File:Winglet and nav light arp.jpg|
Boeing 747-400 canted winglet File:Sharklet of HB-JLT (27011749440).jpg|
Airbus A320 blended "sharklet" File:Delta Air Lines 767-400ER @LHR.jpg|
Boeing 767-400ER with raked wingtips File:Wing.slat.600pix.jpg|
Airbus A310-300 wingtip fence File:Airbus A330neo, new sharklets.jpg|
Airbus A330neo blended wingtip with attached
tufts showing airflow during
NASA tests in 1979–1980 model winglet
flutter tests at
NASA Langley transonic wind tunnel The term "winglet" was previously used to describe an additional lifting surface on an aircraft, like a short section between wheels on fixed undercarriage.
Richard Whitcomb's research in the 1970s at
NASA first used winglet with its modern meaning referring to near-vertical extension of the
wing tips. Another potential benefit of winglets is that they reduce the intensity of
wake vortices. Those trail behind the plane and pose a hazard to trailing aircraft, such as a smaller plane taking off (or landing) after a larger plane. Minimum spacing requirements between aircraft operations at airports are largely dictated by these factors. Aircraft are
classified by weight (e.g., "Light", "Heavy", etc.) because the vortex strength grows with the aircraft
lift coefficient, and thus, the associated turbulence is greatest at low speed and high weight, which produced a high
angle of attack. Winglets and wingtip fences also increase efficiency by reducing vortex interference with laminar airflow near the tips of the wing, by 'moving' the confluence of low-pressure (over wing) and high-pressure (under wing) air away from the surface of the wing. Wingtip vortices create turbulence, originating at the leading edge of the wingtip and propagating backwards and inboard. This turbulence 'delaminates' the airflow over a small triangular section of the outboard wing, which destroys lift in that area. The fence/winglet drives the area where the vortex forms upward away from the wing surface, since the center of the resulting vortex is now at the tip of the winglet. The
fuel economy improvement from winglets increases with the mission length. Blended winglets allow a steeper angle of attack reducing
takeoff distance.
Early development F
Richard T. Whitcomb, an engineer at
NASA's
Langley Research Center, further developed Hoerner's concept in response to the sharp increase in the cost of fuel after the
1973 oil crisis. With careful aeronautical design he showed that, for a given bending moment, a near-vertical winglet offers a greater drag reduction compared to a horizontal span extension. Whitcomb was the first to realize a net benefit in drag reduction by careful design to keep profile drag to a minimum. The same month, he filed a U.S. patent for "wingtip airfoils", published in 1986.
Implementations , the first commercial aircraft with winglets Learjet exhibited the prototype
Learjet 28 at the 1977
National Business Aviation Association convention. It employed the first winglets ever used on a production aircraft, either civilian or military. Learjet developed the winglet design without NASA assistance. Although the Model 28 was intended to be a prototype experimental aircraft, performance was such that it resulted in a production commitment from Learjet. Flight tests showed that the winglets increased range by about 6.5 percent and improved directional stability. Learjet's application of winglets to production aircraft continued with newer models including the
Learjet 55,
31,
60,
45, and
Learjet 40.
Gulfstream Aerospace explored winglets in the late 1970s and incorporated winglets in the
Gulfstream III,
Gulfstream IV and
Gulfstream V. The Gulfstream V
range of allows nonstop routes such as New York–Tokyo, it holds over 70 world and national flight records. Conventional winglets were fitted to Rutan's
Rutan Voyager, the first aircraft to circumnavigate the world without refueling in 1986. The aircraft's wingtips were damaged, however, when they dragged along the runway during takeoff, removing about from each wingtip, so the flight was made without benefit of winglets.
Wingtip fence A wingtip fence refers to the winglets including surfaces extending both above and below the wingtip, as described in Whitcomb's early research. Other Airbus models followed with the
A300-600, the
A320ceo, and the
A380. Other Airbus models including the
Airbus A320 Enhanced,
A320neo,
A350 and
A330neo have blended winglets rather than wingtip fences. The
Antonov An-158 uses wingtip fences.
Canted winglets Boeing announced a new version of the
747, the
747-400, in 1985, with an extended range and capacity, using a combination of winglets and increased span to carry the additional load. The winglets increased the 747-400's range by 3.5% over the 747-300, which is otherwise aerodynamically identical but has no winglets. The 747-400D variant lacks the wingtip extensions and winglets included on other 747-400s since winglets would provide minimal benefits on short-haul routes while adding extra weight and cost, although the -400D may be converted to the long-range version if needed. The Aviation Partners/Boeing extensions decrease
fuel consumption by 4% for long-range flights and increase range by for the 737-800 or the derivative
Boeing Business Jet as standard. In 2006, Airbus tested two candidate blended winglets, designed by Winglet Technology and Airbus for the
Airbus A320 family. In 2009, Airbus launched its "Sharklet" blended winglet, designed to enhance the
payload-range of its
A320 family and reduce fuel burn by up to 4% over longer sectors. This corresponds to an annual CO2 reduction of 700 tonnes per aircraft. The A320s fitted with Sharklets were delivered beginning in 2012. They are used on the
A320neo, the
A330neo and the
A350. They are also offered as a retrofit option.
Raked wingtip Raked wingtips, where the tip has a greater
wing sweep than the rest of the wing, are featured on some
Boeing Commercial Airplanes and
Embraer aircraft to improve
fuel efficiency, takeoff and climb performance. Like winglets, they increase the effective
wing aspect ratio and diminish
wingtip vortices, decreasing lift-induced drag. In testing by Boeing and NASA, they reduce drag by as much as 5.5%, compared to 3.5% to 4.5% for conventional winglets. is an example of raked wingtips utilization. Raked wingtips offer several weight-reduction advantages relative to simply extending the conventional main
wingspan. At high load-factor structural design conditions, the smaller
chords of the wingtip are subjected to less load, and they result in less induced loading on the outboard main wing. Additionally, the leading-edge
sweep results in the
center of pressure being located farther aft than for simple extensions of the span of conventional main wings. At high load factors, this relative aft location of the center of pressure causes the raked wingtip to be twisted more leading-edge down, reducing the bending moment on the inboard wing. However, the relative aft-movement of the center of pressure accentuates
flutter. Raked wingtips are installed on the
Boeing 767-400ER (first flight on October 9, 1999), -200LR/-300ER/F variants of
Boeing 777 (June 12, 1994) including the upcoming
777X, the 737-derived
Boeing P-8 Poseidon (25 April 2009), all variants of the
Boeing 787 (December 15, 2009) (the cancelled
Boeing 787-3 would have had a wingspan to fit in
ICAO Aerodrome Reference Code D, as its wingspan was decreased by using blended winglets instead of raked wingtips ), and the
Boeing 747-8 (February 8, 2010). The Embraer
E-jet E2 and
C-390 Millennium wings also have raked wingtips.
Split-tip The
McDonnell Douglas MD-11 was the first aircraft with split-tip winglets in 1990. For the
737 Next Generation, third-party vendor
Aviation Partners has introduced a similar design to the 737 MAX wingtip device known as the split scimitar winglet, with
United Airlines as the launch customer. The
Boeing 737 MAX uses a new type of wingtip device, the Advanced Technology Winglet. Resembling a three-way hybrid of a winglet, wingtip fence, and raked wingtip, Boeing claims that this new design should deliver an additional 1.5% improvement in fuel economy over the 10-12% improvement already expected from the 737 MAX.
Gliders glider with factory winglets
winch-launching In 1987,
mechanical engineer Peter Masak called on aerodynamicist
Mark D. Maughmer, an associate professor of aerospace engineering at the
Pennsylvania State University, about designing winglets to improve performance on his wingspan racing
sailplane. Others had attempted to apply Whitcomb's winglets to gliders before, and they did improve climb performance, but this did not offset the parasitic drag penalty in high-speed cruise. Masak was convinced it was possible to overcome this hurdle. By trial and error, they ultimately developed successful winglet designs for
gliding competitions, using a new PSU–90–125
airfoil, designed by Maughmer specifically for the winglet application. At the 1991
World Gliding Championships in
Uvalde, Texas, the trophy for the highest speed went to a winglet-equipped 15-meter class limited wingspan glider, exceeding the highest speed in the unlimited span
Open Class, an exceptional result. Masak went on to win the 1993 U.S. 15 Meter Nationals gliding competition, using winglets on his prototype
Masak Scimitar. profile The Masak winglets were originally retrofitted to production sailplanes, but within 10 years of their introduction, most high-performance gliders were equipped from the factory with winglets or other wingtip devices. It took over a decade for winglets to first appear on a production airliner, the original application that was the focus of the NASA development. Yet, once the advantages of winglets were proven in competition, adoption was swift with gliders. The point difference between the winner and the runner-up in soaring competition is often less than one percent, so even a small improvement in efficiency is a significant competitive advantage. Many non-competition pilots fitted winglets for handling benefits such as increased
roll rate and roll authority and reduced tendency for wing tip
stall. The benefits are notable, because sailplane winglets must be removable to allow the glider to be stored in a
trailer, so they are usually installed only at the pilot's preference. The
Glaser-Dirks DG-303, an early glider derivative design, incorporating winglets as factory standard equipment. == Non-planar wingtip ==