Abstract:The vertical takeoff and landing (VTOL) fixed wing unmanned aerial vehicle (UAV) has many advantages, such as low requirements for takeoff and landing site, good maneuverability, high cruise speed and long endurance, etc., which is a hot topic in the aviation field. This paper describes the existing VTOL fixed wing UAV development status and their features around the world, and then analyzes the technical problems faced by these different types of VTOL fixed wing UAVs. It indicates that the VTOL fixed wing UAV with higher cruise speed, longer battery life, and stronger ability of task load seems to be the main developing direction and inevitable trend in the future. Although the tilting rotor configuration and tailstock configuration are still the mainstream configuration of the VTOL fixed wing UAV in nowadays, the distributed electric propulsion (DEP) VTOL fixed wing UAV technology will become the hottest issues in the field of aerospace, therefore, it is necessary to enhance the evolutionary research in the new-concept configurations and new principles of the high-performance VTOL fixed wing UAVs.

Abstract:In order to summarize the research methods for numerical simulation method of ditching, provide support for ditching analysis of civil aircraft design, this paper reviews the research progress of numerical simulation methods available for civil aircraft ditching, mainly including plane element method, finite volume method, smoothed particle hydrodynamic method and finite element method. In this paper, the basic principles and applications of these methods are summarized, and the results of different methods are compared and analyzed for future research direction.

Abstract:The door is an important part of the aircraft structure. The door test is an important means to verify that the door design meets the requirements of reliability, safety and airworthiness. There are design verification tests and certification tests for doors of civil airplane. Based on the experience and lessons of civil airplane doors’ development, the paper summarizes the necessary test items and contents during the civil airplane doors’ developing process and the purpose , significance and necessity of each test, proposes the design of test benches and the simplified designing principle of test-pieces, and gives the methods and steps of the tests.

Abstract:Air traffic complexity is the essential attribute of air traffic situation, and it is therefore one of the drivers for air traffic controller"s workload. Scientific evaluation of air traffic complexity is the key to realize air traffic refined management and is a research hotspot of air traffic management. This study introduces the Chinese and global research teams on air traffic complexity, summarizes the differences and associations of air traffic complexity with workload and safety level, and elaborates the concrete clues in the existing research. Then the future research trends and directions of air traffic complexity are prospected on basis of characterization of new-generation air traffic management system.

Abstract:The future air warfare is developing in the direction of unmanned and autonomous, and autonomous air warfare decision-making methods are one of the important support methods for future air warfare. Due to dimensional limitations, traditional air combat decision-making methods cannot handle continuous action and long-sighted decision-making problems. Based on the Actor-Critic method, this paper proposes a unified architecture for continuous decision-making in air combat. Combining air combat training experience, the state space, action space, reward and training subjects are rationally designed, and a variety of continuous action space reinforcement learning algorithms are tested in high uncertainty. The learning effect in the air combat scenario has been visually verified. The results show that: based on the method architecture proposed in this paper, long-sighted value optimization under continuous actions can be realized, the agent can make optimal decisions in complex air combat situations, and has a high kill rate against random maneuvering flying targets. And the air combat maneuver trajectory is highly reasonable.

Abstract:Traditional aerodynamic optimization design requires multiple time-consuming CFD analyses; while widely-used surrogate-based optimization (SBO) can effectively reduce the number of CFD analyses, but it cannot speed up a single CFD analysis. Hence, this paper proposes a hot-start strategy using the proper orthogonal decomposition-back propagation based neural network (POD-BPNN), and applies it in surrogate-based aerodynamic optimization. First, the POD-BPNN model is built from geometric design variables to flowfield data through the initial samples in an SBO. Then, during iteration of the SBO, the flowfield of a new sample is predicted by the built model, and is used as the initial flowfield of the hot-start CFD analysis for the new sample. At the same time, the new sample is used to update the POD-BPNN model until the end of the optimization. The results of the aerodynamic optimization design of the transonic airfoil indicate: the hot-start strategy using the POD-BPNN can reduce the time of a single CFD analysis by 68%, and improves the efficiency of the SBO by 37%.

Abstract:The multi-body dynamic model of telescopic landing gear with two wheels is established to study the low-frequency brake-induced multi-degree-of-freedom coupled vibration. Parameter study regarding landing gear structure and braking torque is conducted. The results indicate that the strut stiffness of landing gear and the amplitude of braking torque have a significant effect on coupled vibration. When the longitudinal strut stiffness reduces by 30%，the longitudinal acceleration of landing gear increases by more than 60%. When the braking moments on the left and right wheels are the same，30% amplitude of braking moment increases leads to 50% increases of the longitudinal acceleration. In the case of asymmetric braking，the landing gear will have multi-degree-of-freedom coupled vibration. When the difference in braking moments amplitude between two wheels increases from 20% to 40%，the lateral and torsional amplitude，acceleration and load will increase by more than 90%.

Abstract:Composite structures have been widely used in the field of aerospace, in order to study the mechanical properties of composites in hygrothermal environments, the pull-through tests of a type of polyimide composite laminates were carried out under three test environments: cold temperature dry(CTD), room temperature dry (RTD) and elevated temperature wet (ETW). The numerical simulation analysis of the RTD test process was carried out. The pull-through strength and failure mode of two typical laminates were obtained by experimental, and the damage evolution process was qualitatively analyzed combined with the simulation results. The results show that the type of polyimide composites have excellent thermal stability. The pull-through strength of the composites under CTD condition is 8.1% ~ 9.0% higher than that under RTD condition, and the pull-through strength of the composites under ETW condition is equivalent to that under RTD condition. Compared with (40/50/10) ply, (30/60/10) ply has higher pull-through strength.

Abstract:The cost of obtaining a large amount of flow field structure by traditional experiment or CFD is unacceptable, so it is significance to develop faster forecasting calculation methods. Proper Orthogonal Decomposition (POD) was used in this paper to extract the dominant mode of the tandem flow field. Radial Basis Function Network (RBFN) is used to respond to the coefficients of the POD basis functions to realize the construction of the reduced-order prediction model of the flow field. Then the adaptive sampling method was developed for the reduced order model. The prediction model is verified by the unsteady flow field data of a cascade cascade. It is concluded that the hybrid method can be utilized to accurately predict the aerodynamics parameters and flow field of tandem cascade. Compared with static sampling, the number of samples required for adaptive sampling to achieve the same reconstruction accuracy is reduced by about 25%.

Abstract:Aiming at Daxing Airport and Tianfu International Airport’s cross-runway, approaching aircraft may have a missed approach in one landing mode, which will affect the safety of take-off and departure aircraft on another runway, and affect the different distances from the approaching aircraft to the end of the runway. The timing of aircraft release was studied. First, calculate the distance from the approaching and go-around aircraft to the end of the runway by establishing a collision risk model; then establish the wake interval model between the cross-runway approach and go-around and take-off and departure aircraft, and calculate the tail generated by the take-off and departure aircraft Whether the flow affects the go-around aircraft to determine the wake safety distance, and finally compare the safety interval calculated by the collision risk model with the safety interval calculated by the wake model, whichever is greater, is the final safety of the approaching aircraft from the end of the runway distance. The controllers of Daxing Airport and Tianfu International Airport can determine the time to release aircraft for take-off based on the safety interval to ensure the safety of aircraft entering and leaving the field.

Abstract:High lift-to-drag ratio design is has become a urgent key problem to be solved, and the hull is the decisive part to the lift-to-drag ratio of the whole airship. Pointing at the difficulty of the high lift-to-drag ratio airship configuration design and complicate constrained requirements, effectively combined with airship hull fine design, flow control technology and lifting body concept, using high precision aerodynamic numerical simulation method, explore and build several new airship hull configuration types, such as airship hull with lift-enhanced strake and center airfoil body hull with end-plates, research on the influence of key geometric parameters on the high lift-to-drag ratio features, get a few new buoyancy-lifting airship hull with high lift-to-drag ratio. The research shows, compare to the original airship hull, with the constraint of volume, adjusting the width of the hull properly, the maximum lift-drag ratio of the airship hull with lift-enhanced strake is 77% larger , the maximum lift-drag ratio of the center airfoil body hull with end-plates is 3.95, in contrast to the original airship hull’s maximum lift-drag ratio which is 2.13, the promotion amount is at least 85.4%, related achievements can provide technical solution and reference to future new conceptual heavy load buoyancy-lifting airship design of our country.

Abstract:In the test of the flexural performance of the honeycomb sandwich structure, due to the different test methods, there is a situation that the data dispersion is large, which causes the reliability to be reduced, which is not conducive to the evaluation of the true performance of the structure. The flexural performance of the honeycomb sandwich structure was studied by flexural method measurement; flexural performance average method analysis and lateral pressure method, and the discrete difference of data was compared to evaluate the effectiveness of the three test methods. Through the test and analysis of the test pieces, the flexural performance data of the honeycomb sandwich panel is obtained. The results show that: the dispersion coefficient of the flexural performance data measured according to the ASTM method is greater than 0.1, which conceals the authenticity of the test results; according to the mean value of the flexural performance The method substituting the honeycomb core shear modulus into the relational formula to solve the flexural performance of the sandwich structure, the dispersion coefficient is less than 0.09, the result is credible; according to GB/T 1454-2005 lateral compression method, the lateral compression modulus of the sandwich structure is lower than that of flexural test, considering the influence of the stiffness of the panel itself, the result of the lateral pressure method is more authentic and the dispersion coefficient is less than 0.07, which is credible The degree is further improved.

Abstract:Due to the good pressure capacity and designability, the stiffener design and buckling analysis of stiffened spherical shell have always been classic and challenging problems. In this paper, the parametric finite element modeling method of stiffened spherical shell based on ABAQUS is given, and the parametric finite element model of the stiffened spherical shell is established, which greatly improves the efficiency of the finite element modeling.. The accuracy of the model is verified by comparing with literature data. Using the critical buckling pressure Pc and the critical buckling pressure to weight ratio Pc/W as main indexes, the influence of shell thickness, stiffener layout, stiffener section size and other parameters on the buckling of aluminum alloy stiffened spherical shell is studied. The finite element analysis results show that circumferential stiffener has more significant influence on the overall buckling of the structure, while the influence of meridional stiffener is not obvious. Increasing the shell thickness and the section height of the reinforcement can also effectively improve the buckling performance of the stiffened spherical shell.

Abstract:In view of the complex flow field structure of the rear intake system, it is necessary to clarify its influence on the double-sided composite impeller, so as to provide reference for the structural design of the rear intake system. Compared with the traditional straight rear inlet scheme, two radial rear inlet schemes, namely elliptical and symmetrical airfoil rear inlet schemes, were designed. Numerical simulation was used to analyze the influence of different rear inlet systems on the compression characteristics and flow field structure of double-sided composite impeller. The results show that compared with the straight type rear intake pipe, the elliptic type rear intake pipe and the symmetrical airfoil type rear intake pipe are slightly worse in compression performance, but there is no significant difference in flow range. At the same time, the radial inlet with elliptical rear inlet is better, which can match the compression characteristics of double-sided composite impeller and meet the needs of stable exhaust of tail nozzle. As the axial velocity at the blade root of the auxiliary impeller decreases, the pressure gradient increases and the separation vortex is generated, which affects the performance of the double-sided composite impeller. This paper extends the understanding of the influence mechanism of the rear intake system with radial intake on the double-sided composite impeller.

Abstract:Life control of aero-engine is an important part of quality management of aviation maintenance. To solve problems, such as existing multiple state life, single using strategy and serious state life consumption, a multi-state life control model of aero-engine was developed by using multi-objective decision-making model and considering various state life consumption constraints respectively. Combined with the proposed life control strategy injection method based on engine service process simulation, the rationality and feasibility of the proposed model and method are verified. The research results can provide technical support and method reference for the development of engine life control strategy for aviation equipment users and maintenance staff.

Abstract:The flap sinking hinge mechanism of civil aircraft is a widely used retractable motion mechanism, and its maintenance cost has a great impact on operating economy. In view of the large gap between the maintenance cost of the flap sinking hinge mechanism of civil aircraft and the actual operation value, a maintenance cost estimation method is proposed based on the MSG-3 (Maintenance Steering Group 3) analysis method. Firstly, damage tolerance analysis results are used as reference data, the inspection method, threshold value and inspection interval of the flap sinking hinge mechanism are obtained through MSG-3 analysis. According to the nature and source of maintenance tasks, a Direct Maintenance Cost (DMC) prediction model is established to predict the maintenance cost of flap sinking hinge mechanism. Finally, the feasibility and effectiveness of the method is verified by taking the flap sinking hinge mechanism of a specific model as an example. The results show that this method can more comprehensively estimate the maintenance cost of airframe structure, and is closer to actual operation than other methods.

Abstract:The establishment of deployment spare parts package is of great significance to the support of combat aviation materials of our army. The primary problem is to determine the variety, this paper puts forward the logical decision diagram and principal component analysis method. From the 10 factors of criticality,replaceability, life control, combat damage, reliability, universality, redundant structure, consumption, economy and financing,through the comprehensive analysis of aviation materials and maintenance, the score and ranking of spare parts are calculated, the rationality of this method is verified by an example, and a scientific method for determining the variety of spare parts package is put forward.

Abstract:Shell parts are widely used in aeroengine control accessories. A large number of small aperture threads are distributed on the surface of these parts. In the whole process of shell production and processing, thread processing is the core process that affects the processing efficiency and accuracy The existing thread processing technology is as follows: first, roughly milling the shell thread by using the NC machining center and then conducting manual tapping. This processing technology has the disadvantages of poor consistency, low processing efficiency, and many special fixtures. At the meantime, the phenomenon of positive cone is easy to appear when milling the thread. In view of these problems, this paper proposes and designs a special thread milling method for processing, which solves the programming problem caused by the shortening of the cutting edge through macro programming. Therefore, the thread can be processed together with the bottom hole, which reduces the manual tapping process and various threads with the same pitch and different specifications can be processed by one cutter. Finally, two batches of parts are verified bt experimental process, and the experimental results are analyzed to verify the reliability of the scheme of processing optimization.

Abstract:The aircraft is impact by severe weather on parking apron, and the aerodynamic research of parking is most important for parking safety. In order to analyze the aerodynamic difference of typical civil aircraft induced by ground cross-wind, and determine the typical Tie-Down loads, the paper aim at two typical civil aircraft layout, adopt scale mode and fixed ground plate in wind tunnel to simulate aircraft park, measure the aerodynamic forces of aircraft which induced by cross-wind with the angles from 0 to 180 degree, and furthermore use the disassemble test method to analyze the empennage aerodynamic coupling. The research confirm the empennage aerodynamic coupling is the reason of large pitching moment of high HTP layout and small pitching moment of low HTP layout at cross-wind, finally estimate the nose landing gear Tie-Down loads for rear tipping condition. In this paper, the aerodynamic characteristics of two typical civil aircraft on ground cross-wind are compared completely, it’s useful for the aerodynamic research of parking and taxing civil aircraft , which is significant for parking Tie-Down load analysis.

Abstract:Aiming at the requirement of regular field testing and fault diagnosis of the electrical characteristics of the airborne GJB289A bus network, the GJB289A bus network is modeled and simulated by the ADS (Advanced Design System) software, and the typical electrical fault characteristics of the GJB289A bus network are studied. According to the distribution parameters of transformer and terminal resistance, and the lossy coupling transmission line model of the GJB289A bus system, a two-port network model containing two coupling transformers is constructed in the ADS software, and the effectiveness of the simulation model based on distributed parameters is verified by theoretical derivation and laboratory test comparison analysis. Based on the distributed parameter model of two port network, the characteristic waveforms and parameters of typical electrical fault types are analyzed and sorted out to realize the rapid judgment of typical electrical faults. Combined with the topology, physical size and distribution parameters of the actual GJB289A bus network, the accurate waveforms of the test port and the characteristic parameters of typical electrical faults can be simulated by using this method, which provides technical support for optimal design of bus detection equipment and the health management of the bus network state.