Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
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 CEAS Aeronautical JournalJournal Prestige (SJR): 0.248 Citation Impact (citeScore): 1Number of Followers: 29      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1869-5582 - ISSN (Online) 1869-5590 Published by Springer-Verlag  [2467 journals]
• Aerodynamic validation for compressor blades’ structural morphing
concepts

Abstract: Abstract For increasing an aircraft’s engine efficiency and reducing emissions, the use of adaptive blades capable of guaranteeing an optimal performance at different flight phases is researched. An aerodynamic design point blade shape and some exemplary possible morphed shapes for different operational conditions are introduced and analyzed from a structural as well as from an aerodynamic point of view. For this purpose, the structural design process developed to calculate the blade geometries that can be reached through structurally integrated actuation is introduced and explained with the help of three morphing blade example geometries. Furthermore, the aerodynamic methods used for the evaluation of the structurally achieved morphed geometries is also studied with the help of the introduced examples.
PubDate: 2022-11-24

• An explanatory approach to modeling the fleet assignment in the global air
transportation system

Abstract: Abstract Airlines’ fleet assignment heavily affects the economic and ecological performance of the global air transportation system (ATS). Consequently, it is inevitable to include potential changes of the fleet assignment when modeling and assessing future global ATS scenarios. Therefore, this article presents a novel explanatory approach to modeling the fleet assignment in the global ATS. The presented approach is based on formulating and solving an optimization problem, which describes the fleet assignment in the ATS through a suitable combination of objective function and constraints. While the objective function combines both the airline and the passenger perspective on the fleet assignment, the constraints include additional operational and technological aspects. In comparison to the available global fleet assignment models in the literature, which rely on statistical approaches, the advantages of the presented approach via an optimization problem lie in the overall scenario capability and the consideration of explicit aircraft types instead of simplifying seat categories. To calibrate and validate our model, we use 10 years of historic flight schedule data. The results underline the strengths and weaknesses of the presented approach and indicate potential for future improvement.
PubDate: 2022-11-24

• Prediction of transonic wing buffet pressure based on deep learning

Abstract: Abstract In the present study, a deep learning approach based on a long short-term memory (LSTM) neural network is applied for the prediction of transonic wing buffet pressure. In particular, fluctuations in surface pressure over a certain time period as measured by a piezoresistive pressure sensor, are considered. As a test case, the generic XRF-1 aircraft configuration developed by Airbus is used. The XRF-1 configuration has been investigated at different transonic buffet conditions in the European Transonic Wind tunnel (ETW). During the ETW test campaign, sensor data has been obtained at different local span—and chordwise positions on the lower and upper surface of the wing and the horizontal tail plane. For the training of the neural network, a buffet flow condition with a fixed angle of attack $$\alpha$$ and a fixed sensor position on the upper wing surface is considered. Subsequent, the trained network is applied towards different angles of attack and sensor positions considering the flow condition applied for training the network. As a final step, the trained LSTM neural network is used for the prediction of pressure data at a flow condition different from the flow condition considered for training. By comparing the results of the wind tunnel experiment with the results obtained by the neural network, a good agreement is indicated.
PubDate: 2022-11-18

• Evaluation of the controllability of a remotely piloted high-altitude
platform in atmospheric disturbances based on pilot-in-the-loop
simulations

Abstract: Abstract In the context of the project HAP, the German Aerospace Center (DLR) is currently developing a solar-powered high-altitude platform that is supposed to be stationed in the stratosphere for 30 days. The development process includes the design of the aircraft, its manufacturing and a flight test campaign. Furthermore, a high-altitude demonstration flight is planned. While the high-altitude flight will be performed using a flight control and management system, during take-off and landing and at the beginning of the low-altitude flight test campaign, the aircraft will be remotely piloted. The aircraft has a wing span of 27 m and operates at extremely low airspeeds, being in the magnitude of around 10 m/s equivalent airspeed, and is therefore profoundly susceptible to atmospheric disturbances. This is particularly critical at low altitudes, where the airspeed is lowest. Hence, both time and location for take-off, landing or low-altitude flight test campaigns need to be selected thoroughly to reduce the risk of a loss of aircraft. In this regard, the knowledge about the operational limits of the aircraft with respect to atmospheric conditions is crucial. The less these limits are known, the more conservative the decision about whether to perform a flight on a certain day or not tends to be. On the contrary, if these limits have been adequately investigated, the amount of days and locations that are assessed as suitable for performing a flight might increase. This paper deals with a pilot-in-the-loop simulation campaign that is conducted to assess the controllability of the high-altitude platform in atmospheric disturbances. Within this campaign, the pilots are requested to perform practical tasks like maintaining track or altitude, flying a teardrop turn or performing a landing while the aircraft is subject to different atmospheric disturbances including constant wind, wind shear, continuous turbulence, and discrete gusts of different magnitudes. This paper describes the desktop simulator used for the campaign, outlines the entity of investigated test points and presents the assessment method used to evaluate the criticality of the respective disturbances. Finally, a set of restrictions on the acceptable wind conditions for the high-altitude platform are found. The underlying limits comprise a constant wind speed of 3.0 m/s in any direction, except during landing, maximum wind shear of 0.5 $$\text { m/s}^{2}$$ and gusts with peak speeds of 1.5 to 2.0 m/s, depending on the direction.
PubDate: 2022-11-15

• Flight mechanical analysis of a solar-powered high-altitude platform

Abstract: Abstract The German Aerospace Center (DLR) is currently developing an unmanned experimental solar-powered fixed-wing high-altitude platform designed to be stationed in the stratosphere for several days and to carry payload for earth observation missions. This paper deals with a flight mechanical analysis of the aircraft within the preliminary design phase. For this purpose, it briefly describes all disciplines involved in the preliminary design and gives an insight into their methods used. Subsequently, it presents an assessment of the aircraft in terms of stability and control characteristics. Doing so, it first deals with a dynamic stability investigation using a non-linear 6-degrees-of-freedom flight dynamic model with a simple quasi-stationary approach to account for flexibility, in which the aerodynamic derivatives are given for different airspeed-dependent flight shapes. The investigations show that the aircraft is naturally stable over the complete flight envelope. It does not have a typical short period mode. Instead, the corresponding mode involves altitude and airspeed changes to a large extent. At low airspeeds, the Dutch roll and spiral modes couple and form two non-classical modes. Second, it presents a control surface design evaluation process for the aircraft based on a flight mechanical requirement. This requirement addresses the necessary control authority to counteract the aircraft’s responses due to gust encounters to not exceed afore-defined limits and to prevent the aircraft from entering a flight condition that it cannot be recovered from.
PubDate: 2022-11-07

• Interview with Luc Tytgat, EASA Director, Strategy and Safety Management
Directorate

PubDate: 2022-11-04

• UNICADO: multidisciplinary analysis in conceptual aircraft design

Abstract: Abstract In this paper, different iterative methods, so-called architectures, within the multidisciplinary analysis in conceptual aircraft design of the UNICADO software are elaborated, applied and analyzed. Possible execution sequences in the sequential method (Gauss-Seidel architecture) are derived via a graph-based algorithm in combination with expert knowledge. Sensitivities of the design disciplines are analyzed and a permitted residual for stable convergence characteristic for the aircraft design with UNICADO is derived. Prerequisites for the application of a parallel iterative method, the Jacobi architecture are conducted. Runtime and convergence characteristics of the Gauss-Seidel architecture and the Jacobi architecture are evaluated. A damping method is applied to the Jacobi architecture to enhance the convergence characteristics. The Gauss-Seidel and Jacobi architectures are used to design two different aircraft, the CSR and the CSMR, with an iteration accuracy of 2.5e–3. For these use cases studied, the Gauss-Seidel architecture converges more stably and faster than the Jacobi architecture and is, therefore, the more favorable. The aircraft design with the implemented Jacobi architecture oscillates and does not converge. Only with an implemented damping method, convergence is achieved. If the iteration time of the design loop increases, e.g., when using higher fidelity methods for aircraft design, the choice of architecture must be re-evaluated.
PubDate: 2022-10-29

• Bio-based hybrid cabin door of ultralight helicopter with variable-axis
fiber design

Abstract: Abstract This paper presents the development of an integrated technology concept for the production of semi-structural fiber composite aerospace components with a bio-based hybrid laminate structure. In this context, the high lightweight potential of a variable-axial hybrid fiber-reinforced laminates compared to a multiaxial laminate design is of particular importance. As a demonstrator, a double-shell cabin door based on the cabin door of the ultra-light helicopter CoAx 2D of EDM Aerotec GmbH was redesigned in hybrid bio-based mixed composite construction using selected finite-element method (FEM) simulation and optimization tools, manufactured and characterized. The obtained results illustrate that compared to the reference carbon fiber-reinforced polymer (CFRP) component, the developed bio-based hybrid composite with local tailored fiber placement (TFP) reinforcement has a 30% biomass content, exhibits comparable mechanical properties and significantly contributes to increase energy and resource efficiency significantly.
PubDate: 2022-10-26

• Alternative procedure to verify the H–V diagram after external
installations on helicopters

Abstract: Abstract Certification of external installations on helicopters, for modifications for which CS27/29.865 is not applicable, often requires the showing of compliance of paragraph CS XX.79—limiting height-speed envelope—which might imply, ultimately, a certain degree of H–V testing. Due to the implications on safety during the investigation of the H–V curve, a preliminary analytical investigation is advisable, to understand whether H–V test can be drastically reduced. Analytical investigation, though, is usually based on the extensive use of simulation data, based on validated dynamic mathematical models, which are usually not available to the applicant. The authors recently proposed an alternative method, based on the analysis of a set of flight tests, which is meant to assess quantitatively the different phases of the physical/mechanical phenomena related to the emergency maneuver performed by the pilot as a consequence of a power loss, within or in the proximity of the H–V curve. More in details, the analysis of the autorotation phenomenology reveals that the maneuver is made up by different phases and dedicated tests have been proposed to assess each of these phases. The whole test campaign is hence meant to gain a thorough insight of how, and specifically in which part of the maneuver, the external modification could affect the helicopter H–V characteristic. Depending on this substantiation, H–V testing can be avoided or drastically reduced, limiting the investigation to a few meaningful points. The proposed method has been recently assessed on an external basket installation, making use of purposely developed Flight Instrumentation and post-processing tools. More in details, results and conclusions are based on the analysis of static and dynamic flight parameters, acquired with a non-intrusive Flight Test Instrumentation, which monitors and correlates cockpit parameters and flight commands, following a back-to-back approach (i.e., pre- and post-modification). The method demonstrated was witnessed by EASA and found acceptable as an alternative method for showing of compliance to the applicable requirements.
PubDate: 2022-10-17

• Numerical analyses of a reference wing for combination of hybrid laminar
flow control and variable camber

Abstract: Abstract The objective of the LuFo VI-1 project CATeW (Coupled Aerodynamic Technologies for Aircraft Wings) consists in multifidelity analyses to assess the potential for aerodynamic efficiency increase by combined application of hybrid laminar flow control and variable camber technologies to the wing of a transonic transport aircraft. Individually, both technologies have proven to lead to major aerodynamic drag reductions. An evaluation of the coupled technologies is, therefore, expected to show an even higher potential due to synergy effects. To derive conclusions on system level, low-fidelity (LowFi) overall aircraft design methodologies will be applied for the analysis of a medium haul reference aircraft in the course of the project, while complex aerodynamic phenomena are modelled with high-fidelity (HiFi) computational fluid dynamics methods. The paper at hand presents results of aerodynamic analyses on both fidelity levels for the wing of the turbulent reference configuration CATeW-01, featuring the technology combination as a retrofit. Furthermore, this work encompasses adaptations and implementations performed within both the LowFi and HiFi toolchains. The LowFi toolchain already incorporates several modules for the proposed technology combination. A short presentation of the LowFi-toolchain is given, along with the modeling approach in the HiFi framework using mesh deformations and a mass flux boundary condition. Comparative studies of the turbulent flow field around the wing show good agreement of predicted load distributions in both numerical frameworks, studies based upon the HiFi approach attest the potential for efficiency increase due to the variable camber technology, incorporated by means of Adaptive Dropped Hinge Flap (ADHF) deflections. Considering the coupled application, four different constant suction mass flow rates are examined, where the maximum mass flow causes laminar flow extending over the entire suction panel, thus moving the transition location from the wing’s leading edge to the end of the suction panel. When being coupled with ADHF deflections, again the variable camber technology leads to a reduction of the wing’s pressure drag component with the simultaneous application of boundary layer suction further promoting drag reduction with increasing suction rate. While the combined application shows no mutual inhibition, major reciprocal effects are not directly observable when applying the combination as a retrofit to the reference configuration CATeW-01. This is mainly attributed to the limited extend of laminar flow, thus indicating the necessity for optimization in wing geometry and operating parameters, to achieve extensive areas of laminar flow and to promote the aspired synergy effects.
PubDate: 2022-10-01

• Flight and engine control laws integration based on robust control and
energy principles

Abstract: Abstract Integration aspects of flight and engine control laws in the context of the longitudinal motion control of commercial aircraft are the concern in this paper. The application of the entailing concepts in the scope of an energy-based multivariable control design is developed along with a case study using dedicated aircraft and engine models. It consists of an enhancement of the Total Energy Control System (TECS), which is modified with respect to the following aspects: (a) the inclusion of engine feedback variables to its core control loop, which is extended and improved with respect to the command interface from the throttle control channel, and (b) the use of a two degree of freedom linear control law based on independent multivariable gain scheduled feed-forward and feedback controllers. Additionally, a systematic design framework is proposed to account for the robustness of stability and performance of the control law in face of plant uncertainties, as well as to allow the evaluation and integration of engine restrictions already in the early design stages.
PubDate: 2022-10-01

• Aeroelastic-tailoring of a wind-tunnel model for passive alleviation of

Abstract: Abstract Composite materials allow to tailor the elastic properties of a structure. In aeroelasticity, this opens up the possibility to passively enhance the coupled aerostructural characteristics. In this work, the design of a composite wing is addressed with the aim to alleviate static and dynamic aeroelastic loads; these two objectives are quantified by the root-bending-moment in a high load-factor condition and the deformation amplitude of the wing under gust. A two-step approach of the optimal design of the structure is adopted. A Pareto front is computed via an aeroelastic model of the wing; the aerodynamic loads are modelled, depending on the load-case, either via the DLM or the RANS equations. The best-compromise design is chosen via a criterion based on the jig-shape and, finally, the stacking-sequences are computed via a specialised evolutionary algorithm.
PubDate: 2022-09-24

• Integration of propelled yaw control on wing tips: a practical approach to
the Icaré solar-powered glider

Abstract: Abstract In this practical approach to distributed propulsion, the solar-powered manned motorglider icaré 2 has been used as a testbed for wingtip propulsion. The large wingspan and slow cruising speed of icaré 2 are highly suitable to assess the influence and potential of propellers at the wingtips for yaw control. The paper describes the work of a multidisciplinary team consisting of researchers, engineers, pilots and students, starting from the initial idea to use propellers at the wingtips of icaré 2 up to the actual flight test campaign. First, the design and development of the modular wingtip pods are described to house the propeller, electric motor, battery and further sensors and control systems. Furthermore, the modifications required for integrating the wingtip pods on the aircraft itself are outlined and the electrical and mechanical interfaces are defined and described. To obtain a permit to fly for the new configuration of the aircraft, several tests on system level of the wingtip pods needed to be conducted and documented for the authorities. Finally, the flight test campaigns carried out to date are outlined and described including the planning, lessons learned and results.
PubDate: 2022-09-06
DOI: 10.1007/s13272-022-00603-4

• Numerical Whirl–Flutter analysis of a tiltrotor semi-span wind
tunnel model

Abstract: Abstract This work presents the modeling and preliminary Whirl–Flutter stability results achieved within the Advanced Testbed for TILtrotor Aeroelastics (ATTILA) CleanSky2 project. The project addresses the design, manufacturing, and testing of a semi-span wind-tunnel model of the Next Generation Civil TiltRotor. The preliminary multibody models developed in support of the wind-tunnel testbed design are described, illustrating the modeling technique of each subcomponent of the model, namely the wing, the rotor, the blades, and the yoke. The methodologies used to analyze the stability of systems subjected to periodic aerodynamic excitation when the problem is modeled using full-featured multibody solvers are presented in support of Whirl–Flutter identification during wind-tunnel testing.
PubDate: 2022-09-01
DOI: 10.1007/s13272-022-00605-2

• Structural optimization of an aeroelastic wind tunnel model for unsteady
transonic testing

Abstract: Abstract The reduction of loads, ultimately leading to a weight reduction and thus an increase in aircraft performance, plays an important role in the design of modern aircraft. To this end, two aeroelastic tailoring methodologies, independently developed at ONERA and DLR and aiming at load reduction by means of a sophisticated application of composite materials, were applied to a common model geometry. A choice was made in favor of the publicly available NASA Common Research Model (CRM) wing, featuring a comprehensive database with respect to geometry, as well as analytical and experimental research results. The span of the wing half to be investigated was set to 0.55 m, limited by the test section dimensions. While wind tunnel testing was part of ONERA’s workshare, the model building was performed by DLR. This paper at hand focuses on the structural, aeroelastic optimization of the DLR wing. It is based on an optimization framework developed and constantly being enhanced and extended at the DLR - Institute of Aeroelasticity (DLR-AE). The paper describes the consideration of different structural objective functions, structural and aeroelastic constraint combinations, design field considerations, as well as the application of an aero load correction applied in the course of the optimization. The final results consist of the selection of an appropriate fiber type, optimized fiber layers represented as stacking sequence tables for the upper and lower wing skins, and the corresponding optimized jig twist distribution, required for manufacturing the lamination molds; in summary, all data required to start the construction of the wind tunnel model.
PubDate: 2022-09-01
DOI: 10.1007/s13272-022-00612-3

• Aeroelastic method to investigate nonlinear elastic wing structures

Abstract: Abstract Stiffness directions of wing structures are already part of the optimisation in aircraft design. Aircraft like the A350 XWB and the Boeing 787 mainly consist of such composite material, whose stiffness directions can be optimised. To proceed with this stiffness optimisation, the aim of this work is to modify and optimise also the linear stress-strain relation. On that account, the Hooke’s law is exchanged by a multi-linear formulation to analyse any nonlinear elastic structural technology on wing structures. The wing structures, which are used to investigate the nonlinear behaviour, are deduced from a mid-range and a long-range aircraft configuration. These wings are analysed with an extended beam method and coupled with a VLM solution to calculate the aeroelastical loading. The proposed beam method is capable of analysing any multi-linear wing structure technology. A degressive structural behaviour shows up a good potential to reduce the bending moment which is one of the main drivers of the structural weight.
PubDate: 2022-08-29
DOI: 10.1007/s13272-022-00596-0

• Expansion of the cabin description within the CPACS air vehicle data
schema to support detailed analyses

Abstract: Abstract The air vehicle data schema CPACS (Common Parametric Aircraft Configuration Schema) provides a large variety of options for describing passenger aircraft on different levels of fidelity and exchanging product information in collaborative processes. The section describing the aircraft cabin has been applied primarily in the context of preliminary design processes in the past. However, in the wake of recent developments to integrate more detailed analyses in fields such as vibro-acoustics or passenger comfort, the limitations of the present cabin definition have become increasingly obvious. In this paper, a revised version of the cabin definition is, therefore, presented, which has been adopted as of CPACS version 3.4. A key objective of the new definition is the integration of high-fidelity component geometry models, provided as either polygonal 3D meshes or CAD geometry. For efficient data storage, individual components are collected in a library node in CPACS and subsequently placed inside the fuselage via references. The range of available cabin component types is extended by including paneling elements and luggage compartments. Furthermore, nodes for referencing structural elements are provided to enable modeling of structural connections, e.g., in finite-element models. Aside from the sheer parametric description of the cabin in CPACS, its correct geometric interpretation is also a key aspect, which will be highlighted throughout this work. It is demonstrated using a reference implementation, which allows for the generation of 2D and 3D models for validation.
PubDate: 2022-08-23
DOI: 10.1007/s13272-022-00610-5

• Enhancement of the virtual design platform for modeling a functional
system architecture of complex cabin systems

Abstract: Abstract Model-based systems engineering (MBSE) is a fundamental approach for the end-to-end use of digital models in the development of complex systems. The aviation industry in particular, where system complexity is constantly increasing, needs new concepts and methods to overcome ecological and socio-economic challenges. Therefore, domain-specific models are needed for the design and evaluation of systems to support the various system investigations, such as requirements management, installation space optimization, or failure analyses. An end-to-end coupling and linking of these mostly heterogeneous systems offer many advantages (e.g. shorter development times) over working with isolated digital sub-models, natural language documents, and purely physical prototypes. In addition, digitalization allows global and interdisciplinary collaboration of multiple teams of experts on the same virtual product. Since this approach is particularly promising for the configuration of aircraft cabins, a virtual development platform is developed at the German Aerospace Center (DLR) for the conceptual design of the aircraft cabin and its systems. As a result, virtual prototypes of cabin configurations are quickly generated to allow new concepts to be visualized and investigated at an early design stage. Extending the conceptual cabin system design process with a functional system architecture and executable system architecture models promotes information traceability, early failure detection, and requirements verification. The methodology used for this purpose is presented in this paper. The systems modeling language (SysML) is used to build a model for the functional depiction of cabin systems and to link it to existing models of the conceptual cabin design process. The modeling is performed exemplarily for the passenger service functions. Subsequently, the results are automatically transferred to the virtual development platform to experience the generated cabin concept.
PubDate: 2022-08-22
DOI: 10.1007/s13272-022-00608-z

• The importance of coupling aerodynamic and cost analysis in aircraft
design

Abstract: Abstract Companies are increasingly required to improve their quality, flexibility and innovation while maintaining or reducing their costs. However, engineering and finance are often handled by different staff groups at different times in the manufacturing process, and by uncoupling engineering and finance, a company runs the risk of overlooking important interactions between the two. A design system that performs engineering and financial analysis simultaneously may, therefore, improve upon the efficiency and effectiveness of the traditional methods, as the existing practice of designing aircraft from a technical perspective without simultaneously considering the impact on overall program value is not optimal in a business sense. A coupled performance/financial framework enables an integrated approach to technical design and programmatic decisions. This work thus seeks to couple aero performance and financial design. Specifically, a multi-objective trade study is conducted to see the impact on the direct operating cost (DOC) and manufacturing cost of parametrically varying aircraft wing thickness to chord ratio along the wing span. While the present process is only partially automated, the purpose is to establish a useful foundation for further developments and to gain insight into the interactions between technical and program design.
PubDate: 2022-08-03
DOI: 10.1007/s13272-022-00600-7

• Virtual testing of multifunctional moveable actuation systems

Abstract: Abstract This work presents the current state of the virtual testing activities performed within the Virtual Product House (VPH) start-up project. In this project a multidisciplinary, collaborative end-to-end process for virtual product design is developed. On the basis of preliminary design and concept studies on aircraft level, the process focusses on design, manufacturing and testing of aircraft systems and structural components with special attention to certification aspects. The initial use case considers the trailing edge flap of a long-range aircraft and its actuation system. Design and analysis tools are integrated in a remote workflow execution environment to automatically generate designs and evaluate them by virtual test means. Virtual tests facilitate knowledge on properties and behavior of the virtual product in early development phases and allow to optimize design flaws in consecutive design iterations to hence reduce the risk of costly corrections later in the development process. The testing is setup in multiple stages. Currently, domain-specific tests are carried out for the moveable structure and its actuation system, with the latter being in focus for the current text. These tests address the functional verification of the actuation system in nominal and failure cases. A SysML model comprising system requirements and architecture is used to model test cases and trace test results. On the basis of these test cases, simulation configurations for virtual tests are automatically built, executed and evaluated. With this method, a continuous evaluation of designs in terms of functional verification of the moveable actuation system is possible. Moreover, the automated execution of all steps allows to determine the effects of design changes quickly without a large amount of labor-intensive and error-prone work.
PubDate: 2022-08-01
DOI: 10.1007/s13272-022-00602-5

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