Human Systems Integration Division @ NASA Ames

One of the most fundamental changes to the air traffic management system in NextGen is the concept of trajectory based operations (TBO). With the introduction of fundamental change, system safety and resilience is a critical concern, in particular, the ability of systems to 'degrade gracefully'. In order to design graceful degradation into a TBO envrionment, knowledge of the potential causes of degradation and appropriate solutions is required. Previous research has predominantly explored the technological contribution to graceful degradation, frequently neglecting to consider the role of the human operators in an environment in which humans, especially air traffic controllers, play a safety critical role. In addition, the environmental context in which the technological or human breakdowns occur also play a critical role in how well the system can degrade gracefully, which is also neglected in the literature. These oversights are out of step with real-world operations, and potentially limit an ecologically valid understanding of achieving graceful degradation in an air traffic control environment. Therefore, an integration approach to the human-machine system must be applied in order to achieve graceful degradation. The following literature review aims to identify and summarize the literature to date on the potential causes of degradation in air traffic control and the solutions that may be applied within a TBO context, with a specific focus on the contribution of the air traffic controller. A framework of graceful degradation, developed from the literature, is presented. The framework encompasses the potential impact of technology or human operator breakdown, as well as the complexity of the air traffic environment at the time of the breakdown, and categorizes them into different phases of detection and recovery. The aim of the framework is to develop research questions and design solutions to develop a resilient TBO system and procedures using a holistic view of human-machine system integration.