The Calculation of Collision Risk on Air-Routes Based on Variable Nominal Separation

In this paper,a new method to calculate collision risk of air-routes,based on variable nominal separation,is proposed. The collision risk model of air-routes,based on the time variable and initial time interval variable,is given. Because the distance and the collision probability vary with time when the nominal relative speed between aircraft is not zero for a fixed initial time interval,the distance,the variable nominal separation,and the collision probability at any time can be expressed as functions of time and initial time interval. By the probabilistic theory,a model for calculating collision risk is acquired based on initial time interval distribution,flow rates,and the proportion of aircraft type. From the results of calculations,the collision risk can be characterized by the model when the nominal separation changes with time. As well the roles of parameters can be shown more readily.

A Theoretical Approach to Estimating Bird Risk of Collision with Wind Turbines Where Empirical Flight Activity Data Are Lacking

There are standard procedures for collecting data on numbers of birds at sites being proposed for wind farm development and evaluating collision risk for each key species. However, methods do not work well for all species. Where a local bird population is depleted, empirical data cannot provide estimates of likely collision mortality numbers if that population returns to satisfactory conservation status. Field survey methods are also inadequate for cryptic bird species. Both these problems can be important for evaluation of impacts of proposed wind farms on bird populations protected by the EU Birds Directive. We present an alternative method, based on energy constrained activity budgets and natural history, which permits assessment of likely collision numbers where empirical data are inadequate. Two case studies are presented where this approach has been successfully used to resolve disputed planning applications, one for a hen harrier population where numbers present are much below the population size at designation, and one for a cryptic species (greenshank). Our novel method helps reduce uncertainty in assessments constrained by difficulties in collecting suitable empirical data.