Slat for an aircraft wing

Abstract

A slat (108) for the leading edge of a swept aircraft wing includes slat tracks (114) that dictate the path of movement of the slat as it moves from a retracted position (FIG. 7) to a fully deployed position (FIG. 15). Each slat track (114) has a shape that follows a helical path. The motion of the slat thus includes a component of rotation about a first axis, which may be perpendicular to the line of flight (120) and a component of translational movement parallel to the first axis. When viewed from above the slat may move predominantly in a direction parallel to the line of flight (120).

Claims

1. A slat for a leading edge of an aircraft wing, the slat including: at least two slat tracks that in use dictate a path of movement of the slat as the slat moves from a retracted positon to a fully deployed position, wherein each of the at least two slat tracks has a shape that follows a helical path, and an aerofoil surface fixed to the at least two slat tracks, wherein the aerofoil surface and the at least two slat tracks are configured to move along the helical path as the aerofoil surface and the at least two slat tracks deploy forward of the leading edge of the aircraft wing.

2. The slat according to claim 1, wherein: each slat track of the at least two slat tracks includes at least two external surfaces on opposite sides of the slat track when viewed in cross-section, and the two external surfaces of each of the slat tracks are defined by two surfaces swept out by two notional fixed shape lines when moved along the helical path relative to the aerofoil surface of the slat.

3. The slat according to claim 1, wherein each slat track has a cross-sectional shape which remains constant for a majority of a length of the slat track.

4. The slat according to claim 1, wherein the helical path corresponding to one of the slat tracks is a helix having a first radius and the helical path corresponding to another of the slat tracks is a helix having a second radius from the first radius.

5. The slat according to claim 2, wherein the aerofoil surface is rigidly supported by at least one of the two or more slat tracks.

6. The slat according to claim 2, wherein the slat forms part of a swept aircraft wing.

7. A swept aircraft wing including: a leading edge; a trailing edge; a slat configured to extend from the leading edge of the aircraft wing; and at least two slat tracks supporting the slat and each having a shape configured to move the slat and the at least two slat tracks along a helical path as the at least two slat tracks and the slat extend forward of the leading edge of the aircraft wing.

8. The swept aircraft wing according to claim 7, wherein each slat track of the two or more slat tracks has a shape that follows a helical path along at least a portion of the slat track extending forward of the leading edge of the aircraft wing.

9. The swept aircraft wing according to claim 8, wherein each slat track of the two or more slat tracks has a cross-sectional shape that remains constant for a majority of a length of the slat track.

10. The swept aircraft wing according to claim 8, wherein at least one of (a) the helical path along which the slat moves and (b) the helical path defining a shape of at least one of the slat tracks, is in a shape of a helix wherein an axis of the helix and a pitch of the helix are configured such that lateral edges of the slat move parallel to a vertical plane aligned with a line of flight of the wing.

11. The swept aircraft wing according to claim 8, wherein at least one of (a) the helical path along which the slat moves and (b) the helical path defining a shape of at least one of the slat tracks, is in a shape of a helix wherein an axis of the helix is aligned with a leading edge of the slat.

12. The swept aircraft wing according to claim 7, including two sets of rollers, wherein the two sets of rollers guide a movement of each slat track, and the two sets of rollers are spaced from each other in a direction along a length of the slat track, and each set of the two sets of rollers constrains movement of the track in two orthogonal directions perpendicular to a direction of motion of the slat track through the two set of rollers.

13. The swept aircraft wing according to claim 12, including at least two pairs of track ribs wherein: the ribs of each pair of the at least two pairs of track ribs are positioned on either side of a slat track, at least one roller of the two sets of rollers is supported between a pair of track ribs, and each track rib when viewed in plan extends in a direction aligned with the line of flight.

14. The swept aircraft wing according to claim 7, wherein there is a fixed surface of the swept aircraft wing which is adjacent a lateral surface of the slat, wherein a path of movement as the slat moves from a retracted positon to a deployed position is such that a minimum separation between the fixed surface and the lateral surface is constant.

15. The swept aircraft wing according to claim 14, wherein the fixed surface is part of an engine pylon or a part of an aircraft fuselage.

16. The swept aircraft wing according to claim 7, wherein the swept aircraft wing has a sweep in a range of 20 to 30 degrees.

17. An aircraft including the swept aircraft wing according to claim 7.

18. A method comprising: deploying or retracting a slat on a swept aircraft wing to move the slat between a fully deployed position and a fully retracted position, wherein the slat includes an aerofoil surface supported by at least two slat tracks which dictate a path of movement; wherein a movement of the slat from the fully retracted position to the fully deployed position includes: extending of both the aerofoil surface and the at least two slat tracks forward of a leading edge of the swept aircraft wing along the path of movement; rotation of the aerofoil surface and the at least two slat tracks about a first axis fixed in space relative to the swept aircraft wing and spaced from a notional envelope relative to the swept aircraft wing within which the slat moves during the movement, and translational movement parallel to the first axis, wherein a speed of the translation is proportional to a speed of the rotation about the first axis.

19. The method according to claim 18, wherein: the swept aircraft wing has a sweep in a range of 20 to 30 degrees, the movement of each of the at least two slat tracks is guided by rollers fixed to the swept aircraft wing, the slat tracks have a shape which causes the slat to move with the speed of the component of translational movement being proportional to the speed of rotation about the first axis.

20. A slat for a leading edge of an aircraft wing, the slat including: an aerofoil surface positioned forward of a leading edge of the aircraft wing; at least two slat tracks supporting the aerofoil surface and extending into the aircraft wing, wherein each slat track of the at least two slat tracks is configured to extend forward of the leading edge of the aircraft wing, wherein each slat track of the at least two slat tracks has a helical shape along a length of the slat track.

Description

DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

(2) FIG. 1 shows an aircraft in plan view;

(3) FIGS. 2 to 5 illustrate schematically arrangements which can be compared and contrasted with the embodiments;

(4) FIGS. 6 to 17 show a slat according to a first embodiment as it moves from a retracted position to a deployed position, as viewed at various stages and at various angles of viewing;

(5) FIGS. 18 and 19 illustrate schematically the arrangement of the first embodiment in a manner similar to that shown in FIGS. 2 to 5, to aid comparison; and

(6) FIG. 20 is a schematic flow diagram illustrating the steps of a method in accordance with a second embodiment relating to moving a slat on a swept wing of an aircraft.

DETAILED DESCRIPTION

(7) FIG. 1 shows schematically an aircraft 100 according to a first embodiment of the invention. The aircraft has two swept wings 102, the sweep angle being about 27 degrees. Each wing 102 carries an engine 104 which is supported via an engine pylon 106. The wing includes various slats 108 on the leading edge of the wing. (The shape and arrangement of the slats shown in FIG. 1 are shown schematically.) FIGS. 2 to 5 show in highly schematic format a close up of slat arrangements that are not in accordance with the present invention. FIGS. 2 and 3 represent an arrangement on a swept wing with a slat 108 that moves from its stowed position (FIG. 2) to its deployed position (FIG. 3) in a direction that is perpendicular to the leading edge, in the conventional manner. Without any special measures being taken a gap 110 is present between a lateral edge of the slat when deployed and the edge of the pylon. FIGS. 4 and 5 represent an arrangement in which the pylon 106 has a bulge 112 incorporated to mitigate against the effects that would otherwise be introduced by the present of a gap (i.e. a gap 110 of the sort shown in FIG. 3), with FIG. 4 showing the slat 108 in its stowed position and FIG. 5) showing the slat 108 in a deployed position. Other solutions for filling the gap include adding extra moving parts to fill the gap when the slat is deployed.

(8) FIGS. 6 to 17 show a slat 108 and part of the aircraft wing 102 of the first embodiment in various perspective views. FIGS. 6 to 9 show the slat in its fully stowed position (viewing from various angles), FIGS. 10 to 13 show the slat in a partially deployed position (viewing from the same set of various angles) and FIGS. 14 to 17 show the slat in a fully deployed position (again, viewing from the same set of various angles). FIGS. 6, 10, and 14 show the slat from behind (i.e. looking in the direction of the line of flight). FIGS. 7, 11, and 15 are views from above. FIGS. 8, 12, and 16 are views from one side and above, whereas FIGS. 9, 13, and 17 are views from the other side and below. The slat is shown as including two slat tracks 114 having a generally square-shaped cross-section (although in reality the cross-sectional shape may be more complicated in cross-section—for example being having a cross-sectional shape that is similar to shapes currently used in slat tracks of the prior art). Each slat track has a shape which follows a helical path along its length. In this example the shape can be described as that defined by a constant cross-section (shown as a square in the drawings) following a helical path in space. The shape of the slat track appears to twist in space (compare FIGS. 6, 10 and 14 for example). The helix defined by the path defined by the centre point of each slat track has the same, constant radius, and the same constant pitch.

(9) The slat tracks 114 are substantially rigidly attached (whilst allowing for some flexure—see below) to the structure that supports the aerofoil surface 116 of the slat 108. The slat tracks are each arranged to pass through fixed axis rollers 118 as the slat moves between its stowed and deployed positions. The rollers are arranged between parallel-arranged slat track ribs 124, which extend in a direction substantially aligned with the line of flight. There are two sets of rollers per slat track, each set having four rollers, one for each side of the cross-sectional shape of the slat track. Thus, there is a set path of travel of the slat tracks as they move through the rollers. The set path is, as a result of the geometry of the helically shaped slat tracks, a helix. The helix has a constant pitch, a constant radius and a helix axis which is fixed in space relative to the wing when the slat moves from one position to another. The slat revolves about the axis of the helix by about 30 degrees between its fully stowed position and its fully deployed position. It will be appreciated that the radius of the helix is therefore relatively large compared to the distance moved by the slat between its fully stowed position and its fully deployed position and lies at a position significantly below and spaced apart from the leading edge of the wing. The slat and slat tracks do not at any point intersect the axis of the helix during their movement.

(10) The movement of the slat through space as it moves from its fully stowed position to its fully deployed position follows a helical path. The axis of the helix (defining the helical path taken) is substantially parallel to the leading edge of the slat, and has a radius and pitch such that the slat appears to move parallel to the line of flight of the wing, when viewed from above. As it moves, the leading edge of the slat stays approximately parallel with the leading edge of the region of the wing from which it extends. Discounting any flexure in components, the movement of the tracks through space are such that the position of the shape of a cross-section of a slat track at a given fixed distance from the rollers is maintained substantially exactly as the slat track moves through the rollers (in a manner conceptually similar to a shape of material caused by means of being extruded as it passes through an extrusion die with a twisted passageway).

(11) With reference to FIGS. 7, 11 and 15 it will be observed that the lateral edges of the slat move substantially parallel to the line of flight (indicated by the arrow 120) of the wing 102. FIG. 18 (plan view of slat when stowed) and FIG. 19 (plan view of slat when partially deployed) show schematically the benefit of such an arrangement. It will be see that the engine pylon 106 can have a conventional shape with edges aligned with the line of flight, the lateral edges of the slat 108 may be generally aligned with the line of flight, and the movement of the slat—being generally in the line of flight when observed from above—is also in the direction of the line of flight. Thus, no gaps are created when the slat is moved from one position to another which might otherwise need to be treated in some way (compare with FIGS. 2 to 5). The separation between the lateral edge of the slat and the corresponding lateral edge of the pylon, when viewed in plan, remains about the same during the movement of the slat between its fully stowed position and its fully deployed position. Also, the separation between the other lateral edge of the slat and the corresponding surface of the fuselage, when viewed in plan, remains about the same during the movement of the slat between its fully stowed position and its fully deployed position.

(12) FIG. 20 is a schematic flow diagram 25 illustrating the steps of a method when moving a slat on a swept wing of an aircraft, in accordance with a second embodiment. At step 260, the slat is in its fully deployed position. Step 262 represents the movement of the slat from the deployed position to the retracted position. As part of this step the slat moves with only two principal components of motion represented by the two boxes 264 and 266 shown in FIG. 18. A first component (box 264) consists of rotation about a first axis and represents the major component of the motion of the slat. Thus, the movement of the slat may, as a first approximation, be described as movement in an arc with a centre of rotation about the first axis. The extent of the movement through this arc of the slat when the movement of the slat from the deployed position to the retracted position is less than 50 degrees about the first axis. The first axis is approximately level with the horizontal (within a margin of +/−20 degrees, say) and lies beneath and spaced apart from the wing. The first axis is also substantially parallel (when viewed from above) with the leading edge of the slat (within a margin of +/−5 degrees, say). There is a notional envelope, which may be considered as being fixed in position and shaped relative to the wing, within which the slat moves during the movement. The radius of curvature of the movement about the first axis is large enough that the first axis is spaced apart from the notional envelope within which the slat moves. A second component (box 266) consists of translational movement parallel to the first axis. The amount of movement of the second component is directly proportional to the amount of movement of the first component, so that the speed of translation movement of this second component is proportional to the speed of rotation about the first axis.

(13) 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. By way of example only, certain possible variations will now be described.

(14) The slat may have three slat tracks, and possibly four, in alternative embodiments, and possibly more. One or more of the tracks may be driven, but there may be slave tracks that are not driven. At least some of the rollers may be resiliently mounted to offer some flexing of the tracks relative to each other, or to accommodate wing flexure, during loading.

(15) The motion of the slat does not need to be such that all parts of the slat have the same main axis of (helical) rotation. Successive slat tracks may describe helical paths with successively greater radii (each helix concerned having a constant radius) in the spanwise direction. The slat track may describe a path which can be described as helical but which nevertheless is not exactly aligned with a mathematically perfect helix.

(16) It will be appreciated that the angle through which the slat revolves, about the axis of the helix, between its fully stowed position and its fully deployed position will differ depending on aircraft requirements and could be as low as 15 degrees, or lower, and could be as high as 40 degrees, or higher.

(17) 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 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.

(18) The term ‘or’ shall be interpreted as ‘and/or’ unless the context requires otherwise.