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## 2.1 SRM and Safety Assurance 

## 2.1.1 Introduction to Managing System Safety 

As Air Traffic Organization (ATO) operational procedures and National Airspace System (NAS) equipment (i.e., hardware and software) evolve, their interaction and interdependency across organizations within the ATO and throughout the Federal Aviation Administration (FAA) must be addressed. In a system as large and diverse as the NAS, the discovery of a safety hazard and reduction of its risk often falls within the purview of multiple organizations. 

The effects of safety hazards and associated risk reduction methods across multiple organizations, domains, and implementation timelines must be properly understood to achieve the highest practical level of safety. Safety risk deemed acceptable for an individual element of the NAS may lead to unintentional safety risk in another if a safety assessment is not conducted with a “system of systems” philosophy. As emerging NAS equipment, operations, and procedures are tested and implemented, safety risk assessments must account for their potential safety impact on existing/legacy tools and procedures and vice versa. Sharing safety data and conducting cooperative analyses using an integrated safety management approach helps identify and resolve issues requiring the consideration of multiple disciplines. The goal of an integrated approach to safety management is to eliminate gaps in safety analyses by assessing NAS equipment, operations, and procedures across three planes: vertical, horizontal, and temporal. The vertical plane is hierarchical, providing assessments from a specific project up to the NAS-level system of systems of which the project is a part. The horizontal plane spans organizations, programs, and systems. Finally, the temporal plane attempts to eliminate safety gaps across program and system implementation timelines. 

Figure 2.1 depicts several factors in each of the three planes that should be considered to ensure an integrated approach to safety management. Refer to the current version of the Safety Risk Management Guidance for System Acquisitions for more information. 

## 2.1.2 Safety Assessment Using the Tenets of SRM and Safety Assurance 

In acknowledging the complexity of the NAS and its various system interdependencies, the ATO uses the systematic processes and tenets of Safety Risk Management (SRM) and Safety Assurance to identify and address safety hazards and risks across the NAS. 

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The remainder of this chapter discusses the foundational concepts and practices used to identify and address safety issues and consider potential ramifications in an integrated way. It 

