Abstract:Morphing aircraft can change its aerodynamic configurations to obtain optimized aerodynamic performance. Smart material actuator and flexible skin are the key technologies of morphing aircraft. The research of actuators made of shape memory alloys, piezoelectric materials and magnetostrictive materials is introduced. The development of flexible skin based on material elasticity and structure design is analyzed. The related research issue and interests are summarized and prospected.

Abstract:With the widespread application of ceramic matrix composites in hot end components of advanced aero-engines, it becomes particularly important to conduct efficient and accurate nondestructive characterization of defects/damages formed during the whole life cycle. Due to the complex preparation and forming process of ceramic matrix composites and the high heterogeneity and anisotropy caused by multiphase composite, the traditional nondestructive testing technology based on the assumption of global homogenization faces many challenges. Based on the application of ceramic matrix composites in aero-engine field, the typical defect/damage types and characteristics in the whole life cycle of ceramic matrix composites were analyzed. The research progress and application of nondestructive characterization techniques of ceramic matrix composites in recent years were reviewed, the main challenges faced by existing nondestructive characterization techniques were summarized, and the future development trend was prospected.

Abstract:The aircraft power supply system is the power source of all electrical equipment on board, thus its safety and reliability are pretty important. Against the backdrop of environmental protection and high-efficiency development needs, research and application of more/all electric aircraft technology with electric power as the core is advanced. The widespread use of electric drive devices and power electronic devices has led to the complexity of aircraft power supply system structure, which puts forward higher requirements for aircraft reliability, safety, testability and maintainability, so that researches on fault diagnosis technology for aircraft power supply systems are of great significance. This paper firstly introduced the composition structure and respective functions of aircraft power supply system. Secondly, the development process of aircraft power supply system was outlined. Thirdly, the characteristics of typical domestic and foreign power supply systems were compared. Fourthly, the main failure modes, fault characteristics and failure causes of aircraft power supply system were summarized, and a design architecture of aircraft power health management system was proposed. Fifthly, the research progress of fault diagnosis methods based on model and data were reviewed, then, the characteristics of various diagnostic methods were evaluated from aspects such as accuracy, data demand, applicability and implementation difficulty. Finally, this paper gave the challenges and development trends of fault diagnosis technology for aircraft power supply system.

Abstract:The classic sled-type landing gear makes it challenging to take off and land in challenging terrain, with the widespread usage of rotorcraft UAVs in both civil and military domains. This research develops a two-stage buffered adaptive landing gear that is similar to a human leg in order to increase the landing area and application range of rotorcraft UAVs. An adaptive landing gear attitude adjustment strategy was proposed after researching the positive and negative kinematics of the bionic leg. A bionic quadruped hexacopter UAV landing dynamics model was established, landing dynamics simulation was carried out using the multi-body dynamics software simcenter 3D, and a comparison of landing performance with the conventional sled landing gear was carried out. The research demonstrates that the two-stage cushioned adaptive landing gear in the landing leg style and its attitude adjustment strategy can reduce roll angle by 95.69% and overload coefficient by 34.06%, proving that the two-stage cushion adaptive landing gear has excellent shock absorption and cushioning capability in the face of complex terrain.

Abstract:In aerospace engineering, it is important to study the influence of wet and thermal environment on the interlayer fracture toughness of resin matrix composites. In this paper, the microstructure of type I and type II interlayer fracture toughness experiments under different wet and thermal conditions were analyzed, and the effect of wet and thermal environment on the interlayer fracture toughness of resin matrix composites was obtained. The research results indicate that the humid and hot environment has a completely opposite effect on the interlayer fracture toughness of type I and type II resin composite materials. As the temperature increases, the interlayer fracture toughness of type I resin composite laminates shows an upward trend, while the interlayer fracture toughness of type II resin composite laminates shows a downward trend. During Type I delamination, a large number of fiber bridging phenomena occur. In humid and hot environments, the resin softens and fiber bridging phenomena increase, leading to an increase in Type I interlayer fracture toughness with increasing temperature; In a humid and hot environment, as the temperature increases, the shear strength of the resin gradually decreases, and the interfacial shear strength between the resin and fibers also gradually decreases, resulting in a decrease in type II interlayer fracture toughness with increasing temperature.

Abstract:Fault prediction technology has important application value in ensuring the reliable operation of instrument landing system and improving ATC effectiveness. Combining the operation characteristics of instrument landing system and actual operation and maintenance work, a fault prediction method of instrument landing system based on GRU is proposed. Taking heading beacons as the research object, the monitoring parameters are used as fault characteristic parameters after analyzing the relationship between their monitoring parameters and equipment operation status. Then, the GRU algorithm is used to predict the future change trend of the monitoring parameters according to their time step and significant time-varying characteristics. Finally, the probability of "failure" is calculated according to the subordinate function of the monitoring parameters, and the prediction of heading beacon failure is realized. The relative prediction accuracy of the GRU prediction model is over 95% after two years of training with the monitoring parameter data. By comparing the prediction of heading beacon failure data and normal operation data, the validity of the monitoring parameters as failure characteristics to characterize the operation of the heading beacon and the effectiveness of the GRU-based failure prediction method are verified.

Abstract:Practice has shown that big data technology can empower the management process. As an important project in the complex high-end program of commercial aircraft development, the commercial aircraft MOC9 test project will generate a large amount of project management data during development. Therefore, it is necessary to study how to use big data technology to promote such projects to achieve project objectives. Based on the characteristics of the MOC9 test project under the commercial aircraft development program and its demand for big data management, this article conducts study on the MOC9 test project from multiple aspects such as architecture planning, data acquisition and storage, data cleaning and processing, analysis mining, and visual display, combined with big data technology processing processes and methods. The study results show that establishing a quantitative visual model for MOC9 projects through big data technology is very helpful for project managers to master the overall situation of the project, locate the root causes of problems, and identify potential risks of the project.

Abstract:The long landing distance from 50 ft to touchdown is an over-limit event frequently occurring during the landing phase and also significantly increase the risk of landing accidents. The study on the impacts of geographical environmental factors of the over-limit event can provide references for airport site selection and flight quality evaluation. Based on the flight QAR (Quick Access Record) data, topographic data and climate data of the airports, global and local correlation analysis were adopted to identify the main factors influencing the over-limit event. The regression model between the event frequency and elevation, fluctuation, air temperature was established, based on the geographical weighted regression model. According to the regression coefficients, the impact modes of these factors were divided into five categories using K-means method, so as to explore the spatial pattern and mechanism of geographical environmental factors on the over-limit event. The results show that elevation, fluctuation, air pressure and air temperature have a significant impact on the frequency of the "long landing distance" over-limit event. There is an obvious spatial differentiation of the impact of geographical environment factors. The spatial distribution of airports under the same impact mode shows clustering.

Abstract:A quality risk identification and assessment method for aircraft manufacturing and maintenance based on FMEA is applied to analyze the potential failure modes and their causes of aircraft in manufacturing and maintenance, evaluate these failure modes, and formulate recommended measures for important failure modes to reduce or avoid the occurrence of failures. This paper presents a set of mapping rules for the application of DFMEA analysis results in risk identification and assessment of manufacturing and maintenance quality. The analysis scope is extended from the design end to the use and maintenance of aircraft. Through the combination of the above methods and measures, the technology realizes the analysis and evaluation of the potential failure mode, failure cause, Severity, recommended measure effect, measure coverage and repeatability in the manufacturing and maintenance process starting from the design stage, which can more scientifically and comprehensively analyze, evaluate and deal with the quality risk of aircraft manufacturing and maintenance.

Abstract:The configuration management of civil aircraft brake control system plays a key role in the process of system design and development and airworthiness compliance verification. In order to improve the configuration management capability of civil aircraft brake system, the software designed and developed can meet the airworthiness requirements, this paper introduces the concept and method of brake system control software configuration management, and illustrates how to combine configuration management with software design by means of system thinking and information flow to carry out whole-life-cycle configuration management. By combining with the requirements of DO-178C, configuration data digital management mechanism based on product configuration is established, unique data source of brake control system development is created. The result shows that a unified configuration database is established with configuration baseline management combination in which the information and status are accurately recorded strictly to ensure the real-time, traceability, integrity and effectiveness of status information, and achieve the final configuration control goal to meet the airworthiness requirements.

Abstract:The landing-gear retracting and releasing system and braking system of UAV plays a crucial role in the process of takeoff, landing, and braking of UAVs. Electrostatic hydraulic systems not only retain the advantages of traditional hydraulic systems, but also have the advantages of electric actuation. According to the working principle of the electro-hydrostatic actuator, an electro-hydrostatic system integrating the landing-gear retracting and releasing and braking functions of unmanned aerial vehicles is designed. The improved PID control method is applied to the landing-gear retracting and releasing function, and two fuzzy PID control methods are designed to apply to the anti-skid braking function. On this basis, a co-simulation based on AMESim and MATLAB/Simulink is conducted to verify the system performance, Finally, the simulation results are compared and analyzed. The results show that the designed control method can normally complete the landing-gear retracting and releasing and braking of unmanned aerial vehicles, and the control effect is good.

Abstract:The integral inertial particle separator is a helicopter air inlet protection device. It has excellent performance and wide application compared with other protection devices, which is of great significance to ensure the regular operation and improve the service life of helicopter engines. This paper summarizes the research progress of integral inertial particle separators, including the following aspects: 1) The classification and aerodynamic parameters of the integral inertial particle separators are introduced. 2)The research methods and their results of the integral inertial particle separators are sorted out. 3)The factors affecting the performance of the integral inertial particle separators are summarized and analyzed. 4)The future development of integral inertial particle separators is predicted. This paper can be the reference for future study and the guide to integral inertial particle separators’ optimization design.

Abstract:With the increase of service time, the maintenance quality of old helicopters has brought more challenges. This article introduces the application of aviation non-destructive testing in the field of aviation maintenance and the characteristics and maintenance status of old helicopters, We explores and determines the key parts and key components of non-destructive testing for old helicopters based on the structural characteristics and usage of helicopters, elaborates on the specific application methods for testing key parts of helicopters based on the characteristics of different non-destructive testing technologies, and studies the timing of using non-destructive testing technology in the maintenance practice of old helicopters. Finally, we have made prospects for the application of non-destructive testing technology in the maintenance of old helicopters.

Abstract:To reduce the probability of helicopters being discovered during mission execution, based on the geometric optics method and consistent diffraction theory, the effects of different tail rotor airfoil thickness, curvature, and scissor angle of tail rotor on RCS were studied for the helicopter tail rotor. Using radar to irradiate the tail rotor from the ground and radar to irradiate the tail rotor from the rear of the helicopter, the RCS of the tail rotor is analyzed using two different irradiation radar orientations. By comparing the RCS peak and mean values of different parameters of the tail rotor, the more favorable conditions for the stealth of the helicopter tail rotor are determined. When illuminating the tail rotor from the ground, the RCS with small thickness and curvature of the tail rotor will be smaller, and changes in the angle of the scissors will cause changes in the peak phase of the RCS. When the radar illuminates the tail rotor from the rear, the RCS of the tail rotor with smaller thickness is smaller, while the RCS peak of the tail rotor with larger curvature is smaller. Based on comprehensive analysis, the smaller the thickness and curvature of the tail rotor, the more favorable it is to reduce the RCS of the helicopter tail rotor.

Abstract:The widespread application of composite materials in blades also makes the force and stiffness characteristics of blades more complex than traditional blades. In order to reduce the dynamic stress and vibration level of rotor blades, it is necessary to analyze the dynamic characteristics of rotor blades. This article first designs the overall parameters of the rotor and the aerodynamic parameters of the blade. Secondly, the CFD method is used to analyze the aerodynamic characteristics of the rotor in hover. Finally, the three-dimensional nonlinear elastic model of the blade is decomposed into a two-dimensional linear profile model and a one-dimensional nonlinear beam model for dynamic characteristics analysis. The results show that the rotor can successfully pull up the 230kg unmanned helicopter, the hover efficiency is greater than 0.65, the natural frequency of the blade under the working speed keeps a certain range with the frequency of the aerodynamic excitation force below the 8th order, avoid the speed resonance region and meet the requirements of the blade dynamics design.

Abstract:Multipurpose, intelligent, and strong terrain adaptability are important trends in the development of helicopters in the future. The landing gear is a key component to ensure the safety of helicopter takeoff and landing. Due to the poor terrain adapt-ability of the traditional landing gear, a leg landing gear system is designed using the bionics design concept to solve the problem of the helicopter"s smooth land observation in complex terrain environment. Starting from the design require-ments of leg landing gear, the landing architecture was analyzed and the leg structure design was completed. Then, based on the designed leg mechanism, the kinematics analysis and dynamics analysis are completed, and the relevant models are established as the basis for the motion control of the leg landing gear. Finally, motion testing of the leg landing gear was completed in the laboratory, proving the rationality of the structural design and the accuracy of the control algorithm.

Abstract:The structural characteristics, manufacturing requirements and interface accuracy requirements of helicopter composite duct are analyzed. According to the structural characteristics and requirements, a new manufacturing technology of helicopter composite duct is proposed, which includes precision manufacturing technology of parts, adhesive assembly technology of duct structure and finishing technology. The technology is discussed and its application is reported. Compared with the traditional dolphin helicopter duct manufacturing technology in many aspects, the new helicopter composite duct manufacturing technology has achieved the effects of reducing cost, shortening manufacturing cycle, simplifying tooling, improving quality and ensuring interface accuracy, which has important reference value for the precision manufacturing of other helicopter parts.

Abstract:In order to ensure the high surface quality and high dimension precision of the helicopter landing gear wheel shaft after spraying tungsten carbide coating. In this paper, the research on tungsten carbide coating grinding technology for wheel shat is carried out from three aspects of grinding strategy, clamping tool and grinding strategy. First, we used the orthogonal experimental method to find out the grinding parameters that could make the surface roughness of the parts reach Ra0.4; Then, the problems of ellipse and taper in the process of outer circle grinding are eliminated by improving the fixture, adjusting the way of grinding wheel feed and improving the grinding strategy; Finally, the outer circle dimensions of 15axles were collected and calculated, and the process capability index was not less than 1.33. The feasibility and stability of the whole grinding process are proved.

Abstract:In order to effectively evaluate the maritime emergency rescue capability of helicopters and improve their emergency rescue efficiency, it is proposed that the safety issues in the three stages of "pre-prevention--in-event response--post-event recovery" in the rescue process be taken into account in the helicopter maritime emergency rescue system.Based on the "5W1H" analysis method, the research framework was designed, and the evaluation indicators of helicopter maritime emergency rescue capability were screened through literature analysis, questionnaire survey, expert consultation and other methods, and 21 evaluation indicators were determined to build the evaluation index system of helicopter maritime emergency rescue capability. The analytic hierarchy method based on D-S evidence theory was used to determine the index weight, and the fuzzy comprehensive evaluation method was used to construct a comprehensive evaluation model of helicopter maritime emergency rescue capability. The evaluation model was applied to the rescue exercise taking the injury of offshore wind turbine maintenance personnel as an example, and the score was 86.89, and the rescue ability was judged to be "strong".The results show that the evaluation index system and evaluation model have certain practicality, and can effectively evaluate the ability of helicopter emergency rescue at sea.

Abstract:Helicopter maritime search and rescue (MSAR) is one of important component in aviation emergency rescue sys-tem. However, the MSAR unit usually analyzes distress information and makes response plans according to previous experience. As a result, it needs theoretical guidance and software support. This paper focuses on the process from receiving the distress message to performing the MSAR mission, and puts forward a kind of decision-making support technology architecture for helicopter MSAR mission facing the operation support issues. Then the re-sponse plan is carried out around which plays a key role in the implementation of this mission. What is more, the MSAR decision-making support system for people in distress has been designed and developed, which can pro-vide effective support for decision maker. Finally, the reasonablility and practicability of prototype system has been verified from the 2020 MSAR comprehensive practice of Xiamen City.