Rear engine mast substructure

Abstract

An engine pylon rear structure for an aircraft comprising an engine pylon (30) suspending an engine (20) from a wing (10), comprising a front attachment interface (310) adapted to be attached to a primary structure of the engine pylon (30); a rear attachment interface (320) adapted to be attached to a primary structure of the wing (10); a composite beam (301) connecting the front attachment interface (310) and the rear attachment interface (32) and linked thereto; the composite beam comprising a first section (501) and a second section (502) integral with the first section; the second section comprises two branches (511, 512); the first section (501) being connected to the rear attachment interface (320) and the second section (502) to the front attachment interface (310); frames (330) capable of supporting fairing panels (340) being fixed on an external surface of the first section of the composite beam Figure 3

Description

Title of the invention: Rear substructure of engine mast Technical field

[0001] The invention belongs to the field of aeronautical structures, more particularly to that of the connection of an engine with an aerostructure, in particular, but not exclusively, with a wing of an aircraft. Prior art

[0002] The rear substructure of an engine pylon, particularly a jet engine, commonly referred to by the acronym RSS for "Rear Secondary Structure", is essentially a fairing for aerodynamic purposes. This substructure is attached by 3 fixing points between the primary structure of the pylon supporting the engine and the primary structure of the aircraft wing, for example.

[0003] Its shape is substantially a hollow truncated half-conoidal shape, flared at the interface with the mast and whose section tapers both vertically and transversely as it moves away from the mast towards the trailing edge up to its junction with the wing.

[0004] Two other components are assembled to this substructure, which are also aerodynamic fairings, a lower fairing, commonly designated by the acronym APF for "Aft Pylon Fairing", in the continuity of the shape of the RSS and subjected to the flow of hot gases (> 170°C) emitted by the engine and which is in fact made of materials capable of resisting heat, for example titanium alloys, and a fairing at the end of the RSS, called a gutter or "gutter" in Anglo-Saxon terms, which extends the conoidal shape of the RSS to the surface of the wing.

[0005] It is the RSS substructure which also supports these two fairings: APF and gutter.

[0006] The substructure being a hollow shell, it can accommodate equipment which it protects from environmental constraints: fire, lightning, impacts, etc.

[0007] Although this assembly does not participate in supporting the weight of the engine or in transmitting the thrust, this substructure must nevertheless be able to withstand severe mechanical stresses.

[0008] Beyond the aerodynamic loading during flight, the structure must in particular resist and maintain its integrity when it is subjected to very strong vibrations generated by the engine in the event of degraded operation of the latter following, for example, accidents such as the ingestion of an object, the breakage of rotating blades and more generally an imbalance of the rotating parts.

[0009] In order to ensure this resistance with minimum weight, this structure is, according to the art prior, designed as a lattice-type assembly, comprising a framework made up of frames and side members, fixed together by rivet-type fasteners and on which panels are assembled, generally made up of a monolithic composite material or sandwich structure.

[0010] Due to its rigidity, this structure is not very compliant, that is to say that it cannot tolerate, through its own flexibility, variations in shape, inherent in any mass manufacturing process, both between the assembled elements constituting the rear substructure, frames, spars, panels, and between the substructure itself and its anchor points on the mast and the aerostructure, in particular the primary structure of the wing. The slightest deviations cause significant mechanical stresses during assembly, in the substructure itself and in the aerostructure with which it is assembled.

[0011] As a result, in particular, the aerodynamic shape of the cowlings is simplified to flat or almost flat surfaces with a large radius of curvature to avoid creating too much difference in shape between the assembled parts due to the dispersions in the manufacturing dimensions, which are always greater on parts with a more complex shape and consequently the aerodynamics are not optimal, without however simplifying the assembly with the mast and primary structure interfaces.

[0012] The entire substructure, side members, frames, panels must be produced with precision to limit dimensional dispersions and ensure an assembly that does not generate constraints, which implies a high manufacturing cost.

[0013] Finally, the design of the frame leaves a small volume for installing equipment and makes access to the interior of the RSS difficult for the control and maintenance of this equipment. Summary of the invention

[0014] These shortcomings of the prior art are addressed by a rear engine pylon substructure for an aircraft comprising an engine pylon suspending an engine from a wing, the rear engine pylon substructure comprising

[0015] a front attachment interface, adapted to be attached to a primary structure of the engine pylon;

[0016] a rear attachment interface, adapted to be attached to a primary structure of the wing;

[0017] a composite beam connecting and bonded to the front attachment interface and the rear attachment interface;

[0018] the composite beam comprising a first section and a second section made from the same material as the first section;

[0019] the second section comprises. ;

[0020] the first section being connected to the rear fixing interface and the second section to the front fixing interface;

[0021] frames capable of supporting fairing panels being fixed on an external surface of the first section of the composite beam.

[0022] Thus the composite beam, substantially Y-shaped, provides both the rigidity of the assembly on which the other means of producing the fairing are positioned, the frames on the beam and the panels on the frames,

[0023] The beam is a single piece and made with precision, which avoids the lengthening of the dimension chains.

[0024] The assembly is lighter, which improves its resistance to vibrations, and the interior volume for the installation of equipment is increased compared to the solutions of the prior art.

[0025] This technical solution can be implemented according to the embodiments and variants set out below which can be considered individually or according to any technically operative combination.

[0026] According to one embodiment, the composite beam has a U-shaped section.

[0027] According to one embodiment, the frames comprise 3 fixing lugs in re turning to be fixed to the composite beam on 3 external faces of the U-shaped section and an external surface suitable for supporting the fairing panels.

[0028] According to alternative embodiments, the outer surface of the frames is adapted to support fairing panels whose shape is selected from flat panels, single-curved panels and double-curved panels.

[0029] Advantageously, the U-shaped section of the first section of the composite beam is scalable and widens from the rear fixing interface towards the second section.

[0030] Advantageously, the U-shaped sections of the two branches of the second section are scalable and widen towards the front fixing interface.

[0031] According to one embodiment, a first average plane, in which the first section extends, and a second average plane, in which the second section extends, are intersecting.

[0032] According to an exemplary embodiment, the composite beam is made of a composite material comprising a polymer matrix and continuous carbon fiber reinforcements.

[0033] According to one embodiment, all or part of the frames are made of a metallic material chosen from an aluminum alloy and a titanium alloy.

[0034] According to one variant, all or part of the frames are made of a composite material comprising a polymer matrix and a reinforcement comprising continuous carbon fibers.

[0035] Advantageously, at least one of the fairing panels comprises an inspection hatch. Brief description of the drawings

[0036] The technical solution can be implemented according to the preferred embodiment, which is in no way limiting, set out below with reference to [Fig.l] to [Fig.6] in which: Fig.l

[0037] [Fig.l] relating to the prior art shows in a partial perspective view the positioning of an RSS on an aircraft; Fig.2

[0038] [Fig.2] relating to the prior art represents in a perspective view an example of construction of a RSS framework; Fig. 3

[0039] [Fig.3] shows in perspective view an example of the embodiment of an RSS according to the claimed technical solution; Fig.4

[0040] [Fig.4] shows in perspective view the framework of the RSS represented [Fig.3]; Fig.5

[0041] And [Fig.5] is a perspective view of the composite beam of the frame shown [Fig.4] and its sections shown in folded sections; Fig.6

[0042] [Fig.6] shows in a perspective view an example of the embodiment of a panel double-curved fairing. Description of the embodiments

[0043] [Fig.l] according to an exemplary embodiment relating to the prior art, a rear substructure of the engine mast, called RSS (100), is connected on one side, front, to a mast (30) making it possible to suspend an engine (20) from a wing (10) of an aircraft, and on the other side, rear to the wing (10).

[0044] This substructure essentially has an aerodynamic fairing purpose and supports on a lower face a lower fairing (120), called APF, subjected to the flow of hot gases ejected by the engine (20), and a rear end fairing (130), called gutter, which terminates the aerodynamic shape ending on the intrados face of the wing (10).

[0045] [Fig.2] according to an exemplary embodiment of the prior art, the framework of an RSS is consisting of a set of formed and machined metal parts, for example in aluminum alloy firmly assembled together, in particular via fittings and by riveting, according to a lattice structure principle making this structure very rigid. This rigidity is given by the set of parts thus assembled, constituting a together.

[0046] It comprises a front attachment point (210) for connecting it to the engine mast and two rear attachment points (221, 222) for connecting it to a primary structure of a wing.

[0047] Panels, generally made of sandwich composite material, are fixed to the outer faces of the frames and side members of this framework in order to constitute the fairing.

[0048] The presence of these structural elements leaves little space inside the frame to install equipment.

[0049] This design involves dimension chains passing through several parts. Thus, for illustration purposes, a distance d between the rear fixing points (221, 222) involves at least 8 structural elements (201, 202, 203, 204, 205, 206, 207, 208) and consequently depends on the sum of the manufacturing and assembly tolerances of these elements. This requires precise and expensive manufacturing.

[0050] In the same way as the dimension chains, still for illustrative purposes, a variation in this distance (deformation) during operation produces forces which are transmitted throughout these elements and in particular via the connections between them.

[0051] This requires, in particular, the implementation of assembly fittings to reinforce these connections, which increases the mass of the assembly and consequently the level of stresses generated by strong vibrations, in particular in the event of an engine problem causing an imbalance of the rotating parts.

[0052] [Fig.3] according to an exemplary embodiment, an RSS (300) meeting the shortcomings of the prior art comprises a composite beam (301) constituting a “backbone” of the substructure, to which are connected:

[0053] a front fixing interface (310),

[0054] a rear attachment interface (320)

[0055] support frames (330) for fairing panels (340).

[0056] [Fig.4] in comparison with [Fig.2] shows the simplification of the frame. The composite beam (301) is the structural element of the frame and all the other parts, in particular the frames (330) are positioned on it.

[0057] To this end, the frames (330), here 4 frames, each comprise 3 upturned fixing lugs (431, 432) which make it possible to assemble said frames with the composite beam (301) resting on the external faces of said beam,

[0058] This has the consequence of considerably reducing the dimension chains and of passing the force flows through this composite beam which is dimensioned accordingly.

[0059] According to this exemplary embodiment, the front (310) and rear (320) fixing interfaces are linked respectively to the first frame and to the last frame.

[0060] The fairing panels are fixed on an outer surface (435) of the frames. The frames are represented here with a curved external surface but the same frame architecture or even the same composite beam (301) can receive frames having a flat external surface (435) independently of their fixing on the composite beam which would remain ensured by the same 3 fixing lugs on the 3 external surfaces of the composite beam.

[0061] Thus, [Fig.6], by separating the structural support function, provided by the composite beam, and the panel support function, the frame allows, without further assembly difficulty, the installation of fairing panels (340) with double curvature, i.e. having curvatures in at least two intersecting directions (601, 602).

[0062] This form of fairing panels is more efficient from an aerodynamic point of view.

[0063] However, the architecture of the frame also allows the assembly of flat or simply curved panels, possibly as a replacement for an existing structure.

[0064] The architecture of the frame frees up space inside the RSS for the installation of equipment.

[0065] This larger space, less cluttered by structural elements compared to the prior art, allows access to all or part of this equipment without dismantling the fairing panels, these comprising for this purpose one or more inspection hatches (640).

[0066] [Fig.5] according to an exemplary embodiment, the composite beam (301) comprises two sections (501, 502) made from one material of the other, the first section extends in a first average plane (51) the second section extending in a second average plane (52), two average planes (51, 52) being intersecting.

[0067] The second section comprising two branches (511. 512).

[0068] The beam is a single-piece U-shaped section (550) which varies in section and thickness in both the first and second sections and in the branches. The sections are in particular reinforced at the locations (531, 532) where the frames are assembled with the beam, and the sections of the two branches (511, 512) widen going from the connection to the first section towards the front fixing interface. These variations in section are obtained by calculation by any means known to those skilled in the art as a function of the loading conditions of the structure.

[0069] By way of non-limiting example, the beam is made of a thermosetting resin reinforced by continuous carbon fibers, i.e. extending continuously from one edge to the other of the part with a reinforcement rate of between 50% and 60%.

[0070] This constitution makes the composite beam very strong, rigid and light which is particularly advantageous for resisting strong vibrations.

[0071] By way of example, the mass of such a composite beam, included in a quadratic volume of 1811 x 337 x 425 mm3, with a thickness of 3.63 mm, a minimum section of 551 mm2 and a maximum section of 883 mm2 is less than 2 kg.

[0072] The composite beam is produced by injecting a HexFlow® RTM 6 type resin, marketed by Hexcel®, into a fiber preform, for example by the RTM (“Resin Transfer Molding”) process or other equivalent process.

[0073] This method allows the production of the composite beam of relatively complex shape in a single-piece configuration, without assembly and with a reproducible production precision of less than 0.4 mm, the external faces of the beam, in particular those on which the frames rest, are in contact with the molding surface of said mold.

[0074] Alternatively, the composite beam is made of a thermoplastic polymer matrix reinforced by continuous carbon fibers.

[0075] In this case the beam is obtained for example by consolidation in the form of pre-impregnated folds or by stamping a thermoplastic composite blank.

[0076] The frames are for example made of aluminum alloy or titanium alloy, by forming or machining.

[0077] Alternatively, the frames are made of a composite material with a polymer matrix and fiber reinforcement.

[0078] The frames are positioned and assembled on flat surfaces of the beam by their fixing lugs, which leaves a great deal of latitude on the shape of the fairing panels.

[0079] During assembly, the frames are positioned on the composite beam by positioning tools and pins made by pilot holes made on the frames and the composite beam.

[0080] The frames are fixed to the composite beam in counter-drilled holes using HL LITE™ type fixings (LISI AEROSPACE).

[0081] The fairing panels are then assembled to the frames.

[0082] Thus, compared to the solutions of the prior art, the number of assemblies and fixings is greatly reduced.

[0083] Thus the proposed technical solution allows the production of a lighter RSS (300), with a gain of approximately 30% in mass compared to the prior art, more precise in production, with fewer assemblies, while offering more flexibility in the choice of the shape of the fairing panels with a free internal volume for the installation of larger equipment and improved accessibility to this equipment.

Claims

Claims

1. A rear engine mast substructure for an aircraft comprising an engine mast (30) suspending an engine (20) from a wing (10), the rear engine mast substructure comprising a front attachment interface (310) adapted to be attached to a primary structure of the engine mast (30); a rear attachment interface (320) adapted to be attached to a primary structure of the wing (10); a composite beam (301) connecting the front attachment interface (310) and the rear attachment interface (32) and linked thereto; the composite beam comprising a first section (501) and a second section (502) integral with the first section; the second section comprises two branches (511, 512); the first section (501) being connected to the rear attachment interface (320) and the second section (502) to the front attachment interface (310);frames (330) capable of supporting fairing panels (340) being fixed on an external surface of the first section of the composite beam.;

2. A rear engine mast substructure according to claim 1, wherein the composite beam is of U-shaped section (550).

3. Rear engine mast substructure according to claim 2, in which the frames (330) comprise 3 fixing lugs (431, 432) in reverse to be fixed to the composite beam on 3 external faces of the U-shaped section and an external surface (435) adapted to support the fairing panels.

4. A rear engine mast substructure according to claim 3, wherein the outer surface (435) of the frames (330) is adapted to support fairing panels (340) whose shape is selected from flat panels, single-curved panels and double-curved panels.

5. A rear engine mast substructure according to claim 2, wherein the U-shaped section (550) of the first section (501) of the composite beam is scalable and widens from the rear attachment interface (320) towards the second section (502).

6. Rear engine mast substructure according to claim 2, in which the U-shaped sections of the two branches (511, 512) of the second section (502) are scalable and widen towards the front fixing interface (310).

7. Rear engine mast substructure according to claim 1, in which a first mean plane (51) in which the first section (501) extends and a second mean plane (52) in which the second section (502) extends are intersecting.

8. The rear engine mast substructure of claim 1, wherein the composite beam (301) is made of a composite material comprising a polymer matrix and continuous carbon fiber reinforcements.

9. The rear engine mast substructure of claim 1, wherein the frames (330) are made of a material selected from an aluminum alloy, a titanium alloy, and a composite material comprising a polymer matrix and a reinforcement comprising continuous carbon fibers.

10. The rear engine mast substructure of claim 1, wherein a fairing panel (340) includes an inspection hatch (640).

Images