Failure Condition Classification
Section 06: System Safety & Functional Safety
Definition
The categorization of failure conditions by their severity of effect on the aircraft and its occupants. Five classifications are defined: (1) Catastrophic — failure conditions that would result in multiple fatalities, usually with the loss of the aircraft; (2) Hazardous (also called Severe-Major) — failure conditions that would reduce the capability of the aircraft or the ability of the crew to cope with adverse operating conditions to the extent that there would be a large reduction in safety margins or functional capabilities, physical distress or higher workload such that the crew could not be relied upon to perform their tasks accurately or completely, serious or fatal injury to a relatively small number of occupants; (3) Major — failure conditions that would reduce the capability of the aircraft or the ability of the crew to cope with adverse operating conditions to the extent that there would be a significant reduction in safety margins or functional capabilities, significant increase in crew workload or in conditions impairing crew efficiency, or discomfort to occupants possibly including injuries; (4) Minor — failure conditions that would not significantly reduce aircraft safety and that involve crew actions well within their capabilities, including slight reduction in safety margins, slight increase in workload, or some physical discomfort to occupants; (5) No Safety Effect — failure conditions that have no effect on safety.
Where This Shows Up
Failure condition classification drives the entire downstream safety and development assurance process. The classification determines the quantitative probability objective, the Development Assurance Level (DAL) for software and hardware, and the rigor of verification and validation activities. Catastrophic conditions require the most stringent development assurance (DAL A) and the lowest probability (extremely improbable, on the order of 10^-9 per flight hour), while no safety effect conditions have no specific development assurance requirements.
Primary Sources
The regulation establishing failure condition severity classifications and their relationship to probability objectives.
Provides detailed definitions and examples for each failure condition classification.
EASA acceptable means of compliance providing equivalent classification guidance.
Across Jurisdictions
Related Terms
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