ILLUSTRIOUS CLASS

Name                               Builders                         laid down         launched     completed

Illustrious                Vickers Armstrong             27/04/37           05/04/39       25/05/40

Formidable             Harland and wolfe           17/06/37           17/08/39        25/11/40

Victorious             Vickers Armstrong             04/05/37           14/09/39        15/05/41

Indomitable             Vickers Armstrong           10/11/37            26/03/40       10/10/41    

TYPE: fleet aircraft-carrier Displacement: 23,000 tons standard and 25, 500 tons full load

Dimensions: length 229. T m (T53.5 ft); beam 29.2 m (95.T5 ft); draught Z3 m (24 ft)

Propulsion: 3-shaft geared steam turbines delivering 110,000 shp (8202T kW)

Speed: 31 kts

Armour: belt and hangar wall 114 mm (4.5 in) except indomitable 38 mm

( 1.5 in); deck T6 mm (3 in)

Armament: eight twin 114-mm (4.5-in) DP, six octuple 2-pdr AA, and eight 20-mm AA guns

Aircraft: about 45 except Indomitable about 65

Complement: 1,400 including aircrew

NOTES

The Ark Royal was very much a prototype, combining speed with capacity and new standards of protection. Though late coming, she had hardly been launched when a new 'Illustrious' class of four aircraft-carriers was laid down in 1937 to respond to the already increasing likelihood of war. Operational experience was, therefore, not a part of the later concept, which took the scale of the Ark Royals belt and horizontal protection, and added a 114mm (4.5-in) hangar well. Thus the whole of the vulnerable aircraft accommodation became an armoured box, but so much weight high in the ship limited the protection to only one hangar and, though HMS Illustrious, HMS Victorious and HMS Formidable (all launched in 1939) were not significantly smaller than the Ark Royal, they carried far fewer aircraft. There must have been second thoughts on reducing the ships' primary arm so drastically, for HMS Indomitable, launched in 1940 as last of the four, and the two 'Implacable' class ships that followed, reverted to lighter protection and an extra half-length hangar.

The immense strength of the ships stood them in good stead, for their war turned out to be one of air, rather than submarine attack. Soon after Taranto, the Illustrious survived punishment from dive-bombing that would have sunk any other carrier afloat, a performance echoed by the Formidable after Matapan. In the Pacific War most of them withstood one or even two kamikaze strikes without having to leave station. But all these immense blows were absorbed mainly by the ships' horizontal protection and it would seem in retrospect that the vertical armour was bought at an excessive price in operational efficiency even though, in the Pacific, the class worked with something like 60 per cent over its designed aircraft complement. When the Americans copied the armoured deck concept, it was not at the cost of capacity, so carrier sizes began their inevitable escalation. The ships were scrapped in 1956, 1969, 1955 and 1953 respectively.