Incident Overview
A pilot planned a visual flight rules (VFR) flight at an altitude of 1,000 ft above ground level (AGL) over hilly terrain. According to the pilot, climb performance was noticeably low and smoke was coming from the left engine. The pilot entered a mountain pass and discovered he could not find an exit from the high terrain. In response, the pilot made a sharp turn to maneuver away from the hills.
Witness Observations
Witnesses observed the airplane flying at low altitude. They reported that the airplane "started a turn to the left and then went straight down, nose first." The witnesses did not mention seeing plumes of black smoke or hearing abnormal engine sounds.
Engine Examination
An examination of the left engine revealed that one magneto was not functioning. Other than this issue, no anomalies were found that would have prevented the engine from running.