Propulsion system for an aircraft with improved pylon fairing

Abstract

The invention provides an aircraft and a propulsion system (10) for an aircraft, of the type comprising: - a turbomachine (14) having a longitudinal axis (A) defining a longitudinal direction; - a turbomachine fairing (18); - a mounting pylon (24) for the turbomachine (14) on a structure (12) of the aircraft, the pylon (24) having a radial mounting orientation with respect to the longitudinal axis (A); - and a fairing (38) for the pylon, of the type in which the fairing (38) for the pylon comprises a front fairing (39) having a front fairing wall (40) which covers a front face of the pylon (24), characterized in that the front fairing (39) is rigidly fixed with respect to the turbomachine fairing (18) and is fixed to the pylon (24) with at least one degree of freedom in translation along the longitudinal direction relative to the pylon (24) Figure of the abstract: FIG. 3.

Description

Title of the invention: Propulsion system for an aircraft with improved pylon fairing. Technical field

[0001] The invention relates to the field of propulsion assemblies for an aircraft, in particular the field of propulsion assemblies comprising a turbomachine and a mounting pylon for mounting the turbomachine on a structure of the aircraft, the propulsion assembly comprising a front fairing for the pylon. Technical background

[0002] The invention relates in particular to propulsion systems for commercial passenger aircraft. In this type of aircraft, propulsion is most often provided by one or more turbomachines, i.e., for example, turbojet or turboprop engines, which generate thrust to provide the necessary lift for the aircraft to fly. This refers to aircraft in which at least one turbomachine is connected to an aircraft structure by a mounting pylon. The aircraft structure to which the turbomachine is attached is, for example, either a wing or the fuselage, typically a rear portion of the fuselage, near or on a tail section of the fuselage.

[0003] For example, the turbomachine is mounted under a wing, or connected to the fuselage, by a pylon. In an under-wing installation, the pylon is typically arranged so that the turbomachine is at least partially offset forward relative to the wing's leading edge. The pylon's primary role is therefore to support the turbomachine on the aircraft structure and to transmit the propulsion force generated by the turbomachine to the aircraft structure. Naturally, the pylon is equipped with a fairing, in particular a forward fairing that covers one of the pylon's forward faces. This fairing is crucial for proper aerodynamic integration of the pylon with the aircraft's overall aerodynamics.

[0004] As is known, the turbomachine can be integrated into a nacelle, said nacelle including, in particular, a substantially cylindrical fairing for the turbomachine. In the case of turbomachines of the open-fan type (sometimes referred to in English as "propfan" or "open rotor"), the turbomachine has a fairing around certain parts of the turbomachine.

[0005] For perfect aerodynamic integration, the pylon fairing, and in particular its front fairing, and the turbomachine fairing must connect geometrically as best as possible.

[0006] However, it is also known that, although the connection between the turbomachine and the aircraft structure, via the pylon, is inherently rigid, the size of the components—namely the turbomachine, its fairing, the pylon and its fairing—and even more so the forces generated by the turbomachine's thrust, result in relative displacements between the components during normal aircraft operation. These relative displacements are due to unavoidable elastic structural deformations. Relative displacements can also result from differential thermal expansion, particularly due to differences in materials, geometries, etc., and / or exposure to different temperatures for different components and / or different parts of these components.During normal aircraft operation, such relative displacements can exceed ten millimeters between the turbomachine and the structure to which it is attached by the pylon. These deformations and relative displacements must be taken into account in the interface zones between the different components, and in particular in the connection zone between the pylon fairing, especially the forward fairing, and the turbomachine fairing.

[0007] For good aerodynamic performance, the geometry of such connection zones must be perfectly controlled, by adopting optimized geometries defined during the design phase. However, these fairing connection zones are necessarily affected by the relative displacement of the components, particularly the relative displacement between the turbomachine on the one hand and the pylon on the other. To account for these relative displacements, it is necessary to provide either sufficient clearances or geometries compatible with the relative displacements, with the consequence in both cases of a geometry that is not optimized from an aerodynamic point of view for these connection zones.

[0008] The invention therefore aims to propose a new design for a propulsion system that ensures optimal aerodynamic integration of the propulsion system under all normal aircraft operating conditions. Description of the invention

[0009] To this end, a propulsion system for an aircraft is described below, of the type comprising: - a turbomachine having a longitudinal axis; - a turbomachine fairing; - a pylon for attaching the turbomachine to a structure of the aircraft, the pylon having a radial attachment orientation relative to the longitudinal axis; - and a fairing for the pylon.

[0010] In such a propulsion assembly, the fairing for the pylon includes a front fairing having a front fairing wall which covers a front face of the pylon.

[0011] In such a propulsion assembly, the front fairing is rigidly fixed relative to the turbomachine fairing and is fixed to the pylon with at least one degree of freedom in translation along the longitudinal direction relative to the pylon.

[0012] In certain embodiments, the front fairing is attached to the pylon by a mechanical linkage with moving parts. Such a linkage with moving parts allows for good control of relative movement by limiting or controlling unwanted movements, particularly in directions perpendicular to the longitudinal direction. In some variations of these embodiments, the front fairing is attached to the pylon by a slide having a sliding direction with a longitudinal component, which makes it possible to limit or even eliminate any unwanted movements in directions other than the longitudinal direction. In other variations of these embodiments, the front fairing is attached to the pylon by an articulated quadrilateral mechanism comprising articulation axes perpendicular to the longitudinal direction. Such a linkage allows for good control of the forces in the connection.In some examples of such variations, the articulation axes of the articulated quadrilateral mechanism are perpendicular to the longitudinal direction and to the radial attachment orientation in order to limit or even cancel any parasitic movements along the transverse direction.

[0013] In some embodiments, elastic return means return the front fairing to a rest position relative to the pylon, to control a preferred relative position of the front fairing relative to the pylon and to the elements which are rigidly linked to the pylon.

[0014] In some embodiments, the front fairing is fixed to the pylon by an elastic deformable connection, for example in order to limit the cost of production.

[0015] In some embodiments, the turbomachine includes a housing, and the front fairing is rigidly fixed relative to the housing of the turbomachine, so as to ensure precise relative positioning between the two.

[0016] In certain embodiments, the front fairing has a connection area with the turbomachinery fairing. In some of these embodiments, the front fairing has side walls on each side of the front fairing wall that extend parallel to the longitudinal direction and the radial attachment orientation, and the connection area of ​​the front fairing with the turbomachinery fairing has a lateral connection portion between a side wall of the front fairing and the turbomachinery fairing. In such a configuration, the fact that the front fairing is rigidly fixed to the turbomachinery fairing allows the lateral portions of the connection area to proximal connection of more complex shapes, which are not necessarily purely longitudinal, and which can for example follow a curve which includes a boss, without creating interference during the inevitable relative movements between the turbomachine and the aircraft structure.

[0017] Also described is an aircraft comprising at least one propulsion assembly having any of the preceding characteristics. Brief description of the drawings

[0018] [Fig-1]: [Fig.1] is a schematic view of an example of the implementation of a propulsion assembly, including a turbomachine of the turbojet type, under an aircraft wing.

[0019] [Fig.2]: [Fig.2] is a schematic view of another example of the implementation of a propulsion assembly, comprising a turbomachine of the turbojet type with an unfaired fan, under an aircraft wing.

[0020] [Fig.3]: The [Fig.3] is a schematic side-section view of an example of the installation of a propulsion assembly under an aircraft wing.

[0021] [Fig.4]: [Fig.4] is a partial schematic sectional view along line IV-IV of the [Fig.3].

[0022] [Fig.5]: The [Fig.5] is a schematic side-section view of another example of the installation of a propulsion assembly under an aircraft wing.

[0023] [Fig.6] : The [Fig.6] is a partial schematic sectional view along line BB of the [Fig.5]. Detailed description

[0024] Figures 1 and 2 illustrate two examples of the installation of a propulsion unit 10 for an aircraft, in which the propulsion unit 10 is mounted under a wing 12 of an aircraft. However, the invention can be implemented in other configurations in which the propulsion unit is mounted on other structural elements of an aircraft, for example on an aircraft fuselage, particularly in a rear section of the fuselage, or on a tail section of the fuselage.

[0025] The propulsion assembly 10 includes a turbomachine 14, for example a turbojet or a turboprop.

[0026] In the example of [Fig. 1], the turbomachine 14 is a turbojet engine, for example a turbofan engine with a fan, integrated into a nacelle 16. The nacelle 16 has an outer fairing 18 that rotates substantially about a longitudinal axis A corresponding to the longitudinal axis of rotation of the rotating elements of the turbojet engine, in particular the turbines and compressors of the turbojet engine 14. The longitudinal axis A defines a longitudinal direction. In such a case, the The outer fairing 18 of the nacelle 16 forms a complete 360° fairing around the longitudinal axis for the turbomachine, with a wall of revolution extending 360° around the longitudinal axis A. The outer fairing 18 has a front air inlet and a rear exhaust outlet. In the example of [Fig. 1], typical of a turbofan engine, the entire turbomachine 14 is contained within the outer fairing 18 of the nacelle 16. The outer fairing 18, which here belongs to the nacelle 16, therefore forms a turbomachine fairing.

[0027] In the example of [Fig.2], the turbomachine 14 is a turbojet with an unfaired fan 20 (sometimes referred to in English as a "propfan" or "open rotor"). In the example, the fan 20 is located at the front longitudinal end of the turbomachine and therefore has large-diameter rotating blades. In the illustrated example, the turbomachine also includes, longitudinally behind the fan 20, fixed blades 22 distributed at 360° around the longitudinal axis A. The fixed blades 22, whose role is primarily to straighten the secondary airflow stirred by the fan 20, do not rotate around the longitudinal axis A, but can each be orientable around their axis substantially radial with respect to the longitudinal axis A. In this example, the propulsion assembly 10 has an external fairing 18 substantially of revolution around a longitudinal axis A.For example, the outer fairing 18 is designed to house, within its enclosed volume, the main part of the turbomachine, including the compressor(s), combustion chamber(s), and turbine(s) of the turbomachine 14. The forward longitudinal end of the outer fairing 18 is, for instance, located longitudinally just behind the fan 20, and the outer fairing 18 extends rearward to the nozzle section of the turbomachine. In this example, the fixed blades 22 are anchored to the forward longitudinal end of the outer fairing 18. The outer fairing 18 thus also forms a turbomachine fairing. It should be noted that the outer fairing 18, in this case of a turbojet with an unfaired fan 20, has a maximum external diameter that is smaller than the diameter of the fan 20.

[0028] Figures 3 and 4 on the one hand, and Figures 5 and 6 on the other hand, schematically illustrate two examples of the installation of a propulsion unit 10 under an aircraft wing 12, schematically showing certain internal elements of the propulsion unit 10.

[0029] In the examples, the propulsion unit 10 includes a mounting pylon 24 for attaching the turbomachine 14 to the aircraft structure, in this case, the wing of an airplane. The pylon 24 has, relative to the turbomachine 14, a principal orientation, called the radial mounting orientation, along a radial direction with respect to the longitudinal axis A of the turbomachine 14. In the example of an installation of the unit propulsion 10 under an aircraft wing, this radial attachment orientation is arranged in a plane substantially vertical with respect to gravity, for example a vertical plane or a plane perpendicular to the curvature of the wing 12. The pylon 24 has an extension, in the longitudinal plane containing this radial attachment orientation, between a distal portion 26 of the pylon 24, here an upper portion, which is attached at the level of an underside 28 of the wing, and a proximal portion 30 of the pylon 24, here an underside, on which the turbomachine 14 is attached.In other configurations, particularly for cases of the installation of a propulsion unit 10 on a tail segment of an aircraft fuselage, especially in the case of an aircraft comprising two propulsion units 10 arranged on either side of the tail, diametrically opposite each other, the radial attachment orientation of the pylon could correspond to a substantially horizontal direction.

[0030] Such an arrangement of a propulsion unit 10 with a pylon 24 is known in the prior art and allows for a propulsion unit offset from the structure 12 to which the propulsion unit 10 is attached. The attachment means 32 of the pylon 24 to the aircraft structure 12 and the attachment means 34 of the turbomachine 14 to the pylon 24 can be of any type known to those skilled in the art. They are not illustrated in Figures 1 and 2, but are shown schematically in Figures 3 and 5, and are not described further in this text. The attachment means 32 of the pylon 24 cooperate with complementary means of the internal structure of the aircraft structure 12, in this case, for example, ribs or spars of the wing 12.The attachment means 34 of the turbomachine 14 on the pylon 24 cooperate with complementary attachment means of the turbomachine, for example fixed on a metal casing 15 of the turbomachine 14 which surrounds the rotating elements of the turbomachine.

[0031] The geometry of the pylon 24 varies in a known manner depending on the exact desired positioning of the turbomachine 14 relative to the structure on which it is attached. However, the geometry of a pylon is generally elongated along the longitudinal direction of the turbomachine, which is substantially parallel to the direction of travel of the aircraft. Conversely, the geometry of the pylon 24 generally has a thickness dimension, in a transverse direction perpendicular to the radial attachment orientation and the longitudinal direction, which is relatively small compared to the dimension of the pylon 24 along the longitudinal direction.In both illustrated examples, pylon 24 has a geometry which determines, in a plane containing the longitudinal direction and the radial attachment orientation, a principal axis A24 of pylon 24 which extends from the proximal portion 30 of pylon 24, longitudinally to the center of the attachment means 34 of the turbomachine 14 on pylon 24, to the distal portion 26 of pylon 24. longitudinally at the center of the attachment means 32 of the pylon 24 on the structure 12. In the illustrated examples, in which a position offset forward of a leading edge of the wing 12 is sought for the turbomachine 14, the main axis A24 of the pylon 24 is oriented in a plane containing the longitudinal direction and the radial attachment orientation, therefore here a longitudinal and vertical plane, forming, in this plane, a pylon angle with the orientation of the longitudinal axis A of the turbomachine 14. In the example of [Fig.1], in which the turbomachine 14 is close to the structure 12 of the aircraft on which it is attached, and in which a forward longitudinal offset of the turbomachine 14 relative to its anchoring point on the structure is sought, the pylon angle is relatively closed, for example on the order of 20 to 40°. In the example of [Fig.2], the pylon angle is, for example, in the order of 30 to 60°.

[0032] As is known and schematically represented in Figures 3 and 5, and without going into detail, the pylon 24 comprises a primary structure 36 which absorbs the majority of the mechanical stresses connecting the turbomachine 14 to the aircraft structure 12, to which the propulsion unit 10 is attached. As is known, the primary structure 36 may include box-type elements and / or tubular or lattice-type elements. In the examples, the attachment means 32 of the pylon 24 to the structure 12 are arranged at a distal end of the primary structure 36, and the attachment means 34 of the turbomachine 14 to the pylon 24 are arranged at a proximal end of the primary structure 36 of the pylon 24.

[0033] As is known, the propulsion assembly includes a pylon fairing 38 for the pylon 24. The pylon fairing 38 includes at least one front fairing having a front fairing wall 40 facing the longitudinal direction of travel of the aircraft. The front fairing wall 40 covers a front face of the pylon 24. The front fairing wall 40 has a general orientation substantially parallel to the principal extension axis A24 of the pylon 24 and parallel to the transverse thickness direction of the pylon 24. The front fairing wall 40 forms, aerodynamically, a leading edge for the pylon fairing 38.

[0034] The fairing of pylon 38 can be made in several parts.

[0035] The pylon fairing 38 generally comprises side walls 42, which extend on each side from the lateral edges of the front fairing wall 40. These lateral walls 42 therefore have a general orientation substantially parallel to the main axis of extension A24 of the pylon 24 and parallel to the longitudinal direction. Naturally, to improve aerodynamics, the front fairing wall 40 is preferably curved rearward at its lateral edges, so as to connect seamlessly with the lateral walls 42.

[0036] In the examples illustrated in Figures 4 and 6, the front fairing wall 40 and the side walls 42 are joined without any geometric discontinuity, so as to present, in profile in a longitudinal and transverse plane, an ogive shape. These side walls 42 may be part of the front fairing 39, or part of another part of the pylon fairing 38. In the example, the side walls 42 are considered to be part of the front fairing 39 or integral with the front fairing 39. Consequently, the side walls 42 are considered to have a fixed position relative to the front fairing wall 40, including under operating conditions in which the propulsion assembly undergoes deformation.

[0037] The pylon fairing 38, in particular the front fairing 39, may include an internal structure, possibly made in several parts, which supports the front fairing wall 40, and possibly the side walls 42.

[0038] Although not shown in the figures, the pylon fairing 38 has a rear edge which forms a trailing edge for the aerodynamic flow along the pylon 24.

[0039] At the distal end 26 of the pylon 24, the pylon fairing 38 has a distal connection zone 44 with the structure 12 to which the pylon 24 is attached, in this case a connection zone 44 with the underside 28 of the wing 12. Similarly, the pylon fairing 38 has, at the proximal end 30 of the pylon 24, a proximal connection zone 46 with the fairing 18 of the turbomachine 14. Each connection zone 44, 46 has a front portion corresponding to the front fairing wall 40 and lateral portions corresponding to the side walls 42 of the fairing 38 of the pylon 24. Thus, in the examples, the proximal connection zone 46 of the front fairing 39 with the fairing 18 of the turbomachine presents a lateral connecting portion between a side wall 42 of the front fairing 39 and the turbomachine fairing 18.

[0040] In the examples illustrated in Figures 3 and 5, the lateral portions of the proximal connection zone 46 follow a curve that includes a boss 47. In the example, this boss deviates significantly from a purely longitudinal orientation. It should be noted that, in the proximal connection zone 46, the turbomachine fairing 18 extends in the transverse direction, which prevents any transverse clearance of the side wall 42 of the front fairing 39 from the turbomachine fairing 18. This boss is therefore a difficult area to manage in terms of the connection between the front fairing 39 of the pylon fairing 38 and the turbomachine fairing 18.

[0041] Advantageously, at least a part of the pylon fairing 38, for example the front fairing 39, and in any case at least the front fairing wall 40, is rigidly fixed relative to the turbomachine fairing 18 14 and is fixed to the pylon 24, for example on the primary structure 36 of pylon 24, with at least one degree of freedom in translation along the longitudinal direction relative to pylon 24.

[0042] In this assumption, the fairing 18 of the turbomachine 14 is considered to be rigidly connected to the turbomachine 14, for example by being rigidly fixed relative to the housing 15 of the turbomachine 14, by means known to those skilled in the art, which are not described further. In such an assumption, any possible displacement of the fairing 18 of the turbomachine 14 relative to the turbomachine 14, and in particular relative to its housing 15, is considered negligible.

[0043] In the illustrated examples, at least part of the pylon fairing 38, in particular the front fairing 39, and in any case at least the front fairing wall 40, is rigidly fixed relative to the turbomachine 14, for example relative to its casing 15. Preferably, any possible displacement of the front fairing 39 of the pylon fairing 38, in any case of its front fairing wall 40, relative to the casing 15 of the turbomachine 14, will be negligible or can be considered negligible relative to any possible displacement of the pylon fairing 38, in any case of its front fairing wall 40, relative in particular to the primary structure 36 of the pylon 24.

[0044] Thus, in the event of relative displacement between the turbomachine 14 and the aircraft structure 12, for example the wing, on which the turbomachine is attached, the front fairing 39 will move with the turbomachine 14. In a known manner, such a relative displacement of the turbomachine 14 with respect to the aircraft structure on which it is attached will have a majority component along the longitudinal direction parallel to the longitudinal axis A of the turbomachine 14.

[0045] By providing that the front fairing 39 carrying the front fairing wall 40 is fixed to the pylon 24, for example to the primary structure 36 of the pylon 24, with at least one degree of freedom in translation along the longitudinal direction, this front fairing wall 40 and the side walls 42 are thus able to follow the principal movements of the turbomachine 14, and therefore to follow the principal movements of the fairing 18 of the turbomachine 14. Thus, during aircraft operation, there will be little or no relative displacement between, on the one hand, the front fairing wall 40 and possibly the side walls 42, and on the other hand, the fairing 18 of the turbomachine 14. In this way, it is possible to maintain an optimal geometry of the proximal connection zone 46 between the pylon fairing 38, at least at the level of its fairing wall. before 40, and the fairing 18 of the turbomachine.This proximal connection zone 46 can therefore be achieved with minimal clearances, and with surface geometries that do not require allowing relative displacements.

[0046] Preferably, the front fairing 39 is fixed to the pylon 24 by a mechanical linkage with moving parts. Such a mechanical linkage with moving parts allows, through the movement of the moving parts of the mechanism forming the mechanical linkage, relative movement between the front fairing 39 and the pylon 24. In a mechanical linkage with moving parts, this relative movement is permitted without deformation of the parts of the mechanism forming the mechanical linkage.

[0047] In the example of Figures 3 and 4, the front fairing wall 40 is fixed to the pylon 24, in this case to the primary structure 36 of the pylon 24, by means of a articulated quadrilateral mechanism 48 comprising articulation axes A50.1, A50.2, A52.1, A52.2 which are parallel to each other and perpendicular to the longitudinal direction. In the example of Figures 3 and 4, the articulated quadrilateral mechanism 48 is a quadrilateral mechanism whose articulation axes are perpendicular to the longitudinal direction and to the radial attachment orientation.

[0048] In the example of Figures 3 and 4, the articulated quadrilateral mechanism 48 comprises two connecting rods 50, 52. Each connecting rod 50, 52 is articulated, has a first end, on the pylon 24, more particularly on the primary structure 36 of the pylon 24, around a first articulation axis A50.1, A52.1 respective for each connecting rod 50, 52. The first articulation axis A50.1 of one of the two connecting rods and the first articulation axis A52.1 of the other of the two connecting rods are not aligned with each other. Each connecting rod 50 52 is also articulated, at a second end, on the front fairing 39 of the pylon fairing 38, more particularly on the front fairing wall 40, and in particular on an internal face of the front fairing wall 40 turned towards the primary structure 36 of the pylon 24, around a second articulation axis A50.2, A52.2. The second articulation axis A50.2 of one of the two connecting rods and the second articulation axis A52.The two connecting rods 50 and 52 are not aligned. The articulation axes form the vertices of a deformable quadrilateral, two opposite sides of which are formed respectively by one of the two connecting rods 50 and 52, and the other two opposite sides of which are formed respectively by a portion of the front fairing of the pylon fairing 38 and by a portion of the primary structure 36 of the pylon 24. By pivoting the connecting rods 50 and 52, the articulated quadrilateral mechanism 48 allows a relative displacement of the pylon fairing 38 with respect to the primary structure 36 of the pylon 24. The relative arrangement of the connecting rods 50 and 52 and their articulation axes A50.1, A50.2, A52.1, and A52.2 is such that this relative displacement has a predominant component along the longitudinal direction.In the example, the quadrilateral formed by the articulation axes is a parallelogram, thus preserving the relative orientation between the pylon fairing 38, more particularly the front fairing wall 40, and the primary structure 36 of the pylon 24. In this case, the relative movement of the front fairing 39 with respect to the . Pylon 24, which is made possible by the mechanical link with moving parts, is a circular translation.

[0049] In the example, the two connecting rods 50, 52 are offset from each other along the direction of the main axis A24 of the pylon 24, with 50 being on the distal end 26 side of the pylon 24 and 52 on the proximal end 30 side of the pylon. In a nominal position, the connecting rods are arranged in an orientation perpendicular to the longitudinal direction, such that any initial movement from this position has a majority component along the longitudinal direction. However, it could be envisaged that, in a nominal position, the connecting rods are arranged in an orientation forming an angle with respect to the longitudinal direction, for example, between 20 and 70 degrees, or between 30 and 60 degrees, such that any initial movement from this position has a component along the longitudinal direction and a component along the radial attachment orientation.

[0050] In the example shown in Figures 5 and 6, the front fairing 39 is fixed to the pylon 24 by a mechanical linkage with moving parts forming a slide 54 having a slide direction A54 with a longitudinal component. In the example illustrated in Figures 5 and 6, the front fairing 39 is fixed to the pylon 24 by several slides 54, in this case four slides 54, each having a slide direction A54 parallel to each other. In the example of [Fig. 5], it is noted that the slides 54 are arranged between the side walls 42, which are integral with or part of the front fairing 39, and the primary structure 36 of the pylon 24. In this example, the relative movement between the front fairing 39 and the primary structure 36 of the pylon 24, which is permitted by the slides 54, is a translation. In this example, this translation is purely along the longitudinal direction parallel to the longitudinal axis A of the turbomachine 14.However, the direction of translation could present an angle with respect to this longitudinal axis A. With a mechanical link with moving parts forming a slide 54, the front fairing 39 is fixed on the pylon 24 with a single degree of freedom, in translation along the direction of the slide, which therefore has a majority component along the longitudinal direction.

[0051] In all cases, the front fairing 39 of the pylon fairing 38, and more particularly the front fairing wall 40, can move relative to the pylon 24, more particularly relative to the primary structure 36 of the pylon 24, between a distant position and a close position. Preferably, the distance between these two positions, along the longitudinal direction, is between 5 millimeters and 50 millimeters, for example between 10 millimeters and 25 millimeters.

[0052] Elastic return means 55 can be provided to return the front fairing 39 to a rest position relative to the pylon, this rest position being be the offset position mentioned above. The elastic return means 55 may include one or more helical springs, and / or one or more spiral springs, and / or one or more elastic pads, and / or one or more elastic blades, etc. arranged for example between the pylon fairing 38 and the primary structure 36 of the pylon 24.

[0053] As an alternative to, or in addition to, the mechanical connection with moving parts, the front fairing 39 could be fixed to the pylon by a deformable connection, for example, an elastic one. Such an elastic deformable connection may include one or more helical springs, and / or one or more spiral springs, and / or one or more elastic pads, and / or one or more elastic blades, etc., arranged, for example, between the front fairing 39 and the primary structure 36 of the pylon 24.

[0054] A propulsion assembly 10 having a front fairing 39 fixed to the pylon 24 can be designed, on the one hand, by a mechanical connection with moving parts, for example by a connecting rod similar to one of the two connecting rods of the mechanism 48 described above, and on the other hand by an elastic deformable connection. In other words, starting for example from the example in [Fig. 3], a connecting rod can be replaced by an elastic deformable connection,

[0055] In the example, the front fairing 39 of the pylon fairing 38 extends substantially over the entire length of the pylon 24 between its proximal end 30 and its distal end 26. In other words, the front fairing 39 extends to the aircraft structure 12 to which the propulsion assembly is attached, i.e., in the example, the underside 28 of the wing 12. That is to say, the front fairing 39 extends to the distal connection area 44. In such a case, it is necessary to manage the relative displacement between the front fairing 39 and the aircraft structure 12 to which the propulsion assembly is attached, in the distal connection area 44. In the example, a connecting joint 56 is provided between the distal end of the front fairing 39 and the structure 12. This joint connection 56 can be a polymer material joint capable of absorbing relative displacements between the distal end of the front fairing 39 and the structure 12.In the example, the connecting joint 56 has a Y-shaped profile with a proximal lip for fixing to the distal end of the front fairing 39 and two distal lips bearing on the structure 12. In such a joint, the deformation of the profile allows the relative displacements between the distal end of the front fairing 39 and the structure 12 to be absorbed.

[0056] However, it can be foreseen that the front fairing 39, which is rigidly fixed relative to the turbomachine fairing 18 and which is fixed to the pylon 24 with at least one degree of freedom in translation along the longitudinal direction relative to the pylon 24, extends only over a proximal portion of the pylon 24, i.e.- to say that only a portion going from its proximal end 30 to an intermediate portion between the proximal end 30 and the distal end 26. We can then provide a connecting joint between the distal end of the front fairing 39 and the intermediate portion of the pylon.

[0057] Preferably, the connection between the front fairing 39 and the pylon 24, in particular with the primary support 36 of the pylon 24, is rigid in the transverse direction, perpendicular to the longitudinal direction and to the radial orientation of attachment, in order to limit relative displacements in the transverse direction.

Claims

Demands

1. Propulsion assembly (10) for an aircraft, of the type comprising: - a turbomachine (14) having a longitudinal axis (A) defining a longitudinal direction; - a turbomachine fairing (18); - a pylon (24) for attaching the turbomachine (14) to a structure (12) of the aircraft, the pylon (24) having a radial attachment orientation with respect to the longitudinal axis (A); - and a fairing (38) for the pylon, of the type in which the fairing (38) for the pylon comprises a front fairing (39) having a front fairing wall (40) which covers a front face of the pylon (24), characterized in that the front fairing (39) is rigidly fixed relative to the turbomachine fairing (18) and is fixed to the pylon (24) with at least one degree of freedom in translation along the longitudinal direction relative to the pylon (24).

2. Propulsion assembly for an aircraft according to claim 1, characterized in that the front fairing (39) is fixed to the pylon (24) by a mechanical linkage with moving parts (48, 54).

3. Propulsion assembly for an aircraft according to claim 2, characterized in that the front fairing (39) is fixed to the pylon (24) by a slide (54) having a slide direction (A54) with a longitudinal component.

4. Propulsion assembly for an aircraft according to claim 2, characterized in that the front fairing (39) is fixed to the pylon (24) by an articulated quadrilateral mechanism (48) comprising articulation axes (A50.1, A50.2, A52.1, A52.2) perpendicular to the direction of the longitudinal axis.

5. Propulsion assembly for an aircraft according to claim 4, characterized in that the articulation axes of the articulated quadrilateral mechanism (48) are perpendicular to the longitudinal direction and to the radial latching orientation.

6. Propulsion assembly for an aircraft according to any one of claims 2 to 5, characterized in that elastic return means (55) return the front fairing (39) to a rest position relative to the pylon (24).

7. Propulsion assembly for an aircraft according to any one of the preceding claims, characterized in that the front fairing (39) is fixed to the pylon by an elastic deformable link.

8. Propulsion assembly for an aircraft according to any one of the preceding claims, characterized in that the turbomachine (14) comprises a casing (15), and in that the front fairing (39) is rigidly fixed relative to the casing (15) of the turbomachine (14).

9. Propulsion assembly for an aircraft according to any one of the preceding claims, characterized in that the front fairing (39) has side walls (42), on each side of the front fairing wall (40), which extend parallel to the longitudinal direction and the radial attachment orientation, in that the front fairing (39) has a connection zone (46) with the turbomachine fairing (18), and in that the connection zone (46) of the front fairing with the turbomachine fairing (18) has a lateral connection portion between a side wall (42) of the front fairing (39) and the turbomachine fairing (18).

10. Aircraft comprising at least one propulsion unit (10) according to any one of the preceding claims.

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