nonoperability

Nonoperability is the condition in which a system, device, or process cannot perform its intended function. It can be temporary or permanent and may affect hardware, software, or procedures. The term describes an incapacity to operate as designed, rather than simple downtime caused by external disturbances, and it is distinct from obsolescence, which means a system has been retired from use.

Causes include physical wear or damage, mechanical failure, software faults, design flaws, degradation of materials, loss of power, supply shortages for parts, or regulatory and safety constraints that prohibit operation. Nonoperability can arise during development and testing or during routine operation as conditions exceed acceptable limits.

Implications and management: Nonoperability reduces readiness, safety margins, and performance; it is a central concern in reliability engineering, maintenance planning, and risk assessment. It is often described alongside unavailability and downtime. Quantitative measures such as availability, mean time to failure, and mean time to repair are used to evaluate and compare nonoperable states.

Mitigation typically involves redundancy, preventive maintenance, design improvements, robust diagnostics, and supply-chain resilience. In mission-critical fields, rapid fault isolation and fail-safe modes can limit the duration of nonoperability and preserve safety.