South Africa the Republic of South Africa, is the southernmost country in Africa. It is bounded to the south by 2,798 kilometres of coastline of Southern Africa stretching along the South Atlantic and Indian Oceans. South Africa is the largest country in Southern Africa and the 25th-largest country in the world by land area and, with over 57 million people, is the world's 24th-most populous nation, it is the southernmost country on the mainland of the Eastern Hemisphere. About 80 percent of South Africans are of Sub-Saharan African ancestry, divided among a variety of ethnic groups speaking different African languages, nine of which have official status; the remaining population consists of Africa's largest communities of European and multiracial ancestry. South Africa is a multiethnic society encompassing a wide variety of cultures and religions, its pluralistic makeup is reflected in the constitution's recognition of 11 official languages, the fourth highest number in the world. Two of these languages are of European origin: Afrikaans developed from Dutch and serves as the first language of most coloured and white South Africans.
The country is one of the few in Africa never to have had a coup d'état, regular elections have been held for a century. However, the vast majority of black South Africans were not enfranchised until 1994. During the 20th century, the black majority sought to recover its rights from the dominant white minority, with this struggle playing a large role in the country's recent history and politics; the National Party imposed apartheid in 1948. After a long and sometimes violent struggle by the African National Congress and other anti-apartheid activists both inside and outside the country, the repeal of discriminatory laws began in 1990. Since 1994, all ethnic and linguistic groups have held political representation in the country's liberal democracy, which comprises a parliamentary republic and nine provinces. South Africa is referred to as the "rainbow nation" to describe the country's multicultural diversity in the wake of apartheid; the World Bank classifies South Africa as an upper-middle-income economy, a newly industrialised country.
Its economy is the second-largest in Africa, the 34th-largest in the world. In terms of purchasing power parity, South Africa has the seventh-highest per capita income in Africa; however and inequality remain widespread, with about a quarter of the population unemployed and living on less than US$1.25 a day. South Africa has been identified as a middle power in international affairs, maintains significant regional influence; the name "South Africa" is derived from the country's geographic location at the southern tip of Africa. Upon formation, the country was named the Union of South Africa in English, reflecting its origin from the unification of four separate British colonies. Since 1961, the long form name in English has been the "Republic of South Africa". In Dutch, the country was named Republiek van Zuid-Afrika, replaced in 1983 by the Afrikaans Republiek van Suid-Afrika. Since 1994, the Republic has had an official name in each of its 11 official languages. Mzansi, derived from the Xhosa noun umzantsi meaning "south", is a colloquial name for South Africa, while some Pan-Africanist political parties prefer the term "Azania".
South Africa contains human-fossil sites in the world. Archaeologists have recovered extensive fossil remains from a series of caves in Gauteng Province; the area, a UNESCO World Heritage site, has been branded "the Cradle of Humankind". The sites include one of the richest sites for hominin fossils in the world. Other sites include Gondolin Cave Kromdraai, Coopers Cave and Malapa. Raymond Dart identified the first hominin fossil discovered in Africa, the Taung Child in 1924. Further hominin remains have come from the sites of Makapansgat in Limpopo Province and Florisbad in the Free State Province, Border Cave in KwaZulu-Natal Province, Klasies River Mouth in Eastern Cape Province and Pinnacle Point and Die Kelders Cave in Western Cape Province; these finds suggest that various hominid species existed in South Africa from about three million years ago, starting with Australopithecus africanus. There followed species including Australopithecus sediba, Homo ergaster, Homo erectus, Homo rhodesiensis, Homo helmei, Homo naledi and modern humans.
Modern humans have inhabited Southern Africa for at least 170,000 years. Various researchers have located pebble tools within the Vaal River valley. Settlements of Bantu-speaking peoples, who were iron-using agriculturists and herdsmen, were present south of the Limpopo River by the 4th or 5th century CE, they displaced and absorbed the original Khoisan speakers, the Khoikhoi and San peoples. The Bantu moved south; the earliest ironworks in modern-day KwaZulu-Natal Province are believed to date from around 1050. The southernmost group was the Xhosa people, whose language incorporates certain linguistic traits from the earlier Khoisan people; the Xhosa reached the Great Fish River, in today's Eastern Cape Province. As they migrated, these larger Iron Age populations
Sonar is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name "sonar": passive sonar is listening for the sound made by vessels. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may be used in air for robot navigation, SODAR is used for atmospheric investigations; the term sonar is used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from low to high; the study of underwater sound is known as underwater hydroacoustics. The first recorded use of the technique was by Leonardo da Vinci in 1490 who used a tube inserted into the water to detect vessels by ear, it was developed during World War I to counter the growing threat of submarine warfare, with an operational passive sonar system in use by 1918.
Modern active sonar systems use an acoustic transponder to generate a sound wave, reflected back from target objects. Although some animals have used sound for communication and object detection for millions of years, use by humans in the water is recorded by Leonardo da Vinci in 1490: a tube inserted into the water was said to be used to detect vessels by placing an ear to the tube. In the late 19th century an underwater bell was used as an ancillary to lighthouses or light ships to provide warning of hazards; the use of sound to "echo-locate" underwater in the same way as bats use sound for aerial navigation seems to have been prompted by the Titanic disaster of 1912. The world's first patent for an underwater echo-ranging device was filed at the British Patent Office by English meteorologist Lewis Fry Richardson a month after the sinking of the Titanic, a German physicist Alexander Behm obtained a patent for an echo sounder in 1913; the Canadian engineer Reginald Fessenden, while working for the Submarine Signal Company in Boston, built an experimental system beginning in 1912, a system tested in Boston Harbor, in 1914 from the U.
S. Revenue Cutter Miami on the Grand Banks off Newfoundland. In that test, Fessenden echo ranging; the "Fessenden oscillator", operated at about 500 Hz frequency, was unable to determine the bearing of the iceberg due to the 3-metre wavelength and the small dimension of the transducer's radiating face. The ten Montreal-built British H-class submarines launched in 1915 were equipped with Fessenden oscillators. During World War I the need to detect; the British made early use of underwater listening devices called hydrophones, while the French physicist Paul Langevin, working with a Russian immigrant electrical engineer Constantin Chilowsky, worked on the development of active sound devices for detecting submarines in 1915. Although piezoelectric and magnetostrictive transducers superseded the electrostatic transducers they used, this work influenced future designs. Lightweight sound-sensitive plastic film and fibre optics have been used for hydrophones, while Terfenol-D and PMN have been developed for projectors.
In 1916, under the British Board of Invention and Research, Canadian physicist Robert William Boyle took on the active sound detection project with A. B. Wood, producing a prototype for testing in mid-1917; this work, for the Anti-Submarine Division of the British Naval Staff, was undertaken in utmost secrecy, used quartz piezoelectric crystals to produce the world's first practical underwater active sound detection apparatus. To maintain secrecy, no mention of sound experimentation or quartz was made – the word used to describe the early work was changed to "ASD"ics, the quartz material to "ASD"ivite: "ASD" for "Anti-Submarine Division", hence the British acronym ASDIC. In 1939, in response to a question from the Oxford English Dictionary, the Admiralty made up the story that it stood for "Allied Submarine Detection Investigation Committee", this is still believed, though no committee bearing this name has been found in the Admiralty archives. By 1918, Britain and France had built prototype active systems.
The British tested their ASDIC on HMS Antrim in 1920 and started production in 1922. The 6th Destroyer Flotilla had ASDIC-equipped vessels in 1923. An anti-submarine school HMS Osprey and a training flotilla of four vessels were established on Portland in 1924; the U. S. Sonar QB set arrived in 1931. By the outbreak of World War II, the Royal Navy had five sets for different surface ship classes, others for submarines, incorporated into a complete anti-submarine attack system; the effectiveness of early ASDIC was hampered by the use of the depth charge as an anti-submarine weapon. This required an attacking vessel to pass over a submerged contact before dropping charges over the stern, resulting in a loss of ASDIC contact in the moments leading up to attack; the hunter was firing blind, during which time a submarine commander could take evasive action. This situation was remedied by using several ships cooperating and by the adoption of "ahead-throwing weapons", such as Hedgehogs and Squids, which proj
A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, it is sometimes used or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Although experimental submarines had been built before, submarine design took off during the 19th century, they were adopted by several navies. Submarines were first used during World War I, are now used in many navies large and small. Military uses include attacking enemy surface ships, attacking other submarines, aircraft carrier protection, blockade running, ballistic missile submarines as part of a nuclear strike force, conventional land attack, covert insertion of special forces. Civilian uses for submarines include marine science, salvage and facility inspection and maintenance. Submarines can be modified to perform more specialized functions such as search-and-rescue missions or undersea cable repair. Submarines are used in tourism, for undersea archaeology.
Most large submarines consist of a cylindrical body with hemispherical ends and a vertical structure located amidships, which houses communications and sensing devices as well as periscopes. In modern submarines, this structure is the "sail" in American usage and "fin" in European usage. A "conning tower" was a feature of earlier designs: a separate pressure hull above the main body of the boat that allowed the use of shorter periscopes. There is a propeller at the rear, various hydrodynamic control fins. Smaller, deep-diving and specialty submarines may deviate from this traditional layout. Submarines use diving planes and change the amount of water and air in ballast tanks to change buoyancy for submerging and surfacing. Submarines have one of the widest ranges of capabilities of any vessel, they range from small autonomous examples and one- or two-person vessels that operate for a few hours, to vessels that can remain submerged for six months—such as the Russian Typhoon class, the biggest submarines built.
Submarines can work at greater depths than are practical for human divers. Modern deep-diving submarines derive from the bathyscaphe, which in turn evolved from the diving bell. Whereas the principal meaning of "submarine" is an armed, submersible warship, the more general meaning is for any type of submersible craft; the definition as of 1899 was for any type of "submarine boat". By naval tradition, submarines are still referred to as "boats" rather than as "ships", regardless of their size. In other navies with a history of large submarine fleets they are "boats". According to a report in Opusculum Taisnieri published in 1562: Two Greeks submerged and surfaced in the river Tagus near the City of Toledo several times in the presence of The Holy Roman Emperor Charles V, without getting wet and with the flame they carried in their hands still alight. In 1578, the English mathematician William Bourne recorded in his book Inventions or Devises one of the first plans for an underwater navigation vehicle.
A few years the Scottish mathematician and theologian John Napier wrote in his Secret Inventions the following: "These inventions besides devises of sayling under water with divers, other devises and strategems for harming of the enemyes by the Grace of God and worke of expert Craftsmen I hope to perform." It's unclear whether he carried out his idea. The first submersible of whose construction there exists reliable information was designed and built in 1620 by Cornelis Drebbel, a Dutchman in the service of James I of England, it was propelled by means of oars. By the mid-18th century, over a dozen patents for submarines/submersible boats had been granted in England. In 1747, Nathaniel Symons patented and built the first known working example of the use of a ballast tank for submersion, his design used leather bags. A mechanism was used to cause the boat to resurface. In 1749, the Gentlemen's Magazine reported that a similar design had been proposed by Giovanni Borelli in 1680. Further design improvement stagnated for over a century, until application of new technologies for propulsion and stability.
The first military submarine was the Turtle, a hand-powered acorn-shaped device designed by the American David Bushnell to accommodate a single person. It was the first verified submarine capable of independent underwater operation and movement, the first to use screws for propulsion. In 1800, France built a human-powered submarine designed by the Nautilus; the French gave up on the experiment in 1804, as did the British when they considered Fulton's submarine design. In 1864, late in the American Civil War, the Confederate navy's H. L. Hunley became the first military submarine to sink an enemy vessel, the Union sloop-of-war USS Housatonic. In the aftermath of its successful attack against the ship, the Hunley sank because it was too close to its own exploding torpedo. In 1866, the Sub Marine Explorer was the first submarine to dive, cruise underwater, resurface under the control of the crew; the design by German American Julius H. Kroehl incorporated elements that are still used in modern submarines.
In 1866, the Flach was built at the request of the Chilean government, by Karl Flach, a German engineer and immigrant
The United Kingdom the United Kingdom of Great Britain and Northern Ireland, sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world; the Irish Sea lies between Great Ireland. With an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world, it is the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017. The UK is constitutional monarchy; the current monarch is Queen Elizabeth II, who has reigned since 1952, making her the longest-serving current head of state.
The United Kingdom's capital and largest city is London, a global city and financial centre with an urban area population of 10.3 million. Other major urban areas in the UK include Greater Manchester, the West Midlands and West Yorkshire conurbations, Greater Glasgow and the Liverpool Built-up Area; the United Kingdom consists of four constituent countries: England, Scotland and Northern Ireland. Their capitals are London, Edinburgh and Belfast, respectively. Apart from England, the countries have their own devolved governments, each with varying powers, but such power is delegated by the Parliament of the United Kingdom, which may enact laws unilaterally altering or abolishing devolution; the nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the UK, being Crown dependencies with the British Government responsible for defence and international representation. The medieval conquest and subsequent annexation of Wales by the Kingdom of England, followed by the union between England and Scotland in 1707 to form the Kingdom of Great Britain, the union in 1801 of Great Britain with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland.
Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain and Northern Ireland. There are fourteen British Overseas Territories, the remnants of the British Empire which, at its height in the 1920s, encompassed a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language and political systems of many of its former colonies; the United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity. It has a high-income economy and has a high Human Development Index rating, ranking 14th in the world, it was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power, with considerable economic, military and political influence internationally, it is sixth in military expenditure in the world. It has been a permanent member of the United Nations Security Council since its first session in 1946.
It has been a leading member state of the European Union and its predecessor, the European Economic Community, since 1973. The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the G20, NATO, the Organisation for Economic Co-operation and Development and the World Trade Organization; the 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain". The term "United Kingdom" has been used as a description for the former kingdom of Great Britain, although its official name from 1707 to 1800 was "Great Britain"; the Acts of Union 1800 united the kingdom of Great Britain and the kingdom of Ireland in 1801, forming the United Kingdom of Great Britain and Ireland. Following the partition of Ireland and the independence of the Irish Free State in 1922, which left Northern Ireland as the only part of the island of Ireland within the United Kingdom, the name was changed to the "United Kingdom of Great Britain and Northern Ireland".
Although the United Kingdom is a sovereign country, Scotland and Northern Ireland are widely referred to as countries. The UK Prime Minister's website has used the phrase "countries within a country" to describe the United Kingdom; some statistical summaries, such as those for the twelve NUTS 1 regions of the United Kingdom refer to Scotland and Northern Ireland as "regions". Northern Ireland is referred to as a "province". With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice revealing one's political preferences"; the term "Great Britain" conventionally refers to the island of Great Britain, or politically to England and Wales in combination. However, it is sometimes used as a loose synonym for the United Kingdom as a whole; the term "Britain" is used both as a synonym for Great Britain, as a synonym for the United Kingdom. Usage is mixed, with the BBC preferring to use Britain as shorthand only for Great Britain and the UK Government, while accepting that both terms refer to the United K
A dry dock is a narrow basin or vessel that can be flooded to allow a load to be floated in drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction and repair of ships and other watercraft; the use of dry docks in China goes at least as far back the 10th century A. D. In 1088, Song Dynasty scientist and statesman Shen Kuo wrote in his Dream Pool Essays: At the beginning of the dynasty the two Che provinces presented two dragon ships each more than 200 ft. in length. The upper works included several decks with palatial cabins and saloons, containing thrones and couches all ready for imperial tours of inspection. After many years, their hulls decayed and needed repairs, but the work was impossible as long as they were afloat. So in the Hsi-Ning reign period a palace official Huang Huai-Hsin suggested a plan. A large basin was excavated at the north end of the Chin-ming Lake capable of containing the dragon ships, in it heavy crosswise beams were laid down upon a foundation of pillars.
So that the basin filled with water, after which the ships were towed in above the beams. The water was pumped out by wheels so that the ships rested quite in the air; when the repairs were complete, the water was let in again. The beams and pillars were taken away, the whole basin covered over with a great roof so as to form a hangar in which the ships could be protected from the elements and avoid the damage caused by undue exposure; the first English and oldest surviving dry dock still in use was commissioned by Henry VII of England at HMNB Portsmouth in 1495. This dry dock holds the world's oldest commissioned warship, HMS Victory; the earliest description of a floating dock comes from a small Italian book printed in Venice in 1560, called Descrittione dell'artifitiosa machina. In the booklet, an unknown author asks for the privilege of using a new method for the salvaging of a grounded ship and proceeds to describe and illustrate his approach; the included woodcut shows a ship flanked by two large floating trestles, forming a roof above the vessel.
The ship is pulled in an upright position by a number of ropes attached to the superstructure. The Saint-Nazaire's Chantiers de l'Atlantique owns one of the biggest in the world: 1,200 by 60 metres; the largest graving dock of the Mediterranean as of 2009 is at the Hellenic Shipyards S. A.. The Alfredo da Silva Dry Dock in Almada, was closed in 2000; the largest roofed dry dock is at the German Meyer Werft Shipyard in Papenburg, Germany, it is 504 m long, 125 m wide and stands 75 m tall. Harland and Wolff Heavy Industries in Belfast, Northern Ireland, is the site of a large dry dock 556 by 93 metres; the massive cranes are named after the Biblical figures Goliath. Dry Dock 12 at Newport News Shipbuilding at 662 by 76 metres is the largest dry dock in the USA; the largest floating-dock in North America is named The Vigorous. It is operated by Vigor Industries in Portland, OR, in the Swan Island industrial area along the Willamette River. A graving dock is the traditional form of dry dock, it is narrow basin made of earthen berms and concrete, closed by gates or by a caisson.
When open, a vessel is floated in and the water pumped out, leaving the craft supported on blocks. The keel blocks as well as the bilge block are placed on the floor of the dock in accordance with the "docking plan" of the ship. Routine use of dry docks is for the "graving" i.e. the cleaning, removal of barnacles and rust, re-painting of ships' hulls. Some fine-tuning of the ship's position can be done by divers while there is still some water left to manoeuvre it about, it is important that supporting blocks conform to the structural members so that the ship is not damaged when its weight is supported by the blocks. Some anti-submarine warfare warships have protruding sonar domes, requiring that the hull of the ship be supported several metres from the bottom of the drydock. Once the remainder of the water is pumped out, the ship can be inspected or serviced; when work on the ship is finished, water is allowed to re-enter the dry dock and the ship is refloated. Modern graving docks are box-shaped, to accommodate the newer, boxier ship designs, whereas old dry docks are shaped like the ships that are planned to be docked there.
This shaping was advantageous because such a dock was easier to build, it was easier to side-support the ships, less water had to be pumped away. Dry docks used for building Navy vessels may be built with a roof; this is done to prevent spy satellites from taking pictures of the dry dock and any ships or submarines that may be in it. During World War II, fortified dry docks were used by the Germans to protect their submarines from Allied air raids. Today, covered dry docks are used only when servicing or repairing a fleet ballistic missile submarine. Another advantage of covered dry docks is. A floating dry dock is a type of pontoon for dry docking ships, possessing floodable buoyancy chambers and a "U"-shaped cross-section; the walls are used to give the dry dock stability when the floor or deck is below the surface of the water. When valves are opened, the
Oerlikon 20 mm cannon
The Oerlikon 20 mm cannon is a series of autocannons, based on an original German 20 mm Becker design that appeared early in World War I. It was produced by Oerlikon Contraves and others, with various models employed by both Allied and Axis forces during World War II, many versions still in use today. During World War I, the German industrialist Reinhold Becker developed a 20 mm caliber cannon, known now as the 20 mm Becker using the Advanced Primer Ignition blowback method of operation; this had a cyclic rate of fire of 300 rpm. It was used on a limited scale as an aircraft gun on Luftstreitkräfte warplanes, an anti-aircraft gun towards the end of that war; because the Treaty of Versailles banned further production of such weapons in Germany, the patents and design works were transferred in 1919 to the Swiss firm SEMAG based near Zürich. SEMAG continued development of the weapon, in 1924 had produced the SEMAG L, a heavier weapon that fired more powerful 20x100RB ammunition at a higher rate of fire, 350 rpm.
In 1924 SEMAG failed. The Oerlikon firm, named after the Zürich suburb of Oerlikon where it was based acquired all rights to the weapon, plus the manufacturing equipment and the employees of SEMAG. In 1927 the Oerlikon S was added to the existing product line; this fired a still larger cartridge to achieve a muzzle velocity of 830 m/s, at the cost of increased weight and a reduced rate of fire. The purpose of this development was to improve the performance of the gun as an anti-tank and anti-aircraft weapon, which required a higher muzzle velocity. An improved version known as the 1S followed in 1930. Three sizes of gun with their different ammunition and barrel length, but similar mechanisms, continued to be developed in parallel. In 1930 Oerlikon reconsidered the application of its gun in aircraft and introduced the AF and AL, designed to be used in flexible mounts, i.e. manually aimed by a gunner. The 15-round box magazine used by earlier versions of the gun was replaced by drum magazine holding 15 or 30 rounds.
In 1935 it made an important step by introducing a series of guns designed to be mounted in or on the wings of fighter aircraft. Designated with FF for Flügelfest meaning "wing-mounted", these weapons were again available in the three sizes, with designations FF, FFL and FFS; the FF fired a larger cartridge than the AF, 20x72RB, but the major improvement in these weapons was a significant increase in rate of fire. The FF weighed 24 kg and achieved a muzzle velocity of 550 to 600 m/s with a rate of fire of 520 rpm; the FFL of 30 kg fired a projectile at a muzzle velocity of 675 m/s with a rate of fire of 500 rpm. And the FFS, which weighed 39 kg, delivered a high muzzle velocity of 830 m/s at a rate of fire of 470 rpm. Apart from changes to the design of the guns for wing-mounting and remote control, larger drums were introduced as it would not be possible to exchange magazines in flight. For the FF series drum sizes of 45, 60, 75 and 100 rounds were available, but most users chose the 60-round drum.
The 1930s were a period of global re-armament, a number of foreign firms took licenses for the Oerlikon family of aircraft cannon. In France, Hispano-Suiza manufactured development of the FFS as the Hispano-Suiza HS.7 and Hispano-Suiza HS.9, for installation between the cylinder banks of its V-12 engines. In Germany, Ikaria further developed the FF gun as firing 20x80RB ammunition, and the Imperial Japanese Navy, after evaluating all three guns, ordered developments of the FF and FFL as the Type 99-1 and Type 99-2. The incorporation of the improvements of the FFS in a new anti-aircraft gun produced, in 1938, the Oerlikon SS. Oerlikon realized further improvements in rate of fire on the 1SS of 1942, the 2SS of 1945 which achieved 650 rpm. However, it was the original SS gun, adopted as anti-aircraft gun, being widely used by Allied navies during World War II; this gun used a 400-grain charge of IMR 4831 smokeless powder to propel a 2,000-grain projectile at 2,800 feet per second. The Oerlikon FF was installed as armament on some fighters of the 1930s, such as the Polish PZL P.24G.
Locally produced derivatives of the Oerlikon cannon were used much more extensively, on aircraft, on ships and on land. In the air, the Ikaria MG FF was used as armament on a number of German aircraft, of which the most famous is the Messerschmitt Bf 109; the Japanese Navy used their copy of the FF, designated the Type 99 Mark One cannon on a number of types including the Mitsubishi A6M Zero. In the war, they equipped fighters including the Zero with the Type 99 Mark Two, a version of the more powerful and faster-firing Oerlikon FFL; the French firm of Hispano-Suiza was a manufacturer of aircraft engines, it marketed the moteur-canon combination of its 12X and 12Y engines with a H. S.7 or H. S.9 cannon installed between the cylinder banks. The gun fired through the hollow propeller hub, this being elevated above the crankcase by the design of the gearing; such armament was installed on the Morane-Saulnier M. S.406 and some other types. Similar German installations of the MG FF were not successful.
The Oerlikon became best known in its naval applications. The Oerlikon was not looked upon favorably by the Royal Navy as a short-range anti-aircraft gun. All through 1937-1938 Lord Louis Mountbatten a Captain in the Royal Navy, waged a lone campaign within the Royal Navy to set up an unprejudiced trial for the Oerlikon 20 mm gun, but it was all in vain, it was not until the Commander-in-Chief of the Home Fleet, Admiral Sir Roger Backhouse, was appointed First Sea Lord tha
A periscope is an instrument for observation over, around or through an object, obstacle or condition that prevents direct line-of-sight observation from an observer's current position. In its simplest form, it consists of an outer case with mirrors at each end set parallel to each other at a 45° angle; this form of periscope, with the addition of two simple lenses, served for observation purposes in the trenches during World War I. Military personnel use periscopes in some gun turrets and in armoured vehicles. More complex periscopes using prisms or advanced fiber optics instead of mirrors and providing magnification operate on submarines and in various fields of science; the overall design of the classical submarine periscope is simple: two telescopes pointed into each other. If the two telescopes have different individual magnification, the difference between them causes an overall magnification or reduction. Johannes Gutenberg, known for his contribution to printing technology, marketed a kind of periscope in the 1430s to enable pilgrims to see over the heads of the crowd at the vigintennial religious festival at Aachen.
Johannes Hevelius described an early periscope with lenses in 1647 in his work Selenographia, sive Lunae descriptio. Hevelius saw military applications for his invention. In 1854, Hippolyte Marié-Davy invented the first naval periscope, consisting of a vertical tube with two small mirrors fixed at each end at 45°. Simon Lake used periscopes in his submarines in 1902. Sir Howard Grubb perfected the device in World War I. Morgan Robertson claimed to have tried to patent the periscope: he described a submarine using a periscope in his fictional works. Periscopes, in some cases fixed to rifles, served in World War I to enable soldiers to see over the tops of trenches, thus avoiding exposure to enemy fire; the periscope rifle saw use during the war - this was an infantry rifle sighted by means of a periscope, so the shooter could aim fire the weapon from a safe position below the trench parapet. During World War II, artillery observers and officers used specifically-manufactured periscope binoculars with different mountings.
Some of them allowed estimating the distance to a target, as they were designed as stereoscopic rangefinders. Tanks and armoured vehicles use periscopes: they enable drivers, tank commanders, other vehicle occupants to inspect their situation through the vehicle roof. Prior to periscopes, direct vision slits were cut in the armour for occupants to see out. Periscopes permit view outside of the vehicle without needing to cut these weaker vision openings in the front and side armour, better protecting the vehicle and occupants. A protectoscope is a related periscopic vision device designed to provide a window in armoured plate, similar to a direct vision slit. A compact periscope inside the protectoscope allows the vision slit to be blanked off with spaced armoured plate; this prevents a potential ingress point for small arms fire, with only a small difference in vision height, but still requires the armour to be cut. In the context of armoured fighting vehicles, such as tanks, a periscopic vision device may be referred to as an episcope.
In this context a periscope refers to a device that can rotate to provide a wider field of view, while an episcope is fixed into position. Periscopes may be referred to by slang, e.g. "shufti-scope". An important development, the Gundlach rotary periscope, incorporated a rotating top with a selectable additional prism which reversed the view; this allowed a tank commander to obtain a 360-degree field of view without moving his seat, including rear vision by engaging the extra prism. This design, patented by Rudolf Gundlach in 1936, first saw use in the Polish 7-TP light tank; as a part of Polish–British pre-World War II military cooperation, the patent was sold to Vickers-Armstrong where it saw further development for use in British tanks, including the Crusader, Churchill and Cromwell models as the Vickers Tank Periscope MK. IV; the Gundlach-Vickers technology was shared with the American Army for use in its tanks including the Sherman, built to meet joint British and US requirements. This saw post-war controversy through legal action: "After the Second World War and a long court battle, in 1947 he, received a large payment for his periscope patent from some of its producers."The USSR copied the design and used it extensively in its tanks (including the T-34 and T-70.
The copies were based on Lend-Lease British vehicles, many parts remain interchangeable. Germany made and used copies. Periscopic sights were introduced during the Second World War. In British use, the Vickers periscope was provided with sighting lines, enabling front and rear prisms to be directly aligned to gain an accurate direction. On tanks such as the Churchill and Cromwell, a marked episcope provided a backup sighting mechanism aligned with a vane sight on the turret roof. US-built Sherman tanks and British Centurion and Charioteer tanks replaced the main telescopic sight with a true periscopic sight in the primary role; the periscopic sight was linked to the gun itself. The sights formed part of the overall periscope, providing the gunner with greater overall vision than possible with the telescopic sight. In modern use, specialised periscopes can provide night vision; the Embedded Image Periscope designed and patented by Kent Periscopes provides standard unity vision periscope functionality for normal daytime viewing of the vehicle surroundings plus