Fault Tree Analysis
The Fault Tree Analysis (FTA) technique was developed by H.R. Watson of Bell Telephone Laboratories in 1962. Fault Tree Analysis was first applied to anti-ballistic systems. Boeing further developed and refined the process becoming the foremost proponents of the method.
It is an accepted technique used to analyze system safety. Not only is Fault Tree Analysis used for safety-critical systems analysis but also for mission-critical systems analysis. Hardware, software and human factors can be analyzed in an integrated fashion. Fault Tree Analysis is particularly suited to the analysis of complex systems consisting of several functionally related or dependent subsystems with different performance objectives. This is especially true whenever the system design requires the collaboration of many specialized technical design groups.
A fault tree is a symbolic logic diagram, in the form of an inverted tree, showing the cause and effect relationship between an undesired event and contributing causes. Fault trees clearly show the parallel and sequential combinations of events that can constitute a hazard. Fault Tree Analysis always begins assuming that an undesired event has taken place. It is a backward moving process which attempts to determine all possible causes for the undesired event to occur.
Fault Tree Analysis can imply different things to different people as reflected by the wide range of depths of analysis that exist. Coverage in the areas of:
- fault tree verification,
- minimal cut set analysis,
- common cause analysis,
- importance analysis, and
- supporting material
varies dramatically as does fault tree quality. There truly are some scary FTA's out there. A military client of ours showed us a SAR produced by a well-known defense company. We noticed a problem with the top event of the tree!
What criteria should be applied to determine whether to accept or reject fault tree analyses? There are 28 attributes (recently updated) to look for. In a recent survey most fault tree analysts did not come close to answering this question. If you work for government branches (e.g., FAA, FDA, FRA, DOD, and MOD), clients, auditors, or system integrators, and are a reviewer of contract deliverables, you should know this. For additional information, click here.
HCRQ has over 30 years experience in Fault Tree Analysis and we can teach you how to perform one the right way (our Hands-On Fault Tree Analysis Course is famous). We critique other's fault tree analyses, such as those from light rail transit systems (the worst fault tree analyses (e.g., containing branches such as wire breaks, incorrect maintenance, incorrect design, incorrect construction/installation) we have seen have come from this sector), every day.
Do you know the disadvantages of using Fault Tree Analysis?