Ōsumi-class tank landing ship

300px LST 4003 Kunisaki with the American hospital ship USNS Mercy.
Class overview
Builders:	Mitsui Engineering & Shipbuilding, Tamano Hitachi Zosen, Maizuru
Operators:	Japan Maritime Self-Defense Force
Planned:	3
Completed:	3
Active:	3
General characteristics
Class & type:	Ōsumi class LST
Displacement:	8,900 tons standard 14,000 tons full load
Length:	178 m
Beam:	25.8 m
Draught:	17.0 m
Draft:	6.0 m
Propulsion:	2 × Mitsui 16V42M-A Diesel (2 shafts propulsion, 26,000 bhp.) 1 × bow thruster
Speed:	22 knots (41 km/h)
Complement:	138 crews + (330 troops)
Sensors and processing systems:	OPS-14C air search radar,OPS-28D surface search radar,OPS-20 navigation radar, TACAN
Electronic warfare & decoys:	4 × Mark 36 SRBOC
Armament:	2 × 20 mm Phalanx CIWS,2 × 12.7mm machine gun M2
Aircraft carried:	up to 8 helicopters
Notes:	Two Landing Craft Air Cushion (LCAC) Troops: 330/1000 long/short duration up to 10 main battle tanks

The Ōsumi class LST (おおすみ型輸送艦), is a Japanese amphibious transport dock. The class is also known as the Oosumi class. While the JMSDF describes the Ōsumi class as tank landing ships, they lack the bow doors and beaching capability traditionally associated with LSTs. Functionally, their well deck makes the Ōsumi class more like a dock landing ship (LSD).

As of 2014 there are 3 Ōsumi vessels active with the Japanese Maritime Self-Defence Force.

Design and specifications

File:JDS Ohsumi LST-4001.jpg

Ōsumi (LST-4001), Yokosuka

File:LCAC JMSDF 1.jpg

LCAC

Globalsecurity.org noted in its report on the Ōsumi class that "the program originated in a proposal for a small carrier for defensive and mine countermeasures (MCM) purposes, but this was deemed politically unacceptable, and the project was reworked as an amphibious ship" (actually a “Maritime Operational Transport", see below). Later the JMSDF returned to the idea with helicopter carriers with the larger Hyūga class.

The Ōsumi class increases its carrying capacity with a flat-top open air upper vehicle parking deck, it has an elevated island superstructure offset to starboard giving the appearance of a small aircraft carrier though the helicopter flight deck only comprises the stern of the ship. Small deck elevators accessing the enclosed lower parking deck are for vehicles rather than helicopters, the lower vehicle deck has access to the well deck. There is no enclosed aircraft hangar and any helicopters are tied down topside.

The MSDF developed the Maritime Operational Transport concept as an alternative to what was then (mid-1990s) the politically denied development of an amphibious doctrine. This concept is intended to "deliver JGSDF reinforcement units to an area where an enemy landing is possible or probable, or where an enemy has already landed but that is still under Japanese control. The point is that the landings would be on Japanese territory, not foreign soil. So, in theory, this concept does not involve amphibious assault. The tempo of helicopter transport and the types of helicopters required would be very different from those in an assault amphibious landing."

Osumi gives the JMSDF a modest lift capability, especially in defense of the outer islands. The "Osumi" type of vessel enables the efficient transport of ground troops to strategic locations, and the rescue of civilians in case of large scale natural disaster. The massive hull features armored and opening deck. The rear of hull houses an armored landing deck for two large CH-47 helicopters. The well-dock in the rear of the ship houses the two Landing Craft Air Cushion (LCAC) hovercraft. Forward, there is a 100m deck below the main deck, but the single elevator accessing these spaces is too small for anything but a small helicopter. A VSTOL aircraft or a larger helicopter will simply not fit on the elevator. These spaces below the forward main deck are used primarily for vehicle storage so those fighting and/or armored vehicles can access the well deck.

At least two members of the class, JDS Ōsumi (LST-4001) and JDS Kunisaki (LST-4003), participated in search & rescue and other disaster relief operations in the aftermath of the 2011 Tōhoku earthquake and tsunami.

In January 2014, The Japanese Ministry of Defence (MoD) has confirmed reports that it will perform a major refit on the Japan Maritime Self-Defense Force's (JMSDF's) Osumi-class tank landing ships (LST) to embark MV-22 Ospreys, and Assault Amphibious Vehicles (AAV7s) to improve their amphibious capabilities. The MoD allocated JPY20 million (USD190,000) in its fiscal year 2014 budget to conduct research on the refit.

Ships in the class

Pennant No.	Name	Home port	Unit	Shipyard	Plan	Laid down	Launched	Commissioned
LST 4001	Ōsumi	Kure	Landing Div 1	Mitsui, Tamano	1993	6 December 1995	18 November 1996	11 March 1998
LST 4002	Shimokita	Kure	Landing Div 1	Mitsui, Tamano	1998	30 November 1999	29 November 2000	12 March 2002
LST 4003	Kunisaki	Kure	Landing Div 1	Hitachi, Maizuru	1999	7 September 2000	13 December 2001	26 February 2003

External links

• GlobalSecurity.org - LST Osumi Class