FAA Part 25 Rewrite Could Reset Aircraft Certification Timelines
A notable development in the realm of certification policy was the announcement of the FAA that it is working on a potentially groundbreaking initiative to revise Part 25 of airworthiness regulations for transport airplanes and a wide array of critical subjects covered by them: structures, flight controls, systems and cabin safety among others.
While acceleration of the certification process per se is not the primary concern of the engineering and program management teams, what is of importance is the FAA desire to get out of the case-by-case certification of some decisions and to put these decisions into the rulebook.
Currently, when the design of the airplane no longer complies with the rule language designed for the older generation of the airplanes, the manufacturer needs to undergo a long process of obtaining special conditions, exemption or equivalent level of safety finding to be able to certify their design. It is a tedious task for applicant and regulator alike and is becoming increasingly frequent with the advent of composite materials, fly-by-wire flight control systems, intensive electronic and software systems and automation.
The importance of this issue comes from the fact that the problem of certification delays affects not just the airframer, but all the suppliers: engines, avionics, structural parts and others, as their products become delayed due to certification of the parent aircraft program.
The FAA describes the rewrite as modernization, but not deregulation. The Federal Register notice on the subject states that the proposed rewrite will reduce certification costs and time via codification of frequently used exemptions, special conditions and equivalent level of safety findings while maintaining or improving safety. The notice references a variety of advisory- and accident-investigation bodies’ recommendations, as well as Section 312 of the FAA Reauthorization Act of 2024.
It is obvious that some of the targets are quite pragmatic, as they include recurring conflicts between prescriptive regulations and newer aircraft designs and systems architectures, such as emergency exits, lighting, cabin interior, electrical power supply and other similar issues as well as attempt to bring some regulations closer to EASA CS-25 where possible. It can help for those companies selling their products in both the United States and Europe to minimize duplicate certification that does not contribute to safety of the aircraft.
It is the policy context of the issue that makes the subject controversial. While many people will agree that the need of regulations rewrite exists, the question is about whether modernized rules can coexist with a stricter oversight following the reforms made after 737 MAX certification process. The certification approach for the 737 MAX has been widely criticized by Congress and federal investigators, who cited it as one of the reasons of passing the Aircraft Certification, Safety, and Accountability Act in 2020 that tightened the oversight of the delegated certification process. Since that time the FAA has been pushing for wider reforms including reduced usage of delegation of authority, more thorough analysis of system interactions, consideration of more human factors and increased usage of Technical Advisory Board for large programs. The efforts of the agency are described on its certification reform web page.
In this context, concerns of the safety advocates and former regulators about the possible adverse effect of the modernization of the Part 25 regulation are quite understandable. They are worried that the problems of the certification process discovered in recent years were not caused by the outdated rules, but the governance, transparency and delegation of the oversight in addition to the rule language itself. A streamlined Part 25 will help to minimize the friction in these areas, but it cannot provide the solution to the questions of novel hazards identification, assumptions testing or the amount of independent review of software-intense systems.
This is especially important for the aircraft designs relying on advanced automation and pilot interface. Industry observers expect that the FAA will focus its attention on software- and automation-dependent systems, evaluation of derivative aircraft and human factors.
This is not a surprise modern transport airplanes are increasingly becoming the system of systems and certification of them should take into account the interaction between these systems. In particular, the FAA stresses that the systems such as fly-by-wire architecture and advanced avionics require a more thorough assessment of their safety because of the hazards arising at the intersection of the legacy regulatory categories.
Of course, there are limitations to what the rewrite can accomplish. Some issues, such as injury criteria for multiple occupancy side-facing seats will remain in the domain of the special conditions and will not be included in the new rules. This is a good reminder that not all of the emerging design issues are ready for codification and sometimes the standardization should wait for the accumulation of knowledge.
One of the limitations is the time factor it is an early stage of the rulemaking process. The FAA has to prepare, publish and process the notice of proposed rulemaking, receive public comments, coordinate with international regulators and complete the revision. Usually this process takes several years, but the timeline for the completion of the final version of the rule has yet to be specified by the agency. Therefore, while the direction taken is important, this does not mean that the manufacturers should consider the rewrite as a shortcut for the current certification process.
The main takeaway from this issue is that Part 25 modernization will be a litmus test for whether the U.S. certification policy can incorporate software-intensive designs, advanced materials and innovative propulsion concepts without becoming either outdated or permissive.
Thomas Caldwell – AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion and safety policy.
