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Development
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 Merlin "power eggs" powerplant installations developed for the Beaufighter II, installed on a larger wing. At first the aircraft was called Avro Type 683 Manchester III and later renamed the Lancaster. The prototype aircraft BT308 was assembled by the Avro experimental flight department at Ringway Airport, Manchester. 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. The Lancaster discarded the stubby central third tail fin of the early Manchesters and used the wider span tailplane and larger elliptical twin fins from the later Manchester IA.
The majority of Lancasters built during the war years were manufactured by Avro at their factory at Chadderton near Oldham, Greater Manchester and test flown from Woodford Aerodrome in Cheshire. Other Lancasters were built by Metropolitan-Vickers (1,080, also tested at Woodford) and Armstrong Whitworth. It was also produced at the Austin Motor Company works in Longbridge, Birmingham, later in the Second World War and postwar by Vickers-Armstrongs at Chester as well as at the Vickers Armstrong factory, Castle Bromwich, Birmingham. Only 300 of the Lancaster B II fitted with Bristol Hercules engines were constructed; this was a stopgap modification caused by a shortage of Merlin engines as fighter production was of higher priority. The Lancaster B III had Packard Merlin engines but was otherwise identical to contemporary B Is, with 3,030 B IIIs built, almost all at Avro's Newton Heath factory. The B I and B III were built concurrently and minor modifications were made to both marks as new batches were ordered. Examples of these modifications were the relocation of the pitot head from the nose to the side of the cockpit and the change from de Havilland "needle blade" propellers to Hamilton Standard or Nash Kelvinator made "paddle blade" propellers.
In 1943, a Lancaster was converted to become an engine test bed for the Metropolitan-Vickers F.2 turbojet. Lancasters were later used to test other engines, including the Armstrong Siddeley Mamba and Rolls-Royce Dart turboprops, and the Avro Canada Orenda and STAL Dovern turbojets.
Of later variants, only the Canadian-built Lancaster B X, manufactured by Victory Aircraft in Malton, Ontario, was produced in significant numbers. A total of 430 of this type were built, earlier examples differing little from their British-built predecessors, except for using Packard-built Merlin engines and American-style instruments and electrics. The first Lancaster produced in Canada was named the "Ruhr Express".
The final production version was the Lancaster Mark VII and was made by the Austin motor company at their Longbridge factory. The main design difference with the Mark VII was the use of the American-built Martin dorsal gun turret in place of the English Nash & Thompson turret and mounted slightly further forward on the fuselage for weight balance. All were produced too late for the war in Europe and were tropicalised and upgraded as the Mark VII (FE) for use in the Far East against Japan. A total of 7,377 Lancasters of all marks were built throughout the duration of the war, each at a 1943 cost of £45–50,000.
Sources:
Wikipedia
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