With the ever-increasing demand for air traffic over the years, safety risk assessment has become significant in maintaining the operational safety of the air transport system for long-term development towards sustainability. This paper conducts a safety risk assessment of the air traffic control (ATC) system based on game theory and cloud matter element analysis. The safety risk of the ATC system is evaluated from four aspects, including human, machine, environment, and management. The Nash equilibrium is introduced from game theory to weigh the indicators. The cloud matter element assessment adopts the cloud model from fuzzy sets and probability theory to replace the certain value in conventional matter element theory, which takes the randomness, ambiguity, and incompatibility of the indicators into consideration. In this sense, the safety risk level of the ATC system can be evaluated by calculating the correlation degree of the standard cloud matter element between the indicators and the risks. This paper expands the research scope by introducing and combing game theory and cloud matter element analysis. Furthermore, the applicability and the robustness of the method are examined with a case study of the ATC system, which enriches the existing literature and points out the direction for future work.

The effect of crosswinds on paired approach (PA) procedures for Closely Spaced Parallel Runways (CSPR) is investigated in this paper by fully utilizing the crosswind environment to implement a more efficient PA and increase runway capacity. An improved wake dissipation model is used to quickly predict the change in the wake velocity field for the PA procedures. The change in the width of the hazard zone is explored in detail using the roll moment coefficient as a determination index. The calculation method for the hazard zone of a wake encounter in a PA is designed considering the influence of crosswind, turbulence, and ground effect. The results show the diffusion rate of the hazard zone and a decrease in the width of the maximum hazard zone under a breezeless environment with increases in the turbulence intensity. The maximum hazard zone width decreases with an increase in crosswind speed. Favorable crosswinds can reduce wake separation and improve the efficiency of a PA. Lower turbulence intensity has a better crosswind effect under a normal PA. The 3-degree offset PA can accommodate larger unfavorable crosswinds, with a higher turbulence intensity having a better crosswind effect. The 3-degree offset PA can substantially increase the proportion of time when no wake affects the PA procedure.