	Related Topics and Links:
	Failure Modes and Reliability Analysis

Using Mirror Groups in an FMRA

In both Xfmea/RCM++/RBI and BlockSim, you can use the Mirrors commands in the FMRA tab of the ribbon to place the exact same cause record in more than one location in the FMRA.

This is useful when you need to consider common cause failures (i.e., single faults that result in the failure of multiple components). Typical examples of common cause failures include impact, vibration, temperature, contaminants, miscalibration, improper maintenance, and so forth.

All cause records in a mirror group (i.e., "mirrored causes") represent the very same cause for the purpose of FMRA calculations/simulations. To accommodate this, the use of mirror groups will change the properties of cause records in the following ways. Note that there is no undo for changed cause properties.

When a cause is added to a new mirror group or an existing empty group (i.e., one that includes no other causes), that cause’s properties will determine the group’s properties.
When a cause is added to a mirror group that already includes other causes, that cause’s properties (e.g., the short description, reliability policy, etc.) will be changed to match the group’s properties.
If you change the properties of a mirrored cause, that change will also be applied to all other causes in the same mirror group.

Also note that, because mirror groups are Synthesis resources, clearing or removing the causes will not delete the mirror group resource from the project. To delete a resource, use the Resource Manager.)

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