Abstract:Jet noise is the dominating component of aircraft noise, and causes severe environmental pollution and health threats. Yet lack of a fundamental understanding of how turbulent eddies generate noise radiation poses great challenges in designing accurate noise prediction methodologies and efficient noise reduction devices. This paper reviews the progresses and limitations of the studies on the turbulent noise source identification and noise source mechanisms in open literature. Judging by the cause-effect reasoning that the turbulent fluctuations generate acoustic perturbations, it seems promising to develop physically more accurate models and governing equations to separate the acoustic and turbulent fluctuations in future research. By explicitly formulating the former as the generalized function of the latter, the dynamic process how turbulent eddies generate noise radiations may be revealed.

Abstract:Aluminium-alloys have been widely used in aeronautical engineering due to the advantages of high strength and easy processing. Low temperature is an inevitable environmental factor in using of aluminium-alloys, and cryogenic crack propagation of aeronautic aluminium-alloys has been greatly concerned by the engineering and academics overseas and domestically. The experiment researches on cryogenic crack growth of aeronautic aluminium-alloys in recent years were generally reviewed here, meanwhile, the cryogenic fracture failure mechanisms were analyzed. After that, the characterization model and life evaluation methodology on cryogenic crack growth of aeronautic aluminium-alloys were summarized and further research problems were clarified, which provides a technical support for engineering design and application of aeronautic aluminium-alloys.

Abstract:With the continuous progress and development of aviation technology, the technical problems of one-way long-distance flight are being solved. Sleep deprivation has a significant impact on pilots'cognitive impairment in the complex environment of long-term flight and high cognitive load. This paper begins with the analysis of the effect of sleep deprivation on cognitive function of subjects, and then analyses the effect of sleep deprivation on cognitive attention and executive function. Combining with pilots'cognitive needs, it summarizes the experimental methods and research conclusions of related studies, and analyses the effects of sleep deprivation on pilots from three aspects of perception, decision-making and execution. The effects of sleep deprivation on pilots'cognitive decision-making are discussed, which can be used for reference in the overall design of cockpit under long-term flight conditions.

Abstract:The aviation industry belongs to the high-end equipment manufacturing industry, one of the eight strategic emerging industries. The aviation industry of major countries in the world is taking the road of integration of civil-military integration. Since the establishment of the aviation industry in China, the "military" and "civilian" have been inseparable. The integration of military and civilian development has become the main theme of the development of the aviation industry. This paper analyzes the development process of civil-military integration in aviation industry at home and abroad, and combines the current stage of China's policies and the development level of aviation industry, combing the existing aviation industry military-civilian integration development strategic guidance and advice from the three aspects of legal guarantee, demolition and promotion of competition, and then from the industrial level, it explores the clustering, modularization and platform development mode of aviation industry and civilian integration. Based on this, the shortcomings of existing research in research depth, micro level and comprehensive research are summarized and the future research directions are proposed for reference.

Abstract:This paper has carried out research on task-oriented capability analysis, function analysis based on fault degradation and parameterized health assessment for complex systems represented by military aircraft. First, we obtained "aircraft based on mission analysis". Indicator) - task function (secondary indicator) - influence parameter" two-level mapping, as the object of health assessment; then, the combination of deterioration degree and severity is proposed to evaluate the "task function" secondary index, using the pole The large entropy improved interval analytic method obtains the “function” weight, introduces the penalty factor for the key functions, and evaluates the “aircraft” to obtain the whole machine health assessment result. This method starts from the actual demand and use process of military health management, and carries out method research, combined with specific example objects and parameter analysis, so the evaluation method and results are highly credible, can support task and maintenance decision, and have good engineering practical value. The application research of a certain type of aircraft is carried out, and the results prove the feasibility and practicability of the method.

Abstract:Based on the momentum source method, a numerical calculation and analysis method for the rotor/propeller/fuselage interaction characteristics of a high-speed helicopter with double-thrust-propeller was developed. The momentum source was used to replace the rotor and the propeller. Firstly, numerical examples of isolated rotor and rotor/fuselage interaction were given to verify the accuracy of the numerical method. Then, the disturbing flow field in the hovering and forward flight state of the double-thrust-propeller high-speed composite helicopter was numerically simulated by using the constructed method. The disturbance of the fuselage to the hovering flow field and the rotor/propeller/fuselage interaction characteristics at different forward flight velocities were analyzed. The calculation results show that the blocking effect of the fuselage on the airflow reduces the lift of the rotor while the propeller is under the rotor. The acceleration of the wash air increases the lift of the rotor; the rotor/propeller/fuselage interaction is greater at low-speed forward flight, which is mainly reflected in the deflection of the propeller slipstream caused by the downwash of the rotor and the increase of the pressure distribution on the upper surface of the wing, while the interaction is smaller at high-speed forward flight.

Abstract:Forward looking imaging is an important work mode for airborne radar and missile-borne radar. It can be used to assist aircraft landing in bad weather condition or precision guidance. Aiming at the forward looking imaging application of ship targets at sea, we present a forward looking imaging angle resolution enhancement method based on compressive sensing with complex approximated message passing (CAMP) algorithm. The linear observation signal model of forward-looking imaging is established. The iterative calculation process of CAMP and the processing flow of multi-channel radar forward-looking imaging are presented. The validity of the method is verified by simulation data and processing results of X band radar measured data.

Abstract:That is necessary to simulate effects of propeller power, when the Aircraft with propeller is considered stall performance by scaled free-flight test. Combined with the analysis of simulate methods propeller power and criterion of dynamic similitude for modeling flight, and advanced the simulation method of propeller aircraft were investigated the stall, spin and recovery characteristics by free-flight test. Actual free-flight tests were performed to examine the method on four turbo-prop engines. The free-flight test results shows that the method real reflected the state of propeller power operation at the stall, the stall speed and stall characteristics were exactly obtained on influence of propeller power for full-size aircraft.

Abstract:A improved multi-index evaluation model based on TOPSIS is proposed in this article to build an air combat effectiveness evaluation model. This New model improves the shortcoming that the traditional evaluation method can only make a comprehensive evaluation of air combat effectiveness on a macro level, but cannot make a micro evaluation by comparing different aircraft strengths and weaknesses. Different index systems have been established for the over-the-horizon and dogfight air warfare tasks, and according to the defects of subjective method and objective method when evaluating the weights of indicators, the combined weighting method is constructed by using the minimum entropy principle to synthesize the two different types of weighting technologies: structural entropy weight and entropy weight. The algorithm verification shows that not only can the combined weighting method reflect the different characteristics of the index importance degree under the two line-of-sight conditions, but also the improved model can correct the evaluation errors of the original model, indicating that the method proposed in this paper is feasible and effective.

Abstract:Aiming at the problems of traditional trajectory prediction methods, such as large model simplification and less consideration, combined with the characteristics of flight trajectory continuity, time series and interactivity, a trajectory prediction method based on bidirectional long short term memory neural network is proposed. The position, heading, pitch, roll and relative information of the intruder UAV are simultaneously used as the input of the trajectory prediction model, which is more in line with the true trajectory change law. A Bi-LSTM-based trajectory prediction model is established, which can simultaneously learn the implicit information in the forward and backward trajectories, and adopt the adaptive learning rate learning algorithm to train the model. The simulation results show that compared with the Elman neural network, the average absolute error of the model predicted by 200 points in different directions is less than 4m, and the 3D prediction effect is better, and the trajectory prediction can be performed more accurately.

Abstract:In view of a deficiency that in the field of complex network, the traditional network defense strategies didn’t consider the main factors which will affect the aviation network defense resource optimization. Therefore, an aviation network strategy considering airport location and traffic flow based on the reality of aviation system was proposed to reduce the total risk of network. The relationship between different types of defense resource and node defense capability was determined based on the node vulnerability reduction model. By making some adjustments in importance evaluation matrix method, the traffic flow, airport location and some other factors are considered to rank the nodes, and the relationship between nodes and the aviation network total risk was analyzed. In the end, under the circumstance that the defense resource is limited, the problem was solved by simulated annealing algorithm to reduce the total risk of network. As the tests on randomly generated network and Chinese aviation network show, this optimization algorithm is capable of telling the difference between node location and traffic flow when allocating defense resources, and more efficient in lowering the risk of network compared with traditional methods.

Abstract:As the aerospace vehicle gradually enters the era of refined design, especially for civil aviation aircraft with high subsonic economic cruising and fighters with high maneuverability at transonic speed, the demand for high-performance transonic wind tunnels is becoming more and more urgent, and the numerical simulation of the high-speed section of the tunnel has certain reference significance for the design of transonic wind tunnel. Therefore, an 8.50 plane asymmetric diffuser has been calculated firstly, the separation and reattachment points agree with the experiment; Secondly, the convergence criterion, initial condition and slotted wall divergence angle of high-speed section for transonic wind tunnel have been considered, the results indicated that the mach number of monitoring points in model section has represented numerical convergence. Also, the influence on velocity distri-bution at model section and streamline in slot with different initial conditions is negligible. Moreover, the slotted wall divergence angle 0.3° has acquired more uniform flow fields than divergence angle 0.0°.

Abstract:The drag of coaxial helicopter hub accounts for more than 50% of the total helicopter’s waste drag. It is necessary to research drag characteristics and reduction design of the hub. Wind tunnel test is carried out on a coaxial helicopter hub model, drag reduction scheme and drag reduction scheme with vortex generator. The drag characteristics of coaxial helicopter hub is researched. The drag reduction effect of the drag reduction scheme and drag reduction scheme with vortex generator is verified. The results show that the azimuth, rotation speed and attack angle have little influence on the drag of hub and tis drag reduction scheme. The drag reduction scheme can reduce drag by about 30%, and the drag effect of the vortex generator is not obvious.

Abstract:The blade cross-section design of the helicopter rotor is the basis for studying the rotor dynamics design. A two-stage optimization design method combining joint topology optimization and shape optimization is proposed, which can be used for the design of blade cross-section. The first-level optimization uses SIMP as the material interpolation method for topology optimization. The blade volume minimization is the design goal, the displacement and stress of the blade joint are constrained, and the topology optimization model of the blade is established. The second-level optimization uses the reconstructed blade model to optimize the shape, reduce local stress concentrations, and find reasonable boundary node locations. The finite element analysis of the optimized model shows that the topology optimization and shape optimization can achieve the structural layout that meets the requirements of strength and stability, and provide a guiding plan for the structural design and optimization of the blade.

Abstract:In this paper, composition and principle of cable engine control system were firstly introduced. Based on the test of cable control system, the accuracy characteristics are analyzed from three dimensions: one-way accuracy, stroke accuracy and repeatability accuracy. Through experiment bases on single variable method, the effects of different spring force arm and stiffness coefficient, cable guide sleeve routing and cable length on precision of the control system are compared. The result shows that the absolute value of one-way accuracy is less than 5%, the stoke accuracy outside the dead zone is less than 3%, the repeatability accuracy is not greater than 2%.Then the dead zone range in the cable system can be reduced by reasonable design of the cable length and spring stiffness factor. Finally, the lateral spacing between the ends of cable guide sleeve is too large to reduce the accuracy of the control system. The research results have practical guidance for the development of high-precision cable-type control system.

Abstract:The building in test of the aircraft could identify the fault on the automatic flight control computer when the automatic flight control computer is broke down. The crew on ground deliver the automatic flight control computer to supplier for testing and maintenance,which is wasting time and ineffective.we design the general automatic testing platform for this problem.We identify the interface and functiona simulated by the general automatic testing platform by researching relationship of the automatic flight control computer. The general automatic testing technology include hardware platform based on PXIe、PXI and GPIB bus architecture and software platform described by ATML language based on IEEE standard,which make the hardware extensible free and software independent to each other are portable independent of hardware and operating system. We design the test methods and test flow of the functional modules based on the relationship、function and architecture of the automatic flight control computer. The test suite are designed by ATML language. The general automatic testing technology perform well and effective in the tryout of consumers.

Abstract:According to the characteristics and management status of airline flight signer, this paper analyzes and studies the efficiency quantification and efficiency evaluation, and establishes an evaluation model suitable for the operation efficiency of airline flight signer in China through the combination of analytic Hierarchy process (AHP) and matter-element extension model.In order to make the evaluation index more targeted and operable in practice, 4 criteria and 16 indexes are put forward based on the evaluation Index system of the operation efficiency of the signer, and the research on the model of the operation efficiency of the airline is hoped to bring some reference significance to the airline.

Abstract:The electrical arc and short circuit faults caused by metal redundancy in three-phase AC circuit of aircraft are simulated in laboratory. In three-phase alternating current circuit, electric arc and short circuit will cause damage of wiring and equipment. To analyze the protection function of traditional TCB for electric arc and short circuit. Traditional TCB cannot protect electric arc. It is very important to study the hazards and protection of aviation electric arc and short circuit. In this paper, several new methods of electric arc detection and protection are studied.