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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 has 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 begin 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 alternative operational procedure.
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 has 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 begin 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 alternative operational procedure.
FMEA Definitions
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.
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.
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What is FMEA?
How FMEA is Done
Types of FMEA
Benefits of FMEA
FMEA Books
FMEA Software
FMEA Examples
Other Resources