Variants

B I

The original Lancasters were produced with Rolls-Royce Merlin XX engines and SU carburettors. Minor details were changed throughout the production series - for example the pitot head design was changed from being on a long mast at the front of the nose to a short fairing mounted on the side of the fuselage under the cockpit. Later production Lancasters had Merlin 22 and 24 engines. No designation change was made to denote these alterations.

B I Special

Adapted to take first the super-heavy "Tallboy" and then "Grand Slam" bombs. Upgraded engines with paddle-bladed propellers gave more power, and the removal of gun turrets reduced weight and gave smoother lines. For the Tallboy, the bomb-bay doors were bulged; for the Grand Slam, they were removed completely and the area faired over. For some Tallboy raids, the mid upper turret was removed. This modification was retained for the Grand Slam aircraft, and in addition the nose turret was later removed. Two airframes (HK541 and SW244) were modified to carry a dorsal "saddle tank" with 1,200 gal (5,455 L) mounted aft of a modified canopy for increasing range. No. 1577 SD Flight tested the aircraft in India and Australia in 1945 for possible use in the Pacific, but the tank adversely affected handling characteristics when full and flight refuelling was later used instead.

PR 1

B 1 modified for photographic reconnaissance, operated by RAF No. 82 and No. 541 Squadrons, wartime. All armament and turrets were removed with a reconfigured nose and a camera carried in the bomb bay. The type was also operated by 683 Squadron from circa 1950 for photographic reconnaissance based at Aden and subsequently Habbaniya in Iraq until disbanded 30 November 1953.

B I (FE)

In anticipation of the needs of the Tiger Force operations against the Japanese in the Far East (FE), a tropicalized variant was based on late production aircraft. The B I (FE) had modified radio, radar, navaids and a 400 gal (1,818 L) tank installed in the bomb bay. The mid-upper turret was also removed.

B II

Bristol Hercules (Hercules VI or XVI engines) powered variant, of which 300 were produced by Armstrong Whitworth. One difference between the two engine versions was that the VI had manual mixture control, requiring an extra lever on the throttle pedestal. These aircraft were almost always fitted with an FN.64 ventral turret and pronounced step in the bulged bomb bay.

B III

These aircraft were fitted with Packard-built Merlin engines and produced at the same time as the B I, the two marks being indistinguishable externally. The minor differences between the two variants were related to the engine installation, and included the addition of slow-running cut-off switches in the cockpit, a requirement due to the Bendix Stromberg pressure-injection carburettors fitted to the Packard Merlin engines.

B III (Special)

Known at the time of modification as the "Type 464 Provisioning" Lancaster, this variant was built to carry the "Upkeep" bouncing bomb for the dam busting raids. The bomb-bay doors were removed and Vickers-built struts to carry the bomb were fitted in their place. A hydraulic motor, driven by the pump previously used for the mid upper turret was fitted to spin the bomb. Lamps were fitted in the bomb bay and nose for the simple height measurement system which enabled the accurate control of low-flying altitude at night. The mid-upper turret was removed to save weight, and the gunner moved to the front turret to relieve the bomb aimer from having to man the front guns so that he could assist with map reading.

ASR III/ASR 3

B III modified for air-sea rescue, with three dipole ventral antennas fitted aft of the radome and carrying a lifeboat in the re-configured bomb bay. The armament was often removed and the mid-upper turret faired-over, especially in postwar use. Observation windows were added to both sides of the rear fuselage, a port window just forward of the tailplane, and a starboard window into the rear access door. A number of ASR 3 conversions were fitted with Lincoln-style rudders.

GR 3/MR 3

B III modified for maritime reconnaissance.

B IV

The B IV featured an increased wingspan and lengthened fuselage and new Boulton Paul F turret (two X 0.5in) with re-configured framed "bay window" nose glazing. The prototypes (PW925, PW929 and PW932) were powered by two-stage Merlin 85s inboard and later, Merlin 68s on the outboard mounts. The prototypes became the basis of the renamed Lincoln B 1.

B V

Increased wingspan and lengthened fuselage, two-stage Merlin 85s. Later renamed Lincoln B 2

B VI

Nine aircraft converted from B IIIs. Fitted with Merlin 85/87 which had two-stage superchargers, giving much improved high altitude performance. The Merlin 85/87 series engines were fitted with annular cowlings similar to the post war Avro Lincoln and four bladed paddle-type propellers were fitted. These aircraft were only used by Pathfinder units; by No. 7 Squadron RAF, No. 83 Squadron RAF, No. 405 Squadron RCAF and by No. 635 Squadron RAF. Often used as a "Master Bomber" the B VI's allocated to RAF Bomber Command (2 being retained by Rolls Royce for installation and flight testing) had their dorsal and nose turrets removed and faired-over. The more powerful engines proved troublesome in service and were disliked by ground maintenance staff for their rough running and propensity to 'surge and hunt', making synchronisation impossible. The B VI was withdrawn from service in November 1944 and the surviving aircraft were used by Rolls Royce, the Royal Aircraft Establishment and the Bomb Ballistics Unit (BBU) for various testing and experimental duties.

B VII

The B VII was the final production version of the Lancaster. The Martin 250CE mid-upper turret was re-positioned slightly further forward than on previous Marks, and the Nash & Thomson FN-82 tail turret with twin 0.50 in (12.7 mm) Browning machine guns replaced the FN.20 turret with four 0.303 in (7.7 mm) Browning machine guns.

B X

The B X was a Canadian-built B III with Canadian- and US-made instrumentation and electrics. On later batches the heavier Martin 250CE was substituted for the Nash & Thomson FN-50 mid-upper turret, mounted further forward to maintain centre of gravity balance. Canada was a long term operator of the Lancaster, utilising modified aircraft in postwar maritime patrol, search and rescue and photo-reconnaissance roles until 1964. The last flight by the RCAF was flown on 4 July 1964 at the Calgary International Air Show.