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Aerospace, Volume 7, Issue 1 (January 2020) – 9 articles

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Cover Story (view full-size image) As the aerodynamic characteristics of delta wings depend greatly on the state of the leading-edge [...] Read more.
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Open AccessEditorial
Acknowledgement to Reviewers of Aerospace in 2019
Aerospace 2020, 7(1), 9; https://doi.org/10.3390/aerospace7010009 - 19 Jan 2020
Viewed by 483
Abstract
The editorial team greatly appreciates the reviewers who have dedicated their considerable time and expertise to the journal’s rigorous editorial process over the past 12 months, regardless of whether the papers are finally published or not [...] Full article
Open AccessArticle
An Agent-Based Empirical Game Theory Approach for Airport Security Patrols
Aerospace 2020, 7(1), 8; https://doi.org/10.3390/aerospace7010008 - 18 Jan 2020
Viewed by 542
Abstract
Airports are attractive targets for terrorists, as they are designed to accommodate and process large amounts of people, resulting in a high concentration of potential victims. A popular method to mitigate the risk of terrorist attacks is through security patrols, but resources are [...] Read more.
Airports are attractive targets for terrorists, as they are designed to accommodate and process large amounts of people, resulting in a high concentration of potential victims. A popular method to mitigate the risk of terrorist attacks is through security patrols, but resources are often limited. Game theory is commonly used as a methodology to find optimal patrol routes for security agents such that security risks are minimized. However, game-theoretic models suffer from payoff uncertainty and often rely solely on expert assessment to estimate game payoffs. Experts cannot incorporate all aspects of a terrorist attack in their assessment. For instance, attacker behavior, which contributes to the game payoff rewards, is hard to estimate precisely. To address this shortcoming, we proposed a novel empirical game theory approach in which payoffs are estimated using agent-based modeling. Using this approach, we simulated different attacker and defender strategies in an agent-based model to estimate game-theoretic payoffs, while a security game was used to find optimal security patrols. We performed a case study at a regional airport, and show that the optimal security patrol is non-deterministic and gives special emphasis to high-impact areas, such as the security checkpoint. The found security patrol routes are an improvement over previously found security strategies of the same case study. Full article
(This article belongs to the Special Issue Aviation Logistics and Supply Chain Management)
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Open AccessReview
Development of the Minimum Equipment List: Current Practice and the Need for Standardisation
Aerospace 2020, 7(1), 7; https://doi.org/10.3390/aerospace7010007 - 17 Jan 2020
Viewed by 804
Abstract
As part of the airworthiness requirements, an aircraft cannot be dispatched with an inoperative equipment or system unless this is allowed by the Minimum Equipment List (MEL) under any applicable conditions. Commonly, the MEL mirrors the Master MEL (MMEL), which is developed by [...] Read more.
As part of the airworthiness requirements, an aircraft cannot be dispatched with an inoperative equipment or system unless this is allowed by the Minimum Equipment List (MEL) under any applicable conditions. Commonly, the MEL mirrors the Master MEL (MMEL), which is developed by the manufacturer and approved by the regulator. However, the increasing complexity of aircraft systems and the diversity of operational requirements, environmental conditions, fleet configuration, etc. necessitates a tailored approach to developing the MEL. While it is the responsibility of every aircraft operator to ensure the airworthiness of their aircraft, regulators are also required to publish guidelines to help operators develop their MELs. Currently, there is no approved standard to develop a MEL, and this poses a challenge to both aviation regulators and aircraft operators. This paper reviews current MEL literature, standards and processes as well as MEL related accidents/incidents to offer an overview of the present state of the MEL development and use and reinstate the need for a systematic approach. Furthermore, this paper exposes the paucity of MEL related literature and the ambiguity in MEL regulations. In addition, it was found that inadequate training and guidance on the development and use of MEL as well as lack of prior experience in airworthiness topics can lead to mismanagement and misapplication of the MEL. Considering the challenges outlined above, this study proposes the combination of system engineering and socio-technical system approaches for the development of a MEL. Full article
Open AccessArticle
Estimation of Performance Parameters of Turbine Engine Components Using Experimental Data in Parametric Uncertainty Conditions
Aerospace 2020, 7(1), 6; https://doi.org/10.3390/aerospace7010006 - 16 Jan 2020
Viewed by 534
Abstract
Zero-dimensional models based on the description of the thermo-gas-dynamic process are widely used in the design of engines and their control and diagnostic systems. The models are subjected to an identification procedure to bring their outputs as close as possible to experimental data [...] Read more.
Zero-dimensional models based on the description of the thermo-gas-dynamic process are widely used in the design of engines and their control and diagnostic systems. The models are subjected to an identification procedure to bring their outputs as close as possible to experimental data and assess engine health. This paper aims to improve the stability of engine model identification when the number of measured parameters is small, and their measurement error is not negligible. The proposed method for the estimation of engine components’ parameters, based on multi-criteria identification, provides stable estimations and their confidence intervals within known measurement errors. A priori information about the engine, its parameters and performance is used directly in the regularized identification procedure. The mathematical basis for this approach is the fuzzy sets theory. Synthesis of objective functions and subsequent scalar convolutions of these functions are used to estimate gas-path components’ parameters. A comparison with traditional methods showed that the main advantage of the proposed approach is the high stability of estimation in the parametric uncertainty conditions. Regularization reduces scattering, excludes incorrect solutions that do not correspond to a priori assumptions and also helps to implement the gas path analysis with a limited number of measured parameters. The method can be used for matching thermodynamic models to experimental data, gas path analysis and adapting dynamic models to the needs of the engine control system. Full article
(This article belongs to the Special Issue 9th EASN International Conference on Innovation in Aviation & Space)
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Open AccessEditorial
Publishing in “Aircraft Design” with a Continuous Open Access Special Issue
Aerospace 2020, 7(1), 5; https://doi.org/10.3390/aerospace7010005 - 14 Jan 2020
Viewed by 626
Abstract
The article looks at publishing options in the field of aircraft design to find that no dedicated journal on aircraft design exists. For this reason, a Continuous Special Issue Aircraft Design of the well established journal “Aerospace” at the Open Access publisher MDPI [...] Read more.
The article looks at publishing options in the field of aircraft design to find that no dedicated journal on aircraft design exists. For this reason, a Continuous Special Issue Aircraft Design of the well established journal “Aerospace” at the Open Access publisher MDPI is started. Often special issues of a journal are introduced for “hot topics”. Here, the subset “special issue” is used for a scientific domain—in this case “aircraft design”. Recurring single special issues are numbered in sequence and are identified by the year of the deadline for manuscript submissions. This allows for the delivery of several single special issues over time in a row without the need to define a publishing schedule up front. Together these single issues form the Continuous Special Issue Aircraft Design and offer a new publishing home for the aircraft design community. Full article
(This article belongs to the Special Issue Aircraft Design (SI-2/2020) )
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Open AccessArticle
Pulsed Blowing Interacting with a Leading-Edge Vortex
Aerospace 2020, 7(1), 4; https://doi.org/10.3390/aerospace7010004 - 10 Jan 2020
Viewed by 668
Abstract
Manipulation of vortex instabilities for aerodynamic performance increase is of great interest in numerous aeronautical applications. With increasing angle of attack, the leading-edge vortex of a semi-slender delta wing becomes unsteady and eventually collapses, endangering the flight stability. Hence, active flow control by [...] Read more.
Manipulation of vortex instabilities for aerodynamic performance increase is of great interest in numerous aeronautical applications. With increasing angle of attack, the leading-edge vortex of a semi-slender delta wing becomes unsteady and eventually collapses, endangering the flight stability. Hence, active flow control by pulsed blowing stabilizes the vortex system, enlarging the flight envelope for such wing configurations. The most beneficial outcome is the reattachment of the separated shear layer during post-stall, contributing to a lift increase of more than 50%. In contrast to high power consuming brute-force actuation, manipulating the flow instabilities offers a more efficient alternative for mean flow field control, which has direct repercussions on the aerodynamic characteristics. However, the flow mechanisms involving jet–vortex and vortex–vortex interactions and the disturbance convection through the flow field are little understood. This paper reports on the unsteady flow field above a generic half delta wing model with a 65 ° sweep angle and its response to periodic blowing. Numerical and experimental results are presented and discussed in a synergistic manner. Full article
(This article belongs to the Special Issue Aeronautical Systems for Flow Control)
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Open AccessArticle
A Magnetometer-Only Attitude Determination Strategy for Small Satellites: Design of the Algorithm and Hardware-in-the-Loop Testing
Aerospace 2020, 7(1), 3; https://doi.org/10.3390/aerospace7010003 - 05 Jan 2020
Viewed by 720
Abstract
Attitude determination represents a fundamental task for spacecraft. Achieving this task on small satellites, and nanosatellites in particular, is further challenging, because the limited power and computational resources available on-board, together with the low development budget, set strict constraints on the selection of [...] Read more.
Attitude determination represents a fundamental task for spacecraft. Achieving this task on small satellites, and nanosatellites in particular, is further challenging, because the limited power and computational resources available on-board, together with the low development budget, set strict constraints on the selection of the sensors and the complexity of the algorithms. Attitude determination is obtained here from the only measurements of a three-axis magnetometer and a model of the Geomagnetic field, stored on the on-board computer. First, the angular rates are estimated and processed using a second-order low-pass Butterworth filter, then they are used as an input, along with Geomagnetic field data, to estimate the attitude matrix using an unsymmetrical TRIAD. The computational efficiency is enhanced by arranging complex matrix operations into a form of the Faddeev algorithm, which is implemented using systolic array architecture on the FPGA core of a CubeSat on-board computer. The performance and the robustness of the algorithm are evaluated by means of numerical analyses in MATLAB Simulink, showing pointing and angular rate accuracy below 10° and 0.2°/s. The algorithm implemented on FPGA is verified by Hardware-in-the-loop simulation, confirming the results from numerical analyses and efficiency. Full article
(This article belongs to the Special Issue Spacecraft Attitude Determination and Control)
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Open AccessArticle
Superhydrophobic Coatings as Anti-Icing Systems for Small Aircraft
Aerospace 2020, 7(1), 2; https://doi.org/10.3390/aerospace7010002 - 02 Jan 2020
Viewed by 811
Abstract
Traditional anti-icing/de-icing systems, i.e., thermal and pneumatic, in most cases require a power consumption not always allowable in small aircraft. Therefore, the use of passive systems, able to delay the ice formation, or reduce the ice adhesion strength once formed, with no additional [...] Read more.
Traditional anti-icing/de-icing systems, i.e., thermal and pneumatic, in most cases require a power consumption not always allowable in small aircraft. Therefore, the use of passive systems, able to delay the ice formation, or reduce the ice adhesion strength once formed, with no additional energy consumption, can be considered as the most promising solution to solve the problem of the ice formation, most of all, for small aircraft. In some cases, the combination of a traditional icing protection system (electrical, pneumatic, and thermal) and the passive coatings can be considered as a strategic instrument to reduce the energy consumption. The effort of the present work was to develop a superhydrophobic coating, able to reduce the surface free energy (SFE) and the work of adhesion (WA) of substrates, by a simplified and non-expensive method. The developed coating, applied as a common paint with an aerograph, is able to reduce the SFE of substrates by 99% and the WA by 94%. The effects of both chemistry and surface morphology on the wettability of surfaces were also studied. In the reference samples, the higher the roughness, the lower the SFE and the WA. In coated samples with roughness ranging from 0.4 and 3 µm no relevant variations in water contact angle, nor in SFE and WA were observed. Full article
(This article belongs to the Special Issue 9th EASN International Conference on Innovation in Aviation & Space)
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Open AccessArticle
Assessment of Aircraft Surface Heat Exchanger Potential
Aerospace 2020, 7(1), 1; https://doi.org/10.3390/aerospace7010001 - 19 Dec 2019
Viewed by 874
Abstract
Providing sufficient cooling power for an aircraft will become increasingly challenging with the introduction of (hybrid-) electric propulsion. To avoid excessive drag from heat exchangers, the heat sink potential of the aircraft surface is evaluated in this study. Semi-empirical correlations are used to [...] Read more.
Providing sufficient cooling power for an aircraft will become increasingly challenging with the introduction of (hybrid-) electric propulsion. To avoid excessive drag from heat exchangers, the heat sink potential of the aircraft surface is evaluated in this study. Semi-empirical correlations are used to estimate aircraft surface area and heat transfer. The impact of surface heating on aircraft drag is qualitatively assessed. Locating surface heat exchangers where fully turbulent flow is present promises a decrease in aircraft drag. Surface cooling potential is investigated over a range from small regional aircraft to large wide body jets and a range of surface temperatures. Four mission points are considered: Take-off, hot day take-off, climb and cruise. The results show that surface heat exchangers can provide cooling power in the same order of magnitude as the waste heat expected from (hybrid-) electric drive trains for all sizes of considered aircraft. Also, a clear trend favouring smaller aircraft with regards to the ratio of available to required cooling power is visible. Full article
(This article belongs to the Special Issue 9th EASN International Conference on Innovation in Aviation & Space)
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