Definition

A reduced level of service invoked by equipment outage or malfunction, staff shortage or procedures becoming inadequate as a knock-on effect of one or several deficient system elements.

Description

Degraded modes of operation are defined to occur when staff continue to maintain levels of service when elements of the underlying technical infrastructure are unavailable. Degraded modes of operation occur when members of staff find ways of working around failures in the underlying technical infrastructure. They should not jeopardise safety given that they are subject to appropriate levels of risk assessment. Degraded modes describe failures that stop short of the loss of an air traffic control facility such as an area control centre (ACC), however, they may be precursors to contingencies if further failures occur. For 'emergency', 'degraded' and 'service continuity modes of operation', it is important to conduct both a safety assessment and a security risk assessment. The aim is to ensure that the planned contingency measures meet safety and security requirements set at the policy step.