As defined in MIL-STD-1629, quantitative failure mode criticality numbers are calculated by multiplying the failure effect probability (beta), failure mode ratio (alpha), part failure rate (lamda-p), and operating time (t). Doing the math, this should indicate how often failure modes occur during the mission operating time. Criticality numbers have no units because failure effect probability and failure mode ratio have no units and the part failure rate and operating time units cancel.
Windchill Quality Solutions 10.1 calculates criticality numbers by multiplying the item failure rate, failure effect probability, mode percentage, and mode operating time but unfortunately ignores the item failure rate units. Since item failure rates are in failures per million hours, criticality numbers effectively indicate how often failure modes occur during a million missions - a very different answer. Please consider correcting this error.
Windchill Quality Solutions 10.1 also has no provision for plotting quantitative failure mode criticality numbers on a MIL-STD-1629 criticality matrix. Please consider adding this capability.
