Agency Advisory Circular: Reduced Reliability Flight Safety System Design, Test, and Documentation

DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 450</CFR> <DEPDOC>[Docket No. FAA-2025-0798]</DEPDOC> <SUBJECT>Agency Advisory Circular: Reduced Reliability Flight Safety System Design, Test, and Documentation</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), Department of Transportation (DOT). <HD SOURCE="HED">ACTION:</HD> Notification and request for comments. <SUM> <HD SOURCE="HED">SUMMARY:</HD> FAA invites public comments about our intention to publish an advisory circular. This Advisory Circular (AC) provides guidance to demonstrate compliance with the design, test, and documentation requirements for a Reduced Reliability Flight Safety System (RRFSS) of commercial space launch or reentry vehicles. This AC presents one acceptable means of compliance (MOC), but this is not the only acceptable MOC. Launch and reentry license applicants may use this AC to guide their internal processes, format their license applications, or both. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Written comments should be submitted by June 13, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Please send written comments: <E T="03">By Electronic Docket: www.regulations.gov</E> (Enter docket number into search field). <E T="03">By mail:</E> Charles Huet, 800 Independence Avenue SW, Room 331, Washington, DC 20591. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Charles Huet by email at: <E T="03">Charles.huet@faa.gov;</E> phone: 202-267-7427. </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">I. Authority</HD> The Commercial Space Launch Act of 1984, as amended and codified at 51 U.S.C. 50901 through 50923, authorizes the DOT, and the FAA through delegation, to oversee, license, and regulate commercial launch and reentry activities, and the operation of launch and reentry sites as carried out by U.S. citizens or within the United States. The FAA exercises these responsibilities consistent with public health and safety, safety of property, and the national security and foreign policy interests of the United States. See 51 U.S.C. 50905. <HD SOURCE="HD1">II. Text of Draft Advisory Circular</HD> <HD SOURCE="HD1">1.1 Purpose</HD> 1.1.1 This Advisory Circular (AC) provides guidance to demonstrate compliance with the design, environment, test, analyses, and documentation requirements for a Flight Safety System (FSS) under 14 CFR 450.143. 1.1.2 Per § 450.108(b)(2), a vehicle operator using flight abort as a hazard control strategy to meet the safety criteria of § 450.101 must use a FSS that either: (1) Meets the requirements of § 450.145 if the consequence of any reasonably foreseeable failure mode in any significant period of flight is greater than 1x10  <E T="51">−2</E> conditional expected casualties (CEc) in uncontrolled areas; or (2) Meets the requirements of § 450.143 when the consequence of any reasonably foreseeable failure mode in any significant period of flight is between 1x10  <E T="51">−2</E> and 1x10  <E T="51">−3</E> CEc for uncontrolled areas. A FSS that meets the requirements of § 450.145 is known as a Highly Reliable Flight Safety System (HRFSS). A FSS that meets the requirements of § 450.143 is known as a Reduced Reliability Flight Safety System (RRFSS). This AC only provides guidance for an RRFSS. Compliance with § 450.143 should ensure that no credible fault (§ 450.143(b)) can lead to increased risk to the public beyond nominal safety-critical system operation. The guidance of this AC (see Figure below) should be used to develop a program-specific means of compliance (MOC) document, which must be expanded to include component-specific design and test details, similar to the most updated Range Commanders Council (RCC) 319 and RCC 324 content such as test matrices and definition of performance tests. <GPH SPAN="3" DEEP="121"> <GID>EP14MY25.001</GID> </GPH> <HD SOURCE="HD1">Figure 1: AC 450.143-1 Document Flow</HD> 1.1.3 Other approaches that fulfill regulatory objectives may be acceptable to the Federal Aviation Administration (FAA) Office of Commercial Space Transportation (AST). This AC presents one, but not the only, acceptable MOC with the requirements of § 450.143. The FAA should consider other MOC that an applicant may elect to present that also satisfy the entrance and exit criteria defined within this AC. 1.1.4 Applicants are advised to refer to AC 450.108-1, Flight Abort Rule Development, for all un-crewed vehicles whose FSSs used during commercial space launch or reentry operations are required to have flight abort capability and comply with § 450.108(b)(2) and AC 450.107-1, Hazard Control Strategies Determination, to determine which strategies to use. <HD SOURCE="HD1">1.2 Scope</HD> 1.2.1 This initial release of AC 450.143-1 is for a single-use FSS only. 1.2.2 A FSS is composed of two major sub-systems: the Flight Termination System (FTS) and the Range Tracking (and Telemetry) System (RTS). This initial release of AC 450.143-1 provides a MOC for the FTS of an RRFSS, but does not address FSS component software, such as that contained on an Automated Flight Termination Unit and typically managed under RCC 319-19 Appendix A for HRFSS, or RTS components for an RRFSS. <HD SOURCE="HD1">1.3 Exception</HD> An applicant should perform design, testing, and documentation in compliance with § 450.143 for FSSs, except for FSSs for which an operator demonstrates through its flight hazard analysis that the likelihood of any hazardous condition specifically associated with the system that may cause death or serious injury to the public is extremely remote, pursuant to § 450.109(b)(3). Thus, this AC does not apply to crewed vehicles that have safety-critical systems for which an operator must demonstrate—using a flight hazard analysis—that the likelihood of any hazardous condition that may cause death or serious injury is extremely remote, pursuant to § 450.109(b)(3). <HD SOURCE="HD1">1.4 Licensing and Regulatory Applicability</HD> 1.4.1 This AC presents one, but not the only, acceptable MOC with the associated regulatory requirements. The FAA will consider other MOC that an applicant may elect to present. In addition, an operator may tailor the provisions of this AC to meet its unique needs, provided the changes are accepted as an MOC by the FAA. Throughout this document, the word “must” characterizes statements that directly follow from regulatory text and therefore reflect regulatory mandates, or that an applicant must satisfy in order to use this AC as a MOC. The word “may” describes variations or alternatives allowed within the accepted MOC set forth in this AC. 1.4.2 The guidance in this AC is for launch and reentry license applicants and operators required to comply with 14 CFR part 450. The guidance in this AC is for those seeking a launch or reentry vehicle operator license, a licensed operator seeking to renew or modify an existing vehicle operator license. 1.4.3 The material in this AC is advisory in nature and does not constitute a regulation. This guidance is not legally binding in its own right and will not be relied upon by the FAA as a separate basis for affirmative enforcement action or other administrative penalty. Conformity with this guidance document (as distinct from existing statutes and regulations) is voluntary only, and nonconformity will not affect rights and obligations under existing statutes and regulations. This AC describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. 1.4.4 The material in this AC does not change or create any additional regulatory requirements, nor does it authorize changes to, or deviations from, existing regulatory requirements. <HD SOURCE="HD1">2 Applicable Regulations and Related Documents</HD> <HD SOURCE="HD1">2.1 Related U.S. Statute</HD> Title 51 U.S.C. subtitle V, chapter 509, Commercial Space Launch Activities. <HD SOURCE="HD1">2.2 Related FAA Commercial Space Transportation Regulations</HD> The following regulations from title 14 of the CFR must be accounted for when showing compliance with § 450.143. The full text of these regulations can be downloaded from the U.S. Government Printing Office e-CFR. A paper copy can be ordered from the Government Printing Office, Superintendent of Documents, Attn: New Orders, PO Box 371954, Pittsburgh, PA 15250-7954. • Section 401.7, <E T="03">Definitions.</E> • Section 450.101, <E T="03">Public Safety Criteria.</E> • Section 450.107, <E T="03">Hazard Control Strategies.</E> • Section 450.108, <E T="03">Flight Abort.</E> • Section 450.109, <E T="03">Flight Hazard Analysis.</E> • Section 450.115, <E T="03">Flight Safety Analysis Methods.</E> • Section 450.141, <E T="03">Computing Systems.</E> • Section 450.131, <E T="03">Probability of Failure Analysis.</E> • Section 450.143, <E T="03">Safety-Critical System Design, Test, and Documentation.</E> • Section 450.145, <E T="03">Highly Reliable Flight Safety System.</E> • Section 450.161, <E T="03">Control of Hazard Areas.</E> • Section 450.209, <E T="03">Compliance Monitoring.</E> <HD SOURCE="HD1">2.3 Related U.S. Statute</HD> These FAA Advisory Circulars are or will be available through the FAA website, <E T="03">https://www.faa.gov</E> . • AC 450.35-1, <E T="03">Means of Compliance Process,</E> when published. • AC 450.101-1, <E T="03">High Consequence Event Protection,</E> May 20, 2021. • AC 450.107-1, <E T="03">Hazard Control Strategies Determination,</E> July 27, 2021. • AC 450.108-1, <E T="03">Flight Abort Rule Development,</E> July 27, 2021. • AC 450.141-1A, <E T="03">Computing Systems Safety,</E> August 16, 2021. • AC 450.143-2, <E T="0 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 75k characters. 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