AIRCRAFT FLIGHT SAFETY ANALYSIS IN LOW ALTITUDE AIRSPACE

The low altitude airspace will be open in China, general aviation flights are tremendously increased. Whether aircrafts can fly safely and how to determine the requirements of safety flight are the problems needed to be confirmed. Under this circumstances, based on the international Civil Aviation Organization（ICAO） criteria and the standards made by CAAC, this paper adopts the ＂See and Avoid＂ principle. Under the binding conditions of flight rules, visibility requirements, responding time, the aircraft speed, circle banking angle or the climbing angle, based on its study on aircraft dynamics principles, this paper establishes a mathematical collision avoidance model for head-to-head traffic and crossing converging traffic at the same level. And the safety separation requirements of the aircrafts in low altitude flight are equantitatively analyzed. Finally, the Matlab software is used to analyze the above method. The result shows that the safe traffic avoidance of the converging traffic at the same level meets certain flight conditions, while intersecting the traffic at the same level can safely avoid the collision.

AUCTIONING METHOD FOR AIRSPACE CONGESTING RESOURCE ALLOCATION AND GAME EQUILIBRIUM ANALYSIS

The airspace congestion is becoming more and more severe.Although there are traffic flow management（TFM）initiatives based on CDM widely applied,how to reschedule these disrupted flights of different airlines integrating TFM initiatives and allocate the limited airspace resources to these airlines equitably and efficiently is still a problem.The air traffic management（ATM）authority aims to minimizing the systemic costs of congested airspaces.And the airlines are self-interested and profit-oriented.Being incorporated into the collaborative decision making（CDM）process,the airlines can influence the rescheduling decisions to profit themselves.The airlines maybe hide the flight information that is disadvantageous to them,but is necessary to the optimal system decision.To realize the coincidence goal between the ATM authority and airlines for the efficient,and equitable allocation of airspace resources,this paper provides an auction-based market method to solve the congestion airspace problem under the pre-tactic and tactic stage of air traffic flow management.Through a simulation experiment,the rationing results show that the auction method can decrease the total delay costs of flights in the congested airspace compared with both the first schedule first service（FSFS）tactic and the ration by schedule（RBS）tactic.Finally,the analysis results indicate that if reallocate the charges from the auction to the airlines according to the proportion of their disrupted flights,the auction mechanism can allocate the airspace resource in economy equitably and decrease the delay losses of the airlines compared with the results of the FSFS tactic.

Beamforming of Whole Airspace Phased Array TT&C System Based on Linear Subarrays

The whole airspace phased array telemetry,track and command(TT&C)system is regarded as the development tendency of next generation TT&C system,and the distribution of the antenna units and the beamforming technology have sparked wide interest in this field.A method for antenna distribution is proposed based on the linear subarrays technology.A symmetrical truncated cone conformal array is composed of the linear subarrays placed on the generatrix.The impact of truncated cone bottom radius and elevation angle on beamforming are studied and simulated.Simulation results verify the system design.

Research on Operation of UAVs in Non-isolated Airspace

In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial vehicles was researched.According to the results of risk analysis,a strategy for solving the conflict of aircraft is proposed,and the risk assessment experiment of unmanned aerial vehicle(UAV)in non-isolated airspace conflict is carried out.The results show that under the experimental conditions,large unmanned aerial vehicles equipped with ADS-B,TCAS and other airborne sensing systems will indeed interfere with other aircraft in airspace when they enter non-isolated airspace.Especially when the number of aircraft in airspace is large,the automatic avoidance system of UAV will increase the avoidance time and trigger the safety alarm,but the safety level is still acceptable.This indicates that it is relatively safe for UAVs to enter non-isolated airspace under limited conditions.The results can be used as a reference for the safe operation of unmanned aerial vehicle(UAV)in non-isolated airspace.

Analysis on Potential Conflict Frequency of Intersected Air Routes in Terminal Airspace Design

In order to obtain accurate conflict risks in terminal airspace design,the concept and calculation model of potential conflict frequency for intersected routes are proposed.Conflict frequency is represented by the product of horizontal conflict frequency and vertical conflict probability.The horizontal conflict frequency is derived from the probability density distribution of conflicts in a period of time.Based on the recorded radar trajectory data,the concept and model of ROUTE distance are proposed,and the probability density function of aircraft height at a specified ROUTE distance is deduced by kernel density estimation.Furthermore,vertical conflict probability and its horizontal distribution are achieved.Examples of three intersected arrival and departure route design schemes are studied.Compared with scheme 1,the conflict frequency values of the other two improved schemes decrease to53% and 24%,respectively.The results show that the model can quantify potential conflict frequency of intersected routes.

Dynamic airspace sectorization via improved genetic algorithm

This paper deals with dynamic airspace sectorization （DAS） problem by an improved genetic algorithm （iGA）. A graph model is first constructed that represents the airspace static structure. Then the DAS problem is formulated as a graph-partitioning problem to balance the sector workload under the premise of ensuring safety. In the iGA, multiple populations and hybrid coding are applied to determine the optimal sector number and airspace sectorization. The sector constraints are well satisfied by the improved genetic operators and protect zones. This method is validated by being applied to the airspace of North China in terms of three indexes, which are sector balancing index, coordination workload index and sector average flight time index. The improvement is obvious, as the sector balancing index is reduced by 16.5 %, the coordination workload index is reduced by 11.2 %, and the sector average flight time index is increased by 11.4 % during the peak-hour traffic.

Design Issues for Use of Solid State Transmitter Radars in the Terminal Airspace

Abstract

ESTIMATION METHOD OF AIRSPACE CONNECTIVITY PROBABILITY IN MILITARY AANET

Connectivity is the premise and foundation of networking and routing.For the probabilistic flight path of military aircraft resulting in the difficulty of Aeronautical Ad hoc NETwork(AANET) research,an estimation method of connectivity probability is proposed.The method takes airspace as the research object,starts with actual flight characteristics,and applies conclusions of random waypoint mobility model.Building a connectivity model by establishing Airspace Unit Circle(AUC) from the perspective of circle-circle coverage,the method obtains a theory of airspace network connectivity.Experiment demonstrates its correctness.Finally,according to the actual condition simulation,relationship between the number of aircraft,communication radius,and the flight area under connectivity probabilities is achieved,results provide reference for creating a network that under certain aerial combat condition.

Optimization of a Route Network in Dakar Airspace: Surface Navigation

In this paper, the map of a network of air routes was updated by removing the non-optimal routes and replacing them with the best ones. An integer linear programming model was developed. The aim was to find optimal routes in superspace based on performance-based navigation. The optimal routes were found from a DIJKSTRA algorithm that calculates the shortest path in a graph. Simulations with python language on real traffic areas showed the improvements brought by surface navigation. In this work, the conceptual phase and the upper airspace were studied.

Design of Simulation System for Effectiveness Evaluation of Future Airspace Window Shooting

Future Airspace Window Shooting is a newly developed technology, which needs effectiveness evaluation before widely used. Future airspace window shooting technology, simulation system development principles and software chosen to develop the simulation system are introduced in the first. And then the overall design of the system, realization of the system and effectiveness evaluation through simulation are discussed in detail. Through the simulation, it is known that the FAW shooting has more superior performance when facing maneuvering targets.

Dynamic reconfiguration for en-route airspace

As the air traffic demand is anticipated to be increased significantly in the near future,dynamic and effective allocation of the airspace resource is becoming a world-wide focus in the research field of air traffic management（ATM）.Taking the U.S.targeting the en-route airsapce,a dynamic airspace configuration（DAC） algorithm to reconfigure the airspace in consideration of higher efficiency and safety is presented.First,a modeling technique based on graph theory is proposed to generate a mathematical model for the airspace,and then,the graph model is partitioned into subgraphs for the purpose of sectorizatoin.The final step generates sector configuration with desirable geometry shape.Through analysis on the Cleveland airspace center（ZOB） in the U.S.,the algorithm is proved to be robust to time-varying traffic load.

An Improved AOMDV Routing Protocol for Airspace Communication Network

The airspace communication network based on spacecraft has a wide range of applications in regional information enhancement and emergency communication. In this paper, a routing algorithm for congestion degree detection of multipath routing (CD_AOMDV) is proposed. The method of combining the whole congestion degree detection and local congestion degree detection before service initiation is adopted. Timely and accurate judgment of the congestion degree reduced the loss rate of the hot nodes, so the average packet loss rate reduced. Simulation results show that compared with the traditional AOMDV protocol, the CD_AOMDV proposed in this paper has reduced the packet loss and improved delay performance, which is more suitable for the airspace communication network.

Performance Evaluation of Terminal Airspace System Safety, Delay and Predictability of Muritala Mohammed International Airport, Ikeja Lagos, Nigeria

This paper outlines a multi-dimensional user-oriented performance metrics approach in evaluating the operation of the terminal airspace system to aid in the airport and airspace planning and decision making. Safety, delay and predictability metrics contribute to the analytical framework. From the findings, the occurrence of air incidence has a high severity level at departure, and arrival phases of flight, higher likelihood at the radar room and much of the incidences were as a result of faulty equipment and inherent absence of modern airspace infrastructure. Also, in Lagos terminal airspace, the number of incidences has no close correlation with the level of traffic complexity. Total schedule arrival delay ranges from 1 - 392 minutes representing an average of 7.8 - 17.9 minutes per aircraft that arrived Lagos airport at that period. Besides, the total approach contact time ranges from 1 - 57 minutes, translating to 4.6 - 7.1 minutes per aircraft. However, variability in arrival time of 1 - 5 minutes is common from published airline arrival scheduled time. In the same vein, the variability of 1 - 5 minutes is common from approach contact times of aircraft. These figures indicate sound arrival predictability signature for Lagos airport. Also, departure time variability above 30 minutes is familiar from the ATC clearance time for the various routes under study. However, there is about or more 25% variability of more than 15 minutes, and this indicates possible inconsistency of predicting departure times from the times Air Traffic Control (ATC) clearance was acquired. Above all, the predictability of departure times in Lagos airport is weak compared to those of the arrival. Taken by it, this may be a sign of airspace congestion or ATC deficiencies at the Lagos airport. This is an indication of the lack of users’ confidence in Nigeria’s air transport industry to deliver just-in-time service.

Convective Weather Avoidance Prediction in Enroute Airspace Based on Support Vector Machine

With the rapid growth of global air traffic,flight delays are increasingly serious.Convective weather is one of the influential causes for flight delays,which has affected the sustainable development of civil aviation industry and became a social problem.If it can be predicted that whether a weather-related flight diverts,participants in air traffic activities can coordinate the scheduling,and flight delays can be reduced greatly.In this paper,the weather avoidance prediction model(WAPM)is proposed to find the relationship between weather and flight trajectories,and predict whether a future flight diverts based on historical flight data.First,given the large amount of weather data,the principal component analysis is used to reduce the ten dimensional weather indicators to extract 90%information.Second,the support vector machine is adopted to predict whether the flight diverts by determining the hyperparameters c and γ of the radial basis function.Finally,the performance of the proposed model is evaluated by prediction accuracy,precision,recall and F1,and compared with the methods of the k nearest neighbor(kNN),the logistic regression(LR),the random forest(RF)and the deep neural networks(DNNs).WAPM’s accuracy is 5.22%,2.63%,2.26%and 1.03%greater than those of kNN,LR,RF and DNNs,respectively;WAPM’s precision is 6.79%,5.19%,4.37%and 3.21%greater than those of kNN,LR,RF and DNNs,respectively;WAPM’s recall is 4.05%,1.05%,0.04%greater than those of kNN,LR,and RF,respectively,and 1.38%lower than that of the DNNs;and F1 of WAPM is 5.28%,1.69%,1.98%and 0.68%greater than those of kNN,LR,RF and DNNs,respectively.

Chronic airspace disease:Review of the causes and key computed tomography findings

Chronic airspace diseases are commonly encountered by chest,body or general radiologists in everyday practice.Even though there is significant overlap in the imaging findings of different causes of chronic airspace disease,some key clinical,laboratory and imaging findings can be used to guide the radiologist to the correct diagnosis.The goal of this article is to review and compare these features.

低空空域无人机运行安全保障技术研究综述

低空空域飞行活动日趋频繁,无人机类型多样且性能差异较大,飞行过程中易与建筑物或其他航空器发生飞行冲突。为实现低空空域的规范化、安全化、精细化和智慧化管控,需不断提升保障无人机运行安全的技术手段,例如冲突风险探测、安全风险评估等。文章从无人机的轨迹预测与意图识别、低空空域飞行冲突探测、低空空域风险评估及预警告警等3方面进行了研究。首先,总结了在无人机轨迹预测和意图识别方面的研究成果和面临的问题挑战;其次,基于低空空域冲突探测形式,分析不同探测方法的优缺点;随后,围绕低空空域风险评估及预警告警技术,分析当前研究需要解决的核心问题;最后,对无人机冲突探测和风险评估技术等方面进行了展望。

数字低空空域栅格化的表征度量与最优标定

低空飞行空间范围小、目标速度慢、环境要素杂,传统的经纬度表征方式无法满足智联环境下的低空精细管理要求,为此本文研究了数字低空空域栅格化的表征度量与最优标定问题。首先,从“点-线-面”视角构建了多维度低空空域结构要素量化表征规则,提出了低空空域多层级栅格量化表征方法;然后,通过判定不同空域栅格的“点-线-面”位置关系,提出了基于栅格交集矩阵的低空空域拓扑关系度量方法;最后,综合考虑低空无人机碰撞指数、低空栅格利用指数等优化目标,以及节点与栅格匹配约束、空间位置约束、无人机与无人机/障碍物安全约束等限制条件,建立了面向多维性能的低空空域栅格粒度最优标定模型。针对城市低空典型飞行任务场景对所提方法的有效性及优化效果进行了验证分析。实验结果表明,针对任意设定的低空空域和无人机飞行任务,在可接受的无人机碰撞指数和栅格利用指数下,所提方法可对数字低空栅格粒度进行最优配置,从根源上有效确保低空飞行活动的安全和高效。研究成果对于支撑数字低空空域精细化管理和异质飞行器融合运行具有一定的理论价值和应用意义。

防空作战中多边形责任区预警机空域配置方法

针对防空作战中不规则多边形责任区预警机空域配置问题,基于预警机巡逻航线最短直飞距离和最小转弯直径所形成的实时探测区,通过寻优算法确定预警机责任子区和相应的预警机巡逻可用空域,再基于预警机稳定覆盖度评估准则,对其空域配置进一步寻优,得到预警机空域配置优化方案。通过算例仿真验证了此种方法在不规则多边形责任区中规划预警机空域配置的可行性和提升作战效能的有效性,其方法具有较强的实用价值和军事价值。

空天信息网络中通导融合技术综述

空天信息网络是推动社会经济发展和保障国家安全的重要基础设施。空天信息网络将陆基网络、卫星网络及航空网络构成一体化网络架构,深度耦合通信、导航、遥感等功能,实现信息的高效传输和高精度位置服务。文章分析卫星网络、移动通信网络、局域通信网等多种无线网络通信导航融合定位技术的发展现状,并阐述其面临的挑战,提出多网融合方法可以提升室内外广域无缝高精度位置服务的可靠性。利用5G移动通信网络,与北斗/GNSS卫星导航系统结合,实现相互增强。最后,从天地一体定位导航与授时体系和仿生通信定位导航两方面探讨空天信息网络中通信导航融合定位技术的未来发展趋势。

无人机安全间隔的确定方法

为准确描述无人机空中运行风险,并确定安全间隔,建立了一种综合考虑碰撞概率和冲突率的碰撞风险模型。首先根据无结构空域中两种不同的运行条件,分别建立了碰撞概率模型,针对空域内无法获取动态且无避撞措施的无人机,建立了结合航向的不确定性和位置误差的碰撞概率模型,计算碰撞概率对应的安全间隔;针对空域内可以获取动态且采取避撞措施的无人机,基于其机动性能以及位置误差,系统误差和人为因素,确定避撞所需的安全间隔并计算相应碰撞概率。然后,根据多旋翼无人机在无结构空域运行的特点,使用气体模型以确定空域内的冲突率,将前一步计算得到的安全间隔作为冲突距离,输入进气体模型,计算空域内的冲突频率。最后结合安全间隔对应的碰撞概率和冲突率,得到空域内的碰撞风险。以物流无人机为例,使用上述方法计算无结构空域内碰撞风险和安全间隔,并对两种不同模式进行比较分析,结果表明在无法获取空域内其他无人机的动态信息且无避撞措施时,5%碰撞概率对应的安全间隔为最佳;在可获取动态信息并采取避撞措施时,碰撞风险随着冲突条件下的碰撞概率减少而减少。两种模型均为可行的和有效的,可以为在此两种条件下运行的无人机安全间隔提供参考。