METHOD FOR ASSEMBLING PARTS FOR AN AIRCRAFT PROPULSION SYSTEM
The proposed assembly process for aircraft propulsion sets addresses the challenge of aerodynamic walking by using a sacrificial extra thickness on the second part's aerodynamic surface, which is machined to align with the first part's surface, resulting in improved aerodynamic continuity and reduced assembly tolerances.
Patent Information
- Application Number
- FR2022005591
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-06-10
- Publication Date
- 2025-05-02
- Estimated Expiration
- 2042-06-10
AI Technical Summary
Current assembly methods for aircraft propulsion sets face challenges in achieving aerodynamic continuity due to aerodynamic walking between assembled parts, which is difficult to minimize with existing techniques.
A process involving the assembly of a first part with a finite aerodynamic surface and a second part with a composite material aerodynamic surface, featuring a sacrificial extra thickness at the edge, which is machined to align with the first part's surface, thereby minimizing aerodynamic walking.
This process significantly reduces aerodynamic walking, ensuring improved aerodynamic continuity and facilitating better compliance with manufacturing and assembly tolerances.
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Abstract
Description
Title of the invention: METHOD FOR PRODUCING AN ASSEMBLY OF PARTS FOR AN AIRCRAFT PROPULSION UNIT Technical field of the invention
[0001] The present invention relates to a method for producing an assembly of parts for a propulsion unit and the associated assembly of parts. Technological background
[0002] A classic example of a propulsion unit 1 for an aircraft, well known in the art, is shown in [Fig.l]. This propulsion unit 1 has a longitudinal axis X and comprises an engine 2, for example a turbomachine, housed inside a nacelle 3 which extends around the axis X. The nacelle 3 has an air inlet 4 through which a total air flow F1 enters which then separates into a primary air flow inside the engine 2 and into a secondary air flow F2, F2' around the engine 2. In [Fig.l], the direction of air flow is symbolized by arrows. Also, it will be understood that in the following, the terms "upstream" and "downstream" are defined in relation to this air flow. In particular, the air flow flows from upstream to downstream of the propulsion unit in a space defining an aerodynamic vein 5a, 5b.The nacelle 3 can also integrate thrust reversers 6, 6' which, in use, allow the secondary airflow F2, F2' to be redirected towards the outside of the nacelle 3. In the example of [Fig.l], the thrust reversers 6, 6' are door reversers but can also be obstacle or grid reversers. In this example, the thrust reverser 6' is open and closes the aerodynamic vein 5b, thus directing the secondary airflow F2' towards the outside of the nacelle 3. Unlike the thrust reverser 6 which is closed and remains in the continuity of the aerodynamic vein 5a.
[0003] Thus, different elements make up a propulsion unit in which the optimization of the air flow is essential in order to ensure its proper functioning. For this, the space in which the air flow flows inside the propulsion unit, that is to say the aerodynamic vein, must have walls whose profile is as aerodynamic as possible, in other words with the least discontinuities.
[0004] Currently, the aerodynamic vein cannot be defined by a single part. It is therefore the result of an assembly of several parts, fixed to each other.
[0005] [Fig.2] represents an assembly of these parts as generally produced. This assembly 10 comprises a first part 11 with a first aerodynamic surface 12 and a second part 13, adjacent to the first, with a second aerodynamic surface 14. In this example, the first part 11 and the second part 13 are each made in one piece and extend around the axis X. In addition, the second aerodynamic surface 14 comprises at least one edge 15a, 15b which must extend in the extension of the first aerodynamic surface 12 so as to ensure the continuity of the aerodynamic vein 5a, 5b. The first part 11 and the second part 13 are fixed together by at least one support 16, such as for example a fishplate.
[0006] When assembling these two parts 11, 13, to have aerodynamic continuity between the first and second aerodynamic surfaces 12, 14, that is to say that the second aerodynamic surface 14 is in the extension of the first aerodynamic surface 12, these must be aligned radially with respect to each other, in other words they are leveled. This leveling of the first and second aerodynamic surfaces 12, 14 of each of the parts 11, 13 is ensured by means of a shim 17 which is generally inserted between, for example, the first part 11 and the support 16.
[0007] However, since the first part 11 and the second part 13 are each made of a single piece, it is difficult to ensure continuity between the first and second aerodynamic surfaces 12, 14 over the entirety of the two parts 11, 13. In fact, a setting on one side (at a point located on a circumference centered on the X axis) causes an offset on the other (at a diametrically opposite point), and vice versa, as shown in [Fig.2] for example. Thus, in this example, if, on one side, the edge 15a of the second aerodynamic surface 14 extends in the extension of the first aerodynamic surface 12, on the other side, the edge 15b of the second aerodynamic surface 14 has a step S with the first aerodynamic surface of the first part 11. This step S, called aerodynamic step, harms the aerodynamic continuity of the aerodynamic vein 5b.
[0008] The example in [Fig.2] represents an extreme case in order to accentuate the reality of the aerodynamic step. In practice, we will seek to have an average setting of the parts, with the installation of point shims or with shims distributed around the axis in a predefined manner, which makes it possible to have an average aerodynamic step over the entire circumference of the interface between the parts.
[0009] However, the technical requirements require a very low maximum aerodynamic step which is very difficult to obtain with the assembly method as described above.
[0010] Also, an objective of the invention is to propose a method for producing an assembly of parts for an improved aircraft propulsion unit which does not have at least one of the aforementioned drawbacks.
[0011] Another objective of the invention is to propose a method whose implementation makes it easier to comply with manufacturing tolerances for parts for a propulsion unit, as well as assembly tolerances.
[0012] Another objective of the invention is to propose a method whose implementation makes it possible to reduce as much as possible the aerodynamic step between two parts so as to improve the aerodynamic continuity. Summary of the invention
[0013] A method is therefore proposed for producing an assembly of parts for an aircraft propulsion unit, this assembly comprising a first part made from a first material and comprising a first aerodynamic surface and a second part adjacent to the first part and made from a second material, this second material being composite, this second part comprising a second aerodynamic surface of which at least one edge must extend in the extension of the first aerodynamic surface, the method comprising the following steps: - producing the first part with a first finished aerodynamic surface, - producing the second part with a second aerodynamic surface which comprises, at the level of the at least one edge, a sacrificial excess thickness, - assembling the first and second parts,- machining the sacrificial excess thickness of the second part so that at least one edge of the second aerodynamic surface extends in the extension of the first aerodynamic surface.
[0014] Thus, thanks to the method according to the invention, the first and second parts are assembled together before the machining of the second part, and in particular its sacrificial surface located at the edge of the second aerodynamic surface of this second part. The machining of the sacrificial excess thickness is carried out locally so that the edge of the second part is in the extension of the aerodynamic surface of the first part. In other words, an alignment of the first and second aerodynamic surfaces of the first and second parts is ensured. In this way, the aerodynamic movement of the assembly is reduced to its minimum, which makes it possible to obtain aerodynamic continuity in the propulsion assembly. Furthermore, the portion of sacrificial excess thickness which is removed is variable depending on the locations where the machining is carried out because it depends on the arrangement of the first and second parts relative to each other.Thus, the sacrificial excess thickness can, in some places, be completely removed while in other places of the second part, part of the sacrificial excess thickness may remain.
[0015] The method according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: - the method, after the machining step, comprises the following step: applying a finishing coating to the second aerodynamic surface of the second part; - the first part is made of metal alloy or composite material; - the composite material of the second part comprises a stack of layers of fibers embedded in a polymer matrix; - the second part comprises layers of fibers which extend over the entire extent of the second part, and comprises additional layers of fibers at the at least one edge to define the sacrificial excess thickness; - the fiber layers comprise carbon fibers, and the additional fiber layers comprise carbon fibers or glass fibers; - the fiber layers have a different color than the additional fiber layers; - the fiber layers are separated from the additional fiber layers by a fiber layer or film of a different color from that of the fiber layers and the additional fiber layers; - the sacrificial excess thickness has a thickness of between 0.5 mm and 5.0 mm, advantageously between 1.5 mm and 5.0 mm and preferably between 1.5 mm and 2.5 mm; - the first and second parts and the first and second aerodynamic surfaces are annular and extend around the same axis, the parts being arranged next to each other along this axis, and the at least one edge being an annular edge of the second aerodynamic surface; - the first and second parts are fixed to the same support; - the support is annular; - in relation to the support, the second part comprises through holes for the passage of elements for fixing the second part to the support, said through holes being filled with a finishing coating so that the second aerodynamic surface extends in the extension of the first aerodynamic surface.
[0016] The invention also relates to an assembly of parts for implementing the method as described above, this assembly comprising a first part made from a first material and comprising a first aerodynamic surface and a second part adjacent to the first part and made from a second material, this second material being composite, this second part comprising a second aerodynamic surface of which at least one edge must extend into the pro along the first aerodynamic surface, the second aerodynamic surface of the second part comprising, at the level of said at least one edge, a sacrificial excess thickness.
[0017] The assembly, according to the invention, may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: - the first part is a nacelle air inlet lip and the second part is an internal nacelle air inlet duct; - the first part is an inner body and the second part is a thrust reverser cowl. Brief description of the figures
[0018] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which:
[0019] [Fig.l] represents a schematic view, in longitudinal section, of an example of an aircraft propulsion unit according to the prior art,
[0020] [Fig. 2] represents a schematic view of an assembly of parts for an aircraft propulsion unit according to the prior art,
[0021] [Fig.3] represents a schematic perspective view of an air intake of a nacelle of [Fig.l],
[0022] [Fig.4] represents a schematic sectional and partial view of [Fig.3] along the section axis AA,
[0023] [Fig.5] represents a schematic view of a detail of [Fig.4],
[0024] [Fig.6] represents a schematic perspective view of a thrust reverser of the nacelle of [Fig.l],
[0025] [Fig.7] represents a schematic view of the second part of an assembly of parts for an aircraft propulsion unit according to the invention,
[0026] [Fig.8] represents a block diagram of the method of producing an assembly of parts for an aircraft propulsion unit according to the invention,
[0027] [Fig.9] represents a schematic view of a step of the method of producing the assembly according to the invention,
[0028] [Fig. 10] represents a schematic view of a step of the method of producing the assembly according to the invention, in particular after the step of [Fig. 9],
[0029] [Fig. 11] represents a schematic view of another step of the method for producing the assembly according to the invention, in particular after the step of [Fig. 10]. Detailed description of the invention
[0030] [Fig.l] and [Fig.2], each showing the prior art, have been described in the foregoing.
[0031] We are interested in figures 3 to 6 which illustrate examples of an assembly 10 of parts for an aircraft propulsion unit 1.
[0032] Thus, in general, an assembly 10 of parts for an aircraft propulsion unit 1 comprises a first part 11 and a second part 13 which is adjacent to the first part 11. The first part 11 may be located upstream or downstream (with reference to the flow of the air flow in the propulsion unit 1) of the first part 11. The first part 11 further comprises a first aerodynamic surface 12 and the second part 13 comprises a second aerodynamic surface 14 of which at least one edge 15 extends in the extension of the first aerodynamic surface 12.
[0033] The first part 11 and the second part 13 can be fixed to the same support 16. In such a case, each of the parts 11, 13 comprises through holes 17, 18 for the passage of fixing elements 19 of the part 11, 13 concerned to the support 16.
[0034] The first part 11 is also made from a first material which may be a metal alloy or a composite material.
[0035] When the first part 11 is made of a metal alloy, it cannot be remachined as will be explained in more detail below, and its first aerodynamic surface 12 then generally serves as a reference for the alignment of the second aerodynamic surface 14 of the second part 13.
[0036] We will now focus more specifically on the second part 13, illustrated in [Fig.7]. This figure represents a schematic sectional view of the second part 13 according to the invention.
[0037] The second part 13 is made of a second material which is a composite material. The second part 13 further comprises, at the edge 15 of its second aerodynamic surface 14, a sacrificial excess thickness 20. This sacrificial excess thickness 20 also extends in a radial direction relative to the longitudinal axis X and extends circumferentially relative to this same axis X. The sacrificial excess thickness 20 may be annular and extend over 360° (degree) around the longitudinal axis X if, for example, the second part 13 is annular, as described later. Alternatively, the sacrificial excess thickness 20 may extend over a localized and predefined circumferential portion, i.e. over an angle of less than 360°.
[0038] Advantageously, the composite material of the second part 13 comprises a stack of layers of fibers 21, called structural layers 21, embedded in a polymer matrix. The term “structural layers” means the layers of fibers which give the second part its mechanical characteristics. In other words, their degradation can harm the structural integrity of the second part 13.
[0039] In such a case, the second part 13 comprises a body 13a which comprises structural layers 21, which extend over the entire extent of the second part 13, i.e. along the longitudinal axis X. The second part 13 can then also comprise a stack of additional fiber layers 22, at the edge 15, to define the sacrificial excess thickness 20. These additional fiber layers 22 are also easily machinable.
[0040] The structural layers 21 of the body 13a of the second part 13 may contain carbon fibers. The additional fiber layers 22, defining the sacrificial excess thickness 20, may, in a non-limiting manner, contain carbon fibers or glass fibers.
[0041] Advantageously, the structural layers 21 of the body 13a have a color different from the color of the additional fiber layers 22. In other words, the sacrificial extra thickness 20 has a color different from the rest of the second part 13, and in particular from the second aerodynamic surface 14.
[0042] The structural layers 21 of the body 13a and the additional fiber layers 22 of the sacrificial extra thickness 20 may also be separated by a demarcation 23 of a color different from those of the structural layers 21 of the body 13a and the additional fiber layers 22. This demarcation 23 marks the boundary between the additional fiber layers 22 of the extra thickness 20 and the structural layers 21. In such a case, the structural layers 21 of the body 13a and the additional fiber layers 22 may have the same color or have different colors, as long as these are of a color different from that of the demarcation 23.
[0043] This demarcation 23 may be a layer of fibers, called a separating layer, made of carbon fibers or glass fibers, or it may be a film, for example an adhesive film.
[0044] The color differences described above make it possible to give a visual indicator to an operator during the assembly, indicating the machining limit. Indeed, as soon as a color difference appears, this means that, locally, the sacrificial excess thickness 20 is entirely removed and that continuing the machining risks harming the structural integrity of the second part 13.
[0045] The sacrificial excess thickness 20 of the second aerodynamic surface 14 may have a thickness of between 0.5 mm (millimeter) and 5.0 mm, advantageously of between 1.5 mm and 5.0 mm, and preferably of between 1.5 mm and 2.5 mm.
[0046] The sacrificial excess thickness 20 may also extend from the edge 15 of the second aerodynamic surface 14 over a strip of width between 0.5 cm (centimeter) and 15 cm, advantageously between 1 cm and 15 cm, and preferably between 2 cm and 10 cm.
[0047] Returning to [Fig. 3], a first example of assembly 10 of parts is shown there. In this particular example, the assembly 10 forms an air inlet 4 of nacelle 3 of an aircraft propulsion unit 1. Figures 4 and 5 are details of [Fig.3]. In particular, [Fig.4] shows a partial sectional view along the section axis AA of the assembly 10 of parts of [Fig.3], while [Fig.5] shows an enlarged view of the arrangement between the first and second parts 11, 13 of [Fig.4],
[0048] In this configuration, the first and second parts 11, 13 and the first and second aerodynamic surfaces 12, 14 are annular and extend around the same longitudinal axis X. The edge 15 of the second aerodynamic surface is therefore also annular. The first and second parts 11, 13 are further arranged next to each other along this longitudinal axis X.
[0049] With reference to [Fig.4] and 5, the first and second annular parts 11, 13 are fixed together by a support 16 which is also annular.
[0050] In the particular case of figures 3 to 5, the first part 11 is a lip 7 of the air inlet 4 of the nacelle 3 and the second part 13 is an internal duct 8 of the air inlet 4 of this nacelle 3. The internal duct 8 also extends downstream of the lip 7. In practice, the lip 7 is generally made of a metallic material or a metallic alloy, having already benefited from a prior finish (for example a mirror effect). It is therefore preferable not to re-machine it. The internal duct 8 is, for its part, made of a composite material based on carbon fibers embedded in a polymeric resin, more suitable for new machining.
[0051] [Fig. 6] shows another example of assembly 10 of parts for an aircraft propulsion unit, and in particular thrust reverser parts 6.
[0052] In this particular example, the assembly 10 comprises a plurality of parts adjacent to each other and extending around the longitudinal axis X. It is thus possible to identify several pairs of first part 11, 11” and second part 13, 13', 13”.
[0053] For example, a first pair comprises a first part 11, which is an annular inner body 8', and a second part 13, which is a movable cowl 9 of the thrust reverser 6. Thus, the edge 15 of the second part 13 is aligned with the first part 11.
[0054] A second pair comprises, for example, a first part 11 and a second part 13'. Thus, the edge 15' of the second part 13' is aligned with the first part 11.
[0055] Another pair may also comprise a first part 11' and a second part 13”. Thus, the edge 15” of the second part 13' is aligned with the first part 11. In this case, the first part 11' may also be the second part 13'.
[0056] It is understood that the second part can, in certain cases, also be the first piece of another piece.
[0057] We now turn to Figures 8 to 11 which illustrate, according to the invention, a method 100 for producing an assembly 10 of parts for a propulsion unit 1 as described above.
[0058] [Fig.8] represents a block diagram of the method 100.
[0059] Thus, in a step 102, a first part 11 with a first aerodynamic surface 12 is made of a first material. As indicated previously, this first part 11 may be made of a metal alloy or a composite material.
[0060] In a step 104, which can take place simultaneously with step 102, a second part 13 with a second aerodynamic surface 14 is made of a second material, this second material being composite as described above. The second part 13 is made such that its second aerodynamic surface 14 comprises at least one edge 15 configured to be adjacent to the first part 11. The second aerodynamic surface 14 further comprises, at the edge 15, a sacrificial excess thickness 20. This sacrificial excess thickness 20 is as described above.
[0061] At a step 106, taking place after steps 102 and 104, the first and second parts 11, 13 are assembled. The first and second parts 11, 13 can thus be fixed to each other by means of a support 16, as shown in [Fig. 9]. In which case, each of the parts 11, 13 comprises through holes 17, 18 for the passage of fixing elements 19 of the part 11, 13 concerned to the support 16. These holes 17, 18 are pre-drilled beforehand during steps 102 and 104 before being drilled during the assembly of the parts in step 106.
[0062] At a step 108, following step 106, and with reference to [Fig. 10], the sacrificial excess thickness 20 of the second part 13 is machined so that the edge 15 of the second aerodynamic surface 14 extends in the extension of the first aerodynamic surface 12. The machining is carried out locally on the sacrificial excess thickness 20. This means that the machining operation is carried out at several points of the assembly and that at the end of these different machining operations, the remaining sacrificial excess thickness 20 can vary from one point to another, or even all around the X axis, depending on the arrangement of the first and second parts 11, 13 relative to each other.
[0063] When the additional fiber layers 22 of the sacrificial extra thickness 20 and the fiber layers 21, called structural layers 21, of the body 13a of the second part 13 are of different colors, the sacrificial extra thickness 20 is removed, at most, until the color of the structural layers 21 appears. When a demarcation 23, for example a fiber layer or a film, of a different color from the structural layers 21 and the additional fiber layers 22 separates these same layers 21, 22 from each other, the sacrificial extra thickness 20 is removed, at most, until the color of the structural layers 21 appears. appearance of the color of the demarcation 23.
[0064] Generally speaking, the change in color is a visual indicator for the operator, signifying to him that, locally, the sacrificial excess thickness 20 is entirely removed. Continuing the machining then risks reaching the structural layers 21 of the second part 13, with the risk of degrading the latter.
[0065] In a step 110, following step 108, and with reference to [Fig. 11], a finishing coating 24 is advantageously applied to the second aerodynamic surface 14 of the second part 13 to fill any roughness so as to ensure aerodynamic continuity. The presence of holes or bumps would generate pressure losses and therefore a disturbance in the aerodynamic vein. Also, when the second part 13 comprises through holes 18 for the passage of fixing elements 19 of the second part 13 to a support 16, this finishing coating 24 is applied to fill the through holes 18 so that the second aerodynamic surface 14 extends in the extension of the first aerodynamic surface 12.
[0066] When assembling 10 the first and second parts 11, 13, a gap 25 may exist between each of the two parts 11, 13. Also, during step 110, the finishing coating 24 may be applied to fill this gap 25 with an element 24' so as to ensure aerodynamic continuity.
[0067] The method for producing an assembly of parts for an aircraft propulsion unit as described above allows an improvement in the alignment of the first and second aerodynamic surfaces of the first and second parts. Indeed, the sacrificial excess thickness located at the edge of the second aerodynamic surface is easily removed by machining until it is in the extension of the first aerodynamic surface. In this way, the aerodynamic step of the assembly is reduced to its minimum, lower than that obtained with existing methods, which makes it possible to obtain improved aerodynamic continuity in the propulsion unit.
[0068] Another advantage is to improve the control of the aerodynamic movement between the first and second parts. Indeed, the difference in color of the additional fiber layers of the sacrificial excess thickness, whether with the fiber layers, called structural layers, of the body of the second part or the fiber layer or the film of the demarcation, gives a visual indicator to the operator during machining. This visual indicator makes it possible to indicate the machining limit by alerting the operator that the sacrificial excess thickness has been completely removed locally. Continuing machining would then risk reaching the structural layers of the second part, with the risk of damaging the latter.
Claims
Claims
1. Method for producing an assembly (10) of parts for an aircraft propulsion unit, this assembly (10) comprising a first part (11) made of a first material and comprising a first aerodynamic surface (12) and a second part (13) adjacent to the first part (11) and made of a second material, this second material being a composite comprising a stack of layers of fibers (21, 22) embedded in a polymer matrix, this second part (13) comprising a second aerodynamic surface (14) of which at least one edge (15) must extend in the extension of the first aerodynamic surface, said method comprising the following steps: - producing the first part (11) with a finished first aerodynamic surface (12), - producing the second part (13) with a second aerodynamic surface (14) which comprises layers of fibers (21) extending over the entire extent of the second part,and comprising additional fiber layers (22) at said at least one edge (15) to define a sacrificial excess thickness (20), said fiber layers (21) extending over the entire extent of the second part being separated from the additional fiber layers (22), by a demarcation (23), for example a fiber layer or a film, of a color different from those of the fiber layers (21) and the additional fiber layers (22), - assembling the first and second parts (11, 13), - machining the sacrificial excess thickness of the second part (13), at most, until the color of the demarcation (23) appears, so that said at least one edge (15) of the second aerodynamic surface (14) extends in the extension of the first aerodynamic surface (12).,
2. Method according to claim 1, comprising, after the machining step, the following step: - applying a finishing coating (24) to the second aerodynamic surface (14) of the second part (13).
3. A method according to any one of claims 1 or 2, wherein the first part (11) is made of a metal alloy or a composite material.
4. A method according to any one of claims 1 to 3, wherein the fiber layers (21) comprise carbon fibers, and the additional fiber layers (22) comprise carbon fibers or glass fibers.
5. A method according to claim 1 to 4, the fiber layers (21) have a different color than the additional fiber layers (22).
6. A method according to any one of claims 1 to 5, wherein the sacrificial excess thickness has a thickness of between 0.5 mm and 5.0 mm, advantageously between 1.5 mm and 5.0 mm and preferably between 1.5 mm and 2.5 mm.
7. A method according to any one of claims 1 to 6, wherein the first and second parts (11, 13) and the first and second aerodynamic surfaces (12, 14) are annular and extend around the same axis (X), the parts being arranged next to each other along this axis and said at least one edge being an annular edge of the second aerodynamic surface.
8. Method according to any one of claims 1 to 7, in which the first and second parts (11, 13) are fixed to the same support (16).
9. A method according to the combination of claims 7 and 8, wherein the support (16) is annular.
10. Method according to any one of claims 8 or 9, in which, in relation to the support (16), the second part (13) comprises through holes (18) for the passage of fixing elements (19) of the second part to the support, said through holes (18) being filled with a finishing coating (24) so that the second aerodynamic surface (14) extends in the extension of the first aerodynamic surface (12).
11. Assembly (10) of parts for implementing the method according to any one of claims 1 to 10, this assembly comprising a first part (11) made of a first material and comprising a first aerodynamic surface (12) and a second part (13) adjacent to the first part (11) and made of a second material, this second material being composite, this second part comprising a second aerodynamic surface (14) of which at least one edge (15) must extend in the extension of the first aerodynamic surface, the second aerodynamic surface of the second part comprising, at the level of said at least one edge, a sacrificial excess thickness (20).
12. Assembly (10) according to claim 11, in which the first part (11) is a lip (7) for an air inlet (4) of a nacelle (3) and the second part (13) is an internal duct (8) for an air inlet of the nacelle.
13. Assembly (10) according to claim 11, wherein the first part (11) is an inner body (8') and the second part (13) is a movable cowl (9) of a thrust reverser (6, 6').