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Landing Craft Assault (LCA) was a British Navy landing craft used extensively in World War II. Its primary purpose was to ferry troops from transport ships to attack enemy-held shores. The craft derived from a prototype designed by John I. Thornycroft Ltd. of Woolston, Hampshire, UK. During the war it was manufactured throughout the United Kingdom in places as various as small boatyards and furniture manufacturers. Typically constructed of hardwood planking and selectively clad with armour plate, this shallow-draft, barge-like boat with a crew of four could ferry an infantry platoon of 31, with space to spare for five additional specialist troops, to shore at 7 knots (13 km/h). Men generally entered the boat by walking over a gangplank from the boat deck of a troop transport as the LCA hung from its davits. When loaded, the LCA was lowered into the water. Soldiers exited by the boat's bow ramp. The LCA was the most common British and Commonwealth landing craft of World War II, and the humblest vessel admitted to the books of the Royal Navy on D-Day. Prior to July 1942, these craft were referred to as "Assault Landing Craft" (ALC), but "Landing Craft; Assault" (LCA) was used thereafter to conform with the joint US-UK nomenclature system. The Landing Craft Assault's design's sturdy hull, load capacity, low silhouette, shallow draft, little bow wave, and silenced engines were all assets that benefited the occupants. The extent of its light armour, proof against rifle bullets and shell splinters with similar ballistic power recommended the LCA. Also, many a Tommy and GI looked favourably upon the luxury of seating in the well for the soldier passengers. Throughout the war in the Atlantic, the Mediterranean, and the Indian Ocean, the LCA was the most likely sea assault transport of British Commandos, United States Army Rangers, and other Special Forces. ==Origins== For centuries the Royal Navy had been landing soldiers on hostile shores, prominent examples being Quebec 1759, Peking 1900, Zeebrugge Raid of 1918, and during the Dardanelles campaign 1915-16.〔Keyes, p. 8.〕 During the inter-war period, however, a combination of recent experience and economic stringency contributed to the delay in producing a modern infantry assault landing craft. The costly failure of the Gallipoli campaign during World War I coupled with the emerging potential of airpower satisfied many in naval and military circles that the age of amphibious operations had come to a close. Still, throughout the 1920s and 1930s, animated discussion in Staff Colleges in Britain and the Indian Army Staff College, Quetta surrounded the strategic potential of the Dardanelles campaign compared with the strategic stalemate of the Western Front. The economic austerity of the worldwide economic depression and the government's adoption of the Ten Year Rule assured that such theoretical talk would not result in the procurement of any equipment. The Munich Agreement of 1938 delayed the inevitable war between Britain and Germany. Munich also led to many changes in Imperial General Staff policies, among which was the acceptance of a proposal in November from the Inter-Service Training and Development Centre (ISTDC) at Fort Cumberland for amphibious assault procedures and for a new type of landing craft. Up to this time the Landing Craft Committee had produced some Motor Landing Craft but had not formed procedures for the assault role of these boats. Now there were specifications for what the new boat must be able to do. It must weigh less than ten long tons, enabling lifting by passenger liner davits. The new craft also had to be built around the load - apart from crew it should carry the thirty-one men of a British Army platoon and five assault engineers or signallers – and be so shallow drafted as to be able to land them, wet only up to their knees, in eighteen inches of water. The troops had to unload quickly. All of these specifications made the LCA personnel carriers; a separate set of requirements were laid down for a vehicle and supplies carrier, although previously the two roles were combined in the Motor Landing Craft. When the ISTDC approached the Director of Naval Construction (DNC) at the Admiralty to design a craft to these specifications the DNC staff were urgently engaged in designing new ships to serve more immediate priorities. Germany's coastline was small and the army would be able to engage the enemy through France. Any urgent need for landing craft was not apparent and ISTDC were told it would take seven months to design what was required. The Board of Trade was therefore approached and asked to suggest a maritime architect. Mr. Fleming of Liverpool was proposed who soon came down to Fort Cumberland and the design of the first LCA began. Following many visits with new drawings and proposals, a plan was ready by November 1938. Approval was sought from the DNC to build a prototype Fleming LCA. A wooden mock-up of the craft had been built in the model shed in Portsmouth dockyard. Fully equipped troops had practiced embarking and disembarking from it, and the design was altered to meet the practical difficulties discovered. The craft to be put into service was to be built of Birmabright, an aluminium alloy. A meeting with the DNC was convened to discuss the results. The Fleming craft had few friends in the DNC, though their criticisms were not specific. They introduced representatives of three shipbuilding firms. The ISTDC were only interested in the Fleming design submitted already, and in trying the craft at a landing on the east coast of England in a matter of months. The DNC accepted this, but asked ISTDC to give their specifications to the firms present so that they could also submit designs. Two of the firms were unable to tender, the third, Messrs Thornycroft, had a proposal on the drawing board in forty-eight hours and ISTDC and the DNC agreed that construction of a prototype should be paid for. The craft might be constructed for experimental purposes on the understanding that the DNC held no responsibility. J. S. White of Cowes built a prototype to the Fleming design. Eight weeks later the craft was doing trials on the Clyde. The craft behaved admirably, though it tended to bury its nose in the sea at full throttle. The din from the engines, however, was tremendous. The metal hull served as an amplifier for the two 120 hp Chrysler engines. Also, there remained the difficulty of applying armour plate to the hull. The sides were not flat, but rounded – a complicated shape for which to roll an armoured skin. The Birmabright alloy used also presented chemical and physical obstacles for the application of hardened steel plates. The Thornycroft design was being built at the same time with a hull of mahogany, the internal arrangements for the troops and exit being generally similar to the mock-up that had been built in Portsmouth Dockyard. The power plant of two 65 hp Ford V8 engines would be much quieter. The two craft were brought down to Langstone Harbour for competitive trials. On its trials on a misty morning, the noise from the two 120 hp Chryslers in the Birmabright alloy hull scared some mothers who hurried their children away from the Isle of Wight beaches as the craft came inshore. The conclusions of the trial left no one in doubt. A platoon of Royal Marines disembarked from the Fleming craft in a quarter of the time taken by the platoon in the Thornycroft, the silhouette of the Fleming craft was less, it created less disturbance when steaming, and it beached better. But, and this was later the deciding factor, the Birmabright craft was so noisy that it meant sacrificing tactical surprise, while it was impossible to mount armour on its sides. The failings of the Thornycroft craft on the other hand could all be overcome. A second prototype from Thornycroft had a double-diagonal mahogany hull with twin engines and those features — low silhouette, quiet engines, little bow wave — which appealed to the Centre's staff in their search for a craft that could make surprise landings. The craft beached satisfactorily, a quality retained in all LCA designs, but the troops took too long to disembark across this prototype's narrow ramp. Armour could easily take the place of the outer mahogany planking, the exit could be lowered, the silhouette could be cut down and the engines could be so silenced that they would not be heard at twenty-five yards. So although the Fleming boat won at the trial, it was the Thornycroft design, duly altered, that became the assault landing craft. A third prototype — ALC No 2 — was therefore built after the DNC had worked with Thornycroft on modifications to the design. 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「Landing Craft Assault」の詳細全文を読む スポンサード リンク
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