Abstract:Runway excursion ranks second among the most catastrophic symptoms. Research on the risk assessment of runway excursion has been done by domestic and international civil aviation research institutes, specialists, and academics in an effort to lessen both its likelihood and its effects. Several important contributing variables have been the subject of recent study, including unfavorable weather circumstances, runway surface conditions, pilot mistakes, and mechanical issues. These issues can be resolved by improving runway maintenance and improving pilot training. The accomplishments and flaws are compiled by looking at the current designs of both domestic and international experts on the runway excursion occurrences. The study directions and contents of local and international experts are compared, and a summary of the risk factors for runway excursion events is produced. The techniques for predicting and analyzing the danger of a runway excursion are described, and suggestions for more research are made for future study.

Abstract:Due to the wear particles in lubricating oil contain important information about the wear of engine components, wear particle monitoring is an effective method for judging the health status of engines and providing early fault warning. Online monitoring technology can provide real-time equipment status information. This article introduces the current online monitoring technologies for lubricating oil and abrasive particles, including capacitance method, resistance method，magnetic induction method, optical method, and acoustic method monitoring technologies. It discusses the monitoring principles, research results, advantages and disadvantages of each technology, analyzes the application status of the five monitoring technologies, and finally discusses the future development trend of lubricating oil and abrasive particle online monitoring technology.

Abstract:The short takeoff and landing aircraft using distributed electric propulsion is a novel concept, for which the design method of its key parameters needs to be explored. In this paper, taking the conventional turboprop aircraft retrofitted with distributed electric propellers as an illustrative aircraft, the design problem of the aircraft key parameters is formulated as an optimization problem, and then the design optimization process for the key aircraft parameters is presented using the optimization method with surrogate model. Multidisciplinary analysis for the such aircraft conceptual design is used to evaluate the values of objective and constraint functions in optimization problems. The multidisciplinary analysis consists of several analysis modules including geometry, aerodynamics, propulsion, weight and performance. After optimization for the key parameters of the illustrative aircraft concept, the demanding requirements for the ground roll distance during takeoff and landing can be met at the minimum weight penalty. The ground roll distance during takeoff is less than 100m; the ground roll distance during landing is less than 70m. The optimal results also indicate that the distributed propellers are installed beneath the wing at a certain angle of inclination with moderate rotation speed and diameter, the wing area is increased slightly and required power for the turboprop engine is reduced significantly.

Abstract:As rotor positions have significant effect on aerodynamic characteristics of hybrid configuration Unmanned Aerial Vehicle(UAV), it is necessary to investigate the criteria of rotor positions arrangement. The aerodynamic characteristics of a typical hybrid configuration UAV is analyzed by numerical method. Taking the lift-to-drag ratio and longitudinal static stability as the optimization objectives, a three-factor four-level orthogonal experimental of the chordwise, spanwise and vertical positions of the rotor is designed. The effects of three factors of rotor position are discussed by means of intuitive analysis and computational analysis. The results show that the maximum lift-to-drag ratio of the optimized design parameter combination obtained by the orthogonal test design result is about 2 times larger than that of the initial design parameter combination, and the slope of the pitch moment coefficient curve increases by about 15%. For present configuration, the results show that the effect of factors on the lift-to-drag ratio and the slope of the pitch moment coefficient curve are in a descending order as follows: chordwise, spanwise and vertical positions.

Abstract:Compared to conventional powered aircraft, the solar-powered aircraft have characteristics of high-altitude and long-endurance. They can modularly change the task loads and carry out related special tasks. Based on the working principle of long endurance solar-powered aircraft, the coupling relationship between the all-day cruising altitude and wing load of solar-powered aircraft under the energy balance design system was analyzed. The coupling parameters, including aerodynamic parameters, solar panels efficiency and paving rate, propulsion system efficiency and load power factor, flight season and flight latitude, were systematically analyzed for sensitivity, The results indicate that the design or optimization of appropriate lift and drag coefficients should be the first consideration for long endurance solar-powered aircraft to achieve best aerodynamic efficiency; When the efficiency of solar panels reaches 0.35 or above, increasing the installation rate of solar panels has a weaker impact on the all-day cruising altitude, but it helps to increase the upper limit of wing load. The research results can serve as a reference for the overall design and improvement optimization of solar-powered aircraft.

Abstract:Aircraft maneuver recognition is an important basis for flight action evaluation, flight load spectrum research, flight simulation and other research work. Aiming at overcoming the disadvantage that most of the existing maneuvers are based on the existing standard actions, combined with the important points of the time sequence, an adaptive maneuver recognition method based on horizontal and vertical plane flight trajectory projection merging is proposed. This method extracts the maneuvers in the flight data according to the trend of the two-dimensional plane trajectory data and combines and refines the maneuvers with the idea of maneuvers splicing. A maneuver recognition case study is carried out with complete aircraft takeoff and landing data. It is found that this proposed method can enhance the recognition efficiency of flight maneuvers and the division efficiency.

Abstract:The high-performance attitude controller can effectively suppress comprehensive effects caused by uncertainties and external dynamic disturbances, and ensure that the quadrotor can safely and reliably fly to complete the designated mission. Therefore, nonlinear uncertainties of quadrotor flight systems are approximated by a radial function neural network (RBFNN) quadrotor, and an extended state observer is designed to estimate lumped disturbances caused by RBFNN approximation errors and external disturbances in this paper. The black box problem of RBFNN is solved by using a model identification error and a tracking error as decision variables. Then, an adaptive robust anti-disturbance attitude tracking controller is designed for quadrotor flight systems based on dynamic surface control and Lyapunov stability theory, and an auxiliary system is constructed to suppress the effect of filtering error on the closed-loop system performance. Finally, Simulation results show that the quadrotor can precisely track the desired attitude angles, and the proposed controller has strong robustness and stability in the presence of uncertainties and disturbances.

Abstract:Airfoil slotted is a passive flow control technology to improve the stall characteristics of airfoil by using slot jet. In order to explore the influence of the slot parameters change on the aerodynamic characteristics of multi-element airfoil, the CFD method is used to study the slotting of GAW-1 two-element airfoil in the paper. Nine kinds of slot configurations are designed, and the geometric relations among three types of slot configurations, namely straight line, curve and deflector, are given, and a curved trapezoidal slot configuration is proposed. It is found that the slot position is the key factor to restrain the stall development of airfoil, and the optimal slot position of curved trapezoidal slot configuration is 13.5% c; the slot has the strongest ability to restrain stall, the stall angle of attack of airfoil is delayed by 7°, and the maximum lift coefficient is increased by 19.5%, reaching 3.89. Finally, the influence of the deflector slot configuration on the aerodynamic characteristics of the airfoil is studied. The deflector slot configuration can not only weaken the damage of the slot to the aerodynamic characteristics at a small angle of attack, but also slow down the stall development and improve the stall characteristics of the airfoil. In this paper, the research ideas and results of slotted multi-element airfoil can provide a reference for the subsequent research of other slotted multi-element airfoil.

Abstract:Tiltrotor which combines the advantages of helicopters and fixed wing aircraft, is a key direction for future aviation equipment development. This article focuses on the key component of tiltrotor - pylon conversion actuator. The tilting actuation principle of tiltrotor is introduced, the advantages and disadvantages of V-22 and BA609 pylon conversion actuator configurations are analyzed and compared, and the key technologies of pylon conversion actuator of tiltrotor are discussed, including power summing technology, double-layer telescopic ball screw technology, ball screw end shock damper technology. The power summing technology can realize double-system synthesis by speed summing or force summing, which is the key to improve the reliability of pylon conversion actuator. Double-layer telescopic ball screw can effectively shorten the volume after the actuator is retracted, reduce the space on the aircraft nacelle, and greatly improve the safety of the actuator; Shock damper is a means to effectively restrain the impact caused by the screw end collision, which is very suitable for linear output mechanism such as ball screw.

Abstract:The landing gear spin-up and spring back loads are an important part of the aircraft landing load, and the dynamic analysis method can be used to analyze it effectively at the beginning of the design stage. In this paper, the landing gear drop test dynamic model is established by using the nonlinear spring damping system at the axle to simulate the strut elasticity, and the spin-up and spring back loads and its corresponding slip rate change trend under the two motion forms of wheel reversal and wheel start-up are analyzed. The effects of aircraft heading speed, track slip rate curve and wheel pre-rotation speed on landing gear spin-up and spring back loads are analyzed. The results show that reducing the heading speed of the aircraft, giving the wheel pre-rotation speed and reducing the friction coefficient between the tire and the ground can reduce the spin-up loads.

Abstract:The configuration characteristics of multi rotor unmanned aerial vehicles determine that they are difficult to adapt to complex flight missions. To meet different mission requirements, combining and assembling specific configuration aircraft should be a feasible development direction. Before and after assembly, various flight characteristics of the aircraft change to varying degrees, and the impact of external disturbances also varies, posing great challenges to the design and verification of flight control systems. This article designs a spliced tilted twin rotor aircraft and establishes its flight dynamics model. Based on this, the control strategy of the pre and post assembly aircraft and the position and attitude controllers based on linear active disturbance rejection control (LADRC) are designed, and the simulation verification of aircraft control in gust interference environments is completed. Compared with traditional PID controllers, the superiority of LADRC has been verified. Finally, a real aircraft attitude stability control verification was conducted, and the research results showed that the spliced tilt-rotor dual rotor aircraft and its linear active disturbance rejection controller had strong anti-interference and robustness. The aircraft had good flight control effects before and after assembly.

Abstract:The performance of guidance system is the key factor of automatic carrier landing system. The positioning principles, measurement errors and effects on automatic carrier landing of airborne visual guidance architecture are investigated. The coplanar P4P relative positioning issue by means of cooperative landing aids is studied firstly, and by analyzing measurement error factors, types, probability distributions of the imaging devices, the three-axis positioning results affected by the errors are obtained using calculated coordinate transformation and the guidance error systems are modeled. Considering F/A-18A carrier-based aircraft automatic landing, the simulated positioning measurement accuracy of airborne visual guidance from gliding to touchdown are estimated. Further, the disturbances of automatic carrier landing system delay, airborne sensor noises, air-wake and deck motion are introduced, multi-factor coupled simulation system is modeled and touchdown position standard errors are calculated based on Monte-Carlo simulations influenced by the disturbances. The positioning accuracy and automatic landing performance of the proposed airborne visual guidance architecture achieves the performance of traditional guidance architectures. The deck motion and air-wake play important roles in automatic carrier landing performance.

Abstract:Researching the deformation prediction of domestic 7050 aluminum alloy aviation thin-walled parts during turning processing and establishing an accurate finite element model for predicting turning deformation is of great significance for ensuring the machining precision and dimensional stability of aviation thin-walled parts, as well as improving the structural strength and reliability of aircraft. This thesis employs simulation and experimental demonstration methods to study the influence of the coupling effect between the initial residual stress of domestic 7050 aluminum alloy and the turning residual stress on the deformation of thin-walled bearing frames during processing. Firstly, based on the machining process of aviation thin-walled bearing frames, a turning deformation simulation model of the bearing frame was established using the birth and death element method. Further, the initial residual stress field of the bearing frame blank and the turning surface residual stress were obtained through the blind hole method and turning experiments, respectively. Lastly, based on the turning deformation simulation model, the deformation of the bearing frame under the coupling effect of the initial residual stress field and turning residual stress was predicted and experimentally verified. The results show that the error of the bearing frame deformation simulation prediction model is less than 15%. The conclusions of this thesis can provide technical support for the control of bearing frame machining deformation.

Abstract:At present, the in-depth application of aero-engine performance model in the field of test flight has become a hot spot under the background of digital test flight, which is of great value and significance to the planning and organization of test sites in the process of flight test, risk identification and analysis, and auxiliary analysis and evaluation of test flight results. This paper studies the performance modeling of a two-rotor hybrid turbofan engine based on a general object-oriented simulation architecture. The model is constructed according to the actual air path connection and rotor physical connection between components, and considers the uneven distribution of fan outlet section parameters, the influence of high / low pressure turbine cooling and variable heat effect on the engine performance. In order to improve the model prediction accuracy, a correction method of the characteristics of rotating components based on the actual joint working line, and the deviation of the performance parameters under different working conditions is less than 3%; Finally, through the steady performance and transient performance of the model under different working conditions, the performance characteristics of the engine in the working envelope and the thrust transient characteristics of the sea level standard atmospheric environment are presented.

Abstract:In operation of civil aircraft, the maximum takeoff weight is limited by the performmance when one engine fails, and it"s of great significance to optimize takeoff performance by excuting different obstacle clearing methods to increase the maximum takeoff weight. Based on the theoretical analysis of the takeoff flight path defined in the regulations, this paper calculated the maximum takeoff weight corresponding to the standard second segment, extended second segment, and fourth segment obstacle clearing method, and analysed their obstacle clearence, climb gradients, and takeoff distance to ascertain the key factor which limits the maximum takeoff weight. Different distances and gradients are combined to simulate various terrain conditions, and the takeoff weights of standard second segment and forth segment obstacle clearing method in those terrain conditions are calculated. The result shows that using of fourth segment obstacle clearing method can effectively improve the maximum takeoff weight of the aircraft. And the larger the gradient of the obstacle is, the more significant the improvement is. At plateau airports with complex terrain, the use of fourth segment obstacle clearing method can significantly improve takeoff performance and operational efficiency.1\

Abstract:In view of the fact that there is no one that can comprehensively characterize the aerodynamic quality characteristics of military aerocraft, the concept of aerodynamic integrity is proposed for the first time and its research is carried out. It is believed that the aerodynamic integrity of military aerocraft can comprehensively characterize its aerodynamic mass characteristics in the process of combat use. Firstly, the process and definition of the concept of aerodynamic integrity are introduced, and the basic connotation and basic characteristics are discussed. It is believed that the aerodynamic integrity of military aerocraft is the basis of the combat effectiveness of aerocraft. The characterization method of Aerocraft aerodynamic integrity is introduced, and the main influencing factors of military aerocraft aerodynamic integrity are analyzed. The new concept of aerodynamic integrity of military aerocraft is introduced aims to provide reference for the development of military aerocraft design, manufacturing, testing and support in China.

Abstract:With the improvement of the digitization degree of the aircraft, a large amount of multi-source and heterogeneous data will be generated throughout the full lifecycle of an aircraft, which plays a crucial role in ensuring its safety. This article reviews common types of data sources within the aircraft"s lifecycle, including initial airworthiness design data, operational reliability data, operational maintenance data, and onboard equipment data. By combining the data characteristics of different data source types, the article introduces measures for the fusion application of multi-source heterogeneous data and provides a detailed analysis of the four stages that data fusion technology has undergone. On this basis, the fault diagnosis method of fusion data is introduced. Compared with the fault diagnosis analysis of traditional single data source, it is concluded that the fusion application of multi-source heterogeneous data can analyze the fault causes more accurately, and play a role in assisting troubleshooting and maintainability design, which is the development trend of data application technology in aircraft fault diagnosis.

Abstract:The load prediction based on the data used in aircraft plays an important role in the damage analysis and life prediction of aircraft, which can provide technical support for the active on-condition maintenance of aircraft. In this paper, forward neural network is used to establish the load model of shear force, bending moment and torque of the tail wing root of a large transport aircraft. Compared with the load calculated by finite element model, the prediction errors of the neural network model meet the engineering requirements, and compared with the prediction results of the multivariate linear regression model, the results show that the prediction accuracy of the neural network model is better than that of the multivariate linear regression model. The neural network model provides a feasible method for measuring the loads on key structures of a large transport aircraft.

Abstract:Aircraft modular design can increase the types of missions and reduce costs. In the initial stage of wing modular structure design, the unclearness of wingtip deformation limits the ability to assess the contribution differences of structural stiffness characteristics among wings with different spans to the system objective function (minimal structural weight).Aiming at the above problems, this paper introduces the weight coefficients of each subsystem level in the system level on the basis of the sensitivity coordinated optimization method to simulate the phenomenon that different subsystems contribute differently to the objective function of the system in the actual design work, and gives the computation methods of weight coefficients of the wing structures with different spreading lengths (different subsystems levels), forming the sensitivity coordinated optimization method with subsystem level weights. Finally, the preliminary structure design method of modular wing is verified by solving the modular truss and modular wing structure optimization example. The results show that the sensitivity-coordinated optimization method that includes subsystem weights can obtain a modular wing preliminary structure that satisfies both strength requirements and a certain degree of stiffness.

Abstract:Sensor aircraft and integrated wings embody the integrated design concept of integrating functional components and structures. However, there are problems with discontinuous skin force transmission and difficult connection in the wing structure, making the connection strength of functional skin a control factor in the design process. Therefore, this article combines the functional requirements and structural characteristics of the integrated wing, adopts a simplified connection calculation method, conducts force transfer analysis and connection characteristics analysis on the key sections at the separation surface of the functional skin design, obtains the ideal connection load and connection parameters at the separation surface, completes the connection design and size design, and verifies it through finite element analysis and optimization analysis. The results show that the estimated bending moment distribution of the box section using this force transfer analysis method is consistent with the finite element analysis results; The calculated size distribution of each section of the box section structure is similar to the optimization results, which can meet the requirements of connection strength and stability; The larger the effective height of the wing beam in the box section structure, the greater the load it bears, and the more consistent the optimization results with the force transfer analysis results.

Abstract:In order to reveal the influence of hygrothermal environment on the mechanical properties of aeronautical composite connection structure, a numerical simulation model of composite interference-fit structure was established based on the mechanical ontological relationship and continuous damage model of composites under the hygrothermal environment with the object of composite interference-fit structure. The model was utilized to analyze the static strength and damage failure of interference-fit structures in the hygrothermal cycle of 0 days, 30 days, 60 days, 90 days and 120 days respectively, and was validated with the hygrothermal aging experiment. The results show that the ultimate load of the composite interference-fit structure decreases by 3.33%, 5.63%, 8.83% and 10.81% respectively, as the hygrothermal cycling period increases from 0 days to 120 days; the hygrothermal environment causes the aging reaction within the composite matrix, results in a rapid deterioration of the matrix performance, while has little effect on the fiber damage. The validity of the numerical simulation model was verified by comparing the experimental results with the simulation results.