GB2583498A

GB2583498A - Mechanism for use in moving a wing tip device

Info

Publication number: GB2583498A
Application number: GB1906061.5A
Authority: GB
Inventors: graham kirk James; Wilson Thomas
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2019-04-30
Filing date: 2019-04-30
Publication date: 2020-11-04
Also published as: GB201906061D0

Abstract

An aircraft having a wing (120, figure 3) comprising a fixed wing (126), a wing tip device 250 and a wing tip mechanism 260 moving the wing tip device relative to the fixed wing. The wing tip mechanism comprises a wing tip actuator 262 (for example a linear actuator such as a screw jack actuator 262) and a latch 272 and latch trap 274. When the latch is latched by the latch trap the wing tip device is movable relative to the fixed wing under the control of the wing tip actuator, and when the latch is unlatched the wing tip device is released from the control of the wing tip actuator. In the unlatched state the wing tip can move under the action of aerodynamic forces exerted on the wing tip to provide passive load alleviation on the wing. The wing may be moved from a latched state to one of a flight configuration and a ground configuration. The latch may comprise a spring-loaded pin which is held in a recess 274 when the actuator 262 is in an engaged configuration.

Description

MECHANISM FOR USE IN MOVING A WING TIP DEVICE

BACKGROUND OF THE INVENTION

100011 The present disclosure relates to an aircraft with a moveable wing tip device. In particular, the present disclosure relates to mechanisms for use in moving such wing tip devices.

[0002] Aircraft may be equipped with moveable wing tip devices attached to fixed wings. The wing tip devices may be used to allow load-alleviation during flight, for example, in the event of wind gusts. Typically, large loads cause the wing tip device to move from a flight configuration in which the wing tip device is effectively a continuation of the fixed wing portion to a load-alleviating configuration in which the load on the wing is reduced. Once the cause of the requirement to enter the load-alleviating configuration has passed, it is often desirable to move the wing tip device back into the flight configuration. W02017/118832, the contents of which are fully incorporated herein by reference, discloses such a wing tip device, that is moveably mounted about a hinge.

[0003] Further, there is a trend towards increasingly large passenger aircraft, for which it is desirable to have correspondingly large wing spans. An increased wingspan can lead to a reduction in induced drag, and therefore enhance operational efficiency. However, the maximum aircraft span is effectively limited by airport operating rules which govern various clearances required when manoeuvring around the airport (such as the span and/or ground clearance required for gate entry and safe taxiway usage). Moveable wing tip devices may be used to enable the wing span to be reduced in a ground configuration. [0004] An actuator, for example an electro-mechanical or hydraulic actuator, may be used to move the wing tip device between different configurations. Such an actuator may require a substantial load and/or torque capacity, particularly where the actuator is to be used during flight.

[0005] An actuator may be used in conjunction with a clutch device for selectively transmitting torque between the actuator and the wing tip device. The clutch device may be capable of selectively disengaging the wing tip device from the actuator (for example to protect the actuator componentry from torques and/or bending moments caused by forces acting upon the wing tip device during flight). As such, the clutch device may be required to function under, and withstand, significant torques. Further, on-board space is an important consideration on aircraft. Some aircraft may not have enough space for a sufficiently powerful clutch device capable of withstanding torques as desired.

[0006] The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved mechanism for moving a wing tip device. Alternatively or additionally, the present invention seeks to provide an improved aircraft and/or aircraft wing. Alternatively or additionally, the present invention seeks to provide an improved method of controlling an aircraft wing having a movable wing tip device.

SUMMARY OF THE INVENTION

[0007] According to a first aspect, there is provided a wing tip mechanism for moving a wing tip device relative to a fixed wing of an aircraft. The wing tip mechanism comprises a wing tip actuator for moving the wing tip device. The wing tip mechanism is arranged to be able to latch and / or unlatch the wing tip actuator in relation to the wing tip device. For example, the wing tip mechanism may comprise a latch member and a latch trap for latching the latch member, the wing tip mechanism being so configured that, in use, when the latch member is latched by the latch trap the wing tip device is movable relative to the fixed wing under the control of the wing tip actuator, and preferably only under the control of the wing tip actuator. The wing tip device is released from the control of the wing tip actuator, by unlatching the latch.

[0008] In embodiments of the invention, when the latch is unlatched, the wing tip device is able to move freely relative to the fixed wing, in that its movement is unconstrained by the wing tip actuator (which for example may comprise one or more motors and/or gearboxes). Also, when the latch is unlatched, movement of the wing tip actuator does not cause movement of the wing tip device. The latch may be used for selectively disengaging the wing tip device from the wing tip actuator. As such, the wing tip actuator may, when unlatched, be protected from torque acting upon or caused by the wing tip device. A latch is thus able to provide a way in which the wing tip device can be controlled (moved by an actuator), locked in place and/or released, without the use of a friction clutch.

[0009] The wing tip actuator may comprise a linear actuator. It may be that the linear actuator has a shape and configuration that fits effectively and efficiently in the space available within the wing. The linear actuator may be generally elongate. The linear actuator may extend lengthways in the direction in which actuation is effected, and may be generally aligned with the direction of actuation. The linear actuator may be generally aligned with the span-wise direction in the wing. The linear actuator may be orientated so as to be substantially transverse to a hinge line of the wing tip device. The linear actuator may be orientated so as to be substantially perpendicular to the hinge line.

[0010] It is preferred for the wing tip actuator to be non-back-driveable. For example, the actuator may be configured such that it cannot be driven by its load, for example due to the frictional forces generated between gears in the actuator in response to the load. The wing tip actuator may for example assist in locking the wing tip device in place during operation, when the latch is in its latched state. The wing tip actuator may comprise a screw jack actuator.

[0011] The latch member is preferably spring-loaded. For example, the latch member may be spring-loaded so as to urge the latch member into the latch trap, thus resisting unlatching.

[0012] It may be the case that the latch member is arranged to unlatch and thus release the wing tip device from the control of the wing tip actuator in a passive manner. The wing tip device may for example, at least partially, be moveable to a load alleviating configuration (for example from a flight configuration in which the wing tip device effectively extends the span of the fixed wing) purely under the action of aerodynamic force acting on it during flight, and/or under gust loads. For example, the wing tip device may be allowed to passively (i.e. under aerodynamic forces) move from a flight configuration to a load alleviating configuration, if and when the wing tip device imparts a load on the wing tip actuator which exceeds a threshold load. Selectively disengaging the wing tip device from the wing tip actuator may prevent the wing tip actuator from being back-driven, and may thus reduce the likelihood of damage or wear to the wing tip actuator. The latch may be arranged to selectively decouple the wing tip actuator from the wing tip device. As such, the wing tip actuator may be reversibly and repeatably couplable with the wing tip device.

[0013] The wing tip mechanism may further comprise a latch actuator for latching and/or unlatching the latch member in relation to a latch trap. The provision of a latch actuator may enable the latch member to be latched and/or unlatched in relation to the latch trap in an active manner, thus latching and/or unlatching the wing tip device from the wing tip actuator in an active manner. The latch actuator may be arranged to operate a cam to selectively latch or unlatch the latch member. For example, the cam may be arranged to move the latch member into or out of the latch trap. The latch member may be arranged to slide along a bearing surface when unlatched. Additionally or alternatively, the latch member may be arranged to travel within a slot when unlatched. The latch actuator may be arranged to cause relative rotational motion between the latch member and the latch trap. In certain embodiments, the rotational motion so caused is about an axis which is parallel (or at least substantially parallel) to the direction of travel of the wing tip actuator when moving the wing tip device. In different embodiments, the rotational motion so caused is about an axis which is perpendicular (or at least substantially perpendicular) to the direction of travel of the wing tip actuator when moving the wing tip device.

[0014] The wing tip mechanism may further comprise at least one lever arranged between the wing tip actuator and the wing tip device. For example one or more levers may be configured to convert motion from the wing tip actuator into motion of the wing tip device. For example, the one or more levers may convert linear motion from the wing tip actuator into rotary motion of the wing tip device. The one or more levers may provide a mechanical advantage for moving the wing tip device. The wing tip mechanism may further comprise one or more rods arranged between the wing tip actuator and the wing tip device, the one or more rods transmitting loads in a direction substantially parallel with the direction of actuation of the wing tip actuator. One or more such rods may also act as a lever.

[0015] The wing tip mechanism may comprise a control unit. Such a control unit may be arranged to control the latching of the latch member. The control unit may be arranged to -5 -control the unlatching of the latch member. The control unit may be arranged to control the operation of the wing tip actuator and thus movement of the wing tip device when the latch member is latched. For example, the control unit may be arranged to control movement of the wing tip device to the flight configuration, as mentioned herein. The control unit may, additionally or alternatively, be arranged to control movement of the wing tip device to a ground configuration, as mentioned herein.

[0016] There may be a latch sensor arranged to detect at least one of (i) whether the latch member is latched and (ii) whether the latch member is unlatched. Such a latch sensor may be connected to a control unit, for example to facilitate control of the wing tip mechanism. The control unit may be arranged to receive a signal from such a latch sensor. The latch sensor may be arranged to detect only when the latch member is latched, such that the control unit deems the latch member unlatched in the absence of a signal from the latch sensor representing the latched state. The latch sensor may be arranged to detect only when the latch member is unlatched, such that the control unit deems the latch member latched in the absence of a signal from the latch sensor representing the unlatched state. The latch sensor may provide a binary output, for example closed circuit and open circuit states. The latch sensor may comprise a switch, for example a microswitch. The latch sensor may comprise a non-contact sensor such as a proximity sensor.

[0017] The control unit may be arranged to control the latching of the latch member (for example when starting from an unlatched state) by causing relative movement of a first kind between the latch member and the latch trap (such movement for example being effected by the wing tip actuator) and then relative movement of a second kind, being different from the first kind. For example, the movement of the first kind may be controlled so that the latch member and the latch trap move closer together. It may be the case that the movement of the second kind, and not of the first kind is what causes the latch member and the latch trap to latch together.

100181 It may be that, during flight, the dynamic loads on the wing tip device are such that the position of the latch member relative to the latch trap changes over time. For example there may be occasions when the wing tip device is subject to oscillating motion, -6 -which causes substantially continuous motion between the latch member and the latch trap. The movement of the first kind may bring the latch member into approximate alignment with the latch trap. The movement of the second kind may be configured to allow for correct alignment of the latch member with the latch trap, despite the continued movement of the latch member relative to the latch trap.

[0019] The control unit may be configured to receive an indication of the position of the latch member relative to the latch trap. Tt may be that the position of the latch member relative to the latch trap is known to the control unit. The movement of the first kind may be in the form of an attempt by the control unit to align the latch member with the latch trap, in dependence on an expected/detected position of the latch member relative to the latch trap. The dynamic nature of the loads on the wing tip mechanism and its parts, tolerances of manufacture and/or other real-life factors may mean that the latch member and the latch trap are not sufficiently aligned, after the movement of the first kind, to enable the latch trap to latch the latch member in place. The second kind of movement may be necessary in order to latch the latch member in such a case. The second kind of movement may for example comprise sweeping motion such that the latch member and the latch trap find each other. Such a sweeping motion may have a progressively increasing amplitude. The first kind of movement may be conducted at a first speed to bring the latch member and latch trap close to each other, but without reaching a position at which the latch member and latch trap are fully aligned. The second kind of movement may be conducted at a second speed, lower than the first speed, for example so that the latch member and latch trap engage with each other to cause latching of the latch member when aligned (and not passing the position of alignment without properly latching, which might otherwise happen at a higher speed).

100201 The control unit may additionally or alternatively be arranged to unlatch the latch member in response to detection of a high load event. The wing tip device may thus be placed in its load alleviation configuration sufficiently quickly to reduce unnecessary loading of the fixed wing.

[0021] The latch member may comprise a pin. The latch member may comprise a roller. The pin and/or roller may have a shape and size that corresponds to the shape and size of -7 -a recess which is defined, at least in part, by the structure of the latch trap. The latch member may comprise a bearing surface.

100221 The present invention also provides, according to a second aspect, an aircraft wing incorporating a movable wing tip device. The wing tip device may be one arranged in accordance with the first aspect of the invention as described or claimed herein. The aircraft wing comprises a fixed wing, with the wing tip device being mounted for movement relative to the fixed wing. The aircraft wing also includes a wing tip mechanism configured to move the wing tip device relative to the fixed wing. The wing tip mechanism may be one arranged in accordance with the first aspect of the invention as described or claimed herein. The wing tip device may be mounted for rotational movement about a hinge axis. It may be that a wing tip actuator is arranged to cause movement of the wing tip device about its hinge axis, for example via an elongate load carrying member (such as a lever and/or rod, for example). For example the wing tip actuator may be a linear actuator arranged to cause rotational movement of the wing tip device by means of such a lever/rod. In certain embodiments of the invention, such a lever may form a part of the wing tip device. Alternatively or additionally, the lever, rod or other elongate load carrying member may form a part of the wing tip mechanism.

100231 The wing tip device may have a flight configuration. The wing tip device typically forms an extension of the fixed wing when in the flight configuration, and preferably is in a position which maximises the span of the wing (i.e. the wing has its greatest span with the wing tip in the flight configuration). For example, in the flight configuration, the wing tip device may be in-plane with the wing. There may however be other positions that the wing tip device can take when in its flight configuration. For example, the wing tip device may be arranged to adopt different fold angles depending on the flight phase, when in in the flight configuration. The wing tip device may have a load alleviating configuration. In the load alleviating configuration, the wing tip device may be free to move across a range of positions, such that no significant lift loads are transmitted from the wing tip device to the fixed wing. The wing tip device may have a ground configuration. The wing tip device when in its ground configuration may be fixed in a single predetermined position, for example one which shortens the wingspan of the -8 -aircraft as compared to the wingspan when the wing tip device is in the flight configuration.

[0024] In certain embodiments, the wing tip device is mounted for rotation about a hinge axis. The hinge axis may be defined by a hinge mechanism, which connects the wing tip device to the fixed wing. The hinge axis may be orientated non-parallel to the line-offlight direction. The hinge axis may be orientated such that the hinge axis at the trailing edge of the wing is further inboard than the hinge axis at the leading edge of the wing (for example when viewed from above). The hinge axis may be orientated such that in a load alleviating configuration, the mean incidence of the wing tip device is reduced. The hinge axis may be orientated substantially perpendicular to the swept mean chord axis of the wing. The swept mean chord axis may be parallel to the longitudinal direction of the wing box. Such an arrangement has been found to be beneficial in terms of enabling a load reduction (in comparison with a hinge axis that is orientated parallel to the line-offlight). Furthermore, such an orientation of hinge axis has been found to facilitate movement of the wing tip device to a stable load alleviating configuration. For example, when the hinge axis is in such an orientation, the wing tip device tends to move to a static-aeroelastically stable position even under purely aerodynamic loading. The hinge axis may be orientated substantially perpendicular to the leading edge of the wing in some cases. The orientation of the hinge axis may be chosen such that it acts to stabilise flutter.

[0025] The wing tip device may be a wing tip extension; for example the wing tip device may be a planar tip extension. In other embodiments, the wing tip device may comprise, or consist of, a non-planar device, such as a winglet.

[0026] There is also provided, in accordance with third aspect of the invention, a method of controlling an aircraft wing comprising a wing tip movably mounted at an end of a fixed wing. The wing tip has an unlatched state in which the wing tip is allowed to move under the action of aerodynamic forces exerted on the wing tip and thus provide load alleviation for the wing. The wing tip also has a latched state in which the wing tip is moveable under the control of an actuator. The method includes a step of moving the wing tip when in its latched state, for example under the control of the actuator. The -9 -method may include moving the wing tip to a flight configuration. The method may include moving the wing tip to a ground configuration.

[0027] The method may include a step of moving the wing tip, when in its latched state and when in flight, to a configuration between the flight configuration and the ground configuration. There may for example be at least one intermediate configuration providing different span-wise loading on the wing during flight as compared to the flight configuration and/or providing advantageous aerodynamic performance. The intermediate position of the wing tip device may be selected in dependence on the flight phase. The wing tip device may be arranged to be moved between multiple different positions, for example being used as a spoiler device.

[0028] There may be a step of latching the wing tip before the step of moving the wing tip. Such a step may include a control unit assisting in moving a latch member to a target position in which it is then able to latch the wing tip. The control unit may perform a sweep and find operation in order to align the latch member with the target position. In embodiments of the invention, the sweep and find operation may be conducted such that the latch member is caused to move in a predetermined manner until it is correctly aligned with the target position (i.e. successfully finding the target position) [0029] The method may include a step of a control unit causing the wing tip to be unlatched in response to detecting a high load event. Such a high load event may be encountered for example if there is a particularly strong gust on the wing. A high load may, additionally or alternatively, be encountered if the aircraft is manoeuvred in a certain way during flight. One or more sensors may be provided to detect and/or predict a high load event, for example providing signals to the control unit. One or more sensors may be provided to detect the load on the wing, for example.

100301 The present invention also provides, according to fourth aspect, an aircraft comprising a movable wing tip device or the like. The aircraft may comprise an aircraft wing according to the second aspect of the invention as claimed or described herein. Alternatively or additionally, the aircraft may be configured for use in the method of the invention as claimed or described herein. The wing tip device of the aircraft may be rotatably mounted on a hinge at the tip of a fixed wing such that the wing tip device may -10 -rotate, about the hinge, relative to the fixed wing. The hinge may be orientated nonparallel to the line-of-flight direction of the aircraft.

100311 The aircraft may comprise an actuator, for example a linear actuator such as a screw jack actuator, and an associated mechanism, for example a lever arrangement, which together have an engaged configuration in which they are operable to rotate the wing tip device about the hinge to any one of a plurality of different positions relative to the fixed wing (e.g. to a ground configuration and/or to a flight configuration). The actuator and its associated mechanism may, in the engaged configuration, also be configured to hold the wing tip device in position. The actuator and its associated mechanism may also have a disengaged configuration. It may be that in the disengaged configuration, the wing tip device is released and able to rotate about the hinge independently of the actuator.

100321 The aircraft may include a resiliently biased (e.g. spring loaded) latching apparatus, for example comprising a resiliently biased latching member (e.g. a spring-loaded pin) and an associated structure having a latch trap (e.g. a recess) in which the latch member (e.g. pin) is receivable (the latch member being received when the actuator and its associated mechanism are in the engaged configuration). For example in embodiments of the invention, in the engaged configuration, the latch member is held in position relative to its associated structure, whereas when the actuator (e.g. screw jack actuator) and associated mechanism (e.g. lever arrangement) are in the disengaged configuration, the latch member is not received in the latch trap (e.g. the pin is not received in the recess). It may be that in the disengaged configuration, the latch member is arranged to move relative to the associated structure (and for example to move along a bearing surface forming a part of or otherwise being attached to the associated structure) as the wing tip device rotates about the hinge.

100331 The aircraft may include a control unit which is arranged to control movement of the latch member (e.g. pin) into and out of the latch trap (e.g. recess). The control unit may be arranged to place the actuator (e.g. the screw jack actuator) and associated mechanism (e.g. the lever arrangement) in the engaged configuration by moving the latch member relative to the associated structure in a pattern of movement, for example causing the latch member to search and find the latch trap. The control unit may be configured to control a cam actuator, operable to move a cam so as to cause latching and/or unlatching of the actuator (e.g. screw jack actuator) and its associated mechanism (e.g. lever arrangement). The same control unit may thus be configured to control such a cam actuator as well as the main wing tip actuator.

[0034] It may be that the actuator (e.g. screw jack actuator) and its associated mechanism (e.g. lever arrangement) are latched together when engaged and unlatched when disengaged. Alternatively, it may be that the actuator (e.g. screw jack actuator) and its associated mechanism (e.g. lever arrangement) are together latched to the wing tip device or structure associated with the wing tip device when engaged and are both unlatched from the wing tip device (or associated structure) when disengaged.

100351 The aircraft is preferably a passenger aircraft. The passenger aircraft preferably comprises a passenger cabin comprising a plurality of rows and columns of seat units for accommodating a multiplicity of passengers. The aircraft may have a capacity of at least 20, more preferably at least 50 passengers, and more preferably more than 50 passengers. The aircraft is preferably a powered aircraft. The aircraft preferably comprises an engine for propelling the aircraft. The aircraft may comprise wing-mounted, and preferably underwing, engines. The aircraft may have a maximum take-off weight (MTOW) of at least 20 tonnes, and optionally at least 50 tonnes. The span ratio of the fixed wing relative to the wing tip device may be such that the fixed wing comprises at least 70%, 80%, 90%, or more, of the overall span of the aircraft wing.

[0036] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

DESCRIPTION OF THE DRAWINGS

[0037] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: -12 -Figure 1 shows a schematic plan view of an aircraft according to a first embodiment of the invention; Figure 2 shows a schematic plan view of part of a wing of the aircraft of Figure 1; Figure 3 shows a schematic front view of the aircraft of Figures 1 and 2; Figures 4 to 8 show schematically the different configurations of a wing tip actuation system of the aircraft of the first embodiment; Figures 9 to 13 show schematically different configurations of a wing tip actuation system according to a second embodiment of the invention; Figure 14 shows the wing tip actuation system of the second embodiment including a control unit; Figures 15 and 16 show a wing tip actuator apparatus according to a third embodiment of the invention; and Figure 17 is a flowchart illustrating a method of operating a wing tip device according to a fourth embodiment of the invention.

DETAILED DESCRIPTION

[0038] Figure 1 is a plan view of an aircraft 100 according to a first embodiment of the invention. The aircraft 100 comprises a central fuselage 110 and two main wings 120 extending outwardly from respective wing roots 122.

[0039] Each wing 120 comprises a fixed wing 126 extending from the root 122 to the tip 124 (shown in close up in Figure 2). At the tip 124 of the fixed wing 126, the wing 120 also comprises a moveable wing tip device 150. In this embodiment, the wing tip device 150 comprises a planar wing tip extension. The wing tip device 150 is rotatably mounted on a hinge 155 (depicted with a dashed line in Figures 1 and 2). As such, the wing tip device 150 is able to rotate about the hinge 155 relative to the fixed wing 126.

[0040] In this embodiment, the hinge 155 is orientated non-parallel to a line-of-flight direction of the aircraft 100 (the line-of-flight direction being shown with a dashed line 156 in Figure 2 for comparison). More specifically, in this embodiment, the hinge 155 is orientated perpendicular to the swept mid-chord axis 130. The hinge 155 may have other orientations in other embodiments.

-13 - 100411 The aircraft 100 also comprises a wing tip actuation mechanism 160, as will be described in more detail below. The wing tip actuation mechanism 160 is operable to rotate the wing tip device 150 about the hinge 155 to and/or from a flight configuration and/or a ground configuration. The wing tip actuation mechanism 160 includes a latching mechanism 170 arranged to selectively engage and disengage the wing tip actuation mechanism 160 from the wing tip device 150. The wing tip actuation mechanism 160 is thus also operable to move the wing tip device 150 to and/or from a load alleviating configuration.

100421 Figure 3 is a composite drawing showing part of the aircraft with the wing tip device 150 rotated about the hinge 155 by different amounts so as to adopt three different configurations. Thus, Figure 3 shows the wing tip device 150 in a flight configuration (wing tip device in the position labelled 1500, a load-alleviating configuration (wing tip device in the position labelled 1501), and a ground configuration (wing tip device in the position labelled 150g). In the flight configuration, the wing tip device 150f is an extension of the fixed wing 126. Accordingly, the upper and lower surfaces of the fixed wing 126 are continuous with the upper and lower surfaces of the wing tip device 150f in this embodiment. The leading and trailing edges of the fixed wing 126 are also continuous with the respective leading and trailing edges of the wing tip device 150 (see Figures 1 and 2). Such an arrangement is beneficial as it provides a relatively large wing span, thereby providing an aerodynamically efficient aircraft. However, a large span can result in correspondingly large loads on the wing 120, particularly a large wing root bending moment, especially during high load events such as gusts or extreme manoeuvres. The wing 120 may be sized to cope with these maximum loads, which can result in a relatively heavy wing. The ability of the wing tip device 150 to move to the load-alleviating configuration seeks to address that problem.

100431 The wing tip device 150 is rotatable, upwards, from the flight configuration to the load alleviating configuration (see the wing tip device labelled 1501). The wing tip device 150 is rotatable such that the lower surfaces between the fixed wing 126 and the wing tip device 150 are no longer continuous with one another. Since the hinge 155 is angled with respect to the airstream-wise direction, when the wing tip device 150 rotates upwards its -14 -mean incidence is reduced. In this configuration the lift generated by the wing tip device 150 is significantly reduced and the load on the wing 120 is also significantly reduced. The wing tip actuation mechanism 160 is able to cause the wing tip device 150 to adopt this configuration during flight. Such an arrangement has been found to be especially beneficial when the aircraft is undergoing roll. Load alleviation has also been found to be especially beneficial during low-speed operations (e.g. during take-off climb and/or landing). By moving the wing tip device to the load alleviating configuration, the onset of stall may be alleviated. This may assist the aircraft in meeting low speed requirements, especially for take-off and climb. Loads at the wing root 122 may be reduced, which might otherwise be significant in a gust if the wing tip device were in the flight configuration.

100441 The wing tip device 150 is also configurable in a ground configuration in which the wing tip device 150 is rotated yet further, to a substantially upright position (see the wing tip device labelled 150g in Figure 3). The wing tip device 150 is moveable to this configuration when the aircraft 100 is on the ground. Once rotated to such a position, the span of the aircraft 100 is sufficient to meet airport compatibility gate limits. Thus, the aircraft 100 of the first embodiment can have a large span (exceeding gate limits) during flight, but is still able to comply with gate limits when on the ground.

[0045] The wing tip device 150 and the wing tip actuation mechanism 160 are shown in highly schematic form in their various configurations in Figures 4 to 8. Figure 4 shows the wing tip device in a flight configuration and the wing tip actuation mechanism 160 in a latched state. The wing tip actuation mechanism 160 comprises a linear actuator 162 which is connected to the wing tip device 150 via linkage mechanism 164, 166, 168 and a latching mechanism 170. The linkage mechanism comprises an actuator shaft 164 and a wing tip lever 168, being connected via an intermediate rod 166. The actuator shaft 164 is movable along a single direction, being the direction of actuation of the linear actuator 162. The wing tip lever 168 is rigidly connected to, or otherwise forms part of, the wing tip device 150. The intermediate rod 166 is pivotally connected between the other two members 164, 168.

-15 - 100461 In the configuration shown in Figure 4, the wing tip device 150 is held in the flight configuration position. Figure 5 shows the wing tip device 150 in the load alleviation configuration, the latching mechanism 170 having been unlatched (represented by the circle representing the latching mechanism being shown in dotted line). The wing tip device 150 is thus freed to move under aerodynamic loads, by rotating about its hinge 155. Lift loads caused at the wing tip 150 are therefore not reacted through the fixed wing 126 and loads on the wing root are thus alleviated/reduced. During flight, it may be necessary to recover the freely moving wing tip device 150 so as to re-engage the actuator 162 with the linkage mechanism. Figure 6 shows the actuator 162 having been operated to cause the actuator shaft 164 to move to a position in which the latch mechanism 170 can re-connect to the intermediate rod 166, and therefore regain control of the wing tip device lever 168. Figure 7 shows the latching mechanism 170 having been engaged to latch the actuator shaft 164 and the intermediate rod 166 together again Figure 8 shows the wing tip device 150 in the ground configuration, with the latching mechanism 170 engaged.

[00471 It will be seen that the first embodiment of the invention provides a latch mechanism which is operable to selectively release the wing tip device for operation in a load alleviating configuration and also to control the position of the wing tip device, either to hold the device in a flight configuration or in a ground configuration. The latching mechanism 170 effectively acts as a clutch in that it allows for selectively connecting and disconnecting the linear actuator and the wing tip moveable by that linear actuator. The latching mechanism 170 also acts to protect the componentry of the wing tip actuation mechanism 160 from mechanical stress and/or back-driving by being able to be quickly disengaged from the wing tip device 150 in the case of a high load event.

100481 Figures 9 to 14 show a wing tip mechanism 260 according to a second embodiment of the invention. The same parts are labelled with reference numerals sharing the same last two digits. A wing tip device 250 is mounted for rotation about a hinge 255 and is movable between various configurations. The wing tip device 250 is activated via a turnbuckle 202 which is hinged at a lower edge 203 of the wing tip device 250 set apart from the hinge 255 axis thus providing a lever arrangement. The turnbuckle -16 - 202 is provided so as to facilitate setup and configuration of the overall mechanism 260. After setup/configuration, the turnbuckle 202 simply acts as a fixed length rod hinged at either end. The turnbuckle 202, and therefore the wing tip device 250, are moved by means of a slide member 204 which is mounted on a linear bearing 205 and thus able to translate along the bearing (in the left-right direction as shown in Figure 9). The slide member 204 is driven by a screw jack linear actuator 262 via a lock lever 264. The lock lever 264 is shown latched to the slide member 204 in Figure 9. The lock lever 264 has a latch member in the form of a pin 272 which is received in a latch trap in the form of a recess 274 in the slide member 204. The pin 272 is held in place by a lock spring 206 which urges down on the lock lever 264. Figure 9 shows the lock lever 264 latched to the slide member 204. The apparatus of Figure 9 has an associated control unit and sensors, which will be described later.

100491 Figure 10 shows the lock lever 264 unlatched from the slide member 204, the pin 272 having been lifted out from its associated recess 274. This then allows the wing tip device 250 to move freely about its hinge 255. In this configuration, the wing tip device 250 can thus provide load alleviation. In this embodiment, the unlatching of the mechanism 260 is caused actively, by means of a cam actuator 282 rotating a cam 280 which engages with the lock lever 264 and lifts the lever and therefore the pin 272 against the action of the lock spring 206. The cam actuator 282 is provided in the form of an electric rotary servo motor (a hydraulic servo motor, or other driver, could alternatively be used). The unlatching of the lock lever 264 from the slide member 204 is detected by means of a microswitch 286 which is switched on when the lock lever 264 is latched to the slide member 204 and switched off when the lock lever 264 is lifted off the slide member 204 by the cam 280. In alternative embodiments, a proximity sensor may be used instead of, or in addition to, the microswitch. Control of the wing tip device 250 by the linear actuator 262 may be regained by latching the lock lever 264 and slide member 204 back together. Figure 11 shows how this is achieved. The cam 280 is rotated back to the position shown in Figure 9 such that the lock spring 206 pushes the lock lever 264 down onto the slide member 204. The control unit (not shown in Figure 11) instructs the linear actuator 262 to move the lock lever 264 (to the right as shown in Figure 11) so that -17 -the pin 272 "finds" its recess 274. The movement caused by the control unit is in the form of a pattern of movement including sweeping the region in which the recess 274 is located. Thus, the lock lever 264 is moved to a target position, being the best estimate that the control unit can make of the correct location of the pin 272 relative to its recess 274. Once the lock lever 264 is moved to this target position the pin 272 may immediately drop down into its recess 274 to achieve a successful latching of the lock lever 264 to the slide member 204. Successful latching of the lock lever 264 to the slide member 204 is detected by the microswitch 286 being switched on by means of contact with the lock lever 264. If successful latching is not achieved immediately however, the control unit then moves the lock lever 264 successively left and right by progressively larger distances until the pin 272 drops into the recess 274 under the action of the spring 206. The speed of motion during this stage of sweeping is slower than the initial stage in which the lock lever 264 is moved to its initial target position by the control unit. This slower speed improves the chance of the pin 272 dropping into its recess 274 when the pin 272 is aligned with the recess 274 during its motion. It will be appreciated that during the process of the control unit causing the pin to find its recess, movement of the wing tip device (still being free to move independently of the wing tip actuator) will also cause relative movement between the pin and recess.

[00501 Figure 12 shows the pin 272 having dropped into the recess 274, the mechanism 260 thus being in its latched state. The linear actuator 262 thus has control over the movement of the wing tip device 250. The linear actuator 262 can then move, under the control of the control unit, the wing tip device 250 back to its flight configuration, as shown in Figure 9. Alternatively, the actuator can move the wing tip device 250 to a ground configuration as shown in Figure 13. The control unit is configured such that, in flight, both port and starboard wing microswitches 286 must indicate that the mechanism is latched before the actuators 262 on the wings can be moved. This may avoid asymmetric loading of the port and starboard wing tip devices.

100511 Figure 14 shows the control unit 290 which performs the steps illustrated by Figures 9 to 13. The control unit 290 receives an input from the microswitch 286 and also from a sensor device 292 (or multiple sources of information) from which a high -18 -load event can be detected and/or predicted. Detection of a high load event, or prediction of a high load event occurring imminently, enables the control unit 290 to quickly unlatch the mechanism 260 and allow the wing tip device 250 to provide load alleviation. The control unit 290 is also connected to the linear actuator 262 for moving the lock lever 264. Similarly, the control unit 290 is connected to the cam actuator 282 for rotating the cam 280. Power to the control unit 290 and also to the actuators 262, 282 may be provided by one or more batteries (not shown in the Figures).

[0052] The control unit 290 unlatches the apparatus, for example when an oncoming gust is detected. Such an arrangement enables the wing tip device 250 to be securely held in the flight configuration during normal cruise flight, but by unlatching the mechanism 260 the wing tip device 250 is movable quickly to the load alleviating configuration. This means the wing can avoid being subjected to high gust loadings. This in turn may enable the wing to have a relatively large span, without necessarily having to incur the associated weight penalty, because it can be designed for a lower magnitude of maximum load.

[0053] Figure 15 shows a wing tip actuator apparatus according to a third embodiment. The same parts are labelled with reference numerals sharing the same last two digits. In this embodiment the function of the lock lever, the slide member, and the latching mechanism provided by the pin and recess of the second embodiment are combined in a telescopic barrel arrangement 361. The telescopic arrangement 361 includes an outer cylinder 363 which accommodates a sliding rod 365. The outer cylinder 363 and sliding rod 365 are coaxially arranged along a common longitudinal axis 367. The outer cylinder 363 has a longitudinal slot 371, which runs parallel to the longitudinal axis. The sliding rod 365 carries latch member in the form of a pin 372, which when the wing tip device is in its load alleviation configuration travels freely along the length of the slot 371. The longitudinal slot 371 of the outer cylinder 363 also includes latch trap in the form of a recess 374 for catching the pin 372, and locking it in place relative to the longitudinal axis 367. The outer cylinder 363 is mounted for rotation about the longitudinal axis 367 and therefore relative to the sliding rod 365 and its pin 372. Figure 16 shows schematically a cross-section of the telescopic arrangement 361. The outer surface, or at -19 -least part of it, of the outer cylinder 363 is provided with teeth 375 (shown schematically in Figure 15) to allow the outer cylinder 363 to be rotated by a drive member 380, which is provided with corresponding teeth (again which in this embodiment are arranged over part only of the outer surface of the drive member 380). The drive member 380 is spring loaded so that it urges the outer cylinder 363 to rotate in a direction that lifts the recess 374 towards the pin 372. The drive member 380 is operable to rotate the outer cylinder 363 in the opposite direction thus rotating the recess 374 away from the pin 372 and unlatching the sliding rod 365 from the outer cylinder 363. One end of the outer cylinder 363 is connected to a linear actuator (not shown) for actuating movement of the wing tip device, and at the opposite end, an end of the sliding rod 365 is attached to a lever assembly (not shown) which moves with the wing tip device (not shown). The outer cylinder 363 is provided with four such longitudinal slots 371 (two being visible in Figure 15) arranged at 90° intervals around the circumference of the cylinder 363 and the rod 365 comprises four pins 372. Four such rod-pin-slot arrangements are provided in order to give redundancy to the system. Alternative embodiments may comprise a different numbers of pins and/or slots, and the slots may be spaced (e.g. staggered) to avoid stress raisers within the cylinder.

100541 The barrel arrangement 361 is operable, under the control of a control unit, linear actuator, and the driver 380 to selectively latch/unlatch the movement of the wing tip device to/from the linear actuator. This facilitates the wing tip device to be allowed to freely rotate in a load alleviating mode (in an unlatched mode). It also facilitates the retrieval of control over the active movement of the wing tip device so that the linear actuator may rotate the wing tip device (in a latched mode) to a (wider wing span) flight position and when on the ground to a (narrower wing span) ground position, and also to lock (hold) the wing tip device in such a position.

100551 Figure 17 is a flowchart schematically illustrating a method of controlling an aircraft wing according to fourth embodiment of the invention. The aircraft wing so controlled may be in accordance with the first to third embodiments or another different embodiment of the invention. The wing comprises a wing tip mounted for rotation about a hinge at an end of a fixed wing. Movement of the wing tip is controlled by an actuator, -20 -which in turn is controlled by a control unit. The wing tip has an unlatched state in which the wing tip is allowed to move under the action of aerodynamic forces exerted on the wing tip and thus provide load alleviation for the wing. The wing tip has a latched state in which the wing tip is moveable under the control of the actuator. Initially, step 410, the actuator is latched to the wing tip and the wing tip device is elevated in its ground configuration. The aircraft then moves from the gate and the wing tip device is moved by the actuator to a flight configuration (step 430). The aircraft takes off and then assumes I g flight conditions. A high gust is detected (step 440) by the control unit, which causes automatic release of the wing tip device by the actuator, the actuator being unlatched from the wing tip device (step 450). In the unlatched state, the wing tip device is free to rotate about its hinge, thus providing passive load alleviation for the wing. Once the high load event has passed, the control unit initiates a sequence of movements of the actuator in order to recover the control of the wing tip device. The sequence of movements includes the control unit moving the actuator to perform a sweeping motion such that it eventually finds the correct position for aligning the apparatus so that the wing tip device can be latched to the actuator (step 460). At this moment, the wing tip device is in an intermediate configuration. The control unit then causes movement of the actuator to move the wing tip device back to the flight configuration (step 470). In embodiments, there may also be a further step of determining that both the port and starboard wing tip devices are latched to their respective actuator before the control unit instructs the actuators to move the wing tip to the flight configuration.

[0056] While not shown in Figure 17, the method may additionally include a step of moving the wing tip, when in its latched state and when in flight, to a configuration between the flight configuration and the ground configuration. There may for example be at least one intermediate configuration providing different span-wise loading on the wing during flight from the flight configuration and providing advantageous aerodynamic performance. The wing tip device may be arranged to be moved between multiple different positions, for example being used as a spoiler device.

[0057] 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 -21 -invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0058] The unlatching of the wing tip from its actuator may be achieved actively -under the control of a control unit -or passively, if designed differently from the illustrated embodiments. For example, with reference to the embodiment shown in Figures 9 to 13, the latching pin may be arranged to be pushed out of the recess by shaping the recess and pin and by sizing the load spring in such a way that above a threshold load exerted by the wing tip device on the slide member, the pin is forced out of the recess, thus passively unlatching the slide member and lock lever.

[0059] In the illustrated embodiments, the spring loading of the latch mechanism causes the latch pin or the like to be urged towards the recess so that the action of the spring needs to be overcome to unlatch the mechanism. It would also be possible to spring-load the latch mechanism so that it is urged into the unlatched position, so that active movement of the latch mechanism, for example by a latch actuator, is required in order to cause the latching. Continued actuation of the latch actuator may then be required to maintain the latched state.

[0060] The latch pin and or other latch members shown in the Figures, may include roller bearings or other bearing arrangements to reduce friction when performing translational movement in the load alleviation configuration.

[0061] The various parts of the apparatus illustrated in the Figures may be duplicated, to provide redundancy. The geometrical arrangements may be different without departing from the function provided. There may be more than one lock lever and/or slide member, for example. There may be multiple actuators.

[0062] The telescopic arrangement shown in Figures 15 and 16 could be replicated, with multiple telescopic arrangements being provided in parallel. One or more pinion gears could be provided between them so as to achieve simultaneous rotation of the outer cylinder, and therefore simultaneous locking and unlocking of the pin from the slot. 100631 The telescopic arrangement shown in Figures 15 and 16 could be installed within the body of a linear actuator, possibly forming part of the actuator system rather than being connected in series with it.

-22 - 100641 In the embodiments, the locking of the wing tip device in position is provided solely by the non-back driveable wing tip actuator (i.e. the linear actuator). In other embodiments, the locking of the wing tip device in position may additionally or alternatively be provided by other locking mechanisms.

[0065] 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 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, may not be desirable, and may therefore be absent, in other embodiments.

[0066] The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims. Features described in relation to one example or embodiment may be used in other described examples or embodiments, e.g. by applying relevant portions of that disclosure. The term 'or' shall be interpreted as and/or' unless the context requires otherwise.

Claims

-23 -CLAIMS1. A wing tip mechanism for moving a wing tip device relative to a fixed wing of an aircraft, the wing tip mechanism comprising a wing tip actuator for moving the wing tip device, a latch member and a latch trap for latching the latch member, the wing tip mechanism being so configured that, in use, when the latch member is latched by the latch trap the wing tip device is movable relative to the fixed wing under the control of the wing tip actuator, and when the latch is unlatched the wing tip device is released from the control of the wing tip actuator.
2. A wing tip mechanism according to claim 1, wherein the wing tip actuator comprises a linear actuator.
3. A wing tip mechanism according to claim I or claim 2, wherein the wing tip actuator comprises a screw jack actuator.
4. A wing tip mechanism according to any preceding claim, wherein the latch member is spring-loaded.
5. A wing tip mechanism according to any preceding claim, further comprising a latch actuator for latching and/or unlatching the latch member in relation to a latch trap.
6. A wing tip mechanism according to claim 5, wherein the latch actuator arranged to operate a cam to selectively latch or unlatch the latch member.
7. A wing tip mechanism according to claim 5 or claim 6, wherein the latch actuator is arranged to cause relative rotational motion between the latch member and the latch trap.
-24 - 8. A wing tip mechanism according to any preceding claim, wherein the wing tip mechanism further comprises at least one lever configured to convert motion from the wing tip actuator into motion of the wing tip device.
9. A wing tip mechanism according to any preceding claim, further comprising a control unit arranged to control the latching of the latch member, control the unlatching of the latch member, and control the operation of the wing tip actuator and thus movement of the wing tip device when the latch member is latched.
10. A wing tip mechanism according to claim 9, further comprising a latch sensor arranged to detect at least one of (i) whether the latch member is latched and (ii) whether the latch member is unlatched, and wherein the control unit is arranged to receive a signal from the latch sensor.
11. A wing tip mechanism according to claim 9 or claim 10, wherein the control unit is arranged to control the latching of the latch member by actuating the wing tip actuator to cause relative movement of a first kind between the latch member and the latch trap so that they move closer together, and then relative movement of a second kind, being different from the first kind, between the latch member and the latch trap to cause latching of the latch member.
12. An aircraft wing comprising a fixed wing, a wing tip device mounted for movement relative to the fixed wing, and a wing tip mechanism according to any preceding claim, the wing tip mechanism being configured to move the wing tip device relative to the fixed wing.
13. An aircraft wing according to claim 12, wherein the wing tip device is mounted for rotational movement about a hinge axis, being orientated such that the hinge axis at -25 -the trailing edge of the wing is further nboard than the hinge axis at the leading edge of the wing.
14. An aircraft wing according to claims 12 or 13, wherein the wing tip actuator is arranged to cause movement of the wing tip device via a lever.
15. An aircraft wing according to any of claims 12 to 14, wherein the wing tip device has a flight configuration, a load alleviation configuration, and a ground configuration.
16. A method of controlling an aircraft wing, wherein the wing comprises a wing tip movably mounted at an end of a fixed wing by an actuator, wherein the wing tip has (i) an unlatched state in which the wing tip is allowed to move under the action of aerodynamic forces exerted on the wing tip and thus provide load alleviation for the wing, and (ii) a latched state in which the wing tip is moveable under the control of the actuator, and the method includes a step of moving the wing tip when in its latched state to at least one of (a) a flight configuration, and (b) a ground configuration.
17. A method of controlling an aircraft wing according to claim 16, wherein the method includes a step of latching the wing tip before the step of moving the wing tip.
18. A method of controlling an aircraft wing according to claim 17, wherein the step of latching the wing tip includes a control unit performing a sweep and find operation in order to align a latch member with a target position in which it is then able to latch the wing tip.
-26 - 19. A method of controlling an aircraft wing according to any of claims 16 to 18, wherein a control unit causes the wing tip to be unlatched in response to detecting a high load event.
20. An aircraft comprising an aircraft wing according to any of claims 12 to 15 and/or being configured for use in the method of any of claims 16 to 19.
2 I. An aircraft according to claim 20, comprising the fixed wing and the wing tip device, the wing tip device being rotatably mounted on a hinge at the tip of the fixed wing such that the wing tip device may rotate, about the hinge, relative to the fixed wing, wherein the hinge is orientated non-parallel to the line-of-flight direction of the aircraft.
22. An aircraft comprising: a wing with a wing tip device rotatably mounted on a hinge such that the wing tip device may rotate, about the hinge, relative to the rest of the wing; a linear actuator and lever arrangement having (a) an engaged configuration in which they are operable to rotate the wing tip device about the hinge to any one of a plurality of different positions, and to hold the wing tip device in such a position and (b) a disengaged configuration in which the wing tip device is released and able to rotate about the hinge independently of the linear actuator; and a spring-loaded pin and associated structure having a recess in which the pin is received when the linear actuator and lever arrangement are in the engaged configuration, the pin and associated structure being arranged such that when the linear actuator and lever arrangement are in the disengaged configuration, the pin is not received in the recess and is arranged to move relative to the associated structure as the wing tip device rotates about the hinge.
23. An aircraft according to claim 22 further comprising a control unit arranged to control movement of the pin into and out of the recess.
-27 - 24. An aircraft according to claim 23 wherein the control unit is arranged to place the linear actuator and lever arrangement in the engaged configuration by moving the pin relative to the associated structure in a pattern of movement causing the pin to search and find the recess.
25. An aircraft according to any of claims 22 to 24, wherein the linear actuator is a screw jack actuator.