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The A- and B-class destroyers were a group of 18 destroyers built for the Royal Navy during the late 1920s, with two additional ships built for the Royal Canadian Navy. The British ships were divided into two flotillas of eight destroyers, each with a flotilla leader. ==Design and description== The A-class design was derived from the 1926 prototypes and for the 1927–28 Naval Construction Programme. The initial staff requirements were unrealistic and would have resulted in a much larger, unaffordable ship; they were scaled back, both to reduce the size of the ship and to save money.〔Friedman, pp. 195–202〕 Nonetheless, the design had an improved gun armament, heavier torpedo armament, and greater range, at the cost of of speed, in comparison with the prototypes. The As were fitted with the Two-Speed Destroyer Sweep (TSDS) minesweeping gear and only had a residual anti-submarine ability while the Bs were equipped with Type 119 Asdic (sonar) and had a full complement of depth charges, but could not use the TSDS. This was the beginning of the Admiralty's policy of alternating TSDS and anti-submarine capabilities between destroyer flotillas.〔Lenton, pp. 150–52〕 The ships displaced at standard load and at deep load. They had an overall length of , a beam of and a draught of .〔Whitley, pp. 97, 99〕 The A class had a metacentric height of at deep load.〔March, p. 256〕 The ships' complement was 138 officers and ratings as built,〔 but increased in size up to 162 during the war.〔March, p. 258〕 The destroyers were powered by two Parsons geared steam turbines, each driving one propeller shaft, using steam provided by three water-tube boilers equipped with superheaters. Five of the As and all of the Bs had Admiralty three-drum boilers that operated at a pressure of and a temperature of while ''Ardent'' and ''Anthony'' were fitted with Yarrow boilers of pressure at the same temperature. ''Acheron'' was given experimental Thornycroft boilers that had a working pressure of and a temperature of to examine the weight and economy savings.〔Friedman, p. 198〕 Her specific fuel consumption was reduced from /hp/hour in her sisters to /hp/hour,〔Lenton, p. 151〕 although she was plagued by mechanical problems for her whole life.〔English, p. 19〕 In the event the trials were inconclusive, and the Admiralty continued to use the lower-temperature and pressure Admiralty three-drum boiler until the of 1942, nearly ten years after other major navies began to use higher-pressure and temperature boilers.〔Rippon, pp. 241–45〕 The turbines developed a total of for a designed speed of and the ship exceeded that during their sea trials.〔March, pp. 247, 260〕 The destroyers carried a maximum of of fuel oil that gave them a range of at .〔Lenton, p. 152〕 All of the ships had the same main armament, four quick-firing (QF) guns in single mounts with enlarged gun shields, designated 'A', 'B', 'X', and 'Y' from front to rear. Although the A class were intended to be equipped with gun mounts that could elevate up to 40°, and 'B' gun on a high-angle mount capable of 60°, all four guns ultimately had a maximum elevation of 30°.〔March, pp. 247, 250, 252, 260〕 They fired a shell at a muzzle velocity of to a range of .〔Campbell, p. 48〕 Each gun was provided with 190 rounds. For anti-aircraft (AA) defence, the A- and B-class ships carried two QF two-pounder Mark II AA guns mounted on platforms between the funnels, each with 500 rounds. They were fitted with two quadruple mounts for 21-inch (533 mm) torpedo tubes.〔Friedman, p. 198〕 The A-class ships were initially going to be fitted with two throwers and four chutes for eight depth charges, but they interfered with the TSDS equipment so the throwers, one chute and two depth charges were removed.〔Friedman, p. 197〕 The Bs were equipped with two throwers and one rack for twenty depth charges.〔March, p. 260〕 While not initially fitted with ASDIC, space was reserved for it, and at least some of the As received it beginning in the late 1930s.〔English, pp. 17, 19, 24〕 The fire-control system for these ships was little advanced over their First World War-era predecessors. A pedestal-mounted, manually operated Destroyer Director Sight and a separate rangefinder positioned to its rear were situated above the bridge; the director sent elevation and traverse orders to the main guns and the searchlight using data derived from the rangefinder. They had no capability for anti-aircraft fire and the anti-aircraft guns were aimed solely by eye. No fire-control computer was initially installed, but an Admiralty Fire Control Clock Mark II was retrofitted after it had been proven in the subsequent C-class destroyers.〔Campbell, p. 14; Friedman, p. 207; Hodges & Friedman, p. 10〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「A- and B-class destroyer」の詳細全文を読む スポンサード リンク
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