Aircraft wing and method of adjusting aircraft wing

Abstract

The invention relates to an aircraft wing and a method of adjusting an aircraft wing. The invention relates to an aircraft wing comprising: a fixed wing having a tip; a wing tip device rotatably mounted at the hinge at the tip of the fixed wing such that the wing tip device is rotatable about the hinge; and an actuation system for rotating the wing tip device about the hinge wherein the actuation system comprises a motor, at least one geared rotary actuator, a reduction gearbox, a clutch for selectively disconnecting rotation of the motor from rotation of the geared rotary actuator, the geared rotary actuator is drivable by the motor and is arranged to convert a rotary motion into a different rotary motion and to rotate the wing tip device relative to the tip of the fixed wing, the clutch is coupled to the geared rotary actuator by a shaft and the shaft is rotationally fixed to a mass disposed radially outward from the shaft.

Description

Technical Field

[0001] The present invention relates to an aircraft wing having a movable wingtip arrangement. Background Art

[0002] It is known, for example, from WO2017118832 to use movable wingtip devices during flight. The document teaches an aircraft wing having a fixed wing with a wingtip device movably mounted at its tip, wherein the fixed wing has an upper surface and a lower surface, and the wingtip device has an upper surface and a lower surface, and the wingtip device is capable of operating between: (i) a flight configuration for use during flight, in which the upper and lower surfaces of the wingtip device are a continuation of the upper and lower surfaces of the fixed wing; and (ii) a load-relieved configuration for reducing loads during flight, in which the wingtip device moves relative to the fixed wing so that at least one of the upper and lower surfaces of the wingtip device moves away from the corresponding surface of the fixed wing and the load on the wing is reduced; wherein the aircraft includes a restraint assembly capable of operating between a restraint mode and a release mode, in which the restraint force is used to hold the wingtip device in the flight configuration, and in which the restraint force on the wingtip device is released so that the wingtip device can adopt the load-relieved configuration.

[0003] Once the restraint assembly is in the release mode, the wing tip device can be actuated completely passively to the load-relieved configuration. The wing tip device can move under the action of aerodynamic forces urging the wing tip device toward the load-relieved configuration. Combining the restraint assembly with the articulated wing tip device can be referred to as a "semi-aeroelastic" arrangement.

[0004] The wingtip device may be rotatably mounted on a hinge at the tip of the wing so that it can rotate about the hinge between a flight configuration and a load-reduced configuration. The wingtip device is also movable about the same hinge to a ground configuration for use during ground-based operations, in which the wingtip device is moved away from the flight configuration so that the span of the aircraft wing is reduced.

[0005] The actuation system may be arranged to move the wing tip device between the flight configuration and the ground configuration. The actuation system may also be arranged to move the wing tip device from the load-relieved configuration back to the flight configuration.

[0006] It has been found that when in a load-relieved condition, it may be necessary to adjust the movement of the wing tip arrangement. Summary of the invention

[0007] A first aspect of the present invention provides an aircraft wing, which includes: a fixed wing having a tip; a wingtip device, which is rotatably mounted on a hinge located at the tip of the fixed wing so that the wingtip device can rotate around the hinge; and an actuation system for rotating the wingtip device around the hinge, wherein the actuation system includes a motor, at least one gear-driven rotary actuator, a reduction gearbox, and a clutch for selectively disconnecting the rotation of the motor from the rotation of the gear-driven rotary actuator, the gear-driven rotary actuator being capable of being driven by the motor and arranged to convert the rotational motion into a different rotational motion and being arranged to rotate the wingtip device relative to the tip of the fixed wing, wherein the clutch is connected to the gear-driven rotary actuator via a shaft and the shaft is rotationally fixed to a mass block arranged radially outward from the shaft.

[0008] By this arrangement, the rotational inertia of the wingtip device increases as it rotates relative to the fixed wing. This increase in the rotational inertia of the wingtip device reduces the wingtip flapping frequency and thus increases the flutter speed. Adding a mass that rotates with the shaft minimizes the additional weight required to reduce the gradient of the wingtip device's flapping frequency with increasing aircraft speed, compared to alternative solutions such as adding weight to the wingtip device itself, because the shaft motion is geared relative to the motion of the wingtip device and the inertia of the mass coupled to the shaft is proportional to the square of the gear ratio of the reduction gearbox.

[0009] The hinge may have an articulation line and the shaft may have an axis of rotation coaxial with the articulation line.

[0010] The geared rotary actuator may be arranged along the hinge line of the hinge and have an outer diameter. The shaft may have a shaft diameter that is significantly smaller than the outer diameter of the geared rotary actuator, and the mass may have an outer diameter about the axis that is substantially the same as the outer diameter of the geared rotary actuator.

[0011] The mass can rotate as the wing tip device rotates about the hinge.

[0012] Due to the gearing of the geared rotary actuator, the mass can be rotated at an angular velocity faster than the angular velocity of the wingtip arrangement about the hinge.

[0013] The mass may be in the form of an annulus or a wheel or a ring.

[0014] The shaft may extend through a hole in the mass.

[0015] The mass may comprise tungsten.

[0016] The mass may be less than about 20%, preferably less than 15% of the mass of the wing tip device.

[0017] The mass may be less than about 10%, preferably less than 7%, of the mass of the combined wing tip device and actuation system.

[0018] The mass may increase the rotational inertia of the wing tip arrangement about the hinge by at least 20%, preferably at least 30% or at least 40% or at least 50% compared to the same aircraft wing without the mass.

[0019] The aircraft wing may also include a plurality of geared rotary actuators arranged along the hinge line of the hinge.

[0020] The mass may be disposed between the geared rotary actuator and the clutch.

[0021] The mass may be positioned forward of the geared rotary actuator towards the leading edge of the wing.

[0022] The mass may be disposed between a pair of geared rotary actuators.

[0023] The actuation system may have a maximum damping value that allows oscillatory flapping motion of the wing tip arrangement rotating about the hinge during normal operation with the clutch disengaged.

[0024] The actuation system is back-driveable when the clutch is disengaged to decouple rotation of the motor from rotation of the geared rotary actuator as the wing tip arrangement rotates about the hinge.

[0025] The actuation system may also include a reduction gearbox.

[0026] A reduction gearbox may be disposed between the clutch and the geared rotary actuator along a drive train between the motor and the geared rotary actuator.

[0027] The actuation system may also include means for preventing movement of the geared rotary actuator when the clutch is engaged.

[0028] The actuation system is capable of operating in the following modes: i) a driving mode, in which the clutch is engaged and the motor is driven to rotate the wingtip device about the hinge; ii) a flapping mode, in which the clutch is disengaged and the wingtip device is able to rotate about the hinge by a force external to the wingtip device; and iii) a braking mode, in which the clutch is engaged and the brake prevents rotation of the wingtip device about the hinge.

[0029] The geared rotary actuator may have a first knuckle fixed to the fixed wing and a second knuckle fixed to the wingtip device, wherein the first knuckle and the second knuckle are driven by the geared rotary actuator to rotate relative to each other using motive force provided by the motor.

[0030] The clutch may be configured to disengage during flight for one or more of a) load relief or b) when the aircraft is flying at a relatively low speed or altitude and a relatively high roll rate is required.

[0031] Another aspect of the invention provides a method of tuning an aircraft wing, wherein the aircraft wing is based on the first aspect and the method comprises customising the mass to change the inertia and thereby the frequency at which the wing tip oscillates about the hinge when the clutch is disengaged during flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0033] Figure 1 A plan view of an aircraft having wings and folding wingtip devices is shown;

[0034] Figure 2 Shows Figure 1 A front view of an aircraft with the wing tip device in various configurations;

[0035] Figure 3a , Figure 3b , Figure 3c and Figure 3d Shown in detail Figure 2 wingtip devices;

[0036] Figure 4a Schematically illustrates an actuation system for moving a wingtip device according to the invention;

[0037] Figure 4b More generally shown in block diagram form is Figure 4a Actuation system;

[0038] Figure 4c Shows Figure 4a Detailed views of sections of an actuation system;

[0039] Figure 5 A mechanical actuator according to the invention is shown;

[0040] Fig. 6A shows a graph indicating the increase in flutter velocity due to adding mass to the actuation system;

[0041] Figure 6B shows a graph indicating the change in flap-bending mode coupling due to the addition of mass to the actuation system;

[0042] Figure 7a schematically illustrates a wing tip device operating in a driven mode of operation;

[0043] Figure 7b shows a representation of an actuation system configured to operate in a drive mode;

[0044] Figure 8a schematically illustrates a wingtip device operating in a flapping wing operation mode;

[0045] Figure 8b shows a representation of an actuation system configured to operate in a flapping wing mode;

[0046] Figure 9a schematically shows a second example of an actuation system for moving a wingtip device according to the invention;

[0047] Figure 9b More generally shown in block diagram form is Figure 9a Actuation system;

[0048] Fig.10a A third example of an actuation system for moving a wingtip device according to the invention is schematically shown;

[0049] Fig.10b More generally shown in block diagram form is Fig.10a Actuation system;

[0050] Fig.11a A fourth example of an actuation system for moving a wingtip device according to the invention is schematically shown;

[0051] Fig.11b More generally shown in block diagram form is Fig.11a Actuation system;

[0052] Fig.12a schematically illustrates a wing tip device operating in a braking mode of operation;

[0053] Figure 12b shows a representation of an actuation system configured to operate in a braking mode;

[0054] Fig.13a schematically illustrates a wing tip device operating in a fixed operating mode;

[0055] Fig.13b shows a representation of an actuation system configured to operate in a fixed mode;

[0056] Fig.14 A fifth example of an actuation system for moving a wingtip device according to the invention is schematically shown;

[0057] Fig.15 schematically shows a sixth example of an actuation system for moving a wingtip device according to the invention;

[0058] Fig.16a schematically shows a seventh example of an actuation system for moving a wingtip device according to the invention;

[0059] Fig.16b More generally shown in block diagram form is Fig.16a Actuation system;

[0060] Fig.17a schematically illustrates an eighth example of an actuation system for moving a wingtip device according to the invention;

[0061] Fig.17b More generally shown in block diagram form is Fig.17a actuation system. DETAILED DESCRIPTION

[0062] Figure 1 is a plan view of an aircraft 1. The aircraft comprises a central fuselage 3 and two main wings 5 ​​extending outwardly from respective wing roots 5'.

[0063] Each wing 5 comprises a fixed wing 7 extending from a root 5' to a tip 7'. At the tip 7' of the fixed wing 7, the wing 5 further comprises a movable wingtip device 9 in the form of a flat wingtip extension. The wingtip device 9 is rotatably mounted around a hinge 11. The hinge 11 can be oriented non-parallel to the flight direction line F (or outwardly flared relative to the flight direction line F). The hinge 11 can alternatively be parallel to the flight direction line F.

[0064] In the fixed flight configuration, the wingtip device 9 is fixed relative to the fixed wing 7. The wingtip device 9 may be an extension of the fixed wing. Thus, the upper surface 7a and the lower surface 7b of the fixed wing 7 may be continuous with the upper surface 9a and the lower surface 9b of the wingtip device 9 (see Figure 3a and Figure 2 The leading edge and trailing edge of the fixed wing 7 may also be continuous with the corresponding leading edge and trailing edge of the wing tip device 9. This arrangement is beneficial because it provides a relatively large wing span, thereby providing an aerodynamically efficient aircraft.

[0065] However, a larger wingspan may result in correspondingly larger loads on the wing 5, in particular larger wing root bending moments, and especially during high load events such as gusts or extreme maneuvers. Such larger wing root bending moments may be a problem for relatively large span wings. The wing 5 must be arranged to cope with these maximum loads which may result in a relatively heavy wing, which may not be permissible.

[0066] The wing tip device 9 is in the mobile flight configuration (see Figure 2 , Figure 3b and Figure 3d ) attempts to address this problem. In this configuration, the wing tip device 9 is substantially able to rotate freely about the hinge 11 with passive damping, as will be described further below.

[0067] like Figure 3b In Figure 2 The wingtip device 9 can be rotated upwards, as shown in the second position from the uppermost position in FIG. 1 , so that the lower surfaces between the fixed wing 7 and the wingtip device 9 are no longer continuous with each other. In addition, if the hinge 11 is angled relative to the direction of the airflow (i.e., opposite and parallel to the line of the flight direction F) when the wingtip device 9 is rotated upwards, the average angle of attack of the wingtip device 9 is reduced.

[0068] like Figure 3d In Figure 2 As shown in the lowermost position in FIG. 1 , the wingtip device 9 can also be rotated downward so that the upper surfaces between the fixed wing 7 and the wingtip device 9 are no longer continuous with each other.

[0069] In the moving flight configuration and the other moving flight configuration, the loads on the wing 5 generated by the wing tip device 9 are significantly reduced. The wing tip device 9 can be released to any of these configurations during flight (described in more detail below). By providing this load relief function during flight, the maximum load that the wing needs to be designed for can be reduced, and therefore the wing 5 can be made relatively light.

[0070] The wingtip device 9 can also be configured in a ground configuration, in which the wingtip device 9 is further rotated to a substantially upright position (in Figure 3c In Figure 2 1. The wingtip device is shown in an upright position in FIG. 1. The wingtip device can be moved to this configuration when it is on the ground (described in more detail below). Once rotated to such a position, the wingspan of the aircraft 1 is reduced. Thus, the aircraft 1 can have a large wingspan (exceeding airport gate compatibility restrictions) during flight, but still be able to comply with gate restrictions when on the ground.

[0071] like Figure 3d As shown in , the hinge 111 allows the wing tip device 9 to rotate upward and downward in the mobile flight configuration. This arrangement enables both positive and negative g loads to be mitigated.

[0072] Figure 4a and Figure 4bAn example of an actuation system 20 for rotating the wing tip device 9 about the hinge 11 is shown. The actuation system 20 comprises a motor 22, at least one geared rotary actuator (GRA) 24 and a clutch 28. In the case where the actuation system 20 comprises a plurality of geared rotary actuators 24, the geared rotary actuators 24 are arranged along the hinge line of the hinge 11. The motor 22 may form part of a power drive unit (PDU) incorporating a brake, or may be a clutch 28. Figure 4a and Figure 4b The illustrated arrangement is provided with a separate brake 23. The geared rotary actuator 24 is a rotary actuator arranged to convert a first rotary motion into a different second rotary motion, for example at a different angular rotation rate and / or torque and / or direction.

[0073] In the illustrated example, there are three geared rotary actuator (GRA) "slices" 24 arranged along the articulation line of the hinge 11. The three GRAs can be driven by a common shaft 26a connected to the motor 22. The shaft 26a can have a rotation axis coaxial with the articulation line. The motor 22 (or PDU) is arranged at one end of the three GRA slices. Each GRA 24 is arranged on the articulation line of the hinge 11.

[0074] exist Figure 4a The fairing 30 is shown in dashed lines. The fairing 30 is sized to accommodate the actuation system 20. Figure 4c As illustrated in , clutch 28 may have the same outer diameter as each of GRAs 24 so that the front surface area of ​​actuation system 20 and fairing 30 is minimized. Shaft 26a has a diameter that is significantly smaller than the diameter of the GRAs, such as less than half the diameter.

[0075] Each of the GRAs 24 has a first steering knuckle 24a (or a pair of first steering knuckles) coupled to the fixed wing 7 and a first steering knuckle 24a (or a pair of first steering knuckles) coupled to, for example, the fixed wing 7. Figure 5 24. The second knuckle 24b (or a pair of second knuckles) of the wing tip device 9 shown in FIG. Each of the GRAs 24 is substantially identical and includes an internal gear transmission device for applying a gear ratio to the torque applied to the GRA via the common shaft 26a. When the motor 22 is enabled to drive the common drive shaft 26a via the gearbox 26, the second knuckle 24b rotates relative to the first knuckle 24a of the GRA 24. This drives the articulation of the wing tip device 9 about the hinge 11 relative to the fixed wing 7. The rotation can be a positive rotation or a negative rotation.

[0076] In order to increase the effective rotational inertia of the wing tip device 9 to reduce the wing tip flapping frequency and thus increase the flapping speed, the mass 40 can be fixed to the shaft 26a in a rotational manner and arranged radially outward from the shaft 26a (see Figures 4a to 4c). The mass 40 may be an annular member, a wheel, a ring or any other suitable configuration. In this way, the shaft 26a may extend through a hole in the mass 40, but the mass may alternatively be positioned between two sections of a separate shaft (not shown) - the mass being formed integrally or separately. Adding the mass 40 to the actuation system 20, and in particular to the rotatable shaft 26a, minimizes the additional weight required to reduce the gradient of the flapping frequency of the wingtip device 9 as the aircraft speed increases, compared to alternative solutions such as adding weight to the wingtip device 9. This is in Fig. 6A , where the addition of a mass 40 to the actuation system 20 provides increased rotational inertia, the effect of the increased rotational inertia being to reduce the wingtip flapping frequency (dashed line 61 indicating the actuation system 20 with the mass 40) relative to the wing 5 without the mass (solid line 60 indicating the actuation system 20 without the mass). Figure 6B The effect of the mass 40 on the flap-bending mode coupling is shown, where the local minimum of damping is shifted to a slightly higher airspeed, while the damping around the local minimum is also increased compared to the example without the mass 40. By delaying the frequency incorporation, more air damping is available to help ensure stability.

[0077] In this way, when the shaft 26 a rotates, the mass 40 rotates accordingly to generate a rotational inertia that dampens the movement of the wing tip device 9 .

[0078] Since the GRA includes a reduction gear arrangement, the angular velocity of the wingtip device 9 is less than the angular velocity of the shaft 26a. Therefore, fixing the mass 40 to the shaft 26a instead of directly to the wingtip device 9 achieves a relatively high rotational inertia, because the inertia of the mass 40 increases with the square of the transmission ratio between the movement of the wingtip device and the movement of the shaft 26a with which the mass 40 rotates.

[0079] It should be understood that the rotational inertia generated by the mass 40 will depend on several factors, including the mass and diameter of the mass 40. High density materials are generally advantageous due to the increased rotational inertia generated compared to a similarly sized mass 40 having a lower density. The mass 40 may include tungsten or a similar dense material having a density greater than 10,000 kg / m3, and more preferably greater than 15,000 kg / m3. The mass 40 may have a density greater than the density of the components of the actuation system 20, such as the clutch 28, the gearbox 26, and the geared rotary actuator 24.

[0080] Due to the rotation of the mass 40, the inertia generated is greater than the inertia that would otherwise be generated by adding the mass to the wing tip device 9. For example, the mass 40 may be less than about 20% or less than about 15% of the mass of the wing tip device 9, and less than about 10% or less than 7% of the mass of the combined wing tip device 9 and actuation system 20, while the rotational inertia of the wing tip device 9 about the hinge 11 is increased by 20% or more, 30% or more, 40% or more, or even 50% or more compared to the rotational inertia achieved by the same aircraft wing 5 without the mass 40.

[0081] It will be appreciated that properties of mass 40, such as its size and weight, may be varied to customize mass 40, thereby in turn varying the rotational inertia produced by mass 40. For example, mass 40 may be selected for assembly into actuation system 20 according to the flight handling requirements of aircraft 1.

[0082] In this way, the frequency at which the wing tip device 9 oscillates about the hinge 11 can be customized when the clutch 28 is disengaged during flight. For example, the mass 40 can be customized to select a frequency at which the wing tip device 9 oscillates about the hinge 11 that does not intersect the natural frequency of the wing tip device 9 at airspeeds above the maximum design speed of the wing 5, or alternatively intersects the natural frequency of the wing tip device 9 at airspeeds above the maximum design speed of the wing 5 to avoid flutter.

[0083] To ensure that the mass 40 generates rotational inertia when the clutch 28 is disengaged (e.g., during flapping mode), the mass 40 can be located on the side of the clutch 28 opposite the motor 22. It will be understood that the "sides" refer to relative positions along the drive train, and not necessarily their physical positions on the wing 5.

[0084] Engaging the clutch 28 enables the motor 22 to drive the GRA 24 in the drive mode to rotate the wing tip device 9 about the hinge 11. Figure 7a An example of the actuation system 20 operating in the drive mode is shown, with the curved arrow indicating the direction in which the motor 22 rotates the wingtip device 9 (e.g., counterclockwise when looking backward). It should be noted that the motor 22 may alternatively rotate the wingtip device 9 about the hinge 11 in the opposite (e.g., clockwise) direction. Figure 7b It is illustrated how the clutch 28 and brake 23 are configured to allow the motor 22 to drive the wingtip device 9 .

[0085] Disengaging the clutch 28 enables the GRA 24 to rotate substantially freely, thereby allowing the wingtip device 9 to rotate substantially freely about the hinge 11 (with passive damping due to the mechanical resistance of the actuation system) relative to the fixed wing 7 when in the flapping wing operating mode. Once the brake 23 and clutch 28 are released, the wingtip device 9 can be actuated completely passively in the flapping wing mode. For example, the wingtip device 9 can move under the influence of aerodynamic forces and / or gravity. The option of braking or releasing the wingtip device 9 can be referred to as a "semi-aeroelastic" arrangement. By Figure 8a A schematic representation of the actuation system 20 operating in flapping mode is illustrated, with the curved arrows indicating the permissible rotation of the wingtip device 9 . Figure 8b It is illustrated how the clutch 28 and the brake 23 are configured to allow the wing tip device 9 to rotate freely about the hinge 11 .

[0086] An increase in the gear ratio between the GRA 24 and the motor 22 can be provided by adding a gearbox 26, such as Figure 9a and Figure 9b In this example, a gearbox 26 is provided between the clutch 28 and the motor 22 .

[0087] Alternatively, the gearbox 26 may be disposed between the GRA 24 and the clutch 28, such as Fig.10a and Fig.10b The advantage of this arrangement is that the clutch 28 can be designed to handle lower torques because it is arranged before the gear ratio is applied to the torque from the motor 22 to the gearbox 26. This can reduce the size, weight, cost and complexity of the clutch 28.

[0088] In the examples of Figures 9 and 10, it should be noted that the mass 40 is disposed between the GRA 24 and the gearbox 26. Alternatively, the mass 40 may be disposed between the clutch 28 and the gearbox 26 to take advantage of the gear ratio of the gearbox 26, i.e., the mass 40 is positioned upstream of the gearbox 26 toward the motor 22 due to the increased rotational speed of the shaft 26a at this location compared to the gearbox 26 downstream toward the GRA 24. Fig.11a and Fig.11b An example of such an arrangement is shown in .

[0089] When the clutch 28 is disengaged, the gearbox 26 can be driven in reverse, so that the gearbox 26 can be operated by a movement of the wingtip device 9 rotating about the hinge 11 .

[0090] The clutch 28 may be disengaged during flight for many other reasons. Allowing the wingtip device 9 to rotate substantially freely can be used to reduce the loads acting on the wing 5 due to external forces. Thereby, the maximum load for which the wing 5 needs to be designed can be reduced, and the wing 5 can therefore be made relatively light. Alternatively, the wingtip device 9 can be allowed to rotate freely so that the span of the wing 5 is effectively reduced. Reducing the span of the wing 5 may be beneficial, for example, during relatively low speed or low altitude flight where high lift levels are not required, or when relatively high roll rates are required.

[0091] When the brake 23 (optionally the brake 23 of the PDU) is engaged and the clutch 28 is also engaged, the actuation system 20 operates in a braking mode in which the brake 23 is used to prevent the wingtip device 9 from rotating about the hinge 11 relative to the fixed wing 7. The braking operating mode may correspond to a zero angular position or a non-zero angular position of the wingtip device 9 about the hinge 11. In this zero position, the upper surface 9a and the lower surface 9b of the wingtip device 9 form a substantially zero angle with the upper surface 7a and the lower surface 7b of the fixed wing 7, so that the overall span of the wing 5 is maximized. By Fig.13a A schematic representation of the actuation system 20 operating in a braking mode is illustrated. Fig.13b It is illustrated how the clutch and brake are configured to prevent the wing tip device 9 from rotating about the hinge 11 .

[0092] The actuation system 20 is also operable in a fixed mode in which the clutch 28 is engaged and the brake 23 is disengaged so that the motor 22 can drive the rotation of the wingtip device 9 about the hinge 11. Fig.14 A schematic representation of the actuation system 20 operating in a fixed mode is illustrated, with the dashed line indicating a non-zero target position of the wingtip device 9 and the curved arrow indicating the direction in which the motor 22 drives the wingtip device 9 to reach the target position. Fig.14 It is illustrated how the clutch and brake are configured to allow the motor 22 to drive the wingtip device 9 .

[0093] The actuation system 20 is capable of operating in any combination of the above-described operating modes and can change between operating modes during flight.

[0094] In the above example, the mass 40 is disposed between the gear-driven rotary actuator 24 and the clutch 28. Alternatively, the mass 40 may be disposed in front of the gear-driven rotary actuator 24, such as toward the leading edge of the wing 5. Fig.15, so that the mass 40 is closer to the leading edge of the wing 5 than the geared rotary actuator 24. Positioning the mass 40 in front of the geared rotary actuator 24 can facilitate packaging the actuation system 20 within the fairing 30. In addition, in any of the above examples, the mass 40 can have a diameter that is substantially the same as the diameter of the geared rotary actuator 24, the gearbox 26, and other components of the actuation system 20 to maintain a compact package within the fairing 30.

[0095] In some examples, the mass 40 may be positioned between a pair of geared rotary actuators 24 , such as shown in FIG. 16 .

[0096] Fig.17a Another embodiment (combinable with any of the previous disclosures) is shown, in which the actuator mechanism 20 includes a second gearbox 27, which is arranged between the clutch 28 and the motor 22. Providing a gearbox 26 and a second gearbox 27 allows the torque from the motor 22 to be increased in two stages, first by the second gearbox 27 and then by the gearbox 26 before the torque is transmitted through the clutch 28. Therefore, the transmission ratio and therefore the size of each of the gearbox 26 and the second gearbox 27 can be made smaller than the single gearbox 26 used as shown in the previous example. This can help to reduce the overall size of the actuation system 20 and therefore help to reduce the size of any fairing 30 arranged around the braking system 20. In addition, this can allow the reduction ratio of the gearbox 26 to be selected based on the desired damping characteristics of the articulated joint when it is driven in reverse, while still using the second gearbox 27 to provide sufficient torque to drive the wingtip device 9. Fig.17b This arrangement is shown more generally in a block diagram.

[0097] The actuator mechanism 20 may alternatively be configured as follows Fig.17a As shown in FIG. 1 , the motor 22 is arranged on the opposite side of the gear-driven rotary actuator 24 from the clutch 28 and the gearbox 26. This arrangement can position the clutch 28 and the gearbox 26 in front of the leading edge of the wing 5, such as Fig.17a This is useful, for example, for packaging components within a fairing 30. Although shown as including a second gearbox 27, this configuration can also be applied to an actuation system that includes only a single gearbox 26. Fig.17b An example of an actuation system 20 configured in this manner is shown in an exploded view in FIG. In this example, a drive shaft 27a connected to a second gearbox 27 transfers torque to a clutch 28, but does not act on the gear-driven rotary actuator 24. Once engaged, the clutch 28 transfers torque to the gearbox 26, which in turn uses, for example, Figure 4cThe common shaft 26a ( Fig.17b (not shown) drives the gear-driven rotary actuator 24.

[0098] Where the word "or" appears, this will be interpreted as meaning "and / or" such that the referred items are not necessarily mutually exclusive and can be used in any appropriate combination.

[0099] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. An aircraft wing, the aircraft wing comprising: a fixed wing having a tip; a wingtip device rotatably mounted on a hinge at the tip of the fixed wing so that the wingtip device can rotate about the hinge; and an actuation system for rotating the wingtip device about the hinge, wherein the actuation system comprises a motor, at least one geared rotary actuator, a clutch for selectively decoupling the rotation of the motor from the rotation of the geared rotary actuator, the geared rotary actuator being drivable by the motor and arranged to convert a rotary motion into a different rotary motion and arranged to rotate the wingtip device relative to the tip of the fixed wing, wherein the clutch is coupled to the geared rotary actuator via a shaft and the shaft is rotationally fixed to a mass disposed radially outwardly from the shaft.

2. The aircraft wing according to claim 1, wherein: The hinge has an articulation line and the shaft has an axis of rotation coaxial with the articulation line.

3. The aircraft wing according to claim 2, wherein: The gear-driven rotary actuator is arranged along the hinge line of the hinge and has an outer diameter, the shaft has a shaft diameter that is significantly smaller than the outer diameter of the gear-driven rotary actuator, and the mass block has an outer diameter around the axis that is basically the same as the outer diameter of the gear-driven rotary actuator.

4. An aircraft wing according to any preceding claim, wherein: The mass rotates as the wing tip device rotates about the hinge.

5. An aircraft wing according to claim 4, wherein: Due to the gearing of the geared rotary actuator, the mass rotates at a faster angular velocity than the angular velocity of the wingtip device about the hinge.

6. An aircraft wing according to any preceding claim, wherein: The mass is an annular member or a wheel or a ring.

7. An aircraft wing according to any preceding claim, wherein: The shaft extends through a hole in the mass.

8. An aircraft wing according to any preceding claim, wherein: The mass includes tungsten.

9. An aircraft wing according to any preceding claim, wherein: The mass is less than about 20%, preferably less than 15% of the mass of the wing tip device.

10. An aircraft wing according to any preceding claim, wherein: The mass is less than about 10%, preferably less than 7%, of the mass of the combined wing tip device and actuation system.

11. An aircraft wing according to any preceding claim, wherein: The mass increases the rotational inertia of the wing tip arrangement about the hinge by at least 20%, preferably at least 30% or at least 40% or at least 50% compared to the same aircraft wing without the mass.

12. An aircraft wing according to any preceding claim, further comprising a plurality of said geared rotary actuators arranged along a hinge line of said hinge.

13. An aircraft wing according to any preceding claim, wherein: The mass is disposed forwardly of the geared rotary actuator towards the leading edge of the wing.

14. An aircraft wing according to any one of claims 1 to 12, wherein: The mass is disposed between the gear-driven rotary actuator and the clutch.

15. The aircraft wing of claim 12, wherein: The mass block is disposed between a pair of the gear-driven rotary actuators.

16. An aircraft wing according to any preceding claim, wherein: The actuation system has a maximum damping value that allows oscillatory flapping motion of the wing tip device rotating about the hinge during normal operation when the clutch is disengaged.

17. An aircraft wing according to any preceding claim, wherein: The actuation system is back-drivable when the clutch is disengaged to decouple rotation of the motor from rotation of the geared rotary actuator when the wingtip arrangement rotates about the hinge.

18. An aircraft wing according to any preceding claim, wherein: The actuation system also includes a reduction gearbox.

19. An aircraft wing according to any preceding claim, wherein: The reduction gearbox is disposed between the clutch and the geared rotary actuator along a drive train between the motor and the geared rotary actuator.

20. An aircraft wing according to any preceding claim, wherein: The actuation system also includes means for preventing movement of the geared rotary actuator when the clutch is engaged.

21. The aircraft wing of claim 18, wherein: The actuation system is operable in the following modes: i) a drive mode in which the clutch is engaged and the motor is driven to rotate the wingtip arrangement about the hinge; ii) a flapping mode in which the clutch is disengaged and the wingtip device is able to rotate about the hinge by a force external to the wingtip device; and iii) a braking mode in which the clutch is engaged and the brake prevents rotation of the wingtip arrangement about the hinge.

22. An aircraft wing according to any preceding claim, wherein: The geared rotary actuator has a first knuckle fixed to the fixed wing and a second knuckle fixed to the wingtip device, wherein the first knuckle and the second knuckle are driven by the geared rotary actuator to rotate relative to each other using a motive force provided by the motor.

23. An aircraft wing according to any preceding claim, wherein: The clutch is configured to disengage during flight for one or more of a) load relief or b) when the aircraft is flying at a relatively low speed or altitude and a relatively high roll rate is required.

24. A method for adjusting a wing of an aircraft, wherein: The aircraft wing is as claimed in any preceding claim, and the method comprises customising the mass to change the inertia and thereby the frequency at which the wing tip oscillates about the hinge when the clutch is disengaged during flight.

Images