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The ''America''-class amphibious assault ships (formerly the ''LHA(R)'' class) of the U.S. Navy are designed to put ashore a Marine Expeditionary Unit using helicopters and MV-22B Osprey V/STOL transport aircraft, supported by AV-8B Harrier II or F-35 Lightning II V/STOL aircraft and various attack helicopters. The first of these warships was commissioned by the U.S. Navy in 2014 to replace the of the ''Tarawa''-class amphibious assault ships; as many as eleven will be built.〔 The design of the ''America'' class is based on that of the , the last ship of the ''Wasp'' class, but the "Flight 0" ships of the ''America'' class will not have well decks, and they have smaller on-board hospitals in order to give more space for aviation uses. Although they only carry helicopters and V/STOL aircraft, USS ''America'', with a displacement of about 45,000 long tons, is similar in size to the French fixed wing aircraft carrier Charles de Gaulle and the Indian Vikramaditya. Also, while more than 120 ft shorter, they are of comparable displacement to the former US Navy Midway-class aircraft carriers. The ''America'' can be used as a small aircraft carrier with a squadron of jet fighters plus several multipurpose helicopters, such as the SH-60 Seahawk. It can carry about 20 AV-8Bs, F-35Bs, or a mixture of the two, but the future ships of this class, starting with LHA-8, will have smaller aircraft hangars to leave room for larger amphibious warfare well decks.〔Freedberg, Sydney J. Jr. ("Navy's Newest, LHA-6, A Dead End For Amphibious Ships?" ) 3 October 2012.〕 ==Design== The design of USS ''America'' is based on the , herself an improved version of the ''Wasp''-class amphibious assault ships with gas turbine power. About 45 percent of the "Flight 0" design of this class is based on that of the ''Makin Island'', but with her well deck omitted to allow more room for aircraft, their spare parts and weapons, and their fuel. Note that the gas turbines of the ''Makin Island'', the ''America'', and her possible successors burn the same kind of fuel (JP-5) that is burned in the gas turbines of their helicopters, the jet engines of their AV-8B Harrier and MV-22 Osprey fixed wing aircraft and, in future ships, the gas turbines of the Landing Craft Air Cushions (LCACs) that they could carry in their well decks. All of this greatly simplifies the storage, distribution, and use of the fuels for these craft. The typical aircraft complement for the first two vessels is expected to be 12 MV-22B Osprey transports, six STOVL F-35B Lightning II multirole jet aircraft, four CH-53K heavy transport helicopters, seven AH-1Z/UH-1Y attack helicopters, and two Navy MH-60S ''Knighthawks'' for air-sea rescue. The exact make-up of the ship's aircraft complements will vary according to her mission. She can carry about 20 AV-8Bs or F-35Bs, and two MH-60Ses〔 to serve as a small aircraft carrier as demonstrated by Landing Helicopter Dock (LHD) operations in Operation Iraqi Freedom. The U.S. Marine Corps is now more concerned about anti-ship missile attacks from fast attack craft, hence the Commandant of the Marine Corps wants to keep the amphibious ships farther offshore. In that case, Marines would be sent ashore in long-ranged MV-22 V/STOL aircraft. The MV-22 is significantly larger than the largest helicopters used by the U.S. Marine Corps and the U.S. Navy in the past. Hence, the ''America'' has twice the displacement of the much older ''Iwo Jima''-class amphibious assault ships (all of which are now decommissioned).〔 Setting the beam of the ''America'' at 106 feet is dictated by the need for these ships to pass through the Panama Canal. The Congressional Budget Office found that LH(X)-class ships would be more cost-effective if they were built with nuclear power—if the price of oil reached and stayed above $140 per barrel by 2040.〔("The Cost-Effectiveness of Nuclear Power for Navy Surface Ships" ). ''CBO'', May 2011.〕 The ''America''-class amphibious assault ships are engineered with a hybrid-electric propulsion system derived from the one used on the . The ships can use diesel-electric propulsion for slow speeds and use gas-turbines for high speeds. The amphibious ships can utilize the diesel-electric engines when operating close to shores in situations that require lower speeds.〔(Navy to Test Hybrid-Propulsion on Destroyers ) - Defensetech.org, 6 August 2013〕 A modified version of the design of USS ''America'', designated the MPF(F), LHA(R), or T-LHA(R), was proposed for two ships of the Maritime Prepositioning Force (Future).〔(【引用サイトリンク】 title=National Defense Authorization Act for Fiscal Year 2008 )〕 The MPF(F) is the Navy's concept for a "sea base" to support operations ashore starting in about 2025. These two ships would hypothetically be manned by a civilian crew from the Military Sealift Command, and hence not armed with weapons.〔 Funding for the MPF(F) and the LHA(R) was tabled by the Senate Armed Services Committee in the fiscal year 2008 budget.〔 The U.S. Navy now intends to buy more ships of the ''America'' class for its fleet of amphibious warfare ships.〔 The so-called "LHX" was a warship that was proposed in the late 1990s to replace the ''Tarawa''-class ships, but with a dry deck for hovercraft rather than a floodable "well deck". After the year 2000, the LHX, the so-called "Amphibious Assault Ship Future Replacement", was put forward to replace all of the LHDs. The new LHX could be a Flight 2 design of the ''America'' class built with a well deck and a smaller island superstructure, which would give it 20 percent more capacity on the flight deck.〔 This would remove the current restriction on MV-22s to land on spots 5 and 6, and also giving room for four MV-22B, three F-35B Lightning IIs, or three CH-53Ks to use the flight deck. In 2008, the procurement of Flight 2 ships was tentatively planned for 2024,〔 but that might not be practical or affordable by then. In January 2014, the U.S. Navy began taking measures on USS ''America'' in order to reduce damage from excessive heat given off by the F-35B and MV-22 to prolong the life of the flight deck. The F-35B engine gives off much more heat than the previous AV-8B Harrier STOVL fighter and the MV-22 Osprey's heat exhaust has been known to damage flight decks. Plans include 14 different modifications to the ship and limiting the number of flight operations that are conducted off the deck. The U.S. Navy is looking for cost-effective solutions that will not affect the combat effectiveness of the ''America''. Restricting the number of flight operations is not expected to decrease its usefulness as amphibious assault ships are made to support quick assaults, while full-sized aircraft carriers have the mission of conducting sustained air operations. Lessons learned from these measures will be applied to USS ''Tripoli'' LHA-7 and LHA-8 ships under construction, which will allow them to perform "complete unrestricted operations."〔(SNA 2014: Heat From F-35, MV-22 Continue to Plague Big Deck Amphibs ) - News.USNI.org, 15 January 2014〕 Some changes to the ''America'' are as small as putting covers over life rafts and refueling stations and moving antennas.〔(Navy Bringing Well Decks Back to Amphibs ) - DoDBuzz.com, 18 January 2014〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「America-class amphibious assault ship」の詳細全文を読む スポンサード リンク
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