Wing tip device

<td> (12)</td><td></td><td colspan="2">Utility model</td><td></td>

<td> (21)</td><td>Application number:</td><td>GM 212/2015</td><td>(51) Int. CI .: B64C 23/06</td><td> (2006.01)</td>

<td> (22)</td><td>Registration date:</td><td> 07.07.2011</td><td>B64C 5/08</td><td> (2006.01)</td>

<td> (24)</td><td>Beginning of the term of protection:</td><td> 15.09.2015</td><td>B64C 3/10</td><td> (2006.01)</td>

<td> (45)</td><td>Published on:</td><td> 15.11.2015</td><td></td><td></td>

<td>Branch from EP 11730015.2 Priority: 7/14/2010 GB 201011843 claimed.</td><td> (73)</td><td>Utility model holder: Airbus Operations Limited BS99 7AR Bristol (GB) Airbus Operations GmbH 21129 Hamburg (DE)</td>

<td></td><td> (72)</td><td>Inventor: Wright Christopher BS99 7AR Bristol (GB) Himisch Jan 21129 Hamburg (DE) Chu James K. BS99 7AR Bristol (GB)</td>

<td></td><td> (74)</td><td>Representative: BEER &amp; PARTNER PATENTANWÄLTE KG VIENNA</td>

AT 14481 U2 2015-11-15 (54) WING TIP DEVICE AND METHOD (57) Wing end device for attachment to an outboard end of a wing (401), the wing defining a plane of flight, with an upper wing-like element (404), which with respect to the Wing plane protrudes upwards and has a trailing edge, and a lower wing-like element (407), which is fixed with respect to the upper wing-like element (404) and has a root chord (412) and a trailing edge, the root chord (412) of the lower wing-like element intersecting with the upper wing-like element (404) and the lower wing-like element (407) protrudes downward from the interface, wherein the upper wing-like element (404) is larger than the lower wing-like element (407) and the trailing edge of the lower wing-like element (407) is adjacent at the interface with the trailing edge of the upper wing-like element (404), and an included angle between the upper (404) and lower (407) wing-like element at the interface is less than or equal to 160 degrees.

<img file="AT14481U2_D0001.tif" />

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description

FIELD OF THE INVENTION

The present invention relates to a wing end device for attachment to the outboard end of a wing. Also a wing with the wing end device, an aircraft with the wing, a method for installing or retrofitting the wing end device on a wing, a method for modifying an existing wing end device and a method for operating a wing with the wing end device.

GENERAL STATE OF THE ART

A wing end assembly is attached to the outboard end of a wing to reduce induced drag on the wing. In the case of an airplane wing, for example, this can lead to improved fuel efficiency and reduced carbon emissions.

Wing end assemblies can take a variety of forms.

A winglet is a wing-like element that extends from the end of the wing. A winglet can extend up or down from the wing tip. NASA TN D8260 under the title "A Design Approach and Selected Wind Tunnel Results at High Subsonic Speeds for Wing-Tip Mounted Winglets (A design approach and selected wind tunnel results at high subsonic speeds for wing-end mounted winglets), Whitcomb, R. T., 1976, describes a wing end assembly that includes a lower winglet (extending downward from the wing end) from an upper winglet (extending upward from the wing end). The dimensioning of these end devices is recommended in NASA ™ 81230 under the title "Effect of Winglets or the Induced Drag of Ideal Wing Shapes", RT Jones and TA Lasinski, 1980.

A hydrofoil end disk is a special form of hydrofoil end device that extends in the vertical direction both above and below the wing end. US 4,714,215 describes a hydrofoil end fence.

Another example of an airfoil end assembly is an uneven airfoil end extension, that is, it extends out of the plane of the airfoil to which it is attached. A winglet can be viewed as a particular example of an uneven wing tip extension. US 2002/0162917 describes an uneven wing end extension which has a continuously increasing curvature of the local dihedron, a continuously increasing sweep (both on the leading and trailing edge) and a profile chord that continuously decreases in the outboard direction.

[0007] A winglet can include a substantially planar portion which is connected to the wing end by a curved transition area in order to form an integrated winglet, as described, for example, in US Pat. No. 5,348,253. The transition area has a constant radius of curvature. The specified integration is said to reduce overlay drag effects at the wing end.

[0008] Alternatively, a winglet can enclose a substantially planar partial area which is connected to the wing end by an uneven wing end extension area, as described for example in WO 2008/061739. The uneven airfoil end extension area has a continuously increasing curvature of the local dihedron in the outboard direction. The wing tip extension area is said to further reduce overlay drag effects at the wing tip compared to an integral winglet with a constant radius transition.

Another example of a wing end assembly is a substantially planar one

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Airfoil end extension, such as the beveled airfoil end described in US Pat. No. 6,089,502, which essentially does not extend out of the plane of the airfoil. Beveled wing tips can achieve drag reduction performance similar to that of winglets.

Wing span restrictions for aircraft, for example due to aerodrome compatibility gate limits or aircraft category flight restrictions, mean that winglets or uneven wing tip extensions, rather than beveled wing tips, must be used to reduce the induced drag on the wing. Because winglets (and, more generally, uneven wing tip extensions) extend out of the plane of the wing to which they are attached, an effective increase in wing elongation (which reduces the vortex-induced drag on the wing) can be achieved without significantly increasing the wing span .

The problem of span restrictions is traditionally solved by optimizing the wing span of the aircraft in the ground form (full fuel charge) when the span restrictions apply. However, due to the deflection induced on the wing shape by aeroelastic effects during flight, the wing span of the resulting flight shape is usually reduced and is therefore no longer optimal. This problem becomes even more noticeable with greater use of relatively flexible airfoils to reduce structural weight which, compared to more rigid designs, tends to result in increased airfoil deflection under aerodynamic load.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a wing tip assembly to be attached to the outboard end of a wing, the wing defining a wing plane, the wing tip assembly comprising: an upper wing-like element which projects upwards with respect to the wing plane and has a trailing edge, and a lower wing-like element which is fastened with respect to the upper wing-like element and which has a root chord and a trailing edge, the root chord of the the lower wing-like element intersects with the upper wing-like element and the lower wing-like element protrudes downward from the interface, wherein the upper wing-like element is larger than the lower wing-like element and the trailing edge of the lower wing-like element at the interface is adjacent to the trailing edge of the upper wing-like element and wherein an included angle between the upper and lower wing-like element at the interface is less than or equal to 160 Degree is.

A second aspect of the invention provides an airfoil having an outboard end and an airfoil end assembly according to the first aspect of the invention attached to its outboard end.

A third aspect of the invention provides an aircraft having a wing according to the second aspect.

A fourth aspect of the invention provides a method for installing or retrofitting a wing end device on a wing, the method comprising attaching a wing end device according to the first aspect to the outboard end of the wing.

A fifth aspect of the invention provides a method for modifying a wing end device that is attached or attachable to the outboard end of a wing, the airfoil defining a wing plane, the existing wing end device comprising a top wing-like element which, in relation to the wing plane protrudes upwards and has a trailing edge, and the method comprises providing a lower wing-like element, which is smaller than the upper wing-like element and has a root profile chord and a trailing edge, and fixing the lower wing-like element on the upper wingar2 / 26

AT 14 481 U2 2015-11-15 Austrian patent office term element includes such that: the root profile chord of the lower wing-like element intersects with the upper wing-like element and the lower wing-like element protrudes downward from the interface, and that the trailing edge of the lower wing-like element at the interface is adjacent to the trailing edge of the upper wing-like element and that an enclosed The angle between the upper and the lower wing-like element at the interface is less than or equal to 160 degrees.

A sixth aspect of the invention provides a method of operating a wing having a wing end device attached to the outboard end of the wing, the wing defining a wing plane and the wing end device comprising: an upper wing-like element which protrudes upwards with respect to the wing plane and has a trailing edge, and a lower wing-like element which is fastened with respect to the upper wing-like element and has a root chord and a trailing edge, the root The profile chord of the lower wing-like element intersects with the upper wing-like element and the lower wing-like element protrudes downward from the interface, wherein the upper wing-like element is larger than the lower wing-like element and the trailing edge of the lower wing-like element at the interface is adjacent to the trailing edge of the upper wing-like element and wherein an included angle between the upper and lower wing-like element at the interface is less than or equal to 160 Degree, and wherein the method comprises subjecting the wing to aerodynamic loads such that that the wing shape undergoes an aeroelastic deformation in a state in which the wing bending causes a rotation of the wing end device around the wing root such that the end of the lower wing-like element extends further outboard in the spanwise direction than the end of the upper wing-like element.

The invention is advantageous in that the lower wing-like element acts to compensate for at least some of the reduction in the wing span that occurs due to aeroelastic deformation in the flight shape, while the upper and lower wing-like elements can still be optimized to meet any applicable span restrictions in the soil shape.

It has been shown that the addition of the lower element to a hydrofoil end device, which comprises only an upper wing-like element (e.g. a winglet), reduces the resistance at the combination of hydrofoil and hydrofoil end device by a total of around another 1.9%, with a further eddy drag reduction of around 25 to 40% in relation to that ensured by the lower element alone.

The approximate correspondence of the trailing edges of the upper and lower elements is important in order to avoid wake vortex turbulence effects. The trailing edges do not have to coincide exactly, but they have to be adjacent to one another in order to avoid the wake vortex of one element acting on the flow via the other element at the interface.

The included angle between the upper and lower wing-like elements at the interface is important such that in flight form the lower element provides an increase in wingspan. The angle of inclination of the lower element (ie, the angle between the vertical xz plane and the element) can be optimized to achieve the maximum span increase in flight shape, with due consideration being given to minimizing overlay effects at the interface. It should be noted that a wing end bridle has an included angle between vertical upper and lower members of approximately 180 degrees and thus the lower member in flight form provides a negligible increase in wingspan.

The upper wing-like element is larger than the lower wing-like element. The lower wing-like element can have an element plan area of ​​less than about 25% of the plan area of ​​the upper wing-like element. It should be noted that the plan area of ​​each element is viewed in a plane that differs from that of the

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Wing plan area differs. The plan area of ​​the lower member can be designed to provide the required span loading while minimizing the cruise drag penalty and providing good high lift performance at low speed. Floor clearance restrictions can limit the size of the bottom element.

The lower wing-like element is immovable with respect to the upper wing-like element. The wing end assembly is immobile with respect to the wing. The invention relates to immobile wing tip assemblies as these are generally heavier than immobile assemblies, which can offset a performance benefit. In addition, solving the problem of span restrictions with movable wing end devices is somewhat trivial.

An included angle between the wing plane and the lower wing-like element can be at least 110 degrees. The lower element therefore extends outboard from the outboard end of the wing, and interference effects between the underside of the wing and the lower element can be minimized.

The included angle between the upper and lower wing-like elements at the interface can be at least 80 degrees and is preferably at least 90 degrees. This helps to minimize overlap effects between the top and bottom elements at the interface.

The lower wing-like element can be essentially flat.

Alternatively, the lower wing-like element can be substantially uneven. In particular, the lower element can have a wing twist, for example a negative twist. The lower member may have a span curvature with an increasingly negative V-shape from the root to the end.

The lower element may have a toe angle with respect to the vertical xz plane.

The lower element can have a positive arrow angle.

In detail, the lower element can have a positively swept front edge. The positive arrow angle of the leading edge of the lower element can be similar to that of the upper element.

The upper wing-like element can contain a substantially planar portion.

The upper wing-like element can be substantially flat. The upper element can be a winglet.

In another embodiment, the upper wing-like element can contain a substantially flat portion and an arcuate transition area which is suitable to allow the outboard end of the wing to run uniformly into the substantially flat portion of the upper wing-like element. The upper wing-like element can be an integrated winglet. The transition area can have a constant radius of curvature. The course helps to reduce overlay drag effects at the wing end.

In yet another embodiment, the upper wing-like element may include a substantially planar portion and an uneven curved wing end extension suitable for smoothly extending the outboard end of the wing into the substantially planar portion of the upper wing-like element. The upper wing-like element can be a winglet that extends into the wing through an uneven wing end extension. The uneven wing tip extension may have an increasing curvature of the local dihedron in the outboard direction. The wing tip extension contributes to overlay drag effects, compared to an integrated one

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Winglet with a constant radius transition, further decrease.

The upper wing-like element can be a substantially unevenly curved airfoil end extension. The extension can have a continuously increasing curvature of the local dihedron, a continuously increasing sweep (both at the leading and trailing edge) and a profile chord that continuously decreases in the outboard direction.

The upper wing-like element can have a wing twist, for example a negative twist, from the root to the end.

The upper wing-like element can have a toe angle in relation to the vertical xz plane.

The upper wing-like element can have a positive arrow angle. In particular, the upper element can have a positively swept front edge. The positive arrow angle of the leading edge of the upper element can be similar to that of the lower element.

The interface between the lower wing-like element and the upper wing-like element can be at the outboard end of the wing.

Alternatively, the interface between the lower wing-like element and the upper wing-like element may be outboard of the outboard end of the wing. This can be particularly advantageous if the upper element is allowed to run smoothly into the outboard end of the wing. In this case, the interface can be on the lower surface of the upper element.

The root chord of the lower element may extend at the intersection along only a portion of the local chord of the upper element.

When the aircraft is on the ground and the wing is deflected downward due to a full fuel charge, the end of the lower wing-like element does not extend further outboard in the spanwise direction than the end of the upper wing-like element. In this way, for example, the ends of both the top and bottom members can be at an airport gate boundary.

When the aircraft is on the ground and the wing is deflected downward due to a full fuel load, the span of the end of the lower wing-like element may be substantially the same as the span of the end of the upper wing-like element. Alternatively, the span extension of the end of the lower wing-like element may be greater than the span extension of the end of the upper wing-like element when the span of the end of the upper element is substantially less than the airport gate boundary.

When the aircraft is in flight, the end of the lower wing-like element may extend further outboard than the end of the upper wing-like element in the spanwise direction due to aeroelastic deformation of the wing shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows an aircraft wing of the prior art with an upper one

Winglet illustrated, shown a) in its ground form and b) in its flight form,

Figure 2 illustrates the detail A of Figure 1, which shows the span limit on the ground and the loss of span as a result of wing deformation under aerodynamic loading,

5/26 Austrian patent office illustrates an aircraft hydrofoil / hydrofoil end device according to a first embodiment, comprising a planar upper winglet and a planar lower winglet, shown a) in its bottom shape and b) in its flight shape, and that of the lower element in FIG Illustrated wing span obtained in flight shape, illustrating the aircraft wing / wing end device according to the first embodiment in detail,

AT 14 481 U2 2015-11-15

Figure 3

Figure 4

Figures 5 and 6 graphically illustrate the further reduction in resistance due to the lower element in the first embodiment,

Figure 7 illustrates an aircraft wing / wing end device (in the bottom shape) according to a second embodiment, having a flat upper winglet and an uneven lower winglet,

Figure 8 illustrates an aircraft wing / wing end device (in the bottom shape) according to a third embodiment, having an integrated upper winglet and a flat lower winglet,

Figure 9 illustrates an aircraft hydrofoil / a hydrofoil end device (in the bottom shape) according to a fourth embodiment, having an upper winglet, which is allowed to run into the wing with an uneven hydrofoil end extension, and a flat lower winglet (although an uneven lower one Winglet can also be used), and

Figure 10

Figure 11

Figure 12

Figure 13 illustrates a perspective view of the aircraft wing / wing end device of the fourth embodiment, illustrates a top view of the aircraft wing / wing end device of the fourth embodiment, illustrates an aircraft wing / wing end device according to a fifth embodiment, having an uneven surface (upper) wing tip extension and a flat lower winglet, and illustrating a perspective view of the aircraft wing / end assembly of the fifth embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENT (S)

FIG. 1 illustrates an aircraft hydrofoil 1 of the prior art, which has an inboard hydrofoil root 2 and an outboard hydrofoil end 3. A wing end device comprising an upwardly extending winglet 4 is on the outboard end 3 of the wing 1. The wing 1 is shown in Figure 1 in a) its bottom shape (ie, with the aircraft on the ground and with a full fuel charge in the wing) and b) its flight shape (ie, with deformation due to aerodynamic loading).

FIG. 2 illustrates detail A from FIG. 1, and the broken line 5 illustrates a span restriction that is imposed on the aircraft, for example due to airport compatibility gate limits or aircraft category flight restrictions. The span limit 5 applies to the bottom shape shown in Figure 2a). Figure 2b) illustrates the loss 6 of wing span due to wing deformation in flight shape. This loss 6 in the span can be up to 3%.

FIG. 3 illustrates an aircraft wing 101 according to a first embodiment, having a flat upper winglet 104 and a flat lower winglet 107. The upper winglet 104 is attached to the outboard end 103 of the wing 101. The wing 101 defines a wing plane 108. The upper winglet 104 protrudes upwards in relation to the wing plane 108. The upper winglet 104 has an end 109 and a root 110. The lower winglet has an end 111 and a root 112. The chord 112 of the lower winglet

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AT 14 481 U2 2015-11-15 Austrian patent office intersects with the upper winglet 104, and the lower winglet 107 protrudes downward from this interface. The upper and lower winglets 104, 107 each have a leading edge and a trailing edge, and the trailing edges are contiguous at the interface. FIG. 3 a) illustrates the aircraft wing 101 in its bottom shape, the end 109 of the upper winglet 104 and the end 111 of the lower winglet 107 at the span limit 105 coinciding. FIG. 3b) illustrates the aircraft wing 101 in its deformed flight shape and shows how a possible loss 106 in the span due to the upper winglet 104 is reduced by an increase 113 in the span obtained from the lower winglet 107. This increase 113 in wingspan due to the lower winglet 107 is approximately 2%.

FIG. 4 illustrates the aircraft wing 101 of the first embodiment in greater detail. The lower winglet 107 is dimensioned and oriented in such a way that the increase in span in flight form is maximized, while overlapping effects at the interface between the lower winglet 107 and the upper winglet 104 are minimized. In addition, a ground clearance height G between the ground and the tip 111 of the lower winglet 107 is taken into account. The resulting geometry ensures an included angle between the upper and lower wing elements of around 132 ° and an included angle between the wing plane 108 and the lower winglet 107 of around 128 °. The lower winglet 107 has a winglet floor plan area of ​​around 20% of the floor plan area of ​​the upper winglet 104. The relatively small size of the lower winglet 107 minimizes the drag penalty in travel while providing the optimal span loading required.

Figures 5 and 6 graphically illustrate the effect of adding the lower winglet element 107 on the lift and vortex resistance characteristics of the wing 101. In Figures 5 and 6, the line with circular markings represents a reference wing corresponding to the wing 101, with a Ends near an imposed span limit without any wing end device. The line with cross markings illustrates the wing 101 with only the upper winglet element 104 (dimensioned as in NASA T 81230 under the title "Effect of Winglets on the Induced Drag of Ideal Wing Shapes". RT Jones and TA Lasinski, 1980, recommended), and the line with the triangular markings represents the wing 101 with both the upper and lower winglet elements 104, 107. Figure 5 illustrates the relationship between the coefficient of lift and drag coefficient (CL, CD) and shows an improvement in the ratio of lift to drag for the wing 101 with both the upper and lower winglet elements 104, 107 compared to both the reference wing also the wing with only one upper winglet element. FIG. 6 illustrates a drag saving due to the addition of the lower winglet element 107 of around 1.9% for the lift coefficient at an average cruising weight (CL = 0.5) in relation to the wing with only the upper element 104 guaranteed eddy drag reduction is a further reduction of around 25 to 40%.

Figure 7 illustrates an aircraft wing 201 according to a second embodiment, having a flat upper winglet 204 and an uneven lower winglet 207. The wing 201 defines a wing plane 208, and the upper winglet 204 protrudes in relation to the wing plane 208 above. The upper winglet 204 is attached to the outboard end 203 of the wing 201. The lower winglet 207 has a root chord 212 that intersects with the upper winglet 204. The lower winglet 207 protrudes downward from the interface. The upper winglet 204 has an end 209 and a root 210. The lower winglet 207 has an end 211 which coincides with the end 209 at the span limit 205 in the span direction. The upper and lower winglets 204, 207 each have a leading edge and a trailing edge, and the trailing edges are contiguous at the interface. The wing 201 is shown in its bottom shape in FIG. 7, the span limit 105 being enforced.

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The lower winglet 207 has an increasing curvature of the local dihedron from the root 212 to the end 211. The lower winglet 207 may have a toe-in or toe-out angle to optimize the low speed performance of the wing tip assembly.

The wing end device for the wing 201 has been optimized so that the span increase under aerodynamic flight loads is maximized, while the overlap effects between the lower winglet 207 and the lower surface of the wing 201 and between the lower and upper winglet 204, 207 are minimized become. The resulting optimized geometry has an included angle between the upper and the lower winglet 204, 207 of around 120 ° and an included angle between the wing plane 208 and the lower winglet 207 of around 138 °. In flight form, the lower winglet 207 ensures a further gain in span compared to the lower winglet 107 of the wing 101, principally due to the increased height of the lower winglet 207 from the root 212 to the end 211 and the flexibility of the lower winglet 207, that straightens itself under flight loads.

Figure 8 illustrates an aircraft wing 301 according to a third embodiment, having an integrated upper winglet 304 and a flat lower winglet 307. The wing 301 has an outboard end 303 to which the integrated upper winglet 304 is attached. The upper winglet 304 has an end 309 and a root 310. The upper winglet 304 is attached to the outboard end 303 of the wing 301 by its root end 310. The upper winglet 304 has an essentially flat partial area 314 and an arcuate transition area 315. The transition area 315 is suitable for allowing the outboard end 303 of the wing 301 to run uniformly into the essentially flat partial area 314. The arcuate transition region 315 has a substantially constant radius of curvature R.

The lower winglet 307 is attached to the lower surface of the transition region 315 of the upper winglet 304. The lower winglet has an end 311 and a root 312. The root chord of the lower winglet 307 intersects the upper winglet 304, and the lower winglet protrudes downward from the intersection. The upper and lower winglets 304, 307 each have a leading edge and a trailing edge, and the trailing edges adjoin one another at the interface.

The transition area 315 helps to reduce overlapping effects between the essentially planar sub-area 314 and the wing 301.

At the span limit 305, the end 309 of the upper winglet 304 essentially coincides with the end 311 of the lower winglet 307 in the vertical xz plane. An included angle between the upper and the lower winglet 304, 307 is around 84 °. It is preferable that this angle is at least 80 ° in order to avoid overlapping effects between the upper and lower winglets 304, 307. Since the intersection is on the lower surface of the integrated transition area 315, the angle between the tangent of the lower transition area surface and the lower winglet 307 is measured. An included angle between the wing plane 308 and the lower winglet 307 is around 125 °. The essentially flat partial area 314 of the upper winglet 304 has an angle of inclination in relation to the vertical xz plane of around 7 ° to 15 °.

The lower winglet element 307 has an element floor plan area of ​​approximately 25% of the floor plan area of ​​the upper winglet element 304. While the upper winglet 307 is essentially flat, it may have some wing twisting from the root 312 to the end 311. The lower winglet 307 may additionally or alternatively have a toe-in or toe-out angle to optimize low speed performance. Similarly, the upper winglet 304 may have some wing twist and may have a toe-in or toe-out angle. The lower winglet 307 has a positive arrow angle, and in particular the leading edge has a positive arrow arrow. The upper winglet 304 is also

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AT 14 481 U2 2015-11-15 Austrian patent office with a positive arrow and has a positively arrowed front edge and a positively arrowed rear edge.

If the ground clearance limits allow, the lower winglet element 307 could be replaced by an uneven lower winglet element, similar to that described above with reference to FIG.

FIG. 9 illustrates a combination of aircraft wing and wing end device, comprising a wing 401, an integrated upper winglet 404 and a flat lower winglet 407. The wing 401 has an outboard end 403 and defines a wing plane 408. The upper winglet 404 includes a substantially planar portion 414 and an integrated transition area 415. The transition area 415 allows the outboard end 403 of the wing 401 to run uniformly into the essentially flat partial area 414 of the upper winglet 404. The transition region 415 is an unevenly curved wing tip extension that has a continuously increasing curvature of the local dihedron, a continuously increasing positive sweep (both at the leading and trailing edge) and a profile chord that continuously decreases in the outboard direction. The unevenly curved wing end extension region 415 ensures an improved drag performance for the upper winglet 404 compared to the integrated upper winglet 304 shown in FIG.

The upper winglet 404 has a root 410 and an end 409. The essentially flat partial area 414 of the upper winglet 404 has an angle of inclination of around 7 ° to the vertical xz plane. A substantially planar lower winglet 407 is attached to the lower surface of the uneven curved airfoil end extension portion 415 of the upper winglet 404. The lower winglet 407 has an end 411 and a root 412. The root chord of the lower winglet 407 intersects with the upper winglet 404, and the lower winglet protrudes downward from the intersection.

An included angle between the upper and the lower winglet 404, 407 at the interface is around 86 °. Since the intersection is on the lower surface of the uneven curved wing tip extension portion 415 of the upper winglet 404, this angle is measured from a local surface tangent to the lower surface of the uneven curved wing tip extension portion 415 at the intersection. This included angle is preferably greater than 80 ° in order to avoid overlapping effects between the upper and lower winglets 404, 407. An included angle between the wing plane 408 and the lower winglet is around 124 °. At the span limit 405, the end 409 of the upper winglet 404 essentially coincides with the end 411 of the lower winglet 407 in the vertical xz plane.

FIGS. 10 and 11 illustrate a perspective view and a top view, respectively, of the combination of aircraft wing and wing end device of the fourth embodiment. From FIG. 10 in particular it can be seen that the trailing edge 416 of the upper winglet 404 and the trailing edge 417 of the lower winglet 407 essentially adjoin one another at the interface. The trailing edges 416, 417 are sufficiently close that the wake vortex from the lower winglet 407 does not essentially overlap with the flow over the upper winglet 404. The upper winglet 404 has a leading edge 418 that is swept positively, and the lower winglet 407 also has a leading edge 419 that is swept positively. The trailing edge 416 of the upper winglet 404 is swept positively, and the trailing edge 417 of the lower winglet 407 is also swept positively.

In FIG. 11, the top view (ie, the view from top to bottom in the x-y plane) illustrates how the upper winglet 404 shades at least part of the lower winglet 407 ″.

This is due to the coincidence of the ends 409, 411 of the upper and lower winglets 404, 407 in the vertical xy plane. As best seen in Figure 10, the root chord 412 of the lower winglet 407 only takes at the intersection

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AT 14 481 U2 2015-11-15 Austrian patent office a part of the local chord of the upper winglet 404. On and the close correspondence of the trailing edges 416, 417, the leading edge 419 of the lower winglet 407 is arranged essentially behind the leading edge 418 of the upper winglet 404.

FIG. 12 illustrates a combination of aircraft wing and wing end device according to a fifth embodiment, comprising a wing 501 with a wing end device which comprises an upper uneven wing end extension 504 and a lower flat winglet 507. The airfoil 501 has an outboard end 503 and defines a wing plane 508. The uneven wing tip extension 504 has a root 510 and an end 509 and is attached to the outboard end 503 of the wing 501 by its root 510. The uneven wing tip extension 504 has a continuously increasing curvature of the local dihedron, a continuously increasing positive sweep (at both the leading and trailing edges 518, 516) and a continuously decreasing chord in the outboard direction, y.

The uneven airfoil end extension 504 is substantially uneven from the root 510 to the end 509. The end 509 forms an angle of inclination of approximately 8 ° with the vertical xz plane. The lower winglet 507 has an end 511 and a root 512, and the chord intersects the uneven curved airfoil end extension 504 with the lower winglet 507 protruding downward from the intersection. An included angle between the uneven airfoil end extension 504 and the lower winglet 507 is approximately 82 °. This angle is measured between the lower winglet 507 and a local surface tangent to the lower surface of the uneven curved airfoil end extension 504 at the intersection. An included angle between the wing plane 508 and the lower winglet 507 is approximately 126 °. The ends 509, 511 of the uneven curved airfoil end extension 504 and of the lower winglet 507 essentially coincide at the span limit 506 in the vertical xz plane.

FIG. 13 illustrates the wing end device according to the fifth embodiment in a perspective view and clearly shows that the trailing edge 516 of the uneven, curved wing end extension 504 at the interface essentially coincides with the trailing edge 517 of the winglet 507. Both the uneven curved wing tip extension 504 and the lower winglet 507 have a positive arrow angle, and the leading and trailing edges 516, 517, 518, 519 each have a corresponding positive arrow angle.

The lower winglet 507 can only be substantially flat and can have a winglet twist from the root to the end and a toe-in or toe-out angle in relation to the free flow flow. Similarly, the uneven curved airfoil end extension 504 may have wing twist and a toe-in or toe-out angle relative to free flow flow. The lower winglet 507 can be replaced by a substantially uneven curved lower winglet, similar to that described above with reference to FIG. 7, if the ground-level clearance limits permit.

Each of the second to fifth embodiments described above with reference to FIGS. 7 to 13 is shown with the respective combination of hydrofoil and hydrofoil end device in its bottom shape. Due to aerodynamic loads on the wing during flight, the deformation of the wing will cause the wing end device to rotate about the wing root such that the end of the lower wing-like element extends further outboard in the spanwise direction than the end of the upper wing-like element. The lower wing-like element therefore always ensures an increase in the wingspan compared to the wing end devices, which in each case only have the upper wing-like element.

The wing end devices described in the first through fifth embodiments can be installed or retrofitted to the outboard end of an aircraft wing that either does not have a wing end device or as a replacement for an existing wing end device. Furthermore, the lower wing-like member can be used as a

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AT 14 481 U2 2015-11-15 modification to be retrofitted for an existing wing end device which has only one upper wing-like element, so as to form a wing end device according to this invention.

Although the invention has been described above with reference to one or more preferred embodiments, it will be recognized that various changes or modifications can be made without departing from the scope of the invention as defined by the appended claims.

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AT 14 481 U2 2015-11-15 Austrian

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