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AVRO 683 LANCASTER - Avro's design team under Roy Chadwick evolved a scheme for a Manchester III powered by four 1,145 hp Rolls-Royce Merlin Xs, to overcome difficulties with the Vulture engine installation in the earlier twin-engined bomber. With a new wider centre section and renamed Avro Lancaster, a prototype flew on January 9, 1941, at first with standard Manchester I triple-fin tail unit and later with Manchester IA enlarged twin fins and wider tailplane. Second prototype, with 1,280 hp Merlin XXs, flown May 13, 1941.
Avro Lancaster B Mk I: Production initiated 1941, replacing final 243 Manchesters on AVRo contracts and 57 on Metropolitan-Vickers contracts, and then continuing on major new contracts placed with Avro (Chadderton and Yeadon), Vickers-Armstrong (Chester and Castle Bromwich), Armstrong Whitworth (Baginton), Austin (Longbridge) and Metrovick (Manchester). Initially with 1,280 hp Merlin XXs; Merlin 22s and Merlin 24s later (1,640 hp 1,223 kW), with higher boost ratings. Armament comprised two 0.303-in (7.7-mm) Browning guns each in nose and dorsal turrets, four in tail turret and provision for two in remotely-sighted ventral barbette, little used, especially after ventral H2S radome fitted; turrets by Frazer Nash or Rose. Some later Mk Is had a single 0.303-in (7.7-mm) or 0.50-in (12.7-mm) ventral gun, manually operated, and a two-gun tail turret. Initial design bomb load, 4,000 Ib (1,816 kg), later increased to 18,000 lb (8,172 kg) without special mods, including standard 8,000 lb (3,632 kg) and 12,000 lb (5,448 kg) bombs. Aircraft of Nos 9 and 617 Sqn modified in 1944 to carry 12,000-lb (5,448-kg) 'Tallboy' bomb and used to attack and sink Tirpitz on November 12, 1944. Avro Lancaster entered service with No 44 (Rhodesia) Sqn, Waddington, and used for first operational sortie on March 3, 1942. Total production, 3,434 (including special Mk I variants noted below).
Avro Lancaster B Mk I (Special): 33 aircraft with Merlin 24s modified 1945 for 617 Sqn to carry 22,000-lb (9,988-kg) 'Grand Slam' bomb, with no bomb-bay doors, and nose and dorsal turrets and H2S removed. First operation.March 14, 1945, against Bielefeld Viaduct. Gross weight, 72,000 lb (32,688 kg). Avro Lancaster B Mk I (FE): Late production aircraft for Tiger Force operation against Japanese targets in the Far East, with modified radio, radar and navaids, and white top/black underside finish. Two Avro Lancaster Is tested (by No 1577 SD Flight) in India and Australia in 1945 with long range saddle tank in upper fuselage aft of cockpit, for possible Tiger Force application. Two other Mk Is used by No 1577 SD Flight to tow Horsa and Hamilcar gliders in trials for India-Burma operations.
Avro Lancaster II: Similar to Mk I but with four 1,725 hp Hercules VI or XVI radial air-cooled engines. Single prototype by Avro, first flown on November 26, 1941, and 300 built by Armstrong Whitworth. Deliveries starting October 1942. Performance, arma-ment and bomb load similar to Mk I.
Avro Lancaster B Mk III: Similar to Mk I but with Packard-built 1,300 hp Merlin 28, 1,390 hp Merlin 38 or 1,620 hp Merlin 224 engines supplied from USA. Armament and bomb load similar to Mk I. Production totalled 3,020 including 136 by Metrovick and 110 by Armstrong Whitworth, the remainder by Avro. Twenty-three Mk IIIs converted by Avro in 1943 to carry Vickers Type 464 spinning bomb for use by No 617 Sqn with front and dorsal turret and bomb doors removed, small VSG hydraulic motor in fuselage to spin weapon before release, and single 0.303-in (7.7-mm) ventral gun fitted. First bomb drop on April 16, 1943, and used to attack Mohne, Eder and Sorpe dams on May 1, 11, 18, 1943.
Avro Lancaster VI: Nine Avro Lancaster IIIs fitted with 1,635 hp Merlin 85 engines and four-blade propellers for general engine development by Rolls-Royce (including other two-stage Merlin marks in due course) and as potential successor to the Mks I and II. First conversion June/July 1943, service trials by Nos 7 and 635 Sqn (with nose and dorsal turrets removed) until November 1944.
Avro Lancaster B Mk VII: Similar to B Mk III, with Packard Merlin engines but with Martin 250 CE 23A dorsal turret mounting two 0.50-in (12.7-mm) machine guns. 180 built by Austin, deliveries starting April 1945; some equipped for Tiger Force in Far East and designated Avro Lancaster B Mk VII (FE).
Avro Lancaster B Mk X: Similar to B Mk III, built in Canada by Victory Aircraft with Merlin 38 or 224, deepened bomb-bay and (later aircraft) Martin dorsal turret. First flown on August 6, 1943; 430 built.
Avro Lancaster X PP: Two Avro Lancaster Xs converted by Victory Aircraft as passenger and mail carriers (CF-CMT, CF-CMU), for TCA, with fairings over nose and tail turret positions, no dorsal turret, extra fuel in bomb bay and ten seats, following similar initial conversion of one Mk I (CF-CMS).
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