A- and B-class destroyer

Class overview
HMS Achates
Name:	A and B class
Operators:	Royal Navy Royal Canadian Navy Royal Hellenic Navy
Preceded by:	Ambuscade and Amazon
Succeeded by:	C and D class
Subclasses:	A, B
Built:	1928–31
In service:	1930–45
Completed:	20
Lost:	10
Scrapped:	10
General characteristics (as built)
Type:	Destroyer
Displacement:	1,350–1,360 long tons (1,370–1,380 t) (standard) 1,778–1,790 long tons (1,807–1,819 t) (deep load)
Length:	323 ft (98 m) (o/a)
Beam:	32 ft 3 in (9.83 m)
Draught:	12 ft 3 in (3.73 m)
Installed power:	34,000 shp (25,000 kW) 3 × Admiralty 3-drum boilers
Propulsion:	2 × shafts; 2 × geared steam turbines
Speed:	35 knots (65 km/h; 40 mph)
Range:	4,800 nmi (8,900 km; 5,500 mi) at 15 knots (28 km/h; 17 mph)
Complement:	138
Armament:	4 × 1 - QF 4.7-inch (120 mm) Mk IX guns 2 × 1 - QF 2-pounder anti-aircraft guns 2 × 4 - 21-inch (533 mm) torpedo tubes
General characteristics Saguenay and Skeena (where different)
Displacement:	1,337 long tons (1,358 t) (standard) 1,805 long tons (1,834 t) (deep load)
Length:	321 ft (98 m) (o/a)
Draught:	12 ft 3 in (3.73 m)
Propulsion:	32,000 shp (24,000 kW)
Range:	5,000 nmi (9,300 km; 5,800 mi) at 15 knots
General characteristics Codrington (A-class flotilla leader)
Displacement:	1,540 long tons (1,560 t) (standard) 2,012 long tons (2,044 t) (deep load)
Length:	343 ft (105 m) (o/a)
Beam:	33 ft 9 in (10.29 m)
Installed power:	39,000 shp (29,000 kW)
Complement:	185
Armament:	5 × 1 - QF 4.7-inch (120 mm) Mk IX guns
Notes:	(where different)
General characteristics Keith (B-class flotilla leader)
Displacement:	1,400 long tons (1,400 t) (standard) 1,821 long tons (1,850 t) (deep load)
Complement:	157
Notes:	(where different)

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.

The A-class design was derived from the 1926 prototypes Amazon and Ambuscade 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. Nonetheless, the design had an improved gun armament, heavier torpedo armament, and greater range, at the cost of 2 knots (3.7 km/h; 2.3 mph) 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. The ships displaced 1,350–1,360 long tons (1,370–1,380 t) at standard load and 1,778–1,790 long tons (1,807–1,819 t) at deep load. They had an overall length of 323 feet (98.5 m), a beam of 32 feet 3 inches (9.8 m) and a draught of 12 feet 3 inches (3.7 m). The A class had a metacentric height of 1.76 feet (0.54 m) at deep load. The ships' complement was 138 officers and ratings as built, but increased in size up to 162 during the war.

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