guidance, and it is applicable when software tools must be qualified per the guidance in RTCA  DO-278A.  When using RTCA DO-278A as a means of ensuring compliance with AMS, Section 4.12, the  associated RTCA DO-278A supplements must also be used where applicable. RTCA DO-331,  RTCA DO-332, and RTCA DO-333 are supplements that address certain software development  techniques and can add, delete, or modify objectives, activities, and lifecycle data in RTCA  DO-278A. Guidance within a particular supplement must be applied when using the addressed  technique. The Plan for Software Aspects of Approval (PSAA) must identify applicable  supplements and describe the intended use of each.  RTCA DO-278A establishes an approval liaison process that has similarities to the RTCA  DO-178C certification liaison process for aircraft software. However, there are also fundamental  differences to be considered. In the case of aircraft, the applicant is external to the FAA and is  regulated by the certification authority. In the case of Communication, Navigation, and  Surveillance (CNS) and Air Traffic Management (ATM) systems, the applicant is internal to the  FAA while the software developers are external. If it is determined through safety analyses that  the CNS/ATM software can affect systems onboard an aircraft, the assigned Development  Assurance Level must be acceptable to the aircraft certification authority. The certification  authority must also be allowed to provide input to the approval process.  RTCA DO-278A and some other standards use terms that have different definitions than those  used in the AMS. For the purposes of this appendix, these definitions apply:  4  Definitions  • An  applicant  is the organization that is the primary sponsor of the system. The  applicant is usually responsible for acquiring a new system or proposing changes to an  existing system, and for asking the approval authority for permission to deploy the  system. For AMS programs, the applicant is typically the Program Office (PO).  • The  approval authority  is the organization that is responsible for approving the safety  aspects of the system (but not the funding or functionality unless that functionality  affects the safety of the system). The ATO authority that accepts and/or approves the  safety aspects of CNS/ATM systems that affect the National Airspace System is the  ATO Chief Safety Engineer.  • The  certification authority  is the aviation authority that accepts and/or approves  software lifecycle data for aircraft.  • A  configuration item  is (1) one or more software components treated as a unit for  software Configuration Management (CM) purposes or (2) software lifecycle data  (i.e., documentation) treated as a unit for software CM purposes.  • A  developer  is usually the prime contractor for the system under development and is  responsible for system integration.  L_SRMGSA_202003  Originally published March 2020  Uncontrolled copy when downloaded  L-2  Note : Approving software lifecycle data (as defined in this appendix) is the method of  providing RTCA DO-278A compliance substantiation. It does not replace established  processes related to FAA acceptance of software. 