The Franklin O-805 (company designation 12AC) was an American air-cooled aircraft piston engine, designed in the mid-1940s and was to be used in radio-controlled pilotless drones that were to be guided from an accompanying control plane. Due to project requirement changes and cancellations the engine was not produced. A smaller displacement 12-cylinder Franklin engine of 1941 was known as the O-595 or 12AC-596.