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Where the table indicates that the risk is currently unacceptable, action must be taken to reduce the probability of occurrence and/or
the severity of the hazard. If neither mitigating measure is available, the system clearly does not satisfy the safety objectives. In any
process where judgement is applied there will be situations where the tolerability is not clearly defined. An issue that falls into this
area of uncertainty is likely to require, before implementation, the endorsement of the individual ultimately accountable for safety
within the organisation.
Guidance on risk analysis 2
Safety Criticality Classification (JAR 25) that results in one or more of the following effects;
Catastrophic Hazardous Major Minor
Loss of the Aircraft. Multiple Fatalities A large reduction in safety margins. Physical distress or a workload such that the flight crew cannot be relied upon to perform their tasks accurately or completely. Serious injury or death of a relatively small pro-portion of the occupants A significant reduction in safety margins. A reduction in the ability of the flight crew to cope with adverse conditions as a result of increase in workload or as a result of conditions impairing their efficiency. Injury to occupants Nuisance. Operating Limitations. Use of alternative or Emergency procedures
Risk Assessment Matrix
Catastrophic Review Unacceptable Unacceptable Unacceptable Unacceptable
Hazardous Review Review Unacceptable Unacceptable Unacceptable
Major Acceptable Review Review Review Review
Minor Acceptable Acceptable Acceptable Acceptable Review
Extremely improbable Extremely remote remote Reasonably probable Frequent
Probability of occurrence definitions
Probability of Occurrence classification Extremely improbable Extremely remote Remote Reasonably probable Frequent
Qualitative definition Should virtually never occur in the whole fleet life. Unlikely to occur when considering several systems of the same type, but nevertheless, has to be considered as being possible Unlikely to occur during total operational life of each system but may occur several times when considering several systems of the same type May occur once or during total operational life of a single system May occur once or several times during operational life
Quantitative definition < 10-9 per flight hour 10-7 to 10-9 per flight hour 10-5 to 10-7 per flight hour 10-3 to 10-5 per flight hour 10-3 per flight hour
The table above is reproduced from JAR 25 and is specifically related to the probability of an event occurring during flight. It is considered that the definitions are equally valid for aircraft movements at an aerodrome but with probabilities decreased as stated in the Safety Objectives in paragraph 3. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：European Action Plan for the Prevention of Runway Incursions(48)
