4,500ft and cruiser shellfire from ranges outside 7,000 yards. They had to be capable of remaining in action after sustaining damage, rather than merely surviving to return to a dockyard for repairs. He briefed Forbes in a series of discussions in his office at the Admiralty, during which Forbes put forward alternative sketch proposals. Armouring the flight deck and hangar of a 23,000-ton, standard displacement ship was not a simple proposition, but Forbes achieved it. There could be no question of double hangars like Ark Royal’s, so a smaller air group would have to be accepted. The eventual design made the single hangar an ‘armoured box’ between the lifts, which were at the forward and aft extremities of the hangar, outside the ‘box’. The flight deck itself comprised 3in armoured plates which were riveted and rabbeted in place to provide a smooth upper surface supported by athwartship beams which were 6ft deep and allowed the whole structure to form the upper strength deck of the hull. The hangar sides and ends were of 4.5in armoured plate. This adjoined 2.5in armour at hangar deck level which was taken outboard to meet the 4.5in waterline belt. There was no anti- torpedo bulge, but there was a 1.5in internal splinter bulkhead behind an area of ‘sandwich’
protection which was designed to be superior to that in Ark Royal.
As in previous British carriers, the hangar was fully enclosed by bulkheads which separated it from the rest of the ship. It could be entered only by lift from the flight deck or through air locks from the side passages outboard of the hangar. It was split into four sections by three steel fire curtains which could be lowered from a control position; care had to be taken to ensure that aircraft were not stowed under the curtains, preventing them from closing properly. A salt-water spray system was installed, taking water from the fire main.
As soon as Henderson was satisfied that the design was what he wanted he got board approval in a month, and in November 1936 the Admiralty invited tenders for the construction of two new aircraft carriers to be named Illustrious and Victorious. The lowest tender came from Vickers- Armstrongs, which was awarded the contracts on 13 April 1937 and built the ships in its yards at Barrow-in- Furness and Newcastle-upon-Tyne respectively. Cost per ship was estimated at £2,395,000. In all there was 5,000 tons of armour, of which 1,500 tons was in the flight-deck structure. Two further ships to the same design were ordered in 1937, to be named Formidable and Indomitable, but the latter was modified to a revised design on the slipway and will be dealt with separately in the next chapter. The first to complete was Illustrious, but delays with Victorious resulted in Formidable finishing second, followed by Victorious.
Illustrious’ designed armour protection scheme. (AUTHOR’S COLLECTION)
One of the biggest causes of delay stemmed from the run-down state of the British armour-plate industry, which had been virtually ‘killed off’ by lack of orders during the period of disarmament and the Depression. Illustrious was the least affected, Victorious the worst. The transverse bulkheads at the ends of the hangar and the armoured doors that closed off the lift wells were made slightly thinner than originally planned. The flight-deck armour was ordered from Vitkovice of Morava Ostrava in Czechoslovakia in 1938 and, fortunately, arrived before war broke out. It was this Czech armour that
was penetrated by German bombs in January 1941.
The class was designed to operate thirty-six aircraft, each with a maximum overload weight of 14,000lb. A single BH-III hydraulic catapult was deemed sufficient, but the shuttle mechanism had to be mounted on top of the armour so as not to penetrate and therefore weaken it. It was placed on the port side forward, inside a shallow structure with sloping, faired-in sides, so that aircraft wheels could move over it when taking off or taxying without it causing an obstruction. It could be fitted with a trolley for launching aircraft fitted with floats, or a shuttle to launch aircraft standing on their wheels in the ‘tail-down’ method, in which they were accelerated forward by a wire strop engaged with hooks on the underside of the aircraft. It was capable of launching a 12,500lb aircraft at an end- speed of 66 knots. The initial design included six arrester wires and two safety barriers of similar specification to those fitted in Ark Royal. Three further arrester wires were added aft while they were still building, and in Victorious and Formidable two arrester wires were installed forward to allow aft-facing landings over the bow.
Four wind breaks were fitted forward of the forward lift; each was 10ft high and designed to lie flush with the deck when not in use. They could be raised to shelter aircraft ranged on deck, but they were not very effective and tended to flex and distort as aircraft ran over them when they were down.
Illustrious was the first British carrier to have a mobile crane on the flight deck when she was completed in 1940. Known as ‘Jumbo’, a generic name that persists into the twenty-first century, the original unit was a petrol-electric crane capable of lifting 5,000lb; its own weight was 6.75 tons. It was destroyed during the attack on 10 January 1941 and replaced by an American ‘Jumbo’ during the subsequent refit in Norfolk, Virginia. She also left the USA with two flight-deck tractors which proved valuable in moving aircraft, and by 1945 she had four.
The two safety barriers were intended at first to give continuity should either fail or be damaged in use. By 1940, however, the landing interval had reduced and two barriers gave an added measure of safety. A third was added later to improve the margin of safety still further. In practice the aft- facing wires were seldom used, and they were unrigged in 1943. The hangar height was kept at 16ft, the minimum considered necessary to allow the contemporary Swordfish, Skuas and Rocs to be struck down on floats. All naval aircraft of the period were designed to be operable on floats so that they could operate from battleships or cruisers as well as aircraft carriers. From 1941 it was essential to increase the number of fighters embarked to take advantage of air warning radar and provide an effective air defence for the fleet. At first this was achieved with a deck park of aircraft which were pushed forward of the barrier by handling parties before aircraft could land-on, and pushed aft of the range for launches. The situation was eased slightly by outrigger stowages, U-shaped beams which projected outboard from the starboard deck edge and in which fighter tailwheels were guided to roll outwards until the main wheels were at the deck edge, clear of the landing area, and the aircraft could be chocked and lashed in place.
Illustrious’ designed armour protection scheme. (AUTHOR’S COLLECTION)
By 1945 these ships were operating an air group of fifty-four US-built Chance Vought Corsair
fighters and Grumman Avenger torpedo-bombers. The latter’s wings folded rearwards like earlier British-built types, but the Corsairs wings folded upwards, and at the vertical they just exceeded 16ft before lowering down with the tips above the fuselage. It was felt that Corsairs would need to spread and fold their wings in the hangar for maintenance, so aircraft contracted for the RN had 6in cut off their wingtips, making them ‘squared’ rather than rounded. Despite fears that this might adversely affect performance, it was found that the modification actually improved the Corsair’s rate of roll and deck-landing performance.
Illustrious after her limited reconstruction in 1946. The forward end of the flight deck has been completely reconstructed, and the island with its radar arrays and close-range armament looks very unlike its original appearance. (AUTHOR’S COLLECTION)
The bulk stowage for avgas was only 50,450gal, effectively half that in Ark Royal and reflecting the smaller air group originally envisaged. This was adequate in 1940 but totally inadequate by 1945, when nearly double the number of larger aircraft were embarked, with the result that frequent under- way replenishment was required.
Since they were designed before radar made fighter-interception techniques viable, these ships had a battery of eight twin 4.5in turrets rather than the open mountings in Ark Royal. They were disposed in groups of two on sponsons port forward and aft, and starboard forward and aft, designated ‘A’ and ‘X’ groups to starboard and ‘B’ and ‘Y’ to port. The turrets were countersunk into the sponsons but, since the staff requirement called for them to be able to fire across the flight deck on to the other beam, the turret tops stood 2ft 6in above deck level and interfered with aircraft movements. The turrets could not be positioned far outboard, and they formed a marked constriction in the width of the flight deck, especially aft, limiting the number of aircraft that could be ranged. The BD Mark II turrets were made by Vickers; the guns themselves were 4.5in Mark III made by the Royal Gun Factory and developed from an army anti-aircraft gun to provide commonality and use the same fixed ammunition. Six Mark VIII eight-barrelled 2pdr ‘pom-poms’ were mounted in positions similar to those in Ark Royal; they were designated S1, S2, S3 and S4; P1 and P2. Large numbers of 20mm Oerlikons and eventually 40mm Bofors were added as the war progressed. Each group of 4.5in turrets had its own Mark IV director capable of directing its own group, more than one group or all four groups. The ‘B’ director had to be raised during construction to give it a better field of view, making it into a potential obstacle for aircraft that drifted left on take-off. In Victorious and Formidable this problem was solved by giving this director hydraulic lowering gear, but this was not
available in time for Illustrious. It was eventually fitted in her 1946 refit.
Illustrious was the first aircraft carrier in the world to be completed with radar. In November 1939 it was decided to delay her completion by two months in order to fit a Type 79Z equipment.
This had separate transmitting and receiving aerials; the latter was placed at the top of the foremast, but a new mainmast was stepped for the latter at the after end of the island. This was fixed in Illustrious but made telescopic in subsequent ships which had more time in the builder’s yard before completion. Type 79 transmitted in two lobes and contact fade between them gave an indication of an aircraft’s height. An aircraft flying towards the carrier at 10,000ft could be detected at about 60 miles; one at 20,000ft at about 100 miles. Radar revolutionised an aircraft carrier’s ability to use its fighters to the best effect in intercepting enemy attacks, but Illustrious’ officers had to overcome early misconceptions about the need for secrecy. When she arrived in the MF in 1940 the Fleet Standing Orders stated that radar was turned on for only one minute in every hour and turned off immediately if an aircraft was detected in case the enemy learnt about it! No communication with fighters was to be made until the enemy was in sight. Fortunately common sense prevailed and Illustrious was able to use her radar and new Fulmar fighters to gain air superiority in the eastern Mediterranean.
Her Type 72DM aircraft homing beacon was moved down to a position on top of the foremast’s tripod to make space for the Type 79 radar receiver at the masthead. She also had high- and medium- frequency direction finders and the best outfit of W/T and radio sets yet fitted in a British carrier.
These included Types 56, 57, 52L and 52M, 52H, 405 and 49C.
Postwar modernisation
During her wartime refits Illustrious had a number of improvements made to her flight deck and was fitted with extra avgas tanks and extra structure to accommodate radar arrays, and given a considerable increase in the close-range armament. Her 1945 refit grew into a modernisation that consolidated wartime experience and made a number of improvements. She was given a new bow and stern at either end of a level flight deck, similar to those being built into the new light fleet carriers, giving the largest deck area that could be contrived on the hull. Consideration had been given to removing the after 4.5in gun turrets and plating over the ‘bottleneck’ they created to give more space for ranging deck-load strikes, but in the event this was not done to save cost.
Consideration was also given to fitting out the space under the flight deck as mess decks to ease the problem of cramped, inadequate accommodation, but cost considerations also prevented this.
Between 1940 and 1945 her scheme of complement had risen from 1,280 to 2,000 because of the extra aircraft that could be embarked, radar and other new equipment and the significant increase in close-range guns.
ABOVE Bomb damage suffered by Illustrious on 10 January 1941. (AUTHOR’S COLLECTION)
LEFT Illustrious carrying out flying trials in 1947. A Sea Fury F.10 is ranged aft, and a Seafire F.45 of 778 NAS is parked on an outrigger forward of the island. (AUTHOR’S COLLECTION)
Significant work included a rebuilt island with sponsons for single 40mm Bofors guns and a new outfit of radars on new fore and mainmasts. A ‘YE’ homing beacon on a mast attached to the funnel replaced the Type 72. Radars included Type 961, 281 and 293M. An American SM-1 radar replaced
‘A’ director, but this was replaced by a British Type 277 at the next refit. The gun directors had Type 285 range-finding gunnery radar. In her final refit in 1952 all remaining 2pdr ‘pom-poms’ and 20mm Oerlikons were removed, leaving her with an all-Bofors close-range armament. A five-bladed propeller was fitted to the centre shaft in 1946, which cured the major vibration problem, but over her remaining life some vibration was caused by the wing shafts at high speed.
The lifts were enlarged to 48ft long by 22ft 9in wide with new platforms strengthened to take the new generation of naval aircraft under development. After the decision to complete her as a trials carrier, she was fitted with a boom aft, taken from Pretoria Castle, which was equipped with a television camera so that landings could be watched remotely and recorded.
Illustrious under attack in Malta Dockyard in January 1941. (AUTHOR’S COLLECTION)
Between 1940 and 1952 alterations and additions to Illustrious increased her deep load displacement from 28,210 tons to 31,630 tons, reducing the height of the flight deck above the water from about 38ft to 36ft. This was less than ideal, and in rough conditions water could, occasionally, wash down the flight deck despite the flared bow design. The fact that the ship was still far below peacetime accommodation standards for an operational fleet carrier was a major factor in extending the 1945/46 refit, and every available space including, even including former boat bays, was turned into accommodation. In September 1945 it was decided to complete her as a trials and training carrier in order to run her with a ship’s company reduced to a practical number while retaining her for use as a fleet carrier in an emergency.
A pilot’s-eye view of Illustrious from an aircraft lined up on final approach. The batsman giving the ‘come-on’ signal is just visible aft of the port after 4.5in gun turret. His yellow bats would stand out better in colour. (AUTHOR’S COLLECTION)
Damage to Illustrious on 10 January 1941
The German Luftwaffe contained a specialised anti-shipping unit known as Fliegerkorps 10, which had operated from Norway in 1940. The core capability was provided by the 54 Junkers Ju 87 dive- bombers of Stukagruppes 1 and 2. After the attack on Taranto it was deployed to Sicily with the specific aim of destroying Illustrious. Their opportunity came on 10 January 1941, during Operation Excess, as the MF closed Malta to take over the escort of four fast merchant ships headed for Alexandria from Force H. Shadowers had followed the fleet since 8 January, but the Fulmars had failed to intercept them. On 10 January, some hours after the rendezvous with the merchant ships, the MF was about 75 miles east of Malta when the enemy dive-bombers carried out a well planned set- piece attack on Illustrious. Five Fulmars were airborne at just after noon when a raid by two Italian SM.79 torpedo-bombers was detected; all five were drawn down to intercept and four Fulmars were launched, but this attack was a feint to achieve just that effect, as none of the Fulmars could then climb fast enough to disrupt an attack by Ju 87s from 12,000ft.
The attack was over in only 10 minutes, during which Illustrious was hit by six bombs of various sizes and a single Ju 87 that crashed into the ship out of control. The three bombs which hit forward inflicted little serious damage, but the three which hit aft put the flight deck out of action, although they failed to damage the machinery or affect the ship’s watertight integrity. Two of the latter hit the unarmoured after lift, and their explosion in the confined space caused most of the damage and fire in the after part of the ship. The third was the only one to hit the armoured section of the flight deck. It defeated the armour forward of the after lift and exploded before hitting the hangar deck. A steering gear failure followed the bomb damage, and when it was rectified Illustrious began the 75-mile journey to Malta at 18 knots; she was still on fire aft and the machinery spaces were filled with smoke and fumes from the foam used to fight the fires. A second attack by Ju 87 dive-bombers added several near misses and a further hit in the after lift well, where it had the beneficial effect of blowing out the fires in some areas.
Formidable shortly after completion. (AUTHOR’S COLLECTION)
Formidable at anchor after her US refit in 1941, flying a church pennant to show a religious service is taking place. A ‘YE’ homing beacon on a telescopic mast attached to the funnel has replaced the Type 72, but the forward round-down still limits the amount of deck space available for parking in Fly 1. (AUTHOR’S COLLECTION)
Illustrious arrived at Parlatorio Wharf in Malta Dockyard at 2215 and firefighters from ashore joined the ship’s company in extinguishing the fires at 0300 on 11 January. Casualties included a number of aircrew who were trapped in the vicinity of the wardroom aft when the fires broke out, and amounted to 126 dead and 91 wounded. The priority in Malta was to allow the steering gear to be