← All chapters Chapter 08

Systematic Derivation of the Top Level Events

Malfunctions derived from state diagrams, not conjured from memory.

A malfunction that is never written down is a fault tree that is never built, so the failure modes of a function must be enumerated completely. From a state diagram they follow mechanically — one false positive per forbidden transition, three modes per specified one — and analog outputs yield the same once their range is divided into functional bands. The chapter derives the wiper's OffNotSlow malfunction.