Abstract:The symmetrical design of the aircraft's wings and control surfaces determines the system framework in which the sensors， computers， and actuators of the flight control system are stributed and symmetrically installed on the aircraft， and the even number n-redundant architectural design is adopted. In the practical engineering， the balanced division of labor in the productive relations of redundant parts and the differences in design and manufacturing between different manufacturers would inevitably appear the case of two singular faults such as：‘ two-party opposition' even separation uncertain fault and‘ mutual disapproval’. The criterion of‘ variation memory， redundancy reconstruction and high probability failure of extreme signals’ for singular faults is proposed. In an even redundancy system， the sample median is calculated based on the signal variation at the endpoint of the median interval. The fault criterion is based on the variation consistency between signal and the participating voting signals. The four signals are reconstructed into the‘ second largest， second smallest and reference signal’， which is a reconstructed triple redundancy. The two signals are reconstructed into‘ original two signals + reference signal’， which is a reconstructed triple redundancy as well. The redundancy econstruction criterion is formed by the four signals reconstruction and two signals reconstruction. The study in this paper provide an effective voting monitoring solution for the four-redundant signal‘ 2∶2 uncertain fault， 1∶1∶1∶1 multiple fault’ and the two-redundant signal 1∶1 fault for fault criterion and the redundancy reconstruction criterion. In the case of three-redundant signal 1∶1∶1 multiple fault， according to the following quality between the signal and the median signal， the non-median signal close to the median is normal， and the non-median signal far from the median is faulty.

Abstract:With the rapid development of aerospace equipment, the reliability requirements of military equipment are gradually increasing, and the reliability of the aircraft lock mechanism is crucial to the safety of aircraft take-off and landing. This paper takes aircraft cabin door lock mechanism as the research object. Firstly, a large number of cabin door lock mechanisms are investigated through literature and the characteristics and failure modes of the lock mechanism are analyzed, and the working principle of the lock mechanism is described. Secondly, the failure mechanism modeling of lock mechanism and the status quo of gradual damage of lock mechanism and the existing problems are described. The reliability research status of locking mechanism at home and abroad is analyzed. The reliability analysis of multi-link mechanism and lock mechanism are classified and combed. Finally, the research ideas of reliability analysis of locking mechanism are summarized, the existing problems and research trends of reliability analysis of complex mechanisms are also prospected.

Abstract:As an important part of the aircraft, the impact resistance of the wing fuel tank cover is of great significance to the safety of the aircraft. This paper systematically introduces the research progress of impact resistance performance of wing fuel tank cover from three aspects: airworthiness regulations requirements, common materials and structural forms, assessment methods and evaluation, summarizes the current research conclusions, and prospects the future development of wing fuel tank cover.

Abstract:In order to study the aerodynamic influence of pitch angle on the contra rotation propeller (CRP) and improve its aerodynamic performance, at the inlet Mach number of 0.453, by adjusting the pitch angle of the aft propeller, a 6×6 contra rotation propeller was numerically calculated, and the variation law of pitch angle on aerodynamic interference between the contra rotation propeller was studied. The Unsteady Reynolds-Averaged Navier-Stokes (URANS) equation combined with the SST turbulence model is used in the calculation, and the T-Rex high quality mesh generation technique is used. The calculation results show that there is complex aerodynamic interference between the front and aft propellers of contra rotating propeller, the aft propellers can absorb a part of the tangential slip flow energy of the front propellers, and the aerodynamic efficiency is higher than that of the front propellers. The aerodynamic parameters of the front and aft propellers fluctuate 12 times in a rotating cycle. When the pitch angle of the front propellers is 54° or 56°, the efficiency of the front propellers is slightly improved when the pitch angle of the aft propellers is reduced, while the pull coefficient and power coefficient of the aft propellers are significantly increased, and the efficiency of aft propellers increased by 4% and 6.4%. The Ct 、 Cp and n fluctuation amplitude of the aft propeller increases. In addition, in order to offset the torque of the front and aft propellers and improve the overall aerodynamic performance of the contra rotation propeller, the pitch angle of the aft propellers should be appropriately reduced under this working condition.

Abstract:The effect of point cloud denoising is very important to the subsequent surface fitting and modeling design in 3D scanning process. How to extract feature points quickly and accurately has become a research hotspot. However, the key point of point cloud denoising lies in the detection of singular values and outliers. Therefore, this paper proposes a denoising model with coupled multi-feature point parameters, and discusses the influence of each feature point parameters on the denoising model respectively. At the same time, the swarm intelligence algorithm is used to solve a set of optimal parameter weights to determine the point cloud denoising model, so as to achieve the optimal denoising effect of three-dimensional scattered point clouds. In this paper, through the denoising simulation of Bunny model and the denoising experiment of a certain type of skin, the simulation and experimental results show that the point cloud denoising model proposed in this paper has faster iteration, less time-consuming and better denoising effect than radius filter, statistical filter and improved voxel filter combined with Gaussian filtering algorithm.

Abstract:Currently, the research on low-frequency braking coupling vibration of aircraft landing gear mainly is relatively lacking. In this paper a taxiing and braking analysis model for rigid-flexible coupling of two-wheel strut landing gear is established in the Simcenter 3D dynamics analysis software. The research results show that the vertical stiffness of the tire has a great influence on the vibration of the landing gear in the lateral and torsional. The vertical stiffness of the tire changes by 33% and the vibration in the lateral and torsional changes by about 5%. The cornering stiffness of the tire has a great influence on the vibration of the landing gear in the lateral. The cornering stiffness of the tire changes by 33% and the vibration in the lateral changes by about 15%.

Abstract:MAV-UAV cooperative air combat is one of the main combat styles of UAV combat application in the future. Based on ACO algorithm, the maneuver decision algorithm of MAV and UAV is designed. According to the defects of optimization ability and long planning time of ACO algorithm, ACO-A star hybrid path planning algorithm is proposed. The improved algorithm takes the planned path of A star algorithm as the reference path, which can effectively improve the planning efficiency of ACO algorithm and improve the path quality with a certain probability. The UAV cooperative decision-making air combat maneuver method under the limited decision-making of MAV is designed, and the tactical strategy of cooperative operation between MAV and UAV is designed. Through simulation, the effectiveness of decision-making algorithm is verified, and the promotion effect of cooperative tactical strategy on combat is also verified.

Abstract:Aircraft maintenance order is the main basis for military aircraft maintenance work. The orders specify all preventive maintenance tasks involved in aircraft basic level maintenance. With the accumulation of aircraft use and maintenance experience, the demand for optimization of maintenance task interval is becoming more and more obvious. Taking the service data as the analysis object and the system reliability as the measurement standard, this paper constructs the mathematical model of preventive maintenance task interval optimization analysis. Taking a maintenance task as an example, this paper analyzes its service data, and gives suggestions on maintenance interval optimization. The example has proved the feasibility of the mathematical model which can be used as a reference for military aircraft maintenance task interval optimization analysis.

Abstract:With the development of artificial intelligence technology, intelligent aircraft engines have gradually become a hot spot in the field of aviation today. Traditional aero-engine control heavily relies on the engine model, and the theoretical modeling approach based on aerothermodynamic formula introduces modeling error that may degrade the performance of controller. This paper proposes a virtual self-learning approah for aero-engine intelligent controller design. Firstly, a virtual environment is established from the testing data of the aero-engine via LSTM neural network; Secondly, the reinforcement learning algorithm based on TD3 is employed for intelligent controller training in the virtual environment, Finally, the JT9D aero-engine model is utilized for controller performance evaluation. The simulation comparisons between intelligent controller and traditional PID control show that the intelligent controller has remarkable performance due to the less overshoot and shorter setting time.

Abstract:Effectively evaluating the post competency of airline maintenance personnel can improve the targeted training plan and the comprehensive ability of the civil aviation maintenance team. Based on job analysis method, behavioral event interviews, and questionnaires, the competency indicators of airline maintenance personnel were initially selected and revised, and 21 evaluation indicators were finally determined. The post competency index system of airline maintenance personnel constructed was divided into basic knowledge and psychology cognition, basic skills, mental skills, and work style. The index weight was determined by the entropy weight method. And the post competency evaluation model of airline maintenance personnel was build by used of the intuitionistic fuzzy grey relational analysis method combined with cumulative prospect theory (IF-CPT-GRA). The post competency scores of 5 airline maintenance personnel evaluated by the well-experienced professionals were acquired, and their ranking order arragged were the same as compared with other decision-making models , and put the model into actual example . The research show that the evaluation model has certain practicability and can effectively evaluate the post competency of airline maintenance personnel.

Abstract:A twin-boom UAV with inverted V-tail is proposed and compared with the existing U-tail one by numerical method. Verification and validation were made on the computational model. Longitudinal, lateral, and directional aerodynamic characteristics and static stability of the two configurations are investigated and compared, with different angles of attack and sideslip angles. The results show that the inverted V-tail can reduce the wetted area, increase the lift drag ratio of the whole aircraft by 2.2%, and increase the stall angle of attack of the tail, but the lateral static stability decreases apparently. Flow fields comparison shows that there is a great difference between the normal force position of the inverted V-tail and that of the U-tail, which is the main reason for the decrease of lateral stability. It is found that when the included angle is less than 90 degrees, the tail can enhance the lateral stability of the aircraft.

Abstract:The shimmy of the front landing gear of an aircraft usually occurs in the process of taking off or landing, which endangers the stability and maneuverability of the aircraft and is a serious aircraft fault. In this paper, based on the theorem of moment of momentum, a mathematical model of shimmy considering landing gear side bending and torsion is established for a certain type of UAV. The different dynamic models when using traditional oil damping damper and electromagnetic damping damper are discussed. For the traditional oil damping damper, the equivalent linear model is used to obtain the upper and lower boundaries of the critical stability damping curve. For the nonlinear model of electromagnetic damping damper, the bifurcation analysis theory is used to determine the shimmy stability area. It is shown that excessive shimmy damping can not suppress shimmy, and the stable region of shimmy on the parameter plane is obtained, It can provide some references for the design of landing gear shimmy reduction.

Abstract:The overall manufacture of the small-diameter variable-section composite air inlet is difficult, and the small size of the inner cavity makes it impossible to carry out surface treatment. Based on this, this paper proposed a manufacturing method to realize the integration of structure and function.The block and combined structure design is adopted, then the skin parts with uniform thickness (surface waviness not exceeding 0.5 mm) and small deformation are formed under the process control. To solve the problem of seam level difference between segmented skins, the synergistic method of flange edge connection and fixed connection with plate is adopted. The composite air inlet that meet the design and usage requirements has been successfully manufactured.

Abstract:This paper introduces a method for self-pressurized civil aircraft hydraulic reservoir volume calculation based on SAE AS5586. Taking a hydraulic reservoir from a civil aircraft as an example, it is gradually analyzed and calculated according to the corresponding method. Provide reference for the similar self-pressurized hydraulic reservoir volume calculation.

Abstract:In order to provide fast, accurate and effective fault isolation procedure and improve the level of aircraft maintenance support, the method of fault isolation procedure analysis based on system schematics and dynamic fault tree is studied in view of the lack of integrity and logic of traditional fault isolation procedure analysis. Taking the fault of the bleed air overheat detection system of an aircraft fire protection system as an example, the system design schematics and fault alarm logic analysis are carried out in depth, and a dynamic fault tree with sequence correlation, function correlation and backup relationship is constructed by using dynamic logic gates, and then correlation fault analysis and troubleshooting flow chart transformation are carried out. The results show that the method can systematically and comprehensively reflect the fault trigger logic, provide a fast and effective fault isolation path, and has good application prospect and popularization value in the Line Maintenance field of complex aircraft systems.

Abstract:At present, the safety analysis of aircraft air conditioning system is based on the fixed fault state, without considering the dynamic development and change of the fault. At the same time, only qualitative analysis can be carried out. It is necessary to carry out accurate safety analysis on aircraft air conditioning system. Based on the root fault parameters in the FMEA of the air conditioning system, Markov time series is used to solve the lateral fault transfer path, and the joint probability distribution and Bayes algorithm are used to solve the fault level and probability, thus realizing the lateral qualitative and quantitative safety analysis; The Monte Carlo simulation is used to solve the longitudinal upgrading path, fault level and probability of the fault, and the longitudinal qualitative and quantitative security analysis is realized. The results show that the dynamic quantitative and qualitative safety analysis can accurately determine the safety of the aircraft air conditioning system, the release conclusion and the release requirements under fault conditions, and has good engineering application value.

Abstract:The thermal field distribution of generator has a great influence on the failure phenomenon of the overheat protection component, which is the key parameter to be considered in the design. Based on the steady-state pressure solver and turbulence model in ANSYS software, the internal thermal field distribution of the motor under fault mode was simulated. The thermal field distribution of the stator, rotor and shell circulating oil circuit were obtained. The results show that the simulated thermal field is consistent with the actual temperature field distribution. The temperature gradient of low-melting alloy in the thermal trip mechanism is accordance with the internal thermal field distribution of the generator. It is helpful to protect the motor from overheating by changing the melting points of some key parts and the special softening temperature points of materials.

Abstract:The installation of 3D printing technology requires that after the completion of the verification of materials and processes, the permissible value test of specimen level additive manufacturing materials and the additive manufacturing part-level test will begin. Due to the process characteristics of additively manufactured parts, there is usually a difference in the mechanical properties of XY direction and Z direction, and there is a difference in the characteristics of the same sex in the design of traditional metal parts, so it is necessary to test its mechanical properties in simulating the real flight state. This paper takes the additive manufacturing gust lock bracket as an example, first calculates the maximum load state in the operation process of the aircraft, selects the most typical load direction for tooling test scheme design, before the test starts, engineering calculation and software simulation are carried out to predict the failure mode and failure load, the test results show that the results of software simulation and engineering calculation are accurate and effective, and the mechanical properties of the additively manufactured titanium alloy gust lock support are stable, can withstand the test of extreme working conditions, and meet the installation requirements.

Abstract:With the increasing instability of the world situation and the participation of more participants in the aviation manufacturing supply chain, the risks faced by the management of the aviation manufacturing supply chain also increase. Therefore, this paper focuses on risk management in the aviation manufacturing supply chain network, using complex networks as a tool to study the identification of key nodes in the supply chain network, in order to help the aviation supply chain improve its risk resistance ability. By analyzing the current situation and characteristics of China"s aviation manufacturing supply chain network, the aviation manufacturing supply chain complex network is constructed and indicators are defined by proposing the formation mechanism of the supply chain and dividing the supply chain hierarchy. Three classical centrality algorithms, namely degree centrality, betweenness centrality and closeness centrality, and the traditional K-Shell method are weighted and improved. And in combination with the entropy-TOPISIS method, a WKC algorithm for identifying the key nodes of the supply chain for the weighted network is proposed. The feasibility and validity of this algorithm are verified by constructing a network to analyze a numerical example. The results indicate that the WKC algorithm proposed in this paper has scientific principles, low computational complexity, and provides a certain reference for risk management in the supply chain of high-end equipment manufacturing industries such as aviation manufacturing.

Abstract:In order to improve the efficiency of flight ground support, an AOE network was constructed according to the flight ground guarantee process of an airport, and the "critical path" of flight ground support operation of the airport was calculated through the flight node data recorded by the airport A-CDM system. By analyzing the compressible process on the critical path, the ground guarantee operation flow of the airport is optimized. Based on the actual data of flight ground guarantee at an airport in southwest China, the abnormal data caused by force majeure were eliminated, and the flight transit time before and after the optimization of the guarantee process was calculated. The comparative analysis shows that, among the 33 sets of flight data, the optimized support operation process using AOE network reduces the ground guarantee operation time by 6.1min/ flight on average, which effectively improves the operation efficiency of the airport.