The I-class ships were improved versions of the preceding H class. They displaced 1370LT at standard load and 1888LT at deep load. The ships had an overall length of 323feet, a beam of 33feet and a draught of 12feet. They were powered by two Parsons geared steam turbines, each driving one propeller shaft, using steam provided by three Admiralty three-drum boilers. The turbines developed a total of 34000shp and were intended to give a maximum speed of 35.5kn. The ships carried enough fuel oil to give them a range of 5500nmi at . Their crew numbered 145 officers and ratings.[1]
The Turkish ships mounted four 4.7-inch (120 mm) Mark IX guns in single mounts, designated 'A', 'B', 'X' and 'Y' from bow to stern. While under construction, their anti-aircraft (AA) armament was augmented by a single 12-pounder AA gun that replaced the planned aft set of torpedo tubes. In addition the intended pair of quadruple mounts for the 0.5 inch Vickers Mark III machine gun were replaced by a pair of 20adj=on1adj=on Oerlikon light AA guns. They were fitted with a single above-water quadruple torpedo tube mount amidships for 21inches torpedoes.[2] One depth charge rack and two throwers were fitted for 35 depth charges.[3] The Turkish ships were fitted with the ASDIC sound detection system to locate submarines underwater[4] and a Type 286 search radar.[1]
Inconstant was laid down as TCG Muavenet for the Turkish Navy by Vickers Armstrong at their Barrow-in-Furness shipyard on 24 May 1939, purchased in September 1939 by the Royal Navy, launched on 24 February 1941 and commissioned on 24 January 1942. The ship participated in the assault on Madagascar in May 1942, and attacked and sank the German submarines in the Mediterranean north-east of Algiers on 12 July 1943 and while in company with the destroyers and in the English Channel south-west of Guernsey on 18 June 1944. Inconstant was returned to Turkey on 9 March 1946 and renamed Muavenet. She was discarded in 1960.
. Henry Trevor Lenton. British & Empire Warships of the Second World War. Naval Institute Press. Annapolis, Maryland. 1998. 1-55750-048-7.