Study On The Model And Application Of Flight Separation Safety Assessment

In the process of civil aviation development,the rapid growth of flight traffic not only increases the workload of air traffic controllers but also leads to airspace congestion,putting tremendous pressure on air traffic management and resulting in more flight conflicts.As a result,the existing operation rules and standards may become the bottleneck restricting the further development of the civil aviation industry,and also serve as major factors limiting airspace capacity and utilization.Therefore,it is essential to conduct reasonable planning for air routes and airspace.During airspace planning,planners should prioritize operational safety while maximizing the rational utilization of limited airspace.A crucial aspect of this is conducting safety assessments for flight separation,calculating the risk of aircraft collisions,and determining the minimum(optimal)safe separation.Conducting research on the safety evaluation of flight separation for different operational scenarios contributes to supporting new aircraft operating methods and providing theoretical foundations for reducing flight separation,this ultimately improves airspace operational efficiency and safety.Therefore,this paper has conducted the following research regarding flight separation safety assessment:(1)Based on the motion process of paired aircraft,the kinematic equations for paired aircraft were established to describe the time-varying characteristics of separation in three directions.Based on these equations,a safety assessment model for paired approach flight separation was developed,taking into account aircraft position errors,and the collision risk during paired approach was analyzed.The longitudinal collision risk between paired aircraft is significantly influenced by the initial longitudinal safe separation and the speed difference between the paired aircraft.The impact of aircraft type combination and initial longitudinal safe separation on vertical collision risk is relatively small,while the initial vertical separation between paired aircraft and the aircraft altitude maintain ability have a significant influence on vertical collision risk.For lateral collision risk during paired approach,a truncation compensation coefficient for the lateral error probability density function was determined based on the actual lateral error situation.The study focused on analyzing the influence of actual navigation performance on lateral collision risk during paired approach,and it analyzed the target values that actual navigation performance should achieve in different operational environments.Computational analysis reveals that under conditions of small runway spacing,strong wind direction,and high wind speed,flight technical errors have a significant impact on lateral collision risk.(2)Based on the motion process of paired aircraft,kinematic equations were established to describe the lateral time-varying separation between paired aircraft.Combining the Reich collision template theory,a safety assessment model for lateral separation during paired approach was developed.The study analyzed the variation of vortex flow velocity in the wing span direction and its attenuation along the longitudinal axis of the aircraft,and proposed an empirical formula for vortex intensity attenuation.The study then considered two cases: the balance between induced moment and damping moment,and the balance among induced moment,damping moment,and control moment.It analyzed the boundaries of the lateral collision zone during paired approach and derived an analytical expression for the distance from the moment balance point to the vortex core.Furthermore,the study analyzed the influence of factors such as initial longitudinal safe separation,crosswind,maximum tangential velocity of the vortex flow field,and the decay rate of tangential velocity on collision risk.(3)An assessment model for lateral separation in oceanic airspace was established using star-based data and the basic principles of Bayesian networks.The study investigated and analyzed the minimum lateral separation for flexible routes and fixed routes in the oceanic area.Through the analysis of collected oceanic data,a data filtering method was proposed considering data completeness and continuity.Based on the characteristics of flexible routes and fixed routes,a route data completion method was designed.Cluster analysis was applied to analyze the lateral errors of oceanic routes.The analysis revealed that the position errors of fixed routes are largely influenced by flight errors,while the position errors of flexible routes are more affected by positioning errors.Based on the above analysis,a safety assessment model for lateral separation in oceanic routes was established using Bayesian networks.The collision risks for fixed routes and flexible routes were analyzed,and their respective minimum route separation were determined.Specifically,for fixed routes,the lateral separation can be reduced to 14 nautical miles,while for flexible routes,the lateral separation can be reduced to 49 nautical miles.(4)The combination prediction-error elimination optimization algorithm for small sample events was proposed,aiming to improve the research on flight separation safety assessment by predicting flight traffic and determining the safety target level in China based on statistical data.The weights of traditional single-item prediction methods were determined using standard deviation,and an error elimination optimization model was established to optimize the combined prediction results.To evaluate the predictive performance of the algorithm,principles for evaluating the optimization performance of the model were proposed.Through analysis,it was found that the combination prediction-error elimination optimization algorithm can improve prediction accuracy.(5)Based on the results of flight separation safety assessment,combined with control theory,the issue of longitudinal separation control for aircraft was explored.For the problem of longitudinal separation control on air routes,the minimum safe longitudinal separation was determined through flight separation safety assessment and used as the control objective.By analyzing aircraft’s QAR data,the relationship between the engine thrust lever(throttle)and aircraft speed variation was identified and fitted.Subsequently,PID control and fuzzy PID control theories were applied separately to design control systems,enabling the control of longitudinal separation for both en-route and paired approach scenarios.The research found that the designed separation control systems could effectively control the aircraft’s longitudinal separation within the target range.