The Dams Raid

The Avro Lancaster

The Avro Lancaster Bomber had its origins in an aircraft designed to specification E.13/36 of 1936 which was for a new generation of heavy twin engine medium bombers. This specification resulted in the Handley Page Halifax and the Avro Manchester. The aircraft was designed by Avro's chief designer Roy Chadwick and was a relatively conventional, but large for its day, mid wing monoplane with low set tail plane and twin fins powered by a pair of Rolls Royce Vulture "X" configuration 24 cylinder engine. The aircraft was protected by a power operated Frazer Nash nose turret armed with a pair of .303 browning machine guns, a similar turret in the tail with four machine guns. Possibly the most unusual feature of the aircraft was its extremely large bomb bay extending along almost half of its underside. The Manchester flew at Ringway on July 24th 1939 but despite substantial efforts which were put into the development of the design it was consistently let down by the underdeveloped Rolls Royce Vulture engines which had a habit of either breaking con rods, bursting into flames, or both.

The aircraft was placed in production regardless as the RAF was in no position to turn down any aircraft by this time due to the start of the war. Despite this Roy Chadwick remembered conversations he had with Rolls Royce engineers about a new mark of Rolls Royce Merlin engine of the type that was fitted to Spitfire fighters. The power output of this remarkable engine had just been increased dramatically by fitting two stage, two speed supercharges and the comment was made that it would improve the performance of the Manchester dramatically. Chadwick decided there was little point in half measures and decided that the solution was to take off the Manchester's wings, replace the engines with Merlin's and so he designed a new centre section wing which mounted a further two Merlin engines before re attaching the original outer wings to the larger centre section. This centre section was really the secret of the Lancaster's success in that it was built extremely strongly, but remained light. When coupled to the very strong bomb bay structure it made for a very strong aircraft. The Merlin engines were proven and reliable and the addition of two extra engines gave the new aircraft remarkable lifting power.

On the 31st January 1941 the prototype Lancaster BT308 made her maiden flight. Other fairly major changes had been from the Manchester design, notably the installation of a dorsal turret armed with two .303 machine guns and a ventral turret with the same armament. The tail plane configuration was experimented with, the aircraft at one stage having triple tail fins, but this was finally settled with the same configuration as the production Manchester but with much enlarged twin fins. This gave the mid upper gunner a much better field of fire. The initially production model of Lancaster was the B1.