HMS Illustrious – the first armoured aircraft carrier

Ship design and development, Ship histories and stories
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RAN Ships
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June 1978 edition of the Naval Historical Review (all rights reserved)

THE ORDER FOR THE HERMES – the first British carrier designed as such – was placed in July 1917, and later in the year the Chilean battleship Almirante Cochrane, then almost ready for launching, was purchased for conversion to a carrier, and renamed Eagle. Both ships were completed at the dockyards in February 1924. Both carriers had full-length flight docks and an ‘island’ on the starboard side, through which passed the funnel uptakes.

But the first true aircraft carrier in the world with a full-length flight deck was the Argus, converted from the hull of the Italian liner Conte Rosso. The liner was purchased while on the slipway in August 1916 and the vessel was redesigned, the upper structure being completely modified. Argus was completed in September 1918, but was too late to take an effective part in the war. Argus was unique in having no funnels, masts or navigating bridge.

The first three carriers were followed by three converted light battle cruisers, the Furious, Courageous and Glorious. My father was in charge of the Aircraft Carrier section at the time and later commented bitterly that ‘a more unsatisfactory way of producing an aircraft carrier I do not know, and cannot imagine’.

Furious had been originally converted in 1917, but was completely modified between 1921 to 1925. Courageous completed her conversion in 1928 and Glorious in 1929. All three carriers had a displacement of about 22,500 tons.

An aircraft carrier was included in the 1934 Programme, this was the Ark Royal, which won great fame in the Second World War. I saw the plans of the 22,000 ton carrier before the contract was awarded and was tremendously impressed with the 800 foot overall length, the two hangar decks, the sixteen high angle guns and the number of aircraft to be carried, which was an incredible 72. Later in service this figure was reduced to 60.

At the time the design was started Britain was advocating at international disarmament conferences that the 1921 Washington Treaty displacement of 27,000 tons for carriers should be reduced to 22,000 tons. In 1936 the new international limit was reduced to 23,000 tons, but this came too late to be incorporated in the Ark Royal, although a lot could have been done with the extra 1,000 tons.

The next development in British carrier design proved to be an epoch making one, the design and construction of the first fully armoured carriers in the world. Two carriers were approved for the 1936 Programme and under normal conditions these would have been improved Ark Royals of 23,000 tons.

In 1936 Britain had begun a major naval rearmament program, and due to the excessive amount of work at the Admiralty, the design of a new type carrier would have taken about two years to complete and there simply was not time for this delay, due to the Hitler menace. So the stage was set for an improved Ark Royal with the same dimensions.

The responsibility for the design and construction of British warships at the time rested in the capable hands of the Controller of the Navy, Admiral Sir Reginald Henderson. This officer had commanded Furious in the twenties and became the first Rear Admiral, Aircraft Carriers in 1931. He had more experience of carriers than any other naval officer. Henderson refused to consider a modified Ark Royal design, he wanted a fully armoured carrier capable of withstanding heavy punishment from the largest bombs then known.

Admiral Henderson, a born leader, was never bound by convention. To get his armoured carrier he would be forced to short circuit the normal channels. For his audacious plan to succeed he needed a brilliant designer with great experience of carriers. Fortunately the head of the Aircraft Carrier section at the Admiralty had more experience of carriers and their design than any other person, and had been the designer of Ark Royal. His name is W.A.D. Forbes.

In 1936 there were no Staff Requirements for an armoured carrier, because nobody had considered it possible to design one on a displacement of 23,000 tons. None the less Henderson was determined to go full speed ahead.

In a letter to the author Mr. Forbes described the unorthodox design of the first armoured carriers.

‘Reggie hated paperwork and just could not wait for Staff Requirements to be prepared’ wrote Forbes, ‘and it was his decision to go ahead without them, which led to the great saving in time in placing orders for the ship. Sir Arthur Johns (then Director of Naval Construction) was sick and absent from the Admiralty (he never returned), his deputy Mr. Fred Bryant was fully occupied in running the department, which was exceedingly busy, so Reggie just sent for me and told me he wanted a fully armoured carrier with a flight deck proof against 500 pound bombs and armour on the sides of the hangar equal to that used for contemporary cruisers. Most of the rest he left to me.

For about two months he sent for me each Friday afternoon and after I had told him how I was getting on, he would stride up and down that great room of his at the Admiralty and talk and talk, and if he stopped for breath I would put in a word and off he would go again. Nobody else was present at these talks.

Several alternative designs had to be worked out before I could get a fully armoured carrier of 23,000 tons and one of the main secrets was that the 3 inch armour plate which formed the flight deck was used both for protection and longitudinal strength. No backing was used under the armour. The 3 inch armour, worked structurally, with riveted and rabbeted laps and butts was worked on the flight deck and 4½ inch on the hangar sides.

Immediately Reggie was satisfied, an official ‘sketch design’ was submitted to the Board by Mr. Bryant and Reggie bulldozed it through and got Board approval in a month, an unprecedented speed. Shortly after this approval of the ‘sketch design’ was given Mr., afterwards Sir, Stanley Goodall was appointed Director of Naval Construction and so the ‘Building Drawings and Specification’ were prepared under his supervision and he signed them in due course before they were submitted for Board stamp.

Sir Stanley had not had much previous experience of carriers. It so happened that I was uniquely equipped to undertake the job. I was familiar with all existing carriers and had witnessed many hundreds of landings of all types of aircraft, and moreover I had the recent experience of being the Constructor in charge of the Ark Royal design. There were few people who had the necessary experience of carriers to do the job (your father was one of the few).’

In November 1936 the Admiralty invited tenders for the construction of the two new carriers, Illustrious and Victorious. The lowest tender was from Vickers Armstrong, who built both ships at Barrow and Newcastleon- Tyne respectively. The two carriers were ordered on 13th April 1937 and the cost per ship was to be 2,395,000 pounds. The time fixed for construction was 36 months. Illustrious completed on 20th April 1940, but Victorious did not complete until May 1941 due to various delays.

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