METHOD FOR PRODUCING AN AIRCRAFT RADOME BY JOINING SKIN PARTS WITH REDUCED DIMENSIONS, AIRCRAFT RADOME AND AIRCRAFT

Description

TECHNICAL FIELD

[0001] The present invention relates to aircraft radomes. More particularly, the invention relates to a method for manufacturing an aircraft radome, as well as to an aircraft radome and an aircraft comprising such a radome. PREVIOUS STATE OF THE ART

[0002] Many aircraft, including civil and military transport aircraft, feature a radome mounted at the front of the fuselage, forming a dome or a pointed shape. The function of such a radome is to protect a radar-type device positioned at the front of the aircraft, while also providing the aircraft with good aerodynamic performance. Because of the presence of a radar beneath the radome, the latter must be made of a material permeable to electromagnetic waves, such as an electrically insulating composite material.

[0003] Existing aircraft radomes are generally "sandwich" constructions, consisting of a rigid assembly with at least one shell, also called a core, sandwiched between two skins. This significantly increases flexural rigidity while providing good transparency to electromagnetic waves, notably by adjusting the radome's thickness to the wavelength of the radar it covers. The role of the core is to support the assembled skins so that the assembly can withstand bending forces; the core itself possesses shear strength characteristics. The skins used for radomes are made of large petals assembled by hand. These petals are generally fabrics (for example, quartz or glass) impregnated with an organic or synthetic resin.Some aircraft radomes feature a "double sandwich" structure, meaning they are made by stacking an outer skin, a first shell, a middle skin, a second shell, and finally an inner skin. Other radomes may have an even more complex "triple sandwich" structure, in which three shells are arranged in an alternating stack of skins and shells. In one manufacturing example, a first skin is assembled onto a mold, then a shell is assembled onto this first skin, and finally a second skin is assembled onto the shell. The shape of the radomes, with its pronounced double curvature, necessitates manual assembly, and the size of the petals is limited by the deformability of the fabric planes relative to the shape of the support structure with this double curvature.

[0004] An example of prior art is provided by document US4620890A.

[0005] The situation can therefore be improved. DESCRIPTION OF THE INVENTION

[0006] An object of the present invention is to propose a method for manufacturing an aircraft radome that can be automated and that reduces the rate of material loss during manufacturing.

[0007] To this end, an aircraft radome is proposed comprising at least one shell, a first skin and a second skin respectively formed from a first assembly of skin pieces and a second assembly of skin pieces, said radome being configured as follows: all or part of the skin pieces of the said first and second assemblies partially covers one or more skin pieces adjacent to the assembly which includes them, and, the ratio between the surface area of ​​a skin piece covering one or more adjacent skin pieces and the total surface area of ​​that skin piece does not exceed a predetermined threshold value.

[0008] Furthermore, a skin layer comprises skin pieces arranged side by side to form at least one circular ring assembled on a rear portion of said radome and skin pieces arranged side by side and forming parallel alignments of skin pieces in a front portion of the radome.

[0009] It is therefore advantageous to perform automated assembly of the skin panels, whose small, homogeneous dimensions allow them to be installed by an automated device, such as an industrial robot. Furthermore, the skin panel assemblies are designed so that partial overlaps provide structural rigidity, and the fact that these overlaps do not exceed a predefined percentage of the surface area per skin panel ensures good transparency to electromagnetic waves. This electromagnetic transparency is particularly advantageous when one or more electromagnetic beams from a radar or antennas positioned in or behind the radome pass through the radome in an area known as the "radio frequency zone."

[0010] The radome according to the invention may also include the following characteristics, considered alone or in combination: The threshold value of said ratio is 30%. The first and second assemblies each reproduce a predetermined assembly pattern. Each skin piece has a rectangular, trapezoidal, or triangular shape. The largest dimension of each skin piece is less than one-third of the largest overall dimension of the radome, preferably less than 42 cm (approximately the length of an A3 sheet), and even more preferably less than 30 cm (approximately the length of an A4 sheet). The skin pieces are made of a composite material comprising a fabric reinforcement of fibers including flax fiber, hemp, simple or very high molecular weight polyethylene, glass fabric, quartz fabric, and aramid fabric, said fabric being pre-impregnated with a thermosetting or thermoplastic organic or synthetic resin.The radome's shell is made of foam, paper, or resin, and has a honeycomb structure.

[0011] The invention also relates to a method for assembling an aircraft radome comprising at least one assembly of a first skin and a second skin on two opposite faces of the same shell, said first skin and said second skin being respectively formed of a first assembly of skin pieces and a second assembly of skin pieces, the method being characterized in that: all or part of the skin pieces of said first and second assemblies partially covers one or more skin pieces adjacent to the assembly which includes them, and, the ratio between the surface area of ​​a skin piece covering one or more adjacent skin pieces and the total surface area of ​​that skin piece does not exceed a predetermined threshold value, said threshold value being preferably equal to 30%.

[0012] Furthermore, a skin layer comprises skin pieces arranged side by side to form at least one circular ring assembled on a rear portion of said radome and skin pieces arranged side by side and forming parallel alignments of skin pieces in a front portion of the radome.

[0013] The invention also relates to an aircraft comprising a radome as previously described. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which: [ Fig. 1 ] is a schematic front-view representation of an aircraft radome according to one embodiment; [ Fig. 2 ] is a schematic perspective view representation of the aircraft radome already shown on the Fig. 1 ; Fig. 3 ] is a diagram illustrating steps in an aircraft radome assembly process already shown on the Fig. 1 And Fig. 2 , according to one embodiment; and, [ Fig. 4 ] illustrates an aircraft comprising an aircraft radome, according to one embodiment. DETAILED EXPLANATION OF IMPLEMENTATION METHODS

[0015] There Fig. 1 This is a schematic representation illustrating an aircraft radome 100 assembled according to one embodiment, viewed from the front. The radome has a general pointed, dome-like shape, designed to be attached to the front of an aircraft fuselage. The front of the aircraft radome 100 is defined here as the tip of the radome (or the apex of the dome), and therefore as the part furthest from the aircraft fuselage components to which the radome is attached. A contrario The rear of the radome is defined as the part closest to the fuselage elements of the aircraft to which the radome is attached. In one embodiment, the radome comprises an assembly of two skins 110 and 130 on a shell 120. In other variations, the aircraft radome 100 may comprise several shells similar to the shell 120, each of the inner and outer faces of these shells being covered with at least one assembly of skin pieces. Such an assembly constitutes a layer of skin pieces, also commonly referred to as a "skin thickness," "skin ply," or "ply." Thus, according to variants, the aircraft radome 100 may comprise an alternation of shells 120 and skin folds, each surface of each shell 120 being covered with at least one skin fold and two shells of a pair of adjacent shells 120 in the alternation being separated by at least one skin fold.

[0016] According to the example described in relation to the Fig. 1 , a first skin 110 constitutes an outer skin of the radome 100 and a second skin 130, not referenced on the Fig. 1 but referenced on the Fig. 2 This constitutes the inner skin of the radome 100. The outer skin 110 of the radome 100 is composed of a plurality of skin pieces 111a and 111b, also called "patches," assembled according to a predefined assembly pattern. The term "assembly pattern" here refers to a combination of positioning of each of the skin pieces of the outer skin 110 or the inner skin 130.

[0017] According to one embodiment, the skin pieces 111a have a rectangular shape and the skin pieces 111b have a trapezoidal shape; these examples are not limiting, and skin pieces may have a different shape, for example, a triangular shape. Only one of the skin pieces 111a and one of the skin pieces 111b are referenced on the Fig. 1 in order to preserve the clarity and legibility of this figure.

[0018] Advantageously and cleverly, all or part of the skin pieces of the first and second assemblies partially cover one or more skin pieces adjacent to the assembly which includes them, so as to obtain structural rigidity and therefore a good capacity for transmitting forces between two adjacent skin pieces.

[0019] Even more advantageously, and just as cleverly, the ratio between the surface area of ​​a piece of skin covering one or more neighboring pieces of skin and the total surface area of ​​that piece of skin does not exceed a predetermined threshold value, such as, for example, a value with a ratio of 30%.

[0020] In addition, each of the skin pieces 111a and 111b has an overall dimension less than a predetermined length depending on the overall size of the radome 100, so that a skin piece has a dimension substantially reduced in relation to the size of the radome 100 and the positioning of a skin piece is made easier in relation to the double curvature of the radome.

[0021] For example, it can be defined that the maximum dimension of a skin piece, such as its length when the skin piece has a rectangular shape, is substantially less than half the largest overall dimension of the radome 100. According to the example described on the Fig. 1 The largest overall dimension of the aircraft radome 100 is the height H1 of the rear of the radome 100. Thus, it is possible to easily manipulate and position a piece of skin, particularly with the help of an automated device such as an industrial assembly robot.

[0022] According to another embodiment, each of the skin pieces used for the assembly of the radome has a rectangular shape of dimension A3 or a trapezoidal or triangular shape with dimensions that fit within a rectangular template of dimension A3.

[0023] According to another embodiment, each of the skin pieces used for the assembly of the radome has a rectangular shape of A4 size or a trapezoidal or triangular shape with dimensions that fit within a rectangular template of A4 size.

[0024] According to yet another example of implementation, each of the skin pieces used for the assembly of the radome has a rectangular shape of dimension A5 or a trapezoidal or triangular shape with dimensions fitting within a rectangular template of dimension A5.

[0025] According to one example of an assembly pattern, rectangular skin pieces 111a are joined end-to-end to form one or more circular rings of the outer skin 110 of the radome 100, starting from the rear of the radome. Then, rectangular skin pieces 111a are joined to form parallel lines in the central portion of the remaining surface of the outer skin 110 of the radome 100, and trapezoidal skin pieces 111b are joined in the remaining surface area to cover the entire surface of the radome, between the circular ring(s) and the aforementioned parallel lines. This advantageously allows for better control of the dimensions of the overlap areas between adjacent skin pieces.

[0026] In one embodiment, each of the inner 110 and outer 130 skins can comprise several layers (also called plies) of skin pieces, each with distinct assembly patterns. Preferably, the overlap areas between the skin pieces are evenly distributed over the surface of the radome so that the electromagnetic transparency is homogeneous or evenly distributed.

[0027] For example, one skin layer may include skin pieces arranged to form vertical parallel lines in the central area of ​​the radome, and two further layers may include skin pieces arranged to form lines oriented at +60° and -60° respectively in the same area of ​​the radome relative to the orientation of the lines in the first layer.

[0028] Similarly, one skin layer may comprise skin pieces arranged to form parallel lines in the central area of ​​the radome, and another layer may comprise skin pieces arranged to form intersecting lines oriented at + / - 90° to the orientation of the lines in the first layer. In one embodiment, a positioning reference for the skin pieces is defined as a line of intersection between a vertical plane passing through the tip of the radome 100.

[0029] It should be noted that the Fig. 1 illustrates a superposition of two assemblies of outer skin pieces 110 or, in other words, of two layers of skin pieces 111a and 111b assembled according to two distinct patterns, thanks to a transparency effect.

[0030] According to one embodiment, the outer skin 110 is made of three layers of skin pieces 111a and 111b having distinct assembly patterns, and the inner skin 130 is made of two layers of skin pieces 131a and 131b having distinct assembly patterns.

[0031] Advantageously, when several layers (or plies) of skin pieces are superimposed to form a skin, the assembly of this skin is carried out so that the overlap areas in one thickness of skin pieces do not overlap the overlap areas in another thickness, so as to optimize the electromagnetic permeability of the radome 100. Indeed, the electromagnetic permeability of the radome 100 depends on several factors, including the thickness of the radome skins.

[0032] There Fig. 2 This is a schematic representation illustrating the aircraft radome 100 assembled according to one embodiment, viewed in perspective. The perspective view shown allows visualization of an assembly of skin pieces 131a and 131b to form the inner skin 130 on the hull 120 and the assembly of skin pieces 111a, 111b to form the inner skin 110 on the hull 120. According to one embodiment, the skin pieces 131a have a rectangular shape and the skin pieces 131b have a trapezoidal shape. According to one embodiment, the assembly patterns of the skin parts 110 are distinct from the assembly patterns of the skin parts 130. Advantageously, the patterns are defined so as to meet constraints for the absorption of forces applied to the radome, for example from computer simulation or on a device, during the reproduction on the ground of stresses representative of a flight or of impacts with third-party objects.

[0033] There Fig. 3 illustrates a method for assembling the aircraft radome 100 according to an embodiment. A step S0 corresponds to a preparation step for the manufacture of the radome 100 at the end of which a concave mold having a shape complementary to the external shape of the radome 100 and almost complementary to the shape of the shell 120 is positioned in a manufacturing workshop.

[0034] Then, in step S1, the first outer skin 110 is assembled by positioning the skin pieces 111a and 111b, in one or more layers, according to a predefined assembly pattern for the outer skin 110. The shell 120 is then positioned and fixed in step S2 against the outer skin 110 applied to the mold. In step S3, the second inner skin 130 is assembled by positioning the skin pieces 131a and 131b onto the shell 120.Advantageously, the largest dimension of each skin piece used in steps S1 and S3 is less than a predetermined length equal to one-third of the largest overall dimension H1 of the radome 100. This allows for easy positioning and enables the assembly of the radome 100 to be carried out either manually or using one or more automated industrial robots programmed to perform positioning according to predetermined assembly patterns. Preferably, each skin piece has a rectangular, trapezoidal, or triangular shape with dimensions that fit within an A3, A4, or A5 format template, since the smaller the skin pieces, the easier it is to automate their assembly into skin layers.

[0035] According to another embodiment, the shell 120 is held on a support during the manufacture of the radome 100 and the assemblies of inner skin parts 130 and outer skin parts 110 are made directly on the shell 120.

[0036] There Fig. 4 represents an aircraft 1 comprising a radome 100 according to one embodiment. Advantageously, the ability to automate the assembly of the radome 100 of aircraft 1, using the described process, allows for a substantial gain in productivity. Furthermore, the use of reduced-dimension skin pieces allows for cutting from strips of material of a fixed and reduced width, which significantly limits material waste and optimizes production costs.

[0037] The invention is not limited to the embodiments and examples cited but more broadly to any method of manufacturing an aircraft radome comprising at least a first assembly of skin pieces for assembling an outer skin on a first surface of a radome shell and a second assembly of skin pieces for assembling an inner skin on a second surface of the same shell, opposite said first surface, with all or part of the skin pieces of said first and second assemblies partially covering one or more skin pieces adjacent to the assembly which includes them, and such that the ratio between the surface area of ​​a skin piece covering one or more adjacent skin pieces and the total surface area of ​​that skin piece does not exceed a predetermined threshold value, for example 30%.Thus, depending on the design, a radome can comprise more than three layers of skin panels on the outer surface of a shell and more than two layers of skin panels on the inner surface of the same shell. Furthermore, the skin panels can be smaller than those previously described. For example, in one variation, a skin panel can be smaller than the dimensions described, such as fitting within a format smaller than A5.

Claims

1. Aircraft radome (100), intended to be installed at the front of the fuselage and form a dome or a tip, comprising at least one shell (120), a first skin (110) and a second skin (130) respectively assembled on two opposite faces of each of the at least one shell (120), said first skin (110) and said second skin (130) respectively being formed from a first assembly of skin pieces (111a, 111b) and a second assembly of skin pieces (131a, 131b), said radome (100) being such that: - all or part of the skin pieces of said first and second assemblies partially overlaps one or more neighbouring skin pieces of the assembly that comprises them, and - the ratio between the surface area of a skin piece overlapping one or more neighbouring skin pieces and the total surface area of that skin piece does not exceed 30%, and said radome being characterized in that: - a skin layer comprises skin pieces arranged side-by-side to form at least one circular crown assembled on a rear portion of said radome and skin pieces arranged side-by-side and forming parallel alignments of skin pieces in a front part of the radome.

2. Aircraft radome (100) according to Claim 1, wherein said first and second assemblies each reproduce a predetermined assembly pattern.

3. Aircraft radome (100) according to either of Claims 1 and 2, wherein each of the skin pieces (111a, 111b, 131a, 131b) has a rectangular, trapezoidal or triangular shape.

4. Aircraft radome (100) according to one of Claims 1 to 3, wherein the largest dimension of each of the skin pieces is smaller than one third of the largest overall dimension of the radome, preferentially smaller than 42 cm, even more preferentially smaller than 30 cm.

5. Aircraft radome according to one of Claims 1 to 4, wherein the skin pieces are made of a composite material comprising a reinforcement made from a fabric of fibres including flax fibre, hemp, simple polyethylene or polyethylene with a very high molecular weight, glass fabric, quartz fabric, aramid fabric, said fabric being pre-impregnated with a thermosetting or thermoplastic organic or synthetic resin.

6. Aircraft radome according to one of Claims 1 to 5, wherein the shell (120) is made from foam, paper or resin, and has a cellular structure.

7. Method for assembling an aircraft radome, intended to be installed at the front of the fuselage and form a dome or a tip, comprising an assembly of a first skin (110) and of a second skin (130) respectively on two opposite faces of one and the same shell (120), said first skin (110) and said second skin (130) respectively being formed from a first assembly of skin pieces (111a, 111b) and a second assembly of skin pieces (131a, 131b), the method being such that: - all or part of the skin pieces of said first and second assemblies partially overlaps one or more neighbouring skin pieces of the assembly that comprises them, and - the ratio between the surface area of a skin piece overlapping one or more neighbouring skin pieces and the total surface area of that skin piece does not exceed a predetermined threshold value, said value being equal to 30%, and the method being characterized in that: - a skin layer comprises skin pieces arranged side-by-side to form at least one circular crown assembled on a rear portion of said radome and skin pieces arranged side-by-side and forming parallel alignments of skin pieces in a front part of the radome.

8. Aircraft comprising an aircraft radome according to one of Claims 1 to 6.