A- and B-class destroyer

A classA-classAA-class destroyerB-classB classB-class destroyerA-class destroyer (1929)A-class destroyersB
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.wikipedia
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British 21-inch torpedo

21 inch (533 mm)21 in21-inch (533 mm)
They were fitted with two quadruple mounts for 21-inch (533 mm) torpedo tubes.
The Mark V was used by the A and B-class destroyers and, with modification, by the Kent-class heavy cruisers.

C and D-class destroyer

D-classC-classC
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.
These ships were based on the preceding B class, but were enlarged to increase their endurance and to allow for the inclusion of a QF 3-inch 20 cwt anti-aircraft gun.

QF 3-inch 20 cwt

3 in3-inchQF 3 inch 20 cwt
Beginning in May 1940, the after bank of torpedo tubes was removed in most ships and replaced with a QF 3 in 20-cwt anti-aircraft gun, the after mast and funnel being cut down to improve the gun's field of fire.
It was also fitted to older destroyers, A to I classes during refits in 1940, replacing a set of torpedo tubes, to increase their AA capabilities.

QF 4.7-inch Mk IX & XII naval gun

4.7-inch (120 mm) Mark IX gunsQF 4.7-inch (120 mm) Mk IX gunsQF 4.7-inch (120 mm) Mk XII guns
All of the ships had the same main armament, four quick-firing (QF) 4.7 in Mark IX guns in single mounts with enlarged gun shields, designated 'A', 'B', 'X', and 'Y' from front to rear.
Mark IX was deployed in single mountings CP Mk XIV on the A-class destroyers of 1930 and on most subsequent destroyer classes up to and including the R class of 1942.

Three-drum boiler

Admiralty 3-drum boilerAdmiralty three-drum boilerDu Temple boiler
Five of the As and all of the Bs had Admiralty three-drum boilers that operated at a pressure of 300 psi and a temperature of 600 °F while Ardent and Anthony were fitted with Yarrow boilers of 275 psi pressure at the same temperature.
Much of the design work was conducted at Admiralty Fuel Experimental Station at Haslar and the first boilers were installed in three of the A class destroyers of 1927.

Destroyer

destroyerstorpedo boat destroyertorpedo-boat destroyer
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.

Royal Navy

RNBritish NavyBritish Royal Navy
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.

Royal Canadian Navy

Canadian NavyCanadian Forces Maritime CommandRCN
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.

Flotilla

fleetflotillasair flotillas
The British ships were divided into two flotillas of eight destroyers, each with a flotilla leader.

Flotilla leader

destroyer leaderdestroyer leadersleader
The British ships were divided into two flotillas of eight destroyers, each with a flotilla leader.

Prototype

prototypingprototypesprototypical
The A-class design was derived from the 1926 prototypes and for the 1927–28 Naval Construction Programme.

Minesweeper

minesweepersminesweepingminesweeping gear
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.

Anti-submarine warfare

ASWanti-submarineantisubmarine warfare
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.

Sonar

ASDICvariable depth sonaractive sonar
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.

Depth charge

depth chargesY-gunK-gun
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.

Admiralty

British AdmiraltyLord High Admiralthe Admiralty
This was the beginning of the Admiralty's policy of alternating TSDS and anti-submarine capabilities between destroyer flotillas.

Displacement (ship)

displaceddisplacementdeep load
The ships displaced 1350 - 1360 LT at standard load and 1778 - 1790 LT at deep load.

Length overall

o/along overalloverall length
They had an overall length of 323 ft, a beam of 32 ft and a draught of 12 ft. The A class had a metacentric height of 1.76 ft at deep load.

Beam (nautical)

beamabeambeams
They had an overall length of 323 ft, a beam of 32 ft and a draught of 12 ft. The A class had a metacentric height of 1.76 ft at deep load.

Draft (hull)

draughtdraftdrew
They had an overall length of 323 ft, a beam of 32 ft and a draught of 12 ft. The A class had a metacentric height of 1.76 ft at deep load.

Metacentric height

righting momentcentre of buoyancymetacenter
They had an overall length of 323 ft, a beam of 32 ft and a draught of 12 ft. The A class had a metacentric height of 1.76 ft at deep load.

Naval rating

ratingsratingrate
The ships' complement was 138 officers and ratings as built, but increased in size up to 162 during the war.

Parsons Marine Steam Turbine Company

ParsonsPametradaParsons steam turbines
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.

Steam turbine

steam turbinesgeared turbinesturbines
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.

Drive shaft

propeller shaftdriveshaftshaft
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.