Grey Incidence Analysis Applied to Civil Aircraft Customization Process

The airlines need to select the optional equipment according to their individual development demands and the manufacture′s standard specification manual when purchasing a new airplane.For this customization process,the selection theory is mainly based on qualitative analysis and quantitative analysis.The grey incidence analysis(GIA)is used for modeling,which evaluates the correlations between optional equipment and airlines′individual demands.Meanwhile,the customization demands are quantitatively processed as different weights in evaluation index system with analytical hierarchy process.Then,the value of grey incidence degree is obtained which shows whether the optional equipment is on the purchasing list or not.Finally,two airlines′customization demands are applied in the example of aircraft cabin′s seats,so two different purchasing priorities and equipment installation lists can be obtained.The results and comparisons verify the reasonable of modeling,which provides an objective scheme of aircraft equipment selection.

Civil Aircraft Assisted Space-Air-Ground Integrated Networks: Architecture Design and Coverage Analysis

In this paper, we propose a novel AIenabled space-air-ground integrated networks(SAGIN). This new integrated networks architecture consists of LEO satellites and civil aircrafts carrying aerial base stations, called "civil aircraft assisted SAGIN(CAA-SAGIN)". The assistance of civil aircrafts can reduce the stress of satellite networks, improve the performance of SAGIN, decrease the construction cost and save space resources. Taking the Chinese mainland as an example, this paper has analyzed the distribution of civil aircrafts, and obtained the coverage characteristics of civil aircraft assisted networks(CAAN). Taking Starlink as the benchmark, this paper has calculated the service gap of CAAN, and designed the joint coverage constellation. The simulation results prove that the number of satellites in CAASAGIN can be greatly reduced with the assistance of civil aircrafts at the same data rate.

Refined Aerodynamic Test of Wide-Bodied Aircraft and Its Application

The large dual-channel wide-bodied aircraft has a long range and a high cruise Mach number.Therefore,its aerodynamic design requires a high level ofwind tunnel test refinement.Based on the requirements of aerodynamic design for the future wide-bodied aircraft and the characteristics of high-speed wind tunnel tests,the error theory is introduced to analyze the factors affecting the accuracy of the test data.This study carries out a series of research on the improvement of refined aerodynamic test technology in an FL-26 wind tunnel,including design and optimization of the support system of wide-bodied aircraft,model attitude angle measurement,Mach number control accuracy,measurement and control system stability,test data correction and perfection,high-precision force balance and standard model development.In addition,the effect of the standard specification of the refined aerodynamic test is investigated to improve the data quality.The research findings have been applied in the standard model test and subsequent models of wide-bodied aircraft.The results show that whenMach numbers are less than 0.9,the control accuracy of Mach numbers in the FL-26 wind tunnel is smaller than 0.001 and the measurement error of attack angle is smaller than 0.01°.Therefore,it has the ability to correct the data influenced by factors,such as support/wall interference,model deformation,floating resistance and airflow deflection angle.The repeatability accuracy of the standard model’s comparison test shows that the lift coefficient is less than or equal to 0.0012,the drag coefficient is less than or equal to 0.00004,pitching moment coefficient is less than or equal to 0.0004.The bending resolution of the model’s deformation measurement is less than 0.2 mm,and the tensional deformation is smaller than 0.04°.The revised aerodynamic data and model deformation measurement results have good agreement with that of the ETW wind tunnel.The results demonstrate that the improved technology presented in this paper can significantly enhance the refined aerodynamic test of wide-bodied aircraft.

Mechanical Dispatch Reliability Prediction for Civil Aircraft Considering Operational Parameters

To effectively predict the mechanical dispatch reliability(MDR),the artificial neural networks method combined with aircraft operation health status parameters is proposed,which introduces the real civil aircraft operation data for verification,to improve the modeling precision and computing efficiency.Grey relational analysis can identify the degree of correlation between aircraft system health status(such as the unscheduled maintenance event,unit report event,and services number)and dispatch release and screen out themost closely related systems to determine the set of input parameters required for the prediction model.The artificial neural network using radial basis function(RBF)as a kernel function,has the best applicability in the prediction of multidimensional,small sample problems.Health status parameters of related systems are used as the input to predict the changing trend ofMDR,under the artificial neural network modeling framework.The case study collects real operation data for a certain civil aircraft over the past five years to validate the performance of the model which meets the requirements of the application.The results show that the prediction quadratic error Ep of the model reaches 6.9×10−8.That is to say,in the existing operating environment,the prediction of the number of delay&cancel events per month can be less than once.The accuracy of RBF ANN,BP ANN and GA-BP ANN are compared further,and the results show that RBF ANN has better adaptability to such multidimensional small sample problems.The efforts of this paper provide a highly efficientmethod for theMDR prediction through aircraft system health state parameters,which is a promising model to enhance the prediction and controllability of the dispatch release,providing support for the construction of the civil aircraft operation system.

Estimation of the Aircraft CO_2 Emissions of China's Civil Aviation during 1960-2009

Based on data collected by Chinese Civil Aviation Statistic Center, the annual CO2 emissions of aircrafts during 1960-2009 were calculated, and the emission intensity and its dynamic characteristics were analyzed. The results show that the total CO2 emissions of aircrafts in China increased from 120×10^3 t in 1960 to 41.44×10^6 t in 2009. The CO2 emission intensity decreased from 2.9 kg （converted t kra）-1 in 1960 to 0.96 kg （converted t km）-1 in 2009 at an average rate of 0.04 kg （converted t km）-I per year. The average share of CO2 emissions of aircrafts on the total CO2 emissions from the sector of transportation, storage and post was 6.6% during 1980-2005, and 0.25% on the total emissions from fossil fuel combustion during 1971-2008.

Hierarchical Colored Timed Petri Nets for Maintenance Process Modeling of Civil Aircraft

Civil aircraft maintenance process simulation model is an effective method for analyzing the maintainability of a civil aircraft. First, we present the Hierarchical Colored Timed Petri Nets for maintenance process modeling of civil aircraft. Then, we expound a general method of civil aircraft maintenance activities, determine the maintenance level for decomposition, and propose the methods of describing logic of relations between the maintenance activities based on Petri Net. Finally, a time Colored Petri multi-level network modeling and simulation procedures and steps are given with the maintenance example of the landing gear burst tire of a certain type of aircraft. The feasibility of the method is proved by the example.

OPTIMAL DESIGN AND AERODYNAMIC CALCULATION OF WING CONFIGURATION OF CIVIL AIRCRAFT

An effective method of optimal design of wing configuration is provided. The SUMT (sequential unconstained minimization technique) method is a good technique for solving the nonlinear programming. The application of penalty in optimal design of wing configuration has been solved well. The present method for the aerodynamic calculation is the combination of both the nonlinear panel method and the suction analogy method of vortexlift spanwise distribution on large swept wing-tip. The calculation results are in good agreement with experimental data. According to the computation and experiment,the mechanism of the increased lift and reduced drag about the sheared wing-tip wing has been analyzed, and some opinions of interest are proposed.

Explorations of China-Russia cooperation on civil aircrafts

Standards must go ahead of the rest in the development of civil aircrafts.They are the most prominent source of technical data for the design,manufacturing and security of civil aircrafts in an internationalized way,playing an essential role in the successful projects on civil aircraft development jointly carried out by China and other countries.

Optimization of Maintenance in Civil Aviation Aircraft Equipments

As the economic level rising,the function and stability of civil aircraft have been greatly improved.However,with the development of science and technology in modern civil aviation transportation,the frequent occurrence of flight accidents has threatened people’s safety.The main reason is the internal failure of the engine body or the daily maintenance management is incomplete.Therefore,the relevant maintenance management departments should attach great importance to the first core research and management of civil aircraft stability and safety.In view of various equipment problems existing in the operation of civil aircraft,the practical application of data collection mode and maintenance information disclosure mode of modern aircraft maintenance equipment is analyzed.This paper describes some characteristics of aircraft maintenance work,and combined with the main factors affecting the risk of civil aircraft maintenance,giving countermeasures and suggestions to effectively improve the level of civil aircraft maintenance risk management.

Discussion on Continuous Airworthiness and Maintenance of Civil Aircraft

With China’s rapid economic development,the civil aviation market’s development area has expanded.On this basis,the state has proposed more extensive and stringent civil aviation rules.Many factors can affect the civil aircraft during the real operation process,and this can have an impact on the aircraft’s regular functioning to some level.To ensure that civil aircraft remain airworthy,appropriate maintenance work must be performed on a regular basis to prevent compromising the aircraft’s safety performance.For the purpose of reference,this paper discusses the continual airworthiness and maintenance of civil aircraft.

CONDITION-BASED MAINTENANCE DECISION MAKING METHODS FOR CIVIL AEROENGINE

To provide some feasible condition-based maintenance （CBM） decision making methods for civil aeroengine, firstly, the theory of aeroengine CBM decision making is described. The proportional intensity（PI） model is established based on the reliability and condition monitoring data. According to the model, the decision making methods are proposed for the optimal preventive maintenance（PM） interval and removal. Then, the time on wing （TOW） is predicted by collecting actual data based on the engine age and operating conditions. Finally, an example of a fleet for CF6-80C2 engines is illustrated. It shows that sufficient engine operation data are the key of accurate decision making. Results indicate that the CBM decision making methods are helpful for engineers in airlines to control engine maintenance actions and TOW, thus decreasing risks and maintenance costs.

SIMULATION OF BLEED AIR BEHAVIOR DURING AIRCRAFT IN FLIGHT BASED ON FLOWMASTER

Bleed air system is one of the most important components of air management system(AMS).It acts as transfer pipes responsible for air supply at high temperature and pressure.The thermal and flow performance of the bleed air system is a key issue for the design of AMS since the characteristics of air source have a great influence on the anti-ice system,the environmental control system and other downstream system in need of high temperature pressurized air.Based on the one-dimensional lumped parameter technology,a computer analysis model of bleed air system is developed in order to analyze the thermal and flow behaviors of the nodal points in the pipeline network.The simulation are performed with a given flight assignment using the analysis model,and the results verify that the system meets the design requirements.

Inspection interval optimization for aircraft composite structures with dent and delamination damage

The optimization of inspection intervals for composite structures has been proposed,but only one damage type,dent damage,has been addressed so far.The present study focuses on the two main damage types of dent and delamination,and a model for optimizing the inspection interval of composite structures is proposed to minimize the total maintenance cost on the premise that the probability of structure failure will not exceed the acceptable level.In order to analyze the damage characteristics and the residual strength of the composite structure,the frequency,energy,size,and depth of the damage are studied,and the situation of missing detection during the inspection is considered.The structural residual strength and total maintenance cost are quantified corresponding to different inspection intervals.The proposed optimization method relieves the constraints in previous simulation methods,and is more consistent with the actual situation.Finally,the outer wing of aircraft is taken as an example,and with the historical cases and experimental data,the optimization method is verified.The optimal inspection interval is shorter than the actually implemented inspection interval,and the corresponding maintenance cost is reduced by 23.3%.The result shows the feasibility and effectiveness of the proposed optimization method.

民机典型机身框段垂直入水冲击特性研究

为了研究民机典型机身框段垂直入水冲击特性,采用入水冲击试验系统开展不同高度下的圆柱体入水冲击试验,研究其入水冲击响应;基于LS-DYNA任意拉格朗日-欧拉(arbitrary Lagrange-Euler,ALE)方法建立流体域均匀网格及局部加密网格模型,通过对比圆柱体入水冲击试验结果验证网格收敛性及流体域模型;基于验证的流体域模型及机身框段模型,研究机身框段在6.02 m/s速度下的入水冲击特性,并分析与刚性地面冲击特性的差异性以及不同入水冲击速度下的机身框段冲击响应特性。结果表明:ALE方法在结构入水冲击方面具有较高的模拟精度,且采用局部加密网格时可以极大减少流体域模型网格数量和入水冲击计算时间。机身框段入水冲击时的失效模式与刚性地面冲击时的失效模式较为一致,但机身框段结构整体变形程度减小,客舱地板横梁变形程度增大;机身框仍是吸能最多的部件,但水也吸收了大量的冲击能量,使得地板导轨处的加速度始终小于刚性地面冲击时的加速度;随着机身框段入水冲击速度的增大,机身框发生弯折和上翘的程度加剧。

基于视觉Transformer飞行员姿态估计

人体姿态估计是行为感知领域中的一个重要环节,也是民用飞机驾驶舱智能交互方式的一项关键技术。为建立民用飞机驾驶舱复杂光照环境与飞行员姿态估计模型性能的可解释联系,提出基于视觉Transformer飞行员姿态(ViTPPose)估计模型,该模型在卷积神经网络(CNN)主干网络末端使用包含多层编码层的双支路Transformer模块,编码层联合Transformer和空洞卷积,在增大感受野的同时捕捉后期高阶特征的全局相关性。基于飞行机组标准操作程序,建立飞行模拟场景下的飞行员操纵行为关键点检测数据集,ViTPPose估计模型在此数据集上完成飞行员坐姿估计,并通过与基准模型对比,验证了其有效性。在驾驶舱复杂光照的背景下,构建坐姿估计热图,分析ViTPPose估计模型对光照强度的偏好,测试其在不同光照等级下的性能,揭示其对不同光照强度的依赖关系。

面向民机可视导航的场面多尺度目标检测

民航飞机视觉辅助驾驶系统通过机载视觉传感器获取周边威胁态势信息,为飞行员提供辅助决策等信息,但是机载视觉传感器获取的机场场面威胁目标尺度变化大,且机载平台算力有限,现有的目标检测方法难以满足视觉辅助驾驶需求.针对上述问题,提出一种基于YOLOv5s算法的轻量化多尺度目标检测算法.首先,为增强场面小目标的特征表达,在加权双向特征金字塔网络(BIFPN)基础上,引入坐标注意力(CA)机制,设计CA-BIFPN特征融合网络,提高模型对多种尺度目标的学习能力.然后,设计GSConv解耦检测头,相互独立优化分类和回归目标,提高目标检测的精度.设计的跨级部分网络轻量化颈部模块可减少因引入解耦头增加的参数量,大幅提高整体网络的检测速度,实现场面目标实时检测.为了验证算法性能,构建机载视觉传感器滑行视角的实测数据、仿真数据组成的多尺度场面目标数据集.在该数据集上的实验结果表明,所提方法检测精度超过Faster R-CNN、SSD和YOLOv6、YOLOv7、YOLOX等经典多尺度目标检测算法,均值平均精度为71.40%,比YOLOv5s提高4.19个百分点;在机载计算仿真实验平台上,检测帧率达到71帧/s,满足实时检测要求.

融入思政元素的飞机工程课程群混合式教学实践

在立德树人背景下,开展课程思政教学是必然趋势。针对专业课程价值塑造弱化的问题,飞机性能工程课程群根据国产民机和签派员岗位能力,依托超星在线教学平台,明确育人目标,将“课程思政”融入线上线下混合式教学,实现思政教学与“双线教学”双向贯通,课程群组成了课堂学习共同体,形成协同效应,打造有温度、有深度的立体课堂,丰富学生的学习方式,建立家国情怀和情感认同,达到“知识——技能——价值”一体化育人目标。

基于LightGBM-SHAP的民机硬着陆可解释预测

为预防民用飞机的硬着陆超限事件,首先,收集包含动力学变量、系统性能和其他工程参数的机载快速存取记录器(QAR)数据,开展机场航段聚类、样本平衡、统计特征提取等数据处理活动;然后,基于轻量级梯度提升机(LightGBM)模型预测民机硬着陆事件,并与极限梯度提升(XGBoost)、决策树(DT)、长短期记忆网络(LSTM)模型进行综合对比;最后,利用Shapley可加性解释(SHAP)算法进一步分析硬着陆事件的致因机制及各飞行参数特征对模型预测结果的影响。结果表明:所提方法不仅显示出良好的硬着陆事件预测性能,准确率、正确率和召回率分别达到99%,92%和88%,还可针对具体航段对硬着陆预测模型的决策过程提供定量的、可视化的解释信息。

高度修正实现刚度等效的梁结构有限元建模方法

民用飞机中对于梁结构的有限元建模,一般采用刚度等效方法将梁建成杆单元与剪切板单元的组合形式,这种有限元简化方法仅能保证截面刚度与真实截面刚度近似等效,但有限元中的截面面积与实际面积却相差较大,致使有限元分析的结果不能准确反映结构严重部位的应力情况。针对传统刚度等效有限元建模方法的不足,提出一种采用高度修正的刚度等效有限元建模方法;将该方法的计算结果与传统建模方法的计算结果、理论计算结果、试验测量结果进行对比。结果表明:本文提出的高度修正的有限元建模方法比传统杆板系建模方法更准确,与试验结果更接近;将该方法用于民用飞机结构有限元建模,能够对真实结构进行更准确地模拟,分析结果也更精确。