Download Fault Tree Analysis PDF

TitleFault Tree Analysis
TagsTechnology Nature Computing And Information Technology
File Size444.9 KB
Total Pages194
Document Text Contents
Page 1

Mission Success Starts With Safety

Fault Tree Analysis (FTA):
Concepts and Applications

Bill Vesely
NASA HQ

Page 2

Mission Success Starts With Safety

Inductive and Deductive Modeling are the
Two Basic Types of Modeling

• Inductive models forwardly induce the consequences
of an event.

• Deductive models backwardly deduce the causes of
an event.

Event Forward Looking Logic Consequences

Induce Forwards

Event Backward Looking Logic Causes

Deduce Backwards

2

Page 97

Mission Success Starts With Safety

Examples of CCFs Usually Included
in FTA

• Redundant sensors having a common calibration
procedure

• Redundant components that can be left in the wrong
configuration due to a common test or maintenance

• Redundant components that are supplied by the
same supplier that have not been independently
tested

• Redundant components that have common
processing that are not subsequently independently
checked

96

Page 98

Mission Success Starts With Safety

Modeling of CCFs in a FT

• When considered applicable, a CCF contribution
needs to be added to independent failures of similar
components

• The AND gate of independent failures is expanded
to become an OR gate with the independent failure
contribution plus the CCF contribution

CCF

97

Page 193

Mission Success Starts With Safety

FTA Project Management Tasks (3)

• Review the work at stages
– FT construction
– Qualitative evaluations
– Quantitative evaluations

• Check and validate the results
– Engineering logic checks
– Consistency checks with experience

• Prepare and disseminate the draft report
– Conclusions/findings
– FTA results
– FTs
– Software inputs/outputs

• Obtain feedback and modify and final report
– Disseminate the report
– Present findings

192

Page 194

Mission Success Starts With Safety

Reference

• “Fault Tree Handbook with Aerospace Applications’,
Version 1.1, NASA Publication, August 2002.

193

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