Frost shape, associated manufacturing process, and flight test method

Abstract

Frost shape, associated manufacturing process, and flight test method. This frost shape (10) comprises: - a support (40) having an attachment surface (42) for attaching to an external surface (12) of an aircraft (14) and an opposing support surface (44); - a rough layer (46) fixed to the support surface (44). The rough layer (46) comprises a plurality of porous grains (62) fixed to the support (40). Figure for the abbreviation: Figure 2

Description

Title of the invention: Frost shape, associated manufacturing process, and flight test method

[0001] The present invention relates to a form of frost, comprising:

[0002] - a support having an attachment surface intended to be fixed to an external surface of an aircraft and an opposing support surface;

[0003] - a rough layer fixed to the support surface.

[0004] Such a form of frost is intended in particular to be fixed on an external surface of an aircraft, for example at the level of a leading edge of a wing, a winglet, a horizontal stabilizer or a fin (or vertical stabilizer), or even a motor mast.

[0005] Such a shape is intended to simulate the presence of ice on the external surface of the aircraft, in particular to carry out aircraft certification tests, in order to verify the flight behavior of the aircraft in icing conditions.

[0006] The frost shape is intended, for example, to simulate a significant accretion of ice, in particular to evaluate the performance of the aircraft when it remains for forty-five minutes in an icing cloud (a "holding" or "holding" type shape).

[0007] Alternatively, the frost shape is intended to simulate a slight accretion, resulting from a brief passage through an icing system, or with a late start-up of the de-icing systems (shape of type "sand paper" or "glass paper") at take-off for example.

[0008] Verifying the behavior of an aircraft in icing conditions is a necessary step in aircraft certification. For this purpose, the ice pattern must be representative of the volume and surface irregularities of the ice that would have actually formed on the aircraft.

[0009] Thus, the frost shape must have adequate roughness, in order to offer aerodynamic behavior similar to that which would be encountered in the presence of a real block of ice.

[0010] To this end, it is known to produce a frost-like form by preparing a support block with the desired shape of the accretion, and then gluing a carpet with fabric loops onto the support block. The carpet is then treated by first manually burning the surface fabric loops, and then coated with a resin, in particular an epoxy resin, using a brush.

[0011] Such a manufacturing process makes it possible to obtain a frost shape of adequate roughness and conforming to document CS-25, Amendment 21, Appendices 2, A2.2.2, while exhibiting good mechanical strength, even after several flights.

[0012] This process, however, requires the implementation of a precise cutting of carpet strips to adapt to the shape of the support block, then a complicated placement and vacuum bonding of these strips onto the support block which immobilizes the aircraft part for a significant time.

[0013] In addition, the characteristics of commercially available carpets change over time, and some ranges of carpets that meet this particular use may no longer be available for a given time or permanently.

[0014] To overcome this problem, it is known for example from US 10,337,952, to develop by computer-aided design electronic models of frost shapes, and then to manufacture frost shapes corresponding to these models by additive or subtractive manufacturing, with suitable surface characteristics.

[0015] Such a manufacturing process is however tedious, since it requires precise modeling of the external surface of the frost shape to give it a random character.

[0016] Moreover, since the part produced is a single piece, it does not always exhibit a behavior representative of that of a layer of ice in formation.

[0017] One object of the invention is therefore to obtain a form of frost which is simple to manufacture and which nevertheless has characteristics very close to those of an ice accretion formed on an external surface of an aircraft, while being light and robust.

[0018] For this purpose, the invention relates to a form of frost of the aforementioned type, characterized in that the rough layer comprises a plurality of porous grains fixed on the support.

[0019] The frost shape according to the invention may comprise one or more of the following characteristics, taken individually or in any technically possible combination:

[0020] - the porous grains are convex and have a plurality of angular edges;

[0021] - the porous grains have a density of less than 650 kg / m3, in particular between 400 kg / m3 and 600 kg / m3, in particular between 460 kg / m3 and 580 kg / m3;

[0022] - the porous grains have a density of less than 500 kg / m3, in particular between 360 kg / m3 and 460 kg / m3, in particular between 400 kg / m3 and 440 kg / m3;

[0023] - the porous grains have a porosity greater than 80%, in particular including between 80% and 120%;

[0024] - the porous grains have a porosity greater than 90%, in particular including between 100% and 200%;

[0025] - the porous grains have a diameter of less than 5.0 mm and include in particular between 2.0 mm and 4.0 mm;

[0026] - the porous grains have a diameter of less than 2.9 mm and include in particular between 1.0 mm and 2.8 mm;

[0027] - the surface density on the porous grain support in the rough layer is in less than 10 grains per cm2, and is notably between 8 grains per cm2 and 10 grains per cm2;

[0028] - the roughness of the rough layer is between 3.1 mm and 4.0 mm, in particular between 3.3 mm and 3.6 mm, or the roughness of the rough layer is less than 2.9 mm, and is in particular between 1.0 mm and 2.8 mm, preferably between 1.0 mm and 1.8 mm or between 1.5 mm and 2.8 mm;

[0029] - the porous grains are formed from vegetable matter;

[0030] - the porous grains are formed from vegetable rachis, in particular from corn rachis;

[0031] - the rough layer has a protective polymer coating, applied on porous grains, in particular an epoxy polymer coating;

[0032] - the rough layer comprises an adhesive layer, in particular a layer cross-linked adhesive, the adhesive layer fixing the porous grains to the substrate;

[0033] - the support is a layer of substantially constant thickness, or in which the support consists of a block with reliefs of varying thickness.

[0034] The invention also relates to a method for manufacturing a form of frost, comprising the following steps:

[0035] - supply or manufacture of a support having an attachment surface intended to fix to an external surface of an aircraft and an opposite support surface;

[0036] - fixing a rough layer onto the support surface,

[0037] characterized in that the rough layer comprises a plurality of porous grains fixed on the support.

[0038] The method according to the invention may comprise one or more of the following features, taken individually or in any technically possible combination:

[0039] - the process comprises the application of a fluid base material intended to form a adhesive layer on the support surface, in particular a base material layer with a thickness between 0.5 mm and 1 mm, the deposition of porous grains on the base material and the solidification of the base material to form a solid adhesive layer fixing the porous grains to the support surface;

[0040] - subsequent to the deposition of the porous grains, the process comprises the application of preferably by spraying, of a protective polymer coating, in particular an epoxy polymer coating.

[0041] The invention also relates to a flight test method, comprising the following steps:

[0042] - fixing at least one form of frost as defined above on a surface external of an aircraft, in particular on at least one element of the aircraft chosen from a wing, a fin, a stabilizer, an aileron, a reactor support mast, and / or a telecommunications dome;

[0043] - flight of the aircraft carrying the or each form of frost.

[0044] The invention will be better understood upon reading the following description, given solely by way of example, and made with reference to the accompanying drawings, in which:

[0045] - [Fig. 1] [Fig. 1] is a top view of an aircraft on which ice forms according to the invention are installed;

[0046] - [Fig.2] [Fig.2] is a cross-sectional view of a "holding" type frost shape (or "holding"), installed on a leading edge;

[0047] - [Fig. 3] [Fig. 3] is a view analogous to [Fig. 2] of a frost-like form "sand paper" also installed on a leading edge;

[0048] - [Fig.4] The [Fig.4] is a front view of the frost shape of the [Fig.2];

[0049] - [Fig. 5] [Fig. 6] Figures 5 and 6 are photographs illustrating rachis grains vegetable matter, in particular corn cob, forming the rough layer applied to the frost shape in figures 2 and 3;

[0050] - [Fig.7] [Fig.7] is a flowchart illustrating the main steps of a process manufacturing the frost shape of [Fig.2] or [Fig.3].

[0051] Examples of frost shapes 10 according to the invention are illustrated in Figures 2 and 3.

[0052] A frost shape 10 according to the invention is intended to be fixed on an external surface 12 of an aircraft 14 schematically illustrated in [Fig. 1].

[0053] The external surface 12 on which a form of frost 10 is suitable to be fixed is, for example, a surface on which a significant accretion of frost is likely to form.

[0054] The external surface 12 is for example a surface located on a wing 16, in particular on a winglet 18 present at the end of the wing 16, a surface of a fin 20 forming a vertical plane or of a stabilizer 22 forming a horizontal plane.

[0055] Alternatively or in addition, the external surface 12 is a surface of a support mast 24 of a reactor 26, connecting the reactor 26 to a fuselage element 28, such as for example a rear part of the fuselage 28, or a lower part of a wing 16.

[0056] Also, the frost shape 10 can be installed on a surface of a leading edge 30 of a wing 16, of the fin 20 or of the stabilizer 22 to simulate limited frost accretion on these elements.

[0057] Frost form 10 of [Fig. 2] is intended to simulate significant frost accretion occurring over a substantial period of time, for example greater than 45 minutes in a freezing zone.

[0058] It comprises a support 40 having an attachment surface 42 of complementary shape to the external surface 12 on which the frost shape 10 is fixed, and an opposite support surface 44.

[0059] The frost form 10 further comprises a rough layer 46 applied to the support surface 44.

[0060] In the example shown in [Fig.2], the support 40 is formed from a block 48 with reliefs and a non-constant thickness.

[0061] The block 48 has for example a base region 50, defining the attachment surface 42, intended to be fixed to the external surface 12. It has at least one region 52 projecting from the base region 50, the projecting region 52 having in this example, in cross-section, an elongated and tapered shape.

[0062] The base region 50 has a curved shape in this example.

[0063] The block 48 is for example formed of a sandwich structure comprising an inner layer of glass fiber defining the attachment surface 42, a central foam machined into shape, defining the general shape of the block 48, and another layer of glass fiber, defining the support surface 44.

[0064] In this example, the attachment surface 42 is concave. To fix the frost shape 10 to the external surface 12, an adhesive layer is interposed between the external surface 12 and the attachment surface 42. Alternatively or in addition, at least one mechanical element, for example a row of fasteners (in particular rivets and / or screws), is used to hold the frost shape 10 to the external surface 12.

[0065] In the variant shown in [Fig.3], the support 40 is formed of a layer of substantially constant thickness, defining on one side the attachment surface 42, and on the other side, the support surface 44. This layer is for example formed of a film, in particular an aluminum adhesive tape film.

[0066] The layer forming the support 40 then has a shape complementary to the external surface 12 on which the frost shape 10 is fixed.

[0067] With reference to figures 2 to 5, the rough layer 46 comprises a layer 60 of porous grains 62, an adhesive layer 64, fixing the porous grains 62 of the layer 60 on the support surface 44, and advantageously, a protective coating 66, covering the porous grains 62 of the layer 60.

[0068] The layer of porous grains 60 is formed of porous grains 62, examples of which are illustrated in Figures 5 and 6. As illustrated in these figures, the porous grains 62 have a generally convex shape. The porous grains 62 have an external surface defining a plurality of randomly oriented angular edges 70, defining, for at least some of the porous grains 62, macroscopic cavities 72.

[0069] In the example of [Fig.2], for "holding" forms, the grains porous 62 preferably have a density less than 500 kg / m3, in particular between 360 kg / m3 and 460 kg / m3, especially between 400 kg / m3 and 440 kg / m3.

[0070] In the example of [Fig.3], for "sandpaper" forms, the porous grains 62 have a density of less than 650 kg / m3, in particular between 400 kg / m3 and 600 kg / m3, in particular between 460 kg / m3 and 580 kg / m3.

[0071] Preferably, the porous grains 62 are formed from plant material. In particular, the porous grains 62 are formed from plant cob, in particular from maize cob.

[0072] The corn cob is by definition the central rachis of the corn ear, on which the female spikelets are implanted, which develop into kernels during the maturation of the plant. The porous kernels 62 that result from it preferably originate from the woody girdle.

[0073] The porous grains 62 exhibit internal porosity within the material constituting them.

[0074] In the example of [Fig.2], for "holding" forms, the internal porosity of the porous grains 62 is for example greater than 70%, in particular greater than 80%, in particular between 80% and 120%.

[0075] In the example of [Fig.3], for "sandpaper" forms, the internal porosity of the porous grains 62 is for example greater than 70%, in particular greater than 90%, in particular between 100% and 200%.

[0076] This porosity is measured by the following method. A given mass of porous grains 62 (for example, 100 g) is placed in a container. The porous grains 62 have been previously dried at room temperature for at least 24 hours. The porous grains 62 are weighed to determine their dry mass DM before being immersed in a volume of water for one hour.

[0077] Following immersion in the volume of water, the porous grains 62 are extracted from the volume of water, and are filtered, before being weighed again to determine their wet mass MH.

[0078] The porosity is determined from the mass of water obtained by difference D between the wet mass MH and the dry mass MS after one hour, divided by the density of water.

[0079] The internal porosity of the porous grains 62 makes the rough layer 46 easy and robust to attach to the support 40, while offering a texture close to that of ice after accretion, and therefore aerodynamic characteristics similar to those of an ice layer.

[0080] In the example of [Fig. 2], for "holding" shapes, the porous grains 62 of the rough layer 46 are calibrated to exhibit a dimension maximum less than 5.0 mm, and generally between 2.0 mm and 4.0 mm, in particular between 2.8 mm and 3.8 mm.

[0081] In the example of [Fig.3], for "sandpaper" shapes, the porous grains 62 of the rough layer 46 are calibrated to have a maximum dimension of less than 5.0 mm, and generally between 2.0 mm and 4.0 mm, in particular between 1 mm and 2.8 mm.

[0082] As previously stated, the porous grains 62 are arranged to preferentially form a monolayer on the support surface 44, as seen in [Fig.4],

[0083] The surface density of porous grains 62 on the surface 44 is preferably less than 12 grains per cm2, and in particular between 8 grains per cm2 and 10 grains per cm2.

[0084] The roughness of the layer of grains 60 thus obtained for the frost shape 10 of the "holding" type of [Fig.2], is greater than 2.5 mm, and is in particular between 3.0 mm and 4.0 mm, in particular 3.3 mm and 3.6 mm.

[0085] On the contrary, for the frost form 10 of the "sandpaper" type of [Fig.3], the roughness of the layer of grains 60 is generally less than 2.9 mm, and is between 1.0 mm and 2.9 mm, preferably between 1.0 mm and 1.8 mm (corresponding to P16 sandpaper) or between 1.5 mm and 2.8 mm (corresponding to P12 sandpaper).

[0086] The surface roughness is measured by the following method: the grains are counted on a masked surface of 30 mm x 30 mm which is divided by 9 to obtain a number of grains per cm2, for example, directly on the frost shape or via a photograph, then the roughness is deduced by photogrammetry or digital microscopy.

[0087] The adhesive layer 64 is interposed between the support surface 44 and the porous grains 62. It has a thickness less than that of the porous grains 62, so that the porous grains 62 protrude outwards beyond the adhesive layer 64.

[0088] The adhesive layer 64 is, for example, made from an elastomeric adhesive. The elastomeric adhesive is in particular a two-component adhesive comprising a base material, preferably fluid, and an activator, intended to crosslink the base material to form the adhesive layer 64.

[0089] For example, the adhesive layer 64 comprises a base material made from a fluorinated elastomer, in particular a fluorocarbon elastomer (FKM) or a per-fluoroelastomer (FPM) obtained from vinylidene fluoride. Alternatively, the elastomer is a propylene tetrafluoroethylene copolymer (FEPM), or a fluorosilicone (FVMQ).

[0090] In other variants, the base material is a sulfide rubber, and the activator is based on a transition metal, such as manganese.

[0091] Preferably, the adhesive layer has a thickness of less than 2.0 mm, in particular between 0.1 mm and 1.5 mm, in particular between 0.4 mm and 1.2 mm.

[0092] The protective coating 66 is, for example, a coating made from a polymer, in particular an epoxy polymer. The polymer is deposited on the porous grains 62 outside the adhesive layer 64 to cover the porous grains 62.

[0093] It forms an advantageously transparent or tinted layer, for example in black, of a thickness less than the thickness of the porous grains 62, in particular less than 1 mm.

[0094] In the example of [Fig. 4], the frost shape 10 has an elongated form. For example, it has a length greater than 10 cm, particularly greater than 20 cm, depending on the external surface 12 to which it is applied. Several frost shapes 10 are preferably arranged on the aircraft 14 to cover one or more regions of the external surface 12.

[0095] A method for manufacturing a form of frost 10 according to the invention will now be described, with reference to [Fig.7].

[0096] Initially, in step 100, a support 40 having a shape corresponding to the external surface 12 is produced, or is provided. In the example of [Fig. 2], the support 40 is produced by draping a first layer of fiberglass defining the attachment surface 42, the shape of which is complementary to the external surface 12, then by positioning and bonding a preformed foam, for example, by machining, and finally by draping a second layer of fiberglass defining the support surface 44

[0097] In the example of [Fig.3], the support 40, formed for example of an aluminum adhesive tape film, is applied directly to a surface of the aircraft, in particular to the surface of the aircraft leading edge.

[0098] Next, in step 102, the base material intended to form the adhesive layer 64 is deposited in fluid form on the support surface 44, the activator having been previously mixed with the base material.

[0099] The base material containing the activator is then spread onto the substrate surface 44, for example using a brush to create a local thickness of less than 2.0 mm, and in particular between 0.4 mm and 1.2 mm. Optionally, a mask is first placed around the substrate surface 44 to precisely delimit the area receiving the adhesive layer 64.

[0100] Then, in step 104, the porous grains 62 are deposited onto the forming adhesive layer 64, preferably in the form of a single layer. The porous grains 62 are deposited by gravity, avoiding manual movement on the adhesive layer 64, in order to limit the formation of agglomerates of porous grains 62 resulting in clumps of grains.

[0101] The layer 60 of porous grains 62 is then inspected to add porous grains 62 in areas where they are missing, or to remove any overlapping porous grains 62. Optionally, overpressure is applied to the porous grains 62 to anchor them in the adhesive layer 64.

[0102] Advantageously, the liquid material intended to form the adhesive layer 64 partially penetrates the internal porosity of the porous grains 62, promoting their fixation on the support surface 44.

[0103] In step 106, the adhesive layer 64 is crosslinked for at least one hour, for example for more than ten hours, in particular between fifteen and twenty hours. It solidifies and holds the porous grains 62 in position on the support surface 44.

[0104] Then, the protective coating 66 is formed in step 108. A precursor material of the coating 66 is preferably applied in liquid form to the layer of porous grains 60, before solidifying around the porous grains 62.

[0105] Advantageously, several passes are used to apply more than two layers of precursor material of coating 66, for example more than five layers of precursor material of coating 66, in particular between five and ten layers of precursor material of coating 66.

[0106] Preferably, a delay of at least 4 minutes, in particular between 5 minutes and 15 minutes, is left between each application of a layer of precursor material of the coating 66, to allow time for the newly deposited material to polymerize around and / or on the surface of the porous grains 62.

[0107] Preferably, each layer of precursor material is applied using a sprayer, for example in the form of a gun, by pressurizing the precursor material of the coating 66 and passing it through a nozzle preferably having a size of less than 5 mm, in particular between 2 mm and 4 mm.

[0108] After drying of the protective coating 66 for a period of more than 3 h, in particular between 6 h and 9 h, the frost form 10 according to the invention is ready to be used.

[0109] A method for carrying out a flight test will now be described. Initially, one or more forms of frost 10 are provided and are applied to the external surface 12 of the aircraft 14 in selected regions.

[0110] The attachment of the attachment surface 42 to the external surface 12 is for example achieved by gluing or by mechanical assembly using at least one mechanical element as described above.

[0111] Having done this, the aircraft 14 performs at least one test flight equipped with or of each form of frost 10.

[0112] Then, once the test flight(s) have been carried out, each frost form 10 is detached of the external surface 12 in the case where they are removable.

[0113] When the frost shape 10 is fixed on an external part of the aircraft 10, for example on a slat, the external part is removed and replaced with a standard part for reuse on another flight, or on another aircraft 14 of the same type.

[0114] The frost shapes 10 according to the invention, thanks to the presence of the porous grains 62 of the layer 60, are light and reproduce in a suitable manner the surface roughness of an ice accretion on the external surface 12 of an aircraft 14.

[0115] Fixing the porous grains 62 to the support surface 44 of the frost shape 10 is very simple to implement, while being robust, thanks to the internal porosity of the grains 62 capable of absorbing fluid adhesive.

[0116] Similarly, the protective coating 66 of the porous grains 62 is applied simply and efficiently to the surface of the porous grains 62, for example by spraying, thanks to the porosity of the porous grains 62 which absorb the precursor material of the coating 66.

[0117] Furthermore, the production of the rough layer 46 by fixing the porous grains 62 avoids the need for vacuum bonding which is necessary in the case of a carpet.

[0118] This simplifies the manufacture of the frost shape 10, even for areas with complex shapes such as masts, satellite domes, or winglets. Furthermore, the frost shape 10 is very easily repairable if it has been damaged.

[0119] The use of porous grains 62 of vegetable origin, in particular porous grains 62 of corn cob, ensures adequate porosity and roughness for carrying out the tests, while offering a significant reduction in the frost shape 10. This reduction is beneficial to its handling, and avoids disturbing the aircraft's center of gravity or unnecessarily weighing down the aircraft 14 with a degraded aerodynamic configuration.

[0120] The porous grains 62 in corn cob are further convex, while exhibiting edges, and are easily calibrated in size by sieving. These porous grains 62 representatively reproduce the aerodynamic surface state of an ice accretion

[0121] Frost shapes 10 of the "hold" type or of the "sandpaper" type can be made interchangeably according to the invention.

Claims

Demands

1. Frost shape (10), comprising: - a support (40) having an attachment surface (42) intended to be attached to an external surface (12) of an aircraft (14) and an opposite support surface (44); - a rough layer (46) fixed on the support surface (44); characterized in that the rough layer (46) comprises a plurality of porous grains (62) fixed on the support (40) and in that the porous grains (62) are convex and have a plurality of angular edges (70).

2. Frost shape (10) according to claim 1, wherein the porous grains (62) have a density of less than 650 kg / m3, in particular between 400 kg / m3 and 600 kg / m3, in particular between 460 kg / m3 and 580 kg / m3.

3. Frost shape (10) according to claim 2, wherein the porous grains (62) have a density of less than 500 kg / m3, in particular between 360 kg / m3 and 460 kg / m3, in particular between 400 kg / m3 and 440 kg / m3.

4. Frost shape (10) according to any one of the preceding claims, wherein the porous grains (62) have a porosity greater than 80%, in particular between 80% and 120%.

5. Frost shape (10) according to claim 4, wherein the porous grains (62) have a porosity greater than 90% in particular between 100% and 200%.

6. Frost shape (10) according to any one of the preceding claims, wherein the porous grains (62) have a caliber of less than 5.0 mm and in particular between 2.0 mm and 4.0 mm.

7. Frost shape (10) according to claim 6, wherein the porous grains (62) have a caliber of less than 2.9 mm and in particular between 1.0 mm and 2.8 mm.

8. Frost shape (10) according to any one of the preceding claims, wherein the surface density on the support (40) of porous grains (62) in the rough layer (46) is less than 10 grains per cm2, and is in particular between 8 grains per cm2 and 10 grains per cm2.

9. Frost shape (10) according to any one of the preceding claims, wherein the roughness of the rough layer (46) is between 3.1 mm and 4.0 mm, in particular between 3.3 mm and 3.6 mm, or in which the roughness of the rough layer (46) is less than 2.9 mm, and is in particular between 1.0 mm and 2.8 mm, preferably between 1.0 mm and 1.8 mm or between 1.5 mm and 2.8 mm.

10. Frost form (10) according to any one of the preceding claims, wherein the porous grains (62) are formed of vegetable matter.

11. Frost form (10) according to claim 10, wherein the porous grains (62) are formed from vegetable rachis, in particular from maize rachis.

12. Frost shape (10) according to any one of the preceding claims, wherein the rough layer (46) comprises a protective polymer coating (66) applied to the porous grains (62), in particular an epoxy polymer coating.

13. Frost shape (10) according to any one of the preceding claims, wherein the rough layer (46) comprises an adhesive layer (64), in particular a cross-linked adhesive layer, the adhesive layer (64) fixing the porous grains (62) to the support (40).

14. Frost shape (10) according to any one of the preceding claims, wherein the support (40) is a layer of substantially constant thickness, or wherein the support (40) comprises a block (48) having reliefs of variable thickness.

15. A method for manufacturing a frost form (10), comprising the following steps: - supplying or manufacturing a support (40) having an attachment surface (42) intended to be attached to an external surface (12) of an aircraft (14) and an opposing support surface (44); - fixing a rough layer (46) onto the support surface (44), characterized in that the rough layer (46) comprises a plurality of porous grains (62) fixed onto the support (40).

16. A method according to claim 15, comprising the application of a fluid base material intended to form an adhesive layer (64) on the support surface (44), in particular a base material layer of thickness between 0.5 mm and 1 mm, the deposition of porous grains (62) on the base material and the solidification of the base material to form a solid adhesive layer (64) fixing the porous grains (62) on the support surface (44).

17. A method according to claim 16, wherein, subsequent to deposit of porous grains (62), the process includes the application, preferably by spraying, of a protective coating (66) made of polymer, in particular an epoxy polymer coating.

18. Flight test method, comprising the following steps: - fixing at least one frost shape (10) according to any one of claims 1 to 14 on an external surface (12) of an aircraft (14), in particular on at least one element of the aircraft (14) selected from a wing (16), a fin (20), a stabilizer (22), an aileron (18), a support mast (24) of a jet engine (26), and / or a telecommunications dome; - flight of the aircraft (14) carrying the frost shape or each of the frost shapes (10).

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