and high octane fuels, and the V12 layout was commonly adopted due to its low vibrations so that the powerful engines did not tear apart the light airframes of fighters. The Allied forces used V12 engines with an "upright" design, while many German engines (aside from the BMW VI, which was designed prior to World War II), used an inverted engine design, which had a lower centre of gravity and improved pilot visibility for single-engined designs. The only American-design inverted V12 engine of any type to see even limited service in World War II was the air-cooled Ranger V-770, which was used in aircraft that were only used for training purposes within the United States, such as the Fairchild AT-21 Gunner. The Rolls-Royce Merlin V12 engine was used in several British aircraft including the Hawker Hurricane and Supermarine Spitfire fighters, and the Avro Lancaster and de Havilland Mosquito bombers. The Hurricane and Spitfire played vital roles in the Battle of Britain. The long, narrow configuration of the V12 contributed to good aerodynamics, while its smoothness allowed its use with relatively light and fragile airframes. In the United States, the Rolls-Royce Merlin engine was produced under license by Packard Motor Car Company, which was used in the P-51 Mustang fighter. This engine was also incorporated into some models of the Curtiss P-40, specifically the P-40F and P-40L. Packard Merlins powered Canadian-built Hurricane, Lancaster, and Mosquito aircraft, as well as the UK-built Spitfire Mark XVI, which was otherwise the same as the Mark IX with its British-built Merlin. The Allison V-1710 was the only liquid-cooled V12 engine designed in the United States that was used on active service during World War II. It was initially used in the P-38 Lightning, but the turbosupercharger system required bulky ductwork and had poor high-altitude performance. In 1943, a version using a more conventional mechanical supercharger began production. After World War II, V12 engines became generally obsolete in aircraft due to the introduction of turbojet and turboprop engines that had more power for their weight, and fewer complications. Usage in automobiles In automobiles, V12 engines are less common than engines with fewer cylinders, due to their size, complexity, and cost. They have been mostly used for expensive sports and luxury cars thanks to their power, smooth operation, and distinctive sound. 1910s One of the earliest recorded uses of V12 engines in automobiles was in October 1913,