The Avro Lancaster is a British four-engined Second World War heavy bomber designed and built by Avro for the Royal Air Force (RAF). It first saw active service with RAF Bomber Command in 1942 and, as the strategic bombing offensive over Europe gathered momentum, it was the central implement for the night-time bombing campaigns that followed.
The origins of the Lancaster stem from a twin-engined bomber design submitted to meet Air Ministry Specification P.13/36, which was for a new generation of twin-engined medium bombers for “worldwide use”, the engine specified as the Rolls-Royce Vulture. The resulting aircraft was the Manchester, which, although a capable aircraft, was underpowered and troubled by the unreliability of the Vulture engine. Only 200 Manchesters were built, with the type withdrawn from service in 1942.
Avro’s chief design engineer, Roy Chadwick, was already working on an improved Manchester design using four of the more reliable, but less powerful Rolls-Royce Merlin engines, in the form of standardised Merlin “power eggs” developed for the Beaufighter II, installed on a larger wing. The aircraft was initially designated Avro Type 683 Manchester III, and later renamed the “Lancaster”. The prototype aircraft BT308 was assembled by Avro’s experimental flight department at Manchester’s Ringway Airport. Test pilot H.A. “Bill” Thorn took the controls for its first flight at Ringway, on Thursday, 9 January 1941. The aircraft proved to be a great improvement on its predecessor, being “one of the few warplanes in history to be ‘right’ from the start.” Its initial three-finned tail layout, a result of the design being adapted from the Manchester I, was quickly changed on the second prototype DG595 and subsequent production aircraft, to the familiar twin-finned specification also used on the later Manchesters.
Some of the later orders for Manchesters were changed in favour of Lancasters; the designs were very similar and both featured the same distinctive greenhouse cockpit, turret nose, and twin tail.