Chances are good that if you’ve flown on a 737 or a 757 lately, you’ve seen some abnormally large pieces of metal sticking straight up off the end. These things, called winglets, look pretty funny if you’re not used to seeing them, but airlines are installing them like they’re going out of style. Why? Yup, you guessed it – they save fuel.
The real problem here is called a wingtip vortex. As airplanes fly through the sky, they obviously disturb the air. At the edge of the wing, drag is created becuase the shape causes the air to swirl around in a funnel shape. And when drag is created, it destroys efficiency.
Aircraft manufacturers realized that if you could reduce these disturbances, you could increase fuel efficiency and therefore range. Airbus was the first commercial manufacturer that I can recall to start tackling the problem with wingtip fences. These extend both above and below the wing and have been used on the A300/A310/A320 families. (A320 at left)
Boeing first got into the game with the 747-400 when it came out in the late 1980’s. They installed winglets, which just go above the wing (though most people use “winglet” as the generic term for wintip fences as well). These winglets weren’t very large, but they had the desired effect or reducing the amount of drag created in flight. Most recently, Boeing has moved toward the “raked wingtip” design. This is essentially a horizontal winglet. The 767-400 was the first Boeing aircraft to receive the raked wingtip, as shown at right.
Now, third parties have started to create after-market winglets that airlines can install themselves. The most popular of these is the Aviation Partners Boeing winglets for the 737s and now the 757s. They are blended, which means they curve directly into the end of the wing. These winglets may be really tall and funny looking, but they enable planes to fly further on each tank of gas. This is good for the environment, it saves money, and it extends the range of each plane, and that’s why US Airways is installing them now. It allows them to carry a full load year-round between Phoenix/Las Vegas and Hawai’i as well as from the East Coast to Europe.
So what’s the next evolution of winglets? Well, it may actually not involve winglets at all. Boeing has found ways to incorporate the drag-reducing technology into the wing itself. The new 787 has a pretty radical looking wing design, and the assumption is that winglets won’t be necessary. Look at this picture on the right to see the amazing curvature that you’ll find in the wing. This new wing along with other fuel saving features mean the 787 should see fuel savings around 30% over the 767 it replaces.