Aviation in the pioneer era
The pioneer era of aviation refers to the period of aviation history between the first successful powered flight accepted to have been made by the Wright Brothers on 17 December 1903, the outbreak of the First World War in August 1914. Once the principles of powered controlled flight had been established there was a period in which many different aircraft configurations were experimented with. By 1914 the tractor configuration biplane had become the most popular form of aircraft design, would remain so until the end of the 1920s; the development of the internal combustion engine—primarily from their use in early automobiles before the start of the 20th century—which enabled successful heavier-than-air flight produced rapid advances in lighter-than-air flight in Germany where the Zeppelin company became the world leader in the field of airship construction. During this period aviation passed from being seen as the preserve of eccentric enthusiasts to being an established technology, with the establishment of specialist aeronautical engineering research establishments and university courses and the creation of major industrial aircraft manufacturing businesses, aviation became a subject of enormous popular interest.
Flying displays such as the Grande Semaine d'Aviation of 1909 and air races such as the Gordon Bennett Trophy and the Circuit of Europe attracted huge audiences and successful pilots such as Jules Védrines and Claude Grahame-White became celebrities. Although the Wright brothers made their first successful powered flights in December 1903 and by 1905 were making flights of significant duration, their achievement was unknown to the world in general and was disbelieved. After their flights in 1905 the Wrights stopped work on developing their aircraft and concentrated on trying to commercially exploit their invention, attempting to interest the military authorities of the United States and after being rebuffed and Great Britain. Attempts to achieve powered flight continued, principally in France. To publicize the aeronautical concourse at the upcoming World's Fair in St. Louis, Octave Chanute gave a number of lectures at aero-clubs in Europe, sharing his excitement about flying gliders, he showed slides of his own glider flying experiments as well as some of the Wrights glider flying in 1901 and 1902.
All these talks were reproduced in club journals. The lecture to members of the Aéro-Club de France in April 1903 is the best known, the August 1903 issue of l'Aérophile carried an article by Chanute that included drawings of his gliders as well as the Wright glider and a description of their approach to the problem, saying "the time is evidently approaching when, the problem of equilibrium and control having been solved, it will be safe to apply a motor and a propeller". Chanute's lecture moved Ernest Archdeacon one of the founder members of the Aéro-Club, to conclude his account of the lectures:Will the homeland of Montgolfier have the shame of allowing this ultimate discovery of aerial science—which is imminent... to be realised abroad? Gentleman scholars, to your compasses! You, the Maecenases. In October 1904 the Aéro-Club de France announced a series of prizes for achievements in powered flight, but little practical work was done: Ferdinand Ferber, an army officer who in 1898 had experimented with a hang-glider based on that of Otto Lilienthal continued his work without any notable success, Archdeacon commissioned the construction of a glider based on the Wright design but smaller and lacking the provision for roll control which made a number of brief flights at Berck-sur-Mer in April 1904, piloted by Ferber and Gabriel Voisin: another glider based on the Wright design was constructed by Robert Esnault-Pelterie, who rejected wing-warping as unsafe and instead fitted a pair of mid-gap control surfaces in front of the wings, intended to be used in a differential manner in place of wing-warping and in conjunction to act as elevators: this is the first recorded use of ailerons, the concept for, patented over a generation earlier by M. P. W. Boulton of the United Kingdom in 1868.
This was not successful and Esnault-Pelterie was to use its failure to support the position that the Wright Brothers claims were unfounded. However his design was not an exact copy of the Wrights' glider in having a increased wing camber. Ferber's copy was unsuccessful: it was crudely constructed, without ribs to maintain the wing camber, but is notable for his addition of a fixed rear-mounted stabilising tail surface, the first instance of this feature in a full-size aircraft. Archdeacon abandoned the 1904 glider after the first attempts and commissioned a second glider, constructed by Gabriel Voisin in 1905. Voisin constructed another glider, mounted on floats and introducing the box kite-like stabilising tail, to be a characteristic of his aircraft: this was towed into the air behind a motor-boat on 8 June 1905, Voisin's glider and a second similar aircraft built for Louis Blériot were tested on 18 July, the flight of Blériots aircraft ending in a crash in which Voisin, the pilot, was nearly drowned.
Voisin and Blériot constructed a powered tandem wing biplane, subjected to a number of modifications without any success. Full details of the Wright Brothers' flight control system was published in l'Aérophile in the January 1906 issue, mak
World War II
World War II known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries; the major participants threw their entire economic and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China, it included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, the only use of nuclear weapons in war. Japan, which aimed to dominate Asia and the Pacific, was at war with China by 1937, though neither side had declared war on the other. World War II is said to have begun on 1 September 1939, with the invasion of Poland by Germany and subsequent declarations of war on Germany by France and the United Kingdom.
From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Finland and the Baltic states. Following the onset of campaigns in North Africa and East Africa, the fall of France in mid 1940, the war continued between the European Axis powers and the British Empire. War in the Balkans, the aerial Battle of Britain, the Blitz, the long Battle of the Atlantic followed. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history; this Eastern Front trapped most crucially the German Wehrmacht, into a war of attrition. In December 1941, Japan launched a surprise attack on the United States as well as European colonies in the Pacific. Following an immediate U. S. declaration of war against Japan, supported by one from Great Britain, the European Axis powers declared war on the U.
S. in solidarity with their Japanese ally. Rapid Japanese conquests over much of the Western Pacific ensued, perceived by many in Asia as liberation from Western dominance and resulting in the support of several armies from defeated territories; the Axis advance in the Pacific halted in 1942. Key setbacks in 1943, which included a series of German defeats on the Eastern Front, the Allied invasions of Sicily and Italy, Allied victories in the Pacific, cost the Axis its initiative and forced it into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and turned toward Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in Central China, South China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands; the war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops, the suicide of Adolf Hitler and the German unconditional surrender on 8 May 1945.
Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August 1945, cementing total victory in Asia for the Allies. Tribunals were set up by fiat by the Allies and war crimes trials were conducted in the wake of the war both against the Germans and the Japanese. World War II changed the political social structure of the globe; the United Nations was established to foster international co-operation and prevent future conflicts. The Soviet Union and United States emerged as rival superpowers, setting the stage for the nearly half-century long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia.
Most countries whose industries had been damaged moved towards economic expansion. Political integration in Europe, emerged as an effort to end pre-war enmities and create a common identity; the start of the war in Europe is held to be 1 September 1939, beginning with the German invasion of Poland. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred and the two wars merged in 1941; this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935; the British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the fo
The Bell X-1, is a rocket-engine–powered aircraft, designated as the XS-1, was a joint National Advisory Committee for Aeronautics–U. S. Army Air Forces–U. S. Air Force supersonic research project built by Bell Aircraft. Conceived during 1944 and designed and built in 1945, it achieved a speed of nearly 1,000 miles per hour in 1948. A derivative of this same design, the Bell X-1A, having greater fuel capacity and hence longer rocket burning time, exceeded 1,600 miles per hour in 1954; the X-1, piloted by Chuck Yeager, was the first manned airplane to exceed the speed of sound in level flight and was the first of the X-planes, a series of American experimental rocket planes designed for testing new technologies. In 1942, the United Kingdom's Ministry of Aviation began a top secret project with Miles Aircraft to develop the world's first aircraft capable of breaking the sound barrier; the project resulted in the development of the prototype turbojet-powered Miles M.52, designed to reach 1,000 miles per hour in level flight, to climb to an altitude of 36,000 ft in 1 min 30 sec.
By 1944, design of the M.52 was 90% complete and Miles was told to go ahead with the construction of three prototypes. That year, the Air Ministry signed an agreement with the United States to exchange high-speed research and data. Miles' Chief Aerodynamicist Dennis Bancroft stated that Bell Aircraft personnel visited Miles in 1944, were given access to the drawings and research on the M.52, but the U. S. reneged on the agreement and no data was forthcoming in return. Unknown to Miles, Bell had started construction of a rocket-powered supersonic design of their own, with a conventional horizontal tail. Bell was battling the problem of pitch control due to "blanking" the elevators. A variable-incidence tail appeared to be the most promising solution; the XS-1 was first discussed in December 1944. Early specifications for the aircraft were for a piloted supersonic vehicle that could fly at 800 miles per hour at 35,000 feet for two to five minutes. On 16 March 1945, the U. S. Army Air Forces Flight Test Division and the National Advisory Committee for Aeronautics contracted with the Bell Aircraft Company to build three XS-1 aircraft to obtain flight data on conditions in the transonic speed range.
The aircraft's designers built a rocket plane after considering alternatives. Turbojets could not achieve the required performance at high altitude. An aircraft with both turbojet and rocket engines would be too complex; the X-1 was, in principle, a "bullet with wings", its shape resembling a Browning.50-caliber machine gun bullet, known to be stable in supersonic flight. The shape was followed to the extent of seating its pilot behind a sloped, framed window inside a confined cockpit in the nose, with no ejection seat. Swept wings were not used; as the design might lead to a fighter the XS-1 was intended to take off from the ground, but the end of the war made the B-29 Superfortress available to carry it into the air. After the rocket plane experienced compressibility problems during 1947, it was modified with a variable-incidence tailplane following technology transfer with the United Kingdom. Following conversion of the X-1's horizontal tail to all-moving, test pilot Chuck Yeager verified it experimentally, all subsequent supersonic aircraft would either have an all-moving tailplane or be "tailless" delta winged types.
The rocket engine was a four-chamber design built by Reaction Motors Inc. one of the first companies to build liquid-propellant rocket engines in the U. S. After considering hydrogen peroxide and aniline, nitromethane as fuels, the rocket burned ethyl alcohol diluted with water with a liquid oxygen oxidizer, its four chambers could be individually turned on and off, so thrust could be changed in 1,500 lbf increments. The fuel and oxygen tanks for the first two X-1 engines were pressurized with nitrogen, reducing flight time by about 1 1⁄2 minutes and increasing landing weight by 2,000 pounds, but the rest used gas-driven turbopumps, increasing the chamber pressure and thrust while making the engine lighter. Bell Aircraft chief test pilot Jack Woolams became the first person to fly the XS-1, he made a glide-flight over Pinecastle Army Airfield, in Florida, on 25 January 1946. Woolams completed nine more glide-flights over Pinecastle, with the B-29 dropping the aircraft at 29,000 feet and the XS-1 landing 12 minutes at about 110 miles per hour.
In March 1946 the #1 rocket plane was returned to Bell Aircraft in Buffalo, New York for modifications to prepare for the powered flight tests. Four more glide tests occurred at Muroc Army Air Field near Palmdale, flooded during the Florida tests, before the first powered test on 9 December 1946. Two chambers were ignited, but the aircraft accelerated so that one chamber was turned off until reignition at 35,000 feet, reaching Mach 0.795. After the chambers were turned off the aircraft descended to 15,000 feet, where all four chambers were tested. After Woolams' death on 30 August 1946, Chalmers "Slick" Goodlin was the primary Bell Aircraft test pilot for the X-1-1, he made 26 successful flights in both X-1s from September 1946 through June 1947. The Army Air Forces was unhappy with the cautious pace of flight envelope expansion and Bell Aircraft's flight test contract for airplane #46-062 was term
The Boeing 747 is an American wide-body commercial jet airliner and cargo aircraft referred to by its original nickname, "Jumbo Jet". Its distinctive hump upper deck along the forward part of the aircraft has made it one of the most recognizable aircraft, it was the first wide-body airplane produced. Manufactured by Boeing's Commercial Airplane unit in the United States, the 747 was envisioned to have 150 percent greater capacity than the Boeing 707, a common large commercial aircraft of the 1960s. First flown commercially in 1970, the 747 held the passenger capacity record for 37 years; the quadjet 747 uses a double-deck configuration for part of its length and is available in passenger and other versions. Boeing designed the 747's hump-like upper deck to serve as a first–class lounge or extra seating, to allow the aircraft to be converted to a cargo carrier by removing seats and installing a front cargo door. Boeing expected supersonic airliners—the development of, announced in the early 1960s—to render the 747 and other subsonic airliners obsolete, while the demand for subsonic cargo aircraft would remain robust well into the future.
Though the 747 was expected to become obsolete after 400 were sold, it exceeded critics' expectations with production surpassing 1,000 in 1993. By July 2018, 1,546 aircraft had been built, with 22 of the 747-8 variants remaining on order; as of January 2017, the 747 has been involved in 60 hull losses. The 747-400, the most common variant in service, has a high-subsonic cruise speed of Mach 0.85–0.855 with an intercontinental range of 7,260 nautical miles. The 747-400 can accommodate 416 passengers in a typical three-class layout, 524 passengers in a typical two-class layout, or 660 passengers in a high–density one-class configuration; the newest version of the aircraft, the 747-8, is in production and received certification in 2011. Deliveries of the 747-8F freighter version began in October 2011. In 1963, the United States Air Force started a series of study projects on a large strategic transport aircraft. Although the C-141 Starlifter was being introduced, they believed that a much larger and more capable aircraft was needed the capability to carry outsized cargo that would not fit in any existing aircraft.
These studies led to initial requirements for the CX-Heavy Logistics System in March 1964 for an aircraft with a load capacity of 180,000 pounds and a speed of Mach 0.75, an unrefueled range of 5,000 nautical miles with a payload of 115,000 pounds. The payload bay had to be 17 feet wide by 13.5 feet high and 100 feet long with access through doors at the front and rear. Featuring only four engines, the design required new engine designs with increased power and better fuel economy. In May 1964, airframe proposals arrived from Boeing, General Dynamics and Martin Marietta. After a downselect, Boeing and Lockheed were given additional study contracts for the airframe, along with General Electric and Pratt & Whitney for the engines. All three of the airframe proposals shared a number of features; as the CX-HLS needed to be able to be loaded from the front, a door had to be included where the cockpit was. All of the companies solved this problem by moving the cockpit above the cargo area. In 1965 Lockheed's aircraft design and General Electric's engine design were selected for the new C-5 Galaxy transport, the largest military aircraft in the world at the time.
The nose door and raised cockpit concepts would be carried over to the design of the 747. The 747 was conceived; the era of commercial jet transportation, led by the enormous popularity of the Boeing 707 and Douglas DC-8, had revolutionized long-distance travel. Before it lost the CX-HLS contract, Boeing was asked by Juan Trippe, president of Pan American World Airways, one of their most important airline customers, to build a passenger aircraft more than twice the size of the 707. During this time, airport congestion, worsened by increasing numbers of passengers carried on small aircraft, became a problem that Trippe thought could be addressed by a larger new aircraft. In 1965, Joe Sutter was transferred from Boeing's 737 development team to manage the design studies for the new airliner assigned the model number 747. Sutter initiated a design study with Pan Am and other airlines, to better understand their requirements. At the time, it was thought that the 747 would be superseded by supersonic transport aircraft.
Boeing responded by designing the 747 so that it could be adapted to carry freight and remain in production if sales of the passenger version declined. In the freighter role, the clear need was to support the containerized shipping methodologies that were being introduced at about the same time. Standard shipping containers are 8 ft square at the front and available in 40 ft lengths; this meant that it would be possible to support a 2-wide 2-high stack of containers two or three ranks deep with a fuselage size similar to the earlier CX-HLS project. In April 1966, Pan Am orde
Early flying machines
Early flying machines include all forms of aircraft studied or constructed before the development of the modern aeroplane by 1910. The story of modern flight begins more than a century before the first successful manned aeroplane, the earliest aircraft thousands of years before. From the earliest times there have been legends of men mounting flying devices or strapping birdlike wings, stiffened cloaks or other devices to themselves and attempting to fly by jumping off a tower; the Greek legend of Daedalus and Icarus is one of the earliest to come down to us. According to Ovid, Daedalus tied feathers together to mimic the wings of a bird. Other ancient legends include the Indian Vimana flying palace or chariot, Ezekiel's Chariot, the Irish roth rámach built by blind druid Mug Ruith and Simon Magus, various stories about magic carpets, mythical British King Bladud, who conjured up flying wings; some tried to build real flying devices birdlike wings, attempted to fly by jumping off a tower, hill, or cliff.
During this early period physical issues of lift and control were not understood, most attempts ended in serious injury or death when the apparatus lacked an effective horizontal tail, or the wings were too small. In the 1st century AD, Chinese Emperor Wang Mang recruited a specialist scout to be bound with bird feathers. In 559 AD, Yuan Huangtou is said to have landed safely following an enforced tower jump. In the seventeenth century, the Algerian historian Ahmed Mohammed al-Maqqari stated that the Andalusian scientist Abbas ibn Firnas made a jump in Cordoba, covering his body with vulture feathers and attaching two wings to his arms. No other sources record the event. Writing in the twelfth century, William of Malmesbury stated that the eleventh century Benedictine monk Eilmer of Malmesbury attached wings to his hands and feet and flew a short distance. Beyond those based on William's account, there are no other known sources documenting Eilmer's life. In 1496, a man named. In 1507, John Damian strapped on wings covered with chicken feathers and jumped from the walls of Stirling Castle in Scotland, breaking his thigh blaming it on not using eagle feathers.
Similar attempts continued with never more than partial success. Francis Willughby's suggestion, published in 1676, that human legs were more comparable to birds' wings in strength than arms, had only occasional influence. On 15 May 1793, the Spanish inventor Diego Marín Aguilera jumped with his glider from the highest part of the castle of Coruña del Conde, reaching a height of 5 or 6 m, gliding for 360 metres; as late as 1811, Albrecht Berblinger jumped into the Danube at Ulm. The kite was invented in China as far back as the 5th century BC by Mozi and Lu Ban; these leaf kites were constructed by stretching silk over a split bamboo framework. The earliest known Chinese kites were flat and rectangular. Tailless kites incorporated a stabilizing bowline. Designs emulated flying insects and other beasts, both real and mythical; some were fitted with whistles to make musical sounds while flying. In 549 AD, a kite made of paper was used as a message for a rescue mission. Ancient and medieval Chinese sources list other uses of kites for measuring distances, testing the wind, lifting men and communication for military operations.
After its introduction into India, the kite further evolved into the fighter kite. Traditionally these are small, unstable single line flat kites where line tension alone is used for control, an abrasive line is used to cut down other kites. Kites spread throughout Polynesia, as far as New Zealand. Anthropomorphic kites made from cloth and wood were used in religious ceremonies to send prayers to the gods. By 1634 kites had reached the West, with an illustration of a diamond kite with a tail appearing in Bate's Mysteries of nature and art. Man-carrying kites are believed to have been used extensively in ancient China, for both civil and military purposes and sometimes enforced as a punishment. Stories of man-carrying kites occur in Japan, following the introduction of the kite from China around the seventh century AD, it is said. In 1282, the European explorer Marco Polo described the Chinese techniques current and commented on the hazards and cruelty involved. To foretell whether a ship should sail, a man would be strapped to a kite having a rectangular grid framework and the subsequent flight pattern used to divine the outlook.
The use of a rotor for vertical flight has existed since 400 BC in the form of the bamboo-copter, an ancient Chinese toy. The bamboo-copter is spun by rolling a stick attached to a rotor; the spinning creates lift, the toy flies when released. The philosopher Ge Hong's book the Baopuzi, written around 317, describes the apocryphal use of a possible rotor in aircraft: "Some have made flying cars with wood from the inner part of the jujube tree, using ox-leather fastened to returning blades so as to set the machine in motion"; the similar "moulinet à noix" appeared in Europe in the 14th century AD. From ancient times the Chinese have understood that hot air rises and have applied the principle to a type of small hot air balloon called a sky lantern. A sky lantern consists of a paper balloon under or just inside. Sky lanterns are traditionally launched during festivals. According to Joseph Needha
London is the capital and largest city of both England and the United Kingdom. Standing on the River Thames in the south-east of England, at the head of its 50-mile estuary leading to the North Sea, London has been a major settlement for two millennia. Londinium was founded by the Romans; the City of London, London's ancient core − an area of just 1.12 square miles and colloquially known as the Square Mile − retains boundaries that follow its medieval limits. The City of Westminster is an Inner London borough holding city status. Greater London is governed by the Mayor of the London Assembly. London is considered to be one of the world's most important global cities and has been termed the world's most powerful, most desirable, most influential, most visited, most expensive, sustainable, most investment friendly, most popular for work, the most vegetarian friendly city in the world. London exerts a considerable impact upon the arts, education, fashion, healthcare, professional services and development, tourism and transportation.
London ranks 26 out of 300 major cities for economic performance. It is one of the largest financial centres and has either the fifth or sixth largest metropolitan area GDP, it is the most-visited city as measured by international arrivals and has the busiest city airport system as measured by passenger traffic. It is the leading investment destination, hosting more international retailers and ultra high-net-worth individuals than any other city. London's universities form the largest concentration of higher education institutes in Europe. In 2012, London became the first city to have hosted three modern Summer Olympic Games. London has a diverse range of people and cultures, more than 300 languages are spoken in the region, its estimated mid-2016 municipal population was 8,787,892, the most populous of any city in the European Union and accounting for 13.4% of the UK population. London's urban area is the second most populous in the EU, after Paris, with 9,787,426 inhabitants at the 2011 census.
The population within the London commuter belt is the most populous in the EU with 14,040,163 inhabitants in 2016. London was the world's most populous city from c. 1831 to 1925. London contains four World Heritage Sites: the Tower of London. Other landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Paul's Cathedral, Tower Bridge, Trafalgar Square and The Shard. London has numerous museums, galleries and sporting events; these include the British Museum, National Gallery, Natural History Museum, Tate Modern, British Library and West End theatres. The London Underground is the oldest underground railway network in the world. "London" is an ancient name, attested in the first century AD in the Latinised form Londinium. Over the years, the name has attracted many mythicising explanations; the earliest attested appears in Geoffrey of Monmouth's Historia Regum Britanniae, written around 1136. This had it that the name originated from a supposed King Lud, who had taken over the city and named it Kaerlud.
Modern scientific analyses of the name must account for the origins of the different forms found in early sources Latin, Old English, Welsh, with reference to the known developments over time of sounds in those different languages. It is agreed; this was adapted into Latin as Londinium and borrowed into Old English, the ancestor-language of English. The toponymy of the Common Brythonic form is much debated. A prominent explanation was Richard Coates's 1998 argument that the name derived from pre-Celtic Old European *lowonida, meaning "river too wide to ford". Coates suggested that this was a name given to the part of the River Thames which flows through London. However, most work has accepted a Celtic origin for the name, recent studies have favoured an explanation along the lines of a Celtic derivative of a proto-Indo-European root *lendh-, combined with the Celtic suffix *-injo- or *-onjo-. Peter Schrijver has suggested, on these grounds, that the name meant'place that floods'; until 1889, the name "London" applied to the City of London, but since it has referred to the County of London and Greater London.
"London" is sometimes written informally as "LDN". In 1993, the remains of a Bronze Age bridge were found on the south foreshore, upstream of Vauxhall Bridge; this bridge either reached a now lost island in it. Two of those timbers were radiocarbon dated to between 1750 BC and 1285 BC. In 2010 the foundations of a large timber structure, dated to between 4800 BC and 4500 BC, were found on the Thames's south foreshore, downstream of Vauxhall Bridge; the function of the mesolithic structure is not known. Both structures are on the south bank. Although there is evidence of scattered Brythonic settlements in the area, the first major settlement was founded by the Romans about four years after the invasion
Aircraft equipped with contra-rotating propellers referred to as CRP, coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of a single piston or turboprop engine to drive two coaxial propellers in contra-rotation. Two propellers are arranged one behind the other, power is transferred from the engine via a planetary gear or spur gear transmission. Contra-rotating propellers are known as counter-rotating propellers, although counter-rotating propellers is much more used when referring to airscrews on separate shafts turning in opposite directions; when airspeed is low, the mass of the air flowing through the propeller disk causes a significant amount of tangential or rotational air flow to be created by the spinning blades. The energy of this tangential air flow is wasted in a single-propeller design, causes handling problems at low speed as the air strikes the vertical stabilizer, causing the aircraft to yaw left or right, depending on the direction of propeller rotation.
To use this wasted effort, the placement of a second propeller behind the first takes advantage of the disturbed airflow. A well designed contra-rotating propeller will have no rotational air flow, pushing a maximum amount of air uniformly through the propeller disk, resulting in high performance and low induced energy loss, it serves to counter the asymmetrical torque effect of a conventional propeller. Some contra-rotating systems were designed to be used at take off for maximum power and efficiency under such conditions, allowing one of the propellers to be disabled during cruise to extend flight time; the torque on the aircraft from a pair of contra-rotating propellers cancels out. Contra-rotating propellers have been found to be between 6% and 16% more efficient than normal propellers; however they can be noisy, with increases in noise in the axial direction of up to 30 dB, tangentially 10 dB. Most of this extra noise can be found in the higher frequencies; these substantial noise problems limit commercial applications.
One possibility is to enclose the contra-rotating propellers in a shroud. It is helpful if the tip speed or the loading of the blades is reduced, if the aft propeller has fewer blades or a smaller diameter than the fore propeller, or if the spacing between the aft and fore propellers is increased; the efficiency of a contra-rotating prop is somewhat offset by its mechanical complexity and the added weight of this gearing that makes the aircraft heavier, thus some performance is sacrificed to carry it. Nonetheless, coaxial contra-rotating propellers and rotors have been used in several military aircraft, such as the Tupolev Tu-95 "Bear", they are being examined for use in airliners. While several nations experimented with contra-rotating propellers in aircraft, only the United Kingdom and Soviet Union produced them in large numbers; the first aircraft to be fitted with a contra-rotating propeller to fly was in the US when two inventors from Ft Worth, Texas tested the concept on an aircraft. A contra-rotating propeller was patented by F. W. Lanchester in 1907.
Some of the more successful British aircraft with contra-rotating propellers are the Avro Shackleton, powered by the Rolls-Royce Griffon engine, the Fairey Gannet, which used the Double Mamba Mk.101 engine. In the Double Mamba two separate power sections drove one propeller each, allowing one power section to be shut down in flight, increasing endurance. Another naval aircraft, the Westland Wyvern had contra-rotating propellers. Variants of the Supermarine Spitfire and Seafire used the Griffon with contra-rotating props. In the Spitfire/Seafire and Shackleton's case the primary reason for using contra-rotating propellers was to increase the propeller blade-area, hence absorb greater engine power, within a propeller diameter limited by the height of the aircraft's undercarriage; the Short Sturgeon used two Merlin 140s with contra-rotating propellers. The Bristol Brabazon prototype airliner used eight Bristol Centaurus engines driving four pairs of contra-rotating propellers, each engine driving a single propeller.
The post-war SARO Princess prototype flying boat airliner had contra-rotating propellers. In the 1950s, the Soviet Union developed the Kuznetsov NK-12 turboprop, it drives an 8-blade contra-rotating propeller and, at 15,000 shp, it is the most powerful turboprop in the world. Four NK-12 engines power the Tupolev Tu-95 Bear, the only turboprop bomber to enter service, as well as one of the fastest propeller-driven aircraft; the Tu-114, an airliner derivative of the Tu-95, holds the world speed record for propeller aircraft. The Tu-95 was the first Soviet bomber to have intercontinental range; the Tu-126 AEW aircraft and Tu-142 maritime patrol aircraft are two more NK-12 powered designs derived from the Tu-95. The NK-12 engine powers another well-known Soviet aircraft, the Antonov An-22 Antheus, a heavy-lift cargo aircraft. At the time of its introduction, the An-22 was the largest aircraft in the world and is still by far the world's largest turboprop-powered aircraft. From the 1960s through the 1970s, it set several world records in the categories of maximum payload-to-height ratio and maximum payload lifted to altitude.
Of lesser note is the use of the NK-12 engine in the A-90 Orlyonok, a mid-size Soviet ekranoplan. The A-90 uses one NK-12 engine mounted at the top of its T-tail, along with two turbofans installed in the nose. In 1994, Antonov produced a heavy transport aircraft, it is powered by four Progress D-27 propfan engines driving contra-rotating propellers. The characteristics of the D-27 engine and its propeller make it a propfan, a hybrid between a turbofan engine and a turboprop engine