Functional Hazard Assessment
FHASection 06: System Safety & Functional Safety
Definition
A systematic, comprehensive examination of aircraft and system functions to identify and classify failure conditions associated with the loss or malfunction of those functions. The FHA is performed at the aircraft level and at the system level. The Aircraft-level FHA (AFHA) identifies failure conditions by examining what happens when each aircraft-level function is lost, malfunctions, or is provided with erroneous information, across all relevant flight phases and environmental conditions. System-level FHAs decompose the aircraft-level functions into system functions and identify additional failure conditions. The output of the FHA is a list of failure conditions, their severity classifications, and the associated safety objectives.
Where This Shows Up
The FHA is the starting point of the safety assessment process defined in ARP4761A and is performed as part of the aircraft development process per ARP4754B. The FHA results drive all subsequent safety analysis activities: the severity classifications determine DAL assignments, and the safety objectives become the targets for the PSSA and SSA. The FHA is typically documented as a structured table listing each function, the failure condition, the flight phase, the effect, and the classification.
Primary Sources
Defines the FHA methodology as part of the overall safety assessment process.
Describes how FHA integrates into the aircraft and system development process.
Artifacts Produced
Tabular document listing aircraft functions, associated failure conditions, flight phases, severity effects, and classifications.
Tabular document listing system functions, associated failure conditions, and their relationship to aircraft-level failure conditions.
Related Terms
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