FMEA, which stands for failure mode and effects analysis, and FMECA, or failure modes, effects and criticality analysis, are methods used to identify ways a product or process can fail. The basic methodology is the same in both processes, but there are important differences between them.
Qualitative Vs. Quantitative
FMEA provides only qualitative information. The process is used widely in industry as a what-if process. For example, NASA uses it as part of its flight assurance program for spacecraft. FMECA provides qualitative as well as limited quantitative information, which means capable of being measured. It attaches a level of criticality to failure modes. For example, the U.S. Army uses it to assess mission-critical equipment and systems.
FMECA is effectively an extension of FMEA. In order to perform FMECA, analysts must perform FMEA followed by critical analysis. FMEA identifies failure modes of a product or process and their effects, while CA ranks those failure modes in order of importance, according to failure rate and severity of failure.
Critical analysis does not add information to FMEA. CA limits the scope of FMECA to the failure modes identified by FMEA as requiring reliability centered maintenance.