The safety and e ciency of free ight will bene t from automated con ict prediction and resolution advisories. Con ict prediction is based on trajectory prediction and is less certain the farther in advance the prediction, however. An estimate is therefore needed of the probability that a con ict will occur, given a pair of predicted trajectories and their levels of uncertainty. This paper presents a method to estimate that con ict probability. The trajectory prediction errors are modeled as normally distributed, and the two error covariances for an aircraft pair are combined into a single, equivalent covariance of the relative position. A coordinate transformation is then used to derive an analytical solution. Numerical examples and a Monte Carlo validation are presented.

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This article describes a unified solution to three types of separation-assurance problems that occur in en-route airspace: separation conflicts, arrival sequencing, and weather-cell avoidance. Algorithms for solving these problems play a key role in the design of future air traffic management systems such as the US's NextGen. Because these problems can arise simultaneously in any combination, it is necessary to develop integrated algorithms for solving them. A unified and comprehensive solution to these problems provides the foundation for a future air traffic management system that requires a high level of automation in separation assurance. This article describes the three algorithms developed for solving each problem and then shows how they are used sequentially to solve any combination of these problems. The first set of algorithms resolves loss-of-separation conflicts. It generates multiple resolutions for each conflict and then selects the one giving the least delay. Two new algorithms, one for sequencing and merging of arrival traffic, referred to as the arrival manager, and the other for weather-cell avoidance are presented. Because these three problems constitute a substantial fraction of the workload of en-route controllers, integrated algorithms to solve them is a basic requirement for automated separation assurance. This article also reviews the advanced airspace concept, a proposed design for a ground-based system that postulates redundant systems for automated separation assurance in order to achieve both high levels of safety and airspace capacity. It is proposed that automated separation assurance be introduced operationally in several steps, each step reducing controller workload further while increasing airspace capacity. A fast time simulation was used to determine performance statistics of the algorithm at up to 3× current traffic levels.

Abstract:The article describes an algorithm for computing horizontal resolution trajectories with a limit on bank angle. If loss of separation can be avoided, the algorithm generates a set of manoeuvres that achieves or exceeds the specified minimum separation. The manoeuvres consist of turns to a specified heading followed by straight-line flight. Both single aircraft and cooperative manoeuvres are generated. In cooperative manoeuvres, both conflict aircraft simultaneously execute resolution manoeuvres, which expedite the resolution process compared to single aircraft manoeuvres. If loss of separation is unavoidable for a specified bank angle limit, the method chooses the manoeuvre that maximizes the minimum separation during the turns. The characteristics of the resolution trajectories have been analysed in a parameter space comprising initial positions, encounter angle, airspeed, predicted minimum separation, and bank angle. Analysis of resolutions for sets of initial conditions provided a road map for the design of an algorithm. The conceptual design of a system is described that resolves close-in conflicts automatically by uplinking resolution advisories to aircraft. Controllers have the option to assign detected conflicts to be resolved by the system. The system also has the authority to uplink resolution advisories to the aircraft without prior controller approval if time to loss of separation falls below a threshold value. The Mode S Specific Services data link is well suited for uplinking resolution advisories to the conflict aircraft. Deployment of the system could be an initial step in building the next-generation air traffic control system.