Development Assurance Levels (DALs) for different hardware and software components. See  Appendix J for further information about DALs.  Development assurance is a safety requirement that must be approved by AJI. The aviation  industry standards that address system development assurance are:  PO planning for development assurance must begin early in the AMS lifecycle so the DALs can  be factored into the Business Case. Typically, this occurs prior to the IARD while the OSA is  being developed. New or modified FAA CNS/ATM systems should impose a system development process such  as that outlined in SAE ARP4754A. Using this methodology, system-level DALs would be  assigned to each function based on the highest severity level within each function. Software  DALs using RTCA DO-278A and hardware DALs using RTCA DO-254 could then be allocated  to each component and better aligned with system-level DALs. The assignment of DALs is  architecture dependent, and the PO should work with ANG to consider designs that not only  ensure safety, but also satisfy business goals.  AMS, Section 4.12, specifically identifies the guidance/standards in RTCA DO-278A as the  recommended means to accomplish software design rigor. If not using RTCA DO-278A, the PO  must propose an equivalent approach that meets the AMS requirement(s) for software design  rigor. Compliance with SAE ARP4754A and RTCA DO-254 is not specifically required; other similar  standards may be equally valid. Regardless, the PO must propose an approach that meets the  AMS requirement for system, hardware, and software rigor.  The Program Requirements Document defines the operational framework and performance  requirements an investment program must achieve. Preliminary program requirements specify  what the new capability must do and how well it must perform its intended functions. Safety is  one of the key disciplines in the AMS that must be addressed in the pPRD. Thus, safety  requirements identified in the OSA become system requirements that must be included as  requirements in the pPRD. The PO must plan for the fulfillment of safety performance  requirements by testing and tagging requirements that are of interest to safety for special  oversight. Writing a safety requirement is no different than writing other engineering  requirements as described in the FAA Systems Engineering Manual.  The DALs that are initially established must also be included in the pPRD though it may be  appropriate to have a stand-alone document to describe the DAL relationship among the  different components and the system.  2. An ARP is a guideline from SAE International. 2_SRMGSA_202003  Originally published March 2020  Uncontrolled copy when downloaded  12 2.3.2.1.5  pPRD • SAE Aerospace Recommended Practice (ARP) 2  ARP4754A,  Guidelines for Development of Civil Aircraft and Systems ; • RTCA DO-254,  Design Assurance Guidance for Airborne Electronic Hardware ; and • RTCA DO-278A,  Software Integrity Assurance Considerations for Communication, Navigation, Surveillance and Air Traffic Management (CNS/ATM) Systems.