Overall external dimensions of the ships-in-class include an overall length of 178 meters with a beam measuring 25.8 meters and a draught of 17 meters. Displacement reaches 8,900 tons under standard loads and this balloons to 14,000 tons under full combat loads.
The aft surface section of the ship is reserved for a pair of medium-lift navy/marine helicopters though no elevator deck or hangar facilities are installed. This restricts the helicopters to the surface and the units need be secured during transport as no shelter is afforded them. All work on the helos must also be done topside. Typically, the spaces are reserved for 2 x Boeing CH-47 "Chinook" medium-lift helicopters of the Japanese Navy or Marine service - though work is ongoing to refit the type to accept the newer Bell-Boeing MV-22 "Osprey" tilt-rotor transports.
Ahead of the island superstructure is a single deck elevator giving access to the lower decks which house vehicles, infantry, and landing craft. At the stern face of the hull is a large loading/unloading ramp used in releasing vehicles and watercraft into the shallows. The warship can house and launch two fully-laden Landing Craft Air Cushion (LCAC) amphibious hovercraft vessels which can help to reinforce Japanese positions by supplying up to ten Main Battle Tanks (MBTs) and up to 1,000 troops.
Installed power includes 2 x Mitsui 16V42M-A marine diesels developing 26,000 horsepower to 2 x shafts. A single bow thruster is used for fine-tuned adjustments. Under full throttle, the vessel can make 22 knots in ideal conditions.
The three ships making up the Osumi-class are JDS Osumi (LST-4001), JSD Shimokita (LST-4002), and JDS Kunisaki (LST-4003). The former pair were constructed at the ship yard at Mitui, Tamano while the latter was completed at Hitachi, Maizuru - this from 1995 until 2000. All are currently assigned to Landing Division 1 at the important (and storied) Japanese Naval port at Kure. The lead ship, JDS Osumi, saw her keel laid down on December 6th, 1995. She was launched for trials on November 18th, 1996, and was formally commissioned for service on March 11th, 1998. All ships are in service as of this writing (2018).
To date (2018), the ships of the class were called-to-action in recovery and humanitarian efforts following the devastating 2011 Tohoku earthquake and subsequent tsunami which claimed nearly 16,000 deaths, injured over 6,150, and caused over 2,500 to go unaccounted. To improve upon the amphibious assault doctrine amidst loosening constitutional restrictions, the JMSDF has invested in the Hyuga-class helicopter carriers (detailed elsewhere on this site) as well as inquired on the purchase of a dedicated amphibious assault ship from the United States, most likely a Wasp-class type. All this is no doubt centered on deterring, or countering, any additional moves by the Chinese across disputed waters and islands in the region.
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