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Why do airplane wings have curved ends? What are winglets and what are they for?

The airplane wings they are a fundamental part of the aerodynamic design of every aircraft, and in recent decades called the wingtips winglets have become increasingly important in improving the aerodynamic efficiency of aircraft. But what exactly are winglets, what differentiates them from sharklets used by Airbus, and why do some planes, such as the Boeing 787 and 777, not have them?

What are winglets and what are they for?

Before going into the merits of the winglets it is necessary to briefly explain the concept lift. Every time the airfoil comes into contact with the accelerating air, the air molecules will follow this profile creating two zones; one low pressure on the top and one high pressure on the bottom. This pressure difference creates the main force called lift which allows the plane to fly.

boomerang lift airfoil airfoil

On the tip of the wingsthe pressure difference between the top and bottom of the wing becomes particularly significant. Air tends to move naturally from an area of ​​high pressure to an area of ​​low pressure to equalize the difference. This interaction of the two air flows with different pressures at the wing tip gives rise to wingtip vortices (wingtip vortices). These are spirals of turbulent air that form and extend outward from the wing tip.

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Wingtip vortices can be visualized as miniature “tornadoes” that twist behind the aircraft as it flies. The bigger and heavier the plane, the the greater the intensity of these vortices. Particularly during takeoff and landing, when the wings generate maximum lift at low speeds, the vortices are strongest. For this reason, safety distances are applied between one plane and another to prevent a plane from coming into contact with these types of turbulence.

With the advancement of technology it has been discovered how the wingletsthat is, of vertical or angled extensions located at the tips of the wings, they can reduce the interaction of these two air flows. That is limits the formation of vortices of the wingtip, reducing energy lost in turbulent vortices and increasing overall flight efficiency. This reduction in drag allows the aircraft to consume less fuelimproving flight efficiency and reducing CO emissions2. Winglets, in fact, can improve the fuel efficiency of an airplane from 3% to 5%depending on the winglet type and flight profile.

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What is the difference between winglets And sharklets

When it comes to winglets And sharklets, essentially refers to two similar designs, but with some distinctive differences. Winglets are mainly used by airplanes Boeing, while sharklets are used by airplanes Airbus. The key difference between the two terms lies in the design and construction philosophy.

Winglets

The winglets classic are generally curves or fold upwards. They were first introduced in the 1980s and have been used on a wide range of aircraft, such as the Boeing 737, 757 and 767. Some more advanced models, such as the Boeing 737 MAX, use the “Split Scimitar Winglets“, which have a double extension: one pointing upwards and one pointing downwards.

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Winglet example. Credit: Premkudva

Sharklets

The sharklets, introduced by Airbus in 2011, have a more angular shape and they remember one shark finfrom which they take their name. They are designed to further reduce drag and improve fuel efficiency, improving performance on takeoff and climb, as well as during cruising.

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Sharklets used by Airbus.

Because some planes don’t have winglets

One of the most frequently asked questions is why modern airplanes like the Boeing 787 Dreamliner and 777 don’t feature winglets or sharklets. The answer lies in the advanced aerodynamic design of their wings. In fact, these are extremely long and thin wingswith a high “aspect ratio” (wing length to chord ratio). This design naturally reduces drag without the need for winglets. The Boeing 787 wings, for example, are designed to be extremely flexible and can bend significantly, allowing it to handle vortices and drag effectively. Furthermore, the wing design is optimized for long distances and high fuel efficiency, making the use of winglets unnecessary.