The Lancaster has its origins in the twin-engine Avro Manchester which had been developed during the late 1930s in response to the Air Ministry Specification P.13/36 for a medium bomber for "world-wide use" which could carry a torpedo internally, and make shallow dive-bombing attacks.

Originally developed as an evolution of the Manchester (which had proved troublesome in service and was retired in 1942), the Lancaster was designed by Roy Chadwick and powered by four Rolls-Royce Merlins and in one of the versions, Bristol Hercules engines.

[4] The versatility of the Lancaster was such that it was chosen to equip 617 Squadron and was modified to carry the Upkeep "bouncing bomb" designed by Barnes Wallis for Operation Chastise, the attack on German Ruhr valley dams.

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.

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.

[note 2][citation needed] The first batch of Canadian Lancasters delivered to England suffered from faulty ailerons; this error was subsequently traced to the use of unskilled labour.

[21] According to aviation authors Brian Goulding and M. Garbett, the Lancaster B.I altered little during its production life, partially as a result of the sound basic structure and design; of the visible changes, the fuselage side windows were deleted, the Perspex chin of the bomb-aimer was enlarged, and a larger astrodome was provided.

[23] A total of 50 Austin-built Lancaster B.Is was constructed to a non-standard configuration, having a Frazer Nash turret installed directly above the bomb bay; however, this modification was largely unpopular due to its obstruction of the internal walkway, hindering crew movements.

The typical aircraft was powered by an arrangement of four wing-mounted Rolls-Royce Merlin piston engines, each of which drove a 13 ft (4.0 m) diameter de Havilland Hydromatic three-bladed propeller.

[21] However, during the first year of the type's career, some instances of structural failures were encountered on Lancaster B.Is and a number of aircraft were lost in accidents as a result of the design limitations having been greatly exceeded.

[23] All of the wing and fuselage sections were manufactured separately, during which they were outfitted with all of the required equipment in advance of final assembly being performed, as a measure intended to accelerate the rate of production.

Before the end of the war, Lancasters built in the UK standardised on the FN-82 fitted with two .50 in (13 mm) machine guns and a gun-laying radar as production allowed, which was also used on early models of the Avro Lincoln.

[47][49] The Type 464 Lancaster was also fitted with VHF radios (normally reserved for fighters) so that Gibson, the squadron leader, could control the operation while over the target,[50] an early example of what became the master bomber role.

[58] Due to the high loss rates typically involved in such operations, daytime bombing missions were performed sparingly until the Allies had achieved a level of aerial supremacy over the Axis powers.

99 Squadrons undertook a bombing raid on the Maschinenfabrik Augsburg-Nürnberg A.G., Augsburg engine manufacturing plant in Southern Germany; despite flying at low altitude, three bombers were shot down by Luftwaffe Bf 109s over France, and at least two more were lost to anti-aircraft fire at the factory itself.

[65] A major improvement to night-time bombing came with the implementation of the Pathfinder Force (PFF) in August 1942, multiple squadrons were transferred from Bomber Command groups to constitute the new unit.

[72] During November, targets in Italy and Germany were alternatively attacked by Lancasters, striking the city of Osnabrück multiple times, conducting a heavy raid against Turin, and destroying supplies for the Afrika Korps in Genoa.

[83] During late July and early August 1943, large numbers of Lancasters participated in the devastating round-the-clock raids on the city of Hamburg during Air Chief Marshal Harris's Operation Gomorrah.

[94] In March 1944, the Berlin raids were somewhat lessened as a compromise, Bomber Command having been directed to destroy enemy communications and other targets around France and the Low Countries ahead of the Normandy landings on D-Day.

[103] In October, Lancasters repeatedly struck the sea wall at Westkapelle, seeing to prevent the Germans from intentionally flooding neighbouring lands to delay Allied ground forces.

[116] Key industrial sites, such as the Auguste Viktoria benzol factory, were struck, while oil installations continued to be a prominent target of bombing raids in the hope of exacerbating the German fuel shortage.

Amongst the final wartime operations performed by the Lancaster was the Bombing of Obersalzberg, aimed at the destruction of Eagle's Nest, the extensive holiday home complex used by German leader Adolf Hitler.

This bomber, with a crew of seven men (five Canadians including pilot Robert Upcott of Windsor, Ontario), took off in bad weather on the morning of 29 April 1945 without a ceasefire agreement from the German forces, and successfully dropped its cargo.

[122] Goulding and Garbett wrote that: "The achievements of the Lancaster and the men who flew it have been widely acclaimed, and the aircraft has been described as the greatest single factor in winning WWII, an exaggeration but a pardonable one".

[120] Aircraft allocated to the Tiger Force were painted in white with black undersides and outfitted with additional radio units and navigational aids to facilitate their use in the Pacific theatre.

"Because the use of a British plane would have caused us many difficulties and delays"[126] As a byproduct of its sound design and operational success, various developments and derivatives of the Lancaster were produced for both military and civilian purposes.

[129] Avro overhauled 59 Lancaster B.Is and B.VIIs at Woodford and Langar which were delivered to the French Aéronavale during 1952/53,[130] which were flown until the mid-1960s by four squadrons stationed in France and New Caledonia in the maritime reconnaissance and search-and-rescue roles.

[134] Immediately following the end of hostilities, the Lancaster was used without any major modifications as a transport aircraft, being used to ferry thousands of prisoners of war (POWs) back to the British Isles from across the continent.

The B MkVII Just Jane, NX611, is based in the East Kirkby Lincolnshire Aviation Heritage Centre, just 9 miles (14 km) east-northeast of PA474 at RAF Coningsby; it is able to taxi but is not airworthy, though there have been plans to eventually return it to flight.

[158] For the 2018 flying season, to commemorate the 75th anniversary of Operation Chastise, the Canadian FM213 Lancaster was painted in the markings used by Guy Gibson's 617 Squadron aircraft (Code AJ-G, ED932) when he commanded the "Dambusters" raids.