Editing Avro Lancaster (section)

===Origins===
In the 1930s, the [[Royal Air Force]] (RAF) was primarily interested in twin-engine [[bombers]].<ref name = "norris 3"/> These designs put limited demands on engine production and maintenance, both of which were already stretched with the introduction of so many new types into service. Power limitations were so serious that the British invested heavily in the development of huge engines in the {{cvt|2000|hp}} class in order to improve performance. During the late 1930s, none of these were ready for production. Both the [[United States]] and the [[Soviet Union]] were pursuing the development of bombers powered by arrangements of four smaller engines; the results of these projects proved to possess favourable characteristics such as excellent range and fair lifting capacity. Accordingly, in 1936, the RAF also decided to investigate the feasibility of the four-engined bomber.<ref name = "norris 3">Norris 1966, p. 3.</ref>

The origins of the Lancaster stem from a twin-engined bomber that had been submitted to British [[Air Ministry]] [[List of Air Ministry specifications|Specification P.13/36]] of 1936 for a twin-engined [[medium bomber]] for "worldwide use" which could carry a torpedo internally, and make shallow dive-bombing attacks.<ref name="Mason Bomber p324-5">Mason 1994, pp. 324–325.</ref><ref name = "robertson1964 7">Robertson 1964, p. 7.</ref> Further requirements of the specification included the use of a mid-mounted [[cantilever]] [[monoplane]] wing, and all-metal construction while the use of the [[Rolls-Royce Vulture]], which was in development was encouraged.<ref name="moyes 3">Moyes 1966, p. 3.</ref> Twin-engine designs were submitted by [[Fairey Aviation Company|Fairey]], [[Boulton Paul Aircraft|Boulton Paul]], [[Handley Page]] and [[Short Brothers|Shorts]], using [[Rolls-Royce Vulture]], [[Napier Sabre]], [[Fairey P.24]] or [[Bristol Hercules]] engines. Most of these engines were still under development and while four-engined bomber designs were considered for specification B.12/36 for a heavy bomber, the extra engines required the wing and overall aircraft structure to be stronger, increasing the structural weight.<ref>Buttler 2004, p. 104.</ref>

[[Avro]] submitted the [[Avro Manchester|Avro 679]] to fulfil Specification P.13/36 and, in February 1937, Avro's submission was selected, along with Handley Page's bid as a backup. In April 1937, a pair of prototypes for each design was ordered.<ref>Buttler 2004, p. 102.</ref><ref name="moyes 3"/> Avro's aircraft, named the Manchester, entered RAF service in November 1940. Although a capable aircraft, the Manchester was underpowered and its Vulture engines proved to be unreliable.<ref name="goul garb 3">Goulding and Garbett 1966, p. 3.</ref><ref name = "robertson1964 911">Robertson 1964, pp. 9–11.</ref> As a result, only 200 were constructed and the type was withdrawn from service in 1942.<ref name="Jackson Avro p355-6">Jackson 1990, pp. 355–356.</ref>