adequately with technical uncertainties
& Quality Management
Event Tree Analysis
Event tree analysis begins where
fault tree analysis ends: At the top event. While fault tree analysis
is used for assessing potential dangerous scenarios within the responsibility of a
safety function, event tree analysis works similar, however for
potential consequences outside the responsibility of the safety
The structure of event trees is a
reversed fault tree structure: On a time axis, fault trees branch out
into the past while event trees branch out into the future.
The twin engine aircraft example may give some insight (see also fault tree analysis and reliability block diagram).
This example is a little bit
different compared to the twin engine examples in other paragraphs.
Instead of a crash landing, its starting point is a single engine failure. This is
only for didactical reasons. Moreover, fault trees with top event = crash landing don't exist in practice,
whereas trees with top event = engine failure do exist.
Event tree calculation yields the probability distribution over various
consequences. In the above example, the result may look like this:
P(regular landing) given one engine failed = 0,99999
landing) given one engine failed = 0,000005
P(crash landing) given
one engine failed = 0,000005