Failure and limit energy of aircraft brake pairs

The test methods of the limit energy of aircraft brake pairs and the confirming methods for their failure were introduced. The test results of the rejected take-off (RTO) of brake pairs were analyzed. It is confirmed that the failure reality for brake pair is the destruction of the friction materials. Therefore, after the limit energy test of brake pairs, three criteria for their failure were put forword. The definition of the maximum brake pressure and the selection of the initial test energy were introduced. The products of USA and domestic substitute of brake pairs for Boeing 737 airplane were tested by these methods. The test results show that the limit energy of brake pairs can be determined by 2 or 3 experiments, thus the test cost is reduced.

THE DECENTRALIZED ROBUST FAULT TOLERANT CONTROL FOR THE SENSOR FAILURE OF THE FIGHTER

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Augmented flight dynamics model for pilot workload evaluation in tilt-rotor aircraft optimal landing procedure after one engine failure

An augmented flight dynamics model is developed to extend the existing flight dynamics model of tilt-rotor aircraft for optimal landing procedure analysis in the event of one engine failure.Compared with the existing flight dynamics model, the augmented model involves with more pilot control information in cockpit and is validated against the flight test data. Based on the augmented flight dynamics model, the optimal landing procedure of XV-15 tilt-rotor aircraft after one engine failure is formulated into a Nonlinear Optimal Control Problem(NOCP), solved by collocation and numerical optimization method. The time histories of pilot controls in cockpit during the optimal landing procedure are obtained for the evaluation of pilot workload. An evaluation method which can synthetically quantify the pilot workload in time and frequency domains is proposed with metrics of aggressiveness and cutoff frequencies of pilot controls. The scale of the pilot workload is compared with those of the shipboard landing procedures, bob-up/bob-down and dash/quickstop maneuvers of UH-60 helicopter. The results show that the aggressiveness of pilot collective and longitudinal controls for the tilt-rotor aircraft optimal landing procedure after one engine failure are higher than those for UH-60 helicopter shipboard landing procedures up to the condition of sea state 4, while the pilot cutoff frequency of collective control is lower than that of the bob-up/bob-down maneuver but the pilot cutoff frequency of longitudinal control is higher than that of the dash/quick-stop maneuver. The evaluated pilot workload level is between Cooper–Harper HQR Level 2 and Level 3.

Simple Adaptive Delta Operator Aircraft Flight Control for Accommodation of Loss of Control Effectiveness

A new proof for stability of delta operator simple adaptive control is presented in terms of a set of Linear Matrix Inequalities (LMIs). The paper shows how to design a feedforward gain to satisfy the LMIs over a polytope of loss of control effectiveness failures. The MATLAB Robust Control Toolbox is used to find the feedforward gain with the smallest norm that satisfies the LMIs. Examples are presented of the F/A-18 aircraft and the Innovative Control Effectors (ICE) tailless aircraft that show the design of a feedforward gain for a loss of control effectiveness in any one control effector. The designs use a fixed eigenstructure assignment controller for an inner loop augmented with the simple adaptive controller. Simulations of both aircraft include simultaneous loss of control effectiveness failure and lateral wind gust. Simulation results for the F/A-18 aircraft show that the adaptive controller achieves almost perfect tracking whereas the nonadaptive controller cannot achieve a coordinated turn when an aileron failure occurs. The ICE tailless aircraft uses sideslip, washed-out stability axis yaw rate, and stability axis roll rate feedback for both the inner loop eigenstructure assignment controller and the simple adaptive controller. However, the adaptive controller also uses bank angle feedback. Simulation results for the ICE tailless aircraft show that the adaptive controller achieves almost perfect tracking whereas the nonadaptive controller diverges when an all moving tip failure occurs.

RELIABILITY EVALUATION MODEL BASED ON DATA FUSION FOR AIRCRAFT ENGINES

Reliability evaluation for aircraft engines is difficult because of the scarcity of failure data. But aircraft engine data are available from a variety of sources. Data fusion has the function of maximizing the amount of valu- able information extracted from disparate data sources to obtain the comprehensive reliability knowledge. Consid- ering the degradation failure and the catastrophic failure simultaneously, which are competing risks and can affect the reliability, a reliability evaluation model based on data fusion for aircraft engines is developed, Above the characteristics of the proposed model, reliability evaluation is more feasible than that by only utilizing failure data alone, and is also more accurate than that by only considering single failure mode. Example shows the effective- ness of the proposed model.

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.

电动飞机蒙皮结构的冲击损伤试验与优化设计

飞机蒙皮结构常受到冰雹、维修碰撞等低能冲击,机身结构易出现损伤,引发飞机性能减退。为了提高蒙皮结构的抗冲击性能,结合Hashin失效准则建立了一种复合材料泡沫夹层结构低速冲击有限元等效模型,并利用超声C扫描对冲击后的复合材料泡沫夹层进行无损检测,试验结果表明,与无损检测结果相比较,模拟结果的误差低于10%,证明了该冲击等效模型的合理性。最后利用该有限元等效模型对某型电动飞机机身复合材料泡沫夹层蒙皮结构进行优化设计,以提高抗冲击能力、减小吸收的破坏能量、降低结构损伤程度为目标,在相同铺层数量下,得到了最优的复合材料泡沫夹层结构铺层设计方案。

不同构型电动垂直起降飞行器动力系统的安全性评估

安全性评估对电动垂直起降飞行器的架构开发、安全管理、设计验证及商业化有着至关重要的作用,但目前国内少有对电动垂直起降飞行器整机构型、系统设计等相关的研究。本文针对4种不同构型的电动垂直起降飞行器,包括垂起尾推固定翼构型、四轴八桨多旋翼构型、固定翼加倾转旋翼构型以及倾转机翼构型,使用功能危害分析和故障树分析方法对4种不同构型的动力系统进行了分析比较。分析表明:垂起尾推固定翼电动垂直起降飞行器动力架构在本文的特定使用场景中相对可靠性更优。2种分析方法的结合,增加了对功能危害理解的全面性和深度,并识别了减轻动力系统失效风险的多种潜在途径。安全性评估结果可以为电动垂直起降飞行器动力构型选择和产品开发提供依据。

基于迭代故障估计的四旋翼飞行器轨迹跟踪

针对四旋翼飞行器飞行过程中转子发生故障的问题,设计了一种基于迭代故障估计的控制策略,实现了对四旋翼飞行器的轨迹跟踪控制。首先,分析了四旋翼飞行器转子故障对控制信号的影响,在考虑外界干扰的情况下建立了转子故障状态下的四旋翼飞行器运动学模型。其次,依据迭代学习控制原理设计了一种迭代故障估计器,实现了对故障信号的估计与补偿,结合积分滑模方法实现了对四旋翼飞行器的轨迹跟踪控制,并运用李雅普诺夫理论证明了系统的稳定性。最后,通过对四旋翼飞行器进行仿真实验,验证了所设计的控制策略的有效性。

飞机电源系统故障诊断方法综述及发展趋势

飞机电源系统是机上一切用电设备的电能来源,其安全性与可靠性至关重要。在环保和高效发展需求的背景下,现代航空工业正在推进以电能为核心的多电/全电飞机技术的研究和应用。电驱动装置和电力电子器件的广泛使用导致飞机电源系统结构的复杂化,对飞机的可靠性、安全性、测试性和维修性提出了更高的要求,研究飞机电源系统的故障诊断技术具有重要意义。本文首先介绍了飞机电源系统的组成结构和各自功能,概述了飞机电源系统的发展历程,对比分析国内外典型电源系统的特征,总结了飞机电源系统中的主要故障模式、故障特点和失效原因,并提出一种飞机电源健康管理系统的设计架构,然后综述了国内外基于模型和基于数据的故障诊断方法研究进展,从准确度、数据需求量、适用性和实现难易程度等方面评述了各类诊断方法的特点,最后指出了飞机电源系统故障诊断技术面临的挑战和发展趋势。

边缘连接结构对飞机座舱盖透明件拉伸及疲劳性能的影响

飞机座舱盖透明件所用材料以定向有机玻璃[聚甲基丙烯酸甲酯(PMMA)]、聚碳酸酯(PC)或者两者层合材料为主,而透明件与骨架的连接位置是飞机座舱盖结构中的薄弱区域,该区域作为保障座舱盖透明件密封性和完整性的关键组成部分,直接影响飞行员飞行安全。评估了单层PMMA和PMMA与PC层合结构透明件在软、硬边缘连接方式下的拉伸性能和疲劳性能,为不同边缘结构的使用寿命及可靠性评估提供数据支撑。研究梳理了单层有机玻璃透明件和层合结构透明件在轴向拉伸和疲劳测试过程中的断裂破坏、疲劳失效的原因及表现,并提出可能出现的缺陷对座舱盖透明件拉伸及疲劳性能的影响。结果表明,层合软连接、单层软连接、层合硬连接和单层硬连接结构试样的拉伸断裂应力分别为21.5,17.58,16.55,21.55 MPa,通过升降法得到的这4种连接结构的条件疲劳极限分别为10.15,10.52,8.01,9.77 MPa。综合实际应用中飞机座舱盖透明件轻质化和抗冲击性能要求,优选出层合软连接结构为四种状态下最佳的边缘连接结构。

基于模型的民机运营阶段失效评估方法研究

基于模型的安全性分析(model-based safety analysis,简称MBSA)方法自提出至今,已经日益成熟,更适用于复杂的民机系统。在当前研究和ARP4761A草案的基础上,运用MBSA方法开展民机在运营阶段的失效评估方法研究,其相较传统方法,将运营数据、功能失效和设备故障集合进同一个模型中,更便于开展运行失效评估。首先,定义运行失效评估模型基本元素,梳理模型构建流程,基于Simulink建立包含失效模块的设备级、系统级和飞机级模型。之后,选择某型号飞机外部照明子系统构建模型,利用某机队运营阶段的运行数据开展算例分析。结果表明,基于模型的失效评估与故障树计算结果误差在可接受范围内,同时开展失效模式与影响分析(failure mode and effect analysis,简称FMEA),利用运行数据计算和仿真得到丧失着陆照明功能危险的发生概率,30次仿真结果表明基于运行数据的发生概率在设计值附近波动,整体略大于设计值,但仍满足安全性要求。

某型飞机减速伞意外掉落故障研究

针对某型飞机减速伞系统在着陆滑跑过程中发生的意外掉伞故障,从故障现场检查、内场产品检查、系统联试检查、失效分析等方面对故障产生的机理进行研究、分析,得出引起此故障的原因为微动开关内部触点异常搭接。

DA42NG飞机涡轮增压系统典型故障分析

涡轮增压系统对于飞机的飞行性能和经济性都有着至关重要的影响,它能够提高发动机效率、减少燃油消耗和排放、提升飞行的操作灵活性和安全可靠性。对于装配有涡轮增压系统的飞机而言,涡轮增压系统故障是发生率和维护成本较高的故障之一。文章以DA42NG飞机的涡轮增压系统为研究对象,首先分析系统的组成和工作原理,其次剖析典型故障的原因,最后提出维护建议,以期为该机型及类似机型相关故障的排除提供参考。

障碍型弹药作用下舰载机着舰失效研究

针对舰载机在障碍型弹药封锁作用下的着舰失效问题,开展了舰载机着舰过程、障碍型弹药封锁作用原理及着舰失效关键区域分析,建立了舰载机着舰失效判据;在此基础上对舰载机着舰功能失效概率进行了研究,提出了失效概率计算公式。本文研究成果对舰载机在障碍型弹药作用下的着舰防护策略优化具有一定借鉴意义。

航空发动机滑油综合监测技术研究

介绍了原子发射光谱仪MOA和金属扫描仪METALSCAN两种仪器的性能特点。根据航空发动机在用滑油的特点和现有油液监测仪器的水平, 探讨了利用这两种仪器对航空发动机滑油进行综合监测的新技术, 以满足故障诊断的实时化和准确性的要求。

Vibration analysis and control technologies of hydraulic pipeline system in aircraft:A review

Vibrations in aircraft hydraulic pipeline system,due to multi-source excitation of high fluid pressure fluctuation and serious vibration environment of airframe,can cause the pipeline system vibration failures through overload in engineering field.Controlling the vibrations in hydraulic pipeline is a challenging work to ensure the flight safety of aircraft.The common vibration control technologies have been demonstrated to be effective in typical structures such as aerospace structures,shipbuilding structures,marine offshore structures,motor structures,etc.However,there are few research literatures on vibration control strategies of aircraft hydraulic pipeline.Combining with the development trend of aircraft hydraulic pipeline system and the requirement of vibration control technologies,this paper provides a detailed review on the current vibration control technologies in hydraulic pipeline system.A review of the general approaches following the passive and active control technologies are presented,which are including optimal layout technique of pipeline and clamps,constrained layer damping technique,vibration absorber technique,hydraulic hose technique,optimal pump structure technique,and active vibration control technique of pipeline system.Finally,some suggestions for the application of vibration control technologies in engineering field are given.

时间硬化蠕变本构方程耦合损伤的应用研究

使用时间硬化的蠕变方程,考虑各向同性蠕变损伤,采用应变等效原理,推导出时间硬化形式的多轴蠕变损伤方程,经过一维简化,提出了通过单轴蠕变实验确定材料参数的方法,并用来确定镍基高温合金Udimet720Li在两个不同温度下的蠕变和损伤参数。通过有限元计算并与实验数据进行了对比,验证了耦合损伤的多轴蠕变方程以及材料参数确定方法应用于实际的可行性。

CESSNA172R飞机飞行操纵钢索故障原因分析

CESSNA172R飞机飞行操纵(副翼、升降舵、方向舵、襟翼)系统钢索多次发生磨损、断裂故障,严重威胁了飞行安全。根据该机型结构设计特点,通过相似机型系统类比、数据可靠性分析等方法分析了各飞行操纵系统钢索失效的主要原因,提出了预防飞行操纵钢索失效的措施。通过调整飞机的操纵钢索系统的维护周期,改进钢索的检查和维护技术,提高飞机在全寿命周期中的安全可靠性。

飞行器故障预测与健康管理(PHM)集成工程环境研究

故障预测与健康管理(PHM)技术能够实现故障监测、诊断、预测、状态评估及综合决策的功能,能够降低飞行器维修、使用和保障费用,提高飞行器战备完好率、任务成功率以及安全性和可用性;在分析了国内外研究现状的基础上,提出了构建飞行器故障预测与综合健康管理的通用化支撑平台和验证环境的设计思路,并展开描述了PHM开发环境、运行环境、验证环境的具体功能组成,研究成果能够为检验飞行器PHM系统工作效能提供有效验证,为降低飞行器PHM验证费用提供借鉴。