USS Yorktown (CV-5) v. HMS Illustrious v. Soryu?

Ultimately, the value of an asset is how its used (look at the Blackburn Skua - wholly inadequate fighting machine, but still sank a cruiser). Both the Lusty and Yorktown were constructed with different philosophies and roles/theatres in mind; would the British have gotten as much valuable service out of the Yorktown and they did with the Lusty and vice versa with the Americans? If either side had no other option, then yes, I believe so, despite each ship's limitations in the different theatres they operated in. I believe the Yorktown might have been more vulnerable in the ETO and in the Med it would have been subjected to heavy attacks, which it's likely it might not have survived, whereas the Lusty, if it were in US hands, in the Pacific its limitations are well documented - Max Hastings' book, which Renrich quotes from is excellent and well worth reading and gives an eye opening view of this all-important aspect of the war in the Pacific; The British really couldn't match US numerical assets, nor operational experience in theatre, but if the US had Illustrious Class carriers they would still have gotten what was asked of the carriers from the outset, despite their limitations of small aircraft numbers and shorter range.

The Royal Navy was hampered considerably post WW1 in terms of aviation for a few reasons; in a fiscally lean post-war environment, followed by nationwide calls for peace and disarmament, carriers were an expensive symbol of militarism and the RN clung desperately onto what it had at the end of the Great War despite the ships' inadequacies - Courageous and Glorious were slated for conversion to carriers as early as 1917 and conversion of Furious into a full flat top only made sense. Also, the RAF took over all naval air operations in 1918, combined with peacetime reduction of capabilities hindered naval aviation growth in Britain after a bright start leading the field during the Great War. It wasn't until 1939 that the FAA gained complete autonomy from the RAF.

So at the outbreak of war Britain's naval aviation is hindered with inadequate aircraft, small budgets and carriers, which are of variable value in a high threat environment, that are restricted in size owing to cost and original design constraints. Yet, the RN and FAA gave astonishingly good service with the equipment they had in extraordinarily trying circumstances, despite all this. So, in conclusion, it's very hard to state which was better in my opinion; both ships had their merits, but would each one have been as effective as the other in the environments that the other was used in by the forces in those theatres?

cherry blossom said:

Illustrious together with all the RN carriers from Ark Royal to Implacable had an opposite limitation as the elevators were kept very small to avoid weakening the flight deck which was also the strength deck. Thus those RN carriers could only carry aircraft with folding wings, which prevented them carrying the early Martlets and also prevented them carrying Spitfires to Malta (hence the use of USS Wasp).



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Indomitable and the two Implacables had a 45 x 33ft forward elevator that could accommodate most fixed wing fighters of the day.

The RN did occasionally use deck parks in the early war period. Illustrious, for example carried about 9 aircraft in a deck park during the Taranto mission.

I wonder if we could examine this issue from a slightly different perspective. Say the Japanese were building Yorktowns instead of the Soryus, and the US had to build Soryus instead of Yorktowns. Assume the other classes are built with perhaps some minor tweaking where necessary, and money is not the problem, just the tonnages set by the treaty.

There were four Yorktowns with a total tonnage of around 100000 tons. They could have had 6 Soryus with an a/c capacity of 378 a/c and a reserve capacity of 54. Individually each hull is more vulnerable but there are 6 of them, carrying more a/c. Combine that with the known US superiority in damage control and I think the US may have been better off with the Soryus. The problem of course is their fragility, though it took more bombs to knock out Hiryu than Yorktown at Midway. probably a fluke I would concede.

Conversely The Japanese had 34000 tons for the hiryus and they also had 8000 tons for the Ryujo. It creates an awkward tonnage issue for them, with 40000, they just don't have the tonnage to build 2 Yorktowns whichever way they cut it.

If they retain the Ryujo, they could build one Yorktown and another Ryujo, but probably better to cheat a bit and build another shoho class. So, in exchange fior their two Soryus, they could get 1 Yorktown and 1 Shoho, and even then have to lie a bit (Shoho had a displacement of 11000 tons).

For the British, there are four alternative scenarios that I can see.

1) Build 3 Ark Royal repeats instead of the 4 Illustrious option. If they scrap or demilitarise the Argus, they could build the 4th Problem here is that these carriers would never be more than 50% full and carried inherent and serious design flaws. The Bucknill Committee, which had been set up to investigate the loss of the Ark Royal produced a report that concluded the lack of backup power sources was a major design failure, which contributed to the loss: Ark Royal depended on electricity for much of her operation, and once the boilers and steam dynamos were knocked out, the loss of power made damage control difficult. Moreover the strakes protecting engine spaces were not of sufficient height to protect the engine spaces from uncontrolled flooding and the two design issues fed off each other in a vicious way. The committee recommended the design of the bulkheads and boiler intakes be improved to decrease the risk of widespread flooding in boiler rooms and machine spaces, while the uninterrupted boiler room flat was criticised. The design flaws were rectified in the Illustrious and later the implacable classes, but these solutions took time.

2) Build the Illustrious class with these design solutions in place, but otherwise to the original design. I think this is the least feasible of the alternatives, because there simply aren't that many advantages to doing that. The Illustriousclass was designed within the restrictions of the London Naval treaty in place, were built to an to an upper limit of 23,000 tons. They were different in conception to the RNs only modern carrier at the time, their predecessor Ark Royal and what may be described as their nearest American contemporaries, the Yorktowns class carriers.

Where other designs emphasised large air groups as the primary means of defence, the Illustrious class relied on their AA and the passive defence provided by an armoured flight deck. This latter aspect has often been thought to been the cause of her small CAG, but this in fact is a furphy Other carriers had armour carried on lower decks (e.g. the hangar deck or main deck); the unprotected flight deck and the hangar below it formed part of the superstructure and were unprotected against even small bombs. However, the hangar could be made larger and thus more aircraft could be carried, but the differences in aircraft capacity between these carriers and their United States Navy (USN) counterparts is largely due to the USN's operational doctrine, which allowed for a permanent deck park of aircraft to augment their hangar capacity. Illustrious's hangar was 82% as large as the Yorktown design. but the US carrier typically carried 30% of her aircraft capacity in her deck park. That equates to 23 a/c, and effectively reduces the air capacity if used as the Illustrious was uses to 51 a/c in the hangar. Indomitable's two hangars were actually larger than Enterprise's but she carried fewer aircraft because she did not have a large permanent deck park. In 1944/45 RN carriers began to carry a permanent deck park of similar size to their USN counterparts and this increased their aircraft complement to an eventual 57 aircraft in the single hangar carriers and up to 81 in the double hangared carriers.

In the Illustrious class, armour was carried at the flight deck level—which became the strength deck—and formed an armoured box-like hangar that was an integral part of the ship's structure. However, to make this possible without increasing the displacement it was necessary to significantly reduce the headroom of the hangar. The later three vessels, Indomitable, Indefatigable and Implacable, had re-designed two-level hangars which enabled them to carry larger air groups than the original design. The size of the air wings was also increased by using outriggers and deck parks. The original design was for 36 aircraft, but eventually the vessels operated with a complement of up to 72 aircraft. However, the smaller overhead height of the hangars (16 ft (4.88 m) in the upper hangars and 14 ft (4.27 m) in the later ships with lower hangars) compared unfavourably to the 17 feet 3 inches (5.3 m) of the Essex class, 17 ft 6 inches (5.38 m) in Enterprise and 20 ft (6.10 m) in Saratoga. This restricted operations with larger aircraft designs, particularly post-war.
This armour scheme was designed to withstand 1,000 pound bombs (and heavier bombs which struck at an angle); in the ETO and MTO it was likely that the carriers would operate within the range of shore-based aircraft, which could carry heavier bombs than their carrier-based equivalents. The flight deck had an armoured thickness of 3 inches, closed by 4.5-inch sides and bulkheads. There were 3-inch strakes on either side extending from the box sides to the top edge of the main side belt, which was of 4.5 inches. The main belt protected the machinery, petrol stowage, magazines and aerial weapon stores. The lifts were placed outside the hangar, at either end, with access through sliding armoured doors in the end bulkheads.
Later in the war it was found that bombs which penetrated and detonated inside the armoured hangar could cause structural deformation, as the latter was an integral part of the ship's structure.
Pre-war doctrine held that the ship's own firepower, rather than its aircraft, were to be relied upon for protection, since in the absence of radar, fighters were unlikely to intercept incoming attackers before they could release their weapons. Accordingly, the Illustrious class was given an extremely heavy Anti-Aircraft armament. The armament was similar to Ark Royal with twin 4.5 inch turrets (in a new "between-decks" or countersunk design) arranged on the points of a quadrant. The guns were mounted sufficiently high so that they could fire across the decks; de-fuelled aircraft would be stowed in the hangar for protection during aerial attack. The Illustrious Class were fitted with four HACS controlled High Angle Director Towers, for fire control of her 4.5" guns.

Bottom line is that without armour scheme, you might get another 10 a/c per carrier. Build to the later Indomitable design, and you might get 1 less carrier and a capacity 20 more a/c across the class

3) Build to the new concepts embodied in the slightly later Unicorn. At 16000 tons, you get 6 carriers instead of 4 with a carrying capacity of 35 instead of a design capacity of 36 (but practical of 53). The air capacity is near as dammit the same, but againwe are at the conundrum of hull numbers versus design strength. Hard to know which strategy is better, but coming from a background of the post war light fleet carriers that came from the unicorn, I tend to favour the unicorn option.

Interesting thought to swap Yorktowns for Soryus, I don't see how that could have really happened unless we're just doing a total what if scenario. I believe the USN already knew that they wanted larger fleet carriers, that's why they built the three Yorktowns, with the spare 15k odd tons left over they built the Wasp, roughly the same size as Soryu and she was no bargain. Some of her problems may have been design flaws but she was only brought to the Pacific (read hotter war zone for CV's) after the early losses, and didn't last long then.

Wasp would be the equivalent of what you're proposing and I'm not sure I see the USN following that path, after Lexington/Saratoga and the Ranger experiment, I don't see the USN going smaller. The Wasp wasn't a Yorktown, 5 grand lighter and 3 knots slower with less than optimal design features (like no armor) although it could be called a modified Yorktown I suppose.

As I said, interesting but after the Fleet Problems of the twenties and thirties, I just don't see the USN going with smaller, less capable flat tops.

The nearest "real life" equivalent" might be to assume repeats of the Wasp, with a couple of thousand tons of displacement added, to be used for whatever purpose might be most appropriate.

Point i was making isnt that the USN would be that much better off, but that the IJN would be much worse off if they tried to replace their Soryus with something equivalent to the Yorktowns. They just dont have the tonnage under the treaties to even consider that .

Some will say that the Japanese were not bound by treaties after 1936, since they did not sign the 2nd london naval treaty. It still greatly influenced their behaviour because of the various escalator clauses contained in the treaty. if Japan was found to be in breach of the treaty, the treaty powers could invoke their escalator clauses. At the time this applied mostly to battleship armament, but if the Japanese broke other parts of the treaty, such as the limits on class tonnages, the other powers could be released from the limits applying to them as well.

This is the main reason the Japanese became so secretive in their naval builds from 1935-41. They wanted to avoid other powers simply increasing their builds and thereby cancel any advantage the Japanese might derive from cheating the system. The Japanese only had enough tonnage to build the two Hiryu/Soryu class. They didnt embark on outright carrier construction until after 1939, with the Shokaku and Zuikaku. Soryu and Hiryu were the last true carriers they could build and not be seen to breach the treaty. Thus they could keep the allies restricted to the treaty whilst doing their best to circumvent it themselves. They did this with their merchant conversion carriers Hiyo and Junyo, which were built as merchant vessels, but designed for easy conversion from their initial design. They did similar expedients with the Shoho class, the Ryuho, the Chitose Chiyoda, Nishin and Mizuho. All of these were built as auxiliaries, but with an easy conversion to carriers always in mind. The US also considered this approach but rejected it until the quick CVE lash ups were insisted upon by Roosevelt.

As carriers these Japanese conversions were not as good as the USN purpose built types, but it also meant the japanese could at least count on parity, and not be swamped for a while at least. If they had not suffered a number of defeats in 1942, it might have worked.

As a generalisation the USN considered these socalled "trade protection carriers" and mercantile conversions, but rejected them as unnecessary. That should not, in the longer term, be seen as a smart design choice. After 1943, the issue became largely academic as vast numbers of Essex class became available. They still were limited in numbers of these big carriers until the latter part of 1944, and had to make do with their own conversions for a while, the Independance Class. They also embarked on their CVE conversions, which by the early part of 1944 were playing a decisive role, although not in pure fleet work (for the USN)

The British convened a committee in 1942 to examine the carrier needs. Though they already had plans to build super carriers, mostly for prestige reasons, the RN was more in favour of the "light fleet carrier" concept, and in this they were absolutely on the money. These trade protection carriers found the key issues were still the closed hangar protection system, not armour as such, good endurance and fuel stowage, back up systems for DC, unitised machinery and a sustained fleet speed of about 24 knots. These led to a series of designs that had they been available earlier, might well have been decisive. As it was, these designs proved far more useful to most of the post war navies over the big and unwieldy USN designs. I refer of course to the Colossus, Majestic, and Centaur classes, which completely dominated the post war small navy carrier market post war, and whose design philospophies continue to dominate over the more traditional US types to this day. In the RANs case, post war, we were offered a fully functional Essex, but went for two Majestics instead, one of which was converted to an angled deck carrier whilst building and not retired until 1983. Even then its service was not done. Purchased at scrap prices by the Chinese, they secretly (and unlawfully) removed the entire upper deck and used that for carrier deck landings and take offs until 2004. They painstakingly reverse engineered the steam catapult and intently studied the unitised machinery spaces and compartment segmentation of the ship. That should at least give an idea of just how far ahead of their time these ideas actually were in 1942.

parsifal - Ahh, now I see, I wasn't getting it before, sorry. For what it's worth I agree, well thought out explanation, thanks.

On a ship for ship basis, its pretty clear that the Yorktown is the winner, but there is more than one way to skin a cat. On a ton for ton basis, I think Id argue the Soryus, and on a man for man probably the Illustrious

Replace the Illustrious with the Ark Royal and then you have a different winner, as the main problem with the Illustrious ie the no of aircraft is increased significantly.

i have to respectfully disagree. you do get a significantly increased air capacity, and Ark Royal was a good ship, but she suffered some damning design flaws that the RN was never keen to publicise. Quoting my post 123...."The Bucknill Committee, which had been set up to investigate the loss of the Ark Royal produced a report that concluded the lack of backup power sources was a major design failure, which contributed to the loss: Ark Royal depended on electricity for much of her operation, and once the boilers and steam dynamos were knocked out, the loss of power made damage control difficult. Moreover the strakes protecting engine spaces were not of sufficient height to protect the engine spaces from uncontrolled flooding and the two design issues fed off each other in a vicious way. The committee recommended the design of the bulkheads and boiler intakes be improved to decrease the risk of widespread flooding in boiler rooms and machine spaces, while the uninterrupted boiler room flat was criticised. The design flaws were rectified in the Illustrious and later the implacable classes, but these solutions took time"

moreover, the limited air capacity of the illustrious was as much about the RN operations philiosphy as it was the limits of the design. illustrious had 83% the hangar space of the yorktown, and unlike the USN, the RN at the beginning of the war refused to accept large permanent deck parks in the same way that the USN did. Fully 23 of the quoted 75 a/c capacity of the yorktowns was due to that deck park. The illustrious, once she also took on a deck park, had a real air capacity of 57 and not the 36 she is often quoted as capable of. We will never know about the max carrying capacity of the ark royal, but i imagine her smaller deck area might limit her to about 80 a/c with a deck park

I certainly agree that the report did make those statements (what else could I say) but the changes were for the most part easy to make. Back up generators were more widely issued to the fleet and I do loath the memories I have of lugging back up diesel powered pumps up and down the ship during damage control exercises.
I don't know the changes needed to increase the height of the strakes but its also worth remembering that poor leadership was a major factor, indeed the primary factor in the loss of the Ark Royal.
The changes were probably not included in the design of the Illustrious as she would have been too far down the design build path by the time the report came out.
When war broke out the Ark Royal although not perfect had first class AA defences, good protection and an aircraft establishment few carriers could match. I have always believed that a fine tuning of the Ark Royal design and a mass production of that design would have resulted in a better earlier carrier fleet and probably for less cost, that the Illustrious and associated classes.

A great website about RN armoured aircraft carriers and their aircraft:

Home

The RN must have known about some of the flaws in the Arks when they were designing the Illustrious. What would an Illustrious look like if she had been designed with aircraft capacity rather than armour as the main defence iirc 1,000 tons of flight deck armour was fitted plus all the extra steel needed for the structure to take the weight. If we say 4,000 tons went to the defence how much length, beam and flight deck height above the waterline can you get without all that weight high up and an extra 4,000 tons to play with in the hull.

First of all why would the RN be aware of the flaws in the Ark Royal, she hadn't been tested in combat so the flaws wouldn't have been known. As to what the Illustrious would look like who knows.
if the RN went for the armoured deck then she would have looked like the Implacable which had a second hanger deck.
If they didn't and went for capacity, then they would have looked a lot like the Ark Royal with a better lift layout and a slightly wider deck

The design flaws of the Ark Royal were not known at the time the illustrious was built, though there were misgivings abiout the machinery arrangements , lack of horizontal protection, limited deck area and the known inability of the vertical strakes around the engine room to stem uncontrolled flooding.

The Illustrious class were meant to be repeat Ark Royals, but pretty quickly the RN reconsidered this option. The RN had such limited crew numbers for the Fleet Air Arm that it made no sense to repeat the Ark Royal. They also wanted a carrier that could withstand up to a 1000 lb bomb dropped from below 10000 feet (might be 5000), and this required a much heavier armouring scheme, basically reducing the number of decks by 1 and limiting the headroom of the hangar severely. The AA suite was the primary air defence weapon and was redesigned in the Illustrious class.

Whilst undergoing this redesign process the Illustrious were modified to adopt better machinery layouts and address the flood vulnerability issues. More tonnage could be devoted to damage control back up systems, so the Illustrious, despite suffering catastrophic damage on a much greater scale than that suffered by the Ark, was able to keep steaming and able to fight the fires that nearly sank her. Illustrious class design was in fact a response to the expected or anticipated flaws of the Ark Royal, coupled with a realistic appraisal about the slow rate the FAA would expand 1938-42.

My understanding is a little different. Once the decision was taken that the new carriers had t withstand a 1000lb bomb any thought of the Illustrious being a follow on from the Ark Royal was discarded, we were automatically in for a totally different design.
No one could deny that the Ark Royal had for its time an exceptional AA defence, but the demand for an overwhelming priority for the AA defence led to the extreme demand that the 4.5in guns could fire across the deck, hence the raised gun turrets. I believe this was the only major difference in the AA protection
Even before completion the significantly reduced aircraft capacity of the Illustrious was subject to criticism so the fourth ship had a second hanger deck that could only be half the length of the ship. The final pair having two full hanger decks.

From this my take is that the Illustrious with one hanger deck was a mistake. The RN moving as fast as it could without disrupting production to increase the aircraft capability back to that carried in the Ark Royal.

So when comparing the immediate pre war carriers the Ark Royal was in my mind a better balanced design than the Illustrious.

The big advantage about just churning out repeat Ark Royals in my opinion is that they would have been available far sooner than the Illustrious. Probably reasonable to assume a 3 carrier delivery 1939-40, instead of the 4 carrier delivery (although 6 were originally planned) hard to argue that the later Implacables were any sort of variation of the Illustruious. Its worth noting this earlier delivery as a tangible advantage to going down the path of repeat Ark Royals, but only three in the short term is really limiting your egg baskets in my opinion. In my book the following Implacables were so different from Illustrious as to be more correctly thought of as a new design

It is true that the illustrious class raised misgivings about their limited air capacity from the start, but then again the RN felt no urgency to adopt US methods of a permanent deck park until the very end of 1943. Overnight this raised the carrying capacity for all 4 of the class to a respectable 57 a/c. Then something strange happened. Indomitable, the last of the class and theoretically designed so as to accommodate 45 a/c in its redesigned hangars, had trouble accepting the increased CAGs of 57 being operated by the others and for the '45 deployment dropped her capacity dropped back to 48 a/c. The revised internal layout had increased hangar space, but at the cost of eating into the machinery spaces, such that her engines were limited to a ten year life span because of excessive overheating. She was refitted 1948-51 to try and address this, but it was useless, and in 1955 she was scrapped, just two years behind the Formidable, which was scrapped in 1953 because of her poor condition.

The two remaining carriers in the class were Illustrious and Victorious. Illustrious went through two refits and served as a training carrier until 1957. Despite having been heavily damaged in 1941 (something she never fully recovered from), the superiority of the design over the later designs is that despite obvious limitations brought about by her wartime service, she was retained longer than either of the two Implacables, both of which were gone by 1955. Their hangars were far too constricted and the machinery spaces so poorly designed as to preclude their effective postwar use, and had they been subjected to really rigorous service, this would have been shown during wartime service.

Victorious was the only wartime fleet carrier in the UK to be considered as having sufficiently good conditions and inherent design advantages to warrant full modernisation. Like most of these wartime completions, modification to angled deck, redesign of the engine spaces and modernisation of the defensive systems meant it took over 8 years to complete the modernisation, but at least her design was good enough in the first place to warrant that effort. The so-called "better" Implacables were not, and really were of such poor design as to preclude any attempt to re-use them

What the RN really needed were bigger dry docks so they could have built longer carriers. A longer single hanger Illustrious would be a better ship than an Implacable which as Parsifal says were a quart in a pint pot. The Yorktowns were 60 feet longer waterline and an extra 60 foot longer in an Illustrious type hangar is about 3,000 sq feet extra still not as big as a Yorktown (iirc 33,000sq ft) but probably give space for 50 aircraft struck below if the Yorktown can fit 60.

An extra 60 feet also possibly allow another lift or 2 of a bigger size plus the engine rooms and accomodation get some much needed elbow room.