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Long wave ultraviolet or UV-A irradiation (between 320 and 400 nm) is used for fluorescent inspections in magnetic particle and liquid penetrant examinations. UV-A irradiation is obtained from either LED, fluorescent, or high intensity discharge lamps that are stationary or portable. Commercially available UV-A lamps possess a large variation in intensity output that may introduce a legitimate concern for possible health hazards. This document reviews the nature of UV-A irradiation emitted by lamps and acceptable UV dosage limits adopted by the American Conference of Governmental Industrial Hygienists (ACGIH®) and European Union and recommendation of proper practices when working with UV-A irradiation.
AMS K Non Destructive Methods and Processes Committee
This method is intended to evaluate the thermal and oxidative stability of synthetic, ester-based aviation lubricants under defined conditions of time and temperature. This method is applicable to lubricants meeting the compositional and performance requirements of AS5780.
E-34 Propulsion Lubricants Committee
This document defines the technical guidelines for the safe integration of Proton Exchange Membrane (PEM) Fuel Cell Systems (FCS), fuel (considered to be liquid and compressed hydrogen storage types only), fuel storage, fuel distribution and appropriate electrical systems into the aircraft. Editorial Note: Today PEM systems and fuel storage represent the most mature FCS technology and currently forms the basis for this standard. Other types of fuel cell systems and fuels (including reforming technologies and electrolyzers), may be covered by a further update to this document.
AE-7F Hydrogen and Fuel Cells
With the increasing demand for multi-unmanned aerial vehicle (UAV) cooperative operations, the design of guidance laws with time and angle synchronization constraints has become a critical technology to enhance strike precision. This paper focuses on a UAV-launched multi-missile cooperative attack scenario, proposing a composite guidance law that integrates the advantages of existing optimal time/angle control guidance laws. By introducing a time error feedback term and an angle constraint term, combined with an adaptive disturbance observer to compensate for aerodynamic errors and target maneuvers, the proposed guidance law ensures a terminal miss distance of less than 0.5 m while achieving a time error ≤0.6 s and an incidence angle deviation ≤2° among multiple missiles. Simulation and test results both demonstrate that the four-missile cooperative attack achieves time dispersion within 1s, satisfying engineering practicality and anti-interference requirements.
Xie, LijunWang, DeshuangYang, XiaodongZhang, TingtingLi, Yang
The rapid advancement of Unmanned Aerial Vehicles (UAVs) has imposed increasingly demanding requirements on aerodynamic force testing. Ground vehicle-mounted testing provides a safe, relatively accurate, and cost-effective experimental method for testing UAV aerodynamic forces. This paper focuses on a ducted fan as the research object and presents a ground vehicle-mounted testing system designed to investigate its aerodynamic characteristics. The testing process includes building a testing platform, ground static testing, vehicle-mounted testing, and systematic data analysis. Comparative results between experimental tests and Computational Fluid Dynamics (CFD) simulations demonstrate that the vehicle-mounted testing method can accurately provide the aerodynamic force of the ducted fan, with errors in aerodynamic force and moment measurements being less than 5%. This approach could provide important technical support for the design and optimization of ducted UAVs.
Mao, SenZhao, ChuangxinWu, ShuangFeng, YupengZhang, YanwuChen, Lin
Terminal guidance is critical for ensuring strike precision in the final phase of flight. However, traditional methods, such as proportional navigation and optimal guidance laws, face significant challenges regarding real-time performance and adaptability to dynamic targets. To address these issues, neural networks offer a promising solution by enabling adaptive adjustments to guidance parameters, thereby improving performance under various constraints.
Ma, HengweiWang, YongfengWen, HongLiu, DiWei, YuanhangDong, LonghaoLuo, Ying
This study focuses on a compact-layout propeller aircraft, investigating how its powerplant influences stall characteristics via combined theoretical analysis of aerodynamic principles and validation with flight test data. Special attention is paid to the effects of propeller slipstream, appropriate evaluation criteria are selected to assess the aircraft’s high-angle-of-attack performance and stall behavior, and the Weissman chart criteria are further adopted to analyze its lateral-directional departure tendencies. A theoretical analysis of the stall characteristics of compact-layout propeller aircraft is conducted. Through flight test data analysis, the stall characteristics of compact-layout propeller aircraft are studied, with an emphasis on understanding how slipstream effects influence their longitudinal and lateral-directional stall characteristics.
Fang, ShengyouYang, XiaoliJiang, TianjunFu, Yi
This paper, for the first time, applies the Divine Religions Algorithm (DRA) to three-dimensional UAV path planning. Targeting the complex terrain of urban-mountain mixed environments, we propose a novel method that incorporates multiple enhancements, including A* initialization, single-point disturbance mutation, and adaptive weighting. First, the A* algorithm is employed to generate high-quality initial paths, serving as the skeleton of the population. Innovative mechanisms such as terrain-adaptive disturbances and dynamic weight adjustment are integrated to achieve both efficiency and robustness in path optimization. Comparative experiments with Genetic Algorithm (GA) and Crowned Porcupine Optimization (CPO) show that the improved DRA algorithm exhibits significant advantages in terms of path length, safety margin, average altitude variation, average turning angle, and overall cost function. It consistently obtains superior paths and achieves faster convergence. The results demonstrate that the proposed approach provides an efficient, adaptive, and practical intelligent optimization tool for UAV path planning in urban-mountain mixed or similarly complex environments, offering promising prospects for engineering applications.
Fang, LianyuYi, Wenjun
In recent years, drone technology has seen widespread application in both civilian and military fields. By 2025, China will introduce supportive policies from multiple dimensions, including industrial development, technological innovation, and application promotion, to significantly increase the number of UAVs in use and their frequency. However, drones are prone to malfunctions due to factors such as bad weather and electromagnetic interference, which may result in serious consequences, including property damage and casualties. Therefore, improving the accuracy of fault detection and the response time of drones is of great significance. Although current research has made progress, there are still deficiencies: First, most of them rely on a single or limited data source, resulting in incomplete information and vulnerability to interference, which leads to low detection accuracy and reliability; Second, traditional methods are mostly based on fixed thresholds or simple rules, lacking real-time dynamic monitoring and adaptive analysis capabilities, making it difficult to issue timely warnings of potential faults. To this end, this study proposes a multi-scale time series prediction model based on multimodal and multi-branch, integrating multimodal data, constructing a dual-branch architecture, and combining deep learning and attention mechanisms to enhance the anomaly detection effect of unmanned aerial vehicles. A dual-branch anomaly detection model based on 1DCNN-BiLSTM and continuous wavelet transform is proposed, including a trajectory prediction difference branch and a full time series data branch. In the dual-branch output stage, the attention gating mechanism is utilized to fuse features and improve the detection performance. The experimental results show that this model performs excellently in both normal trajectory prediction and anomaly detection, providing an effective solution for drone anomaly detection.
Pu, ZhenglinZhang, Lin
Against the backdrop of accelerating urbanization and diversifying social demands, aerospace technology has extensively permeated numerous fields such as logistics and transportation, emergency and disaster relief, environmental monitoring, and urban transportation. Its application scope is expanding from traditional reconnaissance and surveillance to complex scenarios like material transportation, manned operations, and precision maintenance. Within this trend, high-payload, vertical take-off and landing (VTOL), and high-safety aircraft have become key equipment for enhancing operational efficiency across multiple sectors. Among these, high-payload ducted fan aircraft, with their high safety, excellent low-speed performance, and outstanding VTOL capability, demonstrate unique advantages in tall building fire suppression, power lines and towers maintenance, and personal flight experiences. This paper first outlines the diversified application prospects of aerospace technology, then focuses on high-payload ducted fan aircraft. It discusses the technical requirements specific to such aircraft in the aforementioned key scenarios and analyzes the critical technical bottlenecks hindering their broader application, along with potential viable solutions.
Lou, BinLi, ZhuoyuanZhang, YuansongZhou, HaoyuLi, ChengLuo, ZiniuTian, ConglingYang, Chengchuan
Multi-UAV cooperative localization can utilize information fusion between nodes to improve localization accuracy and performance on the target. Distributed state fusion estimation methods have been heavily studied in recent years, but the final estimates in the research results do not converge towards the global optimum. This paper aims to make the state estimates of each individual in the UAV formation for the target converge and converge to reliable values. In this paper, we study a multi-UAV cooperative tracking method based on adaptive weighted fusion, which first evaluates the importance of each node in the UAV formation and the reliability of the local filtering estimation results, and then assigns the weights according to the reliability of the UAV’s local state estimation of the target in the whole at the current moment. Finally, this paper verifies through simulation experiments that the method can not only accomplish the state tracking of the target, but also that the state estimates of each node in the network converge to more accurate state estimates.
Xia, ShengjiWang, ChangqingLiu, FaleiJia, ZhaoxuanZhao, Quanpu
The numerical simulation of the transformation process of multiple droplets into liquid films is a complex problem involving multiphase flow, interface dynamics, and heat and mass transfer. It usually requires the combination of fluid mechanics, interface science, and numerical calculation methods. Based on the smooth particle fluid dynamics method, this paper establishes a multiphase fluid-solid coupling interaction model among droplets, surrounding air and solid walls, and studies the dynamic change process of multiple raindrops dispersed in different grooves. The results show that when the contact Angle is small, the boundaries of multiple raindrops do not come into contact. The multiple raindrops evolve in their respective grooves and eventually form multiple raindrops that approach the steady-state contact Angle. The second situation is that the boundaries of multiple raindrops do not come into contact, the raindrops start to fuse, and multiple raindrops form a larger one. At this point, the contact point of the gas-solid-liquid phase disappears, that is, the "regulating force" of the contact Angle is 0. This paper provides important numerical simulation references for flight safety, aerodynamic performance and anti-icing/de-icing technologies during the flight of aviation aircraft.
Huo, YeChen, YonghengSun, Cunxiang
The climb gradient along the takeoff trajectory at each point during takeoff reflects the aircraft’s ability to clear obstacles and reach a safe altitude, ensuring the safety of civil flights. Airworthiness regulations specify certain requirements for the single-engine-out climb gradient. Given that the data used in conventional calculation methods are significantly influenced by the flight status during the process, this paper explores two new climb performance calculation methods based on the existing ones. A set of data was calculated, and the resulting errors were all no more than 10%, indicating that both new calculation methods are effective and reliable. Therefore, they provide a certain reference value for the climb gradient calculation of transport category aircraft.
Jiang, TianjunLiu, Tao
The structural stiffness of a manned lunar vehicle is a core indicator ensuring its stable operation in the complex lunar environment. The vehicle’s body structure must meet multiple requirements, including high stiffness, lightweight design, and adaptability to lunar surface conditions. Since lunar gravity is only 1/6 of Earth’s and the terrain is rugged and dusty, the body structure must employ a high-stiffness design to withstand driving impacts and resist deformation, thereby preventing mechanical failures or safety hazards for crew members caused by excessive structural distortion. However, excessive structural stiffness would result in an overweight vehicle body, conflicting with the spacecraft’s lightweight requirements. Thus, the structural stiffness index should be optimized to a lower value while ensuring safe operation during lunar surface driving without compromising performance. This paper calculates and determines the structural bending and torsional stiffness indicators for the manned lunar vehicle’s body through simplified model calculation and the FEA method.
Shen, ZhenghuiWu, YingjiaYang, JianfengWang, WeijunZhang, ChongfengHan, Liangliang
Test results of the composite helicopter horizontal central-wing under symmetric and unsymmetric loads showed that the strain value of the lower skin would turn from negative to positive, showing a nonlinear behavior. FEM results of the linear and nonlinear analytical approach showed a great difference. The strain value of the lower skin remains negative and decreases linearly when using a linear FEM analysis. The strain value of the lower skin would turn from negative to positive when a nonlinear FEM analysis is applied, and this result agrees well with the test results. Besides, the results of the FEM buckling analysis showed that the buckling load of the lower skin is considerably higher than the value at which the skin would show a nonlinear behavior. Therefore, the specific behavior is a result of the nonlinear property of the structure, not buckling.
Wang, ZheZhang, TiesongLi, MengjiaChen, PuhuiHuang, ZhiwenWang, Binwen
This study looks at how the human head reacts and gets injured during high-G landing impacts in spacecraft return capsules. We used a vertical drop tower system for the experiments. A standard crash test dummy, called the Hybrid III 50th, was used to imitate how astronauts sit during landing. We applied two common safety standards—the Head Injury Criterion (HIC) and the 3 ms cumulative acceleration rule—to measure head response under high-G impacts. The results show several things. First, head acceleration increases linearly as seat acceleration increases. Second, the peak total acceleration of the head is much higher than the seat acceleration. In particular, acceleration in the X and Z directions is much stronger than in the Y direction. Third, when seat acceleration went over 47.71 g, HIC exceeded the safe limit of 700, and the 3 ms head acceleration also passed the 80 g limit. This suggests that 40 g should be considered a safe upper limit for seat acceleration. This work provides experimental support for improving landing systems to protect astronauts’ heads during high-G impacts.
An, HaoWang, YafengGuo, Yazhou
When quadrotor unmanned aerial vehicles (UAVs) operate in urban low-altitude airspace, especially within complex environments, their sensor perception signals are highly susceptible to blockages, deviations, and the inclusion of high-frequency noise. These factors, in turn, induce nonlinear variations in the UAVs’ flight mechanical properties, giving rise to abnormal flight stability issues such as attitude jitter, altitude fluctuations, and trajectory deviations. To address these challenges, this paper puts forward a method aimed at enhancing the positional accuracy of quadrotor UAVs, which is based on Extended Kalman Filter (EKF) multi-sensor fusion. In conjunction with the redundant configuration of sensors, a proportional-integral controller is specifically designed to allow optical flow sensors to compensate for the speed data generated by inertial sensors. Building on the EKF method, a comprehensive data fusion model is established, encompassing both position and speed states. Leveraging the MATLAB platform, trajectory flight simulations are conducted, utilizing multi-sensor data fused via EKF, with the sensor suite including GPS, IMU, Optical Flow sensors, and Barometers. The simulation results demonstrate that this proposed method can effectively mitigate the adverse impacts of environmental interference and sensor noise on the positional accuracy of quadrotors. By continuously correcting position information and accurately estimating position states, it significantly improves the UAVs’ flight position accuracy. This research outcome lays a robust and theoretically sound foundation for in-depth investigations on critical issues related to general aviation applications, such as the safe and efficient autonomous flight, adaptive and reliable intelligent navigation, and ultra-precise and mission-critical operations of quadrotor UAVs, thereby significantly contributing to the sustained and innovative advancement of the field.
Cui, NanLiu, WenzhiLiu, HanqiWang, JingruiWang, ZhizhongZhi, Haonan
Folding wing mechanisms are widely applied in aircraft structural design. This design reduces the size of the aircraft, making it easier to store and transport. Whether the foldable wing can successfully deploy determines the completion of the flight mission. Therefore, it is crucial to study the kinematic and dynamic parameters of the mechanism during the deployment process. The deployment of the folding wing typically occurs within milliseconds. The flow field imposes aerodynamic loads on the mechanism, causing it to move, while the large deformation motion of the mechanism, in turn, affects the aerodynamic loads from the flow field. This is a typical fluid-structure interaction (FSI) process. Traditional CFD methods for solving the deployment process in a decoupled manner often result in large errors and cumbersome procedures. To investigate the aerodynamic loads and deformation of the folding wing mechanism during deployment, the ALE algorithm in LS-DYNA was selected to directly solve the kinematic and dynamic parameters of the mechanism in unsteady flow fields, guiding the design of foldable wing mechanisms.
Wei, TingTong, ZongkaiLi, Naitian
Civil aircraft, as typical complex product systems, exhibit characteristics such as a high concentration of high-tech technologies, strong interdisciplinarity, a high level of system integration, long development cycles, substantial project investments, and complex management. During the R&D process of civil aircraft projects, there are often high risks in performance, cost, and schedule. Delays in the schedule can lead to losses in project manpower and material resources, as well as project failure. A mature objective criteria system for maturity assessment provides a reference basis for determining whether the project has reached its optimal state at a specific stage, thereby reducing project management risks and increasing the probability of project success. This research will adopt a research approach combining theoretical studies with practical case analysis. First, it will conduct extensive and in-depth investigations into various maturity models and their applications across the entire product lifecycle within relevant fields. A requirement maturity model and requirement maturity KPI (Key Performance Indicator) indicators will be established to clarify the maturity status of requirements at different development stages, enabling judgment of whether the project is ready to proceed to the next development phase. Concurrently, by developing a KPI statistical system platform integrating application servers and data processing tools, a scientific and quantitative inspection mechanism will be implemented to visualize project development progress, status, and risk data. This will provide actionable insights for project decision-making and achieve effective project management and control.
Wang, YiHuang, JunkaiZhang, Xinyu
Flexible cables are widely used in aircraft and are essential for ensuring the proper functioning of critical systems and flight safety. The design and validation of these cables represent a foundational technology in enabling the transmission of electrical power and signals throughout the entire aircraft. To achieve their intended service life, appropriate protective measures and experimental verification must be implemented. Drawing on the development experience of flexible cables for a specific domestic aircraft model, this paper proposes a combined protection method designed to extend the service life of flexible cables. Experimental analysis demonstrates the practicality and reference value of this approach.
Shi, LiqingHu, HuanghuaGe, Zengwen
To ensure the successful implementation of the separation, evacuation, and return processes of manned spacecraft after long-term docking at the space station, regular on-orbit health assessments must be conducted. Based on this requirement, a technical method for evaluation through autonomous on-orbit testing is proposed. First, the docking status and characteristics of the manned spacecraft’s systems, such as information management, crew environmental control, thermal control, power management, docking function, attitude, and orbit control function, are described. Then, the functional requirements for the separation, evacuation, and return of the manned spacecraft, such as the relative measurement, the relay communication, TT&C and data transmission, image and voice, instrument display and alarm, and the attitude measurement, are analyzed. Subsequently, the on-orbit testing system, test items, test procedures, and test methods for health assessment are detailed. It also provides the design of TT&C support, the design of energy support, and the main principle explanation for autonomous on-orbit testing of the system.
Cheng, WeiNan, HongtaoTian, YeZhao, Zheng
To reduce the drag and intense heating faced by the hypersonic vehicle during flight, a novel spike–dual-disk–channel configuration is proposed, featuring a slotted channel at the head and exhaust at the second aerodisk. Numerical simulations were conducted using Fluent at 30 km and 5 Ma in free-flow. The new configuration's comprehensive aerodynamic performance were evaluated and compared to those of the single-disk and dual-disk configurations. The simulation results indicate that the new configuration exhibits superior comprehensive aerodynamic performance compared to the single-disk configuration. In contrast to the dual-disk configuration, the new configuration slightly compromises drag reduction (by approximately 1%), but achieves significantly better thermal protection (by approximately 10%).
Luo, ShenxingFang, ShuzhouYe, Chen