Despite an increasing awareness of the need to procure products of known quality and reliability, the aircraft industry has continued to suffer from the problem of poor quality and bogus fasteners. A few have remained undetected until they have come to light in service, occasionally with catastrophic results. Many others have been discovered at an earlier stage with an embarrassing and costly delay in the program.
Each of these bogus or inferior parts has been supplied against an order placed, in good faith, by a procurement agent of the aircraft industry. In every instance, bonafide manufacturers or distributors would have supplied genuine, quality assured products. Inevitably they are called upon to do so, often at very short notice, to rectify the damage created by the supplier of bogus parts. Thus, notwithstanding the fact that the aircraft industry maintains one of the most comprehensive supplier quality assurance systems, aircraft fasteners of doubtful quality and origin continue to be a problem. Each time a major incident occurs, the bona-fide suppliers may be penalized with costly additional controls which do not contribute to the assurance of their own proven products. The supplier of bogus or inferior quality parts continues to ignore such controls thereby benefiting further on costs.
This Code of Practice has been prepared for the benefit of the end user, the customer. It attempts to define the basic controls required in the manufacturing, quality and distribution of threaded fasteners. Member companies of the Aircraft Locknut Manufacturers Association® (ALMA) strive to observe and maintain these standards. It is intended that the Code of Practice will give procurement agencies the confidence and assurance that threaded fasteners purchased from ALMA members and their distributors will meet the highest standards of quality and reliability.
Reputable manufacturers maintain a system of manufacturing controls that assure the production of high quality fasteners.
Identification of manufacturing process and traceability through these manufacturing processes can be assured by assignment of a unique lot or batch number to each production quantity.
A qualified metallurgist should be on staff to monitor the forming and thermal treatment processes and to assist in manufacturing and design engineering.
Product quality should be evaluated at frequent intervals and inspection operations should be consistent with the requirements of MIL-I-45208A.
A statistical process control program should be in effect to measure and improve manufacturing process capabilities with the ultimate goal of eliminating process variation.
Reputable manufacturers evaluate each lot of raw material to determine if material conforms to prescribed specifications. Lab evaluation and physical tests are conducted to assure that material is of the desired quality and that it will achieve required physical properties. Material Certifications are maintained on file for audit purposes.
Operations such as deep drawing, heading and nut forming (especially when conducted hot) can significantly alter the metallurgical and physical properties of the base material. These operations should be monitored by microscopic evaluation of sectioned samples at not less than 150 x to assure that metallurgical and physical properties have not been adversely affected.
Machining, drilling, tapping, grinding, etc., operations are monitored with calibrated gages to assure the dimensional and surface finish requirements are maintained. The self-locking elements of fasteners are closely defined and monitored by "first article" and "in-process" quality checks. Records are maintained on both dimensional and torque test results.
Metal finishing operations such as cleaning, plating, anodizing, etc., are monitored by qualified Chemical Lab personnel. A regular program for solution control with adequate records will be maintained on file. These records will be available for audit when requested.
Regular process control tests for plating adhension, salt spray resistance, hydrogen embrittlement, porosity and other required tests are conducted and records of test results maintained.
Heat treatment is one of the most critical operations in the manufacturing cycle. As such it should be subject to special monitoring. Each lot of heat treated parts is evaluated to assure that the desired properties have been achieved and that undesirable characteristics are not present.
Thermal processes are performed in furnaces or ovens which have a current uniformity survey and are equipped with calibrated temperature control instruments.
Heat treat processes are performed in accordance with established documented specifications. Records of temperature tests, calibration and other substantiated data are maintained on file for audit.
Each lot or batch of parts is produced against a uniquely numbered work order or record which describes the operations required to produce the part. The results of each inspection and test is documented and maintained as part of the inspection record for that work order.
Reputable manufacturers and distributors ensure that traceability of finished products is maintained from the raw material stage through all manufacturing operations up to and including the point of shipment to the customer.
Inspection records created during manufacturing are maintained on file for a specified period and made available for review upon request.
A Certificate of Test will be issued for each delivery of product, which will summarize all the important mechanical and chemical characteristics of the product. Certificates will be numbered, dated, and signed by the appropriate quality control representatives.
The documents will certify that the parts supplied have been produced in accordance with specific customer requirements, and will ensure complete traceability.
Special efforts will be made to produce tamper-resistant documentation, including "re-certification" by authorized distributors. Additionally, any customer or consumer may verify the authenticity of any certification by contacting the manufacturer direct. The authenticity of product cannot be verified unless the specific product is also examined by the manufacturer.
This special effort is undertaken as a means of maintaining the high standards of quality and traceability demanded in the aerospace industry.
When requested by a customer, a Test Report reflecting the specific test data obtained during the production and testing of the product will be prepared and provided with each shipment. The specific content of the test report will be in accordance with predetermined customer specified requirements.
A reputable fastener supplier will have a quality organization that has the authority and responsibility for formulation of quality policy, implementation of the quality plan and product quality analysis.
Certain fastener products have been subjected to a rigorous testing program which has established not only the product's conformance to specifications but also demonstrates the manufacturer's capability to consistently produce parts to a given standard. Consistency and reliability are assured in that any major changes to manufacturing methods necessitate requalification testing and approval.
When procuring qualified products, particular attention should be given to the following items:
* Item being procured is contained on the Qualified Product List.
* Manufacturing origin.
* The identified manufacturer is listed as qualified to produce the product.
* The product is traceable through the manufacturer's system.
Reputable distributors purchase from manufacturers that observe this Code of Practice.
Additionally, the distributor will assure the integrity of the product by maintaining tractability of all fastener products maintained inventory.
The aerospace industry, both users and suppliers, have a joint responsibility to prevent bogus parts from entering service. This problem can only be dealt with by an aware, enlightened industry. One in which all participants of the procurement cycle are aware of the potential problems and hazards.
This document attempts to enhance that enlightenment by highlighting the necessary elements of control with a fastener manufacturer's system. Obviously, in this brief document, it cannot address every aspect. It does, however, cover the significant requirements which, if satisfied, will provide the procuring agency with the confidence and assurance it must have.
By observing this Code of Practice, the Aircraft Lockout Manufacturers Association members have affirmed their belief and dedication to the concepts of integrity, craftsmanship and technical excellence which have long been the hallmark of the aerospace industry.