World of Warships

Hybrid Carriers in History, and Why They Never Worked

WorldOfWarships7 - Hybrid Carriers in History, and Why They Never Worked
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With the upcoming introduction of the hybrids Tone and Ise into the game, I thought now would be a good time to make a short (and by short i mean ridiculously long) post about why hybrid aircraft carriers are a bad idea and never worked in history. I'll start with the fundamentals and then get to individual examples further down.

Also, some may disagree with my inclusion of the Lexington class, Kaga, and Akagi in the examples section as they were designed as carriers first and foremost and were never intended to get into a surface action as the term "hybrid" would imply they were. I am inclined to agree with that objection, however they were still built with a substantial anti-surface gun battery and I felt that they would make a nice point of comparison.

There are two big factors for why hybrid ships proved impractical. The first is that the space and design requirements for surface combat and flight operations are inherently contradictory. One cannot design a ship to do one thing without compromising its ability to do the other. Flight operations require a lot of deck space to move aircraft around and launch them, even with catapults, and require a hanger to store and maintain aircraft. Gun turrets also require considerable space, both horizontally and vertically, for the guns and the associated machinery to load and aim them. The catapults on the King George V class battleships, for example, take up about as much space as an extra gun turret just to operate a couple of seaplanes. Interwar design studies of hybrids by the US and Britain produced vessels that were underarmed for their size, even when compared to the World War I vintage dreadnoughts, and which carried ridiculously tiny air groups of maybe a dozen or so planes. In short, there is simply not enough space on any practically sized warship to be both an effective battleship and aircraft carrier that is competitive with its peers. At least 40-50% of the ship's length would be needed to be sacrificed to operate a meaningful number of seaplanes, and even more for traditional aircraft.

The second, and related, issue is one of the vulnerability of aviation facilities to damage. Operating aircraft during World War II (and today for that matter) involved all sorts of highly combustible things, such as explosive-filled bombs and 100+ octane aviation gasoline. THe risks of fires are further complicated by the necessity of open space on the hanger deck, which provides a highway for fires to spread rapidly from one end of the ship to the other. One only has to look at Kaga's and Akagi's fate to understand the dangers an out-of-control avgas fire poses to a ship. Even surface ships that weren't designed as hybrids and just carried the odd floatplane for reconnaissance suffered from these vulnerabilities. During the Battle of Savo Island, multiple American cruisers were effectively cut in half by avgas fires started by hits to their amidships floatplane hangers, which significantly compromised the ability of the crew to fight and subsequently conduct damage control operations. Indeed, these fires would subsequently doom USS Astoria in the battle's aftermath as burning gasoline got into her 5" ammunition magazines, with predictable results. Indeed, by the end of World War II the US and Britain were removing aviation facilities from their cruisers, with this vulnerability being a major reason for it. Armoring these sections of the ship also proved rather difficult. Aviation facilities must by their nature be placed high up in the ship, and putting the weight of enough armor to reliably resist battleship-grade firepower that high up in a ship and across so much of its area would inevitably compromise the ship's stability, if it would even float in the first place. Resisting cruiser-grade firepower was possible, as demonstrated by the Royal Navy's Illustrious class armored carriers, who's hanger side armor was similar in thickness to the armor belts installed on the County class in the late 1930s and who's armored flight deck was similar to older battleships' armor decks, but came at a huge cost in aircraft capacity. Despite displacing as much as a Yorktown class, the Illustrious class could only carry about 50 planes at best, whereas the Yorktowns could get up to 70 operational, plus plenty of spare airframes. Additionally, the hangers lacked the extensive machine shops needed for aircraft maintanance that the American ships had, requiring a separate support carrier in the form of HMS Unicorn for that, and had very low ceilings that made it impossible to operate larger late-war aircraft like the Corsair. This is not intended to disparage the Illustrious class, as they were excellent ships that served well throughout the war, but to illustrate the costs associated with armoring hanger decks. You can imagine how the addition of gun turrets and their associated machinery would affect this.

So, with the fundamentals out of the way, let's take a look at some individual hybrids and see how they performed. I'll start with HMS Furious, the original fleet carrier. Furious started life as a "large light cruiser" armed with 2 18 inch guns, minimal armor, high speed, and a shallow draft, intended for use in Jack Fisher's "Baltic Project," an amphibious invasion of Germany on the Baltic coast during World War I. This never went anywhere and it was realized that Furious was singularly useless, even by the standard set by her half-sisters Glorious and Courageous, so the decision was made to convert her into an experimental aircraft carrier while she was still under construction by removing the forward turret and installing a flight deck. The aft turret was initially retained, making her the most heavily armed aircraft carrier to ever put to sea. Launching planes was done as you'd expect, but to land they had to fly parallel to the ship and then sideslip onto the flight deck. This was actually doable due to the short landing distances, light weight, and ridiculous maneuverability of World War I era aircraft (seriously. some of those planes could literally rotate in place like a flying gun turret), but it was extremely difficult and dangerous and was abandoned after only a few tests when the pilot crashed and was killed. This resulted in a series of modifications and changes, starting with the removal of the aft turret and the installation of a landing platform. This also proved unworkable, as exhaust from the ship's funnel and the slipstream of the superstructure created too much turbulence for landing, and moving aircraft between the platforms proved difficult. This resulted in further changes that eventually resulted in the Furious we all know and love in-game, a useful, albeit somewhat small and limited, fleet carrier.

Furious's deficiencies can be excused due to her status as an experimental ship, and she would develop into a useful fleet unit by the late 1920s. She is also a perfect illustration of the problems inherent in hybrid designs, as she only became an effective fleet unit by completely sacrificing her surface combat role.

The next ship is the most successful hybrid design, USS Lexington. A converted battlecruiser, she was the biggest, most advanced, and most powerful aircraft carrier in the world when she entered service in the late 1920s. She was also armed with 8 8" guns in superfiring twin turrets fore and aft of her island, which also contained complete rangefinding and fire control systems for them. No, you did not misread that. She was an aircraft carrier with a USS Pensacola strapped on top. The position of the guns was perhaps as ideal as it got, as they had good arcs of fire without impeding flight operations all that much, and the rangefinding equipment combined with her tall mast made them remarkably accurate. The reason for the inclusion of these weapons was down to the performance, or lack thereof, of early carrier aircraft, specifically their short operational range. This meant that carriers would need to get right up on an enemy fleet before engaging, and when they did their planes didn't hurt all that much. As a result, they were very vulnerable to being run down and forced into a gunfight by enemy cruisers, and in particular the new, powerful, 8" armed treaty cruisers (which weren't technically heavy cruisers yet, as that term was invented by the London Naval Treaty in 1930). The 8" guns were intended to allow Lady Lex to defend herself from such ships. This idea was born out in US wargames and Fleet Problems throughout the late 20s and into the 1930s, when that exact thing happened repeatedly. As a result, both carriers entered World War II with enough firepower to match or outgun a sizable portion of Japanese surface ships, although by this time there was an intention to replace them with anti-aircraft guns. However, even in what I consider to be the optimal cruiser-carrier design the guns were still an overall impediment. They still took up flight and hangar deck space, and the fire control equipment took up valuable real estate in the Lexington class's already small island. Additionally, the guns' blast effects caused severe damage to Lexington's redwood flight deck and would damage or destroy aircraft parked on it during cross-deck firing, which had to be repaired before flight operations could be restarted, something not entirely optimal for a navy that practiced a deck park for their air groups.

Overall, the Lexington class are an example of a cruiser-carrier done right, if such a thing really exists. When new they made a decent bit of sense, but as aircraft became more and more powerful over the course of the 1930s they became less and less useful until they were a complete waste of space by 1939. Even with optimal placement and layout, the guns still had a negative effect on air operations and were very much a weapon of last resort.

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After that we have Kaga and Akagi. I'm not going to linger on them for long, as they are similar in concept to the Lexington class, albeit with a strange triple-stacked flight deck similar to one of Furious's configurations. Six of their 10 8" guns were mounted in casemates low in the hull, where they would not interfere with the hanger and flight deck. This limited the broadside of the ships compared to the Lexington class and also made them largely unworkable in heavy seas due to water coming in through the casemates. They also had two twin turrets on either side of the middle flight deck (look it up. they're quite a sight), which negatively effected flight operations due to them forcing aircraft to squeeze between them during takeoff. Their turrets would be removed along with the lower flight decks during their reconstructions, but they would retain their casemate guns and take them with them to the bottom of the Pacific.

Like the Lexington class, Kaga and Akagi's designs make sense for the time they were constructed. The gun batteries still impeded flight operations and I would argue that they weren't as successful as Lexington, but they did their job. However, they were still an impediment for carrier operations, and much like the Lexingtons the ships were greatly improved by the guns' removal.

Then we have everyone's favorite memebote, Graf Zeppelin. If Lexington was the hybrid carrier done right and Kaga and Akagi was it done acceptably, Graph Zeppelin was the hybrid carrier done *completely wrong. Originally, she was intended to be a relatively small light carrier that would escort the Deutchland class panserschiff on their commerce raiding cruises, acting as scouts, providing fighter cover, and sending aircraft after fleeing merchantmen should a convoy scatter before the formation. However, it was decided that the ship should have some form of dedicated anti-surface armament so the ship could attack merchant ships directly and defend itself from enemy cruisers. This resulted in an escalation in the size of the various design proposals and the fitting of 8 15cm guns in casemates. They were located on the hanger deck, higher up than those found on Kaga and Akagi and thus more workable in heavy seas, but they also cut into the hanger and significantly reduced its capacity. An attempt to address this by combining the single guns into four twin casemates only made things worse due to a miscommunication that resulted in 8 twin casemates, which were even bigger than before. The result was a carrier that displaced 33,000 tons with an air group of 42 aircraft. The outbreak of World War II prevented her completion, and her unfinished hull was captured by the Red Army and sunk as a target after the war. Evidently the Russians were looking for insight on the best way to sink an aircraft carrier. Can't imagine why.

I love Graf Zeppelin in World of Warships. I really do. She's one of the funniest ships in the game. But she's also a terrible, terrible aircraft carrier. She's the size of an Essex class fleet carrier, but can only operate about as many aircraft than the Illustrious class, which was 10,000 tons lighter and way, way better protected. Her anti-surface armament of 16 15cm guns sounds impressive at first as it implies that she should be able to outgun a Brooklyn class machine gun cruiser, but the casemate mountings meant that she could only bring a maximum of 8 to bear on any given target, allowing a Leander class cruiser to engage her on equal terms. Had she been designed as an armored version of USS Lexington, with triple 15cm turrets around the island and an Illustrious style armored hanger then I could maybe see the rationale of her as a commerce raider with a secondary role in the fleet, but even then it would probably have been better to just build a proper fleet aircraft carrier and let the swarms of aircraft do the merchant hunting, or, better still, build several smaller light carriers of about 10,000 tons or so. At least then they could be in more places at once.

Then there's the Ise class, the hybrids that never should have been. The Ise class started out as improvements over the Fuso class battleships, with a revised turret arrangement and internal layout. For the most part they were fairly successful, allegedly hellish crew accomodations aside, and spent most of their lives uneventfully swinging at anchor like the rest of the Japanese battlewagons. And then those pesky Americans just had to show up and ruin everything at the Battle of Midway. Dangerously short on carriers, the Japanese decided to convert the two to help make up the losses. However, it was decided that full conversions would take too long, so they just removed the rear turrets and installed a short flight deck to operate 22 seaplanes, consisting of a split between dive bombers and reconnaissance aircraft (a decision made easier by Hyuga's turret 5 destroying itself in an internal explosion some weeks earlier). The conversion was finished in early 1944, but shortages of aircraft and, more importantly, trained pilots meant that they never really conducted any air operations.

This conversion really highlights the problems with hybrid ships. As battleships, the Ise class had become the least powerful in the world with an armament of a mere 8 14" guns. Even the battlecruiser HMS Renown could take them on with a reasonable chance of victory. The same is true of them as carriers. 22 seaplanes is hardly going to put the fear of God in a purpose-built carrier. The D4Y intended to be the ships' dive bomber was a good design, but seaplane variants always have inferior performance compared to traditional aircraft. These conversions were a desperation move, one which was completed way too late to be relevant and produced ships that were not competitive. The resources used converting these ships would have been much better spent building anything else, like anti-submarine escorts.

And finally we get to Tone, along with the somewhat more obscure Swedish light cruiser Gotland, which had a similar design layout and philosophy. Neither of these ships were designed for combat flight operations. Instead, their purpose was as scouts. The Tone class started out as two additional Mogami class ships, albeit with the 8" guns from the start as Japan had withdrawn from the treaties by this point, but was later revised into scout cruisers for the Japanese aircraft carriers. Japanese carrier doctrine called for all available strike aircraft to be used for strike missions and not for reconnaissance, unlike US and UK doctrine. Scouting would instead be done by aircraft from cruisers or the Kongo class battleships. The Tones were designed with this purpose in mind, and each carried between 4 and 6 seaplanes on their sterns, which were split between long range scouts and shorter ranged aircraft for observing and correcting the fall of shot during surface actions, as well as dropping illumination flairs durning night actions. Overall the system did work, however it was vulnerable due to the problem that if even one plane broke down then scouting efforts would be badly hampered due to the small number of planes. Additionally, it introduced a delay in relaying siting reports from the aircraft to the flagship, as messages first had to be received, processed, and retransmitted by the cruisers first.

Gotland was designed as a scout for the Swedish Sverige class coastal defense battleships. Basically these ships would operate in shallow waters and hide around and behind islands along the rather treacherous Swedish coast. Enemy fleets would need to break up their formations to maneuver in such waters, and Gotland's aircraft would observe them and report back to the battleships about what was going on, which would then engage isolated parts of the enemy's fleet. This would hopefully make any invasion of Scandinavia that included Sweden too costly for an enemy to want to attempt, and I've heard (but haven't definitively confirmed) that this was a major factor in Germany not invading Sweden in addition to Norway, as they didn't have a great answer to this Swedish force (although, again, I do not know how much truth there is in that. it's entirely likely that the Nazis never felt any particular need to invade once Norway and Swedish iron shipments through it were secure).

Incidentally, for such an obscure ship, Gotland actually had a pretty big effect on history, as it was her citing report of the German battleship Bismarck in the opening stages of her voyage that would eventually kick off that whole saga. Pretty impressive for a ship most people have probably never heard of.

Overall, Tone and Gotland were relatively successful hybrid designs. However, this is largely because they were never intended as fleet carriers or to use their aviation units in a combat role, and instead were designed as scouts for more powerful units that would do the real fighting. They were more cruisers with expanded aviation facilities than true hybrid carriers. Additionally, their anti-surface armament still suffered due to the space requirements of the aviation facilities.

So, there you have it. A brief history of battleship-aircraft carriers and why they never worked. Let me know what you think and pease point out any mistakes I've made so they can be corrected. I do hope you enjoyed.

Also, as a slight tangent/aside I typed this on my phone using a bluetooth folding keyboard and a small mouse as a sort of substitute pocket-sized laptop. One might say a… hybrid. I encourage you to try it, as it works surprisingly well. Way better than hybrid aircraft carriers, certainly.

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