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104-1009: The Boeing 737 is an American narrow-body airliner produced by Boeing at its Renton factory in Washington . Developed to supplement the Boeing 727 on short and thin routes, the twinjet retained the 707 fuselage width and six abreast seating but with two underwing Pratt & Whitney JT8D low-bypass turbofan engines. Envisioned in 1964, the initial 737-100 made its first flight in April 1967 and entered service in February 1968 with Lufthansa . The lengthened 737-200 entered service in April 1968, and evolved through four generations, offering several variants for 85 to 215 passengers. The First Generation 737-100/200 variants were powered by Pratt & Whitney JT8D low-bypass turbofan engines and offered seating for 85 to 130 passengers. Launched in 1980 and introduced in 1984,

208-584: A VIP aircraft by the Mexican Air Force for 23 years under registration TP-03. TP-03 would be broken up in 2006. The first 737-100, NASA 515, is on static display in the Museum of Flight in Seattle and is the last surviving example of the type. The 737-200 was a 737-100 with an extended fuselage, launched by an order from United Airlines in 1965 and entered service with the launch customer in April 1968. Its unit cost

312-458: A design team, which cooperated with CFM International to select, modify and deploy a new engine and nacelle that would make the 737-300 into a viable aircraft. They chose the CFM56-3B-1 high-bypass turbofan engine to power the aircraft, which yielded significant gains in fuel economy and a reduction in noise, but also posed an engineering challenge, given the low ground clearance of the 737 and

416-629: A general purpose airfoil that finds wide application, and pre–dates the NACA system, is the Clark-Y . Today, airfoils can be designed for specific functions by the use of computer programs. The various terms related to airfoils are defined below: The geometry of the airfoil is described with a variety of terms : The shape of the airfoil is defined using the following geometrical parameters: Some important parameters to describe an airfoil's shape are its camber and its thickness . For example, an airfoil of

520-516: A gravel deflector on the nose gear and a vortex dissipator extending from the front of the engine. Alaska Airlines used the gravel kit for some of its combi aircraft rural operations in Alaska until retiring its -200 fleet in 2007. Air Inuit , Nolinor Aviation and Chrono Aviation still use the gravel kit in Northern Canada. Canadian North also operated a gravel-kitted 737-200 Combi, but this

624-419: A need for a new aircraft to supplement the 727 on short and thin routes. Preliminary design work began on May 11, 1964, based on research that indicated a market for a fifty to sixty passenger airliner flying routes of 50 to 1,000 miles (100 to 1,600 km). The initial concept featured podded engines on the aft fuselage, a T-tail as with the 727, and five-abreast seating. Engineer Joe Sutter relocated

728-451: A new Boeing aircraft. Lufthansa was the only significant customer to purchase the 737-100 and only 30 aircraft were produced. The -200 was rolled out on June 29, 1967, and had its maiden flight on August 8, 1967. It was then certified by the FAA on December 21, 1967. The inaugural flight for United Airlines took place on April 28, 1968, from Chicago to Grand Rapids, Michigan . The lengthened -200

832-500: A range similar to the Airbus A319LR . The 737-800 was a stretched version of the 737-700 launched on September 5, 1994. The -800 seats 162 passengers in a two-class or 189 passengers in a high-density, one-class layout. Launch customer Hapag-Lloyd Flug (now TUIfly ) received the first one in April 1998. The -800 replaced directly the -400 and aging 727-200 of US airlines. It filled also the gap left by Boeing's decision to discontinue

936-415: A retrofit was provided for active aircraft. Longer nacelle/wing fairings were introduced, and the airflow over the flaps and slats was improved. The production line also introduced an improvement to the flap system, allowing increased use during takeoff and landing. All these changes gave the aircraft a boost to payload and range, and improved short-field performance. Both the first and last 737-100s became

1040-437: A sharp leading edge. All have a sharp trailing edge . The air deflected by an airfoil causes it to generate a lower-pressure "shadow" above and behind itself. This pressure difference is accompanied by a velocity difference, via Bernoulli's principle , so the resulting flowfield about the airfoil has a higher average velocity on the upper surface than on the lower surface. In some situations (e.g., inviscid potential flow )

1144-483: A single-class layout with slimline seats requiring an extra pair of exit doors . The MAX 200 would be 20% more cost-efficient per seat, including 5% lower operating costs than the MAX 8 and would be the most efficient narrow-body on the market when entering service. In mid-November 2018, the first MAX 200 of the 135 ordered by Ryanair rolled out, in a 197-seat configuration. It was first flown from Renton on January 13, 2019, and

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1248-492: A strengthened wing spar . The -400s first flight was on February 19, 1988, and, after a seven-month/500-hour flight-testing run, entered service with Piedmont Airlines that October. The last two -400s, i.e. the last 737 Classics series, were delivered to CSA Czech Airlines on February 28, 2000. The 737-400 was replaced by the 737-800 of the Next Generation series. The 737-400SF was a 737-400 converted to freighter, though it

1352-421: A subsonic flow about a thin airfoil can be described in terms of an outer region, around most of the airfoil chord, and an inner region, around the nose, that asymptotically match each other. As the flow in the outer region is dominated by classical thin airfoil theory, Morris's equations exhibit many components of thin airfoil theory. In thin airfoil theory, the width of the (2D) airfoil is assumed negligible, and

1456-426: A two class and 189 in a high-density, one class layout. The launch customer Alaska Airlines received the delivery on May 15, 2001. The 737-900ER (Extended Range) is the newest and largest variant of the 737NG generation. An additional pair of exit doors and a flat rear pressure bulkhead increased its seating capacity to 180 passengers in a two-class and up to 220 passengers in a one-class configuration. The -900ER

1560-401: Is increased before the wing achieves maximum thickness to minimize the chance of boundary layer separation. This elongates the wing and moves the point of maximum thickness back from the leading edge. Supersonic airfoils are much more angular in shape and can have a very sharp leading edge, which is very sensitive to angle of attack. A supercritical airfoil has its maximum thickness close to

1664-1460: Is insufficient for fully laden operations and operates at reduced capacity like the Airbus A318 , while the Airbus A321LR could replace the less fuel efficient Boeing 757s used since their production ended in 2004. Boeing will face competition and pricing pressure from the Embraer E-Jet E2 family , Airbus A220 (formerly Bombardier CSeries) and Comac C919 . Between 2016 and 2035, FlightGlobal expects 26,860 single-aisles to be delivered for almost $ 1380 billion, 45% Airbus A320 family ceo and neo and 43% Boeing 737 NG and max. By June 2018, there were 10,572 Airbus A320neo and Boeing 737 MAX orders: 6,068 Airbuses (57%, 2,295 with CFMs, 1,623 with PWs and 2,150 with not yet decided engines) and 4,504 Boeings (43%); 3,446 in Asia-Pacific (33%), 2,349 in Europe (22%), 1,926 in North America (18%), 912 in Latin America (9%), 654 in Middle East (6%), 72 in Africa (1%) and 1,213 not yet bounded (11%). Many airlines have shown interest in

1768-912: Is the name given to the 737-300/400/500 series after the introduction of the -600/700/800/900 series of the Boeing 737 family. Produced from 1984 to 2000, a total of 1,988 Classic series were delivered. Close to the next major upgrade of single aisle aircraft at Airbus and Boeing, the price of jet fuel reached a peak in 2008, when airlines devoted 40% of the retail price of an air ticket to pay for fuel, versus 15% in 2000. Consequently, in that year carriers retired Boeing 737 Classic aircraft to reduce fuel consumption; replacements consisted of more efficient 737 Next Generation or A320 family aircraft. On June 4, 2008, United Airlines announced it would retire all 94 of its Classic 737 aircraft (64 737-300 and 30 737-500 aircraft), replacing them with A320 family jets taken from its Ted subsidiary, which has been shut down. This intensified

1872-401: Is the position at which the pitching moment M ′ does not vary with a change in lift coefficient: ∂ ( C M ′ ) ∂ ( C L ) = 0 . {\displaystyle {\frac {\partial (C_{M'})}{\partial (C_{L})}}=0{\text{.}}} Thin-airfoil theory shows that, in two-dimensional inviscid flow,

1976-515: The 737 MAX -7/8/9/10 variants, powered by improved CFM LEAP -1B high-bypass turbofans and accommodating 138 to 204 people, entered service in 2017. Boeing Business Jet versions have been produced since the 737NG, as well as military models. As of October 2024, 16,705 Boeing 737s have been ordered and 11,898 delivered. Initially, its main competitor was the McDonnell Douglas DC-9 , followed by its MD-80 / MD-90 derivatives. In 2013,

2080-474: The Air Transport Association maintenance and engineering conference by chief project engineer Jack Steiner, where its elaborate high-lift devices raised concerns about maintenance costs and dispatch reliability. The original 737 continued to be developed into thirteen passenger, cargo, corporate and military variants. These were later divided into what has become known as the four generations of

2184-635: The Airbus A318 . The 737-700, the first variant of the Next-Generation, was launched in November 1993 with an order of 63 aircraft. The -700 seats 126 passengers in a two-class or 149 passengers in a one-class layout. The launch customer Southwest Airlines took the first delivery in December 1997. The 737-700 replaced the 737-300 and competes with the Airbus A319 . The 737-700C is a convertible version where

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2288-424: The Airbus A321LR or its A321XLR derivative, and other extended-range models, for thin transatlantic and Asia-Pacific routes. Airfoil An airfoil ( American English ) or aerofoil ( British English ) is a streamlined body that is capable of generating significantly more lift than drag . Wings, sails and propeller blades are examples of airfoils. Foils of similar function designed with water as

2392-463: The BAC One-Eleven (BAC-111), Douglas DC-9 , and Fokker F28 were already into flight certification. To expedite development, Boeing used 60% of the structure and systems of the existing 727, particularly the fuselage, which differs in length only. This 148-inch (3.76 m) wide fuselage cross-section permitted six-abreast seating compared to the rivals' five-abreast. The 727's fuselage was derived from

2496-495: The Biot–Savart law , the vorticity γ( x ) produces a flow field w ( x ) = 1 2 π ∫ 0 c γ ( x ′ ) x − x ′ d x ′ , {\displaystyle w(x)={\frac {1}{2\pi }}\int _{0}^{c}{\frac {\gamma (x')}{x-x'}}\,dx'{\text{,}}} oriented normal to

2600-532: The CFM LEAP -1B engine, with American Airlines intending to order 100 of these aircraft. On August 30, 2011, Boeing confirmed the launch of the 737 new engine variant, to be called the Boeing 737 MAX . It was based on earlier 737 designs with more efficient LEAP-1B power plants, aerodynamic improvements (most notably split-tip winglets ), and airframe modifications. It competes with the Airbus A320neo family that

2704-550: The CFM56 . The 737 went on to become the highest-selling commercial aircraft in terms of orders until surpassed by the competing Airbus A320 family in October 2019, but maintains the record in total deliveries. The fuselage is manufactured in Wichita, Kansas , by Boeing spin-off company Spirit AeroSystems , before being moved by rail to Renton. The Renton factory has three assembly lines for

2808-655: The U.S. Air Force . Some were modified into CT-43s, which are used to transport passengers, and one was modified as the NT-43A Radar Test Bed. The first was delivered on July 31, 1973, and the last on July 19, 1974. The Indonesian Air Force ordered three modified 737-200s, designated Boeing 737-2X9 Surveiller . They were used as Maritime reconnaissance (MPA)/transport aircraft, fitted with SLAMMAR (Side-looking Multi-mission Airborne Radar). The aircraft were delivered between May 1982 and October 1983.After 40 years, in March 2008,

2912-1287: The change of variables x = c ⋅ 1 + cos ⁡ ( θ ) 2 , {\displaystyle x=c\cdot {\frac {1+\cos(\theta )}{2}},} and then expanding both dy ⁄ dx and γ( x ) as a nondimensionalized Fourier series in θ with a modified lead term: d y d x = A 0 + A 1 cos ⁡ ( θ ) + A 2 cos ⁡ ( 2 θ ) + … γ ( x ) = 2 ( α + A 0 ) ( sin ⁡ θ 1 + cos ⁡ θ ) + 2 A 1 sin ⁡ ( θ ) + 2 A 2 sin ⁡ ( 2 θ ) + … . {\displaystyle {\begin{aligned}&{\frac {dy}{dx}}=A_{0}+A_{1}\cos(\theta )+A_{2}\cos(2\theta )+\dots \\&\gamma (x)=2(\alpha +A_{0})\left({\frac {\sin \theta }{1+\cos \theta }}\right)+2A_{1}\sin(\theta )+2A_{2}\sin(2\theta )+\dots {\text{.}}\end{aligned}}} The resulting lift and moment depend on only

3016-648: The convolution equation ( α − d y d x ) V = − w ( x ) = − 1 2 π ∫ 0 c γ ( x ′ ) x − x ′ d x ′ , {\displaystyle \left(\alpha -{\frac {dy}{dx}}\right)V=-w(x)=-{\frac {1}{2\pi }}\int _{0}^{c}{\frac {\gamma (x')}{x-x'}}\,dx'{\text{,}}} which uniquely determines it in terms of known quantities. An explicit solution can be obtained through first

3120-411: The trailing edge angle . The slope is greatest if the angle is zero; and decreases as the angle increases. For a wing of finite span, the aspect ratio of the wing also significantly influences the slope of the curve. As aspect ratio decreases, the slope also decreases. Thin airfoil theory is a simple theory of airfoils that relates angle of attack to lift for incompressible, inviscid flows . It

3224-407: The -500. The Boeing 737 Next Generation , abbreviated as 737 Next Gen or 737NG , is the name given to the main models 737-600/700/800/900 series and the extended range -700ER/900ER variants of the Boeing 737 family. It has been produced since 1996 and introduced in 1997, with a total order of 7,097 aircraft, of which 7,031 have been delivered as of May 2019. The primary goal was to re-engine

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3328-663: The 1/4 chord point will thus be C M ( 1 / 4 c ) = − π / 4 ( A 1 − A 2 ) . {\displaystyle C_{M}(1/4c)=-\pi /4(A_{1}-A_{2}){\text{.}}} From this it follows that the center of pressure is aft of the 'quarter-chord' point 0.25 c , by Δ x / c = π / 4 ( ( A 1 − A 2 ) / C L ) . {\displaystyle \Delta x/c=\pi /4((A_{1}-A_{2})/C_{L}){\text{.}}} The aerodynamic center

3432-463: The 1980s revealed the practicality and usefulness of laminar flow wing designs and opened the way for laminar-flow applications on modern practical aircraft surfaces, from subsonic general aviation aircraft to transonic large transport aircraft, to supersonic designs. Schemes have been devised to define airfoils – an example is the NACA system . Various airfoil generation systems are also used. An example of

3536-460: The 707. The proposed wing airfoil sections were based on those of the 707 and 727, but somewhat thicker; altering these sections near the nacelles achieved a substantial drag reduction at high Mach numbers. The engine chosen was the Pratt & Whitney JT8D -1 low-bypass ratio turbofan engine, delivering 14,500 pounds-force (64  kN ) of thrust. The concept design was presented in October 1964 at

3640-460: The 737 Classic series, allowing longer routes with fewer passengers to be more economical than with the 737-300. The fuselage length of the 737-500 is 1 foot 7 inches (48 cm) longer than the 737-200, accommodating up to 140 passengers. Both glass and older-style mechanical cockpits arrangements were available. Using the CFM56-3 engine also gave a 25 percent increase in fuel efficiency over

3744-509: The 737 MAX, has a longer fuselage than the MAX 7. On July 23, 2013, Boeing completed the firm configuration for the 737 MAX 8. Its first commercial flight was operated by Malindo Air on May 22, 2017. The MAX 8 replaced the 737-800 and competed with the A320neo. The 737 MAX 200 , a high-density version of the 737 MAX 8, was launched in September 2014 and named for seating for up to 200 passengers in

3848-592: The 737 MAX; a fourth is planned to open at the Everett factory in 2024. The Boeing 737 Original is the name given to the -100/200 and -200 Advanced series of the Boeing 737 family. The initial model was the 737-100, the smallest variant of the 737 aircraft family, which was launched in February 1965 and entered service with Lufthansa in February 1968. In 1968, its unit cost was US$ 3.7M (1968), $ 32.4M today. A total of 30 737-100s were ordered: 22 by Lufthansa, 5 by Malaysia–Singapore Airlines (MSA) and 2 by Avianca with

3952-418: The 737 project would not be canceled. Consultation with Lufthansa over the previous winter had resulted in the seating capacity being increased to 100. On April 5, 1965, Boeing announced an order by United Airlines for 40 737s. United wanted a slightly larger capacity than the 737-100, so the fuselage was stretched 36 inches (91 cm) ahead of, and 40 inches (102 cm) behind the wing. The longer version

4056-524: The 737 with the high pressure ratio CFM56-7. By the early 1990s, as the MD-80 slowly withdrew from the competition following the introduction of the MD-90, it had become clear that the new A320 family was a serious threat to Boeing's market share. Airbus won previously loyal 737 customers, such as Lufthansa and United Airlines. In November 1993, to stay in the single aisle competition, Boeing's board of directors authorized

4160-428: The 737-100 for commercial flight on December 15, 1967. It was the first aircraft to have, as part of its initial certification, approval for Category II approaches , which refers to a precision instrument approach and landing with a decision height between 98 and 197 feet (30 and 60 m). Lufthansa received its first aircraft on December 28, 1967, and on February 10, 1968, became the first non-American airline to launch

4264-525: The 737-900 and competes with the Airbus A321neo . The 737 MAX 10 was proposed as a stretched MAX 9 in mid-2016, enabling seating for 230 in a single class or 189 in two-class layout, compared to 193 in two-class seating for the A321neo. The modest 66-inch (1.7 m) stretch of fuselage enables the MAX 10 to retain the existing wing and CFM Leap 1B engine from the MAX 9 with a trailing-link main landing gear as

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4368-404: The Boeing 737 family: The launch decision for the $ 150 million (~$ 1.11 billion in 2023) development was made by the board on February 1, 1965. The sales pitch was big-jet comfort on short-haul routes. Lufthansa became the launch customer on February 19, 1965, with an order for 21 aircraft, worth $ 67 million (~$ 494 million in 2023) after the airline had been assured by Boeing that

4472-526: The CFM56 included the U.S. Air Force with its program to re-engine KC-135 tankers. The passenger capacity of the aircraft was increased to 149 by extending the fuselage around the wing by 9 feet 5 inches (2.87 m). The wing incorporated several changes for improved aerodynamics. The wingtip was extended 9 inches (23 cm), and the wingspan by 1 foot 9 inches (53 cm). The leading-edge slats and trailing-edge flaps were adjusted. The tailfin

4576-454: The FAA cleared the MAX to return to service. Before the aircraft can fly again, repairs must be implemented and airlines' training programs must be approved. Passenger flights in the U.S. are expected to resume before the end of the year. Worldwide, the first airline to resume passenger service was Brazilian low-cost Gol , on December 9, 2020. The 737 MAX 7, a shortened variant of the MAX ;8,

4680-524: The MD-80 and MD-90 aircraft, following Boeing's merger with McDonnell Douglas . The 737-800 is the most widely used narrowbody aircraft and competes primarily with the Airbus A320. The 737-900 was launched in 1997 and took its first flight on August 3, 2000. It retains the MTOW , fuel capacity, trading range for payload and also the exit configuration of the -800, limiting its seat capacity to approximately 177 in

4784-409: The NACA 4-digit series such as the NACA 2415 (to be read as 2 – 4 – 15) describes an airfoil with a camber of 0.02 chord located at 0.40 chord, with 0.15 chord of maximum thickness. Finally, important concepts used to describe the airfoil's behaviour when moving through a fluid are: In two-dimensional flow around a uniform wing of infinite span, the slope of the lift curve is determined primarily by

4888-405: The Next Generation program to mainly upgrade the 737 Classic series. In late 1993, after engineering trade studies and discussions with major customers, Boeing proceeded to launch a second derivative of the Boeing 737, the 737 Next Generation (NG) -600/700/800/900 series. It featured a redesigned wing with a wider wingspan and larger area, greater fuel capacity, longer range and higher MTOWs . It

4992-418: The Next Generation series. The 737-500 was offered as a modern and direct replacement of the 737-200. It was launched in 1987 by Southwest Airlines , with an order for 20 aircraft, and it flew for the first time on June 30, 1989. A single prototype flew 375 hours for the certification process, and on February 28, 1990, Southwest Airlines received the first delivery. The -500 incorporated the improvements of

5096-533: The Second Generation 737 Classic -300/400/500 variants were upgraded with more fuel-efficient CFM56-3 high-bypass turbofans and offered 110 to 168 seats. Introduced in 1997, the Third Generation 737 Next Generation (NG) -600/700/800/900 variants have updated CFM56-7 high-bypass turbofans, a larger wing and an upgraded glass cockpit , and seat 108 to 215 passengers. The latest, and Fourth Generation,

5200-472: The aft fuselage instead of as a T-tail. Many designs for the engine attachment strut were tested in the wind tunnel and the optimal shape for high speed was found to be one which was relatively thick, filling the narrow channels formed between the wing and the top of the nacelle, particularly on the outboard side. At the time, Boeing was far behind its competitors; the SE 210 Caravelle had been in service since 1955, and

5304-538: The aircraft to modern specifications, while also retaining commonality with previous 737 variants. In 1980, preliminary aircraft specifications of the variant, dubbed 737-300, were released at the Farnborough Airshow . This first major upgrade series was later renamed 737 Classic. It competed primarily with the MD-80, its later derivative the MD-90 , and the newcomer Airbus A320 family . Boeing engineer Mark Gregoire led

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5408-428: The airfoil at x . Since the airfoil is an impermeable surface , the flow w ( x ) {\displaystyle w(x)} must balance an inverse flow from V . By the small-angle approximation , V is inclined at angle α- dy ⁄ dx relative to the blade at position x , and the normal component is correspondingly (α- dy ⁄ dx ) V . Thus, γ( x ) must satisfy

5512-466: The airfoil generates a circulation around the blade, which can be modeled as a vortex sheet of position-varying strength γ( x ) . The Kutta condition implies that γ( c )=0 , but the strength is singular at the bladefront, with γ( x )∝ 1 ⁄ √ x for x ≈ 0 . If the main flow V has density ρ , then the Kutta–Joukowski theorem gives that

5616-399: The airfoil itself replaced with a 1D blade along its camber line, oriented at the angle of attack α . Let the position along the blade be x , ranging from 0 at the wing's front to c at the trailing edge; the camber of the airfoil, dy ⁄ dx , is assumed sufficiently small that one need not distinguish between x and position relative to the fuselage. The flow across

5720-407: The chord line.) Also as a consequence of (3), the section lift coefficient of a cambered airfoil of infinite wingspan is: Thin airfoil theory assumes the air is an inviscid fluid so does not account for the stall of the airfoil, which usually occurs at an angle of attack between 10° and 15° for typical airfoils. In the mid-late 2000s, however, a theory predicting the onset of leading-edge stall

5824-461: The competition between the two giant aircraft manufacturers, which has since become a duopoly competition . An optional upgrade with winglets became available for the Classic and NG series. Development began in 1979 for the 737's first major revision, which was originally introduced as the 'new generation' of the 737. Boeing wanted to increase capacity and range, incorporating improvements to upgrade

5928-450: The denser, 200-seat MAX 200), and MAX 9 replace the 737-700, -800, and -900 respectively. The further stretched 737 MAX 10 has also been added to the series. The aim was to re-engine the 737NG family using CFM LEAP-1B engines having very high bypass ratio, to compete with the Airbus A320neo family. On July 20, 2011, Boeing announced plans for a third major upgrade and respectively fourth generation of 737 series to be powered by

6032-403: The design of aircraft, propellers, rotor blades, wind turbines and other applications of aeronautical engineering. A lift and drag curve obtained in wind tunnel testing is shown on the right. The curve represents an airfoil with a positive camber so some lift is produced at zero angle of attack. With increased angle of attack, lift increases in a roughly linear relation, called the slope of

6136-435: The engines to the wings which lightened the structure and simplified the accommodation of six-abreast seating in the fuselage. The engine nacelles were mounted directly to the underside of the wings, without pylons, allowing the landing gear to be shortened, thus lowering the fuselage to improve baggage and passenger access. Relocating the engines from the aft fuselage also allowed the horizontal stabilizer to be attached to

6240-604: The final 737-200 aircraft in the U.S. flying scheduled passenger service were phased out, with the last flights of Aloha Airlines . As of 2018, the variant still saw regular service through North American charter operators such as Sierra Pacific Airlines . The short-field capabilities of the 737-200 led Boeing to offer the "Unpaved Strip Kit" (see the Air North example, right). This option reduced foreign object damage when operated on remote, unimproved or unpaved runways, that competing jetliners could not use safely. The kit included

6344-411: The final commercial aircraft delivered to MSA on October 31, 1969. This variant was largely overshadowed by its bigger 737-200 sibling, which entered service two months later. The original engine nacelles incorporated thrust reversers taken from the 727 outboard nacelles. They proved to be relatively ineffective and tended to lift the aircraft up off the runway when deployed. This reduced the downforce on

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6448-598: The first few terms of this series. The lift coefficient satisfies C L = 2 π ( α + A 0 + A 1 2 ) = 2 π α + 2 ∫ 0 π d y d x ⋅ ( 1 + cos ⁡ θ ) d θ {\displaystyle C_{L}=2\pi \left(\alpha +A_{0}+{\frac {A_{1}}{2}}\right)=2\pi \alpha +2\int _{0}^{\pi }{{\frac {dy}{dx}}\cdot (1+\cos \theta )\,d\theta }} and

6552-405: The following important properties of airfoils in two-dimensional inviscid flow: As a consequence of (3), the section lift coefficient of a thin symmetric airfoil of infinite wingspan is: (The above expression is also applicable to a cambered airfoil where α {\displaystyle \alpha \!} is the angle of attack measured relative to the zero-lift line instead of

6656-457: The freestream velocity). The lift on an airfoil is primarily the result of its angle of attack . Most foil shapes require a positive angle of attack to generate lift, but cambered airfoils can generate lift at zero angle of attack. Airfoils can be designed for use at different speeds by modifying their geometry: those for subsonic flight generally have a rounded leading edge , while those designed for supersonic flight tend to be slimmer with

6760-554: The global 737 fleet had completed more than 184 million flights over 264 million block hours since its entry into service. It was the highest-selling commercial aircraft until being surpassed by the competing Airbus A320 family in October 2019, but maintains the record in total deliveries. The 737 MAX, designed to compete with the A320neo , was grounded worldwide between March 2019 and November 2020 following two fatal crashes. Boeing had been studying short-haul jet aircraft designs, and saw

6864-791: The laminar flow, making it turbulent. For example, with rain on the wing, the flow will be turbulent. Under certain conditions, insect debris on the wing will cause the loss of small regions of laminar flow as well. Before NASA's research in the 1970s and 1980s the aircraft design community understood from application attempts in the WW II era that laminar flow wing designs were not practical using common manufacturing tolerances and surface imperfections. That belief changed after new manufacturing methods were developed with composite materials (e.g. laminar-flow airfoils developed by Professor Franz Wortmann for use with wings made of fibre-reinforced plastic ). Machined metal methods were also introduced. NASA's research in

6968-436: The larger diameter of the engine over the original Pratt & Whitney engines. Gregoire's team and CFM solved the problem by reducing the size of the fan (which made the engine slightly less efficient than it had been forecast to be), placing the engine ahead of the wing, and by moving engine accessories to the sides of the engine pod, giving the engine a distinctive non-circular "hamster pouch " air intake. Earlier customers for

7072-428: The last 737-100s in service. The first aircraft used by Boeing as prototype under registration N73700 was later ordered by and delivered to NASA on July 26, 1973, which then operated it under registration N515NA and retired after 30 years on September 27, 2003. The last 737-100 built and also the last operating was originally sold to Malaysia–Singapore Airlines : it was transferred to Air Florida before being used as

7176-594: The leading edge to have a lot of length to slowly shock the supersonic flow back to subsonic speeds. Generally such transonic airfoils and also the supersonic airfoils have a low camber to reduce drag divergence . Modern aircraft wings may have different airfoil sections along the wing span, each one optimized for the conditions in each section of the wing. Movable high-lift devices, flaps and sometimes slats , are fitted to airfoils on almost every aircraft. A trailing edge flap acts similarly to an aileron; however, it, as opposed to an aileron, can be retracted partially into

7280-433: The lift curve. At about 18 degrees this airfoil stalls , and lift falls off quickly beyond that. The drop in lift can be explained by the action of the upper-surface boundary layer , which separates and greatly thickens over the upper surface at and past the stall angle. The thickened boundary layer's displacement thickness changes the airfoil's effective shape, in particular it reduces its effective camber , which modifies

7384-433: The lift force can be related directly to the average top/bottom velocity difference without computing the pressure by using the concept of circulation and the Kutta–Joukowski theorem . The wings and stabilizers of fixed-wing aircraft , as well as helicopter rotor blades, are built with airfoil-shaped cross sections. Airfoils are also found in propellers, fans , compressors and turbines . Sails are also airfoils, and

7488-469: The longer length. Entry into service with launch operator Southwest Airlines was expected in January 2019, but the airline deferred these orders until 2023–2024. The 737 MAX 7 replaced the 737-700 and was predicted to carry 12 more passengers and fly 400 nautical miles (740 km; 460 mi) farther than the competing Airbus A319neo with 7% lower operating costs per seat. The 737 MAX 8, the first variant of

7592-476: The main wheels thereby reducing the effectiveness of the wheel brakes. In 1968, an improvement to the thrust reversal system was introduced. A 48-inch tailpipe extension was added and new target-style thrust reversers were incorporated. The thrust reverser doors were set 35 degrees away from the vertical to allow the exhaust to be deflected inboard and over the wings and outboard and under the wings. The improvement became standard on all aircraft after March 1969, and

7696-747: The moment coefficient C M = − π 2 ( α + A 0 + A 1 − A 2 2 ) = − π 2 α − ∫ 0 π d y d x ⋅ cos ⁡ ( θ ) ( 1 + cos ⁡ θ ) d θ . {\displaystyle C_{M}=-{\frac {\pi }{2}}\left(\alpha +A_{0}+A_{1}-{\frac {A_{2}}{2}}\right)=-{\frac {\pi }{2}}\alpha -\int _{0}^{\pi }{{\frac {dy}{dx}}\cdot \cos(\theta )(1+\cos \theta )\,d\theta }{\text{.}}} The moment about

7800-411: The older 737-200s P&W engines. The 737-500 has faced accelerated retirement due to its smaller size, after 21 years in service compared to 24 years for the -300. While a few 737-300s were slated for freighter conversion, no demand at all existed for a -500 freighter conversion. The 737-500 was replaced by the 737-600 of the Next Generation series, though the -600 was not as successful in total orders as

7904-495: The only major change. The MAX 10 was launched on June 19, 2017, with 240 orders and commitments from more than ten customers. The variant configuration with a predicted 5% lower trip cost and seat cost compared to the A321neo was firmed up by February 2018, and by mid-2018, the critical design review was completed. The MAX 10 has a similar capacity to the A321XLR, but shorter range and much poorer field performance in smaller airports. It

8008-486: The overall flow field so as to reduce the circulation and the lift. The thicker boundary layer also causes a large increase in pressure drag , so that the overall drag increases sharply near and past the stall point. Airfoil design is a major facet of aerodynamics . Various airfoils serve different flight regimes. Asymmetric airfoils can generate lift at zero angle of attack, while a symmetric airfoil may better suit frequent inverted flight as in an aerobatic airplane. In

8112-451: The primary competitor for the 737NG series remained only the A320 family. The 737-600, the smallest model of the Next-Generation, was launched by Scandinavian Airlines (SAS) in March 1995 with the first aircraft delivered in September 1998. A total of 69 aircraft without winglets have been produced with the last one delivered to WestJet in 2006. The 737-600 replaced the 737-500 and is similar to

8216-505: The production standard in June 1971. Boeing also provided the 737-200C ( Combi ), which allowed for conversion between passenger and cargo use and the 737-200QC (Quick Change), which facilitated a rapid conversion between roles. The 1,114th and last delivery of a -200 series aircraft was in August 1988 to Xiamen Airlines . Nineteen 737-200s, designated T-43 , were used to train aircraft navigators for

8320-519: The range nor the passenger-carrying capacity of that period's wide-body aircraft. The re-engined Boeing 737 MAX and Airbus A320neo jets offer 500 miles more range, allowing them to operate the 3,000 miles transatlantic flights between the eastern U.S. and Western Europe, previously dominated by wide-body aircraft. Norwegian Air Shuttle , JetBlue and TAP Portugal will open up direct routes bypassing airline hubs for lower fares between cheaper, smaller airports. The Boeing 737NG 3,300-mile range

8424-404: The region of the ailerons and near a wingtip a symmetric airfoil can be used to increase the range of angles of attack to avoid spin – stall . Thus a large range of angles can be used without boundary layer separation . Subsonic airfoils have a round leading edge, which is naturally insensitive to the angle of attack. The cross section is not strictly circular, however: the radius of curvature

8528-449: The seats can be removed to carry cargo instead. There is a large door on the left side of the aircraft. The United States Navy was the launch customer for the 737-700C under the military designation C-40 Clipper . The 737-700ER (Extended Range ) was launched on January 31, 2006, and featured the fuselage of the 737-700 and the wings and landing gear of the 737-800. A 737-700ER can typically accommodate 126 passengers in two classes with

8632-484: The series has received 5,011 firm orders. In March 2019, civil aviation authorities around the world grounded the 737 MAX following two hull loss crashes which caused 346 deaths. On December 16, 2019, Boeing announced that it would suspend production of the 737 MAX from January 2020, which was resumed in May 2020. In the midyear 2020, the FAA and Boeing conducted a series of recertification test flights. On November 18, 2020,

8736-519: The three European short-haul single aisles slowly withdrew from the competition. Sales were low in the early 1970s and, after a peak of 114 deliveries in 1969, only 22 737s were shipped in 1972 with 19 in backlog. The US Air Force saved the program by ordering T-43s , which were modified Boeing 737-200s. African airline orders kept the production running until the 1978 US Airline Deregulation Act , which improved demand for six-abreast narrow-body aircraft. Demand further increased after being re-engined with

8840-458: The total lift force F is proportional to ρ V ∫ 0 c γ ( x ) d x {\displaystyle \rho V\int _{0}^{c}\gamma (x)\,dx} and its moment M about the leading edge proportional to ρ V ∫ 0 c x γ ( x ) d x . {\displaystyle \rho V\int _{0}^{c}x\;\gamma (x)\,dx.} From

8944-471: The underwater surfaces of sailboats, such as the centerboard , rudder , and keel , are similar in cross-section and operate on the same principles as airfoils. Swimming and flying creatures and even many plants and sessile organisms employ airfoils/hydrofoils, common examples being bird wings, the bodies of fish, and the shape of sand dollars . An airfoil-shaped wing can create downforce on an automobile or other motor vehicle, improving traction . When

9048-441: The wind is obstructed by an object such as a flat plate, a building, or the deck of a bridge, the object will experience drag and also an aerodynamic force perpendicular to the wind. This does not mean the object qualifies as an airfoil. Airfoils are highly-efficient lifting shapes, able to generate more lift than similarly sized flat plates of the same area, and able to generate lift with significantly less drag. Airfoils are used in

9152-505: The wing if not used. A laminar flow wing has a maximum thickness in the middle camber line. Analyzing the Navier–Stokes equations in the linear regime shows that a negative pressure gradient along the flow has the same effect as reducing the speed. So with the maximum camber in the middle, maintaining a laminar flow over a larger percentage of the wing at a higher cruising speed is possible. However, some surface contamination will disrupt

9256-440: The working fluid are called hydrofoils . When oriented at a suitable angle, a solid body moving through a fluid deflects the oncoming fluid (for fixed-wing aircraft, a downward force), resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: lift ( perpendicular to the remote freestream velocity ) and drag ( parallel to

9360-468: Was US$ 4.0M (1968) ($ 35M today). The -200's unit cost was US$ 5.2M (1972) ($ 37.9M today). The 737-200 Advanced is an improved version of the -200, introduced into service by All Nippon Airways on May 20, 1971. After aircraft #135, the 737-200 Advanced has improved aerodynamics, automatic wheel brakes, more powerful engines, more fuel capacity, and hence a 15% increase in payload and range over the original -200s and respectively -100s. The 737-200 Advanced became

9464-449: Was designated the -300SP ( Special Performance ). The 737-300 was replaced by the 737-700 of the Next Generation series. The 737-400 was launched in 1985 to fill the gap between the 737-300 and the 757-200. In June 1986, Boeing announced the development of the 737-400, which stretched the fuselage a further 10 feet (3.0 m), increasing the capacity to 188 passengers, and requiring a tail bumper to prevent tailstrikes during take-off and

9568-476: Was designated the 737-200, with the original short-body aircraft becoming the 737-100. Detailed design work continued on both variants simultaneously. The first -100 was rolled out on January 17, 1967, and took its maiden flight on April 9, 1967, piloted by Brien Wygle and Lew Wallick. After several test flights the Federal Aviation Administration (FAA) issued Type Certificate A16WE certifying

9672-427: Was devised by German mathematician Max Munk and further refined by British aerodynamicist Hermann Glauert and others in the 1920s. The theory idealizes the flow around an airfoil as two-dimensional flow around a thin airfoil. It can be imagined as addressing an airfoil of zero thickness and infinite wingspan . Thin airfoil theory was particularly notable in its day because it provided a sound theoretical basis for

9776-498: Was due to be retired in early 2023. As of September 2023, a relatively high number of 737-200s remain in service compared to other early jet airliners, with fifty examples actively flying for thirty carriers. During the 737 MAX groundings , older 737s, including the 200 and Classic series , were in demand for leasing. C-GNLK, one of Nolinor's 737-200s, is the oldest jet airliner in commercial service as of 2024, having entered service 50 years prior in 1974. The Boeing 737 Classic

9880-409: Was due to enter service in April 2019. The 737 MAX 9, the stretched variant of the MAX 8, was launched with an order of 201 aircraft in February 2012. It made its roll-out on March 7, 2017, and first flight on April 13, 2017; It was certified by February 2018. The launch customer, Lion Air Group, took the first MAX 9 on March 21, 2018, before entering service with Thai Lion Air . The 737 MAX 9 replaced

9984-405: Was equipped with CFM56-7 high pressure ratio engines, a glass cockpit , and upgraded interior configurations. The four main models of the series can accommodate seating for 108 to 215 passengers. It was further developed into additional versions such as the corporate Boeing Business Jet (BBJ) and military P-8 Poseidon aircraft. Following the merger between Boeing with McDonnell Douglas in 1997,

10088-553: Was introduced to meet the range and passenger capacity of the discontinued 757-200 and to directly compete with the Airbus A321 . The Boeing 737 MAX is the name given to the main models 737 MAX 7/8/9/10 series and the higher-density MAX 200 variant of the Boeing 737 family. It is offered in four main variants, typically offering 138 to 230 seats and a range of 3,215 to 3,825 nautical miles [nmi] (5,954 to 7,084 km; 3,700 to 4,402 mi). The 737 MAX 7, MAX 8 (including

10192-431: Was launched in December 2010 and reached 1,029 orders by June 2011, breaking Boeing's monopoly with American Airlines , which had an order for 130 A320neos that July. The 737 MAX had its first flight on January 29, 2016, and gained FAA certification on March 8, 2017. The first delivery was a MAX 8 on May 6, 2017, to Lion Air 's subsidiary Malindo Air , which put it into service on May 22, 2017. As of January 2019,

10296-401: Was not a model delivered by Boeing and hence the nickname Special Freighter (SF) . Alaska Airlines was the first to convert one of their 400s from regular service to an aircraft with the ability to handle 10 pallets. The airline had also converted five more into fixed combi aircraft for half passenger and freight. These 737-400 Combi aircraft were retired in 2017 and replaced by the 737-700F of

10400-495: Was originally based on the 737-700, flying 1,000 nautical miles (1,900 km; 1,200 mi) farther and accommodating two more seat rows at 18% lower fuel costs per seat. The redesign uses the 737-8 wing and landing gear; a pair of over-wing exits rather than the single-door configuration; a 46-inch-longer (1,200 mm) aft fuselage and a 30-inch-longer (760 mm) longer forward fuselage; structural re-gauging and strengthening; and systems and interior modifications to accommodate

10504-418: Was proposed by Wallace J. Morris II in his doctoral thesis. Morris's subsequent refinements contain the details on the current state of theoretical knowledge on the leading-edge stall phenomenon. Morris's theory predicts the critical angle of attack for leading-edge stall onset as the condition at which a global separation zone is predicted in the solution for the inner flow. Morris's theory demonstrates that

10608-447: Was redesigned, the flight deck was improved with the optional EFIS (Electronic Flight Instrumentation System), and the passenger cabin incorporated improvements similar to those developed on the Boeing 757 . The prototype -300, the 1,001st 737 built, first flew on February 24, 1984, with pilot Jim McRoberts. It and two production aircraft flew a nine-month-long certification program. The 737-300 retrofitted with Aviation Partners ' winglets

10712-526: Was unveiled in Boeing's Renton factory on November 22, 2019, and scheduled for first flight in 2020. Boeing also considered parallel development with the 757 replacement, similar to the development of the 757 and 767 in the 1970s. Narrow-body aircraft Historically, beginning in the late 1960s and continuing through the 1990s, twin engine narrow-body aircraft, such as the Boeing 737 Classic , McDonnell-Douglas MD-80 and Airbus A320 were primarily employed in short to medium-haul markets requiring neither

10816-490: Was widely preferred over the -100 by airlines. The improved version, the 737-200 Advanced, was introduced into service by All Nippon Airways on May 20, 1971. The 737 original model with its variants, known later as the Boeing 737 Original , initially competed with SE 210 Caravelle and BAC-111 due to their earlier entry into service and later primarily with the McDonnell Douglas DC-9, then its MD-80 derivatives as

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