Transitional system analysis

During Testability Analyses on equipments it became evident that, if a function failure occurs, a number of other functions may appear to fail at the same time, i.e. each apparent failure event may be caused by that function or another source. Therefore, a failure logic (or pattern) exists for each failure and it follows that there is an affected function logic or operating logic when functions operate normally. This logic is subject to modification upon the change of operating mode or other conditions. Such changes in an operating environment may cause some functions to operate in an unexpected fashion or appear to temporarily fail when a particular set of conditions prevail. Unintended variance, due to systematic problems or failure may have hazardous consequences if not previously identified and compensated. This paper presents an alternative method of system observation during the design process which can identify potential design weaknesses prior to Detail Design and so improve reliability. It may also increase understanding of how system elements interact when the system is used, thus reducing integration problems. The observation method contains a new `fit for purpose´ measuring tool-Normal Operating Mode Effect Analysis (NOMEA)-which is accommodated into the design process to promote design improvements