Degraded Modes of Operation
Degraded Modes of Operation
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.
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.
One critical element that should not be under estimated is the role and ability of engineering and technical support to support the contingency strategy and resulting measures. Appendix G of the EUROCONTROL "Guidelines for Contingency Planning for Air Navigation Services Guidelines" addresses systems engineering perspective of contingency strategies. This provides additional guidance on this important aspect of contingency planning. Similarly, it is important to consider the ways in which external resources can be secured, for instance, from sub-contractors and other maintenance organisations both during degraded modes of operation, as service providers work to rectify a potential problem, and after any contingency has been declared.
- Contingency Lifecycle
- Policy on Contingency
- Letters of Agreement
- Emergency Phase in Contingency
- Fail to Safe
- Conflict Free Routing under Contingency
- Execution and Assurance in Contingency
- CFMU in Contingency Operations
- Degraded Modes Safety for Operational Engineering by EUROCONTROL (A brochure for the ATM engineering personnel aimed to provide overview of the degraded modes and understanding of the relationships between degraded modes and safety culture)
- For further information on Contingency Planning see the EUROCONTROL, Guidelines for Contingency Planning for Air Navigation Services (including Service Continuity) In particular for degraded modes of operation, see Chapter 8 of the guidelines on the Contingency Planning Process: Step 4 and Appendix G of the Guidelines on the Systems Engineering Perspective on Contingency Strategies
- Contingency Planning of ANS-A practical case: Fire in a tower Practical case study, by Professor Chris Johnson
- The Strategic Implications of Safety-Critical Software and Cyber Security on ATM Operations Introduction to the degraded modes of operation by Professor Chris Johnson
- See also the EUROCONTROL Reference Guide to EUROCONTROL Guidelines for Contingency Planning
Additional information, training support etc can also be obtained via the EUROCONTROL Experimental Centre project on degraded modes from B.Kirwan@eurocontrol.int