Winglets make jets economy models

For a relatively small device whose name sounds like it belongs on a sports-bar food menu, winglets — those vertical tips at the end of aircraft wings — are having a fairly big impact in commercial aviation.

Aviation Partners Boeing, a joint venture formed in 1999 to make and sell winglets for Boeing aircraft, is predicting jet fuel savings of more than 5 billion gallons worldwide this year as a result of the devices.

Southwest Airlines says winglets will save it an estimated 54 million gallons of fuel annually.

The airline in January announced a deal to outfit its newest 737-800 aircraft with enhanced Aviation Partners Boeing winglets that are expected to deliver even more fuel savings.

Winglets were the subject of research and testing at NASA in the 1970s in response to that decade's oil crisis. The devices were shown to reduce the aerodynamic drag created during flight, making aircraft more efficient.

Winglets, which help reduce that drag, have been a part of general aviation — the part of air transportation that does not include scheduled airline service — for decades.

"General aviation was way ahead of commercial aviation on this," said Jeff Baum, president and CEO of Wisconsin Aviation in Watertown, Wis.

The winglets by themselves aren't a whiz-bang invention. They are essentially metal wing extensions, albeit with all the technological sophisti­cation and lightweight ­materials that make up aircraft wings.

"It doesn't dramatically alter many airplanes," Baum said.

Collectively, though, the winglets are huge.

"You multiply that by the number of airplanes by the number of hours they fly by the number of gallons they consume, it can add up pretty quick," Baum said.

The fuel tank on a Boeing 737-700 holds 6,875 gallons. At $3.09 a gallon — the jet fuel spot price on Wednesday — filling the jet would cost more than $21,000.

During flight, air flows up over the wingtip and spins off in a vortex, according to NASA. (Baum describes them as mini-tornadoes of air.)

"These vortices produce what is called induced drag and are powerful enough to disrupt aircraft flying too closely to one another — one reason for the carefully monitored spacing between flights at takeoff and in the air," according to NASA.

That drag hampers aircraft efficiency and cuts into fuel mileage, range and speed, NASA says.

Winglets generally reduce drag in a range of 2 to 7 percent, Baum said.

The higher efficiency means that the aircraft can cover more distance on the same amount of fuel.

"And if you don't want to get there faster, you can pull your power back a little bit. That's where your fuel savings comes from."

The latest generation of Aviation Partners Boeing winglets — something called a split scimitar winglet — received FAA certification for installation on 737-800 aircraft on Feb. 6.

Airbus, the European-based aerospace company that competes with Chicago-based Boeing in the jetliner market, also makes and sells its own version of winglets.

Winglets were born of necessity, Baum says.