Global Fastener News

John Wolz

An industrywide working group was formed to solve non-safety-related dimensional discrepancies found by the Federal Aviation Administration.
Representatives from the Industrial Fasteners Institute, Aerospace Industries Association and General Aviation Manufacturers Association have held two-day work sessions in June with the FAA, and a third is planned this August in Seattle.
�There are no safety issues,� Skip Jones, director of engineering & certification for the AIA, emphasized several times in an interview with FIN.\
Jones said the initial Department of Transportation study was the result of the exemption of aerospace fasteners from the Fastener Quality Act. The DOT Office of Inspector General initiated an audit in 1998 of the FAA�s oversight of fastener production used in commercial aviation.
The DOT-OIG audit revealed some non-safety-related dimensional discrepancies, and subsequently the FAA audit began last fall to investigate the cause of variation in measurement, determine airworthiness and assess the fastener industry�s compliance with the FAA.
The FAA collected 2,264 samples from nine production approval holders for inspection and found a total of 5.7% of bolts and 1.1% of nuts were dimensionally nonconforming. Independent laboratories found 11.3% of the test bolts were dimensionally nonconforming.
After a six-month investigation of fasteners the FAA concluded there are no flight safety concerns involving aircraft fasteners.
Jones said the studies pointed to a problem with an inactive spec, MIL-S-8879. The problem is that the �deactivated spec can�t be updated,� Jones explained.
Harris: Taking Proactive Role
IFI managing director Rob Harris said he is pleased the subject has thus far been a �non-issue� because the working groups are taking a proactive role.
�There is no congressional inquiry. There have been no press calls. It is nice to be ahead of the situation,� Harris said.
Excerpts from FAA Findings:
� The difference in percentages due to different types of gages. The FAA found a significant variation between the three types of gages used.
� The FAA �questions the use of a zero-clearance allowance design specification.�
� All 484 crimped nuts passed functional assembly inspection.
� All 288 test pieces met mechanical performance and/or property requirements.
� The dimensional nonconformity did not preclude samples from meeting mechanical performance requirements.
� MIL-S-8879 �is used extensively by the commercial aviation industry, its inactivation without supersession by the DOD has had a negative effect on the industry.�
� MIL-S-8879 inspection and acceptance criteria do not meet FAA regulatory requirements that product conform to approved design data.
Excerpts from FAA conclusions:
� Industry needs standardized criteria for inspection, maintenance and calibration of gages.
� Initial and periodic evaluations and corrective actions as necessary were not taken.
� The manufacturer�s final inspection/acceptance processes contain weaknesses.
� Eight of the nine facilities were deficient arising from measuring and test equipment.
� Seven of nine facilities had deficiencies in statistical sampling inspection plans.
� Six of nine had deficiencies in inadequate in-process controls.
Excerpts from FAA recommendations:
� Industry to develop standardized criteria regarding the inspection, maintenance and calibration of gages.
� Industry to resolve supplier control deficiencies relating to supplier audits, corrective action and accurate flow-down of technical/quality requirements.
� Manufacturers to conduct a comprehensive review of their final inspection/acceptance process, thus ensuring that all products conform to the FAA-approved design data.
� FAA to continue ongoing initiatives placing special emphasis during certificate management functions (surveillance) at PAH facilities. Special emphasis areas address all aspects of manufacturing compliance, use of measuring and test equipment, statistical sampling, supplier surveillance and supplier control.
� FAA to continue to support industry�s commitment to improvement. FAA initiatives include working collaboratively with industry associations, aircraft, aircraft engine propeller and fastener manufacturers to correct quality and manufacturing deficiencies resulting from this audit.
The FAA conducted production lot acceptance tests for mechanical performance and/or material properties on 98% of all part numbers.
The FAA report notes that the �issue of screw thread inspection has been debated extensively for more than 20 years� and there are 30 separate geometrical features and dimensional characteristics in the design and construction of screw threads. �The most rigorous standard for threaded components in the United States inspects 11 major thread characteristics.�
�The FAA and OIG audits showed that the commercial aviation industry makes extensive use of military specification MIL-S-8879. With the Department of Defense initiative to replace military specifications with non-government specifications, the industry convened a task force to develop a commercial specification. That effort, however, failed to reach consensus, and the DOD inactivated MIL-S-8879C without supersession.�
The military spec had been used for non-government applications, creating �a profound effect on FAA design and production approval holders.�
Jones said no deadline has been set yet for the working group � which includes vice president and chief engineer level participants.
�We have a general goal to do it in a year,� Jones said. �It would be good to do it in a year, but it is too early to determine.�
� 2001 FastenerNews.com