Boeing 737 – The Baby Boeing

737-800 of Ryanair seen at Brno, Czech Republic in 2017.

Ubiquity and Omnipresence 

Boeing’s legendary 737 airliner series is so common worldwide that most of us barely take notice when one flies overhead, the truth is that we really should take more notice of it and respect its unique place in aviation.

The 737 is, after all, the world’s most produced and used airliner of any category. By some estimates there are more than 1,000 of the type airborne at any given time and the 737 series represents roughly 25% of all airliners currently in operation.

First flown in 1967, The 737 has been in production for over 50 years with over 10,500 built across four distinct generations as of early 2020. Chances are, if you’ve traveled on shorter airline routes, you’ve likely traveled on a 737.

It is a design that has proven highly adaptable in both civilian and military applications. Beyond its intended commercial airliner role, the 737 has been adapted to cargo, corporate transport, electronic warfare, firefighting, maritime patrol, test flying and training duties

Let’s spend some time with the “Baby Boeing”:

737-700 of Gazpromavia seean at Brno, Czech Republic in 2017.

Playing Catch Up and Hitting Full Stride

It’s perhaps difficult to believe that with as prolific and successful as the 737 has been in its life, Boeing really was a bit late to the party with it.

The market for short haul, narrow body airliners was becoming increasingly lucrative in the early to mid 1960s and by the time Boeing began planning the 737 in 1964 the aircraft’s initial rivals for the market; the British Aircraft Corporation 1-11 and the Douglas DC-9 were well underway. The BAC 1-11 had its maiden flight prior to 1964 and the DC-9 flew for the first time in 1965.

To make up lost time, Boeing used the same fuselage and many systems for the 737 as they had for the 727 before it. As this common fuselage cross section was somewhat wider than those of its counterparts, the 737 could carry more passengers than either the BAC 1-11 or DC-9. Boeing further increased the aircraft’s passenger capacity by placing the engines under the wings rather than on either side of the rear fuselage as was done with the BAC and Douglas designs.

The 737 quickly proved popular as a rugged and reliable machine that could be easily supported and operated from airfields with rudimentary facilities and austere conditions.

When fitted with a system known as a gravel kit, the 737 could operate from semi prepared runways in Canada’s north as well as other spartan regions around the world. The gravel kit consisted primarily of a deflector device fitted around the nose landing gear and a metal pipe attached to the lower lip of each engine intake, air was blown downwards towards the runway through these pipes and prevented debris from being ingested by the engines while the aircraft was taxiing and taking off. This adaptation allowed the 737 to operate in areas that its competitors often could not.

Some 737 variants can be fitted with an Enhanced Short Runway Package that allows them to operate from shorter runways without adversely affecting their flight performance or lifting capability.

As the years have passed, the versatility of the 737 has ensured that later generations of the design are still competive against contemporary descendants of the DC-9 as well as younger short haul designs from Airbus, Bombardier and Embraer.

737-500 of Transaero seen at Pardubice, Czech Republic in 2014

The 737 in Popular Culture 

In its lifetime, the 737 has been operated by more than 500 airlines around the world and served in the air arms of around 25 countries. Such wide distribution has given members of the aircraft family a near omnipresence and visibility that has ensured it a place in popular culture.

Aircraft of the 737 family have made numerous appearances in both minor and major roles in films and television serials from around the world.

In musical circles, the 737 was mentioned the Creedence Clearwater Revival hit from 1970: Travelin’ Band.

American folk band, The Low Anthem, released the song Boeing 737 in 2011. The song is about the September 11, 2001 attacks on the World Trade Centre and the use of 737 aircraft in that infamous event.

An image of a 737 graces the cover of Mark Knopfler’s Sailing to Philadelphia album from 2000.

The 737 is also a very popular aircraft that features prominently in a number of flight simulator programs for computers.

737-200 seen at the Alberta Aviation Museum in Edmonton, Canada in 2012.

The Family Album 

The 737 family is divided into four variant series that each have their own subvariants within them:

The Originals: 737-100 and -200

Distinctive in appearance by their stubby fuselage and long, narrow engine pods that housed the noisy Pratt and Whitney JT8D engines; the initial series of the 737 family very quickly established the aircraft’s reputation for ease of service, versatility, self-sufficiency and ability to operate from remote locations with rudimentary facilities.

Both the -100 and -200 versions first flew in 1967. In that same year, Germany’s Lufthansa became the first commercial operator of the 737 when they took delivery of their first -100 version. In 1968, United Airlines became the first commercial operator of the -200 version.

While the -100 saw only modest production, the -200 was the first major variant of the family with over 1,000 built in total. While production of the -200 is long since finished, modifications to the remaining airworthy examples are still being produced and made available. Many of these modifications concern noise reduction and fuel efficiency issues.

The United States Air Force used the -200 version as the T-43 navigation trainer and as the CT-43 transport. The Indonesian air force used three -200s modified for maritime patrol.

A 737 of the “Classic” series showing the distinctive “Hamster pouch” engine shape unique to the series. Seen at Ostrava, Czech Republic in 2013.

The Classics: 737-300, -400 and -500 

Before the 1970s were out, Boeing was already examining ways to improve upon the great success of the 737-200 and keep demand high for the 737 family of aircraft.

The driving forces which led to the new generation of the aircraft were increased fuel efficiency, passenger carrying capacity and engine noise reduction. In the face of addressing these issues, Boeing also aimed for a significant degree of parts commonality between the 737-200 and the Classic variants.

To tackle the matters of fuel efficiency and noise reduction, a new engine was required. The internationally developed CFM-56 turbofan was selected as the new engine, though incorporating it into the 737 required an adjustment in the position of the engines’ accessory devices to compensate for the 737’s low ground clearance.

The re-positioning of the engine accessory packages from directly under the engines to a spot on the side of them gave the required clearance between the engines and the ground; however, it also created distinctively shaped engine pods which were wider at the bottom and gave raise to the term “Hamster pouch” as a nickname for them when viewed directly from the front.

Fuel efficiency and general flight performance were also improved by refinements in the aerodynamics at various locations around the fuselage, wings and tail. Some aircraft of this generation were retrofitted with winglets on their wingtips to further increase fuel efficiency by reducing drag.

The -300 served as the basis for a firefighting variation of the 737 that debuted in 2018 and is known as the FireLiner. It’s seen use in fighting fires in both Australia and Canada.

737-800 of Smartwings touches down at Brno, Czech Republic in 2019.

The Next Generation: 737-600, -700, -800 and -900 

The same forces which inspired the creation of the “Classic” series of the 737 family through the 1980s were again at play to inspire the development of the “Next Generation” or 737 NG series in the 1990s. This series of the aircraft family was announced in 1993 and the first of them took to the air in 1997.

An additional catalyst for the new developments was the Airbus A319 and A320 series of airliners from Europe. The A319 and A320 brought a great deal of new technology to the short haul sector which the 737 had become the dominant force in and Boeing would need to modernize it in order to stay competitive.

The 737 NG received redesigned engine pods which further increased fuel efficiency and reduced noise. Several drag reducing refinements were also applied to the wings for fuel savings and performance increases.

With the 737-800, a significant increase in size was instituted in order for the aircraft to not only compete more directly with the A320 in passenger capacity, but also to replace Boeing’s own 727 narrow body liner in many airline fleets.

Outside of commercial interests, the 737 NG has found users in the corporate and military sectors as well.

Tail fin of a Turkish E-7 Wedgetail seen at Ostrava, Czech Republic in 2017.

All NG versions can be fitted out as a Boeing Business Jet, or BBJ. The BBJ concept reduces the passenger capacity in favour of a more luxurious cabin for corporate flying.

The 737-700 serves as the basis for the C-40 Clipper transport which first flew in 2001 and serves with the U.S. Air Force and U.S. Navy.

The -700 is also the basis for the E-7 Wedgetail airborne early warning aircraft which first flew in 2004 and  entered service in 2009 with the Royal Australian Air Force. The Wedgetail has since been taken on charge by the Turkish and South Korean air forces as well. The Royal Air Force announced in 2019 that they would be taking the Wedgetail into service and would have a fleet totalling five aircraft that would be delivered through the 2020s.

Developed from the 737-800, the P-8 Poseidon maritime patrol aircraft entered service with the US and Indian navies in late 2013. It entered service with the Royal Australian Air Force in 2016 and the Royal Air Force in 2019.

The 737 Max: Max 7, Max 8, Max 200, Max 9, Max 10 and Max BBJ

In 2011, Boeing announced the fourth generation of the 737, the 737 Max. The main impetus for creating this fourth generation of the aircraft was to keep Boeing competitive on the short haul market against the Airbus A320neo, which had been launched in 2010. Boeing had been planning to replace the 737 with a clean sheet design, but a combination of staying competitive and the 737 NG variants still performing very well in sales took precedence and the 737 was modified once more instead.

The 737 Max first flew in 2016 and had Malaysian based Malindo Air, a subsidiary of Indonesian based Lion Air, as its launch customer in 2017.

The Max 7, 8 and 9 are follow ons to the -700, -800 and -900. Like their 737 NG forbears, these Max versions can be refitted as BBJ versions.

The Max 200 is a variation on the Max 8 that takes that variant’s single class passenger capacity up from 189 to 200.

The Max 10 is a stretched version with a 230 passenger capacity in single class configuration designed to compete with the Airbus A321neo.

One of the most noticeable external changes to create the 737 Max was the engine change to the CFM LEAP engines to increase fuel efficiency and reduce noise emmisions. The Airbus A321neo also uses this same engine. The Max series has a number of other aerodynamic refinements nose to tail that include a new design of winglet at the wingtips.

Unfortunately, following a pair of fatal crashes, a worldwide grounding of the 737 Max fleet was imposed in March of 2019. The findings of the investigations placed the blame on Boeing for omitting critical information about an aspect of the 737 Max flight control system known as the Maneuvering Characteristics Augmentation System (MCAS) from the 737 Max training manual. The investigations also found that not only had Boeing omitted information about the system from the training manuals, they had also made modifications to the system, such as disabling the manual override, that made it an unacceptable flight safety risk.

Not only were pilots not being adequately familliarised with the system’s workings, they had no means of taking over for it if it malfunctioned. In both crashes, the system malfunctioned and the aircraft were sent into fatal dives that the crews could not recover the aircraft from.

The crashes and findings of the investigations shook confidence in both Boeing and the 737 Max. Many airline orders for the 737 Max were cancelled or suspended, Boeing dismissed their CEO and the repurcussions of the grounding were felt throughout the aircraft industry as many of the subcontractors Boeing had doing work on the 737 Max were also affected.

Through most of 2020, Boeing and the Federal Aviation Administration (FAA) worked to fix the problems in the 737 Max. On November 18 of 2020, the grounding of the 737 Max was lifted and the aircraft was cleared to return to service.

737-700 of Westjet seen at Ottawa, Canada in 2019.

The Future of the 737 and Learning More 

The 737 celebrated the 50th anniversary of its first flight in 2017 and, as it stands, the 737 family would certainly seem to have another 50 years of practical service guaranteed to it across commercial, corporate and military sectors.

In spite of the woes of the Max series, the previous NG series still enjoys widespread popularity and serves as a reminder that the 737 is indeed a solid and proven design that has withstood the tests of time very well indeed.

Boeing has talked about replacing the 737 with a clean sheet design for a number of years. However, there seems to be no concrete date set for when the world might see that aircraft come into being.

With the sheer number of 737s built and the number of them still in active service around the world, your chances of seeing one earning their keep at an airport terminal or flying overhead are virtually guaranteed for the forseeable future no matter where you are in the world.

This link will take you to a decently detailed, if dated in spots, website about the 737 and its variants:
The Boeing 737 Technical Site