Aircraft carrier Illustrious class

British carriers Illustrious, Formidable, Victorious, Indomitable.
History, development, service, specifications, statistics, pictures, and 3D model.

Aircraft carrier Victorious
Aircraft carrier Victorious in 1942, with Albacore torpedo bombers on deck.

Illustrious class (4 ships: Illustrious, Formidable, Victorious, Indomitable).
Type: Aircraft carrier.


HMS Illustrious
The class ship Illustrious early in her career.
The 1936 Program provided for the construction of two carriers for the Royal Navy. The 23,000-ton limit set by the Second London Treaty was in force, and it seemed at first that the basic Ark Royal design could be taken, the extra 1,000 tons available being used to incorporate improvements. The spectra of a European war loomed large, however, and with it the realization that the Royal Navy would be forced to operate under constant threat of land-based air attack, particularly in the Mediterranean – where Italy’s intentions had been unpredictable since the early 1930s – and in the North Sea.

A novel approach, guided by the strong representations of Rear-Admiral Henderson, the Third Sea Lord, was adopted to meet the threat: the carriers should be given an unprecedented measure of passive defense, in the form of extensive armoring, plus a heavy anti-aircraft battery, much as in Ark Royal. The primary task was to preserve the carrier’s main armament – her strike aircraft – and so the stowage area was designed as an armored ‘box’ intended to be proof against 500lb (ca. 227 kg) bombs and 6in shells. As in Ark Royal, belt, bulkhead and armor deck protection for machinery and magazines was also to be incorporated.

The problem was one of accomplishing all this within the Treaty displacement limits; clearly, something had to be sacrificed, and the victim was the two-storied hangar arrangement of the earlier design. This would save not only weight in itself, but also top-weight, ensuring the stability of the hull, whose dimensions were more or less fixed for the same reasons as were Ark Royal’s (permitted by dry docking).

As finalized, the hangar was provided with 4 1/2in armored sides, a 3in roof (forming part of the flight deck) and 4 1/2in bulkheads forward and aft, a 3in armored deck acting as the hangar floor and extending to the 4 1/2in main belt which was itself closed by armored bulkheads. Additional armor was included to protect the steering compartments (3in), the flight deck before and abaft the hangar limits (1 1/2in) and the hangar deck ends (1in). The dimensions of the hangar were 458ft (139.6 m) x 62ft (18.9 meters), with a height of 16ft (4.88 meters), providing accommodation for thirty torpedo-bombers and six fighter/dive-bombers, a total capacity half that of Ark Royal’s originally specified complement.
The weak spots in an otherwise totally protected enclosure were the 45ft (13.72 meters) x 22ft (6.71 meters) lifts, which could not be armored because of the weight penalty that would be exacted, but movable armored screens were provided at each end of the hangar, by the lift wells.
The armored hangar concept proved its worth in the Far East where kamikazes caused damage above but not within it, thus not interfering significantly with aircraft operation; this contrasted sharply with US experience.

A three-shaft machinery arrangement was installed, as in Ark Royal, and to counter the weight of the island structure the hull was widened to port. The fixed battery consisted of eight powered 4.5in turrets, their crowns level with the flight deck and hence providing, theoretically, some measure of cross-deck fire. They were controlled by Mk IV directors. One hydraulic catapult (14,000lb (ca. 6,350 kg) capability) was fitted on the flight deck, forward and to port, and six wires aft formed the arresting system. Petrol stowage totaled 50,540 gallons (ca. 191,315 l).

Illustrious and Victorious were the two carriers provided under the 1936 Program, the second pair under the 1937 Program.

HMS Indomitable
HMS Indomitable
Indomitable’s design, however, was modified before she completed. Second thoughts were expressed about the size of the air group, and it was decided to revert to a two-level hangar arrangement, the lower one extending beneath the after half of the upper, 168ft (51.21 meters) long. The 16ft (4.88 meters) height was retained below, but the upper hangar was reduced to 14ft (426.72 cm). The price for this increase in capacity was a reduction in the thickness of the hangar sides to 1 1/2in, but even so Indomitable’s displacement rose to 24,680 tons standard and 29,730 deep load. However, 48 aircraft could be accommodated. She received 8 x 20 mm before completion, and complement stood at 1,592.


Wartime modifications were many and varied. The major structural change was a rebuilding of the flight deck forward and aft, giving an increased usable length of 740ft (745ft in Indomitable). The defensive battery was progressively augmented, first by the addition of 20mms and subsequently by installing 40mms in quadruple, twin and single mountings. By 1945, for example, Illustrious was showing more than fifty of the former and three Bofors AA guns, and Victorious, 45 x 20 mm and 21 x 40 mm.

The adoption of an aircraft deck park system (outriggers were fitted from the flight deck to support aircraft tail wheels) enabled the air group to be increased to 54 machines.
Radar was progressively updated, starting with Type 79 warning and moving through Types 281 (air warning) and 285 (4.5in gunnery) to Types 277 (height-finder) and 960 (air warning).
Arrested wires were strengthened and increased in number of to cope with new, more demanding aircraft, for which reason some ships had their lifts stressed and enlarged. By 1945, the complement had risen to about 2000, and a typical air group was 36 F4U Corsairs and 16 Avengers.

Service Notes

Victorious: Within a few days of commissioning, Victorious was involved in the battleship Bismarck chase, one of her Torpedo planes scoring a hit and slowing the German battleship.
Following escort and ferrying operations, she was engaged in strikes against Norway and cover for Arctic convoys to Russia which included an abortive attack on battleship Tirpitz. Further Malta convoys came in mid 1942, and the carrier was refitted at Norfolk Navy Yard during the winter of 1942-43, subsequently operating’ on loan’ to the US fleet in the Pacific before being relieved by Essex. A further attack was carried out on Tirpitz in the spring of 1944 while returned to the Home Fleet after a refit, but by July 1944 she was in the Far East, forming part of the British Pacific Fleet in 1945. She was hit by two kamikazes in May 1945, which necessitated repairs in Australia.
Of the war-built fleet-carriers, only Victorious was recommissioned into the Royal Navy and reconfigured 1950-1958 to operate jet aircraft. Finally, she was sold in July 1969 and broken up.

Users: British Royal Navy

Animated 3D model of for carrier Victorious of Illustrious class

Specifications for carrier Victorious of Illustrious class


Victorious Specification
Typeaircraft carrier
Displacement 23,000 tons
Displacement (full loaded) 28,210 tons
Length673 ft
Beam95 ft 9 in
Draught24 ft
Boilersix Admirality 3-drum boilers
PropulsionParsons geared turbines with 3 shafts
Power 111,000 hp
Bunkerage 4,850 tons petrol
Speed30.5 kts
Range 11,000 nm at 14 kts
Complement 1,200 (later 1,500, 1945: 2,000)


Victorious Specification
Main Armament16 x 4.5 in guns
Secondary Armament-
Anti-Aircraft 48 x 2pdr (later 56 x 40mm, 8 x 20mm; 1945: 21 x 40mm, 45 x 20mm)
Torpedo tubes-
Aircrafts 36 (1945: 36 Corsairs + 16 Avengers = 52, maximum 54)

Armor Protection:

Side (belt)4 1/2 in
Flight deck 3 in above hangar, 1 1/2 in - 1 in (deck ends)
Armoured aircraft hangar4 1/2 in
Armour main deck4 1/2 in
Armoured deck-
Armour main turrets?
Armour secondary turrets-
Armour barbetts-

Service statistics:

Laid down April 27, 1937 June 17, 1937 May 4, 1937 November 10, 1937
Launched April 5, 1939 August 17, 1939 September 14, 1939 March 26, 1940
Commissioned May 25, 1940 November 24, 1940 May 15, 1941 October 10, 1941
Price per unit ? (US carrier Essex class with 30,800 tons approx. $ 68-78 millions)
Fate thanks to armor, none lost in World War Two - all breaking up between 1953 and 1969.

References and literature

Fighting Ships of the World (Antony Preston)
Kriegsschiffe von 1900 bis heute – Technik und Einsatz (Buch und Zeit Verlagsgesellschaft)
The Illustrated Directory of Warships from 1860 to the present day (David Miller)
Kriegsschiffe 1939-45 (Heyne-Bildpaperback)
Flotten des 2. Weltkrieges (Antony Preston)
Aircraft Carriers of the World, 1940 to the Present – An Illustrated Encyclopedia (Roger Chesneau)
Seemacht – eine Seekriegsgeschichte von der Antike bis zur Gegenwart (Elmar B. Potter, Admiral Chester W.Nimitz)
The Encyclopedia of Weapons of World War II (Chris Bishop)

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