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 Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 97 journals)
 Showing 1 - 30 of 30 Journals sorted alphabetically Acta Astronautica       (Followers: 363) Advances in Space Research       (Followers: 360) Aerospace       (Followers: 43) Aerospace and Electronic Systems, IEEE Transactions on       (Followers: 236) Aerospace Science and Technology       (Followers: 330) Aerospace Scientific Journal       (Followers: 4) AIAA Journal       (Followers: 811) Air Force Magazine       (Followers: 9) Air Medical Journal       (Followers: 5) Aircraft Engineering and Aerospace Technology       (Followers: 180) American Journal of Space Science       (Followers: 134) Annual of Navigation       (Followers: 22) Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences       (Followers: 20) ASTRA Proceedings       (Followers: 1) Aviation       (Followers: 13) Aviation Psychology and Applied Human Factors       (Followers: 19) Aviation Week       (Followers: 257) Aviation, Space, and Environmental Medicine       (Followers: 10) Canadian Aeronautics and Space Journal       (Followers: 29) CEAS Aeronautical Journal       (Followers: 28) Chinese Journal of Aeronautics       (Followers: 18) Ciencia y Poder Aéreo       (Followers: 1) Civil Aviation High Technologies Control Systems       (Followers: 200) Cosmic Research       (Followers: 3) COSPAR Colloquia Series       (Followers: 7) Egyptian Journal of Remote Sensing and Space Science       (Followers: 20) Elsevier Astrodynamics Series       (Followers: 9) Fatigue of Aircraft Structures       (Followers: 12) Frontiers in Astronomy and Space Sciences       (Followers: 10) Gyroscopy and Navigation       (Followers: 201) IEEE Aerospace and Electronic Systems Magazine       (Followers: 151) IEEE Transactions on Circuits and Systems I: Regular Papers       (Followers: 30) International Journal of Aeroacoustics       (Followers: 35) International Journal of Aerodynamics       (Followers: 20) International Journal of Aerospace Engineering       (Followers: 68) International Journal of Aerospace Sciences       (Followers: 24) International Journal of Applied Geospatial Research       (Followers: 4) International Journal of Aviation Management       (Followers: 4) International Journal of Aviation Psychology       (Followers: 14) International Journal of Aviation Technology, Engineering and Management       (Followers: 5) International Journal of Crashworthiness       (Followers: 9) International Journal of Micro Air Vehicles       (Followers: 8) International Journal of Satellite Communications Policy and Management       (Followers: 9) International Journal of Space Science and Engineering       (Followers: 8) International Journal of Space Structures       (Followers: 9) International Journal of Space Technology Management and Innovation       (Followers: 5) International Journal of Sustainable Aviation       (Followers: 2) International Journal of Turbo & Jet-Engines       (Followers: 4) Journal of Aeronautical Materials       (Followers: 6) Journal of Aeronautics & Aerospace Engineering       (Followers: 17) Journal of Aerospace Engineering       (Followers: 60) Journal of Aerospace Information Systems       (Followers: 13) Journal of Aerospace Technology and Management       (Followers: 5) Journal of Aircraft       (Followers: 230) Journal of Airline and Airport Management       (Followers: 7) Journal of Astrobiology & Outreach       (Followers: 1) Journal of Aviation Technology and Engineering       (Followers: 10) Journal of Engineering and Technological Sciences Journal of Guidance, Control, and Dynamics       (Followers: 139) Journal of Konbin : The Journal of Air Force Institute of Technology       (Followers: 2) Journal of Navigation       (Followers: 211) Journal of Propulsion and Power       (Followers: 396) Journal of Space Safety Engineering       (Followers: 1) Journal of Space Weather and Space Climate       (Followers: 22) Journal of Spacecraft and Rockets       (Followers: 570) Journal of Spatial Science       (Followers: 3) Journal of the American Helicopter Society       (Followers: 6) Journal of the Astronautical Sciences       (Followers: 5) Journal of Wind Engineering and Industrial Aerodynamics       (Followers: 7) Life Sciences in Space Research       (Followers: 2) MAD - Magazine of Aviation Development       (Followers: 1) Microgravity Science and Technology       (Followers: 1) New Space       (Followers: 4) Nonlinear Dynamics       (Followers: 16) npj Microgravity       (Followers: 1) Population Space and Place       (Followers: 5) Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering       (Followers: 1) Proceedings of the Human Factors and Ergonomics Society Annual Meeting       (Followers: 10) Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering       (Followers: 41) Progress in Aerospace Sciences       (Followers: 75) Propulsion and Power Research       (Followers: 26) REACH - Reviews in Human Space Exploration       (Followers: 2) Recent Patents on Space Technology       (Followers: 3) RocketSTEM       (Followers: 3) Russian Aeronautics (Iz VUZ)       (Followers: 23) Science and Education : Scientific Publication of BMSTU Space and Polity       (Followers: 4) Space Policy       (Followers: 25) Space Research Today       (Followers: 43) Space Safety Magazine       (Followers: 44) Space Science Reviews       (Followers: 93) SpaceNews       (Followers: 558) Transport and Aerospace Engineering       (Followers: 6) Transportmetrica A : Transport Science       (Followers: 5) Unmanned Systems       (Followers: 3) Вісник Національного Авіаційного Університету       (Followers: 1)
 CEAS Aeronautical Journal   [SJR: 0.499]   [H-I: 6]   [28 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1869-5582    Published by Springer-Verlag  [2354 journals]
• Support of icing flight tests by near real-time data analysis
• Authors: Christian Raab; Per Ohme; Christoph Deiler
Pages: 561 - 577
Abstract: Flight testing of aircraft with altered aerodynamic configuration is a safety critical and time consuming task. For the evaluation of the aircraft characteristics under SLD icing conditions, flight tests with artificial ice shapes were performed. These flight tests were supported by online algorithms for the estimation of aerodynamic parameters. Results were available in near real-time onboard the aircraft or already during the debriefing on ground. Pre-flight data from wind tunnel experiments could be confirmed already during the flight using these online analysis tools, thus the flight tests could be performed in shorter time and more safe. This paper will introduce the developed analysis tools and will present results from the flight test campaign.
PubDate: 2017-12-01
DOI: 10.1007/s13272-017-0260-5
Issue No: Vol. 8, No. 4 (2017)

• Quasi-steady doublet-lattice correction for aerodynamic gust response
prediction in attached and separated transonic flow
• Authors: Diliana Friedewald; Reik Thormann; Christoph Kaiser; Jens Nitzsche
Abstract: A quasi-steady doublet-lattice correction method is used to predict aerodynamic gust responses of two different configurations: a swept wing, the so-called Aerostabil wing, and a transport aircraft configuration, the NASA Common Research Model. The results of the correction method are compared to uncorrected doublet-lattice results, and to results obtained from a nonlinear computational fluid dynamics solver, the DLR TAU-Code. The correction method agrees well with time-marching results obtained by TAU in the limit of dynamically linear gust amplitudes and improves with gust length. In separated transonic flow, an oscillation of the aerodynamic gust response can be computed.
PubDate: 2017-11-17
DOI: 10.1007/s13272-017-0273-0

• Influence of a back-flow flap on the dynamic stall flow topology
• Authors: C. C. Wolf; A. D. Gardner; C. B. Merz; S. Opitz
Abstract: Dynamic stall is a major concern for highly loaded helicopter rotors in fast forward flight. The potential of a back-flow flap for dynamic stall reduction is investigated. The flap assembly is mounted on the suction side of a helicopter main rotor-blade airfoil undergoing deep-stall pitch oscillations. Wind-tunnel experiments using high-speed particle image velocimetry were conducted to identify the flow topology and to investigate the flap’s method of operation. A phase-averaged proper orthogonal decomposition (POD) is used to identify relevant flow events and to compare test cases with and without flap. The evolution of the large-scale dynamic stall vortex in the initial phases of flow separation is analyzed in detail. The back-flow flap splits the vortex into two smaller vortices and thereby reduces the pitching-moment peak. This effect can be described through the eigenmode coefficients of the POD. The study closes with an analysis of different pitching frequencies, which do not affect the flap’s method of operation.
PubDate: 2017-11-13
DOI: 10.1007/s13272-017-0274-z

• Tactile cueing with active cyclic stick for helicopter obstacle avoidance:
development and pilot acceptance
• Authors: Mario Müllhäuser
Abstract: As helicopters land and takeoff in obstructed areas and on unprepared landing sites, the risk of a collision with an obstacle is high. DLR has implemented a function to provide haptic feedback on the controls of a helicopter as a haptic pilot assistance for obstacle avoidance to evaluate it’s benefits for flying in obstructed areas. The cueing forces are provided in the direction away from the obstacle, and the intensity is a function of the distance to the obstacle. Two different force strategies were prepared for evaluation. The first was a steady, continuously increasing counter force in combination with an increasing spring gradient. The second was a repetitive, rectangular-shaped pulsing force with increasing frequency and amplitude. As a proof of concept, three EC135 pilots experienced in helicopter emergency medical service assessed the acceptability of such a system for operational use in the EC135 ACT/FHS simulator cockpit in DLRs Air Vehicle Simulation Center. It achieved a high level of acceptance. This paper presents the development and evaluation results and gives recommendations for the further development.
PubDate: 2017-10-31
DOI: 10.1007/s13272-017-0271-2

• Analysis and design of hybrid electric regional turboprop aircraft
• Authors: Mark Voskuijl; Joris van Bogaert; Arvind G. Rao
Abstract: The potential environmental benefits of hybrid electric regional turboprop aircraft in terms of fuel consumption are investigated. Lithium–air batteries are used as energy source in combination with conventional fuel. A validated design and analysis framework is extended with sizing and analysis modules for hybrid electric propulsion system components. In addition, a modified Bréguet range equation, suitable for hybrid electric aircraft, is introduced. The results quantify the limits in range and performance for this type of aircraft as a function of battery technology level. A typical design for 70 passengers with a design range of 1528 km, based on batteries with a specific energy of 1000 Wh/kg, providing 34% of the shaft power throughout the mission, yields a reduction in emissions by 28%.
PubDate: 2017-10-31
DOI: 10.1007/s13272-017-0272-1

• An automated CFD analysis workflow in overall aircraft design applications
• Authors: Xiangyu Gu; Pier Davide Ciampa; Björn Nagel
Abstract: An automated CFD-based analysis process for applications at the early aircraft development stages is presented. The robustness of the implemented process, which relies on a knowledge-based layer implemented into the automated pre-processing step of the geometrical components, allows taking advantage of high fidelity simulations, also for large explorations of the design space. The well-known aircraft configuration DLR-F6 is chosen to verify the automated analysis process. The CFD analysis process is integrated into the DLR multi-fidelity aircraft design environment, which relies on the DLR open source distributed framework RCE, and the DLR central data model CPACS. The overall aircraft design synthesis is performed for a conventional passenger transportation aircraft configuration, by making use of variable fidelity methods for the aerodynamic analysis. The results discuss the impact of employing CFD-based analysis into overall aircraft design applications.
PubDate: 2017-10-28
DOI: 10.1007/s13272-017-0264-1

• Edge-based approach to estimate the drift of a helicopter during flight
• Authors: Alexander Gatter
Abstract: The Institute of Flight Systems at the German Aerospace Center (DLR) site in Braunschweig Germany has set its goal into making helicopter flying as safe as possible. The new DLR research project “Rettungshubschrauber 2030” addresses the topic of aiding helicopter rescue missions. Research will be conducted to increase the safety of these missions as well as to enable the conduct of missions in circumstances where nowadays a helicopter would not be allowed to operate. One aspect of this research is to increase or maintain the situational awareness of the pilot by processing data from camera images. The paper will focus on the field of visual odometry. It examines, if an edge-based approach for extracting features is a possible alternative or addition to established feature extractors. In the paper, two algorithms for edge extraction will be compared: an algorithm that is based on Hough transform and an algorithm that is based on the Douglas–Peucker method. They are tuned for working with images of rather low resolution and are tested on their ability to detect a sufficient amount of features in camera images as well as on their computational complexity. Then, their ability to detect the drift of a helicopter is assessed using recorded data from flight tests with the advanced control technology/flying helicopter simulator (ACT/FHS) of the DLR. Their performance will be tested on the basis of reference data from the ACT/FHS which have been recorded by the use of a highly accurate INS/DGPS system. The evaluation of the algorithms yields the result that both achieve the proposed accuracy regarding the velocity estimation with the Hough-based method achieving better accuracy while taking significantly more computational time.
PubDate: 2017-10-27
DOI: 10.1007/s13272-017-0270-3

• Multi-use 48-kW power electronics for future aerospace applications
• Authors: Rodolphe De Maglie; Alfred Engler; Roger Birost; Ralf Cremer
Abstract: In the frame of the more electric aircraft and to achieve the goal of replacing hydraulic systems by electrical ones, the power density is one of the major key parameters for electrical designs. Recent advances in predevelopment activities and technologies allow today to be competitive in term of performances and weight with the existing solutions. The paper deals with the development of power electronics converter dedicated to aerospace application like environmental conditioning system and starter generator. The presented power electronic is based on a common platform where converters have been designed for ± 270 VDC network (230 VAC rectified) in duplex architecture, with and without HV input filter and inrush current limiter depending on the application. The presented GRA and SGO systems and inverters are designed and tested for flight demonstration. Descriptions of the E-ECS system and dedicated inverter are given. Many electrical (normal and abnormal steady state conditions, power input, voltage transient, etc.) and environmental (temperature, EMC, vibrations, etc.) tests according to aerospace standards are accomplished successfully: the unit shows through all these tests a high degree of maturity that is necessary to translate the research and development activities into future products. The flight test demonstration is also addressed.
PubDate: 2017-10-23
DOI: 10.1007/s13272-017-0268-x

• Benefit evaluation of hybrid electric propulsion concepts for CS-23
aircraft
• Authors: M. Kreimeier; E. Stumpf
Abstract: The importance of small passenger aircraft design fitting up to nine passengers and the evaluation of associated technologies have been recently increasing. This is related to the upcoming interest in on demand air mobility concepts not only for intra- or inter-urban transport but also for thin-haul routes ranging from 150 km to approximately 500–800 km. Such concepts seem feasible as key enabling technologies (e.g., flight automation and battery technology) are likely to be mature enough to enable these concepts in the foreseeable future. However, until battery specific energy in particular surpasses the threshold of approximately 400 Wh/kg, hybrid electric propulsion concepts could serve as an interim solution. Therefore, this paper deals with the question of how hybrid electric concepts score compared to conventional piston engine aircraft and which concept promises the most benefits. This includes consideration of propulsion-airframe integration benefits of electric engines through distributed electric propulsion (DEP). Results show that the series hybrid electric concept is superior to a parallel setup if at least a 15% higher cruise lift-to-drag ratio can be achieved due to DEP (30–50% increase likely). Despite higher weight, variable operating costs can be reduced by 15–35% with application of series hybrid electric propulsion concepts.
PubDate: 2017-10-14
DOI: 10.1007/s13272-017-0269-9

• Multidisciplinary optimization of an NLF forward swept wing in combination
with aeroelastic tailoring using CFRP
• Authors: Tobias Wunderlich; Sascha Dähne; Lars Heinrich; Lars Reimer
Abstract: This article introduces a process chain for commercial aircraft wing multidisciplinary optimization (MDO) based on high fidelity simulation methods. The architecture of this process chain enables two of the most promising future technologies in commercial aircraft design in the context of MDO. These technologies are natural laminar flow (NLF) and aeroelastic tailoring using carbon fiber reinforced plastics (CFRP). With this new approach, the application of MDO to an NLF forward swept composite wing will be possible. The main feature of the process chain is the hierarchical decomposition of the optimization problem into two levels. On the highest level, the wing planform including twist and airfoil thickness distributions as well as the orthotropy direction of the composite structure will be optimized. The lower optimization level includes the wing box sizing for essential load cases considering the static aeroelastic deformations. In addition, the airfoil shapes are transferred from a given NLF wing design and the natural laminar flow is considered by prescribing laminar–turbulent transition locations. Optimization results of the multidisciplinary process chain are presented for a forward swept wing aircraft configuration on conceptual design level. The results show a fuel burn reduction in the order of 9% for the design mission.
PubDate: 2017-10-10
DOI: 10.1007/s13272-017-0266-z

• Aileron endurance test rig design based on high fidelity mathematical
modeling
Abstract: This paper presents a model-based approach to design aileron endurance test rig (ETR). ETR is a dynamic load simulator which simulates aerodynamic load on-ground for verifying and validating the design, performance and stability of aileron actuator. Aileron actuator is a servo-controlled linear hydraulic actuator used to control the movement of ailerons in aircraft. Aileron is one of the primary flight control surfaces which controls roll of the aircraft. In ETR, Aileron actuator acts as unit under test (UUT) while a double-acting linear hydraulic actuator produces a dynamic load with the help of high pressure fluid source and electro-hydraulic servo valve (EHSV). The design of the test rig depends on load and velocity requirements which vary widely over the whole flight envelop and depends on deflection of surface, angle of attack, aircraft speed and altitude. One of the critical factor in designing ETR is to accurately model the interaction between the UUT and load system. This paper presents a simple yet powerful approach of free body diagram to account the power flow between the two systems. Model-based approach allowed to simulate the complete test rig behavior identifying the values of the critical parameters prior to building it. A high fidelity, non-linear mathematical model of aileron ETR is developed, simulated and verified. An appropriate load actuator and its electro-hydraulic servo valve are chosen to meet load and velocity requirements. The minimum rig structure stiffness is determined to ensure the stability of the load control system. A velocity feed-forward-based load controller along with proportional-integral control is implemented and tuned to meet the load control performance satisfactorily. Finally, the developed model is validated against the experimental data from actual test rig.
PubDate: 2017-10-07
DOI: 10.1007/s13272-017-0267-y

• In-flight tracking and vibration control using the DLR’s multiple
Swashplate system
• Authors: Philip M. Küfmann; Claudio Brillante
Abstract: This paper discusses the design, integration, and test of a higher harmonic control algorithm capable of both vibration control and in-flight blade tracking in conjunction with DLR’s multiple swashplate control system (META), while honoring predefined limits in usable control authority. The design of the control algorithm is described in detail and the results of coupled numerical investigations with both a general purpose multibody code by Politecnico di Milano and DLR’s comprehensive rotor code to determine the algorithm’s performance are presented. The integration of the control algorithm into the real-time control software is shown for the META system, where, for safety reasons, a semi-open loop approach was implemented. First tests of the controllers in-flight tracking mode to reduce 1/rev loads during hover yielded an almost complete reduction in 1/rev vibratory loads while maintaining constant rotor thrust. Following the experiments at DLR’s own facility, extensive wind-tunnel tests were performed in 2016 with META and a 5-bladed rotor system at the large low-speed facility of the German Dutch Wind Tunnels. The control algorithm was adapted to the 5-bladed rotor and successfully applied for in-flight blade tracking as well as the reduction of 5/rev hub loads using multi-harmonic pitch inputs with frequencies from 4/rev to 6/rev in cruise and high-speed flight condition. In both cases, the controller showed excellent performance and yielded satisfactory reductions of 1/rev rotor imbalances as well as a reduction of 5/rev hub vibrations by more than $$80\%$$ , while, at the same time, adhering to user set limits for the higher harmonic control amplitudes.
PubDate: 2017-10-03
DOI: 10.1007/s13272-017-0265-0

• Flight mechanics model for spanwise lift and rolling moment distributions
of a segmented active high-lift wing
• Authors: J. H. Diekmann; D. Keller; E. Faez; R. Rudnik; V. Gollnick
Abstract: In this study, the aerodynamics of wings using an active high-lift system are investigated. The target is the flight mechanical description of the spanwise forces and resulting moments and the influence of the active high-lift system to their distribution. The high-lift system is a blown flap system divided into six segments per wing. Each segment is assumed to be individually controlled, so the system shall be used for aircraft control and system failure management. This work presents a flight mechanical sub-model for the simulation of flight dynamics, which has been derived from high-fidelity CFD results. An assessment of single-segment blowing system failures will be presented including recommendations for compensation of either lift or rolling moment loss. For this investigation, the compensation is required to act at the same wing side on which the failure appears. Thus, the potential for an increase of system reliability shall be proven. The results show that less performance investment in terms of pressurized air is necessary to compensate the rolling moment of a failing segment instead of its lift. However, large blowing performance increases for the remaining wing segments that occur for some of the failure cases.
PubDate: 2017-09-20
DOI: 10.1007/s13272-017-0261-4

• Boundary-layer transition measurements on Mach-scaled helicopter rotor
• Authors: Armin Weiss; Anthony D. Gardner; Christian Klein; Markus Raffel
Abstract: In this work, laminar-turbulent boundary-layer transition is investigated on the suction side of Mach-scaled helicopter rotor blades in climb. The phenomenon is assessed by means of temperature-sensitive paint (TSP). Results are compared to a data sample acquired by infrared (IR) thermography and accompanied by integral thrust- and local surface pressure measurements at two radial blade sections. Spatially, high-resolved data allow for precise detection of boundary-layer transition along the outer 60% of the blade span. Results obtained via TSP and IR show remarkable agreement with minor deviations due to different surface qualities of the respective blades tested. TSP data are obtained at various collective pitch angles and three different rotating speeds corresponding to chord Reynolds and Mach numbers based on blade tip speed of $$Re_{\rm tip} = 4.8 - 9.3\times 10^5$$ and $$M_{\rm tip} = 0.29 - 0.57$$ , respectively. The transition position is detected with an accuracy of better than 1% chord and the findings show overall coherence as blade loading and tip chord Reynolds number are varied. Experimental findings are shown to be consistent with two-dimensional simulations using the $$e^N$$ -envelope method for transition prediction. Based on quantitative agreement between measured and calculated surface pressures, a comparison of the corresponding transition results suggests a critical amplification factor of $$N_{\rm cr.} = 5.5$$ best suited for transition prediction in the rotating test facility of the DLR Göttingen.
PubDate: 2017-09-19
DOI: 10.1007/s13272-017-0263-2

• Numerical modelling of the aerodynamic interference between helicopter and
ground obstacles
• Authors: Giulia Chirico; Damien Szubert; Luigi Vigevano; George N. Barakos
Abstract: Helicopters are frequently operating in confined areas where the complex flow fields that develop in windy conditions may result in dangerous situations. Tools to analyse the interaction between rotorcraft wakes and ground obstacles are therefore essential. This work, carried out within the activity of the GARTEUR Action Group 22 on “Forces on Obstacles in Rotor Wake”, attempts to assess numerical models for this problem. In particular, a helicopter operating in hover above a building as well as in its wake, one main rotor diameter above the ground, has been analysed. Recent tests conducted at Politecnico di Milano provide a basis for comparison with unsteady simulations performed, with and without wind. The helicopter rotor has been modelled using steady and unsteady actuator disk methods, as well as with fully resolved blade simulations. The results identify the most efficient aerodynamic model that captures the wakes interaction, so that real-time coupled simulations can be made possible. Previous studies have already proved that the wake superposition technique cannot guarantee accurate results if the helicopter is close to the obstacle. The validity of that conclusion has been further investigated in this work to determine the minimum distance between helicopter and building at which minimal wake interference occurs.
PubDate: 2017-09-05
DOI: 10.1007/s13272-017-0259-y

• Adaptive backstepping neural network control for three dimensions
trajectory tracking of robotic airships
• Authors: Yueneng Yang; Wenqiang Wang; Ye Yan
Abstract: The robotic airship provides a unique aerostatic platform for various applications, and these applications require high-precise trajectory tracking. However, it is a challenging problem due to nonlinearity and uncertainty of airship dynamics. This paper proposes an adaptive backstepping neural network control (ABNNC) approach to address this problem. First, the kinematics model and dynamics model of the robotic airship are presented. Second, the control problem of trajectory tracking is formulated, and a trajectory controller is designed using backstepping approach. A radial basis function neural network (RBFNN) is employed to approximate the uncertain dynamics model of the airship, and an adaptive law is designed to update the NN weight in the processing of approximation. The ultimate boundedness of the tracking errors are proven based on the Lyapunov theory. Finally, simulations are presented to illustrate the effectiveness and high precision of the designed controller.
PubDate: 2017-09-04
DOI: 10.1007/s13272-017-0262-3

• Numerical simulation of flexible aircraft structures under ditching loads
• Authors: M. H. Siemann; D. Kohlgrüber; H. Voggenreiter
Abstract: Aircraft certification requires demonstrating an aircraft’s structural capacity to withstand hydrodynamic loads as experienced during an emergency landing on water known as ditching. Currently employed means to analyze ditching comprise comparison with previously certified aircraft, sub-scale experimental testing, and semi-analytical as well as uncoupled computational methods; all of these are subject to simplifications that limit their predictability and accuracy. Therefore, there is the motivation to employ advanced, coupled numerical simulations to enhance the analysis capabilities. This paper presents a numerical simulation approach combining Smoothed Particle Hydrodynamics and Finite Element method, which permits investigating the structural behavior under ditching loads within one simulation. Comprehensive validation studies based on comparison with experimental results from novel guided ditching experiments of generic panels in aeronautical design have been undertaken and high accuracy has been achieved regarding acting force and strain time histories. Additionally, the profound analysis of the structural behavior of flexible panels allows assessing the main mechanisms that cause the acting hydrodynamic loads to increase significantly when the structure is being deformed. Presented results extend the fundamental knowledge in this field. The validated simulation approach is finally applied to analyze the structural behavior of a detailed stringer-frame-reinforced panel representing a generic aircraft bottom fuselage structure. Comparison between the structural behavior of the generic panels and the aft fuselage structure is established. Furthermore, conclusions with regard to ditching simulations involving larger or even full aircraft structures are drawn.
PubDate: 2017-07-11
DOI: 10.1007/s13272-017-0257-0

• Aeroelastic tailoring of an NLF forward swept wing
• Authors: Tobias Wunderlich; Sascha Dähne
Abstract: This article introduces the application of a multidisciplinary analysis process chain based on high-fidelity simulation methods for the aeroelastic tailoring of an natural laminar flow (NLF) forward swept wing. With this approach the interactions between aerodynamics, loads and structural sizing are considered in the wing analysis. The resulting process enables an integrated aerostructural wing design including aeroelastic tailoring using carbon fiber reinforced plastics. The main feature of the process chain is the hierarchical decomposition of the problem into two levels. On the highest level, the orthotropy direction of the composite structure will be analyzed. The lower level includes the wing box sizing for essential load cases considering the static aeroelastic deformations. Thereby, the wing box sizing can be performed with a given ply share of the laminate or a ply share optimization. Additionally, the airfoil shapes are transferred from a given NLF wing design. The natural laminar flow is considered by prescribing laminar–turbulent transition locations. The process chain evaluates the wing mass, the lift-to-drag ratio under cruise flight conditions and the corresponding design mission fuel consumption. Results of aerostructural wing design studies and optimizations are presented for an NLF forward swept wing aircraft configuration. The aerostructural wing optimization with 3 orthotropy angles as design parameters shows a wing mass reduction in the order of 8% and a design mission fuel consumption reduction in the order of 4% in comparison to the aeroelastic tailored wing design of the reference aircraft.
PubDate: 2017-06-30
DOI: 10.1007/s13272-017-0251-6

• Automated trajectory generation and airport selection for an emergency
landing procedure of a CS23 aircraft
• Authors: Arno Fallast; Bernd Messnarz
Abstract: Aircraft in general aviation usually are operated in single pilot mode. Especially, in case of an incapability of the pilot to control the aircraft, an automated emergency procedure is desirable in order to reduce the risk of fatalities. The finding of a solution for an emergency landing maneuver includes preselecting possible landing sites with regard to the available aircraft capabilities and creation of feasible trajectories to these sites. A search tree in four-dimensional search space with an efficient implementation of a rapidly exploring random tree algorithm (RRT*) is created. The algorithm performance is increased by use of basic geometrical sets to construct the final route as a combination of Dubins path segments. To further reduce the route length, a gradient based local optimization routine is added after completion of the RRT* algorithm. At the moment of creation, terrain avoidance is verified and accordance with legal airspace structure is considered. An emergency procedure is created by combining a selected landing site and a flyable trajectory to this site. Each of these combinations is scored, and the most promising emergency landing procedure is chosen and delivered to flight management system of the aircraft. The flight management system controls a full-authority auto-flight system that is capable of performing en-route flight and auto-land procedures as well.
PubDate: 2017-06-30
DOI: 10.1007/s13272-017-0252-5

• Numerical and experimental investigations of the propeller characteristics
of an electrically powered ultralight aircraft
• Authors: M. Stuhlpfarrer; A. Valero-Andreu; C. Breitsamter
Abstract: The performance and efficiency of a propeller is crucial for electrically powered propulsion systems. Since the energy of the batteries is limited, it is important to develop propellers with high efficiency. Therefore, numerical and experimental investigations of the propeller characteristics are performed. The wind tunnel experiments are performed on a fuselage–propeller configuration. The electrical motor, batteries, and control units are designed to be integrated in the fuselage. Furthermore, force measurements are conducted to provide a data base for the validation of the numerical results. Two different numerical approaches are presented. First, the propeller is fully resolved by applying a rotational domain and a sliding mesh interface. Second, an actuator disk approach including blade element theory with a panel method one-way coupled with a boundary layer integration method is presented. The latter shall be used to reduce computational and mesh generation costs. The thrust, efficiency as well as pressure distribution and the flow field downstream of the propeller are analyzed. The obtained numerical results show a good agreement with the experimental data for the integral values over a wide operating range. Moreover, the results of the inter-method comparison of the two numerical approaches are in a good accordance regarding the local effects for the two highlighted operating points.
PubDate: 2017-06-16
DOI: 10.1007/s13272-017-0245-4

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