Articulation mechanism for forming a lock to hold a wing tip device in a ground configuration

An aircraft wing is disclosed having a wing tip device configurable between a flight configuration for use during flight and a ground configuration for use during ground-based operations to reduce the span. The wing includes an actuator and an actuation assembly having an articulation mechanism having a master bell crank connected to the actuator and a slave link connecting the master bell crank with the wing tip device. The slave link is pivoted, at one end, to the master bell crank about a first pivot, and at the other end, to the wing tip device about a second pivot. The master bell crank being pivotably mounted, at its base, about a third pivot.

RELATED APPLICATIONS

The present application claims priority to Great Britain Patent Application Number 1520290.6, filed Nov. 18, 2015, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to aircraft wings and wing tip devices, and more specifically, but not exclusively, to aircraft wings with moveable wing tip devices, actuation assemblies for use in such wings, aircraft incorporating such wings, and to methods of moving a wing tip device.

There is a trend towards increasingly large passenger aircraft, for which it is desirable to have correspondingly large wing spans. 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 have been suggested for use on passenger aircraft, where a wing tip device is movable between a flight configuration for use during flight, and a ground configuration for use during ground-based operations. In the ground configuration, the wing tip device is moved away from the flight configuration such that the span of the aircraft wing is reduced, thereby allowing use of existing gates and safe taxiway usage. By way of example, US 2013/0292508 discloses an arrangement in which the wing tip device is rotatable about a hinge located on the fixed (inner) wing. Other arrangements, such as that disclosed in WO2011/051699, enable a more complex movement of the wing tip device.

Aircraft having moveable wing tip devices, must be suitable for flight when the wing tip device is in the flight configuration yet must also be able to move the wing tip device, during ground-based operations. This can pose some difficulties:

Firstly, in the flight configuration it tends to be desirable to have a seal between the wing tip device and the fixed wing to ensure smooth airflow in this region and to minimise drag losses. However, if seals are used, they tend to be susceptible to significant wear during movement between the flight and the ground configurations.

Secondly, it is necessary for flight loads on the wing tip device to be adequately transferred into the main wing. Providing an arrangement in which the flight loads can be adequately transferred, whilst still enabling the wing tip device to be moved from that flight configuration to the ground configuration when required, can pose significant design difficulties.

There are also other technical challenges in providing a practical arrangement for moving a wing tip device between the flight and ground configurations. Amongst the issues to be addressed are: the problem of providing a safe and reliable arrangement to enable such movement without impacting unduly on the design of the wing; the problem of providing a compact and lightweight drive to effect the movement of the wing tip device; and the problem of how to secure the wing tip device in one or both of the flight and/or ground configurations.

The present invention seeks to mitigate at least some of the above-mentioned problems.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided an aircraft wing comprising a fixed wing and a wing tip device at the tip thereof, wherein the wing tip device is configurable between: (i) a flight configuration for use during flight and (ii) a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is moved away from the flight configuration such that the span of the aircraft wing is reduced, wherein the wing comprises an actuator and an actuation assembly, the actuation assembly comprising an articulation mechanism for transmitting the actuation force from the actuator such that actuation of the actuator moves the wing tip device between the flight and the ground configurations, wherein the articulation mechanism comprises a master bell crank connected to the actuator and a slave link connecting the master bell crank with the wing tip device, the slave link being pivoted, at one end, to the master bell crank about a first pivot, the slave link being pivoted, at the other end, to the wing tip device about a second pivot, and the master bell crank being pivotably mounted, at its base, about a third pivot, and wherein the articulation mechanism is arranged such that when the wing tip device is in the ground configuration, the master bell crank and the slave link are in an over-centre position such that the first pivot is out of line with the second and third pivots, thereby forming an over-centre lock to hold the wing tip device in the ground configuration.

Having the master bell crank and the slave link in an over-centre position forms an over-centre lock to hold the wing tip device in the ground configuration. This provides a simple, yet effective lock for holding the wing tip device in this configuration. Furthermore, since the actuator is connected to the articulation mechanism (to transmit the actuation force such that actuation of the actuator moves the wing tip device between the flight and the ground configurations) the same actuator can be used to both move the wing tip device, and to form the lock (by moving master bell crank and slave link into the over-centre condition). This removes the need for a separate actuator to lock/unlock the wing tip device in the ground configuration.

The actuator may be connected to the master bell crank at a rotatable connection. The rotatable connection is preferably constrained to move along a pre-determined locus upon actuation of the actuator.

The rotatable connection may be constrained to move along a groove, the shape of the groove determining the locus of movement of the connection.

At least part of the locus is preferably curved. The curve preferably curves downwards (when viewed moving along from the flight to the ground configurations). Shaping the locus in this manner preferably causes the master bell crank to rotate downwardly (as the connection moves along that curve). This in turn, may move the first pivot downwards. The curved locus may be arranged such that, when the wing tip device is in the ground configuration, the first pivot has moved below a notional line linking the second and third pivots (thereby forming the over centre lock).

The actuation assembly may be arranged such that the wing tip device is moved from the flight configuration to the ground configuration in a two-stage movement. The two-stage movement may comprise a first stage in which the wing tip device is translated away from the flight configuration in a linear movement only, and a second, subsequent stage, in which the wing tip device is rotated to the ground configuration.

A two stage movement, particularly a two stage movement in which the first stage is a linear movement only, has been found to be particularly beneficial. For example, having a first stage that is only a linear movement, tends to reduce the wear on any sealing arrangement between the fixed wing and the wing tip device, because it tends to avoid relatively rotation occurring between sealing surfaces. Alternatively or additionally, having a first stage that is only a linear movement, may facilitate engagement between the fixed wing and the wing tip device to ensure an effective load-transfer arrangement.

In principle, the second stage of movement may comprise some translational movement in combination with the rotational movement. In preferred embodiments of the invention however, the wing tip device, in the second stage of movement, undergoes substantially no translational movement. In that second stage of movement, the wing tip device is preferably rotated in a rotational movement only.

In the flight configuration the trailing edge of the wing tip device is preferably a continuation of the trailing edge of the fixed wing. The leading edge of the wing tip device is preferably a continuation of the leading edge of the fixed wing. There is preferably a smooth transition from the fixed wing to the wing tip device. It will be appreciated that there may be a smooth transition, even where there are changes in sweep or twist at the junction between the inner wing and wing tip device. However, there are preferably no discontinuities at the junction between the fixed wing and wing tip device. The upper and the lower surfaces of the wing tip device may be continuations of the upper and lower surfaces of the fixed wing.

The first stage of movement is preferably arranged to separate the wing tip device from the fixed wing. When separated, the upper and lower surfaces of the wing tip device are preferably no longer continuations of the respective upper and lower surfaces of the fixed wing. The respective upper and lower surfaces are preferably separated such that they no longer abut, or otherwise contact, each other. The respective upper and lower surfaces are preferably separated such that they are spaced apart in the direction of movement of the first stage.

One of the fixed wing and the wing tip device may comprise a plurality of male members, such as spigots. The other of the fixed wing and the wing tip device may comprise a plurality of corresponding female members, such as bushes. The female members may be arranged to receive the male members when the wing tip device is in the flight configuration, such that flight loads may be transferred, via the male members, from the wing tip device into the fixed wing. Such an arrangement tends to be beneficial because it enables flight loads to be adequately managed and reacted into the fixed wing.

The male and female members may be arranged to transfer bending moments into the fixed wing. The male and female members may be arranged to transfer vertical and/or forward/aft shear loadings into the fixed wing. The male and female members may be arranged such that they are substantially unable to transfer inboard/outboard loads (along the span of the wing) into the fixed wing. For example, the male and female members may be arranged such that they are substantially unable to transfer loads in a direction along the mean chord line, into the fixed wing.

The longitudinal axes of the male members may extend in a first direction. The actuation assembly may be arranged such that the first stage of movement is a translation in the first direction only. Such an arrangement has been found to be beneficial because it minimises the wear and/or out-of-plane forces, acting on the male member during movement from the flight to the ground configuration.

The first stage of movement is preferably a translation in an outboard direction along the length of the wing. The outboard direction is preferably substantially parallel to a main spar of the fixed wing. The outboard direction may be substantially perpendicular to the ribs of the fixed wing.

The actuation assembly may comprise a hinge about which the wing tip device is rotatable during the second stage of movement. In some embodiments of the invention, the wing tip device may be prevented from rotating during the first stage of movement, but be free to rotate during the second stage of movement.

The actuation assembly may comprise a sliding chassis, slideably moveable relative to the fixed wing. The sliding chassis may be coupled to the wing tip device. The sliding chassis may comprise, or otherwise be associated with, the hinge. The hinge may be fixed, relative to the sliding chassis. The actuation assembly may be arranged such that, during the first stage of movement, the sliding chassis is arranged to translate, thereby creating a linear movement of the wing tip device (for example via the linear movement of the hinge).

The actuation assembly may comprise a translational stop feature, arranged to limit the extent of the translational movement, away from the flight configuration. The translational stop feature may be arranged to limit the extent of the translational movement of the sliding chassis.

The sliding chassis may contain the articulation mechanism.

The articulation mechanism may be arranged to transfer the actuation force into the wing tip device at a location remote from the hinge, thereby creating a moment arm to rotate the wing tip device. For example, the second location may be remote from the hinge and the second direction may be such that the force is offset from the hinge.

Actuation of the master bell crank preferably results in a tensile or compressive force along the slave link (that force being arranged to act on the wing tip device). The tensile or compressive force is preferably in a direction that is non-parallel to the direction of the actuation force (for example non parallel to the extension direction of a linear actuator).

The third pivot may be slideably moveable relative to the sliding chassis. master bell crank may be pivotably mounted on the sliding chassis about the third pivot. The first location (on which the actuation force acts) may be located between the third pivot and the first pivot at the other end of the bell crank (at which the link is attached).

In principle, the sliding chassis may be mounted on the fixed wing in any manner that enables sliding movement. More preferably however, the actuation assembly comprises a fixed chassis onto which the sliding chassis is slideably mounted. The fixed chassis may be fixedly attached to the fixed wing. Providing a fixed chassis on which the sliding chassis is mounted has been found to be especially beneficial because it enables the actuation assembly to be pre-assembled as a unit, and for example tested, at a location remote from the aircraft wing. Such an articulation assembly may then be able to be installed in the wing in an efficient manner.

In embodiments in which the wing undergoes a two-stage movement, the actuation assembly is preferably arranged such that the same actuator is arranged to effect both the first and the second stages of movement. Such an arrangement is beneficial from both a weight and an airworthiness perspective as it minimises the number of critical components being used. The actuator is preferably a linear actuator. The actuator may be coupled to the fixed wing at one end, and coupled to the actuation assembly (for example the articulation mechanism) at the other end.

In the flight configuration, the span of the aircraft may exceed an airport compatibility gate limit. In the ground configuration the span of the aircraft is preferably reduced such that the span (with the wing tip device in the ground configuration) is less than, or substantially equal to, the airport compatibility gate limit.

When the wing tip device is in the ground configuration, the aircraft incorporating the wing, may be unsuitable for flight. For example, the wing tip device may be aerodynamically and/or structurally unsuitable for flight in the ground configuration. The aircraft is preferably configured such that, during flight, the wing tip device is not moveable to the ground configuration. The aircraft may comprise a sensor for sensing when the aircraft is in flight. When the sensor senses that the aircraft is in flight, a control system is preferably arranged to disable the possibility of moving the wing tip device to the ground configuration.

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.

The two-stage movement described herein tends to be described with reference to movement of the wing tip device from the flight configuration to the ground configuration. The actuation assembly is preferably arranged to also move the wing tip device from the ground configuration to the flight configuration in a two-stage movement. The two stage movement is preferably the reverse of the movement from the flight to the ground configuration. In other words, the wing tip device is rotated from the ground configuration, and then, subsequently, translated towards the flight configuration in a linear movement only. For the sake of clarity, each and every feature is not described herein with reference to both directions of movement. Instead, it will be appreciated that any features described with reference to one direction of movement, may be equally applicable, in reverse, to the reverse direction of movement.

According to another aspect of the invention, there is provided an actuation assembly as described herein. The actuation assembly may comprise the articulation mechanism arranged such that when the wing tip device is in the ground configuration, the master bell crank and the slave link are in an over-centre position such that the first pivot is out of line with the second and third pivots, thereby forming an over-centre lock to hold the wing tip device in the ground configuration.

The assembly may comprise a fixed chassis for installation into a wing and a sliding chassis, slideably mounted in the fixed chassis. The sliding chassis may comprise a hinge, fixed relative thereto, about which a wing tip device may be mounted for rotational movement. The sliding chassis may carry an articulation mechanism for transferring an actuation force acting at a first location, and in a first direction, into an actuation force acting in a second location and in a second direction, such that a force may be applied to rotate the wing tip device about the hinge.

The actuation assembly may comprise a fixed chassis for installation into a wing and the sliding chassis is slideably mounted in the fixed chassis.

According to another aspect of the invention there is provided a wing tip device coupled to the actuation assembly described herein.

According to another aspect of the invention there is provided an aircraft comprising the aircraft wing described herein. 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.

According to yet another aspect of the invention, there is provided a method of moving, and subsequently locking, a wing tip device in position using a common actuator, the wing tip device being in an aircraft wing comprising a fixed wing and a wing tip device at the tip thereof, wherein the wing tip device is configurable between: (i) a flight configuration for use during flight and (ii) a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is moved away from the flight configuration such that the span of the aircraft wing is reduced, the method comprising the step of: providing an articulation mechanism comprising a master bell crank connected to the actuator and a slave link connecting the master bell crank with the wing tip device, the slave link being pivoted, at one end, to the master bell crank about a first pivot, the slave link being pivoted, at the other end, to the wing tip device about a second pivot, and the master bell crank being pivotably mounted, at its base, about a third pivot, and actuating the actuator to move the wing tip device from the flight to the ground configuration, the articulation mechanism being arranged such that when the wing tip device is in the ground configuration, the master bell crank and the slave link are in an over-centre position such that the first pivot is out of line with the second and third pivots, thereby forming an over-centre lock to hold the wing tip device in the ground configuration.

DETAILED DESCRIPTION

FIG. 1is a schematic drawing showing an aircraft1having aircraft wings3according to a first embodiment of the invention. The end of one of the wings3on the aircraft1is shown in more detail inFIGS. 2aand 2b, to which reference is now made:

The wing3comprises a fixed wing5extending from the wing root at the aircraft fuselage, to a tip. At the tip of the fixed wing5there is a wing tip device7. The wing tip device7is moveable between a flight configuration (shown inFIG. 2a) and a ground configuration (shown inFIG. 2b).

In the flight configuration the wing tip device7is effectively an extension of the fixed wing5, such that the leading and trailing edges9′,11′ of the wing tip device are continuations of the leading and trailing edges9,11of the fixed wing5, and the upper and lower surfaces of the wing tip device7are continuations of the upper and lower surfaces of the fixed wing5. The fixed wing and the wing tip device together form a main wing3on the aircraft1.

The wing tip device7is moveable from the flight configuration (shown inFIG. 2a) to a ground configuration (shown inFIG. 2b). In the ground configuration, the wing tip device7is moved such that the span of the aircraft1is reduced (relative to the flight configuration). This enables the aircraft1to have a relatively large span during flight (which flight span exceeds airport gate limits), whilst still complying with airport gate limits, safe taxiway usage etc., when on the ground.

Having a moveable wing tip device per se, to achieve this span reduction on the ground, is known. However, the first embodiment of the invention provides an improved way of moving the wing tip device between the two configurations, as will now be explained with reference to the other Figures.

Many of the Figures have been produced from Computer Aided Design (CAD) packages. Thus, it will be appreciated that some of the Figures include constructional lines, and/or some lines showing hidden, or internal, features of the embodiment.

FIGS. 3ato6show the position of the wing tip device7at different times (and from different viewpoints) as the wing tip device7moves from the flight configuration to the ground configuration.

FIGS. 3aand 3bare both views of the end of the wing3with the wing tip device7in the flight configuration. As best illustrated inFIG. 3a(which is a frontal view), the upper and lower surfaces of the wing are substantially continuous across the junction between the fixed wing5and the wing tip device7. The interfacing edges13,15of the fixed wing5and the wing tip device7comprise resiliently deformable “P” seals (not visible in the Figures), which are compressed in the flight configuration to seal the junction and prevent aerodynamic leakage flow across it.

The flight configuration is for use during flight, so it is important that the wing tip loads (arising from aerodynamic forces and/or inertial loads) are transferred into the fixed wing5. In this respect, the fixed wing5of the first embodiment comprises three pairs of fixed spigots17a,17b,17c. Two pairs17a,17bprotrude from the outboard ends of the main spar19and front spar21, and one pair17cprotrude from an inboard structure23of the spars, such that some of the loads can be reacted inboard on the fixed wing5. A support frame25of the wing tip device7comprises corresponding holes27a-c, lined with bushes, arranged to receive the spigots17a,17b,17cwhen the wing tip device7is in the flight configuration. The engaging spigots/bushes17a-c/27a-cenable loads in the wing tip device7to be reacted into the spars19,21of the fixed wing5.

The longitudinal axes of the spigots (and the bushes) extend in an outboard direction, substantially aligned with the spars19,21, and substantially in the plane of the fixed wing5. Thus, the engaging spigots/bushes17a-c/27a-care particularly effective in transferring vertical and forward/aft loads (which are the predominant loads experienced by the wing tip device5during flight).

The spigots and bushes17a-c/27a-care best illustrated inFIGS. 3b, and 13a-c, in which the wing skin has been removed for clarity.FIG. 3aalso shows close-up view of one of the pairs of spigots17a, in phantom, extending through the bushes27ain the root25′ of the support frame25.

FIGS. 4aand 4bshow the wing after a first stage of movement of the wing tip device7towards the ground configuration. The wing tip device7has undergone a translational movement in an outboard direction along the wing (shown by the large arrow inFIG. 4b). It is important to note that this movement is only a translation and it does not comprise any rotational component of movement. Having this type of initial movement away from the flight configuration, has been found to give rise to two advantages. Firstly, the movement is parallel to the axes of the pairs of spigots17a-c. Thus it enables the wing tip device7to readily disengage from the spigots17a-c(i.e. the spigots17a-care moved clear of the bushes27a-c) without requiring secondary mechanisms to retract, or otherwise move, the spigots. Secondly, this translational movement enables the “P” seals to be broken (i.e. separated) without a relative rotational component of movement. Having a rotational component of movement when breaking a seal has been found to increase wear of the seal, so ensuring a linear separation tends to minimise any wear and may enable an improved sealing arrangement.

In the first embodiment of the invention, the movement to the ground configuration is a two-stage movement. The first stage is the translational movement described above and with reference toFIGS. 4aand 4b(i.e. to separate the seals and move the spigots clear of the bushes). The second stage is a rotational movement described below with reference toFIGS. 5aand5b.

After the first stage of movement, the wing tip device7is arranged to rotate (and only rotate) to the ground configuration. As shown inFIGS. 5aand 5b, the rotation is about a hinge29located near the upper surface of the wing. The wing tip device7is rotated to bring it into a slightly over-vertical position (FIG. 5b). This position is geometrically stable and also maximises the span reduction that can be achieved. The wing tip device7is held in position by a lock (described in more detail below with reference toFIG. 10b).

Having a second stage of movement that is a substantially pure rotation has been found to be beneficial because it avoids any increase in span that might otherwise occur with a translational movement outboard.

The wing tip device7is also moveable in the reverse of the above-described movement when moving from the ground configuration to the flight configuration. In other words, when moving into the flight configuration (for example is preparation for take-off) the wing tip device7is first rotated downwardly about the hinge29until it is substantially in-plane with the fixed wing5. The wing tip device7is then translated onto the spigots17a-csuch that they engage with the bushes27a-cand such that the wing tip device7abuts the tip of the fixed wing5, thereby compressing the seal at the interface.

The description above, with reference toFIGS. 3ato 5bof the first embodiment of the invention, illustrates the nature of the two-stage movement of the wing tip device7. That movement is enabled by an actuation assembly31located in the fixed wing. The details of the actuation assembly31are shown inFIG. 6onwards, and will now be described:

FIG. 6is an exploded view of the actuation assembly. The actuation assembly31comprises a sliding chassis33, contained in a fixed chassis35. The sliding chassis33is mounted on two pairs of spring-loaded bogies37such that the sliding chassis33is slideably moveable along two respective tracks39within the interior side faces of the fixed chassis35. The sliding chassis33comprises a lip41that protrudes through an open channel43in the top of the fixed chassis35thereby forming a translational stop feature (discussed in more detail below).

The fixed chassis35is itself fixedly attached to a bath-tub fitting45located between the front and rear spars of the fixed wing5(seeFIG. 7a).

The sliding chassis33contains an articulation mechanism47comprising a master bell crank49and a slave link51. The slave link51is pivoted, at one end, to the master bell crank49about a first pivot52. The slave link51is pivoted, at the other end, to the wing tip device7about a second pivot54, The master bell crank49is pivotably mounted at one end about a third pivot56that is mounted on a slider53, arranged to move along a central rail55in the sliding chassis33. Between the ends of the bell crank49the centre of the bell crank is connected, at a rotational connection58, to a linear actuator assembly57comprising two linear actuators57. This rotational connection58is constrained to move along a drooping groove61defined in the sliding chassis structure.

The sliding chassis33is also connected to the wing tip device7via the hinge29located at the distal end of the sliding chassis31. The outer ends of the hinge include a kidney-shaped end-cap63. The end-caps63are arranged to abut (in the flight configuration) an abutment surface65on the fixed chassis35thereby forming a rotational stop feature (discussed in more detail below).

FIGS. 7ato 7cshow the actuation assembly31when the wing tip device7is in the flight configuration. At this time, the actuators57are fully retracted and the sliding chassis33is at its rearmost (i.e. furthest inboard) position such that it is flush with the end of the fixed chassis35. The lip41on the sliding chassis33that extends out of the open channel43in the fixed chassis35is a linear distance X from the end of the channel. The articulation mechanism47is pulled back as far as possible by the actuators57such that the link51is almost horizontal. As shown inFIG. 7c, the kidney-shaped end-stop63on the hinge29is received in a tight fit against the abutment surface65of the fixed chassis35.

To begin the movement to the ground configuration, and more specifically to effect the first stage of that movement, the actuators57are extended. The kidney-shaped end-stop63is prevented from rotating by the abutment surface65on the fixed chassis35, and the wing tip device7is thus unable to rotate relative to the actuation assembly31. Instead, the extension of the actuators57pushes the sliding chassis33(via the articulation mechanism47which is forced to act as a rigid link due to the presence of the rotational stop63,65). This causes a pure translational movement in the actuation assembly31, relative to the fixed chassis35. Such movement is parallel to the axes of the spigots17a-c. Since the wing tip device7is coupled to the sliding chassis33, along the hinge29, this movement acts to push the wing tip device7along the length of the spigots17a-cuntil they are clear of the bushes27a-c. The moment at which the spigots17a-chave just cleared the bushes27a-cis shown inFIGS. 8ato8d.

As most clearly shown inFIGS. 8aand 8b, the lip41of the sliding chassis33, has at this point reached the end of the channel43in the fixed chassis35(i.e. the distance X inFIG. 7ais only fractionally longer than the length of the spigots17a-cthat had been received in the bushes27a-c). The lip41abuts the end of the channel43and prevents further linear movement of the sliding chassis33beyond this point. However, the rotational stop feature63,65is designed such that, at the same time the lip41abuts the end of the channel43, the kidney-shaped end caps63simultaneously reach the end of the abutment surface65(seeFIG. 8d) such that the wing tip device7is freed to rotate about the hinge29.

Continued extension of the actuators57thus ceases to effect a translational movement, and instead effects a rotation of the wing tip device7about the hinge29(i.e. the second stage of movement). As best illustrated inFIGS. 9aand 9b, the sliding chassis33now remains stationary but the articulation mechanism47moves along the central rail55. The locus of the rotational connection58on the bell crank49(at which the actuator is attached) follows the drooping groove61(as best illustrated inFIG. 10b). The groove61is shaped, along its first half, to maintain the link51in an orientation that is approximately inline with the rotational connection58and the first and second pivots52,54and to transfer the actuation force onto the wing tip device7at a location remote from (i.e. offset from) the hinge29. This creates a moment arm, about the hinge29, which acts to rotate the wing tip device7upwardly.

FIGS. 9cand 9dshow how the end-cap of the hinge no longer prevents rotation, as it is clear of the abutment surface.

Continued extension of the actuators57moves the wing tip device7into the ground configuration (shown inFIGS. 10aand 10b) in which the wing tip device7is upright, above the hinge29. The end of the groove61is drooped so that the primary component of force along the bell-crank49continues to act to pull the slider53along the rail55, rather than merely generating large vertical reactionary forces against the rail55. In the ground configuration, the bell-crank49and slave link51form an over-centre lock (discussed in more detail below).

FIG. 10cshows how the end-cap63of the hinge29continues to allow rotation, as it is clear of the abutment surface65.

The actuation assembly31in the first embodiment of the invention has been designed to be quickly and easily installed on the aircraft fixed wing5. In particular, the actuation assembly31comprises a fixed chassis35and a sliding chassis33(the latter containing the articulation mechanism47). Since all components in the actuation assembly31move relative to the fixed chassis35, the fixed chassis35can simply be held whilst the assembly31is bench-tested prior to installation on the spars19,21of the wing. There is no need for all testing to take place during, or after, installation on the fixed wing5. This may enable the actuation assembly31to be a ‘line replaceable unit’ (LRU).

As shown inFIGS. 11 and 12, the fixed chassis35comprises laterally extending flanges67for attachment to a bath tub fitting45(FIG. 12) on the fixed wing spars19,21.

The installation of the actuation assembly31takes place in two steps. Referring toFIGS. 13aand 13b, the actuation assembly31is first secured relative to the fixed wing5by inserting the assembly from underneath the wing, and fastening the fixed chassis flanges67to the bathtub fitting45. Referring now toFIG. 13c, the actuators57are then attached at one end to a bar69extending between the spars19,21, and at their other end to the rotational connection58on the bell crank49.

To install the wing tip device7, the actuation assembly31is set to its configuration in the ground configuration (i.e. the actuators57are fully extended). Referring toFIG. 14, the wing tip device frame structure25is then lowered into the hinge29and the slave link51is attached to the frame25at the offset location from the hinge29.

Referring back toFIG. 10b, the articulation mechanism is arranged such that when the wing tip device7in the ground configuration, the master bell crank49and the slave link51are in an over-centre position. More specifically, the first pivot52(between the bell crank49and the slave link51) is out of line with the second pivot54(between the link51and the wing tip device7) and the third pivot56(at which the bell crank49is pivoted on the slider53). This creates an over centre lock to lock the wing tip device in the ground configuration. That lock can only be unlocked by retraction of the actuator57. It will be appreciated that the over-centre lock is also created by that same actuator57as it extends to move the wing tip device into the ground configuration. Thus, the same actuator is arranged to move the wing tip device and make/break the over centre lock that holds the wing tip device in the ground configuration. This removes the need for a separate actuator to lock/unlock the wing tip device in the ground configuration.

FIGS. 15aand 15bare sectional views along a spar-wise cut in the wing, showing the actuation assembly31, with particular focus on a track and follower arrangement between the fixed chassis35and the sliding chassis33, as will now be described:

The sliding chassis33is received inside the fixed chassis35on a follower in the form of two pairs of spring loaded bogies71a,71b(only one of each pair71a,71bis visible in the views ofFIGS. 15aand 15b). The bogies71a,71bare received in a C-track73shaped into the inner surface of the fixed chassis35, and are moveable along the track73to enable a sliding movement of the sliding chassis33relative to the fixed chassis35(it will be appreciated that a sliding movement need not necessarily be restricted to being via only a sliding contact; this term also encompasses a rolling contact as per this first embodiment of the invention).

The track73comprises first portions73awhich are relatively wide of width Wa (the vertical direction inFIGS. 15aand 15b), and second portions73b, located outboard of the respective first portions73a, that are relatively narrow of width Wb.

When the wing tip device7is in the flight configuration (seeFIG. 15a), the spring loaded bogies71a,71bare located along the first portions of the track. They are spring-biased into an expanded orientation in which each bogie is at an angle such that it the wheels of the bogie71a,71bare in contact with both sides of the track73(for example the bogie is inclined to the longitudinal axis of the track such that one wheel is in contact with one side, and another wheel is in contact with the other side). The spring biasing force is relatively weak however. Thus, when the wing tip device is subjected to loads, such as flight loads, the spring loaded bogies71a,71bcannot provide any load transfer path, to transfer these forces into the fixed wing5(the bogies71a,71bwould just change orientation under the action of a force, rather than transfer that force into the fixed wing5). Instead, the loads are only transferred via the three pairs of spigots and bushes (17a-c/27a-c) previously discussed.

Such an arrangement ensures that the sliding chassis33, and other parts of the actuation assembly31, are effectively isolated from the flight loads on the wing tip device7, when the device is in the flight configuration. The actuation assembly31does not, therefore, need to be sized to cope with the flight loads, enabling the actuation assembly to be relatively small and/or lightweight.

As described above, the track73comprises both relatively wide portions73aand relatively narrow portions73b. The track73is shaped such that when the wing tip device has undergone the first stage of translational movement, the sliding chassis moves along the track73such that the bogies71a,71bhave moved from the wide portions73aof the track to the narrow portions73b. The narrow portions of the track are substantially the same width as the diameter of the wheels on the bogies71a,71bsuch that the bogies71a,71bare urged into alignment with the longitudinal axis of the track73and are held in a tight fit.

After this translational movement, the spigots17a-care clear of the bushes27a-c(see description above with reference toFIGS. 3ato 4b). These spigots cannot, therefore act to transfer any loads. However, in the first embodiment of the invention, the actuation mechanism is at this stage no longer isolated from the wing tip loads because the bogies are received in a tight fit in the narrow portion73bof the track73; the bogies cannot move within the width of the track and therefore facilitate load transfer into the fixed wing5.

Embodiments of the present invention recognise that the loads from the wing tip device are typically lower once it is no longer in the flight configuration, because at that stage there tend to be no flight-induced loads (the loads typically only being the weight of the wing tip device and/or gust loading on the wing tip device when it is folded upwardly). Thus, the actuation assembly can be relatively lightweight yet still be arranged to transfer these loads.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein.