Movable flap for the leading edge of an aircraft wing, having a curved nominal shape in order to adapt to the bending of the wing in flight

Abstract

The invention relates to a movable flap (16) for the leading edge of an aircraft wing, the flap being intended to be mounted on a fixed part (8) of the wing and comprising two flap ends (16a, 16b) positioned opposite one another along the span (17) of the flap, the flap defining a leading edge zone from which a lower surface and an upper surface extend, the surfaces being spaced apart from one another over the height (21) of the flap. According to the invention, the flap has a generally upwardly concave shape in its nominal state in order to limit fatigue stresses on the flap during flight.

Description

[0001] A movable leading-edge flap of an aircraft wing, having a nominal curved shape to adapt to the wing's deformation in flight.

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates to the field of aircraft wings, of the type comprising a fixed part of the wing carrying one or more movable leading edge flaps, also called "Slats" in English.

[0005] The invention relates more particularly to the general shape of these movable leading edge flaps, and the problem of their fatigue resistance.

[0006] It is noted that the invention applies to all types of aircraft, such as a flying wing, a tail-engine aircraft, a supersonic aircraft, etc.

[0007] STATE OF PRIOR ART

[0008] On aircraft, each of the two wings of the wing is generally equipped with movable high-lift flaps, mounted on the leading edge and trailing edge of the wing.

[0009] As is well known, flaps are deployed during takeoff and landing to increase lift at low and medium speeds. Conversely, during high-speed cruise flight, the flaps are retracted to reduce drag. The movement and guidance of each flap are achieved conventionally using systems housed within the fixed wing section, also known as the wing center section.

[0010] The evolution of aircraft leads to the design of increasingly longer, thinner wings with increased flexibility in order to improve aerodynamic performance.

[0011] In flight, each wing undergoes elastic deformation due to the aerodynamic forces acting upon it. This elastic deformation is essentially a bending, which is therefore more pronounced the more flexible the wing. Under nominal flight conditions, this bending consequently gives the fixed part of the wing a generally upward-concave shape, which contrasts with the straighter shape of the movable flaps attached to the front of this fixed part of the wing. Indeed, under these nominal flight conditions (loading at IG), given the stresses on the flap and the fixed part of the wing, these two elements deform differently.

[0012] This results in particularly high mechanical stresses in flight, which lead to fatigue resistance problems for the movable flaps, constrained by the fixed part of the wing which deforms.

[0013] It is possible to address this problem by oversizing the movable shutters so that they have better fatigue resistance, but this solution often proves too penalizing in terms of overall mass.

[0014] Consequently, there remains a need to optimize aircraft wing design in order to limit fatigue problems on the leading edge flaps resulting from wing flexing during flight.

[0015] DESCRIPTION OF THE INVENTION

[0016] To meet this need, the invention first relates to a high-lift movable leading-edge flap for an aircraft wing comprising a free wingtip, the flap being intended to be mounted on a fixed part of the wing, and comprising two flap ends opposite each other in a span direction of the flap, the flap extending, in the span direction from one to the other of its two opposite ends, over a total flap length (Lv), the flap defining a leading-edge area from which extend an intrados and an extrados spaced apart in a direction of the height of this flap, the flap comprising, along the span direction, a central flap section on either side of which are two opposite flap end sections, comprising respectively the two opposite flap ends.

[0017] According to the invention, in a nominal state of the movable flap, corresponding to a state unattached to the fixed part of the wing and unconstrained, the central section of the flap exhibits, in the span direction, a generally upward concave shape. The invention thus breaks with conventional designs by providing a leading-edge movable flap that is no longer manufactured with a generally straight shape in the span direction, conforming to the shape of the fixed part of the wing at rest, but rather with a generally curved shape on at least one central section of this flap. This concave shape, applied to the central section and also preferably to the two flap end sections, proves suitable since it conforms to the shape of the fixed part of the wing under nominal flight conditions. This advantageously results in a reduction of fatigue stresses on the flap, thereby increasing its service life.

[0018] Other aspects of the invention will be described by enumerating the following optional features, intended to be implemented individually or in combination.

[0019] Preferably, the flap comprises a spar having a web, the flap spar web having two spar web ends opposite each other in the span direction, and the web having, along the span direction, a central web section on either side of which are two web end sections, respectively comprising the two opposite web ends. Furthermore, in the nominal state of the flap, the central web section has, in the span direction, a generally upward concave shape.

[0020] Preferably, the web of the spar is flat, this web therefore having, at least within the central web section, an upper edge concave upwards, and a lower edge convex downwards.

[0021] Preferably, the central section of the flap, generally concave upwards in the nominal state of the movable flap, extends in the span direction along a central section length (Le), so that the ratio Lc / Lv is greater than or equal to 0.5.

[0022] According to a first preferred embodiment of the invention, in the nominal state of the movable flap, each of the two opposing flap end sections also has, in the span direction, a generally upward concave shape, such that the entire movable flap, moving from one to the other of its two opposite ends, has a generally upward concave shape. According to a second preferred embodiment of the invention, in the nominal state of the movable flap, each of the two opposing flap end sections has, in the span direction, a generally upward convex shape.

[0023] Regardless of the preferred embodiment envisaged, the overall upward concave shape of the central section of the flap preferably has, over at least a portion of the central section of the flap extending in the span direction, a concavity of curvature greater than or equal to 4.5 x 10 -6 mm 1 , this part extending in the span direction preferably over a length of part of maximum concavity (Lcm), so that the ratio Lcm / Lc is greater than or equal to 0.1.

[0024] It is noted that all the curvature and ratio values ​​described above are therefore applicable to the movable flap considered in its general form, but they also apply identically to the web of the flap spar, and always in the unassembled state of the flap on the fixed part of the wing, and unstressed.

[0025] Preferably, the movable shutter has several guide and / or drive rails.

[0026] Preferably, the movable flap is made in whole or in part using metallic elements, so as to best resist any impacts, particularly from birds.

[0027] The invention also relates to an aircraft wing with a free wingtip, the wing comprising a fixed portion at the front of which is mounted a movable, high-lift leading-edge flap as described above, said flap being movable relative to the fixed portion of the wing, between a retracted and a deployed position, the movable flap extending further forward in the deployed position than in the retracted position, relative to the fixed portion of the wing. Furthermore, each wing may preferably comprise several movable flaps, each or only some of them having a design specific to the present invention.

[0028] Preferably, the fixed part of the wing includes means for righting the movable flap, and in the wing's rest state, occupied when the wing is fixed to the aircraft with the aircraft on the ground and stationary, and in the retracted position of the movable flap, said righting means apply an elastic deformation force to the central section of the movable flap, so that it exhibits a general concave shape with a curvature less pronounced than that observed in its nominal state. Preferably, the righting means cooperate with a support member integral with a spar of the movable flap.

[0029] Preferably, under nominal flight conditions, the fixed wing section is deformed by aerodynamic forces acting upon it, giving it a generally upward concave shape. In this regard, it is noted that under nominal flight conditions, the curvature of the deformed fixed wing section is preferably, locally, identical or substantially identical to the curvature of at least a portion of the flap's center section, and more preferably of the entire flap's center section. Conversely, these two curvatures differ, even significantly, when the fixed wing section is considered on the ground with the aircraft stationary and not subjected to aerodynamic forces, and when the movable flap is considered in its unattached and unconstrained state.

[0030] Preferably, the fixed part of the wing includes a front spar comprising a planar web, and under nominal wing flight conditions, the web of the front spar is deformed by aerodynamic forces applied to the fixed part of the wing, giving this web a general upward concave shape, with an upward concave upper edge, and a downward convex lower edge.

[0031] Preferably, under nominal flight conditions of the wing with the movable flap in its retracted position, the elastic deformation force applied to the movable flap by the righting means is zero, or strictly less than that applied when the wing is in its rest state with the movable flap in the retracted position.

[0032] Finally, the invention relates to an aircraft comprising at least one wing of the design described above, and preferably two wings of the same design, arranged respectively on either side of the aircraft fuselage, without a loop connection between these two wings. In other words, it is not a looped wing, but two independent wings, each fixed to the fuselage and extending laterally to its free wingtip, also known as the wingtip. These are therefore conventional wings, also called straight, swept, or delta wings, with a leading edge and a trailing edge. Other advantages and features of the invention will become apparent in the detailed, non-limiting description below.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] This description will be made with reference to the attached drawings, among which are;

[0035] [Fig. 1] represents a perspective view of an aircraft;

[0036] [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;

[0037] [Fig. 3A] represents a perspective view of the movable leading edge flap shown on the wing in Figure 2 and presented according to a first preferred embodiment of the present invention, in a nominal state corresponding to a state in which the movable flap is not yet assembled on the fixed part of the wing, and in which it is unconstrained;

[0038] [Fig. 3B] represents a schematic front view of the leading edge movable flap shown in Figure 3A, in its nominal state;

[0039] [Fig. 3B'] represents an enlarged schematic view of part of the flap shown in figure 3B;

[0040] [Fig. 4A] represents a perspective view of a portion of the wing shown in Figure 2, the wing in a resting state, occupied when the wing is fixed to the aircraft with the aircraft on the ground and stationary, and the movable flap in the retracted position;

[0041] [Fig. 4B] represents a schematic front view of part of the wing shown in figure 4A, in its resting state and with the movable flap in the retracted position;

[0042] [Fig. 5A] represents a perspective view similar to that of figure 4A, the wing being in a state under nominal flight conditions, with the movable flap in the retracted position;

[0043] [Fig. 5B] represents a schematic front view of a part of the wing shown in Figure 5A, in its state under nominal flight conditions and with the movable flap in the retracted position; [Fig. 6] represents a schematic front view similar to that of Figure 3B, with the leading edge movable flap in the form of a second preferred embodiment of the invention;

[0044] [Fig. 7] represents a schematic cross-sectional view similar to that of figure 2, showing optional features of the invention.

[0045] DETAILED EXPLANATION OF PREFERRED METHODS OF IMPLEMENTATION

[0046] With reference first to figure 1, an aircraft 1 is represented having a wing 2 made up of a plurality of wing elements, also called lifting aerodynamic surfaces.

[0047] Throughout the description that follows, the terms "front" and "rear" are to be considered in relation 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 arrow 3, and also called "flight direction".

[0048] Among the wing elements of aircraft 1, there are two main wings, called wings 4, a vertical fin 6, as well as two horizontal tail fins 7 located at the rear of this aircraft.

[0049] Each of the two wings 4 has a design with a first wingtip 108' for its attachment to the aircraft fuselage, and a free wingtip 108'' set apart from the first wingtip, along a wingspan 17 of the wing. The free wingtip 108'', also called the wingtip, is thus located further laterally from the fuselage 106 than is the first wingtip 108' of a single wing. Therefore, it is not a looped wing, but two independent wings 4, each attached to the fuselage and extending laterally to its free wingtip 108''.

[0050] Conventionally, each wing 4 supports at least one propulsion unit 110 with a nacelle 112, via a mounting mast 114. Each propulsion unit 110, equipped with an engine, usually projects forward from the wing 4 that supports it. However, the invention applies more generally to an aircraft comprising such conventional free-rooting and free-tip wings, with the propulsion units mounted on these wings, or in the rear fuselage. As mentioned above, the wings 4 each comprise a fixed wing section 8, also called the fixed wing center section or main center section, this fixed section constituting almost the entire wing, and being located behind a leading edge 10 of the wing.

[0051] 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 leading-edge movable flap 16, known as a "slat" in English. Typically, several leading-edge movable flaps 16 are arranged in succession along the fixed section 8, according to the span direction 17 of the wing 4, which is also considered the span direction of the fixed section 8, and of each of the movable flaps 16 of the wing.

[0052] Each of these flaps 16 is intended to be connected to the fixed part 8 by a conventional displacement system 40, which will be described below. Figure 2 shows the leading-edge flap 16, which has an aerodynamic part 19, for example, box-shaped. Figure 2 represents the flap 16 in a retracted position, while the deployed, or extended, position is shown only partially and schematically at the bottom of Figure 2. As is known, the flap 16 extends further forward in the deployed position than in the retracted position, relative to the fixed part 8 of the wing.

[0053] In this regard, it is noted that by deployed position, it is understood that the flap 16 is fully deployed, according to its maximum deployment stroke. Consequently, during its deployment, and its retraction in the opposite direction, the mobile flap 16 can adopt intermediate positions, in which it remains partially deployed / extended.

[0054] In the retracted position, the flap 16 is flush with the leading edge of the fixed part 8 of the wing 4, also known as the leading edge 10a of the fixed part. In this case, the movable flap 16 is in its rearmost position.

[0055] In the deployed / extended position, flap 16 is positioned forward of the leading edge 10a of the fixed section 8 and downwards. This fully deployed position is adopted particularly during the landing phase to increase lift at low and medium speeds. Conventionally, flap 16 is also deployed during takeoff to increase lift, but in an intermediate position to avoid excessively increasing drag.

[0056] Preferably, each flap 16 extends only over a portion of the wing along the span direction 17, as is most common on aircraft. Thus, each wing is generally equipped with several movable flaps 16 arranged in succession along the span direction 17. Also, in the case of several movable flaps 16 on the same wing, each is designed to cooperate with a deployment system specific to the invention, although certain elements of these deployment systems may be common to several movable flaps.

[0057] As is known, the aerodynamic portion 19 of the flap 16 comprises a leading edge area 10b, from which extend rearward an intrados 24 and an extrados 26, the latter terminating in a trailing edge 27 of the flap. Also as is known, the intrados 24 and the extrados 26 are spaced apart along a direction corresponding to the height 21 of this flap.

[0058] Furthermore, the movable flap 16 presents, in a plane orthogonal to the span direction 17 such as the cross-sectional plane in 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 be considered a chord line of the movable flap 16, and it is noted that this line 23, as well as the two directions 17 and 21, are preferably orthogonal to each other.

[0059] The aerodynamic section 19 can be closed at the rear by a closing skin (not shown), also called the rear skin, designed to conform to or closely approximate the leading edge 10a of the fixed wing section 8 when the flap 16 is in its retracted position. Such a closing skin can be formed by the flap spar, which will be described below.

[0060] Indeed, the flap 16 comprises a spar 60 extending along its entire length in the span direction 17, preferably parallel to it. The flap spar 60 has a web 62, preferably flat, for example oriented in a plane parallel to the directions 17 and 21. The web 62 extends over the entire height of the aerodynamic part 19 in which it is located, and the flap spar 60 is completed by ribs 64 integral with the web 62, forming, for example, with it a spar section in the general shape of a C or an E. Two of these ribs 64 are respectively fixed internally to the lower surface 24 and to the upper surface 26.

[0061] Figures 3A to 5B represent a first preferred embodiment of the invention. In these figures, the curvatures of the flap and its components have been deliberately exaggerated for the sake of clarity in explaining the invention.

[0062] As can be seen in Figure 3A, the movable flap 16 comprises two flap ends 16a, 16b opposite each other in the span direction 17, and two opposite ends 62a, 62b of the web 62 of the flap spar 60 extend respectively to these two flap ends 16a, 16b.

[0063] In the span direction 17, the flap 16 extends from one of its two opposite ends 16a, 16b to the other over a total flap length, referenced Lv. Along this same direction 17, the flap comprises a central flap section 100, on either side of which are two opposing flap end sections 102a, 102b, comprising respectively the two opposing flap ends 16a, 16b. These sections 100, 102a, 102b are continuous with each other in the span direction 17, and the interfaces between them are not necessarily materialized on the manufactured flap. The identification of these three shutter sections serves to clarify the disclosure of the invention, even though in this first preferred embodiment of the invention, the three sections have similar general shapes, namely concave upwards as will be detailed below.

[0064] The fixed wing section 8 has a leading edge space 30, located in front of a wing box 31, the latter preferably being delimited forward by a leading edge spar 32 of this box. The space 30 forms a portion of the leading edge 10a of the fixed wing section 8.

[0065] The forward spar 32 comprises a web 33 that is preferably flat, for example, also arranged in a plane parallel to the directions 17 and 21. The spar 32 of the fixed wing section is, for example, supplemented by ribs 35 integral with the web 33, and respectively fixed to the upper surface 34 and lower surface 36 of this fixed wing section 8. The forward spar 32, which has a structural function, thus extends parallel to the span 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 figures. The wing box 31 conventionally provides a structural function to the wing, but it can also be at least partially filled with fuel.At the front of this box 31, the wall which forms the leading edge 10a of the fixed part 8 of the wing has a shape which is complementary or substantially complementary to that of the rear closing cover of the aerodynamic part of the flap 16.

[0066] The system 40 for moving the flap 16 allows the flap to be moved from its retracted position to its extended position, and vice versa. Preferably, this involves a rotational movement of the flap 16 around a rotation axis 18. However, more complex flap movements can be envisaged, for example, kinematics involving such a rotation combined with one or more other movements, without departing from the scope of the invention.

[0067] In any case, the movement of the flap 16 is achieved using several movable rails, which are part of the movement system 40 and form an integral part of the flap 16. These rails may be dedicated to guiding the flap during its movement, and / or to driving the flap, and / or to both guiding and driving the flap. Figures 2 and 3A illustrate this last case, with two movable rails 42 for guiding and driving the flap 16. Each rail 42, generally shaped like an arc, interacts with guide rollers 44 belonging to the system 40 and integrated into the fixed part 8 of the wing. Furthermore, the rail 42 interacts with a drive mechanism that also belongs to the movement system 40.It includes a drive wheel 46 in contact with the rail 42, preferably with a toothed track for driving this rail, the wheel 46 being set in motion by a motor 48 of the drive device, for example fixed on the front longitudinal member 32.

[0068] The rollers 44 have been shown in the forward space 30 of the fixed part of the wing, but they could be located at least partly in the wing box 31. In this regard, it is specified that the rear part of the rail 42 can also be located in the wing box 31, by passing through an opening in the forward spar 32.

[0069] Conversely, the rail 42 has a connecting end 50 fixed to the movable shutter 16. This connecting end 50 is fixed by conventional fasteners 52 to a rear portion of the shutter, for example, bolts or rivets. These fasteners 52, shown only schematically in the figures, connect the connecting end 50 to a mounting bracket 54 extending rearward from the web 62 of the shutter spar 60. The mounting bracket 54 can be integral with the spar 60 or attached to it. Within the central section of the shutter, the web 62 defines a central web section 200, on either side of which are two web end sections 202a, 202b, each comprising two opposing web ends 62a, 62b.Naturally, the two web end sections 202a and 202b are arranged within the two opposing flap end sections 102a and 102b, respectively, and have the same lengths along direction 17. The same applies to the central web section 200, which is located within the central flap section 100, having the same length along the span direction 17, as well as the same curvature, as will be detailed below. One of the distinctive features of the invention lies in the general shape of the movable flap, as adopted in its nominal state shown in Figures 3A and 3B. This nominal state corresponds to the flap 16 being unassembled on the fixed part 8 of the wing, and to an unconstrained state of this flap. In other words, it is the state of the flap at the end of its manufacture, before it is mounted on the wing, and when it is not subjected to any external stress.As an example, this nominal state is observed when the flap is supported only by its rails 42, regardless of the means of support used, and regardless of the points of these rails with which they cooperate in order to support the flap 16. This nominal state is therefore preferably also encountered when the flap is assembled on the fixed part of the wing, but is in the deployed position.

[0070] In this nominal state, the central section 100 of the flap 16 has a general shape concave upwards. In other words, at the level of this central section of flap 100, the intrados 24 has a convex surface 66, bulging downwards, and the extrados 26 has a concave surface 68, open upwards.

[0071] In this first preferred embodiment of the invention, the same applies to the two opposing end sections of the flap 102a, 102b, which also each have, in the span direction, a generally upward concave shape. Thus, the entire movable flap 16 formed by its three sections 100, 102a, 102b has, in the direction from one to the other of its two opposing ends 16a, 16b, a generally upward concave shape.

[0072] Furthermore, still in this nominal state of the flap, the web 62 of the flap spar 60, moving from one end to the other of its two opposite ends 62a, 62b, exhibits its central flap section 200 with the same general upward concave shape. The same is true for the two opposing web end sections 202a, 202b, which also each exhibit, moving in the span direction 17, a general upward concave shape. Here too, the entire web 62, formed by its three sections 100, 102a, 102b, exhibits, moving from one end to the other of its two opposite ends 62a, 62b, a general upward concave shape.

[0073] Moreover, in Figure 3B, the only element shown schematically from the front corresponds both to the flap 16 as a whole, and to the web 62 of its spar 60. The same is true for Figures 4B and 5B.

[0074] Therefore, with regard to the plane 62 core inscribed in a plane parallel to the directions 17, 23, this core also has an upper edge 70 concave upwards, and an lower edge 72 convex downwards.

[0075] In this first preferred embodiment, at every point of the flap 16 between its two ends 16a, 16b, the concave curvature is preferentially always present, so as to form the aforementioned concavity. In other words, along direction 17, the sign of the curvature always remains the same, without reversing, even if the value of this curvature may vary along the flap.

[0076] In this respect, all along the span direction 17, the concavity preferably has a minimum curvature value of l.5.10 -6 mm 4However, this minimum curvature value could be lower, particularly near the ends 16a, 16b, at which point the upward concave curvature could become zero or almost zero.

[0077] Furthermore, with reference to Figure 3B', it is noted that the general upward concave shape of the central section of flap 100 exhibits, over at least a portion 104 of this section 100 extending in the span direction 17, a concavity of curvature greater than or equal to 4.5.10 -6 mm 1Preferably, this refers to the central part 104 of the central section of the flap 100. In this first preferred embodiment of the invention, the curvature value in the recess can be constant along the entire length of the flap, or it can vary. In the latter case, this curvature value can be maximized within part 104, and then gradually decrease towards each of the two flap ends 16a, 16b.

[0078] As an indicative example, part 104, in which the upward concave curvature is greater than or equal to 4.5.10 -6 mm 4, extends in the span direction 17 over a length of maximum concavity part referenced Lcm, fixed so that the ratio Lcm / Lc is greater than or equal to 0.1. The length referenced Le corresponds to the length of the central section of flap 100 along direction 17, and it is fixed so that the ratio Lc / Lv is greater than or equal to 0.5. It is specified that all these lengths Lv, Le, Lcm are considered in the nominal state of the flap.

[0079] Furthermore, it is noted that all the geometric characteristics and values ​​described above, in relation to the general shape of the flap 16 along the span direction 17, apply in an identical or analogous manner to the general shape of the web 62 of the flap spar 60, along this same direction 17.

[0080] Preferably, the flap 16 is made entirely or partially of metallic elements, generally offering satisfactory mechanical resistance, particularly against impacts. The same is preferably true for all or part of the elements of the fixed section 8 of the wing.

[0081] Wing 4 is shown in its resting state in Figures 4A and 4B, with the movable flap 16 in its retracted position. The wing's resting state corresponds to an occupied state when wing 4 is fixed at one of its ends to the aircraft, with the aircraft on the ground and stationary. In this state, the fixed part of the wing is considered to have a generally straight shape in the span direction 17, or possibly slightly concave downwards due to the overhang.

[0082] To compensate for the difference in shape between the fixed wing section 8 and the flap 16, this fixed section 8 incorporates means 74 for righting the movable flap. Indeed, in the wing's rest state with the flap retracted, these righting means 74 apply a mechanical force of elastic deformation to the central flap section 100, so that this section exhibits a generally concave shape with a curvature less pronounced than that observed in its nominal state. This righting principle can also be implemented at several points on the flap along its span direction 17, even at points outside the central flap section 100, therefore closer to the flap tips 16a, 16b.

[0083] Thus, the intrados 24 still has its convex surface 66, bulging downwards, but with a less pronounced curvature, and the extrados 26 still has its concave surface 68, with a hollow open upwards, also with a less pronounced curvature than in the nominal state of the flap 16. Similarly, the web 62 of the flap spar still has its upper edge 70 concave upwards, as well as its lower edge 72 convex downwards, these two edges remaining with a less pronounced curvature than in the nominal state of the flap.

[0084] However, the straightening process can be such that the flap conforms to the shape of the fixed part 8 of the wing, potentially even exhibiting elastic deformation that gives it a generally straight shape, or one that is only very slightly concave upwards. In this regard, it should be noted that in all the figures, the curvatures have been exaggerated compared to those actually observed, in order to facilitate understanding of the invention. The straightening means 74, shown schematically in Figures 4A and 4B but most clearly visible in Figure 2, therefore cooperate at least partially with the central section of the flap 100, and more specifically, preferably with its portion 104 of maximum curvature in the nominal state. They bear on a support member 76 provided on the flap 16, preferably fixed to or integrated into the spar 60 of this flap.

[0085] The righting means 74, projecting forward from the leading edge 10a of the fixed part 8, preferably have a rounded shape, as does the support member 76. This allows these parts to slide against each other at the end of the retraction stroke of the flap, or at the beginning of its deployment stroke.

[0086] With reference now to Figures 5A and 5B, the wing 4 is shown in flight, specifically under nominal flight conditions (loaded at IG). In this state, the fixed part 8 of the wing is conventionally deformed by the aerodynamic forces acting upon it, giving it a generally upward concave shape. This same generally upward concave shape is observed in an identical or analogous way for the web 33 of the leading spar 32 of the fixed part 8 of the wing. Thus, this web 33 also has an upper edge 80 that is concave upward and a lower edge 82 that is convex downward, whereas these same edges 80 and 82 were straight or slightly downward concave in the wing's rest state, shown in Figures 4A and 4B.

[0087] In this state, under nominal flight conditions of wing 4, with flap 16 in its retracted position, the elastic deformation force applied to flap 16 by the righting means 74 is zero, or strictly less than that applied when the wing is in its rest state described previously, with the movable flap in the retracted position. Consequently, flap 16 returns to its nominal general shape, or a shape very close to it.

[0088] In this state, under nominal flight conditions of wing 4, it is therefore desirable that the concavity of the fixed part of the wing be identical or similar to the concavity of flap 16, at the level of the wing portion that carries this movable flap. The same observation can be made for the concavities of the two spar webs 33 and 62.

[0089] The originality of the invention lies in applying a curvature during the manufacturing of the flap, before deformation occurs in operation. This curvature, which is maintained under nominal flight conditions, allows the flap to adapt to the deformation of the fixed part of the wing during flight, particularly under these nominal flight conditions. This advantageously results in a reduction of the flap's fatigue stress, thereby increasing its lifespan.

[0090] Figure 6 shows a second preferred embodiment of the invention, in which, in the nominal state of the flap 16, it no longer exhibits concavity along the entire span direction 17. Indeed, only the central section of the flap 100 has a generally upward concave shape, preferably with the same properties as those shown for the first preferred embodiment. Conversely, still in the nominal state of the movable flap 16 as shown in Figure 6, each of the two opposing end sections of the flap 102a, 102b, along the span direction 17, has a generally upward convex shape. A reversal of the sign of curvature is therefore achieved at the two interfaces between the three flap sections 100, 102a, 102b, the curvature thus remaining zero at these interfaces, which can be considered as two inflection points.

[0091] This configuration advantageously limits the elevation of the flap ends 16a, 16b relative to the fixed part of the wing, especially at their trailing edges, when the aircraft is on the ground and stationary, with the movable flap 16 in its retracted position.

[0092] The concave curvature of the central section of shutter 100 is preferentially more pronounced than the convex curvature of the end sections of shutter 102a, 102b. As an example, part 104 of the central section of shutter 100 has a curvature concavity greater than or equal to 4.5 x 10 -6 mm 4 , and locally reaching a value of 3.10 -5 mm 1or even more, but each of the two opposing end sections of the flap 102a, 102b has a curvature of opposite sign and whose absolute value never reaches this last maximum value associated with part 104. For example, the convexity of the two opposing end sections of the flap 102a, 102b has a maximum curvature on the order of 1.5 x 10 -5 mm 4 .

[0093] Finally, it is noted that, as with the first preferred embodiment, the values ​​and shapes described for the shutter sections 100, 102a, 102b apply identically to the web sections 200, 202a, 202b.

[0094] In operation, the flap of the second preferred embodiment functions in the same or a similar manner to that described for the first preferred embodiment. Figure 7 illustrates an optional feature of the invention, in which the upper surface 26 of the movable flap 16 terminates downstream with an end portion 27' exhibiting greater flexibility than the rest of this upper surface. In other words, the end portion 27', which terminates at the trailing edge 27 of the flap, is more easily elastically deformed in bending, due to contact with the fixed part of the wing 8. This lower rigidity of the end portion 27', preferably in the form of a wall, can be achieved in various ways. For example, its wall thickness can be reduced.Such a reduction in thickness can result from the fact that, upstream of this end portion 27', the upper surface 26 is formed by the superposition of an outer upper surface skin and a rear closure cladding. In this case, the end portion 27' can correspond to the extension of the outer upper surface skin of the flap, downstream of the point where the rear closure cladding of the flap terminates. Another possibility is to attach the end portion 27' to the downstream side of the flap, for example, by making it from a different material than the rest of the flap, in order to provide the required flexibility. It could thus be a flexible tab extending along the wingspan direction. By way of example, the materials considered for this end portion 27' are: glass or carbon fiber composite, aluminum, stainless steel, titanium, or a combination of several of the aforementioned materials.

[0095] This flexibility makes it possible to mitigate the effects of differences in nominal wing shape between the fixed part of the wing and the flap when the latter is retracted with the aircraft on the ground and stationary. Thanks to this increased local flexibility, the stresses placed on the flap are advantageously reduced.

[0096] Due to the flap's curvature in its nominal state, the most significant effects on the flap's load from its bearing against the fixed wing section are observed at the two flap tips, opposite each other along the span direction. Therefore, it is possible to implement the flexibility principle described above at both flap tips. For example, the flexibility of the tip section 27' can increase in directions from the center of this section 27', considered along the span direction 17, towards each of the two opposite flap tips. Alternatively, flexibility can be provided only at these two flap tips, for example, by adding flexible elements to a central area of ​​the tip section Tl', which itself could retain conventional stiffness.Note that in Figure 7, the wingtip section TT is schematically represented as a solid line in its deformed state by the fixed wing section 8. This state is observed particularly when the flap is retracted and the aircraft is on the ground and stationary. However, this wingtip section TT is also represented as a dashed line in its unconstrained state by the fixed wing section 8. This latter state is observed, for example, when the movable flap 16 is extended, both in flight and on the ground.

[0097] Figure 7 illustrates another optional feature, which can be implemented independently of the previous one, or simultaneously. This consists of one or more stops 47, whose function is to mechanically unload the trailing edge 27 in the event of significant deformation of the fixed part of the wing during flight. Indeed, in the event of a high wing load, typically exceeding IG and encountered, for example, following strong gusts, the fixed part 8 may bend even further and exceed the curvature level of the flap 16. To limit the risks associated with this abnormal and temporary deformation, in terms of stress on the trailing edge 27 of the flap, the stops 47 allow for the introduction of an alternative load path between the fixed part 8 and this flap 16.To achieve this, the stops 47 are supported, for example, by the flap spar, its closing cover, or preferably by the two flap closing ribs, in the span direction 17. For example, on each of these two transverse closing ribs, a protrusion carrying a contact pad with the fixed part 8 may be provided. However, a clearance is maintained between these two elements under nominal flight conditions, to be used only in the event of exceptional loading of the fixed part 8 of the wing, such as in gusts as described above. Such clearance is also provided when the aircraft is on the ground and stationary, with the flap in the retracted position.

[0098] Alternatively, such stops 47 could be provided on the leading edge 10a of the fixed part 8, without going out of the scope of the invention.

[0099] Of course, various modifications can be made by a person skilled in the art to the invention just described, only by way of non-limiting examples, and the scope of which is delimited by the attached claims.

Claims

DEMANDS 1. A leading-edge, high-lift movable flap (16) for an aircraft wing comprising a free wingtip (108"), the flap being intended to be mounted on a fixed part (8) of the wing, and having two flap ends (16a, 16b) opposite each other in a span direction (17) of the flap, the flap extending, in the span direction (17) from one to the other of its two opposite ends (16a, 16b), over a total flap length (Lv), the flap defining a leading-edge area (10b) from which extend an lower surface (24) and an upper surface (26) spaced apart in a direction of the height (21) of this flap, the flap having, along the span direction (17), a central flap section (100) on either side of which are two opposing shutter end sections (102a, 102b), comprising respectively the two opposing shutter ends (16a, 16b),characterized in that, in a nominal state of the movable flap, corresponding to a state not assembled on the fixed part (8) of the wing and unconstrained, the central section of the flap (100) presents, going in the span direction (17), a general shape concave upwards.

2. Movable flap according to claim 1, characterized in that it comprises a spar (60) having a web (62), the flap spar web having two spar web ends (62a, 62b) opposite each other in the span direction (17), and the web having, along the span direction (17), a central web section (200) on either side of which are two web end sections (202a, 202b), respectively comprising the two opposite web ends (62a, 62b), and in that in the nominal state of the flap, the central web section (62) has, in the span direction (17), a generally upward concave shape.

3. Movable flap according to claim 1 or 2, characterized in that the central section of the flap (100), generally concave upwards in the nominal state of the movable flap, extends in the span direction (17) along a central section length (Le), so that the ratio Lc / Lv is greater than or equal to 0.

5.

4. Movable flap according to any one of the preceding claims, characterized in that in the nominal state of the movable flap, each of the two opposite flap end sections (102a, 102b) also has, going in the span direction (17), a general upward concave shape, so that the whole movable flap has, going from one to the other of its two opposite ends (16a, 16b), a general upward concave shape.

5. Movable flap according to any one of claims 1 to 3, characterized in that in the nominal state of the movable flap, each of the two opposite end sections of the flap (102a, 102b) has, going in the span direction (17), a generally upward convex shape.

6. Movable flap according to any one of the preceding claims, characterized in that the general upward concave shape of the central flap section (100) has, on at least a portion (104) of the central flap section extending in the span direction (17), a concavity of curvature greater than or equal to 4.5 x 10 -6 mm 1 , and in that this part (104) extends in the span direction (17) preferably over a length of part of maximum concavity (Lcm), so that the ratio Lcm / Lc is greater than or equal to 0.

1.

7. Movable flap according to any one of the preceding claims, characterized in that it comprises several guide and / or drive rails (42).

8. Movable flap according to any one of the preceding claims, characterized in that it is made in whole or in part using metallic elements.

9. Aircraft wing (4) with free wingtip (108''), the wing comprising a fixed part (8) in front of which is mounted a movable high-lift leading-edge flap (16) according to any one of the preceding claims, said flap being movable relative to the fixed part (8) of the wing, between a retracted position and a deployed position, the movable flap extending further forward in the deployed position than in the retracted position, relative to the fixed part (8) of the wing.

10. Wing according to claim 9, characterized in that the fixed part (8) of the wing comprises means (74) for righting the movable flap, and in that in a rest state of the wing, occupied when the wing is fixed to the aircraft with the latter on the ground and stationary, and in the retracted position of the movable flap (16), said straightening means (74) apply an elastic deformation force on the central section of the movable flap (100), so that it presents a general concave shape of lower curvature than that observed in its nominal state.

11. Wing according to claim 10, characterized in that the righting means (74) cooperate with a support member (76) integral with a spar (60) of the movable flap (16).

12. Wing according to any one of claims 9 to 11, characterized in that under nominal flight conditions of the wing, the fixed part (8) of the wing is deformed by aerodynamic forces applied to it, giving it a general upward concave shape.

13. Wing according to claim 12, characterized in that the fixed part (8) of the wing comprises a front spar (32) including a planar web (33), and in that under nominal flight conditions of the wing, the web (33) is deformed by aerodynamic forces which apply to the fixed part (8) of the wing, giving this web a general shape concave upwards, with an upper edge (80) concave upwards, and a lower edge (82) convex downwards.

14. Wing according to claim 13 combined with claim 10, characterized in that under nominal flight conditions of the wing with the movable flap (16) in its retracted position, the elastic deformation force applied on the movable flap by the righting means (74) is zero, or strictly less than that applied when the wing is in its rest state with the movable flap in the retracted position.

15. Aircraft (1) comprising at least one wing (4) according to any one of claims 9 to 14, and preferably one wing (4) on each side of a fuselage (106) of the aircraft, without loop connection between these two wings (4).

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