A dock landing ship (also called landing ship, dock or LSD ) is an amphibious warfare ship with a well dock to transport and launch landing craft and amphibious vehicles . Some ships with well decks, such as the Soviet Ivan Rogov class , also have bow doors to enable them to deliver vehicles directly onto a beach (like a tank landing ship ). Modern dock landing ships also operate helicopters.
19-656: Two dock landing ships of the United States Navy have been named USS Tortuga , after the Dry Tortugas , islands off Florida . The first USS Tortuga (LSD-26) was commissioned in 1945, in action during the Korean War and the Vietnam War, and decommissioned in 1970. The second USS Tortuga (LSD-46) was commissioned in 1990 and
38-483: A landing platform dock also has a hangar, and a landing helicopter dock or landing helicopter assault has a full-length flight deck . The LSD ( U.S. Navy hull classification for landing ship, dock) came as a result of a British requirement during the Second World War for a vessel that could carry large landing craft across the seas at speed. The predecessor of all modern LSDs is Shinshū Maru of
57-622: A meridian travels approximately one minute of geographic latitude in one hour. The length of the internationally agreed nautical mile is 1 852 m . The US adopted the international definition in 1954, having previously used the US nautical mile ( 1 853 .248 m ). The UK adopted the international nautical mile definition in 1970, having previously used the UK Admiralty nautical mile ( 6 080 ft or 1 853 .184 m ). (* = approximate values) The speeds of vessels relative to
76-452: A distance in nautical miles on a chart can easily be measured by using dividers and the latitude scales on the sides of the chart. Recent British Admiralty charts have a latitude scale down the middle to make this even easier. Speed is sometimes incorrectly expressed as "knots per hour", which would mean "nautical miles per hour per hour" and thus would refer to acceleration . Prior to 1969, airworthiness standards for civil aircraft in
95-622: A fourth ship of the class—previously in RFA service—is now operated by the Royal Australian Navy . Former U.S. LSDs include the Ashland class , Casa Grande class , Thomaston class , and Anchorage class . Knot (unit) The knot ( / n ɒ t / ) is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.151 mph or 0.514 m/s ). The ISO standard symbol for
114-472: A standard nautical chart using Mercator projection , the horizontal (East–West) scale varies with latitude. On a chart of the North Atlantic, the scale varies by a factor of two from Florida to Greenland. A single graphic scale , of the sort on many maps, would therefore be useless on such a chart. Since the length of a nautical mile, for practical purposes, is equivalent to about a minute of latitude,
133-500: Is 14.40 {\displaystyle 14.40} metres per knot. Although the unit knot does not fit within the SI system, its retention for nautical and aviation use is important because the length of a nautical mile , upon which the knot is based, is closely related to the longitude / latitude geographic coordinate system . As a result, nautical miles and knots are convenient units to use when navigating an aircraft or ship. On
152-401: Is different from Wikidata All set index articles Dock landing ship A ship with a well deck (docking well) can transfer cargo to landing craft in rougher seas far more easily than a ship which has to use cranes or a stern ramp. The U.S. Navy hull classification symbol for a ship with a well deck depends on its facilities for aircraft —a (modern) LSD has a helicopter deck ,
171-609: Is on active service as of 2016. [REDACTED] [REDACTED] List of ships with the same or similar names This article includes a list of ships with the same or similar names. If an internal link for a specific ship led you here, you may wish to change the link to point directly to the intended ship article, if one exists. Retrieved from " https://en.wikipedia.org/w/index.php?title=USS_Tortuga&oldid=1055209664 " Categories : Set index articles on ships United States Navy ship names Hidden categories: Articles with short description Short description
190-707: The Imperial Japanese Army , which could launch her infantry landing craft using an internal rail system and a stern ramp. She entered service in 1935 and saw combat in China and during the initial phase of Japanese offenses during 1942. The first LSD of the Royal Navy came from a design by Sir Roland Baker who had designed the British landing craft tank . It was an answer to the problem of launching small craft rapidly. The landing ship stern chute, which
209-533: The International Civil Aviation Organization list the knot as permitted for temporary use in aviation, but no end date to the temporary period has been agreed as of 2024 . Until the mid-19th century, vessel speed at sea was measured using a chip log . This consisted of a wooden panel, attached by line to a reel, and weighted on one edge to float perpendicularly to the water surface and thus present substantial resistance to
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#1732798276626228-430: The fluids in which they travel (boat speeds and air speeds ) can be measured in knots. If so, for consistency, the speeds of navigational fluids ( ocean currents , tidal streams , river currents and wind speeds ) are also measured in knots. Thus, speed over the ground (SOG; ground speed (GS) in aircraft) and rate of progress towards a distant point (" velocity made good ", VMG) can also be given in knots. Since 1979,
247-541: The sailing master 's dead reckoning and navigation . This method gives a value for the knot of 20 + 1 ⁄ 4 inches per second or 1.85166 kilometres per hour. The difference from the modern definition is less than 0.02%. Derivation of knots spacing: 1 kn = 1852 m/h = 0.5144 m/s {\displaystyle 1~{\textrm {kn}}=1852~{\textrm {m/h}}=0.5144~{\textrm {m/s}}} , so in 28 {\displaystyle 28} seconds that
266-605: The U.S. Navy, two related groups of vessels classified as LSDs are in service as of 2023, the Whidbey Island and Harpers Ferry classes , mainly used to carry hovercraft ( LCACs ), operate helicopters, and carry Marines . The British Royal Fleet Auxiliary (RFA) operates three Bay-class landing ships based on the Dutch-Spanish Enforcer design in support of the Royal Navy's operations, while
285-668: The United States Federal Aviation Regulations specified that distances were to be in statute miles, and speeds in miles per hour. In 1969, these standards were progressively amended to specify that distances were to be in nautical miles, and speeds in knots. The following abbreviations are used to distinguish between various measurements of airspeed : The indicated airspeed is close to the true airspeed only at sea level in standard conditions and at low speeds. At 11 000 m ( 36 000 ft), an indicated airspeed of 300 kn may correspond to
304-464: The knot is kn . The same symbol is preferred by the Institute of Electrical and Electronics Engineers ( IEEE ), while kt is also common, especially in aviation, where it is the form recommended by the International Civil Aviation Organization ( ICAO ). The knot is a non- SI unit. The knot is used in meteorology , and in maritime and air navigation. A vessel travelling at 1 knot along
323-427: The water moving around it. The chip log was cast over the stern of the moving vessel and the line allowed to pay out. Knots tied at a distance of 47 feet 3 inches (14.4018 m ) from each other, passed through a sailor's fingers, while another sailor used a 30-second sand-glass (28-second sand-glass is the currently accepted timing) to time the operation. The knot count would be reported and used in
342-522: Was a converted train ferry ( Train Ferry No. 1 which had been built for British Army use in the First World War ), was an early attempt. Thirteen landing craft mechanized (LCM) could be launched from these ships down the chute. The landing ship gantry was a converted tanker with a crane to transfer its cargo of landing craft from deck to sea—15 LCM in a little over half an hour. The design
361-428: Was developed and built in the U.S. for the U.S. Navy and the Royal Navy. The LSD could carry 36 LCM at 16 knots (30 km/h). It took one and a half hours for the dock to be flooded down and two and half to pump it out. When flooded they could also be used as docks for repairs to small craft. Smaller landing craft could be carried in the hold as could full-tracked and wheeled amphibious assault or support vehicles. In
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