Continuously variable transmission
A continuously variable transmission known as a shiftless transmission, single-speed transmission, stepless transmission, pulley transmission, or, in case of motorcycles, a'twist-and-go', is an automatic transmission that can change seamlessly through a continuous range of effective gear ratios. This contrasts with other mechanical transmissions; the flexibility of a CVT with suitable control may allow the input shaft to maintain a constant angular velocity as the output speed varies. A belt-driven design offers 88% efficiency, while lower than that of a manual transmission, can be offset by lower production cost and by enabling the engine to run at its most efficient speed for a range of output speeds; when power is more important than economy, the ratio of the CVT can be changed to allow the engine to turn at the RPM at which it produces greatest power. This is higher than the RPM that achieves peak efficiency. In low-mass low-torque applications a belt-driven CVT offers ease of use and mechanical simplicity.
A CVT does not require the presence of a clutch. In some vehicles, a centrifugal clutch is added to facilitate a "neutral" stance, useful when idling or manually reversing into a parking space. Simple rubber belt CVTs are used in small motorized vehicles, where their mechanical simplicity and ease of use outweigh their comparative inefficiency. Nearly all snowmobiles, utility vehicles, golf carts and motor scooters use CVTs the rubber belt or variable pulley variety. CVTs, along with several other electronic systems and driver aids were prohibited from Formula 1 in 1994 due to concerns over escalating research and development costs, maintaining a specific level of driver involvement with the vehicles. More CVT systems have been developed for go-karts and have proven to increase performance and engine life expectancy; the Tomcar range of off-road vehicles utilizes the CVT system. Some vehicles that offer CVT are the Chrysler Pacifica hybrid, the Ford C-MAX hybrid, the Mitsubishi Lancer, the Dodge Caliber, the Toyota Corolla, the Scion iQ, the Honda Insight, Fit, CR-Z hybrid, CR-V, Honda Civic, Honda Accord, the Nissan Tiida/Versa, Juke, Altima, Maxima, 2013 1.2 Note, Rogue, X-Trail, Pathfinder and the non-Mexican Micra, the Jeep Patriot and Compass, the Suzuki SX4 S-Cross, the Subaru Forester, Legacy and Crosstrek, Suzuki Kizashi, Toyota Allion 2009 onwards, Toyota Premio 2009 onwards, Toyota Avalon, Toyota Mark X, etc.
CVTs should be distinguished from power-sharing transmissions, as used in newer hybrid cars, such as the Toyota Prius and Camry, the Nissan Altima, newer-model Ford Escape Hybrid SUVs. CVT technology uses only one input from a prime mover and delivers variable output speeds and torque, whereas PST technology uses two prime mover inputs and varies the ratio of their contributions to output speed and power; these transmissions are fundamentally different. Farm equipment, namely harvester combines, used variable belt drives as early as the 1950s, as well. Many small tractors and self-propelled mowers for home and garden use simple rubber belt CVT. Hydrostatic systems are more common on the larger units—the walk-behind self-propelled mowers are of the slipping belt variety. Ratcheting CVT converting rotary motion to oscillating motion and back to rotary motion using roller clutches are well adapted to reciprocating engines when the oscillating movement is synchronized with that of the pistons; this solution could have a bright future because such ratcheting CVT are IVT, have a high energy efficiency.
They could help automakers comply with the future emission standards, while improving the reciprocating engines performance. Instead of being dimensioned according to the maximum torque, the motors using this type of CVT may be dimensioned by matching the maximum power with the maximum desired speed; such CVT is used only at startup or in case of mechanical overload, may be disconnected most of the time, the engine transferring the torque directly to the output. New concepts adapting the transmission ratio to the resistant torque and centrifugal clutches may be used to make these changes automatic. A ratchet CVT has been proposed for bicycles; the crankset causes a lever to swing, which in turn causes the reciprocating movement of a double rack that rotates the wheel as it moves backward and as it moves toward the wheel. The NuVinci Continuously Variable Transmission has been available since 2007. Hydrostatic CVTs are common in small to medium-sized earthmoving equipment; as the engines in these machines are run at constant power settings to provide hydraulic power or to power machinery, losses in mechanical efficiency are offset by enhanced operational efficiency, such as reduced forward-reverse shuttle times in earthmoving operations.
Transmission output is varied to control direction. This is beneficial in equipment designed to pivot or skid steer through differential power application as the required differential steering action can be supplied by independent CVTs, allowing steering to be accomplished without braking losses or loss of tractive effort and allowing the machine to pivot in place. In mowing or harvesting operations a CVT allows the forward speed of the tractor or combine harvester to be adjusted
The Boeing 757 is a mid-size, narrow-body twin-engine airliner, designed and built by Boeing Commercial Airplanes. It is the manufacturer's largest single-aisle passenger aircraft and was produced from 1981 to 2004; the twinjet has a two-crew member glass cockpit, turbofan engines of sufficient power to allow takeoffs from short runways and higher altitudes, a conventional tail and, for reduced aerodynamic drag, a supercritical wing design. Intended to replace the smaller three-engine 727 on short and medium routes, the 757 can carry 200 to 295 passengers for a maximum of 3,150 to 4,100 nautical miles, depending on variant; the 757 was designed concurrently with a wide-body twinjet, the 767, owing to shared features, pilots can obtain a common type rating that allows them to operate both aircraft. The 757 was produced in two fuselage lengths; the original 757-200 entered service in 1983. The stretched 757-300, the longest narrow-body twinjet produced, began service in 1999. Passenger 757-200s have been modified to special freighter specification for cargo use, while military derivatives include the C-32 transport, VIP carriers, other multi-purpose aircraft.
Private and government operators have customized the 757 for research and transport roles. All 757s are powered by Rolls-Royce Pratt & Whitney PW2000 series turbofans. Eastern Air Lines and British Airways placed the 757 in commercial service in 1983; the narrow-body twinjet succeeded earlier single-aisle airliners, became used for short and mid-range domestic routes, shuttle services, transcontinental U. S. flights. After regulators granted approval for extended flights over water in 1986, airlines began using the aircraft for intercontinental routes. Major customers for the 757 included U. S. mainline carriers, European charter airlines, cargo companies. The airliner has recorded eight hull-loss accidents, including seven fatal crashes, as of September 2015. Production of the 757 ended in October 2004; the 757-200 was by far the most popular model, with 913 built. Diminished sales amid an airline industry trend toward smaller jetliners led Boeing to end production without a direct replacement, in favor of the 737 family.
The last 757 was delivered to Shanghai Airlines in November 2005. In July 2017, 666 of the narrow-body twinjets were in airline service. In the early 1970s, following the launch of the wide-body 747, Boeing began considering further developments of its narrow-body 727 trijet. Designed for short and medium length routes, the three-engined 727 was the best-selling commercial jetliner of the 1960s and a mainstay of the U. S. domestic airline market. Studies focused on improving the most successful 727 variant. Two approaches were considered: a stretched 727-300, an all-new aircraft code-named 7N7; the former was a cheaper derivative using the 727's existing technology and tail-mounted engine configuration, while the latter was a twin-engine aircraft which made use of new materials and improvements to propulsion technology which had become available in the civil aerospace industry. United Airlines provided input for the proposed 727-300, which Boeing was poised to launch in late 1975, but lost interest after examining development studies for the 7N7.
Although the 727-300 was offered to Braniff International Airways and other carriers, customer interest remained insufficient for further development. Instead, airlines were drawn to the high-bypass-ratio turbofan engines, new flight deck technologies, lower weight, improved aerodynamics, reduced operating cost promised by the 7N7; these features were included in a parallel development effort for a new mid-size wide-body airliner, code-named 7X7, which became the 767. Work on both proposals accelerated as a result of the airline industry upturn in the late 1970s. By 1978, development studies focused on two variants: a 7N7-100 with seating for 160, a 7N7-200 with room for over 180 seats. New features included a redesigned wing, under-wing engines, lighter materials, while the forward fuselage, cockpit layout, T-tail configuration were retained from the 727. Boeing planned for the aircraft to offer the lowest fuel burn per passenger-kilometer of any narrow-body airliner. On August 31, 1978, Eastern Air Lines and British Airways became the first carriers to publicly commit to the 7N7 when they announced launch orders totaling 40 aircraft for the 7N7-200 version.
These orders were signed in March 1979, when Boeing designated the aircraft as the 757. The shorter 757-100 was dropped; the 757 was intended to be more capable and more efficient than the preceding 727. The focus on fuel efficiency reflected airline concerns over operating costs, which had grown amid rising oil prices during the Yom Kippur War of 1973. Design targets included a 20 percent reduction in fuel consumption from new engines, plus an additional 10 percent from aerodynamic improvements, versus preceding aircraft. Lighter materials and new wings were expected to improve efficiency; the maximum take-off weight was set at 220,000 pounds, 10,000 pounds more than the 727. The 757's higher thrust-to-weight ratio allowed it to take off from short runways and serve airports in hot and high climates, offering better takeoff performance than that offered by competing aircraft. Competitors needed longer takeoff runs at airports at higher elevations, with higher ambient temperatures and thinner air.
The Boeing 727 is an American midsized, narrow-body three-engined jet aircraft built by Boeing Commercial Airplanes from the early 1960s to 1984. It can carry 149 to 189 passengers and models can fly up to 2,700 nautical miles nonstop. Intended for short and medium-length flights, the 727 can use short runways at smaller airports, it has three Pratt & Whitney JT8D engines below the T-tail, one on each side of the rear fuselage with a center engine that connects through an S-duct to an inlet at the base of the fin. The 727 is the only Boeing trijet, as a commercial design entering production; the 727 followed the 707, a quad-jet airliner, with which it shares its upper fuselage cross-section and cockpit design. The 727-100 first flew in February 1963 and entered service with Eastern Air Lines in February 1964; the 727 became a mainstay of airlines' domestic route networks and was used on short- and medium-range international routes. Passenger and convertible versions of the 727 were built; the highest production rate of the 727 was in the 1970s.
As of July 2018, a total of 44 Boeing 727s were in commercial service with 23 airlines, plus a few more in government and private use. Airport noise regulations have led to 727s being equipped with hush kits. Since 1964, there have been 118 fatal incidents involving the Boeing 727. Successor models include variants of the 737 and the 757-200; the last commercial passenger flight of the type was in January 2019. The Boeing 727 design was a compromise among United Airlines, American Airlines, Eastern Air Lines. United Airlines requested a four-engine aircraft for its flights to high-altitude airports its hub at Stapleton International Airport in Denver, Colorado. American Airlines, operating the four-engined Boeing 707 and Boeing 720, requested a twin-engined aircraft for efficiency. Eastern Airlines wanted a third engine for its overwater flights to the Caribbean, since at that time twin-engine commercial flights were limited by regulations to routes with 60-minute maximum flying time to an airport.
The three airlines agreed on a trijet design for the new aircraft. In 1959, Lord Douglas, chairman of British European Airways, suggested that Boeing and de Havilland Aircraft Company work together on their trijet designs, the 727 and D. H.121 Trident, respectively. The two designs had a similar layout, the 727 being larger. At that time Boeing intended to use three Allison AR963 turbofan engines, license-built versions of the Rolls-Royce RB163 Spey used by the Trident. Boeing and de Havilland each sent engineers to the other company's locations to evaluate each other's designs, but Boeing decided against the joint venture. De Havilland had wanted Boeing to license-build the D. H.121, while Boeing felt that the aircraft needed to be designed for the American market, with six-abreast seating and the ability to use runways as short as 4,500 feet. In 1960, Pratt & Whitney was looking for a customer for its new JT8D turbofan design study, based on its J52 turbojet, while United and Eastern were interested in a Pratt & Whitney alternative to the RB163 Spey.
Once Pratt & Whitney agreed to go ahead with development of the JT8D, Eddie Rickenbacker, chairman of the board of Eastern, told Boeing that the airline preferred the JT8D for its 727s. Boeing had not offered the JT8D, as it was about 1,000 lb heavier than the RB163, though more powerful. Boeing reluctantly agreed to offer the JT8D as an option on the 727, it became the sole powerplant. With high-lift devices on its wing, the 727 could use shorter runways than most earlier jets. 727 models were stretched to carry more passengers and replaced earlier jet airliners such as the Boeing 707 and Douglas DC-8, as well as aging propeller airliners such as the DC-4, DC-6, DC-7, the Lockheed Constellations on short- and medium-haul routes. For over a decade, more 727s were built per year than any other jet airliner; the airliner's middle engine at the rear of the fuselage gets air from an inlet ahead of the vertical fin through an S-shaped duct. This S-duct proved to be troublesome in that flow distortion in the duct induced a surge in the centerline engine on the take-off of the first flight of the 727-100.
This was fixed by the addition of several large vortex generators in the inside of the first bend of the duct. The 727 was designed for smaller airports, so independence from ground facilities was an important requirement; this led to one of the 727's most distinctive features: the built-in airstair that opens from the rear underbelly of the fuselage, which could be opened in flight. Hijacker D. B. Cooper used this hatch when he parachuted from the back of a 727, as it was flying over the Pacific Northwest. Boeing subsequently modified the design with the Cooper vane so that the airstair could not be lowered in flight. Another innovation was the auxiliary power unit, which allowed electrical and air-conditioning systems to run independently of a ground-based power supply, without having to start one of the main engines. An unusual design feature is that the APU is mounted in a hole in the keel beam web, in the main landing gear bay; the 727 is eq
A gas turbine called a combustion turbine, is a type of continuous combustion, internal combustion engine. There are three main components: An upstream rotating gas compressor. Above. A fourth component is used to increase efficiency, to convert power into mechanical or electric form, or to achieve greater power to mass/volume ratio; the basic operation of the gas turbine is a Brayton cycle with air as the working fluid. Fresh atmospheric air flows through the compressor. Energy is added by spraying fuel into the air and igniting it so the combustion generates a high-temperature flow; this high-temperature high-pressure gas enters a turbine, where it expands down to the exhaust pressure, producing a shaft work output in the process. The turbine shaft work is used to drive the compressor; the purpose of the gas turbine determines the design so that the most desirable split of energy between the thrust and the shaft work is achieved. The fourth step of the Brayton cycle is omitted, as gas turbines are open systems that do not use the same air again.
Gas turbines are used to power aircraft, ships, electrical generators, gas compressors, tanks. 50: Earliest records of Hero's engine. It most served no practical purpose, was rather more of a curiosity. 1000: The "Trotting Horse Lamp" was used by the Chinese at lantern fairs as early as the Northern Song dynasty. When the lamp is lit, the heated airflow rises and drives an impeller with horse-riding figures attached on it, whose shadows are projected onto the outer screen of the lantern. 1500: The Chimney Jack was drawn by Leonardo da Vinci: Hot air from a fire rises through a single-stage axial turbine rotor mounted in the exhaust duct of the fireplace and turning the roasting spit by gear-chain connection. 1629: Jets of steam rotated an impulse turbine that drove a working stamping mill by means of a bevel gear, developed by Giovanni Branca. 1678: Ferdinand Verbiest built a model carriage relying on a steam jet for power. 1791: A patent was given to John Barber, an Englishman, for the first true gas turbine.
His invention had most of the elements present in the modern day gas turbines. The turbine was designed to power a horseless carriage. 1861: British patent no. 1633 was granted to Marc Antoine Francois Mennons for a "Caloric engine". The patent shows that it was a gas turbine and the drawings show it applied to a locomotive. Named in the patent was Nicolas de Telescheff, a Russian aviation pioneer. 1872: A gas turbine engine designed by Berlin engineer, Franz Stolze, is thought to be the first attempt at creating a working model, but the engine never ran under its own power. 1894: Sir Charles Parsons patented the idea of propelling a ship with a steam turbine, built a demonstration vessel, the Turbinia the fastest vessel afloat at the time. This principle of propulsion is still of some use. 1895: Three 4-ton 100 kW Parsons radial flow generators were installed in Cambridge Power Station, used to power the first electric street lighting scheme in the city. 1899: Charles Gordon Curtis patented the first gas turbine engine in the US.
1900: Sanford Alexander Moss submitted a thesis on gas turbines. In 1903, Moss became an engineer for General Electric's Steam Turbine Department in Lynn, Massachusetts. While there, he applied some of his concepts in the development of the turbosupercharger, his design used a small turbine wheel, driven by exhaust gases. 1903: A Norwegian, Ægidius Elling, built the first gas turbine, able to produce more power than needed to run its own components, considered an achievement in a time when knowledge about aerodynamics was limited. Using rotary compressors and turbines it produced 11 hp. 1906: The Armengaud-Lemale turbine engine in France with a water-cooled combustion chamber. 1910: Holzwarth impulse turbine achieved 150 kilowatts. 1913: Nikola Tesla patents the Tesla turbine based on the boundary layer effect. 1920s The practical theory of gas flow through passages was developed into the more formal theory of gas flow past airfoils by A. A. Griffith resulting in the publishing in 1926 of An Aerodynamic Theory of Turbine Design.
Working testbed designs of axial turbines suitable for driving a propellor were developed by the Royal Aeronautical Establishment proving the efficiency of aerodynamic shaping of the blades in 1929. 1930: Having found no interest from the RAF for his idea, Frank Whittle patented the design for a centrifugal gas turbine for jet propulsion. The first successful use of his engine occurred in England in April 1937. 1932: BBC Brown, Boveri & Cie of Switzerland] starts selling axial compressor and turbine turbosets as part of the turbocharged steam generating Velox boiler. Following the gas turbine principle, the steam evaporation tubes are arranged within the gas turbine combustion chamber. 1934: Raúl Pateras de Pescara patented the free-piston engine as a gas gener
The turbofan or fanjet is a type of airbreathing jet engine, used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the turbo portion refers to a gas turbine engine which achieves mechanical energy from combustion, the fan, a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a turbojet passes through the turbine, in a turbofan some of that air bypasses the turbine. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust; the ratio of the mass-flow of air bypassing the engine core divided by the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together. Most commercial aviation jet engines in use today are of the high-bypass type, most modern military fighter engines are low-bypass. Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines.
Modern turbofans have either a smaller fan with several stages. An early configuration combined a low-pressure fan in a single rear-mounted unit. Turbofans were invented to circumvent an awkward feature of turbojets, that they were inefficient for subsonic flight. To raise the efficiency of a turbojet, the obvious approach would be to increase the burner temperature, to give better Carnot efficiency and fit larger compressors and nozzles. However, while that does increase thrust somewhat, the exhaust jet leaves the engine with higher velocity, which at subsonic flight speeds, takes most of the extra energy with it, wasting fuel. Instead, a turbofan can be thought of as a turbojet being used to drive a ducted fan, with both of those contributing to the thrust. Whereas all the air taken in by a turbojet passes through the turbine, in a turbofan some of that air bypasses the turbine; because the turbine has to additionally drive the fan, the turbine is larger and has larger pressure and temperature drops, so the nozzles are smaller.
This means. The fan has lower exhaust velocity, giving much more thrust per unit energy; the overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed. In effect, a turbofan emits a large amount of air more whereas a turbojet emits a smaller amount of air, a far less efficient way to generate the same thrust; the ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together. Most commercial aviation jet engines in use today are of the high-bypass type, most modern military fighter engines are low-bypass. Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines; the bypass ratio of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core.
A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core. Turbofan engines are described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition bpr is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of high bypass turbofans; this allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption with increasing BPS. BPR can be quoted for lift fan installations where the fan airflow is remote from the engine and doesn't physically touch the engine core. Bypass provides a lower fuel consumption for the same thrust. If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed.
For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The trade off between mass flow and velocity is seen with propellers and helicopter rotors by comparing disc loading and power loading. For example, the same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor. Bypass refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where the sole requirement for bypass is to provide cooling air; this sets the lower limit for bpr and these engines have been called "leaky" or continuous bleed turbojets and low bpr turbojets. Low bpr has bee
The Boeing 767 is a mid- to large-size, mid- to long-range, wide-body twin-engine jet airliner built by Boeing Commercial Airplanes. It was its first airliner with a two-crew glass cockpit; the aircraft has two turbofan engines, a conventional tail, for reduced aerodynamic drag, a supercritical wing design. Designed as a smaller wide-body airliner than earlier aircraft such as the 747, the 767 has a seating capacity for 181 to 375 people, a design range of 3,850 to 6,385 nautical miles, depending on variant. Development of the 767 occurred in tandem with a narrow-body twinjet, the 757, resulting in shared design features which allow pilots to obtain a common type rating to operate both aircraft; the 767 is produced in three fuselage lengths. The original 767-200 entered service in 1982, followed by the 767-300 in 1986 and the 767-400ER, an extended-range variant, in 2000; the extended-range 767-200ER and 767-300ER models entered service in 1984 and 1988 while a production freighter version, the 767-300F, debuted in 1995.
Conversion programs have modified passenger 767-200 and 767-300 series aircraft for cargo use, while military derivatives include the E-767 surveillance aircraft, the KC-767 and KC-46 aerial tankers, VIP transports. Engines featured on the 767 include the General Electric CF6, Pratt & Whitney JT9D and PW4000, Rolls-Royce RB211 turbofans. United Airlines first placed the 767 in commercial service in 1982; the aircraft was flown on domestic and transcontinental routes, during which it demonstrated the reliability of its twinjet design. The 767 became the first twin-engined airliner to be used on extended overseas flights in 1985; the aircraft was used to expand non-stop service on medium- to long-haul intercontinental routes. In 1986, Boeing initiated studies for a higher-capacity 767 leading to the development of the 777, a larger wide-body twinjet. In the 1990s, the 767 became the most used airliner for transatlantic flights between North America and Europe; the 767 is the first twinjet wide-body type to reach 1,000 aircraft delivered.
As of January 2019, Boeing has received 1,244 orders for the 767 from 74 customers with 1,135 delivered. A total of 742 of these aircraft were in service in July 2018; the most popular variant is the 767-300ER with 583 delivered. Delta Air Lines is the largest operator with 77 aircraft. Competitors have included the Airbus A300, A310, A330-200. Non-passenger variants of the 767 remain in production as of 2019 while the passenger variant's successor, the 787, entered service in 2011. In 1970, Boeing's 747 became the first wide-body jetliner to enter service; the 747 was the first passenger jet wide enough to feature a twin-aisle cabin. Two years the manufacturer began a development study, code-named 7X7, for a new wide-body aircraft intended to replace the 707 and other early generation narrow-body jets; the aircraft would provide twin-aisle seating, but in a smaller fuselage than the existing 747, McDonnell Douglas DC-10, Lockheed L-1011 TriStar wide-bodies. To defray the high cost of development, Boeing signed risk-sharing agreements with Italian corporation Aeritalia and the Civil Transport Development Corporation, a consortium of Japanese aerospace companies.
This marked the manufacturer's first major international joint venture, both Aeritalia and the CTDC received supply contracts in return for their early participation. The initial 7X7 was conceived as a short take-off and landing airliner intended for short-distance flights, but customers were unenthusiastic about the concept, leading to its redefinition as a mid-size, transcontinental-range airliner. At this stage the proposed aircraft featured two or three engines, with possible configurations including over-wing engines and a T-tail. By 1976, a twinjet layout, similar to the one which had debuted on the Airbus A300, became the baseline configuration; the decision to use two engines reflected increased industry confidence in the reliability and economics of new-generation jet powerplants. While airline requirements for new wide-body aircraft remained ambiguous, the 7X7 was focused on mid-size, high-density markets; as such, it was intended to transport large numbers of passengers between major cities.
Advancements in civil aerospace technology, including high-bypass-ratio turbofan engines, new flight deck systems, aerodynamic improvements, lighter construction materials were to be applied to the 7X7. Many of these features were included in a parallel development effort for a new mid-size narrow-body airliner, code-named 7N7, which would become the 757. Work on both proposals proceeded through the airline industry upturn in the late 1970s. In January 1978, Boeing announced a major extension of its Everett factory—which was dedicated to manufacturing the 747—to accommodate its new wide-body family. In February 1978, the new jetliner received the 767 model designation, three variants were planned: a 767-100 with 190 seats, a 767-200 with 210 seats, a trijet 767MR/LR version with 200 seats intended for intercontinental routes; the 767MR/LR was subsequently renamed 777 for differentiation purposes. The 767 was launched on July 14, 1978, when United Airlines ordered 30 of the 767-200 variant, followed by 50 more 767-200 orders from American Airlines and Delta Air Lines that year.
The 767-100 was not offered for sale, as its capacity was too close to the 757's seating, while the 777 trijet was dropped in favor of standardizing around the twinjet configuration. In the late 1970s, operating cost replaced capacity as the primary factor in airliner purchases; as a result, the 767's design process emphasized fuel efficiency from the outset. Bo
An airliner is a type of aircraft for transporting passengers and air cargo. Such aircraft are most operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is defined as an aeroplane intended for carrying multiple passengers or cargo in commercial service; the largest of them are wide-body jets which are called twin-aisle because they have two separate aisles running from the front to the back of the passenger cabin. These are used for long-haul flights between airline hubs and major cities. A smaller, more common class of airliners is the single-aisle; these are used for short to medium-distance flights with fewer passengers than their wide-body counterparts. Regional airliners seat fewer than 100 passengers and may be powered by turbofans or turboprops; these airliners are the non-mainline counterparts to the larger aircraft operated by the major carriers, legacy carriers, flag carriers, are used to feed traffic into the large airline hubs. These regional routes form the spokes of a hub-and-spoke air transport model.
The lightest of short-haul regional feeder airliner type aircraft that carry a small number of passengers are called commuter aircraft, commuterliners and air taxis, depending on their size, how they are marketed, region of the world, seating configurations. The Beechcraft 1900, for example, has only 19 seats; when the Wright brothers made the world’s first sustained heavier-than-air flight, they laid the foundation for what would become a major transport industry. Their flight in 1903 was just 11 years before what is defined as the world’s first airliner; these airliners have had a significant impact on global society and politics. In 1913, Igor Sikorsky developed the first large multi-engine airplane, the Russky Vityaz, refined into the more practical Ilya Muromets with dual controls for a pilot plus copilot and a comfortable cabin with a lavatory, cabin heating and lighting; the large four-engine biplane was derived in a bomber aircraft, preceding subsequent transport and bomber aircraft.
Due to the onset of World War I, it was never used as a commercial airliner. It first flew on December 10, 1913 and took off for its first demonstration flight with 16 passengers aboard on February 25, 1914. In 1915, the first airliner was used by Elliot Air Service; the aircraft was a Curtiss JN 4, a small biplane, used in World War I as a trainer. It was used as a tour and familiarization flight aircraft in the early 1920s. In 1919, after World War I, the Farman F.60 Goliath designed as a long-range heavy bomber, was converted for commercial use into a passenger airliner. It could seat 14 passengers from 1919, around 60 were built. Several publicity flights were made, including one on 8 February 1919, when the Goliath flew 12 passengers from Toussus-le-Noble to RAF Kenley, near Croydon, despite having no permission from the British authorities to land. Another important airliner built in 1919 was the Airco DH.16. In March 1919, the prototype first flew at Hendon Aerodrome. Nine aircraft were built, all but one being delivered to the nascent airline, Aircraft Transport and Travel, which used the first aircraft for pleasure flying, on 25 August 1919, it inaugurated the first scheduled international airline service from London to Paris.
One aircraft was sold to the River Plate Aviation Company in Argentina, to operate a cross-river service between Buenos Aires and Montevideo. Meanwhile, the competing Vickers converted its successful WWI bomber, the Vickers Vimy, into a civilian version, the Vimy Commercial, it was redesigned with a larger-diameter fuselage, first flew from the Joyce Green airfield in Kent on 13 April 1919. The world's first all-metal transport aircraft was the Junkers F.13 from 1919, with 322 built. The Dutch Fokker company produced the Fokker F. II and the F. III; these aircraft were used by the Dutch airline KLM when it reopened an Amsterdam-London service in 1921. The Fokkers were soon flying to destinations across Europe, including Bremen, Brussels and Paris, they proved to be reliable aircraft. The Handley Page company in Britain produced the Handley Page Type W as the company's first civil transport aircraft, it housed two crew in 15 passengers in an enclosed cabin. Powered by two 450 hp Napier Lion engines, the prototype first flew on 4 December 1919, shortly after it was displayed at the 1919 Paris Air Show at Le Bourget.
It was the world's first airliner to be designed with an on-board lavatory. Meanwhile in France, the Bleriot-SPAD S.33 was a great success throughout the 1920s serving the Paris-London route, on continental routes. The enclosed cabin could carry four passengers with an extra seat in the cockpit. By 1921, aircraft capacity needed to be larger for the economics to remain favourable; the English company de Havilland, therefore built the 10-passenger DH.29 monoplane, while starting work on the design of the DH.32, an eight-seater biplane with a less powerful but more economical Rolls-Royce Eagle engine. Owing to the urgent need for more capacity, work on the DH.32 was stopped and the DH.34 biplane was designed, accommodating 10 passengers. The Fokker trimotor was an important and popular transport, manufactured under license in Europe and America. Throughout the 1920s, companies in Britain and France were at the forefront of the civil airliner industry considerably aided by governme