Avro Lancaster - Design and Development

Design and Development

The origins of the Lancaster stem from a twin-engined bomber design submitted to meet 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 Only 200 Manchesters were built, with the type withdrawn from service in 1942.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 designer, Roy Chadwick, was already working on an improved Manchester design using four of the more reliable, but less powerful Rolls-Royce Merlin engines 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. 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 Lancaster is a mid-wing cantilever monoplane with an oval all-metal fuselage. The wing was constructed in five main sections, the fuselage in five sections. All wing and fuselage sections were built separately and fitted with all the required equipment before final assembly. The tail unit had twin elliptical fins and rudders. The Lancaster was initially powered by four wing-mounted Rolls-Royce Merlin piston engines with three-bladed airscrews. It had retractable main landing gear and fixed tail-wheel, with the hydraulically operated main landing gear raising rearwards into the inner engine nacelles.

The majority of Lancasters built during the war years were manufactured by Avro at their factory at Chadderton near Oldham, Lancashire, and test flown from Woodford Aerodrome in Cheshire. Other Lancasters were built by Metropolitan-Vickers (1,080, also tested at Woodford), and Armstrong Whitworth. The aircraft 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. Many BIIs were lost after running out of fuel. 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.

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 instrumentation and electrics. The final production version was the 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 one; they had to be mounted slightly further forward on the fusalage for weight balance. All were produced too late for the war in Europe and were tropicalized 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 (approximately £1.5 million-£1.67 million today).