Why Did Boeing Build The 737 Without Winglets?

Winglets are devices installed at the end of an aircraft’s wings. They have become a popular addition for most modern commercial aircraft as they greatly increase an aircraft’s efficiency. By reducing drag while maintaining lift, winglets can reduce fuel burn by 2-5%. However, not all Boeing 737s are fitted with winglets.

Even some Next Generation examples don’t have them, as winglets were an optional extra that some airlines chose not to invest in to save weight and costs. Some pilots lovingly refer to these quirky jets as ‘straight-wingers’. In this article, you can learn more about the 737s without winglets, why some carriers opt for 737s without winglets, why it is getting harder to see them, and the future of 737 winglets.

The Reason Some 737s Have No Winglets

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The vast majority of active 737s have been either built with winglets or have had them fitted aftermarket. B737.org.uk estimates that 85% of 737s have winglets. Therefore, ‘straight-wingers’ are a rare spot for enthusiasts.

Whether a Boeing 737 has winglets attached all depends on the variant of 737 in question, and whether the carrier has decided to have them fitted after market. The table below breaks down the 737s with and without winglets:

As can be seen, most 737s have at least the option of having winglets installed. However, avid planespotters will have noticed that occasionally a 737 can be spotted with no winglets. This is because winglets add additional weight and are costly to install. A 737 winglet installation is estimated to cost $725,000 for parts and a 1-week installation process costing $25,000-$85,000. Additional costs may be incurred if structural changes to the wings are required. Winglets are also heavy at 375-518 lbs (170-235 kg). This weight is offset by having to carry less fuel due to efficiency improvements, but flights under an hour don’t reach enough fuel savings. As a result, the fuel savings may not be high enough for carriers to justify such an investment if they are using 737s for short routes. On the other hand, winglets’ benefits are most profound for long routes.

The Benefits of Flying With Winglets

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B737.org.uk has outlined a number of winglet benefits specific to 737s across all stages of an aircraft’s flight. During climb, an aircraft with winglets can climb more steeply and with reduced thrust (a 3% derate is possible). Due to the derate, the noise footprint during takeoff can be reduced by 6.5% and NOx emissions by 5%. Such advantages are crucial as legislators continue to take action to force the aviation sector to reduce its astronomical environmental impact.

The advantages continue during cruise, with fuel use reduced by 6%. Enhanced climb performance also allows the 737’s ceiling of 41,000 ft to be reached much faster. With lower congestion at such altitudes, pilots can plot more direct routes and shortcuts, cutting down on flight time.

By 2004, Boeing was already recognizing that convincing more of its customers to invest in blended winglet installation would have a substantial impact on the 737’s capabilities. Aviation Partners Boeing CEO, Mike Marino, said: “Blended Winglet-equipped commercial aircraft save fuel, operate with enhanced performance due to a higher lift wing, and are measurably more environmentally friendly. Today’s 500 Blended Winglet-Equipped 737s are saving over 50 million gallons of fuel each year. If all Boeing aircraft worldwide were retrofitted with Blended Winglet Systems, worldwide fuel savings would be close to 1.8 billion gallons each year.”

Boeing’s Past Lack of Commitment to Winglets is Surprising

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Variants of the 737, including the 737 Next Generation, were built without winglets, without always giving the option to include them aftermarket. This design decision is unexpected, given that Boeing was a winglet innovator. Both Airbus and Boeing began to consider winglets after Bombardier successfully implemented them for the Learjet 28 in 1977. While Airbus introduced the A310-200 with winglets, improving cruise fuel consumption by 1.5%, Boeing launched the Boeing 747-400 with winglets in the same year. Boeing’s design included a broader wingspan and canted winglets, the first time they were introduced into the commercial aviation market.

The canted winglets were 6 ft (1.8 m) tall. Compared with the previous 747-400 without winglets, the -400’s winglets alone improved the 747’s range by 3.5%. Airbus later emulated the canted winglet design in 1993 for its A340 and in 1994 for the A330. Yet, even with these early winglet aircraft, Boeing acknowledged that not all carriers would want them. In October 1991, the -400D Domestic entered service for the domestic Japanese market. As these aircraft would be engaging in shorter routes, largely within Japan’s home islands, the advantages of having winglets were negligible. Therefore, some Japanese carriers preferred to save on weight, purchasing, and leasing costs.

737s Without Winglets Are Getting Rarer

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As carriers start replacing older 737s, which are more likely not to have winglets than newer examples, with 737 MAXs, it is getting harder for planespotters to see these unusual aircraft. The past year has seen several stories of notable 737 retirements, including Alaska Airlines’ decision to retire the world’s first 737-900. This aircraft was ferried off to the notorious Pinal Airpark in Arizona in April. This famous boneyard is capable of storing hundreds of aircraft in its desert climate, which reduces the corrosion of retired aircraft.

Along with its historic significance, N302AS was noteworthy as Alaska Airlines decided against retrofitting it with blended winglets. Instead, they stuck to its straight wing design. Another quirky feature was N302AS’ original over-cockpit windows, known as eyebrows. Advancements in avionics have meant such ‘eyebrows’ are now obsolete.

The retirement brought decades of first-rate service for both Alaska Airlines and Boeing to a sudden end. Designated N737X, the prototype served as a testbed for the largest 737 Next Generation variant. It undertook a grueling 381-hour testing and certification program. The aircraft then amassed almost 68,000 hours of flight time over 22 years of service with Alaska.

The New 737 MAXs Always Have Winglets

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While Boeing experimented with flat wings for the 737 Next Generation, the new 737 MAXs are always fitted with winglets. This is due to the aircraft’s higher range, allowing more flight time for the winglets’ benefits to take effect, and the improved quality of winglets. Boeing claims that the split winglets are “the most efficient winglet on any airplane.” The 737 MAX has a unique winglet appearance, combining a conventional winglet with a ventral strake pointing downwards. The manufacturer claims that the winglets provide a 2.2% fuel use reduction that will save carriers hundreds of millions of dollars a year and dramatically reduce environmental impact.

Boeing explained how the split winglet works: “In addition to the inward, upward, and slightly forward lift components of the upper aerofoil, the new lower aerofoil generates a vertical lift component that is vectored away from the fuselage, and also slightly forward.”

The unique split winglets come as a development of the 737 Next Generation’s split-scimitar winglets. These winglets offered an efficiency enhancement on the older Next Generation blended winglets. Boeing claims that the 737 MAX winglets are distinct from the 737 NG’s split-scimitars. Yet, with the two winglets appearing highly similar, there has been some speculation that this is merely branding.

Will Future 737s Have Winglets?

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Should there be a generation of 737s after the 737 MAX, if Boeing decides against a clean sheet design in a decade, it is impossible to know if it will have winglets. However, given the holistic move away from the 737 Next Generation’s straight-wing design, it is unlikely such an aircraft would have no winglets. Winglets have also become lighter and more efficient, greatly reducing the circumstances where it is more efficient and cost-effective not to use winglets. Moreover, there has been a general move towards winglets across the aviation industry’s latest designs, including on the Boeing 777X.

It is also unknown what the winglets aboard a future 737 will look like. Technological advancements and decades of winglet testing have generated the designs on contemporary Boeing aircraft. It is safe to assume that the ideal winglet will look entirely different in a decade. Only time will tell.