The Avro Lancaster flew from 1941 and became the RAF's principal heavy bomber. Over 7,300 were built, and they flew more than 156,000 sorties in the strategic bombing campaign against Germany.
It came from a failure
The Lancaster was derived from the Avro Manchester, a twin-engine bomber built around the Rolls-Royce Vulture engine. The Vulture was unreliable and underpowered, and the Manchester was a poor aircraft that was withdrawn.
Avro's designer Roy Chadwick reworked the airframe with a longer wing and four Rolls-Royce Merlins in place of the two Vultures. The result flew well immediately, and it is one of the clearer cases of a good aircraft emerging directly from a bad one.
The bomb bay
The Lancaster's defining feature was an unobstructed bomb bay over 10 metres long. That let it carry ordnance nothing else could.
It carried the 4,000 lb "cookie" blast bomb routinely. Modified aircraft carried the 12,000 lb Tallboy and the 22,000 lb Grand Slam — the largest conventional bombs used in the war, designed by Barnes Wallis as earthquake bombs to penetrate deep and detonate underground beside hardened targets.
Those weapons were used against U-boat pens, viaducts and the battleship Tirpitz, which was capsized by Tallboys in 1944.
The Dambusters
617 Squadron's attack on the Ruhr dams in May 1943 used Lancasters modified to carry Wallis's bouncing bomb, released at very low level over water to skip over torpedo nets and sink against the dam wall.
The Möhne and Eder dams were breached. Of 19 aircraft, 8 were lost and 53 of 133 aircrew were killed. The raid's material effect on German war production is debated; its effect on morale and its technical audacity are not.
The Canadian dimension
No. 6 Group of RAF Bomber Command was a Royal Canadian Air Force formation, operating from Yorkshire with Canadian crews. It flew Halifaxes and then Lancasters, including the Canadian-built Lancaster Mk X, produced by Victory Aircraft at Malton, Ontario — the plant that later became Avro Canada and built the Arrow.
Roughly 10,000 Canadians died serving in Bomber Command. It was among the most dangerous duties of the war for Canadian personnel.
The cost and the argument
Bomber Command lost 55,573 aircrew killed, out of roughly 125,000 who served — a death rate approaching 45%. It is one of the highest loss rates of any Allied formation in the war.
The strategic bombing campaign remains contested, particularly the area bombing of German cities and specifically the destruction of Dresden in February 1945. That the campaign was costly in aircrew lives is not disputed; what it achieved, and at what cost to German civilians, is argued to this day.
Two Lancasters remain airworthy — one in Britain and one in Canada, at Hamilton, Ontario. When they fly together, which happens rarely, it draws crowds.