The Case For (Or Against) Armoured Flight Decks in WW2

Warship design and construction, terminology, navigation, hydrodynamics, stability, armor schemes, damage control, etc.
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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby dunmunro » Wed Dec 10, 2014 12:49 am

I've pointed out that USN carriers are not directly comparable to RN carriers because of differences in doctrine, armament and displacement.

The first 3 RN AFD carriers had their hangar sides armoured against 6in gunfire, while the last 3 dropped this requirement in favour of an extra 1/2 length hangar. USN operational doctrine was different from RN doctrine and emphasized operational deck parks, where approximately 1/2 the carrier's aircraft complement was stored. The RN didn't use large deck parks until later in the war when they had access to sufficient numbers of trained aircrew, and aircraft. In 1940/41/42 aircraft and aircrew were in short supply and the RN had trouble filling the hangars of their aircraft carriers and when used, deck parks were small. For example, in late May 1941 Formidable was operating only about 25 aircraft during the Crete battle, because there were no more to be had in the Eastern Med.

An interesting comparison can be made between Illustrious (in the Indian Ocean) and Enterprise (in the Philippine Sea) in late June 1944 when both carriers were operating with large deck parks. Illustrious was operating 57 aircraft and Enterprise 69. To operate such large numbers Illustrious had to carry 24 aircraft as a permanent deck park, while Enterprise had to be blistered to maintain adequate stability while operating with heavier aircraft, increased AA armament and larger crew complements. RN AFD carriers had greater beam and were able to absorb larger increases in weight while maintaining adequate stability, compared to Enterprise, and their lower overall height meant that increased weight at the flight deck level had less detrimental effect than on Enterprise and Essex. Enterprise carried much less armament and armour than Essex, yet the USN conceded that even Essex was not well protected against bombs, even the comparatively light bombs carried by the IJNAF. If we were to increase Enterprise's armament and armour to Essex levels, she would have not been able to carry nearly so many aircraft and would have been much less impressive compared to Illustrious in terms of air complement.

Compare Taiho and Essex, to get an idea of how an RN AFD carrier would compare to Essex if built to the same standard displacement.

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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby aurora » Wed Dec 10, 2014 2:08 am

The ten ships of the Essex class, with the thirteen closely-related Ticonderoga class carriers and the Oriskany, a highly modified sister that was the prototype of the SCB-27 modernization program, constituted the industrial age's largest class of heavy warships. In fact, a total of thirty-two was ordered, with twenty-four entering service between 1942 and 1950. Two more were cancelled while under construction and six others before their keels had been laid down.

The preceding Yorktown class carriers formed the basis from which the Essex class was developed. Intended to carry a larger air group, and unencumbered by the now-obsolete naval limitations treaties, USS Essex was over sixty feet longer, nearly ten feet beamier and more than a third heavier. A longer, wider flight deck and a deck-edge elevator facilitated more efficient aviation operations, enhancing the ships' offensive and defensive air power. Machinery arrangement and armor protection was greatly improved. These features, with the provision of more anti-aircraft guns, gave the ships much-enhanced survivability. In fact, two of them, Franklin and Bunker Hill, came home under their own power after being greviously damaged.

Their construction greatly accelerated, the Essexes and the first few Ticonderogas formed the backbone of the Navy's mobile air striking power during the climactic years of the Pacific War. With their larger contemporaries of the Midway class, these carriers sustained the Navy's air power through the rest of the 1940s, during the Korean War era and beyond. Even after the arrival of the Forrestal-type "super carriers", the Essex class and its sisters remained vital elements of naval strength. By the mid-1950s, fourteen of them of them had been modernized along the lines of Oriskany, with all but one of those being further updated under the SCB-125 program to facilitate operation of high-performance fighters and heavy attack aircraft.
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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby aurora » Wed Dec 10, 2014 11:07 am

The name "Oriskany" was originally assigned to CV-18, but that hull was renamed Wasp when the keel was laid in 1942. CV-34 was laid down on 1 May 1944 by the New York Naval Shipyard (NYNSY), launched on 13 October 1945, and sponsored by Mrs. Clarence Cannon. Construction was suspended on 12 August 1947, when the ship was approximately 85% complete.
Oriskany was redesigned as the prototype for the SCB-27 modernization program. To handle the new generation of carrier aircraft, the "flight deck structure" was "massively reinforced". Stronger elevators, more powerful hydraulic catapults, and new arresting gear were installed. The island structure was rebuilt, the anti-aircraft turrets were removed, and blisters were added to the hull. Blistering the hull (also known as adding bulges) increases the cross-sectional area of a ship's hull, thereby increasing its buoyancy and stability. It also provides increased bunker volume. In the case of the Oriskany, this would have been for aviation fuel.
These features would have been crucial to a ship that had so much topside weight added after its original design. Oriskany was commissioned in the New York Naval Shipyard on 25 September 1950,
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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby aurora » Wed Dec 10, 2014 2:22 pm

POST WAR AFTERMATH
HMS Formidable (R67) was an excellent example of this; while she weathered a severe kamikaze hit in 1945 which cratered her deck armour, the hit caused severe internal structural damage and permanently warped the hull (damage worsened in a postwar aircraft-handling accident wherein a Vought Corsair rolled off a lift and raked the hangar deck with 20mm cannon fire, causing a severe fire); but plans to rebuild her as per Victorious were abandoned due to budget cuts, not structural damage, and she lingered in reserve until 1956 before being towed off to the breakers. The Royal Navy planned to rebuild most of the armoured carriers in the early post war period:

Illustrious suffered a similar battering, especially off of Malta in 1941 when hit by German dive bombers and late in the war was limited to 22 knots (41 km/h) because her centreline shaft was disabled due to accumulated wartime damage; she spent five years as a training and trials carrier (1948–53) and was disposed of in 1954.

Indomitable was completely refit to like-new condition, only to suffer a severe gasoline explosion on board, which caused "considerable structural and electrical damage to the ship". Indomitable was refitted between 1948 and 1950 and served as flagship of the Home Fleet then served a tour of duty in the Mediterranean, where she was damaged by the petrol explosion. She was partially repaired before proceeding under her own power to Queen Elizabeth II's 1953 Coronation Review, before being placed in reserve in 1954. Indomitable was scrapped in 1956.

The explosion which occurred on Indomitable's hangar deck, while severe, would also have caused severe casualties and extensive damage to an Essex-class carrier, several of which returned to service after hangar explosions, primarily due to the USN's considerable financial and material resources.

The postwar Royal Navy could only afford to rebuild Victorious and had to abandon plans to rebuild four other armoured carriers due to cost, and to provide crews to man the postwar built carriers, such as Ark Royal, due to reductions in manpower.
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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby Garyt » Wed Dec 10, 2014 8:32 pm

I'd say an armored flight deck's importance varies by the needs of that nation.

For Instance, it would have been great for Japan if the Ships of Kido Butai would have had armored flight decks from the beginning of the war for a few major reasons:

1) Survivability - Japan did not have a large industrial base, making the carriers more survivable would have been a huge plus.
2) US bombers, Torpedoes vs Bombs - At the start of the war, neither US torpedoes or torpedo bombers were very good. Most damage done to Japanese carriers was by bomb. An armored flight deck makes bombs far far less effective.
3) Japanese lack of radar - Early in the war the Japanese carriers were sitting ducks when performing flight operations without early warning radar. Armored flight decks also solve this problem, as you are not going to have the hangar fires that destroyed early war Japanese carriers.

You will need a few more carriers to get the Job done as the air complements will be smaller, though a deck park could fix that and be less dangerous to a carrier than a if it did not have an armored deck.

With the US, having an armored flight deck was far less important, though it would have prevented the extensive damage a few of the carriers received from kamikazes. Whether this makes sense or not given the loss of air complement I am not sure. Really, as only a few carriers were subject to the intense fire damage received by the Bunker Hill for instance I'd say no. The US had far more resources to draw upon to replace the occasional burnt out carrier.

Lastly, I'd make sure the carriers had open hangars even if they had armored flight decks. It would help a lot in damage control, and prevent a ship from sharing the fate of the Taiho.

The only US carrier that I know of to have a build up of AVGAS and an explosion from the same was the Lexington, and I believe that carrier was of a closed hangar construction.

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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby Steve Crandell » Wed Dec 10, 2014 8:57 pm

I agree.

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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby aurora » Thu Dec 11, 2014 10:24 am

My thanks to Garyt for a well reasoned reply-this thread was deliberately headed as a For or Against a Concept of Design. As Gary said it all boiled down to what a particular navy required to fight and survive it's battles-certainly not what was good for all navies. Japan ,like GB had limited resources to build capital ships-she fortunately chose not to armour the FD of her carriers -the USA did not, but produced certainly 30 excellent Essex Class and survived nonetheless-only two lost from it's OOB.
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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby dunmunro » Thu Dec 11, 2014 5:44 pm

Garyt wrote:I'd say an armored flight deck's importance varies by the needs of that nation.

For Instance, it would have been great for Japan if the Ships of Kido Butai would have had armored flight decks from the beginning of the war for a few major reasons:

1) Survivability - Japan did not have a large industrial base, making the carriers more survivable would have been a huge plus.
2) US bombers, Torpedoes vs Bombs - At the start of the war, neither US torpedoes or torpedo bombers were very good. Most damage done to Japanese carriers was by bomb. An armored flight deck makes bombs far far less effective.
3) Japanese lack of radar - Early in the war the Japanese carriers were sitting ducks when performing flight operations without early warning radar. Armored flight decks also solve this problem, as you are not going to have the hangar fires that destroyed early war Japanese carriers.

You will need a few more carriers to get the Job done as the air complements will be smaller, though a deck park could fix that and be less dangerous to a carrier than a if it did not have an armored deck.

With the US, having an armored flight deck was far less important, though it would have prevented the extensive damage a few of the carriers received from kamikazes. Whether this makes sense or not given the loss of air complement I am not sure. Really, as only a few carriers were subject to the intense fire damage received by the Bunker Hill for instance I'd say no. The US had far more resources to draw upon to replace the occasional burnt out carrier.

Lastly, I'd make sure the carriers had open hangars even if they had armored flight decks. It would help a lot in damage control, and prevent a ship from sharing the fate of the Taiho.

The only US carrier that I know of to have a build up of AVGAS and an explosion from the same was the Lexington, and I believe that carrier was of a closed hangar construction.


Wasp was also lost due to AVGAS explosions; no closed hangars there. Open hangars are a bad idea because they are structurally inefficient and costly in terms of displacement.

Franklin was nearly lost due to her fires and it seems certain that if she replaced Yorktown at Coral Sea or Hornet at Santa Cruz, and suffered her historical 1945 damage, that she would have been lost. Franklin only survived because the USN had total sea control; in a contested sea control environment, as during the 1942 carrier battles, she would have been scuttled

At 27000 tons there is very little difference in air complement between an AFD carrier and a well armed carrier with extensive armour below the flight deck, as in Essex. I imagine that if a nation built enough unarmoured ships with battleship sized guns that that nation could defeat another equipped with traditional battleships, but is this then an argument that armour is worthless? Additionally, an AFD Essex, for example, would have had about the same amount of armour as Essex, but it would have been rearranged, so there's no particular extra cost or difficulty in construction. All post Essex class USN fleet carriers have been built to be "survivable" with AFDs and there's no doubt that with hindsight the USN would have built the Essex class with an AFD.

Even at 23000 tons, an AFD design will not differ greatly in air complement with a non-AFD design equipped with similar AA armament. Again compare Enterprise, post blistering, with Implacable.

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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby aurora » Thu Dec 11, 2014 5:57 pm

Quote dunmunro
"All post Essex class USN fleet carriers have been built to be "survivable" with AFDs and there's no doubt that with hindsight the USN would have built the Essex class with an AFD".

aurora wrote:The name "Oriskany" was an Essex, originally assigned to CV-18, but that hull was renamed Wasp when the keel was laid in 1942. CV-34 was laid down on 1 May 1944 by the New York Naval Shipyard (NYNSY), launched on 13 October 1945, and sponsored by Mrs. Clarence Cannon. Construction was suspended on 12 August 1947, when the ship was approximately 85% complete.
Oriskany was redesigned as the prototype for the SCB-27 modernization program. To handle the new generation of carrier aircraft, the "flight deck structure" was "massively reinforced". Stronger elevators, more powerful hydraulic catapults, and new arresting gear were installed. The island structure was rebuilt, the anti-aircraft turrets were removed, and blisters were added to the hull. Blistering the hull (also known as adding bulges) increases the cross-sectional area of a ship's hull, thereby increasing its buoyancy and stability. It also provides increased bunker volume. In the case of the Oriskany, this would have been for aviation fuel.
These features would have been crucial to a ship that had so much topside weight added after its original design. Oriskany was commissioned in the New York Naval Shipyard on 25 September 1950,

And so it came to pass
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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby Garyt » Thu Dec 11, 2014 7:58 pm

Wasp was also lost due to AVGAS explosions; no closed hangars there.


Franklin was nearly lost due to her fires and it seems certain that if she replaced Yorktown at Coral Sea or Hornet at Santa Cruz, and suffered her historical 1945 damage, that she would have been lost. Franklin only survived because the USN had total sea control; in a contested sea control environment, as during the 1942 carrier battles, she would have been scuttled


I think you misunderstand me here. I am not saying that open hangars make a carrier less vulnerable to fires. What I am saying that open hangars prevent the build up of AVGAS vapor which in turn leads to an explosion well after the attack has occurred. This buildup of vapor can be prevented with proper ventilation. Look at the situation with the Taiho - the Japanese realized the AVGAS vapors were building up, and had even started breaking out portholes to try to ventilate the vessel. We all know what happened next, and this would be a lot less likley to happen with the ventilation of an open hangared carrier. To my knowledge, I am not ware of an open hangared design blowing up from AVGAS fume buildup.

The Wasp was different - raging fires that could not be put out, NOT a build up of vapors detonating well after the attack. the Franklin as well was fire damage, not a build up of AVGAS vapors. The US was better of here for 2 reasons. One, the majority of our carriers were of the open hangar design. Two, we did a better job in AVGAS storage protecting the tanks from being ruptured in the even of damage to the vessel. But one of our few closed hangar carriers, the Lexington also suffered this fate.

Open Hangars also have other benefits. You can warm planes up down below prior to launch. Open hangars also allow ordinance to be jettisoned over the side far easier than a closed hangar design would allow. It also makes the vessel more accessible to ship trying to help the carrier with damage control.

EDIT: I forgot to add that open hangar construction can make a hangar deck bomb blast less damaging. With open hangar construction, the blast is not confined as tightly and is not as damaging. Sure you will blow out some of the garage roller style metal doors that make up the walls of an open hangar, but these are far less confining than solid hangar walls.

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Re: The Case For (Or Against) Armoured Flight Decks in WW2

Postby aurora » Thu Dec 11, 2014 8:52 pm

Quote Garyt

"Open Hangars also have other benefits. You can warm planes up down below prior to launch. Open hangars also allow ordinance to be jettisoned over the side far easier than a closed hangar design would allow. It also makes the vessel more accessible to ship trying to help the carrier with damage control".

---and did this factor create a new doctrine for post WW2 carriers-will research that tomorrow-Off Line
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