Rewrite of Part 23 basis for new ASTM performance test
Low Stress structures not subject to cyclic test
Type Certification of Part 23 aircraft high standards of safety still
ASTM has issued a new low-stress structures test, that permits the TC certificate applicant to seek an airworthiness determination for a component without cyclic test. How did we get here?
Part 23 Aircraft certification remained pretty much the same from its 1964 promulgation until the start of the 21st century. In 2009 an industry and airworthiness authorities task force began a very careful examination of the prescription-based regulations which defined the standards for determining the airworthiness of Normal Category Airplanes for all those years,
The external team process, eventually named the Part 23 Reorganization Aviation Rulemaking Committee (ARC), moved through several iterations and offered a proposal based on performance-based standards. Congress passed two bills (FAMRA and SARA ) in 2013. which required the FAA to issue a final rule on the revised Part 23 soon. Two years later an NPRM was issued.
The basic premise of the new Part 23 is that the FAA in assessing the safety of GA aircraft no longer relies on the old checklist. The new regime, very briefly, starts with an assessment of the proposed design, identifying elements for which there are proven operational histories and then focusing on new systems, structures, architecture. As to the novel aspects of a TC request, ASTM would use its trusted engineering expertise to define measures of performance which will test its airworthiness. The FAA, having participated in this process, then likely incorporates this airworthiness measure
ASTM Committee F44 on General Aviation Aircraft as contemplated by the Part 23 rewrite, is available for such analyses. That Committee addresses issues related to design and construction, systems and performance, quality acceptance tests, and safety monitoring for general aviation aircraft. Using its collective knowledge and experience (approximately 250) a more performance based document, setting standards for the proposed TC design of aircraft is drafted.
ASTM WK61232, New Practice for Low Stress Airframe Structure, according to Terry Ercolani, ASTM International member and Textron Aviation senior specialist/engineer, proposed a standard, under which the TC applicant would be able to designate applicable small aircraft components as low-stress structures. Such designated components would not have to undergo the structural durability assessments that are required as part of the ASTM standard specification covering small aircraft. He said:
“In particular, a user would not be required to perform a cyclic test of the component [that is] designated as low stress, saving cost and schedule during a new product development and certification effort.”
by Kerry Lynch
– August 4, 2021, 10:56 AM
ASTM International is proposing a new standard that would establish the requirements for small aircraft components to be considered as “low-stress structures” and able to bypass certain durability testing. The standards-setting agency’s general aviation aircraft committee, F44, is developing the proposed standard, which carries the designation of WK61232.
With the proposed standard, manufacturers, working with aircraft design regulatory agencies, would be able to designate applicable small aircraft components as low-stress structures. Such designated components would not have to undergo the structural durability assessments that are required as part of the ASTM standard specification covering small aircraft.
“In particular, a user would not be required to perform a cyclic test of the component [that is] designated as low stress, saving cost and schedule during a new product development and certification effort,” said Terry Ercolani, ASTM International member and Textron Aviation senior specialist/engineer.
While the F44 committee continues work on this and other general aviation standards, Ercolani noted that the committee is continually seeking new participants, especially those with aircraft structural durability expertise in both metallic and composite construction, and said interested participants should reach out to ASTM.
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