An afterburner is a component present on some jet engines those used on military supersonic aircraft. Its purpose is to provide an increase in thrust for supersonic flight and combat situations. Afterburning is achieved by injecting additional fuel into the jet pipe downstream of the turbine. Afterburning increases thrust without the weight of an additional engine, but at the cost of high fuel consumption and decreased fuel efficiency, limiting its practical use to short bursts. Pilots can activate and deactivate afterburners in-flight, jet engines are referred to as operating wet when afterburning is being used and dry when not. An engine producing maximum thrust wet is at maximum power, while an engine producing maximum thrust dry is at military power. Jet-engine thrust is governed by the general principle of mass flow rate. Thrust depends on two things: the mass of that gas. A jet engine can produce more thrust by either accelerating the gas to a higher velocity or by having a greater mass of gas exit the engine.
Designing a basic turbojet engine around the second principle produces the turbofan engine, which creates slower gas but more of it. Turbofans are fuel efficient and can deliver high thrust for long periods, but the design trade-off is a large size relative to the power output. Generating increased power with a more compact engine for short periods can be achieved using an afterburner; the afterburner increases thrust by accelerating the exhaust gas to a higher velocity. The temperature of the gas in the engine is highest just before the turbine, the ability for the turbine to withstand these temperatures is one of the primary restrictions on total dry engine thrust; this temperature is known as the Turbine Entry Temperature, one of the critical engine operating parameters. Because a combustion rate high enough to consume all the intake oxygen would create temperatures high enough to overheat the turbine, the flow of fuel must be restricted to an extent that fuel rather than oxygen becomes the limiting factor in the reaction, leaving some oxygen to flow past the turbine.
After passing the turbine, the gas expands at a near constant entropy, thus losing temperature. The afterburner injects fuel downstream of the turbine and reheats the gas; as a result of the temperature rise in the tailpipe, the gas is ejected through the nozzle at a higher velocity. The mass flow is slightly increased by the addition of the fuel. Afterburners produce markedly enhanced thrust as well as a visible flame at the back of the engine; this exhaust flame may show shock diamonds, which are caused by shock waves formed due to slight differences between ambient pressure and the exhaust pressure. These imbalances cause oscillations in the exhaust jet diameter over a short distance and cause visible banding where the pressure and temperature is highest. A similar type of thrust augmentation but using additional fuel burnt in a turbofan's cold bypass air only, instead of the combined cold and hot gas flows as in a conventional afterburning engine, is Plenum chamber burning, developed for the vectored thrust Bristol Siddeley BS100 engine for the Hawker Siddeley P.1154.
In this engine, where the cold bypass and hot core turbine airflows are split between two sets of nozzles and rear, in the same manner as the Rolls-Royce Pegasus, additional fuel and afterburning was applied to the front cold air nozzles only. This technique was developed to give greater thrust for take-off and supersonic performance in an aircraft similar to, but of higher weight, than the Hawker Siddeley Harrier. A jet engine afterburner is an extended exhaust section containing extra fuel injectors. Since the jet engine upstream will use little of the oxygen it ingests, additional fuel can be burned after the gas flow has left the turbines; when the afterburner is turned on, fuel is injected and igniters are fired. The resulting combustion process increases the afterburner exit temperature resulting in a steep increase in engine net thrust. In addition to the increase in afterburner exit stagnation temperature, there is an increase in nozzle mass flow, but a decrease in afterburner exit stagnation pressure.
The resulting increase in afterburner exit volume flow is accommodated by increasing the throat area of the propulsion nozzle. Otherwise, the upstream turbomachinery rematches; the first designs, e.g. Solar afterburners used on the F7U Cutlass, F-94 Starfire and F-89 Scorpion, had 2-position eyelid nozzles. Modern designs incorporate not only VG nozzles but multiple stages of augmentation via separate spray bars. To a first order, the gross thrust ratio is directly proportional to the root of the stagnation temperature ratio across the afterburner. Due to their high fuel consumption, afterburners are used as little as possible, they are used only when it is important to have as much thrust as possible. This includes during takeoff from short runways, assisting catapult launches from aircraft carriers, during air combat situations. A notable exception is the Whitney J58 engine used in the SR-71 Blackbird. In heat engines such as jet engines, efficiency is best when combustion is done at the highest pressure and temperature possible, expanded down to ambient pressure.
Since the exhaust gas has reduced oxygen due to previous combustion, since the fuel is not burning in a com
Mean sea level is an average level of the surface of one or more of Earth's oceans from which heights such as elevation may be measured. MSL is a type of vertical datum – a standardised geodetic datum –, used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and aircraft flight levels. A common and straightforward mean sea-level standard is the midpoint between a mean low and mean high tide at a particular location. Sea levels can be affected by many factors and are known to have varied over geological time scales; however 20th century and current millennium sea level rise is caused by global warming, careful measurement of variations in MSL can offer insights into ongoing climate change. The term above sea level refers to above mean sea level. Precise determination of a "mean sea level" is difficult to achieve because of the many factors that affect sea level. Instantaneous sea level varies quite a lot on several scales of space.
This is because the sea is in constant motion, affected by the tides, atmospheric pressure, local gravitational differences, salinity and so forth. The easiest way this may be calculated is by selecting a location and calculating the mean sea level at that point and use it as a datum. For example, a period of 19 years of hourly level observations may be averaged and used to determine the mean sea level at some measurement point. Still-water level or still-water sea level is the level of the sea with motions such as wind waves averaged out. MSL implies the SWL further averaged over a period of time such that changes due to, e.g. the tides have zero mean. Global MSL refers to a spatial average over the entire ocean. One measures the values of MSL in respect to the land. In the UK, the Ordnance Datum is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921. Prior to 1921, the vertical datum was MSL at the Victoria Liverpool. Since the times of the Russian Empire, in Russia and other former its parts, now independent states, the sea level is measured from the zero level of Kronstadt Sea-Gauge.
In Hong Kong, "mPD" is a surveying term meaning "metres above Principal Datum" and refers to height of 1.230m below the average sea level. In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and offers the longest collapsed data about the sea level, it is used for main part of Africa as official sea level. As for Spain, the reference to measure heights below or above sea level is placed in Alicante. Elsewhere in Europe vertical elevation references are made to the Amsterdam Peil elevation, which dates back to the 1690s. Satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001 and the Ocean Surface Topography Mission on the Jason-2 satellite in 2008. Height above mean sea level is the elevation or altitude of an object, relative to the average sea level datum, it is used in aviation, where some heights are recorded and reported with respect to mean sea level, in the atmospheric sciences, land surveying.
An alternative is to base height measurements on an ellipsoid of the entire Earth, what systems such as GPS do. In aviation, the ellipsoid known as World Geodetic System 84 is used to define heights; the alternative is to use a geoid-based vertical datum such as NAVD88. When referring to geographic features such as mountains on a topographic map, variations in elevation are shown by contour lines; the elevation of a mountain denotes the highest point or summit and is illustrated as a small circle on a topographic map with the AMSL height shown in metres, feet or both. In the rare case that a location is below sea level, the elevation AMSL is negative. For one such case, see Amsterdam Airport Schiphol. To extend this definition far from the sea means comparing the local height of the mean sea surface with a "level" reference surface, or geodetic datum, called the geoid. In a state of rest or absence of external forces, the mean sea level would coincide with this geoid surface, being an equipotential surface of the Earth's gravitational field.
In reality, due to currents, air pressure variations and salinity variations, etc. this does not occur, not as a long-term average. The location-dependent, but persistent in time, separation between mean sea level and the geoid is referred to as ocean surface topography, it varies globally in a range of ± 2 m. Adjustments were made to sea-level measurements to take into account the effects of the 235 lunar month Metonic cycle and the 223-month eclipse cycle on the tides. Several terms are used to describe the changing relationships between sea level and dry land; when the term "relative" is used, it means change relative to a fixed point in the sediment pile. The term "eustatic" refers to global changes in sea level relative to a fixed point, such as the centre of the earth, for example as a result of melting ice-caps; the term "steric" refers to global changes in sea level due to thermal expansion and salinity variations. The term "isostatic" refers to changes in
Rockwell B-1 Lancer
The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It is called the "Bone", it is one of three strategic bombers in the U. S. Air Force fleet as of 2018, the other two being the B-2 Spirit and the B-52 Stratofortress; the B-1 was first envisioned in the 1960s as a platform that would combine the Mach 2 speed of the B-58 Hustler with the range and payload of the B-52, would replace both bombers. After a long series of studies, Rockwell International won the design contest for what emerged as the B-1A; this version had a top speed of Mach 2.2 at high altitude and the capability of flying for long distances at Mach 0.85 at low altitudes. The combination of the high cost of the aircraft, the introduction of the AGM-86 cruise missile that flew the same basic profile, early work on the stealth bomber all affected the need for the B-1; this led to the program being canceled in 1977. The program was restarted in 1981 as an interim measure until the stealth bomber entered service.
This led to a redesign as the B-1B, which had lower top speed at high altitude of Mach 1.25, but improved low-altitude performance of Mach 0.96. The electronics were extensively improved during the redesign, the airframe was improved to allow takeoff with the maximum possible fuel and weapons load; the B-1B began deliveries in 1986 and formally entered service with Strategic Air Command as a nuclear bomber in 1986. By 1988, all 100 aircraft had been delivered. In the early 1990s, following the Gulf War and concurrent with the disestablishment of SAC and its reassignment to the newly formed Air Combat Command, the B-1B was converted to conventional bombing use, it first served in combat during Operation Desert Fox in 1998 and again during the NATO action in Kosovo the following year. The B-1B has supported U. S. and NATO military forces in Afghanistan and Iraq. The Air Force had 66 B-1Bs in service as of September 2012; the B-1B is expected to continue to serve into the 2030s, with the Northrop Grumman B-21 Raider to begin replacing the B-1B after 2025.
The B-1s in inventory will be retired by 2036. In 1955, the USAF issued requirements for a new bomber combining the payload and range of the Boeing B-52 Stratofortress with the Mach 2 maximum speed of the Convair B-58 Hustler. In December 1957, the USAF selected North American Aviation's B-70 Valkyrie for this role; the Valkyrie was a six-engine bomber. Soviet interceptor aircraft, the only effective anti-bomber weapon in the 1950s, were unable to intercept the high-flying Lockheed U-2. By the late 1950s, antiaircraft surface-to-air missiles could threaten high-altitude aircraft, as demonstrated by the 1960 downing of Gary Powers' U-2; the USAF Strategic Air Command was aware of these developments and had begun moving its bombers to low-level penetration before the U-2 downing. This tactic reduces radar detection distances through the use of terrain masking. Additionally, radars of the era were subject to "clutter" from stray returns from the ground and other objects, which meant a minimum angle existed above the horizon where they could detect a target.
Bombers flying at low altitudes could remain under these angles by keeping their distance from the radar sites. This combination of effects made SAMs of the era ineffective against low-flying aircraft; the same effects meant that low-flying aircraft were difficult to detect by higher-flying interceptors, since their radar systems could not pick out opposing aircraft against the clutter from ground reflections. The switch from high-altitude to low-altitude flight profiles affected the B-70, whose design was tuned to provide the desired high-altitude performance. Planners outlined a series of low-level profiles for the B-70, but higher aerodynamic drag at low level limited the B-70 to subsonic speed while decreasing its range; the result would be an aircraft with somewhat higher subsonic speed than the less range. Unsuited for the new low-altitude role, because of a growing shift to the intercontinental ballistic missile force, the B-70 bomber program was cancelled in 1961 by President John F. Kennedy, the two XB-70 prototypes were used in a supersonic research program.
Although never intended for the low-level role, the B-52's flexibility allowed it to outlast its intended successor as the nature of the air war environment changed. The B-52's huge fuel load allowed it to operate at lower altitudes for longer times, the large airframe allowed the addition of improved radar jamming and deception suites to deal with radars. During the Vietnam War, the concept that all future wars would be nuclear was turned on its head, the "big belly" modifications increased the B-52's total bomb load to 60,000 pounds, turning it into a powerful tactical aircraft which could be used against ground troops along with strategic targets from high altitudes; the much smaller bomb bay of the B-70 would have made it much less useful in this role. Although effective, the B-52 was not ideal for the low-level role; this led to a number of aircraft designs known as penetrators, which were tuned for long-range low-altitude flight. The first of these designs to see operation was the superso
A bullet is a kinetic projectile and the component of firearm ammunition, expelled from the gun barrel during shooting. The term is from Middle French and originated as the diminutive of the word boulle, which means "small ball". Bullets are made of a variety of materials such as copper, steel, polymer and wax, they are available either singly as in muzzleloading and cap and ball firearms or as a component of paper cartridges, but much more in the form of metallic cartridges. Bullets are made in a large number of shapes and constructions depending on the intended applications, including specialized functions such as hunting, target shooting and combat. Though the word "bullet" is used incorrectly in colloquial language to refer to a cartridge round, a bullet is not a cartridge but rather a component of one. A round of ammunition cartridge is a combination package of the bullet, the case, the propellant and the primer; this use of the term "bullet" when intending to describe a cartridge leads to confusion when the components of a cartridge are referred to.
Bullet sizes are expressed by their weights and diameters in both imperial and metric measurement systems. For example: 55 grain.223 caliber bullets are of the same weight and caliber as 3.56 gram 5.56mm caliber bullets. The bullets used in many cartridges are fired at muzzle velocities faster than the speed of sound — about 343 metres per second in dry air at 20 °C — and thus can travel a substantial distance to a target before a nearby observer hears the sound of the shot; the sound of gunfire is accompanied with a loud bullwhip-like crack as the supersonic bullet pierces through the air creating a sonic boom. Bullet speeds at various stages of flight depend on intrinsic factors such as its sectional density, aerodynamic profile and ballistic coefficient, extrinsic factors such as barometric pressure, air temperature and wind speed. Subsonic cartridges fire bullets slower than the speed of sound; this means that a subsonic cartridge, such as.45 ACP, can be quieter than a supersonic cartridge such as the.223 Remington without the use of a suppressor.
Bullets do not contain explosives, but damage the intended target by transferring kinetic energy upon impact and penetration. The first use of gunpowder in Europe was recorded in 1247, it had been used in China for hundreds of years. The cannon appeared in 1327. In 1364, the hand cannon appeared. Early projectiles were made of stone. Stone was used in hand cannon. In cannon it was found that stone would not penetrate stone fortifications which gave rise to the use of heavier metals for the round projectiles. Hand cannon projectiles developed in a similar fashion following the failure of stone from siege cannon; the first recorded instance of a metal ball from a hand cannon penetrating armor occurred in 1425. In this photograph of shot retrieved from the wreck of the Mary Rose, sunk in 1545 and raised in 1982; the round shot are of different sizes and some are stone while others are cast iron. The development of the hand culverin and matchlock arquebus brought about the use of cast lead balls as projectiles.
"Bullet" is derived from the French word boulette, which means "little ball". The original round musket ball was smaller than the bore of the barrel, it was loaded into the barrel first, just resting upon the powder, using some sort of material as a wadding, between the ball and the powder as well as over the ball to keep it in place, it held the bullet in the barrel and against the powder. The loading of muskets was, easy with the old smooth-bore Brown Bess and similar military muskets; the original muzzle-loading rifle, was loaded with a piece of leather or cloth wrapped around the ball, to allow the ball to engage the grooves in the barrel. Loading was a bit more difficult when the bore of the barrel was fouled from previous firings. For this reason, because rifles were not fitted for a bayonet, early rifles were not used for military purposes; the first half of the nineteenth century saw a distinct change in the shape and function of the bullet. In 1826, Henri-Gustave Delvigne, a French infantry officer, invented a breech with abrupt shoulders on which a spherical bullet was rammed down until it caught the rifling grooves.
Delvigne's method, deformed the bullet and was inaccurate. Square bullets have origins that pre-date civilization and were used by slingers in slings, they were made out of copper or lead. The most notable use of square bullet designs was done by, James Puckle and Kyle Tunis who patented them, where they were used in one version of the Puckle gun; the early use of these in the black-powder era was soon discontinued due to irregular and unpredictable flight patterns. Delvigne continued to develop bullet design and by 1830 had started to develop cylindro-conical bullets, his bullet designs were improved by Francois Tamisier with the addition of "ball grooves" which are known as "cannelures", these moved the resistance of air behind the center of gravity of the bullet. Tamisier developed progressive rifling; the rifle grooves were deeper toward the breech, becoming shallower as they progressed toward the muzzle. This causes the bullet to be progressively molded into the grooves which incre
A supersonic transport is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. To date, the only SSTs to see regular service have been Concorde and the Tupolev Tu-144; the last passenger flight of the Tu-144 was in June 1978 and it was last flown in 1999 by NASA. Concorde's last commercial flight was in October 2003, with a November 26, 2003 ferry flight being its last airborne operation. Following the permanent cessation of flying by Concorde, there are no remaining SSTs in commercial service. Several companies have each proposed a supersonic business jet, which may bring supersonic transport back again. Supersonic airliners have been the objects of numerous ongoing design studies. Drawbacks and design challenges are excessive noise generation, high development costs, expensive construction materials, great weight, an increased cost per seat over subsonic airliners. Despite these challenges, Concorde was claimed to operate profitably, although, due to write off of all development and construction costs plus the willingness of passengers to pay high fares.
In 2016, NASA announced. The designing team is led by Lockheed Martin Aeronautics. Throughout the 1950s an SST looked possible from a technical standpoint, but it was not clear if it could be made economically viable. Lift is generated using different means at supersonic speeds, these methods are less efficient than subsonic methods, with one-half the lift-to-drag ratio; this implies that for any given required amount of lift, the aircraft will have to supply about twice the thrust, leading to greater fuel use. This effect is pronounced at speeds close to the speed of sound, as the aircraft is using twice the thrust to travel at about the same speed; the relative effect is reduced. Offsetting this increase in fuel use was the potential to increase sortie rates of the aircraft, at least on medium and long-range flights where the aircraft spends a considerable amount of time in cruise. SST designs flying at least three times as fast as existing subsonic transports were possible, would thus be able to replace as many as three planes in service, thereby lower costs in terms of manpower and maintenance.
Serious work on SST designs started in the mid-1950s, when the first generation of supersonic fighter aircraft were entering service. In Britain and France, government-subsidized SST programs settled on the delta wing in most studies, including the Sud Aviation Super-Caravelle and Bristol 223, although Armstrong-Whitworth proposed a more radical design, the Mach 1.2 M-Wing. Avro Canada proposed several designs to TWA that included Mach 1.6 double-ogee wing and Mach 1.2 delta-wing with separate tail and four under-wing engine configurations. Avro's team moved to the UK. By the early 1960s, the designs had progressed to the point where the go-ahead for production was given, but costs were so high that the Bristol Aeroplane Company and Sud Aviation merged their efforts in 1962 to produce Concorde. In the early 1960s, various executives of US aerospace companies were telling the US public and Congress that there were no technical reasons an SST could not be produced. In April 1960, Burt C Monesmith, a vice president with Lockheed, stated to various magazines that an SST constructed of steel weighing 250,000 pounds could be developed for $160 million and in production lots of 200 or more sold for around $9 million.
But it was the Anglo-French development of the Concorde that set off panic in the US industry, where it was thought that Concorde would soon replace all other long range designs after Pan Am took out purchase options on the Concorde. Congress was soon funding an SST design effort, selecting the existing Lockheed L-2000 and Boeing 2707 designs, to produce an more advanced, larger and longer ranged design; the Boeing 2707 design was selected for continued work, with design goals of ferrying around 300 passengers and having a cruising speed near to Mach 3. The Soviet Union set out to produce its own design, the Tu-144, which the western press nicknamed the "Concordski." The SST was seen as offensive due to its sonic boom and the potential for its engine exhaust to damage the ozone layer. Both problems impacted the thinking of lawmakers, Congress dropped funding for the US SST program in March 1971, all overland commercial supersonic flight was banned. Presidential advisor Russell Train warned that a fleet of 500 SSTs flying at 65,000 ft for a period of years could raise stratospheric water content by as much as 50% to 100%.
According to Train, this could hamper the formation of ozone. In relation to stratospheric water and its potential to increase ground temperatures, although not mentioning Concorde as the source of the "recent decline in water vapor is unknown", in 2010 the National Oceanic and Atmospheric Administration noted that Stratospheric Water Vapor levels in the 1980s and 1990s were higher than that in the 2000s, by 10%, with Susan Solomon of NOAA calculating that it is this change, responsible for the slow down in the rise in surface temperatures from global warming by about 25 percent when compared to the warming rate in the 1990s. Russell Train's other, water-ozone concern, was however countered by Fred Singer in a letter to the journal Nature in 1971, "which upset those who claimed that supersonic transports might affect stratospheric ozone". An additional threat to the
British Airways is the flag carrier and the second largest airline in the United Kingdom based on fleet size and passengers carried, behind easyJet. The airline is based in Waterside near its main hub at London Heathrow Airport. In January 2011 BA merged with Iberia, creating the International Airlines Group, a holding company registered in Madrid, Spain. IAG is the world's third-largest airline group in terms of annual revenue and the second-largest in Europe, it is listed in the FTSE 100 Index. BA was created in 1974 after a British Airways Board was established by the British government to manage the two nationalised airline corporations, British Overseas Airways Corporation and British European Airways, two regional airlines, Cambrian Airways from Cardiff, Northeast Airlines from Newcastle upon Tyne. On 31 March 1974, all four companies were merged to form British Airways. After 13 years as a state company, BA was privatised in February 1987 as part of a wider privatisation plan by the Conservative government.
The carrier expanded with the acquisition of British Caledonian in 1987, Dan-Air in 1992, British Midland International in 2012. Its preeminence highlights the reach of the country's influence as many of its destinations in several regions were part of the British Empire, it is a founding member of the Oneworld airline alliance, along with American Airlines, Cathay Pacific and the now defunct Canadian Airlines. The alliance has since grown to become the third largest, after Star Alliance. Proposals to establish a joint British airline, combining the assets of the British Overseas Airways Corporation and British European Airways were first raised in 1953 as a result of difficulties in attempts by BOAC and BEA to negotiate air rights through the British colony of Cyprus. BOAC was protesting that BEA was using its subsidiary Cyprus Airways to circumvent an agreement that BEA would not fly routes further east than Cyprus to the important oil regions in the Middle East; the Chairman of BOAC, Miles Thomas, was in favour of merger as a potential solution to this disagreement and had backing for the idea from the Chancellor of the Exchequer at the time, Rab Butler.
However, opposition from the Treasury blocked the proposal. It was only following the recommendations of the 1969 Edwards Report that a new British Airways Board, managing both BEA and BOAC, the two regional British airlines Cambrian Airways based at Cardiff, Northeast Airlines based at Newcastle upon Tyne, was constituted on 1 April 1972. Although each airline's individual branding was maintained two years the British Airways Board unified its branding establishing British Airways as an airline on 31 March 1974. Following two years of fierce competition with British Caledonian, the second-largest airline in the United Kingdom at the time, the Government changed its aviation policy in 1976 so that the two carriers would no longer compete on long-haul routes. British Airways and Air France operated the supersonic airliner Aerospatiale-BAC Concorde, the world's first supersonic passenger service flew in January 1976 from London Heathrow to Bahrain. Services to the US began on 24 May 1976 with a flight to Washington Dulles airport, flights to New York JFK airport followed on 22 September 1977.
Service to Singapore was established in co-operation with Singapore Airlines as a continuation of the flight to Bahrain. Following the Air France Concorde crash in Paris and a slump in air travel following the 11 September attacks in New York in 2001, it was decided to cease Concorde operations in 2003 after 27 years of service; the final commercial Concorde flight was BA002 from New York JFK to London Heathrow on 24 October 2003. In 1981 the airline was instructed to prepare for privatisation by the Conservative Thatcher government. Sir John King Lord King, was appointed chairman, charged with bringing the airline back into profitability. While many other large airlines struggled, King was credited with transforming British Airways into one of the most profitable air carriers in the world; the flag carrier was privatised and was floated on the London Stock Exchange in February 1987. British Airways effected the takeover of the UK's "second" airline, British Caledonian, in July of that same year.
The formation of Richard Branson's Virgin Atlantic in 1984 created a competitor for BA. The intense rivalry between British Airways and Virgin Atlantic culminated in the former being sued for libel in 1993, arising from claims and counterclaims over a "dirty tricks" campaign against Virgin; this campaign included allegations of poaching Virgin Atlantic customers, tampering with private files belonging to Virgin and undermining Virgin's reputation in the City. As a result of the case BA management apologised "unreservedly", the company agreed to pay £110,000 damages to Virgin, £500,000 to Branson and £3 million legal costs. Lord King stepped down as chairman in 1993 and was replaced by his deputy, Colin Marshall, while Bob Ayling took over as CEO. Virgin filed a separate action in the US that same year regarding BA's domination of the trans-Atlantic routes, but it was thrown out in 1999. In 1992 British Airways expanded through the acquisition of the financially troubled Dan-Air, giving BA a much larger presence at Gatwick airport.
British Asia Airways, a subsidiary based in Taiwan, was formed in March 1993 to operate between London and Taipei. That same month BA purchased a 25% stake in the Australian airline Qantas and, with the acquisition of Brymon Airways in May, formed British Airways Citiexpress. In September 1998, British Airways, along with American Airlines, Cathay Pacific and Canadian
A fighter aircraft is a military aircraft designed for air-to-air combat against other aircraft, as opposed to bombers and attack aircraft, whose main mission is to attack ground targets. The hallmarks of a fighter are its speed and small size relative to other combat aircraft. Many fighters have secondary ground-attack capabilities, some are designed as dual-purpose fighter-bombers; this may be for national security reasons, for advertising purposes, or other reasons. A fighter's main purpose is to establish air superiority over a battlefield. Since World War I, achieving and maintaining air superiority has been considered essential for victory in conventional warfare; the success or failure of a belligerent's efforts to gain air superiority hinges on several factors including the skill of its pilots, the tactical soundness of its doctrine for deploying its fighters, the numbers and performance of those fighters. Because of the importance of air superiority, since the early days of aerial combat armed forces have competed to develop technologically superior fighters and to deploy these fighters in greater numbers, fielding a viable fighter fleet consumes a substantial proportion of the defense budgets of modern armed forces.
The word "fighter" did not become the official English-language term for such aircraft until after World War I. In the British Royal Flying Corps and Royal Air Force these aircraft were referred to as "scouts" into the early 1920s; the U. S. Army called their fighters "pursuit" aircraft from 1916 until the late 1940s. In most languages a fighter aircraft is known as hunting aircraft. Exceptions include Russian, where a fighter is an "истребитель", meaning "exterminator", Hebrew where it is "matose krav"; as a part of military nomenclature, a letter is assigned to various types of aircraft to indicate their use, along with a number to indicate the specific aircraft. The letters used to designate a fighter differ in various countries – in the English-speaking world, "F" is now used to indicate a fighter, though when the pursuit designation was used in the US, they were "P" types. In Russia "I" was used, while the French continue to use "C". Although the term "fighter" specifies aircraft designed to shoot down other aircraft, such designs are also useful as multirole fighter-bombers, strike fighters, sometimes lighter, fighter-sized tactical ground-attack aircraft.
This has always been the case, for instance the Sopwith Camel and other "fighting scouts" of World War I performed a great deal of ground-attack work. In World War II, the USAAF and RAF favored fighters over dedicated light bombers or dive bombers, types such as the Republic P-47 Thunderbolt and Hawker Hurricane that were no longer competitive as aerial combat fighters were relegated to ground attack. Several aircraft, such as the F-111 and F-117, have received fighter designations though they had no fighter capability due to political or other reasons; the F-111B variant was intended for a fighter role with the U. S. Navy, but it was cancelled; this blurring follows the use of fighters from their earliest days for "attack" or "strike" operations against ground targets by means of strafing or dropping small bombs and incendiaries. Versatile multirole fighter-bombers such as the McDonnell Douglas F/A-18 Hornet are a less expensive option than having a range of specialized aircraft types; some of the most expensive fighters such as the US Grumman F-14 Tomcat, McDonnell Douglas F-15 Eagle, Lockheed Martin F-22 Raptor and Russian Sukhoi Su-27 were employed as all-weather interceptors as well as air superiority fighter aircraft, while developing air-to-ground roles late in their careers.
An interceptor is an aircraft intended to target bombers and so trades maneuverability for climb rate. Fighters were developed in World War I to deny enemy aircraft and dirigibles the ability to gather information by reconnaissance over the battlefield. Early fighters were small and armed by standards, most were biplanes built with a wooden frame covered with fabric, a maximum airspeed of about 100 mph; as control of the airspace over armies became important, all of the major powers developed fighters to support their military operations. Between the wars, wood was replaced in part or whole by metal tubing, aluminium stressed skin structures began to predominate. On 15 August 1914, Miodrag Tomić encountered an enemy plane while conducting a reconnaissance flight over Austria-Hungary; the Austro-Hungarian aviator waved at Tomić, who waved back. The enemy pilot took a revolver and began shooting at Tomić's plane. Tomić fired back, he swerved away from the Austro-Hungarian plane and the two aircraft parted ways.
It was considered the first exchange of fire between aircraft in history. Within weeks, all Serbian and Austro-Hungarian aircraft were armed; the Serbians equipped their planes with 8-millimetre Schwarzlose MG M.07/12 machine guns, six 100-round boxes of ammunition and several bombs. By World War II, most fighters were all-metal monoplanes armed with batteries of machine guns or cannons and some were capable of speeds approaching 400 mph. Most fighters up to this point had one engine.