HMSImogen
Class overview
Name	I class
Operators	Royal Navy  Turkish Navy
Preceded by	G and H class
Succeeded by	Tribal class
In commission	1937–1960
Completed	13
Lost	6
Scrapped	7
General characteristics (as built)
Type	Destroyer
Displacement	1,370 long tons (1,390 t) (standard) 1,888 long tons (1,918 t) (deep load)
Length	323 ft (98.5 m)
Beam	33 ft (10.1 m)
Draught	12 ft 5 in (3.8 m)
Installed power	34,000 shp (25,000 kW) 3Admiralty 3-drum boilers
Propulsion	2 shafts; 2 gearedsteam turbines
Speed	36knots (67 km/h; 41 mph)
Range	5,530 nmi (10,240 km; 6,360 mi) at 15 knots (28 km/h; 17 mph)
Complement	137 (peacetime), 145 (wartime)
Sensors and processing systems	ASDIC
Armament	4 × 1 -QF 4.7-inch (120 mm) Mk IX guns 2 × 4 -0.5-inch (12.7 mm) machine guns 2 × 5 -21-inch (533 mm)torpedo tubes 20 ×Depth charges, 1 rack and 2 throwers 60mines (minelayers only)

TheI-class destroyers were a group of ninedestroyers, including aflotilla leader, built for theRoyal Navy during the 1930s. Four similar ships were ordered by theTurkish Navy, of which two were purchased for the Royal Navy, bringing the number of these ships in British service to 11—although three of the original ships had been lost by the timeInconstant andIthuriel were commissioned. The I-class served inWorld War II and six were lost, with a seventh ship being written off.

The I-class was a repeat of the precedingH class, except that they had ten torpedo tubes (two banks of five) instead of eight. They incorporated the new bridge and wheelhouse layout as tested inHero andHereward (except the flotilla leaderInglefield).Inglefield also had a larger tripod foremast, her sisters having pole masts. The extra weight of the torpedo tubes and the fitting of minesweeps and depth charge gear (previous vessels carried one or the other) on the same hull as the H class, caused a loss of stability, needingballast when bunker levels were low.

All ships were fitted forminesweeping and withdepth charges andAsdic foranti-submarine (A/S) work and were capable of conversion tominelayers. For this, they landed 'A' and 'Y' 4.7 inch guns, the torpedo tubes and their minesweeps, allowing carriage of up to 60 mines but only four ships were used like this (see below).

The Turkish I-class ships were of a similar design to their British counterparts but shipped only eight torpedoes (two banks of four) like the British H class.

Early war modifications involved replacing the after bank of torpedoes with aQF 12-pounder (3 inch/76 mm)anti-aircraft (AA) gun, cutting down the after funnel and mainmast to improve its field of fire and adding a pair ofQF 20 mm Oerlikon guns in the bridge wings. Radar Type 286, a metric wavelength surface-warning set, was added as it became available and the ineffective multiple 0.5 in (13 mm)Vickers machine guns were replaced with Oerlikons; the central tube was deleted from the torpedo launchers to lessen topweight.Icarus lost 'Y' gun to stow extra depth charges (for a total load of 110) and their mortars. Surviving ships received a third pair of Oerlikons, added abreast the searchlight position and the 12-pounder was deleted to increase depth charge stowage. In some ships, 'A' gun was replaced with aHedgehog forward-throwing A/S weapon but this alteration seems to have been reversed at a later stage.Ilex,Intrepid,Impulsive andIsis had 'B' gun removed and twoQF 6-pounder 10 cwt (2.25 inch/57 mm L/47) guns were added on the twin mounting Mark I* along with a Hedgehog, the former for anti-E boat work.

Inglefield later had the second bank of torpedo tubes re-instated but like her sisters, the central tube was removed. A 4 in (100 mm) AA gun was added instead of 'X' gun and she had six Oerlikons. Type 291 radar was later added at the foremast head as well asHuff-Duff in some ships.

The ex-Turkish ships were modified along similar lines to their I-class sisters.Inconstant later received Type 270 radar, a centimetric wavelength target-indication set, in place of the director and rangefinder on the bridge. Again, eventually, six Oerlikons were carried.

Four ships were ordered for theTurkish Navy in 1938. Upon the outbreak of war, two were purchased by the British but two were delivered to Turkey in 1942 as theSultanhisar and theDemirhisar.

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