A Time-Space Diagram as Controller Support Tool for Closed Path Continuous Descent Operations

Tactical control during a closed-path Continuous Descent Operation stops the aircraft from following its optimized descent. To mitigate tactical control, air traffic controllers apply arbitrary large spacing buffers to account for the unpredictability of the aircraft trajectory from the controller’s point of view. A controller support tool is required for early de-confliction, spacing, and sequencing to facilitate these operations without the need to apply large buffers. The Time-Space Diagram controller support tool was developed to make the constraints and complexity of a Continuous Descent Operation perceptually evident and provide tools and information to the controller to be an active problem solver. This paper addresses the further development and validation of the interface. The concept of Visual Momentum was applied to enhance the efficiency of working the multi-display interface that consists of the Plan View Display and Time-Space Diagram. Direct Manipulation Interfaces were added to enable the controller to plan and implement actions, such as speed and altitude control. A controller-in-the-experiment was setup to validate the interface. In the experiment the subjects used either the Time-Space Diagram support tool or a stack list that provided the required spacing and time to lose or gain as a baseline. Both interfaces enabled the subjects to space the aircraft safely and efficiently. Compared to the baseline, the Time-Space Diagram interface freed time to plan traffic ahead using the Direct Manipulation Interfaces, which according to all subjects worked intuitively. The number of instructions per aircraft was decreased by 25%. Early accurate speed control was applied and use of heading vectors was no longer necessary in most scenarios. As a result aircraft commenced their continuous descent at a higher altitude and greater distance from the runway. The controller workload was significantly reduced and the level of Situational Awareness increased.Control & OperationsAerospace Engineerin

Barents Sea polar bears ( Ursus maritimus

This paper examines how anthropogenic threats, such as disturbance, pollution and climate change, are linked to polar bear (Ursus maritimus) population biology in the Svalbard and Barents Sea area, with the aim to increase our understanding of how human activity may impact the population. Overharvesting drastically reduced the population of polar bears in the Barents Sea region from about 1870 to 1970. After harvesting was stopped—in 1956 in Russia and 1973 in Norway—the population grew to an estimated 2650 individuals (95% confidence interval 1900–3600) in 2004, and maternity denning in the Svalbard Archipelago became more widely distributed. During recent decades, the population has faced challenges from a variety of new anthropogenic impacts: a range of pollutants, an increasing level of human presence and activity as well as changes in ice conditions. Contaminants bioaccumulate up through the marine food web, culminating in this top predator that consumes ringed, bearded and harp seals. Females with small cubs use land-fast sea ice for hunting and are therefore vulnerable to disturbance by snowmobile drivers. Sea-ice diminution, associated with climate change, reduces polar bears’ access to denning areas and could negatively affect the survival of cubs. There are clear linkages between population biology and current anthropogenic threats, and we suggest that future research and management should focus on and take into consideration the combined effects of several stressors on polar bears