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The paper presents results of the wake vortex safety analysis conducted for selected unmanned aircraft systems (UAS) operating alongside commercial aircraft in the terminal zone. The approach is developed on the basis of a dynamic model of an aircraft entering an upstream wake vortex that allows evaluating changes in the important aerodynamic parameters following the wake vortex interaction and assessing the operational safety risks in application to variable-size UAS. The employed variable-fidelity approach integrates reduced-order models of wake generation, evolution and interaction incorporating both theoretical and high-fidelity predictions. The benchmark parametric study estimates UAS responses in terms of the roll control ratios (RCR) developed by the follower aircraft depending on their position and orientation relative to the wake shed by the leader B-737 aircraft, as well as the duration of the wake-UAS interaction. The UAS dynamic reaction is examined in the context of several possible flight control scenarios that include a timedelayed maximum aileron deviation.

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When making policy, procedural, or technological changes to a complex system that has safety implications, a key question decision makers must answer is: What are the risks to the users of the system that will result from making these changes to the system? This chapter illustrates a method to explore different facets of this question using mathematical modeling and probabilistic risk assessment techniques, with the objective of assessing the safety impact of changes to the National Airspace System that follow from the Federal Aviation Administration's next generation air traffic modernization program. The authors describe the development of an Integrated Safety Assessment Model as a structured approach to evaluating current and emerging risks in National Airspace System operations. This process addresses the previously stated risk question by combining fault tree and event sequence diagram modeling techniques, hazard identification and analysis methods, opinions from subject matter experts, and concepts from business intelligence.