Abstract:Drag-reduction and fuel conservation, one of the significant benefits of active center of gravity (CG) Control function, plays an important role in iterative and optimal design of function scheme. Based on its principle and scheme, the active CG control function of a certain aircraft was modelled，coupling with flight control system model, automatic flight control system model, fuel system model, aerodynamic model，engine model and aircraft 6-DOF model, with the consideration of effect of CG variations induced by fuel consumption. At the given altitude and Mach number, the benefits of active CG control function were estimated, through setting different target CG positions. The results show that it can bring considerable benefits to aircraft with the application of active CG control technology, especially the more backward the target CG is, the more obvious benefits will be generated. The Mach number has an impact on the benefits of the function. Under the same conditions, the larger the Mach number is, the greater the return will be.

Abstract:In order to study the lift enhancement effect of the retractable belly flap on the flying wing configuration, a flying wing configuration model was taken as the initial shape of flying wing configuration aircraft, the distribution of crevices on the retractable belly flap are studied by the method of numerical simulation, and the variation of aerodynamic forces under different retracted states of the belly flap is obtained. Results show that, the retractable belly flap, when it is fully extended, can effectively lighten the air separation behind it and enhance the lift. When the crevice width is the same as the width of the hill shaped rudder, the effect of lift r enhancement is the best. The pitching moment shows a quasi-linear growth with the decrease of the height of the retractable belly flap during the belly flap retraction process. Moreover, the lift enhancement effect of the retractable belly flap is better than that of the seamless belly flap at the same height.

Abstract:Strength Design and Research Department，AVIC Chengdu Aircraft Design and Research Institute，Chengdu 610091) Abstract：The nonlinearity of free play is common in the structure of fully moving wing, which may not only affect the validity of the ground vibration test data, but also lead to the deviation of aeroelastic stability boundary. Therefore it is necessary to carry out the aeroelastic response analysis considering the nonlinearity of free play. The free play in rotation direction of fully moving wing is taken as the research object. The fictitious mass method is used to normalize the modal shapes. Then a set of unified modal shapes that can express the whole response domain is established. The rational function is used to transform the unsteady aerodynamic force to the time domain. The limit cycle response characteristics corresponding to different parameters of free play are studied. The calculation results show that when there is free play in the fully moving wing structure system, the nonlinear oscillation phenomenon called limit cycle oscillation will occur when the velocity is lower than the linear flutter boundary. The parameters of free play will affect the amplitude and frequency of the limit cycle oscillation, as well as the entry critical velocity pressure and divergence critical velocity pressure.

Abstract:With the development of world economy and trade, medium business jet are more and more favored by customers. In order to further improve the general aerodynamic performance of high-speed turbofan business jet, the optimization methods based on the full potential equation (TRANAIR), sequential quadratic programming （SQP）and free form deformation （FFD）tecnology of class function/shape function transformation（CST）are used to carry out the multi-point optimization study for the wing of a medium business jet. The results show that the drag coefficient of the optimized wing is reduced obviously, and the drag divergence characteristic has been significantly improved. The optimization method effectively guide the wing aerodynamic shape to change with better aerodynamic performances.

Abstract:The rotor blade double-swept-tip geometry can not only improve the aerodynamic performance ,but also effectively reduce the rotor noise. However,due to the particularity of the geometric structure of the double swept blade,the changes of the sweep-forward angle and the backward sweep angle have a great impact on its dynamic characteristics,so it is necessary to study the dynamic characteristics of the double swept blade. The motion equation of the balde was derived with the Hamilton theory,the rotor system was simplified with the finite element method,the natural frequency of the blade were obtained by solving the generalized eigenvalue.In this basis,the influence of sweep-forward angle and sweep-backward angle on blade dynamic characteristics were analyzed,the results showed that sweep-forward angle and sweep-backward angle have little influence on the low natural frequencies of the balde,and the fourth and fifth natural frequencies of the blade gradually decrease with the increase of sweep-backward angle.The research results provide technical support for the optimization design of double-swept blades.

Abstract:The super large conformal absorber plays an increasingly important role in the stealth design of aircraft wing edge. Due to the limitations of complex structure, super large size, manufacturing technology and other conditions, the research on radar cross section of conformal absorber after its installation on aircraft is less, and it is urgent to strengthen the research on both simulation and experiment. In this paper, starting from the manufacturing process of super large conformal absorber and the design based on simulation evaluation, the layered structure parameters of conformal absorber are optimized, and the installed RCS test verification of conformal absorber an leading edge of wing is completed. The RCS reduction effect of the designed super large conformal absorber is 4.4dB to 22dB from 2GHz to 18GHz, and the error of RCS simulation evaluation is within 6dB.

Abstract:According to the current common methods of flight load modeling, based on the exhaustive method and genetic algorithm, the comprehensive influence of bridge index and load equation index on the load model is considered, and an optimized flight load modeling method is proposed for the complex structure aircraft (taking the multi-beam and multi-wall structure as an example), and the error comparison between the optimized method and the traditional method is carried out. This method can satisfy both simple and complex structure flight load modeling methods. The ground load calibration test data of an aircraft wing are used to establish the load equation, and the comparison with the traditional method proves that the shear equation established by the optimized method has higher accuracy and iterative stability, and the bending moment equation errors of the two methods are similar and meet the requirements. The results of applying this method to measure the flight load of each measurement profile of the wing show that the model obtained by this method is accurate and reliable, and can be used for flight load measurement and safety monitoring.

Abstract:Some problems such as large number of grids, high calculation cost, large proportion of memory and slow calculation efficiency may be encountered when calculating the dynamic characteristics of full-scale aircraft structures.In order to exclude the redundant local mode from the frequency range of interest and emphasize the main overall mode,the method of increasing the out-of-plane stiffness of the shell element is proposed. The accuracy and efficiency of the method are verified by using a box model and a full-scale aircraft model.The simulation results show that, the calculation efficiency of full-scale aircraft structure is increased by more than 100 times. As a result, the file storage space is reduced by nearly 10 times. The maximum error of the first 6-order modal frequency of full-scale aircraft is only around 4%.

Abstract:For helicopter with large suspension load, the coupling between body and load will significantly affect the maneuverability and stability of the helicopter. The pilot’s handling makes suspension swing, which lead to the residual oscillation of the helicopter, improper hanging by pilot can easily induce PIO phenomenon. In this paper, it is mainly studied that lateral stability control of heavy helicopter suspension flight, the model is simplifying by using some assumption, and a control method oriented to engineering application is proposed: combining model-following control with adaptive control and input-shaping. The result shows that the method not only ensures good maneuverability, but also solve the problem of the residual oscillation of the helicopter.

Abstract:Aircraft icing will affect flight safety and sometimes cause serious flight accidents. It is of great significance to study the adhesion strength between icing and substrate, which can provide specific index requirements for aircraft anti-icing and deicing system. The adhesive strength is affected by many factors. This paper focuses on the effect of the initial temperature of frozen water used to freeze ice on the adhesion strength in the frozen ice experiment, and analyzes the variation law based on the nucleation theory. Firstly, based on the direct mechanical test method, an experimental platform for measuring the shear adhesion force was built. Then, the adhesion force of the substrate under different freezing temperatures was measured, and the temperature changes of water/ice during freezing were collected. Finally, the experimental phenomena are analyzed by nucleation theory. The results show that with the increase of initial temperature of freezing water, the shear adhesion strength between ice and aluminum plate increases gradually; With the increase of the initial temperature of freezing water, the degree of supercooling of water before freezing increases gradually; Different initial temperature of freezing water can change the nucleation barrier and nucleation rate by changing the undercooling degree, and finally affect the adhesion strength.

Abstract:Virtualization technology has tremendous advantages in dealing with resource allocation，application migration and isolation. To meet the demands of integration and intelligence in the field of aviation computing field，as well as the constraints of real-time performance，power consumption and volume of airborne embedded systems，the application research of virtualization technology in the field of aviation computing field is carried out in this paper. Firstly，the basic principle of virtualization technology is introduced，and the main characteristics of virtual machine and container are compared. Secondly，three examples of virtualization technology applications are analyzed，which includes the application of virtualized operating system on multi-core processor，hybrid container computing architecture，and continuous delivery process of DevOps software. Finally，two application conceptions of airborne software DevOps comprehensive development environment and multi-core high-performance computing unit are proposed，the technical ideas of the application of virtualization technology in the field of aeronautical computing are proposed，and the basic design architecture is given.

Abstract:As the fault of Nose Wheel Steering（NWS）system is of concealment under the existing planned maintenance system，the potential fault early warning method of NWS is studied by mining the post flight Quick Access Recorder（QAR）data. Firstly，on the basis of analyzing the failure mode of NWS，the monitoring QAR parameters relating to the NWS failure are selected and handled. Secondly，based on the normal and faulty cases of NWS，combined with the operational principle of NWS，the Pearson correlation coefficient analysis method is used to determine the potential failure characteristics of the low correlation between the command value and actual value，so as to realize the detection of potential failure. Finally，the actual case of NWS is used to verify the effectiveness of the potential fault warning method based on QAR data，which provides a reference for the formulation of condition based on maintenance strategy of NWS.

Abstract:SiC ceramic matrix composites are one of the key materials for the development of hypersonic aircraft and engines with high thrust/weight ratio, which have high requirements for impact fracture toughness, defect and crack sensitivity. In this paper, Charpy impact test was used to measure the fracture toughness of 3D needled C/SiC composites. The effects of U-shaped notch and V-shaped notch on the impact fracture toughness were studied in different distribution directions parallel to and perpendicular to the needling, and the fracture morphology was analyzed in detail by means of scanning electron microscope and optical microscope. The fracture toughness of the material with U-shaped notch is more sensitive to the relative position of the notch line and the needle than that of V-shaped notch, and the fracture toughness is the worst when the notch line is parallel to the needle fiber bundle, and the fracture toughness is higher when the notch line is vertical. From the fracture, it is found that the intersection of needle fiber bundle and 0° and 90° non-woven cloth layup is relatively weak, and the shear resistance of raw materials is weakened. The notch line is parallel to the impact section of the acupuncture and parallel to the plane of the notch, and the fiber bundles are pulled out long and many. The notch line is perpendicular to the impact section of the acupuncture, and the uniform appearance is oblique section. The pulled-out fiber bundles are short and less, and there is obvious stratification phenomenon.

Abstract:In terms of the long period, high cost and importance of the civil aircraft landing gearing sampling program, this paper discusses methods of confirming sample size based on IP44, which is the core of the civil aircraft landing gearing sampling program. In addition, this paper suggests that choose the sampling model according to the actual aircraft’s servicing time interval and operating environment. On this basis, using linear analysis method forecast failure tendency and establish the assumption verification standards of the landing gear restoration task interval, which verify the suggested analysis methods. The results turns out that methods in this article could justify the rationality of the landing gear restoration task interval and provide a guidance on domestic researching and developing civil aircraft landing gear restoration program independently. Furthermore, this project fills the blank domain of the landing gear restoration sampling program for domestic civil aircraft.

Abstract:In order to improve the operation efficiency of airport traffic, a prediction model of departure and departure time based on BP neural network was established. The key factors influencing the actual slip out time were analyzed, and the correlation was tested by SPSS. The model was verified by two weeks" actual operation data of an airport in central and southern China, and the root mean square error (RMSE), mean absolute error (MAE) and mean absolute error percentage (MAE) were analyzed. The results show that the new quantifiable factor, that is, the mean taxi time within one hour, has a significant effect on the actual taxi time. Although the time of the flight can also be quantified, the accuracy of the prediction is significantly reduced when this factor is added. The error between the prediction and the actual value was less than 5min, accounting for 84%.

Abstract:In order to implement the airworthiness verification of the workload of the aircraft crew under different operating scenarios of the civil aircraft effectively. Firstly, according to the airworthiness verification requirements CCAR25.1523 and Appendix D of the China Civil Aviation Regulations (CCAR), the workload verification human-machine interactive airworthiness content and verification process are established, through the interpretation of the airworthiness verification clauses of the crew workload of transport aircraft. Secondly, the design principles for the crew workload scenario are established and the crew workload airworthiness scenario dimensions are designed. The crew workload human-machine interaction airworthiness scenario is designed from the four dimensions of the airworthiness verification test crew, flight operation process, flight operation environment and aircraft operating status. Finally, combining unit workload evaluation strategy and measurement method comparison, the crew workload verification method is proposed. The results show that the civil aircraft human-computer interaction airworthiness verification scenario constructed in this paper is reasonable and effective, and can be applied to the crew workload verification analysis. The proposed crew workload airworthiness verification method can provide a reference for the airworthiness verification of civil aircraft crew workload.

Abstract:The wastewater system is an important aircraft part of civil aircraft. The effective sewage discharge is closely related to the ride comfort and health of passengers. In this work, Euler method was used to simulate the gas-liquid solid three-phase flow in wastewater system, and the effect of flight height and working condition of toilet on wastewater emission has been analyzed. Results show that: when only the farthest toilet works, with the increase of flight altitude, the core peak time of waste water flow is brought forward, and the time required for waste water to be completely discharged are significantly shortened from 3.31s to 1.87s, and the waste water can be quickly discharged into the waste water tank. When the three toilets work at the same time, the negative pressure in the waste water pipeline will be reduced, and the flow rate of different cross sections will decrease by 66.5% on average, the toilet close to the waste water tank will reduce the discharge efficiency of the farthest toilet, resulting in the waste water cannot be discharged quickly. When the flushing time of toilet close to wastewater tank is adjusted to 2s, and the farthest toilet needs to be opened separately, the wastewater in the farthest toilet can be fully discharged into the wastewater tank.

Abstract:Abstract: The lug/bolt type structural is widely used in modern civil aircraft structure design. The conventional forward design idea is that the structure design comes first and the strength analysis comes second, which has the problems of tedious iterations, long time consuming and error-prone human calculations. Taking aluminum alloy (7075-T6) lug as an example, this paper establishes a correlation equation between the classical load-bearing capacity, the performance parameters and the structural parameters of the lug through reversal design. By means of the design variables method, a set of parametric design method is formed, which can realize the automatic lug design guided by the demand result mode. The visual program developed by MATLAB and solved by an example show that：this method can quickly solve the relevant parameters of the lug and greatly improve the design efficiency under the given load conditions and target requirements.

Abstract:Aircraft engine extended operations（Extended Operations, abbreviated to ETOPS）eligibility is the basis for aircraft extended operations. With the purpose of guiding domestic aircraft engine ETOPS type design and compliance verification, this article studies the formation process of the ETOPS regulation, and design and test requirement for aircraft engine early ETOPS eligibility, and analyzes the connotation and relevance between ETOPS airworthiness of aircraft and engine. An aircraft engine ETOPS type design and compliance verification idea is proposed. It can be a reference for early ETOPS type design and compliance verification for domestic civil aircraft engine.

Abstract:Centrifuge impeller is a key component in micro aviation gas turbine. It is required to reduce the weight of the structure as much as possible on the premise of satisfying the aerodynamic performance. Traditional design and manufacturing technology has been basically played to the extreme, but the development of additive manufacturing technology and topology optimization design method has expanded new space for its further optimization design. In order to solve the weight reduction design problem of centrifugal impeller of a certain aviation micro gas turbine, based on additive manufacturing and topology optimization design technology, the static strength analysis of the centrifugal impeller is carried out first, and then the centrifugal impeller topology optimization based on the skeleton model and achievable process design is developed. And finally check the optimized model. The optimized design results show that the optimized design scheme can reduce the weight of the centrifugal impeller by 8.7%, and the power-gain ratio of the micro-gas turbine can be further improved.At the same time, the maximum deformation is reduced by 7.5%.The maximum equivalent stress is reduced by 0.59%, which improves the safety margin of centrifugal impeller when working.The optimized effect is obvious and the manufacturing process is feasible.

Abstract:The civil aircraft spare parts support network is a necessary medium for the main manufacturer to provide customers with aviation materials. The rationality of its construction is conducive to improving the service quality of the main manufacturer and the customer"s operational capability. Based on the Kriging method, this paper proposes a qualitative and quantitative combination of qualitative and quantitative methods for weighing the location factors of the civil aircraft spare parts support network. The location factors are sorted and classified, and the data requirements for quantitative analysis of the location are obtained. The aircraft material support network site selection weighs, and then the importance of site selection factors is evaluated. The validity and applicability are verified by comparing the proposed method with response surface method and Monte Carlo method. The results show that the proposed method can effectively evaluate the importance of site selection factors and lay a foundation for the construction of civil aircraft aviation materials support network.

Abstract:Thunderstorm weather has a serious impact on the safety of aircraft operation. During approach segment, thunderstorm weather can result in uneconomical route changing, poor real-time performance and low efficiency etc, this theory adopt advanced dynamic window algorithm (DWA) to simulate the approach trajectory under thunderstorm weather. In the early stage of the algorithm, the aircraft motion model under DWA is established and the thunderstorm trajectory is artificially set for simulation to verify the functionality of the algorithm to avoid thunderstorm diversion simulation. Then, by fitting the thunderstorm displacement coordinates in the case with time correlation, the thunderstorm predicted movement trajectory is obtained and brought into the algorithm for simulation. Finally, analyse the cosine similarity, economy and practicability of the actual and simulation diversion track. The results show that the algorithm can effectively avoid thunderstorms in the approach segment, and the trajectory is more smooth, economical and feasible. Combined with the new route technology, it has strong practicability.