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]
• Experimental investigation of the acoustic emission of an electrically
driven propeller in thrust and recuperation mode in a wind tunnel

Abstract: Abstract This paper presents the results of an experimental performance study of an electrically driven propeller in thrust and power recuperation mode in a subsonic wind tunnel. Using the reverberation chamber method, acoustic measurements were performed to evaluate them as a reference in relation to the performance data obtained. The three approaches to recuperation were investigated: Fixed pitch propeller at speed reduction (case 1), controllable pitch propeller with negative angle of attack (case 2), and inverted, backward running propeller (case 3). Results show that in-flight recuperation can be optimized in terms of low noise emissions and generating shaft power from the flow efficiently by choosing the respective operating point. For the latter, case 3 shows the greatest potential for a two bladed propeller, while case 2 has the lowest noise emissions and might reach higher values in recuperated power by increasing the propeller blade number.
PubDate: 2023-01-30

• An operational concept flying GLS approaches using satellite-based
augmentation systems

Abstract: Abstract A new converter technology allows suitably equipped aircraft to use data provided by the satellite-based augmentation system in receivers originally designed for the ground-based augmentation landing system. For these aircraft, that system enables a lower decision altitude and, hence, improved access to airports. To make this technology usable, air crews require an operational concept and the flight crew has to be presented with the appropriate information in the form of approach charts. Two different possibilities for an operational concept were developed and the corresponding approach charts created. One option is a modified area navigation approach chart, to which the specific information is added. The other chart is an entirely separate procedure for the approach. These two options were tested with airline pilots in an Airbus A320 full-flight training simulator. During the simulator flights, aircraft performance data was recorded and the participants filled in questionnaires regarding workload and quality of the operational concept. The results show different behavior during the intercept of the final course, but all approaches remained within the required limits. The questionnaires revealed that the workload is higher during the area navigation variant and that all participants prefer the separate ground-based augmentation landing system variant.
PubDate: 2023-01-28

• Cabin aircraft comfort evaluation over high fidelity simulated flight

Abstract: Abstract The primary purpose of this paper is to investigate the possibility of using a Full Flight Simulator (FFS) as an experimental setup for passengers’ comfort analysis. Results based on subjective measurements are thus presented to assess comfort levels experienced during a simulated flight. A preliminary investigation has been conducted on a sample of 125 candidates to gain insight into the elements influencing the comfort level perceived based on the participants’ actual flight experience; this suggested that the seat configuration is of great importance. Then, the experiment carried out by means of the FFS have been conducted on a reduced sample of 20 candidates for economic and organizational reasons. The behaviour of the 65% of the candidates has been analysed in a seating configuration comparable to the seat of a business-class aircraft. While the experience of the remaining 35% has been studied in an economy-type seat arrangement. Although the main variable under consideration was the seat, several environmental parameters were also considered during the experimental tests to evaluate their effects on perceived comfort level. During each simulated flight, passengers have been subjected to different levels of light intensity, noise, temperature and vibration associated with the different flight phases. Subjective data were collected using a questionnaire concerning every parameter and submitted to the passengers for each flight phase. The aim of varying the environmental parameters inside the cabin was to look for a relation between the subjective comfort level and each comfort parameter. In addition to perceived comfort based on the questionnaire, statistical analysis with parametric and non parametric tests revealed significant effects of environmental variables.
PubDate: 2023-01-27

• Thermal analysis of a high-altitude solar platform

Abstract: Abstract High Altitude Long Endurance (HALE) aircraft operate under adverse thermal conditions, with ambient pressures and temperatures very low and at the same time high amounts of heat introduced by sun radiation. Thus, thermal management of the aircraft systems, such as electronics and batteries is a very challenging task. A first step in solving this is generating accurate models of the thermal dynamics of the HALE. This paper presents the thermal analysis of a solar-electric stratospheric HALE at the ground case. A thermal mathematical model based on first principles was developed for such an analysis. In a further step, an initial test campaign was performed. The test campaign included static and dynamic temperature measurements on an aircraft wing structure segment. The experiments throughout this test campaign showed good compliance of the results with the previously derived mathematical models, with differences of less than 5  $$\,^{\circ }$$ C between the measured and simulated temperature curves.
PubDate: 2023-01-18

• Numerical simulation of wake interactions on a tandem wing configuration
in high-speed stall conditions

Abstract: Abstract In this work, the interaction of the separated wake of the front wing with the rear wing of a tandem configuration is investigated for high-speed stall conditions by means of hybrid RANS/LES simulations, using the zonal AZDES method. After a characterization of the transonic buffet on the front wing, the development of the separated turbulent wake behind the wing is investigated. The interaction of the separated wake with the rear wing is then analyzed in detail. The results reveal that there is a strong variation in the wake characteristics over the buffet cycle, caused by the varying amount of separation on the front wing. During the upstream movement of the shock, the flow is largely separated, resulting in a thick wake with strong, high-frequent fluctuations that can be attributed to large turbulent vortices. On the contrary, when the shock travels downstream, there is only a small amount of separation present, resulting in a thin wake with comparatively low fluctuations that are caused by corresponding smaller turbulent vortices. The impact of the wake of the front wing causes a strong variation in the rear wing loading. An oscillation with a comparatively low frequency can be distinguished from high-frequent fluctuations. The low-frequent oscillation is caused by the variation in the downwash behind the front wing as its lift changes during the buffet cycle. The high-frequent fluctuations are due to the impingement of the turbulent structures onto the rear wing. Because both size and frequency of those vortices vary significantly within the buffet cycle, the amplitude and frequency of the lift and surface pressure fluctuations also change accordingly.
PubDate: 2023-01-17

• Recent developments of common numerical methods and common experimental
means within the framework of the large passenger aircraft program

Abstract: Abstract For the exploration and validation of the integration of efficient propulsion concepts and new technologies for future large passenger aircraft, it is necessary to establish suitable design, evaluation and measurement tools. Therefore, as one major activity of the Large Passenger Aircraft (LPA) Platform 1 of the Clean Sky 2 initiative, the so-called Cross-Capability Demonstrator (XDC), has been set up to develop and demonstrate powerful numerical and experimental methods for aerodynamic, aeroacoustics, and aeroelastic simulation and measurement tasks. The paper will give an overview of the activities to be performed within the XDC and present some of the latest achievements related to this demonstrator.
PubDate: 2023-01-16

• Time-resolved pressure-sensitive paint measurements for cryogenic wind
tunnel tests

Abstract: Abstract A first time-resolved pressure-sensitive paint (PSP) test campaign at the European Transonic Wind Tunnel (ETW) was conducted within the research initiative “Unsteady flow and interaction phenomena at High Speed Stall conditions”. One of the objectives of this wind tunnel campaign was to resolve time-series of surface pressure distributions caused by complex 3-D buffet phenomena on a full-span airplane model XRF-1 transport aircraft configuration. At higher angle-of-attack and high Mach number, pressure fluctuations with a frequency of several hundred Hertz are expected to occur on the main wing and the horizontal tail plane (HTP) caused by the buffet effect. To capture the expected buffet phenomena by PSP, the German Aerospace Center developed a time-resolved PSP measurement and data acquisition system as well as a post-processing method for measurements in ETW. The measurements were conducted on the main wing and HTP simultaneously, with a camera frame rate of up to 2 kHz. The transonic buffet phenomena were observed at the flight relevant Reynolds number Re = 12.9 × 106 and Re = 25.0 × 106. The time-varying surface pressure distribution on the model was successfully captured by PSP. The time-series and spectra of both PSP and pressure transducer data match very well.
PubDate: 2023-01-10

• Time-efficient simulations of fighter aircraft weapon bay

Abstract: Abstract A cavity flow exhibits aero-acoustic coupling between the separated shear layer and reflecting waves within the walls of the cavity, which leads to emergence of dominant modes. It is of primary importance that this flow mechanism inside the cavity is understood to provide insights and control the relevant parameters and that it can be properly predicted using state-of-the-art CFD tools. In this study, an open-cavity configuration with doors attached on the sides and a length-to-depth ratio of $$\mathbf{5}.7$$ have been studied numerically using the TAU code developed by the German Aerospace Center for transonic flows with three simulation methods such as DES with wall functions and SST-SAS with resolved wall flow or wall function techniques. The free-stream conditions investigated are Mach number (Ma) $$\mathbf{0}.8$$ with Reynolds number (Re) $$\mathbf{12} \times \mathbf{10} ^\mathbf{6 }$$ . The Rossiter modes occurring in the cavity due to the acoustic feedback mechanism have been numerically computed and validated. The SST-SAS model is around 90% more computationally efficient compared to the hybrid RANS-LES model providing excellent accuracy in predicting the Rossiter modes. The SST-SAS model with wall functions is 50% more computationally efficient than wall-resolving SAS simulations showing good behaviour in predicting modal frequencies and shapes, with further scope for improvement in the spectral magnitude levels.
PubDate: 2023-01-06

• Experimental assessment of wing lower surface buffet effects induced by
the installation of a UHBR nacelle

Abstract: Abstract The installation of large bypass ratio engines on classical under wing configurations may lead to shock/boundary layer interaction on the wing lower surface, limiting the flight envelope in a similar way to classical buffet occurring on the wing suction side at high incidences in transonic flight. In this study, buffet effects on the lower surface of the wing induced by the installation of a Ultra-High-Bypass-Ratio through flow nacelle are assessed by means of wind tunnel testing. Unsteady pressure sensitive paint measurements were used to assess the pressure field on the wing with high temporal and spatial resolution. Strong unsteady shock motion associated with shock induced separation was found on the wing lower surface for various combinations of Mach number, Reynolds number and angle of attack. The wing lower surface buffet effects are found to increase with reducing angle of attack and are present over a wide range of Reynolds numbers. Preliminary spectral analysis suggests an upper limit for the buffet frequency at a Strouhal number of about 0.4.
PubDate: 2022-12-22

• A semi-automated approach for requirement-based early validation of flight
control platforms

Abstract: Abstract With the current trends in aviation like Single-Pilot-Cockpits and more autonomous functions in aircraft, flight control avionics are bound to become more complex. Future platforms will need to compensate for one or even both pilots, which will require systems that are more reliable. However, state-of-the-art development of flight control avionics does not yet support these demands efficiently. The development process involves numerous stakeholders who are communicating without streamlined interfaces. This leads to a slow and error-prone process during development. New methods are required to improve efficiency and to pave the way for future technologies. In this work, the authors introduce a semi-automatic toolchain which derives usable code for the configuration of devices from natural language requirements. The requirements are noted through modular components, stored as a model-based configuration file and are transformed into executables in the last step. This novel approach allows engineers to input their expertise when defining requirements, while removing tedious transformation tasks. Through automatic configuration testing, the validity of the approach is confirmed.
PubDate: 2022-12-20

• Integrated model-based design and functional hazard assessment with SysML
on the example of a shock control bump system

Abstract: Abstract Integrating new functions into the aircraft can, for example, increase performance or reduce fuel consumption. Since the installation of such additional functions increases the overall aircraft complexity, it is crucial to adapt methods and tools that support the development and ensure traceability, consistency, and verifiability. In this context, model-based systems engineering and the associated Systems Modeling Language (SysML) have been established as a standard methodology. This paper presents an overview of a system development and modeling process with SysML at the concept design stage using a position-variable shock control bumps system as an example. In addition to the system modeling, safety and reliability analyses have to be considered during the design process. To keep both, the model and the associated safety assessment consistent, this work introduces an extension of SysML to enable the execution of a functional hazard assessment (FHA) according to the ARP4754A and ARP 4761 guidelines. This is the first step in conducting a model-based safety assessment. Furthermore, a modeling process with concepts management methods is performed. In summary, the presented modeling process consists of three main parts: the system modeling, functional hazard assessment and concept management.
PubDate: 2022-12-19

• SystemXF: a novel approach for holistic system modeling in aircraft
conceptual design

Abstract: Abstract In aircraft conceptual design, systems are typically represented by historical regressions without considering system architecture. For novel technologies, this is no longer possible. Alternative approaches are either hard coded solutions for special system architectures or lack the analysis capabilities necessary for conceptual aircraft design. The novel SystemXF approach intends to close this gap by providing a framework for system modeling that is not technology specific and allows for the integration of different analysis disciplines within a single model. A central XML file is used for system specification which can be edited using a SysML interface. A mass estimation and a safety analysis tool are available. An example system which is inspired by a real pitch control system is used to illustrate the method and to show the applicability. This modeling example shows that the proposed model is capable to represent and analyze realistic systems in conceptual aircraft design. The analysis tools can be used for system studies and to provide inputs for a conceptual aircraft design process.
PubDate: 2022-12-15

• Engine thrust model determination and analysis using a large operational
flight database

Abstract: Abstract Different engine thrust models are developed from operational flight data with limited a priori knowledge as part of a novel process for aircraft flight performance model determination. The given big data problem is solved by application of fundamental engineering knowledge and a specific data evaluation strategy. The resulting smart data approach is fundamentally different from existing artificial intelligence methods to solve such big data problems. A linear, a local-linear and a complex nonlinear thrust model are determined on the example of a given large database of operational flights with Airbus A 320neo aircraft. Even with limited information about the actual engine thrust from the available data, the resulting models allow to (well) predict the engine thrust characteristics within the required flight envelope. In addition, a temperature correction is predicted for the thrust model results to further enhance the model’s accuracy. Finally, the characteristics of the different thrust model implementations, evaluation results and thrust prediction quality are discussed.
PubDate: 2022-12-13

• Comparative environmental life cycle assessment and operating cost
analysis of long-range hydrogen and biofuel fueled transport aircraft

Abstract: Abstract The aviation industry is currently experiencing a social shift in the attitude towards flying due to the increasing awareness of the impact on climate change. This has led governments and industries to set emissions targets, although their achievement for long-range flights is subject to an ongoing debate. Among promising candidates are hydrogen and sustainable aviation fuels such as biofuel. To provide a meaningful ecological and economic assessment, an environmental life cycle assessment method supplemented by a direct operating cost analysis has been developed and is described in this paper. A wide-body transport aircraft (A330 class) serves as a reference design for developing conceptual aircraft designs with a planned entry-into-service in 2040 powered by liquid hydrogen or drop-in biofuels (based on algae, produced with oil-rich biomass (BtL) or hydrogenated vegetable oil (HVO) processes). Due to the large demand for assumptions, the ecological and economic assessment results have to be interpreted as benchmarks. The results for long-range aircraft show that based on the current fuel and energy production methods both hydrogen and biofuel as aviation fuel are more harmful (have a higher environmental impact) than conventional aircraft. For hydrogen aircraft, an increase in energy consumption of $$2.87\%$$ leads to an increased environmental impact of $$14.8\%$$ . Due to the high energy demand for biofuel production, its environmental impact increases by $$548\%$$ (BtL) and $$238\%$$ (HVO). Nevertheless, for a future scenario based on electrolysis as a hydrogen production process and on renewable energy to generate electricity, both hydrogen and biofuel-powered aircraft are less harmful when compared to the reference aircraft. The environmental impact reduces by $$59.5\%$$ (hydrogen), $$35.8\%$$ (BtL), and $$112\%$$ (HVO). However, the introduction of the new propellants involves a high direct operating cost penalty of $$10.8\%$$ for hydrogen and $$108\%$$ for both biofuels.
PubDate: 2022-12-02

• A framework for the bi-level optimization of a generic transport aircraft

Abstract: Abstract The aeroelastic loads and design processes at the German Aerospace Center, Institute of Aeroelasticity in the framework of multi-disciplinary optimization are constantly evolving. New developments have been made in the in-house model generation tool ModGen, which allow us to create detailed fuselage models for preliminary design. As a part of the subsequent developments to integrate the fuselage structure in our aeroelastic design process, a new framework for optimizing the fuselage structure has been developed. The process is based on a bi-level optimization approach which follows a global–local optimization methodology to simplify a large optimization problem. A sub-structuring procedure is used to define stiffened panels as independent structures for local optimization. The panels are sized with stress and buckling constraints with consideration of several aeroelastic load cases. Furthermore, in this paper, we present a physical sub-structure grouping process which enables reduced number of panel optimizations and saves considerable computational effort with little compromise in the solution accuracy.
PubDate: 2022-11-30

• 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
DOI: 10.1007/s13272-022-00619-w

• 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
DOI: 10.1007/s13272-022-00626-x

• 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
DOI: 10.1007/s13272-022-00621-2

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