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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 123 journals)
Showing 1 - 30 of 30 Journals sorted alphabetically
Acta Astronautica     Hybrid Journal   (Followers: 496)
Advances in Aerospace Engineering     Open Access   (Followers: 70)
Advances in Aerospace Science and Technology     Open Access   (Followers: 8)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 1)
Advances in Space Research     Full-text available via subscription   (Followers: 458)
Aeronautical Journal, The     Hybrid Journal   (Followers: 13)
Aerospace     Open Access   (Followers: 60)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 19)
Aerospace Science and Technology     Hybrid Journal   (Followers: 430)
Aerospace Scientific Journal     Open Access   (Followers: 18)
Aerospace Systems     Hybrid Journal   (Followers: 6)
Aerospace technic and technology     Open Access   (Followers: 3)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 4)
AIAA Journal     Hybrid Journal   (Followers: 1196)
Air Force Magazine     Full-text available via subscription   (Followers: 10)
Air Medical Journal     Hybrid Journal   (Followers: 8)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 264)
Annual of Navigation     Open Access   (Followers: 22)
Artificial Satellites     Open Access   (Followers: 23)
ASTRA Proceedings     Open Access   (Followers: 3)
Astrodynamics     Hybrid Journal   (Followers: 4)
Aviation     Open Access   (Followers: 17)
Aviation Advances & Maintenance     Open Access   (Followers: 5)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 10)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 27)
Aviation Week     Full-text available via subscription   (Followers: 438)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 34)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 30)
Chinese Journal of Aeronautics     Open Access   (Followers: 21)
Ciencia y Poder Aéreo     Open Access   (Followers: 2)
Civil Aviation High Technologies     Open Access   (Followers: 5)
Control Systems     Hybrid Journal   (Followers: 315)
Cosmic Research     Hybrid Journal   (Followers: 5)
COSPAR Colloquia Series     Full-text available via subscription   (Followers: 11)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 24)
Elsevier Astrodynamics Series     Full-text available via subscription   (Followers: 12)
Fatigue of Aircraft Structures     Open Access   (Followers: 15)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 12)
Gravitational and Space Research     Open Access  
Gyroscopy and Navigation     Hybrid Journal   (Followers: 260)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 279)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 385)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 39)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 41)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 37)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 2)
International Journal of Aerospace Engineering     Open Access   (Followers: 82)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 23)
International Journal of Aerospace Sciences     Open Access   (Followers: 32)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
International Journal of Aviation Management     Hybrid Journal   (Followers: 9)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 7)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 5)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 12)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 11)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 13)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 11)
International Journal of Space Structures     Full-text available via subscription   (Followers: 17)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 10)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
International Journal of Turbo and Jet-Engines     Hybrid Journal   (Followers: 6)
Investigación Pecuaria     Open Access   (Followers: 3)
Journal of Aerodynamics     Open Access   (Followers: 18)
Journal of Aeronautical Materials     Open Access   (Followers: 9)
Journal of Aeronautics & Aerospace Engineering     Open Access   (Followers: 31)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 69)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 18)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 22)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 34)
Journal of Aerospace Technology and Management     Open Access   (Followers: 7)
Journal of Aircraft     Hybrid Journal   (Followers: 337)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 9)
Journal of Airline and Airport Management     Open Access   (Followers: 12)
Journal of Astrobiology & Outreach     Open Access   (Followers: 3)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 11)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 1)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 205)
Journal of KONBiN     Open Access   (Followers: 3)
Journal of Navigation     Hybrid Journal   (Followers: 280)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 615)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 8)
Journal of Space Weather and Space Climate     Open Access   (Followers: 27)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 773)
Journal of Spatial Science     Hybrid Journal   (Followers: 3)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 8)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 9)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 1)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 17)
Life Sciences in Space Research     Hybrid Journal   (Followers: 4)
MAD - Magazine of Aviation Development     Open Access   (Followers: 2)
Mekanika : Jurnal Teknik Mesin i     Open Access   (Followers: 1)
Microgravity Science and Technology     Hybrid Journal   (Followers: 2)
New Space     Hybrid Journal   (Followers: 6)
Nonlinear Dynamics     Hybrid Journal   (Followers: 20)
npj Microgravity     Open Access   (Followers: 3)
Open Aerospace Engineering Journal     Open Access   (Followers: 1)
Perspectives of Earth and Space Scientists i     Open Access  
Population Space and Place     Hybrid Journal   (Followers: 9)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 46)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 81)
Propulsion and Power Research     Open Access   (Followers: 68)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 17)
RocketSTEM     Free   (Followers: 6)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 24)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Space and Polity     Hybrid Journal   (Followers: 4)
Space Policy     Hybrid Journal   (Followers: 29)
Space Research Today     Full-text available via subscription   (Followers: 48)
Space Safety Magazine     Free   (Followers: 51)
Space Science International     Open Access   (Followers: 202)
Space Science Reviews     Hybrid Journal   (Followers: 97)
SpaceNews     Free   (Followers: 825)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Technical Soaring     Full-text available via subscription   (Followers: 1)
Transport and Aerospace Engineering     Open Access   (Followers: 1)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 9)
Unmanned Systems     Hybrid Journal   (Followers: 5)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 2)

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Aerospace
Journal Prestige (SJR): 0.305
Citation Impact (citeScore): 1
Number of Followers: 60  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2226-4310
Published by MDPI Homepage  [233 journals]
  • Aerospace, Vol. 8, Pages 120: β-Band Analysis from Simulated Flight
           Experiments

    • Authors: Válber César Cavalcanti Roza, Octavian Postolache
      First page: 120
      Abstract: Several safety-related improvements are applied every year to try to minimize the total number of civil aviation accidents. Fortunately, these improvements work well, reducing the number of accident occurrences. However, while the number of accidents due to mechanical failures has decreased, the number of accidents due to human errors seems to grow. On that basis, this work presents a contribution regarding the brain’s β-band activities for different levels of volunteers’ expertise on flight simulator, i.e., experienced, mid-level and beginner, in which they acted as pilots in command during several simulated flights. Spectrogram analysis and statistical measurements of each volunteer’s brain’s β-band were carried out. These were based on seven flight tasks: takeoff, climb, cruise flight, descent, approach, final approach and landing. The results of the proposed experiment showed that the takeoff, approach and landing corresponded to the highest brain activities, i.e., close to 37.06–67.33% more than the brain activity of the other flight tasks: when some accidents were about to occur, the intensities of the brain activity were similar to those of the final approach task. When the volunteers’ expertise and confidence on flight simulation were considered, it was shown that the highest brain magnitudes and oscillations observed of more experienced and confident volunteers were on average close to 68.44% less, compared to less experienced and less confident volunteers. Moreover, more experienced and confident volunteers in general presented different patterns of brain activities compared to volunteers with less expertise or less familiarity with fight simulations and/or electronic games.
      Citation: Aerospace
      PubDate: 2021-04-21
      DOI: 10.3390/aerospace8050120
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 121: Accuracy of Noise-Power-Distance Definition
           on Results of Single Aircraft Noise Event Calculation

    • Authors: Oleksandr Zaporozhets, Larisa Levchenko
      First page: 121
      Abstract: Aircraft performance and noise database together with operational weights (depending on flight distances) and operational procedures (including low noise procedures) significantly influence results of noise exposure contour maps assessment in conditions of real atmosphere. Current recommendations of the Standard SAE-AIR1845A allow the definition of flight profiles via solutions of balanced motion equations. However, differences are still supervised between the measured sound level data and calculated ones, especially in assessing the single flight noise events. Some of them are well explained by differences between balanced flight parameters (thrust and velocity first of all) and monitored ones by the traffic control system. Statistical data were gathered to make more general view on these differences and some proposal to use them in calculations has been proven. Besides, the real meteorological parameters provide inhomogeneous atmosphere conditions always, which are quite different from the main assumptions of the SAE-AIR1845A, stipulating inaccuracies of sound level calculations.
      Citation: Aerospace
      PubDate: 2021-04-21
      DOI: 10.3390/aerospace8050121
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 122: Sources of Onboard Fumes and Smoke Reported
           by U.S. Airlines

    • Authors: Judith Anderson
      First page: 122
      Abstract: This paper describes the relative frequency of reports of oil and hydraulic fluid fumes in the ventilation supply air (“fume events”) compared to other types of fumes and smoke reported by U.S. airlines over 10 years. The author reviewed and categorized 12,417 fume/smoke reports submitted to the aviation regulator to comply with the primary maintenance reporting regulation (14 CFR § 121.703) from 2002–2011. The most commonly documented category of onboard fumes/smoke was electrical (37%). Combining the categories of “bleed-sourced”, “oil”, and “hydraulic fluid” created the second most prevalent category (26%). The remaining sources of onboard fumes/smoke are also reported. To put the data in context, the fume event reporting regulations are described, along with examples of ways in which certain events are underreported. These data were reported by U.S. airlines, but aviation regulations are harmonized globally, so the data likely also reflect onboard sources of fumes and smoke reported in other countries with equivalent aviation systems. The data provide insight into the relative frequency of the types of reported fumes and smoke on aircraft, which should drive design, operational, and maintenance actions to mitigate onboard exposure. The data also provide insight into how to improve current fume event reporting rules.
      Citation: Aerospace
      PubDate: 2021-04-22
      DOI: 10.3390/aerospace8050122
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 123: Global Skewness and Coherence for Hypersonic
           Shock-Wave/Boundary-Layer Interactions with Pressure-Sensitive Paint

    • Authors: Carson L. Running, Thomas J. Juliano
      First page: 123
      Abstract: The global surface pressure was measured on a 7° half-angle circular cone/flare model at a nominally zero angle of attack using pressure-sensitive paint (PSP). These experiments were conducted to illustrate fast PSP’s usefulness and effectiveness at measuring the unsteady structures inherent to hypersonic shock-wave/boundary-layer interactions (SWBLIs). Mean and fluctuating surface pressure was measured with a temperature-corrected, high-frequency-response (≈10 kHz) anodized-aluminum pressure-sensitive paint (AA-PSP) allowing for novel, global calculations of skewness and coherence. These analyses complement traditional SWBLI data-reduction methodologies by providing high-spatial-resolution measurements of the mean and fluctuating locations of the shock feet, as well as the frequency-dependent measure of the relationship between characteristic flow features. The skewness indicated the mean locations of the separation and reattachment shock feet as well as their fluctuations over the course of the test. The coherence indicated that the separation and reattachment shock feet fluctuate about their mean location at the same frequency as one another, but 180 degrees out of phase. This results in a large-scale ‘breathing motion’ of the separated region characteristic of large separation bubbles. These experimental findings validate the usefulness of AA-PSP, and associated data-reduction methodologies, to provide global physical insights of unsteady SWBLI surface behavior in the hypersonic flow regime. Similar methodologies can be incorporated in future experiments to investigate complex and novel SWBLIs.
      Citation: Aerospace
      PubDate: 2021-04-22
      DOI: 10.3390/aerospace8050123
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 124: Tightly Coupled Integrated Navigation
           Algorithm for Hypersonic Boost-Glide Vehicles in the LCEF Frame

    • Authors: Kai Chen, Sensen Pei, Fuqiang Shen, Shangbo Liu
      First page: 124
      Abstract: According to the trajectory characteristics of hypersonic boost-glide vehicles, a tightly coupled integrated navigation algorithm for hypersonic vehicles based on the launch-centered Earth-fixed (LCEF) frame is proposed. First, the strapdown inertial navigation mechanization algorithm and discrete update algorithm in the LCEF frame are introduced. Subsequently, the attitude, velocity, and position error equations of strapdown inertial navigation in the LCEF frame are introduced. The strapdown inertial navigation system/global positioning system (SINS/GPS) pseudo-range and pseudo-range rate measurement equations in the LCEF frame are derived. Further, the tightly coupled SINS/GPS integrated navigation filter state equation and the measurement equation are presented. Finally, the tightly coupled SINS/GPS integrated navigation algorithm is verified in the hardware-in-the-loop (HWIL) simulation environment. The simulation results indicate that the precision of tightly coupled integrated navigation is better than that of loosely coupled integrated navigation. Moreover, even when the number of effective satellites is less than four, tightly coupled integrated navigation functions well, thus verifying the effectiveness and feasibility of the algorithm.
      Citation: Aerospace
      PubDate: 2021-04-23
      DOI: 10.3390/aerospace8050124
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 125: An Explosion Based Algorithm to Solve the
           Optimization Problem in Quadcopter Control

    • Authors: Mohamad Norherman Shauqee, Parvathy Rajendran, Nurulasikin Mohd Suhadis
      First page: 125
      Abstract: This paper presents an optimization algorithm named Random Explosion Algorithm (REA). The fundamental idea of this algorithm is based on a simple concept of the explosion of an object. This object is commonly known as a particle: when exploded, it will randomly disperse fragments around the particle within the explosion radius. The fragment that will be considered as a search agent will fill the local space and search that particular region for the best fitness solution. The proposed algorithm was tested on 23 benchmark test functions, and the results are validated by a comparative study with eight well-known algorithms, which are Particle Swarm Optimization (PSO), Artificial Bee Colony (ABC), Genetic Algorithm (GA), Differential Evolution (DE), Multi-Verse Optimizer (MVO), Moth Flame Optimizer (MFO), Firefly Algorithm (FA), and Sooty Tern Optimization Algorithm (STOA). After that, the algorithm was implemented and analyzed for a quadrotor control application. Similarly, a comparative study with the other algorithms stated was done. The findings reveal that the REA can yield very competitive results. It also shows that the convergence analysis has proved that the REA can converge more quickly toward the global optimum than the other metaheuristic algorithms. For the control application result, the REA controller can better track the desired reference input with shorter rise time and settling time, lower percentage overshoot, and minimal steady-state error and root mean square error (RMSE).
      Citation: Aerospace
      PubDate: 2021-04-27
      DOI: 10.3390/aerospace8050125
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 126: A Hybrid Incremental Nonlinear Dynamic
           Inversion Control for Improving Flying Qualities of Asymmetric Store
           Configuration Aircraft

    • Authors: Chang-ho Ji, Chong-sup Kim, Byoung-Soo Kim
      First page: 126
      Abstract: Highly maneuverability fighter aircrafts are equipped with various weapons for successful air-to-air and air-to-ground missions. The aircraft has abrupt transient response due to ejection force generated when store of one wing is launched and the movement of lateral center-of-gravity (YCG) changing by the mass distribution of both wings after launched. Under maintaining 1 g level flight with manual trim system in the asymmetric store configuration, the aircraft causes unexpected roll motion for the pure longitudinal maneuver because the change of AoA and airspeed changes the amount of trim for level flight of the aircraft. For this reason, the pilot should continuously use the roll control stick input to maintain level flight. This characteristic increases the pilot’s workload and adversely affects the flying qualities of the aircraft, which is a major cause of deteriorating mission efficiency for combat maneuver. In this paper, we propose a hybrid control that combines model- and sensor-based Incremental Nonlinear Dynamic Inversion (INDI) control based mathematical model of the supersonic advanced trainer to minimize the transient response of the aircraft when the store is launched and to effectively reduce the unexpected roll motion that occurs for the pure longitudinal maneuvering in the asymmetric store configuration. As a result of the frequency- and time-domain evaluation, the proposed control method can effectively reduce the transient response for store launch and minimize unexpected roll motion for the pure longitudinal maneuver. Therefore, this control method can effectively improve flying qualities and mission efficiency by reducing the pilot’s workload in the operation of the asymmetric store configuration
      Citation: Aerospace
      PubDate: 2021-05-02
      DOI: 10.3390/aerospace8050126
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 127: InnoCube—A Wireless Satellite Platform to
           Demonstrate Innovative Technologies

    • Authors: Benjamin Grzesik, Tom Baumann, Thomas Walter, Frank Flederer, Felix Sittner, Erik Dilger, Simon Gläsner, Jan-Luca Kirchler, Marvyn Tedsen, Sergio Montenegro, Enrico Stoll
      First page: 127
      Abstract: A new innovative satellite mission, the Innovative CubeSat for Education (InnoCube), is addressed. The goal of the mission is to demonstrate “the wireless satellite”, which replaces the data harness by robust, high-speed, real-time, very short-range radio communications using the SKITH (SKIpTheHarness) technology. This will make InnoCube the first wireless satellite in history. Another technology demonstration is an experimental energy-storing satellite structure that was developed in the previous Wall#E project and might replace conventional battery technology in the future. As a further payload, the hardware for the concept of a software-based solution for receiving signals from Global Navigation Satellite Systems (GNSS) will be developed to enable precise position determination of the CubeSat. Aside from technical goals this work aims to be of use in the teaching of engineering skills and practical sustainable education of students, important technical and scientific publications, and the increase of university skills. This article gives an overview of the overall design of the InnoCube.
      Citation: Aerospace
      PubDate: 2021-05-04
      DOI: 10.3390/aerospace8050127
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 128: Effect of Two-Head Flared Hole on Film
           Cooling Performance over a Flat Plate

    • Authors: Xuan-Truong Le, Duc-Anh Nguyen, Cong-Truong Dinh, Quang-Hai Nguyen
      First page: 128
      Abstract: Film cooling is commonly utilized in turbine blades to decrease the temperature of the air stream from the combustion chamber that contacts directly with the blades. The shape of a cylindrical hole (CH) with the geometrical variations at inlet and outlet ports was examined using the 3D Reynolds-averaged Navier–Stokes equations (RANS) with a shear stress transport (SST k − ω) turbulence model to study the effect of the two-head flared hole on film cooling effectiveness (FE) at high accuracy with a small y+ value. To assess the effect of the changes, each geometry of the hole was changed one after another while the other parameters were kept invariable at the test value (cylindrical hole). The numerical laterally averaged film cooling effectiveness (ηl) of the CH case was validated and compared to the experimental data. The simulation results with the two-head flared hole indicated that most of these shape changes increase the FE as compared to the CH case. In particular, the maximum spatially averaged film cooling effectiveness (ηs) with hole shape expanded along the flow direction at the outlet port reached 60.787% in comparison to the CH case.
      Citation: Aerospace
      PubDate: 2021-05-04
      DOI: 10.3390/aerospace8050128
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 129: Methods of Identifying Correlated Model
           Parameters with Noise in Prognostics

    • Authors: Ting Dong, Nam H. Kim
      First page: 129
      Abstract: In physics-based prognostics, model parameters are estimated by minimizing the error or maximizing the likelihood between model predictions and measured data. When multiple model parameters are strongly correlated, it is challenging to identify individual parameters by measuring degradation data, especially when the data have noise. This paper first presents various correlations that occur during the process of model parameter estimation and then introduces two methods of identifying the accurate values of individual parameters when they are strongly correlated. The first method can be applied when the correlation relationship evolves as damage grows, while the second method can be applied when the operating (loading) conditions change. Starting from manufactured data using the true parameters, the accuracy of identified parameters is compared with various levels of noise. It turned out that the proposed method can identify the accurate values of model parameters even with a relatively large level of noise. In terms of the marginal distribution, the standard deviation of a model parameter is reduced from 0.125 to 0.03 when different damage states are used. When the loading conditions change, the uncertainty is reduced from 0.3 to 0.05. Both are considered as a significant improvement.
      Citation: Aerospace
      PubDate: 2021-05-05
      DOI: 10.3390/aerospace8050129
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 130: The Use of Machine Learning for the
           Prediction of the Uniformity of the Degree of Cure of a Composite in an
           Autoclave

    • Authors: Yuan Lin, Zhidong Guan
      First page: 130
      Abstract: The difference in the degree of cure of the composite in an autoclave is one of the main characterization parameters of the uniformity of the degree of cure of the composite material. Therefore, it is very important to develop an effective method for predicting the difference in the curing degree of a composite autoclave to improve the uniformity of the curing degree of the composite materials. We researched five machine learning models: a fully connected neural network (FCNN) model, a deep neural network (DNN) model, a radial basis function (RBF) neural network model, a support vector regression (SVR) model and a K-nearest neighbors (KNN) model. We regarded the heating rate, holding time and holding temperature of the composite material’s two holding-stage cure profile as input parameters and established a rapid estimation model of the maximum curing degree difference at any time during the molding process. We simulated the molding process of the composite material in an autoclave to obtain the maximum difference in the curing degree as the test sample data to train five machine learning models and compared and verified the different models after the training. The results showed that the RBF neural network model had the best prediction effect among the five models and the RBF was the most suitable algorithm for this model.
      Citation: Aerospace
      PubDate: 2021-05-05
      DOI: 10.3390/aerospace8050130
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 131: Towards a Circular Economy in the Aviation
           Sector Using Eco-Composites for Interior and Secondary Structures. Results
           and Recommendations from the EU/China Project ECO-COMPASS

    • Authors: Jens Bachmann, Xiaosu Yi, Konstantinos Tserpes, Carmen Sguazzo, Lucia Gratiela Barbu, Barbara Tse, Constantinos Soutis, Eric Ramón, Hector Linuesa, Stéphane Bechtel
      First page: 131
      Abstract: Fiber reinforced polymers play a crucial role as enablers of lightweight and high performing structures to increase efficiency in aviation. However, the ever-increasing awareness for the environmental impacts has led to a growing interest in bio-based and recycled ‘eco-composites’ as substitutes for the conventional synthetic constituents. Recently, the international collaboration of Chinese and European partners in the ECO-COMPASS project provided an assessment of different eco-materials and technologies for their potential application in aircraft interior and secondary composite structures. This project summary reports the main findings of the ECO-COMPASS project and gives an outlook to the next steps necessary for introducing eco-composites as an alternative solution to fulfill the CLEAN SKY target.
      Citation: Aerospace
      PubDate: 2021-05-05
      DOI: 10.3390/aerospace8050131
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 132: Design and Optimization of a Large Turboprop
           Aircraft

    • Authors: Fabrizio Nicolosi, Salvatore Corcione, Vittorio Trifari, Agostino De Marco
      First page: 132
      Abstract: This paper proposes a feasibility study concerning a large turboprop aircraft to be used as a lower environmental impact solution to current regional jets operated on short/medium hauls. An overview of this market scenario highlights that this segment is evenly shared between regional turboprop and jet aircraft. Although regional jets ensure a large operative flexibility, they are usually not optimized for short missions with a negative effect on block fuel and environmental impact. Conversely, turboprops represent a greener solution but with reduced passenger capacity and speed. Those aspects highlight a slot for a new turboprop platform coupling higher seat capacity, cruise speed and design range with a reduced fuel consumption. This platform should operate on those ranges where neither jet aircraft nor existing turboprops are optimized. This work compares three different solutions: a high-wing layout with under-wing engines installation and both two- and three-lifting-surface configurations with low-wing and tail tips-mounted engines. For each concept, a multi-disciplinary optimization was performed targeting the minimum block fuel on a 1600 NM mission. Optimum solutions were compared with both a regional jet such as the Airbus A220-300 operated on 1600 NM and with a jet aircraft specifically designed for this range.
      Citation: Aerospace
      PubDate: 2021-05-06
      DOI: 10.3390/aerospace8050132
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 133: Development of a Flexible and Expandable UTM
           Simulator Based on Open Sources and Platforms

    • Authors: Sugjoon Yoon, Dongcho Shin, Younghoon Choi, Kyungtae Park
      First page: 133
      Abstract: In order to study air traffic control of UAS’s (Unmanned Aerial Systems) in very low altitudes, the UTM (UAS Traffic Management) simulator has to be as flexible and expandable as other research simulators because relevant technologies and regulations are not matured enough at this stage. Available approaches using open sources and platforms are investigated to be used in the UTM simulator. The fundamental rationale for selection is availability of necessary resources to build a UTM simulator. Integration efforts to build a UTM simulator are elaborated, using Ardupilot, MavProxi, Cesium, and VWorld, which are selected from the thorough field study. Design requirements of a UTM simulator are determined by analyzing UTM services defined by NASA (National Aeronautics and Space Administration) and Eurocontrol. The UTM simulator, named eUTM, is composed of three components: UOS (UTM Operating System), UTM, and multiple GCSs (Ground Control Stations). GCSs are responsible for generation of flight paths of various UASs. UTM component copies functions of a real UTM such as monitoring and controlling air spaces. UOS provides simulation of environment such as weather, and controls the whole UTM simulator system. UOS also generates operation scenarios of UTM, and resides on the same UTM computer as an independent process. Two GCS simulators are connected to the UTM simulator in the present configuration, but the UTM simulator can be expanded to include up to 10 GCS simulators in the present design. In order to demonstrate the flexibility and expandability of eUTM simulator, several operation scenarios are realized and typical deconfliction scenarios among them are tested with a deconfliction algorithm. During the study, some limits are identified with applied open sources and platforms, which have to be resolved in order to obtain a flexible and expandable UTM simulator supporting relevant studies. Most of them are related to interfacing individual sources and platforms which use different program languages and communication drivers.
      Citation: Aerospace
      PubDate: 2021-05-08
      DOI: 10.3390/aerospace8050133
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 134: Load-Identification Method for Flexible
           Multiple Corrugated Skin Using Spectra Features of FBGs

    • Authors: Zhaoyu Zheng, Jiyun Lu, Dakai Liang
      First page: 134
      Abstract: Flexible corrugated skins are ideal structures for morphing wings, and the associated load measurements are of great significance in structural health monitoring. This paper proposes a novel load-identification method for flexible corrugated skins based on improved Fisher discrimination dictionary learning (FDDL). Several fiber Bragg grating sensors are pasted on the skin to monitor the load on multiple corrugated crests. The loads on different crests cause nonuniform strain fields, and these discriminative spectra are recorded and used as training data. The proposed method involves load-positioning and load-size identification. In the load-size-identification stage, a classifier is trained for every corrugated crest. An interleaved block grouping of samples is introduced to enhance the discrimination of dictionaries, and a two-resolution load-size classifier is introduced to improve the performance and resolution of the grouping labels. An adjustable weight is introduced to the FDDL classification scheme to optimize the contribution from different sensors for different load-size classifiers. With the proposed method, the individual loads on eight crests can be identified by two fiber Bragg grating sensors. The positioning accuracy is 100%, and the mean error of the load-size identification is 0.2106 N, which is sufficiently precise for structural health monitoring.
      Citation: Aerospace
      PubDate: 2021-05-09
      DOI: 10.3390/aerospace8050134
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 135: A Modified Dynamic Programming Approach for
           4D Minimum Fuel and Emissions Trajectory Optimization

    • Authors: Kawser Ahmed, Kouamana Bousson, Milca de Freitas Coelho
      First page: 135
      Abstract: 4D flight trajectory optimization is an essential component to improve flight efficiency and to enhance air traffic capacity. this technique not only helps to reduce the operational costs, but also helps to reduce the environmental impact caused by the airliners. This study considers Dynamic Programming (DP), a well-established numerical method ideally suited to solve 4D flight Trajectory Optimization Problems (TOPs). However, it bears some shortcomings that prevent the use of DP in many practical real-time implementations. This paper proposes a Modified Dynamic Programming (MDP) approach that reduces the computational effort and overcomes the drawbacks of the traditional DP. In this paper, two numerical examples with fixed arrival times are presented, where the proposed MDP approach is successfully implemented to generate optimal trajectories that minimize aircraft fuel consumption and emissions. Then the obtained optimal trajectories are compared with the corresponding reference commercial flight trajectory for the same route in order to quantify the potential benefit of reduction of aircraft fuel consumption and emissions.
      Citation: Aerospace
      PubDate: 2021-05-11
      DOI: 10.3390/aerospace8050135
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 136: Eeloscope—Towards a Novel Endoscopic
           System Enabling Digital Aircraft Fuel Tank Maintenance

    • Authors: Florian Heilemann, Alireza Dadashi, Kai Wicke
      First page: 136
      Abstract: In this research article, a novel endoscopic system, which is suited to perform a digital inspection of the aircraft wing fuel tanks, is introduced. The aim of this work is to specifically design and develop an assisting system, called `Eeloscope’, to allow accessing and diving through an aircraft kerosene tank in a minimally invasive matter. Currently, mechanics often suffer from the harsh working environment and the arduous maintenance duties within the tank. To address such challenges and derive a tailored solution, an adapted Design Thinking (DT) process is applied. The resulting system enables a fully digital inspection and generation of 3-dimensional structural inspection data. Consequently, devices such as the Eeloscope will facilitate a more efficient and continuous inspection of fuel tanks to increase the transparency regarding the condition of hardly accessible aircraft structures and provide a work relief for mechanics at the same time.
      Citation: Aerospace
      PubDate: 2021-05-12
      DOI: 10.3390/aerospace8050136
      Issue No: Vol. 8, No. 5 (2021)
       
  • Aerospace, Vol. 8, Pages 90: Numerical Investigation of a Dynamic Stall on
           a Single Rotating Blade

    • Authors: Yin Ruan, Manfred Hajek
      First page: 90
      Abstract: Dynamic stall is a phenomenon on the retreating blade of a helicopter which can lead to excessive control loads. In order to understand dynamic stall and fill the gap between the investigations on pitching wings and full helicopter rotor blades, a numerical investigation of a single rotating and pitching blade is carried out. The flow phenomena thereupon including the Ω-shaped dynamic stall vortex, the interaction of the leading edge vortex with the tip vortex, and a newly noticed vortex structure originating inboard are examined; they show similarities to pitching wings, while also possessing their unique features of a rotating system. The leading edge/tip vortex interaction dominates the post-stall stage. A newly noticed swell structure is observed to have a great impact on the load in the post-stall stage. With such a high Reynolds number, the Coriolis force exerted on the leading edge vortex is negligible compared to the pressure force. The force history/vortex structure of the slice r/R = 0.898 is compared with a 2D pitching airfoil with the same harmonic pitch motion, and the current simulation shows the important role played by the swell structure in the recovery stage.
      Citation: Aerospace
      PubDate: 2021-03-30
      DOI: 10.3390/aerospace8040090
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 91: Two-Phase Flow Phenomena in Gas Turbine
           Compressors with a Focus on Experimental Investigation of Trailing Edge
           Disintegration

    • Authors: Adrian Schlottke, Bernhard Weigand
      First page: 91
      Abstract: Two-phase flow in gas turbine compressors occurs, for example, at heavy rain flight condition or at high-fogging in stationary gas turbines. The liquid dynamic processes are independent of the application. An overview on the processes and their approach in literature is given. The focus of this study lies on the experimental investigation of the trailing edge disintegration. In the experiments, shadowgraphy is used to observe the disintegration of a single liquid rivulet with constant liquid mass flow rate at the edge of a thin plate at different air flow velocities. A two side view enables calculating droplet characteristics with high accuracy. The results show the asymptotic behavior of the ejected mean droplet diameters and the disintegration period. Furthermore, it gives a detailed insight into the droplet diameter distribution and the spreading of the droplets perpendicular to the air flow.
      Citation: Aerospace
      PubDate: 2021-03-26
      DOI: 10.3390/aerospace8040091
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 92: Shape Optimization of Labyrinth Seals to
           Improve Sealing Performance

    • Authors: Yizhen Zhao, Chunhua Wang
      First page: 92
      Abstract: To reduce gas leakage, shape optimization of a straight labyrinth seal was carried out. The six design parameters included seal clearance, fin width, fin height, fin pitch, fin backward, and forward expansion angle. The CFD (Computational Fluid Dynamics) model was solved to generate the training and testing samples for the surrogate model, which was established by the least square support vector machine. A kind of chaotic optimization algorithm was used to determine the optimal design parameters of the labyrinth seal. As seal clearance, fin width, fin height, fin pitch, fin backward and forward expansion angles are 0.2 mm, 0.1 mm, 7 mm, 9 mm, 0°, and 15°, the discharge coefficient can reach its minimum value in the design space. The chaotic optimization algorithm coupled with least square support vector machine is a promising scheme for labyrinth seal optimization.
      Citation: Aerospace
      PubDate: 2021-04-01
      DOI: 10.3390/aerospace8040092
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 93: Velocity Obstacle Based Conflict Avoidance in
           Urban Environment with Variable Speed Limit

    • Authors: Marta Ribeiro, Joost Ellerbroek, Jacco Hoekstra
      First page: 93
      Abstract: Current investigations into urban aerial mobility, as well as the continuing growth of global air transportation, have renewed interest in conflict detection and resolution (CD&R) methods. The use of drones for applications such as package delivery, would result in traffic densities that are orders of magnitude higher than those currently observed in manned aviation. Such densities do not only make automated conflict detection and resolution a necessity, but will also force a re-evaluation of aspects such as coordination vs. priority, or state vs. intent. This paper looks into enabling a safe introduction of drones into urban airspace by setting travelling rules in the operating airspace which benefit tactical conflict resolution. First, conflicts resulting from changes of direction are added to conflict resolution with intent trajectory propagation. Second, the likelihood of aircraft with opposing headings meeting in conflict is reduced by separating traffic into different layers per heading–altitude rules. Guidelines are set in place to make sure aircraft respect the heading ranges allowed at every crossed layer. Finally, we use a reinforcement learning agent to implement variable speed limits towards creating a more homogeneous traffic situation between cruising and climbing/descending aircraft. The effects of all of these variables were tested through fast-time simulations on an open source airspace simulation platform. Results showed that we were able to improve the operational safety of several scenarios.
      Citation: Aerospace
      PubDate: 2021-04-01
      DOI: 10.3390/aerospace8040093
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 94: An Assembly Method for the Multistage Rotor
           of An Aero-Engine Based on the Dual Objective Synchronous Optimization for
           the Coaxality and Unbalance

    • Authors: Yue Chen, Jiwen Cui, Xun Sun
      First page: 94
      Abstract: The assembly quality of an aero-engine directly determines its stability in high-speed operation. The coaxiality and unbalance out of tolerance caused by improper assembly may give rise to complicated vibration faults. To meet the requirements of the dual objective and reduce the test cost, it is necessary to predict the optimal assembly angles of the rotors at each stage during pre-assembly. In this study, we proposed an assembly optimization method for a multistage rotor of an aero-engine. Firstly, we developed a coordinate transmission model to calculate the coordinates of any point in the rotors at each stage during the assembly processes of a multistage rotor. Moreover, we proposed two different pieces of assembly optimization data for the coaxiality and unbalance, and established a dual objective evaluation function of that. Furthermore, we used the genetic algorithm to solve the optimal assembly angles of the rotors at each stage. Finally, the Monte Carlo simulation technique was used to investigate the effects of the geometric measured errors of each rotor on the proposed genetic algorithm. The simulation results show that the process of the dual objective optimization had good convergence, and the obtained optimal assembly angles of each rotor were not affected by the geometric measured errors. In addition, the dual objective optimization can ensure that both the coaxiality and unbalance can approach their respective optimal values to the most extent, and the experimental results also verified this conclusion. Therefore, the assembly optimization method proposed in this study can be used to guide the assembly processes of the multistage rotor of an aero-engine to achieve synchronous optimization for the coaxality and unbalance.
      Citation: Aerospace
      PubDate: 2021-04-01
      DOI: 10.3390/aerospace8040094
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 95: On-Orbit Pulse Phase Estimation Based on
           CE-Adam Algorithm

    • Authors: Yusong Wang, Yidi Wang, Wei Zheng
      First page: 95
      Abstract: Pulse phase is the basic measurements of X-ray pulsar-based navigation, and thus how to estimate a pulse phase for an orbiting spacecraft is important. The current methods for on-orbit pulse phase estimation could provide an accurate estimation performance enhancing with the photon amount, but its central processing unit (CPU) time cost also increases sharply with the increase of photon amount. In this paper, an on-orbit pulse phase estimation method based on the cross-entropy adaptive moment estimation (CE-Adam) algorithm is proposed to reduce the CPU time cost while retaining decent estimation accuracy. This method combines the CE and Adam algorithms, and is able to obtain a global optimum with low CPU time cost. The performance of the proposed algorithm is verified by simulation data and real data from the Neutron Star Internal Composition Detector (NICER). The results show that the proposed algorithm could greatly reduce the CPU time cost, which is about 1.5% of the CE algorithm, and retain similar estimation accuracy of pulse phase with CE algorithm.
      Citation: Aerospace
      PubDate: 2021-04-01
      DOI: 10.3390/aerospace8040095
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 96: An Experimental Investigation of the
           Convective Heat Transfer on a Small Helicopter Rotor with Anti-Icing and
           De-Icing Test Setups

    • Authors: Abdallah Samad, Eric Villeneuve, Caroline Blackburn, François Morency, Christophe Volat
      First page: 96
      Abstract: Successful icing/de-icing simulations for rotorcraft require a good prediction of the convective heat transfer on the blade’s surface. Rotorcraft icing is an unwanted phenomenon that is known to cause flight cancelations, loss of rotor performance and severe vibrations that may have disastrous and deadly consequences. Following a series of experiments carried out at the Anti-icing Materials International Laboratory (AMIL), this paper provides heat transfer measurements on heated rotor blades, under both the anti-icing and de-icing modes in terms of the Nusselt Number (Nu). The objective is to develop correlations for the Nu in the presence of (1) an ice layer on the blades (NuIce) and (2) liquid water content (LWC) in the freestream with no ice (NuWet). For the sake of comparison, the NuWet and the NuIce are compared to heat transfer values in dry runs (NuDry). Measurements are reported on the nose of the blade-leading edge, for three rotor speeds (Ω) = 500, 900 and 1000 RPM; a pitch angle (θ) = 6°; and three different radial positions (r/R), r/R = 0.6, 0.75 and 0.95. The de-icing tests are performed twice, once for a glaze ice accretion and another time for rime ice. Results indicate that the NuDry and the NuWet directly increased with V∝, r/R or Ω, mainly due to an increase in the Reynolds number (Re). Measurements indicate that the NuWet to NuDry ratio was always larger than 1 as a direct result of the water spray addition. NuIce behavior was different and was largely affected by the ice thickness (tice) on the blade. However, the ice acted as insulation on the blade surface and the NuIce to NuDry ratio was always less than 1, thus minimizing the effect of convection. Four correlations are then proposed for the NuDry, the NuWet and the NuIce, with an average error between 3.61% and 12.41%. The NuDry correlation satisfies what is expected from heat transfer near the leading edge of an airfoil, where the NuDry correlates well with Re0.52.
      Citation: Aerospace
      PubDate: 2021-04-01
      DOI: 10.3390/aerospace8040096
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 97: Coupled Fluid–Solid Numerical Simulation
           for Flow Field Characteristics and Supporting Performance of Flexible
           Support Cylindrical Gas Film Seal

    • Authors: Junfeng Sun, Meihong Liu, Zhen Xu, Taohong Liao, Xiangping Hu, Yuxian Li, Juan Wang
      First page: 97
      Abstract: A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.
      Citation: Aerospace
      PubDate: 2021-04-02
      DOI: 10.3390/aerospace8040097
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 98: Design and Development of an Experimental
           Setup of Electrically Powered Spinning Rotor Blades in Icing Wind Tunnel
           and Preliminary Testing with Surface Coatings as Hybrid Protection
           Solution

    • Authors: Eric Villeneuve, Caroline Blackburn, Christophe Volat
      First page: 98
      Abstract: In order to study ice protection systems for rotating blades, a new experimental setup has been developed at the Anti-Icing Materials International Laboratory (AMIL). This system consists of two small-scale rotating blades in a refrigerated icing wind tunnel where atmospheric icing can be simulated. Power is brought to the blades through a slip ring, through which the signals of the different sensors that are installed on the blades also pass. As demonstrated by the literature review, this new setup will address the need of small-scale wind tunnel testing on electrically powered rotating blades. To test the newly designed apparatus, preliminary experimentation is done on a hybrid ice protection system. Electrothermal protection is combined with different surface coatings to measure the impact of those coatings on the power consumption of the system. In anti-icing mode, the coatings tested did not reduce the power consumption on the system required to prevent ice from accumulating on the leading edge. The coatings however, due to their hydrophobic/superhydrophobic nature, reduced the power required to prevent runback ice accumulation when the leading edge was protected. One of the coatings did not allow any runback accumulation, limiting the power to protect the whole blades to the power required to protect solely the leading edge, resulting in a potential 40% power reduction for the power consumption of the system. In de-icing mode, the results with all the substrates tested showed similar power to achieve ice shedding from the blade. Since the coatings tested have a low icephobicity, it would be interesting to perform additional testing with icephobic coatings. Also, a small unheated zone at the root of the blade prevented complete ice shedding from the blade. A small part of the ice layer was left on the blade after testing, meaning that a cohesive break had to occur within the ice layer, and therefore impacting the results. Improvements to the setup will be done to remedy the situation. Those preliminary testing performed with the newly developed test setup have demonstrated the potential of this new device which will now allow, among other things, to measure heat transfer, force magnitudes, ice nucleation, and thermal equilibrium during ice accretion, with different innovative thermal protection systems (conductive coating, carbon nanotubes, impulse, etc.) as well as mechanical systems. The next step, following the improvements, is to measure forced convection on a thermal ice protection system with and without precipitation and to test mechanical ice protection systems.
      Citation: Aerospace
      PubDate: 2021-04-02
      DOI: 10.3390/aerospace8040098
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 99: Online Identification-Verification-Prediction
           Method for Parallel System Control of UAVs

    • Authors: Yixin Huang, Xiaojia Xiang, Han Zhou, Dengqing Tang, Yihao Sun
      First page: 99
      Abstract: In order to solve the problem of how to efficiently control a large-scale swarm Unmanned Aerial Vehicle (UAV) system, which performs complex tasks with limited manpower in a non-ideal environment, this paper proposes a parallel UAV swarm control method. The key technology of parallel control is to establish a one-to-one artificial UAV system corresponding to the aerial swarm UAV on the ground. This paper focuses on the computational experiments algorithm for artificial UAV system establishment, including data processing, model identification, model verification and state prediction. Furthermore, this paper performs a comprehensive flight mission with four common modes (climbing, level flighting, turning and descending) for verification. The results of the identification experiment present a good consistency between the outputs of the refined dynamics model and the real flight data. The prediction experiment results show that the prediction method in this paper can basically guarantee that the prediction states error is kept within 10% about 16 s.
      Citation: Aerospace
      PubDate: 2021-04-02
      DOI: 10.3390/aerospace8040099
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 100: Aeroelastic Stability Analysis of Electric
           Aircraft Wings with Distributed Electric Propulsors

    • Authors: Mohammadreza Amoozgar, Michael I. Friswell, Seyed Ahmad Fazelzadeh, Hamed Haddad Khodaparast, Abbas Mazidi, Jonathan E. Cooper
      First page: 100
      Abstract: In this paper, the effect of distributed electric propulsion on the aeroelastic stability of an electric aircraft wing was investigated. All the electric propulsors, which are of different properties, are attached to the wing of the aircraft in different positions. The wing structural dynamics was modelled by using geometrically exact beam equations, while the aerodynamic loads were simulated by using an unsteady aerodynamic theory. The electric propulsors were modelled by using a concentrated mass attached to the wing, and the motor’s thrust and angular momentum were taken into account. The thrust of each propulsor was modelled as a follower force acting exactly at the centre of gravity of the propulsor. The nonlinear aeroelastic governing equations were discretised using a time–space scheme, and the obtained results were verified against available results and very good agreement was observed. Two case studies were considered throughout the paper, resembling two flight conditions of the electric aircraft. The numerical results show that the tip propulsor thrust, mass, and angular momentum had the most impact on the aeroelastic stability of the wing. In addition, it was observed that the high-lift motors had a minimal effect on the aeroelastic stability of the wing.
      Citation: Aerospace
      PubDate: 2021-04-02
      DOI: 10.3390/aerospace8040100
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 101: Aerospace Best Paper Awards 2019

    • Authors: Aerospace Editorial Office Aerospace Editorial Office
      First page: 101
      Abstract: Aerospace has launched annual awards to recognize outstanding papers published in the journal [...]
      Citation: Aerospace
      PubDate: 2021-04-02
      DOI: 10.3390/aerospace8040101
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 102: Wing Structure of the Next-Generation Civil
           Tiltrotor: From Concept to Preliminary Design

    • Authors: Marika Belardo, Aniello Daniele Marano, Jacopo Beretta, Gianluca Diodati, Mario Graziano, Mariacarmela Capasso, Pierpaolo Ariola, Salvatore Orlando, Francesco Di Caprio, Nicola Paletta, Luigi Di Palma
      First page: 102
      Abstract: The main objective of this paper is to describe a methodology to be applied in the preliminary design of a tiltrotor wing based on previously developed conceptual design methods. The reference vehicle is the Next-Generation Civil Tiltrotor Technology Demonstrator (NGCTR-TD) developed by Leonardo Helicopters within the Clean Sky research program framework. In a previous work by the authors, based on the specific requirements (i.e., dynamics, strength, buckling, functional), the first iteration of design was aimed at finding a wing structure with a minimized structural weight but at the same time strong and stiff enough to comply with sizing loads and aeroelastic stability in the flight envelope. Now, the outcome from the first design loop is used to build a global Finite Element Model (FEM), to be used for a multi-objective optimization performed by using a commercial software environment. In other words, the design strategy, aimed at finding a first optimal solution in terms of the thickness of composite components, is based on a two-level optimization. The first-level optimization is performed with engineering models (non-FEA-based), and the second-level optimization, discussed in this paper, within an FEA environment. The latter is shown to provide satisfactory results in terms of overall wing weight, and a zonal optimization of the composite parts, which is the starting point of an engineered model and a detailed FEM (beyond the scope of the present work), which will also take into account manufacturing, assembly, installation, accessibility and maintenance constraints.
      Citation: Aerospace
      PubDate: 2021-04-02
      DOI: 10.3390/aerospace8040102
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 103: Aircraft Fleet Health Monitoring with
           Anomaly Detection Techniques

    • Authors: Luis Basora, Paloma Bry, Xavier Olive, Floris Freeman
      First page: 103
      Abstract: Predictive maintenance has received considerable attention in the aviation industry where costs, system availability and reliability are major concerns. In spite of recent advances, effective health monitoring and prognostics for the scheduling of condition-based maintenance operations is still very challenging. The increasing availability of maintenance and operational data along with recent progress made in machine learning has boosted the development of data-driven prognostics and health management (PHM) models. In this paper, we describe the data workflow in place at an airline for the maintenance of an aircraft system and highlight the difficulties related to a proper labelling of the health status of such systems, resulting in a poor suitability of supervised learning techniques. We focus on investigating the feasibility and the potential of semi-supervised anomaly detection methods for the health monitoring of a real aircraft system. Proposed methods are evaluated on large volumes of real sensor data from a cooling unit system on a modern wide body aircraft from a major European airline. For the sake of confidentiality, data has been anonymized and only few technical and operational details about the system had been made available. We trained several deep neural network autoencoder architectures on nominal data and used the anomaly scores to calculate a health indicator. Results suggest that high anomaly scores are correlated with identified failures in the maintenance logs. Also, some situations see an increase in the anomaly score for several flights prior to the system’s failure, which paves a natural way for early fault identification.
      Citation: Aerospace
      PubDate: 2021-04-07
      DOI: 10.3390/aerospace8040103
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 104: Numerical Evaluation of Structural Safety of
           Linear Actuator for Flap Control of Aircraft Based on Airworthiness
           Standard

    • Authors: Dong-Hyeop Kim, Young-Cheol Kim, Sang-Woo Kim
      First page: 104
      Abstract: Airworthiness standards of Korea recommend verifying structural safety by experimental tests and analytical methods, owing to the development of analysis technology. In this study, we propose a methodology to verify the structural safety of aircraft components based on airworthiness requirements using an analytical method. The structural safety and fatigue integrity of a linear actuator for flap control of aircraft was evaluated through numerical analysis. The static and fatigue analyses for the given loads obtained from the multibody dynamics analysis were performed using the finite element method. Subsequently, the margin of safety and vulnerable area were acquired and the feasibility of the structural safety evaluation using the analytical method was confirmed. The proposed numerical analysis method in this study can be adopted as an analytical verification methodology for the airworthiness standards of civilian aircraft in Korea.
      Citation: Aerospace
      PubDate: 2021-04-07
      DOI: 10.3390/aerospace8040104
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 105: Bearing Strength and Failure Mechanisms of
           Riveted Woven Carbon Composite Joints

    • Authors: Mauricio Torres-Arellano, Manuel de Jesus Bolom-Martínez, Edgar Adrian Franco-Urquiza, Ruben Pérez-Mora, Omar A. Jiménez-Arévalo, Philippe Olivier
      First page: 105
      Abstract: This research aimed to determine riveted carbon/epoxy composites’ mechanical performance when fabricated by resin transfer molding (RTM). As this manufacturing process is gaining importance in the aeronautics and automotive industries, assembly methods and their reliability must be studied in terms of their airworthiness and transportation implementation. The study case resumes the determination of the bearing strength of RTM-woven carbon composites for different rivet joint diameters (1/8, 5/32 and 3/16 in). The joint shear strength was obtained following the ASTM D5961 instructions, and post-failure analysis was carried out by a computerized tomography scan. A residual strength curve is provided with the results to infer the bearing strength for the riveted composites as a function of the rivet width-to-diameter ratio. A discussion of the fracture mechanism and tensile strength is carried out to assess the understanding of the riveted woven composites.
      Citation: Aerospace
      PubDate: 2021-04-09
      DOI: 10.3390/aerospace8040105
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 106: Global Visualization of Compressible Swept
           Convex-Corner Flow Using Pressure-Sensitive Paint

    • Authors: Kung-Ming Chung, Yi-Xuan Huang
      First page: 106
      Abstract: This study used pressure-sensitive paint (PSP) and determined the surface pressure distributions for a compressible swept convex-corner flow. The freestream Mach numbers were 0.64 and 0.83. The convex-corner angle and swept angle were, respectively, 10–17° and 5–15°. Expansion and compression near the corner apex were clearly visualized. For the test case of shock-induced boundary layer separation, there were greater spanwise pressure gradient and curved shocks. The acquired PSP data agree with the experimental data measured using the Kulite pressure transducers for a subsonic expansion flow. For a transonic expansion flow, the discrepancy was significant. The assumption of a constant recovery factor is not valid in the separation region, and temperature correction for PSP measurements is required.
      Citation: Aerospace
      PubDate: 2021-04-11
      DOI: 10.3390/aerospace8040106
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 107: Radiation Risks in Cis-Lunar Space for a
           Solar Particle Event Similar to the February 1956 Event

    • Authors: Fahad A. Zaman, Lawrence W. Townsend
      First page: 107
      Abstract: Solar particle events (SPEs) can pose serious threats for future crewed missions to the Moon. Historically, there have been several extreme SPEs that could have been dangerous for astronauts, and thus analyzing their potential risk on humans is an important step towards space exploration. In this work, we study the effects of a well-known SPE that occurred on 23 February 1956 on a mission in cis-Lunar space. Estimates of the proton fluence spectra of the February 1956 event were obtained from three different parameterized models published within the past 12 years. The studied geometry consists of a female phantom in the center of spherical spacecraft shielded by aluminum area densities ranging from 0.4 to 40 g cm−2. The effective dose, along with lens, skin, blood forming organs, heart, and central nervous system doses, were tallied using the On Line Tool for the Assessment of Radiation In Space (OLTARIS), which utilizes the High Z and Energy TRansport code (HZETRN), a deterministic radiation transport code. Based on the parameterized models, the results herein show that thicknesses comparable to a spacesuit might not protect against severe health consequences from a February 1956 category event. They also show that a minimum aluminum shielding of around 20 g cm−2 is sufficient to keep the effective dose and critical organ doses below NASA’s permissible limits for such event. In addition, except for very thin shielding, the input models produced results that were within good agreement, where the doses obtained from the three proton fluence spectra tended to converge with slight differences as the shielding thickness increases.
      Citation: Aerospace
      PubDate: 2021-04-14
      DOI: 10.3390/aerospace8040107
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 108: Fault Diagnosis and Reconfigurable Control
           for Commercial Aircraft with Multiple Faults and Actuator Saturation

    • Authors: Yishi Liu, Sheng Hong, Enrico Zio, Jianwei Liu
      First page: 108
      Abstract: Active fault-tolerant control systems perform fault diagnosis and reconfigurable control. There is a bidirectional uncertainty between them, and an integrated scheme is proposed here to account for that. The system considers both actuator and sensor faults, as well as the external disturbance. The diagnostic module is designed using an unknown input observer, and the controller is constructed on the basis of an adaptive method. The integrated strategy is presented, and the stability of the overall system is analyzed. Moreover, different kinds of anti-windup techniques are utilized to modify the original controllers, because of the different controller structures. A simulation of the integrated anti-windup fault-tolerant control method is demonstrated using a numerical model of Boeing 747. The results show that it can guarantee the stability of the post-fault aircraft and increase the control performance for the overall faulty system.
      Citation: Aerospace
      PubDate: 2021-04-14
      DOI: 10.3390/aerospace8040108
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 109: Sol–Gel Waveguide-Based Sensor for
           Structural Health Monitoring on Large Surfaces in Aerospace Domain

    • Authors: Maxime Royon, Damien Jamon, Thomas Blanchet, François Royer, Francis Vocanson, Emmanuel Marin, Adriana Morana, Aziz Boukenter, Youcef Ouerdane, Yves Jourlin, Rolf Evenblij, Thijs Van Leest, Marie-Anne de Smet, Sylvain Girard
      First page: 109
      Abstract: The potential of sol–gel-based optical sensors is investigated for applications in the aerospace domain. To this aim, a low-cost and non-intrusive sol–gel sensor based on waveguides, arranged as a 2D matrix structure, is fabricated by UV photolithography for delamination and damage detection. Two different organic–inorganic sol–gels were selected to fabricate the photonic device: TiO2–SiO2 and ZrO2–SiO2, acting as the waveguide core and the cladding, respectively. A systematic study was performed to determine the manufacturing parameters controlling their properties. The results show that large surfaces can be functionalized via sol–gel methods using the direct laser-writing approach. The structures are characterized in terms of refractive index, and the guiding properties were investigated through simulations and experiments, indicating an excellent behavior regarding the light guidance in a straight waveguide or in the 2D matrix structure grid. Additionally, preliminary tests show that the presence of impact can be easily detected after damage through the induced optical losses on large surfaces. This proof of concept sensor is a promising tool for structural health monitoring. To achieve the ultimate goal, the integration of this photonic sensor will be later performed on aircraft wings.
      Citation: Aerospace
      PubDate: 2021-04-14
      DOI: 10.3390/aerospace8040109
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 110: Special Issue “9th EASN International
           Conference on Innovation in Aviation & Space”

    • Authors: Spiros Pantelakis, Andreas Strohmayer
      First page: 110
      Abstract: This Special Issue contains selected papers from works presented at the 9th EASN International Conference on Innovation in Aviation & Space, which was successfully held in Athens, Greece, between the 3rd and 6th of September 2019 [...]
      Citation: Aerospace
      PubDate: 2021-04-14
      DOI: 10.3390/aerospace8040110
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 111: Special Issue “10th EASN International
           Conference on Innovation in Aviation & Space to the Satisfaction of
           the European Citizens”

    • Authors: Liberata Guadagno, Spiros Pantelakis, Andreas Strohmayer
      First page: 111
      Abstract: This Special Issue contains selected papers from works presented at the 10th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens, which was held successfully from the 2nd until the 4th of September, 2020 [...]
      Citation: Aerospace
      PubDate: 2021-04-14
      DOI: 10.3390/aerospace8040111
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 112: A Text-Driven Aircraft Fault Diagnosis Model
           Based on a Word2vec and Priori-Knowledge Convolutional Neural Network

    • Authors: Zhenzhong Xu, Bang Chen, Shenghan Zhou, Wenbing Chang, Xinpeng Ji, Chaofan Wei, Wenkui Hou
      First page: 112
      Abstract: In the process of aircraft maintenance and support, a large amount of fault description text data is recorded. However, most of the existing fault diagnosis models are based on structured data, which means they are not suitable for unstructured data such as text. Therefore, a text-driven aircraft fault diagnosis model is proposed in this paper based on Word to Vector (Word2vec) and prior-knowledge Convolutional Neural Network (CNN). The fault text first enters Word2vec to perform text feature extraction, and the extracted text feature vectors are then input into the proposed prior-knowledge CNN to train the fault classifier. The prior-knowledge CNN introduces expert fault knowledge through Cloud Similarity Measurement (CSM) to improve the performance of the fault classifier. Validation experiments on five-year maintenance log data of a civil aircraft were carried out to successfully verify the effectiveness of the proposed model.
      Citation: Aerospace
      PubDate: 2021-04-14
      DOI: 10.3390/aerospace8040112
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 113: Aircraft Maintenance Check Scheduling Using
           Reinforcement Learning

    • Authors: Pedro Andrade, Catarina Silva, Bernardete Ribeiro, Bruno F. Santos
      First page: 113
      Abstract: This paper presents a Reinforcement Learning (RL) approach to optimize the long-term scheduling of maintenance for an aircraft fleet. The problem considers fleet status, maintenance capacity, and other maintenance constraints to schedule hangar checks for a specified time horizon. The checks are scheduled within an interval, and the goal is to, schedule them as close as possible to their due date. In doing so, the number of checks is reduced, and the fleet availability increases. A Deep Q-learning algorithm is used to optimize the scheduling policy. The model is validated in a real scenario using maintenance data from 45 aircraft. The maintenance plan that is generated with our approach is compared with a previous study, which presented a Dynamic Programming (DP) based approach and airline estimations for the same period. The results show a reduction in the number of checks scheduled, which indicates the potential of RL in solving this problem. The adaptability of RL is also tested by introducing small disturbances in the initial conditions. After training the model with these simulated scenarios, the results show the robustness of the RL approach and its ability to generate efficient maintenance plans in only a few seconds.
      Citation: Aerospace
      PubDate: 2021-04-17
      DOI: 10.3390/aerospace8040113
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 114: Self-Oscillations of The Free Turbine Speed
           in Testing Turboshaft Engine with Hydraulic Dynamometer

    • Authors: Oleksandr Lytviak, Vasyl Loginov, Sergii Komar, Yevhen Martseniuk
      First page: 114
      Abstract: Self-oscillations are one of the common problems in the complex automatic system, that can occur due to the features of the workflow and the design of the governor. The development of digital control systems has made it possible to damp self-oscillations by applying complex control laws. However, for hydromechanical systems, such way is unacceptable due to the design complexity and the governor cost. The objective of this work is to determine the parameters of the hydromechanical free turbine speed controller, ensuring the absence of self-oscillations during ground tests of the turboshaft engine with a hydraulic dynamometer. The TV3-117VM engine (Ukraine) with the NR-3VM regulator pump (Ukraine) was selected as the object of the study. However, self-oscillations can also occur in any modifications of the TV3-117 engine with any NR-3 regulator pump. The results of the research may be of interest to engineers and scientists who investigate the dynamics of automatic control systems for similar engines. The paper analyses the nonlinear features of the empirical characteristics of the FTSC leading to self-oscillations of the engine speed. The authors propose the mathematical model of the automatic control system dynamics, which takes into account all the features of the engine and regulator pump. It is shown that the load characteristics of the water brake and the helicopter main rotor can differ significantly. Research of the dynamic characteristics of the TV3-117VM engine was carried out. The analysis showed a good agreement between the calculation results and the field test results, and made it possible to determine the parameters of the controller, which lead to self-oscillations during test. Two cases are considered. The first case includes ground tests of the engine with a water brake; the second case—flight tests of the engine as part of the helicopter’s power plant. The data obtained make it possible to develop recommendations for adjusting the hydromechanical governor without testing it on the engine.
      Citation: Aerospace
      PubDate: 2021-04-17
      DOI: 10.3390/aerospace8040114
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 115: Multi-Aircraft Trajectory Collaborative
           Prediction Based on Social Long Short-Term Memory Network

    • Authors: Zhengfeng Xu, Weili Zeng, Xiao Chu, Puwen Cao
      First page: 115
      Abstract: Aircraft trajectory prediction is the basis of approach and departure sequencing, conflict detection and resolution and other air traffic management technologies. Accurate trajectory prediction can help increase the airspace capacity and ensure the safe and orderly operation of aircraft. Current research focuses on single aircraft trajectory prediction without considering the interaction between aircraft. Therefore, this paper proposes a model based on the Social Long Short-Term Memory (S-LSTM) network to realize the multi-aircraft trajectory collaborative prediction. This model establishes an LSTM network for each aircraft and a pooling layer to integrate the hidden states of the associated aircraft, which can effectively capture the interaction between them. This paper takes the aircraft trajectories in the Northern California terminal area as the experimental data. The results show that, compared with the mainstream trajectory prediction models, the S-LSTM model in this paper has smaller prediction errors, which proves the superiority of the model’s performance. Additionally, another comparative experiment is conducted on airspace scenes with aircraft interactions, and it is found that S-LSTM has a better prediction effect than LSTM, which proves the effectiveness of the former considering aircraft interaction.
      Citation: Aerospace
      PubDate: 2021-04-19
      DOI: 10.3390/aerospace8040115
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 116: Investigation of the Film-Cooling
           Performance of 2.5D Braided Ceramic Matrix Composite Plates with Preformed
           Hole

    • Authors: Chenwei Zhao, Zecan Tu, Junkui Mao
      First page: 116
      Abstract: The film-cooling performance of a 2.5D braided ceramic matrix composite (CMC) plate with preformed holes was numerically studied. Four numerical models containing braided structures were established: one model with film-cooling holes preformed through fiber extrusion deformation (EP-Hole), one model with film-cooling holes directly woven through fibers (WP-Hole), and two models with directly drilled holes (DP-Hole1,2). Besides, the influence of the ratio between the equivalent thermal conductivities on the axial and radial directions of fiber Kr was investigated. The results show that the preformed holes have better performance in controlling the thermal gradient with the increase of Kr. The maximum thermal gradient around the DP-Hole is significantly higher than that of the WP-Hole and EP-Hole, and the maximum relative variation reaches 123.3%. With Kr increasing from 3.32 to 13.05, the overall cooling effectiveness on the hot-side wall decreases for all models, by about 10%. Compared with the traditional drill method, the new preformed film-cooling hole studied in this paper can reduce the temperature and the thermal gradient in the region around the holes.
      Citation: Aerospace
      PubDate: 2021-04-19
      DOI: 10.3390/aerospace8040116
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 117: Methodology for Evaluating Risk of Visual
           Inspection Tasks of Aircraft Engine Blades

    • Authors: Jonas Aust, Dirk Pons
      First page: 117
      Abstract: Risk assessment methods are widely used in aviation, but have not been demonstrated for visual inspection of aircraft engine components. The complexity in this field arises from the variety of defect types and the different manifestation thereof with each level of disassembly. A new risk framework was designed to include contextual factors. Those factors were identified using Bowtie analysis to be criticality, severity, and detectability. This framework yields a risk metric that describes the extent to which a defect might stay undetected during the inspection task, and result in adverse safety outcomes. A simplification of the framework provides a method for go/no-go decision-making. The results of the study reveal that the defect detectability is highly dependent on specific views of the blade, and the risk can be quantified. Defects that involve material separation or removal such as scratches, tip rub, nicks, tears, cracks, and breaking, are best shown in airfoil views. Defects that involve material deformation and change of shape, such as tip curl, dents on the leading edges, bents, and battered blades, have lower risk if edge views can be provided. This research proposes that many risk assessments may be reduced to three factors: consequence, likelihood, and a cofactor. The latter represents the industrial context, and can comprise multiple sub-factors that are application-specific. A method has been devised, including appropriate scales, for the inclusion of these into the risk assessment.
      Citation: Aerospace
      PubDate: 2021-04-19
      DOI: 10.3390/aerospace8040117
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 118: A Breakdown of System of Systems Needs Using
           Architecture Frameworks, Ontologies and Description Logic Reasoning

    • Authors: Ludvig Knöös Franzén, Ingo Staack, Petter Krus, Christopher Jouannet, Kristian Amadori
      First page: 118
      Abstract: Aerospace systems are connected with the operational environment and other systems in general. The focus in aerospace product development is consequently shifting from a singular system perspective to a System-of-Systems (SoS) perspective. This increasing complexity gives rise to new levels of uncertainty that must be understood and managed to produce aerospace solutions for an ever-changing future. This paper presents an approach to using architecture frameworks, and ontologies with description logic reasoning capabilities, to break down SoS needs into required capabilities and functions. The intention of this approach is to provide a consistent way of obtaining the functions to be realized in order to meet the overarching capabilities and needs of an SoS. The breakdown with an architecture framework results in an initial design space representation of functions to be performed. The captured knowledge is then represented in an ontology with description logic reasoning capabilities, which provides a more flexible way to expand and process the initial design space representation obtained from the architecture framework. The proposed approach is ultimately tested in a search and rescue case study, partly based on the operations of the Swedish Maritime Administration. The results show that it is possible to break down SoS needs in a consistent way and that ontology with description logic reasoning can be used to process the captured knowledge to both expand and reduce an available design space representation.
      Citation: Aerospace
      PubDate: 2021-04-20
      DOI: 10.3390/aerospace8040118
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 119: Exemplification of Detecting Gas Turbine
           Blade Structure Defects Using the X-ray Computed Tomography Method

    • Authors: Józef Błachnio, Marek Chalimoniuk, Artur Kułaszka, Henryk Borowczyk, Dariusz Zasada
      First page: 119
      Abstract: X-ray computed tomography is more often applied in non-destructive testing the quality of construction elements significantly crucial for reliability and safety of device elements, machines and complex industrial systems. This article describes the computed tomography (CT) system used to inspect the technical condition of turbine blades of the aircraft engine. The impact of the experimental conditions on the correctness of the obtained results was determined. The appropriate selection of parameters for the experiment was given, and the correct test results of gas turbine blades were presented. Failures, manufacturing defects, material deviations of nickel-cobalt alloyed blades were identified. The thickness of walls was measured in the selected cross-sections with the accuracy of 0.01 mm, and selected manufacturing defects of cooling passages were diagnosed. It was demonstrated that the application of the CT system allows for detailed non-destructive inspection of the technical condition of machine parts. The test results proved that the X-ray computed tomography could be applied in the production and repairs of machines.
      Citation: Aerospace
      PubDate: 2021-04-20
      DOI: 10.3390/aerospace8040119
      Issue No: Vol. 8, No. 4 (2021)
       
  • Aerospace, Vol. 8, Pages 58: Harmonic Forcing from Distortion in a
           Boundary Layer Ingesting Fan

    • Authors: Hans Mårtensson
      First page: 58
      Abstract: Integrating a fan with a boundary layer ingestion (BLI) configuration into an aircraft fuselage can improve propulsion efficiency by utilizing the lower momentum airflow in the boundary layer developed due to the surface drag of the fuselage. As a consequence, velocity and total pressure variations distort the flow field entering the fan in both the circumferential and radial directions. Such variations can negatively affect fan aerodynamics and give rise to vibration issues. A fan configuration to benefit from BLI needs to allow for distortion without large penalties. Full annulus unsteady computational fluid dynamics (CFD) with all blades and vanes is used to evaluate the effects on aerodynamic loading and forcing on a fan designed to be mounted on an adapted rear fuselage of a Fokker 100 aircraft, i.e., a tail cone thruster. The distortion pattern used as a boundary condition on the fan is taken from a CFD analysis of the whole aircraft with a simplified model of the installed fan. Detailed simulations of the fan are conducted to better understand the relation between ingested distortion and the harmonic forcing. The results suggest that the normalized harmonic forcing spectrum is primarily correlated to the circumferential variation of inlet total pressure. In this study, the evaluated harmonic forces correlate with the total pressure variation at the inlet for the first 12 engine orders, with some exceptions where the response is very low. At higher harmonics, the distortion content as well as the response become very low, with amplitudes in the order of magnitude lower than the principal disturbances. The change in harmonic forcing resulting from raising the working line, thus, increasing the incidence on the fan rotor, increases the forcing moderately. The distortion transfers through the fan resulting in a non-axisymmetric aerodynamic loading of the outlet guide vane (OGV) that has a clear effect on the aerodynamics. The time average aerodynamic load and also the harmonic forcing of the OGV vary strongly around the circumference. In particular, this is the case for some of the vanes at higher back pressure, most likely due to an interaction with separations starting to occur on vanes operating in unfavorable conditions.
      Citation: Aerospace
      PubDate: 2021-02-24
      DOI: 10.3390/aerospace8030058
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 59: Evaluation of the Climate Impact Reduction
           Potential of the Water-Enhanced Turbofan (WET) Concept

    • Authors: Regina Pouzolz, Oliver Schmitz, Hermann Klingels
      First page: 59
      Abstract: Aviation faces increasing pressure not only to reduce fuel burn, and; therefore, CO2 emissions, but also to provide technical solutions for an overall climate impact minimization. To combine both, a concept for the enhancement of an aircraft engine by steam injection with inflight water recovery is being developed. The so-called Water-Enhanced Turbofan (WET) concept promises a significant reduction of CO2 emissions, NOx emissions, and contrail formation. Representative missions for an A320-type aircraft using the proposed new engine were calculated. Applying a first-order one-dimensional climate assessment prospects the reduction of more than half of the Global Warming Potential over one hundred years, compared to an evolutionarily improved aero-engine. If CO2-neutrally produced sustainable aviation fuels are used, climate impact could be reduced by 93% compared to today’s aircraft. The evaluation is a first estimate of effects based on preliminary design studies and should provide a starting point for discussion in the scientific community, implying the need for research, especially on the formation mechanisms and radiation properties of potential contrails from the comparatively cold exhaust gases of the WET engine.
      Citation: Aerospace
      PubDate: 2021-02-25
      DOI: 10.3390/aerospace8030059
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 60: Generation and Mitigation Mechanism Studies
           of Nonlinear Thermoacoustic Instability in a Modelled Swirling Combustor
           with a Heat Exchanger

    • Authors: Yuze Sun, Dan Zhao, Xiaowei Zhu
      First page: 60
      Abstract: In the present work, 3D Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are performed to investigate the generation and mitigation mechanism of combustion-sustained thermoacoustic instabilities in a modelled swirl combustor. The effects of (1) swirling number SN, (2) inlet air flow rate Va and (3) inlet temperature Ti on the amplitudes and frequencies of swirling combustion-excited limit cycle oscillations are examined. It is found that the amplitude of acoustic fluctuations is increased with increasing SN and Va and decreased with the increase of Ti. The dominant frequency of oscillations is also found to increases with the increase of SN and Va. However, increasing Ti leads to the dominant frequency being decreased first and then increased. An alternative passive control method of installing an adjustable temperature heat exchanger on the combustion chamber wall is then proposed. Numerical results show that thermoacoustic oscillations could be excited and mitigated by setting the heat exchanger temperature to TH. Global and local Rayleigh indexes are applied to further reveal the excitation and attenuation effects on mechanisms. The present study is conducive to developing a simulation platform for thermoacoustic instabilities in swirling combustors. It also provides an alternative method to amplify or mitigate thermoacoustic oscillations.
      Citation: Aerospace
      PubDate: 2021-02-26
      DOI: 10.3390/aerospace8030060
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 61: Aircraft Requirements for Sustainable
           Regional Aviation

    • Authors: Dominik Eisenhut, Nicolas Moebs, Evert Windels, Dominique Bergmann, Ingmar Geiß, Ricardo Reis, Andreas Strohmayer
      First page: 61
      Abstract: Recently, the new Green Deal policy initiative was presented by the European Union. The EU aims to achieve a sustainable future and be the first climate-neutral continent by 2050. It targets all of the continent’s industries, meaning aviation must contribute to these changes as well. By employing a systems engineering approach, this high-level task can be split into different levels to get from the vision to the relevant system or product itself. Part of this iterative process involves the aircraft requirements, which make the goals more achievable on the system level and allow validation of whether the designed systems fulfill these requirements. Within this work, the top-level aircraft requirements (TLARs) for a hybrid-electric regional aircraft for up to 50 passengers are presented. Apart from performance requirements, other requirements, like environmental ones, are also included. To check whether these requirements are fulfilled, different reference missions were defined which challenge various extremes within the requirements. Furthermore, figures of merit are established, providing a way of validating and comparing different aircraft designs. The modular structure of these aircraft designs ensures the possibility of evaluating different architectures and adapting these figures if necessary. Moreover, different criteria can be accounted for, or their calculation methods or weighting can be changed.
      Citation: Aerospace
      PubDate: 2021-02-26
      DOI: 10.3390/aerospace8030061
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 62: Analysis of the Cosmic Ray Effects on
           Sentinel-1 SAR Satellite Data

    • Authors: Hakan Köksal, Nusret Demir, Ali Kilcik
      First page: 62
      Abstract: Ionizing radiation sources such as Solar Energetic Particles and Galactic Cosmic Radiation may cause unexpected errors in imaging and communication systems of satellites in the Space environment, as reported in the previous literature. In this study, the temporal variation of the speckle values on Sentinel 1 satellite images were compared with the cosmic ray intensity/count data, to analyze the effects which may occur in the electromagnetic wave signals or electronic system. Sentinel 1 Synthetic Aperture Radar (SAR) images nearby to the cosmic ray stations and acquired between January 2015 and December 2019 were processed. The median values of the differences between speckle filtered and original image were calculated on Google Earth Engine Platform per month. The monthly median “noise” values were compared with the cosmic ray intensity/count data acquired from the stations. Eight selected stations’ data show that there are significant correlations between cosmic ray intensities and the speckle amounts. The Pearson correlation values vary between 0.62 and 0.78 for the relevant stations.
      Citation: Aerospace
      PubDate: 2021-03-03
      DOI: 10.3390/aerospace8030062
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 63: A Numerical Investigation on Stress Modal
           Analysis of Composite Laminated Thin Plates

    • Authors: Yadong Zhou, Youchao Sun, Weili Zeng
      First page: 63
      Abstract: Because of the light weight and high strength, composite laminates have many advantages in aircraft structures; however, they are frequently subjected to severe dynamic loadings during flight. To understand the dynamic properties of composite laminated thin plates at the stress scale, this paper studies the stress modal analysis (SMA) of composite laminated thin plates by finite element method (FEM). Firstly, the basic theory on SMA of composite laminates was given from the classical displacement modal analysis. Secondly, a square laminated thin plate was numerically studied to obtain some distribution laws of the stress mode shapes (SMSs) from the layup and stress component perspectives. Then, based on the characteristics of SMSs in different plies, a modified layup configuration was conducted for possible lower magnitude and more uniform distributions of SMSs. Results indicate that ±45° layups can improve the performance of SMSs of the square plate, without excessively decreasing the modal frequencies. Such fact manifests that ±45° layups are critically vital for the dynamic stress reduction of the square composite laminated plates. Modal participation factor and strain energy were evaluated to assist the determination of critical modes. Lastly, the aspect ratio of the composite plate on layup design was considered. Numerical investigation in this study can serve as a preliminary step of SMSs perspective for the analysis and optimization of dynamic composite laminates.
      Citation: Aerospace
      PubDate: 2021-03-04
      DOI: 10.3390/aerospace8030063
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 64: Development of a Novel Deployable Solar Panel
           and Mechanism for 6U CubeSat of STEP Cube Lab-II

    • Authors: Shankar Bhattarai, Ji-Seong Go, Hongrae Kim, Hyun-Ung Oh
      First page: 64
      Abstract: The structural safety of solar cells mounted on deployable solar panels in the launch vibration environment is a significant aspect of a successful CubeSat mission. This paper presents a novel highly damped deployable solar panel module that is effective in ensuring structural protection of solar cells under the launch environment by rapidly suppressing the vibrations transmitting through the solar panel by constrained layer damping achieved using printed circuit board (PCB)-based multilayered thin stiffeners with double-sided viscoelastic tapes. A high-damping solar panel demonstration model with a three-pogo pin-based burn wire release mechanism was fabricated and tested for application in the 6U CubeSat “STEP Cube Lab-II” developed by Chosun University, South Korea. The reliable release function and radiation hardness assurance of the mechanism in an in-orbit environment were confirmed by performing solar panel deployment tests and radiation tests, respectively. The design effectiveness and structural safety of the proposed solar panel module were validated by launch vibration and in-orbit environment tests at the qualification level.
      Citation: Aerospace
      PubDate: 2021-03-05
      DOI: 10.3390/aerospace8030064
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 65: Spoken Instruction Understanding in Air
           Traffic Control: Challenge, Technique, and Application

    • Authors: Yi Lin
      First page: 65
      Abstract: In air traffic control (ATC), speech communication with radio transmission is the primary way to exchange information between the controller and aircrew. A wealth of contextual situational dynamics is embedded implicitly; thus, understanding the spoken instruction is particularly significant to the ATC research. In this paper, a comprehensive review related to spoken instruction understanding (SIU) in the ATC domain is provided from the perspective of the challenges, techniques, and applications. Firstly, a full pipeline is represented to achieve the SIU task, including automatic speech recognition, language understanding, and voiceprint recognition. A total of 10 technique challenges are analyzed based on the ATC task specificities. In succession, the common techniques for SIU tasks are categorized from common applications, and extensive works in the ATC domain are also reviewed. Finally, a series of future research topics are also prospected based on the corresponding challenges. The author sincerely hopes that this work is able to provide a clear technical roadmap for the SIU tasks in the ATC domain and further make contributions to the research community.
      Citation: Aerospace
      PubDate: 2021-03-05
      DOI: 10.3390/aerospace8030065
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 66: Numerical Investigation of an Optimized Rotor
           Head Fairing for the RACER Compound Helicopter in Cruise Flight

    • Authors: Patrick Pölzlbauer, Andreas Kümmel, Damien Desvigne, Christian Breitsamter
      First page: 66
      Abstract: The present work is part of the Clean Sky 2 project Full-Fairing Rotor Head Aerodynamic Design Optimization (FURADO), which deals with the aerodynamic design optimization of a full-fairing rotor head for the Rapid And Cost-Effective Rotorcraft (RACER) compound helicopter. The rotor head is a major drag source and previous investigations have revealed that the application of rotor head fairings can be an effective drag reduction measure. As part of the full-fairing concept, a new blade-sleeve fairing was aerodynamically optimized for cruise flight. Within this publication, the newly developed blade-sleeve fairing is put to test on an isolated, five-bladed rotor head and compared to an already existing reference blade-sleeve fairing, which was developed at Airbus Helicopters. Numerical flow simulations are performed with ANSYS Fluent 2019 R2 considering a rotating rotor head with cyclic pitch movement. The aerodynamic forces of the isolated rotor head are analyzed to determine the performance benefit of the newly developed blade-sleeve fairing. A drag reduction of 4.7% and a lift increase of 20% are obtained in comparison to the Airbus Helicopters reference configuration. Furthermore, selected surface and flow field quantities are presented to give an overview on the occurring flow phenomena.
      Citation: Aerospace
      PubDate: 2021-03-05
      DOI: 10.3390/aerospace8030066
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 67: Fuel Planning Strategies Considering
           Operational Uncertainties of Aerodynamic Formation Flight

    • Authors: Majed Swaid, Tobias Marks, Florian Linke, Volker Gollnick
      First page: 67
      Abstract: The operational concept of aerodynamic formation flight, also referred to as aircraft wake-surfing for efficiency (AWSE), has high potential in terms of fuel savings and climate impact mitigation. In order to implement this concept, many technological and operational challenges have to be coped with. As the fuel consumption during a mission strongly depends on a successful execution of AWSE, the existing uncertainties regarding flight planning increase. While a conservative fuel planning ensures a follower to complete the mission even in the case of a formation failure, it might result in high amounts of excess fuel and, therefore, additional fuel consumption. In this study, this issue is addressed by the adaptation of flight planning procedures to the requirements of AWSE focusing on fuel planning in particular, considered from the perspective of a designated follower aircraft of a two-aircraft formation. This trade-off is modeled as an n-action two-event decision-making problem. Each of the possible actions is represented by a combination of mission routing and a corresponding diversion airport, taking atmospheric effects (e.g., wind) into account in order to determine the resulting amount of trip fuel. The two events under consideration are a total formation failure in contrast to a complete success. Based on a scenario with a set of double origin destination pairs characterizing the formations and representative weather patterns for the North Atlantic region, each action is analyzed with regard to the expected fuel consumption and expense. Based on a set of assumed formation success probabilities, we find that the proposed method holds a savings potential to reduce the follower’s fuel consumption by 4.8% and its monetary expenses by 1.2% compared with a conventional flight planning. In order to gain a monetary profit margin applying this method, the required formation success probability is shown to vary between 92% and 96%, depending on the assumed fuel price.
      Citation: Aerospace
      PubDate: 2021-03-07
      DOI: 10.3390/aerospace8030067
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 68: Rendezvous in Cis-Lunar Space near
           Rectilinear Halo Orbit: Dynamics and Control Issues

    • Authors: Giordana Bucchioni, Mario Innocenti
      First page: 68
      Abstract: The paper presents the development of a fully-safe, automatic rendezvous strategy between a passive vehicle and an active one orbiting around the Earth–Moon L2 Lagrangian point. This is one of the critical phases of future missions to permanently return to the Moon, which are of interest to the majority of space organizations. The first step in the study is the derivation of a suitable full 6-DOF relative motion model in the Local Vertical Local Horizontal reference frame, most suitable for the design of the guidance. The main dynamic model is approximated using both the elliptic and circular three-body motion, due to the contribution of Earth and Moon gravity. A rather detailed set of sensors and actuator dynamics was also implemented in order to ensure the reliability of the guidance algorithms. The selection of guidance and control is presented, and evaluated using a sample scenario as described by ESA’s HERACLES program. The safety, in particular the passive safety, concept is introduced and different techniques to guarantee it are discussed that exploit the ideas of stable and unstable manifolds to intrinsically guarantee some properties at each hold-point, in which the rendezvous trajectory is divided. Finally, the rendezvous dynamics are validated using available Ephemeris models in order to verify the validity of the results and their limitations for future more detailed design.
      Citation: Aerospace
      PubDate: 2021-03-08
      DOI: 10.3390/aerospace8030068
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 69: Background Pressure Effects on the
           Performance of a 20 kW Magnetically Shielded Hall Thruster Operating in
           Various Configurations

    • Authors: Antonio Piragino, Farbod Faraji, Maryam Reza, Eugenio Ferrato, Annalisa Piraino, Tommaso Andreussi
      First page: 69
      Abstract: The paper reports the characterization results of a 20 kW-class magnetically shielded Hall thruster in three different configurations and operating with a centrally mounted cathode. The characterization was carried out at two different pumping speeds in SITAEL’s IV10 vacuum chamber, resulting in two different background pressure levels for each tested operating point. A linear behavior of discharge current and thrust values versus the anode mass flow rate was noticed for both pumping speeds levels and for all the three configurations. In addition, the thrust and discharge current values were always found to be lower at lower background pressure levels. From the performance levels, a preliminary estimate of the ingested mass flow rates was performed, and the values were then compared to a recently developed background flow model. The results suggested that, for this thruster and in the tested operating regimes, the change in performance due to background pressure could be ascribed not only to the ingestion of external mass flow coming from the chamber but also to other physical processes caused by the flux of residual background neutrals.
      Citation: Aerospace
      PubDate: 2021-03-09
      DOI: 10.3390/aerospace8030069
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 70: Phasing Maneuver Analysis from a Low Lunar
           Orbit to a Near Rectilinear Halo Orbit

    • Authors: Giordana Bucchioni, Mario Innocenti
      First page: 70
      Abstract: The paper describes the preliminary design of a phasing trajectory in a cislunar environment, where the third body perturbation is considered non-negligible. The working framework is the one proposed by the ESA’s Heracles mission in which a passive target station is in a Near Rectilinear Halo Orbit and an active vehicle must reach that orbit to start a rendezvous procedure. In this scenario the authors examine three different ways to design such phasing maneuver under the circular restricted three-body problem hypotheses: Lambert/differential correction, Hohmann/differential correction and optimization. The three approaches are compared in terms of ΔV consumption, accuracy and time of flight. The selected solution is also validated under the more accurate restricted elliptic three-body problem hypothesis.
      Citation: Aerospace
      PubDate: 2021-03-09
      DOI: 10.3390/aerospace8030070
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 71: Human Machine Interface Design for Monitoring
           Safety Risks Associated with Operating Small Unmanned Aircraft Systems in
           Urban Areas

    • Authors: Max Friedrich, Mark Vollrath
      First page: 71
      Abstract: The envisioned introduction of autonomous Small Unmanned Aircraft Systems (sUAS) into low-altitude urban airspace necessitates high levels of system safety. Despite increased system autonomy, humans will most likely remain an essential component in assuring safety. This paper derives, applies, and evaluates a display design concept that aims to support safety risk monitoring of multiple sUAS by a human operator. The concept comprises of five design principles. The core idea of the concept is to limit display complexity despite increasing the number of sUAS monitored by primarily visualizing highly abstracted information while hiding detailed information of lower abstraction, unless specifically requested by the human operator. States of highly abstracted functions are visualized by function-specific icons that change hue in accordance to specified system states. Simultaneously, the design concept aims to support the human operator in identifying off-nominal situations by implementing design properties that guide visual attention. The display was evaluated in a study with seven subject matter experts. Although preliminary, the results clearly favor the proposed display design concept. The advantages of the proposed design concept are demonstrated, and the next steps for further exploring the proposed display design concept are outlined.
      Citation: Aerospace
      PubDate: 2021-03-10
      DOI: 10.3390/aerospace8030071
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 72: Special Issue: Deicing and Anti-Icing of
           Aircrafts

    • Authors: Sakaue
      First page: 72
      Abstract: In-flight icing for aircrafts is a large concern for all those involved in aircraft operations. This Special Issue assembles a diverse selection of research papers on topics related to the deicing and anti-icing of aircrafts. These topics span experimental, numerical, and data science studies from droplet scale [1,2] to the system level [3–6], as summarized in Table 1. The editor is pleased to assemble 11 articles in this Special Issue. The readers will enjoy this variety of high-quality research on the deicing and anti-icing of aircrafts. [...]
      Citation: Aerospace
      PubDate: 2021-03-10
      DOI: 10.3390/aerospace8030072
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 73: Task Planning for Multiple-Satellite
           Space-Situational-Awareness Systems

    • Authors: Yutao Chen, Guoqing Tian, Junyou Guo, Jie Huang
      First page: 73
      Abstract: Space situational awareness (SSA) plays an important role in maintaining space advantages. Task planning is one of the key technologies in SSA to allocate multiple tasks to multiple satellites, so that a satellite may be allocated to supervise multiple space objects, and a space object may be supervised by multiple satellites. This paper proposes a hierarchical and distributed task-planning framework for SSA systems with focus on fast and effective task planning customized for SSA. In the framework, a global task-planner layer performs satellite and object clustering, so that satellites are clustered into multiple unique clusters on the basis of their positions, while objects are clustered into multiple possibly intersecting clusters, hence allowing for a single object to be supervised by multiple satellites. In each satellite cluster, a local task planner performs distributed task planning using the contract-net protocol (CNP) on the basis of the position and velocity of satellites and objects. In addition, a customized discrete particle swarm optimization (DPSO) algorithm was developed to search for the optimal task-planning result in the CNP. Simulation results showed that the proposed framework can effectively achieve task planning among multiple satellites and space objects. The efficiency and scalability of the proposed framework are demonstrated through static and dynamic orbital simulations.
      Citation: Aerospace
      PubDate: 2021-03-12
      DOI: 10.3390/aerospace8030073
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 74: A Review of Current Research in Subscale
           Flight Testing and Analysis of Its Main Practical Challenges

    • Authors: Alejandro Sobron, David Lundström, Petter Krus
      First page: 74
      Abstract: Testing of untethered subscale models, often referred to as subscale flight testing, has traditionally had a relatively minor, yet relevant use in aeronautical research and development. As recent advances in electronics, rapid prototyping and unmanned-vehicle technologies expand its capabilities and lower its cost, this experimental method is seeing growing interest across academia and the industry. However, subscale models cannot meet all similarity conditions required for simulating full-scale flight. This leads to a variety of approaches to scaling and to other alternative applications. Through a literature review and analysis of different scaling strategies, this study presents an overall picture of how subscale flight testing has been used in recent years and synthesises its main issues and practical limitations. Results show that, while the estimation of full-scale characteristics is still an interesting application within certain flight conditions, subscale models are progressively taking a broader role as low-cost technology-testing platforms with relaxed similarity constraints. Different approaches to tackle the identified practical challenges, implemented both by the authors and by other organisations, are discussed and evaluated through flight experiments.
      Citation: Aerospace
      PubDate: 2021-03-12
      DOI: 10.3390/aerospace8030074
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 75: Tribology in Space Robotic Actuators:
           Experimental Method for Evaluation and Analysis of Gearboxes

    • Authors: Erik Nyberg, Dídac Llopart i Cervelló, Ichiro Minami
      First page: 75
      Abstract: Liquid lubricants are critical to enable long-life operation of high-performance machinery, such as geared actuators employed in robotics. In space applications, actuator gearboxes must operate in low temperatures, where liquid lubricants face inherent problems related to low temperature rheology. Heaters are relied upon to provide acceptable gearbox temperatures. Unfortunately, heating is energy-intense and does not scale well with increasing mechanism mass and performance. Effective boundary lubrication (BL), on the other hand, can minimize problems of low temperature rheology. BL relies on tribofilm formation over conventional fluid film separation. Effective space grade boundary lubricants can potentially allow for drastically reduced amounts of oil and the accompanying rheological problems. In this work, we describe the design of a methodology to evaluate and analyze tribology of actuator gearboxes operated under cryogenic oil-starved conditions in N2 atmosphere. The devised methodology enables research pertinent to space actuator tribology by accelerated testing and advanced analysis, as demonstrated by a lubricant candidate case study. Complementary microscopy techniques are discussed, and a novel methodology devised for gear internal microstructure analysis by X-ray microtomography (XMT) is presented.
      Citation: Aerospace
      PubDate: 2021-03-13
      DOI: 10.3390/aerospace8030075
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 76: Remote Sensing Image Super-Resolution for the
           Visual System of a Flight Simulator: Dataset and Baseline

    • Authors: Wenyi Ge, Zhitao Wang, Guigui Wang, Shihan Tan, Jianwei Zhang
      First page: 76
      Abstract: High-resolution remote sensing images are the key data source for the visual system of a flight simulator for training a qualified pilot. However, due to hardware limitations, it is an expensive task to collect spectral and spatial images at very high resolutions. In this work, we try to tackle this issue with another perspective based on image super-resolution (SR) technology. First, we present a new ultra-high-resolution remote sensing image dataset named Airport80, which is captured from the airspace near various airports. Second, a deep learning baseline is proposed by applying the generative and adversarial mechanism, which is able to reconstruct a high-resolution image during a single image super-resolution. Experimental results for our benchmark demonstrate the effectiveness of the proposed network and show it has reached satisfactory performances.
      Citation: Aerospace
      PubDate: 2021-03-15
      DOI: 10.3390/aerospace8030076
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 77: On the Handling Qualities of Two Flying Wing
           Aircraft Configurations

    • Authors: Luís M. B. C. Campos, Joaquim M. G. Marques
      First page: 77
      Abstract: The coupling of the longitudinal and lateral stability modes of an aeroplane is considered in two cases: (i) weak coupling, when the changes in the frequency and damping of the phugoid, short period, dutch roll, and helical modes are small, i.e., the square of the deviation is negligible compared to the square of the uncoupled value; (ii) strong coupling, when the coupled values may differ significantly from the uncoupled values. This allows a comparison of three values for the frequency and damping of each mode: (i) exact, i.e., fully coupled; (ii) with the approximation of weak coupling; (iii) with the assumption of decoupling. The comparison of these three values allows an assessment of the importance of coupling effects. The method is applied to two flying wing designs, concerning all modes in a total of eighteen flight conditions. It turns out that lateral-longitudinal coupling is small in all cases, and thus classical handling qualities criteria can be applied. The handling qualities are considered for all modes, namely the phugoid, short period, dutch roll, spiral, and roll modes. Additional focus is given to the pitch axis, considering the control anticipation parameter (CAP). The latter relates to the two kinds of manouever points, where damping vanishes, that are calculated for minimum speed, take-off, and initial and final cruise conditions. The conclusion compares two flying wings designs (the “long narrow” and “short wide” fuselage concepts) not only from the point of view of flight stability, but also from other viewpoints.
      Citation: Aerospace
      PubDate: 2021-03-16
      DOI: 10.3390/aerospace8030077
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 78: Aspect Ratio Driven Relationship between
           Nozzle Internal Flow and Supersonic Jet Mixing

    • Authors: Kalyani Bhide, Kiran Siddappaji, Shaaban Abdallah
      First page: 78
      Abstract: This work attempts to connect internal flow to the exit flow and supersonic jet mixing in rectangular nozzles with low to high aspect ratios (AR). A series of low and high aspect ratio rectangular nozzles (design Mach number = 1.5) with sharp throats are numerically investigated using steady state Reynolds-averaged Navier−Stokes (RANS) computational fluid dynamics (CFD) with k-omega shear stress transport (SST) turbulence model. The numerical shadowgraph reveals stronger shocks at low ARs which become weaker with increasing AR due to less flow turning at the throat. Stronger shocks cause more aggressive gradients in the boundary layer resulting in higher wall shear stresses at the throat for low ARs. The boundary layer becomes thick at low ARs creating more aerodynamic blockage. The boundary layer exiting the nozzle transforms into a shear layer and grows thicker in the high AR nozzle with a smaller potential core length. The variation in the boundary layer growth on the minor and major axis is explained and its growth downstream the throat has a significant role in nozzle exit flow characteristics. The loss mechanism throughout the flow is shown as the entropy generated due to viscous dissipation and accounts for supersonic jet mixing. Axis switching phenomenon is also addressed by analyzing the streamwise vorticity fields at various locations downstream from the nozzle exit.
      Citation: Aerospace
      PubDate: 2021-03-16
      DOI: 10.3390/aerospace8030078
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 79: Unmanned Aerial Vehicle Operating Mode
           Classification Using Deep Residual Learning Feature Extraction

    • Authors: Carolyn J. Swinney, John C. Woods
      First page: 79
      Abstract: Unmanned Aerial Vehicles (UAVs) undoubtedly pose many security challenges. We need only look to the December 2018 Gatwick Airport incident for an example of the disruption UAVs can cause. In total, 1000 flights were grounded for 36 h over the Christmas period which was estimated to cost over 50 million pounds. In this paper, we introduce a novel approach which considers UAV detection as an imagery classification problem. We consider signal representations Power Spectral Density (PSD); Spectrogram, Histogram and raw IQ constellation as graphical images presented to a deep Convolution Neural Network (CNN) ResNet50 for feature extraction. Pre-trained on ImageNet, transfer learning is utilised to mitigate the requirement for a large signal dataset. We evaluate performance through machine learning classifier Logistic Regression. Three popular UAVs are classified in different modes; switched on; hovering; flying; flying with video; and no UAV present, creating a total of 10 classes. Our results, validated with 5-fold cross validation and an independent dataset, show PSD representation to produce over 91% accuracy for 10 classifications. Our paper treats UAV detection as an imagery classification problem by presenting signal representations as images to a ResNet50, utilising the benefits of transfer learning and outperforming previous work in the field.
      Citation: Aerospace
      PubDate: 2021-03-16
      DOI: 10.3390/aerospace8030079
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 80: Strength Analysis of Alternative Airframe
           Layouts of Regional Aircraft on the Basis of Automated Parametrical Models
           

    • Authors: Dmitry V. Vedernikov, Alexander N. Shanygin, Yury S. Mirgorodsky, Mikhail D. Levchenkov
      First page: 80
      Abstract: This publication presents the results of complex parametrical strength investigations of typical wings for regional aircrafts obtained by means of the new version of the four-level algorithm (FLA) with the modified module responsible for the analysis of aerodynamic loading. This version of FLA, as well as a base one, is focused on significant decreasing time and labor input of a complex strength analysis of airframes by using simultaneously different principles of decomposition. The base version includes four-level decomposition of airframe and decomposition of strength tasks. The new one realizes additional decomposition of alternative variants of load cases during the process of determination of critical load cases. Such an algorithm is very suitable for strength analysis and designing airframes of regional aircrafts having a wide range of aerodynamic concepts. Results of validation of the new version of FLA for a high-aspect-ratio wing obtained in this work confirmed high performance of the algorithm in decreasing time and labor input of strength analysis of airframes at the preliminary stages of designing. During parametrical design investigation, some interesting results for strut-braced wings having high aspect ratios were obtained.
      Citation: Aerospace
      PubDate: 2021-03-17
      DOI: 10.3390/aerospace8030080
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 81: Dust Ingestion in a Rotorcraft Engine
           Compressor: Experimental and Numerical Study of the Fouling Rate

    • Authors: Alessandro Vulpio, Alessio Suman, Nicola Casari, Michele Pinelli
      First page: 81
      Abstract: Helicopters often operate in dusty sites, ingesting huge amounts of contaminants during landing, take-off, hover-taxi, and ground operations. In specific locations, the downwash of the rotor may spread soil particles from the ground into the environment and, once ingested by the engine, may stick to the compressor airfoils. In the present work, the Allison 250 C18 engine’s multistage axial-flow compressor is employed to study the fouling rate on rotor blades and stator vanes from both numerical and experimental standpoints. The compressor is operated in a typical ground-idle operation, in terms of the rotational regime and contaminant concentration, in laboratory-controlled conditions. The mass of deposits is collected from the airfoil surfaces at the end of the test and compared to that estimated through the numerical model. The experimental test shows that the airfoils collect almost 1.6% of the engine’s total mass ingested during a ground-idle operation. The capability of numerical methods to predict the fouling rate on the rotating and stationary airfoils of a multistage compressor is tested through the implementation of literature based deposition models. Sticking models show a good agreement in terms of the relative results; nevertheless, an overestimation of the deposited mass predicted is observed.
      Citation: Aerospace
      PubDate: 2021-03-18
      DOI: 10.3390/aerospace8030081
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 82: Modular Line-Focused Space Solar Power
           Satellite

    • Authors: Yang Yang, Guanheng Fan, Xiangfei Ji, Mengchen Pei
      First page: 82
      Abstract: The Space Solar Power Satellite is an ultra-large space structure, which collects sunlight directly in space and then transmits it into the ground. Since the idea was invented in 1968, scientists around the world have proposed several typical conceptual design models. Nevertheless, the conceptual models have not been implemented for technological, manufacturing, and cost reasons. This paper presents a novel Space Solar Power Satellite scheme with modular line-focused concentrators and low concentration photovoltaic modules. First, the line-focused mode is analyzed and the optical performance of the circular trough concentrator is evaluated via ray-trace technique. Then, shape optimization for the cell array based on the Bézier curve is carried out to improve the optical property. Numerical examples indicate that the optimized cell array could obtain high power collection efficiency and suitable energy distribution. Moreover, the area of the photovoltaic cell array is reduced, which is conducive to cost reduction. Furthermore, modular design is conducted on the circular trough concentrator. Finally, the primary scheme of the novel Space Solar Power Satellite is designed with the previous modular concentrator and optimized cell array.
      Citation: Aerospace
      PubDate: 2021-03-18
      DOI: 10.3390/aerospace8030082
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 83: Experimental Heat Loads for Electrothermal
           Anti-Icing and De-Icing on UAVs

    • Authors: Richard Hann, Adriana Enache, Mikkel Cornelius Nielsen, Bård Nagy Stovner, Jeroen van Beeck, Tor Arne Johansen, Kasper Trolle Borup
      First page: 83
      Abstract: Atmospheric in-flight icing on unmanned aerial vehicles (UAVs) is a significant hazard. UAVs that are not equipped with ice protection systems are usually limited to operations within visual line of sight or to weather conditions without icing risk. As many military and commercial UAV missions require flights beyond visual line of sight and into adverse weather conditions, energy-efficient ice protection systems are required. In this experimental study, two electro-thermal ice protection systems for fixed-wing UAVs were tested. One system was operated in anti-icing and de-icing mode, and the other system was designed as a parting strip de-icing system. Experiments were conducted in an icing wind tunnel facility for varying icing conditions at low Reynolds numbers. A parametric study over the ice shedding time was used to identify the most energy-efficient operation mode. The results showed that longer intercycle durations led to higher efficiencies and that de-icing with a parting strip was superior compared to anti-icing and de-icing without a parting strip. These findings are relevant for the development of energy-efficient systems in the future.
      Citation: Aerospace
      PubDate: 2021-03-18
      DOI: 10.3390/aerospace8030083
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 84: Sensitivity Study of Ice Accretion Simulation
           to Roughness Thermal Correction Model

    • Authors: Kevin Ignatowicz, François Morency, Héloïse Beaugendre
      First page: 84
      Abstract: The effects of atmospheric icing can be anticipated by Computational Fluid Dynamics (CFD). Past studies show that the convective heat transfer influences the ice accretion and is itself a function of surface roughness. Uncertainty quantification (UQ) could help quantify the impact of surface roughness parameters on the reliability of ice accretion prediction. This paper aims to quantify ice accretion uncertainties and identify the key surface roughness correction parameters contributing the most to the uncertainties in a Reynolds-Averaged Navier-Stokes (RANS) formulation. Ice accretion simulations over a rough flat plate using two thermal correction models are used to construct a RANS database. Non-Intrusive Polynomial Chaos Expansion (NIPCE) metamodels are developed to predict the convective heat transfer and icing characteristics of the RANS database. The metamodels allow for the computation of the 95% confidence intervals of the output probability distribution (PDF) and of the sensitivity indexes of the roughness parameters according to their level of influence on the outputs. For one of the thermal correction models, the most influential parameter is the roughness height, whereas for the second model it is the surface correction coefficient. In addition, the uncertainty on the freestream temperature has a minor impact on the ice accretion sensitivity compared to the uncertainty on the roughness parameters.
      Citation: Aerospace
      PubDate: 2021-03-19
      DOI: 10.3390/aerospace8030084
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 85: Active Energy Management Based on
           Meta-Heuristic Algorithms of Fuel Cell/Battery/Supercapacitor Energy
           Storage System for Aircraft

    • Authors: Hasan Çınar, Ilyas Kandemir
      First page: 85
      Abstract: This paper presents the application of an active energy management strategy to a hybrid system consisting of a proton exchange membrane fuel cell (PEMFC), battery, and supercapacitor. The purpose of energy management is to control the battery and supercapacitor states of charge (SOCs) as well as minimizing hydrogen consumption. Energy management should be applied to hybrid systems created in this way to increase efficiency and control working conditions. In this study, optimization of an existing model in the literature with different meta-heuristic methods was further examined and results similar to those in the literature were obtained. Ant lion optimizer (ALO), moth-flame optimization (MFO), dragonfly algorithm (DA), sine cosine algorithm (SCA), multi-verse optimizer (MVO), particle swarm optimization (PSO), and whale optimization algorithm (WOA) meta-heuristic algorithms were applied to control the flow of power between sources. The optimization methods were compared in terms of hydrogen consumption and calculation time. Simulation studies were conducted in Matlab/Simulink R2020b (academic license). The contribution of the study is that the optimization methods of ant lion algorithm, moth-flame algorithm, and sine cosine algorithm were applied to this system for the first time. It was concluded that the most effective method in terms of hydrogen consumption and computational burden was the sine cosine algorithm. In addition, the sine cosine algorithm provided better results than similar meta-heuristic algorithms in the literature in terms of hydrogen consumption. At the same time, meta-heuristic optimization algorithms and equivalent consumption minimization strategy (ECMS) and classical proportional integral (PI) control strategy were compared as a benchmark study as done in the literature, and it was concluded that meta-heuristic algorithms were more effective in terms of hydrogen consumption and computational time.
      Citation: Aerospace
      PubDate: 2021-03-19
      DOI: 10.3390/aerospace8030085
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 86: Recent Advances of the BIRALET System about
           Space Debris Detection

    • Authors: Tonino Pisanu, Giacomo Muntoni, Luca Schirru, Pierluigi Ortu, Enrico Urru, Giorgio Montisci
      First page: 86
      Abstract: Space debris is internationally recognized as a planetary threat. Efforts to enhance the worldwide radar monitoring networks have been intensified in the last years. Among the new radars employed for the observations, one of the most promising is the Bistatic Radar for Low Earth Orbit (LEO) Tracking (BIRALET), which employs the Sardinia Radio Telescope as a receiving segment. The Sardinia Radio Telescope (SRT) has recently been proven to be a reliable instrument for space debris monitoring and, for this purpose, over the years has undergone some substantial modifications in order to be able to rise to the status of a fully functional radar receiver. However, an extensive measurement campaign, in order to assess the real potential of the radar, has never been done before. In this paper, the authors present the first real space debris measurement campaign of the SRT, made between December 2018 and October 2019 using the new dedicated channel of the P-band receiver. A total of 27 objects were correctly detected during this campaign, characterized by a radar cross section (RCS) interval between 0.13 and 13.4 m2 and a range interval between 459 and 1224 km.
      Citation: Aerospace
      PubDate: 2021-03-19
      DOI: 10.3390/aerospace8030086
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 87: Influence of the Apron Parking Stand
           Management Policy on Aircraft and Ground Support Equipment (GSE) Gaseous
           Emissions at Airports

    • Authors: Lucas Sznajderman, Gabriel Ramírez-Díaz, Carlos A. Di Bernardi
      First page: 87
      Abstract: The purpose of this study is to analyze the concept of a hybrid apron with a fixed number of parking positions considering the management model influence for the average delay per aircraft and the gaseous emissions generated by aircraft and ground support equipment (GSE) altogether. The apron is studied based on two gate management models: in the first model, the aircraft are allocated in each gate due to operational factors only; in the second model, the rules of exclusive use of each gate according to the airline are included. The emissions generated by aircraft operations and that of their GSE (produced by the service and movements on the apron) are quantified and compared in the two gate management models: operation in the standard LTO cycle of the studied aircraft, GSE emissions have a similar relation with the compared gasses (NOx and CO), ranging between 1% and 3%. Further, if it compares the emissions between support vehicles and aircraft taking only into account the in-out taxiway, the relation between both CO sources shows similar values to those of the previous comparison, whereas NOx emissions produced by GSE reach an approximately 20%. The study considers different demand conditions obtained from the average day of the peak month of Aeroparque Jorge Newbery airport. Subsequently, through the SIMMOD PLUS software, the aircraft operations are simulated. The gates assignment and the arrival timetables are used as inputs for the GSE study due to an analytical model developed by us. Once the operational dimension is characterized and evaluated, the necessary data to quantify the gaseous emissions from the sources (Aircraft-GSE), based on the International Civil Aviation Organization (ICAO) guidelines, is obtained.
      Citation: Aerospace
      PubDate: 2021-03-19
      DOI: 10.3390/aerospace8030087
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 88: A Survey on Low-Thrust Trajectory
           Optimization Approaches

    • Authors: David Morante, Manuel Sanjurjo Rivo, Manuel Soler
      First page: 88
      Abstract: In this paper, we provide a survey on available numerical approaches for solving low-thrust trajectory optimization problems. First, a general mathematical framework based on hybrid optimal control will be presented. This formulation and their elements, namely objective function, continuous and discrete state and controls, and discrete and continuous dynamics, will serve as a basis for discussion throughout the whole manuscript. Thereafter, solution approaches for classical continuous optimal control problems will be briefly introduced and their application to low-thrust trajectory optimization will be discussed. A special emphasis will be placed on the extension of the classical techniques to solve hybrid optimal control problems. Finally, an extensive review of traditional and state-of-the art methodologies and tools will be presented. They will be categorized regarding their solution approach, the objective function, the state variables, the dynamical model, and their application to planetocentric or interplanetary transfers.
      Citation: Aerospace
      PubDate: 2021-03-19
      DOI: 10.3390/aerospace8030088
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 89: Transient Dynamic System Behavior of Pressure
           Actuated Cellular Structures in a Morphing Wing

    • Authors: Patrick Meyer, Sebastian Lück, Tobias Spuhler, Christoph Bode, Christian Hühne, Jens Friedrichs, Michael Sinapius
      First page: 89
      Abstract: High aspect ratio aircraft have a significantly reduced induced drag, but have only limited installation space for control surfaces near the wingtip. This paper describes a multidisciplinary design methodology for a morphing aileron that is based on pressure-actuated cellular structures (PACS). The focus of this work is on the transient dynamic system behavior of the multi-functional aileron. Decisive design aspects are the actuation speed, the resistance against external loads, and constraints preparing for a future wind tunnel test. The structural stiffness under varying aerodynamic loads is examined while using a reduced-order truss model and a high-fidelity finite element analysis. The simulations of the internal flow investigate the transient pressurization process that limits the dynamic actuator response. The authors present a reduced-order model based on the Pseudo Bond Graph methodology enabling time-efficient flow simulation and compare the results to computational fluid dynamic simulations. The findings of this work demonstrate high structural resistance against external forces and the feasibility of high actuation speeds over the entire operating envelope. Future research will incorporate the fluid–structure interaction and the assessment of load alleviation capability.
      Citation: Aerospace
      PubDate: 2021-03-20
      DOI: 10.3390/aerospace8030089
      Issue No: Vol. 8, No. 3 (2021)
       
  • Aerospace, Vol. 8, Pages 37: Fuel Tankering: Economic Benefits and
           Environmental Impact for Flights Up to 1500 NM (Full Tankering) and 2500
           NM (Partial Tankering)

    • Authors: Laurent Tabernier, Esther Calvo Fernández, Andreas Tautz, Robin Deransy, Peter Martin
      First page: 37
      Abstract: The majority of emissions from aviation come from the combustion of the fuel required to operate each flight. Keeping the fuel consumption required for a safe flight to the absolute minimum is therefore the simplest and most effective way to ensure that emissions from that flight are kept to a minimum. In practice, however, the fuel load is determined by each aircraft operator on the basis of a number of criteria maximizing first cost efficiency, rather than fuel savings. In this context, tankering is the practice of carrying more fuel than is necessary for the safe execution of the flight to avoid or minimize refueling at the destination airport. It offers an economic advantage when there is a significant difference in fuel prices between the departure and arrival airports, but considerably increases the amount of emissions produced, because the more fuel an aircraft carries, the heavier it is, and carrying this extra weight increases its fuel consumption. This paper presents the steps followed by EUROCONTROL in conducting a first study to estimate the number of times this practice would offer an economic benefit and the amount of extra CO2 emissions that would result. This study, limited to flights up to 1500 and 2500 NM, corresponding mainly to short and medium-haul flights, estimates that, in 2018, 21% of ECAC (In this paper, ECAC refers to the geographical region defined by the 44 member states that signed the European Civil Aviation Conference) flights would perform fuel tankering beneficially. This would represent a net saving of 265 M€ per year for the airlines, but the burning of 286,000 tonnes of additional fuel (equivalent to 0.54% of ECAC jet fuel used), or 901,000 tonnes of CO2 per year. At a time when aviation is challenged for its contribution to climate change, the use of fuel tankering for economic reasons is therefore highly questionable.
      Citation: Aerospace
      PubDate: 2021-01-31
      DOI: 10.3390/aerospace8020037
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 38: Constrained Urban Airspace Design for
           Large-Scale Drone-Based Delivery Traffic

    • Authors: Malik Doole, Joost Ellerbroek, Victor L. Knoop, Jacco M. Hoekstra
      First page: 38
      Abstract: Large-scale adoption of drone-based delivery in urban areas promise societal benefits with respect to emissions and on-ground traffic congestion, as well as potential cost savings for drone-based logistic companies. However, for this to materialise, the ability of accommodating high volumes of drone traffic in an urban airspace is one of the biggest challenges. For unconstrained airspace, it has been shown that traffic alignment and segmentation can be used to mitigate conflict probability. The current study investigates the application of these principles to a highly constrained airspace. We propose two urban airspace concepts, applying road-based analogies of two-way and one-way streets by imposing horizontal structure. Both of the airspace concepts employ heading-altitude rules to vertically segment cruising traffic according to their travel direction. These airspace configurations also feature transition altitudes to accommodate turning flights that need to decrease the flight speed in order to make safe turns at intersections. While using fast-time simulation experiments, the performance of these airspace concepts is compared and evaluated for multiple traffic demand densities in terms of safety, stability, and efficiency. The results reveal that an effective way to structure drone traffic in a constrained urban area is to have vertically segmented altitude layers with respect to travel direction as well as horizontal constraints imposed to the flow of traffic. The study also makes recommendations for areas of future research, which are aimed at supporting dynamic traffic demand patterns.
      Citation: Aerospace
      PubDate: 2021-02-01
      DOI: 10.3390/aerospace8020038
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 39: Modeling and Control of a Modular Iron Bird

    • Authors: Luciano Blasi, Mauro Borrelli, Egidio D’Amato, Luigi Emanuel di Grazia, Massimiliano Mattei, Immacolata Notaro
      First page: 39
      Abstract: This paper describes the control architecture and the control laws of a new concept of Modular Iron Bird aimed at reproducing flight loads to test mobile aerodynamic control surface actuators for small and medium size aircraft and Unmanned Aerial Vehicles. The iron bird control system must guarantee the actuation of counteracting forces. On one side, a hydraulic actuator simulates the hinge moments acting on the mobile surface due to aerodynamic and inertial effects during flight; on the other side, the actuator to be tested applies an active hinge moment to control the angular position of the same surface. Reference aerodynamic and inertial loads are generated by a flight simulation module to reproduce more realistic conditions arising during operations. The design of the control action is based on a dynamic model of the hydraulic plant used to generate loads. This system is controlled using a Proportional Integral Derivative control algorithm tuned with an optimization algorithm taking into account the closed loop dynamics of the actuator under testing, uncertainties and disturbances in the controlled plant. Numerical simulations are presented to show the effectiveness of the proposed architecture and control laws.
      Citation: Aerospace
      PubDate: 2021-02-02
      DOI: 10.3390/aerospace8020039
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 40: Optimal Sizing and Operation of Airport
           Infrastructures in Support of Electric-Powered Aviation

    • Authors: Lorenzo Trainelli, Francesco Salucci, Carlo E. D. Riboldi, Alberto Rolando, Federico Bigoni
      First page: 40
      Abstract: The adoption of hybrid-electric aircraft is expected to have a considerable impact on airport operations, with the need of new infrastructural requirements to support electric-powered fleets. In particular, battery-charging requirements shall play a decisive role. Preliminary investigations useful to perform scenario studies for the future implementation of electric-powered aviation can take advantage of the ARES methodology presented here, which provides the optimal solution to the sizing of airport battery recharging infrastructures. Based on the flight schedule and on the specifications of the aircraft fleet and the charging equipment, the solution assesses the number and type of charging points, the related electrical consumption in terms of energy and power, and further information needed to guarantee the required operational level while minimizing the procurement and operating costs. The method allows considering and comparing two charging strategies: plug-in recharge and battery swapping. Energy price variation in time is also taken into account and a full description of the optimal time scheduling of recharging operations is provided. Application studies to the reconfiguration of two existing aerodromes, a General Aviation airport and a large regional hub, are discussed, showing the potential of the proposed approach.
      Citation: Aerospace
      PubDate: 2021-02-03
      DOI: 10.3390/aerospace8020040
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 41: Analysis of Continuing Airworthiness
           Occurrences under the Prism of a Learning Framework

    • Authors: James Clare, Kyriakos I. Kourousis
      First page: 41
      Abstract: In this research paper fifteen mandatory occurrence reports are analysed. The purpose of this is to highlight the learning potential incidents such as these may possess for organisations involved in aircraft maintenance and continuing airworthiness management activities. The outputs from the mandatory occurrence reports are aligned in tabular form for ease of inclusion in human factors’ continuation training material. A new incident learning archetype is also introduced, which intends to represent how reported incidents can be managed and translated into lessons in support of preventing event recurrence. This ‘learning product’ centric model visually articulates activities such as capturing the reported information, establishing causation and the iterative nature of developing a learning product.
      Citation: Aerospace
      PubDate: 2021-02-05
      DOI: 10.3390/aerospace8020041
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 42: Towards Determining the Contrail Cirrus
           Efficacy

    • Authors: Michael Ponater, Marius Bickel, Lisa Bock, Ulrike Burkhardt
      First page: 42
      Abstract: Contrail cirrus has been emphasized as the largest individual component of aircraft climate impact, yet respective assessments have been based mainly on conventional radiative forcing calculations. As demonstrated in previous research work, individual impact components can have different efficacies, i.e., their effectiveness to induce surface temperature changes may vary. Effective radiative forcing (ERF) has been proposed as a superior metric to compare individual impact contributions, as it may, to a considerable extent, include the effect of efficacy differences. Recent climate model simulations have provided a first estimate of contrail cirrus ERF, which turns out to be much smaller, by about 65%, than the conventional radiative forcing of contrail cirrus. The main reason for the reduction is that natural clouds exhibit a substantially lower radiative impact in the presence of contrail cirrus. Hence, the new result suggests a smaller role of contrail cirrus in the context of aviation climate impact (including proposed mitigation measures) than assumed so far. However, any conclusion in this respect should be drawn carefully as long as no direct simulations of the surface temperature response to contrail cirrus are available. Such simulations are needed in order to confirm the power of ERF for assessing contrail cirrus efficacy.
      Citation: Aerospace
      PubDate: 2021-02-06
      DOI: 10.3390/aerospace8020042
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 43: In-Flight Lift and Drag Estimation of an
           Unmanned Propeller-Driven Aircraft

    • Authors: Dominique Paul Bergmann, Jan Denzel, Ole Pfeifle, Stefan Notter, Walter Fichter, Andreas Strohmayer
      First page: 43
      Abstract: The high-power density and good scaling properties of electric motors enable new propulsion arrangements and aircraft configurations. This results in distributed propulsion systems allowing to make use of aerodynamic interaction effects between individual propellers and the wing of the aircraft, improving flight performance and thus reducing in-flight emissions. In order to systematically analyze these effects, an unmanned research platform was designed and built at the University of Stuttgart. As the aircraft is being used as a testbed for various flight performance studies in the field of distributed electric propulsion, a methodology for precise identification of its performance characteristics is required. One of the main challenges is the determination of the total drag of the aircraft to be able to identify an exact drag and lift polar in flight. For this purpose, an on-board measurement system was developed which allows for precise determination of the thrust of the aircraft which equals the total aerodynamic drag in steady, horizontal flight. The system has been tested and validated in flight using the unmanned free-flight test platform. The article provides an overview of the measuring system installed, discusses its functionality and shows results of the flight tests carried out.
      Citation: Aerospace
      PubDate: 2021-02-06
      DOI: 10.3390/aerospace8020043
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 44: Physics Guided Deep Learning for Data-Driven
           Aircraft Fuel Consumption Modeling

    • Authors: Mevlut Uzun, Mustafa Umut Demirezen, Gokhan Inalhan
      First page: 44
      Abstract: This paper presents a physics-guided deep neural network framework to estimate fuel consumption of an aircraft. The framework aims to improve data-driven models’ consistency in flight regimes that are not covered by data. In particular, we guide the neural network with the equations that represent fuel flow dynamics. In addition to the empirical error, we embed this physical knowledge as several extra loss terms. Results show that our proposed model accomplishes correct predictions on the labeled test set, as well as assuring physical consistency in unseen flight regimes. The results indicate that our model, while being applicable to the aircraft’s complete flight envelope, yields lower fuel consumption error measures compared to the model-based approaches and other supervised learning techniques utilizing the same training data sets. In addition, our deep learning model produces fuel consumption trends similar to the BADA4 aircraft performance model, which is widely utilized in real-world operations, in unseen and untrained flight regimes. In contrast, the other supervised learning techniques fail to produce meaningful results. Overall, the proposed methodology enhances the explainability of data-driven models without deteriorating accuracy.
      Citation: Aerospace
      PubDate: 2021-02-08
      DOI: 10.3390/aerospace8020044
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 45: Aircraft Flight Stabilizer System by CDM
           Designed Servo State-Feedback Controller

    • Authors: Ekachai Asa, Yoshio Yamamoto
      First page: 45
      Abstract: This research presents an automatic flight control system whose advantage is its ease of modification or maintenance while still effectively meeting the system’s performance requirement. This research proposes a mixed servo state-feedback system for controlling aircraft longitudinal and lateral-directional motion simultaneously based on the coefficient diagram method or CDM as the controller design methodology. The structure of this mixed servo state-feedback system is intuitive and straightforward, while CDM’s design processes are clear. Simulation results with aircraft linear and nonlinear models exhibit excellent performance in stabilizing and tracking the reference commands for both longitudinal and lateral-directional motion.
      Citation: Aerospace
      PubDate: 2021-02-08
      DOI: 10.3390/aerospace8020045
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 46: Special Issue: Civil and Military
           Airworthiness: Recent Developments and Challenges (Volume II)

    • Authors: Kyriakos I. Kourousis
      First page: 46
      Abstract: Effective safety management has always been a key objective for the broader airworthiness sector [...]
      Citation: Aerospace
      PubDate: 2021-02-08
      DOI: 10.3390/aerospace8020046
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 47: Machine Learning and Natural Language
           Processing for Prediction of Human Factors in Aviation Incident Reports

    • Authors: Tomás Madeira, Rui Melício, Duarte Valério, Luis Santos
      First page: 47
      Abstract: In the aviation sector, human factors are the primary cause of safety incidents. Intelligent prediction systems, which are capable of evaluating human state and managing risk, have been developed over the years to identify and prevent human factors. However, the lack of large useful labelled data has often been a drawback to the development of these systems. This study presents a methodology to identify and classify human factor categories from aviation incident reports. For feature extraction, a text pre-processing and Natural Language Processing (NLP) pipeline is developed. For data modelling, semi-supervised Label Spreading (LS) and supervised Support Vector Machine (SVM) techniques are considered. Random search and Bayesian optimization methods are applied for hyper-parameter analysis and the improvement of model performance, as measured by the Micro F1 score. The best predictive models achieved a Micro F1 score of 0.900, 0.779, and 0.875, for each level of the taxonomic framework, respectively. The results of the proposed method indicate that favourable predicting performances can be achieved for the classification of human factors based on text data. Notwithstanding, a larger data set would be recommended in future research.
      Citation: Aerospace
      PubDate: 2021-02-11
      DOI: 10.3390/aerospace8020047
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 48: Tuning of a Linear-Quadratic Stabilization
           System for an Anti-Aircraft Missile

    • Authors: Witold Bużantowicz
      First page: 48
      Abstract: A description is given of an application of a linear-quadratic regulator (LQR) for stabilizing the characteristics of an anti-aircraft missile, and an analytical method of selecting the weighting elements of the gain matrix in feedback loop is proposed. A novel method of LQR tuning via a single parameter ς was proposed and tested. The article supplements and develops the topics addressed in the author’s previous work. Its added value includes the observation that the solutions obtained are symmetric pairs, and that the tuning parameter ς proposed for the designed linear-quadratic regulator enables the selection of suitable parameters for the airframe stabilizing loop for the majority of the analytical solutions of the considered Riccati equation.
      Citation: Aerospace
      PubDate: 2021-02-12
      DOI: 10.3390/aerospace8020048
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 49: Novel Aero-Engine Multi-Disciplinary
           Preliminary Design Optimization Framework Accounting for Dynamic System
           Operation and Aircraft Mission Performance

    • Authors: Alexios Alexiou, Nikolaos Aretakis, Ioannis Kolias, Konstantinos Mathioudakis
      First page: 49
      Abstract: This paper presents a modular, flexible, extendable and fast-computational framework that implements a multidisciplinary, varying fidelity, multi-system approach for the conceptual and preliminary design of novel aero-engines. In its current status, the framework includes modules for multi-point steady-state engine design, aerodynamic design, engine geometry and weight, aircraft mission analysis, Nitrogen Oxide (NOx) emissions, control system design and integrated controller-engine transient-performance analysis. All the modules have been developed in the same software environment, ensuring consistent and transparent modeling while facilitating code maintainability, extendibility and integration at modeling and simulation levels. Any simulation workflow can be defined by appropriately combining the relevant modules. Different types of analysis can be specified such as sensitivity, design of experiment and optimization. Any combination of engine parameters can be selected as design variables, and multi-disciplinary requirements and constraints at different operating points in the flight envelope can be specified. The framework implementation is exemplified through the optimization of an ultra-high bypass ratio geared turbofan engine with a variable area fan nozzle, for which specific aircraft requirements and technology limits apply. Although the optimum design resulted in double-digit fuel-burn benefits compared to current technology engines, it did not meet engine-response requirements, highlighting the need to include transient-performance assessments as early as possible in the preliminary engine design phase.
      Citation: Aerospace
      PubDate: 2021-02-12
      DOI: 10.3390/aerospace8020049
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 50: Climate Impact Mitigation Potential of
           European Air Traffic in a Weather Situation with Strong Contrail Formation
           

    • Authors: Benjamin Lührs, Florian Linke, Sigrun Matthes, Volker Grewe, Feijia Yin
      First page: 50
      Abstract: Air traffic contributes to anthropogenic global warming by about 5% due to CO2 emissions and non-CO2 effects, which are primarily caused by the emission of NOx and water vapor as well as the formation of contrails. Since—in the long term—the aviation industry is expected to maintain its trend to grow, mitigation measures are required to counteract its negative effects upon the environment. One of the promising operational mitigation measures that has been a subject of the EU project ATM4E is climate-optimized flight planning by considering algorithmic climate change functions that allow for the quantification of aviation-induced climate impact based on the emission’s location and time. Here, we describe the methodology developed for the use of algorithmic climate change functions in trajectory optimization and present the results of its application to the planning of about 13,000 intra-European flights on one specific day with strong contrail formation over Europe. The optimization problem is formulated as bi-objective continuous optimal control problem with climate impact and fuel burn being the two objectives. Results on an individual flight basis indicate that there are three major classes of different routes that are characterized by different shapes of the corresponding Pareto fronts representing the relationship between climate impact reduction and fuel burn increase. On average, for the investigated weather situation and traffic scenario, a climate impact reduction in the order of 50% can be achieved by accepting 0.75% of additional fuel burn. Higher mitigation gains would only be available at much higher fuel penalties, e.g., a climate impact reduction of 76% associated with a fuel penalty of 12.8%. However, these solutions represent much less efficient climate impact mitigation options.
      Citation: Aerospace
      PubDate: 2021-02-12
      DOI: 10.3390/aerospace8020050
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 51: Radio Frequency Interference Measurements for
           a Radio Astronomy Observatory Site in Indonesia

    • Authors: Sitompul, Manik, Batubara, Suhandi
      First page: 51
      Abstract: We report on the measurements of radio frequency interference (RFI) at Mount Timau, Kupang, Indonesia, which is intended to host a future radio astronomy observatory. These measurements were taken twice in October 2020 and December 2020 to obtain the RFI environment, at frequencies between 70 and 7000 MHz. Due to the limitations of the measurement data, the results presented in this paper are based on peak detection rather than statistical analysis. Based on the measurement results, the frequency interval between 70–88 MHz and 120–150 MHz is relatively quiet, and the frequency range of 150–300 MHz is relatively clear. The frequency interval of 300 to 800 MHz is relatively quiet, except at the frequency of 600 MHz. The frequency range of 800–1400 MHz is also relatively quiet. The predominant terrestrial services in this band are at 840 MHz, with an amplitude around 32 dB, and 916 MHz, with an amplitude around 12 dB, and the global system for mobile (GSM) signals around 954 MHz have an amplitude around 20 dB above the noise floor. The frequency range of 1400–7000 MHz is also relatively quiet. In this band frequency, we can see RFI at 2145 and 2407 MHz, emitted by local Wi-Fi, and at 2683 MHz, with amplitudes of 18, 40 and 15 dB, respectively, from the noise level. We conclude that, for this period, the frequency band allocated for astronomy can possibly be used for radio telescope development.
      Citation: Aerospace
      PubDate: 2021-02-17
      DOI: 10.3390/aerospace8020051
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 52: Vibration Response Aspects of a Main Landing
           Gear Composite Door Designed for High-Speed Rotorcraft

    • Authors: Maurizio Arena, Antonio Chiariello, Martina Castaldo, Luigi Di Palma
      First page: 52
      Abstract: One of the crucial issues affecting the structural safety of propeller vehicles is the propeller tonal excitation and related vibrations. Propeller rotation during flight generates vibrating sources depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust, and blade geometry. Generally, the higher energy levels generated are confined to 1st blade passing frequency (BPF) and its harmonics, while additional broadband components, mainly linked with the blade shape, the developed engine power, and the turbulent boundary layer (TBL), also contribute to the excitation levels. The vibrations problem takes on particular relevance in the case of composite structures. The laminates in fact could exert damping levels generally lower than metallic structures, where the greater amount of bolted joints allow for dissipating more vibration energy. The prediction and reduction of aircraft vibration levels are therefore significant considerations for conventional propeller aircrafts now entering the commercial market as well as for models currently being developed. In the Clean Sky 2 framework, the present study focuses on a practical case inherent to the AIRBUS-Racer program aiming to design and develop a multi-tasking fast rotorcraft. This paper defines a finite elements (FE)-based procedure for the characterization of the vibration levels of a main landing gear (MLG) composite door with respect to the expected operating tonal loads. A parametric assessment was carried out to evaluate the principal modal parameters (transfer functions and respective resonance frequencies, mode shapes, and damping coefficients) of the landing gear-door assembly in order to achieve reduced vibration levels. Based on the FE analysis results, the influence of the extra-damping, location, and number of ballast elements, the boundary conditions were investigated with respect to failure scenarios of the kinematic line opening the study towards aeroelastic evaluations. Further experimental ground test results serve as a validation database for the prediction numerical methods representative of the composite door dynamic response.
      Citation: Aerospace
      PubDate: 2021-02-19
      DOI: 10.3390/aerospace8020052
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 53: A Numerical and Experimental Investigation of
           the Convective Heat Transfer on a Small Helicopter Rotor Test Setup

    • Authors: Abdallah Samad, Eric Villeneuve, François Morency, Christophe Volat
      First page: 53
      Abstract: In-flight icing affects helicopter performance, limits its operations, and reduces safety. The convective heat transfer is an important parameter in numerical icing simulations and state-of-the-art icing/de-icing codes utilize important computing resources when calculating it. The BEMT–RHT and UVLM–RHT offer low- and medium-fidelity approaches to estimate the rotor heat transfer (RHT). They are based on a coupling between Blade element momentum theory (BEMT) or unsteady vortex lattice method (UVLM), and a CFD-determined heat transfer correlation. The latter relates the Frossling number (Fr) to the Reynolds number (Re) and effective angle of attack (αEff). In a series of experiments carried out at the Anti-icing Materials International Laboratory (AMIL), this paper serves as a proof of concept of the proposed correlations. The objective is to propose correlations for the experimentally measured rotor heat transfer data. Specifically, the Frx is correlated with the Re and αEff in a similar form as the proposed CFD-based correlations. A fixed-wing setup is first used as a preliminary step to verify the heat transfer measurements of the icing wind tunnel (IWT). Tests are conducted at a = 0°, for a range of 4.76 ´ 105 £ Re £ 1.36 ´ 106 and at 10 non-dimensional surface wrap locations −0.62 £ (S/c) £ + 0.87. Later, a rotor setup is used to build the novel heat transfer correlation, tests are conducted at two pitch angles ((q) = 0° and 6°) for a range of rotor speeds (500 RPM £ (W) £ 1500 RPM), three different radial positions ((r/R) = 0.6, 0.75 and 0.95), and 0 £ S/c £ + 0.58. Results indicate that the fixed-wing Frx at the stagnation point was in the range of literature experimental data, and within 8% of fully turbulent CFD simulations. The FrAvg also agrees with CFD predictions, with an average discrepancy of 1.4%. For the rotor, the W caused a similar increase of Frx for the tests at q = 0° and those at q = 6°. Moreover, the Frx behavior changed significantly with r/R, suggesting the αEff had a significant effect on the Frx. Finally, the rotor data are first correlated with Rem(at each S/c) for q = 0° to establish the correlation parameters, and a term for the αEff is then added to also account for the tests at q = 6°. The correlations fit the data with an error between 2.1% and 14%, thus justifying the use of a coupled approach for the BEMT–RHT and UVLM–RHT.
      Citation: Aerospace
      PubDate: 2021-02-20
      DOI: 10.3390/aerospace8020053
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 54: Configuration Study of Electric Helicopters
           for Urban Air Mobility

    • Authors: Julia A. Cole, Lauren Rajauski, Andrew Loughran, Alexander Karpowicz, Stefanie Salinger
      First page: 54
      Abstract: There is currently interest in the design of small electric vertical take-off and landing aircraft to alleviate ground traffic and congestion in major urban areas. To support progress in this area, a conceptual design method for single-main-rotor and lift-augmented compound electric helicopters has been developed. The design method was used to investigate the feasible design space for electric helicopters based on varying mission profiles and technology assumptions. Within the feasible design space, it was found that a crossover boundary exists as a function of cruise distance and hover time where the most efficient configuration changes from a single-main-rotor helicopter to a lift-augmented compound helicopter. In general, for longer cruise distances and shorter hover times, the lift-augmented compound helicopter is the more efficient configuration. An additional study was conducted to investigate the potential benefits of decoupling the main rotor from the tail rotor. This study showed that decoupling the main rotor and tail rotor has the potential to reduce the total mission energy required in all cases, allowing for increases in mission distances and hover times on the order of 5% for a given battery size.
      Citation: Aerospace
      PubDate: 2021-02-20
      DOI: 10.3390/aerospace8020054
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 55: An Ultrasonic-Based Detection of Air-Leakage
           for the Unclosed Components of Aircraft

    • Authors: Yanlin Lyu, Muhammad Jamil, Pengfei Ma, Ning He, Munish Kumar Gupta, Aqib Mashood Khan, Danil Yurievich Pimenov
      First page: 55
      Abstract: Air-leakage detection is among the most important processes at the assembly stage of unclosed components, especially for large aircraft. A series of air-leakage detecting methods are generally applied during the final assembly, nevertheless, many of them are less effective to detect the leakage at the assembly stage. The present study aims to discuss the principles of ultrasonic generation in negative pressure conditions to detect the air-leakage. An ultrasonic-based detection method is proposed and designed to detect the air-leakage of unclosed components for aircraft. A relationship between the acoustic power, sound pressure, and the leak aperture detection distance was identified and discussed. A leakage rate model related to leakage rate, leak aperture, and system pressure was implemented and confirmed through experiments. Findings have indicated that the air-leakage can be detected effectively within a detection distance of 0.8 m and a leak aperture greater or equal to 0.4 mm with this method. Besides, the leak location, leak aperture, and leakage rate was acquired in an accurate and fast way. It is an effective method of detecting the air-leakage of unclosed components at the aircraft assembly stage reducing the testing time, energy consumption, and cost for the air-leakage detection in the final assembly stage of large aircraft.
      Citation: Aerospace
      PubDate: 2021-02-20
      DOI: 10.3390/aerospace8020055
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 56: A Study on Thermal Buckling and Mode Jumping
           of Metallic and Composite Plates

    • Authors: Javier Gutiérrez Álvarez, Chiara Bisagni
      First page: 56
      Abstract: Composite plates in post-buckling regime can experience mode jumping in their buckling shape, suddenly increasing the number of half-waves. This phenomenon can be advantageous, because the shape change could be used for local morphing or structural adaptability in future aerospace structures. A study of this phenomenon under heating is here presented, combining numerical and experimental techniques. At first, a set of parametric analysis was conducted to identify composite panels that present a mode jump when heated. Three plates were selected, one in aluminum alloy 2024T3, and two in AS4/8552 composite material, with layup [30/−30/5/−5]s and [35/−35/10/−10]s. The plates were tested in a new test setup for thermal buckling based on low thermal expansion fixtures. The mode jumping was successfully obtained experimentally for both composite plates. Numerical simulations predicted the general trends for all plates, and the mode jumps for the composite plates.
      Citation: Aerospace
      PubDate: 2021-02-21
      DOI: 10.3390/aerospace8020056
      Issue No: Vol. 8, No. 2 (2021)
       
  • Aerospace, Vol. 8, Pages 57: Spectral Correlation for Signal Presence
           Detection and Frequency Acquisition of Small Satellites

    • Authors: Jonas Hofmann, Andreas Knopp, Chad M. Spooner, Giovanni Minelli, James Newman
      First page: 57
      Abstract: Challenges in interference-limited satellite detection arising from the low-earth orbit (LEO) and the Industrial, Scientific and Medical (ISM) frequency bands are addressed. In particular, a novel signal presence detector based on cyclostationary signal properties is proposed and analyzed for a low signal-to-noise-plus-interference ratio (SINR) regime. The performance of the proposed detector, which is applicable to various small-satellite scenarios, is evaluated on both simulated and real-world measurement data. This measurement data has been collected from the scientific satellite mission “Picosats Realizing Orbital Propagation Calibrations using Beacon Emitters” (PROPCUBE).
      Citation: Aerospace
      PubDate: 2021-02-22
      DOI: 10.3390/aerospace8020057
      Issue No: Vol. 8, No. 2 (2021)
       
 
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