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 if the safety function fails.

The twin engine aircraft example may give some insight (see also fault tree analysis and reliability block diagrams).


This example is a little bit different compared to the twin engine example in other paragraphs. Instead of a crash landing, the starting point is a single engine failure. This is because fault trees with top event = crash landing don't exist in practice, whereas fault 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
P_{(successful emergency landing)} given one engine failed = 0,000005
P_{(crash landing)} given one engine failed = 0,000005