox.
The investigation
An examination of the engine identified that the right magneto had suffered an internal failure, which led to misfiring. This specific magneto had been installed eight years prior and had operated for approximately 469 hours since its last rebuild. Investigators noted that a service bulletin from the manufacturer required magnetos to be overhauled or replaced five years after the date of original manufacture or last overhaul, regardless of accumulated operating hours.