Float Plane Cruisers (1920-1940)

The introduction of the cruiser float plane after the Great War vastly improved the scouting efficiency of navies. So let's take a closer look at this rather underappreciated naval development. While the aircraft are an interesting subject themselves, the cruisers that operated floatplanes have been severely neglected despite being a critical part of interwar naval strategy.

Japan

Despite the early experiments by the United States and the large number of seaplane tenders and early carriers commissioned by Great Britain, the first navy to put float panes on its cruisers was in fact the Japanese. The Nagara-class light cruisers (lead ship commissioned in 1922) were constructed with flying off platforms above their bow armament and one plane hangers built into their bridges. This unusual arrangement was repeated in the 1924 Sendai-class and the 1926 Furutaka-class heavy cruisers also commissioned with flying off platforms (but mounted on their aft Number 4 turrets rather than their bows and without hangars).

A Nagara-class light cruiser - note the flying off platform forward over the number 2 turret, the hangar is in the second level of the superstructure

However, this setup proved unsatisfactory and all three classes had their flying off platforms replaced by a single amidships catapult in the early 1930s. The Kuma-class light cruisers and Aoba-class heavy cruisers, which had commissioned without aviation facilities, were also retrofitted with catapults at this time. After these rebuilds, the light cruisers all carried a single plane while the heavy cruisers carried two. Interestingly, the light cruisers lost their hangers in this redesign and the Japanese never again used hangers on their cruisers. Instead, float planes were either stored on the catapults or beside them on the open deck.

The first Japanese cruisers commissioned with catapults were the 1928 Myoko-class. These heavy cruisers set the pattern for all succeeding Japanese cruisers with their two amidships catapults and generous aviation deck. The Myoko and Atago-class cruisers both carried up to three float planes while the 1935 Mogami-class carried a maximum of four. The final 1938 Tone-class cruisers were optimized for float plane operations and traded their rear turrets for a large aviation deck. This theoretically allowed them to carry an impressive eight float planes although no more than six were ever actually embarked.

Two floatplanes on a Mogami-class cruiser - note the treaty-era 6" triple turrets

United States

While the first float plane cruisers were Japanese, the first successful ones were American. These were the 1923 Omaha-class scout cruisers, which commissioned with a pair of amidships catapults for two embarked float planes. While this arrangement was repeated in the two 1928 Pensacola-class heavy cruisers, it was the 1930 Northampton-class that set the standard for aviation facilities on American cruisers. While the Northampton-class also had two amidships catapults, it introduced a large hangar for no fewer than four float planes.

Two catapults and a four plane hangar were included on all succeeding American cruisers although the 1937 Brooklyn-class marked the move from amidships facilities to fantail catapults and below-decks stern hangars (this proved to be a good decision as the fighting off Guadalcanal proved the older superstructure hangers were a significant fire risk).

The aviation facilities of a Cleveland-class light cruiser - note the two catapults, large aviation crane, and hangar entrance

Great Britain

Despite its impressive lead in naval aviation at the end of the Great War, the Royal Navy was slow to adopt cruiser float planes. The first British ships to be equipped with them were the 1926 Emerald-class, which, strangely, were built with flying off platforms despite being commissioned three years after the American Omaha-class. It is likely that this was because of budgetary limitations rather than choice as the succeeding Kent-class commissioned without any aircraft facilities at all despite being designed for them. It was not not until the 1929 London-class that the Royal Navy had catapult-equipped cruisers. However, despite being a contemporary of the two-catapult Myoko and Pensacola, the London-class heavy cruisers had an austere aviation fit of just one amidships catapult and a single float plane.

This light fit was continued on every cruiser up to the 1935 Arethusa-class. However, the British were aware of the value of cruiser float planes and conducted a series of refits to add more to the fleet. The first of these was in the early 1930s when the Kent-class received the single catapults and planes they had been designed for. By the mid 1930s the Emerald-class finally had their flying off platforms replaced with catapults and extensive rebuilds of the heavy cruiser force were begun. In these rebuilds one London-class and four Kent-class cruisers received superstructure hangars for two float planes. However, by this point war was coming and it was too late to upgrade the entire fleet. The final prewar British cruisers, the 1937 Town-class, were equipped with a single catapult and two-plane hangars from the start.

An aft view of a Town-class light cruiser showing the large doors to the forward superstructure hangar typical of later British cruisers

France

Despite being one of the second-class navies, the French were rather quick to adopt cruiser float planes. The 1926 Dugauy-Trouin-class light cruisers commissioned with one stern catapult and two planes on the boat deck. The succeeding Duquesne, Suffren, and Emile Bertain-class cruisers had their single catapults mounted amidships but also carried two planes on their decks. The 1934 heavy cruiser Algerie broke this pattern with two amidships catapults and space for three aircraft, while the 1936 La Galissoniere-class light cruisers mounted their catapults on their aft turrets and added a four plane superstructure hangar. Of course, the quick defeat of France in World War II meant that their use of cruiser float planes was not given a chance to evolve during the war.

Italy

The first Italian float plane cruisers were the 1928 Trento-class heavy cruisers. These ships had rather unique aviation facilities consisting of a fixed bow catapult and a below-decks bow hangar for two aircraft. This design was repeated in the Zara-class, but the 1931 Condottieri-class light cruisers moved to a pair of amidships catapults with two planes stored above-decks. The final Italian heavy cruiser, the 1933 Bolzano, had a single amidships catapult with no hangar and three aircraft.

A good view of the bow catapult on a Zara-class cruiser - the hanger entrance is below the guns of the number 1 turret

Germany

After losing her navy in Versailles, Germany was understandably slow to construct modern warships. However, the decision to build the 1929 Konigsberg-class light cruisers without aviation facilities is still somewhat odd. The first German float plane cruisers were the 1931 Leipzig-class, which were built with a single amidships catapult and embarked two aircraft - one on the catapult and the second stowed in a partially disassembled state. Surprisingly, this cumbersome arrangement was continued in the Deutschland-class large cruisers, the mid 1930s refits of the Konigsberg-class, and the 1939 Admiral Hipper-class heavy cruisers (which carried two disassembled aircraft for a total of three float planes). Given that these ships were expected to act as independent commerce raiders, finding their own targets on the high seas, their limited aviation facilities are inexplicable.

USSR

In this period Russia had a third-class navy at best. However, it is worth including as a reminder of how long it often takes for technical advances to trickle down to the minor navies. Despite the major navies building float plane cruisers in the 1920s, Russia did not have one until the early 1930s, when a handful of cruisers were retrofitted with catapults and float planes purchased from Germany. The first Russian cruisers constructed with aviation facilities were the members of the 1938 Kirov-class, which had a single amidships catapult and two aircraft. However, the German invasion of Russia ended the supply of German naval aviation equipment and the indigenous Russian replacements were less than satisfactory. This meant that the Kirov-class did not operate with float planes until after the war had ended.