Қанат ұшы құрылғыларының артықшылықтары мен қауіпсіздігі

Aircraft component fixed to the end of the wings to improve performance

Wingtip devices are intended to improve the efficiency of fixed wing aircraft by reducing drag. 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. 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 greatly increasing the wingspan. Extending the 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 help prevent the flow around the wingtip of higher pressure air under the wing flowing to the lower pressure surface on top at the wingtip, which results in a vortex caused by the forward motion of the aircraft. Winglets also reduce the lift induced drag caused by wingtip vortices and improve lift to drag ratio. This increases fuel efficiency in powered aircraft and increases cross country speed in gliders, in both cases increasing range.

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. Somerville patented the first functional winglets in 1910. Somerville installed the devices on his early biplane and monoplane designs. Vincent Burnelli received US Patent no: 1,774,474 for his "Airfoil Control Means" on August 26, 1930. 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.

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 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.

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. Those trail behind the plane and pose a hazard to other aircraft. Minimum spacing requirements between aircraft operations at airports are largely dictated by these factors. Aircraft are classified by weight (e. g. "Light", "Heavy", etc.) because the vortex strength grows with the aircraft lift coefficient, and thus, the associated turbulence is greatest at low speed and high weight, which produced a high angle of attack. Winglets and wingtip fences also increase efficiency by reducing vortex interference with laminar airflow near the tips of the wing, by 'moving' the confluence of low pressure (over wing) and high pressure (under wing) air away from the surface of the wing. Wingtip vortices create turbulence, originating at the leading edge of the wingtip and propagating backwards and inboard. This turbulence 'delaminates' the airflow over a small triangular section of the outboard wing, which destroys lift in that area. The fence/winglet drives the area where the vortex forms upward away from the wing surface, since the center of the resulting vortex is now at the tip of the winglet. Aircraft such as the Airbus A340 and the Boeing 747 400 use winglets while other designs such as later versions of the Boeing 777 and the Boeing 747 8 have raked wingtips. The fuel economy improvement from winglets increases with the mission length. Blended winglets allow a steeper angle of attack reducing takeoff distance.

Richard T. Whitcomb, an engineer at NASA's Langley Research Center, further developed Hoerner's concept in response to the sharp increase in the cost of fuel after the 1973 oil crisis. With careful aeronautical design he showed that, for a given bending moment, a near vertical winglet offers a greater drag reduction compared to a horizontal span extension. Whitcomb'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. The same month, he filed a U. S. patent for "wingtip airfoils", published in 1986.

NASA's 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, though these were more for directional stability than for drag reduction.

Learjet exhibited the prototype Learjet 28 at the 1977 National Business Aviation Association convention. It employed the first winglets ever used on a production aircraft, either civilian or military. Learjet developed the winglet design without NASA assistance. Although the Model 28 was intended to be a prototype experimental aircraft, performance was such that it resulted in a production commitment from Learjet. Flight tests showed that the winglets increased range by about 6.5 percent and improved directional stability. Learjet's application of winglets to production aircraft continued with newer models including the Learjet 55, 31, 60, 45, and Learjet 40. Gulfstream Aerospace explored winglets in the late 1970s and incorporated winglets in the Gulfstream III, Gulfstream IV and Gulfstream V. The Gulfstream V range of allows nonstop routes such as New York–Tokyo, it holds over 70 world and national flight records.

Conventional winglets were fitted to Rutan's Rutan Voyager, the first aircraft to circumnavigate the world without refueling in 1986. The aircraft's wingtips were damaged, however, when they dragged along the runway during takeoff, removing about 1 feet (0 m) from each wingtip, so the flight was made without benefit of winglets.

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.

A wingtip fence refers to the winglets including surfaces extending both above and below the wingtip, as described in Whitcomb's early research. Other Airbus models followed with the A300 600, the A320ceo, and the A380. Other Airbus models including the Airbus A320 Enhanced, A320neo, A350 and A330neo have blended winglets rather than wingtip fences. The Antonov An 148 uses wingtip fences.

Boeing announced a new version of the 747, the 747 400, in 1985, with an extended range and capacity, using a combination of winglets and increased span to carry the additional load. The winglets increased the 747 400's range by 3.5% over the 747 300, which is otherwise aerodynamically identical but has no winglets. The Aviation Partners/Boeing 2.44 m extensions decrease fuel consumption by 4% for long range flights and increase range by for the 737 800 or the derivative Boeing Business Jet as standard. In 2006 Airbus tested two candidate blended winglets, designed by Winglet Technology and Airbus for the Airbus A320 family. In 2009 Airbus launched its "Sharklet" blended winglet, designed to enhance the payload range of its A320 family and reduce fuel burn by up to 4% over longer sectors. This corresponds to an annual CO2 reduction of 700 tonnes per aircraft. The A320s fitted with Sharklets were delivered beginning in 2012. They are used on the A320neo, the A330neo and the A350. They are also offered as a retrofit option.

Raked wingtips, where the tip has a greater wing sweep than the rest of the wing, are featured on some Boeing Commercial Airplanes to improve fuel efficiency, takeoff and climb performance. Like winglets, they increase the effective wing aspect ratio and diminish wingtip vortices, decreasing lift induced drag. In testing by Boeing and NASA, they reduce drag by as much as 5.5%, compared to 3.5% to 4.5% for conventional winglets. 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. The short range Boeing 787 3 would have had a wingspan to fit in ICAO Aerodrome Reference Code D. Its wingspan was decreased by using blended winglets instead of raked wingtips. Raked wingtips are installed on the Boeing 767 400ER (first flight on October 9, 1999), the Boeing 777 200LR/300ER/Freighter (February 24, 2003), the 737 derived Boeing P 8 Poseidon (25 April 2009), the Boeing 787 (December 15, 2009), the Boeing 747 8 (February 8, 2010) and the Boeing 777X. The Embraer E jet E2 and C 390 Millennium wings has a raked wingtip.

The McDonnell Douglas MD 11 was the first aircraft with split tip winglets in 1990. For the 737 Next Generation, third party vendor Aviation Partners has introduced a similar design to the 737 MAX wingtip device known as the split scimitar winglet, with United Airlines as the launch customer. The Boeing 737 MAX uses a new type of wingtip device. 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.

In 1987, mechanical engineer Peter Masak called on aerodynamicist Mark D. Maughmer, an associate professor of aerospace engineering at the Pennsylvania State University, about designing winglets to improve performance on his wingspan racing sailplane. Others had attempted to apply Whitcomb's winglets to gliders before, and they did improve climb performance, but this did not offset the parasitic drag penalty in high speed cruise. Masak was convinced it was possible to overcome this hurdle. By trial and error, they ultimately developed successful winglet designs for gliding competitions, using a new PSU–90–125 airfoil, designed by Maughmer specifically for the winglet application. At the 1991 World Gliding Championships in Uvalde, Texas, the trophy for the highest speed went to a winglet equipped 15 meter class limited wingspan glider, exceeding the highest speed in the unlimited span Open Class, an exceptional result. Masak went on to win the 1993 U. S. 15 Meter Nationals gliding competition, using winglets on his prototype Masak Scimitar. The Masak winglets were originally retrofitted to production sailplanes, but within 10 years of their introduction, most high performance gliders were equipped from the factory with winglets or other wingtip devices. It took over a decade for winglets to first appear on a production airliner, the original application that was the focus of the NASA development. Yet, once the advantages of winglets were proven in competition, adoption was swift with gliders. The point difference between the winner and the runner up in soaring competition is often less than one percent, so even a small improvement in efficiency is a significant competitive advantage. Many non competition pilots fitted winglets for handling benefits such as increased roll rate and roll authority and reduced tendency for wing tip stall. The benefits are notable, because sailplane winglets must be removable to allow the glider to be stored in a trailer, so they are usually installed only at the pilot's preference. The Glaser Dirks DG 303, an early glider derivative design, incorporating winglets as factory standard equipment.

Aviation Partners developed and flight tested a closed surface Spiroid winglet on a Falcon 50 in 2010. 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. 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. The Schempp Hirth Discus 2 and Schempp Hirth Duo Discus use non planar wingtips.

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. 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. 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,

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 Valkyrie's wingtips were capable of drooping downward in flight, to facilitate Mach 3 flight using waveriding.

Wingtip devices are also used on rotating propeller, 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.

The main rotor blades of the AgustaWestland AW101 (formerly the EH101) have a distinctive tip shape; pilots have found that this rotor design alters the downwash field and reduces brownout which limits visibility in dusty areas and leads to accidents.

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 thrust from a reduced diameter propeller disk; the reduced propeller tip speed reduces noise, according to the manufacturer. However, for certain high volume, low speed designs, wingtip devices may not improve efficiency. 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.