The 737 was a great success story for Boeing. In fact, it was the best-selling aircraft to date. It has been in production for over 50 years and is constantly being adapted and updated by many variants – part of the success story. This article looks at the most important differences in each 737 family – the Original, Classic, Next Generation and MAX.
A long and successful history
The Boeing 737 was introduced in 1967 and has remained so ever since and remained in production. To date, 10,575 have been delivered (according to Boeing data from February 2020), and 15,115 have been ordered. This makes the aircraft the best-selling so far, but the Airbus A320 has now caught up with the orders.
Part of this success was the well-designed design and constant evolution to meet the airline requirements. In the 1960s, the first 737 was designed to beat the competition of the time (especially the Douglas DC-9, but also the BAC One Eleven and the Caravelle of Sud Aviation). As the 737 has moved through its variants, these improvements have continued and are the best choice for many airlines.
What, then, were the main differences for each series?
The 737 Original – the 737-100 and 200
One of the most important features of the first 737s was in fact two engines. It was a driving force for the development of the 737. The previous Boeing aircraft, the 707 and 727, were both very successful. But market attention has shifted to a cheaper two-engine option.
Boeing overtook the competition by placing the two engines of the 737 under the wing, as opposed to the rear of the fuselage. Critically, it enabled a wider fuselage, giving the extra 737 passenger capacity (six vs. five vs. five), and allowing standard cargo containers to be loaded. The simple conversion to cargo use was popular with many airlines.
Only 60 737-100 aircraft were sold, and this was quickly improved with the 737-200. It offers an extensive fuselage, initially requested by United Airlines, and was very popular (with 1095 sales). There was also an advanced version with improved aerodynamics, more powerful engines and a higher fuel capacity and range.
Other amendments have been made to meet the demand of the airline. These include a Combi version for easy conversion to cargo use and the provision of an ‘Unpaved Strip Kit’ for landing on dirt roads.
The 737 Classic – the 737-300, 400 and 500
Production of the ‘Classic’ series began in 1984 with the 737-300. The goal was a transformation that focused on increased capacity and better fuel efficiency. The family would be modified, but retain the common law (in design and flight) with earlier models.
The biggest difference was adding new engines. The 737-300 uses CFM56 turbocharged engines. This increased propulsion (up to 23,500 lbf compared to 16,400 lbf for the Pratt & Whitney engines on the 737-200), but led to some design challenges. The larger engine diameter and the low ground clearance of the 737 meant that they were placed in front of the wing.
The 737-300 offers a small increase in capacity (up to a maximum of 149 compared to 136 for the 737-200), due to the elongation of the fuselage around the wing. Other structural improvements include:
- An increase in wing span and elongation of the wingtips, providing improved aerodynamics
- Redesign of the tail fin
- Various cabin improvements (based on features developed for the Boeing 757)
The 737-400 continued this expansion. By stretching the 737-300 about three meters, the capacity increased to 188. In contrast, the 737-500 was a smaller model. It has returned to the size and capacity of the 737-200, but offers the improvement in the design and efficiency of the Classic range.
The 737 Next Generation – the 737-600, 700, 800 and 900
The series Next Generation (NG) was launched in 1993 (first in 1997). It originated mainly to address the increasing competition from the Airbus A320 family and the then high fuel prices.
The range offered several improvements over the Classic aircraft, including better fuel efficiency, extended range and larger capacity variants (up to 215 passengers). Changes to the aircraft include:
- Improved CFM56-7 engines with improved fuel efficiency
- A redesigned wing, with a larger span and area (and increased fuel capacity)
- Improved digital cabin
- Improvements to the cabin inside, including more trash (with several updates based on 777 designs)
The 737-600 is the smallest in the family with a capacity of 149 passengers. The 737-700 is stretched by about 2.4 meters and also offers a convertible cargo option, the 737-700C.
The 737-800 is stretched further than the 737-700, making it a good replacement for the 737-400. It takes passenger capacity up to 189. It is further expanded on the longest model – the 737-900ER, with capacity up to 220 (the 737-900 is limited to 189, as there is only one smaller set of exit doors).
The 737-800 became the 737 model of Boeing. Simple Flying looked at this in detail and discussed how compromise made it so successful. It offers an excellent combination of range and capacity, not the biggest, but a very versatile option for many airlines.
The 737 MAX Series
The fourth generation of the 737 family was introduced in 2011. The 737 MAX Series competes with the A320neo family (launched in 2010) and once again focuses on improving efficiency.
It uses new, and more efficient, CFM International LEAP engines, and features several aerodynamic adjustments, including distinctive wings.
Like the NG series, there are four MAX variants of different sizes. It usually offers a larger passenger capacity and a greater variety of NG variants. Simple Flying took a closer look at these differences in a previous article.
The 737 MAX, of course, suffered in 2019 under its ground after two accidents. However, it still remained popular with 4,741 orders (based on Wikipedia order data).
It shows the popularity and appeal to airlines. Since 2011 alone, it has been almost 737-800 orders (and it has been on sale since 1993). If Boeing can overcome the problems, the 737 MAX could be a huge success.
The next 737?
While the problems with the MAX series and the aviation loss in 2020 may well change the plans for new aircraft, Boeing already has plans for a new aircraft. It was initially planned by 2030.
It is likely to be a composite airframe construction that provides a light fuel efficient construction. Potential adaptations also include an elli-cross section, offering a wider cabin with the possibility of two aisles. The widening of the cabin was how the 737 Original got its lead, so it will be interesting to see if that happens again.[iticalcross-sectionofferingawidercabinwiththepossibilityoftwoaislesWideningthecabinwashowthe737Originalgotitsleadsoitwillbeinterestingtofollowwhetherthishappensagain[iticalcross-sectionofferingawidercabinwiththepossibilityoftwoaislesWideningthecabinwashowthe737Originalgotitsleadsoitwillbeinterestingtofollowwhetherthishappensagain