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As shown for structural improvable steel 40ХН2МА-Ш, the regulated mechanical properties of the material are achieved at an austenitization temperature of 850°C in the process of heating for quenching due to the formation of a microstructure with the magnitude of the initial austenitic grain with number 8-9. As found, the grain with number 5 obtained by heating above standard quenching temperatures does not provide the necessary mechanical properties of 40XH2MA-Шsteel. The obtained data correlate well with the known results of studies of this steel. The requirement given in the technical specifications, namely, 'the size of the austenitic grain should be no larger than number 5' is intended for the material of the workpiece. This standard cannot be used for structural steels after final heat treatment. With this in mind, it is proposed to carry out the inspection of parts made of 40ХН2МА-Ш steel and other structural steels in compliance with the requirements of technical specifications, namely, to test mechanical properties. [ABSTRACT FROM AUTHOR]

The fused deposition molding (FDM) process is a 3D printing molding process that has received extensive attention and research because of its free molding, strong designability and rapid prototyping. This further expands the application of continuous fiber reinforced composites. This paper reviews the forming principle, process method, equipment and printing materials of the FDM process for continuous fiber reinforced composites. The effects of process parameters, impregnation state and path planning algorithm on the mechanical properties and surface quality of 3D printed continuous fiber reinforced composite samples are analyzed. The problems encountered in the current FDM process and technology development are summarized, and suggestions for the key directions of future development are proposed.

With the large-scale application of radar detection technology in the military field, military combat weapons, such as aircrafts, have been seriously threatened in complex environments. Developing composite materials with the integration of elasticity and microwave absorption performance to achieve high mobility, high cruise and stealth characteristics of military aircrafts whitin radar detection is one of the key measures to improve their survival and military combat capabilities. In this paper, the microwave absorption mechanisms of elastic polymer-based composites are reviewed, and various factors affecting the microwave absorbing and elastic properties are analyzed. The development direction of elastic polymer-based microwave absorbing composites in the future is expected.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recently, new wireless communication systems within aircrafts cabins have drawn higher attention due to the growing demand of passenger services and applications and their corresponding requirements and constraints. In this regard, the fifth generation (5G) of wireless communication becomes an attractive and promising alternative to enable aircraft passengers’ comfort and entertainment along the flight, considering its potential benefits in term of high data transfers and low latencies. Nevertheless, general population concern about radio frequency electromagnetic fields (RF-EMF) safety in general and, in particular to the environmental exposure at which we are all exposed in these flights, increases at the same time. Thus, in this work, we present an experimental campaign of measurements for current passengers’ environmental exposure assessment, performed in different real generalizable type of flights and aircrafts’ cabins, in order to provide current RF-EMF exposure insight within these complex heterogeneous environments. In addition, worst-case uplink 5G scenarios, where all 5G cellular handsets of the passengers operate at the same time, have been simulated by means of an in-house developed 3D Ray Launching (3D-RL) deterministic technique. Before takeoff and after landing, critical scenarios with the aircrafts’ doors closed have been selected and assessed considering different types of modeled aircrafts full of passengers, considering 5G frequency range 2 (5G-FR2) operating links. The obtained results show that the operation frequency and the morphology and topology of the aircraft cabin have a great influence in the environmental RF-EMF passengers’ spatial distribution and overall exposure, but not exceeding, even in worst case conditions, the international established regulatory limits.

During the laser application process, laser energy is usually converted into heat energy, causing high temperature, which affects the (high-speed) aircraft in routine flight. A completely novel photochemical method was investigated to potentially minimize the energy effect of the laser beam. Ag nanoparticles/ C 3 N 4 were synthesized by an ultra-low temperature reduced deposit method with Ag mean diameters of 5–25 nm for photofixation of N 2 . The absorption performance of laser can be improved by using appropriate charge density and small size Ag metal particles. The energy absorption rate was 7.1% over Ag/ C 3 N 4 (−40) at 5 mJ / cm 2 of laser energy. [ABSTRACT FROM AUTHOR]

This paper presents research on the model developed in the Matlab environment for simulating effects of overvoltage in an unmanned aerial vehicle (UAV) upon lightning discharge. They are based on transmittance obtained from voltage surge impulse measured in drone circuits. Overvoltage waveforms were measured at the input and output of different parts of the machine. It was then possible to calculate the transmittance of those (chosen) circuits. The motors, supply system, communication lines, and sensors were primarily tested. Both positive and negative polarization of the surge pulse were used and compared. The shape of pulse, is standardized by international norms for avionics tests (RTCA DO-160). The special surge generators were used to prepare the same repetition of each pulse (for all measurements). The simplified model of surge pulses propagation in drone circuits was prepared in Matlab. The differential between direct and step-by-step paths of pulse propagation in some connected circuits were also compared. [ABSTRACT FROM AUTHOR]

This paper is concerned with a new detection method to realize the real-time judgment of surge precursor by the low-sampling-rate compressor discharge static pressure at onboard environment, and it provides the possibility for antisurge control. Firstly, an improved Hilbert-Huang transform time-frequency analysis algorithm is proposed to get the Hilbert spectrum of the windowed signals in real time. The surge-precursor intensity (SPI) is characterized by counting the signal amplitude in the low-frequency range. The surge early warning signal is judged according to whether the SPI crosses the threshold. Then, this paper handles the misjudgment problem caused by the endpoint effect phenomenon in the detection algorithm by adding data segments at the beginning and end of the analysis signal. Finally, to prevent the possible real-time jump phenomenon of the surge warning signal during the detection process, a judgment logic module is added. The verification results of multiple sets of experimental data showed that the warning time margin is 0.05~0.3 s. This paper also established an antisurge control system. The results verified that the detection method is effective, and the time margin of the early warning signal judged meets the response time requirements of the control system. [ABSTRACT FROM AUTHOR]

Boundary-layer ingestion (BLI) is a propulsor-airframe integration technology that promises substantial fuel consumption benefits for future civil aircraft. This paper discusses an experimental study, conducted within the European Union-funded Horizon 2020 CENTRELINE project, on the aerodynamic performance of an aircraft with a BLI propulsor integrated at the aft-fuselage section (known as the Propulsive Fuselage Concept). The low-speed wind-tunnel experiments were carried out at Reynolds and Mach numbers of 460,000 and 0.12, whereas the Reynolds and Mach numbers are 40,000,000 and 0.82 at full-flight scale. Aerodynamic loads measurements show that the BLI propulsor affects the longitudinal and lateral-directional equilibrium of the aircraft in off-cruise conditions. Moreover, velocity and total pressure measurements characterize the flowfield around the BLI propulsor in cruise and off-cruise conditions. The analysis of the momentum and power fluxes in the flowfield shows that, while around 20% of the total aircraft drag is due to the fuselage body, only less than 5% of the total aircraft drag power is dissipated in the fuselage wake. Furthermore, the BLI propulsor recovers around 50% the axial kinetic energy flux in the fuselage boundary layer (the so-called wake-filling effect), suggesting an increased propulsive efficiency. [ABSTRACT FROM AUTHOR]

In this paper, a new design methodology guaranteeing optimal performance and constraint satisfaction with acceptable risks is presented. This methodology is particularly tailored to conceptual design, wherein variability stemming from modifications that will inevitably occur in downstream design phases must be taken into account. Based on second-order Taylor expansions, a new method allowing the transformation of this robust-optimal design problem with acceptable risks into an equivalent deterministic quadratically constrained quadratic programming (QCQP) problem is provided and then applied to an example problem for validation. Hence, all the available QCQP optimizers can be used to find a robust-optimal solution. The proposed methodology is applied to the blended-wing/body (BWB) at the conceptual design phase, where robust drag minimization is sought under a pitching moment constraint. Numerical results show the impacts on both the BWB optimal planform parameters and guaranteed drag as a function of the acceptable risk levels taken. The study shows that two of the six planform shape variables are significantly affected by the risk level, namely, the kink parameter and the outer wing span. Variations of almost 20% are obtained on these two variables for a risk level of 0.1% as compared to a standard deterministic optimization. [ABSTRACT FROM AUTHOR]

Historical operational usage data give a ground for fatigue damage estimation. Quality of sensors and recorders two or more decades ago were lower then modern one. Lack of resolution in nz-level measurement and recording leads to some errors in fatigue damage calculations. In this paper author propose a method to improve the accuracy of fatigue damage calculations for archived data. The method takes advantage of typical distribution of accumulated cycles for aircrafts. Small correction in representative nz value taken in calculations can reduce the error in fatigue damage assessment.

The aim of this work was to provide a formulation of a non-linear diffusion model with forced convection in the form of a reaction–absorption system. The model was studied with analytical and numerical approaches in the frame of the parabolic operators theory. In addition, the solutions are applied to a gas interaction phenomenon with the intention of producing an inerted ullage in an Airbus A320 aircraft centre fuel tank. We made use of the travelling wave (TW) solutions approach to study the existence of solutions, stability and the precise evolution of profiles. The application exercise sought to answer a key question for aerospace sciences which can be formulated as the time required to ensure an aircraft fuel tank is safe (inerted) to prevent explosion due to the presence of oxygen in the tank ullage. [ABSTRACT FROM AUTHOR]

The paper is devoted to the analysis of international and normative legal acts of the national legislation concerning the legal regime of airspace use by aircraft. The authors came to the conclusion that there is a special kind of institution whose object of regulation is the social relations that are formed in connection with the implementation of the flight both within the sovereign territory and in the open air space.

Copyright of Anuario Español de Derecho Internacional Privado is the property of Iprolex SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aircraft wake is a pair of strong counter‐rotating vortices generated behind a flying aircraft, which might be dangerous to the following aircrafts. The real‐time and precise locating of aircraft wake vortex‐core positions is essential in the aviation safety field, especially in airport traffic management. This study proposes a two‐step vortex‐core locating method which uses the Gabor filter to make a preliminary locating and the velocity range distribution to make a fine locating consequently. The combination of Gabor filter and Doppler velocity distribution can improve the method's adaptability to complex background wind field and mitigate the impact of noise. Numerical examples and field detection campaigns from Changsha Huanghua International Airport and Hong Kong International Airport have well verified the good performance of the method, in terms of both accuracy and real time. [ABSTRACT FROM AUTHOR]

In this paper, we consider a multiuser multiple-input-single-output (MU-MISO) downlink visible light communication (VLC) system deployed in airplane cabins, for serving high-speed Internet to the passengers through the reading lamps. The high number of closely spaced lamps (i.e., transmitters) suggests the use of a transmit precoding scheme to suppress the strong mutual light interference and enhance the performance of the system. Constraints are the complexity of the hardware and the integration into commercial devices (smartphones, tablets, etc.). Since nominal lighting is constrained by LEDs saturation, here we adapt the Tomlinson-Harashima precoding algorithm to the on-board VLC scenario and demonstrate its definite improvement on channel capacity with respect to the unprecoded case and also to the zero-forcing precoding one. The optimum directivity of the sources trades over performance and robustness against source-receiver misalignments (i.e., the passengers' mobility) by validating MISO channels for a number of receivers' positions around the best alignment one with a ray tracer specifically designed.

Aircrafts are widespread used in the modern warfare. A radar therefore should have the capability to classify and identify the aerial targets. In this study, a method based on feature analysis is proposed to classify and identify the aircraft targets. First, multiple features are extracted and analysed for further utilisation, including Doppler shift, relative amplitude, waveform entropy of time and frequency domain, and time–frequency characteristics. Second, the features are employed for classification purpose by means of the support vector machine. Moreover, a method is presented to identify the helicopter with odd or even number of blades, owing to the width of time–frequency distributions of the returned signals. The performance of the discussed method is verified with the experimental results of measured data.

Detection of aircrafts in satellite images is a challenging problem when the background is strongly reflective clouds with varying transparency. We develop a fast and effective detection algorithm that can find almost all aircrafts above and between clouds in Sentinel-2 multispectral images. It exploits the time delay of a few seconds between the recorded multispectral images such that a moving aircraft is observed at different positions due to parallax effects. The aircraft speed, heading and altitude are also calculated accurately. Analysing images over the English Channel during fall 2020, we obtain a detection accuracy of 80%, where the most of the remaining were covered by clouds. We also analyse images in the 1.38 μm water absorption band, where only 61% of the aircrafts are detected.

Aircrafts are widespread used in the modern warfare. A radar therefore should have the capability to classify and identify the aerial targets. In this study, a method based on feature analysis is proposed to classify and identify the aircraft targets. First, multiple features are extracted and analysed for further utilisation, including Doppler shift, relative amplitude, waveform entropy of time and frequency domain, and time–frequency characteristics. Second, the features are employed for classification purpose by means of the support vector machine. Moreover, a method is presented to identify the helicopter with odd or even number of blades, owing to the width of time–frequency distributions of the returned signals. The performance of the discussed method is verified with the experimental results of measured data. [ABSTRACT FROM AUTHOR]

This work elaborates Civil Group Flight as a new concept of aircraft en-route separation in the WATEN (World Air Track Elastic Network – new system of air tracks based on segments of big circles with physical flexibility and commercial elasticity for accommodation of civil commercial air traffic) by the use of exact mathematical formulas. Its main objective is to preserve safety while providing better efficiency of air traffic and improving airspace capacity. In addition to the system operating as a whole, it is also possible to dissect specific calculations, models or subsystems from it, and make it cooperate with other automated systems engaged as supportive to the safety of civil air traffic. It will demonstrate segmentation of the problem into elements as: optimal flight profiles, short and medium term conflict detection, conflict solutions and other aspects of the free flight concept as well as optimization of the routes and route structures, flexible adaptations to physical obstacles (adverse weather, volcanoes etc) and legal restrictions (military operations, nuclear plants, segregated areas etc) and promotion of the Civil Group Flight as a solution to a free flight concept. The work consists of several fully worked out mathematical formulas on how to technically and operationally solve these issues, by the use of methods as the simplex algorithm or the least square method, to achieve the most prominent results. Principles of linear algebra and vector spaces are the core of any procedure used to model these separate categories. The goal of the whole project is to show how modern mathematical methods, conjoined with the concepts of Civil Group Flight and WATEN, may contribute to commercial air traffic economical improvements. This will be achieved through more efficient use of available airspace and improvements of flight economy, by optimization of horizontal and vertical flight profiles. [ABSTRACT FROM AUTHOR]

In this paper we analyse the optimization of lidar systems in order to investigate Clear Air Turbulence (CAT), which is a dangerous weather phenomenon affecting especially the commercial aircrafts. It is assumed that aircrafts can cause air turbulence that can be detected by lidar, since pressure gradients could cause slight variations of the molecular depolarization values. This study will assess the capability of the lidar systems to highlight air turbulence from depolarization profiles. In order to do this, lidar measurements were performed at two sites in Romania: one in Magurele, near Bucharest and one in Cluj-Napoca. The measurements were accompanied by continuous flight path monitoring to mark the incidence events above the measuring locations. [ABSTRACT FROM AUTHOR]

The increasing number of unmanned aerial vehicle poses new challenges in the aviation industry especially the air traffic control, which is responsible for the safe flight operations in the controlled airspaces. In order to protect the conventional aircraft a new operation environment has to be created, which guarantee the safe flying and the possibility of the fulfilment of the flight. In the article drone related safety and operational problems are highlighted. All issue connected to the coexistence of manned and unmanned aircrafts are critical, thus their management have significant importance. Spread and wide use of unmanned aerial vehicle traffic management systems (UTM) can manage the critical operational issues, but is has to be defined that what is the problem, what is the scope, what is the operational environment. Services and functions related to the operation of the UTM system are defined, which are necessary for the safe flying fulfilled by the unmanned vehicles. [ABSTRACT FROM AUTHOR]

The problem of automatic control of rapprochement of aircrafts at the passing, oncoming and cross movements on intersecting courses is formulated. The method of function evaluation of risk of collision of courts on the basis of dynamic programming that allows creating alarm signals for acceptance of precautionary measures for safe management of the lateral and longitudinal motion of the aircraft is offered.

Logistics aspects of programs optimization of the maintenance of the aircrafts flight validity using models of steered semimarkovian processes are considered.

Highlights • We provide non-standard integrated methodology to investigate the effects of internal blast actions on aircrafts. • We design new protection devices: composite structures. • We consider external actions arising at cruising altitude. • Our methodology can be used in general for different structures. Abstract We introduce a numerical approach for evaluating the behaviour of aircraft fuselages subjected to internal explosions. At variance with available approaches, we consider fluid-structure interactions through a novel integrated methodology able to take into account both stress at cruise altitude and blast fast-dynamics in interaction with pressurization not considered as a static load. The precision of the proposed numerical procedure allows us to foresee a nonstandard composite protective device. [ABSTRACT FROM AUTHOR]

The authors report some encouraging results with basis on their calculations to forecast the magnitude of anomalous thrust forces measured in resonant microwave cavities with dielectrics, for two configurations known as Cannae‐Drive and Tapered Drive, when operating for high values of power. Despite of the weakness of the forces, both devices could provide us with a novel future propulsion technology by means of a thrust without ejecting propellant. In the calculations, they applied their theoretical model based on the dipole‐environment interaction via generalised quantum entanglements (GQE) ensuring the momentum conservation principle. They obtain good agreement with the experimental measurements, although the anomalous forces have weak magnitude. The control and enhancement of the effect can be accomplished by applying GQE hypothesis in order to allow the future viability of a new technology based on quantum electromagnetic propulsion of aircrafts and vehicles. [ABSTRACT FROM AUTHOR]

A logistics issue for guided air-drop systems is maintaining batteries inside the airborne guidance unit so that when the system is deployed the batteries are adequately charged to power onboard electronics and actuators. It is typical for a guided air-drop system to be packed and readied for use well before deployment, leading to nonnegligible battery self-discharge. This necessitates a process to both monitor battery life and recharge the systems after a certain time interval. This paper explores, using a small-scale wind turbine system, providing the requisite power for onboard electronics and actuation for a guided air-drop system. Sizing studies are reported to estimate the necessary size of the rotor and generator. Using this information, a full-scale airborne guidance unit was designed, fabricated, and tested in a wind tunnel. Results indicate that a 0.33 m diam turbine system can generate over 3.7 W of continuous power, which is sufficient to provide power to low-power consumption guided air-drop systems, such as a bleed-air actuated system. [ABSTRACT FROM AUTHOR]

In this paper, we consider a multiuser multiple-input-single-output (MU-MISO) downlink visible light communication (VLC) system deployed in airplane cabins, for serving high-speed Internet to the passengers through the reading lamps. The high number of closely spaced lamps (i.e., transmitters) suggests the use of a transmit precoding scheme to suppress the strong mutual light interference and enhance the performance of the system. Constraints are the complexity of the hardware and the integration into commercial devices (smartphones, tablets, etc.). Since nominal lighting is constrained by LEDs saturation, here we adapt the Tomlinson–Harashima precoding algorithm to the on-board VLC scenario and demonstrate its definite improvement on channel capacity with respect to the unprecoded case and also to the zero-forcing precoding one. The optimum directivity of the sources trades over performance and robustness against source-receiver misalignments (i.e., the passengers’ mobility) by validating MISO channels for a number of receivers’ positions around the best alignment one with a ray tracer specifically designed. [ABSTRACT FROM AUTHOR]

The paper is devoted to the analysis of international and normative legal acts of the national legislation concerning the legal regime of airspace use by aircraft. The authors came to the conclusion that there is a special kind of institution whose object of regulation is the social relations that are formed in connection with the implementation of the flight both within the sovereign territory and in the open air space. [ABSTRACT FROM AUTHOR]

Aviation is one of the safest transport in the world. However,every year occurs disasters being caused by many factors. This study is focused on one of the reason of incidents – inadequate or inappropriate aircraft maintenance work quality. The aim of this case is to systematize theoretical assumptions of aircraft maintenance, measure service quality and also purposefully manage them. This study objectives are to reveal the essence of a systematic approach towards the study object, to examine the theoretical potential to manage the quality of services, to etermine the outline of aircraft maintenance quality management specifics. Studies showing management functions affects on ensuring quality of aircraft maintenance were invoked to examine service quality problems. Also, the analizing of management theories with practical adaption leads to greater productivity and higher quality of services. Santrauka Aviacija – viena saugiausių transporto rūšių, bet vis dėlto kasmet įvyksta skaudžių nelaimių. Šiame tyrime koncentruojamasi į vieną incidentų priežasčių – nepakankama ar netinkama atliktų orlaivių techninės priežiūros darbų kokybė. Tyrimo tikslas – susisteminti teorines prielaidas orlaivių techninės priežiūros paslaugų kokybei matuoti ir kartu kryptingai valdyti. Tikslo įgyvendinimo uždaviniai: atskleisti sisteminio požiūrio į tyrimo objektą esmę, išnagrinėti teorinį potencialą paslaugų kokybei valdyti, nustatyti orlaivių techninės priežiūros paslaugų kokybės valdymo specifikos metmenis. Paslaugų kokybės problematikai nagrinėti pasitelkti atlikto empirinio tyrimo rezultatai, rodantys vadybos funkcijų poveikį orlaivių techninės priežiūros darbų kokybei užtikrinti. Be to, nagrinėjamos vadybos teorijos, kurių pritaikymas praktikoje lemia didesnį darbo produktyvumą ir aukštesnę paslaugų kokybę. Reikšminiai žodžiai: orlaiviai; techninė priežiūra; paslauga; vadybos teorija; kokybės matavimas; kokybės valdymas.

This article contains a kinematic analysis of an aircraft chassis mechanism in a range of positions. The mechanism of the chassis is made up of several smaller subsystems with different functions. The first mechanism is used to eject the chassis before landing (touchdown) and fold it to hatchway after the lift off. The second mechanism is designed to perform rotation of the crossover with the wheel, in order to adjust the position of the wheel to fit it in the limited space in the hold. The third mechanism allows movement of the chassis resulting from the change in length of the damper. To determine the position of the following links of the mechanism calculus of vectors was applied in which unit vectors were used to represent the angular position of the links. The aim of the analysis is to determine the angle of convergence and the angle of heel wheels as a function of the variable length of hydraulic cylinder, length of the shock absorber, length of the regulations rods