Abstract:The co-flow jet (CFJ) is a new concept flow control method based on blowing and suction technology. Since it was proposed, it has gradually attracted extensive attention. This paper reviews the basic principles, concepts, research methods and progress of CFJ. The development of the CFJ concept is retrospected. The basic principle, wind tunnel experiment and numerical simulation are introduced. The application research on airfoils/wings, control surfaces, rotating blades and conceptual aircraft design are presented. Finally, several critical problems in the research of the CFJ are proposed, which could guide further research.

Abstract:Casings are key components for the aero engine, and its containment performance is a necessary condition for ensuring flight safety. The types and structural forms of the casing related to containment are briefly introduced. Impact response, damage mechanism and containment ability of casings are summarized from aspects of theoretical researches, simulation analyses and experimental tests. Besides, test methods about casing containment and its researches progresses are analyzed. Numerical simulation researches about casing containment are introduced according to types of casing material. Finally, the containment research status of casings is summarized and the development tendency of casings containment is proposed from aspects of working condition, loading situations and optimization design.

Abstract:The nozzle is one of the key components in the integrated design of the aircraft body/propulsion, which directly affects the thrust-drag matching and pitching moment matching and other characteristics of the aircraft. In order to improve the efficiency of the optimal design of the nozzle, a multi-objective optimization model based on multi-fidelity surrogate model is established. The CFD results based on coarse mesh and inviscid model are used as low-fidelity data, and the CFD results based on fine mesh and SST k-ω turbulence model are used as high-fidelity data, the Cokriging models were constructed with the maximization of thrust coefficient、lift coefficient and pitching moment coefficient as optimization objectives, and the Pareto solution set is obtained by combining NSGA-Ⅱ algorithm. The optimization results show that the three aforementioned objectives are improved by 2.94%, 13.0% and 40.6% respectively with the error less than 0.5%, and the sensitivity analysis is completed; the optimized flow field wave system structure is more complex which changes the wall pressure distribution law; compared with Kriging model, Cokriging model has considerable prediction performance and saves 62% of the construction cost.

Abstract:UAV have gradually replaced manned aircraft to combat with advantages such as high effectiveness and flexible autonomy. Multi-UAV cooperative cambat mission planning has attracted widespread attention. An end-to-end cooperative attack intelligent planning method for multi-UAV based on deep reinforcement learning (DRL) is presented to overcome the shortcomings of traditional mission planning algorithms, such as dependence on static, low-dimensional simple scenarios and slow on-board computing power. The SEAD mission planning is modeled as the Markov decision process. The SEAD intelligent planning model based on PPO algorithm is established and the general intelligent planning architecture is proposed. We introduce domain randomization, maximizing the entropy of policy and the lower-layer network parameter sharing training tricks, to improve the effectiveness and generalization performance of PPO. Simulation results show that the DRL-based model can achieves fast and fine planning through offline training and online planning, adapt to unknown, continuous and high-dimensional environment situation, which reflects provides a new idea for intelligent planning research.

Abstract:With the gradual opening of China"s low-altitude airspace, UAVs are increasingly used in various fields. Facing the rapid growth of flight flow, there is an urgent need to improve the safety of UAV operations, the key of which is to solve the problem of collision avoidance and early warning in UAV flights. In this paper, we establish a reasonable spatial model around the UAV, determines the conflict detection algorithm based on the longitude, latitude and altitude information of the UAV provided by the ADS-B message, screens the UAVs with conflicts in the horizontal and vertical directions, and selects the avoidance strategy of adjusting speed and heading. Through Matlab simulation experiments, the results show that the algorithm can effectively screen out conflicting UAVs and can perform three-level avoidance for them, which provides an effective guarantee for the flight safety of UAVs.

Abstract:The human error of air traffic controller is the main cause of the aircraft collision in the air, and it is a difficult problem to effectively predict the failure probability of human factor of Air Traffic Control (ATC). For this, on the basis of Technique of Human Error Rate Prediction (THERP) and Cognitive Reliability and Error Analysis Method (CREAM), a hybrid prediction method is proposed for failure probability of ATC human factor. When using THERP to evaluate the complex behaviors of controllers, it is difficult to accurately quantify various effects with fewer available data and rough correction calculations. CREAM is introduced to make up for the shortcomings of THERP by quantifying human behavior factors from the early stage and incorporating them into the background reasons for comprehensive consideration, in order to improve the prediction reliability for failure probability of ATC human factor. The actual example shows that the method can not only carry out a more scientific and reasonable analysis, but also find the weak links to formulate targeted control measures. This provides an effective analysis method for studying the failure probability prediction of ATC human factor.

Abstract:Bayesian approach is commonly used in the reliability assessment of repairable systems with small samples in fields such as aerospace. The knowledge about the informative prior and/or failure data from repairable systems may not be collected as precisely as possible due to uncertain factors, but can be obtained in terms of lower and upper bounds. For the case of such interval uncertainty information, this paper studies the Bayesian reliability analysis approach of multiple repairable systems whose failure process follow the power law process (PLP). Under the informative priors, the interval-based Bayesian posterior analysis of the PLP is essentially transformed into solving the constrained optimization problem in which the objective function is just the traditional Bayesian posterior analysis result of the PLP under the informative priors. Considering that the objective function in the constrained optimizations is complicated multiple integrals with no closed-form expressions and is highly nonlinear, the covariance matrix adaptation evolution strategy is employed to find the optimal solution of the optimization problem. Specific engineering examples verify the feasibility and effectiveness of the proposed approach. The proposed interval-based Bayesian approach of the PLP can provide a reference method for the reliability assessment of repairable systems with small samples in consideration of the influence of uncertain factors.

Abstract:The direct maintenance costs (DMC) is the primary economic index that the aircraft manufacture guarantees to the operator. DMC is regarded as a reference baseline for monitoring and controlling the maintenance expenses during the operating phase of aircraft. In this paper, by considering the guaranteed DMC value and the obligated maintenance interval listed in schedule maintenance requirements, we put forward an approach to determine the conductible window of a preventive maintenance task. The data items and process for employing the method are introduced. The economic index of a preventive maintenance task is defined and the principle for obtaining the conductible window is addressed. The conductible window is the interval within which the maintenance expense is regraded as acceptable. To control and optimize the maintenance expense, the aircraft operator can plan to repackage multiple maintenance tasks, if the conductible windows of them overlaps each other.

Abstract:In view of the Continuous Airworthiness event of commercial aircraft, combined with the analysis of the impact on the cost and income of both manufacturers and airlines. Based on the analysis methods of manufacturers" life cycle cost and airlines" operating cost and income, this paper proposes an economic analysis model of Continuous Airworthiness activities of commercial aircraft, and analyzed the data of specific aircraft type. The model can be used analyze the initial operation cost of new model development according to different event classification and its cost and benefit impact, and further predict the Continuous Airworthiness cost of model maturity based on the learning curve theory.

Abstract:In order to study the problem of parking space allocation under resource-constrained conditions such as tractors and controllers, first, an optimization model for parking space allocation with the least aircraft delay time and the largest bridge rate as the multi-objective is constructed. and use heuristic algorithm to solve; secondly, a scene simulation model is built to verify the reliability of the algorithm. Finally, an example was verified through Beijing Daxing International Airport. The results show that compared with the actual operation of the airport, the parking space allocation optimization model established in this paper has reduced aircraft delay time by 25.5% and increased bridge rate by 8.8%. It shows that the parking space allocation strategy proposed in this paper can realize the optimization of surface delay and bridge ratio under the condition of limited resources.

Abstract:The influence on aerodynamic optimization of flying wing configuration is studied based on discrete adjoint method, which 10%, 0%, -10% stability margin are considered in the optimization process, respectively. The free-from deformation (FFD) technique is used to achieve the parametrization of surface unstructured grid, the control point of FFD is selected to serve as design variable, then flowfield and adjoint equation is solved to obtain objective values and residual, the sequential quadratic programming(SQP) algorithm is utilized to obtain the gradient of control points, the final configuration is obtained by multiple iteration. The results show that the adjoint optimization can evidently improve the maximum lift-to-drag ratio under the constraint of geometric thickness and moment trim, and the increment exceeds 8% at these three conditions. The increment of cruise lift-to-drag ratio appears to reduce with the increase of stability margin while lift coefficient is fixed, the lift-to-drag ratio can increase 5.08% when the stability margin is 10%. Therefore, the optimization with higher stability margin can reduce can reduce trim drag and increase cruising lift-to-drag ratio to improve the flight performance of flying wing.

Abstract:A type of vortex generator is designed for a certain type of mountain transport aircraft, which is installed on the lower surface of the horizontal tail to improve the flow pattern of the horizontal tail at a negative angle of attack and delay the negative stall of the horizontal tail. The flow characteristics and mechanism of the horizontal tail airfoil with and without vortex generator are studied by numerical simulation method, the pitching moment characteristics of the airfoil are analyzed, and the flow control effect of the vertex generator is verified; The vortex generator is installed on the lower surface of the horizontal tail from the wing root to the position of 80% wingspan, and the aerodynamic characteristics of the aircraft with and without the vortex generators are compared and analyzed. The calculation results show that the negative stall angle of attack and the pitching moment inflection point of the horizontal tail with the vortex generator is delayed by 4°, and the flight boundary of the aircraft is enlarged.

Abstract:Abstract：The side wall interference and disturbance reflection from the front end wall of the sealed chamber in an extremely low wind speed calibration facility in dynamic operation mode might have influence on the flow field inside the chamber, thus affecting the calibration accuracy. These wall effects are investigated through numerical simulation in this paper. The moving overlapping grid technique is used in solving the URANS equations simulating the flow field in the chamber to investigate the effects of side-wall interference and the disturbance wave reflection from the front (upstream) end wall on the interior flow field and calibration. The flow fields in the cases with and without side walls are computed，both the computed flow velocity contours and the x-direction velocities on the trajectory line of the top center point of the probe strut in the two cases are compared. For the front end wall reflection of the strut rod disturbance, the boundary conditions with and without front end wall are used respectively in computing the flow field in the chamber. The computed flow field velocity contours at several instants in the two cases, and the x-direction velocities of the two cases on the trajectory line of the top center point of the probe strut rod are compared respectively. The computed results show that both the wall effects caused by the selected chamber cross section size and the front end wall reflection of disturbance have negligible influence on calibration accuracy. The numerical simulation provides a valuable technical support to the design of the sealed chamber in the calibration facility.

Abstract:It is important and necessary to study the water landing overload of wing-in-ground(WIG) aircraft, as the damage or buckling step is most likely occurred in body steps, especially in double-stepped cases. The Arbitrary Lagrangian-Eulerian (ALE) finite element method was utilized to simulate the water landing of a wing-in-ground aircraft, and the penalty function method was used in the two-phase interface fluid-solid interaction problem. The effect of different parameters such as horizontal flight velocity, falling velocity, pitch angle on the immersion depth, and overload was analyzed. The results showed that the pressure maxima of the aircraft landing water all occur at the step in this paper. With the increase of the pitch angle, the peak of vertical overload rises and then falls, while the peak of horizontal overload keeps reducing. When the pitch angle is 7°, the vertical overload peak reaches the highest, which is 1.4 times that of the lowest overload in the pitch angle of 15°. On the other hand, the peak of the horizontal overload rises as the horizontal component of flight velocity increases, and it is visible that there is no discernible effect on the peak of vertical overload. Meanwhile, an approximately linear relationship appeared between the peak of vertical overload and the square of falling velocity in this paper.

Abstract:Abstract：The existing specifications and requirements for the general layout parameter design of aircraft landing gear are mainly applicable to traditional fighters. If the landing gear of pusher propeller reconnaissance and strike UAV is designed according to these specifications and requirements, it will bring many problems. This paper starts with the layout and flight characteristics of the pusher propeller reconnaissance and strike UAV, analyzes the definition and connotation of the landing gear general layout parameters, and puts forward a design suitable for the landing gear general parameters and general layout of the pusher propeller reconnaissance and strike UAV. Through the analysis of takeoff and landing characteristic of the pusher propeller integrated reconnaissance/strike UAV, The Tail Down Angle(θTD) can reduce and suggest：≥6°(static, contain clearance); The Turn Over Angle(θTO) can reduce and suggest：11°～12°(static); The Parking Angle can reduce and suggest：-2°～-1°. The main landing gear arrangements can choose this type, which are installed onto fuselage of UAV, at extended position, the main landing gear is at the lower side of fuselage, being shape / \. By comparing the landing gear layout parameters of predator B UAV, the effectiveness of this design is verified. In addition, this design is applied to the landing gear general parameters and general layout of the Wing Loong UAV, and good results have been achieved..

Abstract:Since SiCf/SiC composite is typical heterogeneous and anisotropic material, the metal material quality evaluation system is not fully appli-cable. There is an urgent need to establish a suitable surface quality evaluation method. Combined with the ultrasonic vibration-assisted milling-grinding test, comparing the stability of the 2D roughness Ra and 3D roughness Sa of the milling-grinding surface, and exploring the influence of the size of the Sa measurement area on the measurement results. Combined with the macroscopic, microscopic and 3D morphology, analyzing and studying the experimental results. Based on the area ratio of the more obvious areas with the appearance of pits on the milling-grinding surface, the analysis and research on the surface quality are carried out. The results show that Sa is more suit-able as the characteristic parameter of milling-grinding surface roughness of SiCf/SiC composites. And the Sa minimum measurement area size is 7mm×7mm. Based on roughness analysis, the milling-grinding surface quality can be further evaluated by combining macro-scopic, microscopic and 3D topography. Using the area ratio of obvious pits on the surface, the quantitative analysis of the area that has a great influence on the surface quality is basically realized.

Abstract:The water scooping system is the main part of the extinguishing aircraft system for realizing the water scooping function. Improving the design of water scooping system can shorten the time of water scooping and improve fire extinguishing efficiency as soon as possible. In this paper，CFD-based simulation analysis is performed on the original water scooping system of a certain type of amphibious aircraft.The results show that the unreasonable position of the outlets of the original water scooping system makes the volume flow difference between the two outlets are too large，and the water scooping time is to long, which is not conform to the water scooping requirements.In order to reduce the scooping time, two structural forms of water scooping system at different outlet positions are designed,and obtain the outlet position model with small volume flow difference by simulation analysis,and design the battle model with three different position base on the outlet model with small volume flow difference.when the baffle is 10mm from the center line of the water scooping pipe, the flow rate of the two outlets is roughly the same，and the water scooping time is 50% shorter than that of the original configuration of water scooping system, which is great significance to the subsequent design of the water scooping pipeline of amphibious aircraft.

Abstract:Accurate prediction of aviation material requirements for off-site missions is one of the main elements of a good trip assurance. To this end, this paper proposes a combination of grey correlation (GRA), improved particle swarm algorithm (IPSO) and support vector machine (SVM) as a method for predicting aviation material. Firstly, GRA is applied to analyse the factors influencing the demand for carriage of aviation materials; secondly, the particle swarm algorithm (IPSO) is improved by introducing activity factors and non-linear inertia coefficients, and the SVM parameters are optimised by IPSO; finally, the optimised SVM model is used to predict the demand for aviation materials. The simulation results show that the GRA-IPSO-SVM method has a 0.16 decrease in RMSE, a 2.18% decrease in MAPE and a 0.7s decrease in prediction time compared with the PSO-SVM method.

Abstract:With the development and operation of civil aircraft, aircraft main manufacturers need to simultaneously develop and verify the Preliminary Master Minimum Equipment List (PMMEL) item to improve the reliability of civil aircraft dispatch and obtain approval from the Administrator. In order to manage the relevant data generated during the development and verification of the PMMEL item through a standardized method, the development and application of relevant development platforms are urgently needed. This article first studies the implementation process and industry requirements of the PMMEL item development, and clarifies the data management requirements of the PMMEL development and verification process based on the ATA2300 standard. On this basis, the PMMEL development platform was constructed. After a complete system functional test to ensure the reliability of the platform, the actual PMMEL project data was further used to test for proof of concept, so as to prove the compliance and matching degree of the platform to the business. The results show that the development and verification data of the PMMEL project are further standardized through the construction and use of the platform, which can lay an important data foundation for the compilation of the later operation support manual. The continuous operation of the company will carry out further intelligent expansion.

Abstract:The implementation of green supply chain in aviation development enterprises involves many project stakeholders. The participation expectation of project stakeholders has an important impact on the implementation of green supply chain. Based on the analysis of the stakeholders in the implementation of green supply chain in aviation development enterprises，through literature research，the influencing factors of the plementation of green supply chain in aviation development enterprises are extracted preliminarily from the perspective of project stake?holders preliminarily，the questionnaire survey and factor analysis are used to further screen and classify these influencing factors，and an aviation development enterprise is combined for application analysis. The results show that the implementation of green supply chain in aviation development enterprises is affected by a total of 9 factors in 4 categories，which are expected income，cooperation mechanism，market driving force and the degree of enterprise green management