Japanese aircraft carrier Ryūjō

Ryūjō (Japanese: 龍驤 "prancing dragon") was a light aircraft carrier of the Imperial Japanese Navy. She was laid down by Mitsubishi at Yokohama in 1929, launched in 1931 and commissioned on 9 May 1933. Her final design resulted in a top-heavy unstable vessel and within a year she was back at Kure Naval Yard for modification. With her stability sufficiently improved, Ryūjō was returned to service and employed in operations during the Second Sino-Japanese War. Early on in the Second World War, she participated in subsidiary operations in the Philippines, Java Sea, Bay of Bengal and the Aleutian Islands before being sunk by American carrier aircraft at the Battle of the Eastern Solomons on 24 August 1942. {| class="toc" id="toc"

Contents
[hide] *1 Design
 * 1.1 Hull
 * 1.2 Machinery
 * 1.3 Flight Deck & Hangars
 * 1.4 Armament
 * 2 Operational history
 * 3 Sinking
 * 4 References
 * 5 Bibliography
 * 6 External links
 * }

Design
Ryūjō was originally planned as a seaplane tender to replace the aging  Wakamiya , but this was later changed to a conventional aircraft carrier of around 9,800-ton standard displacement. Her light displacement was intended to exploit a loophole in the Washington Naval Treaty of 1922. Under the Treaty, Japan's total tonnage of aircraft carriers was limited to 81,000-tons, but aircraft carriers under 10,000-ton standard displacement were not regarded as "aircraft carriers".

While Ryūjō was under construction in 1930, the London Naval Treaty finally closed the above mentioned loophole in the Washington Naval Treaty; consequently, Ryūjō was the only light aircraft carrier of her type to be completed by Japan.

Hull
Because of the need to keep Ryūjō's weight under 10,000 tons, no armor could be included, though some protective plating was added to the outer hull where the machinery and magazine spaces were located, thereby providing a modest degree of defense against horizontal fire. She was also designed with only a single hangar, which would have left her with an extremely low profile (there being just 4.6 m (15 ft) of freeboard amidships and 3 m (9.8 ft) aft).[1] Between the time the carrier was laid down in 1929 and launched in 1931, however, the Navy doubled her aircraft stowage requirement to 48 in order to give her a more useful air group. This necessitated the addition of a second hangar atop the first, raising freeboard to 15 m (49 ft). Coupled with the vessel's light displacement and narrow beam, the end result produced an unacceptable degree of instability in rough seas, a common flaw amongst many treaty-circumventing Japanese warships of her generation.[1] Bow view of Ryūjō, taken in 1933 and emphasizing her top-heavy appearance.Even the addition of Sperry active stabilizers failed to compensate for the inherent instability of the new design and in 1934 Ryūjō was taken in hand for extensive modification. Changes included strengthening of the keel, the addition of enlarged bulges to either side of the hull and the removal of two twin 127mm AA gun mountings to reduce her top weight. In 1940 the ship's general seakeeping was improved by raising her forecastle 3.1 m (10 ft) (one deck higher) which reduced the tendency of her bows to dig water in heavier seas.[1]

Machinery
Ryūjō's machinery consisted of two sets of geared turbines (similar to those of the Takao-class heavy cruisers) connected to two shafts. Six oil-fired boilers provided steam power. Total horsepower generated was 65,000 shp (48,000 kW) giving the carrier a top speed of 29 knots (54 km/h; 33 mph) during trials. She carried approximately 2900 tons of oil fuel enabling her to cruise 10,000 nautical miles (19,000 km; 12,000 mi) at 14 knots (26 km/h; 16 mph). The boiler uptakes were trunked to the ship's starboard side, approximately amidships, and exhausted horizontally just below flight deck level through two small downward-curving funnels, the ends of which were supported by heavy bracing. This arrangement served to keep the flight deck clear of smoke and fumes.[2]

Flight Deck & Hangars
Ryūjō was a flush-deck carrier. In place of an island structure, her navigating and control bridge was located just under the forward lip of the flight deck in a long glassed-in "greenhouse". The hangar box was set back 23 m (75 ft) from the ship's stem, giving Ryūjō a distinctive open bow. Her 156 m (512 ft) flight deck extended well beyond the aft end of the hangars and was supported by twin steel pillars. Six transverse arrester wires were installed on the flight deck and later modernized in 1936 to stop a 6,000 kg (13,000 lb) aircraft.[1]

Two elevators serviced the upper and lower hangars and connected them with the flight deck. The forward platform was the largest at 11 m (36 ft) long by 15.7 m (52 ft) wide. The aft platform was much narrower, just 7 m (23 ft) and, by 1940, as larger and more modern carrier aircraft entered service, was only capable of fitting a Nakajima Kate torpedo plane if spotted at an angle with wings folded. This effectively made Ryūjō a single-elevator carrier and considerably hindered her ability to rapidly transfer aircraft in and out of the hangars for rearming and refueling during combat operations. As a result, though she had stowage for 48 aircraft, her normal operating capacity was closer to 37.[1]

Armament
As completed, Ryūjō's primary AA armament comprised six twin 127 mm (5.0 in) dual-purpose guns mounted on projecting sponsons, three on either side of the carrier's hull. In 1934, two of these mountings were removed, resulting in a savings of approximately 60 t (60,000 kg) top-weight and improving the ship's overall stability. Two twin 25 mm (0.98 in) AA guns were added at a later date as well as twelve 13.2 mm (0.52 in) Hotchkiss machine-guns. The light machine-guns were replaced in 1942 with six triple-mount 25 mm (0.98 in) AA guns.[1]

Operational history
In August to December 1937, Ryūjō supported land operations of the Japanese Army in China as flagship of Carrier Division 1. Her aircraft complement consisted of 12 Nakajima A4N fighters and 15 Aichi D1A dive bombers. After her less than satisfactory performance there, Ryūjō received extensive reconstruction.

In World War II, Ryūjō was commanded by Captain Kato Tadao and was the flagship of Carrier Division 4. The presence of large fleet carriers meant that she was initially assigned to secondary tasks. Her reconstruction proved successful and the performance of her air group, as well as the ship herself in high seas, was satisfactory.

In December 1941 Ryūjō supported the invasion of the Philippines, providing air cover for the landings at Davao on 20 December at Jolo on 25 December. Her aircraft complement consisted of 22 Mitsubishi A6M Zero fighters and 16 Aichi D3A "Val" dive bombers. In January 1942 she supported the conquest of Malaya and in February 1942 she attacked American-British-Dutch-Australian forces around Java. On 1 March 1942 she took part in the Battle of the Java Sea, assisting in the sinking of USS Pope (DD-225). In the same month, she operated against the Andaman Islands and along the coast of Burma.

In early April, as part of the Indian Ocean raid, Ryūjō attacked shipping in the Bay of Bengal. Together with the cruisers  Chōkai ,  Kumano ,  Suzuya ,  Mogami ,  Mikuma ,  Yura , and four destroyers, she sank 23 merchant ships. On 6 April she launched air strikes against Cocanada and Vizagapatam in India.

In June 1942 Ryūjō was part of the Northern Force that attacked the Aleutian Islands. Ryūjō's planes struck Dutch Harbor on Unalaska Island on 3 June and 4 June 1942. During this operation, one of the Zero fighters from the Ryūjō, flown by Petty Officer Tadahito Koga, crash landed on the island of Akutan. Koga was killed in the crash due to a broken neck, but the aircraft remained largely intact. The aircraft, later dubbed the Akutan Zero, was the first intact Zero fighter to fall into the hands of U.S. military intelligence.

Sinking
The disabled Ryujo (just right of center) being bombed on 24 August 1942, from high level by B-17 bombers. The destroyer Amatsukaze (center bottom) is moving away from Ryujo at full speed and Tokitsukaze (faintly visible, center right) is backing away from the bow of Ryujo in order to evade the B-17's falling bombs.The sinking of four of Japan's six fleet carriers in the Battle of Midway made Ryūjō much more important to the Japanese Navy. In August 1942 she was reassigned to Carrier Division 2, and with  Shōkaku  and  Zuikaku  she was dispatched to the Solomon Islands. Ryūjō's role in the operation was to support a convoy of transports that were to reinforce and resupply Japanese troops on Guadalcanal, and to attack the Allied air base at Henderson Field. This force was commanded by Rear Admiral Chuichi Hara in the cruiser  Tone . Meanwhile, the fleet carriers operated against the U.S. Navy's aircraft carriers. This operation resulted in the Battle of the Eastern Solomons.[3]

On 24 August 1942, Ryūjō, escorted by the cruiser  Tone  and the destroyers  Amatsukaze  and  Tokitsukaze , launched a strike against Henderson Field on Guadalcanal from a position 161 km (100.0 mi) north of Tulagi. The first wave, launched at 12:20, consisted of six Nakajima Kate attack planes armed with general-purpose bombs and an escort of six Mitsubishi Zero fighters. A second wave of nine Zero fighters was launched at 1248. By 14:00, Rear Admiral Hara's airmen radioed they had successfully bombed the airfield, losing two fighters and three bombers to enemy fire (one other bomber crash-landed on Ndai Island).[4]

Early in the afternoon, the task force was approached by two B-17 bombers, although these aircraft were chased off by anti-aircraft fire and the launch of six Zero fighters. At approximately 15:50, while beginning launching operations, she was attacked by twenty-nine dive bombers and five torpedo bombers from the USS Saratoga (CV-3), and was hit by four bombs (sources differ as to how many) and one torpedo. The torpedo hit flooded the starboard engine room and jammed the ship's rudder, causing Ryūjō to turn in circles and begin listing to starboard. She was soon on fire along her entire length and her engines eventually stopped.[5]

As Amatsukaze went alongside to assist in damage control, two B-17 bombers emerged from the clouds and made an unsuccessful attack against Ryūjō. Though her fires had been brought under control, efforts to contain flooding caused by the torpedo hit proved fruitless and the order to abandon ship was given. By 20:00 the carrier capsized and sank along with approximately 120 of her crew and four aircraft (two Kates and two Zeros) still on board in the hangars. Her remaining survivors, including Captain Kato, had been taken off by her escorts.[5] [6]