System degraded availability

The concept of degraded availability is introduced, and the required definitions and assumptions are presented. Appropriate metrics are formulated for the quantification of degraded availability at function, mission and system level. This degraded availability model is an extension to the model for availability of multifunctional systems (Sols, A., Availability of continuously operated, coherent, multifunctional systems. Master's thesis, Virginia Polytechnic Institute and State University, 1992).