Gas turbine engine is a comprehensive embodiment of the level of national science, technology and industry. Fault diagnosis is an important guarantee for its safe and reliable operation and an essential indicator of engine advancement. However, due to the complicated structure, highly integrated system, harsh service environment, variable mission profiles, the constraints of limited online testing conditions, and the poor supportability of diagnostic information acquisition, the fault diagnosis for aeroengine faces multiple challenges. In this paper, the research status in China and abroad is firstly reviewed and analyzed from three aspects: gas path analysis and performance evaluation, mechanical fault diagnosis and information fusion. Then, the exciting key problems and challenges in the current research are pointed out. Finally, the future development trends are discussed.

TDOA/FDOA localization is an important wireless positioning mechanism for moving emitters， and its location accuracy is greatly affected by measurement errors of TDOA/FDOA and prior measurement errors of sensor models （including sensor position and velocity）. To improve the localization performance under the condition of high-level measurement errors， a TDOA/FDOA cooperative localization method for multiple disjoint sources is proposed based on weighted multidimensional scaling analysis in this paper. The proposed method consists of two calculation stages： Stage-a and Stage-b. Specifically， in Stage-a， two groups of scalar product matrices in multidimensional scaling analysis are employed to form the positioning relationship， which is further used to yield the solutions for the locations of multiple disjoint sources and sensors by constructing a weighting matrix. In Stage-b， a constrained minimization model is established based on the intermediate variables introduced in multidimensional scaling analysis to determine the estimation errors in Stage-a. By solving this optimization problem， the expression for the localization errors in Stage-a are obtained， so as to refine the position and velocity estimates of the multiple disjoint sources as well as the sensors. In addition， the first-order error analysis is employed to prove that the proposed method can asymptotically reach the Cramér-Rao Bound （CRB） accuracy. Simulation results show that the new method outperforms the existing TDOA/FDOA positioning methods.

The engineering advancements during the last two decades have presented opportunities as well as challenges for the Engine Health Management (EHM) system development of civil aero-engines. This R&D review provides an in-depth discussion on EHM needs, gaps and potential solutions/future R&D development directions, focusing on the "up-stream" EHM development modules: Engine gas path diagnostics and prognostics, mechanical diagnostics and prognostics, FADEC diagnostics and prognostics. Results shows the Unscented Kalman Filter (UKF) method and deep-learning neural networks have shown promises on improving the engine gas path diagnostics accuracy; composite fans have found widespread applications in turbo-fan engines; powder metallurgy has seen more and more applications on fabricating aero-engine parts with complex shapes; the accuracies of metal particle sensing technologies have witnessed significant improvements, with technology readiness level matching the aero-engine needs, and paved the way for fusion diagnostics with vibration signal. The result also show that electrification and intelligentization trends of FADEC system presents new challenges for the diagnostics of the traditionally centralized control architecture.

UAV aerial images have more complex backgrounds and a large number of dense small targets compared with natural scene images, which impose higher requirements on the detection network. On the premise of ensuring real-time object detection, a YOLOv5-based UAV real-time dense small object detection algorithm is proposed for the problem of low accuracy of dense small object detection in UAV view. First, combining Spatial Attention Module (SAM) with Channel Attention Module (CAM), the fully connected layer after feature compression in CAM is improved to reduce the computational effort. In addition, the connection structure of CAM and SAM is changed to improve the spatial dimensional feature capture capability. In summary, a Spatial-Channel Attention Module (SCAM) is proposed to improve the model's attention to the aggregated regions of small targets in the feature map; secondly, an SCAM- based Attentional Feature Fusion module (SC-AFF) is proposed to enhance the feature fusion efficiency of small targets by adaptively assigning attentional weights according to feature maps of different scales; finally, a backbone network is introduced in the Transformer in the backbone network, and use the SC-AFF to improve the feature fusion at the original residual connections to better capture global information and rich contextual information, and improve the feature extraction capability of dense small targets in complex backgrounds. Experiments are conducted on the VisDrone2021 dataset. The effects of different network scale parameters and different input resolutions on the detection accuracy and speed of YOLOv5 are first investigated. The analysis concludes that YOLOv5s is more suitable to be used as a benchmark model for UAV real-time object detection. Under the benchmark of YOLOv5s, the improved model improves mAP50 by 6.4% and mAP75 by 5.8%, and the FPS for high-resolution images can reach 46. The mAP50 of the model trained at an input resolution of 1504×1504 can reach 54.5%, which is 11.5% better than that of YOLOv4. The accuracy is improved while the detection speed FPS remains at 46, which is more suitable for real-time UAV object detection in dense small target scenarios.

The electrification degree of airborne equipment continues to increase with the development of science and technology. Owning to this, failure in aircraft power system is posing an increasing threat to flight safety, which granted necessity to fast and accurate health state assessment. The commonly used data-driven fault diagnosis method cannot make use of expert knowledge. Meanwhile, the result of data-driven method is lack of interpretability, and therefore, limits its application in real practice. Knowledge graph has the ability to normalize the storage of such unstructured data as expert knowledge and use it for diagnosis. Moreover, knowledge graph can utilize the unstructured knowledge and supply a reasonable explanation for the cause of the failure. However, in the field of fault diagnosis, there are still few studies on the application of knowledge graph technology. In this article, a knowledge graph construction and application technology for aircraft power system fault diagnosis is proposed. First, ontology of the knowledge graph, which specifies the entity and relation types in the knowledge graph, is constructed based on the priori expert knowledge. Then, Bi-Directional Long Short-Term Memory (Bi-LSTM) method is trained with BMEO-tagged corpus and utilized to extract entities from the unstructured texts. After that, an attention-based Bi-LSTM algorithm is trained with relation-tagged corpus and then utilized to realize relation extraction. Finally, the knowledge graph for aircraft power system fault diagnosis is constructed based on the extracted entities and relations. A fault isolation manual of aircraft power system is used as raw corpus data in the case study to verify the effectiveness of the proposed method by the indicators of precision and recall. Based on the knowledge graph, intelligent searching, recommending and Q & A are realized, which strongly support the application prospect of knowledge graph in the field of fault diagnosis.

Lightweight is a substantial theme in the research and development of aerospace and aeronautical equipment due to its decisive impact on the comprehensive performance and operational efficiency of the equipment. Over the past decades， a handful of innovative optimization design approaches， emerging high-performance materials， and revolutionary manufacturing technologies have been uninterruptedly developed， and the level of lightweighting in aerospace and aeronautical equipment has been significantly advanced. However， the increasing demands for comprehensive performance and multifunctionality of the next generation of equipment present serious challenges to existing lightweight design and manufacturing technologies. Therefore， with a particular emphasis on the layout design， electromechanical system design， materials and structures， high-performance manufacturing and assembly， this paper analyzes the posed challenges and future perspectives.

Based on a comprehensive coverage of the civil aero-Engine Health Management (EHM) needs and goals, this research and development review first analyzes the current status quo & industry trends from the perspectives of the full blown Condition Based Maintenance Plus (CBM+) process, then addresses the challenges and gaps, and points out the critical paths for the future EHM research and development. Furthermore, this research and development review provides in-depth discussions on needs, gaps, and potential EHM solutions/future developments of the three "down-stream" EHM development modules: off-board comprehensive diagnostics, engine life management, intelligent condition based mro (maintenance, repair, overhaul).

The superconducting machine has prospects of a wide range of applications in aviation electric propulsion due to its advantages such as small size， high power density， and high efficiency. The characteristics and current situation of the superconducting pure/hybrid electric drive systems are compared， showing the importance of the superconducting machine for high power aviation electric propulsion. In view of different requirements for motors and generators for the superconducting electric drive system for high power aviation electric propulsion， the operating principles and structural topologies of those prototypes of High Temperature Superconducting （HTS） machines studied in the past are reviewed and classified， and the advantages and disadvantages are summarized and analyzed. On this basis， the key technologies of superconducting machine are outlined in terms of superconducting technology， AC superconducting armature， rotor technology， cryogenic technology and insulation technology. Under the background of aviation electrification， the progress in the application of superconducting electric drive system in aviation electric propulsion is outlined， and future development of superconducting electric aviation is also discussed.

Next-generation Supersonic Transport Aircraft （STA） has become one of the main future directions for civil aviation transport. Compared with subsonic civil aircraft， STA involves a series of technical problems such as sonic boom and is confronted with more strict performance indexes， imposing higher requirements for the conceptual aerodynamic configuration design. This paper classifies the existing supersonic civil aircraft configurations in the world into three generations according to the design strategy and the main technical features. The first-generation configurations mainly adopt a delta wing/ double-delta wing platform to achieve supersonic civil flight and balance both high and low speed performance. The second-generation configurations take the low-boom and low-drag performance into consideration and employ the highly-swept arrow-wing tailless layout， while the third-generation focuses more on the multi-disciplinary comprehensive performance and the technical feasibility. Almost all these configurations adopt the T-tail or V-tail layout and the engine nacelle knapsack or tail crane layout. The technical bottlenecks and difficulties of the new generation STA conceptual-aerodynamic configuration design are then presented. The progress and state of the art of the conceptual design technology， low-boom design technology， supersonic drag reduction technology， and airframe-propulsion integrated design technology are reviewed. Finally， the development trend of a new-generation STA configuration is discussed， stressing some of the key scientific and technical issues to be broken through. Supersonic business jets or small and medium class STA will be the priority in the near future， with technical features approximating those of the third-generation configurations. Comprehensive performance and engineering realizability of factors such as sonic boom， drag reduction， airframe-propulsion integration， aeroelasticity， and man-machine efficacy should be the mainly concern in future research.

SensorCraft is an early warning and surveillance and information synthesis aircraft proposed by the Air Force Research Laboratory， with high ceiling and long endurance. It adopts the platform-payload integration technology， with the dual features of the aircraft and sensor. Coupling of multiple elements between platform and payload means that the overall layout design is different from that of the traditional Intelligence， Surveillance and Reconnaissance （ISR） vehicle. Flight conditions and performance indexes bring new challenges to the aerodynamic design. Aeroelastic problem of large aspect ratio flexible wing not only worsens flight performance， but also leads to loss of electromagnetic performance of wing conformal antenna. This paper summarizes the technical characteristics of SensorCraft， expounds the development history of the United States SensorCraft system from two aspects of the flight platform and conformal antenna. From the perspective of technical characteristics， key technologies supporting SensorCraft are sorted out， such as integrated layout design， laminar drag reduction， gust alleviation， conformal antenna design， deformation measurement & reconstruction， and electromagnetic performance compensation. Relevant applications are introduced. The development trend of this aircraft is also discussed in terms of the flight ability， stealth ability， perception ability and coordination ability of the aircraft， so as to provide reference for the new ISR aircraft.

The development of reusable launch vehicles is the persistent pursuit of aerospace industry. Although the first flight of the fully reusable SpaceX two-stage heavy-lift starship was successfully launched， the starship was ultimately self-destructed due to the loss of control in the subsequent flight. After reviewing evolutionary design and the first flight experience of the heavy-lift starship， this paper analyzed the application modes of the heavy-lift starship based on the overall scheme， identified the key technologies involved， and summarized its impact on aerospace industry. Finally， the enlightenment and suggestions of the heavy-lift starship’s achievements to China’s aerospace industry are provided.

As application scenarios become more complex， the need for autonomous motion planning techniques which aims at generating collision-free path （trajectory） becomes more urgent. Although a large number of planning algorithms adapted to different scenarios have been proposed already， how to properly classify the existing results and analyze the advantages and disadvantages of different methods is still a problem that needs in-depth consideration. In this paper， the basic connotation of motion planning and the key steps of classical algorithms are explained. Secondly， aiming at the contradiction between real-time performance and the quality of solution path （trajectory）， the existing algorithm acceleration strategies are analyzed and summarized hierarchically based on whether differential constraint is considered. Finally， facing the new requirements of planning under uncertainty （i.e.， sensor uncertainty， future state uncertainty and environmental uncertainty） and intelligent planning， the latest achievements and development direction in the field of motion planning are reviewed. It is expected that the review can provide ideas for future research.

Technological breakthroughs have once again spawned a lot of attention to the commercialization of Urban Air Mobility （UAM） in urban low-altitude airspace. The urban low-altitude airspace environment is complex， the density of urban air traffic flow in commercial scenarios is high， and the specifications of vehicles are not uniform. As a new infrastructure for UAM， low-altitude public routes are an important means for UAM to carry out refined management. However， the planning methods of low-altitude public routes， the required infrastructure， and the urban air traffic operation and control mode are still unclear. In response to the above issues， this article sorts out the basic concepts and development history of UAM and low-altitude public air routes， as well as UAM management based on low-altitude public air routes； In addition， an UAM operation management framework is proposed. Suggestions and countermeasures are provided on the possible responsibilities of relevant administrative departments in the development UAM； Finally， the construction method of low-altitude public routes network， the difficulties in the development process of UAM and implementation suggestions are summarized， in order to shed light on the healthy and orderly development of the UAM.

With the increasing convenience of data acquisition for aerial photography of Unmanned Aerial Vehicle （UAV）， the multi-target detection and tracking technology based on the UAV platform has developed rapidly and has broad prospects for applications in civil and military fields. In recent years， the rapid progress of in-depth learning has also provided a variety of more effective solutions. However， the challenging problems such as sudden changes in the appearance of the target， serious occlusion of the target area， and disappearance and reappearance of the target from the perspective of UAV have not been completely solved. In this paper， we summarize the algorithms for multi-target detection and tracking in UAV aerial video based on deep learning， and summarize the latest progress in this field， including multi-target detection and multi-object tracking. The multi-object detection module is divided into two parts： two-stage and one-stage detection. For the multi-object tracking module， according to the two classical frameworks of tracking-based detection and joint-detection tracking， the principles of the two algorithms are described and their advantages and disadvantages are analyzed. Then， the existing public data sets are statistically analyzed， and the optimal schemes of the benchmark challenge VisDrone Challenge in the field of multi-target detection and tracking based on UAV aerial video in recent years are compared and analyzed. Finally， the paper discusses the urgent problems of multi-object detection and tracking from the perspective of UAV and the possible research directions in the future， providing a reference for the follow-up researchers.

In view of the current situation of the future battlefield, such as high complexity of the environment, strong antagonism of the game, high real-time response, information incomplete, and boundary uncertainty, manned/unmanned cooperative combat system can become the core key to win the future and space battlefield by means of its advantages of superposition release of effectiveness, complementarities of combat weaknesses and high efficiency of action coordination. This paper focuses on the research status of manned/unmanned cooperative combat. It is a new direction of high difficulty, rapid development, broad application prospect and multidisciplinary combat. The research status of manned/unmanned cooperative combat is summarized from three aspects: system concept, key technologies and challenges. It focuses on the definition of system combat, winning mechanism and application process. The key technologies such as detection and situational awareness, mission planning, command and decision making, formation control, and effectiveness evaluation are expounded. Finally, the challenges to be solved in the future battlefield of manned/unmanned cooperative combat are analyzed. It provides new development ideas for future intelligent combat technology.

Morphing aircraft， capable of real-time shape deformation according to task requirements and flight conditions to achieve optimal flight performance， has emerged as a significant direction for the future development of aircraft. This paper reviews the research status of deformation modes and key technologies of aerodynamic layout design for morphing aircraft. Firstly， the development of morphing aircraft can be divided into two stages by the progression of time： the mechanical deformation stage and the flexible and muti-dimensional deformation stage. Then， this article summarizes morphing solutions for different parts of the aircraft， namely， the head deformation， wing deformation， power plant deformation， and combined deformation. It particularly explores the developmental history of various wing morphing schemes， discusses their applications in different aerodynamic configurations including variable sweep wing， variable forward sweep wing， folding wing， telescopic wing， oblique wing， continuous variable curvature wing， and analyzes their aerodynamic and stability characteristics， respectively. Next， the implementation objectives of morphing aircraft are summarized and divided into three types： single domain optimal variable configuration， multi-domain fusion variable configuration， and one vessel multi-energy variable configuration. Subsequently， compared with fixed shape aircraft， the key technical challenges in aerodynamic layout and overall coordination design， time-varying aerodynamic effect evaluation， aerodynamic layout scheme optimization， and multidisciplinary coupling design derived from the implementation of morphing aircraft are analyzed， with particular focus on the research progress and current status of dynamic aerodynamic calculation methods and aerodynamic optimization design technologies for morphing aircraft. Finally， the future research direction and development prospects of morphing technologies are envisioned. Targeting at the needs of wide velocity domain and large airspace flight， exploring new conceptual deformation methods that can improve the performance of multiple flight missions and establishing intelligent morphing design model and multidisciplinary strong coupling integrated design system will become important development trends.

Blade tip clearance is a key parameter in the process of aeroengines design and test, which directly affects the efficiency and safety. Real-time online monitoring of blade tip clearance for aeroengines has become an essential item in the test program. With the development of new aeroengines, blade tip clearance measurement technologies become more mature and in-depth. This paper introduces the basic measurement principle of blade tip clearance, describes the typical structure and common measurement process of the system, and summarizes six key technologies of the online blade tip clearance measurement. Measurement methods including the discharge probe method, the optical fiber method, the capacitance method, the eddy current method and the microwave method are analyzed in details to introduce their working principles, characteristics, research progress and future research directions. Research results and the latest products of various measurement methods are compared and summarized. The development trend and prospect for blade tip clearance measurement are put forward. Key research directions of the blade tip clearance measurement are summarized from six aspects, which provide references for the follow-up research.

With the development of liquid rocket engine technologies， structural dynamic problems become one of the key factors affecting the life and reliability of engines. In the past decades， the design concepts and methods of the engine gradually developed from the initial static strength and safety life design to the combination of dynamic and static strength， and economic life design， which were widely used in engines， significantly improving the working reliability of the engine structures. However， the increasing size and complex structure and the extreme harshness of the working environment for the new rocket engines require urgent solution to the technical problems of engine structural dynamic design to meet the needs of high performance， high reliability， light weight and reusability. This paper reviews the key technologies such as load prediction， dynamic modeling and model updating， dynamic strength assessment and life prediction， and anti-fatigue design on account of dynamics optimization， based on the analysis of typical dynamic problems in engine structures. The research summary and prospect are also presented. This review will provide guidance for the development of structural dynamic design technology of liquid rocket engines.

Considering the dissociation of combustion products， this paper conducts research on modeling of the working process of the solid rocket scramjet using the Brayton cycle method. Then， the theoretical performance of the engine is analyzed， and the effects of flight parameters and fuel types on engine performance are studied. The flight envelope of scramjet engine is also discussed. The main conclusions are as follows. The performance of solid rocket scramjet decreases with the increase of flight Mach number and flight altitude. When the working equivalent ratio increases， the gravimetric impulse and volumetric impulse decrease， but the specific thrust increases gradually. When the working air-fuel ratio increases， the specific thrust decreases， but the gravimetric impulse and volumetric impulse increase gradually. In the range of air-fuel ratio from 5 to 27， the volumetric impulse of the engine fueled with solid propellant has obvious advantages， but the specific thrust and gravimetric impulse are inferior to the engine fueled with hydrogen and kerosene. Compared with that fueled with hydrogen and kerosene， the boron-based solid propellant scramjet can work in a wider range of Mach numbers， which indicates that the solid rocket scramjet has a potential of wide flight envelope.

For the high-order heterogeneous swarm systems with different intra-layer cooperative control objectives and inter-layer coordination couplings， a definition and the framework for formation-containment tracking control of the swarm systems are proposed. A tracking-leader with time-varying input is applied to generate the macroscopic reference trajectory for the whole swarm systems， overcoming the shortcoming of existing formation-containment control approaches， i.e.， they cannot be used to get an effective control of the macroscopic movement of the whole system. Considering the influences of switching topologies， a distributed formation-containment tracking protocol and a multi-step design algorithm are proposed based on the robust adaptive estimation approach and the predefined containment control strategy. With inter-layer coordination couplings， sufficient conditions for achieving formation-containment tracking by the heterogeneous swarm systems with switching typologies are given using the common Lyapunov stability theory. A simulation example for a group of unmanned aerial vehicles and unmanned ground vehicles is given to verify the effectiveness of the proposed controller.