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  • Have you ever looked out your plane window and wondered what the hell those little curly bits at the end of the wing were for?

  • The development of winglets, as we see them today, started during the 1973 oil crisis.

  • The Arab states put an Oil Embargo on the United States for providing aid to Israel during the Yom Kippur War.

  • This caused oil prices to sky-rocket, forcing engineers to get creative to reduce fuel consumption.

  • Enter, Richard T. Whitcomb. I could probably do an entire video on this guy's contribution to aviation, but let’s focus on his work with Winglet’s for now.

  • Part of his inspiration came from birds that curl their wing feathers up while gliding to achieve more lift.

  • So he got to work testing this theory, and found that it worked exactly as he expected.

  • Let’s take a look at the science.

  • As you probably know from watching my previous videos, planes fly by developing high pressure air under their wings and low pressure air above.

  • Fluids will always flow from high pressure regions to low pressure regions, and this can cause some problems at the tips of the wing.

  • High pressure air from below will bleed into the low pressure air above, creating mini tornadoes off the tips of the wing.

  • This is called induced drag, and it decreases the lift of the wing and increases the fuel consumption of the plane.

  • Winglet’s reduce this airflow by reducing the pressure gradient at the tips of the wings, thus making the vortices much smaller.

  • Their ultimate goal is to create a lift distribution across the wing in the shape of an ellipse.

  • This minimizes the amount of air that wants to flow over the tips of the wing, while maintaining maximum lift.

  • Let’s compare some wing shapes and their lift distributions to see how this works.

  • Here are 3 wing shapes. An elliptical, rectangular and triangular wing, and their lift distributions look like this.

  • As you can see, the elliptical wing also has an elliptical lift distribution.

  • And this is the ideal.

  • The iconic Spitfire was one of the few mass produced planes in history to have this shape, as it is difficult and expensive to manufacture.

  • The rectangular wings lift distribution is quite high at the edges, and this leads to high levels of induced drag.

  • But this is the easiest shape of wing to manufacture and is mostly used in smaller, cheaper aircraft.

  • Our last wing, a triangular wing has high lift in the center, which rapidly drops off towards the edge.

  • This type of wing has low induced drag, but its lift distribution is far from ideal.

  • So the ultimate goal is to tailor the lift across the wing into the shape of an ellipse to maximize lift and minimize induced drag.

  • Winglets are just one way to do this.

  • Boeing's latest plane, the Boeing 787 Dreamliner, has done away with winglets in favor a raked wingtip, which sweeps the tip of the wing backwards.

  • Boeing have said that their raked wingtips have improved fuel efficiency by 5.5% over the 4.5% for conventional wingtips.

  • You can learn why this alters the lift distribution by watching my video: "Why are plane wings angled backwards?"

  • If you'd like to learn more about the costs of air travel, check out this quick preview for a video Wendover Productions that I worked on.

  • An Airbus A320 burns 1.5 gallons of jet fuel for every mile it flies, so flying the 213 miles from New York to D.C. burns 317 gallons, or about 2 gallons per person.

  • Given average jet fuel prices, it only costs 2.50$ in fuel for you to fly from New York to D.C., so why do tickets cost upwards of $80?

  • Well, the short answer is takeoff fees, landing fees, crew costs, taxes, more taxes, airplane fees, maintenance fees, insurance costs, even more taxes, and administrative costs.

  • If you want the long answer? Well then come over to my channel and watch my video, which includes a special appearance by Real Engineering.

Have you ever looked out your plane window and wondered what the hell those little curly bits at the end of the wing were for?

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B1 US wing lift distribution pressure induced elliptical

Winglets - How Do They Work? (Feat. Wendover Productions)

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    alex posted on 2022/01/14
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