Winglet and method of designing a winglet

Abstract

An aircraft (5) including a wing (3) and a winglet (1) at the end of the wing, the winglet including: a root (7); a tip (9); a transition region (11) extending away from the root; and a wing-like region (13) extending from the distal end of the transition region to the tip. When the aircraft wing (3) is under the worst-case static loading, the tip of the winglet is located at the maximum spanwise extent of the winglet (1), but when the aircraft wing (3) is under the no-load condition, the wing-like region (13) is canted inboard such that the tip (9) of the winglet (1) is located inboard of the maximum spanwise extent of the winglet.

Claims

1. An aircraft comprising: a wing, and a winglet at an end of the wing, the winglet comprising: a root, a tip at an upper region of the winglet, a transition region extending away from the root; and a wing-like region extending from a distal end of the transition region to the tip, wherein, when the aircraft wing is under a worst-case static loading, the tip of the winglet is located at a maximum spanwise extent of the winglet; wherein, when the aircraft wing is under a no-load condition, the wing-like region is canted inboard with respect to a vertical plane such that the tip of the winglet is located inboard of the maximum spanwise extent of the winglet, and wherein the winglet while in the no-load condition has a shape corresponding to a jig shape of the winglet.

2. The aircraft according to claim 1, wherein the wing-like region comprises a planar portion extending to the winglet tip.

3. The aircraft according to claim 2, wherein when the aircraft wing is under the worst-case static loading, the planar portion extends vertically downward from the winglet tip such that the planar portion lies along the maximum spanwise extent of the winglet, and when the aircraft wing is in the no-load condition the planar portion is canted inboard with respect to the vertical plane.

4. The aircraft according to claim 2, wherein an entirety of the wing-like region is planar.

5. The aircraft according to claim 1, wherein when the aircraft is in flight under 1-g flight conditions, the wing-like region is canted further inboard, relative to when the aircraft wing is under the no-load condition, such that the tip of the winglet is located yet further inboard of the maximum span of the winglet.

6. A method of designing a winglet for an aircraft wing, the method comprising the steps of: (i) determining a maximum allowable wing span for the aircraft wing when it is under worst-case static loading; (ii) designing the winglet such that, when the aircraft wing is under worst-case static loading, a tip at an upper region of the winglet is located at a maximum winglet span of the winglet and the wing-like region is aligned with a vertical plane, wherein a maximum wing span of the aircraft wing when the winglet is at the maximum winglet span is no greater than the maximum allowable span of the aircraft wing, and (iii) designing a required jig shape of the winglet to achieve the winglet design of step (ii) by canting a wing-like region of the jig shape of the winglet inboard with respect to the vertical plane to locate the tip of the winglet inboard of the maximum span of the winglet, wherein the wing-like region extends from a tip of the winglet to a transition region of the winglet between the tip and a root of the winglet, wherein the jig shape of the winglet corresponds to a non-load condition of the winglet and the jig shape of the winglet positions a portion of the winglet beyond the maximum winglet span of the winglet.

7. The method of manufacturing a winglet, comprising: designing a winglet using the method according to claim 6; and subsequently manufacturing the winglet to the design of the winglet.

8. An aircraft comprising a wing and a winglet at an end of the wing, and the winglet includes a wing-like region extending from a tip at an upper region of the winglet to a curved transition region of the winglet, and wherein when the aircraft wing is under a worst-case static loading, the wing-like region of the winglet extends vertically and upward, and when the aircraft wing is under a no-load condition, the wing-like region of the winglet is canted inboard with respect to a vertical plane such that a tip of the winglet is located inboard of a maximum spanwise extent of the winglet, and wherein the winglet while in the no-load condition has a shape corresponding to a jig shape of the winglet.

Description

DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

(2) FIG. 1 shows a frontal view of a winglet on a wing of an aircraft according to a first embodiment of the invention, the aircraft wing being under a worst-case static load;

(3) FIG. 2 shows a frontal view of the winglet of FIG. 1 in a no-load condition.

(4) FIG. 3 shows a frontal view of the winglet of FIG. 1, the aircraft being under a 1-g flight condition;

(5) FIG. 4 overlays the winglets of FIGS. 1 to 3 in one image;

(6) FIG. 5 shows a frontal view of the aircraft in the first embodiment of the invention;

(7) FIG. 6a shows a comparison between a previously-suggested winglet and the winglet of FIG. 1, when the aircraft is under a worst-case static load;

(8) FIG. 6b shows a comparison between the previously-suggested winglet and the winglet of FIG. 1, when the aircraft is under a 1-g flight condition; and

(9) FIG. 7 overlays winglets of a second embodiment of the invention in one image.

DETAILED DESCRIPTION

(10) FIG. 1 shows a frontal view (i.e. in the y-z plane) of a winglet 1 at the end of a wing 3 of an aircraft 5 according to a first embodiment of the invention (the aircraft being shown schematically in FIG. 5) The winglet comprises a root 7, a tip 9, a curved transition region 11, and an upwardly extending, substantially planar, wing-like region 13 extending from the distal end 11 of the transition region 11 to the tip 9. The leading edge of the winglet is shown as a dashed line.

(11) In FIG. 1, the wing 3 is shown with the aircraft stationary on the ground and with a full fuel load (i.e. the worst-case static load). Under this load condition, the planar portion 13 extends vertically downwards from the tip 9. As indicated by the vertical dashed line 15, the maximum spanwise extent of the winglet 1 is therefore defined by the winglet tip 9 and the vertical planar portion 13 extending downwardly therefrom (marked between two X's in FIG. 1).

(12) It is desirable to maximise the effective length of the wing within the confines of any airport restrictions on wing span. Accordingly, the tip 9 and the vertical portion 13 are also at the maximum span (Smax) set by the airport gate compatibility limit (e.g. see wing spans in FAA groups I to IV or ICAO codes A to F).

(13) In FIG. 2, the wing 3 and winglet 1 are shown in a no-load condition (i.e. in their jig shape). In the jig shape, the planar portion 13 in canted inwardly such that the tip 9 is moved inboard (relative to the worst-case static load condition). Accordingly, the maximum spanwise extent of the winglet 1 is then shifted lower down the winglet 1 to the junction 11 between the transition region 11 and the planar portion 13 (marked with an X in FIG. 2). The magnitude of that span is also slightly reduced (see FIG. 6a).

(14) In FIG. 3, the wing 3 and winglet 1 are shown in a 1-g flight condition. In the flight condition, the wing 3 is flexed upwards under aero-elastic loading and the planar portion 13 in canted further inward such that the tip 9 is moved further inboard (relative to the worst-case static load condition and the no-load condition). The maximum spanwise extent of the winglet is shifted onto the transition region 11 (marked with an X in FIG. 3). The magnitude of that span is also further reduced.

(15) FIG. 4 overlays the images of the winglet in the three load conditions of FIGS. 1 to 3, which illustrates the above-mentioned changes in the magnitude of the span and the location of the point of maximum span on the winglet.

(16) As is evident from FIG. 4, the winglet tip 9 and planar portion 13 are at the maximum spanwise extent when the wing is under worst-case static loading, but are canted inboard (sometimes referred to as being over-canted) in the jig shape. This arrangement is beneficial. Firstly, it ensures the aircraft should always be complying with airport compatibility gate limits as it is sized for the worst-case load scenario. Secondly, by providing the tip and planar portion extending along the span limit (in the worst-case static loading conditions) the total un-rolled length of winglet is relatively long because it pushes the transition region outboard which, when the root and tip locations are fixed, increases the length between these end points, and hence increases the unrolled length of the winglet.

(17) These benefits can be seen in FIGS. 6a and 6b which compare the winglet 1 of the first embodiment of the invention with a previously suggested winglet 101 (shown on the left-most side of FIG. 6a/6b). Referring first to FIG. 6a the winglets 1, 101 are shown overlaid with one another when attached to a common wing 3. FIG. 6a shows the wing under a worst-case static load.

(18) It can be seen from FIG. 6a that the transition region 11 on the winglet of the first embodiment of the invention is necessarily further outboard (than the region 111 on the previously suggested winglet 101) in order to blend into the vertical planar portion 13. Since the root 3 and tip 9, 109 locations are largely the same for both winglets 1, 101 the unrolled length of the winglet 1 of the first embodiment is longer than the unrolled length of the previously suggested winglet 101. This provides a winglet with a longer effective length, and with a more open transition region, both of which give rise to improved aerodynamic performance (primarily in terms of a drag reduction).

(19) FIG. 6b shows the wing under a 1-g flight load. It can be seen that in this load condition, the previously suggested winglet 101 has a planar portion 113 that is essentially vertical, whereas on the winglet of the first embodiment of the invention, the tip 9 of the winglet is moved inboard such that the planar portion 13 is over-canted. The maximum spanwise extent of the winglet 1 is moved lower down the winglet to the transition region. Thus, the tips 9, 109 of the two different winglets are essentially coincident at this load condition, yet the total span of the aircraft is greater with the winglet of the first embodiment of the invention.

(20) Whilst the present invention has been described and illustrated with reference to the first embodiment, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations. By way of example, the winglet may also be used as part of a wing tip device having a downwardly extending winglet 201b. Such an embodiment is shown in FIG. 7, which illustrates such a wing tip device 201 in the three load conditions (worst-case static load (lower-most image), no-load condition (middle image), and 1-g flight load (upper-most image). The upwardly extending winglet 201a is essentially the same as the first embodiment, but the downwardly extending winglet 201b seeks to offset some of the span reduction experienced when the aircraft is in 1-g flight.

(21) Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.