# Extremely improbable quantitative probability of

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Extremely Improbable Quantitative: Probability of occurrence per operational hour is less than 1 × 10 –9 (c) UPES, Not for Reproduction/ Sale
Notes ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ Aviation Safety & Security Management Definitions of Severity and Likelihood An example taken from MIL-STD-882C of the definitions used to define Severity of Consequence and Event Likelihood are in Tables 16.3 and 16.4, respectively. Table 16.3: Severity of Consequence Description Category Definition Catastrophic I Death, and/or system loss, and/or severe environmental damage. Critical II Severe injury, severe occupational illness, major system and/or environmental damage. Marginal III Minor injury, minor occupational illness, and/or minor system damage, and/or environmental damage. Negligible IV Less then minor injury, occupational illness, or less then minor system or environmental damage. Table 16.4: Event Likelihood (Probability) Description Level Specific Event Frequent A Likely to occur frequently Probable B Will occur several times in the life of system. Occasional C Likely to occur some time in the life of the system. Remote D Unlikely but possible to occur in the life of the system. Inprobable E So unlikely, it can be assumed that occurrence may not be experienced. Comparative Safety Assessment Selection of some alternate design elements, e.g., operational parameters and/or architecture components or configuration in lieu of others implies recognition on the part of management that one set of alternatives will result in either more or less risk of an accident. The risk management concept emphasizes the identification of the change in risk with a change in alternative solutions. Safety Comparative Safety Assessment is made more complicated considering that a lesser safety risk may not be the optimum choice from a mission assurance standpoint. Recognition of this is the keystone of safety risk management. These factors make system safety a decision making tool. It must be recognized, however, that selection of the greater safety risk alternative carries with it the responsibility of assuring inclusion of adequate warnings, personnel protective systems, and procedural controls. Safety Comparative Safety Assessment is also a planning tool. It requires planning for the development of safety operating procedures and test programs to resolve uncertainty when safety risk cannot be completely controlled by design. It provides a control (c) UPES, Not for Reproduction/ Sale
UNIT 16: Principle of System Safety Notes ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ system to track and measure progress towards the resolution of uncertainty and to measure the reduction of safety risk. Assessment of risk is made by combining the severity of consequence with the likelihood of occurrence in a matrix. Risk acceptance criteria to be used in the FAA AMS (Acquisition Management System) process are shown in Figure 16.3 and Figure 16.4.

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• Fall '19
• Instrument approach, Runway, Rajiv, Aviation Safety & Security Management

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