همه چیز درباره هواپیمای مسافربری بویینگ 737 / از تاریخچه تا مدلها (Boeing 737)

The Boeing 737 is a narrow-body airliner produced by Boeing Commercial Airplanes at its Renton Factory in Washington. Envisioned in 1964, the initial 737-100 made its first flight in April 1967 and entered airline service in February 1968 with Lufthansa. The lengthened 737-200 entered service in April 1968. Developed to supplement to the 727 on short and thin routes, the twinjet retains the 707 fuselage cross-section and nose with two underwing turbofans. It evolved through four generations, offering several variants for 85 to 215 passengers.

The -100/200 original variants were powered by Pratt & Whitney JT8D low-bypass engines and offered seating for 85 to 130 passengers. Launched in 1980 and introduced in 1984, the 737 Classic -300/400/500 variants were re-engined with CFM56-3 turbofans and offered 110 to 168 seats. Introduced in 1997, the 737 Next Generation (NG) -600/700/800/900 variants have updated CFM56-7s, a larger wing and an upgraded glass cockpit, and seat 108 to 215 passengers. The latest generation, the 737 MAX -7/8/9/10, powered by improved CFM LEAP high bypass turbofans and accommodating 138 to 204 people, entered service in 2017. Boeing Business Jet versions are produced since the 737NG, as well as military models.

As of November 2019, 15,156 Boeing 737s have been ordered and 10,565 delivered, leaving a backlog of 4,591 aircraft. It was the highest-selling commercial jetliner until being surpassed in total orders by the competing Airbus A320 family by the end of October 2019. Before, it competed primarily with the McDonnell Douglas DC-9, then its MD-80/MD-90 derivatives. In March 2019, the Boeing 737 MAX was grounded worldwide following two fatal crashes.

The 737-100 on its maiden flight, April 9, 1967

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Development

Boeing had been studying short-haul jet aircraft designs, and wanted to produce another aircraft to supplement the 727 on short and thin routes. Preliminary design work began on May 11, 1964, and Boeing"s intense market research yielded plans for a 50- to 60-passenger airliner for routes 50 to 1,000 mi (100 to 1,600 km) long.

Initial design featured podded engines on the aft fuselage and a T-tail like the 727, and five-abreast seating, but engineer Joe Sutter instead placed the engines under the wings to lighten the structure, enabling fuselage widening for six-abreast seating. The 737 design was presented in October 1964 at 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 launch decision for the $150 million development was made by the board on February 1, 1965.

Lufthansa became the launch customer on February 19, 1965, with an order for 21 aircraft, worth $67 million in 1965, after the airline received assurances from Boeing that the 737 project would not be canceled. Consultation with Lufthansa over the previous winter resulted in an increase in capacity to 100 seats.

On April 5, 1965, Boeing announced an order by United Airlines for 40 737s. United wanted a slightly larger airplane than the original 737, so Boeing stretched the fuselage 36 in (91 cm) ahead of, and 40 in (102 cm) behind the wing. The longer version was designated 737-200, with the original short-body aircraft becoming the 737-100.

Detailed design work continued on both variants at the same time. Boeing was far behind its competitors when the 737 was launched; rival aircraft 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, the most notable being the fuselage cross-section. This fuselage permitted six-abreast seating compared to the rival BAC-111 and DC-9"s five-abreast layout.

Design engineers decided to mount the nacelles directly to the underside of the wings to reduce the landing gear length and kept the engines low to the ground for easy ramp inspection and servicing. Many thickness variations for the engine attachment strut were tested in the wind tunnel and the most desirable 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.

Originally, the span arrangement of the airfoil sections of the 737 wing was planned to be very similar to that of the 707 and 727, but somewhat thicker. A substantial improvement in drag at high Mach numbers was achieved by altering these sections near the nacelle. The engine chosen was the Pratt & Whitney JT8D-1 low-bypass ratio turbofan engine, delivering 14,500 lbf (64 kN) thrust. With the wing-mounted engines, Boeing decided to mount the horizontal stabilizer on the fuselage rather than the T-tail style of the Boeing 727.

The initial assembly of the Boeing 737 was adjacent to Boeing Field (now officially named King County International Airport) because the factory in Renton was filled to capacity with the production of the 707 and 727. After 271 of the Boeing 737 aircraft were built, production was moved to Renton in late 1970. A significant portion of fuselage assembly—previously done by Boeing in Wichita, Kansas—is now performed by Spirit AeroSystems, which purchased some of Boeing"s assets in Wichita. Key to increasing production efficiencies, the entire fuselage is shipped since the 737 Next Generation while it was sent in two pieces before.

The fuselage is joined with the wings and landing gear and then moves down the assembly line for the engines, avionics, and interiors. After rolling out the aircraft, Boeing tests the systems and engines before a plane"s maiden flight to Boeing Field, where it is painted and fine-tuned before delivery to the customer. The first of six -100 prototypes rolled out in December 1966 and made its maiden flight on April 9, 1967, piloted by Brien Wygle and Lew Wallick.

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. African airline orders kept the production running until the 1978 US Airline Deregulation Act where demand was better for a six-abreast narrow-body aircraft, particularly re-engined with the CFM56, struggling at the time.