Structural Smarts: Aircraft Repairs

Maintaining an aircraft in an airworthy condition requires, among other essential activities, the proper assessment, recording, and repair of structural and system damages. Even minor damage can compromise safety if it is not evaluated and addressed correctly. ICAO defines repair as “the restoration of an aeronautical product to an airworthy condition as defined by the appropriate airworthiness requirements.” This straightforward definition underscores the objective of every repair: bringing the aircraft, engine, propeller, or component back into full compliance with applicable standards.

Assessing the Damage

Whenever damage is found, the first step is to assess whether it falls within the limits established by the Design Approval Holder (DAH). These limits, together with approved repair methods, are provided in documents such as the Structural Repair Manual (SRM) or the Maintenance Manual. These manuals contain the design data, procedures, and Instructions for Continued Airworthiness (ICA) required to perform standard repairs.

If the damage exceeds allowable limits or a standard repair is not provided in the manuals, more extensive action is required. This may include replacing the affected parts or contacting a design organization for technical assistance. Their role is to evaluate the damage, carry out supporting analyses, and design an appropriate repair solution.

Dent and Buckle Charts can be used to map, control, and monitor external damages and repairs on the aircraft. We will explore these practical tools in detail in a future article.

Classification of Repairs

Repairs can be categorized by three main aspects: adherence to approved design data, airworthiness impact on the product, and whether they are temporary or permanent.

Standard vs. Non-Standard Repairs: Certification Specifications

• Standard Repair: Follows design data included in certification specifications issued by the authority. It uses acceptable methods, techniques, and practices, includes the associated Instructions for Continued Airworthiness (ICA), and does not conflict with the Type Certificate (TC) holder’s data. Standard repairs do not require additional approval.

• Non-Standard Repair: Any repair that does not meet the criteria for a standard repair. This may include more complex or unusual damage situations. Non-standard repairs require technical evaluation and approval from a design organization, certification authority, or, in the FAA system, a Designated Engineering Representative (DER)

Major vs. Minor Repairs: Airworthiness Impact

• Major Repair: Has an appreciable effect on airworthiness. Structural performance, weight, balance, systems, operational characteristics, or other characteristics may be affected. For example, a repair is major if it requires extensive static, fatigue, or damage tolerance analysis and/or testing, if it uses uncommon methods, techniques, or practices, or if it requires re-assessment of the original certification data to ensure the aircraft still meets all relevant requirements.

• Minor Repair: Has no appreciable effect on airworthiness. They require minimal or no assessment of the original certification data to ensure that the aircraft still complies with all the relevant requirements.

Temporary vs. Permanent Repairs: Duration

Repairs can also be classified based on their temporary/permanent nature:

• Temporary repair: A provisional repair with a defined limitation or time interval. It must be replaced by a different repair solution once the limit is reached.

• Permanent repair: A full restoration without any life limitation.

Both types may require scheduled inspections: temporary repairs until a permanent solution is installed, and permanent repairs throughout the service life of the product.

Repetitive inspections must be incorporated into the Aircraft Maintenance Program (AMP), ensuring systematic monitoring of the aircraft’s structural integrity.

Repair Design Approval

Design organizations provide the necessary repair design data, and its format varies depending on the organization and the authority. For example, Airbus issues repair approvals through a Repair and Design Approval Form (RDAF), while Boeing uses FAA Form 8100-9, Statement of Compliance with Airworthiness Standards. These documents formally record the approved method of repair and any associated ICA.

Conclusion

Continuing airworthiness relies on a clear understanding of repairs, their classification, and the processes used to manage structural damage. Proper assessment, execution, and monitoring—including any required inspections—ensure that the aircraft remains airworthy throughout its operational life. Repetitive inspections resulting from repairs, as part of the Aircraft Maintenance Program (AMP), provide an added layer of assurance for continuing structural integrity.

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