Why Do Some Aircraft Have Winglets?

Aircraft manufacturers have been using additional ‘bits’ on the ends of wings since the beginning of the 2000s. These small additions, commonly known as winglets, are designed to improve the efficiency of the aircraft by reducing drag. These special wingtips have aerodynamic benefits that come from nature; many birds, especially gliding birds, curl their wings up at the ends to improve the efficiency of their flight.

Airbus A350-941 blended winglet. Photo: Julian Herzog, Wikimedia

How do winglets work?

The purpose of winglets is to reduce vortex drag, which is especially strong during takeoff and landing. Vortices steal energy from an airplane’s motion, so wingtips are technically reducing fuel consumption by minimizing the drag.

To put it simply, the high-pressure air turns over the wingtip into the low-pressure air during takeoff and landing, thus creating wingtip vortex. The drag is created because the wingtip vortex has a lower pressure than the air passing over the wing. There’s a really good visual explanation of how winglets work in the video below:

Winglets have become a more common occurrence in the last decade, with aircraft manufacturers installing them not only for cutting drag but also because they can boost fuel efficiency by up to 5%. In fact, winglets of some shape or form are pretty much standard equipment on modern jets today, and some airlines are even retrofitting them to older aircraft too.

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There are other reasons for using winglets. For example, Aero Magazine argued that the branded winglets on the Boeing 737-800 not only gives the airplane operational benefits by creating more efficient flight characteristics, but they also give it a distinctive appearance.

 

A West Jet Boeing 737-800 with branded winglets. Photo Bill Abbott via Flickr

Not all winglets are the same

While their purpose is largely the same, not all winglets are created equally. Winglets have an impact on aircraft design style, which is one of the reasons they don’t look the same. Some of the most common shapes encountered include squared-off, rounded fences, floppy wingtips, and blended winglets, which are where they curve up from the wing gradually.

Winglets come in several types as well, with the most common being standard winglets with the fin installed at a 90 degrees angle on the wing, blended wings that are slightly curved at about 70 degrees, spiroid winglets that are completely curved over the wing, and split scimitar winglets, which feature an upside-down winglet stuck onto a blended winglet.

Some aircraft have raked wingtips added to improve aerodynamic efficiency. For example, the Boeing 777-300ER has raked wingtips that reduce fuel burn and increase climb performance while reducing the takeoff field length.

Boeing will add folding wingtips on two aircraft in 2020. Photo: Boeing

Why don’t all airplanes have winglets?

Designing winglets is a tough task. Get it wrong, and the end result will not be of any benefit to the aircraft. As adding winglets ads weight, the benefit to the fuel efficiency of the aircraft needs to be enough to counter the extra weight from the add-on.

A far easier way to improve flight efficiency is to increase the span of the wings themselves. However, really wide wings can create a problem with gates at airports, which is why the new Boeing 777X is being designed with folding wingtips, to give it a super-wide span while not requiring modification at the airport end.

For smaller aircraft landing at airports not equipped for jumbos, adding span is not an option, so by going vertical, airlines can realize efficiency improvements. Winglets themselves are always being improved too, with the split scimitar winglets of the 737 MAX offering a 2% improvement over the second generation winglets of the 737-800.

While folding wingtips might be the most notable innovation of recent years, the humble winglet has a lot going for it too. For smaller aircraft such as the A320 and 737, you can be certain of seeing more winglets more often in the future.

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Vince

Never knew these winglets were from “branded” designers like LV and burkins.
I think you meant blended.