Выражение встречается в следующем контексте:

The first step of the cascade is that the requirements contained in the aircraft specification arc transferred into requirements for the next level down, whereby all the requirement standards outlined above should be respected. In aircraft development, the next level down requirements document for the aircraft itself is the Top Level Aircraft Requirements Document (TLARD). It is, for example, further cascaded down into the:
• Top Level Systems Requirements Document (TLSRD);
• Top Level Structural Requirements Document (TLStrRD); as well as into functional requirements documents such as the
• fop Level Maturity Requirements Document (TLMRD);
• Top Level Maintenance, Reliability, Supportability Requirements Document (TLMRSRD);
• top level quality requirements document, TLQRD
to name but the most important ones.

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