Winglet

Winglets are one of the most successful examples of a NASA aeronautical innovation being utilized

around the world on all types of aircraft.

Winglets are vertical extensions of wingtips that improve an aircraft's fuel efficiency and cruising

range. Designed as small airfoils, winglets reduce the aerodynamic drag associated with vortices that develop

at the wingtips as the airplane moves through the air. By reducing wingtip drag, fuel consumption goes

down and range is extended.

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Aircraft of all types and sizes are flying with

winglets -- from single-seat hang gliders and

ultralights to global jumbo jets. Some aircraft are

designed and manufactured with sleek upturned

winglets that blend smoothly into the outer wing

sections. Add-on winglets are also custom made

for many types of aircraft.

The concept of winglets originated with a

British aerodynamicist in the late 1800s, but the idea

remained on the drawing board until rekindled in

the early 1970s by Dr. Richard Whitcomb when the

price of aviation fuel started spiraling upward.

Whitcomb, a noted aeronautical engineer at the

NASA Langley Research Center, refined the winglet

concept with wind tunnel tests and computer studies.

He then predicted that transport-size aircraft with

winglets would realize improved cruising

efficiencies of between 6% and 9%. A winglet flight

test program at the NASA Dryden Flight Research

Center in 1979-80 validated Whitcomb's research

when the test aircraft -- a military version of the

Boeing 707 jetliner -- recorded an increased fuel

mileage rate of 6.5%.

The Benefits of Winglets

Since the 1970s, when the price of aviation

fuel began spiraling upward, airlines and aircraft

manufacturers have looked at many ways to improve

the operating efficiency of their aircraft. Winglets

have become one of the industry's most visible fuelsaving

technologies and their use continues to

expand.

Winglets increase an aircraft's operating

efficiency by reducing what is called induced drag

at the tips of the wings. An aircraft's wing is shaped

to generate negative pressure on the upper surface

and positive pressure on the lower surface as the

aircraft moves forward. This unequal pressure

creates lift across the upper surface and the aircraft

is able to leave the ground and fly.

Unequal pressure, however, also causes air at

each wingtip to flow outward along the lower

surface, around the tip, and inboard along the upper

surface producing a whirlwind of air called a wingtip

vortex. The effect of these vortices is increased drag

and reduced lift that results in less flight efficiency

and higher fuel costs.

Winglets, which are airfoils operating just like

a sailboat tacking upwind, produce a forward thrust

inside the circulation field of the vortices and reduce

their strength. Weaker vortices mean less drag at

the wingtips and lift