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Mil-Std-1629A Related FMEA Definitions
Compensating Provision: Actions available or that can be taken to negate or reduce the effect of a failure on a system.
Criticality: a measure of the frequency of occurrence of an effect. May be based on qualitative judgement or may be based on failure rate data.
Detection Method: The method by which a failure can be discovered by the system operator under normal system operation or by a maintenance crew carrying out a specific diagnostic action.
End Effect: The consequence a failure mode has upon the operation, function or status at the highest indenture level.
Failure Cause: The physical or chemical processes, design defects, quality defects, part misapplication or other processes which are the basic reason for failure or which can initiate the physical process by which deterioration proceeds to failure. (Past)
Failure Effect: The consequence of a failure mode upon the operation, function or status of a system or equipment. (Future)
Failure Mode: The way in which a failure is observed, describes the way the failure occurs, and its impact on equipment operation. (Present)
Indenture Levels: The levels which identify or describe the relative complexity of an assembly or function.
Local Effect: The consequence a failure mode has on the operation, function or status of the specific item being analyzed.
Mission Phase Operational Mode: The statement of the mission phase and mode of operation of the system or equipment in which the failure occurs.
Next Higher Level Effect: The consequence a failure mode has on the operation, functions, or status of the items in the next higher indenture level above the specific item being analyzed.
Severity: Considers the worst possible consequence of a failure classified by the degree of injury, property damage, system damage and mission loss that could occur (Mil-Std-1629A FMECA severities).
Single Point Failure: The failure of an item which can result in the failure of the system and is not compensated for by redundancy or an alternative operational procedure.
Other Related FMEA Definitions
Risk Priority Number (RPN) - Provides an alternate evaluation approach to Criticality Analysis. The risk priority number provides a qualitative numerical estimate of design risk. RPN is defined as the product of three independently assessed factors: Severity(S), Occurrence (O) and Detection (D). RPN = (S) * (O) * (D)
Severity (S) - Severity is a numerical subjective estimate of how severe the customer (next user) or end user will perceive the EFFECT of a failure. Examples of Severities.
Occurrence (O) - Occurrence or sometimes termed LIKELIHOOD, is a numerical subjective estimate of the LIKELIHOOD that the cause, if it occurs, will produce the failure mode and its particular effect. Examples of Occurrence values.
Detection (D) - Detection is sometimes termed EFFECTIVENESS. It is a numerical subjective estimate of the effectiveness of the controls to prevent or detect the cause or failure mode before the failure reaches the customer. The assumption is that the cause has occurred. Examples of Detection values.