Patent Description:
Aerofoil structures that are found in a variety of aircraft, spacecraft and wind turbine applications typically comprise a torsion box structure, which includes one or more longitudinal spars, a plurality of transverse ribs, and is enclosed by structural covers. A fixed leading edge (FLE) structure and/or a fixed trailing edge (FTE) structure may be attached to such a torsion box structure, to form an aerofoil shape.

When applied to aircraft wings and stabilizers the torsion box structure is often referred to as the "wing box". A wing box construction used commonly in commercial airliners includes a front spar, a rear spar, an upper wing cover (skin) extending between the front spar and the rear spar, and a lower wing cover (skin) extending between the front spar and the rear spar. One or more wing box ribs may also be included between the spars and covers. Each of the front and rear spars may be formed as a C-section with upper and lower flanges extending from an upstanding web. The upper and lower wing covers may be attached to the flanges of the front and rear spars. FTE and FLE structures of the wing, such as the leading edge D-nose, may be supported by butt-straps attached to overhanging edges of the upper and lower covers.

The overall shape of the aerofoil structure fixed assembly must conform to a predefined shape, in order to provide desired aerodynamic properties. Any misalignment of various members may result in a shape deviation, which when operated in an aerodynamic flow might result in unintended performance and handling qualities of the aerofoil structure. Therefore; the exact final position of the various members relative to one another in the assembled aerofoil structure (i.e. when fixed in an operational configuration) is of critical importance throughout the assembly process. Variations in the dimensions of the components of the aerofoil structure from an engineering ideal (normally governed by manufacturing drawings) must be controlled within pre-determined angular and linear dimension limits (commonly referred to as engineering tolerances).

Such engineering tolerances can result in gaps between the mating surfaces of components, which must normally be rectified. <CIT> discloses a way of dealing with this issue by using first and second mounting features that engage to prevent relative movement of a torsion box structure and a fixed leading or trailing edge structure in a chordwise direction.

However, an issue that <CIT> does not yet consider is how to prevent movement between the two structures in a vertical direction. In particular, there is no consideration of the potential difference in distance (between an upper attachment point (where the first and second mounting features are) and a lower attachment point) of the two structures.

The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved kit of parts for forming an aerofoil assembly.

A first aspect of the present invention according to claim <NUM> provides a kit of parts for forming an aerofoil assembly, the kit of parts comprising a torsion box structure comprising a first attachment point and a second attachment point, the first and second attachment points being separated from each other along a separation axis, and a fixed leading or trailing edge structure comprising corresponding first and second attachment points for attaching to the first and second attachment points of the torsion box structure, the first and second attachment points being separated from each other along a separation axis, wherein a first structure of the torsion box structure and the fixed leading or trailing edge structure comprises a slidably mounted abutment piece slidable along a slide path extending in a direction parallel to the separation axis of the first structure, and a fixing mechanism for fixing the slidably mounted abutment piece in a chosen location on the slide path, wherein a second structure of the torsion box structure and the fixed leading or trailing edge structure comprises a corresponding abutment feature, for abutting against the slidably mounted abutment piece of the first structure, the abutment feature comprising a first abutment surface facing in a direction parallel to the separation axis of the second structure, such that, in use, the slidably mounted abutment piece of the first structure can be slid to abut the first abutment surface of the second structure and be fixed in that location by the fixing mechanism, to prevent relative movement of the first and second structures in the separation axis.

Such a kit of parts enables movement and fretting of the two structures to be prevented in the separation axis. Hence, the kit of parts allows for a certain amount of tolerance in the difference between the distance between the first and second attachment points of the torsion box structure, on one hand, and the distance between the first and second attachment points of the fixed leading or trailing edge structure, on the other hand.

The two sets of corresponding attachment points are separated by substantially the same, allowing for tolerances, separation distances in all three orthogonal axes. This means the second attachment points (i.e. the second attachment point of the first structure and the second attachment point of the second structure) can be located together when the first attachment points (i.e. the first attachment point of the first structure and the first attachment point of the second structure) are located together.

The second structure is not the first structure. In other words, the second structure is the other/different structure, from the first structure.

The separation axis is not necessarily defined as a single axis notionally drawn directly between the first and second attachment points. Instead, the two attachment points may be separated along the separation axis and also another axis, orthogonal to the separation axis. In other words, the two attachment points are separated by a distance in the separation axis (e.g. z axis). They may also be separated by a distance in an orthogonal axis (e.g. x axis).

The slide path extends in a direction parallel to the separation axis (e.g. z axis) and in one (optionally in a further one) further direction, orthogonal to the separation axis/direction (and each other) (e.g. x and/or y axes).

Similarly, the first abutment surface of the abutment feature faces in a direction parallel to the separation axis of the second structure (e.g. z direction). It also faces one (or alternatively two) further direction, orthogonal to the separation axis/direction (and each other) (e.g. x and/or y axis). The slidably mounted abutment piece may be slidably mounted on the first structure. The slidably mounted abutment piece may be slidable along a slide path on the first structure.

In this document, the terms axis and direction are used to indicate similar, but slightly different things. The term "axis" refers to the line defining both opposite (at <NUM> degrees to each other) directions along that axis. The term "direction" refers to the orientation along only one of the two opposite directions.

For example, vertical axis refers to a notional line extending vertically, both up and down. Vertical direction refers to a line extending only upward (or downward) parallel to, or along, the vertical axis. Similarly, chordwise axis refers to a line extending chordwise, both fore and aft. Chordwise direction refers to a line extending only one way (fore or aft) parallel to, or along, the chordwise axis. Similarly, spanwise axis refers to a line extending spanwise, both left and right (port and starboard). Spanwise direction refers to a line extending only one way (left or right) parallel to, or along, the spanwise axis.

Preferably, the separation axis is a substantially vertical axis, with respect to an intended operational orientation of the aerofoil assembly.

For example, the first and second attachment points of the torsion box structure and fixed leading or trailing edge structure may be aligned vertically with each other, or substantially aligned, such that the first attachment point is substantially above and in line with the second attachment point in the vertical direction. The first and second attachment points may also be separated along a second direction, for example in a chordwise direction/axis, orthogonal to the vertical direction. The first and second attachment points may not be separated in a spanwise direction/axis (orthogonal to the vertical and chordwise directions/axes). The first attachment points may correspond to an upper attachment of the torsion box structure and the fixed leading or trailing edge structure. The second attachment points may correspond to a lower attachment of the torsion box structure and the fixed leading or trailing edge structure.

The slidably mounted abutment piece may be located adjacent to the first or second attachment point of the first structure. The slidably mounted abutment piece may be located adjacent to the second (lower) attachment point of the first structure.

The abutment feature may be located adjacent to the first or second attachment point of the second structure. The abutment feature may be located adjacent to the second (lower) attachment point of the second structure.

The first structure may comprise a main body and a fitting, fixedly attached to the main body, and wherein the slidably mounted abutment piece is slidably mounted on the fitting. The first or second attachment point of the first structure may be located on the fitting. For example, the second (lower) attachment point may be located on the fitting. The fixing mechanism may be located on the fitting.

Preferably, the first structure is the torsion box structure and the second structure is the fixed leading or trailing edge structure.

The fixed leading or trailing edge structure may be a fixed leading edge structure.

The slide path also extends in a second direction, orthogonal to the separation axis.

In other words, the path extends in more than one orthogonal direction. For example, it may extend vertically and in a chordwise direction. This allows the abutment piece to move in more than one orthogonal direction. Hence the abutment piece is able to abut against the abutment feature of the second structure, in more than one axis/direction.

More preferably, the slide path extends in a third direction, orthogonal to the separation axis and second direction.

In other words, the path extends in three orthogonal directions. For example, it may extend vertically and in a chordwise direction and in a spanwise direction. This allows the abutment piece to move in three orthogonal directions. Hence the abutment piece is able to abut against the abutment feature of the second structure, in more than one axis/direction.

Preferably, the slide path is angled such that it extends simultaneously in the direction parallel to the separation axis and in the second direction.

This means that as the location of the abutment piece along the separation axis changes, so does the location of the abutment piece along the second axis/direction. For example, this may mean that if the location in one direction (e.g. the second direction) is fixed, the location in the other direction (e.g. the separation direction) is fixed.

The path may be angled such that it extends simultaneously in the direction parallel to the separation axis and the third direction. This means that as the location of the abutment piece in the separation axis changes, so does the location of the abutment piece in the third axis/direction. For example, this may mean that if the location in one direction (e.g. the third direction) is fixed, the location in the other direction (e.g. the direction parallel to the separation axis) is fixed.

Preferably, the fixing mechanism comprises a fixing arrangement to fix the location of the slidably mounted abutment piece along the second direction.

Hence, this may consequently fix the location of the slidably mounted abutment piece along the direction parallel to the separation axis.

The fixing mechanism may comprise a fixing arrangement to fix the location of the slidably mounted abutment piece along the third direction. Hence, this may consequently fix the location of the slidably mounted abutment piece in the direction parallel to the separation axis.

More preferably, the fixing arrangement comprises a fixing pin, able to fix the abutment piece into abutment with the corresponding abutment feature of the second structure by fixing the location of the abutment piece along the second direction.

The fixing mechanism may comprise a fixing pin, able to fix the abutment piece into abutment with the corresponding abutment feature of the second structure by fixing the location of the abutment piece along the third direction.

The fixing pin may be able to urge the abutment piece into abutment with the corresponding abutment feature of the second structure by urging the abutment piece in the second and/or third directions.

The abutment piece may be slidably mounted relative to an axis of the fixing pin. The fixing pin (axis) may pass through or into a(n angled) slot of the abutment piece.

Preferably, the abutment piece comprises a base portion and a protruding portion protruding from the base portion, the protruding portion providing a number of abutment surfaces for abutting against the abutment feature of the second structure.

The abutment piece may be slidably mounted to the first structure at/by one or more locations on the base portion. For example, the piece may be slidably mounted by one or more runners, the runners being attached to the base portion. Each of the one or more runners may comprise a pin. Each of the one or more runners may be accommodated in a slide slot of the first structure.

More preferably, the protruding portion is in the form of a wedge providing a first angled abutment surface angled to face simultaneously in a direction parallel to the separation axis and in a direction orthogonal to the separation axis.

This allows the protruding portion to abut the second structure in a direction parallel to the separation axis and in a direction orthogonal to the separation axis. The orthogonal direction may be the third direction.

Even more preferably, the protruding portion provides a second abutment surface facing in a direction orthogonal to the separation axis.

This allows the protruding portion to abut the second structure along an orthogonal axis, for example a further orthogonal direction. The (further) orthogonal direction may be the second direction.

Preferably, the protruding portion provides a third abutment surface facing in an opposite direction along the separation axis to the first abutment surface.

This allows for the protruding portion to abut the second structure in the separation axis in two opposite ways/senses/directions.

Preferably, the first abutment surface of the abutment feature is angled to face simultaneously in a direction parallel to the separation axis and in a direction orthogonal to the separation axis.

This allows the abutment feature to abut the abutment piece along the separation axis and in a direction orthogonal to the separation axis. The orthogonal direction may be a direction along a third (spanwise) axis of the second structure. This first abutment surface may abut against the first abutment surface of the abutment piece.

The abutment feature and/or the abutment piece/protruding portion/wedge may allow for the converging abutment of the corresponding surfaces.

More preferably, the abutment feature provides a second abutment surface facing in a direction orthogonal to the separation axis.

This allows the abutment feature to abut the abutment piece in an orthogonal direction. The orthogonal axis may be the second (chordwise) axis. This second abutment surface may abut against the second abutment surface of the abutment piece.

Preferably, the abutment feature provides a third abutment surface facing in an opposite direction along the separation axis to the first abutment surface.

This allows for the abutment feature to abut the abutment piece in the separation axis in two opposite ways/senses/directions. This third abutment surface may abut against the third abutment surface of the abutment piece.

Preferably, the abutment feature comprises a slot for accommodating the slidably mounted abutment piece.

For example, it may accommodate the protruding portion of the abutment piece. The slot may define a number of abutment surfaces, for example the first, second and third abutment surfaces of the abutment feature.

Preferably, the first attachment point of the torsion box structure comprises a first mounting feature and the first attachment point of the fixed leading or trailing edge structure comprises a second mounting feature configured to engage with the first mounting feature, wherein the first mounting feature and the second mounting feature are mutually configured to permit the first and second mounting features to be moved into engagement with each other along a first direction, and to prevent relative movement of the first and second mounting features along a second direction when the first and second mounting features are engaged with each other.

The first direction may be a direction parallel to the separation axis. The first attachment point may be the upper attachment point. The kit of parts may have similarities to that described in <CIT>. For example, the first attachment point may be similar to the first mounting feature of the arrangement of the aerofoil structure of <CIT>.

Preferably, the fixed leading or trailing edge structure comprises one or more systems for actuating a moveable device comprised in or mountable to the aerofoil assembly.

The torsion box structure may comprise one or more further first and second attachment points and the fixed leading or trailing edge structure may comprise one or more further first and second attachment points. The first attachment points may be spaced along the torsion box structure in the spanwise direction according to a predetermined arrangement corresponding to an arrangement of the first attachment points on the fixed leading or trailing edge structure. The second attachment points may be spaced along the torsion box structure in the spanwise direction according to a predetermined arrangement corresponding to an arrangement of the second attachment points on the fixed leading or trailing edge structure. Similarly, a number of sets of slidably mounted abutment pieces, fixing mechanisms and abutment features may be provided correspondingly spaced apart in the spanwise direction along the torsion box structure and fixed leading or trailing edge structure.

Preferably, the fixed leading or trailing edge structure is of a modular design.

According to a second aspect of the invention, there is provided an aerofoil assembly formed from the kit of parts as described above.

Preferably, the aerofoil assembly is an aircraft wing or part of an aircraft wing.

<FIG> shows a top schematic view of an example aircraft <NUM>, including the leading edge structure <NUM> and wing torsion box structure <NUM> of <FIG>.

The aircraft <NUM> comprises a pair of aerofoil structures <NUM>, <NUM>' in the form of wings, which extend approximately horizontally from a fuselage <NUM>. Although only the wing <NUM> is described in detail, it may be assumed that the wing <NUM>' has corresponding features. A further pair of aerofoil structures <NUM>, <NUM>' in the form of horizontal tail planes extend approximately horizontally from either side of a rear portion of the fuselage <NUM>. Yet a further aerofoil structure <NUM> in the form of a vertical tail plane extends vertically from an upper rear portion of the fuselage <NUM>.

The aircraft <NUM> has a set of orthogonal aircraft axes. The longitudinal axis (x) has its origin at the centre of gravity <NUM> of the aircraft <NUM> and extends lengthwise through the fuselage <NUM> from the nose to the tail in the normal direction of flight. The lateral axis or spanwise axis (y) also has its origin at the centre of gravity and extends substantially crosswise from wing tip to wing tip. The vertical or normal axis (z) (not seen in <FIG>) also has its origin at the centre of gravity and passes vertically upwards through the centre of gravity.

A further pair of orthogonal axes is defined for the aerofoil structure <NUM>; a first aerofoil axis <NUM> that is defined by a major (spanwise) dimension of a web <NUM> of a front spar <NUM> (see <FIG>), and a second orthogonal axis <NUM> defined by a minor dimension of the web <NUM> of the front spar <NUM> (see <FIG>). This axis <NUM> coincides with the z axis in this example. At each point along the span of the aerofoil structure <NUM>, there is also defined a (chordwise) aerofoil axis <NUM> that is defined by an imaginary chord line joining the leading edge and trailing edge of the aerofoil structure <NUM> at that point.

As can be seen from <FIG>, the aerofoil structure <NUM> comprises a central (wing box) region <NUM> and a set of high-lift devices called leading edge slats <NUM>, which are mechanically connected to it at the leading edge region <NUM>, in front of the central region. The aerofoil structure <NUM> also comprises a set of high-lift devices called trailing edge flaps <NUM>, which are mechanically connected to it at the trailing edge region <NUM>, behind the central region. The slats <NUM> and flaps <NUM> are moveable (i.e. non-fixed) devices, being actuatable during operation between a fully deployed position and a fully retracted position according to the inputs of a pilot. The purpose of the slats <NUM> and flaps <NUM> is to increase the camber and chord length and overall surface area of the wing <NUM> when deployed, thereby increasing the coefficient of lift that the wing <NUM> produces when required for slow flight of the aircraft <NUM>. Adjacent to each slat <NUM> or flap <NUM> and/or in the areas where no high-lift devices are provided, the leading edge and trailing edge structure of the aerofoil structure <NUM> is fixed i.e. not configured to be moveable like the slats <NUM> and flaps <NUM> during operation of the aircraft <NUM>.

Each of the horizontal tail planes <NUM>, <NUM>' and the vertical tail plane <NUM> similarly comprises a leading edge <NUM>, <NUM>', <NUM>, a trailing edge <NUM>, <NUM>', <NUM> and fixed structure.

Any of the aerofoil structures comprised in the aircraft <NUM> may be formed from a kit of parts according to the invention. <FIG> show an example kit of parts <NUM> for forming an aerofoil structure, such as any of the aerofoil structures of the aircraft <NUM>. The kit of parts <NUM> comprises a torsion box structure <NUM> and a fixed leading or trailing edge structure <NUM>.

<FIG> shows a side (spanwise) view of a rib <NUM> of a leading edge structure <NUM>, in location with a lower fitting <NUM> of a wing torsion box structure <NUM> of wing <NUM>. <FIG> shows a side (spanwise) view of the rib and fitting of <FIG>, with an upper fitting <NUM> of the wing torsion box structure <NUM> also shown and the lower fitting <NUM> shown in partly cutaway view.

The rib <NUM> has a front nose portion <NUM> and a rear face <NUM>. Adjacent the rear face <NUM> are two attachment points; an upper attachment point <NUM>, located towards the top of the rib <NUM> and a lower attachment point <NUM>, located towards the bottom of the rib <NUM>.

The torsion box structure <NUM> comprises a front spar <NUM> in the shape of a C-section with an upper flange <NUM>, central web <NUM> and lower flange <NUM>. It also has an upper skin <NUM> and lower skin <NUM>, attached to the upper and lower flanges <NUM>, <NUM> respectively.

The torsion box structure <NUM> also comprises an upper fitting <NUM> and a lower fitting <NUM>, both attached to a front of the spar web <NUM>-<NUM> at upper and lower positions, respectively.

The upper attachment point <NUM> of the leading edge structure <NUM> comprises a pin <NUM> extending spanwise from the rib <NUM>. The pin <NUM> engages with an attachment point on the upper fixing <NUM> of the torsion box structure <NUM>. In particular, as can be seen in <FIG>, the pin <NUM> sits in a hole <NUM> formed by a lower fitting body <NUM> and an upper plate <NUM> of the upper fitting <NUM> of the torsion box structure <NUM>. This arrangement may be similar or the same as that disclosed in <CIT>.

The lower attachment point <NUM> of the leading edge structure <NUM> comprises a hole <NUM> extending through the rib <NUM> (in the spanwise direction) and an attachment bolt <NUM> extending through the hole <NUM>. The bolt <NUM>, surrounded by a sleeve (not shown), two threaded bushed <NUM>, <NUM> and two eccentric bushes <NUM>, <NUM>, also extends through holes <NUM>, <NUM> on the lower fitting <NUM> of the torsion box structure <NUM>. The bolt <NUM> is secured in place with a nut <NUM>, to connect the two structures <NUM>, <NUM> together at the lower attachment point <NUM>, as will be described in more detail later.

The pin <NUM> and hole <NUM> on the leading edge structure <NUM> are designed to be a set distance apart, in both the vertical and chordwise directions. However, as they can only be manufactured to an achievable level of tolerance, these distances may vary slightly.

The pin <NUM> and holes <NUM>, <NUM> on the torsion box structure <NUM> are designed to be a set distance apart, in both the vertical and chordwise directions. However, as they can only be manufactured to an achievable level of tolerance, these distances may vary slightly.

Hence, there will always be some difference in the corresponding locations of the upper and lower attachment points, between the two structures.

Importantly, as can be seen in <FIG>, but will be described in more detail in relation to other Figures, the lower fitting <NUM> of the torsion box structure <NUM> further comprises a slide piece <NUM>, slidably mounted to a main body of the fitting <NUM>. It is mounted using pins <NUM>, <NUM> extending from the slide piece <NUM> through upper and lower slots <NUM>, <NUM> of the fitting <NUM>. The slide piece <NUM> can be fixed in location using a securing pin <NUM> extending through a hole <NUM> of a protruding tab of the fitting <NUM>.

<FIG> shows a top view of the rib <NUM> and lower fitting <NUM>, with the slide piece <NUM> of the fitting shown in an intermediate position. <FIG> shows an enlarged top view of the lower fitting <NUM>, with the slide piece <NUM> shown in a non-abutting position. <FIG> shows an enlarged top view of the lower fitting <NUM>, with the slide piece <NUM> shown in an abutting position.

As will be seen, the slide piece <NUM> can slide from the non-abutting position shown in <FIG>, through the intermediate position of <FIG>, to the abutting position of <FIG>, where it abuts against the leading edge structure <NUM>. The slide piece <NUM>, during this movement, moves in the spanwise direction <NUM>, as well forwards in the chordwise axis (i.e. in the opposite direction to arrow <NUM>) and also downwards (i.e. in the opposite direction to arrow <NUM>, z).

<FIG> shows a perspective view of the lower fitting <NUM>, shown with two pins; bolt <NUM> and a securing pin <NUM>. <FIG> shows an exploded perspective view of the lower fitting <NUM>, shown with the two pins in exploded view.

These <FIG>) will be used to describe the lower fitting <NUM>, including the slide piece <NUM> in more detail.

The lower fitting <NUM> comprises two rear flanges <NUM>, <NUM> which are used to attach the fitting <NUM> to the front of the web <NUM> of the front spar <NUM>. It also has a lower face comprising a central flange <NUM> and two outer flanges <NUM>, <NUM>. These flanges are used to fix the fitting to the lower flange <NUM> of the front spar <NUM>. It also has two protruding tabs <NUM>, <NUM>, which extend outwards (frontwards, chordwise). The protruding tabs <NUM>, <NUM> include a hole each <NUM>, <NUM> for accommodating the bolt <NUM> of the lower attachment point <NUM> of the leading edge structure <NUM>.

Importantly, the fitting <NUM> comprises a back wall <NUM>, extending between the two protruding tabs <NUM>, <NUM>, which is sloped/angled such that it extends in spanwise, chordwise, and also vertical axes. This spanwise and chordwise extending can be seen in <FIG> and <FIG>, for example.

The back wall has two slots; an upper slot <NUM>, seen in <FIG> and <FIG>, and a lower slot <NUM>, only seen in <FIG>. These back wall slots <NUM>, <NUM> are angled/sloped on the face of the back wall and are used to slidably mount the slide piece <NUM> so that it can slide along the slope/angle of the back wall <NUM> and also, simultaneously move up and down along the slope of the slots <NUM>, <NUM>.

The slide piece <NUM> itself comprises an upper and a lower base flange <NUM>, <NUM> with a wedge shaped protrusion <NUM> (protruding forwards in a chordwise direction) in between the two base flanges <NUM>, <NUM>.

The upper base flange <NUM> has an upper pin <NUM> extending backwards from it, such that it is accommodated in the upper slot <NUM> of the back wall <NUM> of the fitting <NUM>. Similarly, the lower base flange <NUM> has a lower pin <NUM> extending backwards from it, such that it is accommodated in the lower slot <NUM> of the back wall <NUM> of the fitting <NUM>.

The wedge-shaped protrusion <NUM> extends forwards towards the rib <NUM> and comprises a number of surfaces:.

<FIG> shows a rear perspective view of the leading edge rib <NUM>, shown with the attachment bolt <NUM> and the slide piece <NUM> in exploded view.

The wedge-shaped protrusion <NUM> also has a long side face (facing in a spanwise direction) which has a slanted slot <NUM> in it. This is most clearly seen in <FIG>. The slanted slot <NUM> is slanted so as to extend vertically as well as chordwise.

The securing pin <NUM> extends through the hole <NUM> in the protruding tab <NUM> of the lower fitting <NUM> and into the slanted slot <NUM> to secure the slide piece <NUM> in a chosen position along the slide slots <NUM>, <NUM>. It is also noted that a bush <NUM> is used surrounding the pin <NUM>, outside of the protruding tab <NUM>.

As can also be seen in <FIG>, at the lower portion of the rear face <NUM> of the rib <NUM> is an inwardly (i.e. inwards towards the front of the rib) extending slot feature <NUM>. This slot feature accommodates the wedge-shaped protrusion <NUM> such that it slides along it.

The slot feature <NUM> comprises an upper backward face <NUM>, which corresponds with the upper base flange <NUM> of the slide piece <NUM>. It has a downwardly facing upper surface <NUM>, which defines the top of the slot. This surface <NUM> corresponds with the first upper surface <NUM> of the wedge-shaped protrusion <NUM>. It has an inner back surface <NUM> which defines the back of the slot. This surface is slanted so as to correspond to the sloped second forward face <NUM> of the wedge-shaped protrusion <NUM>. It has an upwardly facing lower face <NUM>, which defines the bottom of the slot. This surface <NUM> is slanted so as to correspond with the third lower surface <NUM> of the wedge-shaped protrusion <NUM>. It also has a lower backward face <NUM>, which corresponds with the lower base flange <NUM> of the slide piece <NUM>.

In use, the torsion box structure <NUM> is supported in a desired position and/or orientation, for example using a (moveable) jig, or manually by aircraft assembly personnel. The leading edge structure <NUM> is arranged on the torsion box structure <NUM>, for example by moving it downwards, to engage the pin <NUM> on the lower fitting body <NUM>. This prevents the leading edge structure <NUM> moving in a chordwise manner relative to the torsion box structure <NUM>. Any jigs or other support mechanisms used to support the leading edge structure <NUM> may therefore be removed at this point, or later.

The pin <NUM> can then be further secured by upper plate <NUM>. This step may comprise accessing the pin <NUM> and/or lower fitting body <NUM> through an opening (not shown) in an outer skin of the leading edge structure <NUM>.

Then, the hole <NUM> in the lower region of the rib <NUM> is lined up with the holes <NUM>, <NUM> in the lower fitting <NUM> of the torsion box structure <NUM>, and bolt <NUM> is placed through the holes to secure the two structures together at the lower attachment point <NUM>. The eccentric bushes <NUM>, <NUM> are also used and are rotated to achieve the desired position of the leading edge structure <NUM> with respect to the wing torsion box structure <NUM>. Threaded bushed <NUM>, <NUM> are then used to fix the spanwise position of the leading edge structure <NUM> with respect to the wing box structure <NUM>.

In order to then prevent any movement in the vertical direction, the slide piece <NUM> is slid towards its abutting position, where one or more surfaces of the slide piece <NUM> (and in particular, the wedge-shaped protrusion <NUM> of it) will abut against one or more faces of the slot feature <NUM>. For example, all of the faces <NUM>, <NUM> and <NUM> of the rib <NUM> of the leading edge structure <NUM> may be abutted. There will be abutting in various directions, in fact all three orthogonal directions, given the different angles of the surfaces.

The slide piece <NUM> is then secured in that abutting position by the securing pin <NUM>. This prevents the two structures <NUM>, <NUM> from moving and fretting with respect to each other, especially in the vertical (z) direction.

In certain examples, any two or more of the components of the torsion box structure <NUM> may be formed integrally as a unitary member. For example, the front spar <NUM> may be formed integrally with the upper cover <NUM>. The front spar <NUM> has an upstanding web <NUM> (which may be substantially, or close to, vertical in an operational orientation of the aerofoil) which defines a first aerofoil axis, as discussed above. The upper and lower covers <NUM>, <NUM> may be substantially, or close to, perpendicular to the web of the front spar <NUM>. The torsion box structure <NUM> may have any suitable construction (various such constructions are known in the art).

In some examples, the fixed leading edge structure <NUM> may comprise an outer skin fixedly attached to at least one leading edge rib <NUM>, by any suitable mechanism. In other examples, the outer skin may comprise one or more pieces of aluminium sheet (or any composite material) and is bonded to a flange of the leading edge rib such that it defines a desired aerodynamic shape of the leading edge of the completed aerofoil structure. The leading edge rib <NUM> may be formed from composite material, or any other suitable material e.g. aviation grade aluminium alloy. The fixed leading edge structure <NUM> may comprise any number of leading edge ribs <NUM>. In some examples, the fixed leading edge structure <NUM> may comprise one or more pairs of ribs <NUM>, where the spanwise spacing between ribs in a given pair is significantly smaller than the spanwise spacing between a rib in the given pair and the closest rib not in that pair. The rib or ribs may have any suitable construction (various such constructions are known in the art).

In the illustrated example, the torsion box structure <NUM> comprises a first mounting feature (i.e. pin hole <NUM> in upper fitting <NUM> and lower fitting body and upper plate <NUM>, <NUM>) for use in attaching the fixed leading edge structure <NUM> to the torsion box structure <NUM>. The fixed leading edge structure <NUM> comprises a second mounting feature (i.e. pin <NUM>) configured to engage with the first mounting feature. The first mounting feature and the second mounting feature may be similar to or the same as the arrangement described in <CIT>.

The various surfaces, slots etc. may extend in any suitable direction/axis. For example, the front spar <NUM> may have a minor dimension that does not exactly correspond to the z axis, as in the above example. The surfaces/faces of the slot feature <NUM> and slide piece <NUM> may extend in any suitable direction/axis and may be appropriately sloped/angled.

Any suitable pins, bolts, bushes, nuts etc. may be used to effectively secure the arrangement in place.

The fittings <NUM>, <NUM> may be integral, or not, to the torsion box structure.

The arrangement could be the other way around, with the slide piece <NUM> being part of the leading edge structure <NUM> and the slot feature <NUM> may be part of the torsion box structure <NUM>.

Instead of there being abutting by the slide piece <NUM> against all three faces <NUM>, <NUM>, <NUM> of the slot feature <NUM>, there may be abutting against only one or two of these faces. For example, there may be abutting against face <NUM> only. As another example, there may be abutting only against faces <NUM> and <NUM>. The number of different faces being abutted against will depend on how the different tolerances have resulted.

As another example, a nominal gap may be used between faces <NUM> and <NUM> such that face <NUM> is not subject to unwanted loads "running" through that interface. In other words, the (horizontal) loads will run through the attachment bolt <NUM> and the fitting tabs <NUM>, <NUM>, instead of the wedge-shaped portion <NUM>. This prevents the wedge-shaped portion <NUM> pushing the rib forward (and potentially causing issues with pre-stressing).

Any suitable abutment features (such as the slide piece and slot feature) may be used.

In the illustrated example, the fixed leading edge structure <NUM> is a leading edge structure in the form of a D-nose, although in other examples it may be a trailing edge fixed structure, for a wing or for a horizontal or vertical tail plane, or a different form of leading edge fixed structure. The example leading edge structure <NUM> may be provided as a modular assembly, that is, a unitary preassembled structural module (hereinafter referred to as a modular leading edge structure). The leading edge structure <NUM> may also be pre-equipped with systems and/or actuation elements for one or more moveable devices which are to be mounted on the completed aerofoil structure. Such a moveable device may be, for example, a slat, a Krueger, or the like. In examples in which the fixed leading or trailing edge structure is a trailing edge structure, such a moveable device may be, for example, a flap, an aileron, a spoiler, or the like. The use of pre-assembled unitary leading or trailing edge modules is desirable because it allows tolerance gaps to be controlled between a reduced number of components, which reduces the time overall required to assemble an aerofoil structure.

The above embodiments are to be understood as illustrative examples of the invention. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

It should be noted that throughout this specification, "or" should be interpreted as "and/or".

Claim 1:
A kit of parts (<NUM>) for forming an aerofoil assembly, the kit of parts comprising:
a torsion box structure (<NUM>) comprising a first attachment point (<NUM>) and a second attachment point (<NUM>), the first and second attachment points being separated from each other along a separation axis (<NUM>), and
a fixed leading or trailing edge structure (<NUM>) comprising corresponding first (<NUM>) and second attachment points (<NUM>) for attaching to the first and second attachment points of the torsion box structure, the first and second attachment points being separated from each other along a separation axis,
wherein a first structure (<NUM>) of the torsion box structure and the fixed leading or trailing edge structure comprises:
- a slidably mounted abutment piece (<NUM>) slidable along a slide path (<NUM>, <NUM>) extending in a direction (<NUM>) parallel to the separation axis of the first structure, and
- a fixing mechanism for fixing the slidably mounted abutment piece in a chosen location on the slide path,
wherein a second structure (<NUM>) of the torsion box structure and the fixed leading or trailing edge structure comprises a corresponding abutment feature (<NUM>), for abutting against the slidably mounted abutment piece of the first structure, the abutment feature comprising a first abutment surface (<NUM>) facing in a direction parallel to the separation axis of the second structure,
such that, in use, the slidably mounted abutment piece (<NUM>) of the first structure can be slid to abut the first abutment surface of the second structure and be fixed in that location by the fixing mechanism, to prevent relative movement of the first and second structures in the separation axis, characterised in that
the slide path (<NUM>, <NUM>) also extends in a second direction orthogonal to the separation axis (<NUM>) and wherein the slide path (<NUM>,<NUM>) may extend in a third direction orthogonal to the separation axis (<NUM>) and second direction.