The Boeing 737
The Boeing 737 Overview
The Boeing 737 is a short- to medium-range twinjet narrow-body airliner which is the best selling jet commercial airliner. It was developed as a cheaper and shorter twin engine airliner which took inspiration from the designs of the 707 and 727. It can typically hold anywhere from 85 to 215 passengers. There have been many variations of the 737 which improved the airliner in numerous ways. It is estimated that in 2006 there were an average of 1,250 Boeing 737s airborne at any given time, with two departing or landing somewhere every five seconds. It was first flown in April 9th 1967, and commercially introduced by Lufthansa on February 10 the following year. There are four main users of the Boeing 737 which are: Southwest Airlines, Ryanair, United Airlines and American Airlines. Boeing has manufactured 9,522 737s with 4,430 still ordered for completion.
Development
As the Boeing 727 needed a replacement on shorter and thinner routes, this subsequently caused the invention of the Boeing 737. The first of planning started on May 11, 1964. In 1965, United Airlines ordered 40 Boeing 737's, but wanted a larger aircraft than the existing original design. And so, Boeing expanded the 737's fuselage by an additional 91 cm at the front of the aircraft and an additional 102 cm behind the right wing. At this stage of planning, Boeing's biggest competitors for the 737 were the BAC-111, Douglas DC-9. As a result, Boeing was forced to push the 737's planning ahead of schedule, making them use 60% of the 727's design. Boeing had intended the airfoil sections of the 737 to be thicker than that of the 707, 727. The selected for the 737 was the Pratt & Whitney JT8D-1, delivering a total of 14,500lb of thrust from each engine. The Boeing 737 obtained its first client in Lufthansa which ordered 21 planes thus beginning the history of the Boeing 737. 
Testing
After a 150 million USD grant was given to Boeing by the FAA for the development of the 737, testing of individual components began on February 1, 1965. Each individual component of the aircraft had to be tested beforehand to ensure that the integrity of the 737 is maintained through its maiden voyage. 6 prototypes of the 737-100 were made by December 1966 and first flight was made on April 9, 1967. The 737 was the first aircraft to have approval for Category II approaches as part of its initial certification.
Design
Wings
The design of the wings found on the 737 are rather identical, only varying in lenght (wing-span). The wing features the same swept-winged design aboard all different models. The only difference is the winglets found on the tip of the wings. Winglets help reduce fuel burn, reduce engine wear and takeoff noise. The overall fuel effiency can be improved by up to 5%. Winglets were only introduced in the 737-Next Generation aircraft and not before.In the images below, we can see the different winglet designs across the 737-NG lineup.
Engines
Most aircraft engines have circular inlets which the 737 lacks. The new generation of 737s use CFM56 turbofan engines as these are extremely fuel efficient and much quieter than as opposed to the original JT8D engines which are used in the 737-100 and 737-200 variants of the 737. problem occurred as the 737 had a low ground clearance so the engine was placed ahead of the wing rather than underneath it. As the engine was too close to the ground, the Boeing 737 was extremely prone to foreign object damage where debris like things could hit the engine and damage. The new generation of 737-900s and 737-NGs all feature the newest of fuel efficient engines: the CFM International LEAP-1B. These engines are more powerful as well as around 30% more efficient than the JT8D.Fuselage
The 737's landing gear is situated in the middle of the aircraft below and in front of the wings. The legs are concealed by door and are aerodynamically sealed however, the sides of the wheel are exposed in the air. These tires are visible during takeoff and altitude if looked upon from the ground. This trait was left as an iconic feature of the 737, as most aircraft do not have this. Most planes have fuel dump systems for emergencies to lighten the weight of the plane however, the 737 does not use it as the aircraft was small enough for it to not require it. The wings plane was improved for aerodynamic efficiency from previous Boeing aircrafts.
Variants
The different variants of the 737 vary drastically in terms of length, wing-span, engine type and engine power as well as the overall capacity of passengers it was to be able to hold.737-100
The 737-100 was the intended prototype version of the 737 and was never made to be placed into full production. However, as more and more orders were made by airlines such as Lufthansa and Malaysian Airlines, it was decided that the 737-100 will be placed into semi-production till the 737-200's design was to be completed. The first plane rolled off the production floors in January 17, 1967.The original prototype was last operated by NASA over 30 years ago and is the Museum of Flight in Seattle.
737-200
The 737-200 is essentially the exact same model as the 737-100 with some minor changes. First produced in 1967, an extension was made in the form of an added 2 meters to the nose and tail of the aircraft, making it 4 meters longer than its predecessor. The 737-200 also had its fuselage slightly redesigned, making it more aerodynamic. More powerful engines were also added, bigger fuel tanks filled up most of the wing space and automatic wheel brakes were put in place. All in all, the 737-200 provided airlines with a much more affordable and efficient platform of air travel.Nineteen 737-200s were used to train aircraft navigators for the U.S. Air Force, designated T-43. 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.
737-Classic
The Boeing 737-Classic is given to the variants -100, -200, -300, -400 and -500. After the Classic series comes the Next Generation; which is variants -600, -700, -800, -900 and -900MX. The Classic series were Produced from 1984 to 2000, with a total of 1,988 aircraft delivered. After engineering trade studies and discussions with major 737 customers, Boeing proceeded to launch the 737 Next Generation series. 737-Next Generation
737-MAX
Specifications
| Variant | 737-100 | 737-200 | 737-300/-400/-500 | 737-600/-700/-800/-900 | 737 MAX | |
|---|---|---|---|---|---|---|
| Cockpit crew | Two | |||||
| 2-class seats | 85 : 12F 73Y | 102 : 14F@38" 88Y@34" | 126/147/110 | 108/128/160/177 | 138/162/180 | |
| 1-class seats | 103@34" - 118@30" | 115@34" - 130@30" | 140-149/159-168/122-132 | 123-130/140-148/175-184/177-215 | 156-172/184-200/204-220 | |
| Exit Limit | 124 | 136 | 149/188/145 | 149/149/189/220 | ||
| Length | 94 ft / 28.65m | 100 ft 2in / 30.53m | 102-120 ft / 31-36.4m | 102-138 ft / 31.24-42.11 m | 117-138 ft / 35.6-42.2 m | |
| Span | 93 ft / 28.35m | 94 ft 9 in / 28.9 m | 112 ft 7 in / 34.32 m winglets: 117 ft 5in / 35.79m | 117 ft 10 in / 35.9 m | ||
| Wing area | 979.9 sq ft (91.04 m2) | 1,341.2 sq ft (124.60 m2) | ||||
| Wing sweep | 25 degrees | |||||
| Height | 37 ft / 11.3 m | 36 ft 6 in / 11.1 m | 41 ft / 12.6 m | 40 ft 4 in / 12.3 m | ||
| Cabin width | 139.2 in / 3.54 m | |||||
| Fuselage width | 148 in / 3.76 m | |||||
| Cargo | 650 ft³ / 18.4 m³ | 875 ft³ / 24.8 m³ | 882-1,373 ft³ / 23.3-38.9 m³ | 720-1,826 ft³ / 20.4-51.7 m³ | 1,543-1,814 ft³ / 43.7-51.4 m3 | |
| MTOW | 110,000 lb / 49,895 kg | 128,100 lb / 58,105 kg | 133,500-150,000 lb / 60,550-68,040 kg | 144,500-187,700 lb / 65,544-85,139 kg | 177,000-194,700 lb / 80,286-88,314 kg | |
| OEW | 62,000 lb / 28,123 kg | 65,300 lb / 29,620 kg | 70,440-76,760 lb / 31,950-34,820 kg | 80,200-98,495 lb / 36,378-44,677 kg | ||
| Fuel capacity | 4,720US gal / 17,865L | 5,970US gal / 22,596L | 5,311USgal / 20,100L | 6,875-7,837 US gal / 26,022-29,666 L | 6,853 US gal (25,941 L) | |
| Cruise | Mach 0.745 (430 kn; 796 km/h) | Mach 0.785 (453 kn; 838 km/h) | ||||
| MMO | Mach 0.82 (473 kn; 876 km/h) | |||||
| Takeoff | 6,099 ft (1,859 m) | 7,500-8,690 ft / 2,286-2,649m | 6,161-7,598 ft (1,878-2,316 m) | |||
| Range | 1,540 nmi (2855 km)> | 2,600 nmi (4,800 km) | 2,060-2,375 nmi (3,815-4,398 km) | 2,935-3,010 nmi (5,436-5,575 km) | 3,515-3,825 nmi (6,510-7,084 km) | |
| Ceiling | 37,000 ft (11,300 m) | 41,000 ft (12,500 m) | ||||
| Engines (x2) | Pratt & Whitney JT8D-7/-9/-5/-17 | CFM International CFM56-3 series | CFM International CFM56-7 series | CFM International LEAP-1B | ||
| Thrust (x2) | 14,000 lbf / 62.3 kN | 14,500-16,400 lbf (64-73 kN) | 20,000-23,500 lbf (89-105 kN) | 20,000-26,000 lbf (89-116 kN) | up to 28,000 lbf (125 kN) | |
Credit : Rabindar Singh
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