Journal of Civil Aviation University of China

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Flight status conformance assessment of fly-by turns based on time tolerance

WU Renbiao, AN Li, ZHANG Zhe, WANG Peng

Journal of Civil Aviation University of China 2021, 39 (1): 1-5.

Abstract （1510）

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Flight status changes during maneuvering flight cannot be effectively identified by common fixed distance threshold assessing method, in senarios with large amount of monenvering flight. To resolve this problem, aiming at the reasonable time variation during flight operation, and according to the initial turning time distribution, the fly-by turning position distribution model is built by using Monte Carlo method and then the flight status conformance assessing method basing on time tolerance is obtained. Practical flight data are used to verify the effectiveness of the current method and the results show that: this method can effectively demonstrate the fly-by turning flight status conformance extent; compared with fixed distance threshold assessing method, this method can effectively warn abnormal turning status in advance and improve the effectiveness and rationality of assessing results.

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Arrival aircraft route planning based on arrival procedure selection

SONG Xiangbo, MOU Lei, YANG Yue

Journal of Civil Aviation University of China 2021, 39 (1): 6-10.

Abstract （1671）

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In order to improve the efficiency of arrival aircraft in the terminal control area and solve the increasing flight delay, a route planning model for arrival aircraft based on PBN is established and simulated with the goal to realize conflict pre-allo cation. Experimental resulf shows that, the simulated number of aircraft entering terminal control area is greater than the actual hourly maximum flow at each en-try point after the optimized allocation of the arrival procedures. On the basis of improving the efficiency of aircraft entering the terminal control area and reducing the number of flight conflicts, this method can assist controllers to sequence arrival aircrafts and reduce their workload.

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SWIM network routing mechanism based on NDN

WU Zhijun, XU Xinran

Journal of Civil Aviation University of China 2021, 39 (1): 11-16.

Abstract （1531）

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In order to reduce the data transmission delay and the high load of data source node, NDN routing mechanism is introduced into SWIM network, naming the information in a hierarchical way to improve the aggregation degree of the route. Caching strategy is adopted to improve the response speed to the same request. Aiming at the possible node failure, a rerouting mechanism is proposed to reduce the transmission delay. Simulation results show that the proposed mechanism can achieve fast response to the same information request and reduce the average load of network. When node failure appears, the rerouting mechanism can effectively reduce the network delay as well as the average number of retransmissions, and reduce negative impact on network performance.

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Crowd counting algorithm based on multi-scale feature fusion via adversarial neural network#br#

HAN Ping, LIU Zhanfeng, JIA Yunfei, NIU Yonggang

Journal of Civil Aviation University of China 2021, 39 (1): 17-22.

Abstract （1690）

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The crowd counting algorithm of adversarial neural network based on multi-scale feature fusion is proposed to solve the difficulty in crowd feature extraction and information loss in feature fusion. First, shallow crowd features at different scales are extracted through multi-scale feature extraction structure with different size convolution kernels extracts. Next, shallow crowd features and deep-level crowd features of the convolutional network are connected through residual structure to achieve the fusion of crowd features at different scales and depths.Finally, the alternate learning between generator network and discriminator network is realized through adversarial method in order to generate high-quality crowd density maps. Experimental results on two datasets of ShanghaiTech and UCF_CC_50 show that this model can greatly improve the accuracy and robustness of crowd counting in complex crowd environments compared with traditional neural network models.

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Parameter identification of magneto-rheological damper Bouc-Wen model

YANG Yonggang, DING Youchuang

Journal of Civil Aviation University of China 2021, 39 (1): 22-27.

Abstract （2617）

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It is not easy to identify the parameters of magneto-rheological damper dynamic model. Therefore, it is proposed to build a Bouc-Wen model in Simulink, choosing nonlinear least square algorithm to conduct iteration; relation between current and damping force controlling parameters is determined by using the curve fitting toolbox parameter estimation, and then all the parameter identification results are determined. Finally, Bouc-Wen model is validated by the test data of other amplitude frequencies. Results show that there exists high fitting degree between test results and simulation results, proving the effectiveness of the current method in parameter identification.

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Development of parameterized modeling simulation platform for magnetorheological shimmy damper#br#

TIAN Jing, LI Xiaofei

Journal of Civil Aviation University of China 2021, 39 (1): 28-33.

Abstract （1404）

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There exist problems such as large similar work, complex finite element analysis process and long R&D cycle of the designing process of magneto-rheological shimmy dampers. Basing on the parameter description of magnetorheological damper parts‘sizes, the parameterized modeling and simulation platform of magneto-rheolo-gical damper structure is built by secondary development of CATIA and ANSYS in VB 6.0 environment. Simulation results show that this platform can quickly model the damper and conduct simulating analyses on the magnetic field distribution of dampers with different size parameters, which simplifies the designing process and shortens the R&D cycle.

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Influencing factors of aircraft dynamic response under unevenness excitation

YUAN Jie, WU Yifang, ZHANG Zhekai, LIU Shifu

Journal of Civil Aviation University of China 2021, 39 (1): 34-40.

Abstract （1611）

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The runway roughness analysis software ProFAA developed by FAA is used to run simulation on common commercial aircraft types such as B727, B737 and B747 under random excitation, cosine excitation, and measured runway excitation, studying the relation between aircraft dynamic response and speed, wavelength, amplitude as well as roughness indices. Simulation results show that: the aircraft dynamic response is proportional to the taxiing speed and excitation amplitude; aircrafts are more sensitive to the unevenness excitation of medium and long waves, and the value of sensitive wavelength is related to the aircraft type and taxiing speed; the increase of roughness indices aggravates the dynamic response of aircraft, but the correlations among them are different, BBI (Boeing bump index) has the highest correlation with the dynamic response of aircraft.

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Assessment system construction and trend foresight of UAV ground impact risk#br#

HAN Peng, ZHAO Yifei, LIU Hong

Journal of Civil Aviation University of China 2021, 39 (1): 40-47.

Abstract （2223）

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With increasing application scenarios and the growth of flight time, the risk of ground impact in low-altitude airspace flight has been increasingly focused. Main inducements of ground hazards are obtained through the existing UAV operation data and accident investigation conclusion. Combing current UAV ground impact risk assessment modeling points, UAV system failure model, impact area model, ground object distribution model and the injury evaluation model are summarized according to the risk assessment process. Some typical models are compared, summarizing the shortcomings existing in these researches including single failure mode, non-uniform distribution and injury model, etc. Finally, the research trend of UAV operation risk and related technologies are prospected, ground hazard risk assessment system and the development trend of industry and regulatory technologies are summarized.

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Application of fault tree method in time limited dispatch

HU Wei, CAI Jing

Journal of Civil Aviation University of China 2021, 39 (1): 48-51.

Abstract （1338）

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TLD analysis is an important part of aircraft system safety analysis. One of the important links is to calculate the system LOTC rate after component failure. The current function analyzing method is cmparatively conservative, and its application in complex systems is insufficient. Therefore, the fault tree method is applied to the TLD analysis and is proved simple and accurate. It can be used in any complex system and help to improve the operability and accuracy of TLD analysis.

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Impact resistance of TC4 plate against blunt projectile under different layer orders#br#

HU Jing, WANG Lujun, HU Ang

Journal of Civil Aviation University of China 2021, 39 (1): 52-58.

Abstract （1738）

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In order to study the ballistic resistance and failure modes of TC4 titanium alloy plate under different material layer orders, high velocity impact experiment of blunt projectile on TC4 titanium alloy target plate is conducted by light gas gun. Based on the analysis of experimental phenomena, validity of simulation model and material parameters are verified by ABAQUS, and the influence of layer order and material on the ballistic resistance of TC4 titanium alloy is further analyzed. Experimental results indicate that the TC4 titanium alloy has certain toughness characteristics, the failure of shear plugging is mainly caused by annular shear force under the penetration of blunt projectile. Delamination decreases the ballistic resistance of TC4 plate, layer order
influences its ballistic resistance, the impact resistence performance with layer order with soft target in front of hard target is better than that with the reverse layer order.

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Consistency rule mining algorithm based on variable precision dominance relation rough set model#br#

TAO Zhi, HU Liu, WANG Dan

Journal of Civil Aviation University of China 2021, 39 (1): 59-64.

Abstract （1209）

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In order to conduct data mining in dominance-based information system with noise data, the modified knowledge granularity is proposed as the uncertainty measure for the improved rough rule set, and the relative reduction of heuristic information attributes is obtained. Then, the consistency rule set is derived basing on the parameter values provided by variable precision dominance relation rough set, analyzing the influential sensitivity degree of parameter values on rule set. Obviously, the consistency rule set obtained by the algorithm has higher certainty and coverage, the inconsistency caused by data noise is also eliminated, thus ensuring the accuracy and rationality of prediction and classification. Instance analysis proves that this algorithm is an effective method for rule acquisition.

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Stationarity and nonlinearity test of air traffic flow time series

WANG Fei

Journal of Civil Aviation University of China 2021, 39 (2): 1-6.

Abstract （1303）

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In order to provide a reasonable criterion for the real-time analysis and short-term prediction of air traffic flow based on nonlinear theory, the stationarity and nonlinearity test methods of air traffic flow time series are studied. Firstly, the time series of traffic flow is constructed with 40-day data and 15-minute statistical interval; Then, the stability of the time series is analyzed by both qualitative method based on autocorrelation graph and quantitative method based on ADF(augmented Dickey-Fuller test) and PP(Phillips-Perron)test; Then, the non-linearity of the time series is studied by using surrogate data method; Finally, the effects of length, time delay and statistical scale on nonlinearity are analyzed. Results show that the autocorrelation coefficient of time series decreases rapidly and tends to zero, and there is no unit root in the generation process of time series data, which indicates that time series is stationary. The third -order time inverse asymmetry, third -order autocorrelation and third - order autocovariance are used as test statistics, and the third null hypothesis is rejected, which indicates that time series has a non-linear component, and the component originates from the dynamic process of the system itself. In addition, long-length time series often reflects more stable non-linearity, and short-length time series often does not reflect non -linearity. Time delay has a greater impact on the third -order statistics of time inverse asymmetry, but a smaller impact on the statistics. Time series with 30-minute scale is more suitable for shortterm prediction of Sanya No.4 Sector

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Calculation of maximum failure speed of military aircraft

ZHENG Fengmin, AN Y an

Journal of Civil Aviation University of China 2021, 39 (2): 7-11.

Abstract （1231）

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According to the calculation principle of failure speed, the aircraft motion simulation model is established. The key point is to combine the brake model, pneumatic model, engine model and landing gear system model, and to compile the calculation program to simulate the aircraft‘s acceleration run -off section and brake stop section. Taking one military aircraft as an example, a high-precision model solver based on the fourth-order Runge Kutta method is established, and the calculation method of the maximum failure speed of military aircraft is given. Calculation result of the algorithm can well fit the actual test flight data, providing reference for the actual training of troops.

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Prediction of wake turbulence separation reduction effect based on RECAT-EU

WANG Xueyao, LYU Jiahang, WEI Zhiqiang

Journal of Civil Aviation University of China 2021, 39 (2): 12-15.

Abstract （1452）

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RECAT-EU is proposed by EUROCONTROL as a wake turbulence separation standard. In order to analyze the implementation effect of RECAT-EU, firstly, the background of which is studied, then the corresponding mode are established and the expected capacity increase calculation software is developed by Matlab. Take Guangzhou Baiyun International airport as an example, the capacity increasing effect in different time periods and for different types of aircrafts is analyzed by using this software. Results show that the RECAT-EU wake turbulence separation standard can increase the capacity by about 6%

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Frequency-domain characteristics of DME interference signal

LI Dongxia, CHEN Pei, LIU Haitao, WANG Lei

Journal of Civil Aviation University of China 2021, 39 (2): 16-20.

Abstract （1546）

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DME signal is the main interference source of L -DACS1. It is necessary to research the frequency -domain characteristics of DME signals in order to find the effective DME interference suppression algorithm. Firstly, a normalized DME signal model is established, and the closed -form mathematical expressions of spectrum and power spectrum of baseband DME signal and carrier offset DME signal are derived. Then, basing on the transmission characteristics of the ideal low-pass filter, the spectrum and power spectrum of the carrier offset DME signal after low-pass filter are given. Finally, the average power of DME signal after filtering is calculated. Simulation result shows that the power attenuation of carrier offset DME signal after low-pass filtering is about 33 dB, verifying the correctness of the theoretical derivation.

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High-precision position solution method for airport scene monitoring

WANG Li, Lei

Journal of Civil Aviation University of China 2021, 39 (2): 21-25.

Abstract （1390）

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Optimizing the monitoring points of complicated airport scenes can effectively improve the operating efficiency of airport scenes. However, the real-time positioning of monitoring points with high precision is still unresolved. Aiming at this problem, an adaptive niche ejection particle swarm algorithm combined with Taylor series expansion method is proposed. The positioning results of the proposed algorithm are taken as initial reference points for Taylor series iteration, solving the dependence of traditional Taylor series expansion method on the initial reference point selection. Simulation results show that the positioning estimation accuracy of the improved particle swarm algorithm combined with the Taylor series expansion method is greatly improved compared with the simple Taylor series expansion method.

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Irregular flight recovery based on loss of airline

DA I Fuqing, ZHANG Shunyao

Journal of Civil Aviation University of China 2021, 39 (2): 26-30.

Abstract （1753）

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In order to solve the irregular flights caused by weather, flow control, engineering maintenance and passenger factors, a flight recovery model is built with the objective function of minimizing the sum of direct and indirect loss of airlines. The impact of passengers disappointment in different cabins caused by flight delay on the future ticket sales of airlines is categorized. The concept of opportunity cost is applied into the function in order to improve the calculation of loss types. A dynamic decision algorithm is designed to find the solution of the model, and instance shows that the irregular loss of flights can be reduced to 44% by this algorithm, proving the advantages of this algorithm in solving flight recovery problems.

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Multi-objective optimization model for hub city selection in airline network

FAN W ei, NING Junwen

Journal of Civil Aviation University of China 2021, 39 (2): 31-36.

Abstract （1340）

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The selection of hub city is one of the key issues of airline network design. Aiming at the different orientation of each city in the airline network, the ELECTRE algorithm is used to screen the candidate hub city set; then, a multi-objective optimization model based on priority and multi-allocation p-hub location without capacity limit has been proposed, and the multi-objectives is solved step by step. Results show that with more accessible cities and more hub cities, the optimized airline network structure can propose optimal airline network structure basing on rational selection of hub city and effectively reduce the total transportation cost

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Effects of flight experience and hazardous attitude on flight safety performance

WANG Lei, GAO Shan, ZHANG Jingyi

Journal of Civil Aviation University of China 2021, 39 (2): 37-41.

Abstract （1759）

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In order to study the effects of hazardous attitude of airline pilots on flight safety performance, flight experience is considered and 45 data samples of airline pilots忆 exceedance rates are collected. The occurrence frequency of exceedance events is set as an index to evaluate flight safety performance. Then the risk psychological variables of pilots are measured by using hazardous attitude scale and the data are analyzed by Pearson correlation and partial correlation methods. Result shows that flight experience, hazardous attitude and exceedance rate of airline pilots are correlated and the flight experience exacerbates the effect of hazardous attitude on exceedance rate. It is concluded that the hazardous attitude level of pilots can partially predict exceedance behaviors and safety performance. Moreover, airline pilots need to pay attention to the correction and training of their hazardous attitude and avoid the occurrence of 耶alternative爷 events when their flight hours and experience increase.

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Certification requirement analyses based on HUD guidance capability

ZHANG Fan, WANG Ruixuan, XIAO Guosong , WANG Peng

Journal of Civil Aviation University of China 2021, 39 (2): 42-46.

Abstract （1274）

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In order to enhance the ability of all-weather operation of civil aviation, and improve the safety level, head-up display(HUD) is developed. The application of HUD guidance function not only supports the takeoff and landing with low visibility, but also puts forward new safety requirements. In order to solve the problem of insufficient support for the verification and evaluation of HUD guidance function in the existing domestic operation certification standard system, the functional development verification and operational evaluation requirements are analyzed, and the targeted certification elements and review requirements are given, which can provide theoretical support for the airworthiness certification of HUD guidance function

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Contour measuring and cutting method for high-voltage cable joints

MAO Jie, LI Peibo, GUAN Enguang , LIU Jihao , ZHAO Y anzheng

Journal of Civil Aviation University of China 2021, 39 (2): 47-53.

Abstract （1574）

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A new measuring and cutting method is proposed aiming at the problem of high surface roughness and low profile consistency in high-voltage cable processing. Firstly, the error model of installation parameters is established袁 the joint contour is scanned by laser displacement sensor, and the cross-section contour is fitted by least square method. The contour fitting error is less than 0.12% , making it possible to reconstruct the contour and axis trajectory of joints with high precision. Then the tool feeding is obtained and the discrete feeding is smoothed by using interpolation algorithm, which can effectively solve the contradiction between control system bandwidth and cutting surface roughness. By designing this new cutting machine, the contour measuring and cutting method of high-voltage cable joints is verified, proving that this method is reliable and effective and can meet the technical requirements of high-voltage cable joint forming.

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Action recognition method based on depth image and skeleton information

ZHANG Liang, QIAN Yimin

Journal of Civil Aviation University of China 2021, 39 (2): 54-60.

Abstract （1771）

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The complexity of human body movements, within-class differences and perspective changes hinder the accurate recognition of human movements. Depth camera can simultaneously record depth images and extract skeleton information; basing on that, a motion recognition method is proposed. Depth image sequence is used to generate a motion history point cloud and extract global features and local motion features from 3D skeleton information. Point cloud features and skeleton features are fused to construct a multi-modal feature fusion action recognition method. Test on two data sets of MSR-Action3D and UTKinect-Action3D shows that recognition rates are above 95% and 98.0%, which proves the effectiveness of the method

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Influences of adhesive film on bonded-bolted hybrid single-lap joints’ performance

XU Chen, SUN Y ongbo

Journal of Civil Aviation University of China 2021, 39 (2): 61-64.

Abstract （1242）

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A 3D model of bonded-bolted hybrid single -lap joints contending is established based on ABAQUS, damage criteria and stiffness attenuation criterion are added in order to achieve progressive damage analysis. The model is used to analyze the influences on the structure while the thickness and ductility was altered. Results indicate that applied with brittle adhesive film, thicknessincrease can improve the bearing performance of the structure. Varying degrees of ductile adhesive film could provide similar improvement to the bearing performance of the structure. The proposed calculating methods and conclusions could provide reference to composite structure design.

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Congestion prediction of flow system of air traffic network based on GA-BP neural network

ZHANG Zhaoning , ZHANG Yingying , JI Shanshan

Journal of Civil Aviation University of China 2021, 39 (3): 1-5.

Abstract （1267）

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From the perspective of the air traffic network flow system, the large-scale flight delay problem is converted into the congestion problem of the air traffic network flow system, and its congestion prediction is performed. Firstly, the relationship between capacity, flow and flow demand of the air traffic network flow system is analyzed, and the four forecast indicators including flow demand, cumulative delay flight change rate, capacity change in the previous period and capacity change in period are extracted using congestion degree as a congestion evaluation index. Then based on genetic algorithm(GA) optimization back propagation(BP) neural network, a congestion prediction model is established to predict the degree of congestion. Finally, the actual data of an air traffic network flow system is used to analyze examples. The results show that the model has a good prediction and can provide a decision basis for the air traffic flow management department.

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Track identification in terminal airspace based on self-organizing neural network

XIE Chunsheng , ZHAO Long , LIU Yuepeng

Journal of Civil Aviation University of China 2021, 39 (3): 6-9.

Abstract （1326）

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The trajectory pattern recognition can further support track prediction, airspace structure optimization and air traffic situation monitoring. Firstly, a series of trajectory point sets are formed by screening and processing the initially obtained automatic dependent surveillance-broadcast (ADS-B) data. Secondly, the similarity degree between trajectory data composed of trajectory points is calculated. The training set and test set are selected according to a certain ratio; then, the training set is used for learning and training, and a self-organizing neural network (SONN) is established to obtain a competition unit. Finally, the test set is input and identified by the resulting neural network to analyze its correctness. Simulation results show that the algorithm can better identify the trajectory in the airspace of terminal area.

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Fast detection method of signal interference on Beidou B1 signal

LIU Ruihua, ZHANG Shuo

Journal of Civil Aviation University of China 2021, 39 (3): 10-15.

Abstract （1744）

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Interference detection is the basis of interference monitoring, which can effectively ensure the quality of Beidou B1 signal. Due to the poor detection performance of traditional CME (consecutive mean excision) algorithm, large amount of computation work of FCME(forward consecutive mean excision) and double threshold FCME algorithm makes it difficult to achieve fast interference detection. Therefore, an improved algorithm based on FCME is proposed. Firstly, according to the operational characteristics of FFT (fast Fourier transform), the interference detection sample points are reduced; then the differential algorithm is used to replace the sorting algorithm in FCME and calculate the initial threshold, so as to reduce the complexity of the algorithm; finally, the algorithm is verified by the measured data, and results show that the improved detection algorithm can effectively reduce the computational complexity, and has good detection performance for interference signals.

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Flight control and simulation of quad-rotor UAV under wind field disturbance

YANG Yonggang , SONG Wei

Journal of Civil Aviation University of China 2021, 39 (3): 16-21.

Abstract （2930）

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Aiming at the problem that quad-rotor UAV is usually disturbed by wind in the field, a flight control method of quad-rotor UAV under wind disturbance is proposed. Based on force analysis of quad-rotor UAV, the nonlinear mathematical model is established by considering the gyroscope effect, and the external wind field disturbance is introduced to establish the dynamic model under the action of wind field. The backstep controller is designed to realize the position and attitude control of the quad-rotor UAV. Lyapunov stability theory is used to prove the stability of the system, and Matlab/Simulink is used to simulate and analyze the control strategy effect. Under the action of natural wind, this model accurately reflects the dynamic characteristics of the system, and the backstep controller can also track the trajectory of the four-rotor UAV, which has good stability

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Damage detection of aero-engine blades based on improved ZF network

XING Zhiwei , LI Longpu , HOU Xiangkai , SHI Yazhong , WANG Hao

Journal of Civil Aviation University of China 2021, 39 (3): 22-28.

Abstract （3102）

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In order to achieve the accurate detection of aero-engine blade damages, a Zeiler-Fergus(ZF) network improvement method based on the faster region-based convolutional neural network(Faster R-CNN) model is proposed. Firstly, the aero-engine blades damage detection is abstracted as the object detection problem, and aiming at the problem, a ZF network is used to detect the damage location and type. Then, some convolutional layers are added into the original ZF network according to the detection effect. Hyper -parameters such as kernel size in the convolutional layers and the stride size in the pooling layers are adjusted, and the added convolutional layers are included in the shared convolutional layers to extract more detailed damage features. Finally, the existing dataset is divided into three sub-datasets, on which the network performance before and after improvedment is experimentally compared. Results show that the mean average precision of the improved ZF network is up to 5.5% compared with that of the original network, which proves that the improved ZF network can predict engine blades damage more accurately

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Fault diagnosis of aero-engine gas path based on GA-LSSVM

TIAN Jing, HU Hexiang

Journal of Civil Aviation University of China 2021, 39 (3): 29-33.

Abstract （1439）

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Aiming at the lack of data sample and nonlinearity of aero-engine gas-path fault, the genetic algorithm (GA) optimized least square support vector machine (LSSVM) is applied to aero-engine gas-path fault diagnosis. Firstly, the key parameters of LSSVM algorithm is analyzed, and the regularization parameter(C) and kernel parameter ( g ) of LSSVM are optimited with GA. Secondly, GA-LSSVM is used to diagnose the gas path fault of a biaxial turbofan engine. Finally, SVM, LSSVM, GA-SVM and GA-LSSVM are compared from three aspects of diagnosis accuracy, anti-noise ability and training time. Results show that GA-LSSVM is superior to the other three algorithms in diagnosis accuracy and anti noise intensity, but its training time is longer due to the optimization process of GA-LSSVM.

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Design and optimization of deformable wing driven by shape memory alloy

LIU Bingfei, ZHANG Chao, ZHANG Wei

Journal of Civil Aviation University of China 2021, 39 (3): 34-38.

Abstract （1644）

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The aerodynamic performance of wings designed by traditional methods strongly depends on flight conditions. Aiming at this problem, a deformable wing structure driven by shape memory alloy(SMA) wire is designed. The structure can automatically adjust the wing shape according to different flight states, so as to simultaneously optimize its aerodynamic performance. Firstly, the driving point of SMA driver is connected to the stringer inside the airfoil to drive the stringer up and down and deform the flexible skin. Secondly, by using the integrated optimization platform of Isight , the wing modelling and hydrodynamics analysis are conducted to achieve the optimal design of deformable wing. Finally, basing on the optimization design results and SMA constitutive relation, the driving structure scheme of deformable wing is determined. Research results show that the SMA driver can realize the deformation driving of the deformable wing, through temperature control in the range of 30- 140 ℃, the deformation of the upper and lower skins of the wing can be achieved by 0-8 mm, and the maximum lift-to-drag ratio can be increased by 21.87%.

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Comprehensive evaluation on ability of handling emergency situation of civil aviation crew

LI Ye, LI Pengfei , WANG Shuo , LI Shu, WANG Lei

Journal of Civil Aviation University of China 2021, 39 (3): 39-44.

Abstract （1544）

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Pilot’s emergency situation handling ability is directly related to the safety performance of flight crew. Through document analyses and expert interviews, emergency situation handling ability of flight crews is divided into three dimensions including knowledge, skills and individual qualities; by further designing and distributing questionnaires, 26 valid questionnaires are obtained, indices weights are determined by applying of the entropy weight method, a complete evaluation index system of emergency situation handling ability is built. Combining with the scores of airline N, the evaluation result of cloud model show that the emergency situation handling ability of flight crews of airline N is in a good level. The current evaluation index system can provide reference for pilot selection and evidence-based training.

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Security evaluation standardization method for civil aviation information system

HAN Yanzheng, ZHANG Xugao , QIU Xiaorui , WANG Yong, JIANG Laiwei

Journal of Civil Aviation University of China 2021, 39 (3): 45-48.

Abstract （1325）

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Aiming at the quantifying difficulty of security evaluation for civil aviation information system due to various kinds of evaluation indicators, a standardization method for security evaluation is proposed. Firstly, the evaluation indicators are divided into qualitative and quantitative indicators of compliance degree of security. Then, description tables of compliance degree of security and index matrix tables of compliance degree of security are set for qualitative indicators, quantitative indicators are divided into positive indicators and reverse indicators. Finally, the normalized operator is used to transform the evaluation results into percentile form. The standardization method can provide a relatively intuitive reference for security managers to understand the security status of information systems.

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Influence of rain ingestion on aerodynamic performance of aero-engine fan

BAI Jie , CHEN Yankang, FU Wenguang, SUN Peng

Journal of Civil Aviation University of China 2021, 39 (3): 49-55.

Abstract （1349）

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In order to investigate the influence of rain ingestion on the aerodynamic performance of aero-engine fan, fan component of DGEN380 is taken as research object, numerical simulation is conducted to explore the influence of different rain ingestion volumes and raindrop diameters on the aerodynamic performance of the fan, and the variation of flow field with different rain ingestion volumes is analyzed emphatically. Results show that all the three indicators including fan efficiency， pressure ratio, and stability margin decrease with the increase of rain ingestion volume, and the greater the rain ingestion volume becomes, the greater the decline is. When the rain ingestion volume is 4% and the raindrop diameter is 0.5 mm, 1.0 mm and 2.0 mm, the pressure ratio of the fan changes little, the efficiency decreases mainly near the block boundary. Under the conditions of 0%, 4% and 8% rain ingestion volume, loss caused by wake and tip leakage vortices in fan rotor passage increases with the increase of rain ingestion volume; the mixing loss caused by raindrops increases in the high region of the upper lobe of stator channel.

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Top-N recommendation algorithm based on user’s interest drift

LIU Haohan, MA Xiaolu, HE Huaiqing

Journal of Civil Aviation University of China 2021, 39 (3): 56-61.

Abstract （1350）

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Traditional recommendation algorithms are mostly based on the static attributes of users without considering the drift of user’s interest. To this end, Top-N recommendation algorithm integrating user’s interest drift detection is proposed. The new algorithm makes full use of long short-term memory(LSTM) in processing time series data to represent short -term interest shift of users, compromises a fixed vector obtained by matrix factorization to represent long-term interest of users, and incorporates the attention mechanism into the representation of hidden state of the long short-term memory network to obtain the effect of the user’s long-term interest on the shortterm interest. Compared with current popular algorithms, performance of the proposed algorithm is superior in Top-N item recommendation.

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Construction of new codebook based on affine space over finite field

LIU Xuemei, JIA Lihua

Journal of Civil Aviation University of China 2021, 39 (3): 62-64.

Abstract （1096）

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Codebooks are widely applied in code division multiple access systems to separate the signals of different users. Basing on the affine spaces over finite fields, a class of new codebooks are constructed. By the counting theorems of affine spaces, parameters of the codebook are obtained. Sufficient and necessary conditions for the codebooks are given to meet the Welch bound, and the conditions for the the maximum cross correlation amplitude astmptotically attains to the Welch bound are calculated.

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Deviation of Beidou GBAS airborne receiver in final approach segment

LIU Ruihua, GAO Yi

Journal of Civil Aviation University of China 2021, 39 (4): 1-7.

Abstract （1340）

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Deviation is an important performance indicator for airworthiness demonstration of GBAS (ground-based augmentation system) airborne receiver. According to the requirements of deviation outputs for GBAS airborne receiver DO-253D issued by RTCA (Radio Technical Commission for Aeronautics), the source of deviation is analyzed, the complete solution process of deviation is given, and the threshold of deviation is derived. Accordingly, the deviation outputs of Beidou-based GBAS airborne receiver are simulated and analyzed in static and dynamic scenarios. Simulation results show that the deviation outputs of Beidou-based GBAS receiver can meet the requirements of precision approach guidance outputs, which provides theoretical support for the formulation of GBAS airborne receiver airworthiness standards in China.

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Numerical simulation analysis of different winglets under medium-high speed conditions

WANG Hui, CHEN Zezhou

Journal of Civil Aviation University of China 2021, 39 (4): 8-12.

Abstract （1373）

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In order to study the drag reduction characteristics of different winglets, four types of winglets and winglet extensions are selected as the research objects. Under the same extended winglet and medium-high speed flight conditions (Ma = 0.6), five different winglet devices are numerically simulated using the k-ω SST (shear stress transfer) two-equation model. The pressure characteristics of the wing surface and the winglet flow field of five types of winglet are studied. The drag reduction characteristics of different winglet are compared and analyzed, along with the principle of induced drag changes. Research results show that the airflow guidance direction of different winglets the surface flow field of the wing and affects the winglet pressure distribution; under the conditions of medium-high speeds and with same wing length, the fused and raked winglets have better drag reduction effect, and the double-feathered winglet can effectively disperse the winglet vortex.

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Application of point merge flight procedure in regional approach sector

HEI Yanru, WANG Zi, ZHANG Zhendong

Journal of Civil Aviation University of China 2021, 39 (4): 13-18.

Abstract （1307）

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According to the basic concepts and methods of point merge flight procedure, the potential applicability of point merge in regional approach sectors is investigated. Data from the simulation platform of AirTOP and its performance evaluation show that point merge is applicable to regional approach sectors and can effectively improve the efficiency of approach flight flow.

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Optimization of flight schedule of airport group based on flight procedure intersection

ZHAI Wenpeng, WANG Weiqing, YANG Qunting

Journal of Civil Aviation University of China 2021, 39 (4): 19-24.

Abstract （1533）

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The concept of procedure intersection capacity constraint is proposed to optimize the flight schedule. Firstly, the flight procedure is adaptively selected, and the arrival time at the procedure intersection is reasonably controlled. Then, the flight schedule adjustment is reasonably allocated to the airlines in the airport group, and the flight schedule optimization model is constructed based on the simulated annealing algorithm. Taking flight schedule of the Yangtze River Delta airport group as an example, the simulation is verified by using the AirTOP simulation software. Results show that compared with the airport group flight schedule of traditional optimization model , the total amount of adjustment in this method has increased by 370 minutes, the average flight delay is reduced by 24.6%, and the number of controllers coordinating incoming flight conflicts is reduced by 46.3%, the capacity restriction of procedure intersection has effectively alleviated the aircraft aggregation near the conflict point and lowered the rate of the average flight delay.

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Stability assessments of complex airways network for large airport

WANG Xinglong , XUE Yichen , AN Zhicai

Journal of Civil Aviation University of China 2021, 39 (4): 25-31.

Abstract （1647）

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Assessing the stability of complex networks on large airport airways is of great significance for airway network design, emergency response, and flight delay reducing. Firstly, the airway network stability is defined. Then, based on the basic theories such as complex network and stability, the airway stability, node stability, city pair, hub airport indicators, flight delay data are collected, the stability evaluation index is determined based on the propagation delay distance, the number of delayed airports and the number of airport delays. A total of 35 airports with an annual passenger throughput of more than 10 million in 2018 are selected. The city-to-airway network and hub-airway network are respectively established. The airway delay statistics within a week are conducted and the evaluation indicators are calculated. Finally, statistical methods are used to compare and analyze the stability of airline network. Results show that under the same circumstances, the maximum numbers of the absolute delays of the city-to-airway network and the hub airway network are respectively 1 417 and 496. Thus the hub airway network is more stable than the city-to-airway network.

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