Method and system for optimizing the maintenance of an aircraft structure against corrosion.

Abstract

- Method and system for optimizing the maintenance of an aircraft structure against corrosion. - The method comprises a step (E1) of collecting corrosion incidents (6) on a plurality of aircraft (AC), a step (E3) of determining the zones (71, 73) and the corrosion incident rates in each of the zones (71, 73), a step (E4) of determining risk zones (19), a step (E5) of determining a corrosion depth (Eb), a step (E6) of determining a corrosion rate, and a step (E7) of determining a proposed inspection frequency for each of the risk zones (19) based on its corrosion rate and a predetermined limit depth (Ec) of each of the risk zones (19). The method makes it possible to obtain a more precise inspection frequency proposal adapted to the different parts of the aircraft structure. Figure for the abstract: Fig. 1

Description

Title of the invention: Method and system for optimizing maintenance of an aircraft structure against corrosion. technical field

[0001] The present invention relates to a method for optimizing the maintenance of an aircraft structure, for example of an aircraft fuselage or wings, against corrosion. State of the art

[0002] Currently, during the manufacture of an aircraft, the parts of the aircraft structure, and in particular the parts of the wings or fuselage of said aircraft, undergo different levels of corrosion protection. This protection depends, among other things, on the location and function of said parts.

[0003] For example, fuselage parts located on the lower part of the aircraft generally require greater corrosion protection than parts located on the upper part of the aircraft. Similarly, movable fuselage parts, such as doors or the landing gear bay, generally require greater corrosion protection than fixed fuselage parts.

[0004] There are currently different levels of protection against corrosion, namely, in increasing order from least important to most important: level 1, level 2, level 3 and level 4.

[0005] Corrosion protection is established at the level of the individual part and at the assembly level.

[0006] The protection performed at the elementary part level comprises 4 levels:

[0007] Level 1 includes a surface treatment, such as tribo-finishing, cadmium plating, anodizing, galvanizing, etc. Level 1 also includes a sealant-free installation.

[0008] Level 2 includes a surface treatment and a coat of paint. Level 2 also includes an installation with sealant in the interposition between two parts.

[0009] Level 3 includes a surface treatment and two coats of paint. Level 3 also includes an installation with sealant at the interposition between two parts, as well as a bead of sealant around the entire perimeter.

[0010] Level 4 includes a surface treatment, two coats of paint, and a water-repellent treatment. Level 4 also includes an installation with sealant between two parts, as well as a bead of sealant covering the edges.

[0011] Furthermore, the fuselage parts are classified into different categories depending on of their need for protection against corrosion: category 1, category 2, category 3, category 4 and category 5.

[0012] Category 1 includes parts and assemblies that require little protection against corrosion (level 1 and 2).

[0013] Category 2 includes parts that require level 2 protection and assemblies that require level 3 protection.

[0014] Categories 3 and 4 include parts and assemblies that require level 3 protection.

[0015] Category 5 includes parts and assemblies that require level 3 or 4 protection.

[0016] There is currently a two-dimensional map of the aircraft indicating the corrosion areas and the respective protection categories of each of the fuselage parts, as well as the inspection frequencies of the different parts ([Fig.3]).

[0017] However, this mapping is fixed and not necessarily optimal. Indeed, the corrosion rate of an aircraft can differ depending on its use and the climate in which it is usually operated. The current fixed mapping is therefore not entirely satisfactory. Description of the invention

[0018] The present invention aims to overcome the aforementioned drawbacks, and in particular to take into account environmental constraints for the adaptation of maintenance inspection intervals.

[0019] For this purpose, it relates to a method for optimizing the maintenance of an aircraft structure against corrosion, the aircraft structure comprising at least one aircraft structural part.

[0020] According to the invention, the process comprises the following steps: - a collection step implemented by a collection unit to collect a plurality of corrosion incidents on a plurality of aircraft, each corrosion incident comprising a location of the corrosion incident, a remaining thickness of the aircraft structural part at the location of the corrosion incident, and an age of the aircraft for which the corrosion incident was collected, - a reporting step implemented by a reporting unit to report the plurality of corrosion incidents collected onto a digital twin virtually defining an aircraft structure comprising at least one aircraft structural part, - a first determination step implemented by a first determination unit to determine corrosion incident zones and rates in each zone for each part of the aircraft structure of the digital twin, the corrosion incident rate of each zone being equal to a ratio between number of corrosion incidents collected in each of the zones and number of aircraft from the plurality of aircraft on which the plurality of corrosion incidents were collected, - a second determination stage implemented by a second determination unit to identify risk zones, the risk zones corresponding to areas where the corrosion incident rate is greater than or equal to a predetermined corrosion incident rate, - a third determination step implemented by a third determination unit to determine a corrosion depth for each part of the aircraft structure located in the risk zones based on the remaining thickness, - a fourth determination step implemented by a fourth determination unit to determine a corrosion rate for each of the risk zones based on the corrosion depth and the age of the aircraft for each part of the aircraft structure containing a risk zone, - a fifth determination step implemented by a fifth determination unit to determine a proposed inspection frequency for each of the risk zones based on its corrosion rate and a predetermined depth limit for each of the risk zones, - a transmission step implemented by a transmission unit to transmit to a user device the proposed inspection frequency for each of the risk zones.

[0021] Thus, by determining areas on aircraft structure parts where there are high rates of corrosion incidents, it is possible to determine more precisely and appropriately the necessary inspection frequencies before excessive corrosion occurs.

[0022] The proposed inspection frequency corresponds to a correction of the inspection frequency initially defined for maintenance. The inspection frequency initially defined for maintenance can therefore be adjusted based on the number of corrosion incidents collected, when it is determined that the inspection intervals are not optimally defined.

[0023] The aircraft maintenance plan can thus be optimized, allowing the frequency of inspections of risk areas to be reduced, and therefore limiting aircraft downtime and reducing maintenance tasks to be performed.

[0024] Advantageously, the first determination step comprises the following substeps: - a first cutting sub-step implemented by a first cutting sub-unit to cut each part of the aircraft structure of the digital twin according to a mesh of zones comprising areas of predetermined size, - a first calculation sub-step implemented by a first calculation sub-unit to calculate a corrosion incident rate for each of the zones of the zone mesh.

[0025] Furthermore, the first determination step also includes the following sub-steps implemented if at least two zones of the zone mesh of a part of the aircraft structure exhibit a corrosion incident rate difference greater than a predetermined difference: - a second cutting sub-step implemented by a second cutting sub-unit to cut the aircraft structure part according to a sub-mesh of zones comprising zones of predetermined size smaller than the predetermined size of the zones in the zone mesh, - a second calculation sub-step implemented by a second calculation sub-unit to calculate a corrosion incident rate for each of the zones of the zone sub-mesh.

[0026] Furthermore, the corrosion depth of an aircraft structure part determined in the third determination step is equal to a difference between a nominal thickness of the aircraft structure part and the remaining thickness of the aircraft structure part.

[0027] In addition, the corrosion rate of each of the risk zones determined in the fourth determination step is equal to a ratio between the average corrosion depth in each of the risk zones and a time at the end of which this corrosion depth is reached.

[0028] Furthermore, the fifth determination step comprises the following sub-steps: - a third calculation sub-step implemented by a third calculation sub-unit to calculate the inspection frequency required for each of the risk zones so that the corrosion depth reaches the predetermined limit depth, - a determination sub-step implemented by a determination sub-unit to determine the proposed inspection frequency, the proposed inspection frequency being strictly less than the inspection frequency required for each of the risk areas for the corrosion depth to reach the predetermined limit depth.

[0029] The invention also relates to a system for optimizing the maintenance of an aircraft structure against corrosion, the aircraft structure comprising at least one part of the aircraft structure.

[0030] According to the invention, the optimization system comprises: - a collection unit to collect a plurality of corrosion incidents on a plurality of aircraft, each corrosion incident including a position of the corrosion incident, the remaining thickness of the aircraft structural component at the location of the corrosion incident, and the age of the aircraft for which the corrosion incident was recorded. - a reporting unit to report the plurality of corrosion incidents collected onto a digital twin virtually defining the aircraft structure comprising at least one part of the aircraft structure, - a first unit of determination to determine corrosion incident zones and rates in each zone for each aircraft structural part of the digital twin, the corrosion incident rate of each zone being equal to a ratio between the number of corrosion incidents collected in each zone and the number of aircraft in the plurality of aircraft on which the plurality of corrosion incidents were collected, - a second unit of determination to identify risk zones, with risk zones corresponding to areas where the corrosion incident rate is greater than or equal to a predetermined corrosion incident rate, - a third unit of determination to determine the corrosion depth for each part of the aircraft structure located in each of the risk zones, based on the remaining thickness, - a fourth determination unit to determine a corrosion rate for each of the risk zones based on the corrosion depth and the age of the aircraft for each part of the aircraft structure containing a risk zone, - a fifth determination unit to determine a proposed inspection frequency for each of the risk zones based on its corrosion rate and a predetermined depth limit for each of the risk zones, - a transmission unit to transmit to a user device the proposed inspection frequency for each of the risk zones.

[0031] Advantageously, the first unit of determination comprises: - a first cutting subunit to cut each part of the aircraft structure of the digital twin according to a mesh of zones comprising areas of predetermined size, - a first calculation subunit to calculate a corrosion incident rate for each of the zones in the zone mesh.

[0032] Furthermore, the first unit of determination also comprises: - a second cutting subunit to cut the aircraft structure part according to a sub-mesh of zones comprising areas of predetermined size smaller than the predetermined size of the zones in the zone mesh, - a second calculation subunit to calculate a corrosion incident rate for each of the zones of the zone sub-mesh.

[0033] Furthermore, the fifth unit of determination comprises: - a third calculation subunit to calculate the inspection frequency required for each of the risk zones so that the corrosion depth reaches the predetermined limit depth, - a determination subunit to determine the proposed inspection frequency, the proposed inspection frequency being strictly less than the inspection frequency required for each of the risk areas for the corrosion depth to reach the predetermined limit depth. Brief description of the figures

[0034] The accompanying figures will clearly illustrate how the invention can be implemented. In these figures, identical reference numerals designate similar elements.

[0035] Fig. 1 schematically represents the optimization process.

[0036] Fig. 2 schematically represents a cross-section of a fuselage part having a nominal thickness.

[0037] Fig. 3 represents a fixed two-dimensional map of an aircraft showing fuselage parts to which protection categories have been assigned.

[0038] Fig. 4 represents part of an aircraft digital twin on which collected corrosion incidents have been reported.

[0039] Fig. 5 represents two curves showing the evolution of the corrosion depth of a fuselage part as a function of time.

[0040] Figure 6 schematically represents the optimization system.

[0041] Fig. 7 represents a profile view of one aircraft from the plurality of aircraft on which corrosion incidents are collected. Detailed description

[0042] The optimization process is schematically represented in [Fig.1].

[0043] The optimization method is intended to optimize the maintenance of an aircraft structure, or part of an aircraft, including the wings and the aircraft structure, against corrosion. The aircraft structure is defined here as the mechanical structure of an AC aircraft, also called the “airframe” of the AC aircraft. In the following description, the method will be described for a fuselage 1, but it is of course applicable to other elements of the aircraft structure, such as the wings. The fuselage 1 comprises at least one fuselage part 4.

[0044] The optimization process comprises the following steps: - a collection step El implemented by a COL 10 collection unit (COL for "collecting unit" in English), - a reporting step E2 implemented by a reporting unit REP 12 (REP for (reporting unit in English), - a first determination step E3 implemented by a first determination unit DET1 13 (DET for "determining unit" in English), - a second determination step E4 implemented by a second determination unit DET2 14, - a third determination step E5 implemented by a third determination unit DET3 15, - a fourth determination step E6 implemented by a fourth determination unit DET4 16, - a fifth determination step E7 implemented by a fifth determination unit DET5 17, - a transmission step E8 implemented by a TRANS 18 transmission unit (TRANS for "transmitting unit" in English).

[0045] The collection step El is intended to be implemented to collect a plurality of corrosion incidents 6 on a plurality of AC aircraft such as the one shown in [Fig. 7]. Each corrosion incident 6 includes parameters such as the location of the corrosion incident 6, the remaining thickness Ea of the fuselage part 4 at the location of the corrosion incident 6, and the age of the AC aircraft for which the corrosion incident 6 was collected. For example, in this collection step El, the plurality of corrosion incidents are collected and stored in a database DB 11 (DB for "database"). The collection unit 10 can be a data entry device, such as a keyboard. The database 11 can thus group the in-service returns of the plurality of AC aircraft.

[0046] A "corrosion incident" is defined as a region or area of ​​the fuselage 1 that exhibits corrosion. The corrosion incident includes at least the location on the fuselage 1 of the region exhibiting corrosion. This location may correspond to the location of a corroded surface.

[0047] The E2 transfer step is intended to be implemented to transfer the plurality of corrosion incidents 6 collected onto a digital twin 2 simulating a fuselage 1 comprising at least one fuselage part 4. Thus, each of the corrosion incidents 6 is transferred onto the digital twin 2 at its respective position ([Fig. 4]). [Fig. 4] represents a fuselage part 4 of the digital twin 2 or a portion of the fuselage 1 of the digital twin 2.

[0048] The digital twin 2 corresponds to a three-dimensional model of an AC aircraft. This model can be implemented by a processor of a computer, such as a computer.

[0049] The first determination step E3 is intended to be implemented to determine zones 71, 73 and corrosion incident rates in each of said zones zones 71,73 for each part 4 of the fuselage of the digital twin 2. The corrosion incident rate of each of the zones 71, 73 is equal to a ratio between a number of corrosion incidents 6 collected in each of the zones 71, 73 of the AC aircraft plurality and a number of AC aircraft equal to the number of aircraft in the AC aircraft plurality.

[0050] The first determination step E3 may include the following substeps: - a first sub-step E31 of cutting implemented by a first cutting sub-unit CUTI 131 (CUT for "cutting unit" in English), - a first sub-step E32 of calculation implemented by a first computing sub-unit COMP1 132 (COMP for "computing unit" in English). The first E31 cutting sub-step is intended to be implemented to cut each fuselage part 4 of the digital twin 2 according to a mesh of zones 70 comprising zones 71 of predetermined size.

[0051] The mesh of zones 70 can correspond to a mesh having square-shaped cells or any other shape suitable for part 4. These cells correspond to zones 71.

[0052] Figure 4 represents a mesh of zones 70 in solid lines. This mesh of zones 70 defines the zones 71. The predetermined size of the zones 71 depends on the desired accuracy for determining the corrosion incident rates for each of the zones 71. The zones 71 of the mesh of zones 70 may be smaller than the size of a fuselage part 4.

[0053] The first calculation substep E32 is intended to be implemented to calculate a corrosion incident rate for each of the zones 71 of the zone mesh 70.

[0054] Furthermore, the first determination step E3 may also include the following sub-steps: - a second cutting sub-step E33 implemented by a second cutting sub-unit CUT2 133, - a second calculation sub-step E34 implemented by a second calculation sub-unit COMP2 134.

[0055] Substeps E33 and E34 are implemented if at least two zones 71 of the zone mesh 70 of a fuselage part 4 exhibit a corrosion incident rate difference greater than a predetermined difference.

[0056] The second substep E33 is intended to be implemented to cut the fuselage part 4 according to a sub-mesh of zones 72 comprising zones 73 of predetermined size less than the predetermined size of the zones 71 of the mesh of zones 70.

[0057] For example, a zone 71 of the zone mesh 70 is cut out by a sub-mesh of zones 72 comprising zones 73. As with the zone mesh 70, the sub- zone mesh 72 can correspond to a mesh with square-shaped cells or any other shape suitable for part 4 or for the cells of zone mesh 70. These cells of the zone sub-mesh 72 correspond to zones 73.

[0058] For example, [Fig.4] shows in dotted lines, a sub-mesh of zones 72 comprising zones 73 having a size less than the size of zones 71.

[0059] The second calculation substep E34 is intended to be implemented to calculate a corrosion incident rate for each of the zones 73 of the zone sub-mesh 72.

[0060] The second determination step E4 is intended to be implemented to determine risk zones 19. Risk zones 19 correspond to zones 71, 73 whose corrosion incident rate is greater than or equal to a predetermined corrosion incident rate ([Fig.4]).

[0061] The third determination step E5 is intended to be implemented to determine a corrosion depth Eb for each fuselage part 4 located in the risk areas 19 from the remaining thickness Ea ([Fig.2]).

[0062] The corrosion depth Eb of a fuselage part 4 can be equal to a difference between a nominal thickness E of the fuselage part 4 and the remaining thickness Ea of the fuselage part 4.

[0063] The fourth determination step E6 is intended to be implemented to determine a corrosion rate for each of the risk zones 19 from the corrosion depth Eb and the age of the aircraft for each fuselage part 4 having a risk zone 19.

[0064] The corrosion rate of each of the risk zones 19 can be equal to a ratio between the average corrosion depth Eb in each of the risk zones 19 and a time at the end of which this corrosion depth Eb is reached.

[0065] According to one embodiment, the corrosion rate determined in the fourth E6 determination step can be modulated by at least one parameter dependent on the climate or climatic conditions in which the aircraft are likely to fly.

[0066] The fifth determination step E7 is intended to be implemented to determine a proposed inspection frequency for each of the risk zones 19 based on its corrosion rate and a predetermined limit depth Ec for each of the risk zones 19. Each fuselage part 4 may have a different predetermined limit depth Ec than the other fuselage parts 4. This predetermined limit depth Ec may depend on a limit thickness of the part 4 in question or on a minimum allowable thickness for corrosion of the part 4 in question.

[0067] The fifth determination step E7 may include the following substeps: - a third calculation substep E71 implemented by a third subunit COMP3 171 calculation, - a determination sub-step E72 implemented by a determination sub-unit DET 172.

[0068] The third calculation substep E71 is intended to be implemented to calculate the inspection frequency required for each of the risk zones 19 so that the corrosion depth Eb reaches the predetermined limit depth Ec.

[0069] The determination substep E72 is intended to be implemented to determine the proposed inspection frequency. The proposed inspection frequency is strictly less than the inspection frequency required for each of the risk zones 19 for the corrosion depth Ea to reach the predetermined limit depth Ec.

[0070] The transmission step E8 is intended to be implemented to transmit to a user device USER 20 (USER for "user device" in English) the proposed inspection frequency for each of the risk zones 19.

[0071] The user device 20 may include a display device for displaying the digital twin 2 accompanied by the proposed inspection frequency for each of the risk zones 19.

[0072] By way of example, [Fig. 5] shows two curves, Vcl and Vc2, representing the evolution of the corrosion depth Eb (for example, in millimeters) as a function of time t (for example, in years). The line Ec represents the predetermined limit depth. A different evolution can be observed between the two curves, Vcl and Vc2. This difference in evolution corresponds to a modulation of the corrosion rate by the parameter(s) dependent on the climate or climatic conditions in which the aircraft are likely to fly. It can also be noted that a proposed inspection frequency higher than t0 may be too high to prevent the predetermined limit depth from being reached. Indeed, at t0, the curves converge at a point 5 above the predetermined limit depth Ec.Furthermore, depending on the evolution of the corrosion depth Eb, inspection frequencies may differ according to the modulation parameter(s) dependent on the climate or climatic conditions in which the aircraft are likely to fly. For example, if the corrosion depth Eb evolves according to the Vcl curve, a higher inspection frequency may be proposed at t1 than if the corrosion depth Eb evolves according to the Vc2 curve, which is at t2.

[0073] The invention also relates to an optimization system S for the maintenance of an aircraft fuselage 1 against corrosion ([Fig. 6]). The system S can be implemented by a processor of a computer, such as a computer.

[0074] The optimization system S comprises: - the collection unit 10 to collect a plurality of corrosion incidents 6 on a plurality of AC aircraft, - the reporting unit 12 for reporting the plurality of corrosion incidents 6 collected on the digital twin 2 simulating a fuselage comprising at least one fuselage part 4, - the first determination unit 13 to determine corrosion incident zones and rates in each of the zones 71, 73 for each part 4 of the fuselage of the digital twin 2, - the second unit of determination for identifying risk zones 19, - the third determination unit 15 to determine a corrosion depth Eb for each fuselage part 4 located in each of the risk zones 19 from the remaining thickness Ea, - the fourth determination unit 16 to determine a corrosion rate for each of the risk zones 19 from the corrosion depth Eb and the age of the aircraft AC for each fuselage part 4 containing a risk zone 19, - the fifth determination unit 17 to determine a proposed inspection frequency for each of the risk zones 19 from its corrosion rate and a predetermined limit depth Ec of each of the risk zones 19, - the transmission unit 18 to transmit to a user device 20 the proposed inspection frequency for each of the risk zones 19.

[0075] The first unit of determination 13 may comprise: - the first cutting subunit 131 to cut each fuselage part 4 of the digital twin 2 according to a mesh of zones 70 comprising zones 71 of predetermined size, - the first calculation subunit 132 to calculate a corrosion incident rate for each of the zones 71 of the zone mesh 70.

[0076] The first unit of determination 13 may further comprise: - the second cutting subunit 133 for cutting the fuselage part 4 according to a sub-mesh of zones 72 comprising zones 73 of predetermined size smaller than the predetermined size of the zones 71 of the zone mesh 70, - the second calculation subunit 134 to calculate a corrosion incident rate for each of the zones 73 of the sub-mesh of zones 72.

[0077] Furthermore, the fifth unit of determination 17 may include: - the third calculation subunit 172 to calculate the inspection frequency required for each of the risk zones 19 so that the corrosion depth Eb reaches the predetermined limit depth Ec, - the determination subunit 172 to determine the proposed inspection frequency.

[0078] The optimization system S may include the database 11 in which The plurality of corrosion incidents 6 are stored. However, according to another embodiment, the database can be understood by another system distinct from the optimization system S.

Claims

1. Demands A method for optimizing the maintenance of an aircraft structure against corrosion, the aircraft structure comprising at least one aircraft structural part, characterized in that it comprises the following steps: - a collection step (El) implemented by a collection unit (10) to collect a plurality of corrosion incidents (6) on a plurality of aircraft (AC), each of the corrosion incidents (6) comprising a position of the corrosion incident (6), a remaining thickness (Ea) of the aircraft structure part (4) at the position of the corrosion incident (6) and an age of the aircraft (AC) for which the corrosion incident (6) was collected, - a reporting step (E2) implemented by a reporting unit (12) to report the plurality of corrosion incidents (6) collected on a digital twin (2) virtually defining an aircraft structure comprising at least one aircraft structural part (4), - a first determination step (E3) implemented by a first determination unit (13) to determine zones (71, 73) and corrosion incident rates in each of the zones (71, 73) for each part (4) of the aircraft structure of the digital twin (2), the corrosion incident rate of each of the zones (71, 73) being equal to a ratio between the number of corrosion incidents (6) collected in each of the zones (71, 73) and a number of aircraft (AC) of the plurality of aircraft (AC) on which the plurality of corrosion incidents (6) were collected, - a second determination step (E4) implemented by a second determination unit (14) to determine risk zones (19), the risk zones (19) corresponding to the zones whose corrosion incident rate is greater than or equal to a predetermined corrosion incident rate, - a third determination step (E5) implemented by a third determination unit (15) to determine a corrosion depth (Eb) for each part (4) of the aircraft structure located in the risk areas (19) to starting from the remaining thickness (Ea), - a fourth determination step (E6) implemented by a fourth determination unit (16) to determine a corrosion rate for each of the risk areas (19) from the corrosion depth (Eb) and the age of the aircraft for each part (4) of the aircraft structure comprising a risk area (19), - a fifth determination step (E7) implemented by a fifth determination unit (17) to determine a proposed inspection frequency for each of the risk areas (19) from its corrosion rate and a predetermined limit depth (Ec) of each of the risk areas (19), - a transmission step (E8) implemented by a transmission unit (18) to transmit to a user device (20) the proposed inspection frequency for each of the risk areas (19).

2. A method according to claim 1, characterized in that the first determination step (E3) comprises the following substeps: - a first cutting substep (E31) implemented by a first cutting subunit (131) to cut each part (4) of the aircraft structure of the digital twin (2) according to a zone mesh (70) comprising zones (71) of predetermined size, - a first calculation substep (E32) implemented by a first calculation subunit (132) to calculate a corrosion incident rate for each of the zones (71) of the zone mesh (70).

3. A method according to claim 2, characterized in that the first determination step (E3) further comprises the following substeps implemented if at least two zones (71) of the zone mesh (70) of a part (4) of the aircraft structure exhibit a difference in corrosion incident rate. greater than a predetermined difference: - a second cutting substep (E33) implemented by a second cutting subunit (133) to cut the aircraft structure part (4) according to a zone sub-mesh (72) comprising zones (73) of predetermined size less than the predetermined size of the zones (71) of the zone mesh (70), - a second calculation substep (E34) implemented by a second calculation subunit (134) to calculate a corrosion incident rate for each of the zones (73) of the zone sub-mesh (72).

4. A method according to any one of claims 1 to 3, characterized in that the corrosion depth (Eb) of a part (4) of the aircraft structure determined in the third step (E5) of determination is equal to a difference between a nominal thickness (E) of the part (4) of the aircraft structure and the remaining thickness (Ea) of the part (4) of the aircraft structure.

5. A method according to any one of claims 1 to 4, characterized in that the corrosion rate of each of the risk zones (19) determined in the fourth step (E6) of determination is equal to a ratio between the average corrosion depth (Eb) in each of the risk zones (19) and a time at the end of which this corrosion depth (Eb) is reached.

6. A method according to any one of claims 1 to 5, characterized in that the fifth determination step (E7) comprises the following substeps: - a third calculation substep (E71) implemented by a third calculation subunit (171) to calculate the inspection frequency required for each of the risk zones (19) for the corrosion depth (Eb) to reach the predetermined limit depth (Ec), - a determination substep (E72) implemented by a determination subunit (172) to determine the proposed inspection frequency, the proposed inspection frequency being strictly less than the inspection frequency required for each of the risk zones (19) so that the corrosion depth (Ea) reaches the predetermined limit depth (Ec).

7. System for optimizing the maintenance of an aircraft structure against corrosion, the aircraft structure comprising at least one aircraft structural part, characterized in that it comprises: a collection unit (10) for collecting a plurality of corrosion incidents (6) on a plurality of aircraft (AC), each corrosion incident (6) comprising a position of the corrosion incident (6), a remaining thickness (Ea) of the aircraft structure part (4) at the position of the corrosion incident (6) and an age of the aircraft (AC) for which the corrosion incident (6) was collected, a reporting unit (12) for reporting the plurality of corrosion incidents (6) collected onto a digital twin (2) virtually defining an aircraft structure comprising at least one aircraft structure part (4), a first determination unit (13) for determining corrosion incident zones and rates in each of the zones (71, 73) for each aircraft structure part (4) of the digital twin (2), the corrosion incident rate of each of the zones (71,73) being equal to a ratio between the number of corrosion incidents (6) collected in each of the zones (71, 73) and a number of aircraft (AC) in the plurality of aircraft (AC) on which the plurality of corrosion incidents (6) were collected, a second unit of determination for determining risk zones (19), the risk zones (19) corresponding to the zones (71, 73) whose corrosion incident rate is greater than or equal to a predetermined corrosion incident rate, a third determination unit (15) to determine a corrosion depth (Eb) for each part (4) of the aircraft structure located in each of the risk zones (19) from the remaining thickness (Ea), a fourth determination unit (16) to determine a corrosion rate for each of the risk areas (19) from the corrosion depth (Eb) and the age of the aircraft (AC) for each part (4) of the aircraft structure comprising a risk area (19), a fifth unit of determination (17) to determine a proposed inspection frequency for each of the risk areas (19) from its corrosion rate and a predetermined limit depth (Ec) of each of the risk areas (19), a transmission unit (18) to transmit to a user device (20) the proposed inspection frequency for each of the risk zones (19).

8. System according to claim 7, characterized in that the first determination unit (13) comprises: - a first cutting subunit (131) for cutting each part (4) of the aircraft structure of the digital twin (2) according to a zone mesh (70) comprising zones (71) of predetermined size, - a first calculation subunit (132) for calculating a corrosion incident rate for each of the zones (71) of the zone mesh (70).

9. System according to claim 8, characterized in that the first determination unit (13) further comprises: - a second cutting subunit (133) for cutting the aircraft structure part (4) according to a zone sub-mesh (72) comprising zones (73) of predetermined size less than the predetermined size of the zones (71) of the zone mesh (70), - a second calculation subunit (134) for calculating a corrosion incident rate for each of the zones (73) of the zone sub-mesh (72).

10. System according to any one of claims 7 to 9, characterized in that the fifth unit of determination (17) comprises: - a third calculation subunit (172) to calculate the inspection frequency required for each of the risk zones (19) so that the corrosion depth (Eb) reaches the predetermined limit depth (Ec), - a determination subunit (172) to determine the proposed inspection frequency, the proposed inspection frequency being strictly less than the inspection frequency required for each of the risk zones (19) for the corrosion depth (Ea) to reach the predetermined limit depth (Ec).

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