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2024 | Book

Novel Techniques in Maintenance, Repair, and Overhaul

Proceedings of the International Symposium on Aviation Technology, MRO, and Operations 2022

Editors: T. Hikmet Karakoc, Ivan A. Kostić, Aleksandar Grbović, Jelena Svorcan, Alper Dalkiran, Ali Haydar Ercan, Ognjen M. Peković

Publisher: Springer Nature Switzerland

Book Series : Sustainable Aviation


About this book

The International Symposium on Aircraft Technology, MRO, and Operations (ISATECH) is a multi-disciplinary symposium presenting research on current aerospace issues. The conference provides a platform offering insights on the latest trends in aircraft technology, maintenance, repair, overhaul, and operations that offer innovative solutions to the aviation industry's challenges. Coverage includes the operational and MRO needs of hybrid, electric, all-electric, and fuel cell air vehicles adapted to new technology standards. ISATECH allows researchers, scientists, engineers, practitioners, policymakers, and students to exchange information, present new technologies and developments, and discuss future direction, strategies, and priorities.

Table of Contents

Influence of Thickness Ratio on the Aerodynamic Characteristics of a Family of Hybrid Semielliptical Dolphin Airfoils

The authors of this paper have recently been involved in the development of a novel family of semielliptical hybrid Dolphin airfoils for general aviation applications. The previous work has shown noticeable improvements in aerodynamic characteristics of the modified hybrid Dolphin 2415 airfoil. In this paper, the same method has been applied to the airfoils of different thickness ratios. All numerical calculations were performed using RANS equations with the k−ω SST turbulence model. A comparison between a series of four-digit NACA 24xx, the original Dolphin, and the novel hybrid semielliptical Dolphin airfoils was made. Results have shown that in the range of thickness ratios above 15% and under 12%, the semielliptical hybrid Dolphin airfoils have shown a slight decrease in some aerodynamic characteristics compared to their NACA counterparts. This led to the conclusion that the semielliptical modification approach of the airfoil in its nose domain shows the best results within the 12–15% range of thicknesses, which is an important clue for further research of the hybrid Dolphin airfoils.

Zorana Z. Dančuo, Ivan A. Kostić, Olivera P. Kostić, Aleksandar Č. Bengin, Goran S. Vorotović
The Effect of T6 Heat Treatment on AlSi12 Alloy

Al-Si alloys are widely preferred in aerospace, defense, automobile, and general engineering industries. Major alloying element is silicon, and it is main reason for achieving good mechanical properties. AlSi12 is the most studied and preferred alloy in the literature. The impact of the T6 heat treatment process is investigated on the microstructure and mechanical properties of AlSi12 alloy. According to the obtained results, the improvement of mechanical properties of AlSi12 alloy is attributed to morphological transformation in the microstructure.

Fatih Bozkurt
Outline the Possible Application of Artificial Intelligence in the Aircraft MRO Process Development

Aircraft maintenance development is connected directly to aircraft technology, and today, in a field characterized by being fast-growing and innovative, technology has become a crucial asset for operation and process optimization. The maintenance industry must adapt to the continuous aircraft changes, which can also be well visible in the technology roadmap of aircraft development. The air transportation sector is aiming to reach higher safety levels, which can only be achieved by minimizing the risk of human-based errors. Additionally, the stakeholders expect cost reduction and higher market share. With the start of the Industry 4.0 revolution, new possibilities for data analysis, evaluation, and decision-making algorithms are being explored and investigated. It is well observed that Artificial Intelligence (AI) is present in most of the research work conducted in this field. AI can influence the daily workflow for companies working in the field of Maintenance, Repair, and Overhaul (MRO) as well as the machine-human synergy and cooperation. Hence, the present paper aims to introduce and discuss the possibilities of AI application in aircraft maintenance, its contribution, and its influence on the industry.

Sally Ichou, Árpád Veress, Dániel Rohács
A Computational Study of the Heat Transfer Coefficient for Lithium-Ion Battery Temperature

In this study, the thermal behavior of a prismatic lithium-ion battery was examined by considering both the maximum battery temperature and the minimum battery temperature. The battery temperatures were obtained by implementing the NTGK modeling. A commercially available computational fluid dynamics software, ANSYS Fluent, was used to model the battery thermal profile. The highest maximum battery temperature was obtained for the battery with the lowest heat transfer coefficient while the lowest maximum battery temperature was observed for the battery with the highest heat transfer coefficient. The results showed that the battery temperature could be controlled by the heat transfer coefficient. The results also indicated that if a temperature difference of 1 K was acceptable, the heat transfer coefficient of 20 W m−2 K−1 was sufficient for the battery. The heat transfer coefficient should be adjusted to its optimum value for a battery thermal management system. This study can be used to select suitable heat transfer coefficients for battery thermal management systems.

Ugur Morali
Wind Tunnel Measurement of Pitch-Damping Derivative Using Forced Oscillation Technique

The main task of dynamic experiments in wind tunnels is to obtain model-scale stability information of an aircraft at realistic Reynolds and Mach numbers. The forced oscillation technique is the most widely used wind tunnel technique for stability derivatives measurements. The oscillatory motion is induced to a model in one (the primary) degree of freedom. The aerodynamic reaction measured in the primary degree of freedom determines direct damping derivatives. Stability derivatives are obtained from in-phase and out-of-phase components of the measured aerodynamic reactions. This paper describes the determination of the pitch-damping derivative in the T-38 wind tunnel. The T-38 pitch/yaw apparatus is a full-model forced oscillation apparatus with primary angular oscillation around the wind tunnel model transversal axis. The model is forced to oscillate at constant amplitude. Test results obtained in the T-38 wind tunnel are compared with published experimental data of one of the world’s leading wind tunnels: Arnold Engineering Development Center-von Karman (AEDC, USA).

Marija Samardžić
Optical Velocity Measurement and Fluid Flow Visualization Techniques

Numerous fluid flow phenomena intrigue researchers worldwide. Flow visualization usually precedes experimental research and gives insight into flow structures. It can be used to show how the fluid flows around the model, in a jet, in closed systems, in turbomachinery, etc. In numerous cases, geometries are very complex, and some chemical reactions occur, but they are not treated here. Smoke, tufts, paints, sewing thread, smoke, and tuft probes are employed together with illumination systems, like LED lamps or lasers. With the laser development, a new era of fluid flow velocity measurement techniques started. Soon after the laser invention, a laser Doppler velocimetry (LDV) was developed and applied in fluid mechanics. Nonintrusive era of fluid flow investigation has started. Various laser models, from continuum, and diode ones to impulse are widely used. Three-component systems, even five beams probes, are employed today in complex research. In-plane, stereoscopic, multi-plane stereoscopic, time-resolved, micro, holographic, scanning, tomographic, and thermographic particle image velocimetry (PIV) have been used. In this case, besides illumination devices, contemporary applications employ fast cameras nowadays. Research of the turbulent swirling flow in pipe, behind the axial fan impeller, with the help of the LDV and PIV systems, as well as some results on wing tip vortex research in wind tunnel tests, are presented.

Đorđe S. Čantrak
Numerical Investigation of Impinging Synthetic Jets on the Flow Field and Heat Transfer at Low Orifice-to-Plate Distances

A numerical study has been performed in order to investigate synthetic jet impingement on a flat plate for orifice-to-plate distances (H/d) of less than one. The aim was to show the effect of low H/d on heat transfer and flow field for a single circular orifice. Investigations have been done for frequencies of f = 250 Hz and 500 Hz, and 0.10 ≤ H/d ≤ 0.75. The results showed that at the stagnation region, the highest heat transfer values could be obtained for H/d = 0.75. On the other hand, more uniform temperature distributions have been observed for H/d = 0.10. Overall, this study provides guidance for the design of synthetic jet impingement cooling in small spaces with high thermal power densities.

Eda Ergur, Tamer Calisir
Comparison of Flow Characteristics of Wake Regions of Single and Lined up in a Row Torpedo-Like Geometries at Uniform Flow Conditions

In this study, the comparison of the flow characteristics in the wake of two identical torpedo-like geometries having an elliptical nose and conical stern lined up in a row with a single model for a length-diameter ratio L/D = 5 was investigated using the Particle Image Velocimetry (PIV), method in a closed-loop open water channel. The Reynolds number calculated based on the characteristic length (L = 200 mm) of the model is Re = 20x103. The experiments were carried out under uniform flow conditions. The uniform flow velocity is 100 mm/s. The space between the two models is denoted by G. The dimensionless space ratio between the models is taken as G/L = 0.15. In comparisons, instantaneous velocity field (V), time-averaged streamline topologies <Ψ>, pointwise variations of streamwise velocity component <u/Uꝏ>, cross-streamwise velocity contours <v/Uꝏ>, velocity fluctuations in cross-streamwise <vrms/U∞> and instantaneous vorticity contours wL/U∞ were found to be different significantly from the single-torpedo-like geometry. It has been observed that the flow separations in the torpedo-like geometry wake region at G/L = 0.15 are delayed and move toward the end of the geometry stern section. In addition, it has been observed that the rotational flow regions areas covered by the contours get smaller and approach the geometry.

Ezgi Akbudak, Ertuğrul Şekeroğlu, Bülent Yanıktepe, Ömer Kenan, Muammer Özgören, Besir Sahin
Accounting for the Effects of Experimental Setting in Propeller Flow Computation

Various computational approaches differing in complexity and accuracy can be used to simulate flows around rotating lifting surfaces. Here, the flow field around a hovering propeller is estimated by two disparate methods, Reynolds-averaged Navier-Stokes (RANS) equations vs. wall-modelled large eddy simulation (WMLES), and compared to experimental data. In both cases, the computed thrust is somewhat lower than the measured value, mostly because the measuring equipment, located behind the propeller, disrupted the wake, thus changing the aerodynamic loads over the blades. However, the effect of the computational grids and approaches to resolving the rotational motion and turbulence are not negligible. They can be quantified in a particular case of a small-scale propeller operating at nominal angular frequency. For that reason, different computational domains, grids and numerical set-ups are tried and compared. It is observed that by careful geometric modelling, fine meshes, LES and inclusion of actual experimental set-up, a much-improved correspondence between the two sets of data can be achieved.

Jelena Svorcan, Kan Wang, Aleksandar Kovačević
Development and Construction of a Radio-Controlled Aircraft with Distributed Electric Propulsion: Persian Sky-O

In this paper, the design and construction of a radio-controlled airplane that is propelled using distributed electric propulsion (DEP) is studied. The airplane, named Persian Sky-O, is a part of the Persian Sky program, whose focus is on the design, development, and construction of all-electric civil aircraft using high-efficiency, innovative technologies. Persian Sky-O includes six propellers installed along the wings and powered by high-efficiency electric motors. An existing model airplane using some modifications is considered as the base of the project. The ground and flight tests are performed, and a testbed is developed which can be used for any model airplane in a proper size. The development of Persian Sky-O can help the study of distributed electric propulsion in real conditions with more safety and lower cost.

S. Ahmad Fazelzadeh, Abbas Mazidi, Mohammad Tashakorian
Improve Aircraft Pilots’ Training Using Structural Failure Incidents: A Serious Game Approach

Problem-based learning (PBL), as well as serious games and simulations, allow students to understand and associate theory discussed in class with its applications in real-life incidents. This paper supports the view that successful air disaster management during flight needs a proactive, multifaceted educational approach with a combination of theoretical knowledge, simulation, and actual flying training. Using simulations and games in education increases students’ motivation and engagement, improves their skills, and optimizes their learning, but also enhances their critical thinking and decision-making. To this end, we propose the development and use of a digital, interactive educational platform that can bridge academic education and flight training using case study analysis for in-flight risk management. An added bonus of our digital platform is that the trainees can also access it remotely and use the educational material anytime and, in any place, even if they are away from their training squadron.

Ioanna K. Lekea, Dimitrios G. Stamatelos, Stefanos Giannopoulos
Neural Control of Space Trajectories with Pseudolinear Models

This paper describes an approach to neural control of a satellite trajectory. A pseudolinear model is created to generate the necessary training data for the neural network. This model uses an H∞ to stabilize the relative motion of a satellite concerning another satellite. The purpose of this paper is to show the feasibility of such an approach and to better understand the benefits of using a previously trained neural network to control a satellite.

Pedro M. C. Belizário, K. Bousson, Filipe Senra
H-Infinity Control of Orbital Trajectories with Stochastic Models

This paper describes the formulation and numerical investigation of the robust H∞ control problem for the orbital transfer of a spacecraft between two non-coplanar orbits subject to parameter uncertainties and external disturbance. The dynamic model of relative motion illustrated by Tschauner-Hempel (T-H) equations is used to define the orbital transfer model. An illustrative example is provided to show the effectiveness of the proposed control design method.

Luís G. Andrade, K. Bousson
Numerical Analysis of Narrow-Body Fuselage Upper Panel Redesign

As a consequence of a huge risk that development of a new structural solution inevitably brings (which is additionally emphasized by the compelling need of the profits increase), the importance of striving for the best technical solution is now quite diminished. As a result, instead of pursuing for the new and more advanced structures, today we aspire for partial redesign of the old models, which proved to be reliable in the past. Yet, this may be the right way if it involves keeping those options that still do not have a better alternative, instead of chasing innovation at any cost, but can become very dangerous if the mentioned approach is so abused that it settles to the application of alterations in which even basic principles are not followed, that we all know has happened within ‘the Max affair’. However, when it comes to the concept of redesign, between the two mentioned extremes, there is a whole range of different approaches, of which we will analyse the one we have observed within Boeing’s structural solutions and would simply define it as a mitigation of a bad design in the case where, according to our opinion, the whole solution should be completely rejected.

Daniela Dukic, Aleksandar Grbović, Mirko Dinulović, Gordana Kastratović, Nenad Vidanović
Structural and Flow Analysis of Launch Vehicle for CubeSats

Space has always been a matter of curiosity for humanity. With the development of satellite technologies, the number of CubeSats has increased. Accessibility to space has become easier with CubeSat technology. CubeSats are provided with access to space with launch vehicles. This study examined the structural and flow analyses of the previously designed launch vehicle. The main task of the launch vehicle is to bring the CubeSat placed in the CubeSat orbital deployer into the stratosphere layer of the atmosphere. CubeSat will be used for educational purposes. Information about the launch vehicle and the CubeSat to be placed is given. Structural analysis and flow analysis were carried out, taking into account atmospheric conditions. For the structural analysis, total deformation, equivalent stress, and maximum and principal stresses analysis under the effect of maximum acceleration that the launch vehicle will encounter were examined. For flow analysis, a wind turbine model with the launch vehicle was created. Flow path, flow velocity values, and dynamic pressure analyses on the launch vehicle were examined. In this study, the structural and flow analyses of the launch vehicle, which will take the CubeSat to be used for educational purposes up to the stratosphere layer of the atmosphere, were examined, and its suitability for the task was discussed.

Alper Şanlı, Tuncay Yunus Erkeç
Development of a Model of the TCAS Autonomous Diagnostic System Using Non-contact Current Sensors

In the work, the problem associated with a false alarm of the TCAS system is investigated when there is not a single conflicting aircraft in the system’s coverage area. The article analyzes the existing problem and ways to solve it using non-contact current sensors for autonomous diagnostics of the TCAS system. As a solution to the problem, a model of autonomous diagnostics with non-contact current sensors is proposed. As a result, it is shown that autonomous diagnostics of the TCAS system can be implemented using a Hall sensor and a Rogowski coil, which allow non-contact monitoring of operating currents, which makes it possible to detect and eliminate false alarms of the system.

I. A. Isgandarov, T. R. Aliyev
Testing and Integration of a Hydrogen Fuel Cell in a Hybrid-Electric Propulsion Rig for UAV

A parallel architecture hybrid-electric propulsion system for unmanned aerial vehicles has been proposed based on a hydrogen fuel cell. The system was tested in hybrid mode, to evaluate the performance of the fuel cell to power one of the motors and to demonstrate the combination of two power sources in a parallel hybrid layout.

João Farinha, Luís Miguel Silva, Jay Matlock, Frederico Afonso, Afzal Suleman
Effects of the Partial Use of Diesel Fuel with Kerosene on the Exergetic Sustainability Performance of a UAV Jet Engine in Case of Emergency

This study aims to analyze the effects of using diesel fuel partially with kerosene on the jet engine’s performance by using exergetic sustainability parameters in obligatory cases where there is no or limited access to JP-8 fuel. Low altitude use will also overcome the negative effects of diesel use at low temperatures. To this extent, firstly, the exergy analysis was implemented on the jet engine components. Exergy flows were determined as fuel and product for each component: compressor, combustion chamber, gas turbine, and nozzle. Exergy destructions for each component were obtained. The calculated exergy destructions were one of the key figures to understand the improvement potentials of the jet engine components. Then four exergetic sustainability parameters: exergy efficiency (EE), waste exergy ratio (WER), environmental effect factor (EEF), and exergetic sustainability index (ESI), were studied. According to the findings, it was concluded that partial use of diesel can be an alternative for low altitudes in small UAV turbojet engines in case of emergencies.

Cem Tahsin Yucer, Yavuz Nacakli
Swarm Control of a Group of Unmanned Aerial Vehicle Under Fixed Consensus Topology

In this paper, a consensus-based formation control of a group of UAV is realized to obtain a deltoid formation. Before designing the CC algorithm, the mathematical expressions of the double integrator UAV dynamics are given briefly. Then, to achieve a deltoid formation shape, the communication graph between UAVs was first described to define the adjacency matrix. After that, the Laplacian matrix was obtained via adjacency and degree matrix. By using the graph Laplacian matrix and local information exchange between the vehicles, the proposed CC algorithm was designed depending on the DID of the UAV. Also, a collision avoidance algorithm was added to the main control algorithm to avoid any collision between the UAVs. The simulation results show the effectiveness of the CC algorithm.

Kaan Can, Abdullah Başçi
Aviation MRO Operators Assessment by SHELL Model

The human factor influences the performance of aviation maintenance services in the dynamic socio-technical environment of aircraft maintenance operations and overhauls. Management’s contribution and capacity to offer the necessary facilities, equipment, spare parts, and labor, together with a convenient environment and maintenance processes, are key performance indicators for maintenance operations. There are numerous ways to measure and assess the human factor in aviation MRO systems. In this research, the SHELL model is used to represent the impact of aircraft operators in the maintenance system. In order to do this, the analytical hierarchy process (AHP) was applied to construct a questionnaire of a two-level hierarchy model based on the SHELL model to evaluate, prioritize the key functions, and rank the significant and crucial maintenance criteria of the present MRO systems, 14 participants of two groups of aviation MRO professionals contributed to this study namely: (i) aircraft maintenance technicians and mechanics and (ii) aircraft maintenance engineers.

Omar Alharasees, Dániel Rohács, Utku Kale
Wind Tunnel Operation and Testing in the Twenty-First Century: The Case of VTI’s Test Facilities

The concept of the twenty-first-century laboratory emerged at the turn of the century in preparation for future changes in conducting research that will have been brought about by significant technological advances achieved in the previous period. At an extreme end, views were expressed that wind tunnels would have been mostly obsoleted and replaced by computational tools in the first decades of the century. Contrary to expectations, however, there has constantly been rising demand for wind tunnel testing during the last twenty years, but ironically, it has been followed by the overall decline in the number of wind tunnel runs. This apparent contradiction can be explained by the gradual abandoning of conventional wind tunnel test methods with high data volume as a main measure of productivity and transition to the techniques described collectively as the Modern Design of Experiments. Wind tunnel operation and testing in a new era of technology will be explained using the case of VTI’s test facilities. These facilities were built 40 to 70 years ago; some are well beyond their design lifetimes, but they have constantly provided unique testing capabilities in subsonic, transonic, and supersonic speed ranges. The present paper summarizes capability upgrades and embracing the principles of modern design of experiments by the VTI’s wind tunnels, in order to address current and future aerodynamic performance technical challenges.

Biljana Ilić
Comparative Analysis of Flow Fields Around NACA 23012 Airfoil at Three Characteristic Angles-of-Attack

Flow fields around the airfoil NACA 23012, developed over 80 years ago but still much employed, at Mach number M = 0.18 and Reynolds number Re = 1.8 million were experimentally and numerically investigated. Three different characteristic angles of attack (AoA) were selected. The angle includes a zero-degree AoA where drag is minimal, optimal AoA where the lift-to-drag ratio is maximal, and critical AoA where the lift is maximal. These selections are made to understand better the main flow features such as transition, flow separation, (unsteady) wake behavior, and turbulent structures appearing around the airfoil, as well as to investigate the possibilities of their modeling. Two principally different numerical approaches were employed: Reynolds-averaged Navier-Stokes (RANS) equations vs. wall-modelled large eddy simulation (WMLES). Both results were compared to recent experimental data. In both cases, the computational domain was the same (circular, spanning 0.2 chord length in spanwise direction), and the two generated meshes are comparable, particularly in the vicinity of the wall. Values of velocity and pressure were assigned to the outer boundaries, and sides were periodic. In contrast, airfoil walls were treated differently depending on the solver (no-slip vs. algebraic equilibrium wall model). Excellent correspondence between global results (aerodynamic coefficients) was achieved, particularly at lower AoAs. However, it was found that in order to accurately predict flow behavior at critical AoA and to capture the main turbulent structures, WMLES should be utilized.

Jelena Svorcan, Brett Bornhoft, Konrad Goc
Fuel Optimal Aircraft Conflict Resolution Under Various Wind Characteristics

One of the main weather components that must be considered in aircraft conflict resolution is the wind. Wind includes two essential elements that affect the individual routes of flights: speed and direction. Studies show that stochastic programming approaches considering both wind speed and direction uncertainties have advantages in terms of efficient air traffic management compared to the deterministic approaches. However, the savings of the stochastic approaches may change regarding the wind uncertainty parameters considered. Prevailing wind directions, average wind speeds, and wind speed variation between levels may vary regionally. The study aims to evaluate the performance of the stochastic approach in terms of fuel savings under various wind characteristics. Wind data are obtained from three different wind stations provided by the weather sound database. A stochastic conflict resolution model is developed, and flight level change strategy is used for conflict resolution. The objective function is determined as the minimization of total fuel consumption. As a result, it is revealed how the savings of the stochastic model vary according to different wind characteristics.

Kadir Dönmez, Ramazan Kursat Cecen
Implicit LES Using New Slope Limiters

In this paper, we study the Implicit Large-Eddy Simulation (ILES) based on new unstructured-grid polynomial-ratio slope limiter functions proposed recently (Jan/2022) by Hiroaki Nishikawa. The slope limiters showed improved resolution characteristics on simple convection test problems. Following that, the ILES approach is tested here on the Taylor and Green vortex test case representing complex flow with transitional and turbulent behavior. The results showed favorable characteristics of the methodology.

Nikola Mirkov, Ognjen Peković, Toni Ivanov, Aleksandar Kovačević, Aleksandar Simonović
Nanoceramics as Reinforcement for Polymer Matrices and Composite Materials for Aircraft Structures

In the recent development of structural composite materials, there is an approach to enhancing existing and synthesis of new, strong, and resistant fibers, and there is an approach to the synthesis of more efficient interlayer adhesives and polymer matrices. This research considers potential new hybrid composite binders based on epoxy resin and poly(vinyl butyral), PVB, reinforced with nanostructures of several engineering ceramics: SiC, INT-WS2, BN, and B4C. First stage of the research consisted of preparation and examination of hybrid polymer matrices in the form of thick films for characterization. FTIR was applied to confirm the chemical interaction between the two polymer components and to exclude their chemical interaction with the nano reinforcement. Mechanical performance was examined through tensile test and hardness measurement. The addition of nano reinforcements has improved tensile strength and the Shore hardness values of composite polymer matrix films, especially in the case of INT-WS2. The second stage of research was the implementation of the reinforced binders in carbon fiber laminated composites. INT-WS2 reinforced composite was selected and examined through tensile testing and resistance to bending test. Results obtained encourage further research and more detailed characterization of the new composites for potential application in the automotive, naval, and aerospace industries, in civil engineering, protective equipment, etc.

Danica Bajić, Milica Marjanović, Srđa Perković, Bojana Fidanovski
Evaluation of Architectural Structures in Electric Taxiing Systems

In order to reduce the dependence on fossil fuels, which are limited in our world, and to minimize the emissions caused by the use of these fuels, fully electric aircraft are being developed. In the context of this concept, the taxiing systems of aircraft are also designed as electrical. Different architectural systems have been proposed for the development of electric taxiing. In this study, the differences of the proposed systems are discussed and it is aimed to help the developers to design a new system.

Onur Cömert, Işıl Yazar, T. Hikmet Karakoc
High-Altitude Wind Resource Potential for AWE in Portugal

Airborne wind energy (AWE) systems aim to harvest wind energy at higher altitudes than conventional technology. To dimension the system and assess the potential power one can extract from a given location, its wind resource, namely the wind speed vertical profile, has to be characterized. The vertical profile is influenced by the location’s topography, surface roughness, and atmospheric stability conditions, which are often disregarded in AWE studies. This paper aims to assess the impact of these factors in wind speed and power vertical profiles for a region of Portugal and, by doing it, estimate the wind resource for a potential AWE exploration. One concluded that harnessing high-altitude wind energy was more advantageous in onshore locations; in addition, stable atmospheric conditions provided larger wind speeds and, therefore, the wind power available was larger. For the studied region of Portugal, one projected a maximum sustained wind speed of 18 m/s at a height of 250 m. Finally, one studied the wind resource for three specific locations, potential sites for AWE exploration employing a “Drag-mode” system, and verified that the rural site of Alenquer presented the best wind resource.

André Filipe da Cunha Pereira, João Melo de Sousa
Conceptual Design, Development, Test and System Identification of a Novel Tri-Rotor Configuration for a VTOL Fixed Wing Aircraft

In this paper a novel tri-rotor configuration is proposed with the goal of enabling vertical take-off and landing capability to a canard fixed-wing aircraft while minimizing the overall weight of the vehicle and the aerodynamic drag developed in horizontal flight. The novelty in the presented configuration is related not only to the thrust vectoring capabilities of all three rotors but also to the constraints surrounding the action of the rear rotor, which will be required to operate both in vertical and horizontal flight phases while drawing power from an internal combustion engine fixed inside the aircraft’s fuselage. The proposed design will later be translated into a test vehicle, which will serve as a proof of concept of the solutions developed. Finally, both a time and a frequency-response based system identification technique is applied to flight test data in order to obtain a more robust computational model of the aircraft’s dynamics.

António Arco, José Lobo do Vale, Sean Bazzocchi, Afzal Suleman
Measurement, Exploitation and Method Finalization of PIV Systems

Other than in aerodynamic laboratories that primarily deal with aircraft tests, PIV visualization methods can be successfully used to test currents in various technical systems (pipes of different geometries and dimensions), biological systems, flows around buildings, bridges, overpasses, towers, currents around means of transport, trains, cars, ships, for testing fluids of different properties. Modern development of computer technology and digital image processing enable automatic analysis of the effects of current visualization and obtaining qualitative and quantitative values of flow parameters, which cannot be obtained by classical, conventional measurement techniques.

Pavle Petrović, Miloš Januzović, Nebojša Petrović, Goran Vorotović, Aleksandar Bengin
Methodology for Testing Damaged Composite Helicopter Rotor Blades

The proposed methodology defines the procedure for testing composite blades of helicopter rotors that have suffered damage due to direct hits of projectiles of different origins. The methodology involves the integration of a number of types of tests in order to assess the quality of the composite structure of the blade, on the one hand, as well as in order to determine the ability of the blade to perform vital function on a helicopter. It is known that the evident lack of data on the behavior of helicopter rotor blades that are damaged (particularly in combat conditions of military use) causes a careful approach to the problem of defining the plan and program of testing such structures, especially from the aspect of using composite materials in blade structure.

Goran Vorotović, Aleksandar Bengin, Časlav Mitrović, Mirko Dinulović, Nebojša Petrović, Boško Rašuo, Miloš Januzović
Procedures in Testing the Mechanical Characteristics of Composite Structures and the Possibility of Application to Biodegradable Materials: An Overview

This paper presents the static testing of the composite material’s mechanical characteristics. An overview of the standards is made by which various tests are performed, and then an analysis of the results of the parameters obtained by the conventional method-stretching and optical (DIC system-bending) of carbon epoxy composite structures is given. These results represented the basis for the preparation and further application of biocomposite materials; that is, the testing procedure will be performed identically on composites containing mycelia. The mould for pressing biomaterial connected with mycelium is made of two parts. The primary purpose of the mould is to bring the loose natural material into a solid preparation following the standards ASTM D3039 and ASTM D7078, which include testing the technologically prepared and hardened sample for bending and shearing.

Marija Baltić, Milica Ivanović, Dragoljub Tanović, Miloš Vorkapić, Ivana Mladenović
Aviation Carbon Accounting for Climate Change Mitigation: The Case of Turkey

Global warming has become one of the biggest challenges of our world. Aviation industry, as a major contributor, is expected to play its own part in fighting the global warming by accounting for its carbon emissions. This study examines the approaches and strategies of airline companies for carbon accounting and reducing their contribution to global warming. Turkish Airlines, Turkey’s largest airline, is studied to reflect how Turkey’s air transport industry addresses the challenges of global warming and accounts for its carbon emissions. The study aims to set an example for other countries and businesses by showcasing the approaches and strategies of Turkish airline companies on carbon accounting.

Orhan Yucel, Alper Dalkiran, Seval Kardes Selimoglu, T. Hikmet Karakoc
Maintenance of Unmanned Aircraft

The topic of this paper is the maintenance of unmanned aircraft. The paper will present the maintenance process, as well as the basic principles of maintenance. The reason that this paper is dedicated to unmanned aerial vehicles is that they are expanding today and there are more and more of them. Nowadays, people who buy and use drones are not aware of the consequences they can cause. In order to safely handle unmanned aircraft, it is necessary that they are in perfect condition, which requires their maintenance.

Petar Mirosavljević
The Conversion of Ocean Wind Energy into Storable Energy: A Review of Current Developments

A brief review of the most recent developments of “energy ships” is presented. Energy ships are sailing ships equipped with hydrokinetic turbines to enable the conversion of the wind energy over the oceans into storable energy. This “energy ship concept” was first proposed in 2009 and a considerable number of analytical and computational studies have been conducted to evaluate its potential. However, only recently attempts were made to assess the fidelity of the predictions in sea trials. In this paper, these recent developments are described and summarized.

M. F. Platzer, N. Sarigul-Klijn, D. Kim, V. S. Neary, S. Currie
A Perspective on Oscillating Foil Propulsion

In this paper, a brief review is given of the physics of oscillating foil propulsion. It is then shown that the jet flow generated by an oscillating foil can be used as a flow control device. Experimental and computational fluid dynamic investigations are presented that show that the separated flow downstream of a rounded foil trailing edge can be reattached by positioning an oscillating foil in the separated flow region. Therefore, further studies of the interaction between small oscillating foils placed in the boundary layer or wake regions of stationary foils appear warranted.

M. F. Platzer, B. Anilir, D. F. Kurtulus
Flow Analysis Inside the Blade of Tip-Jet Cold Cycle Helicopter

This paper is focused on the flow inside the blades of cold type tip-jet helicopters. The phenomena of additional compression of the air through the blades due to the existence of the centrifugal effect shows that there is more potential in such types of tip-jet helicopters compared to hot cycle ones. CFD 3D analysis is used to simulate the flow and results are compared to values obtained by 1D hand calculation with differential equations. Results clearly indicate that not only all pressure losses, i.e. pressure drop, inside the blades are compensated by effect of centrifugal force there is a significant increase of pressure at the blade tip.

Nenad Latković, Nenad Kolarević, Nikola Davidović, Miloš Stanković, Dimitrije Mihajlović
Preliminary Full Configuration Drag Estimation of Fixed-Wing UAV Using Analytical Aerodynamics

This paper presents an estimate of the drag polar of the complete configuration of fixed-wing UAV using equivalent skin friction coefficient accounts for light aircraft derived for similar categories. Coefficients are derived from an aerodynamic analysis of UAV used for surveillance, reconnaissance, and artillery support in various civilian and military operations. The UAV’s parasitic drag is significantly influenced by the presence of miscellaneous components like nonretractable landing gears, motors and propellers on the tail-boom section or gimbal. These components are responsible for more than half of an UAV’s total parasitic drag. This calculation is used for the initial sizing of the UAV for a surveillance or reconnaissance mission.

Milica Milic, Jelena Svorcan
1D Modeling of an Onboard Inert Gas Generation System During Flight Conditions

In the event of an attack on aircraft or lightning strikes, there is a risk of fire in fuel tanks. Different methods are used to eliminate the risk of fire, one of which is to reduce the oxygen content in fuel tanks. OBIGGS (ONBOARD INERT GAS GENERATION SYSTEM) is a system that reduces the concentration of oxygen in the tank and increases the nitrogen partial pressure. This paper includes the 1D modeling of an OBIGGS application during flight. The results show that, 17 airplane crash has been reported until 2005 due to fuel tank explosion without usage of the OBIGGS and this study aims to show how this system prevents the explosions in any specific flight scenario.

Berat Gungor, Ethem Berk Ozdes, Zeki Yilmazoglu
Analysis of Sustainability Activities in Airlines

Air transport affects people mainly through air pollution and climate change at the local and regional levels and on a global scale. Approximately 4.9% of all emission levels that contribute to climate change come from it. The demand for air transportation has increased along with recognition of the possible environmental risks connected with it. Emissions from the aviation industry, which account for about 5% of national greenhouse gas emissions, will need to be decarbonized and reduced. With the increasing demands, the aviation industry needs to consider activities for sustainability practices. In this study, the sustainability activities of the world’s top 5 airlines and Turkish Airlines are compared and evaluated to analyse how sustainability creates value for the aviation industry.

Nazlı Ebru Akdeniz, Gamze Orhan
CO2 Dilution Effect of Methane Combustion at Premixed Model Gas Turbine Combustor

As a result of the climate crisis caused by energy efficiency and post-combustion emissions, the importance of studies on alternative fuels and combustion processes has also increased. In this study, the effect of dilution effect on flame temperature, brightness and flue gas emission values was investigated by adding CO2 gas to a pure methane flame at constant thermal power in a swirl supported and premixed burner. The thermal power of the burner was determined as 5 kW and the equivalence ratio was fixed at 0.9. While the burner outlet temperature of the pure methane flame was 1058 K under the specified conditions, it decreased to 1032 K with the addition of 30% CO2. With the decrease in the combustion temperature, the NOx value measured at 17 ppm in the pure methane flame was reduced to 13 ppm as a result of 30% CO2 dilution. On the other hand, as a result of the addition of CO2 under the same conditions, CO emissions increased from 303 ppm to 1687 ppm.

B. Alabaş
Electrical Conductivity Characteristics of Nanoparticle-Reinforced Polymers Produced by Additive Manufacturing

Nowadays, the technological, scientific and industrial use of micro- or nanoscale products has become rapidly widespread. Nanoparticles are added to metal, ceramics, and polymer materials, producing nanocomposite material. Polymeric nanocomposites are advantageous to other materials in terms of weight, performance, and price. Because of the lack of the mechanical properties of thermoplastic materials as the literature is known, it is possible to make nanoscale additions to thermoplastic materials, to give a new feature, or to improve its existing feature. The use of thermoplastic matrix in the industrial area has been the focus of nanocomposites due to its low cost, ease of manufacture, and recycling. Research on the use of 3D printers in the production of nanoscale-contributed thermoplastics has been found to be fewer. 3D prints are an additive manufacturing method compared to traditional processing methods. Additive manufacturing is based on the added layer by layer to reduce production costs and reduce the production cycle. In this study, nanocomposite material will be prepared by adding nano-sized graphene and silicon nitride (Si3N4) to the thermoplastic material. Samples will be produced using the fused filament fabrication (FFF-3D) printer. The electrical conductivity of the sample will then be examined.

Osman Dalar, Alperen Doğru, Melise Karatay Kutman, Fazilet Zumrut Biber Muftuler, Coskun Harmansah
Markov Chain Model Development for Forecasting the Lisbon TMA Capacity

The increase in demand registered in the air transport sector is directly reflected in the increase in the aircraft flow density in all essential regions for its operations, especially in terminal maneuvering areas (TMAs). The main objective of this paper was to analyze, in a concrete and critical way, the complexity in optimizing the TMAs capacity management via the predictive estimation of the traffic flow to a given TMA, preventing the occurrence of congestion. Using Markov chain theory, it was possible to detect the operating pattern of the air traffic flow in the Lisbon TMA related to which the proposed concepts were computationally tested using actual traffic flow data. The genericity of the methodology makes it possible to be used for other TMAs.

Cátia A. Simão, Kouamana Bousson
Removing Kerosene Tax Exemption from Aviation: The Future of Taxation Principles in Europe

Kerosene is used in aircrafts, and it causes damage to the environment. However, there was a tax exemption concerning this fuel within the European Union borders. At the same time, there was no exemption about such a tax for the countries out of the union. But the aircrafts operating in the European Union have emitted more gas than other countries. This normally requires a tax. Nevertheless, when levied such a tax, some criteria should be considered. These criteria are called taxation principles. When thought about this exemption, it is understood that removing kerosene tax exemption is realized on the basis of universal taxation principles. Therefore, in this study, it is concluded that taxation principles are going to become stronger day by day in eliminating the damage of fuels such as kerosene.

Filiz Ekici, Öner Gümüş, Rabia Kolukirik
Torsional Divergence Analysis of Missile Fins Based on Galerkin’s Method

In the present paper, the static aeroelastic phenomenon known as torsional divergence is investigated on rocket stabilizers (fins) made of composite materials. Using analytic approach, the differential equation for torsional divergence of composite trapezoidal stabilizer is derived. The equation obtained was in the form of second-order differential equation with variable coefficients. The solution to divergence equation was obtained using Galerkin’s approach and the complete solution procedure is presented. It was found that Galerkin’s approach can be successfully deployed in solving differential divergence equation and divergence speed (VD) of composite stabilizer in subsonic airflow can be effectively calculated.

Mirko Dinulović, Aleksandar Grbović, Hamad Alarafati, Marta Trninić
Effects of Covid-19 on Aviation Sector in Turkey

The civil aviation industry is one of the sectors most affected by the pandemic. In this study, it is aimed to reveal how the civil aviation industry in Turkey has been affected by Covid-19. In this research, document analysis method, which is the quantitative research methods, was used to obtain the results. The universe of the research is the flight data of Turkish Airlines. The sample of the research consists of Turkish Airlines’ number of flights, revenue, number of passengers, cargo revenue, load factor and flight cancellations in 2019, 2020 and 2021. According to the results obtained from the study, the number of flights, revenue, number of passengers and load factor of Turkish Airlines in 2020 decreased significantly compared to 2019.

Gonca Mine Kalaman, Ilkay Orhan
Express Method for Detection of Microbiological Contamination of Aviation Fuel for Preventing Damage to Aviation Military Equipment

Microbiological contamination is a specific type of contamination, capable of self-reproduction and expansion, which under favorable conditions can cause biological damage to fuel systems and fuels for military aviation (as well as civil aviation, marine vessels, and fuel and refueling complex). The interrelation of the occurrence of microbiological contamination and the consequences it causes for fuel and means of operation, transportation, and storage testifies to the complex influence of microbiological contamination and justifies the importance of ensuring the microbiological stability of fuels at each stage of their life cycle. The proposed method using ninhydrin makes it possible to promptly detect the presence of microbiological contamination in fuels and prevent the occurrence of biological damage to fuel systems and tanks and ensures the airworthiness of aircraft.

Iryna Shkilniuk, Sergii Boichenko
Implementation of RE in the 6R Strategy in Considering the Sustainable Development of Parts for the Aviation Industry Using Additive Technologies

The 6R strategy plays an essential role in the sustainable development of the aviation industry, which is reflected in the application of new materials and new technologies. Additive technologies enabled rapid prototyping production and modified components as a quick response to market turbulence. The aim is to show the primacy of additive technologies concerning conventional manufacturing methods. This paper will define the reverse engineering (RE) implementation algorithm in the 6R strategy. The emphasis here is on using nonmetallic materials: polymers, composites and other materials. Mentioned materials are gaining an increasing role in those places where the geometry of parts is complex. By definition, the 6R strategy includes reduction of waste material (Reduction), reuse of waste material (Reuse), waste collection (Recycling), regeneration of raw materials and energy from waste material (Recovery), redesign of a product or a complete business process (Redesign) and reproduction that includes disassembly, cleaning, measurement and testing of parts (Remanufacturing). Applying RE makes it possible to design a new spare part based on the existing fundamental machine part. The RE procedure is realized from creating a digital 3D model, through the permanent improvement and optimization of model parameters, to the production of the finished part using additive technologies.

Miloš Vorkapić
Validation of the Laboratory Facility for the Nanofluids Forced Convection Research

This paper deals with a laboratory setup intended for nanofluid forced convection research. It presents a technical solution for the part of the laboratory facility related to the measurement of convective heat transfer parameters and the results of its validation. The facility parameters were validated with distilled water, and the measured data were compared with the results obtained from the theory equations. It has been shown that the measured data match theoretical data very well. The maximum relative deviation of the experimental and theoretical local Nusselt number is 9.8%, which follows the values from the literature.

Saša Laloš, Maša Bukurov, Milan Vraneš, Snežana Papović, Darko Knežević, Siniša Bikić
Analysis of Ground Services for Air Carriers: System Dynamics Approach

In the years when commercial flights started, airlines carry out their ground operations with their own means; with the growth of the sector, today they are mostly carried out by Ground Service Agents (GSAs). Airlines flying to hundreds of different destinations around the world carry out ground operations at airports in different countries, only by cooperating with local service providers. GSAs, which receive services in many areas such as Ground Operations, Passenger Services, Lost and Found, and Ticket Sales, directly or indirectly affect the profitability of the airlines as well as the quality of service provided. One of the biggest expenses of airline companies is fuel consumption. So, many studies are being carried out in the field of fuel saving, and airlines are implementing many new applications to reduce consumption. This study aimed to show that differences can be made by small contributions during the standard services given to an aircraft prepared for flight. The results obtained by using the system dynamics approach show that ground services personnel can contribute to fuel savings, due to reducing the difference between the average weight values and the real values, by updating the flight plan according to actual data and planning the load distribution on the aircraft in the ideal CG range. As a conclusion, it is aimed to show how much the study can contribute to the airlines with similar calculations to be made for different aircraft types and different flight routes, by revealing the average earnings that can be obtained per flight over the sample taken at the end of the study.

Yiğit Nelik, Okan Tuna
Design Methodology Development for UAS Integrating Business Assessment and Optimization Processes

Unmanned Aircraft Systems (UAS) represent a young, dynamically growing market, with significant value potential and high growth rate. In order to unlock this market potential, UAS need to be designed to match the value generating business direction defined. This paper presents the overview of the method development and application for a business assessment-based conceptual level design methodology for UAS integrating optimization tools into the process. The methodology is presented through the example of an industrial-academic collaborative research project, where an existing BWB configuration UAS and the related potential business application had to be developed simultaneously. As the project does not present a clean sheet design opportunity, significant, conflicting constraints were placed towards the UAS design. As such widespread exploration of the design space was necessary, which was performed using an optimization-based methodology. Further optimization of shortlisted concept designs was performed in order to develop the designs with the potential to achieve the identified business potential.

Dávid Sziroczák, Dávid Szilágyi
Operating eVTOLs in the Emergency Response Service

One of the electric vertical take-off and landing vehicles (eVTOLs) most promising field of application is the medical emergency response service. The aim of this study is to demonstrate a method, suitable for the analysis of the benefits of integrating eVTOL vehicles into the services. In Hungary, due to the scattered location of settlements and natural obstacles, it is often not possible to reach rural areas on road within the desired timeframe. This problem could be solved by integrating eVTOL vehicles into the services. They could help to reduce emergency response times and hospital arrival times. They can have lower operating costs and a locally smaller environmental footprint than traditional helicopters, facilitating a wide range of applications. According to the analysis results, the percentage of the population receiving emergency care within 15 min can be increased from 85% to 99%. This requires 30 eVTOL stations with about 40 vehicles, which have at least 34 km service radius and are capable of 157 km/h cruise speed.

Dávid Szilágyi, Dávid Sziroczák
Experimental Thermal Analysis of Prismatic Lithium Iron Phosphate (LiFePO4) Battery

Characterizing the thermal parameters of a lithium-ion battery is an important step for estimating the temperature distribution of battery cell modules. In this study, an experimental method based on distance-dependent heat transfer analysis of the battery pack has been developed to simultaneously determine the thermal conductivity of the battery cell and the specific heat of the battery pack. Prismatic lithium iron phosphate cells are used in this experimental test. The time-dependent results were measured by measuring the temperature change of the cell surface. It is observed that the thermal parameters of the cell increase linearly with increasing operating temperature. Moreover, while the operating temperature has a more significant effect on the specific heat of the cell than the thermal conductivity, the effect of its state according to the C ratios used in charging and discharging has a maximum effect on these two parameters. The current method shows an effective and practical way to simultaneously determine the thermal conductivity of the cell and temperature changes.

Burak Tarhan, Elif Koruyucu, T. Hikmet Karakoc
Assessment of Entropy Management for Piston Engines Considering Fuel Preference in the Flight Process

Piston engines, which have increased their sectoral potential with the developments in their technologies in recent years, include features that can be used in different preferences for emission management together with fuel preferences. While the fuel preferences in the piston engines sector mostly use AVGAS, the use of LNG and LPG has been discussed from different perspectives in recent years. In this study, a comparative thermodynamic and environmental analysis is presented over three fuel preferences for the reference engine. By investigating the entropy potentials of the engine depending on fuel preferences, the environmental effects they cause are discussed through two different parameters: the Environmental Performance Index and the Sustainability Index. The environmental performance effects of fuel preference in the engine were also evaluated over the outputs obtained in the study.

M. Ziya Sogut
Energy and Environmental Evaluation on LPG Transition for Piston Engine of the Plane

Sectoral pressures created by the awareness of global warming and climate change have made the control of emissions important in the aviation industry. Fuel preference is a priority issue, especially for fuel-based energy and environmental sustainability. Liquefied petroleum gas (LPG), a solution for land vehicles, may be a choice for aircraft using piston engines. In this study, first of all, performance analyses were made for one piston engines together with the current AVGAS consumption. Then, the performance effect of the engine due to LPG usage was examined. In this context, the environmental effects of engine performance changes are also discussed within the scope of entropy management. The review aircraft were compared at different altitudes and flight conditions. The analysis shows a 54.37% saving in LPG consumption due to classical consumption. At the end of the study, the sectoral use of LPG was evaluated.

M. Ziya Sogut
Assessment of Thermodynamics Performance for Prop Engine Based on Temperature Effect of Flight Altitude

In recent years, significant gains have been made in aircraft engine technologies, which have increased their sectoral potential. However, irreversibility based on fossil fuel consumption has an important environmental pollutant role. For engines, the fuel consumption combined with the emission management-related altitude conditions is an important input to evaluate the potential. Generally, three different altitude definitions are valid for airplanes in engine performance measures. In particular, flight altitude is an important input for decision processes and this is valid for 9000 ft in sectoral structure. First law and second law analyses were developed for the defined boundary temperature values of the flight altitude for the prop engine referenced in this study. Then, the entropy potential of the temperature effect at the boundary conditions for the altitude conditions was evaluated, and the environmental effect was evaluated. At the end of the study, evaluations of entropy management were made for performance effects.

M. Ziya Sogut, Muhsin Kılıç
Novel Techniques in Maintenance, Repair, and Overhaul
T. Hikmet Karakoc
Ivan A. Kostić
Aleksandar Grbović
Jelena Svorcan
Alper Dalkiran
Ali Haydar Ercan
Ognjen M. Peković
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