Japanese Seaplane Tender Akitsushima (秋津洲)

Akitsushima (秋津洲) was a seaplane tender of the Imperial Japanese Navy during World War Two.  Her name translates to “Dragonfly Island”, an ancient name for Japan.  She had a length of 376 feet 8 inches (114.8 m) and a beam of 51 feet 10 inches (15.8 m) with a displacement of 5,000 tons. Four Kampon 8,000 HP (6,000 Kw) diesels provided propulsion.  She was well armed for an auxiliary with two twin Type 89 127mm mounts, two twin 25mm cannon, and depth charges for anti-submarine defense.

The IJN operated two types of large four-engine long range flying boats during the Pacific War, the H6K “Mavis” and the H8K “Emily”.  The purpose of the Akitsushima was to provide a logistical base for these flying boats where the aircraft could be serviced and to house and feed their crews.  She carried enough supplies and provisions on board to support combat operations for a detachment of eight flying boats for two weeks.  A Japanese wartime newsreel showing Mavis and Emily operations here:  https://www.youtube.com/watch?v=bygNXMe1dY4

The ship was not intended to launch aircraft herself. Akitsushima was to anchor in a protected harbor and the aircraft were to fly in to join her.  The aircraft would moor to buoys in the harbor, then they would be serviced and crews transferred using the ship’s boats.  If repairs or maintenance was required, the large crane on the fantail could hoist the aircraft aboard.  The aircraft was positioned on a cradle and could be rotated on a turntable as needed.

Akitsushima was commissioned on 29APR42 and shortly thereafter sailed for the Japanese base at Rabaul, New Guinea. She spent the rest of the year supporting operations in the South Pacific, moving between Buka, Rabaul, Kavieng, and the Shortlands.  She was subjected to aerial bombardment on several occasions but did not suffer any significant damage.  In December she sailed for Yokosuka, returning again to Kavieng in JAN43.

On 23JAN43 USS Guardfish (SS 217) torpedoed and sank the Japanese destroyer Hakaze which was escorting Akitsushima at the time. Akitsushima reacted quickly and was able to save the majority of the crew.  She spent the next several months on operations, returning to Japan for drydocking at Yokohama in November.

On 17FEB44 she was at Truk Lagoon when the anchorage was raided by carrier aircraft and surface ships from TF 58 during Operation Hailstone. She received two bomb hits on the 17th and a third on the 18th.  Akitsushima suffered severe damage but remained afloat, forcing her return to drydock in Yokosuka for repairs.  Japanese losses were heavy, losing 40 ships and 250 aircraft.  One of the casualties was the 10,000 ton repair ship Akashi.  This left the Imperial Navy lacking in deployable repair capability so it was decided to add  workshops to Akitsushima during her repairs.  It is likely that her search radar and additional anti-aircraft weapons were also added at this time, bringing her total to four triple, two twin, and three single 25mm AA.  She was to remain in Japanese waters for most of the summer, sailing for the Philippines in September.

On 24SEP44 she was anchored at Coron, Philippines along with several other Japanese vessels when US Navy carrier aircraft from TF 38 raided the anchorage. Akitsushima was not so lucky this time.  She was hit by three bombs which blew out much of her plating under the aircraft cradle.  She quickly rolled onto her side and sank.  The majority of her crew was rescued or swam to shore.  Akitsushima lies on her port side at a depth of 108 feet (33 meters) and is a popular destination for wreck divers.

Akitsushima running sea trials just prior to her commissioning on 18APR42. This remarkably clear picture is perhaps the best wartime photograph of a Japanese Naval vessel to come out of the Pacific War.  Many interesting details can be seen, including the frame structures for the three collapsible deck shelters on the main deck aft of the stack.  Her unique camouflage is displayed to advantage.  Note the small wedge of Dark Green on the port quarter hull side just forward of the deckhouse – a detail missed by many modelers.  Lookouts can be seen studying the photographer using the pedestal binoculars on the bridge wing.
A very poor photograph, but the only known surviving picture which shows Akitsushima with an H6K “Mavis” flying boat. The collapsible deck houses are  in place, and her forward whaleboats are rigged out on their davits.
Another overhead view, this time underway. The 13m motor launches normally stowed on the main deck aft are missing, showing their supports.  Twin 25mm cannon are visible on either side of the forward superstructure.
Akitsushima underway showing her starboard side. The camouflage pattern is similar to the port side, but there are more stripes on the forward part of the hull.
Underway at low speed, the large electric crane on the fantail is unmistakable.
Akitsushima’s Captain Haruo Mayuzumi welcomes Commander 11th Air Fleet Vice Admiral Nishizo Tsukakara aboard at Rabaul. VADM Tsukakara lost his left arm during the fighting in China.  CAPT Mayuzumi would later command the heavy cruiser Tone.  This is a view of the main deck amidships looking forward.  Replacement wing floats are stowed against the bulkhead to the left, above them is a rack for storing wooden shoring.  The twin Type 89 127mm gun is trained to starboard.  Details of the camouflage on the main mast are visible as well.
A Kawasaki H8K1 “Emily” of the 802 Kokutai is hoisted aboard. The electric crane had a capacity of 70,000 lbs (31,820 kg), the loaded weight of an Emily was 53,900 lbs (24,500 kg).  The 802Ku was assigned the “N1” tail prefix from January to August of 1943.  A composite unit, they also operated the A6M2-N “Rufe” floatplane fighter. Note the rather substantial heal of the ship while hoisting the weight of the aircraft.  Details of the aircraft cradle are seen to the left of the picture.  The cylinder covered in canvas in the center is a mooring line reel, battens and canvas were secured over the reel to protect the lines from the elements when not in use.
The Emily is being positioned on the deck cradle facing aft. One of the deck shelters is in place forward, the other two have been struck down.  Sharp-eyed observers can see the funnel now wears a band of black at the top to hide discolorations from the diesel exhaust.
Akitsushima seen from an American aircraft, underway and making for the open sea during Operation Hailstone, 17 – 18 February 1944. Her white false bow wave and wake have been painted over with a dark color in this picture, but her stripes and spots remain.
During the war the Imperial Navy increased the light anti aircraft armament of their warships. Akitsushima received four triple 25mm mounts – three on the aft deckhouse situated around the crane and one more aft of the stack.  Three single mounts were also added, two atop the bridge and one at the extreme bow.  Photographs of her wreck show the original 25mm twins were retained on either side of the superstructure.  This is a picture of one of Akitsushima’s triple mounts.  Wreck divers have placed a 127mm projectile atop the breach of the center gun.
Akitsushima’s crane lies on the seabed where she was sunk at Coron, Philippines. This view shows the internal structure.  The wreck is a popular destination for experienced divers.  Bomb damage allows easy access to the interior and many internal compartments can be explored, provided the diver does not suffer from claustrophobia!

Model construction of the Akitsushima in 1/72 scale here:  https://inchhighguy.wordpress.com/2018/12/09/1-72-akitsushima-%e7%a7%8b%e6%b4%a5%e6%b4%b2-ijn-seaplane-tender-scratchbuild-part-i/