FHAs

FHAs, short for Functional Hazard Analyses, are a class of hazard analysis techniques used in safety engineering to identify and assess hazards associated with the functions of a system. They are commonly applied to safety-critical domains such as aerospace, automotive safety systems, and rail transportation, and are described in standards such as SAE ARP 4761. In these contexts, an FHA aims to determine which system functions could fail in a way that jeopardizes safety, and to classify the associated hazards by severity and risk.

The FHA process typically starts with a structured description of the system and its functions. For each function, potential malfunctions are identified, the consequences are analyzed, and the hazard level is assessed using criteria such as severity, exposure, and probability. The results are used to derive functional safety goals and to guide the allocation of safety requirements, often in support of a Hazard Analysis and Risk Assessment (HARA) in ISO 26262 or equivalent frameworks. The output is usually a formal FHA report listing hazards, affected functions, possible malfunctions, hazard classification, and proposed mitigations or safety goals.

Limitations and scope: FHAs are most effective when conducted early in the design life cycle and updated as system understanding evolves. They focus on functional failures rather than component failures, and they are typically complemented by other analysis techniques such as FMEA, Fault Tree Analysis, or HAZOP.

Related methods include FMEA, HAZOP, and the Hazard Analysis and Risk Assessment framework of ISO 26262, along with ARP 4761 guidance used in aerospace.