Ōsumi-class Tank Landing Ship
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The ''Ōsumi'' class (), is a Japanese tank landing ship. The class is also known as the ''Oosumi'' class. While the
Japan Maritime Self-Defense Force The , abbreviated , also simply known as the Japanese Navy, is the maritime warfare branch of the Japan Self-Defense Forces, tasked with the naval defense of Japan. The JMSDF was formed following the dissolution of the Imperial Japanese Navy ( ...
(JMSDF) describes the ''Ōsumi'' class as tank landing ships (LSTs), they lack the bow doors and beaching capability traditionally associated with LSTs. Functionally, their
well deck In traditional nautical use, well decks were decks lower than decks fore and aft, usually at the main deck level, so that breaks appear in the main deck profile, as opposed to a flush deck profile. The term goes back to the days of sail. Late-2 ...
makes the ''Ōsumi'' class more like a dock landing ship (LSD). As of 2024 there are three ''Ōsumi'' vessels active with the Japanese Maritime Self-Defence Force.


Design and specifications

''
GlobalSecurity.org GlobalSecurity.org is an American independent, nonpartisan, nonprofit organization that serves as a think tank, and research and consultancy group. Focus The site is focused on national and international security issues; military analysis, sys ...
'' 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 . The ''Ōsumi'' class increases its carrying capacity with a flat-top open air upper vehicle parking deck, it has an elevated island
superstructure A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships. Aboard ships and large boats On water craft, the superstruct ...
offset to
starboard Port and starboard are Glossary of nautical terms (M-Z), nautical terms for watercraft and spacecraft, referring respectively to the left and right sides of the vessel, when aboard and facing the Bow (watercraft), bow (front). Vessels with bil ...
giving the appearance of a small aircraft carrier though the helicopter
flight deck The flight deck of an aircraft carrier is the surface on which its aircraft take off and land, essentially a miniature airfield at sea. On smaller naval ships which do not have aviation as a primary mission, the landing area for helicopters ...
only comprises the
stern The stern is the back or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite the bow, the foremost part of a ship. O ...
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 In traditional nautical use, well decks were decks lower than decks fore and aft, usually at the main deck level, so that breaks appear in the main deck profile, as opposed to a flush deck profile. The term goes back to the days of sail. Late-2 ...
. There is no enclosed
aircraft hangar A hangar is a building or structure designed to hold aircraft or spacecraft. Hangars are built of metal, wood, or concrete. The word ''hangar'' comes from Middle French ''hanghart'' ("enclosure near a house"), of Germanic origin, from Frankish ...
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."Yoji Koda, “Jieikan no Genyu Seiryoku to Shyorai Tenbo” he Present and Future of JMSDF Ships in Sekai no Kansen (January 2009), p. 129 The ''Ōsumi''s gives the JMSDF a modest lift capability, especially in defense of the outer islands. The ''Ōsumi'' class enables the transport of ground troops to strategic locations, and the rescue of civilians in case of large scale natural disaster. The hull features armored and opening deck. The rear of hull houses an armored landing deck for two large
CH-47 The Boeing CH-47 Chinook is a tandem-rotor helicopter originally developed by American rotorcraft company Piasecki Helicopter, Vertol and now manufactured by Boeing Defense, Space & Security. The Chinook is a Military transport helicopter, heav ...
helicopters. The well dock in the rear of the ship houses the two Landing Craft Air Cushion (LCAC) hovercraft. Forward, there is a deck below the main deck, but the single elevator accessing these spaces is too small for anything but a small helicopter. A
VSTOL A vertical and/or short take-off and landing (V/STOL) aircraft is an airplane able to take-off or land vertically or on short runways. Vertical takeoff and landing (VTOL) aircraft are a subset of V/STOL craft that do not require runways at al ...
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.


Ships in the class


Service history

At least two members of the class, ''Ōsumi'' and ''Kunisaki'', participated in search and rescue and other disaster relief operations in the aftermath of the
2011 Tōhoku earthquake and tsunami On 11 March 2011, at 14:46:24 Japan Standard Time, JST (05:46:24 UTC), a  9.0–9.1 Submarine earthquake, undersea megathrust earthquake occurred in the Pacific Ocean, east of the Oshika Peninsula of the Tōhoku region. It lasted approx ...
. In January 2014, The Japanese Ministry of Defence (MoD) confirmed reports that it will perform a major refit ''Ōsumi''-class tank landing ships to embark
MV-22 Osprey The Bell Boeing V-22 Osprey is an American multi-use, tiltrotor military transport aircraft, military transport and cargo aircraft with both vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) capabilities. It is designed ...
s, and Assault Amphibious Vehicles (AAV7s) to improve their amphibious capabilities. The MoD allocated JPY20 million (US$190,000) in its fiscal year 2014 budget to conduct research on the refit. In 2014, Japanese Defense Minister Itsunori Onodera expressed the intention of buying one
amphibious assault ship An amphibious assault ship is a type of warship employed to land and support ground forces on enemy territory during an armed conflict. The design evolved from aircraft carriers converted for use as helicopter carriers (which, as a result, ar ...
from the United States to provide more amphibious capabilities than the current ''Ōsumi'' class. A was most likely candidate for acquisition. However, that acquisition did not move forward. In the interim, the ''Ōsumi'' class have been modestly upgraded to be able to land Boeing MV-22s, which began delivery to the Japanese military in 2020, and also to carry the AAV7A1 Amphibious Assault Vehicles.


Gallery

File:LST-4001 おおすみ (8).jpg, JS ''Ōsumi'' File:Japanese Maritime Self Defence Force ship Shimokita MOD 45165997.jpg, JS ''Shimokita'' File:LST-4003 くにさき (1).jpg, JS ''Kunisaki'' File:おおすみ型輸送艦.jpg, Three ''Ōsumi''-class vessels underway in formation in 2008.


References


External links


GlobalSecurity.org - LST Osumi Class

JDS Kunisaki - Humanitarian response to the 2004 Indian Ocean earthquake from JMSDF

JDS Ōsumi - Rescue and aid ,2013 Typhoon Wipha by KyodoNews

JDS Ōsumi - Rescue and aid ,2013 Typhoon Haiyan from JMSDF
{{DEFAULTSORT:Osumi Class Lst Amphibious warfare vessel classes Helicopter carriers Osumi class tank landing ship Ships built in Japan Amphibious warfare vessels of the Japan Maritime Self-Defense Force