GB2568731A

GB2568731A - Modifying the chord length of an aircraft wing

Info

Publication number: GB2568731A
Application number: GB1719583.5A
Authority: GB
Inventors: Alderman James; John Lyons Neil
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2017-11-24
Filing date: 2017-11-24
Publication date: 2019-05-29
Anticipated expiration: 2037-11-24
Also published as: GB2568731B; GB201719583D0

Abstract

A system for modifying the chord of a wing 1 of an aircraft comprises a flap 10 and an actuating system configured to translate the flap 10 in a direction substantially parallel to the chord of the wing, between a first position (figure 1a) and a second position (figure 1b), such that the wing has a first chord length when the flap 10 is in the first position, and a second different chord length when the flap 10 is in the second position. The actuating system is configured to move the flap to a deployed position (figure 4a) wherein the flap 10 is translated aft and rotated about a longitudinal axis of the flap, relative to the first position. The system comprises a lower shroud 30 configured to form a substantially continuous surface between a lower surface of the wing and a lower surface of the flap when the flap is in the first position and in the second position. The lower shroud 30 may move up to contact an upper shroud 40, when the flap 10 is in the deployed position, creating a slot 60.

Description

TECHNICAL FIELD [0001] The present invention relates to systems and methods to modify the chord length of an aircraft wing, to an aircraft wing, and to an aircraft.

BACKGROUND [0002] Many aircraft wings comprise components such as spoilers and flaps, designed to change the shape of the aircraft wing and thus alter the performance characteristics of the aircraft wing. A flap normally forms part of a trailing edge of an aircraft wing and can be movable relative to a main fixed wing portion. The chord length of an aircraft wing is generally fixed in cruise flight.

SUMMARY [0003] A first aspect of the present invention provides a system for modifying the chord length of a wing of an aircraft, the system comprising a flap, an actuating system configured to move the flap from a first position to a second position and to a deployed position, wherein in the second position the flap is translated relative to the first position in a direction substantially parallel to the chord of the wing, such that the wing has a first chord length when the flap is in the first position, and a second different chord length when the flap is in the second position, and in the deployed position, the flap is translated aft and rotated about a longitudinal axis of the flap, relative to the first position, and a lower shroud configured to form a substantially continuous surface between a lower surface of the wing and a lower surface of the flap when the flap is in the first position and in the second position.

[0004] Optionally, the orientation of the flap is substantially the same in the first position and the second position.

[0005] Optionally, the lower shroud is configured to remain in contact with the lower surface of the flap when the flap is translated by the actuating system between the first position and the second position.

[0006] Optionally, the system comprises an upper shroud to form a substantially continuous surface between an upper surface of the wing and an upper surface of the flap when the flap is in the first position and in the second position.

[0007] Optionally, the upper shroud is configured to remain in contact with respective upper surface of the flap when the flap is translated by the actuating system between the first position and the second position.

[0008] Optionally, the upper shroud is a spoiler. Optionally, the lower shroud is a spoiler.

[0009] Optionally, the lower shroud is biased towards a position in which the lower shroud is in contact with the lower surface of the flap.

[0010] Optionally, at least a portion of the lower shroud is flexible.

[0011] Optionally, when the flap is in the deployed position, the lower shroud is configurable in a slotted position and in a contact position, wherein, in the slotted position, the lower shroud is positioned to create a slot between a trailing edge of the wing and a leading edge of the flap, and wherein, in the contact position, the lower shroud is in contact with the lower surface of the flap.

[0012] Optionally, the actuating system is configured to translate the flap non-uniformly across the span of the flap.

[0013] Optionally, the actuating system comprises a plurality of tracks along the span of the flap, wherein each track of the plurality of tracks extends in a direction substantially parallel to the chord of the wing, and wherein the actuating system is configured to translate the flap along a first track of the plurality of tracks by a first amount, and along a second track of the plurality of tracks by a second different amount.

[0014] Optionally, the system comprises a controller configured to cause the actuating system to translate the flap between the first position and the second position, and adjust the orientation of the lower shroud to maintain contact between the lower shroud and the lower surface of the flap during the translation.

[0015] A second aspect of the present invention provides a method of modifying the chord length of a wing of an aircraft, the method comprising translating a flap with an actuating system in a direction substantially parallel to the chord of the wing, between a first position and a second position, such that the wing has a first chord length when the flap is in the first position, and a second different chord length when the flap is in the second position, and maintaining a substantially sealed aerofoil during the translating, wherein the actuating system is further configured to move the flap from the first position to a deployed position in a fowler motion.

[0016] Optionally, the method comprises maintaining contact between an upper surface of the flap and an upper shroud and between a lower surface of the flap and a lower shroud, during the translating.

[0017] Optionally, the method comprises performing the translating non-uniformly across the span of the flap.

[0018] A third aspect of the present invention provides an aircraft wing comprising a main fixed wing portion, a flap, and a mechanism to translate the flap in a direction substantially parallel to the chord of the wing and to move the flap in a fowler motion, wherein the aircraft wing is configured to remain in a substantially sealed aerofoil configuration when the flap is translated by the mechanism.

[0019] A fourth aspect of the present invention provides an aircraft comprises a system according to the first aspect of the present invention or an aircraft wing according to the third aspect of the present invention.

[0020] A fifth aspect of the present invention provides an aircraft configured to perform a method according to the second aspect of the present invention during a cruise phase of flight.

BRIEF DESCRIPTION OF THE DRAWINGS [0021] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0022] Figures la and lb show schematic cross-sectional side-views of an aircraft wing according to an embodiment of the present invention;

[0023] Figure 2 shows a schematic cross-sectional side-view of an aircraft wing according to an embodiment of the present invention;

[0024] Figures 3a and 3b show schematic plan views of an aircraft wing according to an embodiment of the present invention;

[0025] Figures 4a and 4b show schematic cross-sectional side-views of an aircraft wing according to an embodiment of the present invention;

[0026] Figure 5 shows a schematic diagram of a system according to an embodiment of the present invention;

[0027] Figure 6 is a flow diagram showing an example of a method according an embodiment of the present invention; and [0028] Figure 7 is a schematic front view of an example of an aircraft according to an embodiment of the present invention.

DETAILED DESCRIPTION [0029] Some types of flap motion include aft translation accompanied with downward rotation of a flap, relative to a main fixed wing portion. An example of such a motion is fowler motion. When an aircraft wing flap is moved from a retracted position to a deployed position with fowler motion a slot effect is observed when a gap is formed between the main fixed wing portion and the flap. The gap forces high pressure air from below the wing over the flap, to help airflow over the wing remain attached to the flap, thus increasing lift. Fowler motion is typically used to increase wing lift during low speed parts of the flight envelope, such as approach and take-off. Although this application describes a system configured to move a flap in a fowler motion, the present invention could be applied to other types of flap motion.

[0030] Figures la and lb show schematic cross-sectional side-views of an aircraft wing according to embodiments of the present invention. The wing 1 comprises a main fixed wing portion 2 and a flap 10, the flap 10 positioned aft of the main fixed wing portion 2 relative to a direction of travel X. The flap 10 is movable in a fowler motion. The flap 10 may extend across a portion of the span of the wing 1 or across substantially all of the span of the wing 1. The flap 10 may comprise a plurality of flap elements positioned longitudinally adjacent to one another along the span of the wing 1. Figure la shows the flap 10 in a first position relative to the main fixed wing portion 2. The flap 10 is oriented relative to the main fixed wing portion 2 such that the wing 1 has a substantially aerofoil cross-section. When the flap 10 is in the first position, the wing 1 has a first chord length A.

[0031] Figure lb shows the wing 1 in a configuration wherein the flap 10 has been translated from the first position to a second position relative to the main fixed wing portion 2. In the second position, the flap 10 is further aft of the main fixed wing portion than in the first position. In the second position, the flap 10 has substantially the same orientation relative to the main fixed wing portion 2 as in the first position, such that the wing 1 has a substantially aerofoil cross-section. When the flap 10 is in the second position, the wing 1 has a second chord length B that is different to the first chord length A. In embodiments of the invention, the second position may be any other position forward or aft of the first position, wherein the orientation of the flap 10 in the second position is substantially the same as the orientation of the flap 10 in the first position.

[0032] In some embodiments, an aircraft wing comprises a main fixed wing portion, a flap, and a mechanism to move the flap in a fowler motion and to translate the flap in a direction substantially parallel to the chord of the wing. The aircraft wing is configured to remain in a substantially sealed aerofoil configuration when the flap is translated by the mechanism. In some embodiments, the mechanism may be comprised in an actuating system.

[0033] Figure 2 shows a schematic cross-sectional side-view of the aircraft wing 1 according to some embodiments of the present invention. The aircraft wing 1 comprises a system 100 for modifying the chord length of the wing 1. The system 100 comprises the flap 10, an actuating system 20 and a lower shroud 30.

[0034] The actuating system 20 is configured to move the flap 10 between a first position, a second position, and a deployed position. In some embodiments, the flap 10 is moved by the actuating system 20 in a fowler motion. In the first position, the flap 10 is substantially parallel to the wing 1. In the second position, the flap 10 is substantially parallel to the wing 1, and further forward or aft of the first position. In the deployed position, the flap 10 is translated aft and rotated about a longitudinal axis of the flap 10, relative to the first position. The actuating system 20 is further configured to translate the flap 10 in a direction substantially parallel to the chord of the wing, between a first position and a second position, such that the wing has a first chord length A when the flap 10 is in the first position, and a second different chord length B when the flap 10 is in the second position (as shown in Figures la and lb). That is, the actuating system 20 is configured to move the flap 10 between the first and second positions substantially without rotating the flap about an axis parallel to a longitudinal axis of the flap 10. That is, the flap 10 may rotate by ±5° relative to the main fixed wing portion as the flap 10 is translated by the actuating system 20.

[0035] The chord length of the wing 1 may be changed during a cruise phase of flight to change the amount of lift generated by the wing 1. The amount of lift may need to be changed due to a number of different operational parameters, for example the speed of the aircraft. For example, at higher aircraft speeds it may be beneficial to reduce the chord length of the wing 1 and to de-camber the wing 1 by rotating the flap 10 upwards by up to 5° relative to the main fixed wing portion. Rotation of the flap 10 may be achieved by altering a path along which the flap 10 is translated between the first and second positions.

[0036] The lower shroud 30 is configured to form a substantially continuous surface between a lower surface 3 of the wing 1 and a lower surface 13 of the flap 10 when the flap 10 is in the first position and in the second position. The substantially continuous surface may be enabled by the use of a shroud, as described below. Such a configuration helps to allow the wing 1 to maintain an aerofoil shape regardless of whether the flap 10 is in the first position or in the second position which, in turn, can help to configure the wing planform to reduce drag at selected flight conditions.

[0037] In some embodiments, the lower shroud 30 is a spoiler. In some embodiments, the lower shroud 30 is configured to remain in contact with the lower surface 13 of the flap 10 when the flap 10 is translated by the actuating system 20 between the first position and the second position. In the embodiment shown in Figure 2, a leading edge 31 of the lower shroud 30 is pivotally connected to the main fixed wing portion 2 at a lower shroud pivot 34. This allows a trailing edge 33 of the lower shroud clockwise and anti-clockwise about the lower shroud pivot 34 to stay in contact with the lower surface 13 of the flap 10 as the flap 10 is translated between the first and second positions.

[0038] In some embodiments, the lower shroud 30 is biased towards a position in which the lower shroud 30 is in contact with the lower surface 13 of the flap 10. A biasing force may be applied by an actuator or a spring, for example. In some embodiments, at least a portion of the lower shroud 30 is flexible, thereby providing the biasing force. For example, an aft portion of the lower shroud 30 may be flexible and configured to flex to stay in contact with the lower surface 13 of the flap 10 as the flap 10 is translated between the first and second positions.

[0039] In some embodiments, the system 100 comprises an upper shroud 40 configured to form a substantially continuous surface between an upper surface 4 of the wing 1 and an upper surface 14 of the flap 10 when the flap 10 is in the first position and in the second position. Such a configuration helps to allow the wing 1 to maintain an aerofoil shape regardless of whether the flap 10 is in the first position or in the second position which, in turn, can help to reduce drag.

[0040] In some embodiments, the upper shroud 40 is a spoiler. In some embodiments, the upper shroud 40 is configured to remain in contact with the upper surface 14 of the flap 10 when the flap 10 is translated by the actuating system 100 between the first position and the second position. In the embodiment shown in Figure 2, a leading edge 41 of the upper shroud 40 is pivotally connected to the main fixed wing portion 2 at an upper shroud pivot 44. This allows a trailing edge 43 of the upper shroud to move up and down relative to the main fixed wing portion 2 to stay in contact with the upper surface 14 of the flap 10 as the flap 10 is translated between the first and second positions.

[0041] In some embodiments, the upper shroud 40 is biased towards a position in which the upper shroud 40 is in contact with the upper surface 14 of the flap 10. A biasing force may be applied by an actuator, a spring, or the flexibility of the shroud for example.

[0042] Figure 3 a shows a schematic plan view of the aircraft wing 1 according to some embodiments of the present invention, with the flap 10 in the first position. The actuating system 20 may comprise any suitable actuating system for translating the flap 10 between the first and second positions. For example, the actuating system may comprise one or more of an actuator, for example a hydraulic actuator, a motor, a track, and a 4- or 6-bar linkage. Translating the flap 10 causes the planform of the wing 1 to change, thus altering the operational characteristics of the wing 1. In the embodiment shown in Figure 3 a, the actuating system comprises a plurality of tracks 22 along the span of the flap 10. The plurality of tracks 22 define a path along which the flap 10 is moved by the actuating system 20. The plurality of tracks extend in a direction Y substantially parallel with the chord of the wing in plan view, as denoted by arrow Y in Figure 3a, and thus permit movement of the flap 10 in the direction Y. The flap 10 is connected to the plurality of tracks 22 by a plurality of respective carriages (not shown). Movement of each carriage along its respective track 22 is controlled by the actuating system 20. In some embodiments, a leading end of each of the plurality of tracks 22 is substantially parallel to the camber of the wing 1 to permit translation of the flap 10 between the first and second positions.

[0043] In some embodiments, the actuating system 20 is configured to translate the flap non-uniformly across the span of the flap. Such a configuration can help to further increase the operational capabilities of the wing 1. In such embodiments, each of the plurality of respective carriages may be configured to permit a limited amount of rotation of the flap 10 about an axis that is perpendicular to the path defined by the respective track. For example, each carriage may comprise a gimbal.

[0044] By way of example only, translating an outer end 16 of the flap 10 further aft relative to the main fixed wing portion 2 than an inner end 15 of the flap 10 may help to increase the sweep of the wing, which increases the outboard area of the wing 1. This may, for example, help to improve the buffet boundary on the wing 1 so that the aircraft can climb straight to cruise altitude, and/or may increase the load that an aircraft comprising the system 100 can carry.

[0045] In the embodiments shown in Figures 3a and 3b, non-uniformly translating the flap 10 across its span is achieved by the actuating system 20 being configured to translate the flap 10 along a first track of the plurality of tracks 22 by a first amount, and along a second track of the plurality of tracks 22 by a second different amount, as shown by way of example in Figure 3b. In some embodiments, non-uniformly translating the flap 10 across its span is achieved by the actuating system 20 being configured to translate the flap 10 along a first track of the plurality of tracks 22 at a first translation rate, and along a second track of the plurality of tracks 22 by a second different translation rate.

[0046] Figure 3b shows a schematic plan view of the aircraft wing 1 according to embodiments of the present invention, with the flap 10 in the second position. The flap 10 has been translated from the first position (shown in Figure 3a) to the second position by the actuating system 20 moving the flap 10 along each track 22 by a different amount. The inner end 15 of the flap 10 has been translated further aft relative to the main fixed wing portion 2 than the outer end 16 of the flap 10. Such a translation of the flap 10 relative to the main fixed wing portion 2 as shown in Figure 3b can help to move loading on the wing toward an inner end of the wing 1 which, in turn, can help to reduce stress on the outer end of the wing. It will be understood that any other non-uniform translation of the flap 10 can be achieved by varying the distance and/or speed the flap 10 travels along each track 22.

[0047] The actuating system 20 is configured to move the flap 10 to a deployed position in which the flap 10 is translated aft and rotated about a longitudinal axis of the flap 10, relative to the first position. In some embodiments, the flap 10 is translated along the plurality of tracks 22. Figures 4a and 4b show the wing 1 configured with the flap 10 in the deployed position. In some embodiments, the lower shroud 30 is configurable in a slotted position and in a contact position. In some embodiments, the lower is pivotable between the slotted and contact positions at lower shroud pivot 34.

[0048] Figure 4a shows the wing 1 with the flap 10 in the deployed position, and the lower shroud 30 in the slotted positon. In the slotted position, the lower shroud 30 is positioned to create a slot 60 between a trailing edge of the main fixed wing portion 2 and a leading edge 15 of the flap 10. Such a configuration increases lift forces on the wing 1. Embodiments of the present invention permit the use of a lower shroud 30 to form a substantially continuous surface between the main fixed wing portion 2 and the flap 10 when the flap 10 is in the first and second positions, and to form a slot 60 between the main fixed wing portion 2 and the flap 10 when the flap 10 in is the deployed position.

[0049] Figure 4b shows the wing 1 with the flap 10 in the deployed position, and the lower shroud 30 in the contact position. In the contact position, the lower shroud 30 is in contact with the lower surface 13 of the flap 10. Such a configuration may be particularly beneficial during a take-off procedure by improving the lift-to-drag ration, and may thus help to reduce the distance travelled by the aircraft during the take-off procedure.

[0050] In some embodiments, when the system 100 comprises an upper shroud 40, the upper shroud 40 may be configured to be in contact with an upper surface 14 of the flap 10 when the flap 10 is in the deployed position. For example, the upper shroud 40 may pivot about upper shroud pivot 44 to maintain contact between the upper shroud 40 and an upper surface 14 of the flap 10 when the flap 10 is in the deployed position. Such embodiments allow the wing 1 to remain in a substantially sealed aerofoil configuration when the flap is moved to the deployed position.

[0051] Figure 5 shows a schematic view of an embodiment of the system 100. In the embodiment shown in Figure 5, the system 100 comprises a controller 70. The controller 70 is configured to cause the actuating system 20 to translate the flap 10 between the first position and the second position, and to adjust the orientation of the lower shroud 30 to maintain contact between the lower shroud 30 and the lower surface 13 of the flap 10 during the translation. In embodiments wherein the system 100 comprises an upper shroud 40, the controller 70 may be configured to adjust the orientation of the upper shroud 40 to maintain contact between the upper shroud 40 and the upper surface 14 of the flap 10 during the translation. The controller may also be configured to cause the actuating system 20 to move the flap 10 to the deployed position and to move the lower shroud 30 to the slotted position or the contact position when the flap 10 is in the deployed position.

[0052] In some embodiments, the controller 70 is comprised in the wing 1. For example, the controller 70 is positioned within the main fixed wing portion 2. In other embodiments, the controller 70 is comprised in the fuselage of the aircraft. The controller 70 is connected to a central aircraft control system, and may send commands to the actuating system 20 automatically, in response inputs from other systems in the aircraft, and/or the controller 70 may send commands to the actuating system 20 in response to commands received from the cockpit of the aircraft.

[0053] Embodiments of the present invention comprise a method 200 of modifying the chord length of a wing of an aircraft, as depicted in Figure 6. The method 200 comprises translating 210 a flap with an actuating system in a direction substantially parallel to the chord of a wing, between a first position and a second position, such that the wing has a first chord length A when the flap is in the first position, and a second different chord length B when the flap is in the second position. The method 200 further comprises maintaining 220 a substantially sealed aerofoil during the translating 210. The actuating system is configured to move the flap from the first position to a deployed position in a fowler motion. The method may be performed by any embodiment of the system 100 as described herein. The method may be controlled by the controller 70.

[0054] In some embodiments, the method 200 comprises maintaining contact 230 between an upper surface of the flap and an upper shroud and between a lower surface of the flap and a lower shroud, during the translating. In some embodiments, the method comprises performing 240 the translating 210 non-uniformly across the span of the flap.

[0055] Embodiments of the invention provide an aircraft 300, as shown in Figure 7. In some embodiments, the aircraft comprises one or more main landing gears 710 and a nose landing gear 720. In some embodiments, the aircraft 300 comprises a system 100 according to any of the embodiments described herein. Embodiments of the invention provide an aircraft 300 comprise a wing 1 according to any of the embodiments described herein, as shown in Figure 7. Embodiments of the invention provide an aircraft 300 configured to perform a method 200 according to any of the embodiments described herein, during a cruise phase of flight.

[0056] Modifying the chord length of an aircraft wing can provide a larger range of wing configurations, which can help to increase the operational capabilities of the aircraft. For example, a change in chord length of an aircraft wing can increase the area of the wing to reduce sectional loading, and/or change the compressibility drag by changing the thickness-to-chord ratio of the wing, and/or change the skin friction drag by changing the surface area of the wing. Further, being able to modify the chord length of an aircraft wing means that the lift-to-drag ratio of the wing can be optimised for a particular set of flying conditions or a flight phase. In particular, it may be advantageous for the chord length of an aircraft wing to be modifiable whilst the aircraft upon which the aircraft wing is mounted is in a cruise phase, travelling at high speed compared to other phases of flight. It may also be beneficial to modify the chord length of an aircraft wing when an aircraft is in a cruise phase at a non-optimal altitude. Further, the invention can be used to modify the wing during a constant flight level phase as fuel is burned.

[0057] The present invention provides systems and methods to provide a larger range of wing configurations of an aircraft wing. Embodiments of the present invention are concerned with increasing or decreasing the chord length of an aircraft wing without significantly altering the flow of air over the aircraft wing, particularly during a cruise phase of flight. Embodiments of the present invention may help to tailor an aircraft wing to particular operational requirements, rather than needing a different aircraft.

[0058] It is to noted that the term “or” as used herein is to be interpreted to mean “and/or”, unless expressly stated otherwise.

[0059] The above embodiments are to be understood as non-limiting illustrative examples of how the present invention, and aspects of the present invention, may be implemented. Further examples of the present invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the present invention, which is defined in the accompanying claims.

CLAIMS:

Claims

CLAIMS:

1. A system for modifying the chord length of a wing of an aircraft, the system comprising:

a flap;

an actuating system configured to move the flap from a first position to a second position and to a deployed position, wherein;

in the second position, the flap is translated relative to the first position in a direction substantially parallel to the chord of the wing, such that the wing has a first chord length when the flap is in the first position, and a second different chord length when the flap is in the second position; and in the deployed position, the flap is translated aft and rotated about a longitudinal axis of the flap, relative to the first position; and a lower shroud configured to form a substantially continuous surface between a lower surface of the wing and a lower surface of the flap when the flap is in the first position and in the second position.

2. A system according to claim 1, wherein the orientation of the flap is substantially the same in the first position and the second position.

3. A system according to claim 1 or claim 2, wherein the lower shroud is configured to remain in contact with the lower surface of the flap when the flap is translated by the actuating system between the first position and the second position.

4. A system according to any one of the preceding claims, comprising an upper shroud to form a substantially continuous surface between an upper surface of the wing and an upper surface of the flap when the flap is in the first position and in the second position.

5. A system according to claim 4, wherein the upper shroud is configured to remain in contact with the upper surface of the flap when the flap is translated by the actuating system between the first position and the second position.

6. A system according to claim 4 or claim 5, wherein the upper shroud is a spoiler.

7. A system according to any one of the preceding claims, wherein the lower shroud is a spoiler.

8. A system according to any one of the preceding claims, wherein the lower shroud is biased towards a position in which the lower shroud is in contact with the lower surface of the flap.

9. A system according to any one of the preceding claims, wherein at least a portion of the lower shroud is flexible.

10. A system according to any one of the preceding claims, wherein, when the flap is in the deployed position, the lower shroud is configurable in a slotted position and in a contact position, wherein, in the slotted position, the lower shroud is positioned to create a slot between a trailing edge of the wing and a leading edge of the flap, and wherein, in the contact position, the lower shroud is in contact with the lower surface of the flap.

11. A system according to any one the preceding claims, wherein the actuating system is configured to translate the flap non-uniformly across the span of the flap.

12. A system according to claim 11, wherein the actuating system comprises a plurality of tracks along the span of the flap, wherein each track of the plurality of tracks extends in a direction substantially parallel to the chord of the wing, and wherein the actuating system is configured to translate the flap along a first track of the plurality of tracks by a first amount, and along a second track of the plurality of tracks by a second different amount.

13. A system according to any one of the preceding claims, comprising a controller configured to:

cause the actuating system to translate the flap between the first position and the second position; and adjust the orientation of the lower shroud to maintain contact between the lower shroud and the lower surface of the flap during the translation.

14. A method of modifying the chord length of a wing of an aircraft, the method comprising:

translating a flap with an actuating system in a direction substantially parallel to the chord of the wing, between a first position and a second position, such that the wing has a first chord length when the flap is in the first position, and a second different chord length when the flap is in the second position; and maintaining a substantially sealed aerofoil during the translating, wherein the actuating system is further configured to move the flap from the first position to a deployed position in a fowler motion.

15. A method according to claim 14, comprising maintaining contact between an upper surface of the flap and an upper shroud and between a lower surface of the flap and a lower shroud, during the translating.

16. A method according to claim 14 or claim 15, comprising performing the translating non-uniformly across the span of the flap.

17. An aircraft wing comprising:

a main fixed wing portion;

a flap; and a mechanism to translate the flap in a direction substantially parallel to the chord of the wing and to move the flap in a fowler motion;

wherein the aircraft wing is configured to remain in a substantially sealed aerofoil configuration when the flap is translated by the mechanism.

18. An aircraft comprising a system according to any of claims 1-13 or an aircraft wing according to claim 17.

19. An aircraft configured to perform the method of any one of claims 14-16 during a cruise phase of flight.

Intellectual Property Office

Application No: GB1719583.5

Claims searched: 1-19

Examiner: Mr Philip Osman