When it became clear to Avro's cheif designer, Roy Chadwick, in 1938 that the new Rolls Royce Vulture engines intended for the Manchester were suffering from a lack of development, the company set about revising the design to include an additional pair of engines, preferably the well proven "Merlin". As a matter of fact, so dire was the Manchester situation that the Ministry of Aircraft production seriously considered scrapping the production line at the Avro factory at Newton Heath at Manchester after its contract for 200 Manchesters had been completed, and switch to the rival Handley-Page design, the Halifax. Fortunately, the plan never came to fruition and Avro was allowed to continue development of the Manchester III. (the name Lancaster had not yet become officially chosen)
In September 1940, a contract was signed with Avro for two prototype aircraft, the first of which was to fly within four months. To do this, Avro was to use as many existing Manchester componenets as possible to reduce cost and the timescale. Within a month, Avro had prepared the requisite technical drawings for the Lancaster and things progressed smoothly with the first flight being made on 9 January 1941. The first aircraft was very much a hybrid design, and a more representative aircraft followed in May 1941. The second prototype had larger tail fins, a new under carriage and improved Merlin engines and the true potential of the aircraft could now be tested. Test flying continued throughout the summer and the first production Lancaster Mk.I was flown on the last day of October 1941.
Throughout the remainder of 1942, the transition to Lancasters in Bomber Command was relatively slow, but the increase in the total tonnage of bombs in operations was increasing rapidly because of the ability of the Lancaster to carry bombs greater than the 4,000 pound High Capacity.
( the only aircraft that could do so.)
Almost half of all Lancasters delivered during the war ( 3,345 out of 7,373) were lost on operations with the loss of over 21,000 crew members.
The basic Lancaster, the B.I was such an excellent airframe that few changes were made to improve it. The B.II was a Bristol Hercules-powered variant built to counter possible supply problems with the Merlins; the B.III was powered by improved Merlins and, along with the B.I, the standard mount of many Lancaster squadrons. The final version built in significant numbers was the Mark X which was built under license in Canada.
Of those 7,000+ aircraft built, only two airworthy examples exist as a tribute to the many thousands who lost their lives in Bomber Command; one with the RAF's Battle of Britain Memorial Flight and the second based in Canada at the Canadian Warplane Heritage Museum - Hamilton, Ontario.
