Summary of Advisory Circular 43-18: Fabrication of Aircraft Parts by Maintenance Personnel
Introduction
Advisory Circular (AC) 43-18, published by the Federal Aviation Administration (FAA), provides guidance for maintenance personnel involved in the fabrication of parts for aircraft. Its primary objective is to ensure that parts fabricated during maintenance or alterations achieve an equivalent level of safety compared to those produced by the original design holder.
The AC outlines acceptable methods, techniques, and practices for part design and fabrication, ensuring compliance with Title 14 of the Code of Federal Regulations (14 CFR) Parts 21 and 43. It's important to remember that an AC is not mandatory and doesn't hold the same weight as a regulation. However, it serves as a valuable resource for maintenance personnel seeking to safely and compliantly fabricate aircraft parts.
Key Principles of AC 43-18
Safety Equivalence: The core principle of AC 43-18 is ensuring that fabricated parts possess the same level of safety as original parts. This is achieved through adherence to established design and manufacturing practices.
Alternative Methods: The AC acknowledges that there may be alternative methods for achieving safety equivalence besides those outlined in the document. However, the FAA must approve any chosen alternative to ensure it meets the required standards.
Regulatory References: The AC references relevant regulations from 14 CFR, including Part 21 on Certification Procedures for Products and Parts, and Part 43 on Maintenance, Preventive Maintenance, Rebuilding, and Alteration.
Steps in Fabrication Process
While AC 43-18 doesn't dictate a specific step-by-step process, it highlights crucial elements involved in successful part fabrication:
Data Acquisition: Maintenance personnel must acquire necessary technical data for the part they intend to fabricate. This data typically includes drawings, specifications, and material certifications.
Design Approval: The design of the fabricated part needs approval based on its criticality category. The AC references the Category Parts List (CPL), an FAA-maintained resource that categorizes aircraft parts based on their criticality to safety. Less critical parts may require less stringent design approval processes compared to those designated as critical.
Fabrication Quality Control System (FQCS): An FQCS needs to be established to ensure the quality and consistency of the fabrication process. This system outlines procedures for material selection, inspection, and documentation.
Personnel Qualification: Personnel involved in fabrication must possess the necessary skills and qualifications for the specific tasks they perform. This may involve training in areas like welding, machining, and non-destructive testing.
Documentation: Proper documentation of the entire fabrication process is crucial. This includes records of materials used, inspection results, and final part certification.
Additional Considerations
AC 43-18 also addresses other significant aspects related to part fabrication:
Conformity to Original Design: Whenever possible, the fabricated part should conform to the original design specifications. Deviations from the original design may require additional approvals and justifications.
Special Manufacturing Processes: Certain parts may require specific manufacturing processes not typically encountered in routine maintenance. In such cases, the AC recommends consulting with the original equipment manufacturer (OEM) or a qualified repair station for guidance.
Post-Installation Inspections: Following installation of the fabricated part, the AC recommends performing appropriate inspections to verify functionality and ensure no adverse effects on the aircraft's systems.
Conclusion
By following the guidance provided in AC 43-18, maintenance personnel can ensure the safe and compliant fabrication of aircraft parts. This reduces downtime, potentially lowers costs, and promotes efficient aircraft maintenance practices. It's important to note that AC 43-18 serves as a general guideline, and maintenance personnel should always consult with relevant regulatory bodies and qualified personnel when undertaking part fabrication tasks.
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