Top level mishap

Defense-in-depth is the provision for multiple defenses (or safety features) as mitigations against a hazard or a top-level mishap (TLM). This approach is similar to the layers of protection (LOP) concept. Defense-in-depth is a design approach taken to preclude single failures from causing a particular UE through the incorporation of various LOP. Protection methods may include any one or more of the following ... 

See Top-Level Mishaps (TLMs) for additional related information. 

MORT analysis is essentially an FTA that asks what oversights and omissions could have occurred to cause the UE or mishap, and why in terms of the management system. In some ways, MORT analysis is like using the basic MORT diagram as a checklist to ensure everything pertinent is considered. Figure 2.48 shows the top level of the ideal MORT analysis from the MORT User s Manual. 

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