Aircraft lattice structure designed to prevent the spread of fire and aircraft

Abstract

A lattice structure (1) configured to form the structural part of an aircraft, in particular an airship (D), said lattice structure (1) defining a plurality of three-dimensional meshes (10) and comprising at least one fire containment envelope (2) positioned in a three-dimensional mesh (10) or in a plurality of consecutive three-dimensional meshes (10). Abstract figure: Figure 1

Description

Title of the invention: Aircraft lattice structure for preventing the spread of fire and aircraft Technical field

[0001] The present invention relates to the field of aircraft comprising a lattice-type structure, in particular, an aircraft of the dirigible type.

[0002] Known in the prior art is an aircraft comprising a lattice structure defining a set of three-dimensional meshes together forming the structural skeleton of the aircraft. Each three-dimensional mesh comprises a set of structural bars and defines a mesh volume whose structural bars form the edges. Such a lattice structure is advantageously light and can be used advantageously in an airship.

[0003] It is known to mount certain aircraft equipment inside three-dimensional meshes, such as a gas turbine, an electric generator and batteries in order to provide electrical energy to electric propulsion motors. During their operation, such equipment is likely to heat up and must be thermally insulated to protect its environment, in particular in the case of a hypothetical fire to prevent its spread. Such thermal insulation must in particular protect other thermally sensitive aircraft equipment which is located near the lattice structure, such as the external skin of an airship.

[0004] Incidentally, it is known from patent application FR3060652A1 to equip an aircraft turbojet nacelle with a firewall to isolate the compartment from equipment in the event of a fire. Such a firewall is mounted against the solid structural walls delimiting the compartment, known to those skilled in the art by the abbreviation IFS ("Internal Fixed Structure"), to ensure its support. If such a firewall is effective, it is however not suitable for being mounted on a lattice structure, which, by definition, is free of solid walls. Indeed, the mounting of such a firewall on the structural bars of a three-dimensional mesh is laborious and reduces the performance of the lattice structure, in particular by significantly increasing its mass and reducing its absorption of forces.

[0005] The invention thus aims to prevent the spread of a fire in a lattice structure of an aircraft. PRESENTATION OF THE INVENTION

[0006] The invention relates to a lattice structure configured to form the part structural of an aircraft, in particular of an airship, said lattice structure defining a plurality of three-dimensional meshes.

[0007] The invention is remarkable in that the lattice structure comprises at least one fire containment envelope positioned in a three-dimensional mesh or in a plurality of consecutive three-dimensional meshes.

[0008] The invention advantageously makes it possible to prevent the spread of a fire in an aircraft with a lattice-type structure by means of one or more containment envelopes forming a fire barrier, through which the flames cannot pass. A fire containment envelope advantageously makes it possible to thermally insulate one or more aircraft equipment mounted in the lattice structure, on the one hand, to protect them from the fire, and on the other hand, to retain the flames at the envelope if said aircraft equipment is the cause of the fire, in order to protect the rest of the lattice structure and its environment.Such an envelope is also suitable for being mounted in a lattice structure, by definition free of solid walls, which makes it possible to optimize the performance of the lattice structure in terms of mass and to avoid transmitting mechanical forces to the containment envelope and by reaction to the lattice, unlike a nacelle fire partition for an aircraft turbojet engine which needs to be supported by a solid structure.

[0009] Preferably, a fire containment envelope is positioned in a single three-dimensional mesh so as to protect each three-dimensional mesh individually from fire. This thus makes it possible to individually protect each aircraft equipment.

[0010] According to one aspect of the invention, the fire containment envelope is flexible so as not to absorb any bending force, i.e. without significant internal stress. It behaves structurally like a membrane. Such an envelope advantageously makes it possible to absorb the movements of the lattice structure, which avoids having to reinforce it against the forces induced by the surrounding structure or vibrations. In addition, such flexibility makes it easier to mount the envelope in the lattice structure and to increase its service life.

[0011] Preferably, the fire containment envelope has a thickness of less than 2 cm, and preferably greater than 0.1 mm to promote its flexibility while giving it great robustness. A low thickness also makes it possible to limit the mass of the envelope and thus to maintain a light lattice structure.

[0012] According to a preferred aspect of the invention, the fire containment envelope delimits a closed protective volume making it possible to prevent the spread of a fire. The fire containment envelope thus advantageously forms an overall barrier separating the closed protective volume from the rest of the lattice structure. This makes it possible to prevent the spread, on the one hand, of an external fire towards the interior of the volume of closed protection, and on the other hand, a fire inside the closed protection volume towards the outside. Thus, if equipment housed in the containment envelope catches fire, the other equipment is advantageously protected.

[0013] Preferably, a three-dimensional mesh defines a mesh volume (VI) and comprises a plurality of structural bars forming the edges of the mesh volume. A lattice structure is thus free of solid walls, which gives it its lightness.

[0014] According to a preferred aspect, the closed protection volume (V2) satisfies the following relationship: V2 < 0.75 * VI, and preferably: V2 > 0.35 * VI. In other words, the fire containment envelope delimits a volume strictly smaller than that of the three-dimensional mesh of the lattice structure in which it is mounted (or strictly smaller than the sum of the volumes of the three-dimensional meshes in which it is mounted). This advantageously makes it possible to keep the fire containment envelope at a distance from the structural bars of the three-dimensional meshes to promote thermal insulation. In other words, a volume of air separates the fire containment envelope from the structural bars of the three-dimensional meshes to prevent heat transfer by conduction.

[0015] Preferably, the closed protective volume has a shape similar to the mesh volume, to facilitate the assembly of the fire containment envelope and to allow homogeneous thermal insulation between the three-dimensional meshes and the fire containment envelope over its entire periphery.

[0016] According to a preferred aspect of the invention, the fire containment envelope comprises a fabric, preferably comprising fibers resistant to high temperatures of the order of 1200°C, preferably ceramic and / or basalt fibers. The use of a fabric advantageously gives flexibility to the fire containment envelope. The ceramic and the basalt guarantee the robustness of the fire containment envelope. Preferably, the fire containment envelope is made of fabric.

[0017] Preferably, the containment envelope comprises a coating to improve the sealing of the wall and allow better management of the drainage of flammable products. According to a preferred aspect, the coating comprises a flexible resin resistant at least for the duration of the fire extinction to high temperatures, of the order of 1200°C, preferably silicone. According to another preferred aspect, the coating comprises a coating configured to consume endothermically in the presence of fire, that is to say by absorbing energy while burning.

[0018] According to a preferred aspect, the coating is metallized, so as to be reflective, in order to reduce the thermal emissivity of the fire containment envelope. This also makes it possible to improve the sealing of the fabric.

[0019] According to another preferred aspect, the coating comprises an intumescent paint, know how to swell under the effect of heat, in order to thermally protect the fire containment envelope.

[0020] Preferably, the fire containment envelope comprises a thermal insulator, preferably in the form of a layer fixed against the fabric, to form a fire barrier preventing the spread of fire, but also a thermal barrier, preventing the spread of high temperatures.

[0021] Preferably, the fire containment envelope is water-repellent, and preferably hydrophobic, in order to be impervious to fluids and in particular to flammable fluids to avoid the wick effect in the event of fire.

[0022] According to one aspect of the invention, the fire containment envelope is connected to the three-dimensional mesh(es) by a plurality of attachment devices ensuring the maintenance of the fire containment envelope on a lattice structure.

[0023] According to a preferred aspect, each fastening device comprises a fastening tab connected to the three-dimensional mesh by a closing element. This allows easy mounting of the fire containment envelope on the lattice structure, by wrapping each fastening device around a structural bar.

[0024] Preferably, the closing element is in the form of a button, a snap fastener, a zipper or a hook-and-loop fastener, easily mounted and dismounted manually by an operator.

[0025] According to another preferred aspect, the attachment device comprises a spring, preferably connected to the three-dimensional mesh by a closing element or a hook. Such a spring advantageously makes it possible to improve the absorption and transmission of forces between the lattice structure and the fire containment envelope. The hook is advantageously easily mounted and dismounted.

[0026] According to one aspect of the invention, each attachment device comprises a thermal break element configured to thermally insulate the three-dimensional mesh(es) of the fire containment envelope. Thus, the lattice structure is entirely insulated from the fire containment envelope, even at the attachment devices. Preferably, the thermal break element has a thickness less than or equal to twice the thickness of the fire containment envelope.

[0027] According to one aspect of the invention, the fire containment envelope comprises at least one closable opening allowing access to the interior of the fire containment envelope. This makes it possible to facilitate the maintenance of equipment housed in the fire containment envelope.

[0028] According to one aspect of the invention, the lattice structure comprises at least one thermal shield surrounding a plurality of three-dimensional meshes and configured to protect a thermally sensitive aircraft element located near the meshes three-dimensional. Such a heat shield advantageously forms a barrier preventing the transfer of high temperatures in a complementary manner to the fire containment envelope which primarily forms a fire barrier. The heat shield and the fire containment envelope together protect the thermally sensitive element from both the fire and the high temperatures it generates.

[0029] The invention also relates to an assembly of a lattice structure as described above and a thermally sensitive aircraft element located near three-dimensional meshes surrounded by a thermal screen. Preferably, the thermally sensitive element is in the form of an external aircraft skin.

[0030] Preferably, the heat shield comprises a fabric, preferably comprising fibers resistant to high temperatures of the order of 1200°C, preferably comprising ceramic and / or basalt fibers. The use of a fabric advantageously gives flexibility to the heat shield. The ceramic and the basalt guarantee the robustness of the heat shield.

[0031] Preferably, the heat shield comprises a coating to promote its resistance to fire and high temperatures.

[0032] According to a preferred aspect, the coating comprises a flexible resin resistant at least for the duration of the fire extinction to high temperatures, of the order of 1200°C, preferably silicone. According to another preferred aspect, the coating comprises a coating configured to consume endothermically in the presence of fire, that is to say by absorbing energy while burning.

[0033] According to a preferred aspect, the coating is metallized so as to be reflective, in order to reduce the thermal emissivity of the fire containment envelope. This also makes it possible to improve the sealing of the fabric.

[0034] According to another preferred aspect, the coating comprises an intumescent paint, namely configured to swell under the effect of heat, in order to thermally protect the fire containment envelope.

[0035] Preferably, the heat shield comprises a thermal insulator, preferably in the form of a layer fixed against the fabric, to form both a fire barrier, i.e. preventing the spread of fire, and a thermal barrier, i.e. preventing the spread of high temperatures.

[0036] Preferably, the heat shield is water-repellent, and preferably hydrophobic, in order to be impervious to fluids, and in particular to flammable fluids, to avoid the wick effect in the event of fire.

[0037] Preferably, the heat shield is connected to the three-dimensional mesh(es) by a plurality of attachment devices ensuring the heat shield is held on a lattice structure.

[0038] According to a preferred aspect, each attachment device comprises a tab connected to the three-dimensional mesh by a closing element. This allows easy mounting of the heat shield on the lattice structure, by wrapping each fastening device around a structural bar.

[0039] Preferably, the closure element is in the form of a button, a snap fastener, a zipper or a hook-and-loop fastener, easily mounted or dismounted.

[0040] Preferably, each attachment device comprises a thermal break element configured to thermally insulate the heat shield from the lattice structure. The thermal break element is preferably in the form of a spacer providing an air gap between the lattice structure and the heat shield. Thus, the lattice structure is completely insulated from the heat shield, even at the attachment devices. Preferably, a plurality of thermal bridges separate the fire containment envelope from the lattice structure.

[0041] According to a preferred aspect of the invention, the attachment devices of a fire containment envelope and a heat shield are mounted alternately on a three-dimensional mesh, in particular, on a given structural bar. This makes it possible to effectively maintain several elements on the same structural bar.

[0042] According to one aspect of the invention, the lattice structure comprises at least one auxiliary thermal protection mounted at the interface between two consecutive three-dimensional meshes so as to thermally insulate them from each other. Preferably, the auxiliary thermal protection is in the form of a local thermal screen. Preferably, the auxiliary thermal protection is mounted between at least two structural bars common to the two three-dimensional meshes.

[0043] According to one aspect of the invention, each three-dimensional mesh comprises a plurality of structural bars, at least one structural bar comprising a thermal protection sheath. This makes it possible to protect the lattice structure from heat in the event of a fire. Preferably, each structural bar comprises such a thermal protection sheath.

[0044] The invention also relates to an assembly of a lattice structure as described above and at least one aircraft equipment mounted in the fire containment envelope. Preferably, the aircraft equipment is in the form of one of the following elements: a turbogenerator, a gas turbine, an electric generator and a battery.

[0045] According to one aspect of the invention, the assembly comprises: • at least one support member structurally connecting the aircraft equipment to a three-dimensional mesh and extending through the fire containment envelope via a passage opening, and • at least one element for closing the passage opening mounted between the support member and the fire containment envelope so as to prevent the passage of fire through the passage opening.

[0046] Preferably, the support member is in the form of a connecting rod. Preferably, the closure element is in the form of a fire containment veil mounted on the support member by means of a ring. This allows the lattice structure to support and maintain the aircraft equipment without transmitting forces to the fire containment envelope. The closure element advantageously makes it possible to maintain a closed protective volume so that the fire containment envelope forms an overall fire barrier despite the passage of a support member. Preferably, several support members structurally connect the aircraft equipment to a three-dimensional mesh.

[0047] The invention also relates to an aircraft propulsion assembly comprising a lattice structure and a plurality of aircraft equipment, each equipment being mounted in a fire containment envelope.

[0048] The invention also relates to an aircraft comprising a lattice structure as described above, preferably in the form of an airship. The fire containment envelope advantageously makes it possible to have only a very small impact on the mass of the lattice structure, which is particularly advantageous for an airship. PRESENTATION OF FIGURES

[0049] The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0050] [Fig.l] is a schematic representation of an aircraft comprising a lattice structure according to one embodiment of the invention.

[0051] [Fig.2] is a schematic perspective representation of the lattice structure of [Fig.l],

[0052] [Fig.3] is a schematic representation in cross-sectional view of two three-dimensional meshes of the lattice structure of [Fig.2].

[0053] [Fig.4] is a schematic perspective representation of a structural bar of the lattice structure of [Fig.2] common to two meshes.

[0054] [Fig. 5] is a schematic representation of an aircraft comprising a lattice structure according to another embodiment of the invention.

[0055] [Fig.6] is a schematic representation in top view of two three-dimensional meshes of the lattice structure of [Fig.5].

[0056] [Fig.7] is a schematic representation in top view of two tridi meshes dimensions of an aircraft lattice structure according to another embodiment of the invention.

[0057] [Fig.8] is a schematic perspective representation of a structural bar of a lattice structure according to another embodiment of the invention.

[0058] [Fig.9] is a schematic representation in top view of a three-dimensional mesh of the lattice structure of [Fig.2] in which aircraft equipment is mounted.

[0059] [Fig. 10] is a schematic representation in profile view of a three-dimensional mesh of the lattice structure of [Fig. 2] with a closable opening in the closed position on the left and in the open position on the right.

[0060] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0061] With reference to [Fig.l], the invention relates to an aircraft comprising a lattice-type structure 1 in which one or more fire containment envelopes 2 are mounted to prevent the spread of a fire and protect the lattice structure 1 and its environment. As will be seen later, the fire containment envelopes 2 advantageously make it possible to form a fire barrier around aircraft equipment E mounted in the lattice structure 1, which are likely to heat up thermally and be the cause of a hypothetical fire outbreak. As will be seen later, this also makes it possible to protect one or more thermally sensitive aircraft elements.

[0062] In the example of [Fig. 1], the aircraft is in the form of an airship D for which a lattice structure 1 has the advantage of being light and robust, with in particular good absorption of forces. The invention could also be applied to a lattice structure 1 of any aircraft, such as an airplane, in particular in a turboprop propulsion system. By way of non-limiting examples, the aircraft equipment E mounted in the lattice structure 1 is in the form of one or more of the following elements: a gas turbine, an electric generator and batteries. A thermally sensitive element designates, by way of non-limiting example, the external skin P of the airship D located outside the lattice structure 1. Still in the example of [Fig.l], the lattice structure 1 shown is located at the level of the main body of the airship D but it goes without saying that it could extend into any area of ​​the aircraft, in particular at the level of the ailerons F in the case of an airship D. .

[0063] With reference to [Fig.2], we recall that a lattice structure 1 designates by definition a set of three-dimensional meshes 10 each defining a mesh volume VI and comprising structural bars 11 forming the edges of the mesh volume VI. Thus, a three-dimensional mesh 10 is free of a solid wall and the mesh volume V1 is open, which gives the lattice structure 1 its lightness. In addition, as illustrated in [Fig.2], two consecutive three-dimensional meshes 10 comprise one or more common structural bars 11. In this example, the lattice structure 1 comprises six three-dimensional meshes 10 of parallelepiped shape with twelve structural bars 11 each. Still in this example, the three-dimensional meshes 10 are distributed in two rows and three columns, so that a three-dimensional mesh 10 of the upper row shares its lower structural bars 11 with the three-dimensional mesh 10 aligned on the lower row.It goes without saying that the number, shape and distribution of the three-dimensional meshes 10 are arbitrary within the scope of the invention. In particular, a portion of the three-dimensional meshes 10 may not extend in alignment with the others.

[0064] In the example of Figures 1 and 2, a fire containment envelope 2 is mounted in each three-dimensional mesh 10 of the lattice structure 1 and a single piece of aircraft equipment E is mounted in each fire containment envelope 2. Alternatively, a fire containment envelope 2 could be mounted in several consecutive three-dimensional meshes 10. In addition, a fire containment envelope 2 could make it possible to collectively confine several pieces of aircraft equipment E. A fire containment envelope 2 could also be mounted in a three-dimensional mesh 10 free of aircraft equipment E.

[0065] As illustrated in Figures 2 and 3, each fire containment envelope 2 comprises walls 20 as well as attachment devices 21 to ensure that the envelope 2 is held on the mesh 10 in which it is mounted. With reference to [Fig.2], the walls 20 extend into the mesh volume VI and delimit a protection volume V2, which is preferably closed. The closed protection volume V2 is included in the mesh volume VI and preferably satisfies the following relationship: V2 < 0.75 * VI, and preferably: V2 > 0.35 * VI.

[0066] Also preferably, the closed protection volume V2 has a shape similar to the mesh volume VI, in this example parallelepiped, in particular cubic. Thus, as illustrated in Figures 2 and 3, the walls 20 of an envelope 2 extend at a distance from the structural bars 11 and the walls 20 of the neighboring fire containment envelopes 2. This advantageously makes it possible to limit the heat transfers between a fire containment envelope 2 and structural bars 11, as well as between several fire containment envelopes 2.

[0067] Still with reference to [Fig.2], the walls 20 of each fire containment envelope 2 are flexible, flexibility being defined here as the capacity to deform under the action of a bending force. In other words, each wall 20 behaves structurally like a membrane. A flexible structure envelope 2 is advantageously suitable for being mounted in a lattice structure 1 because it allows its force absorption and lightness properties to be retained. A flexible structure envelope 2 also facilitates mounting on the structural bars 11.

[0068] Preferably, the walls 20 comprise a fabric, preferably based on ceramic fibers (of the Nextel® type for example) and / or basalt (of the FILAVA® type for example) to ensure the fire resistance and structural strength of the fire containment envelope 2. The fabric preferably has a tight weave to ensure its robustness. Also preferably, the walls 20 comprise a layer of thermal insulation assembled against the fabric, by gluing or sewing for example. The thermal insulation is preferably in the form of quartz and / or Min-K® fibers. The walls 20 may in particular comprise a layer of thermal insulation sandwiched between two fabrics to reinforce its robustness and its effectiveness as a fire barrier. Still preferably, the walls 20 also comprise a surface coating.The surface coating is, for example, in the form of a reflective metallized deposit, a flexible resin such as silicone, a coating that reacts endothermically with fire, or a layer of intumescent paint, for example of the PyroTarp® type. Still preferably, the walls 20 also include a water-repellent and / or hydrophobic treatment so as to be impervious to fluids, in particular flammable fluids, in order to avoid a wick effect in the event of a fire.

[0069] With reference to [Fig. 3] and as described previously, each fire containment envelope 2 is mounted in a three-dimensional mesh 10 by means of fastening devices 21 each connecting the walls 20 to a structural bar 11. According to a preferred aspect, each fastening device 21 is in the form of a fastening tab, fixed locally on the walls 20 and attached to a structural bar 11. Preferably, the fastening tab is wrapped around the structural bar 11 and held by a closing element, such as a button, a snap button, a zipper or a hook-and-loop fastener. Preferably, the fastening tab is mounted with play in order to allow a certain elasticity. According to another preferred aspect, each fastening device 21 is in the form of a spring each connecting the walls 20 to a structural bar 11, and preferably, fixed to the structural bar 11 by a hook.Such attachment devices 21 advantageously allow easy mounting on the structural bars 11 and their elastic nature promotes the absorption of the forces to which the lattice structure 1 is subjected. It goes without saying that the attachment devices 21 could be in a form other than those mentioned above.

[0070] With reference to Figures 3 and 4 and as previously described, two tridi meshes consecutive structural bars 10a, 10b comprise at least one common structural bar 11, in this example the two structural bars 11 located in the center. The envelopes 2 of the two three-dimensional meshes 10a, 10b are connected to the two central structural bars 11. For this, as illustrated in [Fig.4], the attachment devices 21a of the mesh 10a and the attachment devices 21b of the mesh 10b are mounted alternately along the central structural bars 11. This advantageously allows for uniform and distributed support.

[0071] Preferably, as illustrated in [Fig. 3], each attachment device 21 comprises a thermal bridge breaking element 22 in order to avoid forming a thermal bridge between a fire containment envelope 2 and a three-dimensional mesh 10. The attachment devices 21 being the only elements ensuring contact between an envelope 2 and a mesh 10, this makes it possible to avoid any heat transfer by conduction. Preferably, the thermal bridge breaking element 22 has a low heat transmission cross-section and comprises, in particular, a thickness less than or equal to twice the thickness of the walls 20. More preferably, the thermal bridge breaking element 22 comprises a thermal insulating material.

[0072] Preferably, the closed protection volume V2 verifies: V2 = K.(A-(2*B+'V2*C))3, where A verifies VI = A3, B designates the diameter of a structural bar 11, C the length of a thermal break element 22 and K an adjustment coefficient between 0.8 and 1.

[0073] Figures 5 and 6 illustrate another embodiment of the invention in which the lattice structure 1 further comprises one or more heat shields 3 surrounding several three-dimensional meshes 10. This makes it possible to prevent the propagation of high temperatures in the lattice structure 1 during a fire, thus offering protection complementary to that offered by the fire containment envelopes 2. This allows overall protection at several levels in the lattice structure 1. Indeed, a fire containment envelope 2 forms a fire barrier while a heat shield 3 forms a thermal barrier against high temperatures which would succeed in passing through the fire containment envelope 2.

[0074] In the example of [Fig.5], the heat shield 3 surrounds all of the three-dimensional meshes 10 and advantageously protects the external skin P of the airship D, which is thermally sensitive. However, it goes without saying that a heat shield 3 could also surround part of the three-dimensional meshes 10 as illustrated in [Fig.6], in particular to protect other thermally sensitive elements. The heat shield 3 is positioned on the structural bars 11 to ensure optimal thermal conduction and thus dissipate any thermal calories captured by the meshes 10.

[0075] As illustrated in [Fig.6], the heat shield 3 comprises a flexible structure so as to be wrapped around the structural bars 11. Preferably, the heat shield 3 is in the form of a fabric, like the fire containment envelope 2, with or without a coating and / or layer of thermal insulation depending on the degree of thermal insulation required. Reference will be made to the description of the fire containment envelope 2 for the material and shape of the heat shield 3.

[0076] As illustrated in [Fig. 6], the heat shield 3 also comprises fastening devices 31 connected to the structural bars 11. In this example, two fastening devices 31 located at the upper left corner and at the lower right corner hold the heat shield 3. Preferably, the fastening devices 31 are in the form of fastening tabs as previously described for the fire containment envelope 2. Also preferably, the fastening devices 31 comprise a thermal break element in the form of a spacer, preferably toroidal in shape around the structural bar 11, providing a space between the heat shield 3 and the structural bar 11. Furthermore, preferably, the fastening devices 31 are mounted alternately with the fastening devices 21 on the structural bars 11 as illustrated in [Fig. 4].

[0077] [Fig.7] illustrates another embodiment of the invention in which the The lattice structure 1 further comprises one or more auxiliary thermal protections 4 located at the interface between two consecutive meshes 10. This advantageously promotes thermal insulation between two neighboring fire containment envelopes 2, particularly in an area particularly exposed to high temperatures. A single auxiliary thermal protection 4 mounted between the mesh 10a and the mesh 10b is shown in this example. The auxiliary thermal protection 4 is preferably in the form of a heat shield 3 wrapped around the two structural bars 1 common between the two meshes 10a, 10b and connected to them by attachment devices 4L. Reference will be made to the description of the fire containment envelope 2 for the material and shape of the auxiliary thermal protection 4 as well as its attachment devices 4L.

[0078] [Fig.8] illustrates another embodiment of the invention in which all or part of the structural bars 11 further comprises a heat protection sheath 5. Preferably, the sheath 5 is in the form of a thermal insulator. Such a sheath 5 provides thermal insulation as well as the thermal break element 22 of an envelope 2, a thermal screen 3 or an auxiliary thermal protection 4.

[0079] The mounting of aircraft equipment E, such as a gas turbine, an electric generator and batteries, inside a [Fig. 9] is described below with reference to [Fig. 9]. three-dimensional mesh 10 equipped with a fire containment envelope 2.

[0080] As illustrated in [Fig.9], the equipment E is held by means of support members 6 mounted on the mesh 10 and extending through a passage opening 24 formed in the fire containment envelope 2. More precisely, each support member 6 connects the equipment E to a structural bar 11, all of the support members 6 together ensuring the holding of the equipment E. In this example, two support members 6 are shown but it goes without saying that their number is arbitrary and depends on the equipment E. Such an assembly advantageously makes it possible to support the equipment E by a structural part, namely the mesh 10, the fire containment envelope 2 not allowing such support. Preferably, the support member 6 is in the form of a connecting rod.Also preferably, to keep a protection volume V2 closed, a closure element 7 is mounted between the support member 6 and the fire containment envelope 2 so as to prevent the passage of fire via the passage opening 24. The closure element 24 is preferably in the form of a veil, in this example in the form of a collar, which is fixed to the envelope 2 and mounted on the support member 6 by means of a ring 8. Preferably, the veil makes it possible to close the fire containment envelope 2 despite the presence of the passage opening 24.

[0081] According to one aspect of the invention, as illustrated in [Fig. 10], the fire containment envelope 2 comprises a closable opening 23 in order to allow access to the closed protective volume V2. This advantageously allows access to aircraft equipment E during maintenance, for example. Preferably, the closable opening 23 is in the form of an opening comprising a closing element, such as buttons, snap fasteners, a zipper or a self-gripping fastener. It is specified that the opening is in the closed position on the left of [Fig. 10] and in the open position on the right of [Fig. 10].

[0082] In addition, other openings could be provided, in particular to provide ventilation and to cool aircraft equipment E. The ventilation may be natural or forced, by means of inlet and / or outlet ducts mounted in the opening in particular. The ventilation could alternatively be provided by means of a looser weave locally in the fire containment envelope 2, with an intumescent paint coating to provide protection against fire. Ventilation openings and / or a looser weave could also be provided for the heat shield 3. A ventilation space is advantageously provided between the fire containment envelopes 2 and with the heat shield 3.

[0083] Also preferably, to facilitate maintenance, the heat shield 3 and / or the fire containment envelope 2 comprise a fabric sufficiently robust to support the mass of an operator walking on it.

[0084] Thus, thanks to the invention, an aircraft lattice structure 1 is effectively protected from the risk of propagation in the event of a possible fire outbreak. Fire containment envelopes 2 mounted on the lattice structure 1 in fact make it possible to form fire barriers and are arranged so as to delimit several closed protection volumes V2, in which the aircraft equipment E is positioned. Such segmentation of the lattice structure 1 advantageously makes it possible to confine the fire in a restricted area. Such envelopes 2 are also easy to mount on the structural bars 11, thanks to attachment lugs, and comprise a flexible structure so as not to penalize the lattice structure 11, which is hard-working and light.

[0085] The invention further proposes to install thermal screens 3 to protect the environment of the lattice structure 1, as well as auxiliary thermal protections 4, thermal break elements 22 and insulating sheaths 5 to reinforce the protection locally. The invention also proposes support members 6 for practical maintenance of the aircraft equipment E as well as closable openings 23 in the envelopes to facilitate maintenance.

Claims

Claims

1. Lattice structure (1) configured to form the structural part of an aircraft, in particular of an airship (D), said lattice structure (1) defining a plurality of three-dimensional meshes (10) and being characterized in that it comprises at least one fire containment envelope (2) positioned in a three-dimensional mesh (10) or in a plurality of consecutive three-dimensional meshes (10), the fire containment envelope (2) delimiting a closed protection volume (V2) strictly smaller than the volume (VI) of said three-dimensional mesh (10) or of said plurality of consecutive three-dimensional meshes (10) in which the fire containment envelope (2) is mounted.

2. A lattice structure (1) according to claim 1, wherein the fire containment envelope (2) is flexible so as to deform under the action of a bending force.

3. Lattice structure (1) according to one of claims 1 and 2, in which the fire containment envelope (2) is connected to the three-dimensional mesh(es) (10) by a plurality of attachment devices (21) ensuring the maintenance of the fire containment envelope (2), each attachment device (21) preferably comprising a thermal break element (22) configured to thermally insulate the three-dimensional mesh(es) (10) from the fire containment envelope (2).

4. Lattice structure (1) according to one of claims 1 to 3, wherein the fire containment envelope (2) comprises at least one closable opening (23) allowing access to the interior of the fire containment envelope (2).

5. Lattice structure (1) according to one of claims 1 to 4, comprising at least one thermal screen (3) surrounding a plurality of three-dimensional meshes (10) and configured to protect a thermally sensitive aircraft element located near the three-dimensional meshes (10).

6. Lattice structure (1) according to one of claims 1 to 5, comprising at least one auxiliary thermal protection (4) mounted at the interface between two consecutive three-dimensional meshes (10) so as to thermally insulate them from each other.

7. Lattice structure (1) according to one of claims 1 to 6, in which each three-dimensional mesh (10) comprises a plurality of structural bars (11), at least one structural bar (11) comprising a thermal protection sheath (5).

8. Assembly of a lattice structure (1) according to one of claims 1 to 7 and at least one aircraft equipment (E) mounted in the fire containment envelope (2).

9. Assembly according to claim 8, comprising: • at least one support member (6) structurally connecting the aircraft equipment (E) to a three-dimensional mesh (10) and extending through the fire containment envelope (2) via a passage opening (24), and • at least one element (7) for closing the passage opening (24) mounted between the support member (6) and the fire containment envelope (2) so as to prevent the passage of fire via the passage opening (24).

10. Aircraft comprising a lattice structure (1) according to one of claims 1 to 7, preferably in the form of an airship (D).

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