Staff Writer (Updated: 2/24/2016):
In its prototype form, the Lancaster went airborne for the first time on January 9th, 1941. With World War 2 in full swing and the British commitment extensive, the prototype was quickly handed to Boscombe Down for formal evaluations. Development was so speedy that a production-quality form was airborne as early as October 1941 and the series, upon passing its requisite trials, was adopted for operational service in February of 1942, quantitative orders forthcoming. Early production versions were born for Manchester airframes still on Avro lines and inducted into RAF service as the Lancaster B.Mk I.
With production in full swing, the Lancaster was immediately placed into frontline action. Each aircraft required a standard operating crew of seven to include the pilot, bombardier, navigator, flight engineer, radio operator, dorsal gunner and rear gunner. Each man was specifically trained for their respective positions about the craft that ranged from the nose to the tail. The bomb bay was given much of the central internal volume. The flight deck consisted of a heavily glazed canopy with conventional seating and controls. The nose was equally glazed over to provide the bombardier and his equipment unfettered views of the action ahead and below. The undercarriage incorporated two main landing gear legs (single wheeled) with a tail wheel at rear. Outwardly, the Lancaster followed the same design style of other British bomber aircraft of the war, nothing beautiful but full of business. Original Lancasters showcased a bomb bay initially intended to carry up to 4,000lbs of ordnance. During the height of the war, a typical Lancaster set off with approximately 14,000lbs of conventional drop bombs and eventually even fielded the massive 22,000lb "Grand Slam" bombs (their size forced the bomb bay doors to be removed altogether).
Beyond its bomb load out for its offensive armament, the Lancaster was outfitted with no fewer than 8 x 7.7mm Browning machine guns for self-defense across three Frazer-Nash hydraulically-powered turrets at the nose, dorsal spine and tail. Two were installed in a nose/chin turret and operated by the bombardier. Two were fitted to the dorsal turret at amidships along the fuselage spine. Four were installed in a powered tail turret at the extreme aft of the aircraft. Unlike its American brethren, the Lancaster series (on the whole) lacked a belly turret and beam waist gunners for additional defense and utilized a smaller-caliber (7.7mm/0.303) machine gun (as opposed to 0.50 caliber). At one point, the thought of adding a belly turret as standard was entertained but never followed-up. Only a small number of early-form Lancasters were outfitted with ventral turrets (these armed with 2 x 0.303 machine guns).
The need for capable Lancasters was such that its production was tied to other much-needed aircraft meaning that there proved a near-shortage of available Merlin engines threatening manufacture. To supplement stocks of Rolls-Royce Merlins, the American concern of Packard was brought into the fold to produce the same powerplant in the United States (under license). In extreme circumstances, the RAF took on Lancasters fitted with Bristol Hercules VI/XVI radial piston engines of 1,735 horsepower. As Melin engines themselves evolved so too did the various Lancasters coming off the assembly lines - new mounts included the Merlin XX, 22 and 24 series.