Winglets are vertical extensions to a wing that serve to reduce drag. Some of the higher-pressure air flowing along the underside of a wing spills off the wing tip, creating small, tornado-like wingtip vortices. These energy-zapping vortices take a toll on the overall performance of the aircraft.
It stands to reason, then, that if you can block the spanwise flow that creates the wingtip vortices, you should see a performance boost. And that is the theory behind winglets.
Nearly 30 years ago Richard Whitcomb, a NASA engineer, heralded the potential of winglets to increase the speed of a large transport aircraft in cruise flight. By throttling back to achieve the same cruise speed as without winglets, the airplane consumes less fuel for the same trip length. Since then winglets have gradually gained acceptance on airplanes of almost any size.
On its Web site, the Boeing Commercial Airplane Company posts a long list of benefits that winglets impart to the "Next Generation" 737: longer range, lower fuel consumption, reduced engine maintenance, lower noise, more payload, better takeoff and climb performance, and higher altitude capability.
Winglets are more effective on larger airplanes. In fact, the so-called blended winglets (the name refers to the gradual transition from the horizontal span of the wing to the canted angle of the winglet) on the 737 are eight feet tall and four feet wide at the base, weigh 132 pounds each, and together add five feet to total wingspan.
The accompanying photo shows a much smaller winglet on a Piper Navajo, a popular general aviation piston twin. The winglet is an aftermarket modification offered by Colemill Enterprises in Nashville, Tennessee.
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