Generalizing Aspects of System Safety to Broaden Applicability 2021-01-0037

The Safety Assessment Process, defined by SAE ARP4761 and associated regulatory guidance, is described in the context of conventional, crewed civil aircraft. While this material has been used for decades to evaluate airplanes and rotorcraft, the evolution of technology challenges it. As new entrants venture into aviation, they bring perspectives, which may not clearly align to those conventional concepts. For those skilled in the art of aviation safety assessment, the approach to new technologies might appear straight forward. Such an individual might easily perceive the accommodations for unconventional applications. Once accommodations are made, and failure conditions are established and classified to those new architectures, the rest of the process is somewhat mechanical -they flow out of these conditions. However, the context of their experience betrays the reality of the process description in the ARP and guidance. Such accommodations are not discussed in them, and the process objectives, which are fulfilled by the process, are not explicit. One example of such a challenge regards how failure condition effects and classification are described. The guidelines state that the effects and classification should consider the aircraft, flight crew, and occupants. What are the safety considerations for an unmanned cargo airplane the size of a transport aircraft? How is the “crew effect” of a ground station considered? Is a passenger who simply provides a waypoint to a full autonomous vehicle considered the “crew”? Such cases easily demonstrate how the conventional ARP process limits its own universality in its initial process step. This paper recommends ways to broaden SAE ARP4761 and some regulatory guidance through improving the description of functions, failure conditions, and their classifications. This paper discusses aspects of these concepts and their downstream processes. The intent of this paper is to identify how to make the ARP’s processes accessible to future applications while supporting conventional applications, towards providing comprehensive safety coverage for all air and space vehicles.