Wing tip device and methods

[0001] The present invention relates to a wing tip device for attachment to the outer wing end. Also, wings with wing tip device, aircraft with wing; method of attachment or attachment during modernization of the device wing tip to wing; how to modify the existing wing tip device and how to operate the wing with the wing tip device.

BACKGROUND OF THE INVENTION [0002] The wing tip device is attached to the outer end of the wing to reduce the aerodynamic drag on the wing. For example, in the case of an aircraft wing, this can lead to lower fuel consumption and reduced carbon emissions. Wing tip devices can take many forms.

[0003] The diffuser (edge ​​vortices) is a wing-type element that extends from the wing tip. The diffuser may extend up or down from the wing tip. In NASA TN D-8260 entitled "A Design Approach and Selected Wind-Tunnel Results at High Subsonic Speeds for WingTip Mounted Winglets"; Whitcomb, RT, 1976 describes a wing tip device having a bottom spreader (extending downward from the wing tip) in front of the upper spreader (extending upward from the wing tip). The sizes of these wing tip devices are recommended in NASA TM 81230 entitled "Effect of Winglets or the Induced Drag of Ideal Wing Shapes", RT Jones and TA Lasinski 1980.

[0004] The aerodynamic comb of the wing tip is a special form of the wing tip device that extends vertically both above and below the wing tip. In US 4,714,215 a wing tip comb is described.

[0005] Another example of a wing tip device is the non-flat extension of the wing tip, i.e. it extends outwardly from the plane of the wing to which it is attached. The aerodynamic comb can be considered as a special example of a non-flat wing tip extension. US 2002/0162917 describes a non-planar wing tip extension having a continuously increasing curvature of local blade elevation, a continuously increasing positive skew bias (both on the leading edge and trailing edge) and a continuously diminishing chord in the outward direction.

[0006] The diffuser may comprise a substantially flat portion connected to the wing tip through a curved transition portion to form a gently connected diffuser, such as described in US 5,348,253. The transition part has a constant radius of curvature. The described smooth transition has been found to reduce interference resistance at the wing tip.

[0007] Alternatively, the diffuser may comprise a substantially flat portion connected to the wing tip by a non-flat wing tip extension part, such as described in WO 2008/061739. The non-planar portion of the wing tip extension has a rising curvature of local wing lift in the outward direction. A portion of the wing tip extension has been found to further reduce the phenomenon of aerodynamic interference compared to a combined diffuser with a fixed transition radius.

[0008] Another example of a wing tip device is a substantially flat wing tip extension, such as the deflected wing tip described in US 6,089,502, which does not extend substantially

EP 2 593 362 B1 outwards from the wing plane. The deflected wing tips can achieve a similar reduction in aerodynamic drag as the diffusers.

[0009] Limits in aircraft span, due to, e.g., airport gate compatibility or flight limitations for aircraft types mean that spreaders or non-plane wing tip extensions instead of deflected wing tips should be adapted to reduce aerodynamic drag on the wing. Because the diffusers (and more generally non-flat wing tip extensions) extend outward from the wing plane to which they are attached, an effective increase in wing elongation can be obtained (which reduces the aerodynamic resistance exerted by vortices on the wing) without significantly increasing the wingspan.

[0010] The problem of span restrictions has traditionally been solved by optimizing the wingspan of an airplane in a (fully loaded fuel) ground shape in which span restrictions apply. However, due to the bending of the wing due to the effects of aeroelasticity during the flight, the wingspan of the resulting shape during the flight is usually reduced and for this reason is no longer optimal. This traditional approach results in a decrease in performance. This problem becomes even more pronounced with the greater use of relatively flexible wings to reduce structural weight, which usually leads to increased deflection of the wing under the influence of aerodynamic force compared to stiffer structures.

[0011] US 4,365,773 describes a wing tip comb for a double "rhomboidal" wing system that is substantially not aerosolastically deformed during flight.

[0012] US 4 674 709 A discloses a wing with the features of the introduction to claim 1.

SUMMARY OF THE INVENTION [0013] A first aspect of the invention provides a wing having an outer end defining a wing plane and a wing tip device attached to the outer wing end, the wing tip device comprising: an upper wing type element attached in an immobilizing manner relative to the wing and protruding upwards relative to the wing plane , wherein the upper wing type element has a trailing edge; and is characterized by a bottom wing-type element fixed in a fixed way relative to the upper wing-type element, where the lower wing-type element has a chord chord and a trailing edge, while the chord of the base of the lower wing-type element intersects with the upper wing-type element, and the lower wing-type element protrudes downwards from the intersection, with the upper wing type element being larger than the lower wing type element, and the trailing edge of the lower wing type element is adjacent to the trailing edge of the upper wing type element at the intersection, and the angle between the upper and lower wing type elements at the intersection on the outside of the wing tip device in the direction of the span is less than or equal to 160 degrees.

[0014] A second aspect of the invention provides an aircraft having a wing according to the first aspect.

[0015] A third aspect of the invention provides a method of attaching, or attaching during modernization, a wing tip device to a wing to form a wing according to the first aspect, the method comprising attaching the wing tip device according to the first aspect to an outer end of the wing.

[0016] A fourth aspect of the invention provides a method of modifying a wing tip device attached to the outer end of a wing, wherein the wing defines the plane of the wing, and the existing wing tip device includes an upper wing type element attached in a manner

EP 2 593 362 B1 immobilizing relative to the wing and protruding upwards relative to the plane of the wing, and the upper wing-type element includes a trailing edge, and the method includes providing a lower wing-type element, smaller than the upper wing-type element, and comprising chord chord and trailing edge, and attachment lower wing type element to upper wing type element in such a way that: the lower wing type element is fixed relative to the upper wing type element, the chord of the base of the lower wing type element intersects with the upper wing type element and the lower wing type element protrudes downwards from the intersection; and the trailing edge of the bottom wing-type element is adjacent to the trailing edge of the upper wing-type element at the intersection; and that the angle between the upper and lower wing-like elements at the intersection on the outside of the wing tip device in the span direction is less than or equal to 160 degrees.

[0017] A fifth aspect of the invention provides a method of operating a wing comprising a wing tip device attached to the outer end of the wing, the wing defining a wing plane, and the wing tip device comprising: an upper wing-type element attached in an immobilizing manner relative to the wing and protruding upwards relative to the wing plane and the upper wing type element has a trailing edge; and is characterized by a bottom wing type element attached in a fixed manner to the upper wing type element, the bottom wing type element comprising a root chord and trailing edge, the chord base of the bottom wing type element intersects with the upper wing type element, and the bottom wing type element protrudes down from the intersection, where the upper wing type element is larger than the lower wing type element, and the trailing edge of the lower wing type element is adjacent to the trailing edge of the upper wing type element at the intersection, and the angle between the upper and lower wing type elements at the intersection on the outside of the wing tip device in the direction of the span is less than or equal to 160 degrees, and the method includes subjecting the wing to aerodynamic forces in such a way that the shape of the wing undergoes aerosolastic deformation to its condition, wherein the bending of the wing causes the wing tip device to rotate around the base of the wing, such that the tip of the bottom wing-type element extends further outward towards the span than the tip of the upper wing-type element.

[0018] The invention is advantageous in that the lower wing-like element works to compensate for at least a part of the reduction of the wingspan that occurs due to the aero-elastic deformation in shape during the flight, while the upper and lower wing-like element can still be optimized for meet applicable ground-shaped span limits.

[0019] The addition of a bottom element to the wing tip device containing only the top wing type element (e.g. diffuser) has been shown to reduce aerodynamic drag on the wing / wing tip device combination by a total of about 1.9%, with a further reduction of aerodynamic drag about 25 to 40% relative to the reduction provided only by the top element.

[0020] The close convergence of the trailing edge of the upper and lower wing-like elements is important to avoid the phenomenon of follower disturbances. Trailing edges do not have to coincide exactly, but they must be adjacent so as to avoid the influence of one stream following one flow on the flow above the other element at the intersection.

[0021] The angle between the upper and lower wing-type elements at the intersection on the outside of the wing tip device in the direction of the span, hereinafter referred to as the angle between the upper and lower wing-type elements at the intersection, is important in that the lower element provides an increase in the span in the shaped during the flight. The angle of the lower element (i.e. the angle between the vertical plane)

And the element) can be optimized to obtain the maximum increase in shape span during flight with due regard to minimizing interference phenomena at the intersection. It should be noted that the wing tip comb has an angle between the upper and lower vertical elements of about 180 degrees, so that the lower element provides a negligible increase in shape span during flight.

[0022] The upper wing type element is larger than the lower wing type element. The lower wing type element may have a top view element area less than about 25% of the top view area of ​​the upper wing type element. Note that the top view area of ​​each item is seen in a plane different from the wing area in the top view. The area in the top view of the bottom element can be designed to provide the desired load along the span, minimizing the cost of viscous resistance and ensuring good performance of high lift at low speed. Restrictions for ground height gauge may limit the size of the bottom element.

[0023] The lower wing type element is fixed relative to the upper wing type element. The wing tip device is fixed relative to the wing. The invention does not apply to movable wing tip devices, since these are generally heavier than fixed devices, which may offset any performance advantage. Also, the solution to the problem of span restrictions is somewhat trivial for movable wing tip devices.

[0024] The angle included between the plane of the wing and the bottom member of the wing type may be at least 110 degrees. The lower element therefore extends outwardly from the outer end of the sash, and the phenomenon of interference between the lower surface of the sash and the lower element can be minimized.

[0025] The angle between the upper and lower wing-like elements at the intersection may be at least 80 degrees, preferably at least 90 degrees. This helps minimize interference between the top and bottom elements at the intersection.

[0026] The lower sash-like element may be substantially flat.

[0027] Alternatively, the bottom wing-like element may be substantially non-flat. In particular, the lower element may have a wing twist, e.g. a positive flap dislocation. The lower element may have a curvature in the direction of the span with an increasing negative rise from the root to the wing tip.

[0028] The bottom element may have a taper angle with respect to the vertical plane xz.

[0029] The lower element may have a rearward slant angle. In particular, the bottom member may have a leading edge which is tilted back. The bevel angle to the rear of the leading edge of the lower element may be similar to the bevel angle to the rear of the upper element.

[0030] The upper wing-like element may comprise a substantially flat part.

[0031] In one embodiment, the upper sash-like element may be substantially flat. The top element can be a diffuser.

[0032] In another embodiment, the upper wing-like element may comprise a substantially flat portion and part of the arch-shaped passage adapted to smoothly transition the outer wing end into a substantially flat portion of the wing-like upper member. The upper element can be a gently connected diffuser. Part of the transition may have a constant radius of curvature. The smooth transition helps to reduce the phenomenon of aerodynamic interference of the wing tip.

[0033] In yet another embodiment, the upper wing-type element may comprise a substantially flat portion and a non-planar curved wing tip extension adapted to smoothly transition the outer wing-tip into a substantially flat portion of the wing-type upper member.

EP 2 593 362 B1

The upper element may be a diffuser going into the wing through the non-flat part of the wing tip extension. The non-planar portion of the wing tip extension may have an increasing curvature of local wing lift in the outward direction. Part of the wing tip extension helps further reduce the phenomenon of aerodynamic interference compared to a gently connected diffuser with a fixed transition radius.

[0034] The upper wing-type element may be a substantially non-planar curved wing tip extension. The extension may have a continuously increasing curvature of the local lobe lift, a continuous backward slant (both at the leading edge and trailing edge) and a continuously diminishing chord towards the outside.

[0035] The upper wing-type element may have a wing twist from root to tip, e.g., positive wing dislocation.

[0036] The upper wing-type element may have a taper angle with respect to the vertical plane xz.

[0037] The upper wing-type element may have a slant back angle. In particular, the upper element may have a leading edge tilted backwards. The bevel angle to the rear of the leading edge of the upper element may be similar to the bevel angle to the rear of the lower element.

[0038] The intersection between the lower wing type element and the upper wing type element may be at the outer end of the wing.

[0039] Alternatively, the intersection between the lower wing type element and the upper wing type element may be outside the outer end of the wing. This can be particularly advantageous when the upper element gently passes into the outer wing end. In this case, the cut may be on the lower surface of the upper element.

[0040] The lower chord chord may extend along only the local portion of the upper chord at the intersection.

[0041] When the airplane is on the ground and the wing is subjected to downward bending due to full fuel loading, the tip of the bottom wing-type element may extend outward towards the span no more than the tip of the upper wing-type element. In this way, for example, both the top and bottom ends can be within the airport gate.

[0042] When the airplane is on the ground and the wing is subjected to downward bending due to full fuel load, the span towards the tip span of the bottom wing type element may be substantially equal to the span towards the tip span of the upper wing type element. Alternatively, the span towards the wing tip of the lower wing type element may be greater than the span towards the wing tip of the upper wing type element when the span of the upper element tip is substantially smaller than the boundaries of the airport gate.

[0043] When the aircraft is in flight, the tip of the lower wing-type element may extend further outward in the direction of the span than the tip of the upper wing-type element, due to the aerosolastic deformations of the wing shape.

BRIEF DESCRIPTION OF THE DRAWINGS [0044] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 shows a state of the art aircraft wing with an upper diffuser, shown a) in its ground shape and b) in its shape during flight;

EP 2 593 362 B1

Figure 2 is detail A of Figure 1 showing the span limits on the ground and the loss of span due to wing deformation under aerodynamic loading conditions;

Figure 3 shows the wing / wing tip device according to the first embodiment, having a flat top spreader and a flat bottom spreader, shown a) in its above ground shape and b) in its shape during flight and shows the increase in span obtained by the bottom shaped element during flight;

Figure 4 shows in detail the wing / wing tip device (ground-shaped) according to the first embodiment;

Figures 5 and 6 graphically show a further reduction of the aerodynamic drag on the bottom element in the first embodiment;

Figure 7 shows a wing / wing tip device (ground-shaped) according to a second embodiment having a flat upper diffuser and a non-flat lower diffuser;

Figure 8 shows a wing / wing tip device (ground-shaped) according to a third embodiment, gently combined upper diffuser and flat lower diffuser;

Figure 9 shows the wing / wing tip device (ground-shaped) according to the fourth embodiment having a top diffuser gently connected to the wing with a non-flat wing tip extension and a flat bottom diffuser (although a non-flat bottom diffuser may also be used); and

Figure 10 is a perspective view of the wing / wing tip device according to the fourth embodiment;

Figure 11 shows a top view of the wing / wing tip device according to the fourth embodiment;

Figure 12 shows a wing / wing tip device according to a fifth embodiment having a non-planar (upper) wing tip extension and a flat lower spreader; and

Figure 13 is a perspective view of the wing tip device according to the fifth embodiment.

DETAILED DESCRIPTION OF EXAMPLE (EXAMPLES) OF FIGURE [0045] Figure 1 shows a prior art wing 1 having an inner wing 2 wing base and an outer wing 3 tip. The wing tip device comprising the upwardly extending diffuser 4 is attached to the outer end 3 of the wing 1. The wing is shown in Figure 1 a) in its above-ground shape (i.e. with an airplane on the ground with a full fuel load in the wing) and b) in its shaped during flight (i.e. with deformation due to aerodynamic force).

[0046] Figure 2 shows detail A of Figure 1, and the dashed line 5 illustrates the spread limit imposed on the aircraft due to, e.g., airport gate compatibility restrictions or flight restrictions for the airplane category. The span restriction applies to the ground shape shown in Figure 2a). Figure 2b) shows the loss of wingspan due to deformation of the wing during flight. This 6 span loss can be up to 3%.

[0047] Figure 3 shows an aircraft wing 101 according to the first embodiment having a flat top spreader 104 and a flat bottom spreader 107. The top spreader 104 is attached to

The outer end 103 of the wing 101. The wing 101 defines the plane 108 of the wing. The top spreader 104 projects upward with respect to the wing plane 108. The upper diffuser 104 has a tip 109 and a socket 110. The lower diffuser has a tip 111 and a socket 112. The chord 112 of the lower diffuser attachment cuts the upper diffuser 104, and the lower diffuser 107 protrudes downwards from this intersection. Each top and bottom diffuser 104, 107 has a leading edge and trailing edge, and trailing edges are adjacent at the intersection. Figure 3a) shows a ground-shaped wing 101 in which the tip 109 of the upper diffuser 104 and the tip 111 of the lower diffuser 107 adjoin the span border 105. Figure 3b) shows wing 101 in its shape deformed in flight and shows how the potential loss of spread 106 due to the top spreader is reduced by increasing the spread 113 obtained from the lower spreader 107. This increase in spread 113 due to the lower spreader 107 is about 2%.

[0048] Figure 4 shows the aircraft wing 101 according to the first embodiment in more detail. Bottom spreader 107 is sized and oriented to maximize the increase in shape span during flight while minimizing interference at the intersection between bottom spreader 107 and top spreader 104. In addition, the ground height G gauge between ground and bottom 111 spreader 107 is included. The resulting geometry provides an angle between the upper and lower wing element of about 132 ° and provides an angle between the plane 108 of the wing and the lower diffuser 107 about 128 °. The lower diffuser 107 has a top view of the diffuser about 20% of the top view of the upper diffuser 104. The relatively small size of the lower diffuser 107 minimizes the costs of viscous drag for the passage while providing the required optimal load along the span.

[0049] Figures 5 and 6 graphically illustrate the effect of adding the lower diffuser element 107 on the lift force and resistance characteristics of the edge eddies of the wing 101. In Figures 5 and 6, the line with circular markers represents the reference wing corresponding to the wing 101 with the tip near the imposed span limit without any device wing tips. The line with cross markers illustrates wing 101 only with element 104 of the upper diffuser (of the size recommended in NASA TM 81230 document entitled "Effect of Winglets on the Induced Drag of Ideal Wing Shapes", RT Jones and TA Lasinski 1980), and the line with triangular markers represents wing 101, both with the upper and lower element 104, 107 of the diffuser. Figure 5 shows the relationship between the lift force and aerodynamic drag coefficients (CL, CD) and shows the improvement of the lift to aerodynamic drag ratio for wing 101 with both the top and bottom elements 104, 107 of the diffuser, compared with both the reference wing and the wing only with the top element of the diffuser. Figure 6 shows the reduction of aerodynamic drag due to the addition of the lower diffuser element 107 about 1.9% for the lift coefficient (CL = 0.5) in half flight relative to the wing only with the upper diffuser element 104. The reduction in aerodynamic drag of the edge vortices provided by the lower diffuser element 107 is an additional reduction of about 25 to 40%.

[0050] Figure 7 shows an aircraft wing 201 according to a second embodiment having a flat upper diffuser 204 and a non-flat lower diffuser 207. The wing 201 defines the plane 208 of the wing and the upper diffuser 204 protrudes upwards relative to the plane 208 of the wing. The upper spreader 204 is attached to the outer end 203 of wing 201. The lower spreader 207 includes a chord string 212 that intersects with the upper spreader 204. Bottom spreader 207 protrudes downwards from

EP 2 593 362 B1 intersection. The top spreader 204 has a tip 209 and a base 210. The bottom spreader 207 has a tip 211 which coincides in the direction of the span with the tip 209 at the border 205 of the span. Each upper and lower diffuser 204, 207 has a leading edge and trailing edge, and trailing edges are adjacent at the intersection. Wing 201 is shown in Figure 7 in its above ground shape, where the 205 span limit applies.

[0051] The lower spreader 207 has an increasing curvature of local negative blade rise from base 212 to tip 211. The lower spreader 207 may have a convergence angle or divergence angle suitable to optimize the operation of the wing tip device at low speeds.

[0052] The wing tip device for wing 201 has been optimized to maximize span increase during aerodynamic loading during flight while minimizing interference between lower spreader 207 and lower surface of wing 201 as well as between upper and lower spreader 204, 207. The resulting optimized geometry has an angle between the upper and lower diffuser 204, 207 about 120 ° and an angle between the plane 208 of the wing and lower diffuser 207 about 138 °. Shaped in flight, the lower spreader 207 provides an additional increase in span compared to the lower spreader 107 of the wing 101, mainly due to the increased height from base 212 to the tip 211 of the lower spreader 207 and the flexibility of the lower spreader 207, which straightens under load.

[0053] Figure 8 shows an aircraft wing 301 according to a third embodiment having a gently connected upper diffuser 304 and a flat bottom diffuser 307. Wing 301 has an outer end 303 to which a gently connected upper diffuser 304 is attached. The top diffuser 304 has a tip 309 and a cap 310. The top spreader 304 is attached to the outer end 303 of wing 301 through its end 310 of the root. The upper diffuser 304 has a substantially flat portion 314 and an arcuate transition portion 315. The transition portion 315 is adapted to gently connect the outer end 303 of the wing 301 to the substantially flat portion 314. The arch transition portion 315 has a substantially constant radius R of curvature.

[0054] The lower diffuser 307 is attached to the lower surface of the transition portion 315 of the upper diffuser 304. The lower diffuser has a tip 311 and a base 312. The chord of the lower diffuser base 307 intersects with the upper diffuser 304 and the lower diffuser protrudes downwards from the intersection. Each top and bottom 304, 307 diffuser has a leading edge and trailing edge, and trailing edges are adjacent at the intersection. The transition portion 315 helps reduce interference between the substantially flat portion 314 and the wing 301.

[0055] The tip 309 of the upper diffuser 304 is substantially tapered in the vertical plane xz with the tip 311 of the lower diffuser 307 at the border 305 of the span. The angle between the upper and lower diffusers 304, 307 at the intersection is approximately 84 °. Preferably, this angle is at least 80 ° to avoid interference between the upper and lower diffusers 304, 307. Since the cut is on the lower surface of the gently connecting transition portion 315, this angle is measured between the tangent of the lower surface of the transition portion and the lower diffuser 307. The angle between the plane 308 of the wing and the lower diffuser 307 is about 125 °. The substantially flat portion 314 of the upper diffuser 304 has a deflection angle relative to the vertical plane x from about 7 ° to 15 °.

[0056] The lower diffuser element 307 has a top view area of ​​about 25% of the top view area of ​​the upper diffuser element 304. Although the lower diffuser 307 is substantially flat, it may have some wing twist from base 312 to tip 311. Lower diffuser 307 may furthermore or

Alternatively have an angle of convergence or divergence to optimize operation at low speeds. Similarly, the upper diffuser 304 may have a taper or divergence angle. The lower spreader 307 has a slant back angle, and in particular the leading edge is slanted back. The upper diffuser 304 is also inclined backwards and has a leading edge inclined backwards as well as a trailing edge inclined backwards.

[0057] If the ground height gauge allows, the lower diffuser element 307 may be replaced by a non-flat lower diffuser element similar to that described above with reference to Figure 7.

[0058] Figure 9 shows the wing / wing tip device combination of the aircraft, comprising wing 401, gently attached upper diffuser 404 and flat lower diffuser 407. Wing 401 has an outer end 403 and defines plane 408 of the wing. Upper diffuser 404 includes a substantially flat portion 414 and a gently connecting transition portion 415. Transitional portion 415 gently connects the outer wing tip 403 of the wing 401 to a substantially flat portion 414 of the upper diffuser 404. The transition portion 415 is a non-planar curved extension of the wing tip, having a continuously increasing curvature of the local blade lift, a continuous backward deviation (both at the leading edge and trailing edge) and a continuously decreasing chord in the outward direction. The non-planar curved portion 415 of the wing tip extension provides improved aerodynamic drag performance for the upper diffuser 404 compared to the gently connected upper diffuser 304 shown in Figure 8.

[0059] The upper diffuser 404 has a base 410 and a tip 409. The substantially flat portion 414 of the upper diffuser 404 has a tilt angle of about 7 ° relative to the vertical plane xz. A substantially flat bottom diffuser 407 is attached to the bottom surface of the non-planar curved portion 415 of the wing extension of the upper diffuser 404. The bottom diffuser 407 has a tip 411 and a base 412. The chord of the lower diffuser 407 intersects with the upper diffuser 404 and the lower diffuser protrudes downwards from the intersection.

[0060] The angle between the upper and lower diffusers 404, 407 at the intersection is about 86 °. Since the intersection is on the lower surface of the non-planar curved portion 415 of the wing tip extension of the upper diffuser 404, this angle is measured from the tangent of the local surface to the lower surface of the non-flat curved wing portion 415 of the wing tip extension at the intersection. The tan included angle is preferably greater than 80 ° to avoid interference between the upper and lower diffuser 404, 407. The included angle between the plane 408 of the wing and the lower diffuser is about 124 °. The tip 409 of the upper diffuser 404 is substantially tapered in the vertical plane xz with the tip 411 of the lower diffuser 407 at the border 405.

[0061] Figures 10 and 11 show a perspective view and a top view of the wing / wing tip device combination of the fourth embodiment. In Figure 10 in particular, it can be seen that the trailing edge 416 of the upper diffuser 404 and the trailing edge 417 of the lower diffuser 407 are substantially contiguous at the intersection. Trailing edges 416, 417 are close enough so that the downstream stream from the lower diffuser 407 does not substantially interfere with the flow around the upper diffuser 404. The upper diffuser 404 has a leading edge 418 which is deflected backwards and the lower diffuser 407 also has a leading edge 419 which is tilted back. The trailing edge 416 of the upper diffuser 404 is tilted back and the trailing edge 417 of the lower diffuser 407 is also tilted back.

[0062] In Figure 11, the top view (i.e., top-down view in the xy plane) shows how the top diffuser 404 obstructs at least part of the bottom diffuser 407. This is because of the convergence of the top tips 409, 411 and lower diffuser 404, 407 in the vertical xz plane. As best shown in Figure 10, the chord root 412 of the lower spreader 407 occupies only a portion of the local chord of the upper spreader 404 at the intersection. Due to the close convergence of the trailing edge 416, 417, the leading edge 419 of the lower diffuser 407 is positioned substantially toward the tail from the leading edge 418 of the upper spreader 404.

[0063] Figure 12 shows the wing / wing tip device combination according to the fifth embodiment, comprising wing 501 with wing tip device comprising an upper non-flat wing tip extension 504 and a lower non-flat diffuser 507. Wing 501 includes an outer end 503 and defines the plane 508 of the wing. The non-planar wing tip extension 504 includes the base 510 and the tip 509 and is attached to the outer end 503 of the wing 501 by its base 510. The non-planar curved wing tip extension 504 has a continuously increasing curvature of local wing lift, continuously increasing backward tilt (both on the leading edge and trailing edge 517, 516) and in a continuous decreasing chord in the outer direction y.

[0064] The non-planar curved wing tip extension 504 is substantially non-planar from the root

510 to tip 509. Tip 509 creates an angle of inclination of about 8 ° with the vertical xz plane. The lower spreader 507 has a tip 511 and a base 512, and the chord of the root intersects with the non-planar curved wing tip extension 504, and the lower spreader 507 protrudes downward from the intersection. The angle between the non-planar wing tip extension 504 and the lower diffuser 507 at the intersection is about 82 °. This angle is measured between the lower diffuser 507 and the tangent of the local surface and the lower surface of the non-planar extension 504 of the lower diffuser at the intersection. The angle between the plane 508 of the sash and the lower diffuser 507 is about 126 °. The tips 509, 511 of the non-planar curved extension 504 of the wing tip and lower diffuser 507 are substantially tapered in the vertical xz plane at the span border 506.

[0065] Figure 13 is a perspective view of the wing tip device according to the fifth embodiment and clearly shows that the trailing edge 516 of the non-planar curved wing tip extension 504 is substantially coincident with the trailing edge 517 of the lower diffuser 507 at the intersection. But both the non-planar curved wing tip extension 504 and the bottom spreader 507 have a rearward tilt angle and each of the leading and trailing edges 516, 517, 518, 519 has a corresponding rearward tilt angle.

[0066] The lower diffuser 507 may only be substantially flat and may include a twist of the diffuser from root to tip and an angle of convergence or divergence with respect to undisturbed flow. Similarly, the non-planar curved wing tip extension 504 may have a wing twist and a taper angle or a divergence angle relative to the undisturbed flow. The lower spreader 507 may be replaced by a substantially non-planar curved lower spreader, similar to that described above with reference to Figure 7, if the ground height gauge allows it.

[0067] Each of the second to fifth embodiments described above with reference to Figures 7 to 13 is shown with the appropriate wing / wing tip device combination in its ground shape. Due to aerodynamic loads on the wing during flight, deformation of the wing will cause the wing tip device to rotate around the base of the wing, so that the tip of the lower element

The wing type extends further outward in the span direction than the tip of the upper wing type element. The lower wing type element in each case therefore provides an increase in wingspan compared to wing tip devices having only the upper wing type element in each case.

[0068] The wing tip devices described in the first to fifth embodiments above may be mounted or mounted during modernization at the outer wing of the aircraft, or not including the wing tip device, or as part of replacing an existing wing tip device. In addition, a bottom wing type element may be provided as a modification during the modernization of an existing wing tip device comprising only the upper wing type element so as to form a wing tip device according to the present invention.

[0069] Although the invention has been described above with reference to one or more preferred embodiments, it should be noted that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.