Plan Z:
British Carriers, Part One
by Mike Bennighof, Ph.D.
May 2021

While the British government is often portrayed as having done little or nothing to prepare for the Second World War, this stretches the truth. Winston Churchill, a Member of Parliament in the mid-1930’s, indeed harangued that body and the public with a series of motions and speeches decrying Britain’s lack of sufficient modern weaponry. Complaints are easy to lodge: speak or write a few words, and you’ve done your bit. Prime Minister Stanley Baldwin had the unenviable task of actually accomplishing re-armament.

During 1934 and 1935, the “Peace Ballot,” a widely-based poll of British voters (more than 11 million respondents) showed Britons in favor of the League of Nations and against a military buildup by overwhelming margins. Nevertheless, the Baldwin government commenced a huge military program, rebuilding every useful Royal Navy battleship and commencing many new warships, including the Illustrious-class aircraft carriers, four of which were laid down in 1937 and completed in 1940 and 1941. Soon British shipyards were working at maximum capacity.

The Illustrious class was followed by the two-ship Implacable class, laid down in 1939 and completed in 1944. Implacable began as an improved Illustrious, but the list of improvements soon expanded as did the ship herself. Illustrious had many fine qualities, particularly her armored flight deck, but an enormous drawback: an air group smaller than those of ships the Japanese and Americans classed as light carriers. The new ship needed to be faster than Illustrious as well, and carry a heavier anti-aircraft armament.

Those changes went far beyond simple improvements, and Implacable would have to be a new design (though she incorporated many features of Illustrious). To accommodate more planes, Implacable would have a second, lower hangar. Initial plans put the upper hangar’s height at only 14 feet, and the lower hangar’s at 16 feet (the same as the single hangar of Illustrious). Fourteen feet was considered acceptable for any aircraft likely to come into Fleet Air Arm service, so both hangars were set at that height, allowing the addition of a gallery deck between the hangars to accommodate the increased aircrew and support personnel.

Implacable shows her low-ceilinged upper hangar.

With the additional hangar plus a deck park, Implacable could carry an air group of 72 planes, exactly twice that of Illustrious (33 in the upper hangar, 15 in the lower hangar, 24 on deck). But the decision to reduce the hangar height meant that Implacable would not be able to operate late-war American aircraft like the F4U Corsair. The heavier anti-aircraft armament resulted in an oddly-shaped flight deck, with numerous cut-outs to accommodate gun positions and their fields of fire.

To make her designed speed of 31 knots, Implacable simply had four sets of turbines and boilers, each producing 37,000 horsepower and driving its own propeller shaft, where Illustrious had three identical sets for 111,000 horsepower. Implacable actually beat her target speed on trials, making 32 knots; Illustrious had made 30.

Implacable was laid down in March 1939 and her sister Indefatigable in November; wartime priorities slowed their construction and both were completed in 1944. They saw action in the bombing raids against the German battleship Tirpitz and in the Far East against the Japanese. Scheduled for modernization in the 1950’s, the delays and cost overruns incurred in rebuilding Victorious caused the project’s cancellation. After a proposed sale of Indefatigable to Argentina fell through both were scrapped in the mid-1950’s, having seen only a few years of active service.

The larger, more capable carriers of the Audacious class helped make the earlier carriers expendable. Discussion of a new carrier had begun immediately after Implacable was ordered, with the first preference going to a simple repeat of the design. War had just broken out and the Admiralty wished to get more carriers into service as quickly as possible, and did not want to expend its resources designing and building ships that might not contribute to the current conflict.

Repair work and construction of badly-needed escort craft took priority in the shipyards, delaying the orders for the new carrier class. During that delay, wartime experience filtered into the design, with the Admiralty now asking for a larger carrier with a wider beam for greater stability, better internal subdivision and arrangements to prevent the large-scale flooding that doomed the carrier Ark Royal, increased close-range anti-aircraft armament, and once again a larger air group.

The new carrier would displace 32,000 tons but meet Implacable’s 31-knot speed with four sets of boilers and turbines producing 152,000 horsepower. Like Implacable, each set would power its own shaft. Anti-aircraft protection would be formidable, with eight deck-edge 4.5-inch dual mounts fitted flush with the light-deck, and eight sextuple 40mm Bofors mounts, each with its own fire director.

Audacious would carry an air group of 78 planes, in two hangars plus a deck park. They could be much larger aircraft than those of Implacable: the hangar height of 17 feet, 6 inches would accommodate any carrier plane then in service or contemplated, and the elevators could lift planes of up to 20 tons, far more than any current plane weighed.

The 1942 Programme included four ships, all ordered from private shipyards. These had even lower priority than the previous class, and only one would be laid down in 1942, another in 1943 and a third the next year; the fourth ship would never be built. Construction proceeded very slowly, and the design – never settled before orders were placed – continually evolved as wartime experience demanded changes.

Ark Royal (ii) as completed.

Two ships would be completed in the early 1950’s, with the third scrapped on the slipway. Despite their wartime construction (their hulls showed much faster corrosion than expected) they served the Royal Navy well, undergoing regular modernizations and deploying repeatedly until the 1970’s when a political decision to abandon fixed-wing carriers sent them to the breakers.

The two completed ships, Ark Royal and Eagle, went through a number of name changes during construction. They appear in Second World War at Sea: Plan Z in their original design, under their original names (Irresistible and Audacious), since the original Ark Royal and Eagle also show up in Plan Z scenarios.

They are formidable weapon systems – in contrast to the German Plan Z, the Royal Navy designed and built high-quality warships even under wartime conditions. They carry a large air group and are tough to sink should an attack get through their dense anti-aircraft fire. Plus they have British crews.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and NASA Journalist in Space finalist, he has a whole passel of books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold. Leopold is well-designed.