The set of default failure severities that can be assigned to different failure effects are listed in the following table, along with the MIL-STD-1629A Severities that can be easily set up as alternative severity settings within eXpress (both sets are listed in order of decreasing severity):
Default Severities
MIL-STD-1629A Severities
Value
Loss of Life
5
Loss of Equipment
Category I - Catastrophic
4
Loss of Mission
Category II - Critical
3
Loss of Operation
Category III - Marginal
2
Degraded Performance
Category IV - Minor
1
No Effect
0
Defining a Custom Severity
Custom severity settings can be set up by defining a checklist Attribute named "Severity" and associating it with failure effects using the Attribute Definitions dialog. The Attribute must be marked as "Mutually Exclusive" and numeric values must be assigned to the different entries in the checklist (the most severe receiving the highest value). If you wish for custom severity settings to remain compatible with existing selections, make sure that the new settings are assigned comparable values (eXpress actually keeps track of severity settings internally using these numeric values). If you wish to insert values between two existing values, you can use fractional values (3.5, for example, can be assigned to a severity that falls between 3 and 4).
eXpress includes a checklist Attribute that has been set up with the MIL-STD-1629A severity setting listed in the table above. To use this Attribute, create a Design Template Data Source and link it to the design template file "Custom Severity (MIL-STD-1629A).ext" (this template can also be selected when the Analyst invokes the Create Design from Template operation).
When a design contains a custom severity Attribute, the enumerated severity values that can be selected on the Failure Effects and Design Failure Effects panels will be replaced with those defined in the checklist Attribute. Also, the values that are listed in the FMECA chart and the Criticality Report will be taken from the custom severity Attribute.
