Improved guidance and drive system for a leading-edge movable flap on an aircraft wing

Description

51601AP-P 2 adopts an angle of attack placing its trailing edge flush with the fixed part of the wing when this flap is in its retracted position, and preferably also during an initial phase of its extension, for example, until it reaches its partially deployed position adopted at takeoff. This helps to limit wing drag and thus reduce fuel consumption. However, it may also be desirable for the movable flap to adopt an angle of attack placing its trailing edge away from the fixed part of the wing when this flap is in its deployed position as adopted at landing. Indeed, the circulation of airflow between the movable flap and the fixed part of the wing during landing reduces the risk of stalling. More generally, it can be advantageous to be able to adjust the flap's angle of incidence in all or part of its positions during its extension and retraction movements. Consequently, there remains a need to optimize aircraft wing design to address the need expressed above.and preferably so that this design reduces drag as much as possible, and / or presents a safety function called "Failsafe" in English, and / or has a compact aspect.15 STATEMENT OF THE INVENTION To meet at least partially this need, the invention first relates to a guidance and drive system for a movable leading edge flap for an aircraft wing, the flap being intended to be mounted on a fixed part of the wing, so as to be able to be moved between a retracted position and a deployed position relative to the fixed part of the wing, the system comprising: -a first assembly for guiding and driving the flap, comprising a first guide rail, as well as a drive track for the flap, the first guide rail and the drive track being integral; -a second shutter guide assembly, adjacent to the first assembly in a span direction of the shutter, the second assembly comprising a second guide rail; -a guide device for the first and second rails,intended to be mounted on the fixed part of the wing; BE2025 / 5007 51601AP-P 3 - a connecting device intended for connecting the first and second guide rails to the movable flap, the connecting device comprising a structural element intended to be integral with the flap, this device forming: - a first mechanical connection between a first front end of the first rail and the structural element, the first mechanical connection preferably defining a first axis of rotation; and - a second mechanical connection between a second front end of the second rail and the structural element, the second mechanical connection preferably defining a second axis of rotation, the system being configured such that during at least a determined part of a displacement of the first and second rails relative to their guide device, the The first and second rails undergo a relative displacement with respect to each other, causing the structural element of the connecting device to move relative to the first front end of the rail.and preferably to pivot relative to this first forward end of the rail, along the first axis of rotation. 15 The invention is advantageous in that it offers a design capable, during the flap's extension relative to the fixed part of the wing, of applying an additional relative movement between the flap and the first rail, preferably a pivoting movement around the first axis of rotation. Other movements can nevertheless be envisaged, without departing from the scope of the invention, and always resulting 20 from the relative movement between the two guide rails. This design thus provides an additional degree of freedom of movement to the flap, allowing control of its angle of attack in addition to the extent of its extension. The solution provided contrasts with a conventional solution in which the flap is simply moved in rotation relative to the fixed part of the wing,along a trajectory dictated by the same circular shape of all the guide and / or drive rails of this flap. This additional degree of freedom of movement can be advantageously used to precisely control the relative position between the fixed part of the wing and the trailing edge of the flap. BE2025 / 5007 51601AP-P 4 Furthermore, grouping the first and second guide assemblies within the same flap guidance and drive system allows for a compact design, reducing drag. This drag is further reduced as the passage of the two adjacent guide assemblies is preferentially achieved through a single opening in the leading edge of the fixed wing section. Here again, 5 this contrasts with conventional solutions in which each guide and / or drive rail passes through a specifically dedicated opening on the leading edge of the fixed wing section. Reducing the number of these openings advantageously reduces drag during flight phases when the flap is at least partially deployed.particularly at takeoff, which induces a positive impact on consumption.10 Finally, it is noted that the design proposed by the invention remains perfectly compatible with the implementation of a "Failsafe" safety function with regard to the transmission of forces between the flap and the fixed part of the wing. Other aspects of the invention will be described by way of enumeration of the following optional features, intended to be implemented individually or in combination. Preferably, the first rail has two opposing first guide tracks, each cooperating with the guide device, the second rail has two opposing second guide tracks, each cooperating with the guide device, and the first tracks have a different shape from the second tracks. It is this differentiation in shape between the adjacent rails of the system that makes it possible to generate the desired relative displacement between these rails, to cause the additional movement of the shutter. Other solutions can of course be considered to generate this principle specific to the invention,such as providing, within the guide device, differentiated guide elements for the two rails, so that these follow distinct guide paths. 25 Preferably, the first two guide tracks are in the shape of a circular arc. The second two guide tracks may, however, have a more complex curvilinear shape, dictated by the nature of the additional movement desired for the shutter relative to the first guide rail. BE2025 / 5007 51601AP-P 5 Preferably, the first mechanical linkage is located in front of the second mechanical linkage. Preferably, the guiding device comprises several guide rollers, each participating in the guidance of the first and second rails. Different rollers could nevertheless be provided to guide the first and second rails without departing from the scope of the invention. Preferably, the first guide and drive assembly of the shutter is supported against the second guide assembly of the shutter, with a sliding layer being able to be arranged between the first and second guide assemblies. Alternatively,A small amount of play could be maintained between these two assemblies, in the span direction of the 10th shutter. According to various possible designs, the shutter drive track is arranged between the first and second rails, in the span direction, or the first guide rail is arranged between the shutter drive track and the second guide rail, also in the span direction. Preferably, the shutter drive track is a toothed drive track. Preferably, the shutter drive track is fixed to the first guide rail, preferably using screws. A one-piece, i.e., monobloc, construction is also possible for these two parts, without departing from the scope of the invention. Preferably, the structural element of the connecting device comprises a body, as well as first and second fixing legs projecting rearward from this body, and spaced apart along the span direction. According to a preferred embodiment envisaged,The first mechanical linkage includes a first axle mounted on each of the first and second fixing legs, and the second mechanical linkage includes a second axle mounted on each of the first and second fixing legs, and passing through a passage hole made through the first front end of the first rail. In this embodiment, the connecting device may include a structural element of the backup, doubling the body, as well as each of the first and second mounting lugs. 30 BE2025 / 5007 51601AP-P 6 According to another preferred embodiment envisaged, the structural element of the connecting device also includes a third mounting lug projecting rearward from the body, arranged so that the second mounting lug is located between the first and third mounting lugs in the span direction. The first mechanical connection then includes a first shaft mounted on each of the first and third mounting lugs, and passing through a through-hole formed through the second mounting lug.and the second mechanical linkage includes a second axis mounted on each of the second and third fixing legs. The invention also relates to an aircraft wing comprising a fixed wing portion, a movable leading edge flap, and such a guidance and drive system 10 for the movable flap. The fixed wing portion has a leading edge with an opening through which the first and second adjacent assemblies of the flap guidance and drive system pass. Preferably, the movable flap is associated with two guidance and drive systems spaced apart along the wingspan direction of the flap. The leading edge of the fixed wing portion has two openings spaced apart along the wingspan direction, to be respectively traversed by the two flap guidance and drive systems. This contrasts with the prior art solutions, in which there are usually four openings. cuts made through the fixed part of the wing to connect the same flap,and not two openings as proposed above. As previously indicated, this arrangement reduces drag and decreases fuel consumption. Moreover, it is noted that the wing may preferably comprise several movable flaps, each or only some of them being associated with guidance and drive systems having a design specific to the present invention. Preferably, each movable flap guidance and drive system is configured 25 so that during the flap's final travel towards its deployed position, the relative movement of the first and second rails causes the structural element of the connecting device to move relative to the first forward rail end, so that a trailing edge of the movable flap moves away from the fixed part of the wing. This thus allows the flap to be intentionally arranged and maintained at an angle of attack placing its trailing edge 30 BE2025 / 5007 51601AP-P 7 away from the fixed part of the wing, at least when the flap is in its deployed position as adopted during landing. With this trailing edge spacing,An airflow advantageously circulates between the rear of the movable flap and the fixed part of the wing during landing, which reduces the risk of aerodynamic stall. Finally, the invention relates to an aircraft comprising at least one wing of design 5 as described above, and preferably two wings conforming to this same design. Other advantages and features of the invention will appear in the detailed, non-limiting description below. BRIEF DESCRIPTION OF THE DRAWINGS 10 This description will be made with regard to the attached drawings, among which; [Fig. 1] represents a perspective view of an aircraft; [Fig. 2] represents a schematic and partial cross-sectional view of a forward part of an aircraft wing, equipped with a movable leading-edge flap, which is shown in the retracted position; [Fig. 2A] represents a simplified perspective view of the flap shown in Figure 2,with its two guidance and drive systems shown schematically only; [Fig. 3] represents a perspective view of one of the two guidance and drive systems of the leading edge movable flap shown on the wing of Figure 2A, and 20 presented according to a first preferred embodiment of the present invention; [Fig. 4] represents another perspective view of the guidance and drive system shown in Figure 3, from another angle of view; [Fig. 5] represents a cross-sectional view of the guidance and drive system shown in Figures 3 and 4, the cross-sectional line following the general curvature of the rails equipping this 25 guidance and drive system; [Fig. 6] represents a cross-sectional view of the guidance and drive system shown in the preceding figure, along line VI-VI of Figure 5; BE2025 / 5007 51601AP-P 8 [Fig. 7] represents a cross-sectional view of the guidance and drive system shown in Figure 5, along line VII-VII of Figure 5; [Fig. 8] represents a cross-sectional view of the front part of the wing, similar to that of Figure 2,with the flap in the position adopted during the beginning of the flap's extension movement; 5 [Fig.9] represents a cross-sectional view similar to that of the previous figure, with the flap in the position adopted during takeoff; [Fig.10] represents a cross-sectional view similar to that of the previous figure, with the flap in the position adopted during landing; [Fig.11] is a schematic view of the movement of the two mechanical links associated 10 with the front ends of the two rails equipping the guidance and drive system, during a movement of the flap from its retracted position to its deployed position, in a frame of reference associated with the fixed part of the wing; [Fig. 12] shows a cross-sectional view similar to that of Figure 5, with the guidance and drive system in the form of a second preferred embodiment 15 of the invention; [Fig. 13] shows a cross-sectional view of the guidance and drive system shown in Figure 12, along line XIII-XIII of Figure 12; [Fig. 13A] shows a cross-sectional view similar to that of Figure 13,the guidance and drive system being represented in the form of an alternative; 20 [Fig.14] represents a cross-sectional view similar to that of Figure 13, with the guidance and drive system being represented in the form of another alternative; [Fig.15] represents a cross-sectional view similar to that of Figure 5, with the guidance and drive system being represented in the form of a third preferred embodiment of the invention; 25 [Fig.16] represents a cross-sectional view of the guidance and drive system shown in Figure 15, along line XVI-XVI of Figure 15. BE2025 / 5007 51601AP-P 9 DETAILED STATEMENT OF PREFERRED ENGINEERING METHODS With reference first to Figure 1, an aircraft 1 is shown having a wing 2 made up of a plurality of wing elements, also called lifting aerodynamic surfaces. In the description that follows, the terms "front" and "rear" are to be considered 5 with respect to a direction of forward movement of the aircraft encountered as a result of the thrust exerted by the aircraft's engines, this direction being schematically represented by the arrow 3,and also referred to as "flight direction". The terms "upstream" and "downstream" could replace the two preceding terms, with the same meaning. Among the wing elements of the aircraft 1, there are two main wings, called wings 10 4, a vertical fin 6, as well as two horizontal tail fins 7 located at the rear of this aircraft. As regards the wings 4, as mentioned above, each of these comprises a fixed part 8 of the wing, also called the fixed central wing body or main central portion, this fixed part constituting almost the entire wing, and being 15 located behind a leading edge 10 of the wing. As schematically shown in Figure 2, it is the leading edge 10 of each of the two wings 4 that can be equipped with at least one movable leading edge flap 16, called a "Slat" in English. Usually, there are several movable leading edge flaps 16 which follow one another along the fixed part 8, in a span direction 20 17 of the wing 4, which is also considered as the span direction of the fixed part 8,and each of the movable flaps 16 of the wing. Each of these flaps 16 is intended to be connected to the fixed part 8 by guidance and drive systems 40, specific to the present invention and which will be described below. In Figure 2, the movable leading edge flap 16 is shown, having an aerodynamic part 25, for example box-shaped. Figure 2 represents the movable flap 16 in a retracted position, while the deployed position, or extension position, is shown in Figure 10. In this regard, it is noted that by deployed position, it is understood that the flap 16 is fully deployed, according to a maximum deployment / extension stroke. Consequently, during its deployment and retraction Conversely, the movable flap 16 can adopt intermediate positions, in which it remains partially deployed / extended. These intermediate positions of the flap 16 are shown in Figures 8 and 9. In the retracted / retracted position of Figure 2, the flap 16, with its trailing edge 5 13, is flush with the leading edge of the fixed part 8 of the wing 4.also referred to as the leading edge 10 of the fixed part. In such a case, the movable flap 16 is in its rearmost position. In the deployed / extended position of Figure 10, the flap 16 is at a distance forward from the leading edge 10 of the fixed part 8 and downwards, this fully deployed position 10 being adopted particularly during the landing phase, in order to increase lift at low or medium speeds. In this position, the trailing edge 13 of the flap is moved away from the leading edge 10 of the fixed part of the wing, in order to create a space 5 between these two parts allowing the circulation of an external airflow 77, delaying wing stall. The method of generating this space 5, specific to the invention, will be described 15 later. As is known, the aerodynamic part 19 of the flap 16 comprises a leading edge zone 10b, from which extend, rearward, an intrados 24 and an extrados 26, the latter terminating at the trailing edge 13 of the flap. Also as is known, the intrados 24 and the extrados 26 are spaced from each other along a direction of the height 20 21 of this flap. Furthermore,The movable flap 16 presents, in a plane orthogonal to the span direction 17 such as the transverse cutting plane of figure 2, an axial line 23 passing through the leading edge of the flap, and also passing through a trailing edge of the wing (not shown) with the flap in its retracted position. This axial line 23 thus defined can 25 be considered as a chord line of the movable flap 16, and it is noted that this line 23, as well as the two directions 17, 21, are preferably orthogonal to each other. The aerodynamic part 19 can be closed at the rear by a closing skin 27, also called a rear skin, and designed to closely follow the leading edge 10 of the fixed part of the wing 8, when the flap 16 occupies its retracted position. Such a closing skin 27 can constitute all or part of a flap spar, corresponding to a structural element of this flap 16. The closing element 27 extends from the lower surface 24 to the trailing edge 13 of the flap. Alternatively, a spar (not shown) could be added,extending upstream of the closing skin 27 along the entire length of the flap in the direction of the wingspan 5 17, preferably parallel to it. The type of longeron comprises a web, for example with a cross-section in the general shape of a bend E, and whose two lower and upper edges are respectively fixed internally on the lower surface 24, and on the upper surface 26. The fixed part 8 of the wing presents for itself a leading edge space 30, located in front of 10 a wing box 31, the latter being preferably delimited forward by a leading edge 32 of this box. The space 30 forms a portion of the leading edge 10 of the fixed part 8 of the wing. The forward spar 32 comprises a web 33, preferably planar, being, for example, also arranged in a plane parallel to the directions 17 and 21. The spar 3215 of the fixed part of the wing is, for example, completed by ribs 35 integral with the web 33, being respectively fixed to the upper surface 34 and the lower surface 36 of this fixed part 8 of the wing. The forward spar 32, of structural function, therefore extends parallel to the wingspan direction 17,over substantially the entire length of the wing. It thus forms the fixed wing box 31 with the upper surface 34 and the lower surface 36, and a rear spar not visible in the 20 figures. The wing box 31 provides a structural function to the wing in a conventional manner, but it can also be at least partially filled with fuel. In front of this box 31, the wall which forms the leading edge 10 of the fixed part 8 of the wing has a shape complementary or substantially complementary to that of the rear closing skin, of the aerodynamic part of the flap 16.25 As has been schematically represented in Figure 2A, each flap 16 is associated with two guidance and drive systems 40, spaced apart along the direction 17. These two systems 40 can be of identical or similar design. Thus, one of the The particulars of the invention lie in the fact that the leading edge 10 of the fixed part 8 of the wing presents only two openings 50 spaced apart along the direction 30 BE2025 / 5007 51601AP-P 12 of wingspan 17,being respectively traversed by the two guidance and drive systems 40 of the flap. Only one of these two openings 50 is visible in figure 2. They allow the deployment and retraction movements of the flap relative to the fixed part, and their reduced number limits drag, as well as fuel consumption. The systems 40 allow the movement of the flap 16, so as to bring it from its retracted position to its deployed position, and vice versa. This preferably involves a rotational movement of the flap 16, around an axis of rotation 18, combined with at least one other movement of the flap during at least part of this rotational movement, in particular to manage the angle of attack of the flap, and whether its trailing edge 13 is flush or not with the outer surface of the fixed part 8 of the wing. With reference now to Figures 2 to 11, one of the two guidance and drive systems 40 will be described.according to a first preferred embodiment of the invention. The system 40 comprises a moving part which is based on the implementation of a first assembly 52 for guiding and driving the shutter, and a second assembly 52b for guiding this shutter. The two assemblies 52a, 52b are adjacent along the direction 15 of span 17, for example by bearing against each other, while allowing relative movement between them, preferably a sliding movement relative to each other in their interface plane. A sliding layer may be arranged between the first and second assemblies 52a, 52b, in order to limit friction between them during their relative movement. Alternatively, a small clearance could be maintained between these two assemblies 52a, 52b, in the direction of span 17. The first assembly 52a comprises a first guide rail 54a, as well as a drive track for the flap 56, integral with the first rail 54a. These two elements 54a, 56 are pressed against each other along the span direction 17, and fixedly assembled to each other,preferably using screws 58. The drive track 56 is a toothed drive track 25, like a rack, with a general curvature identical or similar to that of the first rail 54a to which it is fixed. It cooperates with a drive device also belonging to the system 40. The drive device includes a drive wheel 60 in contact with the track 56, this wheel 60 being set in motion by a motor 62, for example, fixed to the front side member 32. 30 BE2025 / 5007 51601AP-P 13 In this first preferred embodiment, the second shutter guide assembly 52 comprises a second guide rail 54b, having a rail web bearing against a web of the second rail 54b. The two rails 54a, 54b may have a general shape of C, arranged back-to-back in the direction of the span 17. Consequently, the first rail 54a is arranged between the drive track 56 and the second guide rail 54b, according to the direction of the span 17 in which these three elements are stacked. It is noted that screws 59 can also pass through the second rail 54b, but simply for safety and with clearance.so that they do not hinder the relative movement capacity between the two rails during the deployment and retraction movements of the flap. 10 The system 40 also includes a rail guidance device 54a, 54b, mounted on the fixed part 8 of the wing. This device is preferably made up of guide rollers 64, distributed on either side of the two rails according to the direction of height, each of these rollers 64 participating in the guidance of each of the first and second rails 54a, 54b. The rollers 64 can be common to both rails or discrete to each rail, particularly in the case 15 of an overhang of the drive track 56 as shown in Figure 13A, which will be described below. It is noted that the first rail 54a has two first guide tracks 66a opposite along direction 21, and that the second rail 54b has two second guide tracks 66b also opposite along direction 21. The first tracks 66a are preferably identical and parallel to each other, as are the second tracks 66b. On the other hand,The first tracks 66a are of a different shape from the second tracks 66b. The first two guide tracks 66a are in the shape of an arc of a circle, while the two second guide tracks 66b may have a more complex curvilinear shape, dictated by the nature of the additional movement desired for the 25th panel 16 in relation to the first guide rail 54a, as will be explained below. For example, it is provided that two upper rollers 64 each cooperate with the two upper tracks 66a, 66b of the rails, as well as two lower rollers 64 each cooperate with the two lower tracks 66a, 66b of the rails. BE2025 / 5007 51601AP-P 14 One or more other guide rollers 68 may be provided for guiding the drive rail 56, as can be seen in Figures 3 and 4. The system 40 also includes a connecting device 70, allowing the connection of the first and second rails 54a, 54b to the shutter. More precisely, the connecting device 70 includes a structural element 725 integral with the shutter, with a body 74,corresponding, for example, to a plate fixed to the closing cover 27 of the shutter, using screws, rivets, bolts, or other conventional fasteners. The structural element 72 can be considered a connecting rib, and even extend inside the aerodynamic part 19 to form an internal transverse rib of the shutter. Alternatively, its body 74, in addition to being fixed to the closing cover 27, can be attached to such an internal transverse rib of the shutter. According to yet another alternative, the body 74 can be fixed to such an internal transverse rib of the shutter, simply obstructing the closing cover 27. Similar designs are also conceivable with the body 74 fixed to a side rail of the shutter, rather than to its closing cover 15 27. In addition to the body 74 forming a plate, the structural element 72 comprises a first and a second fixing lug 76a, 76b, projecting from this body towards the rear,and being spaced apart from each other along the span direction17. The structural element72 thus takes the form of a two-headed yoke76a,76b. In order to ensure a failsafe function20, the connection device70 may include a structural backup part78, for example in the general shape of a U, so as to double the body74, as well as each of the first and second fixing lugs76a,76b. Such a part, preferably made in one piece like the structural element72 it doubles, is schematically represented in Figure 5. It is arranged between the two lugs76a,76b.25 The connection device70 first forms a first mechanical connection80a between a first front end of rail82a provided on the first guide rail54a, and the legs 76a, 76b of the structural element 72. This first mechanical connection 80a preferably defines a first axis of rotation 84a, preferably parallel or substantially parallel to the span direction 17. To do this, the first mechanical connection 30 BE2025 / 5007 51601AP-P 15 80a includes a first axis 86a, oop,centered on the first axis of rotation 84a. This axis 86a, for example formed using a bolt as shown in Figure 7, is mounted on each of the first and second fixing lugs 76a, 76b which it passes through. The axis 86a is also mounted in an opening in the first front end of rail 82a, located between the two fixing lugs 76a, 76b. It can be ball-jointed, that is to say, associated with a radial ball joint 88, allowing to accommodate the small parasitic movements of the shutter. A slip can also be tolerated for the first front end of rail 82a, between the two fixing lugs 76a, 76b, along the axis of rotation 84a. It is noted that the first axis 86 also passes through the legs of the spare part 78.10 Furthermore, the connecting device 70 forms a second mechanical link 80b between a second front rail end 82b provided on the second guide rail 54b, and the legs 76a, 76b of the structural element 72. This second mechanical link 80b preferably defines a second axis of rotation 84b, preferably parallel or substantially parallel to the span direction 17. To this end,The second mechanical linkage 80b15 includes a second axle 86b, centered on the second axis of rotation 84b. This axle 86b, for example formed using a bolt, is mounted on each of the first and second mounting lugs 76a, 76b, which it passes through. The axle 86b is also mounted in an opening in the second front end of the rail 82b, located between the two mounting lugs 76a, 76b, to the rear of the first axle 86b. In other words, the second front end 20 of the rail 82b stops before the first front end 82a, and also before the first axle 86a. Here too, the second axle 86b can be pivoted, in the same way as the first axle 86a shown in Figure 7. Furthermore, the second axle 86b passes through an opening in passage90 made through the first front end of rail82a. The clearance is sufficiently large so as not to impede the relative movement between the two rails54a,25,54b, during the opening and closing of the shutter. As mentioned previously, figure2 represents the shutter16 in a positionP0 corresponding to the retracted position,adopted for example in cruise regime. Figure 9 represents flap 16 in a partially deployed position P2, adopted for example at takeoff, while position P1 in figure 8 corresponds to an intermediate position between positions P0 and P2. Finally, figure 10 represents flap 16 in a position P3 corresponding to the deployed position, at the end of the deployment stroke, adopted at landing. Preferably, in and between positions P0 to P2, the trailing edge 13 of the flap is in contact with the leading edge 10 of the fixed part of the wing, in order to prevent the circulation of the aforementioned external airflow 5 77 between these two parts. Also, preferably, it is only from the movement of the flap from position P2, towards position P3, that the space 5 is provided between the trailing edge 13 of the flap and the leading edge 10 of the fixed part of the wing, for the circulation of the external airflow 77. These four positions P0-P3 have been shown in Figure 11, schematically illustrating the movement 10 of the two mechanical links 80a,80 during a movement of the flap from its retracted position to its deployed position. For greater clarity, the evolution of the position of their respective rotation axes 84a, 84b has been represented in a frame X, Z associated with the fixed part of the wing. In addition, two trajectories 92a, 92b have been represented in this figure 11, corresponding respectively to the trajectories of the two rotation axes 84a, 84b in the frame X, Y. The first trajectory 92a has a shape identical to that of the first two guide tracks 66a of the first rail, while the second trajectory 92b has a shape identical to that of the second two guide tracks 66b of the second rail. The system 40 is configured such that during at least a determined part of a 20 movement of the first and second rails 54a, 54b relative to the rollers 64, and more precisely during the end of the shutter's travel towards its deployed position, the distinct interactions between the rollers 64 and the tracks 66a, 66b generate a relative displacement of the two rails 54a, 54b relative to each other. This relative displacement,corresponding to a slide of one relative to the other in their interface plane, causes the second axis 25 of rotation 84b to move upward relative to the first axis of rotation 84b, by pivoting between the second front end of rail 82 and the legs 76a, 76b. This pivoting generates another pivoting of the legs 76a, 76b relative to the first front end of rail 82a, around the axis of rotation 84a. This last movement causes the entire structural element 72 to pivot relative to the first front end 30 BE2025 / 5007 51601AP-P 17 of rail 82a, along the first axis of rotation 84a. With such a pivoting, the entire flap 16 is set in rotation around the axis 84a, in a direction such that its edge of The flap 13 moves away from the outer surface of the fixed part of the wing. It is this movement of separation, observed at the end of the deployment stroke, that creates the space 5 between the rear of the flap and the fixed part of the wing, as shown in Figure 10.5. In Figure 11,The first trajectory 92a was represented as an arc of a circle centered on the axis of rotation 18 of the flap. The second trajectory 92b can also be largely in the form of an arc of a circle centered on the axis of rotation 18, before adopting at the end of its travel a more complex shape, triggering the desired relative displacement between rails 54a, 54b. The second trajectory 92b could be more complex, over a greater extent of this one, particularly if necessary to keep the trailing edge 13 of the flap flush with the leading edge 10 of the fixed part of the wing, between positions P0 and P2. More generally, the shape of this trajectory 92b allows control, in any way desired, the incidence of the flywheel at any point during its extension / retraction movement. With reference to Figures 12 and 13, a second preferred embodiment of the invention is shown, which differs from the previous embodiment essentially in that the drive rail 56 is arranged between the first and second rails 54a, 54b. The sliding between the two assemblies 52a, 52b therefore takes place at the center of the second rail 54b.etlapiste20 d'entraînement56. In an alternative design shown in Figure 13A, the drive track 56 is partially arranged in the space defined between the webs of the two guide rails 54a, 54b. This track 56 can indeed be designed to have a support portion 56a, of reduced thickness along the span direction 17, in order to be arranged between the webs of the two rails 25 and thus delimit the lever arm between these guide rails 54a, 54b. The track 56 also includes an active portion 56b, equipped with the teeth, and supported by the support portion 56a. The active portion 56b projects inwards from the two rails relative to their curvature, so as to offset the teeth from the volume swept by the guide rails. BE2025 / 5007 51601AP-P 18 54a,54b. This active part 56b can thus have, in the span direction, a thickness greater than that of the support part 56a. In an alternative shown in Figure 14, the first assembly 52a includes an additional rail 54a',for example, made in one piece with the first rail 54a. This embodiment provides a recess between the two rails 54a, 54a', in order to accommodate the drive rail 56. To do this, the double rail 54a, 54a' can take a general shape of U or π. This allows the second rail 54b to slide on the additional rail 54a' of the first assembly. Moreover, in this second preferred embodiment, the structural part of the course 78 is arranged externally with respect to the legs 76a, 76b. 10 Finally, with reference to