Proceedings of the 6th China Aeronautical Science and Technology Conference

Composite materials are widely used in many parts of navigable aircraft. The defects of composite materials will seriously affect flight safety. In this paper, it is proved by simulation that the minimum diameter of defect detection accuracy is 8 mm when the correlation coefficient is 5. Based on this, an accurate detection method for internal waterlogging defects of aircraft composites based on infrared thermography detection was designed to realize the identification and location of waterlogging defects of aircraft composite structures, including defect type, size and accurate depth. The data collected by infrared detection system is recognized by YOLOv5 neural network. The test results show that the confidence of water point defect is greater than 0.9, and the detection depth is about 1mm. This study will expand the use cases of infrared nondestructive testing technology at home and abroad, and help to solve the problem of composite defect location detection for navigable aircraft.

In order to improve the fault diagnosis accuracy of airborne hydraulic system and enhance the safety and reliability level of aircraft, aiming at the problem that the flow rate of hydraulic system is difficult to be measured, a flow prediction model using eXtreme Gradient Boosting (XGBoost) method is proposed. In addition, three feature attribution methods are used to analyze the interpretability of the flow prediction model, and the key features affecting the flow prediction are obtained. SHAP (SHapley Additive exPlanations) algorithm is used to calculate the contribution of different features at a single sample in the flow prediction model, which improved the interpretability of the prediction model. The experimental result shows that the model possesses high prediction accuracy, and the important features obtained by three methods are accordant, which verifies the effectiveness of this method.

The dynamic derivative is a necessary parameter in the process of analyzing the stability of the aircraft and designing the control law. In view of the urgent need of the high-precision dynamic derivative wind tunnel test data for the development of large-scale military and civil aircraft and advanced layout aircraft in China, a new wind tunnel dynamic test system is developed driven by the coupling of electro-hydraulic motor and servo motor and whose oscillating mechanism is decoupled from the static angle-changing mechanism based on FL-51 wind tunnel of AVIC Aerodynamics Research Institute, which can conduct dynamic derivative test of pitch/yaw/roll oscillation modes with test model at the scale of 1–2.5 m under the wind speed range of 20–50 m/s. This test system uses electro-hydraulic motor to drive the oscillation mechanism and servo motor to drive the static angle-changing mechanism. We design the drive control scheme and introduce key technologies involved in the system design in detail. According to the Test index, we debug the motion index of the test system, and carry out the wind tunnel verification test with the standard dynamic model at the scale of 1 m and the wing-body fusion layout model at the scale of 2.4 m. The debugging results show that the test system has good static/dynamic control precision, and the performance index and function can achieve the design requirements. The wind tunnel test results indicate that the test system can obtain dynamic derivatives data with high accuracy and reasonable regularity, which can provide test platform support for the demand of dynamic derivative test data for the development of large wingspan military and civilian aircraft in China.

On the basis of summarizing the research of prediction and Health Management at home and abroad, this paper describes the development and research of air turbine Starter Health Management (SHM). Combining with its principle and its own structural characteristics, this paper reviews the trend and direction of air turbine starter health management technology. The main functional framework of starter health management system is established, the selection basis of key monitoring elements is analyzed, and the domestic research on air turbine starter is improved. Finally, the paper briefly introduces the basic function composition of the first quality monitoring and fault rapid diagnosis system “QM&FDS” for air turbine starter in China, which provides method support for the follow-up exploration of health management research and development of air turbine starter.

In this paper, the whole process of T-type friction stir welding of aluminum alloy is analyzed by full thermal-mechanical coupling finite element method. The three steps of T-type friction stir welding process are analyzed and simulated: pressing, preheating and welding. In order to solve the problem of element distortion in the calculation process, the arbitrary Lagrange-Euler method (ALE) will be used; in order to accurately describe the strain hardening, work hardening effect and thermal softening effect of metal materials during friction stir welding, the Johnson-Cook material constitutive equation was adopted. In order to verify the finite element simulation results, a T-shaped friction stir welding experimental device was established for welding verification. The results show that during the T-type friction stir welding process, the maximum temperature on the workpiece is 500 ℃ when the welding is stable, reaching 86% of the melting point of the base metal 582 ℃; the friction between the workpiece and the tool shoulder is the main source of heat in the friction stir welding process. The change of equivalent plastic strain value in the welding area is gradient, and the welding area is fish scale distribution. The stress on the workpiece during the whole welding process is symmetrical about the welding direction; the stirring head will be subjected to a very large reaction force in the pressing stage.

Environmental responsibility is a focus of researchers in Aviation and power generation industry. The aim of this paper is the experimental investigation of the influence on the reduction of nitrogen oxides emissions and overall performance of aero derivative gas turbine on the basis of wet low emissions technology. An economical and practical emissions reduction scheme was proposed by studying the mechanism of nitrogen oxides production and its suppression measures. Experiments have been carried out through improving the design of the fuel supply system and optimizing the control strategy based on aero derivative gas turbine. Combined with the combustion chamber research results conducted prior to the experiment, this study focuses on the reduction in gaseous emissions and performance changes of the aero derivative gas turbine by introducing a dynamic fuel emulsification system. From the experimental data it was determined that the exhaust gas composition was significantly affected by the water injection. Additionally, the effects o on the power output and thermal efficiency of the engine were also determined to be significant. The research reveals great potential for the successful application of emulsified fuel on the aero derivative gas turbine and providing technical reference for the engineering application of wet low emissions technology.

The prediction of cavity noise is one of the key technologies for the internal weapon bay of high-speed aircraft. Numerical simulations were conducted on open cavity with a length to depth ratio of 5 at different Mach numbers using the improved delayed detached-eddy simulation (IDDES) method and the non-linear acoustics solver (NLAS) method for solving the non-linear disturbance equations. The calculation results show that both methods can effectively predict the overall sound pressure level of wall under subsonic flow conditions; Under the condition of supersonic inflow, the sound pressure level of each mode obtained by the NLAS method is in good agreement with the experimental results, while the results obtained by the IDDES method are relatively small. The frequency of each mode obtained by the two methods is in good agreement with the experimental results. The reason for the difference is that when the IDDES method transitions from RANS to LES, the turbulent kinetic energy dissipation is relatively large, while the NLAS method can simulate the noise propagation process accurately due to its low dissipation. The comparison of the computing resources required by the two methods shows that the IDDES method requires fine mesh and a small time step, which requires more computing resources; The NLAS method uses the method of artificially synthesized turbulence to simulate small-scale fluctuations, which can select rough mesh and large time step to save computing resources.

Curing agents and additives are necessary in composite materials to obtain well solidified shape and required properties. The effect of curing agents and additives for electromagnetic wave (EMW) absorbing materials is investigated in this work. The reflection loss (RL) difference is no more than 0.5 dB between unfilled matrix composites solidified by typical curing agent 4,4’-diaminodiphenylmethane (DDM) and ethylenediamine (EDA). Curing agents have low effect on composite absorbing. The reason for low effect of curing agents on absorbing is attributed to its chemical reaction level role in matrix, producing a transparent effect to EM wave. The loss difference is about 1 dB between diphenyl amidophosphate (DAP) and 1,3-dichloro-2-propanol phosphate (DPP) added matrix of composites, solidified by commercial curing agent 5772. Additives have relative higher effect than curing agents, relating to the additive types. The effect of additives is related to additive types. Composites with graphene nanosheets (GNS) and exfoliated manganese oxides (EMO) filled are taken as a typical investigated case. Curing agents and additives of non electromagnetic (EM) response will not give rise to an essential effect to EMW absorbing generally. Matrix of non EM response is independent to EMW absorbing effect for filled composites. Factually, this is a prerequisite of most absorbing investigation on filled composites in literatures. An unaware potential factor for absorbing composites of EMW is clarified.

Aircraft component assembly and general assembly are characterized by long operation cycle, multiple resources involved, and a wide range of specialties. Especially in the case of batch production, the assembly plants are large in area, and the aircraft assembly stations are widely distributed. How to effectively monitor on-site abnormal problems and respond promptly has become a practical problem to be solved in the assembly site to reduce costs and increase efficiency. Based on the characteristics of aircraft assembly site, this paper classified and analyzed the typical abnormal problems in the assembly site. On this basis, combined with the requirements of production site management and control, the on-site abnormal monitoring and analysis platform for the aircraft assembly process was built to support the monitoring and rapid response of abnormal problems in the assembly site. Finally, through the practical application of the platform in an aviation equipment manufacturing enterprise, its effectiveness and practicability were verified, providing a feasible reference solution for the industry.

The cable driving motion simulation platform takes the cable as the driving link. Because of the unidirectional force of the cable, the traditional parallel control scheme is no longer applicable. In order to realize the force-position hybrid control of the system, a force-position hybrid control based on the position loop of the driving unit is designed in this paper. First of all, the inverse kinematics of the system is solved, and then the overall dynamic model of the cable-driven platform and the driver unit is established. Secondly, in order to ensure that the cable is always in a tensioned state during the movement, the cable force distribution is calculated according to the established dynamic equation of the motion platform, and the reference cable force is provided for the system tension control. Finally, in order to realize the high-precision motion of the motion platform and ensure the reasonable distribution of the cable force during the motion process, the force-position hybrid control strategy was designed to realize the force-position parallel control mode, reduce the system position error, and improve the control response speed. According to the simulation results, the proposed control strategy has a good effect and is rich in application value.

A PIV technique-based measurement method of near-field sonic boom in wind tunnel has been proposed. Sonic boom which imposes restrictions on the development of supersonic transport is a peculiar acoustic phenomenon to supersonic flight. To verify the low boom design, measurements of near-field sonic boom are usually carried out in wind tunnels with pressure rails. The pressure rails introduce disturbances to flow fields. Furthermore, the rails are difficult to be fabricated and installed in small size wind tunnels. The near-field sonic boom is essentially formed by a series of shock and expansion waves. On this basis, the off-body pressure distributions can be obtained from the corresponding velocity field measured with PIV technique. Starting with an undisturbed point, flow parameters are calculated by the oblique shock wave formulas and the P-M expansion wave formulas respectively in compression regions and expansion regions, which are determined by the velocity magnitude. Numerical simulation has been conducted to validate the proposed measurement method. The calculated results are agreed well with the real results. Analysis of effects of parameters’ errors shows that the random errors of velocity magnitude have a significant effect on the sonic boom results.

This paper investigates the scheduling of rescue helicopters after flood disasters. In order to improve rescue efficiency and robustness, this study considers the matching degree between the capabilities of helicopters and the demands of rescue tasks, as well as the time satisfaction of the rescue tasks. The bilateral matching degree is described by the matching perception satisfaction of the rescue helicopters and the rescue tasks based on prospect theory, and the time satisfaction of the rescue tasks is evaluated by a piecewise linear function based on the soft time window method. A scheduling model for emergency rescue helicopters is established to maximize the matching perception satisfaction and task time satisfaction. The non-dominated sorting genetic algorithm with elite strategy (NSGA-II) is used to solve the model and an optimal scheduling solution set containing the task assignment and execution order for each helicopter can be obtained. Finally, the rescue of the floods in Zhejiang Province is used as an example to verify the feasibility and effectiveness of the model and algorithm from multiple perspectives, which demonstrates that the model in this paper can improve the effectiveness and efficiency of rescue.

This paper takes the electric power system of more-electric aircraft as the research object, analyzes the future power topology, energy transmission, and usage characteristics of more-electric aircraft, and presents an optimized design scheme and control strategy for the aircraft power system based on energy storage. Combining application scenarios, an optimization algorithm model for the power system is constructed, and multi-objective optimization is performed on the control strategy. Simulation analysis shows that the energy optimization and integrated management of the aircraft power system based on the complementary operation mode of energy storage and generator have a good effect on improving the energy utilization efficiency of the aircraft and reducing the bus current fluctuation. It has potential application value in engineering practice, which can support the improvement of aircraft economy and the realization of long-range flight.

2D-Direct numerical simulation (2D-DNS) with complex chemistry is carried out to study the spray autoignition process of n-heptane/air under low initial air temperature, i.e. $$T_{{{\text{air}}}} = 740{\text{K}}$$ T air = 740 K . The ignition process presents three-stage, and there exist three types of propagation flames controlled by low-, intermediate- and high-temperature chemical (LTC, ITC and HTC) reactions respectively. The low temperature ignition occurs in the lean mixture, and LTC stage lasts about 13 ms. However, the intermediate- and high- temperature ignition occur successively in the rich mixture due to the propagating cool flame, and the value of the most reactive mixture fraction is larger than the homogeneous simulations.

The DISC method is suitable for the design and optimization of airfoil, especially in engineering. Low Reynolds number airfoil design has been conducted using DISC method, coupled with N-S equations. Detailed DISC theory and equations have been elaborated. The effectiveness of the method is validated by choosing the FX63-137 airfoil as the initial airfoil, and the NACA0012 as the target. A low Reynolds number airfoil profile is obtained using the method by giving a favourable target pressure distribution. Results show that its aerodynamic characteristics in low Reynolds number are satisfactory. The transition location of the airfoil is about 60% of the chord length, which means it has wide laminar flow range and is suitable for near space vehicles.

Laminar airfoil has extensive application prospect because of its low drag characteristic. In order to optimize the high lift-drag ratio airfoils of solar powered unmanned aerial vehicles in near space at low Reynolds number, the research on FX63-137 airfoil has been conducted. Firstly, numerical simulations are carried out using both transition SST model and transition $$k - k_{L} - \omega$$ k - k L - ω model, and are compared with the wind tunnel test results. Secondly, the parameterized modeling method and optimization algorithm for the airfoil are applied, and an airfoil optimization design platform has been built. An optimized airfoil has been designed based on FX63-137 airfoil using the platform. Results show that, the maximum lift-drag ratio of the optimized airfoil is increased by 6.83%, and the pitching moment is reduced by 0.015, which further improves the aerodynamic characteristics of FX63-137 airfoil and reduces the influence of trimming on aerodynamic efficiency.

Considering the suitability of various engine nacelle models for the propulsion airframe integration of the blended wing body transport, this study employed the Computational Fluid Dynamics approach to compare the engine simulation effects, internal and external flow dynamics, and aerodynamic performance of flow through and powered nacelles. The aerodynamic characteristics of both nacelles when integrated with the airframe were further investigated. The results indicate that the intake mass flow rate is the predominate factor affecting internal and external flow of an isolated nacelle. The influence of the power effect on the airframe surface flow varies greatly under both high and low speed conditions of the installed nacelle. At high speed conditions, the influence of power effect on the airframe surface flow is very small, but the influence is quite great at low speed conditions. To simplify the design process and improve its efficiency, it is recommended to utilize the flow through nacelle in the initial propulsion airframe integration analysis at high speed conditions, subsequently investigating the power effect on the integrated design at both low and high speed conditions.

There are two important problems in applications of the Fiber Bragg Grating (FBG) strain sensor in Aircraft High Temperature Structure Test. One is its reliable installation in high temperature, and the other is the cross sensitivity of strain and temperature. In order to solve these problems, the installation technology research, and the temperature-strain response research of FBG sensor were carried out in high temperature environment. The result shows that FBG sensor can be installed on the sample reliably by using the laser welding process and the plasma spraying process. By using infrared radiation equipment and trapezium cantilever, the temperature responsive coefficient from 30 ℃ to 1000 ℃ and the strain responsive coefficient from 0 με to 550 με of the FBG sensor were obtained. Meanwhile, the FBG measurement value was calibrated from 20 με to 6000 με by bone shape sample and regular strain gauge. Finally, the FBG sensor was applicated in high temperature structure test, and the steady strain value was obtained at 700 ℃.

This article addresses the issue of insufficient heat sinks due to the rapid increase in aircraft thermal load. It analyzes the challenges faced by existing fuel thermal management and factors affecting the heat dissipation performance of heat sinks. The paper proposes an improved heat dissipation method for fuel heat sinks based on the integration of aircraft and engines. It provides an optimized control strategy for high-temperature return oil to alleviate heat accumulation in fuel tanks. Moreover, a fuel thermal management proxy model for aircraft engines is constructed in combination with application scenarios. Simulation analysis shows that the optimized fuel thermal management scheme has a good effect on improving the efficiency of onboard heat sink utilization, and it has potential application value in practical engineering.

Based on the high precision and simplification requirements of multi-sensor centralized power supply for aircraft actuator system, a high precision design method of airborne high-frequency power supply is proposed in this paper. The circuit used the hardware logic scheme to obtain accurate sine instructions, which can improve the precision of sine power supply frequency and anti-interference ability, solve the problem of low precision of power supply frequency and easy interference in the centralized power supply of aircraft multi-sensors, and ensure the measurement accuracy of sensors. The linear amplifying circuit is used to ensure the output quality, and the power amplification is achieved by using the over-current locking control and overcoming the crossover distortion, which improves the voltage accuracy and power supply stability, and is used to solve the problems of complex control and low voltage accuracy of the centralized power supply network. The reactive power compensation method with damping is adopted to give consideration to reactive power compensation efficiency and ensure the system stability, which can realize the reactive power compensation of centralized power supply, solve the problem of sinusoidal distortion of power output, and provide strong support for the airborne products “small, low and light”.

Tapered composite laminates are commonly adopted to accommodate the need of varying thickness in aircraft structures. In this work, experimental investigations on the damage evolution and the failure mechanism of tapered composite laminates under tensile load were conducted. Four types of tapered configurations were tested, consisting of different drop-off sequences and different thin section lengths. The results indicate that the geometric eccentricity of mid-planes between thin and thick sections leads to a bending tendency of the tapered laminates. High-level stress concentration caused by the terminated plies prompts the delamination occurrence and propagation. Different delamination initiation loads and propagation loads are observed in specimens with varying layup sequences in the tapered section. Nevertheless, the thin section length influences the ultimate strength and the failure mode evidently. The failure of all tested articles are characterized by the shearing out of the bulk of discontinuous plies, accompanied with fiber fracture in the vicinity of dropped plies.

Inter-dimensional coupling is a key factor affecting the accuracy of multi-component force sensors. In order to further enrich the decoupling algorithm theory of the spoke-type force sensor, develop a high-precision force sensor, and optimize the decoupling technology of the spoke-type multi-component sensor. From the perspective of engineering technology, the most widely used optimization algorithm is the least squares linear fitting decoupling algorithm. The traditional nonlinear decoupling algorithm has disadvantages such as low precision. This paper proposes a matrix decoupling solution based on genetic algorithm. Implementation form. In order to verify the performance of the algorithm, this paper takes the hub-and-spoke multi-component sensor as the experimental object, and applies the improved algorithm to the nonlinear decoupling of the sensor. The decoupling experiment shows that the decoupling accuracy of the matrix decoupling solution based on the genetic algorithm is higher. The convergence time is shorter and it has stronger adaptability to nonlinear decoupling. It can provide some references for the design of the decoupling algorithm of the hub-and-spoke sensor, and it will be applied to the decoupling of multi-dimensional force information in multiple occasions.

In the management of airport runway engineering project, scientific and reasonable arrangement of construction schedule is an important factor to ensure the short construction period, low cost, good quality and good environment. In this paper, firstly a 3D solid model of the runway, quantitative data such as engineering quantity and cost of the runway, and initial construction schedule are built using BIM series software. Then, a mathematical model considering activity overlap is established for optimizing the objective functions of construction period, cost, quality, and environment. And a multi-objective optimization software for airport runway construction progress is developed using genetic algorithm and Matlab GUI language. Finally, based on an actual airport runway engineering case, this method and software are applied to multi-objective optimization of runway construction progress, verifying the effectiveness and practicality of the method and software. It provides a guiding basis for the formulation of the construction schedule of the airport runway.

The application of constant-power control electronically technology in LEHGS (Local Electrical Hydraulic Generation System) is introduced briefly in this paper. The combination of variable speed motor and fixed displacement pump serves as the power source for the LEHGS. The shaft torque and the system output pressure are characterized by phase current load analysis method. The constant-power control electronically strategy is realized through the way that a controller controls the motor speed. The simulation analysis of the electronically controlled constant-power EMP (electric motor pump) is performed by using commercial AMESIM software, and the principle prototype was produced according to the simulation results. Results show that the application of constant-power control electronically technology in LEHGS is capable of meeting the needs of low-pressure large flow and high-pressure low-flow conditions, which ensures that the special flow needs of aircraft hydraulic users under extremely harsh conditions.

The traditional aircraft skin inspection is mainly manual inspection, which has low efficiency, large workload, and is prone to missed and misdetected inspections. In order to improve the efficiency of aircraft skin detection, an end-to-end aircraft skin damage detection method based on Ghostnet is proposed. By introducing a scale factor to adjust the convolution method in Ghostnet, the multi-scale feature extraction module extracts the texture features of aircraft skin, which increases the range of receptive fields in the backbone network. Secondly, a multi-layer feature fusion module is introduced to integrate shallow and deep features. The angular margin is introduced to improve the confidence function to improve the confidence of each damage category. Based on the self-made data containing 1730 pieces of aircraft skin damage, the detection accuracy of the model can reach 89.28%, the detection speed is 36 frames per second, and the detection accuracy is improved by 9.28%.

With the complexity of aerospace structures, the demand for vibration and noise reduction technology is increasing. It is well known that locally resonant acoustic metamaterials have significant elastic bandgap characteristics, which can effectively control the low-frequency vibration of structures. And the locally resonant structure can be formed by using the distributed dynamic vibration absorbers. For realizing the control of vibration, in this paper, a locally resonant acoustic metamaterial based on vibration absorbers is constructed on a free-free beam. The ratio of the total mass of vibration absorbers to the mass of the beam was changed to explore its ability to tune the bandgap. Furthermore, the relationship between the bandgap characteristics and the mass ratio is discussed experimentally.

In this paper, the problem of accurate landing has always been an important problem to be solved in the application process of carrier-based UAV. To this end, the Auto-Regressive (AR) model is used to predict the deck motion process. On the basis of the commonly used system identification method - recursive least square method, the dynamic adjustment of weights for new and old data is realized by introducing a forgetting factor, and the convergence speed of the recursive fitting process is improved by extending the innovation dimension used in the single recurrence. For different sea conditions, the designed deck motion predictor is simulated and verified. Compared with other methods, the results show that the least square method with multi-innovation forgetting factor can control the error of deck motion prediction in a smaller range, and improve the accuracy and success rate of landing.

Recently, data analysis of aviation sensors is a hot topic because it is important to aviation safety. Many researchers propose temporal models (RNN, LSTM, etc.) to predict the accuracy performance degradation of sensors, due to the mechanical property, and filter out anomaly data of sensors. However, aerial sensor data is usually long-term data because of intensive sample rates and long runs. The traditional models usually lose the gradients during the training phase for long-sequence data. To reduce this problem, in this paper, Residual-Cascaded LSTM (RC-LSTM) is proposed. It can effectively extract the rich features from large inputs to model large-range independence. Besides, it is found that the volume of anomaly data is much less than that of normal samples. Thus, a distribution-aware shuffling scheme is designed to assist models to learn more reasonable representations for input data. A large number of experiments are performed on the simulated flight sensor dataset and two public datasets (earthquake, Lightning2). The proposed RC-LSTM is better than the most advanced method (RNN, LSTM, etc.), and its accuracy is 80%.

Aiming at the problem of serious internal failure of composite laminates used in aerospace product structures after low-speed impact, the VUSDFLD subroutine was developed based on the simplified three-dimensional Hashin failure criterion. The simulation method of the low-speed impact process of T800 unidirectional prepreg alternately laminated composite laminates was established, the mechanism, severity and evolution of damage during a typical low-speed impact are analyzed. Analysis of post-buckling problems of composite laminates containing internal damage after being subjected to different impact levels based on finite element simulation method. The damage to the internal fibers and matrix of the laminate under different impact conditions, the ultimate compressive strength and energy threshold corresponding to the sudden drop in structural bearing capacity under different damage levels was explored. This provides a reference for studying the damage mechanism and mechanical properties of this type of composite materials under low-speed impact.

Since the height of the center of gravity of an aircraft generally changes slightly in flight, it does not materially affect the maneuverability and stability characteristics of the aircraft. In the aerodynamic layout design stage, the height attribute of the center of gravity is usually ignored, and it is usually located on the construction horizontal line by default. However, in this paper, an example is given to illustrate that the influence of the height variation of center of gravity on the maneuverability and stability characteristic must be considered in the retrofit design of AEW, Especially at the boundary state of high Angle of attack at takeoff and landing, the longitudinal static stability of the aircraft is greatly reduced. Especially at the boundary state of high Angle of attack during takeoff and landing, the longitudinal static stability is greatly reduced and the pitching moment characteristics may diverge prematurely. This paper theoretically analyzes the reasons for the decrease of longitudinal static stability, and the parameter sensitivity analysis of the height variation of center of gravity on longitudinal static stability is analyzed to guide the retrofit design of AEW.

The items in CCAR-25 related to CCAR-33 mainly appear in the E subpart of the CCAR-25 standards. As a representatively interconnecting system, there are great meanings and expected economic value for the TC application that the lubrication system verification be reasonably scheduled and maximum extent reviewed through both the aircraft OEM and the engine suppliers. Based on the requirement analysis of CCAR-25-R4 and CCAR-33-R2, this paper draws up a preliminary aircraft TC plan of lubrication system compliance by the five relationships of referencing, selecting, supplementing, resembling, and differing among the airworthiness standards to optimize the relevant conclusions in CCAR-33 compliance for CCAR-25 requirements during the type verification schedule state, and maximizes the use of validations and conclusions of the lubrication system in CCAR-33. The conclusions of the compliance activities are used to support the verification of the CCAR-25 requirements, expecting to provide reference and assistance for the aircraft design and type certification process.

Due to the global warming and industrial environment pollution, many effected issues have been implemented to achieve the improvements. The international standards limiting the emissions from turbojet and turbofan aircraft engines are contained in International Civil Aviation Organization (ICAO) Annex 16 Volume II to the Convention on ICAO. The Committee on Aviation Environmental Protection (CAEP), led by ICAO, has progressively strengthened the requirements for aircraft emissions, with detailed classifications of aircraft emission components, and continuously improvements of the emission component test validation procedures and data processing methods. This paper summarizes the revision process of ICAO Annex 16 Volume II, and makes a tentative discussion on the trend of the airworthiness regulations on emission requirements with the comparisons with the technological development paths of OEMs. Meanwhile, the impact of the revised regulations on the emission certification process is analyzed to provide a reference for the domestic commercial aviation products airworthiness certification process.

The reconfigurable frequency selective rasorber has the ability to switch its transmission band into absorption band and thus, has the potential to mitigate the contradiction between radar detection and radar stealth. However, the increasing complication of the feeding circuit of the active elements make it difficult to improve a frequency selective rasorber from narrowband to wideband transmission, as well as from single to dual polarization. In this paper, we proposed a dual-polarized metasurface with switchable transmission/absorption covering the X band. The unit cell design and feeding strategy of the proposed metasurface are discussed in detail. Simulation shows an 8–12 GHz transmission and absorption switch ability with good angular stability and polarization insensitivity is achieved, which is the key function to realize the dual-polarized frequency selective rasorber with wideband transmission.

Distributed electric propulsion (DEP) is a popular research area in the aerospace field, with most research focusing on investigating the aerodynamic features of DEP configurations through numerical simulations. However, little has been done to optimize the coupling of distributed power and airframe. This paper starts with a problem of the propeller/wing aero-propulsion characteristics and a multidisciplinary analysis framework for electric aircraft, followed by a simplified aerodynamic analysis method for the propeller/wing aero-propulsion analysis. The geometric model of placing a propeller at the leading edge of a wing was analyzed using the RANS method for aerodynamic analysis, and the results were compared with those of the simplified aerodynamic analysis method to validate the rationality of the simplified analysis method. The model established in this paper was used for aerodynamic analysis, aerodynamic optimization design, and electric propulsion system parameter analysis of typical distributed electric propulsion aircraft. This provides valuable reference for the design of distributed electric propulsion aircraft.

Aerial-aquatic vehicles are an innovative technology that has attracted significant research attention due to their wide potential applications. In this paper, we introduce a tandem dual-rotor unmanned aerial-aquatic vehicle (UAAV) that includes an aerial power system and an underwater power system. This configuration allows the UAAV to move flexibly underwater, especially through narrow spaces. Based on this configuration, we studied underwater trajectory tracking control of UAAV. The dynamic model of the vehicle’s underwater operation mode is established. Then, a boundary layer sliding mode control method is adopted for underwater trajectory tracking control of UAAV to overcome the influence of external disturbances and system uncertainties. In addition, the pseudo-inverse method and virtual control variables were used to achieve control allocation for the underactuated system. Finally, simulation results are presented to demonstrate the validity of the proposed controller considering external disturbances and measurement errors.

Due to the accumulation of a large amount of maintenance text information recorded by maintenance personnel based on experience in aircraft maintenance, due to its strong professionalism and diverse expression methods, intelligent analysis has not yet been achieved, making it difficult to fully utilize these data. In response to this issue, this article proposes an aircraft maintenance record analysis method based on the ALBERT-TextCNN model, which solves the fault causes to assist maintenance personnel in correct troubleshooting work. Firstly, the vectorization representation of the preprocessed text and the preliminary feature extraction are performed by using ALBERT; Secondly, the TextCNN model is used to extract deeper features to improve the accuracy of model analysis; Finally, compared with other commonly used text analysis models, the results show that the method used in this article can accurately analyze the causes of faults in aircraft maintenance records, effectively improving the accuracy and speed of analysis.

Tapered laminate structures with ply drop-off are used extensively in aeronautic and astronautic applications. However, ply drop-off involves inherent structural discontinuities that create stress concentrations, potentially resulting in failure below the loading capability of the structure. We performed experiments to study the mechanical properties of a tapered laminate structure in the movable wing skin of an aircraft, and examined the effects of fatigue and damp-heat exposure on such properties. The mechanical behavior and failure modes of the structure were simulated using finite element analyses and compared with the experimental results. The experimental findings were found to agree satisfactorily with the simulation results. This study provides useful information to support the design and production of such composite structures.

In order to solve the displacement synchronization problem in the electric thrust reverser actuation system of the air-craft cascade thrust reverser, the synchronization performance of the transmission mechanism was studied. First, based on the operating principle of the synchronous mechanism, the mathematical model and Simscape model of the synchronous mechanism are established. Then, the influence of actuator transmission ratio, flexible shaft flexibility and asynchronous load on the system synchronism are analyzed by simulation. The simulation results show that the one-side and two-sides synchronization precision of the electric thrust reverser actuation system can reach 1.19% and 1.72%, respectively. The synchronization precision can be better than 1% by optimizing the parameters of the actuator transmission ratio and the flexible shaft flexibility. The influence of actuator transmission ratio and flexible shaft flexibility on synchronization performance is greater, the smaller the actuator transmission ratio and flexible shaft flexibility is, the higher the synchronization precision is, however, the influence of the asynchronous loads between actuators on the synchronism is less. The research results provide a reference for the parameter design and fault diagnosis of the synchronous mechanism of the electric thrust reverser actuation system.

The civil aircraft maneuvering process during approach is complicated, and the aircraft may be affected by wind shear, cross winds and other adverse weather conditions, which will influence flight safety. To achieve real-time assessment and early warning of civil aircraft flight safety during approach, the flight requirements of civil aircraft during approach are analyzed according to flight manuals, and the decision requirements of the approach phase are formed. Flight states, including engine speed, aircraft descent rate and heading angle, are selected as monitoring parameters to represent the flight safety of civil aircraft during approach. The historical flight data of the approach phase in the flight operations quality assurance database are divided into two categories: safe approach and abnormal approach by using a cluster analysis algorithm. Based on the analysis of cluster calculation results and the characteristics of the flight mission in the approach phase, the value requirements of flight safety monitoring parameters and their combinations during the approach phase are proposed, and the criteria and evaluation methods of flight safety in the approach phase are established. Taking the incident of the Shenzhen Airlines runway undershoot as an example, the aircraft’s flight status during approach is evaluated based on cluster analysis. The results show that the abnormal approach state in the event can be accurately and timely identified before the aircraft descends to the decision height, reserving time and space for pilots to execute the go-around procedure and improving the flight safety of civil aircraft during approach.

The application of the front engine jet in the external blowing flap was studied by numerical simulation. The effects of different parameters such as jet intensity, jet angle and flap angle on the aerodynamic performance of the ground effect wing were compared. The results show that the front engine jet can increase the lift of the ground effect wing during takeoff. When the engine jet intensity and jet angle change, the change of its position will affect the lift effect, and the lift coefficient reaches the maximum when the jet directly acts on the flap surface. Increasing the flap deflection angle during external blowing will strengthen the ground effect, but it will aggravate the flow separation on the flap surface while increasing the lift of the ground effect wing. The numerical results describe the flow field characteristics of the external blowing flap under strong ground effect conditions. The optimal lift enhancement scheme depends on the matching design of the engine and the ground effect wing.

A fast sequencing genetic algorithm, NSGA-II is applied to the performance optimization of axial flow electric fans on multi eletric aircraft to improve the effectiveness of environmental control systems (ECS) and reduce fuel penalty. The degree of sweep and curve of blades is set as the optimization parameters, while low power and large flow rate is set as the optimization objectives to optimize the initial design. NSGA-II algorithm is used to control the optimization parameters, and an automated simulation analysis process is established to achieve automatic iteration and optimization. The power of the optimized fan model is reduced by 8.8% compared to the prototype. The results show that the method used in this paper has good effects in dealing with multi-objective and multi-parameter performance optimization problems of axial flow fans. The method has also certain reference value for the optimization design of other turbomachine.

The respiratory status of fighter pilot is crucial for flight safety. How to effectively detect the respiratory status of pilots and provide effective protection have been a key research both domestically and internationally in which effective detection of respiratory status is a technical challenge. In this paper, a method is proposed for evaluating pilot respiratory status based on mask pressure. Firstly, by analyzing the mask pressure measured by regulator, the data was divided into several one-min segments and filtered. Then respiratory rate was calculated using frequency analysis method, respiratory depth was calculated using linear normalization and standard deviation method. Furthermore, respiratory depth and respiratory rate were applied to define the tidal volume. Finally, the abnormal probability of respiration can be obtained. Adequate experiments were conducted on the data of fourteen flights of a fighter aircraft. The results indicate that our method can evaluate the respiratory status and obtain the abnormal probability of respiration effectively.

In order to accelerate the development cycle of aviation systems and improve the development efficiency of serialized products, a method of integrating adaptive solvers is proposed for joint simulation systems based on the FMI standard. The method is divided into two types of solvers: fixed step solvers and variable step solvers. The fixed step solvers mainly include Euler and Runge Kutta methods, while the variable step solvers include CVODE and LSODAR methods. Taking the fuel system as the main research object, the efficiency of traditional solver integration and adaptive solver integration is compared in terms of solution time, convergence tolerance, and error. The results show that as the convergence tolerance decreases, the proposed adaptive solver method is more stable, with relatively smooth errors, and better accuracy than the traditional integrated solver method; From the perspective of solution time, under the same solution time, the adaptive solver can reach the set calculation end time quickly, at least 500 times as fast as the traditional combined solver method.

An analysis method based on notch geometry parameters is presented to quickly estimate the fatigue life of notched parts by taking the stress gradient effect at the notch root into account. This method adopts the notch geometry parameters to calculate the stress gradient by assuming that the principal stress decreases linearly at the notch root, and then combines the point method(PM) of the theory of critical distance (TCD) to obtain the fatigue damage parameter. The fatigue damage parameter is the function of the absolute stress gradient $$\overline{\chi }$$ χ ¯ and stress concentration factor KT. Compared with traditional methods, this method does not require refined finite element analysis of the area near the notch. The fatigue test data of four different notches of two kinds of materials are collected to verify the method. The results show that the method proposed can accurately predict the fatigue life of notched components, and all the predicted lives fall within the 3-time error band.

Aiming at the waste of airborne heat due to the relative independent design of the air conditioning subsystem and the equipment cooling subsystem in the traditional environmental control system, this paper proposes a way of crosslinking the air conditioning subsystem and the equipment cooling subsystem from the point of view of heat management and utilization. Based on AMESim software platform, the proposed system architecture is simulated and compared with the traditional independent subsystem design. It is concluded that thermal comprehensive utilization loop control system can effectively reduce the flow requirements of the engine bleed under the air conditioning heating mode, as well as share the heat pressure of the fuel system and reduce the heat compensation loss of the system.

The continuous increase in the power of airborne electronic equipment and the decrease of the airborne available heat sinks are the inevitable trends of the next generation aircraft. The lack of cabin heat dissipation capacity makes the operating environment temperature of airborne electronic equipment rise and the reliability decrease, thus affecting the combat performance of aircraft. Therefore, it is urgent to study the cooling capacity of the cabin area. In order to obtain the real-time variation of the cabin thermal environment during the whole flight process, the one-dimensional thermal path system of the oil and hydraulic cooling system AMESim is innovatively established to obtain the thermal boundary conditions of the equipment changing with time. Moreover, Fluent was substituted into the three-dimensional simulation analysis of the cabin environment and cabin equipment temperature field, and the simulation results of the transient temperature field and steady-state temperature field were compared. This method can be extended to the external environment under different flight conditions and the internal thermal equipment conditions to quickly and real-time evaluation of different cabin thermal environments. It can provide effective support and input conditions for the environmental thermal design of next generation aircraft cabin areas.

Hydraulic system load will produce heat and bring a certain degree of temperature rise to the system, after the oil after the hydraulic system pipeline and main heat dissipation accessories back to the tank, and then be inhaled into the hydraulic pump cycle. The working temperature of the hydraulic system needs to be guaranteed in a certain range, which will result in the efficiency of the hydraulic system performance and the failure of the system, which will cause the system to work normally, and ultimately affect the safety of the aircraft and the task execution. Therefore, the hydraulic system needs to be thermal protection, so that the temperature control within a certain range. In this paper, based on AMESIM software, thermal power of hydraulic system is designed, the temperature control of the system is simulated, the dynamic temperature change and the heat dissipation demand of the system are obtained, which lays the foundation formal design of hydraulic system.

According to the requirements of the fire prevention clause of CCAR33.17, the components, pipelines and cables in the designated fire area of electronic and electrical components should have the functions of fire prevention and fire resistance. This paper analyses different fire prevention conditions of an electrical electronic controller (EEC). Based on Pyrosim pre-processing tool and FDS solver, the simulation of standard flame burner is carried out. Combined with the commercial software ANSYS Fluent, the fluid-solid-thermal coupling simulation of EEC was carried out, the temperature and flow velocity field impacted by flame are solved and the weakest surface and the most severe working condition of the component were obtained, which provided reference for the follow-up fire prevention test of electronic components.

Civil aircraft engineering simulator is a complex test platform composed of multiple structures, involving airborne software and hardware equipment, system simulation models, simulation equipment and structures, and auxiliary equipment for test platform development. In view of the complexity of its composition, it is necessary to develop a configuration management method for civil aircraft engineering simulators to control its configuration. In this paper, the objectives, objects and implementation of configuration management of civil aircraft engineering simulator are preliminarily discussed and analyzed. And this paper takes the engineering simulator of a certain type of domestic large aircraft as an example to discuss the implementation process of its configuration management activities in detail.

The bypass dual throat nozzle (BDTN) is capable of achieving thrust vectoring by introducing secondary flow from upstream through the bypass channel. In order to investigate the aerodynamic vectoring characteristics of the axisymmetric BDTN, numerical simulations are performed to analyze the internal flow field of the nozzle at different nozzle pressure ratios (ratio of total inlet pressure to ambient pressure, NPR) in three dimensions. The results show that the influence of the bypass secondary flow causes a significant asymmetry in the parameter distribution of the flow field of the axisymmetric nozzle, and the flow also undergoes lateral expansion in the axial direction. As the total inlet pressure increases, the internal flow velocity and temperature are more stable, while the pressure and density gradually increase. Compared with the 2D configuration, the lateral expansion within the nozzle cavity reduces the degree of asymmetric difference in the internal flow field structure, resulting in a vector deflection effect. The thrust vector angle decreases as the NPR increases, and the thrust coefficient increases slightly and then decreases.

In this study, the composite fuselage panel with a hat stringer was taken as the research object. The compression tests of the non-damaged panel, the bonded repair panel and the bolted repair panel were completed. The effects of different repair methods were discussed. The tests verified that the bearing capacity of the panels repaired by adhesive and bolt can reach the strength level of the original structure. Both the bonded repair test specimens and the bolted repair test specimens keep the structure stable under 67% ultimate compression load and the structure does not fail under 100% ultimate load, which meet the design requirements of composite panel for battle damage repair. Compared with non-damaged panel, the ability of bolted repair test to withstand compression load is improved, which is caused by the increase of stiffness in the repair area. The ability of the bonded repair test to withstand the compression load is equivalent to the non-damaged panel.

In this paper, the investigation on effects of hygrothermal environment on the bending behavior of composite panel with PMI foam is finished. The hat stringer panel is taken from composite rear pressure bulkhead of fuselage. The tests under room temperature and hygrothermal environment are carried out to verify the bending behavior of composite panel. The effect of bending behavior with 70 ℃ and 85% relative hygrothermal environment is discussed. The results show that the average failure load of hat stringer panel with PMI foam are decreased under upward and downward bending load. Besides, the hygrothermal environment has an influence on the failure mode of hat stringer panel with PMI foam. The failure mode of hat stringer panel with PMI foam alters from cracking of hat stringer to breaking of dome skin under the hat stringer. The results contribute to establishing the hygrothermal behavior assessment method of composite hat stringer panel with PMI foam.

When the landing gear system of civil aircraft is in the fault state, the backup release system will be enabled, in this case, the landing gear system and the landing gear cabin door are in no-driven mode, and its extension only relies on gravity. In this process, if the static friction force between the landing gear tire and the landing gear cabin door is too large, the landing gear system will be stuck and fail to extension. It’s important to measure the static friction in early design to avoid this. In this paper, a simple and high efficiency test bench is designed to measure the static frictional force coefficient between the tire and door. There is only one parameter measured in the test bench, based on which the test bench is high efficiency, high repeatability and high precision of the test results.

In the cruising process of electric aircraft, due to the adverse climatic environment, It is easy to cause line break of the motor position sensor in the electric propulsion system and endanger the flight safety of aircraft. A redundant control method of electric aircraft motor based on digital twin is proposed to solve the open circuit fault of position sensor. Firstly, the digital twin model of PMSM is constructed based on MRAS. Secondly, the digital model is used to estimate the rotational speed and compare it with the actual value. After judging the sensor fault, the system is switched to the observed value in time to ensure the stable operation of the system. Finally, to verify the feasibility of the proposed method, a simulation model of the system is built, and the system simulation test is carried out. The simulation results show that the control strategy can ensure the normal operation of the system when the position sensor breaks down.

To verify the effectiveness of the health assessment model, experimental validation research on helicopter dynamic component was conducted. Firstly, the health representation of bearing signals was self-learning by stacked auto-encoder, and the health representation was input to Mahalanobis distance for health assessment. Then, the comprehensive design of test and verification profile for evaluating the degradation capability of bearing performance was carried out. Finally, the bearing degradation test and signal acquisition was carried out, and the collected vibration signals was analyzed and processed using the stacked auto encoder and Mahalanobis distance method, which verified the effectiveness of the health assessment methods proposed in this paper.

The monitoring and analysis of oil status is an important means of condition monitoring and fault diagnosis for aeroengines. With the development of artificial intelligence technology, deep learning methods have been gradually applied in various fields, including the field of fault diagnosis. To achieve the prediction of fault diagnosis of aeroengine lubrication system, based on the actual airborne flight data, this paper describes a BiLSTM and LSTM network to establish an engine lubrication system model of the flight process, including oil pressure difference, pressure altitude, Mach number, oil level, oil return temperature and other parameters. The attention mechanism is also introduced to improve the prediction accuracy of the model. The calculation results of the model are in good agreement with the flight test results, indicating the feasibility and effectiveness of the model prediction. Compared with other deep learning models, the prediction results of BiLSTM-BiLSTM-LSTM-Attention model are more accurate.

The development of unmanned aerial vehicle (UAV) swarm technology has opened up new possibilities for various applications, such as search and rescue, precision agriculture, and surveillance. However, the coordination of a large-scale UAV swarm is a complex task that requires intelligent, efficient, and scalable techniques. In recent years, the emergence of microservice architecture has provided a promising approach to addressing the challenges of UAV swarm coordination with intelligent techniques. In this paper, we first provide scenario analyses to demonstrate how intelligent microservices allow UAV swarm coordination more effective and efficient. Then, we present key technologies for UAV swarm coordination based on intelligent microservices. Specifically, we introduce our solutions to address the three main challenges, i.e., service split, service registration and discovery, and security and privacy in implementing the intelligent microservice-based UAV swarm coordination system. Finally, we present the possible future directions of this research area, i.e., optimization of computing resource allocation, integration of advanced AI algorithm, and human-UAV interaction.

In view of the development of intelligent equipment system of system (SOS) technology in the future, the sequential developments of foreign drone swarm technology concept, project layout, technology break-through and equipment formation are analyzed, and furtherly the future intelligent equipment SOS related technology development trend is proposed. According to actual combat cases of equipment SOS, it can be speculated that the future development of intelligent equipment SOS will focus on the optimization of SOS construction, intelligent game confrontation and big data analysis. By means of a large amount of SOS confrontation simulation, intelligent analysis of massive actual combat data and accumulation of SOS confrontation experiences, the three key points above will promote the spiral upward development of intelligent equipment SOS by combining theory with practice. Consequently, the implementation of equipment SOS intelligence will be accelerated.

To enhance the efficiency of the experience replay method, this article proposes an improvement by incorporating the past experience reward value and the timing difference error (TD error) to form a prioritized R-T experience parameter. Additionally, an attention mechanism is introduced to determine data priority based on the R-T experience parameter. This improved experience replay method is then applied to the multi-agent deep deterministic policy gradient algorithm, resulting in improved algorithm training efficiency and stability.

The airborne equipment is organized according to the system/subsystem. And the equipment library is constructed. And when the actual installation, the spatial positioning and authority control are carried out under the assembly based on the dynamic view. Then the review, issuance and solidification of the installation status are carried out with the installed assembly. When changing, it is managed according to two ways: version change and number change. The dynamic view can ensure that the equipment change process is controlled and the installation status is clear. The equipment installation status of any flight can be dynamically extracted in real time. Airborne equipment management technology has been successfully applied to the development of large aircraft. On the basis of ensuring the construction of equipment product structure, space installation, engineering changes and controllable installation status, it has improved the standardization level of equipment management and ensured the completeness, controllability and traceability of large aircraft product data.

The motion reliability of the landing gear retraction mechanism is influenced by multiple random factors during the aircraft’s service life, resulting in poorer motion reliability and undesirable motion characteristics. This paper proposes a method to analyze the motion reliability of the retraction mechanism that considers the influence of multi-source random factors, and the proposed method is applied to the rotatable tire-type landing gear retraction mechanism of a hypersonic vehicle. Then the sources of random factors that affect the performance of the retraction mechanism are thoroughly studied, and the probability method is used to determine the randomness of joint clearances, installation deviations, and aerodynamic load. Additionally, to address the issue of the retraction mechanism failure mode being an implicit function, an estimation model of the motion reliability of the retraction mechanism under multi-source random factors is established. The model is based on the Monte Carlo method and neural network, using a verified co-simulation model of the retraction mechanism. Finally, the impact of the mean and standard deviation of joint clearances, installation deviations, and aerodynamic load on motion reliability is evaluated. Key inspection guidelines are also provided for the operation and maintenance of the retraction mechanism.

The water ingestion test should be conducted by the type certificate applicant for a new designed civil transport aircraft. The water bed was one of the most important test facilities for this test. The applicant could not find the perfect runway to install the water bed. The runway length might be limited, which meant there was no sufficient distance for aircraft accelerating to target entry speed, or decelerating safely. The brake system over heat problem could also be encountered due to the extreme test conditions such as maximum takeoff weight and high speed. This article was based on the successful water ingestion test experience in aircraft X type certification program. The test points arrangement, dispatch brake temperature limitation, self-taxi distance control and initial deceleration sign setting techniques were discussed.

Soft aerial refueling is considered to be a high-risk flying subject, the height matching among oil-refueling tanker aircraft, refueling device and oil-receiving aircraft is an important guarantee for docking safety. Based on the refueling configuration of a large soft oil-refueling tanker aircraft and two combat-type oil-receiving aircrafts, this paper decomposes the whole process of the oil-receiving aircrafts’ dynamic approach to the tanker aircraft, analyzes the relationship among the refueling units, the docking of the oil plug and the refueling hose, and the complicated flow field of the tanker aircraft, and extracts the influencing factors of the safety of the formation refueling and docking. It also works out the corresponding operation procedures of the geometric compatibility, aerodynamic compatibility and emergency treatment from the perspective of engineering practice; the relevant conclusions provide a reference for the follow-up domestic in-depth study of precision formation flight and related fields of aerial refueling safety.

Vision guidance has shown increasingly promising capacity in autonomous landing, since it has the merits of low-cost and electromagnetic resistance. In this work, we propose an airborne monocular vision guidance method using region and structured line features. In the approach phase, a region-based pose tracker is adopted to track the pose within the consecutive frames using the contour and color information of the carrier. In the proximity phase, when the structural features of the carrier become distinguishable, the lines forming a particular configuration are detected. Then, a similarity measurement criterion based on direction and distance constraints is exploited to perform line alignment between 3D lines and the detected 2D ones. Once the 2D-3D correspondences are identified, the rotation and translation are successively computed using the structural line constraints. Finally, the optimizer of the pose tracker is utilized to refine the pose for better accuracy. Experiments demonstrate that the proposed method achieve high pose estimation accuracy and real-time efficiency, which is suitable for guidance of autonomous landing.

The high-speed co-axial rotorcraft is a new type of composite high-speed helicopter with good low-altitude maneuverability and a significant speed increase compared to ordinary configuration helicopters. High-speed helicopters with co-axial rotor configuration have two operating conditions: hovering and forward flying. Different rotor speeds under the two operating conditions bring new challenges to helicopter vibration control.The liquid inertial vibration eliminator (LIVE) is a high-efficient vibration isolation device with compact structure and light weight, which is widely used in helicopter vibration control. In this paper, a variable stiffness LIVE considering the principle of smart-spring is designed for a co-axial rotorcraft to control the vibration at different frequencies under different operating conditions. The mechanical model is established, and the equations of vibration isolation frequency and displacement transmission rate are obtained. The parameters that affect the vibration isolation performance are analyzed. The structural parameters are determined and dynamics simulation is carried out. The results show that the LIVE with variable stiffness can control the vibration under different operating conditions for high-speed helicopters. The analysis results verify the feasibility of the relevant design schemes.

In order to reduce the specific fuel consumption of an aero-engine and improve its economy, a partial intake strategy in a pre-swirl system is adopted in the cruising condition to reduce the bleeding air flow from the compressor. The influence of partial intake air on the characteristic parameters such as air supply mass flow rate and air supply temperature of the pre-swirl system is studied. The simulation is conducted mainly for the presence of impellers in the cover-plate cavity under the operating conditions where partial nozzle flow paths are open (full admission/intake) and closed (partial admission/intake). The calculation results show that the decrease of the air supply mass flow rate is smaller than that of the nozzle geometric flow area. With full admission, the fluctuation of the mass flow rate of a single supply hole ranges from −5.0% to 5.3%. The air supply temperature fluctuates by about 0.9K, with temperature non-uniformity coefficient ranging from −0.27% to 0.28%. After partial intake, the fluctuation amplitude of the air supply hole mass flow rate increases approximately 36%, and that of air supply temperature increases 2.1 times. Compared with the system without impellers, the impellers will reduce the decrease of the air supply mass flow rate, reduce the average air supply temperature by more than 2K, increase the non-uniformity range of the air supply mass flow rate by 66.7% and the non-uniformity range of the air supply temperature by about 2.6 times.

The variation characteristics of kerosene propellant temperature in the tank before launch was studied to control the temperature of rocket kerosene. And the goals making full use of the carrying capacity of the rocket and reducing the risk of propellant unloading with delayed launch can be finally achieved. Based on thermodynamic law, a parking temperature model of kerosene in tanks was established, and an identification algorithm of the model coefficient was designed. The temperature variation coefficient was identified and the prediction accuracy of the model was evaluated with pre-launch monitoring data of a rocket. Furthermore, the long-term temperature variation characteristics of kerosene in tanks were analyzed. The results showed that the prediction accuracy and precision of the kerosene temperature model in 7.5 h is better than 1 ℃. Reducing the kerosene temperature at the end of filling has no significant effect on controlling the temperature of kerosene in tanks. The effective means is to equip the rocket body with insulation layers to reduce the temperature variation coefficient.

As an important part of thrust reverser system, the thrust reverser actuation system of aero-engine is of great significance to the aircraft deceleration of the landing. In order to investigate the moving performance of thrust reverser actuation system, the kinematics and dynamics analysis were carried out, and then the mathematic model was established. The co-simulation based on AMESim and Simulink was used to conduct the simulation investigation which is concerned with system buffering characteristic, synchronization performance and temperature effect of hydraulic medium. The results of the simulation investigation indicate that the co-simulation model of thrust reverser actuation system is helpful to estimate the system operation, and is also an effective analytical tool for the system performance assessment. The buffering model used for the thrust reverser actuation system contributes to reduce the actuator piston of system velocity, less than 0.13 m/s, which is conducive to weaken the violent impact on piston and cylinder. The maximum non-synchronization occurs in the extreme positions of system deployment and stowage. Ensuring the pressure synchronization, i.e. flow synchronization, is helps to improving the synchronization performance. The thrust reverser actuation system can also run with the low medium temperature, −54 ℃, but with the low velocity.