A heavy quad-engine all-metal monoplane bomber based on the twin-engine Avro Model 679 Manchester bomber. The first Lancaster prototype flew on January 9, 1941, and the first production model was commissioned on October 31, 1941.
The Lancaster Mk.III, designated the B.Mk.III in 1942, was not powered by the British Rolls Royce Merlin 28, 38, or 224. Instead, equivalent American engines were licensed from Packard. Internal differences between the Mk.I and Mk.III were very few. The two models had identical technical characteristics and armament, but the difference in designation was necessary since the different engines has different service requirements.
The Lancaster first fought in March of 1942. Soon afterward it became the basis of British bombing operations and participated in massive bombing raids over Germany, Italy, and France. Due to the mediocrity of its defensive weaponry, it was mostly used for night raids.
For self-defense, the Lancaster had eight 7.7mm Colt-Browning Mk.II machine guns located in three turrets: two guns were located in the nose, two in the dorsal turret, and four in the tail turret. The maximum ordinance capacity of the Lancaster was the highest of any heavy bomber in World War II: 14,000 lb (6,356 kg). Besides standard bombs, the aircraft could carry an 8,000 lb (3,632 kg) “blockbuster” or two 4,000 lb (1,816 kg) high-explosive “cookie” bombs. Special modifications of the bomber could carry even larger bombs. One of the Lancaster's most successful operations was the sinking of the German navy's flagship, the Tirpitz.
A total of 3,039 Mk.III bombers were produced. The bomber was decommissioned in Great Britain in 1950.