Safety must be placed in its proper perspective a

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unnecessary safety requirements. Safety must be placed in its proper perspective. A correct safety balance cannot be achieved unless acceptable and unacceptable conditions are established early enough in the program to allow for the selection of the optimum design solution and/or operational alternatives. Defining acceptable and unacceptable risk is as important for cost-effective accident prevention as is defining cost and performance parameters. Hazard Analysis Both elements of risk (hazard severity and likelihood of occurrence) must be characterized. The inability to quantify and/or lack of historical data on a particular hazard does not exclude the hazard from this requirement. Hazards are subdivided into sub- categories related to environment such as system states, environmental conditions or “initiating” and “contributing” hazards. Realistically, a certain degree of safety risk must be accepted. Determining the acceptable level of risk is generally the responsibility of management. Any management decisions, including those related to safety must consider other essential program elements. The marginal costs of implementing hazard control requirements in a system must be weighed against the expected costs of not implementing such controls. (c) UPES, Not for Reproduction/ Sale
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Notes ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ ___________________ Aviation Safety & Security Management The cost of not implementing hazard controls is often difficult to quantify before the fact. In order to quantify expected accident costs before the fact, two factors must be considered. These are related to risk and are the potential consequences of an accident and the probability of its occurrence. The more severe the consequences of an accident (in terms of dollars, injury, or national prestige, etc.) the lower the probability of its occurrence must be for the risk to be acceptable. In this case, it will be worthwhile to spend money to reduce the probability by implementing hazard controls. Conversely, accidents whose consequences are less severe may be acceptable risks at higher probabilities of occurrence and will consequently justify a lesser expenditure to further reduce the frequency of occurrence. Using this concept as a baseline, design limits must be defined. Accident Scenario Relationships In conducting hazard analysis, an accident scenario as shown in Figure 16.2 is a useful model for analyzing risk of harm due to hazards. Throughout this System Safety notes, the term hazard will be used to describe scenarios that may cause harm. It is defined as a “Condition, event, or circumstance that could lead to or contribute to an unplanned or undesired event.” Seldom does a single hazard cause an accident. More often, an accident occurs as the result of a sequence of causes termed initiating and contributory hazards. As shown in Figure 16.2, contributory hazards involve consideration of the system state (e.g., operating environment) as well as failures or malfunctions.
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  • Fall '19
  • Instrument approach, Runway, Rajiv, Aviation Safety & Security Management

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