SHIP BUILDER LAID DOWN LAUNCHED COMPLETED
Indefatigable John Brown 03/11/39 08/12/42 03/05/44
Implacable Fairfield 21/02/39 10/12/42 28/02/44
Type:Fleet aircraft-carrier Displacement: 26, 000 tons standard and 31,100 tons full load
Dimensions: length 233.4 m (765. 75 ft); beam 29.2 m (95.'15 ft); draught 7.92 m (26 ft)
Propulsion: 4-shaft geared steam turbines delivering 110,000 shp (8202~ kW)
Speed: 32.5 kts
Armour: belt 114 mm (4.5-in); hangar wall 38 mm ( 1.5 in); deck 76 mm (3 in) Armament: eight twin 114-mm (4, 5-in) DP, six octuple 2-pdr AA and about 38 20-mm AA guns
Aircraft: about 70
Complement: 1,800 including aircrew
Completed some 30 months after the four Illustrious class ships, the two Implacable class aircraft-carriers were more closely related to the prototype Ark Royal, with the hangar walls slimmed down to only 38 mm (1.5 in). This allowed a better weight distribution for the ships' increased displacement, including the all-important lower hangar. The ships were slightly longer but appeared much bulkier than their half sisters, their larger hull containing also a fourth set of machinery. This gave them the extra speed that enabled them to pace an American 'Essex' class unit in the Pacific war, although they were considerably smaller in terms of both size and capacity.
Though both were laid down in 1939, HMS Implacable and HMS Indefatigable were launched in 1942 and 1944 respectively, but their completion went back because of higher shipyard priorities. When they were most needed, they were still on the stocks, underlining the truth that the navy fights a war largely with what it has available at the beginning. Once finally completed in 1944 they were active for a comparatively short period. In March 1944, while still a new ship, the Indefatigable achieved a 'first' in the first-ever deck landing by a twin engine aircraft, a de Havilland Mosquito. Before heading east to join the rapidly-expanding British Pacific Fleet, she participated in some of the
many carrier strikes against the Tirpitz, holed-up in Norwegian waters. Though damaging the target sufficiently to keep her almost permanently under repair, the aircraft of the time were the ship's weakest link until they were replaced. Once in the BPF, the ships were engaged in a war already won, in which the British participation was not welcomed in all quarters. Postwar, they were employed mainly in the training role and were scrapped in 1955 and 1956 after hardly a decade of service, being thought not worth the vast expense of a rebuilding along the lines of the Victorious.