Why winglets are usually only found on large planes

Most modern airlines have some form of extension at the end of their wings, which serves several purposes. However, eagle-eyed avgeeks would have noticed that these “winglets” are mostly found in larger aircraft. In this article, we will look at the reasons for this situation and also look at some larger modern aircraft that do not subscribe to this trend. But first, let’s see why planes are equipped with winglets.

Basics first

Simply put, a winglet is a vertical extension added to each end of an aircraft’s wing. The primary purpose of attaching a winglet to the wing of any aircraft is to help reduce the wingtip vortex that is generated when the aircraft cuts through the air. The winglets are also designed to deflect the vortex away from the wing surface and improve efficiency by reducing vortex drag.

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Wingtip vortex or vortex drag are circular patterns of air left behind when a wing generates lift. Like lift, wingtip vortices are also caused by a pressure difference, but a key difference is the lack of physical separation between high pressure and low pressure areas.

The winglets help increase fuel efficiency by reducing vortex drag. Photo: Luke Peters/Simple Flight

We all know that lift is generated when air passes over the airfoil shape of the wing. Air passing over the wing moves faster and therefore causes less pressure than air passing over the lower part of the wing. The same phenomenon also occurs at the wingtips, but the wing simply ceases to exist at the wingtips, causing the high pressure air from the bottom to spill over the top. This results in the aforementioned circular patterns.


Why only big planes have winglets?

The intensity of wake turbulence generated by any aircraft is directly proportional to the length of its wings. Therefore, smaller aircraft with a relatively short wingspan simply do not need winglets. In fact, adding winglets to smaller aircraft will have the opposite of the desired effect in most cases. The winglet will add extra weight and also create extra drag, which will likely outweigh any efficiency boost it can provide.

On the other hand, the vortices generated by large aircraft are quite violent and generate sufficient wake turbulence to destabilize small aircraft. One such incident occurred in May 2019 in Dubai, where wake turbulence from a Thai Airways Airbus A350-900 on final approach is believed to be the reason a small Diamond DA-62 plane crashed.


Why don’t all modern widebodies have fins?

Now that we’ve established that winglets are pretty much a necessity in big jetliners, the question arises: why don’t all big jets have winglets? Specifically, I’m talking about Boeing’s 787 and 777 jumbo jets, which don’t use any type of winglets. Even the new 777X aircraft is seen without winglets.

Boeing found a way to achieve the same aerodynamic effect as winglets by using angled wingtips. The use of angled wingtips is a clever alternative to bulky, drag-generating vertical winglets. Simple Flying previously looked at the specific reasons why the 787 and 777 aircraft families don’t need or have conventional winglets.

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