experience and addresses approval credit that may be granted when this is the case. Some  primary considerations include:  An applicant may propose an alternative method of approval to RTCA DO-278A. When  proposing alternative methods of approval, applicants should consult FAA AC 20-171. Although  AC 20-171 addresses alternatives to RTCA DO-178B, the guidance can be used for proposing  alternative methods to RTCA DO-278A for CNS/ATM software.  When proposing a method of approval that is alternative to RTCA DO-278A, the applicant must:  The DAL is determined through the safety assessment process. The assessment validates that  the appropriate DAL has been assigned to the correct safety hazards and allocated to the  correct safety requirements. Policy and guidance for approving safety assessments for  acquisitions affecting the NAS are detailed in the SMS Manual.  Detailed guidance for the approval process related to RTCA DO-278A lifecycle data is provided  in  Appendix L and can also be obtained through consultation with the approval authority.  J_SRMGSA_202003 Originally published March 2020  Uncontrolled copy when downloaded  J-8 • Thoroughly document the proposed alternative approach and rationale. • Obtain agreement from the ATO Chief Safety Engineer that the proposed approach meets the original intent of the objectives and/or associated activities. • Provide substantiating evidence to the approval authority, demonstrating that the agreed-upon approach was followed. • Show that the proposed alternative demonstrates a level of safety assurance equivalent to AMS, Section 4.12. RTCA DO-278A establishes a level of safety assurance for software components that supports the demonstration of compliance to AMS, Section 4.12. • Identify a compliance approach that addresses the principles described in this guidance and describe how the alternative approach meets the intent of the objectives and/or activities defined in the RTCA DO-278A process-based approach. • The stability and maturity of the software, including effects of any changes during the service period. • The adequacy of problem reporting to the level that any software failures during the service period were appropriately reported, recorded, and resolved; and • The relevance of service experience, such as time in service, CM, how the software was used, and the relevance of the environment in which it was used; 6.7  Alternative Methods  6.8  Approval Process 