The Pratt & Whitney R-1340 is a radial aircraft engine that was first introduced in the 1920s. It features a nine-cylinder design and has a displacement of 1,340 cubic inches. Known for its reliability and performance, the R-1340 was widely used in various military and civilian aircraft during its production run. This engine produced around 600 horsepower and was commonly found in aircraft such as the Boeing Stearman and the Douglas DC-3. Its robust construction and ease of maintenance contributed to its popularity, making it one of the most successful engines of its time.