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Table of contents

Volume 1226

2022

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International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens (11th EASN 2021) 01/09/2021 - 03/09/2021 Salerno

Accepted papers received: 20 January 2022
Published online: 15 February 2022

Preface

011001
The following article is Open access

The 11th EASN International Conference on "Innovation in Aviation & Space to the Satisfaction of the European Citizens", took place between the 1st and 3rd of September 2021. Due to pandemic-related restrictions, it was the second time that the EASN Conference took place virtually. EASN yearly gatherings enhance physical networking and connection among peers, however pivoting from an in-person event into a compelling virtual experience with the same structure as a typical EASN Conference has surely been a challenge for the EASN Team.

The EASN Association would like to address a big thank you to the Keynote Speakers, Session Chairs, Authors and Presenters, the members of the International Scientific Committee and the Organizing Committee to make this virtual conference a real success.

011002
The following article is Open access

All conference organisers/editors are required to declare details about their peer review. Therefore, please provide the following information:

• Type of peer review: Single-blind

The authors submit their manuscripts on the EASN conference online platform. Initially a preliminary check is performed by the EASN Team, regarding the templates, the page restrictions and the IOP guidelines. Once the paper is corrected, the peer review process follows, otherwise it is returned to the authors with the request to amend their work, according to the rules and guidelines. The corrected papers are then sent to the experts all along with an evaluation form so as to be completed by them. The evaluation form includes all the necessary details required by the IOP Peer Review Policy. After the review process implemented by the reviewer the following options can be done:

1. The paper may be accepted in current form. In this option, the author is notified accordingly. He is asked to return the approved and final manuscript in a print-ready pdf version and to ensure that he agrees with the conditions of the IOP Peer Review Policy and IOP Proceedings Licence.

2. The reviewer's report may be sent to the authors for revision of the paper. The revised paper is sent to the experts for their second evaluation; once the manuscript is accepted it follows the process of option 1.

3. The paper may be rejected. If the paper is not aligned with the technical guidelines or it contains too many errors or problems for the experts to comment fully on the scientific content, then the authors are asked to make corrections and then resubmit the article. In the case that the authors cannot perform the requested modifications, then their work is rejected.

• Conference submission management system: EASN Conference Platform: https://easnconference.eu/2021/abstract_submission

• Number of submissions received: 167

• Number of submissions sent for review: 163

• Number of submissions accepted: 114

• Acceptance Rate (Submissions Accepted / Submissions Received × 100): 68,26%

• Average number of reviews per paper: 2

• Total number of reviewers involved: 84

• Any additional info on review process: -

• Contact person for queries:

Apostolos Chamos: apostolos.chamos@easn.net

Kyriaki Panagopoulou: kyriaki.panagopoulou@easn.net

Please submit this form along with the rest of your files on the submission date written in your publishing agreement. The information you provide will be published as part of your proceedings.

Advanced Manufacturing Technology for Aeronautics

012001
The following article is Open access

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Out-of-Autoclave technologies are emerging as cost-effective alternatives to autoclave cure prepreg. However, their implementation in aerospace industry is still presenting many challenges. A common problem is the shape distortions that results in geometry mismatches with the tool. A way to avoid this and ensure a good final quality part is identifying the mechanisms that induce these deformations and optimize the manufacturing process of each component with the aim of reducing the production of faulty parts. The main objective of ELADINE project is to provide a method for shape distortions prediction on composite integral structures using an experimental-numerical approach. Different manufacturing parameters were monitored using Fiber Bragg Grating (FBG) sensors and DC-dielectric (DC) sensors and the resulting part geometry was examined by means of 3D coordinate analysis. The study performed for LRI (Liquid Resin Infusion) manufactured parts and the scenarios considered for the calibration of a Finite Element Method (FEM) based simulation tool are presented in the article. The resulting model will be implemented in a sub-scale demonstrator and, eventually, in a full 7-meter composite wing-box.

012002
The following article is Open access

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Fiber-reinforced polymer composites perfectly meet the basic requirements of aircraft flaps being weight reduction critical for fuel saving and increased payload. New technologies have been designed and developed to increase competitiveness in the use of composite materials by ensuring a continuous manufacturing process, a streamlined and balanced flow of activities, synchronized as much as possible with customer and market demand, reducing material scraps and non-value-added activities.

Resin excess, tool mark-offs, out of tolerance dimensions are potential defects generated during the hand lay-up process of the skin manufacturing of composite flap.

Innovative technologies for manufacturing of certified narrow body aircraft composite flaps have been designed and developed in order to achieve the best quality of the product and the program ramp-up.

Detailed tooling analysis and several simulations, included process flow and bottlenecks detection, have been performed in order to design the new process with high level of automation and reliable devices for human safety and production repeatability, that fully meets the customer's expectations.

012003
The following article is Open access

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Additive manufacturing (AM) is a computer-controlled 3D printing process with increasing demand in the aerospace sector. This manufacturing process offers the production of lighter components, design flexibility, reduced labour effort and material cost, as well as decreased waste generation compared with subtractive manufacturing. Additionally, AM can provide parts availability at the point of use, significantly improving the supply chain. However, producing advanced high-temperature AM thermoplastic components remains a challenging task as these require a high-temperature build chamber environment that is prone to producing parts with thermal stresses and warpage. PADICTON project aims to develop a tool capable of accurately and rapidly predicting and correcting such distortions, offering improved quality of the produced parts and minimising rejection rates. Creating this tool requires conducting a comprehensive mechanical and thermal characterisation campaign to optimise the print parameters and part geometry. In this study, the concept of the project and the findings of the initial mechanical and optical characterisation tests for two AM processes, namely fused deposition modelling and selective laser sintering, are presented and discussed.

012004
The following article is Open access

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The article describes methods and techniques intended for designing and manufacturing scaled airplane models applicable in experimental flight testing. Reduced model with resized geometric dimensions should be constructed in such way to preserve similarity of its structural properties with properties of the real aircraft. Having kept the similarity of weight, stiffness and aerodynamic load distribution and maintaining properly scaled values of thrust-to-weight and wing loading ratios we can prepare scaled model showing in-flight features identical to the real airplane.

A series of measuring and technological activities have to be undertaken to develop full CAD model mapping airframe geometry and structure of the real aircraft. The process chain includes measuring, design and technological activities. The development of the geometry model includes: scanning outer geometry of the real airframe, development of the surface geometry model in the CAD environment and then introducing inner geometry items which together with outer skin face make a completely assembled model of the aircraft. For the needs of constructing scaled model the full-size CAD model has to be reduced. The structure of that resized model do not have to be the same as the real one. Materials and structural elements can be quite different but after assembling them the similarity of static and dynamic structural effects should be proved. Within the manufacturing phase there are some necessary stages like preparing molds for laminating components, milling solid elements, assembly of structural components, surface finishing of the model-body surface. The final model was subjected to a load test in a special test stand to check its deformability under specific load. In the same way the numerical static analysis of the full-size FEM model was conducted. The distribution of static displacement results obtained in both cases were compared. The other way of checking structural properties of the scaled model is comparable analysis of resonant vibrations. However, in this case, vibration measurements were not carried out and model verification stopped on a comparative analysis of construction mass distribution.

The procedure and results were elaborated on the example of the Tu-154M aircraft, of which the reduced model was developed in the Faculty of Mechatronics, Armament and Aerospace of the Military University of Technology (FMA MUT Warsaw, PL). Constructing and testing dynamically scaled model is one of many tasks solved in the framework of complex research project, of which the general purpose was to give numerical and experimental results useful in explaining the circumstances of the Smolensk disaster.

012005
The following article is Open access

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In this study, the jig-less end-effector system developed to assemble components of a full-scale multifunctional integrated composite thermoplastic lower fuselage section is tested and validated. To offset the environmental impact of higher volume of air transport, the aviation industry wants to design lighter and more environmentally friendly aircraft. To achieve this, there is a need to exploit novel materials and technologies. Advanced thermoplastic composites provide an excellent material option thanks to their weldability, low density, low overall production cost, improved fracture toughness and recyclability. However, to fully appreciate their capabilities and benefits, new manufacturing approaches and techniques are needed. Hence, projects such as TCTool, "innovative tooling, end-effector development and industrialisation for welding of thermoplastic components", aim to develop innovative tooling and end-effector systems for the assembly of a multifunctional thermoplastic fuselage. This study presents the development, operation, and testing of the jig-less end-effector system used in the TCTool project for picking, placing, and temporary welding and fixing fuselage's clips and stringers.

012006
The following article is Open access

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The design and certification of composite structures is based on the building block approach (BBA), following a bottom-up procedure. Starting from the bottom level of Rouchon's pyramid of test, thousands of coupons need to be produced to determine design allowables and capture manufacturing, geometrical and microstructure variability values. The numerical approach provides desirable data to be confirmed by a reduced testing campaign, especially for the preliminary design process stages and material selection.

In this paper a carbon fibers reinforced composite with epoxide resin used for aerospace application has been analyzed, in form of both fabric and unidirectional tape to validate the numerical model considering Salver (of MA Group company) manufacturing process variability data. Hybrid laminates composed of unidirectional plies and woven fabric layers have been tested to pursue a tailored approach based on design guidelines and stress requirements for aircraft flight control surfaces. Benchmarking the experimental-numerical test results allows to assess the statistical reliability of the proposed method.

Aerodynamic Analysis & Design

012007
The following article is Open access

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In the frame of the CA3ViAR Clean Sky 2 (Composite fan Aerodynamic, Aeroelastic, and Aeroacoustic Validation Rig), the main objective is to design a low-speed (low-transonic) fan typical of a future large aircraft UHBR engine, in terms of aerodynamic shaping as well as structural design and analysis to make sure the test article experiences aerodynamic and aeroelastic instabilities in an expected way during wind tunnel (WT) operations. Eventually, open access to all the produced models will be provided, with the objective to establish an "open test-case" for the whole European scientific community, unique in the engine fans landscape. A preliminary fan stage design is presented in this paper, details about the aerodynamic design process and the results of the CFD analysis of the stage are shown. The present UHBR fan design fulfils the initial aerodynamic requirements and represents the starting point for the structural and aeroelastic analysis within the multidisciplinary design process employed to design the final CA3ViAR fan stage.

012008
The following article is Open access

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Distributed electric propulsion is a fertile research topic aiming to increase the wing aerodynamic efficiency by distributing the thrust over the wing span. The blowing due to distributed propulsors shall increase the wing lift coefficient for a given planform area and flight speed. This should bring several advantages as wing area, drag, and structural weight reduction, which in turn reduce fuel consumption, allowing airplanes to fly more efficiently. However, there are no consolidated preliminary design methods to size a distributed propulsion system. Numerical analysis is then performed at early stage, where many design variables have not been fixed yet. Therefore, the design space is vast and exploring all the possible combinations is unfeasible. For instance, low-fidelity methods (VLM, panel codes) have a low computational time, but usually they do not account for flow separation and hence they are unable to predict the wing maximum lift. Conversely, high-fidelity codes (CFD) provide more realistic results, but a single drag polar sweep can last days. This work provides a benchmark of different aerodynamic solvers for a typical regional turboprop wing with flaps and distributed propulsion, to better understand the limits of each software in the prediction of aero-propulsive effects.

012009
The following article is Open access

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In the wake of "flygskam" movement that emerged in Sweden a couple of years ago many voices recently raised denounce the environmental footprint of aviation. Even if the real impact of the sector could appear rather limited the critics reveal the necessity to propose cleaner aircraft to both meet public expectations and environmental goals. Because the classical wing-tube configuration seems to have reached its limits, disruptive designs must be considered. Among the perspectives to reduce emissions, high-aspect ratio wings represent a promising path to be explored within the European CleanSky2 project U-HARWARD. Indeed, substantial diminution of induced drag are expected from those new configurations resulting in fewer fuel consumption. To achieve high-aspect ratio without compromising the structural weight strut can be introduced. They allow for an alleviation of the bending moment at the wing root and therefore lighter structures. However, the consideration of those new wing configuration at early design stages is not straightforward and new methods have to be introduced. In this paper, we present three different fidelity approaches to tackle with (ultra) high-aspect ratio strut-braced wings sizing and weight estimation in preliminary design context. Already existing analytical formulations for the wings are extended, intermediate fidelity aero-structural coupling has been developed and high-fidelity structural representation are considered. Depending on the maturity of the concept these methods could be used to explore the design space, to refine the optimum or to analyse the final concept. Validation with respect to reference configurations is provided. Then the methods are applied to the analysis of strut-braced wings.

012010
The following article is Open access

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The current work presents the preliminary design procedure of a small-scale, fixed-wing Unmanned Aerial Vehicle (UAV), incorporating the novel Blended-Wing-Body (BWB) layout configuration. The UAV is designed to support a Cooperative-Intelligent Transport System (C-ITS), for monitoring traffic conditions at large national highways. The presented UAV design procedure emphasizes on both aerodynamic and stability behavior, aiming to a high aerodynamic efficiency and the satisfaction of the mission requirements. The design is supported by CFD analyses, to determine the aerodynamic and stability coefficients. Following the CFD modeling, the performance parameters of the platform are calculated. Furthermore, an internal layout study is conducted to integrate all the necessary internal components, determining the center of gravity. Finally, the overall UAV design concludes to an optimum configuration of the UAV-ITS, satisfying all the aerodynamic, stability and mission requirements.

012011
The following article is Open access

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Most modern aircraft engines rely on the use of high Bypass Ratios (BPR) turbofans to achieve both high thrust and low specific fuel consumption. However, such configurations are prone to the formation of ground vortices during low-speed operations. This phenomenon arises under specific combinations of wind direction, velocity or inlet air speed, generating engine vibrations and leading to the suction of damaging abrasive particles. Its characterization in early design stages is crucial. In this work, a joint experimental and numerical exploration of operating conditions leading to ground vortex presence is carried out on a scaled wind tunnel configuration. Flow details are investigated for several working points obtained from a specific set of input parameters (intake speed, wind speed, ground clearance). A methodology suitable for both experimental and Computational Fluid Dynamics (CFD) works is developed to extract vortex characteristic quantities, based on a local pressure minimum and Q-criterion contours topology. A very good agreement is obtained when comparing vortex predictions stemming from CFD and experiments. This database shall be used to transpose experimental data probed outside of the nacelle to data within the nacelle using data analytics techniques, paving the way for future data driven predictive models.

012012
The following article is Open access

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We present a numerical procedure to improve the performance of the classical Reynolds-Averaged Navier-Stokes approach for transitional flows by introducing a transition prediction tool in the RANS code. A black-box procedure able to estimate first the boundary layer quantities (starting from the pressure distribution) and then to compute the linear evolution of the fluctuations has been included in an existing RANS code. Thanks to the coupling to the eN method, the transition location is predicted and periodically imposed during the RANS computations. The approach proposed in this paper to predict the transition location and the laminar flow extension is based on a numerical framework based on the coupling between a high-fidelity, Reynolds–Averaged Navier–Stokes (RANS) tool and Linear Stability Equations. According to this method, boundary layer equations are written in conical formulation and the solution of RANS equations and transition onset is obtained through an eN method based on the PSE calculations. The validation of the present approach has been achieved by comparing the numerical results against the experimental data documented in the ETRIOLLA project.

012013
The following article is Open access

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We present a CFD analysis of a wind tunnel model of the new laminar turbo-prop aircraft designed in the frame of the European Clean Sky 2 programme. The work presents the numerical results of the aerodynamic performance of a scaled model of the innovative laminar turboprop A/C wing by using a CFD approach that includes the transition prediction. Numerical results will be compared by considering two different procedures: a) CFD analyses in which the transition location is imposed and b) CFD analyses in which the position of the transition is evaluated. The prediction of the transition location and the laminar flow extension is based on a numerical framework based on the coupling between a high-fidelity RANS tool and a Linear Stability (LNS) solver. According to this method, boundary layer equations are written in the conical formulation and the solution of RANS equations and transition onset is obtained through an eN method based on the LNS calculations.

012014
The following article is Open access

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The configuration of the airfoil has a significant impact on its aerodynamic performance. This paper aims to improve the aerodynamic efficiency of the cycloidal rotor system by using dynamically morphing blades. Three different camber morphing concepts (leading edge deflection, trailing edge deformation and cambered NACA profile) have been applied to a baseline 2-bladed system with rotating and pitching NACA0015 aerofoils. Then, based on these camber concepts, 2D URANS numerical simulations were conducted for blades with different morphing degrees using OpenFOAM. The simulation results verified that the flow field condition could be optimized and significantly higher thrust and efficiency could be achieved by properly tuning the morphing control. Especially, in the case of 10% trailing edge camber and 16% NACA camber, compared with baseline case, 28.1% and 43.5% higher figure of merit values were obtained, respectively. The simulation files and the results for the last rotor revolution of each case presented in this paper are available in the following dataset: https://doi.org/10.18419/darus-2191.

012015
The following article is Open access

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In this work, a study on the impact of passive flow control techniques on an Unmanned Aerial Vehicle (UAV) Blended Wing Body (BWB) is presented. The novel BWB layout integrates smoothly the wing to the fuselage, creating an aerodynamically superior platform. However, the lack of vertical stabilizers in the form of a tail, creates the need for aerodynamically stable and efficient wings that can withstand the spanwise flow. To that end, two passive flow control techniques are implemented in this study, namely the wing fences and the tubercles. Wing fences are vanes or airfoils attached vertically to the lifting surface and are one of the oldest flow control techniques used in aerospace applications to stop the spanwise flow. Wing fences extending from the leading edge to the trailing edge completely stop the spanwise flow. On the other hand, tubercles are sinusoidal modifications of the blade's leading edge. This is a novel flow control technique, with the original concept inspired from the characteristic flipper of the humpback whale (Megaptera Novaeangliae). Each bump creates a set of counter-rotating vortices that acts as a virtual fence and stops the spanwise flow. The results from this comparison show that flow control techniques can offer a considerable benefit to the flying capabilities of a BWB UAV platform, by improving the lift distribution and increasing the maximum coefficient of lift.

012016
The following article is Open access

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The paper presents experimental study results of ground effect influence on the aerodynamic characteristics of the twin fuselage transport airplane in a low-speed wind tunnel. The aerodynamic configuration has the two fuselages distributed under high-wing, and a "TT"–shaped tail. The twin fuselage transport airplane model consists of two fuselages, wing, empennage and external tank. The analysis includes studying the ground effect on the longitudinal and lateral aerodynamic characteristics and horizontal tail effectiveness. The effect of installing an external cryogenic fuel tank under the wing between the fuselages of the model was considered too. The obtained data shows the typical behaviour of the aerodynamic characteristics near the ground plate for aircraft model with high-wing and high placed horizontal tail. Ground proximity significantly increases the maximum lift-to-drag ratio and slightly changes the longitudinal moment characteristics. Horizontal tail effectiveness is maintained for all tailplane angles near the ground plate. The longitudinal and lateral stability of the twin fuselage transport airplane model is maintained in all considered modes near the ground plate.

012017
The following article is Open access

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This paper is discussed the results of study on aerodynamic layout of the cryogenic regional turboprop with a low level of environmental impact. The use of cryogenic fuel (liquid hydrogen, liquefied natural gas) in aircraft will radically reduce harmful emissions into the atmosphere, as well as reduce fuel consumption. But the introduction of cryogenic fuel on transport category aircraft requires solving the problems of its storage on board. A modification of a regional twin-engine turboprop for operation on cryogenic fuel is considered. The problems and features of the placement of the fuel tank for cryogenic fuel are shown. The results of experimental studies of the aerodynamics of an aircraft model with a cryogenic tank and the results of the calculation of flight performance with various types of fuel are presented.

Air Traffic Management (ATM) & Airports

012018
The following article is Open access

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The ATC service has the objective of controlling airspace operations safely and efficiently. This control is becoming more and more difficult due to the increasing complexity of airspace. With the objective of collaborating and facilitating the provision of the control service, FLUJOS project aims to develop a methodology to characterise ATC sectors according to their complexity. This paper shows the first results obtained in this project. A methodology is proposed that first performs a statistical analysis of the data present in the flight plans of individual aircraft. The statistical analysis will be used to estimate the impact of air traffic flows. With this, the complexity of ATC sectors will finally be determined. In addition, a machine learning tool will be added to develop a dynamic methodology. After evaluating the methodology with data from Spanish airspace in 2019, it can be said that the results obtained are logical from an operational point of view, and that they allow a fairly accurate classification of the sectors based on their complexity. However, the proposed methodology is still a preliminary version, so more work will have to be done to add variables to achieve the objective of obtaining an even more accurate and realistic classification.

012019
The following article is Open access

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This article evaluates Machine Learning (ML) classification techniques applied to air-traffic conflict detection. The methodology develops a static approach in which the conflict prediction is performed when an aircraft pierces into the airspace. Conflict detection does not evaluate separation infringements but a Situation of Interest (SI). An aircraft pair constitutes a SI when it is expected to get with a horizontal separation between both aircraft closer than 10 Nautical Miles (NM) and a vertical separation closer than 1000 feet (ft). Therefore, the ML predictor classifies aircraft pairs between SI or No SI pairs. Air traffic information is extracted from The OpenSky Network that provides ADS-B trajectories. ADS-B trajectories do not offer enough SI samples to be evaluated. Hence, the authors performed simulations varying the entry time of the trajectories to the airspace within the same time period. The methodology was applied to a portion of Switzerland airspace, and simulations reached a 5% rate of SI samples. Cost-sensitive techniques were used to handle the strong imbalance of the database. Two experiments were performed: the Pure model considered the whole database, and the Hybrid model considered aircraft pairs that intersect horizontally closer than 20 NM and vertically lower than 1000 ft. The Hybrid model provided the best results achieving 72% recall, representing the success rate of Missed alerts and 82% accuracy, which means the whole predictions' success rate.

012020
The following article is Open access

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Weather conditions and Air Traffic Management (ATM) operations are strongly related, due to the relevant influence that the observed and forecasted weather conditions into assigned airspace have on the operational conditions that are therefore possible for such airspace. In the framework of the SESAR JU funded project CREATE (Innovative operations and climate and weather models to improve ATM resilience and reduce impacts), therefore, a dedicated study has been carried out in order to investigate the relation between weather and ATM. Such study both investigated the consequences that adverse weather conditions can have on ATM and, on the other side, addressed the currently and future available tools that can support ATM in the prediction and management of weather conditions from the aeronautical operations point of view. In this paper, the results of such literature study are outlined. More in details, in the paper first the main outcomes of the study are summarized, in terms of identification of the most relevant weather phenomena that affect the ATM operations, indication of their main impacts on them in terms of operational disruptions and, finally, identification of the associated level of severity. In particular, the above indicated aspects are addressed by taking into specific consideration the enroute and the TMA (Terminal Manoeuvring Area) flight phases and, for each of them, the main affecting weather phenomena and the main affected operations are identified. Then, in the paper the results of the study are summarized about the identification of the most relevant meteo tools that are expressed by state-of-the-art technologies to support the ATM operations in order to properly take into account the weather conditions in a precise and timely manner. This study addresses both the review of available and perspective tools for weather reporting and of the available and perspective numerical models supporting ATM in terms of weather models and air quality models.

012021
The following article is Open access

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The objective of this methodology is to characterise the safety of air routes under a systematic framework, in terms of Separation Minimum Infringements (SMI) between en-route aircraft based on models known as Safety Performance Functions (SPF). Bayesian Networks have been selected as techniques with high predictive capability and low probability event estimation. Moreover, they allow the integration of knowledge modelling with data inference. It is complex to develop a Bayesian Network model for SMI prediction. It is necessary to integrate the available knowledge about the precursors of SMIs together with the accumulated knowledge from the analysis of the collected data into a conceptual framework. This framework underpinning the Bayesian Network model focuses on the Closest Point of Approach (CPA) analysis and considers the general scenario of aircraft evolution in an air traffic sector. In order to translate this conceptual framework into a set of causal sub-networks, the ATM barrier and event tree models are used.

012022
The following article is Open access

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The implementation of Free Route Airspace (FRA) in European Airspace has significantly reduced flight distances. However, there are still elements in the conventional FRA that need to be optimized in order to allow a further improvement in flight efficiency and these are the predefined entry and exit points that are still obligatory to be inserted in a flight plan by the crews and to be flew over during the flight. The introduction of cross-border FRA is another milestone towards the improvement of flight and Air Traffic Management (ATM) systems efficiency. The purpose of the article is to examine the possibility of implementation and expansion of already existing cross-border FRAs and how much distance would be saved if it was possible to fly in a cross-border FRA, instead of a conventional FRA. Thus, two possible scenarios on the extract of a chosen flight route, based on a real-world flight, operated by inter alia LOT Polish Airlines, are examined. Route distance extension was calculated using the Horizontal Flight Efficiency method. Subsequent calculations include potential flight time savings along with fuel waste, CO2 emission and operating costs. The validation of the results obtained through calculation was conducted on X-Plane 11 as a simulation of two examined scenarios, using a Boeing 737-800. The results of the calculations and simulations indicate that the implementation and expansion of cross-border FRA may have a positive impact on flight efficiency improvement due to the reduction of distance and consequently the flight time, fuel waste, CO2 emission and operating costs. It can also mitigate the problem of the European Airspace capacity gradually reaching its maximum level. Thus, there is still a lot of place for further optimization of air traffic flow in European Airspace.

012023
The following article is Open access

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In the history of aviation there were many cases that led to the obligation or necessity to bypass certain airspaces, mainly due to political and safety reasons. One of the latest events is the incident over Belarusian airspace. The fundamental concept of the article is to examine the effects of the necessity to avoid certain airspaces by the operators, using the incident over Belarusian airspace as an example. Based on the observations of air traffic flow over affected region, route distance extension was calculated using the Horizontal Flight Efficiency method. Subsequent calculations include potential increase in flight time, fuel consumption, carbon dioxide emission and operating costs. The results were extrapolated to yearly amounts. based on the air traffic prediction reports. The air traffic prediction analysis as well as the results of the calculations and simulations indicate that the bypass of the airspaces on flight routes important to global economy, has a serious impact on the environment and operators' budget due to increased aircraft's fuel consumption resulting in growth of carbon dioxide emissions as well as operating costs. It also leads to deterioration in the European Airspace's capacity, causing the necessity for Air Traffic Management units to reorganize the air traffic flow over the affected regions. Potential solutions mitigating the problem were also proposed.

012024
The following article is Open access

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This paper reviews major research trends and opportunities in airport demand and capacity management from an economic perspective. Airport capacity constraints lead to operational congestion and delays, which have become major threats to the aviation industry. They impose large costs on airlines and their passengers. Uncertainty in demand or unexpected events can cause a mismatch between capacity and demand, resulting in either capacity over-supply, with a decrease in efficiency, or airport congestion over an extended period. Moreover, airport capacity is rather difficult to define due to its multi-faceted and dynamic nature, and it depends both on the available infrastructure and on operating procedures. The non-linear relationship between airport capacity and on-time performance offers guidelines for congestion mitigation through demand and capacity management. This paper explores and produces an in-depth understanding of the capacity and demand balance problem and provides a roadmap for including economic concepts when evaluating airport capacity expansions.

012025
The following article is Open access

and

In Air Traffic Management (ATM), Safety Management Systems (SMS) form the principal vehicle for implementing safety policies, practices and procedures in accordance with internationally agreed Standards. In a constantly changing operating environment, it is essential to maintain SMS effectiveness to maintain and enhance levels of ATM safety. Research at the University Politehnica of Bucharest (UPB) has analysed the major, fast-rising threats to ATM safety emerging in the cybersecurity field, and the related synergies between formal management systems in the fields of security and safety. Its ultimate objective is to assess the feasibility of equipping SMS with protection against security risks, especially cybersecurity. It further explores the potential effects of cybersecurity threats to aviation safety and the available protection mechanisms. In considering the synergies between Security Management Systems and Safety Management Systems in ATM, the possibility of full integration of the two into a single protection system is explored. Whilst, despite similarities, such a combination is not found to be an optimal arrangement, the examination nevertheless enables the derivation of the security measures required in order to enhance the effectiveness of SMS.

Aircraft Design and Propulsion

012026
The following article is Open access

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System design in an aircraft is still a costly, manual and iterative approach. One major cost driver of changes in system installation are design efforts for creating new pipes in an earlier stage and the costs accumulated during the in service life. To reduce these costs and the time to market, an automation approach with an integrated design optimization encoded in graph-based design languages and executable in a design compiler is proposed.

To generate the pipe work automatically, a set of input data (e.g. start- and end-points of a pipe with tangents and fixing positions) is given by the user. It also contains, among others, the weightings for the optimization criteria (e.g. length of the pipe resp. the weight vs. the number of bends) to influence the evaluation of the generated pipes and thereby the final solution. As an initial step in the automatic pipe generation process, a route through the installation space is searched. Subsequently, the installation space is simplified and a respective minimal distance to each obstacle which a pipe should satisfy is added. Then for each pipe an initial solution is estimated and each pipe is optimized by a simulated annealing algorithm. At last, all given requirements are automatically verified. The capabilities of the newly developed automated piping are demonstrated on the pipe work in an Airbus A320 landing gear bay.

012027
The following article is Open access

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With the increase in the air traffic, reducing the aviation environmental impact is the key challenge of the community. This has called for more research in the area of using alternative fuels which will reduce the greenhouse gas emissions and which can provide similar or better environmental performance. This work presents a preliminary design methodology of a mid-range single aisle commercial aircraft using Hydrogen as fuel which is stored in an integrated tank in the fuselage. The iterative design process was achieved by using overall aircraft design approach through the FAST-OAD open-source software.

This study describes the models used for a first approximation of structural and insulation weight of liquid Hydrogen (LH2) tank and fuel boil off computations. It then presents the impacts of an LH2 storage system on the overall aircraft design with an emphasis on the centre of gravity (CG) travel and the additional fuselage length necessary to accommodate the LH2 tank. An additional parametric study has also been carried out to understand the effect of some design parameters on overall design. Finally, an environmental study has been conducted to evaluate the direct emissions of this aircraft in operation. The only emissions that result from the combustion of hydrogen are nitrogen oxides (NOx) which were evaluated using the Boeing Fuel Flow Method (BFFM2) and water vapor (H2O) which was evaluated based on the fuel burned. As a result of this study significant reduction in NOx and CO2 emissions as compared to existing design are envisaged, thus showing the promising potential of Hydrogen fuelled aircraft.

012028
The following article is Open access

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In this work, the conceptual design methodology of a hybrid Unmanned Aerial Vehicle (UAV) – Unmanned Underwater Vehicle (UUV) platform is presented. As the mission complexity and the need for interoperability between different platforms grows more demanding by the day, hybrid platforms are becoming an essential solution. Hybrid UAV-UUVs can operate seamlessly and repeatedly in both the aerial and underwater environments, something that numerous animal species already execute in an optimized way. The design methodology starts with the review of the few available prototypes, creating initial design trends and continues with analytical calculations. These calculations are based on aircraft design textbooks and are modified to take into account the special characteristics of a hybrid platform, such as the means of transition between the water and the air. A Blended Wing Body (BWB) layout configuration is selected for the numerous aerodynamic advantages that it offers. The analytical calculations are then validated with the use of high fidelity CFD calculations. The results from the conceptual design phase indicate that the proposed methodology for hybrid UAV-UUV configurations provides a good design accuracy. Finally, the outcome of this methodology, which is a hybrid UAV-UUV platform is potentially the answer to the operational gap for missions that include both underwater and aerial environments.

012029
The following article is Open access

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The development of innovative aircraft configurations can be an important contribution to achieve the emission reduction goals set for the aviation industry. However, current common aircraft conceptual design processes only allow the consideration of a limited number of initial configurations thus leaving possibly more efficient solutions out of scope. A significantly wider range of aircraft configurations can be taken into account by applying the Morphological Analysis. After a brief presentation of its historical background and actual applications in other domains, this article focuses on the use of this method and its benefits in aerospace. The summary and comparison of several applications in the field of aircraft design show that these still require a higher level of formalisation and robustness. For this purpose, the main steps required to integrate morphological analysis into the aircraft conceptual design phase based on the Advanced Morphological Approach are identified. These are the definition of the morphological matrix along with the evaluation criteria, the obtaining of option evaluations, filtering the impossible solutions and exploration of the solution space.

012030
The following article is Open access

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This paper describes the exploitation of Genetic Algorithms for the selection and optimization of supersonic airfoils. The main objective of the optimization is to ensure the possibility to reach the maximum efficiency at a given lift coefficient. The surrogate model presented in this paper implements the shock-expansion theory, and the optimization problem is constrained with respect to three design variables, since Bézier curves are used for the parameterization of the Diamond-Shaped and the 40-elements Double Circular Arc airfoil geometries. The airfoils were optimized for three different Mach numbers and two different lift coefficients. A thickness-constrained optimization has been run to evaluate the possibility to obtain a specific lift coefficient at a given Mach number and to understand how this parameter influences the optimized airfoil shape performance in terms of efficiency and the range of feasible angles-of-attack. An off-design evaluation is also presented, allowing for a comparison of the optimized geometries in terms of versatility. High fidelity models were validated with RAE 2822 airfoil using STAR CCM+, and they were compared to the surrogated model to ensure higher quality in the results. In conclusion, the Genetics Algorithms optimization coupled with the shock-expansion theory model results to be a fast and valuable solution to select and optimize airfoil solutions. The application of this approach has shown that a 20% reduction in airfoil thickness leads to a 25% efficiency improvement, while widening the range of viable angles of attack.

012031
The following article is Open access

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The paper deals with the design of a two-stage to orbit rocket launcher loaded with a solid rocket booster, scramjet, and hybrid rocket for delivering a 100kg payload in 200 km circular orbit. The possibility of implementing a cavity-based axisymmetric circular combustor in a scramjet is proposed. Computational analysis on various injector locations in a circular combustor and their validation with the test bench results were performed. The utilisation of a hybrid rocket in the final stage of the launcher to deliver the payload is discussed and the performance characteristics of the circular scramjet combustor and the hybrid rocket are shown. The overall mission proposed based on the sustainable and reusable characteristics.

012032
The following article is Open access

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Microturbines can be used not only in models and education but also to propel UAVs. However, their wider adoption is limited by their relatively low efficiency and durability. Validated simulation models are required to monitor their performance, improve their lifetime, and design engine control systems. The aim of this study is to develop a numerical model of a micro gas turbine for engine performance predictions and prognostics. To build a reliable zero-dimensional model, the available compressor and turbine maps were scaled to available test bench data with the least-squares method, to meet the performance of the engine achieved during bench and flight tests. A steady-state aeroengine model was then developed and compared with experimental operating points. Selected flight data were then used as input for the transient engine model. The EGT temperature and the fuel flow were chosen as the two key parameters to validate the model, comparing the numerical predicted values with the correspondent experimental ones. The observed difference between the model and flight data was lower than 3% for both EGT and fuel flow.

012033
The following article is Open access

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In order to achieve aviation's ambitious emission reduction targets specified by ACARE [1] radical changes in propulsion system concepts will be necessary. To fulfill the goal of carbon dioxide emission neutrality in 2050 and beyond, plenty propulsion system concepts are currently under investigations, mainly focusing on batteries and hydrogen as energy source. Especially for long range aircraft applications, hydrogen might by favorable due to its outstanding specific gravimetric energy density. Therefore, the Composite Cycle Engine (CCE) concept should be evaluated for hydrogen combustion. In a first step, the applied time resolved 0D piston engine performance simulation model of the CCE is adapted for hydrogen combustion. For example, the heat transfer and combustion characteristics of kerosene and hydrogen combustion differ significantly and require specific modeling approaches. The current publication illustrates the piston engine performance simulation model and the modifications needed to account for hydrogen combustion. Furthermore, results of validation case calculations as well as initial sensitivity studies of the hydrogen fueled piston engines model are presented and discussed in the CCE context. For example, sizing effects and the influence of valve timing on piston engine performance will be evaluated.

012034
The following article is Open access

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Re-ignition of aeroengine under high altitude conditions is of great importance to the safety and use of lean-burn engines. The present work investigated the experimental and numerical analysis of flow and re-ignition characteristics in a rectangular burner. A ring-needle type plasma actuator was developed and powered by high voltage nanopulsed plasma generator with different percentage values of amplitude voltage and frequencies. Flow visualizations by using high speed camera and Proper Orthogonal Decomposition (POD) were performed to recognize the dominant flow structures. Experimental results showed the transport effects such as induced flow with an impact on the recirculation zone near the corners of combustor, improving the mixing performance, which could be contribute to the reduction of ignition delay timings. Experimental characterization in non-reactive flow allowed the estimation of the electrical power and the optimal reduced electric field (EN) value, which was then used as input to the numerical study for the flame ignition analysis. Ignition characteristics were analyzed by coupling two different numerical tools ZDPlasKin and Chemkin. It was noticed that time required to achieve the maximum flame temperature with plasma actuation is significantly reduced in compared with autoignition timings (clean case). Maximum reduction in ignition timings was observed at inlet pressure 1 bar (3.5×10-5 s) in respect to clean case (1.1×10-3 s). However, as the inlet pressure is reduced, the ignition delay timings were increased. At 0.6 bar flame ignition was occurred at 0.0048s and 0.0022s and in clean case and plasma actuation case, respectively.

012035
The following article is Open access

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In aerospace sector, reliability is a crucial point. Modern technologies widely use Artificial Intelligence (AI) algorithms together with detections by sensors in order to design a health-based maintenance plan which stops an aircraft only when needed. In this work, an Engine Health Monitoring (EHM) system was developed by exploiting AI algorithms as Artificial Neural Networks (ANNs) trained to estimate a series of Performance Parameters (PPs) used as index of the health status of the main components constituting an engine. A neural network called Feed-Forward Neural Network (FFNN) in combination with a Principal Component Analysis (PCA) for feature reduction was used in this paper. The software Gas turbine Simulation Program (GSP) was used to generate a series of data containing information about engine performance under different flight conditions and compressor degradation levels. The datasets were subsequently used to train the neural networks to estimate the PPs of the degraded component. The final purpose of the present work is to develop an efficient diagnostic system useful to increase flight safety and decrease maintenance costs and fuel consumption.

012036
The following article is Open access

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An objective of this study was to perform an analysis of available working fluids and select those one(s) that will be able to comply with the specific requirements of the ultra-high bypass ratio (UHBR) engine air bleed system and ensure efficient LHP operation. A multi-step approach was applied to analyse more than 700 working fluids and select four potential candidates, taking into account (1) working fluids compliance with EU regulations; (2) working fluids freezing, boiling, and critical points for the operating temperature range; (3) working fluids specific properties that influence the LHP performances. Selected fluids (toluene, acetone, methanol, 1,2-dichlorobenzene) were subjected to accelerated life tests to check their chemical compatibility with AISI 316 stainless steel to be used as the LHP material. Based on the results obtained, the toluene was selected as the working fluid for application in the innovative LHP-based thermal management solution for the UHBR engine air bleed system.

012037
The following article is Open access

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The paper contains the results of CFD analysis of flow inside the simplified engine nacelle, containing the engine in a pusher configuration. The authors have tested a set of solutions to increase an efficiency of the cooling system of this type of engine. Unfortunately, all the positive effects of the fact, that the aircraft engine appears in the wake of the propeller during taxiing and waiting for takeoff, are nonexistent in this type of configuration. An engine overheating is here a problem, because an airflow has to be pulled through the nacelle to cool down the engine block and radiators of cylinder heads. That design demands to analyze the cover shape of the nacelle, to properly use the main propeller pressure jump on the one hand, and rather adequate and complicated flow inside the nacelle to be modelled on the other. The aircraft CAD geometry has been simplified to allow for simple changes of the nacelle cover shape and easily introducing new inlets and outlets. The results prove, that the proper application of scoops gives even better result, than simply removing the cover and baffles from the engine. The exhaust scoops should be placed near the propeller plane in such pusher configuration, because the engine is not covered by the propeller wake.

012038
The following article is Open access

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The complex interrelation of thermal and hydraulic processes in a gas turbine engine bearing chamber requires modelling methods based on the multiphase flow mechanics and Computational Fluid Dynamics (CFD) to predict the fluid distribution and heat transfer phenomena. This paper presents a study of different approaches to CFD modelling of multiphase oil-air flow in the bearing chamber. The Volume of Fluid and Eulerian multiphase models, Steady and Transient solvers, "Realizable k-ε" and "k-ω SST" turbulence models were analysed. The Eulerian Wall Film Model implemented in ANSYS Fluent was applied to model an oil film formation on the bearing chamber walls. The CFD results were compared with available experimental data to formulate practical recommendations for precise modelling of processes in the bearing chamber.

012039
The following article is Open access

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Cyclorotors employ cyclically pitched axial rotor blades to create an extremely maneuverable propulsion system. The pitch angle throughout one rotation is defined so that the resulting blade angle of attack follows a prescribed function that generates lift. The lift and drag produced is also affected by curvilinear flow, dynamic stall, and induced velocities, all of which affect the resulting angle of attack. These factors form complex relationships that are difficult to model analytically, making it hard to predict a cyclorotor's performance. Here, a numerical model is presented which can be used to predict thrust and power draw of different cyclorotor configurations. Parameters include airfoil, number of rotor blades, rotational velocity, pivot function, fluid properties and Reynold's number. The numerical model builds on previously implemented approximations but focuses on time-efficient calculations so that many configurations may be calculated in an iterative process. In each iteration the parameters can be adjusted according to machine learning or other metaheuristic optimization algorithms to determine an optimal configuration.

012040
The following article is Open access

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Fuel sloshing-induced damping is currently being studied extensively within the EU-funded SLOWD project as a means of passively reducing dynamic loads in aircraft wings. It is of interest to be able to determine which parameters have the greatest influence on the added damping from the sloshing motion. An uncertainty in the measured sloshing force has been observed when multiple consecutive and identical oscillation cycles are considered in sinusoidal excitation experiments, leading to variations in the measured energy dissipation. This current work considers liquid undergoing vertical sloshing motions for different fill level and excitation conditions (frequency and amplitude) leading to energy dissipation via several possible physical mechanisms. The sloshing dissipation is measured experimentally across a large number of excitation cycles and for each excitation amplitude, expressed in the form of Froude (Fr) numbers. Depending on the Fr number, distinct sloshing mechanisms dominate the dissipative effects and induce a particular variance across the identical cycles analysed. The sloshing-induced energy dissipation variation is quantified and correlated with different mechanisms depending on Fr number, helping to explain various non-stationary effects that are observed even in well-controlled experimental conditions. As well as improving the insights into the inherent dispersion nature of the studied phenomena, this research also establishes experimental characteristics suitable for future model validation and calibration.

012041
The following article is Open access

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The ambition of the CA3ViAR project is to design an open test case fan that experiences instability mechanisms, which are representative for ultra-high bypass ratio (UHBR) fans of civil aircrafts, and to perform a comprehensive experimental investigation to measure aerodynamic, aeroelastic and aeroacoustic performance in a wide range of operational conditions. Experimental tests will be performed in the Propulsion-Test-Facility (PTF) of the Institute of Jet Propulsion and Turbomachinery (IFAS) of Technische Universität Braunschweig, Germany. The final objective of the project is to provide an open test case for the entire research community, with geometries, numerical and experimental results to establish a new reference for composite UHBR fan design. This will support the development of new methods and tools for the development of safer, lighter and more efficient composite fans for greener UHBR engines. In this work the preliminary design of the low transonic fan (LTF) to be used as test article, whose main requirement is to be operated in a safe and controlled way in conditions of aerodynamic and/or aeroelastic instability during wind tunnel operations, is presented. More in particular, consolidated aerodynamic design, strategy adopted to drive the structural design, flutter analysis taking into account acoustic reflection at the intake, dynamic and stress analyses, as well as aeroacoustic measurement optimization are presented and discussed. The preliminary mechanical design of composite blades and the rotor hub, together with the rotor instrumentation and related studies to embed sensors in the composite blades, are also part of this article, and complemented by manufacturing trials and demonstration tests give the full picture of all the project activities up to the preliminary design review.

012042
The following article is Open access

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The integration of automated tool capabilities for the generation of models for transient dynamic calculations in the scope of the aircraft pre-design is described in this paper. The Python-based DLR framework PANDORA, initially developed for the modelling and the sizing of aircraft structures in multidisciplinary process chains, is considered for this work. The focus lays on the generation of suitable numerical models for the water impact simulation. To enable this, the internal tool database was extended to consider additional features such as contact definitions, mesh-free formulations, enhanced connection models and specific control options. The generation of the CPACS-based FE aircraft model was extended by means of discretisation and additional structural components. The generation of the water domain was also included according to user defined inputs like pool dimensions, initial conditions and the selection of an appropriate fluid modelling approach. In addition, a feature to launch a simulation directly within the framework was included. Finally, options to retrieve and visualize results from finished water impact simulations were also integrated, allowing to display contour and time history plots.

012043
The following article is Open access

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The increasing demand for individual mobility worldwide is leading to the development of new forms of mobility. Individual air mobility (e.g., air taxis) could be one innovative approach to meet this increasing demand. To successfully realise such innovative approaches, interested companies must know the technical, economic, and ecological requirements of all relevant stakeholders and integrate them in their air taxi developments. Based on these diverse requirements, a resilient air taxi concept must first be created that describes the essential characteristics of future air taxis and enables a well-founded assessment. However, in practice, it is often difficult for companies to outline such a concept and then develop it consistently and highly iteratively. To face this challenge, a process has been set up which creates a deep link between the requirements and concept development phase to assure the development of requirement-compliant air taxis in an agile manner. The process is divided into two parts. The first part connects the market analysis, requirements definition and concept creation, thus linking the requirements and concept development phase. It is based on a double diamond model consisting of two phases. In contrast, the second part is focusing on the pre-development until the end of the concept development phase by adapting the SCRUM methodology to derive a sound air taxi concept. Both parts are executed in a highly iterative manner to reflect the significant amount of uncertainty at this early process stages.

012044
The following article is Open access

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This paper presents a description of the algorithm that accelerates the search for design cases of loading the perspective airframe for civil aircraft, which differ from traditional layouts. The results of validation of the algorithm for a regional aircraft with a high aspect ratio wing are presented. It was shown that the use of the proposed algorithm makes it possible to reduce the calculation time for finding the critical loading factors by at least 10 times compared to the traditional algorithm.

012045
The following article is Open access

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REIVON is a Clean Sky 2 Technology Evaluator project that investigates to what extent CO2 emissions of global aviation can be reduced via optimisation of aircraft size/range and flight network. Three alternative global flight networks are created, considering (1) splitting long-haul flights into shorter legs (intermediate stop operations, ISO), (2) reducing frequency to the necessary minimum on busy routes using larger aircraft, and (3) a combination of 1 and 2. In all cases, the use of aircraft optimised for specific combinations of range and seating capacity not existing today will be considered. For the first time, REIVON will carry out a holistic analysis of the impact of an optimised flight network on global air transport system stakeholders, such as passengers, aircraft manufacturers, airlines and airports, and of potential measures to support the implementation of such an alternative network.

012046
The following article is Open access

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Aircraft operational performance is a key driving factor to flight punctuality and airline profitability. The ability of a system to meet its operational requirements in terms of reliability, availability and costs is termed as 'Operability'. It is of high importance for aircraft manufacturers to project operability during the early stages of development of an aircraft in order to make trade-off studies. This paper proposes a hybrid approach of using machine learning and expert knowledge to aid the projection of aircraft operational performance during the early design stages. This approach aims to benefit from the huge amount of in-service data available from the current and past fleet of aircraft. Hence, machine learning techniques are used to learn how different technical issues and their associated maintenance activities impact aircraft operations. Expert knowledge is used to establish the default rules of the simulation model used for the operability projection. Results from machine learning are used to improve these rules allowing one to make holistic projections of the operational performance of future aircraft. This approach allows one to estimate the elapsed time in different operational states of an aircraft like flying, turn-around, etc. which can then be used to calculate different operability Key Performance Indicators (KPIs) like aircraft reliability and maintenance unavailability.

012047
The following article is Open access

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Multidisciplinary collaborative aircraft design is applied to a 90 passengers regional jet aircraft retrofit, highlighting the impact on costs and performance. Two retrofitting packages have been considered: the re-engining of conventional power-plant platform with advanced geared turbofan and the on-board-system modernization, considering different level of electrification. Starting from a reference existing aircraft, the impact of retrofitting process has been carefully evaluated on capital costs and savings at industrial level through a developed methodology. At aircraft level, masses, performance, noise, and emissions have been computed with dedicated competences increasing the estimation reliability. Overall process is implemented in the framework of the AGILE 4.0 research project in a collaborative remote multidisciplinary approach. Results show that such retrofitting activities are expensive and must be evaluated since the design stage with a bottom-up approach requiring competences coming from designer experience to correctly define the process work-breakdown-structure and its implications.

Aircraft Noise

012048
The following article is Open access

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This paper presents a preliminary experimental investigation into the acoustics of two elliptical jet nozzles installed close to a wing model. Acoustic pressure data is obtained for a range of observer polar angles mounted in the far field of the jets. Three nominal jet Mach numbers, namely 0.4, 0.6 and 0.8 are studied. Results suggest that the elliptic jets surveyed provide a noise reduction of the jet-surface installation noise source. The noise reduction is maximum in the forward arc and in the order of 1 dB for the fully-corrected overall sound pressure level data. Additionally, the noise benefit exists only when the minor axis of the elliptical nozzle is mounted parallel to the wing trailing edge. It is hypothesised that the reduction in the jet plume cross-section width limits the scattering of the near pressure field by the wing trailing edge to a lower frequency range. The jet mixing noise source, however, is seen to increase with decreasing nozzle exit-plane aspect ratio. The three jet velocities surveyed suggest the consistency of the key results discussed in the paper. Investigation of the jet turbulent flow structures and jet near pressure field is under way.

012049
The following article is Open access

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This paper presents research related influence of friction powders on enlarging the absorption band of acoustic liners used for reduction of tonal noise in fan duct of aero-engine. Kundt tube measurements done at COMOTI using fine powders (granules) made of various light-weight materials placed in the honeycomb cells of SDOF liners have shown a considerable broadening of the absorbed band of frequencies without a significant decreasing of absorption at the resonance frequency. Although the phenomenon is generally present for any type of powder, it was observed that for some powders the absorption is higher than for others. On the other hand, it was observed that the effect of the filling percentage of the cavity is important. Then, experiments done at the grazing flow facility of CNRS-Le Mans University have shown that the phenomenon is also present for high acoustic incident levels (up to 140dB) and M=0.13 while it still depends by the nature of powder material. The best results were obtained for the cork powder when the honeycomb is filled with powder at 66% of its height. For this material, the broadening of the transmission loss well was maximum. This phenomenon could be explained by the apparition of friction between powder granules which are taking place at very low scale consuming the noise power on a broader range of frequencies. It is supposed that the friction between the particles of powder have major influence because the best noise absorption was obtained for powders with a large distribution of particles' dimensions while for particles with a small dimensional distribution (expanded polyester balls, for example) the transmission well broadening was smaller. The friction powders technology is simple and can be easily adapted to existing acoustic liner technologies with small manufacturing costs. This feature is conferred by the fact that powders can be easily poured in the honeycombs at the required height. The friction powder technology can be applied not only for the fan duct. In future, it could also be applied for reduction of jet noise reflected by pressure side of wing and for cabin noise reduction.

012050
The following article is Open access

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A theoretical prediction method of the scattering of fan tone radiation from a turbofan inlet duct by the airframe fuselage is presented. The fan tone noise is modelled by an acoustic disc source that represents the sound field at the inlet duct termination. Adjacent to the source is a cylindrical fuselage that scatters the fan tone radiation. The prediction method is valid for upstream sound radiation. The acoustic pressure on the cylindrical fuselage is affected by refraction of the sound as it propagates through the fuselage boundary layer. This effect known as boundary layer shielding is more prominent forward of the turbofan, since the fan tone noise radiated from the inlet duct is propagating upstream. An asymptotic approach is used to model sound propagation through a boundary layer which is modelled by a thin linear shear velocity profile. Consequently the scattered pressure field can be computed very quickly, thus providing a fast and efficient prediction method. Although a realistic fuselage turbulent boundary layer does not resemble a linear shear layer, it is shown that the effect of acoustic shielding by a turbulent boundary layer can be modelled by taking a liner shear profile with a shape factor that matches the shape factor for a realistic turbulent profile.

Aircraft Testing

012051
The following article is Open access

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The Goal of the Project GRETEL is to build a composite elastic wing wind tunnel model. This model incorporates morphing aerodynamical structures and is to be delivered for testing in the Large Low speed Facility (LLF) wind tunnel of DNW. In order to be allowed to be tested in a wind tunnel, a ground test is required to assure the integrity of the design of the wing. In this paper a short introduction to the overall setup of the model is given including an overview of integrated sensors. A short introduction into the different configurations of the wing to be tested is given as well as the rationale for the derived test-matrix of the ground tests. The mechanical setup for the ground tests is described. There are two main tests done, on the one hand the static tests of the wingbox, on the other hand the dynamic tests for determination of modal parameters of the model in its different configurations. The static tests are done to identify mechanical responses of the model as built and compare them to the predictions of the Finite Element simulations. The method to derive the boundary conditions, i.e. loads and deformations, for the static tests from the simulation is documented and discussed. The static tests are also used to calibrate the integrated strain gauges to enable load monitoring in the wind tunnel tests. First experimental results from the ground tests are shown and discussed, comparing them to predictions from the simulation.

012052
The following article is Open access

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Building a wind tunnel model with an innovative aerodynamic design including a laminar airfoil concept and morphing parts requires a suitable manufacturing and assembly plan to transfer the virtual model to concrete reality.

The contribution of the INVENT GmbH within the GRETEL consortium is the manufacturing of the main structural components of the Wing and the integration of the Wind Tunnel Model. To realize such a precise projection, the main approach is to implement a high overall accuracy of the later model by realizing a low percentage of geometry deviation already on piece part level. Beginning with a material dedicated tool design concerning cure cycle parameters and induced strain effects, for aspects of geometrical manufacturing accuracy, also suitable inspection techniques, regarding the verification of structural requirements and material conditions are implemented in the integration process at specified steps.

A further part of the integration process of the GRETEL Wind Tunnel Model is the installation of application-related measurement equipment. The Institute of Composite Structures and Adaptive Systems of the German Aerospace Center (DLR) is responsible for the design and realization of such a project customized measurement concept. For the measurement of the pressure distribution along the profile contour with various angles of attack and wing configurations during the testing, the wing is equipped with several pressure taps. Further, the measurement equipment spectrum covers also the registration of acceleration forces and mechanical loads of the inner wing structure components. This concept creates a holistic picture of the coherences between aerodynamical and mechanical dimensions for each tested configuration.

The implementation of all aforementioned aspects into the large-scale model is elucidated and discussed in the light of morphing parts of the model being delivered by another project. The integrated equipment is described and the impact of the integration into the design and assembly of the overall model is illustrated.

012053
The following article is Open access

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This paper presents the development of a cabin noise testing equipment that will be used to evaluate the interior noise of regional aircraft as well as to aid the development of noise reduction techniques. The innovative noise generation system consists of three loudspeaker arrays positioned around the fuselage circumference to synthesize a pressure field that is similar to the pressure field seen by the fuselage during a flight. The acoustic pressure field generated by the loudspeakers is measured by a number of microphones scattered on the fuselage surface. These microphone signals are then fed back to the controller with the purpose of minimising the error between the target pressure field and the measured one by means of an iterative learning approach. The number and location of the microphones used in the control loop are selected through a pre-test optimisation analysis, which aims to reduce the time and cost of the set-up. A small-scale electroacoustic demonstrator has been built to develop the feedback control approach. A frequency domain multi-input multi-output feedback controller is used to replicate the random pressure field generated by the turbulent boundary layer excitation. The multi-harmonics of the propeller induced excitation are then added to the time histories of the broadband noise using a time waveform replication technique. Different arrangements of the driving signal distribution are investigated, and the results are then presented in terms of accuracy of the pressure field reproduction.

012054
The following article is Open access

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The aircraft insulation separates the thermally comfortable cabin interior environment from the extremely cold outside condition. However, the fabrication and installation of the insulation in the aircraft is a labour intensive task. Tailored, rigid particle foam parts could be a solution to speed up installation process. The presented study investigates the feasibility of such a concept from a hygrothermal point of view. Due to the temperature difference between the cold air trapped between aircraft skin and insulation on one side and the warm cabin air on the other side, a buoyancy induced pressure difference forms. This effect drives the warmer air through leakages in the insulation system towards the cold skin. Here, moisture contained in the air condenses on the cold surfaces, increasing the risk for uncontrolled dripping ("rain in the plane") when it melts. Therefore, this study compares the frost build-up of different installations of a rigid particle foam frame insulation with the classical glass fiber capstrip. Tests are hosted in the Fraunhofer Lining and Insulation Test Environment chamber.

012055
The following article is Open access

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The H2020-Cleansky 2 project EULOSAM II supports the development and assessment of an innovative natural laminar aircraft wing by integrating innovative aerodynamic control surfaces and high lift technologies. The project focuses on the modification and completion of a WT-model to enable robust and efficient testing. EULOSAM II is a project funded by the EC through the Clean Sky 2 JU and carried out in cooperation with Dassault Aviation. In order to ensure efficient testing a key element of EULOSAM II was to develop and validate a solution to improve the WT test productivity, which was achieved by designing, manufacturing and testing a remotely controlled, actuated HTP which significantly reduces the time needed in the WT for model-configuration changes. The model under review is a business jet half-model, test will be performed in the ONERA F1 Wind Tunnel, at high Reynolds numbers and low Mach Numbers typical of high-lift conditions. This paper presents the outcome of the whole development process of the actuated solution. This development includes the mechanical design as well as the control-solution to be applied in the WT. Pre-Tests have been performed in order to show that the implemented solution is working well and is robust enough to enable smooth and productive testing operations. In this paper, details on the design as well as explanations on why specific solutions were down-selected and found to be most effective ones are presented. During the final development phase, to investigate the functionality and robustness of the system, ground tests have been conducted with the assembled model on test benches to save WT time and to enable faster troubleshooting. Actuating WT models are seen as key to increase WT test efficiency, therefore this is in particular interesting for WT-test which have high hourly test-costs. Lessons learned for future applications therefore will be given to discuss if solutions found so far can be extrapolated to other, comparable applications.

012056
The following article is Open access

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Virtual test methods can contribute to reducing the great effort for physical tests in the development of composite structure and in particular on the In-service Repair. The present work describes an approach for virtual testing of titanium/composite repair based on the Building Block Approach and the Finite Elements Method. Building on a multitude of physical tests on composite panels and joints, adequate sub-models are developed, validated and the results show that the method used for the substantiation of the generic repairs (GREOs) compared with test results is conservative. This thesis intends to provide a hierarchical virtual testing approach, which enables the prediction of the failure behavior and the strength of composite In-service repairs by means of validated FEM simulation.

In particular the objective of this work will be to investigate the damage mechanisms in composite bonded skin/stringer constructions with metallic (titanium) bolted repair under uniaxial (in-plane/out-of-plane) loading conditions as typically experienced by aircraft flap skin panels.

012057
The following article is Open access

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The aim of this paper is the application of beam element representations for structural skin reinforcements in flexible full aircraft FE models used in ditching simulations. To verify this approach, it was initially analyzed on flexible reinforced bottom-aircraft panels under guided ditching conditions, considering also structural mesh size variations and partly corresponding fluid mesh densities. For this analysis two different numerical methods were used for comparisons, the coupled Finite Element-Smoothed Particle Hydrodynamics and the Arbitrary Lagrangian Eulerian methods. For the generation of the full aircraft model a multidisciplinary process chain approach and a standardized data format description are used. The beam element representations are considered for the modelling of skin reinforcement as well as other structures like cabin and cargo floor structures. By this approach, first time feasible full aircraft ditching simulations and the subsequent analysis of both global kinematics and the local fuselage structural response could be achieved.

Alternative Fuels

012058
The following article is Open access

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The EU Horizon 2020 project HyFlexFuel successfully demonstrated hydrothermal liquefaction (HTL) fuel production chains from different feedstock types to upgraded kerosene products. Now the question arises which commercial scale HTL system design is associated with the lowest environmental impact and production costs. The contribution addresses this research question by establishing a comprehensive process model for different feedstock types (sewage sludge, straw, miscanthus and microalgae) based on experimental biocrude production and upgrading campaigns in pilot and laboratory scale. This model enables evaluating different process configurations and serves as basis for subsequent system analyses by applying techno-economic and life cycle analyses (TEA and LCA). Upgraded biocrude using sewage sludge, representing a waste stream in wastewater management, can be produced at near-competitive price levels. Compared to conventional jet fuel production, greenhouse gases are reduced significantly. However, sewage sludge is a limited resource and only limited amounts of jet fuel could be substituted. Lignocellulosic feedstock such as straw or miscanthus are available in larger quantities and provide the opportunity to produce large amounts of sustainable aviation fuels at moderate costs.

012059
The following article is Open access

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As part of the ENABLEH2 project, modelling studies have been carried out to examine liquid hydrogen release and dispersion behaviour for different LH2 aircraft and airport infrastructure leak/spill accident scenarios. The FLACS CFD model has been used to simulate the potential hazard effects following an accidental LH2 leak, including the extent of the flammable LH2 clouds formed, magnitude of explosion overpressures and pool fire radiation hazards. A comparison has also been made between the relative hazard consequences of using LH2 with conventional Jet A/A-1 fuel. The results indicate that in the event of accidental fuel leak/spill LH2 has some safety advantages over Jet A/A-1 but will also introduce additional hazards not found with Jet A/A-1 that will need to be carefully managed and mitigated against.

Hybrid-electric flight

012060
The following article is Open access

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Moisture - in the form of water or ice – has adverse consequences on the performance of an aircraft including wing stall, tail stall, loss of thrust, engine flameout, and material damage arising from corrosion and electrical shortcuts. During flight, a large flux of supercooled water droplets on the surface of a hybrid electric aircraft per unit time could result into icing. A prototype to detect ice accretion on supercooled aircraft surface using acoustic emissions is developed. Moreover, during descend, a large portion of frost/ice melts rapidly due to rise in temperature. If not controlled, water may seep inside a hybrid electric aircraft body through gaps in joints. Furthermore, for the problem of water ingression in the wiring of hybrid aircrafts, titanium carbonitride-polyvinyl alcohol (TiCN-PVA) composite material is placed in direct water contact to work as grid health monitoring sensor. For the problem of water ingression inside structural parts (floor, bilge, etc.), an electrically conductive epoxy – carbon black composite is fabricated, characterized using SEM, and tested for DC conductivity under dry and wet conditions. Effect of different mixing intensities on morphology of carbon black in epoxy has also been explored. Through literature survey and trial and error, an optimized method at laboratory scale for preparation of carbon black-epoxy composite material has been presented.

012061
The following article is Open access

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A comprehensive analysis for research and development (R&D) of the technical appearance and calculation of the technical characteristics of a new hybrid electric propulsion aircraft/solar airship (HEPA) with LH2 and cryocooling system with high temperature superconductivity (HTS) can be used at any stage of the design process of a hybrid electric passenger aircraft in the implementation of the EU FUTPRINT50 international program. A new conceptual synthesis for the creation of an optimal cryogenic cooling system based on the Brayton reverse cycle using turbomachines with basic design schemes for the use of significant cryogenic power with low temperature values has been created for computational mat. models using test thermodynamic models of individual circuit elements, taking into account the efficiency of each element, their hydraulic losses in the lines of all elements of the system: calculation of hydraulic losses in the channel element, thermal control in regenerative heat exchangers with a turbocharger and calculation of a turbo expander. The real-time use of a low-capacity wireless sensor-detector or additional charging components from solar energy based on the Seebeck-Peltier effect will be more effective due to the introduction of graphene structures in the design. Experimental development of a two-stage electric compressor and a turbo expander for demonstration tests of a cryogenic cooling system in the MAI laboratory has been carried out.

012062
The following article is Open access

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Electric and Hybrid-Electric Aircraft (HEA) propulsion system designs shall bring challenges at aircraft and systems level, mainly in propulsion, electric and thermal management systems (TMS). The electrification of the propulsion system relies on large and high-power electrical equipment (e.g., electrical motors, converters, power electronics, batteries, and others) that dissipate heat at a rate at least one order of magnitude higher than conventional propulsion aircraft systems. As a result, high impacts on weight, drag and power consumption of the TMS/cooling systems at the aircraft level are expected. This paper proposes potential technologies to perform the thermal management of future electric and HEA, in the context of FUTPRINT50 project. For each technology, relevant aspects such as its integration to aircraft, safety, operational and maintenance impacts, certification, technologies readiness level (TRL) and the latest research works are analysed. A quantitative comparison of the several technologies is also proposed considering weight, volume, electric power consumption, pneumatic air flow and cooling air flow per cooling effect. Lastly, we present a set of potential TMS architectures for HEA.

012063
The following article is Open access

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The problems of introducing graphene technologies into the design studies of complex aviation solutions of minimal weight are relevant for the development of high-strength and lightweight composite structures with surface solar nano film energy storage for hybrid electric cryogenic aircraft (hydrogen cryoplanes LH2) and airships (disk-shaped Thermoplane MAI). The optimal design is directly related to the higher specific characteristics of liquid hydrogen fuel systems together with cryocooling systems, taking into account the use of new graphene-based materials and thin flexible solar cells, which is considered for SOLARSTRATOS and MAI projects or for any projects of hybrid electric aircraft/airships and their engines. A design analysis has been carried out to improve the design capabilities when introducing graphene technologies with their unique strength, electrical superconductivity, gas tightness and low mass in the component modification of a hybrid electric propulsion (HEP) and aero elastic energy-recoverable aircraft structures. The choice of rational design solutions using combined graphene composites, quartz dampers-vibration accumulators of structures and film solar energy cells allows you to reduce the weight of larger fuel tanks with liquefied hydrogen at high and low internal pressures and at the same time include electric motors in the cryocooling system – generators, power cables and batteries with additional solar energy charging, which increases the efficiency of on-board electrical systems and reduces the initial energy level and allows to increase energy efficiency and reduce weight costs during design studies.

012064
The following article is Open access

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Current research in hybrid-electric aircraft propulsion has outlined the increased complexity in design when compared with traditional propulsion. However, current design methodologies rely on aircraft-level analysis and do not include the consideration of the impact of new technologies and their uncertainty. This can be a key factor for the development of future hybrid-electric propulsion systems. In this paper, we present a methodology for exploring the design space using the principles of Set-Based Design, which incorporates probabilistic assessment of requirements and multidisciplinary optimisation with uncertainty. The framework can explore every design parameter combination using a provided performance model of the system under design and evaluate the probability of satisfying a minimum required figure of merit. This process allows to quickly discard configurations incapable of meeting the goals of the optimiser. A multidisciplinary optimiser then is used to obtain the best points in each surviving configuration, together with their uncertainty. This information is used to discard undesirable configurations and build a set of Pareto optimal solutions. We demonstrate an early implementation of the framework for the design of a parallel hybrid-electric propulsion system for a regional aircraft of 50 seats. We achieve a considerable reduction to the required function evaluations and optimisation run time by avoiding the ineffective areas of the design space but at the same time maintaining the optimality potential of the selected sets of design solutions.

012065
The following article is Open access

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Urban Air Mobility (UAM) is a recent concept proposed for solving urban mobility problems, such as urban traffic pollution, congestion, and noises. The goal of this investigation is to develop a backward model for an electric aerial taxi in order to estimate the electric consumption and the indirect emissions of carbon dioxide in a specified mission. The model takes as input the time histories of speed and altitude and estimates the power at the rotor shaft during the mission with a quasi-static approach. The shaft power is used as input for the electric drive where the motor is modelled with an efficiency map and a transfer function while an equivalent circuit model which includes aging effects is used for the battery. The emissions of CO2 are calculated as a function of the Greenhouse emission intensity and compared with that of a hybrid electric taxi performing the same mission with the same payload. A plug-in Toyota Prius modelled through the software ADVISOR is considered for the comparison. The results show that the air taxi behaves better than the road taxi not only in terms of trip time but also from the environmental point of view if the charging of the battery is performed with the emission intensity factory expected to be reached in Europe in 2025.

012066
The following article is Open access

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During recent years, aircraft manufacturers focused on environmentally friendly and aerodynamically efficient aircraft concepts that could allow a radical reduction of emissions. The use of a hybrid-electric powertrain is one of the most effective ways to design near-zero-emission aircraft. These aircraft are highly performing and sophisticated so the design process must be extremely accurate. Among the various innovative aspects, the use of distributed engines to improve aerodynamic performance poses new challenges from a structural perspective due to the tip-mounted propeller demanding a complicated design due to reduced flutter performance. This results in higher stiffness requirements and consequently increased mass. Both the weight penalty needed to prevent dynamic instability, and the wing aeroelastic tailoring, crucial to minimize such an additional weight, is of utmost importance. Because of setting up a preliminary approach to estimate the static and dynamic effects of such a non-conventional wing architecture, the present paper shows a comprehensive structural analysis of a wing opportunely designed according to certification specification and equipped with a variable position powertrain. Several different engines are then moved along the wingspan to estimate how it affects the dynamic response using a simplified beam-stick finite element model. The results show that the engine position strongly affects the flutter velocity with a particular band bell curve over the wingspan with the maximum in between 60-70% wingspan. In addition, it is worth noting how the tip propeller may cause a reduction of flutter velocity with respect to the conventional configuration with the turbine mounted in between 30-40% wing-span.

012067
The following article is Open access

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During recent years, aircraft manufacturers focused their attention on environmentally friendly and aerodynamically efficient aircraft concepts that could allow a radical reduction of emissions. The use of hybrid-electric powertrain is one of the most effective ways to design near-zero emission aircraft. These aircraft are highly performing and sophisticated. Hence, the design process must be extremely accurate and should make use of multidisciplinary design optimization. It is indeed crucial to establish both aerodynamic and structural models to simulate the aircraft performance and design required according to top level aircraft requirements. Despite the largely discussed literature about preliminary design of such an unconventional aircraft, there is still a lack of reliable weight estimation approaches, simulation-based mission analysis and optimization tools. In order to step towards higher technological readiness levels, the purpose of this paper is to describe and apply a design platform for conventional, turboelectric, hybrid-electric and full-electric aircraft, integrating aero-propulsive interactions, accurate power system modelling and medium-fidelity structural weight estimation. In particular, the comprehensive structural analysis of the aircraft wing opportunely designed according to certification specification and equipped with different powertrain architectures shows that it is worth looking into structural dynamics from preliminary design to estimate aircraft weight properly. Meanwhile, the mission analysis reveals performance benefits by implementing distributed engines all over the wingspan.

012068
The following article is Open access

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The Project "RS hybrid 1.0" funded by the LuFo Program of the German BMWi is being executed in order to develop and investigate a serial hybrid electric powertrain to be used in a light twin aircraft, that could be exclusively operated on two electric motors. The powertrain includes a generator system, that provides energy to all power sinks like propulsors, batteries and also covers the low voltage demand of the aircraft. In the frame of this project, all necessary components are developed including the electric propulsion units, the hybrid generator system, battery modules, and DC-Link and associated subsystems.

Everything is assembled in an iron bird testbed to be able to run the powertrain in an isolated fashion, to screen for potential issues and to measure operational data. Furthermore, a comprehensive control logic for the overall system and safety management of the powertrain is being developed and tested.

012069
The following article is Open access

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Fully electric environmental control systems for aircraft are designed but currently rarely implemented. Simulation models of such systems in the early design phase have shown a lot of challenges: high electric power demand, complex architecture, difficult design of control strategies and difficult sizing.

In order to explore what performance figures are physically possible, a first principle model has been developed on the basis of purely thermodynamic considerations. Similar to a Carnot thermal engine, which tells what efficiency is reachable, the first principle model of an ECS can serve as a reference system which tells the minimum amount of electric power needed to fulfil the thermal requirements. Different to a specific technical design, this allows for more general conclusions.

012070
The following article is Open access

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Electric propulsion unmanned aerial vehicles (UAVs) attract much attention in aviation industry, with electric vertical take-off and landing (eVTOL) aircraft tending to gain ground. The current development of hybrid eVTOL aircraft intended for urban air mobility is facing many technical challenges. Among these challenges rises the optimal sizing of its hybrid power system (HPS). The latter requires an energy management strategy (EMS). In this paper, the adopted management strategy is based on filtering techniques using frequency-separation. The EMS ensures the optimal distribution of the load power requirement between the different sources while considering their limits. In addition, the optimal sizing allows to strengthen the complementarity between sources and to indirectly reduce their mass. In this work, the studied HPS consists of a fuel cell associated with an energy storage system (ESS), composed of lithium polymer batteries (Li-Po) and supercapacitors. The onboard sources are connected in parallel on the power bus through three DC-DC converters. The results of this study are presented and discussed to highlight the relevance of the proposed approach.

012071
The following article is Open access

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This paper describes a framework for parametric modelling of hybrid-electric powertrain components for innovative airplane configurations. These models are used in scalability studies and performance analysis of novel propulsion architecture. The methodology involves culmination of these models in a set of tools specifically developed to study the initial and conceptual sizing of hybrid-electric aircraft. This allows quick parametric evaluation of various configurations based on components at different technology readiness levels, such as batteries and fuel cells. Characteristics and performance of the power-train components are evaluated using computational analysis as well as laboratory tests. This information is used to develop numerical models described in the paper and to validate the sizing of fundamental propulsion components. Applications to two variants of a commuter aircraft are given, one using a serial hybrid-electric architecture based on a thermal engine, and the other using a fuel-cell system fed by a gaseous hydrogen tank.

012072
The following article is Open access

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This paper addresses a way to implement greener aviation technologies, such as hybrid-electric propulsion, into the air transportation network to respond to the increasing environmental challenges posed by growing air traffic. New routes could be established between small airports to ensure better air connectivity in Europe while also connecting disadvantaged areas and relieve congestion at hub airports. Such routes could, for example, be served by micro feeder or 19-seat hybrid-electric aircraft, which produce low or no emissions, have lower operating costs, and are more applicable to environmental constraints. To achieve this and overcome the various challenges posed by the new hybrid-electric technologies, a new strategic roadmap for short-haul air transport is needed to optimize network services with small hybrid-electric aircraft.

012073
The following article is Open access

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Battery driven aircraft, hydrogen aircraft and hybrid aircraft may begin to appear at airports between 2030 and 2050. The success of their commercialization will also depend on development of accompanying ground infrastructure. We will give an overview of required ground infrastructure for handling battery and hydrogen aircraft including infrastructure for refuelling battery aircraft as well as production, transportation, safety issues and handling requirements.

012074
The following article is Open access

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The electrification of aircraft is an on-going endeavor, currently examined intensively in the general aviation class. However, for the commuter class, the proper selection of the hybrid-electric propulsive architecture is instrumental, to fully exploit the electrification benefit. Within this work, a comparison of two 19-seater aircraft with different hybrid-electric propulsive components is made, using an in-house aircraft conceptual design tool. The first aircraft is based on a twin-turboprop parallel-hybrid configuration that cruises at low Mach number speeds and altitude. On the other hand, the second aircraft variant is based on a tri-fan series/parallel-hybrid configuration with an aft Boundary Layer Ingestion system that operates at both higher altitude and Mach numbers. A design space exploration is performed where different degrees of hybridization and batteries specific energy are considered, to define the technological requirements for each architecture. The evaluation of the propulsive architectures is based on block fuel reduction, overall mission duration, direct operating costs and total environmental impact. The results aim to quantify the benefits of each configuration and determine the one with the closest entry into service. Finally, it is observed that the overall environmental impact reduces by 26 % and 17 % for the turboprop and turbofan variants respectively.

012075
The following article is Open access

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The potential benefits of hybrid-electric or full-electric propulsion have led to the proliferation of many concepts over the past decade. The lack of conceptual design methods capable of grasping the effects of the new propulsive technologies is often due to the absence of industrial data supporting the research. In the present work, two objectives are pursued. On the one hand, the introduction of semi-empirical methods for weight estimation based on the data provided by the industrial partners of the ELICA CS2 project. On the other hand, the establishment of generative engineering as a conceptual design tool for propulsive system architecting and fault tolerance analysis. The applications of the proposed conceptual design methods deal with two different years of entrance in service.

012076
The following article is Open access

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Since the beginning of aviation, reliability has been one of the most important elements in terms of flight safety and certification. Reliability starts from the smallest part of the aircraft and covers all components up to the entire system. The use of a hybrid-electric propulsion system has become one of the important study topics today. When hybrid-electric propulsion architectures are examined, it is seen that some elements are repeating which the authors named as common unit. This common unit is similar to the all-electric propulsion architecture and consists of a battery, battery management system, and power electronics which are used in conjunction with the hybrid-electric systems. In this study, the components and units used in the hybrid-electric propulsion system and the common unit has been examined for reliability. The common unit is proposed as a means of simplification of both the sizing and certification of the hybrid electric architecture. The reliability of the battery, battery management system, and power electronics within the system that makes up the common unit is discussed in detail for determining the reliability of the hybrid electric architecture.

Materials and Structures

012077
The following article is Open access

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For electric aviation drive systems engines with significantly increased power density are required. Combining the technologies of additive manufacturing of metals with the technologies of fiber reinforced composites enables hybrid structures with same or increased functionality and lower mass. Rotors or housings in hybrid design have interfaces to adjacent structures are classically made of metal. Areas for remote load transmission or with increasing distance to the rotation axis can be made of carbon fiber reinforced plastic (CFRP). The interfaces between these two materials, required for such a hybrid metal-CFRP design, can be specifically designed by using the design options of additive manufacturing to fulfill the required functions with a the most even distribution of stress possible. However, the large number of degrees of freedom of the material and the geometry leads to great challenges for engineers in the development of such structures. Within the scope of this publication, an approach for the function-oriented design of a metal-CFRP rotor for an aviation electric motor is proposed (global design). A design and pre-dimensioning method for the intrinsic interface between the materials is presented (local design).

012078
The following article is Open access

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A central process in composite lightweight engineering is the design of different fibre-reinforced parts. Certain steps during the design process have the potential that the overall workload can significantly be reduced, by the use of modern software tools. This often means that a compromise between optimization and increasing development costs must be found in order to balance structural complexity, number of design iteration loops and subsequent changes in the requirements. We introduce a computer-driven automation process for a multi-domain, parameter-driven design optimization. The proposed concept was built around the idea that the methodology can be used with different software tools that are already in operation for the design process of lightweight structures and therefore allows an easy implementation into already existing development chains. The developed process was successfully demonstrated by designing high-speed glass fibre rotors with respect to their structural and dynamic performance. The results showed a significant decrease in time spending during the design phase with the benefit to quickly adapt the design to subsequent changes in the optimization goal. Additionally, a wider solution space can be taken into account, which increases the quality of the optimization results.

012079
The following article is Open access

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Honeycomb sandwich panels are extensively adopted in a wide range of structures including aircraft, ships, automobiles, and infrastructure for being lightweight and occupying high out-of-plane compression and out-of-plane shear properties. They are evenly popular for their attractive energy absorption capability and resistance to ballistic impacts. Reinforcement of the hexagonal honeycomb panels is an efficient way to improve the impact resistance. However, a detailed study on the reinforcement types against ballistic impacts has not yet been reported. Therefore, the current research investigates the improvement of total energy absorption, ballistic limit velocity, and specific energy absorption (SEA) of three different reinforced hexagonal honeycombs, namely, triangular, circular, and hexagonal reinforcements against high-velocity blunt impacts. A parallel study is also carried out without any reinforcement and only thickening the cell wall of the non-reinforced hexagonal honeycomb panel. A numerical approach is adopted with commercial finite element code Ansys Explicit to analyze the virtual impact cases. The plate of the honeycomb panel is assumed as aluminum alloy Al-7075-T6, while the honeycomb core is made of Al-5083-H116. For both the alloy variants, Johnson-Cook flow stress parameters are utilized. For the projectile, a blunt cylindrical-shaped structural steel bullet is considered. It is found that, for the current investigations, triangular and circular reinforcements can significantly improve the overall ballistic performance of the sandwich panels with a penalty of weight increment. However, thickening the cell wall of the hexagonal core without any reinforcement exhibits the best ballistic performance.

012080
The following article is Open access

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The low impact resistance of laminated polymer composites is a significant problem. Even barely visible impact damages can significantly decrease the residual strength of the composite. In this article, the effect of the thickness of a polymer coating based on hollow glass microspheres on the damage tolerance and residual strength of glass fibre-reinforced plastic (GFRP) was studied. 4 mm thick GFRP specimens with polymer coatings of different thicknesses were prepared. The thickness of the coatings varied from 0.4 mm to 1.2 mm. The specimens were tested on a vertical drop tower system with impact energies up to 25 J. The dimensions of the obtained defects were determined using infrared thermography. The residual strength of the specimens was determined using the Flexure-After-Impact protocol. It was found that the 1 mm thick coating with a surface density of 650 g/m2 made it possible to reduce the damaged area by 35% and to increase the residual flexural strength of the GFRP specimens by 27% in comparison with the uncoated ones.

012081
The following article is Open access

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In this work, a model for simulating the laser shock-based disassembly of composite components is developed using the LS-DYNA explicit code. The laser shock technique has been used in the past for the non-destructive testing of adhesive bonds, but with appropriate adjustments it is possible to create a localized tensile stress that is high enough for adhesive failure to occur, making it suitable for use in the disassembly of bonded parts. In this first attempt, we focus on the development of a multiple loading instances simulation process, aiming to completely debond two carbon fiber reinforced plastic (CFRP) plates. The process of laser shock for disassembly requires an increased number of loading instances in order to cover the full bonded area. That, in addition to the short time duration in which the phenomena are evolved, poses a serious challenge for the numerical simulations, and thus a reliable procedure must be defined in terms of functionality and computational cost. Indeed, an iterative method, where the deformed model is used as input in subsequent simulations is evaluated, optimized and compared with a more traditional single model simulation.

Perspectives for Aeronautical Research in Europe

012082
The following article is Open access

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The vision of a third dimension added to hitherto nearly flat urban/metropolitan transport system gained the potential to become a mobility revolution for both logistics operators and, in the near future, for passengers as well. In spite of the expected emergence of this new form of transport and respective benefits for the efficiency of the mobility system at urban and suburban scale, UAM implementation also involves unprecedented and numerous challenges for cities and for all local public and private stakeholders. The local governing bodies are expected to provide policy, regulations and guidance for the implementation of UAM and to assure its integration with the ground mobility systems as well as with other urban functionalities. Taking into account both potential benefits and associated challenges related to UAM implementation, ASSURED-UAM (Acceptance, Safety and SUstainability Recommendations for Efficient Deployment of UAM) project, funded by the H2020 Programme, aims to support that effort, by providing a multidisciplinary study on operational and policy frameworks for the process of the introduction of unmanned modes of UAM.

012083
The following article is Open access

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Learn&Fly is an Erasmus+ project aimed to demystify and to crack STEM subjects to youngsters by showing their importance and application in aeronautics. Concepts in physics and maths are explained by engagement in the construction of an aircraft, aimed to compete in a flight contest. Students must envisage, design, draw and calculate the craft, simulate its flight, make necessary design adjustments, and build it. In its first year the project attracted 121 students, between 17-21 years old; 19.5% were girls. Students work on the glider was accompanied by lectures in physics, materials, and technologies. A questionnaire was used to quantify students' perception on project usefulness. Results show that students considered the project to be effective in improving STEM skills and career awareness, and very effective in improving soft skills. This is expected to result from the stimulating, hands-on STEM learning environment that provided access to contents, tools, and activities not usually available to high school students from the partaking countries.

012084
The following article is Open access

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InnEO'Space PhD project is preparing young researchers for a successful career by developing modernised and transferable PhD courses and learning resources based on innovation skills and employers' needs as well as in-depth knowledge of high stakes and approaches of Earth Observation in many application domains. The mains objectives of Inn'EO Space PhD are to enhance and develop researchers' innovation-oriented mind-sets and skills through Earth Observation, raise awareness about employment opportunities in academia and industry among researchers and scientists, tackle future skills mismatches and create new synergies between PhD students and researchers and potential employers. The first action has been to develop the InnEOStartech where the program was set for European PhD students with the aim of developing their taste for entrepreneurship spirit through idea of founding a company or designing an application. The second action has been to develop a summer school that delivered both technical skills and soft skills, thus providing all the ingredients for an innovation-oriented mindset. From these activities we shall develop a series of SPOCs (Small Private Online Courses) that will be made available to the community for further dissemination and exploitation.

012085
The following article is Open access

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Air traffic controllers play an important role in enabling safe, orderly, and efficient flight management within airspace. By the very nature of their work, they must make critical decisions in a time-critical environment. From a safety point of view, it would be of interest to obtain the workload thresholds (upper and lower limits) in order to define a range in which it would be safe and efficient for air traffic controllers to work. This collaboration project between CRIDA and UPM aims to obtain a methodology to define these workload limits, based on experimental affective-cognitive data and neurophysiological parameters of the performance of air traffic controllers. The workload assessment combines objective and subjective approaches. From the objective point of view, electroencephalography and eye-tracking techniques will be employed. In this paper, the first milestones achieved in the project are presented, as well as the simulation platform to be used in the experiment and the simulation-based set of exercises that has been specially designed for this project.

Small Air Transport (SAT) Technologies

012086
The following article is Open access

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In the last years, transportation demand has grown up as consequence of the increase in leisure, and business for both heavily travelled routes (between major cities) and thin routes (between remote areas, and remote areas with major cities).

In parallel, aviation sustainability issues have become more and more important, being aviation pollution an important source of global environmental pollution. Moreover, several States, as well as private Companies travelling for business, have introduced bans and/or special taxes on short flights covering distances that could be travelled by train in less than 3 hours. These regulations have a major impact on short haul thin routes, which could be covered by small air transport (up to 19 seats). Thus, dedicated research and technology innovation effort has been put in place over the last years to develop eco-friendly, and economically viable, aircraft able to answer sustainability needs, market demand, and cost-effectiveness.

In particular, Clean Sky 2 Joint Undertaking, a public-private partnership between the European Commission and the European aeronautics industry, has co-financed the SAT (Small Air Transport) TA (Transverse Activity) initiative. SAT TA main goal is to address technology innovations to reduce environmental impact as well as operational cost of small commuters, ensuring improved levels of operational safety. SAT TA is a Project with an overall EU (European Union) funding of about 68 mln€, including small aircraft OEMs (Original Equipment Manufacturers), major aircraft suppliers, SMEs (Small and Medium Enterprises), research centres and academia (more than 80 Partners involved).

The research activity has focused on the following main technology streams:

•New generation turboprop engine with reduced fuel consumption, emissions, noise and maintenance costs for 19 seats aircraft.

• More electric digital systems including:

• Affordable fly-by-wire architecture for small aircraft (CS23 certification rules).

• More electric systems replacing pneumatic and hydraulic aircraft systems (hybrid de-ice system, landing gear and brakes, high voltage EPGDS –Electrical Power Generation and Distribution System –).

• Advanced avionics for small aircraft, to reduce pilot workload, paving single pilot operations for 19 seats.

• Affordable airframe structures including:

• Low cost composite wing box and nacelle using OoA (Out of Autoclave) technology, LRI (Liquid Resin Infusion) and automated deposition process.

• Affordable small aircraft manufacturing of metallic fuselage by means of FSW (Friction Stir Welding) and LMD (Laser Metal Deposition).

• Advanced cabin comfort with new materials and more comfortable seats.

To address the abovementioned technologies, two different platforms have been designed: a Reference and a Green aircraft. Reference aircraft is a virtual aircraft designed considering 2014 technologies with an existing engine assuring requested take-off power. Green aircraft is designed integrating the technologies developed within Clean Sky 2.

The present work describes designed aircraft, and preliminary mission analyses, showing the achievement of Project goals (20% CO2, 20% NOx reduction for the design mission).

012087
The following article is Open access

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The increasing interest in Small Air Transportation (SAT), to enhance global connectivity, is highlighting the need for reducing take-off distance: lift coefficient has to be increased without penalizing the configuration drag, weight and complexity.

Within the EU Clean Sky 2 projects, a blown flap configuration has been developed to allow STOL capabilities of a future affordable and green commuter belonging to EASA CS 23.

The blowing system design choice is aimed at keeping the inevitable associated increase in pitching moment very low, and not penalizing performance when blowing fails.

In collaboration between Piaggio Aerospace and the MOTHIF consortium, a wing model was designed, built and tested in the VKI's large subsonic L1-A wind tunnel, reproducing bi-dimensional preliminary results obtained during the design phase.

In order to reduce and predict three dimensional and blockage effects, CFD has been used extensively to obtain a proper test chamber configuration and to reproduce some wind tunnel test results, so that both the accuracy of wind tunnel and design methodology can be assessed.

This work presents the comparison between experimental data and CFD simulations to demonstrate the usefulness of simulations to reduce both the risk for erroneous results in experimental activities and their related cost.

012088
The following article is Open access

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In this paper is explained the need for cost-optimized SAT surveillance system and described one potential approach to the solution which provides a complete protection against traffic, terrain and obstacles at an affordable price. The second part of the paper focuses on the radar. The trade-off analyses of performance, frequency bands and antenna size are described here. The goal of this paper is to highlight the need for securing the frequency spectrum for airborne radars that is under strong pressure of telecommunication lobby.

012089
The following article is Open access

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In the framework of the COAST (Cost Optimized Avionics SysTem) project funded by Clean Sky 2 Joint Undertaking in the European Union's Horizon 2020 Research and Innovation Programme, several key technologies are under development, aimed to enable single pilot operations of Small Air Transport (SAT) vehicles. One of these technologies is AWAS (Advanced Weather Awareness System), which aims to provide and visualize on board of the aircraft updated weather information regarding areas affected by weather hazards, in order to increase the weather awareness of the pilot. The system is composed by three main components: AWAS on-ground, devoted to generate and provide on board data regarding weather hazards observed and forecast along the flight route; AWAS on-board, aimed to send on-ground information concerning aircraft position and current time and to elaborate data provided by AWAS on-ground; AWAS Human Machine Interface (HMI), that visualize data on-board over a Portable Electronic Device (PED). AWAS on-ground and AWAS on-board segments are connected each other via a low-cost satellite communication system. The meteorological information is extracted from MATISSE (Meteorological AviaTIon Supporting System), a prototype software developed by the Meteorology Laboratory of CIRA. This paper describes the main functionalities and components of the system under development, highlighting the advancements achieved with respect to the one presented in 2020, and the work performed to allow the on-board integration of AWAS system. Furthermore, the paper reports the main results obtained during the dedicated flight test campaign successfully completed in summer 2021, validating the technology when integrated into the aircraft.

012090
The following article is Open access

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Modern navigation systems represent an inherent part of avionic equipment onboard all aircraft categories. The standard navigation performance typically defined by accuracy, integrity, availability, and continuity is now complemented by the system's ability to reduce CO2 emissions and fuel consumption. This article describes current navigation system development executed by Honeywell International for SAT (Small Aircraft Transportation) segment defined by CS-MMEL ATA 34 Navigation. The proposed solution is based on INS/GNSS hybridization extended by other aiding sensors available onboard the aircraft. To create a technological solution that meets the system operational requirements of the segment and at the same time comply with SWAP-C (Size, Weight, And Power Consumption Related to Cost) requirements is the aim of this research activity. The article describes proposed integration architecture based on hybridized core and other aiding sensors, such as radar altimeter and magnetometer. The assessment of previously mentioned aiding sensors was performed and impact on navigation performance was determined. The emphasis was mainly put on Inertial Measurement Unit (IMU) meeting the low-cost requirement for the overall architecture. The IMU error model definition and long-term thermal chamber measurements are the main tools for understanding the stochastic behaviour of the IMU's. The accuracy improvement is further supported by implementing SBAS corrections in INS/GNSS hybridization. This is not a usual navigation solution for SAT segment, since, typically, standalone GNSS receiver with SBAS is used instead. The Monte Carlo simulations were performed to compare the performance of the proposed solution against system and operational requirements. A proprietary Honeywell tool for these large-scale simulations is capable to simulate the navigation exercise anywhere on the Earth using pre-defined trajectories with specific duration and simulated GNSS constellation to reflect the impact of the satellite geometry.

012091
The following article is Open access

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Advancements in aircraft technologies and in the process of aircraft electrification allow for the design of new small aircraft transport (SAT) configurations with a significant impact on sustainability, travel time and operating cost. Additionally, the European Flightpath 2050 creates a European-wide political landscape to enable developments in that field to thrive. All this together provides an environment that promises to open new business opportunities in the form of new and revived mobility services. However, the described ecosystem raises the question of what demand exists for SAT and what top-level aircraft requirements (TLAR) need to be achieved to realize customer-centric SAT. Data of the existing traffic patterns in Europe is analyzed to create a demand model, derive the TLAR and ultimately lay the foundation for a successful European SAT transport system. Initially, traffic pattern data is collected with a resolution on county and city level, thereby ensuring a high accuracy of larger and smaller travel distances. Subsequently, to the data collection, the income distribution in European countries is analyzed and in combination with a Willingness To Pay (WTP) function the actual existing SAT demand is determined. The demand optimized TLAR are then derived by varying the demand models input parameters to maximize the demand. The above-described approach allows to extract the potential annual demand in Europe for a certain set of requirements, it also details how a single parameter effects the demand. Hence, it provides sensitivities to illuminate design focal points. In consideration of all the described factors the paper defines the TLAR, thereby enabling the design of new SAT configurations.

Space Technologies

012092
The following article is Open access

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This work, based on an EU-funded project (NEMESIS), is summarising some of the results from the project activities on the research and development on electride-based cathode technology compatible with all kinds of electric propulsion (EP) systems requiring neutralization or electron emission. Further information describing in detail the performed tests and captured measurements can be found in the referenced documents of each section. Different cathode architectures and several emitter configurations with traditional and with alternative propellants are being developed and tested within the project, all of them using C12A7:e-electride material as thermionic electron source. Findings and conclusions derived from these multiple designs are allowing to figure out some of the key factors that determine the best performance of C12A7:e-electride based cathodes. In this work, a discussion of some of these key design and operation factors will be presented based both on the material characterization parameters, and on the performance tests carried out for the different cathode designs.

012093
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This work, based on an EU-funded project, NEMESIS, is aiming at developing electride-based cathode technology which is compatible with all kinds of electric propulsion systems requiring neutralization. Its target is to demonstrate and validate the performance of a novel C12A7:e-electride material as electron emitter instead of traditional thermionic emitters such as lanthanum hexaboride, LaBe, or barium oxide, BaO. In this study, a fair comparison between LaBe and C12A7:e-samples was performed both addressing pure material characterization parameters as well as comparing performance as cathodes under different architectures and operational conditions. In this case, a current/cathode power ratio around 3 mA/W was obtained when using the C12A7:e-sample in a plasma environment with Ar, which is approximately one order of magnitude higher compared to the LaB6 sample.

012094
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Near-Earth Objects (NEO) are the topic of several research studies, with objects smaller than 1km in size posing the most threats and being the less understood of this scientific domain. The Asteroid Impact and Deflection Assessment (AIDA) mission involves NASA and ESA with the main mission goal to perform and analyze the asteroid deflection using the Kinetic Impactor technique. The mission target is Didymos-B, a moon of a binary asteroid called Didymos. NASA oversees the Double Asteroid Redirection Test (DART probe), and ESA is responsible for HERA probe, that will measure the Dydimos-B deflection caused by the impact. The Light Detection and Ranging (LIDAR), the Radar, the Satellite-to-Satellite Doppler tracking, the Seismometer, and the Gravimeter are instruments integrated into HERA spacecraft. Information synergy between the instruments allows the detailed characterization of the asteroid including internal structure. This experiment allows further understanding and will provide important information to improve the current NEO understanding and modelling. In this paper, scientific advances related to the LIDAR instrument are reported, including the innovative optomechanical design resulting from thermal and mechanical optimizations. The LIDAR has a compact design and needs to withstand extreme conditions, such as radiative and thermal conditions, without compromise its high accuracy measurements. The LIDAR is a time-of-flight altimeter instrument that will measure the distances from the HERA spacecraft to the target. It provides information for a 3D topographic mapping and calculates the asteroid reflectivity. The measurements are to be performed at a distance from 500 m to 14 km while operations such as fly byes or landings remain a possibility.

012095
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Space robotics technologies are maturing, bringing new capabilities for In-orbit Services, Manufacturing and Assembly (ISMA). These capabilities will generate on-orbit services improving the orbital infrastructure, creating in turn a very promising business opportunity in terms of market volume. The establishment of a European capacity is necessary for building this new space infrastructure and to capture a fair part of this market. The concrete objectives of the PERIOD project are focusing on the main levers to generate the capabilities, which are the further maturation of the space robotics technologies and the definition of an in-orbit demonstration to be implemented as early as 2026. In the frame of the PERASPERA Strategic Research Cluster (SRC), key enabling products have been selected for technology maturation aiming at an increased technology readiness level (TRL). In support of the PERIOD activities, ESROCOS, ERGO and InFuse will be developed to TRL5 after an alignment of their perimeter to the demonstration objectives. The Standard Interconnects (SI), already at TRL5 at project start, will be tested in a benchmark for evaluating their performance. These SRC building blocks will be integrated in a breadboard at Airbus for supporting the system definition work. The PERIOD Consortium bringing together the competencies of Airbus Defence and Space, DFKI, EASN-TIS, GMV, ISISPACE, SENER Aerospacial and Space Application Services is proposing a very ambitious demonstration scenario and Factory concept. A satellite will be manufactured in an Orbital Factory to be designed in the study at SRR level and injected in LEO for operations. The manufacturing includes the fabrication of an antenna, the assembly of the satellite components and its reconfiguration and inspection in the Factory. Throughout the demonstration mission, the PERIOD facility will be upgraded to extend the level of capability validation from assembly and manufacturing of structures to attachment and refuelling experiments. Dissemination activities will maximize the impact of the project toward the Space Community. This demonstration covers the short and mid-to-long term ISMA business cases and will support the transition into the in-space services, assembly and manufacturing paradigm.

012096
The following article is Open access

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The current paradigm in space robotics is the design of specialized robotic manipulators to meet the requirements for a specific mission profile. This research aims to develop a novel concept of a modular robotic arm for multi-purpose and multi-mission use. The overall approach is based on a manipulator formed by serial connection of identical modules. Each module contains one rotational joint. The joints, rotation axis is tilted under an angle of 45° to the normal axis, which requires less stowage space compared to a traditional joint configuration. A manipulator can be reconfigured in orbit by adding or removing modules and end effectors, therefore modifying the degrees of freedom (DoF) as well as the workspace. Redundancies are introduced, since defect modules may be removed or replaced. This paper outlines the overall concept of modularization of a robotic arm. The development and mechanical design of a terrestrial demonstrator based on the multifunctional interface iSSI (intelligent Space System Interface) is presented, which is intended for OOS and OOA activities. Furthermore, a variant of the modular robotic system with 24 DoF is presented, which can be stowed in a Cubesat-sized environment. It can operate in spaces with limited accessibility and is dedicated for tasks like inspection and delicate repairs. Finally, an outlook to further research potential and future use cases for the modular robotic system is given.

Supersonic Aircraft

012097
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One of the main problems in the development of a supersonic aircraft of the second generation is to ensure a safe level of the sonic boom impact on the environment. Achieving such level at the preliminary design stage is possible with the help of reliable methods for calculating the characteristics of the sonic boom due to impossibility of tube experiments at far field and expensiveness of real flight tests. This paper presents method for determining the shape of the overpressure signatures in the generalized form of an augmented Burgers equation for the case of disturbances propagation in a moving medium (atmosphere with wind). Based on the presented method, the computer code "vBoom" has been developed. The calculation results of the sonic boom characteristics (overpressure waveforms, the loudness in different metrics and the sonic boom carpet on the ground) are presented in comparison with the results obtained by NASA within the international seminar SBPW3 [1] (Sonic Boom Prediction Workshop).

012098
The following article is Open access

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The fundamental difference between the new-generation supersonic civil aircraft (SST) and the existing supersonic aircraft is the need to ensure a minimum level of environmental impact. The task of achieving highly efficient faster-than-sonic flight with minimum impact on the environment requires the development and implementation of a whole set of new technical solutions and technologies for aerodynamic layout, power plant, structural design, control system, etc. The technological advance on the topic formed in Russia to date requires verification of the effectiveness, feasibility and the possibility of integrating a set of technologies and technical solutions in the real flight conditions using a flight demonstrator of SST technologies, which will increase the level of readiness of key technologies, reduce the technical risks of developing a new generation SST and provide a basis for the development of draft regulatory requirements for the environmental performance of advanced SSTs. This paper outlines the goals and objectives of such a demonstrator and discusses some of the key technologies in the interests of creating a new generation SST.

012099
The following article is Open access

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The paper considers the problem of parametric synthesis of design solutions at the stage of preliminary aerodynamic design of an advanced supersonic transport (SST) under epistemic uncertainty. To solve such a problem, optimization models were developed with objective functions and constraints depending on the input and optimizable uncertain parameters, information on which is formed on the basis of expert estimates. The non-deterministic representation of such parameters is formed on the basis of the uncertainty theory by Dr Baoding Liu (Tsinghua University, China), which provides low computational complexity for a wide range of objective functions and constraints at the stage of preliminary aerodynamic design. With the use of the developed non-deterministic optimization models, typical problems of the synthesis of SST design parameters under epistemic uncertainty are formulated and solved.

Systems / Prognostics / Safety

012100
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Helicopter dronization is expanding, as for example with the VSR700 project, and leads to the design and the integration of electromechanical actuators (EMA) into the primary flight control system (PFCS). The PFCS is in charge of controlling the helicopter flight over its 4 axis (roll, pitch, yaw, vertical). It controls the blade pitch through dedicated mechanical kinematics and actuators. The hydraulic technology has been conventionally used in actuators for more than 60 years. On the other hand, the introduction of the EMA technology requires the reconsideration of design practices right at development start. Indeed, the establishment and synthesis of the specification need to deal with – new design drivers (high performance points, wear, fatigue) and - new inherent technological imperfections (friction, inertia and reduction ratio). To address these topics, this paper draws a list of the main EMA design drivers to focus on along with a brief description of the main EMA components. Then, it proposes indicators evaluated over a complete mission profile in time coming from measurement on a given applicative helicopter flight. These indicators are chosen and elaborated to provide an image of the design drivers responsible for rapid and gradual degradations of the actuator components. Also, they give an idea of the importance taken by the actuator imperfections into the global performance. Furthermore, we explain how mission profiles are processed depending of data sources. Finally, through a comparison with a standard aircraft mission profile, we emphasize the specificity of the helicopter application use case.

012101
The following article is Open access

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The aerospace industry makes extensive use of composite materials in the form of fibre fabrics pre-impregnated with thermosetting resin, called prepregs. In order to minimize the resin polymerization before curing, prepregs must be stored at -18°C (0°F). There are therefore expiration dates for prepregs before use. Although manufacturers try to minimize storage time, offcuts and time out of the freezer, it is estimated that 30% to 40% of the prepregs are not used [1]. Today, recertification of expired materials is still complex and expensive, therefore it is generally chosen to send expired prepregs to landfill. The purpose of this work is to correlate physicochemical measurements with the loss of mechanical performance in order to point out and measure the real aging effects during excessive storage time. Processability, physicochemical and mechanical tests were performed in order to understand which tests are truly representative of ageing. This study was illustrated by testing on unidirectional Hexcel carbon/epoxy prepreg. Different expiry dates of this material were studied and the properties were compared. It was shown that the main observed degradation was the processability of the prepreg while mechanical performance was minimally degraded after the expiry date. This study could lead to a simpler measurement of the actual expiry rate of prepregs, which could be useful to speed up recertification procedures or to propose new scenarios to extend the shelf-life of expired prepregs [2].

012102
The following article is Open access

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The carbon fibre recycling industry is not yet able to operate at full capacity. This lack of potential is a repercussion of a low demand for recycled carbon fibres (rCF) to manufacture new composite materials. As a matter of fact, few semi-products containing recycled carbon fibres are available on the market. Moreover, rCF semi-products available do not allow to manufacture high performances composite parts. The MANIFICA project, based on highly realigned carbon fibres after steam thermolysis, aims at producing new semi-products from recycled carbon fibres for high performance composites. In this article we introduce the I2M/Université de Bordeaux re-alignment process producing continuous tapes made of highly aligned long discontinuous fibres. These tapes are then used to manufacture new intelligent rCF semi-products. In the first part, the mechanical properties of rCF composites based on different semi-products are compared. In the second part, several semi products based on realigned fibres tapes are presented. This work demonstrates that high performance products can be targeted with recycled carbon fibres, thanks to the development of these intelligent semi-products.

012103
The following article is Open access

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The aviation industry has been growing continuously over the past decades. To ensure sustainability and competitiveness for the aviation industry sector, a full understanding of the environmental impacts is required, not only during use phase but along the entire life cycle, including "Materials", "Processes and Resources", "Manufacturing and Production", "Lifetime Services" as well as "Reuse, End-of-Life and Recycling". Core engine components, such as integral rotors (Blisks), are comprised of high value metallic alloys that require complex and resource consuming manufacturing processes. This paper will introduce an approach for Life-Cy-cle-Inventory data acquisition during Blisk manufacturing as basis for a Life-Cycle-Assessment (LCA) according to ISO 14040. A particular focus will be set on the data quality and confidence level regarding measuring, acquisition, and analysis of in- and output flows within the Blisk manufacturing process chain in scope. This includes the stages of material generation, forming processes, heat treatments, machining, surface treatments and quality assurance. A greater emphasis is drawn to selected variations on mechanical machining processes. On this basis, first results of an LCA for Blisk-manufacturing will be presented.

012104
The following article is Open access

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This paper discusses the development of short fibre frame clips and system brackets made from recycling CF/LMPAEK factory waste composites employing two technologies (injection molding and 3D-printing). The project will develop and validate fused deposition modeling (FDM) as cost-efficient process to manufacture system brackets using the novel formulation of recycled composite as raw material. Energy directors development for ultrasonic welding is presented for successful joining of the clips to the fuselage, avoiding fasteners. The manufactured parts will be assembled into the lower half of the multifunctional fuselage demonstrator. The results were developed within ECO-CLIP project, which aims to: (1) assess technical aspects of material recyclability and (2) assess the economic and environmental validity of the technology.

012105
The following article is Open access

In this paper the TecALSens project, developed within the Systems ITD of the Clean Sky 2 programme, is presented. The objective of the project is to design and validate a novel load sensor for aeronautic application based on thin-film sensing technology. So far, thin-film as sensing element has not been used in commercial aeronautic products: The outcome of this project tries to close this gap by providing a new class of load sensors complying with demanding aeronautic requirements. More and all electric aircraft configuration can benefit from the implementation of force measurement. This is an example of revolutionary approach to A/C design and a key enabler for achieving the environmental goals set by the European agenda up to 2050. Current project activities show very promising results: TecALSens provides a new approach to the design and manufacturing of load sensors for aeronautic applications. Especially, this new class of load sensors overcomes some of the drawbacks of strain gauge-based solutions. The final outcome of the project complies with the expected technology readiness level (TRL) 5. TecALSens outcome widens the possibilities offered by force sensing in aeronautics and strongly supports the evolution of aircraft design toward a more environmental friendly approach.

012106
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In the design and development phases of electro-hydraulic actuators (EHAs) used for aircraft flight controls, it is often necessary to carry out accurate and high-fidelity fluid dynamics simulations to evaluate the system behaviour within its entire operating range and, if necessary, investigate its most critical issues. These high-fidelity simulations (nowadays achievable with different techniques and commercial software) generally become pretty expensive from a computational perspective. Therefore, especially in the preliminary design phases or implementing system health monitoring algorithms (in real-time), the need to adopt simplified models emerges definitely (albeit capable of guaranteeing the appropriate level of detail and accuracy). These simplified models are also essential for developing effective and reliable model-based prognostic strategies capable of performing early health assessments of EHA valves. This work proposes a new lumped-parameters simplified numerical model, which, despite having a very compact formulation and reduced computational costs, simulates the internal fluid dynamics of the valve, overcoming some critical issues typical of other models available in the literature. It evaluates valve performance as a function of spool position and environmental conditions (e.g. supply pressure), better-assessing flow rate feedback, internal leakages, and other operating conditions (e.g. spool fine adjustment, pressure supply variable, overpressure, or water hammer). The performance of this numerical model is evaluated comparing with other simplified models published in the literature. Moreover, it is validated with a high-fidelity digital twin that simulates the behaviour of the valve, taking into account the geometry of the spool, the properties of the hydraulic fluid, and the local internal fluid-dynamics (laminar or turbulent regime, cavitation, etc.).

012107
The following article is Open access

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The prior knowledge of incipient failures of primary flight command electromechanical actuators (EMAs) with prognostic algorithms can be very beneficial. Indeed, early and proper detection and interpretation of the deterioration pattern can warn for replacing the servomechanism before the actual manifestation of the abnormal behaviour. Furthermore, such algorithms often exploit a model-based approach established on the direct comparison between the actual (High Fidelity) and the monitor (Low Fidelity) systems to identify fault parameters through optimization processes. The monitor model allows the acquisition of accurate and precise results with a contained computational effort. The authors developed a new simplified monitor model capable of faithfully reproducing the dynamic response of a typical aerospace EMA equipped with a Permanent Magnet Sinusoidal Motor (PMSM). This digital twin senses mechanical and electrical faults: friction, backlash, coil short circuit, static rotor eccentricity, and proportional gain. Fault detection and identification task are performed by comparing the output signal of the reference system (real or simulated) with the one obtained from the monitor model. After that, the Genetic Algorithm is chosen as the optimization algorithm to match the two signals by iteratively changing the fault parameters to detect the global minimum of a quadratic error function. Once a suitable fit is obtained, the corresponding optimization parameters are correlated with the considered progressive failures to evaluate the system's health status. The high-fidelity reference models analysed in this work have been previously conceived, developed, implemented in Matlab-Simulink, and validated experimentally by researchers of the ASTRA group of the DIMEAS of Politecnico di Torino.

012108
The following article is Open access

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The work deals with the development and the performance characterization of a novel control strategy for the detection, isolation and accommodation of coil faults in a three-phase Permanent Magnet Synchronous Motor (PMSM), used to drive the propeller of a modern lightweight fixed-wing UAV. The health-monitoring algorithms on motor currents (used to detect the open-circuit fault and to activate the control reconfiguration) are based on a slope method, associated to the evaluation of the current phasor trajectory in the Clarke plane. Actually, when an open-circuit fault occurs in PMSM driven by a standard three-leg converter, the typical circular trajectory of the current phasor in the Clarke plane collapses into a linear track and relevant torque ripples are generated. On the other hand, if the PMSM is driven by a four-leg converter, a control reconfiguration can be applied: the fourth leg of the power bridge is in stand-by when the system operates without faults, but it is enabled to regulate the current flowing at the central point of the Y connection of the 3-phase PMSM. The performances of the fault-tolerant algorithms are assessed via detailed nonlinear simulation of the propulsion system (including propeller loads, electrical faults, mechanical transmission compliance, digital signal processing and sensors errors). The results demonstrate that the health-monitoring algorithms and the fault-tolerant control strategies permit to obtain extremely small detection and isolation latencies, and negligible performance degradation in terms PMSM torque.

012109
The following article is Open access

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In-flight communication (IFC) services offered to passengers and crew are of great importance to the air transport sector. The improvement of the satellite capacity with High Throughput Satellites (HTS) in GEO and the advent of MEO and LEO constellations will support the forecast growth of the IFC market. Antenna equipment for satellite communications will need to address multiple scenarios from G2G (Gate-to-Gate) to multi-operation under GEO-MEO-LEO systems. Under these conditions, antennas with the ability to track multiple satellites and having superior performance and reliability will play a key role. Electronically steered antennas (ESA) have emerged as a viable solution in response to these demands. The EU-funded LESAF project proposes an ESA solution of reduced size and greater efficiency for the next generation of in-flight connectivity services. This will be managed through the requirements definition, system analysis, technology assessment, prototyping and validation of ESAs. The project has successfully passed the first milestone corresponding to requirements consolidation, baseline architecture definition and candidate technology trade-offs. Multi-beam Electronically Steered Antennas, separated apertures for both transmission and reception, a flexible modular approach coupled with planar multilayer integration and an advanced beamformer design are the basis for the proposed concept. The following project phase will be focused on the design and validation of an antenna demonstrator aimed at proving the superior added value of ESAs technological solution for the aviation industry needs.

012110
The following article is Open access

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One of the goals of the CleanSky2 Airframe project is the maturation of model based certification methods, replacing cost intensive and sometimes even impossible tests with simulations. One such impossible test scenario is the hazard assessment in case of an ECS failure in a business jet, leading to a continuous decrease of cabin temperature by conduction to the exterior environment and thus to a potentially hazardous condition for passengers and crew. Such failures have been tested on the Business Jet Cabin Demonstrator in the Fraunhofer Flight Test Facility. With the test data, a model based on the zonal approach is validated. Zonal modelling subdivides the indoor environment into typically 100-1000 zones, thus providing a local resolution of airflow and temperature distribution while still being numerically fast enough to simulate transient profiles. As the study focusses hazard conditions, subject testing is not considered possible while modelling allows for a judgement on the risk level.

012111
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Environmental control systems hold vital importance as they are responsible for aircraft cabin air ventilation and passenger comfort. This paper presents an analytical design of both Conventional & Electrical environmental control systems. The result of the estimated design is represented in a geometrical model that gives freedom to visualize various options in the conceptual design process, using Knowledge-based engineering application as a base for the design and methodology. Flexibility in the model enables the user to control the size and positioning of the system and sub-systems associated with it. The number of passengers serves as the driving input and the three-dimensional model gives the exact representation concerning the volume occupied and dependencies on the number of passengers. It also provides a faster method to alter the system to user needs with respect to the number of air supply pipes, number of ducts, and pipe length.

012112
The following article is Open access

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The present paper describes the development of a mobile platform as a support of the real estate appraisal procedure. Currently, the estate evaluation is performed by an expert that manually collects data, performs measurements, and grabs pictures of the inspected unit to finally evaluate its commercial value. The READ project aims at automatizing this process by developing a solution based on a mobile unit (drone or tablet) able to navigate the indoor environment and record data, which will be later processed on the cloud. To accomplish all these tasks, the platform is equipped with cameras, a LiDAR sensor, and a data process unit, with the goal of 1) understanding its motion and localization; 2) reconstructing a 3D map of the inspected space; 3) performing image-based analyses applying AI algorithms enabling the identification of the indoor space (e.g. bedroom or kitchen), the counting and the classification of furniture objects, and the detection of building imperfections or frauds. Tests have been performed in different scenarios providing promising results, laying the foundations for bringing these technologies into a real operational context.

012113
The following article is Open access

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In any space mission, maintaining subsystems temperature within the allowed limits is a difficult challenge. Parts exposed to the Sun need to be cooled because temperatures rise extremely high, while parts not directly exposed to the Sun need to be heated, because temperatures can drop dramatically. The vacuum does not conduct heat, so the only way to transfer energy is through electromagnetic radiation, generated by the thermal motion of particles in matter. Operating on a planet surface allow convective dissipation and, to a lesser extent, conductive heat dissipation. Furthermore, Mars' thin atmosphere mitigates the strong temperature gradients that would occur in a vacuum. Nevertheless, external parts of the rover are exposed to temperature ranging between – 123°C - +40°C. In this paper, the thermal control system of NASA's Curiosity rover will be presented, analyzing the challenges of maintaining suitable operating conditions in Martian environment and the solutions adopted to allow safe operations.

012114
The following article is Open access

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This paper describes an improved measurement method and sensor development for the assessment of the indoor thermal environment. The disadvantage of the state of the art concept of the equivalent temperature to describe inhomogeneous environments is pointed out and how the DressMAN 3.2 sensor system provides improvements to this measurement principle. The measurement system has been prepared in order to accompany thermal tests in the Passenger Cabin Ground Demonstrator developed within the CleanSky2 Regional project. This shall allow the objective assessment of the passenger comfort in the mock-up without the need for extensive subject test campaigns.