EP-4495014-B1 - METHOD FOR REPAIRING AN AIRCRAFT STRUCTURE, AND REPAIRED AIRCRAFT STRUCTURE

Inventors

• Domenico, Furfari
• Schneider, Daniel D.
• BOUCHET, Régis

Dates

Publication Date

20260506

Application Date

20230721

Claims (11)

1. Method for repairing a damaged aircraft structure (10, 10'), the method comprising - forming a cut-out (C) in the aircraft structure by removing a portion thereof which includes a damage; - closing the cut-out (C) with a repair patch (20), whereby a groove (G, G') is formed along an edge (20e) of the repair patch running along an edge (10e) of the aircraft structure at the cut-out; and - joining the aircraft structure (10, 10') and the repair patch (20, 20') by cold spraying powder material (40) into the groove (G), wherein - the repair patch (20) comprises at least one lip (23) which when the repair patch closes the cut-out (C) overlaps an edge region (11) of the aircraft structure (10).
2. Method according to claim 1, wherein the groove (G, G') is formed by an aircraft structure chamfering (10c, 10'c) at said edge (10e) of the aircraft structure (10, 10') and/or by a patch chamfering (20c, 20'c) at said edge (20e) of the repair patch (20, 20').
3. Method according to one of claims 1 or 2, wherein the groove (G, G') comprises - at least a section having a V-shaped cross section and/or - at least a section having a rounded cross section.
4. Method according to one of the preceding claims, further comprising positioning a sealant (30, 30') between the aircraft structure (10, 10') and the repair patch (20, 20').
5. Method according to one of the preceding claims, wherein the powder material (40) is at least partially the same as a surface material of the aircraft structure (10, 10').
6. Method according to one of the preceding claims, further comprising producing the repair patch (20, 20'), the producing comprising - cutting the repair patch out of a twin component of the aircraft structure (10, 10') or - preforming the repair patch.
7. Method according to one of the preceding claims, wherein the repair patch has at least one positioning means (21, 21') exceeding the removed portion of the aircraft structure, wherein the method further comprises removing the at least one positioning means (21, 21') after said joining the aircraft structure and the repair patch.
8. Method according to one of the preceding claims, further comprising removing excess cold sprayed powder material (40x) overlaying the groove (G, G').
9. Method according to one of the preceding claims, wherein the aircraft structure (10, 10') is at least a portion of an aircraft's skin.
10. Method according to claim 9, wherein said portion forms part of a nacelle inlet cowl, of a wing, or of a tail of the aircraft.
11. Repaired aircraft structure (100) comprising an aircraft structure (10, 10') enclosing a repair patch (20, 20') wherein the repair patch (20) comprises at least one lip (23) which overlaps an edge region (11) of the aircraft structure (10), and cold spray deposited powder material (40) joining the aircraft structure (10, 10') and the repair patch (20, 20').

Description

The present invention addresses a method for repairing a damaged aircraft structure. The invention further concerns a repaired aircraft structure. Aircraft structures such as a skin of a nacelle inlet bowl, of a tail or of a wing, are often prone to accidental damages such as dents, corrosions, or scratches. Such damages potentially increase the Aircraft on Ground (AoG) risk of the fleet. The increase in the number of repairs because of those damages leads to a consequent increased risk of reducing operational reliability of the fleet and increased maintenance cost of the operators. For example, among the typical components of the nacelles, pylons and engine mounts, the air inlet, thrust reverser units and fan cowl are prone to accidental damages during the service life of the aircraft. When a respective aircraft is in long term parking, the engine air inlets are protected with covers creating environmental conditions (e.g., high humidity and moisture) that could cause the onset of corrosion damages. Moreover, various aircraft structures, in particular their skin are often subjected to dents or scratches caused by foreign object impacts during take off and landing operations. Such damages can be also created by mishandled tools used during normal maintenance operation. Dents, scratches and/or corrosions damages must be removed prior to the aircraft re-entering in service. To this end, depending on the respective damage size and criticality, the damaged surfaces can be dressed out (e.g., dent dress-out) or reworked for a blend out removal of the damages, provided the static and fatigue strength of the damaged component is not compromised as the original certification requirements. If the damage is beyond the allowable damage limits as indicated in the SRM (Structural Repair Manual), the damaged part of the structure shall be completely removed (cut-out of the damage part), and an external doubler shall be installed which restores the static and fatigue strength of the component. Conventionally, the load path across component structures and external repair doubler is established via standard fastening joints. To fulfil the aerodynamic constraints for the respective aircraft structure, such external doubler repair solutions based on fastening techniques require a so-called "flush repair". This implies the use of many fasteners, the installation of which requires a high expenditure of time and work. Moreover, although the fastening repair solution is commonly used and is a very reliable means to restore the integrity of the damaged structures as per the original certification requirements, because of the multi-lines of fasteners and no painting requirement of the structures, repair is very visible. Prior art is also shown in CN 116 275 654 A which discloses, according to its abstract, an in-situ first-aid repair method for broken hole damage of a duralumin main load-bearing structure of an airplane. The repair method comprises the following specific process steps: S1, preparation before maintenance; s2, trimming the broken hole; s3, processing a prefabricated patch; s4, welding the patch and the cutting hole. US 2017/369187 A1 discloses, according to its abstract, discloses a method of repairing including the steps of removing material from the substrate around the damage site to form a recess, and cold spraying particulate material into the recess to form a bead of deposited material. It is an object of the present invention to provide an improved technique for repairing a damaged aircraft structure, and a repaired aircraft structure. The object is achieved by a method according to claim 1 and by a repaired aircraft structure according to claim 11. Advantageous embodiments are disclosed in the dependent claims, the description and the figures. A method according to the present invention serves to repair a damaged structure of an aircraft, further referred to as aircraft structure. The method comprises the step of forming a cut-out in the aircraft structure, whereby a portion of the aircraft structure which includes a damage (such as at least one scratch, dent and/or corrosion damage) is removed. The method further comprises the step of closing the cut-out with a repair patch fitting in the cut-out, wherein a groove is formed along an edge of the repair patch running along an edge of the aircraft structure at the cut-out. The aircraft structure and the repair patch are then joined to each other by using cold spray powder deposition technique, as powder material is cold sprayed into the groove. Thereby, the groove or at least a section thereof may preferably be completely filled with said deposited powder material. The repair patch comprises at least one lip which overlaps an edge region of the aircraft structure enclosing the repair patch (when the repair patch closes the cut-out). Thereby, an exact positioning of the repair patch is ensured after this has been inserted into the cut-out and before and during th