How Do Winglets Work?

by Ultimate_Red | February 21, 2015 | (19) Posted in Just Fun


I do not own any of the images used in this article. They are solely being used for your education purposes and not for advertisement or to gain revenue of any sort.


Good that's out of the way.

Welcome to my article on; 


What Do Winglets Do?

    So to understand what winglets do, we first have to understand what happens to a wing during 'normal flight'. That is not whilst stalled or at a high angle of attack for example. In my pervious article I discussed how aircraft fly and if you have read that you should have a good knowledge that above the wing there is a low pressure area and below the wing there is a high pressure area as shown in the image below.


     Yes this is good for making our aircraft fly but it does have disadvantages. At the outside edges of wings the high pressure from beneath the wing forces it's way around the edge into the low pressure above the wing. The slightly over complicated image below shows the arrows of high pressure air coming around the edge to the side with the lower pressure. In doing so, spinning whirls of air known as voritces form and reduce the efficiency of the aircraft. The image below also shows in which direction the vortices spin in which is always from the high pressure to the lower pressure area.




Come On Already Tell Me What Winglets Do!

     Whoa, whoa, slow down! Now that we understand what's happening at a wing edge we can understand what winglets do. Quite simply one could explain a winglet's use to be 'reducing wing vortices' although it's not as simple as that.

     Winglets come in a few shapes, sizes and configurations. The majority of these being;

Standard Winglets - Your average fin stuck onto the wing at 90°.


Blended Winglets - A curved section of wing normally at 70° to the main wing.

Spiroid Winglets - A  blended winglet that is curved completely over and reconnected to the wing. 

And Split Scimitar Winglets - A blended winglet that has an upside down winglet to encourge smooth flow.


     Each of these winglet configurations have specific characteristics but all generally do the same job. We'll use the blended winglet as our example because it is the simplest of all of them. Below you can see an image of a winglet blocking the airflow and eliminationg the large vortices discussed earlier. 


     As I said before winglets only reduce the effects of vortices; they do not get rid of them. It works like this. Winglets block the path of the higher pressure air and stop it from getting to the lower pressure therefore stopping all forming of large vortices discussed earlier. However winglets themselves make tiny vortices because the higher pressure area is now on the outside of the winglet and the low pressure area on the inside. Do you see where this is going? The difference in pressure causes the higher pressure area to move towards the lower pressure are thus making a vortex.

    Yes the vortices cause an inefficiency however they are far more efficient than not having winglets; up to as much as 6% more efficient. These vortices also cause a small amount of inefficiency because they 'use up' less energy which will be explored in the next paragraph.

    Furthermore, winglets produce a forward thrust vector by being rotated toe-out slightly therefore 'stealing' the energy from the vortices and turning it into a 'thrust' allowing the engines to run at a lower rpm to achieve the same airspeed. The forward thrust vector is formed because the higher pressure on the outside pushes the winglet in and forward due to the toe-out attitude.


Why Do We 'Blend' The Winglets?

    On standard winglets we get something called interference drag. This is caused when air flows over sharp angles or curves. Imagine now cutting a knife through butter and how little force is required. This is because a knife is streamlined like the shape in the image below. If you read my previous article 'How Do Aircraft Fly?' you'll understand how shape affects drag.

     The small blue arrow to the rear shows how much drag is being made; very little therefore this shape is efficient. Now imagine dragging a shovel through butter with the face towards yourself. An abstract idea I know but the proof is in the pudding. The large surface area creates alot of drag because it has to move the butter quite far out of the way for the shovel to pass through; expending energy in doing so.

     To quote Sir Isaac Newton "Energy is not created or destroyed, it is merely transferred." For this reason the energy being used up to move the butter out of the way means that the shovel is harder to pull through than a knife because more energy is needed to pull it through at the same speed. This is shown by the large arrow to the rear of the image above signifying the drag of the shape.

      On a standard winglet air flowing over each of the two aerofoils mingle in the right angle formed at the base of the winglet. here small whirls of wind (vortices) are made that reduce efficiency due to the interference drag. The left image  below is similar to a standard winglet.

     The images are computer generated models of winglets the left being less blended than the one on the right. Pay key attention to the swirls in the bend on the left image and the efficiency data at the bottom of the images. The more blended winglet (above right) is 0.0067% more efficient than the less blended winglet (above left). Compared to a standard winglet this efficiency difference would be even bigger. 

     Blended winglets work at higher angles of attack (AOA), remeber AOA being the angle between the wing chord and apparent wind [see 'How Do Aircraft Fly?]'. This is because as AOA increases so does lift. This is caused by the increasing relative pressure difference between above and below the aerofoil (see image below).

     The increasing difference then makes larger and larger vortices like wind gets stronger when more particles want to transfer (below). This is what winglets of any sort are trying to stop from happening because the creation of vortices is incredibly inefficient.

     In some cases the difference in pressure can be so great it will make votices off of the fuselage like on this F/A-18 Superhornet at a high AOA.


What Do Spiroid Winglets Do?

     First used in 1992 on the Gulfstream II, spiroid winglets are like blended winglets and standard winglets but “The Spiroid eliminates concentrated wingtip vortices, which represent nearly half the induced drag generated during cruise.” - FlightBlogger. This is because rather than the pressure coming around the side and trying to get over the tip; it cannot get over because there is no tip of a winglet. For this reason the air flows over like the sphere in a fairing (far above).

     Research done by Tung Wan and Kuei-Wen Lien found that spiroid winglets can save as much as 5% fuel burn however their efficiency decreases with AOA; level flight being their most efficient. Simply, again, spiroid winglets are not going to feature massively on small aircraft because they dont cover the distance or burn enough fuel per year to benefit from the efficiency of winglets.


What Do Split Scimitar Winglets Do?

     Split scimitar winglets may look cool but they give more efficiency than blended winglets, thier predecessor. They take the technology from upward wingtips and lowered wingtips and combines them. Back in the day on the MD-11 they found that lowering the winglet and giving them a toe-in attitude, the opposite of a standard winglet, also gave a forward 'thrust component'. So by combinig these two methods an efficiency saving of 6% can be achieved.

    Also, like blended winglets, they make smaller vortices by making the air travel further around, therby stealing it's energy and because the difference in pressure on each side of both winglets is reduced the passing over of air is slower and weaker.

     We can relate this to our diffusion model above the F/A-18 Superhornet and to wind. On windier days more particle have to diffuse which gives the appearence of wind. on less windier days less particles need to move. In comparison to a wing a windy day would be without winglets, a light breeze would be with blended winglets and a very light breeze would be with split scimitars. You get the jist. Below is the same image with particles for visualisation if you are struggling.


Why Doesn't My Cessna 172 Have Winglets?

    Whilst on your average Sunday flight you might save a few dimes from the aid of winglets; 172s or any small aircraft of any kind simply dont fly fast enough or fly far enough per year to benefit from the tiny gains that winglets provide. Whereas, large airliners can save thousands per year.

     Yes, for one airliner blended winglets save 54 million gallons of fuel. Thats $96,660,000 USD in today's market (£62,776,424 GBP). It not only means that we get cheaper flights but also less CO2 is made; slowing global warming. Furthermore, split scimitar winglets are now the new hype and in the next few years with them being more and more widely accepted we can save much, much more.

To Conclude

     In this article we began by discussing how vortices form on wings. We then talked about the types of winglets including Standard, Blended, Spiroid and Split Scimitar. We then discussed how winglets produce a forward thrust, reduce the effects of vortices and how interference drag is such a nuisance. I then moved on to talk about how Spiroid and Split Scimitar winglets work and we touched base on simple diffusion knowledge. To finish with we asked why small aircraft don't have winglets. Either way one looks at it; having winglets is far more efficient and fuel saving than without them.


Thank you for reading my article. Please leave a comment and a star rating.

Safe Flying!


spastickitten on February 22, 2015
I did a complete science fair on this and got second place in the county! Great to see this now after about a year! Pretty cool!
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Ultimate_Red on February 23, 2015
Congrats. Thanks for commenting!
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Stingray Aviation on February 24, 2015
I did a science fair thing on winglets too and I also got an award for it. I built a little balsa wing and some winglets with various angles (30, 60, 90) and then put them in a wind tunnel to find out how much lift they would produce. The 90 degree ones lifted the most surprisingly.
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ftwingnut on February 22, 2015
I knew quite a bit about winglets and their functions, but didn't realize that they also generated a small amount of forward thrust, being toed-in or out for downturned/upturned winglets. What is the typical amount of toe-out for an upturned winglet? Does it depend on too many variables to give a general answer?
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Ultimate_Red on February 23, 2015
It's not very much or it itself would produce drag. It's normally from <1 degree to as much as about 4 or 5 from what I've seen.
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Ultimate_Red on February 24, 2015
1000 views! Thanks everyone!
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sailorJohn on February 25, 2015
Thanks for the informative article. I have a high wing modified version of the NOOB TUBE and am considering adding winglets maybe sloping outward as it is too touchy on the controls even when nose heavy , always looking for the "HAPPY MISTAKE".
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Randolph Torres on March 3, 2015
excellent thanks much for all your hard research.
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Ultimate_Red on March 1, 2016
Thanks for reading and commenting! Hope you learnt alot!
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Ultimate_Red on February 22, 2015
Updated! Yay!
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akmk10000 on February 22, 2015
Good article.

I live in an area where STOL aircraft are very common as we have a lot of "bush" planes. Many of these have STOL wings which have down-turned tips. I assume these work in a similar manner as blended winglets but are better at high AOA. Is my assumption correct?

Of course, I have also assumed these items have a totally different aim than winglets. They are used to maintain lift at low speeds to decrease stall speed. Can you comment on this?

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Ultimate_Red on February 22, 2015
Your correct. One of a Blended (Inverted or not) winglet's benefits is that they work at high AOA as mentioned in the article above the F/A-18.
They are winglets and will also improve efficiency; it just wont be as noticeable in the pilot's fuel bill. Those winglets that you see on SuperCubs are called 'Madras tips' they effectively increase the aspect ratio (longer wingspan to shorter chord ratio). What this does is it makes the plane more like a glider; slower flight and less like a missile.
Thanks for commenting. I really appreciate it :)
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PeterGregory on May 21, 2015
Really good article, especially seeing how the split scimitar winglets work. I was wondering why we don't just slap winglets on the ends of all our wings on our models but it sounds like the effect is negligible.
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Ultimate_Red on March 1, 2016
Yes, you're right. The effect is incredibly small and slight, but on large airliners that travel every hour of the day, the tiny percentage really begins to stack up. On the little planes, the benefits of having the winglets wont outweigh the downsides of having the extra weight.
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Flite test for life! on February 23, 2015
I didn't know that, that's pretty cool thanks!
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Ultimate_Red on February 23, 2015
Thank you for reading it! It's my pleasure to share my knowledge to the FT community :)
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eagle4 on February 21, 2015
Could you go deeper into the different winglet shapes and their functions? like when you'd use a split one? also you forgot to go into details on how winglets help keep a plane tracking straight if it's a flying wing.
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Ultimate_Red on February 21, 2015
Firstly, yes sure ill work on it tomorrow. Secondly, the winglets on a flying wing a vertical stabilisers. They work like a tail fun on a plane; they stop a sideways slide and unwanted yawing. Like winglets they reduce drag but those are not their sole purpose.
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llebreknit1 on March 2, 2015
It's funny I'm just now seeing this. Maybe about 6months ago I decided, "what can I do to increase the stability, slow flight, and just experiment with the FT flyer." I went crazy overboard but the flight characteristics are phenomenal. When you can hover with the FT flyer or chop the throttle and hold full up and it just lands wings level it was impressive. Did STOL like tips with winglets, stall strips toward inner fuselage, and vortex generators.
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lostcity on April 3, 2015
NIce work. Did you try to see what each individual change did to effect flight on the FT Flyer?
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llebreknit1 on April 4, 2015
I did and the greatest change was adding the winglets and inverted winglets (STOL I guess really) and each addition just slowed it down even more. Now...I can start out at say 100feet, chop the throttle, hold full up elevator and it floats down with little if any wing rock and certainly won't tip stall. I can hover the three channel setup by managing everything appropriately. Cool little addition and test project.
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Ultimate_Red on March 1, 2016
Wow! That's a really cool FT Flyer! Looks like it's had a few beatings ;)
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Neskair on October 31, 2015
Awesome! Thank you for the lesson. I never knew what winglets actuallly did untill now. But i was too lazy to look it up haha
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Ultimate_Red on March 1, 2016
That's what I'm here for! Thanks for reading and replying!
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Jackson T on October 13, 2019
I'm pretty interested in winglets too. I am working on some balsa ones for my 4m scratch built balsa glider ( and it's all very interesting. Where did you learn about winglets, other than random googling?
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How Do Winglets Work?