Aircraft with a wing tip comprising a fuel pod

Abstract

An aircraft comprising a wing, the wing having a connection interface at the tip of the wing, and the wing being interchangeable between a first configuration in which a first wing tip is connected to the connection interface, and a second configuration in which a second wing tip is connected to the connection interface to replace the first wing tip. The second wing tip comprises a fuel pod for carrying additional fuel, and a wing tip device for improving aerodynamic efficiency. The wing may be designed for performance in both configurations.

Claims

1. An aircraft, comprising: an aircraft wing, the wing having a connection interface at the tip of the wing, and the wing being interchangeable between a first configuration in which a first wing tip is connected to the connection interface, and a second configuration in which a second wing tip is connected to the connection interface to replace the first wing tip, wherein the second wing tip comprises a fuel pod and wherein the wing has been designed for performance in both the first and the second configurations, and wherein the second wing tip comprises a winglet for improving aerodynamic efficiency of the aircraft.

2. An aircraft according to claim 1 wherein the center of mass of the fuel pod is positioned along the axis of twist of the wing, such that when the wing changes from the first to the second configuration, the twist of the wing is not altered, thereby maintaining substantially similar handling qualities in the second configuration as in the first configuration.

3. An aircraft according to claim 1, wherein the first wing tip also comprises a fuel pod, the capacity of the fuel pod in the first wing tip being different to the capacity of the fuel pod in the second wing tip.

4. An aircraft according to claim 1, wherein in the aircraft is arranged such that in the second configuration, the second wing tip is unable to be disconnected from the interface during flight.

5. An aircraft according to claim 1, wherein the connection interface is configured to receive a multiplicity of different wing tips, and the wing is interchangeable between a multiplicity of configurations in each of which a different respective wing tip is connected to the connection interface.

6. An aircraft according to claim 5, wherein the wing has been designed for performance in the multiplicity of configurations.

7. A kit of parts comprising: an aircraft according to claim 1, a first wing tip having a connector for connecting to the connection interface, and a second wing tip having a connector for connecting to the connection interface such that the first and second wing tips can be interchangeably used on the wing for flying different mission profiles.

8. A method of designing a wing for an aircraft, the wing having a connection interface at its tip for receiving a plurality of different wing tips, and the wing being interchangeable between a first configuration in which a first wing tip is connected to the connection interface, and a second configuration in which the first wing tip is replaced by a second wing tip connected to the connection interface, wherein the second wing tip comprises a fuel pod, wherein the second wing tip comprises a winglet for improving aerodynamic efficiency of the aircraft, and wherein the method comprises the step of designing the wing for performance in both the first and the second configurations.

9. A method according to claim 8, wherein the step of designing the wing comprises designing for the aircraft flying a first mission profile in the first configuration, and for the aircraft flying a second mission profile in the second configuration.

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 an aircraft according to a first embodiment of the invention;

(3) FIGS. 2a to 2c are schematics showing part of a wing of the aircraft in FIG. 1 in three different configurations;

(4) FIGS. 3a and 3b are close-up view of the wing tip in FIG. 2c;

(5) FIG. 4 is a flowchart showing a method used to design the wing of the aircraft in FIG. 1;

(6) FIG. 5 is a flowchart showing a method according to a second embodiment, by which a wing tip is designed.

DETAILED DESCRIPTION

(7) FIG. 1 shows a passenger aircraft 1 according to a first embodiment of the invention. The aircraft 1 comprises a fuselage 3 and wings 5. The aircraft is shown with its wings in a first configuration in which a winglet 7 is mounted on the end of the wing.

(8) The winglet 7 attaches to its respective wing 5 at a wing-box-to-wing-tip connection interface 9 (not visible in FIG. 1 but see FIGS. 2a to 2c). In the first embodiment of the invention, the connection interface 9 is arranged to receive three different wing tips: firstly, the winglet 7 in FIGS. 1 and 2a, secondly a wing tip 11 comprising the combination of fuel pod 13 and winglet 7 in FIG. 2b, and thirdly a wing tip 15 comprising the combination of fuel pod 13 and (another) winglet 7 in FIG. 2c. The structure of the wing tips and the related advantages will now be described in more detail with reference to FIGS. 2a to 4.

(9) FIGS. 2a to 2c are schematics showing part of a wing 5 of the aircraft in FIG. 1 in three different configurations. In FIGS. 2a to 2c, the wing flaps and ailerons are not shown.

(10) FIG. 2a shows the wing 5 in a first configuration, in which the wing tip comprises the winglet 7. The winglet 7 is joined to the wing at the connection interface 9.

(11) FIG. 2b shows the wing in a second configuration, in which the wing tip of FIG. 2a, has been replaced with a different, second, wing tip 11. The second wing tip 11 comprises both a winglet 7 and a fuel pod 13. This wing tip 11 is connected to the same connection interface 9. The winglet 7 is larger than the winglet 7 of the first wing tip and increases the wing span to 38m (compared to 36m with the first wing tip)

(12) FIG. 2c shows the wing 5 in a third configuration, in which the wing tip 11 of FIG. 2b, has been replaced with a different, third, wing tip 15. The third wing tip 15 comprises a larger fuel pod 13 and a different (larger) winglet 7. This third wing tip 15 is connected to the same connection interface 9. The winglet 7 is larger than the winglets 7 and 7 of the other wing tips and increases the wing span to 42m.

(13) By providing a common connection interface 9 arranged to receive all the wing tips of FIGS. 2a to 2c, it is possible for different wing tips to interchangeably be installed on the wing 5, depending on which wing tip is most suitable for a particular mission profile. This enables the aircraft 1 to be relatively flexible in its use. Furthermore, by providing a wing tip which comprises a fuel pod, the use of the aircraft is especially flexible because the range of the aircraft can readily be increased.

(14) As shown in FIGS. 2b and 2c, in the second and third configurations the wing tips 11, 15 comprise both a fuel pod 13, 13 and a wing tip device 7, 7. The wing tip device increases the effective span of the aircraft (the span increase in FIG. 2c being even greater than the span increase in FIG. 2b). In both configurations this span increase facilitates improved aerodynamic efficiency (compared to just adding the fuel pod in isolation). Providing wing tips that comprise the combination of a fuel pod and a wing tip device, is especially beneficial in increasing the range of an aircraft having a fixed payload (for example a fixed passenger capacity). This is because there is not only additional fuel capacity (in the fuel pod), but the fuel is also more efficiency used by virtue of having the wing tip device . . . . By way of example with reference to the first embodiment, the aircraft 1 can carry 170 passengers over a range of around 2700 nm in the first configuration in FIG. 2a; it can carry 170 passengers over a range of around 3500 nm in the second configuration in FIG. 2b, and it can carry 170 passengers over a range of around 3900 nm in the third configuration in FIG. 2c. The MTOW is increased slightly such that the aircraft is able to operate in the second and third configurations.

(15) FIGS. 3a and 3b are close-up views of the wing tip in FIG. 2c. As shown in FIG. 3a, the fuel pod 13 is an axially-symmetric streamlined body and is mounted such that its underside is substantially flush with the lower surface of the wing 5. This arrangement ensures that the fuel in the pod is able to be access via a gravity feed, in the event of a fuel pump failure. As shown in FIG. 3b, the chord-wise location of the fuel pod 13 is such that the centre of mass of the fuel pod 13 (when full, part-full and empty) lies along the line of twist (not shown) of the wing 5. This ensures the presence of the pod 13 does not significantly alter the handling properties of the wing, when the wing is in the third configuration.

(16) As is well known, the presence of a winglet increases the lift in the tip region of a wing and therefore increases the wing root bending moment. The arrangements in FIGS. 2b and 2c have been found to be particularly beneficial because they recognise that the increase in wing root bending moment can be offset, to at least some extent, by the weight of the fuel pod generating a bending moment in the opposite direction.

(17) In principle, it would be possible to use the above-mentioned common connection interface 9 on an existing aircraft wing. However, that wing will have been designed for use either without a wing tip fitted at all, or with a specific wing tip device fitted. If a different type of wing tip were to be fitted (e.g. any of the tips shown in FIGS. 2a-c), the wing would not have been designed for performance with that different tip device. This may limit the magnitude of any benefits obtainable through use of the new wing tip.

(18) The wings 5 of the aircraft in FIG. 1 has been designed using a novel method according to an embodiment of the present invention. That method is described in the flowchart in FIG. 4, to which reference is now made.

(19) The method starts from a first initial wing design for use in a first configuration with the wing tip of FIG. 2a (i.e. the winglet 7) fitted, a second initial wing design for use in a second configuration with the wing tip 11 of FIG. 2b (i.e. the winglet 7 and fuel pod 13) fitted, and a third initial wing design for use in a third configuration with the wing tip 15 of FIG. 2c (i.e. the winglet 7 and fuel pod 13) fitted. The method comprises iteratively re-designing these initial wings (the loop on the right-hand side of FIG. 4) to arrive at a common design in which the wing is designed for performance with all of the three different wing tips fitted. This iterative design process also takes into account the different mission profiles the aircraft would fly with the respective wing tip device fitted.

(20) Thus, whilst in each configuration in isolation the wing design may be sub-optimal, the present invention recognises that by designing for performance in all the configurations, the final wing design achieves a better balance of performance (in comparison to purely optimising for one configuration as per the prior art). This, in turn, enables the advantages of having interchangeable wing tips, comprising fuel pods, to be more-fully realised.

(21) The first embodiment of the invention provides a wing that is designed for three different configurations of wing tip. It has been recognised that it may also be desirable to provide a combination of fuel pod and wing tip device that is designed for a particular wing. FIG. 5 is a flow-chart of a second embodiment of the invention, showing a novel method of how a wing tip was designed. The method starts from a baseline wing design and the identification of redundant structural margins in that baseline wing (for example redundant structural capacity that has arisen due to the existence of other aircraft components and their influence on the wing structure). The method comprises the steps of iteratively designing three different wing tips (a first tip that just comprises a wing tip device (configuration 1), a second tip that comprises both a fuel pod and a wing tip device (configuration 2), and a third tip that comprises a larger fuel pod and longer wing tip device (configuration 3)). Each wing tip is iteratively designed such that when the respective wing tip is attached to the wing, at least some of the redundant structural margins of the wing are used during flight of the aircraft. The second embodiment of the invention thus recognises that a wing may have redundant structural margins, and that those can be used by appropriately tailoring the wing tip design. For example in the second embodiment, the lift distribution and sweep of the wing tip devices are tailored to make use of the otherwise redundant structural margins.

(22) Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. For example, in the first configuration, the wing tip may comprise just a fuel pod (but no tip device). 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.