ASTM F3833-26

1.1 This guide defines the system-level behaviors for computer-based control of major, hazardous, and catastrophic failure conditions. The approaches identified provide behaviors intended to implement the necessary and sufficient controls for each specific failure condition being controlled. These approaches are applied on a failure-condition-by-failure-condition basis as identified and classified in the provider’s safety assessment (for example, Practice F3309/F3309M – 24a, or an equivalent method acceptable to a CAA). The safety assessment establishes which failure conditions are in scope and provides the basis for determining the necessary control response timing and rigor appropriate to the severity of the failure condition. These behaviors apply to computer-based or complex electronic systems that control safety-critical processes or devices. This includes any hardware, software, firmware, programmable logic, configuration data, and parameter sets used to prevent or mitigate a major, hazardous, or catastrophic failure condition, regardless of the media on which the software or firmware resides. This scope includes any commercial off-the-shelf (COTS) software, firmware, or hardware integrated into the CBCS design; when COTS items are used, the provider should define the CBCS application boundary and provide configuration-controlled evidence that safety-relevant behavior is adequately constrained and maintained within that boundary. CBCS behaviors are applied at the system level. CBCS behaviors need not be applied to lower-level components, such as sensors or actuators, if system-level behavior can be established. A provider may implement an equivalent method of controlling failure conditions acceptable to a CAA, provided it is supported by an auditable assurance argument and configuration-controlled evidence that links failure conditions to the intended behavior, implemented controls, and verification results (failure condition to mitigate requirements to implement and testing evidence). One acceptable way to structure that evidence is the Overarching Properties framework (Intent, Correctness, Innocuity), evaluated at the integrated system level.

1.2 Units—The values given in this guide are in SI units and are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound (or other) units that are provided for information only and are not considered standard. The values stated in each system may not be exact equivalents. Where it may not be clear, some equations provide the units of the result directly following the equation.

1.3 This guide does not aim to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this guide to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.