MTBUR is a measure of reliability related to demand for logistics support. The equation for calculating MTBUR is:

All replacements are unscheduled. This is an assumption of any FRACAS and is not particular to Windchill FRACAS.

Maintenance logs are associated with each specific part or assembly that is repaired as well as with the incident it addressed. In the FRACAS Maintenance Log table or a form for this table, you select Replaced? to indicate that the selected system tree item has been replaced. The total number of items that have been replaced in the currently selected configuration can then be calculated.