Limitations of FMEAs
FMEAs consider only non-simultaneous failure modes. Each failure mode is considered individually, assuming that all other system items are performing as designed. Because of this, FMEAs provide limited insight into anomalous behaviours such as:
• Effects of multiple component failures on system functions.
• Latent manifestations of defects such as timing, sequencing, etc..
• Effects on redundant items.
Other analysis techniques, such as fault tree analysis, sneak circuit analysis, Markov analysis and computer-aided simulation, can be used when such anomalous behaviours occur. For additional information, refer to
Fault Tree Analysis and
Markov Modelling.
Also, the prioritization of failure modes in FMEAs for determining corrective actions can be highly subjective. However, clearly defining the method for assessing risk and developing FMEAs using a team approach greatly reduce their subjectiveness.