Winglet
Encyclopedia
Wingtip devices are usually intended to improve the efficiency of fixed-wing aircraft
. There are several types of wingtip devices, and though they function in different manners, the intended effect is always to reduce the aircraft's drag by partial recovery of the tip vortex energy. Wingtip devices can also improve aircraft handling characteristics and enhance safety for following aircraft. Such devices increase the effective aspect ratio
of a wing without materially increasing the wingspan
. An extension of span would lower 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
).
Wingtip devices increase the lift generated at the wingtip (by smoothing the airflow across the upper wing near the tip) and reduce the lift-induced drag
caused by wingtip vortices
, improving lift-to-drag ratio
. This increases fuel efficiency
in powered aircraft and increases cross-country speed in glider
s, in both cases increasing range
. 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.
s. The upward angle (or cant) of the winglet, its inward or outward angle (or toe), as well as its size and shape are critical for correct performance and are unique in each application. The wingtip vortex, which rotates around from below the wing, strikes the cambered
surface of the winglet, generating a force that angles inward and slightly forward, analogous to a sailboat
sailing close hauled
. The winglet converts some of the otherwise-wasted energy in the wingtip vortex to an apparent thrust
.
This small contribution can be worthwhile over the aircraft's lifetime, provided the benefit offsets the cost of installing and maintaining the winglets. Another potential benefit of winglets is that they reduce the strength of wingtip vortices
, which trail behind the plane. When other aircraft pass through these vortices, the turbulent air can cause loss of control, possibly resulting in an accident. This possibility is greatest near airports and the minimum spacing requirements between aircraft operations at airports is largely due to these factors. Aircraft are classified by weight (e.g. "Light," "Heavy," etc.) in large part because the vortex strength is proportional (not linearly) to the amount of lift being generated by the airfoil. For this reason, wingtip vortices are typically most dangerous when an aircraft is at high lift coefficient and at a heavy gross weight. During takeoff, for example, flaps and slats are typically partially extended, the aircraft is at its heaviest and a large amount of lift is generated as the aircraft reaches rotate velocity and transition to climbout.
Winglets and wing 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 upwards away from the wing surface, since the center of the resulting vortex is now at the tip of the winglet.
Aircraft such as the Airbus A340
and the Boeing 747-400
use winglets. Other designs such as some versions of the Boeing 777
and the Boeing 747-8
omit them in favor of raked wingtips. Large winglets such as those seen on Boeing 737
aircraft equipped with blended winglets are most useful during short-distance flights, where increased climb performance offsets increased drag. Raked wingtips are now preferred over small winglets for long-distance flights, where increased fuel economy during the cruise phase is more important.
patented the first functional winglets in 1910. Somerville installed the devices on his early biplane and monoplane designs.
Vincent Burnelli
received US Patent no: 1,775,474 for his "End Plating Wing Tips" on August 26, 1930.
Dr. Sighard F. Hoerner
was a pioneer in the field, having written a technical paper published in 1952 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.
's Langley Research Center
, in response to the sharp increase in the cost of fuel after the 1973 oil crisis
. Whitcomb's designs were flight-tested in 1979–80 by a joint NASA/Air Force team, using a KC-135 Stratotanker
based at the Dryden Flight Research Center
. A Lockheed L-1011
and McDonnell Douglas DC-10
were also used for testing, and the latter design was directly implemented by McDonnell Douglas on the derivative MD-11
, which was rolled out in 1990. NASA's own most notable application of wingtip devices is on the Boeing 747
Shuttle Carrier Aircraft
. Located on the 747's horizontal stabilizers, the devices increase the tailplane's effectiveness under the weight of the Space Shuttle orbiter
.
incorporated them in his innovative Rutan VariEze
homebuilt aircraft
design, which made its first flight with winglets on May 21, 1975. The VariEze pioneered glass-reinforced plastic
composite construction in homebuilt aircraft, which simplified fabrication of the winglets. He reduced the resulting drag penalty by assigning double duty to the winglets; they also serve as vertical stabilizer
s and rudders in his canard
, pusher configuration
aircraft. They were also used similarly on the derivative Rutan Long-EZ
and reappeared on his Beechcraft Starship
business aircraft design that first flew in 1986. Conventional winglets were fitted to Rutan's Rutan Voyager, the first aircraft to circumnavigate the world without refueling in 1987
. However, the aircraft's wingtips were damaged when they dragged along the runway during takeoff, breaking off about a foot of each wingtip, so the flight was made without benefit of winglets.
at the 1977 National Business Aviation Association
convention. The Model 28 prototype employed the first winglets ever used on a jet and 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 so impressive that it resulted in a production commitment from Learjet. Flight tests, made with and without winglets, showed that the winglets increased range by about 6.5 percent and also 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
also explored winglets in the late 1970s and incorporated winglets in the Gulfstream III, IV
and V
. The performance of the Gulfstream V has been exemplary. Its operational range
of 6500 nmi (12,038 km) permits routine nonstop business travel for routes such as New York–Tokyo. The Gulfstream V also holds over 70 world and national flight records.
Winglets are also applied to several other business jets to reduce take-off distance, enabling operation out of smaller secondary airports, and allowing higher cruise altitudes for overflying bad weather, both of which are valuable operational benefits for corporate travel. In addition to factory-installed winglets on new aircraft, aftermarket vendors developed retrofit kits, for popular jets and turboprops, to improve both aerodynamics and appearance. Winglets became so popular on this class of aircraft that the Dassault Group
, whose French designers resisted applying them on their Dassault Falcon
line until recently, were forced to run a contrarian marketing campaign. Cessna
recently announced they were partnering with Winglet Technology, LLC of Wichita, Kansas
, to test a new wingtip device called Elliptical Winglets, which are designed to increase range and increase payload on hot and high
departures.
announced a new version of the 747
in October 1985, known as the 747-400, with an extended range and capacity. With that particular model, Boeing used a combination of winglets and increased span to carry the additional load. The winglets increased the 747-400's range by 3.5 percent over the 747-300, which is otherwise aerodynamically identical but has no winglets. 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.
In 2002, Boeing first flew a production Next-Generation 737 with its new Blended Winglets, six-foot extensions that decrease fuel consumption by about 4 to 6 percent. The airplane gained supplemental type certification in 2003, and the majority of 737s delivered today are equipped with the devices.
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 15-meter 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
.
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 installed them 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.
, American Airlines
, Southwest Airlines
, WestJet
and Ryanair
advertise their website
s on the inboard side of their 737's winglets.
, employed on all their airliners except for the A330
and A340
families. The A350
however, will make use of winglets rather than wingtip fences.
A blended winglet is attached to the wing with smooth curve instead of a sharp angle and is intended to reduce interference drag at the wing/winglet junction. A sharp interior angle in this region can interact with the boundary layer
flow causing a drag inducing vortex, negating some of the benefit of the winglet. The blended winglet is used on business jets and sailplanes, where individual buyer preference is an important marketing aspect.
Blended winglets have been offered as an aftermarket retrofit for the Gulfstream II, Hawker 800, and the Falcon 2000 with winglets designed by Aviation Partners Inc., a Seattle, Washington-based firm that develops and markets blended winglets. A joint partnership of Aviation Partners, Inc. and Boeing, Aviation Partners Boeing offers blended winglets for the Boeing 737
Classic and Next Generation models, 757
and 767
. The 737 version is now standard on the Boeing Business Jet
derivative. Many operators have retrofitted their fleets with these for the fuel cost savings.
Airbus tested two candidate blended winglets, designed by Winglet Technology and Airbus themselves, for the Airbus A320 family
, but determined that their benefits did not warrant further development. In December 2008, Airbus announced that, in conjunction with Aviation Partners, Inc., they are restarting their winglet testing program for the A320, stating they are putting into practice the lessons learned from tests two years before. The stated aim of the new tests is to consider "an integrated Airbus programme".
In 2009 Airbus launched a new blended winglet design which the company called a "sharklet", designed to enhance the payload-range performance of the A320 Family. Offered as a retrofit option, sharklets are expected to result in a reduced fuel burn of at least 3.5 percent over longer sectors, corresponding to an annual CO2 reduction of around 700 tonnes per aircraft. The A320 will be the first model fitted with sharklets, which will be delivered in 2012.
Raked wingtips are a feature on some Boeing
airliner
s, where the tip of the wing has a higher degree of sweep
than the rest of the wing. The stated purpose of this additional feature is to improve fuel efficiency
and climb performance, and to shorten takeoff field length. It does this in much the same way that winglets do, by increasing the effective aspect ratio
of the wing and interrupting harmful wingtip vortices
. This decreases the amount of lift-induced drag experienced by the aircraft. In testing by Boeing and NASA, raked wingtips have been shown to reduce drag by as much as 5.5%, as opposed to improvements of 3.5% to 4.5% from conventional winglets.
While an equivalent increase in wingspan would be more effective than a winglet of the same length, the bending force becomes a greater factor. A three-foot winglet has the same bending force as a one-foot increase in span, yet gives the same performance gain as a two-foot wing span increase.
For this reason, the short-range Boeing 787-3 design called for winglets instead of the raked wingtips featured on all other 787 variants.
Raked wingtips are installed on, or are planned to be installed on:
Non-planar wingtips are normally angled upwards in a polyhedral wing configuration, increasing the local dihedral near the wing tip. These 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.
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.
Closed surfaces
at the end of winglets are a possible way to eliminate the wake vortices induced at the tips of a wing. An example of a closed-surface winglet is the Spiroid winglet, a design currently under development by Aviation Partners. Initial testing using a Gulfstream II test aircraft has shown the winglet design to reduce fuel consumption in the cruise phase by over 10%. These Spiroid winglets have also been flight tested on a Falcon 50 aircraft.
Non-planar wingtips (without winglets) are or will be employed on:
's wingtips were capable of drooping downward in flight, to facilitate Mach 3
flight using waveriding
.
, helicopter rotor
, and wind turbine
blades to reduce drag, reduce diameter, reduce noise and/or improve efficiency. By reducing aircraft blade tip vortices interacting with the ground surface during taxiing
, takeoff
, and hover, these devices can reduce damage from dirt and small stones picked up in the vortices.
which limits visibility in dusty areas and leads to accidents.
from a reduced diameter propeller disk; the reduced propeller tip speed reduces noise, according to the manufacturer. Modern scimitar propeller
s have increased sweepback at the tips, resembling a raked tip on an aircraft wing.
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...
. There are several types of wingtip devices, and though they function in different manners, the intended effect is always to reduce the aircraft's drag by partial recovery of the tip vortex energy. Wingtip devices can also improve aircraft handling characteristics and enhance safety for following aircraft. Such devices increase the effective aspect ratio
Aspect ratio (wing)
In aerodynamics, the aspect ratio of a wing is essentially the ratio of its length to its breadth . A high aspect ratio indicates long, narrow wings, whereas a low aspect ratio indicates short, stubby wings....
of a wing without materially increasing the wingspan
Wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
. An extension of span would lower lift-induced drag
Lift-induced drag
In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is a drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a lifting body redirecting air to cause lift and also in cars...
, but would increase parasitic drag
Parasitic drag
Parasitic drag is drag caused by moving a solid object through a fluid medium . Parasitic drag is made up of many components, the most prominent being form 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
Gate (airport)
A gate in aviation is a long, movable, "bridge" that allows passengers to embark and disembark their aircraft.* Jetway bridges* Air stairs, either built into the aircraft or from a mobile vehicle* Mobile lounges...
).
Wingtip devices increase the lift generated at the wingtip (by smoothing the airflow across the upper wing near the tip) and reduce the lift-induced drag
Lift-induced drag
In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is a drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a lifting body redirecting air to cause lift and also in cars...
caused by wingtip vortices
Wingtip vortices
Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...
, improving lift-to-drag ratio
Lift-to-drag ratio
In aerodynamics, the lift-to-drag ratio, or L/D ratio, is the amount of lift generated by a wing or vehicle, divided by the drag it creates by moving through the air...
. This increases fuel efficiency
Fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...
in powered aircraft and increases cross-country speed in glider
Glider (sailplane)
A glider or sailplane is a type of glider aircraft used in the sport of gliding. Some gliders, known as motor gliders are used for gliding and soaring as well, but have engines which can, in some cases, be used for take-off or for extending a flight...
s, in both cases increasing range
Range (aircraft)
The maximal total range is the distance an aircraft can fly between takeoff and landing, as limited by fuel capacity in powered aircraft, or cross-country speed and environmental conditions in unpowered aircraft....
. 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.
Winglet
The term "winglet" was previously used to describe an additional lifting surface on an aircraft, e.g., a short section between wheels on fixed undercarriage, but today it refers to a near-vertical extension of the wing tipWing tip
A wing tip is the part of the wing that is most distant from the fuselage of a fixed-wing aircraft.Because the wing tip shape influences the size and drag of the wingtip vortices, tip design has produced a diversity of shapes, including:* Squared-off...
s. The upward angle (or cant) of the winglet, its inward or outward angle (or toe), as well as its size and shape are critical for correct performance and are unique in each application. The wingtip vortex, which rotates around from below the wing, strikes the cambered
Camber (aerodynamics)
Camber, in aeronautics and aeronautical engineering, is the asymmetry between the top and the bottom surfaces of an aerofoil. An aerofoil that is not cambered is called a symmetric aerofoil...
surface of the winglet, generating a force that angles inward and slightly forward, analogous to a sailboat
Sailboat
A sailboat or sailing boat is a boat propelled partly or entirely by sails. The term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a...
sailing close hauled
Points of sail
Points of sail describes a sailing boat's course in relation to the wind direction.There is a distinction between the port tack and the starboard tack. If the wind is coming from anywhere on the port side, the boat is on port tack. Likewise if the wind is coming from the starboard side, the boat...
. The winglet converts some of the otherwise-wasted energy in the wingtip vortex to an apparent thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
.
This small contribution can be worthwhile over the aircraft's lifetime, provided the benefit offsets the cost of installing and maintaining the winglets. Another potential benefit of winglets is that they reduce the strength of wingtip vortices
Wingtip vortices
Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...
, which trail behind the plane. When other aircraft pass through these vortices, the turbulent air can cause loss of control, possibly resulting in an accident. This possibility is greatest near airports and the minimum spacing requirements between aircraft operations at airports is largely due to these factors. Aircraft are classified by weight (e.g. "Light," "Heavy," etc.) in large part because the vortex strength is proportional (not linearly) to the amount of lift being generated by the airfoil. For this reason, wingtip vortices are typically most dangerous when an aircraft is at high lift coefficient and at a heavy gross weight. During takeoff, for example, flaps and slats are typically partially extended, the aircraft is at its heaviest and a large amount of lift is generated as the aircraft reaches rotate velocity and transition to climbout.
Winglets and wing 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 upwards away from the wing surface, since the center of the resulting vortex is now at the tip of the winglet.
Aircraft such as the Airbus A340
Airbus A340
The Airbus A340 is a long-range four-engine wide-body commercial passenger jet airliner. Developed by Airbus Industrie,A consortium of European aerospace companies, Airbus is now fully owned by EADS and since 2001 has been known as Airbus SAS. a consortium of European aerospace companies, which is...
and the Boeing 747-400
Boeing 747-400
The Boeing 747-400 is a major development and the best-selling model of the Boeing 747 family of jet airliners. While retaining the four-engine wide-body layout of its predecessors, the 747-400 embodies numerous technological and structural changes to produce a more efficient airframe...
use winglets. Other designs such as some versions of the Boeing 777
Boeing 777
The Boeing 777 is a long-range, wide-body twin-engine jet airliner manufactured by Boeing Commercial Airplanes. It is the world's largest twinjet and is commonly referred to as the "Triple Seven". The aircraft has seating for over 300 passengers and has a range from , depending on model...
and the Boeing 747-8
Boeing 747-8
The Boeing 747-8 is a wide-body jet airliner developed by Boeing Commercial Airplanes. Officially announced in 2005, the 747-8 is the fourth-generation Boeing 747 version, with lengthened fuselage, redesigned wings and improved efficiency...
omit them in favor of raked wingtips. Large winglets such as those seen on Boeing 737
Boeing 737
The Boeing 737 is a short- to medium-range, twin-engine narrow-body jet airliner. Originally developed as a shorter, lower-cost twin-engine airliner derived from Boeing's 707 and 727, the 737 has developed into a family of nine passenger models with a capacity of 85 to 215 passengers...
aircraft equipped with blended winglets are most useful during short-distance flights, where increased climb performance offsets increased drag. Raked wingtips are now preferred over small winglets for long-distance flights, where increased fuel economy during the cruise phase is more important.
History and applications
The initial concept dates back to 1897, when English engineer Frederick W. Lanchester patented wing end-plates as a method for controlling wingtip vortices.. In the United States Scottish born engineer William E. SomervilleWilliam E. Somerville
William E. Somerville was a Scottish aircraft engineer.- Early life :William E. Sommervile's father was a mechanical engineer in Scotland. Sommerville studied as a marine engineer in Scotland. Somerville immigrated to America in 1862 and worked as an electrical engineer for General Electric in...
patented the first functional winglets in 1910. Somerville installed the devices on his early biplane and monoplane designs.
Vincent Burnelli
Vincent Burnelli
Vincent Justus Burnelli was an American aeronautics engineer, instrumental in furthering the lifting body and flying wing concept.-Early life:...
received US Patent no: 1,775,474 for his "End Plating Wing Tips" on August 26, 1930.
Dr. Sighard F. Hoerner
Dr. Sighard F. Hoerner
Dr. Sighard F. Hoerner was an important figure in the aerodynamics field and is known worldwide for his two compendiums of aerodynamic knowledge, Fluid-Dynamic Drag and Fluid-Dynamic Lift. He is also notable for his design work on the pioneering STOL aircraft, the Fieseler Fi 156 Storch.-Education:Dr...
was a pioneer in the field, having written a technical paper published in 1952 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.
NASA development
Hoerner's concept was further developed by Richard T. Whitcomb, an engineer at NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Langley Research Center
Langley Research Center
Langley Research Center is the oldest of NASA's field centers, located in Hampton, Virginia, United States. It directly borders Poquoson, Virginia and Langley Air Force Base...
, in response to the sharp increase in the cost of fuel after the 1973 oil crisis
1973 oil crisis
The 1973 oil crisis started in October 1973, when the members of Organization of Arab Petroleum Exporting Countries or the OAPEC proclaimed an oil embargo. This was "in response to the U.S. decision to re-supply the Israeli military" during the Yom Kippur war. It lasted until March 1974. With the...
. Whitcomb's designs were flight-tested in 1979–80 by a joint NASA/Air Force team, using a KC-135 Stratotanker
KC-135 Stratotanker
The Boeing KC-135 Stratotanker is an aerial refueling military aircraft. It and the Boeing 707 airliner were developed from the Boeing 367-80 prototype. The KC-135 was the US Air Force's first jet-powered refueling tanker and replaced the KC-97 Stratotanker...
based at the Dryden Flight Research Center
Dryden Flight Research Center
The Dryden Flight Research Center , located inside Edwards Air Force Base, is an aeronautical research center operated by NASA. On March 26, 1976 it was named in honor of the late Hugh L. Dryden, a prominent aeronautical engineer who at the time of his death in 1965 was NASA's deputy administrator...
. A Lockheed L-1011
Lockheed L-1011
The Lockheed L-1011 TriStar, commonly referred to as the L-1011 or TriStar, is a medium-to-long range, widebody passenger trijet airliner. It was the third widebody airliner to enter commercial operations, following the Boeing 747 and the McDonnell Douglas DC-10. Between 1968 and 1984, Lockheed...
and McDonnell Douglas DC-10
McDonnell Douglas DC-10
The McDonnell Douglas DC-10 is a three-engine widebody jet airliner manufactured by McDonnell Douglas. The DC-10 has range for medium- to long-haul flights, capable of carrying a maximum 380 passengers. Its most distinguishing feature is the two turbofan engines mounted on underwing pylons and a...
were also used for testing, and the latter design was directly implemented by McDonnell Douglas on the derivative MD-11
McDonnell Douglas MD-11
The McDonnell Douglas MD-11 is a three-engine medium- to long-range widebody jet airliner, manufactured by McDonnell Douglas and, later, by Boeing Commercial Airplanes. Based on the DC-10, it features a stretched fuselage, increased wingspan with winglets, refined airfoils on the wing and smaller...
, which was rolled out in 1990. NASA's own most notable application of wingtip devices is on the Boeing 747
Boeing 747
The Boeing 747 is a wide-body commercial airliner and cargo transport, often referred to by its original nickname, Jumbo Jet, or Queen of the Skies. It is among the world's most recognizable aircraft, and was the first wide-body ever produced...
Shuttle Carrier Aircraft
Shuttle Carrier Aircraft
The Shuttle Carrier Aircraft are two extensively modified Boeing 747 airliners that NASA uses to transport Space Shuttle orbiters...
. Located on the 747's horizontal stabilizers, the devices increase the tailplane's effectiveness under the weight of the Space Shuttle orbiter
Space Shuttle Orbiter
The Space Shuttle orbiter was the orbital spacecraft of the Space Shuttle program operated by NASA, the space agency of the United States. The orbiter was a reusable winged "space-plane", a mixture of rockets, spacecraft, and aircraft...
.
Composite aircraft
Even before NASA did flight testing on winglets, Burt RutanBurt Rutan
Elbert Leander "Burt" Rutan is an American aerospace engineer noted for his originality in designing light, strong, unusual-looking, energy-efficient aircraft...
incorporated them in his innovative Rutan VariEze
Rutan VariEze
-See also:-References:* "Flying the VariEze", Air Progress, April 1978.* * * * Taylor, John W. R. Jane's All The World's Aircraft 1982–83. London:Jane's Yearbooks, 1982. ISBN 0-7106-0748-2.* * Flight International 1976...
homebuilt aircraft
Homebuilt aircraft
Also known as amateur-built aircraft or kit planes, homebuilt aircraft are constructed by persons for whom this is not a professional activity. These aircraft may be constructed from "scratch," from plans, or from assembly kits.-Overview:...
design, which made its first flight with winglets on May 21, 1975. The VariEze pioneered glass-reinforced plastic
Glass-reinforced plastic
Fiberglass , is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK ....
composite construction in homebuilt aircraft, which simplified fabrication of the winglets. He reduced the resulting drag penalty by assigning double duty to the winglets; they also serve as vertical stabilizer
Vertical stabilizer
The vertical stabilizers, vertical stabilisers, or fins, of aircraft, missiles or bombs are typically found on the aft end of the fuselage or body, and are intended to reduce aerodynamic side slip. It is analogical to a skeg on boats and ships.On aircraft, vertical stabilizers generally point upwards...
s and rudders in his canard
Canard (aeronautics)
In aeronautics, canard is an airframe configuration of fixed-wing aircraft in which the forward surface is smaller than the rearward, the former being known as the "canard", while the latter is the main wing...
, pusher configuration
Pusher configuration
In a craft with a pusher configuration the propeller are mounted behind their respective engine. According to Bill Gunston, a "pusher propeller" is one mounted behind engine so that drive shaft is in compression...
aircraft. They were also used similarly on the derivative Rutan Long-EZ
Rutan Long-EZ
-See also:-External links:****...
and reappeared on his Beechcraft Starship
Beechcraft Starship
The Beechcraft Starship is a twin-turboprop six- to eight-passenger pressurized business aircraft produced by Beech Aircraft Corporation .-Development:...
business aircraft design that first flew in 1986. Conventional winglets were fitted to Rutan's Rutan Voyager, the first aircraft to circumnavigate the world without refueling in 1987
1987 in aviation
This is a list of aviation-related events from 1987:-January:* January 1 – United States Coast Guard HH-65 Dolphins and US Navy H-3 Sea Kings help rescue people trapped inside the Dupont Plaza hotel in Puerto Rico after a fire breaks out there late on December 31, 1986.* January 3 –...
. However, the aircraft's wingtips were damaged when they dragged along the runway during takeoff, breaking off about a foot of each wingtip, so the flight was made without benefit of winglets.
Business aircraft
Learjet exhibited the prototype Learjet 28Learjet 28
-See also:-References:*Michell, Simon. Jane's Civil and Military Aircraft Upgrades 1994-95. Coulsdon, UK:Jane's Information Group, 1994. ISBN 0 7106 1208 7.-External links:***...
at the 1977 National Business Aviation Association
National Business Aviation Association
National Business Aviation Association or NBAA, is a non-profit and nonpartisan 5016 corporation based in Washington, DC, United States. The Association represents more than 8,000 companies....
convention. The Model 28 prototype employed the first winglets ever used on a jet and 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 so impressive that it resulted in a production commitment from Learjet. Flight tests, made with and without winglets, showed that the winglets increased range by about 6.5 percent and also improved directional stability. Learjet's application of winglets to production aircraft continued with newer models including the Learjet 55
Learjet 55
-Development and design:The Learjet 50 series was first announced at the 1977 Paris air show with larger cabins than the current Learjets. The series was to have three variants, the Learjet 54, 55 and 56 but only the Learjet 55 was built. The Learjet 55 was a low-wing cantilever monoplane with NASA...
, 31, 60
Learjet 60
The Learjet 60 is a mid-size cabin, medium range business jet aircraft manufactured by Bombardier Aerospace in Wichita, Kansas, USA. The Learjet 60 is powered by two Pratt & Whitney Canada model 305A turbo fan engines producing 4,600 total pounds of thrust. The manufacturer notes the range of the...
, 45
Learjet 45
-See also:-References:* Taylor, Michael J.H. Brassey's World Aircraft & Systems Directory 1999/2000. London:Brassey's, 1999. ISBN 1 85753 245 7.-External links:*...
and Learjet 40
Learjet 40
-See also:-External links:* *...
.
Gulfstream Aerospace
Gulfstream Aerospace
Gulfstream Aerospace Corporation is a producer of several models of jet aircraft. Gulfstream has been a unit of General Dynamics since 1999.The company has produced more than 1,500 aircraft for corporate, government, private, and military customers around the world...
also explored winglets in the late 1970s and incorporated winglets in the Gulfstream III, IV
Gulfstream IV
The Gulfstream IV and derivatives are a family of twin-jet aircraft, mainly for private or business use. The aircraft was designed and built by Gulfstream Aerospace, a General Dynamics company based in Savannah, Georgia, United States from 1985 until 2003.-Design and development:Gulfstream, in...
and V
Gulfstream V
The Gulfstream V is a business jet aircraft produced by Gulfstream Aerospace. It is also used by the US military under the designation C-37A. The G500 and G550 are improved versions which are currently in production...
. The performance of the Gulfstream V has been exemplary. Its operational range
Range (aircraft)
The maximal total range is the distance an aircraft can fly between takeoff and landing, as limited by fuel capacity in powered aircraft, or cross-country speed and environmental conditions in unpowered aircraft....
of 6500 nmi (12,038 km) permits routine nonstop business travel for routes such as New York–Tokyo. The Gulfstream V also holds over 70 world and national flight records.
Winglets are also applied to several other business jets to reduce take-off distance, enabling operation out of smaller secondary airports, and allowing higher cruise altitudes for overflying bad weather, both of which are valuable operational benefits for corporate travel. In addition to factory-installed winglets on new aircraft, aftermarket vendors developed retrofit kits, for popular jets and turboprops, to improve both aerodynamics and appearance. Winglets became so popular on this class of aircraft that the Dassault Group
Dassault Group
Dassault Group, is a French group of companies led by Serge Dassault.Managing directors are Claude Dassault and Olivier Costa De Beauregard.- Subsidiaries :*Dassault Aviation;...
, whose French designers resisted applying them on their Dassault Falcon
Dassault Falcon
The Dassault Falcon is a family of business jets, manufactured by Dassault Aviation.Aircraft include:* Dassault Falcon 10 Scaled down Falcon 20...
line until recently, were forced to run a contrarian marketing campaign. Cessna
Cessna
The Cessna Aircraft Company is an airplane manufacturing corporation headquartered in Wichita, Kansas, USA. Their main products are general aviation aircraft. Although they are the most well known for their small, piston-powered aircraft, they also produce business jets. The company is a subsidiary...
recently announced they were partnering with Winglet Technology, LLC of Wichita, Kansas
Wichita, Kansas
Wichita is the largest city in the U.S. state of Kansas.As of the 2010 census, the city population was 382,368. Located in south-central Kansas on the Arkansas River, Wichita is the county seat of Sedgwick County and the principal city of the Wichita metropolitan area...
, to test a new wingtip device called Elliptical Winglets, which are designed to increase range and increase payload on hot and high
Hot and high
In aviation, hot and high is a condition of low air density due to high ambient temperature and high airport elevation. Air density decreases with increasing temperature and altitude. Lower air density reduces the amount of lift generated by the wings or the rotors of an aircraft, which may hamper...
departures.
Passenger aircraft
BoeingBoeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
announced a new version of the 747
Boeing 747
The Boeing 747 is a wide-body commercial airliner and cargo transport, often referred to by its original nickname, Jumbo Jet, or Queen of the Skies. It is among the world's most recognizable aircraft, and was the first wide-body ever produced...
in October 1985, known as the 747-400, with an extended range and capacity. With that particular model, Boeing used a combination of winglets and increased span to carry the additional load. The winglets increased the 747-400's range by 3.5 percent over the 747-300, which is otherwise aerodynamically identical but has no winglets. 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.
In 2002, Boeing first flew a production Next-Generation 737 with its new Blended Winglets, six-foot extensions that decrease fuel consumption by about 4 to 6 percent. The airplane gained supplemental type certification in 2003, and the majority of 737s delivered today are equipped with the devices.
Gliders
In 1987, mechanical engineerMechanical engineering
Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the...
Peter Masak
Peter Masak
Peter C. Masak was an engineer, inventor, and glider pilot. He graduated with a Bachelor of Applied Science degree in Mechanical Engineering in May 1981 from the University of Waterloo, Ontario Canada. He earned his glider pilot license at the age of 16 and his power pilot license at the age of...
called on aerodynamicist Mark D. Maughmer
Mark D. Maughmer
Dr. Mark D. Maughmer is a Professor of Aerospace Engineering in the Department of Aerospace Engineering at The Pennsylvania State University...
, an associate professor of aerospace engineering at the Pennsylvania State University
Pennsylvania State University
The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...
, about designing winglets to improve performance on his 15-meter 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
Gliding competitions
Some of the pilots in the sport of gliding take part in gliding competitions. These are usually racing competitions, but there are also aerobatic contests and on-line league tables.-History of competitions:...
, using a new PSU–90–125 airfoil
Airfoil
An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....
, designed by Maughmer specifically for the winglet application. At the 1991 World Gliding Championships
World Gliding Championships
The World Gliding Championships is a gliding competition held every two years or so by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are sometimes held in the summer in the Southern Hemisphere....
in Uvalde, Texas
Uvalde, Texas
Uvalde is a city in and the county seat of Uvalde County, Texas, United States. The population was 14,929 at the 2000 census.Uvalde was founded by Reading Wood Black in 1853 as the town of Encina. In 1856, when the county was organized, the town was renamed Uvalde for Spanish governor Juan de...
, 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
Glider Competition Classes
Competition classes in gliding, as in other sports, mainly exist to ensure fairness in competition. However the classes have not been targeted at fostering technological development as in other sports...
, an exceptional result. Masak went on to win the 1993 U.S. 15 Meter Nationals gliding competition, using winglets on his prototype Masak Scimitar
Masak Scimitar
|-See also:...
.
Roll rate
Roll rate may refer to:* Roll Rate Analysis: involves comparing worst delinquency in a specified “previous x ” months with that in the “next x” months, and then calculating the percentage of accounts that maintain their worst delinquency, get better, or “roll forward” into the next delinquency...
and roll authority and reduced tendency for wing tip stall
Stall (flight)
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded...
. The benefits are notable, because sailplane winglets must be removable to allow the glider to be stored in a trailer
Trailer (vehicle)
A trailer is generally an unpowered vehicle pulled by a powered vehicle. Commonly, the term trailer refers to such vehicles used for transport of goods and materials....
, so they are usually installed only at the pilot's preference.
Advertising
Some airlines capitalize on the visibility of winglets to passengers. AirTran AirwaysAirTran Airways
AirTran Airways, a subsidiary of the Dallas, Texas-based Southwest Airlines, is an American low-cost airline headquartered in Orlando, Florida. AirTran operates over 650 daily flights , primarily in the eastern and midwestern United States...
, American Airlines
American Airlines
American Airlines, Inc. is the world's fourth-largest airline in passenger miles transported and operating revenues. American Airlines is a subsidiary of the AMR Corporation and is headquartered in Fort Worth, Texas adjacent to its largest hub at Dallas/Fort Worth International Airport...
, Southwest Airlines
Southwest Airlines
Southwest Airlines Co. is an American low-cost airline based in Dallas, Texas. Southwest is the largest airline in the United States, based upon domestic passengers carried,...
, WestJet
WestJet
WestJet Airlines Ltd. is a Canadian low-cost carrier that provides scheduled and charter air service to 71 destinations in Canada, the United States, Mexico and the Caribbean. Founded in 1996, WestJet is currently the second largest Canadian air carrier, behind Air Canada, operating an average of...
and Ryanair
Ryanair
Ryanair is an Irish low-cost airline. Its head office is at Dublin Airport and its primary operational bases at Dublin Airport and London Stansted Airport....
advertise their website
Website
A website, also written as Web site, web site, or simply site, is a collection of related web pages containing images, videos or other digital assets. A website is hosted on at least one web server, accessible via a network such as the Internet or a private local area network through an Internet...
s on the inboard side of their 737's winglets.
Notable examples
Winglets are employed on many aircraft types, such as:- Rutan VariEzeRutan VariEze-See also:-References:* "Flying the VariEze", Air Progress, April 1978.* * * * Taylor, John W. R. Jane's All The World's Aircraft 1982–83. London:Jane's Yearbooks, 1982. ISBN 0-7106-0748-2.* * Flight International 1976...
, the first aircraft to use winglets (19751975 in aviationThis is a list of aviation-related events from 1975:-January:* A specially modified McDonnell Douglas F-15 Eagle sets eight time to climb records, including one of 3 minutes 27 seconds from standstill on the runway to a height of 30,000 metres ....
) - Learjet 28/29, the first production jet aircraft to use winglets (19771977 in aviationThis is a list of aviation-related events from 1977:-January:* January 15 – Linjeflyg Flight 618, a Vickers Viscount 838. crashes in Kälvesta, Sweden just outside Stockholm killing all 22 on board....
) - Glaser-Dirks DG-303Glaser-Dirks DG-300The DG-300 is a Standard Class single-seat high-performance glider built of glass-reinforced plastic. The DG-300 was designed by Wilhelm Dirks and manufactured by Glaser-Dirks Flugzeugbau's Slovenian partner company Elan . A total of 511 of all versions were built since production started in 1983...
, an early glider derivative design, incorporating winglets as factory standard equipment - Airbus A310-300Airbus A310The Airbus A310 is a medium- to long-range twin-engine widebody jet airliner. Launched in July 1978, it was the second aircraft created by Airbus Industrie,a consortium of European aerospace companies, Airbus is now fully owned by EADS and since 2001 has been known as Airbus SAS. the consortium of...
, the first airliner to feature wingtip fences (19851985 in aviationThis is a list of aviation-related events from 1985: 1985 was the worst year in history for aviation disasters, among the crashes were Delta Air Lines Flight 191, killing 137 people, Japan Airlines Flight 123 killing 520 people, British Airtours Flight 28M, killing 55, Iberia Airlines Flight 610...
) - Boeing 747-400Boeing 747-400The Boeing 747-400 is a major development and the best-selling model of the Boeing 747 family of jet airliners. While retaining the four-engine wide-body layout of its predecessors, the 747-400 embodies numerous technological and structural changes to produce a more efficient airframe...
, the first mainline airliner to feature winglets (19881988 in aviationThis is a list of aviation-related events from 1988:-January:* January 26 – The French Ministry of Defense approves full-scale development of the Dassault Rafale.* January 30 – A Boeing 747 sets a new around-the-world record of 36 hours 54 minutes....
) - Ilyushin Il-96Ilyushin Il-96The Ilyushin Il-96 is a four-engined long-haul widebody airliner designed by Ilyushin in the Soviet Union and manufactured by the Voronezh Aircraft Production Association in Voronezh, Russia...
, first Russian and modern jet to feature winglets (19881988 in aviationThis is a list of aviation-related events from 1988:-January:* January 26 – The French Ministry of Defense approves full-scale development of the Dassault Rafale.* January 30 – A Boeing 747 sets a new around-the-world record of 36 hours 54 minutes....
) - Bombardier CRJ-100, first regional airliner to feature winglets (19921992 in aviationThis is a list of aviation-related events from 1992:-Events:*The European Commission approves three new regulations to liberalize air travel within the European Union...
) - Tupolev Tu-204Tupolev Tu-204The Tupolev Tu-204 is a twin-engined medium-range jet airliner capable of carrying 210 passengers, designed by Tupolev and produced by Aviastar SP and Kazan Aircraft Production Association. First introduced in 1989, it is considered to be broadly equivalent to the Boeing 757 and has competitive...
, first narrow body aircraft to feature winglets (19941994 in aviationThis is a list of aviation-related events from 1994:-March:* March 23 – Aeroflot Flight 593, an Airbus A310-304, is flying with unauthorized people – the pilots 16-year-old son and 12-year-old daughter – in the cockpit when the 16-year-old unintentionally disengages the autopilot...
)
Wingtip fence
A wingtip fence is a winglet variant, with surfaces extending both above and below the wingtip. Both surfaces are shorter than or equivalent to a winglet possessing similar aerodynamic benefits. Wingtip fences are the preferred wingtip device of AirbusAirbus
Airbus SAS is an aircraft manufacturing subsidiary of EADS, a European aerospace company. Based in Blagnac, France, surburb of Toulouse, and with significant activity across Europe, the company produces around half of the world's jet airliners....
, employed on all their airliners except for the A330
Airbus A330
The Airbus A330 is a wide-body twin-engine jet airliner made by Airbus, a division of EADS. Versions of the A330 have a range of and can accommodate up to 335 passengers in a two-class layout or carry of cargo....
and A340
Airbus A340
The Airbus A340 is a long-range four-engine wide-body commercial passenger jet airliner. Developed by Airbus Industrie,A consortium of European aerospace companies, Airbus is now fully owned by EADS and since 2001 has been known as Airbus SAS. a consortium of European aerospace companies, which is...
families. The A350
Airbus A350
The Airbus A350 is a family of long-range, wide-body jet airliners under development by European aircraft manufacturer Airbus.A consortium originally comprising European aerospace companies from the UK, France, Spain and West Germany, Airbus is now fully owned by EADS and since 2001 has been known...
however, will make use of winglets rather than wingtip fences.
Blended winglets
Boundary layer
In physics and fluid mechanics, a boundary layer is that layer of fluid in the immediate vicinity of a bounding surface where effects of viscosity of the fluid are considered in detail. In the Earth's atmosphere, the planetary boundary layer is the air layer near the ground affected by diurnal...
flow causing a drag inducing vortex, negating some of the benefit of the winglet. The blended winglet is used on business jets and sailplanes, where individual buyer preference is an important marketing aspect.
Blended winglets have been offered as an aftermarket retrofit for the Gulfstream II, Hawker 800, and the Falcon 2000 with winglets designed by Aviation Partners Inc., a Seattle, Washington-based firm that develops and markets blended winglets. A joint partnership of Aviation Partners, Inc. and Boeing, Aviation Partners Boeing offers blended winglets for the Boeing 737
Boeing 737
The Boeing 737 is a short- to medium-range, twin-engine narrow-body jet airliner. Originally developed as a shorter, lower-cost twin-engine airliner derived from Boeing's 707 and 727, the 737 has developed into a family of nine passenger models with a capacity of 85 to 215 passengers...
Classic and Next Generation models, 757
Boeing 757
The Boeing 757 is a mid-size, narrow-body twin-engine jet airliner manufactured by Boeing Commercial Airplanes. Passenger versions of the twinjet have a capacity of 186 to 289 persons and a maximum range of , depending on variant and cabin configuration...
and 767
Boeing 767
The Boeing 767 is a mid-size, wide-body twin-engine jet airliner built by Boeing Commercial Airplanes. It was the manufacturer's first wide-body twinjet and its first airliner with a two-crew glass cockpit. The aircraft features two turbofan engines, a supercritical wing, and a conventional tail...
. The 737 version is now standard on the Boeing Business Jet
Boeing Business Jet
|-External links:* .* .*...
derivative. Many operators have retrofitted their fleets with these for the fuel cost savings.
Airbus tested two candidate blended winglets, designed by Winglet Technology and Airbus themselves, for the Airbus A320 family
Airbus A320 family
The Airbus A320 family is a family of short- to medium-range, narrow-body, commercial passenger jet airliners manufactured by Airbus Industrie.Airbus was originally a consortium of European aerospace companies, and is now fully owned by EADS. Airbus's name has been Airbus SAS since 2001...
, but determined that their benefits did not warrant further development. In December 2008, Airbus announced that, in conjunction with Aviation Partners, Inc., they are restarting their winglet testing program for the A320, stating they are putting into practice the lessons learned from tests two years before. The stated aim of the new tests is to consider "an integrated Airbus programme".
In 2009 Airbus launched a new blended winglet design which the company called a "sharklet", designed to enhance the payload-range performance of the A320 Family. Offered as a retrofit option, sharklets are expected to result in a reduced fuel burn of at least 3.5 percent over longer sectors, corresponding to an annual CO2 reduction of around 700 tonnes per aircraft. The A320 will be the first model fitted with sharklets, which will be delivered in 2012.
Raked wingtip
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
airliner
Airliner
An airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such aircraft are operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers in commercial...
s, where the tip of the wing has a higher degree of sweep
Swept wing
A swept wing is a wing planform favored for high subsonic jet speeds first investigated by Germany during the Second World War. Since the introduction of the MiG-15 and North American F-86 which demonstrated a decisive superiority over the slower first generation of straight-wing jet fighters...
than the rest of the wing. The stated purpose of this additional feature is to improve fuel efficiency
Fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...
and climb performance, and to shorten takeoff field length. It does this in much the same way that winglets do, by increasing the effective aspect ratio
Aspect ratio (wing)
In aerodynamics, the aspect ratio of a wing is essentially the ratio of its length to its breadth . A high aspect ratio indicates long, narrow wings, whereas a low aspect ratio indicates short, stubby wings....
of the wing and interrupting harmful wingtip vortices
Wingtip vortices
Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...
. This decreases the amount of lift-induced drag experienced by the aircraft. In testing by Boeing and NASA, raked wingtips have been shown to reduce drag by as much as 5.5%, as opposed to improvements of 3.5% to 4.5% from conventional winglets.
While an equivalent increase in wingspan would be more effective than a winglet of the same length, the bending force becomes a greater factor. A three-foot winglet has the same bending force as a one-foot increase in span, yet gives the same performance gain as a two-foot wing span increase.
For this reason, the short-range Boeing 787-3 design called for winglets instead of the raked wingtips featured on all other 787 variants.
Raked wingtips are installed on, or are planned to be installed on:
- Boeing P-8 Poseidon
- Boeing 747-8 Freighter
- Boeing 747-8 Intercontinental
- Boeing 767-400ERBoeing 767The Boeing 767 is a mid-size, wide-body twin-engine jet airliner built by Boeing Commercial Airplanes. It was the manufacturer's first wide-body twinjet and its first airliner with a two-crew glass cockpit. The aircraft features two turbofan engines, a supercritical wing, and a conventional tail...
- Boeing 777-200LR
- Boeing 777-300ER
- Boeing 777 Freighter
- Boeing 787-8
- Boeing 787-9
Non-planar wingtip
Aircraft designers employed mostly planar wing designs with simple dihedral after World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, 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
Chord (aircraft)
In aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...
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.
Closed surfaces
Closed wing
A closed wing is a non-planar wing planform concept. The term closed wing encompasses a number of designs, including the annular wing , the joined wing, and the box wing...
at the end of winglets are a possible way to eliminate the wake vortices induced at the tips of a wing. An example of a closed-surface winglet is the Spiroid winglet, a design currently under development by Aviation Partners. Initial testing using a Gulfstream II test aircraft has shown the winglet design to reduce fuel consumption in the cruise phase by over 10%. These Spiroid winglets have also been flight tested on a Falcon 50 aircraft.
Non-planar wingtips (without winglets) are or will be employed on:
- Schempp-Hirth Discus-2Schempp-Hirth Discus-2|-See also:-External links:*...
- Schempp-Hirth Duo DiscusSchempp-Hirth Duo Discus|-See also:-References:*...
- Airbus A350-800 XWB
- Airbus A350-900 XWB
- Airbus A350-1000 XWBAirbus A350The Airbus A350 is a family of long-range, wide-body jet airliners under development by European aircraft manufacturer Airbus.A consortium originally comprising European aerospace companies from the UK, France, Spain and West Germany, Airbus is now fully owned by EADS and since 2001 has been known...
Actuating wingtip devices
There has been research into actuating wingtip devices, including a filed patent application, though no aircraft currently uses this feature as described. The XB-70 ValkyrieXB-70 Valkyrie
The North American Aviation XB-70 Valkyrie was the prototype version of the proposed B-70 nuclear-armed deep-penetration strategic bomber for the United States Air Force's Strategic Air Command...
's wingtips were capable of drooping downward in flight, to facilitate Mach 3
Mach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...
flight using waveriding
Waverider
A waverider is a hypersonic aircraft design that improves its supersonic lift-to-drag ratio by using the shock waves being generated by its own flight as a lifting surface. To date the only aircraft to use the technique is the Mach 3 supersonic XB-70 Valkyrie, which was waverider-like with its...
.
Use on rotating blades
Wingtip devices are also used on rotating propellerPropeller (aircraft)
Aircraft propellers or airscrews convert rotary motion from piston engines or turboprops to provide propulsive force. They may be fixed or variable pitch. Early aircraft propellers were carved by hand from solid or laminated wood with later propellers being constructed from metal...
, helicopter rotor
Helicopter rotor
A helicopter main rotor or rotor system is a type of fan that is used to generate both the aerodynamic lift force that supports the weight of the helicopter, and thrust which counteracts aerodynamic drag in forward flight...
, and wind turbine
Wind turbine
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or...
blades to reduce drag, reduce diameter, reduce noise and/or improve efficiency. By reducing aircraft blade tip vortices interacting with the ground surface during taxiing
Taxiing
Taxiing refers to the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug...
, takeoff
Takeoff
Takeoff is the phase of flight in which an aerospace vehicle goes from the ground to flying in the air.For horizontal takeoff aircraft this usually involves starting with a transition from moving along the ground on a runway. For balloons, helicopters and some specialized fixed-wing aircraft , no...
, and hover, these devices can reduce damage from dirt and small stones picked up in the vortices.
Rotorcraft applications
The main rotor of the AgustaWestland AW101 (formerly the EH101) has a special "winged tip"; pilots have found that this alters the downwash field and reduces brownoutBrownout (aviation)
In aviation, a brownout is an in-flight visibility restriction due to dust or sand in the air.In a brownout, the pilot cannot see nearby objects which provide the outside visual references necessary to control the aircraft near the ground. This can cause spatial disorientation and loss of...
which limits visibility in dusty areas and leads to accidents.
Propeller applications
Hartzell Propeller developed their "Q-tip" propeller used on the Piper PA-42 Cheyenne and several other fixed-wing aircraft types by bending the blade tips back at a 90-degree angle to get the same thrustThrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
from a reduced diameter propeller disk; the reduced propeller tip speed reduces noise, according to the manufacturer. Modern scimitar propeller
Scimitar propeller
A scimitar propeller is shaped like a scimitar sword, with increasing sweep along the leading edge. Typically scimitar propellers are constructed of lightweight or composite materials. In the early 1900s they were made of laminated wood...
s have increased sweepback at the tips, resembling a raked tip on an aircraft wing.
External links
- Boeing 767 Raked Wingtips
- Boeing Press Release for 777-300ER
- About Winglets paper by Mark D. MaughmerMark D. MaughmerDr. Mark D. Maughmer is a Professor of Aerospace Engineering in the Department of Aerospace Engineering at The Pennsylvania State University...
- Winglet Design for Sailplanes paper by Peter MasakPeter MasakPeter C. Masak was an engineer, inventor, and glider pilot. He graduated with a Bachelor of Applied Science degree in Mechanical Engineering in May 1981 from the University of Waterloo, Ontario Canada. He earned his glider pilot license at the age of 16 and his power pilot license at the age of...
- A close Look at Winglets
- Assessment of Wingtip Modifications to Increase the Fuel Efficiency of Air Force Aircraft, National Academies Press, 2007, p.33