Pub Date : 2021-11-10DOI: 10.3846/aviation.2021.15663
N. Kehayas
Induced drag constitutes approximately 40% of the total drag of subsonic civil transport aircraft at cruise conditions. Various types of winglets and several non-planar concepts, such as the C-wing, the joined wings, and the box plane, have been proposed for its reduction. Here, a new approach to induced drag reduction in the form of a combination of an elliptical and an astroid hypocycloid lift distribution is put forward. Lift is mainly generated from high circulation in the center part of the wing and fades away along the semi-span towards the wing tip. Using lifting line theory, the analysis shows that for fixed lift and wingspan the combined lift distribution results in an induced drag reduction of 50% with respect to the elliptical distribution. Due to its wing planform the combined lift distribution leads to a 51.5% higher aspect ratio. If structural constraints are placed, then the higher aspect ratio may affect wing weight. Although any substantial increase of wing weight is not envisaged, further study of the matter is required. Zero-lift drag and lift-dependent drag due to skin friction and viscosity-related pressure remain unaffected. The proposed lift distribution is particularly useful in a blended wing-body design.
{"title":"AN ALTERNATIVE APPROACH TO INDUCED DRAG REDUCTION","authors":"N. Kehayas","doi":"10.3846/aviation.2021.15663","DOIUrl":"https://doi.org/10.3846/aviation.2021.15663","url":null,"abstract":"Induced drag constitutes approximately 40% of the total drag of subsonic civil transport aircraft at cruise conditions. Various types of winglets and several non-planar concepts, such as the C-wing, the joined wings, and the box plane, have been proposed for its reduction. Here, a new approach to induced drag reduction in the form of a combination of an elliptical and an astroid hypocycloid lift distribution is put forward. Lift is mainly generated from high circulation in the center part of the wing and fades away along the semi-span towards the wing tip. Using lifting line theory, the analysis shows that for fixed lift and wingspan the combined lift distribution results in an induced drag reduction of 50% with respect to the elliptical distribution. Due to its wing planform the combined lift distribution leads to a 51.5% higher aspect ratio. If structural constraints are placed, then the higher aspect ratio may affect wing weight. Although any substantial increase of wing weight is not envisaged, further study of the matter is required. Zero-lift drag and lift-dependent drag due to skin friction and viscosity-related pressure remain unaffected. The proposed lift distribution is particularly useful in a blended wing-body design.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48019522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-08DOI: 10.3846/aviation.2021.15678
D. Steinweg, Kai-Daniel Büchter, M. Engelmann, Antoine Habersetzer, Ulrike Schmalz, A. Paul
The air transport system faces pressing challenges arising from CO2-emission reduction targets, fragmented passenger needs, and a highly competitive market environment. Aiming for a reduction of CO2-emissions in the long-haul sector, a holistic solution is suggested incorporating both operational and technological innovations in three areas: (1) changes in the air transport network structure, (2) (liquid) hydrogen as energy carrier, and (3) new aircraft and cabin design. To these ends, this paper focuses on the implications resulting from a passenger-distance improved air transport network. Demand pooling is proposed to enable higher load factors, offer more point-to-point connections for passengers, and generate new revenue sources for airlines. Based on a discussion of traditional airline business models, a seat exchange platform named “ShAirline” is proposed, allowing multiple providers to rent out cabin space. The underlying business model is evaluated considering implications for aircraft and cabin design, new passenger services, additional revenue opportunities, passenger journey times, required aircraft, as well as implications for airports. Findings indicate that the proposed seat exchange platform in conjunction with a change in aircraft ownership structure assist in removing inefficiencies across the current long-haul network and help offset barriers connected to the use of novel eco-efficient technologies.
{"title":"A BUSINESS MODEL ENABLING A PASSENGER-DISTANCE-IMPROVED LONG-HAUL NETWORK TO DECREASE TRANSPORT INEFFICIENCIES","authors":"D. Steinweg, Kai-Daniel Büchter, M. Engelmann, Antoine Habersetzer, Ulrike Schmalz, A. Paul","doi":"10.3846/aviation.2021.15678","DOIUrl":"https://doi.org/10.3846/aviation.2021.15678","url":null,"abstract":"The air transport system faces pressing challenges arising from CO2-emission reduction targets, fragmented passenger needs, and a highly competitive market environment. Aiming for a reduction of CO2-emissions in the long-haul sector, a holistic solution is suggested incorporating both operational and technological innovations in three areas: (1) changes in the air transport network structure, (2) (liquid) hydrogen as energy carrier, and (3) new aircraft and cabin design. To these ends, this paper focuses on the implications resulting from a passenger-distance improved air transport network. Demand pooling is proposed to enable higher load factors, offer more point-to-point connections for passengers, and generate new revenue sources for airlines. Based on a discussion of traditional airline business models, a seat exchange platform named “ShAirline” is proposed, allowing multiple providers to rent out cabin space. The underlying business model is evaluated considering implications for aircraft and cabin design, new passenger services, additional revenue opportunities, passenger journey times, required aircraft, as well as implications for airports. Findings indicate that the proposed seat exchange platform in conjunction with a change in aircraft ownership structure assist in removing inefficiencies across the current long-haul network and help offset barriers connected to the use of novel eco-efficient technologies.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43034465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.3846/aviation.2021.15660
T. Laukkala, E. Pukkala, B. Budowle, A. Sajantila, M. Mäntysaari, H. Huhtala, A. Vuorio
Military pilots undergo rigorous selection compared with civilian professional pilots because of different operational requirements. There are no studies of military pilots’ subsequent civil aviation careers and fatal pilot aviation accidents. This study focuses on Vietnam War (VW) pilots and subsequent fatal aviation accidents in the U.S from 1965 to 2018. In total nine aviation accidents met the inclusion criteria and are described in detail, including the pilots’ previous civil aviation incidents. The VW pilots were healthy, had valid Medicals and continued to fly in demanding pilot positions after their military careers. Although the data are limited, this study suggests that previous military pilots may differ slightly from other pilots in their subsequent civil aviation careers.
{"title":"PREVIOUS MILITARY PILOTS AND THEIR LATER FATAL CIVIL AVIATION ACCIDENTS","authors":"T. Laukkala, E. Pukkala, B. Budowle, A. Sajantila, M. Mäntysaari, H. Huhtala, A. Vuorio","doi":"10.3846/aviation.2021.15660","DOIUrl":"https://doi.org/10.3846/aviation.2021.15660","url":null,"abstract":"Military pilots undergo rigorous selection compared with civilian professional pilots because of different operational requirements. There are no studies of military pilots’ subsequent civil aviation careers and fatal pilot aviation accidents. This study focuses on Vietnam War (VW) pilots and subsequent fatal aviation accidents in the U.S from 1965 to 2018. In total nine aviation accidents met the inclusion criteria and are described in detail, including the pilots’ previous civil aviation incidents. The VW pilots were healthy, had valid Medicals and continued to fly in demanding pilot positions after their military careers. Although the data are limited, this study suggests that previous military pilots may differ slightly from other pilots in their subsequent civil aviation careers.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49193165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.3846/aviation.2021.14554
Michal Hvezda
Satellite navigation has become a very important topic in the air transport industry along with its application in instrument approach procedures. Recently, extracted statistical characteristics of the European Geostationary Navigation Overlay Service (EGNOS) satellite signal have been made available from real measurements in the Czech Republic. The numerical modeling approach is taken for a feasibility study of automatic aircraft control during the Localizer Performance with Vertical Guidance (LPV) precision approach based on such navigation data. The model incorporates Kalman filtering of the stochastic navigation signal, feed-back control of L-410 aircraft dynamics and the calculation of approach progress along the predefined procedure. Evaluation of the performance of the system prototype is performed using the scenarios developed with a strong interest in altitude control. The specific scenario is focused on a curved approach which offers a huge advantage of the approaches based on the Satellite-based Augmentation System (SBAS) compared to ones with the Instrument Landing System (ILS). Outputs of simulation executions are statistically analyzed and assessed against predefined navigation performance goals equivalent to ILS categories with a positive outcome.
{"title":"SIMULATION OF EGNOS SATELLITE NAVIGATION SIGNAL USAGE FOR AIRCRAFT LPV PRECISION INSTRUMENT APPROACH","authors":"Michal Hvezda","doi":"10.3846/aviation.2021.14554","DOIUrl":"https://doi.org/10.3846/aviation.2021.14554","url":null,"abstract":"Satellite navigation has become a very important topic in the air transport industry along with its application in instrument approach procedures. Recently, extracted statistical characteristics of the European Geostationary Navigation Overlay Service (EGNOS) satellite signal have been made available from real measurements in the Czech Republic. The numerical modeling approach is taken for a feasibility study of automatic aircraft control during the Localizer Performance with Vertical Guidance (LPV) precision approach based on such navigation data. The model incorporates Kalman filtering of the stochastic navigation signal, feed-back control of L-410 aircraft dynamics and the calculation of approach progress along the predefined procedure. Evaluation of the performance of the system prototype is performed using the scenarios developed with a strong interest in altitude control. The specific scenario is focused on a curved approach which offers a huge advantage of the approaches based on the Satellite-based Augmentation System (SBAS) compared to ones with the Instrument Landing System (ILS). Outputs of simulation executions are statistically analyzed and assessed against predefined navigation performance goals equivalent to ILS categories with a positive outcome.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45733717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-13DOI: 10.3846/aviation.2021.15336
Jiezhuoma La, I. Heiets
This study aims to provide insights into the impact levels of digitalization and intelligentization on air transport system (ATS) in Australia, China, the US, and India. Air transport system is one of the most efficient transport systems which contains three elements: air traffic control, airport, and airlines. In modern society, the importance of digitalization and intelligentization in ATS is attached to by publics. In this study, firstly, comparative analysis is used to analyze the different states of digitalization and intelligentization level and air transport system in sample countries. Then, correlation analysis is used to study the correlation of the different impact factors with the ATS in different countries. The third one is regression analysis, it is used to analyze the relationship between ATS and the development of digitalization and intelligentization in four sample countries. At last, forecasting analysis is used to predict the future trend of digitalization and intelligentization’s impact on ATS in the sample countries in the next few years. Then, the most significant impact factors for ATS will be obtained. Also, the future development trends of ATS under digitalization and intelligentization’s impact could be forecasted by using econometric models.
{"title":"THE IMPACT OF DIGITALIZATION AND INTELLIGENTIZATION ON AIR TRANSPORTATION SYSTEM","authors":"Jiezhuoma La, I. Heiets","doi":"10.3846/aviation.2021.15336","DOIUrl":"https://doi.org/10.3846/aviation.2021.15336","url":null,"abstract":"This study aims to provide insights into the impact levels of digitalization and intelligentization on air transport system (ATS) in Australia, China, the US, and India. Air transport system is one of the most efficient transport systems which contains three elements: air traffic control, airport, and airlines. In modern society, the importance of digitalization and intelligentization in ATS is attached to by publics. In this study, firstly, comparative analysis is used to analyze the different states of digitalization and intelligentization level and air transport system in sample countries. Then, correlation analysis is used to study the correlation of the different impact factors with the ATS in different countries. The third one is regression analysis, it is used to analyze the relationship between ATS and the development of digitalization and intelligentization in four sample countries. At last, forecasting analysis is used to predict the future trend of digitalization and intelligentization’s impact on ATS in the sample countries in the next few years. Then, the most significant impact factors for ATS will be obtained. Also, the future development trends of ATS under digitalization and intelligentization’s impact could be forecasted by using econometric models.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46175929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-07DOI: 10.3846/aviation.2021.15330
N. Daidzic
Vertical flight performance of Lighter-than-Air free hot-air balloons is derived and discussed. Novel mathematical model using lumped-parameters has been used to model balloon flight dynamics and steady-state performance in particular. Thermal model was not treated as the super-heat is under the control of aeronauts/pilots. Buoyancy or gross lift, net or effective lift, specific lift, and excess specific lift were derived for a general single envelope balloon and can be applied to hot-air, gas and hybrid balloons. Rate-of-climb, absolute ceiling, rate-of-descent, and the maximum rate-of-descent or the uncontrolled terminal descent have all been modeled and sample computations performed for AX8 or AX9 FAI-class hot-air balloons. Lifting index or the specific net/effective lift have been computed treating ambient and hot air as ideal gases at various pressure altitudes and representative envelope temperatures. Drag coefficient in upward and downward vertical flights have been chosen based on best available data. Experimental scale and full-scale flight tests are suggested for more accurate estimates of external aerodynamics in vertical balloon flights. CFD computations of coupled inner- and external-flows are also recommended in future efforts. Knowledge of free balloon’s vertical performance is essential in flight planning and operational safety of flight.
{"title":"MATHEMATICAL MODEL OF HOT-AIR BALLOON STEADY-STATE VERTICAL FLIGHT PERFORMANCE","authors":"N. Daidzic","doi":"10.3846/aviation.2021.15330","DOIUrl":"https://doi.org/10.3846/aviation.2021.15330","url":null,"abstract":"Vertical flight performance of Lighter-than-Air free hot-air balloons is derived and discussed. Novel mathematical model using lumped-parameters has been used to model balloon flight dynamics and steady-state performance in particular. Thermal model was not treated as the super-heat is under the control of aeronauts/pilots. Buoyancy or gross lift, net or effective lift, specific lift, and excess specific lift were derived for a general single envelope balloon and can be applied to hot-air, gas and hybrid balloons. Rate-of-climb, absolute ceiling, rate-of-descent, and the maximum rate-of-descent or the uncontrolled terminal descent have all been modeled and sample computations performed for AX8 or AX9 FAI-class hot-air balloons. Lifting index or the specific net/effective lift have been computed treating ambient and hot air as ideal gases at various pressure altitudes and representative envelope temperatures. Drag coefficient in upward and downward vertical flights have been chosen based on best available data. Experimental scale and full-scale flight tests are suggested for more accurate estimates of external aerodynamics in vertical balloon flights. CFD computations of coupled inner- and external-flows are also recommended in future efforts. Knowledge of free balloon’s vertical performance is essential in flight planning and operational safety of flight.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49613072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-06DOI: 10.3846/aviation.2021.15329
Misagh Ketabdari, E. Toraldo, M. Crispino
Aircraft braking distance is dependent on the friction between the main gear tires and runway pavement surface.Pavement texture, which is divided into macrotexture and micro-texture, has a noticeable effect upon friction, especially when the surface is wet. A risk analysis framework is developed to study the effects of longitudinal and transverse slopes on the aircraft braking distance in wet runway conditions and their influences on the probability of landing overrun accidents.This framework is operating under various water-film thicknesses, Maximum Landing Weights (MLW), and touchdown speed probability distributions for an acceptable range of longitudinal/transverse slopes and pavement texture depths.A simulator code is developed that initially computes the existing water-film thickness, as the result of intense precipitation,under aircraft main gear (depend on aircraft category) and then applies this variable as one of the main inputs to the aircraft braking distance computation. According to the obtained results, longitudinal gradient does not have a significant effect on the existing water depth on the surface although it affects the flow path length. Furthermore, 1% to 1.5% transverse slope causes rapid drainage of water from the runway surface and considerably decreases the probability of runway excursion accidents.
{"title":"ASSESSING THE IMPACT OF THE SLOPES ON RUNWAY DRAINAGE CAPACITY BASED ON WHEEL/PATH SURFACE ADHESION CONDITIONS","authors":"Misagh Ketabdari, E. Toraldo, M. Crispino","doi":"10.3846/aviation.2021.15329","DOIUrl":"https://doi.org/10.3846/aviation.2021.15329","url":null,"abstract":"Aircraft braking distance is dependent on the friction between the main gear tires and runway pavement surface.Pavement texture, which is divided into macrotexture and micro-texture, has a noticeable effect upon friction, especially when the surface is wet. A risk analysis framework is developed to study the effects of longitudinal and transverse slopes on the aircraft braking distance in wet runway conditions and their influences on the probability of landing overrun accidents.This framework is operating under various water-film thicknesses, Maximum Landing Weights (MLW), and touchdown speed probability distributions for an acceptable range of longitudinal/transverse slopes and pavement texture depths.A simulator code is developed that initially computes the existing water-film thickness, as the result of intense precipitation,under aircraft main gear (depend on aircraft category) and then applies this variable as one of the main inputs to the aircraft braking distance computation. According to the obtained results, longitudinal gradient does not have a significant effect on the existing water depth on the surface although it affects the flow path length. Furthermore, 1% to 1.5% transverse slope causes rapid drainage of water from the runway surface and considerably decreases the probability of runway excursion accidents.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45498632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-29DOI: 10.3846/aviation.2021.14540
Ilker Under, Ender Gerede
Defined in the organizational behavior literature as employee avoidance of expressing their feelings, thoughts and ideas, the concept of organizational silence refers to the failure to submit reports voluntarily in the context of aviation safety. Due to various factors, aviation employees may avoid reporting. However, managers need voluntary reports from their employees to prevent future accidents. The primary purpose of this study is to find out why air traffic controllers, one of the most critical safety components of flight operation, fail to do voluntary reporting. In addition, whether controllers are involved in real-life voluntary reporting and whether the factors that prevent voluntary reporting vary by demographic variables. The data collected from 212 controllers were subjected to Confirmatory Factor Analysis by using the Statistical Package for Social Sciences (SPSS) 24 program and the reasons for their failure to do voluntary reporting were identified. Furthermore, the study concluded that approximately 27% of controllers did not submit voluntary reporting on unsafe situations or safety-enhancing recommendations they had seen.
{"title":"SILENCE IN THE TOWER: ANALYSING THE REASONS OF AIR TRAFFIC CONTROLLERS AVOIDING VOLUNTARY REPORTING","authors":"Ilker Under, Ender Gerede","doi":"10.3846/aviation.2021.14540","DOIUrl":"https://doi.org/10.3846/aviation.2021.14540","url":null,"abstract":"Defined in the organizational behavior literature as employee avoidance of expressing their feelings, thoughts and ideas, the concept of organizational silence refers to the failure to submit reports voluntarily in the context of aviation safety. Due to various factors, aviation employees may avoid reporting. However, managers need voluntary reports from their employees to prevent future accidents. The primary purpose of this study is to find out why air traffic controllers, one of the most critical safety components of flight operation, fail to do voluntary reporting. In addition, whether controllers are involved in real-life voluntary reporting and whether the factors that prevent voluntary reporting vary by demographic variables. The data collected from 212 controllers were subjected to Confirmatory Factor Analysis by using the Statistical Package for Social Sciences (SPSS) 24 program and the reasons for their failure to do voluntary reporting were identified. Furthermore, the study concluded that approximately 27% of controllers did not submit voluntary reporting on unsafe situations or safety-enhancing recommendations they had seen.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45249883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-20DOI: 10.3846/aviation.2021.13291
H. Maghsoudi, Amirreza Kosari Kosari
In this study, the three-dimensional optimal trajectory planning of an unmanned fixed-wing aerial vehicle was investigated for Terrain Following – Terrain Avoidance (TF-TA) purposes using the Direct Collocation method. For this purpose, firstly, the appropriate equations representing the translational movement of the aircraft were described. The three-dimensional optimal trajectory planning of the flying vehicle was formulated in the TF-TA manoeuvre as an optimal control problem. The terrain profile, as the main allowable height constraint was modelled using the Fractal Generation Method. The resulting optimal control problem was discretized by applying the Direct Collocation numerical technique and then, was transformed into a Nonlinear Programming Problem (NLP). The efficacy of the proposed method was demonstrated by extensive simulations, and it was particularly verified that the purposed approach can produce a solution satisfying almost all the performance and environmental constraints encountering in a low -altitude flight.
{"title":"GENERATION OF AN OPTIMAL LOW-ALTITUDE TRAJECTORY FOR A FIXED-WING UNMANNED AERIAL VEHICLE IN A MOUNTAINOUS AREA","authors":"H. Maghsoudi, Amirreza Kosari Kosari","doi":"10.3846/aviation.2021.13291","DOIUrl":"https://doi.org/10.3846/aviation.2021.13291","url":null,"abstract":"In this study, the three-dimensional optimal trajectory planning of an unmanned fixed-wing aerial vehicle was investigated for Terrain Following – Terrain Avoidance (TF-TA) purposes using the Direct Collocation method. For this purpose, firstly, the appropriate equations representing the translational movement of the aircraft were described. The three-dimensional optimal trajectory planning of the flying vehicle was formulated in the TF-TA manoeuvre as an optimal control problem. The terrain profile, as the main allowable height constraint was modelled using the Fractal Generation Method. The resulting optimal control problem was discretized by applying the Direct Collocation numerical technique and then, was transformed into a Nonlinear Programming Problem (NLP). The efficacy of the proposed method was demonstrated by extensive simulations, and it was particularly verified that the purposed approach can produce a solution satisfying almost all the performance and environmental constraints encountering in a low -altitude flight.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49018140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-20DOI: 10.3846/aviation.2021.15131
Xue Yang
A compressible air permeability model is developed to simulate the aerodynamic performance of the supersonic porous canopy. And a single-degree-of-freedom model is applied to analyse the static stability of the parachute. By using this method, the flow structure of the parachute system with big attack angle is obtained. The aerodynamic moment coefficients of porous and nonporous canopies are compared to discuss the effect of air permeability on stability of the supersonic parachute. The numerical results show that aerodynamic moment coefficient of the system with air permeability has larger oscillation amplitude and value than that without air permeability. This method can be developed as a potential method to select the supersonic parachute initially.
{"title":"EFFECT OF AIR PERMEABILITY ON STABILITY OF SUPERSONIC PARACHUTE","authors":"Xue Yang","doi":"10.3846/aviation.2021.15131","DOIUrl":"https://doi.org/10.3846/aviation.2021.15131","url":null,"abstract":"A compressible air permeability model is developed to simulate the aerodynamic performance of the supersonic porous canopy. And a single-degree-of-freedom model is applied to analyse the static stability of the parachute. By using this method, the flow structure of the parachute system with big attack angle is obtained. The aerodynamic moment coefficients of porous and nonporous canopies are compared to discuss the effect of air permeability on stability of the supersonic parachute. The numerical results show that aerodynamic moment coefficient of the system with air permeability has larger oscillation amplitude and value than that without air permeability. This method can be developed as a potential method to select the supersonic parachute initially.","PeriodicalId":51910,"journal":{"name":"Aviation","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2021-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46269828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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