Wingtip device

Source: Wikipedia, the free encyclopedia.
Not to be confused with wing fence.

The Airbus A350 wingtip device
Line drawing of wingtip vortices behind a conventional wingtip (on the left) and a blended winglet (on the right)

Wingtip devices are intended to improve the efficiency of fixed-wing aircraft by reducing drag.[1] Although there are several types of wing tip devices which function in different manners, their intended effect is always to reduce an aircraft's drag. Such devices reduce drag by increasing the height of the lifting system, without greatly increasing the wingspan. Extending the span would reduce lift-induced drag, but would increase parasitic drag and would require boosting the strength and weight of the wing. At some point, there is no net benefit from further increased span. There may also be operational considerations that limit the allowable wingspan (e.g. available width at airport gates).

Physics

When a conventional wing generates lift, it also experiences lift-induced drag. Higher pressure air under the wing flows to the lower pressure surface on top at the wingtip, which results in a vortex caused by the forward motion of the aircraft. Trefftz-plane theory shows that increasing the height of the lifting system will decrease induced drag. A vertical fin or winglet will reduce induced drag if it is placed anywhere along the wing off-center of the aircraft, but it is most effective when it is placed at the wingtip.[2]

Benefits

By reducing drag, wingtip devices increase

range. Aircraft performance is increased, allowing reduced takeoff field length due to better climb performance, and increased cruise altitude and cruise speed. Takeoff noise is also reduced.[2] In gliders, reduced induced drag results in a higher cross-country speed, again increasing range.[1] Wingtip devices can also enhance safety for following aircraft, by reducing the strength of wingtip vortices
.

U.S. Air Force studies indicate that a given improvement in fuel efficiency correlates directly with the causal increase in the aircraft's lift-to-drag ratio.[3]

The average commercial jet sees a 4-6 percent increase in fuel efficiency and as much as a 6% decrease in in-flight noise from the use of winglets. Actual fuel savings and the related carbon output can vary significantly by plane, route and flight conditions.[4]

Early history

Wing end-plates

The Ha 137 prototype aircraft, fitted with vertical wing extensions, c.1935–1937

The initial concept dates back to 1897, when English engineer Frederick W. Lanchester patented wing end-plates as a method for controlling wingtip vortices.[5] In the United States, Scottish-born engineer William E. Somerville patented the first functional winglets in 1910. Somerville installed the devices on his early biplane and monoplane designs.[6] Vincent Burnelli received US Patent no: 1,774,474 for his "Airfoil Control Means" on August 26, 1930.[7]

Simple flat end-plates did not cause a reduction in drag, because the increase in profile drag was greater than the decrease in induced drag.[2]

Hoerner wing tips

Heinkel He 162A
with Lippisch-Ohren wingtip devices

Following the end of World War II, Dr. Sighard F. Hoerner was a pioneer researcher in the field, having written a technical paper published in 1952[8] that called for drooped wingtips whose pointed rear tips focused the resulting wingtip vortex away from the upper wing surface. Drooped wingtips are often called "Hoerner tips" in his honor. Gliders and light aircraft have made use of Hoerner tips for many years.[9][8]

The earliest-known implementation of a Hoerner-style downward-angled "wingtip device" on a jet aircraft was during World War II. This was the so-called "Lippisch-Ohren" (Lippisch-ears), allegedly attributed to the

V-E Day.[10]

Winglets

"Winglet" redirects here. For the personal transporter by Toyota, see
Toyota Winglet
.
KC-135 Stratotanker with attached tufts showing airflow during NASA
tests in 1979–1980
Gulfstream V 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.[11]

Another potential benefit of winglets is that they reduce the intensity of

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.[citation needed
]

Winglets and wingtip fences also increase efficiency by reducing vortex interference with laminar airflow near the tips of the wing,[14] 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.[citation needed]

The fuel economy improvement from winglets increases with the mission length.[15] Blended winglets allow a steeper angle of attack reducing takeoff distance.[16]

Early development

Winglet of McDonnell Douglas MD-11F

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.[17] Whitcomb was the first to realize a net benefit in drag reduction by careful design to keep profile drag to a minimum.[2]

Whitcomb's designs were flight-tested in 1979–80 by a joint NASA/Air Force team, using a

MD-11, which was rolled out in 1990.[5]

In May 1983, a high school student at Bowie High School in Maryland won a grand prize at the 34th International Science and Engineering Fair in Albuquerque, New Mexico for the result of his research on wingtip devices to reduce drag.[18][importance?] The same month, he filed a U.S. patent for "wingtip airfoils", published in 1986.[19][importance?]

Implementations

Learjet 28/29
, 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.

range of 6,500 nmi (12,000 km) allows nonstop routes such as New York–Tokyo, it holds over 70 world and national flight records.[5]
The Rutan combined winglets-vertical stabilizer appeared on his Beechcraft Starship business aircraft design that first flew in 1986.

Winglets are also applied to other business aircraft, reducing take-off distance to operate from smaller airports, and allowing higher cruise altitudes. Along winglets on new designs, aftermarket vendors developed retrofits. Winglet Technology, LLC of

Citation X.[20]

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 1 foot (30 cm) from each wingtip, so the flight was made without benefit of winglets.[21]

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.

Antonov An-158
uses wingtip fences.

Canted winglets

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.[1] Winglets are preferred for Boeing derivative designs based on existing platforms, because they allow maximum re-use of existing components. Newer designs are favoring increased span, other wingtip devices or a combination of both, whenever possible.[citation needed
]

The

narrowbody aircraft to feature winglets in 1994. The Airbus A220
(née CSeries), from 2016, has canted winglets.

Blended winglets

A blended winglet is attached to the wing with a smooth curve instead of a sharp angle and is intended to reduce

Falcon 2000
.

On February 18, 2000, blended winglets were announced as an option for the

A330neo and the A350. They are also offered as a retrofit option.[29][30]

Raked wingtip

Raked wingtips, where the tip has a greater

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.[1] While an increase in span would be more effective than a same-length winglet, its bending moment is greater. A 3 ft (91 cm) winglet gives the performance gain of a 2 ft (61 cm) span increase but has the bending force of a 1 ft (30 cm) span increase.[31]

The Boeing 787 Dreamliner 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.[32]

Raked wingtips are installed on the

E-jet E2 and C-390 Millennium
wings also have raked wingtips.

Split-tip

737 MAX split-tip winglet

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,[34] with United Airlines as the launch customer.[35]

The Boeing 737 MAX uses a new type of wingtip device.[36] 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

Schempp-Hirth Ventus-2 glider with factory winglets winch-launching

In 1987,

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.[38] Masak went on to win the 1993 U.S. 15 Meter Nationals gliding competition, using winglets on his prototype Masak Scimitar.[39]

PSU-90-125 winglet airfoil 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.

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.[citation needed
]

The Glaser-Dirks DG-303, an early glider derivative design, incorporating winglets as factory standard equipment.

Non-planar wingtip

A Falcon 50 with a spiroid winglet

Aviation Partners developed and flight tested a closed-surface Spiroid winglet on a Falcon 50 in 2010.[41]

Non-planar wingtips are normally angled upwards in a polyhedral wing configuration, increasing the local

dihedral near the wing tip, with polyhedral wing designs themselves having been popular on free-flight model aircraft designs for decades. Non-planar wingtips provide the wake control benefit of winglets, with less parasitic drag penalty, if designed carefully. The non-planar wing tip is often swept back like a raked wingtip and may also be combined with a winglet. A winglet is also a special case of a non-planar wingtip.[citation needed
]

Aircraft designers employed mostly planar wing designs with simple dihedral after World War II, prior to the introduction of winglets. With the wide acceptance of winglets in new sailplane designs of the 1990s, designers sought to further optimize the aerodynamic performance of their wingtip designs. Glider winglets were originally retrofitted directly to planar wings, with only a small, nearly right-angle, transition area. Once the performance of the winglet itself was optimized, attention was turned to the transition between the wing and winglet. A common application was tapering the transition area from the wing tip

chord to the winglet chord and raking the transition area back, to place the winglet in the optimal position. If the tapered portion was canted upward, the winglet height could also be reduced. Eventually, designers employed multiple non-planar sections, each canting up at a greater angle, dispensing with the winglets entirely.[citation needed
]

The Schempp-Hirth Discus-2 and Schempp-Hirth Duo Discus use non-planar wingtips.

Active wingtip device

Tamarack Aerospace's active wingtip device

Tamarack Aerospace Group, a company founded in 2010 by aerospace structural engineer Nicholas Guida, has patented an Active Technology Load Alleviation System (ATLAS), a modified version of a wingtip device.[42] The system uses Tamarack Active Camber Surfaces (TACS) to aerodynamically "switch off" the effects of the wingtip device when the aircraft is experiencing high-g events such as large gusts or severe pull-ups. TACS are movable panels, similar to flaps or ailerons, on the trailing edge of the wing extension.[42][43] The system is controlled by the aircraft's electrical system and a high-speed servo which is activated when the aircraft senses an oncoming stress event, essentially simulating an actuating wingtip. However, the wingtip itself is fixed and the TACS are the only moving part of the wingtip system. Tamarack first introduced ATLAS for the Cessna Citation family aircraft,[42][43] and it has been certified for use by the Federal Aviation Administration and European Union Aviation Safety Agency.[44][45]

Actuating wingtip device

There has been research into actuating wingtip devices, including a filed patent application,

waveriding
.

Use on rotating blades

Wingtip devices are also used on rotating

hover, these devices can reduce damage from dirt and small stones picked up in the vortices.[47]

Rotorcraft applications

Wingtip device on a NHIndustries NH90

The main rotor blades of the

brownout which limits visibility in dusty areas and leads to accidents.[48]

Propeller applications

sweepback
at the tips, resembling a raked tip on an aircraft wing.

Other applications

Some ceiling fans have wingtip devices. Fan manufacturer Big Ass Fans has claimed that their Isis fan, equipped with wingtip devices, has superior efficiency.[49] However, for certain high-volume, low-speed designs, wingtip devices may not improve efficiency.[50] Another application of the same principle was introduced to the keel of the "America's Cup"- winning Australian yacht Australia II of 1982, designed by Ben Lexcen.

See also

References

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  2. ^ a b c d McLean, Doug (2005). "Wingtip Devices: What They Do and How They Do It" (PDF). 2005 Performance and Flight Operations Engineering Conference. Boeing: Article 4. Retrieved March 18, 2025.
  3. ISBN 978-0-309-38382-0. {{cite book}}: |work= ignored (help)[permanent dead link
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  4. ^ "The impact of winglets on fuel consumption and aircraft emissions". Cirium. Retrieved August 2, 2022.
  5. ^
    ISBN 1493656783
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  6. ^ "2010 Inductees". Illinois Aviation Hall Of Fame. William E. "Billie" Somerville 1869–1950.
  7. ^ US 1774474, Vincent J Burnelli, "Airfoil control means", published August 26, 1930 
  8. ^ a b Hoerner, Dr. Sighard (1952). "Aerodynamic Shape of the Wing Tips" (PDF). USAF Technical Reports. Engineering Division, Air Materiel Command; Wright-Patterson Air Force Base, Dayton, Ohio; United States Air Force archive. Technical Report No. 5752. Archived (PDF) from the original on March 16, 2013.
  9. ^ Sakrison, David (2004). "A German aerodynamicist, a California character, and a corkscrew". Met-Co-Aire. Archived from the original on March 22, 2016.
  10. ^ Creek, J. Richard; Conway, William (1972) [1967]. The Heinkel He 162 (Aircraft in Profile number 203). Leatherhead, Surrey UK: Profile Publications Ltd. p. 5. Archived from the original on August 19, 2013. Retrieved June 18, 2014.
  11. ^
    National Aeronautics and Space Administration. pp. 11–22. Archived from the original
    (PDF) on September 21, 2021. Retrieved November 1, 2017.
  12. ^ Richard T. Witcomb (1976), A design approach and selected wind-tunnel results at high subsonic speeds for wing-tip mounted winglets (PDF), NASA
  13. ^ "Chapter 2" (PDF), London City Airport Wake Turbulence Study, Halcrow Group Limited, December 2010, archived from the original on October 1, 2017{{citation}}: CS1 maint: bot: original URL status unknown (link)
  14. ISBN 978-0-9681928-2-5
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  16. ^ "Winglets allow for steeper climbs" (PDF). FACC AG. Archived from the original (PDF) on November 7, 2017. Retrieved January 6, 2019.
  17. ISBN 978-1119967514
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  19. ^ patent US 4595160 
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  21. ^ "Dick Rutan, Jeana Yeager, and the Flight of the Voyager". U.S. Centennial of Flight Commission.
  22. ^ "From the A300 to the A380: Pioneering leadership". Corporate information – Innovation & technology. Airbus. Archived from the original on April 21, 2009.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
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  25. ^ "Industry Wrap". Frontiers. Vol. 4, no. 10. Boeing. March 2006. Airbus to test new winglets for single-aisle jetliners.
  26. ^ "American Airlines takes delivery of its first A320 Family aircraft" (Press release). Airbus. July 23, 2013. Archived from the original on November 7, 2017. Retrieved November 1, 2017.
  27. ^ "Korean Air Aerospace to manufacture and distribute Sharklets" (Press release). Airbus. May 31, 2010.
  28. ^ "Airbus launches "Sharklet" large wingtip devices for A320 Family with commitment from Air New Zealand". Airbus. November 15, 2009. Archived from the original on November 7, 2017.
  29. ^ a b Gardiner, Ginger (May 1, 2014). "First A320neo features composite Korean Sharklets". CompositesWorld. Retrieved September 9, 2020.
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  32. ^ Herrick, Larry (June 12, 1998). "Blunt Leading-Edge Raked Wingtips" (PDF). Google Patents. Retrieved December 6, 2021.
  33. ^ Rich Breuhaus (May 20, 2008). "787 Dreamliner: A New Airplane for a New World" (PDF). ACI-NA Commissioners Conference. Boeing. Archived from the original (PDF) on March 7, 2017. Retrieved January 6, 2019.
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  43. ^ a b US patent 7900877B1, Guida, Nicholas R., "Active winglet", published March 8, 2011, issued September 24, 2010 
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  47. ^ a b "What is a Q-Tip propeller? What are its advantages?". Product Support: Frequently Asked Questions. Hartzell Propeller. Archived from the original on March 18, 2001. Aerodynamic improvements include a reduced diameter and decreased tip speeds. This results in quieter operation and reduced tip vortices. The 90° bend reduces the vortices that, on traditional blades, pick up debris that can contact the blades and cause nicks, gouges and scratches.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  48. ^ Harvey, Gareth (November 28, 2005). "Super Chopper : Life-Saving Features: No More Brown-Outs". Engineering Archives. National Geographic Channel. Archived from the original on July 21, 2009. Retrieved August 1, 2009. To counteract this, the EH101's 'winged-tip' rotor blades create what its pilots call the "donut effect" – a circular window of clear air inside the dust storm that allows them to see the ground as they come in to land.
  49. ^ Nino Machetti (May 10, 2010). "Isis ceiling fan claims higher efficiency". EarthTechling.
  50. ^ Eddie Boyd (February 4, 2014). "Winglets: Help or Hindrance to HVLS Fan Performance?". MacroAir.
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