OBJECTIVE AND CONTENTS .1 THE CONCEPT OF SAFETY .1

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Chapter 2 BASIC SAFETY CONCEPTS

2.1 OBJECTIVE AND CONTENTS 2.1.1 This chapter reviews the strengths and weaknesses of long-established approaches to safety, and proposes new perspectives and concepts underlying a contemporary approach to safety. 2.1.2 The chapter includes the following topics: a The concept of safety; b The evolution of safety thinking; c Accident causation — The Reason model; d The organizational accident; e People, operational contexts and safety — The SHEL model; f Errors and violations; g Organizational culture; and h Safety investigation. 2.2 THE CONCEPT OF SAFETY 2.2.1 Depending on the perspective, the concept of safety in aviation may have different connotations, such as: a zero accidents or serious incidents — a view widely held by the travelling public; b freedom from hazards, i.e. those factors which cause or are likely to cause harm; c attitudes of employees of aviation organizations towards unsafe acts and conditions; d error avoidance; and e regulatory compliance. 2.2.2 Whatever the connotation, they all have one underlying commonality: the possibility of absolute control. Zero accidents, freedom from hazards, and so forth, convey the idea that it would be possible — by design or intervention — to bring under control, in aviation operational contexts, all variables that can precipitate bad or damaging outcomes. However, while the elimination of accidents andor serious incidents and the achievement of absolute control 2-2 Safety Management Manual SMM is certainly desirable, they are unachievable goals in open and dynamic operational contexts. Hazards are integral components of aviation operational contexts. Failures and operational errors will occur in aviation, in spite of the best and most accomplished efforts to prevent them. No human activity or human-made system can be guaranteed to be absolutely free from hazards and operational errors. 2.2.3 Safety is therefore a concept that must encompass relatives rather than absolutes, whereby safety risks arising from the consequences of hazards in operational contexts must be acceptable in an inherently safe system. The key issue still resides in control, but relative rather than absolute control. As long as safety risks and operational errors are kept under a reasonable degree of control, a system as open and dynamic as commercial civil aviation is considered to be safe. In other words, safety risks and operational errors that are controlled to a reasonable degree are acceptable in an inherently safe system. 2.2.4 Safety is increasingly viewed as the outcome of the management of certain organizational processes, which have the objective of keeping the safety risks of the consequences of hazards in operational contexts under organizational control. Thus, for the purposes of this manual, safety is considered to have the following meaning: Safety. The state in which the possibility of harm to persons or of property damage is reduced to, and maintained at or below, an acceptable level through a continuing process of hazard identification and safety risk management. 2.3 THE EVOLUTION OF SAFETY THINKING 2.3.1