Aircraft Category Research Articles

Active flutter suppression for light sport aircraft by a control surface split

A new method of active flutter suppression is present in the paper and aims at the Light Sport Aircraft category, where it has never been used, designed, or even considered. The novelty of the method lies in splitting the control surface into a part controlled by a pilot with purely mechanical control and into a part controlled by a servo-actuator with a controller. The control law of the actuator is designed to follow the pilot-controlled part of the control surfaces and damp unstable oscillations if they occur. The controller design for flutter suppression is focused on achieving simple solutions. The request for simplicity is important for easy acquisition of airworthiness during a certification process and easy implementation by producers. The contribution of this paper also lies in the analysis of flutter suppression capability based on the varying active control surface span. The results show that it is not necessary to use the entire area of a control surface for active flutter suppression.A mathematical model based on a real aircraft is developed and verified for the simulation of active flutter suppression. In addition, control law design and simulations of the dynamic response are performed. The robustness of the control law and aircraft controllability in the case of active control surface malfunction is investigated.

Flight performance analysis of aerial fire fighting

AbstractThis paper investigates the operational patterns and techniques of aerial fire fighting. It is demonstrated that manoeuvrability and endurance are the main characteristics when choosing air tactical aircraft; focus is on load capability for helicopters and air tankers. Water tank filling and deployment techniques are evaluated. Aircraft using pressure deployment systems are found to produce more uniform and heavy coverage in comparison with gravity systems. ADS-B open source data of flight operations and performance was collected. Operational patterns are found to be independent on the size of particular aircraft category (non-amphibious and amphibious air tanker, helicopter, air-tactical aircraft). Effectiveness and cost are modelled using the retardant dropped per operation and the average number of daily missions. The largest aircraft, Type-I helicopters and very large air tankers (VLAT) are found to be the most effective water- and retardant-dropping aircraft. The best cost-to-litre-dropped ratio for water-dropping aircraft is attributed to Type-III helicopters and amphibious Type-III aircraft; for retardant-dropping aircraft, VLAT are most effective. To maximise fire fighting effectiveness, Type-I helicopters and VLAT should be used as far as possible, with pressure deployment systems.

Analysis of noise distributions at heliports and vertiports: A guide for site selection and land use planning

Purpose: The purpose of this study was to examine the noise profiles of helicopters and eVTOLs at heliports and vertiports in order to support site planning and the development of local land-use compatibility guidelines. Design/methodology/approach: This study used existing helicopter and eVTOL sound profiles to develop noise distribution contours for heliports and vertiports. This study collected noise data from available studies on helicopters and eVTOLs. This data was then entered into dBmap noise mapping tool to develop noise maps for helicopters and eVTOLs. Three air transit facility configurations for each aircraft category were analyzed: open (unobstructed), urban, and rooftop. Two additional vertiport configurations were created by overlaying building and noise data with Google Earth imagery. Noise data was entered into dBmap for processing. Noise contours were mapped for three configurations for both aircraft categories.Findings: Key observations from the noise distribution analysis showed that open (unobstructed) facility configurations have even noise distributions for both eVTOLs and helicopters. Noise maps for urban locations showed areas of attenuation and asymmetrical patterns due to the interactions of sound waves with surrounding buildings. An analysis of a rooftop installation of a heliport or vertiport provided some noise mitigation advantages. Noise contour distributions closely matched those outlined in previous research; however, the sound intensities modeled in this study were lower than indicated in exigent research. Assessments were also conducted for real-world sites with potential future use as vertiports in Seattle, Washington, and Chicago, Illinois.Practical Implications: This study suggests that current land use compatibility guidance may be inadequate for rotorcraft and eVTOL operations. Findings suggest the development of symmetrical noise-impact zones centered around heliports and vertiports. Examples of these zones are outlined, and recommendations for future research are provided. Local planners can use the data from this study to make educated choices about the siting of heliports and vertiports. Additionally, the findings can assist planners in the development of zoning and land use compatibility standards.Social Implications: Land use compatibility standards for heliports and vertiports will help ensure a synergistic relationship between local communities and these air transit facilities. The data from this study can also help protect individuals from excessive noise and annoyance.Originality/value: This study is one of the few on this topic and the only known research on noise distributions of helicopters and eVTOLs with a particular focus on land use compatibility

The Critical Threshold of The Relationship Between Take-Off Load And Powertrain Load of the Aircraft

The critical threshold of the relationship between take-off load and powertrain load of the aircraft has long intrigued researchers and posed significant challenges. Delving into this subject, extensive research has been conducted to comprehend the intricate dynamics between these two variables. This thesis aims to contribute to this ongoing investigation by analyzing and drawing conclusions based on observed load variations and their impact on power system functionality. The study encompasses a comprehensive examination of various aircraft types, ranging from ultralight aircraft to wide-bodied aircraft and Unmanned Aerial Vehicles (UAVs). Each aircraft category presents unique characteristics and demands distinct engine requirements, further complicating understanding the take-off load to powertrain load relationship. By meticulously studying the changes in loads during the crucial take-off phase, this research aims to uncover valuable insights into the essentiality of an efficient power system. The findings of this study have the potential to enhance aircraft design and operations, ultimately leading to safer and more optimized flight experiences.

Automatic interval management for aircraft based on dynamic fuzzy speed control considering uncertainty

A novel real-time autonomous Interval Management System (IMS) is proposed to automate interval management, which considers the effect of wind uncertainty using the Dynamic Fuzzy Velocity Decision (DFVD) algorithm. The membership function can be generated dynamically based on the True Air Speed (TAS) limitation changes in real time and the interval criterion of the adjacent aircraft, and combined with human cognition to formulate fuzzy rules for speed adjusting decision-making. Three groups of experiments were conducted during the en-route descent stage to validate the proposed IMS and DFVD performances, and to analyze the impact factors of the algorithm. The verification experimental results show that compared with actual flight status data under controllers’ command, the IMS reduces the descent time by approaching 30% with favorable wind uncertainty suppression performance. Sensitivity analysis shows that the ability improvement of DFVD is mainly affected by the boundary value of the membership function. Additionally, the dynamic generation of the velocity membership function has greater advantages than the static method in terms of safety and stability. Through the analysis of influencing factors, we found that the interval criterion and aircraft category have no significant effect on the capability of IMS. In a higher initial altitude scenario, the initial interval should be appropriately increased to enhance safety and efficiency during the descent process. This prototype system could evolve into a real-time Flight-deck Interval Management (FIM) tool in the future.

ANALYSIS OF POSSIBLE MODIFICATION OF TRANSPORT AIRCRAFT TO MEDEVAC IN THE CZECH REPUBLIC

With a growing number of coronavirus patients worldwide, military and civilian transport aircraft are increasingly being used for civilian medical evacuation duties (MEDEVAC) on time-critical flights. This article deals with the possibility of converting an aircraft fleet in the Czech Republic to MEDEVAC. The indication for the analysis of the possibility of transforming transport aircraft was the past and current pandemic situation in the Czech Republic. The main research question is how to implement the modification of a selected airline of the Czech Republic to MEDEVAC. An analysis of the technical data of selected aircraft from Airbus and Boeing was used to investigate this problem. Further, an analysis of the medical equipment required for the MEDEVAC aircraft category was also performed using equipment manufactured in the Czech Republic. The results obtained by the analysis and spatial arrangement of the aircraft deck for the transport of patients with medical equipment confirmed the possibility of such a transformation within the Czech Republic. We consider it important to elaborate on a project that would solve, in detail, all the steps of the conversion of a transport aircraft to MEDEVAC.

ST-Net: Scattering Topology Network for Aircraft Classification in High-Resolution SAR Images

Aircraft classification in synthetic aperture radar (SAR) images plays a considerable role in global region management and surveillance. Recently, deep learning has been applied to solve the classification problem and made significant progress. Due to the imaging variability at different angles and component scattering discreteness in SAR images, previous works have had difficulty in achieving desirable classification results. To address these issues, we study the positional and semantic relationship between the scattering points and propose an innovative scattering topology network (ST-Net) in this article. First, considering the diversity of imaging results caused by different target attitude angles, we extract and transform the scattering cluster centers to update the information of various categories. It can guide the model to strengthen the discriminative features and mitigate the impact of imaging variability on classification performance. Second, a novel scattering topology module (STM) is introduced to model the spatial relationships and semantic information interaction of discrete scattering points. In this process, the topology relations and scattering characteristics are enhanced for further accurate classification. Third, context attention excitation (CAE) is designed to capture significant global and semantic information, which is conducive to suppressing background interference and reducing category confusion. In conclusion, the ST-Net is presented with the SAR imaging mechanism and the topology geometric representation of aircraft. We construct the SAR aircraft category dataset (SAR-ACD) and conduct extensive experiments on it to show the effectiveness of ST-Net, which illustrates that our method achieves superior classification performance.

Assessment of hydrogen transport aircraft

Zero-carbon-dioxide-emitting hydrogen-powered aircraft have, in recent decades, come back on the stage as promising protagonists in the fight against global warming. The main cause for the reduced performance of liquid hydrogen aircraft lays in the fuel storage, which demands the use of voluminous and heavy tanks. Literature on the topic shows that the optimal fuel storage solution depends on the aircraft range category, but most studies disagree on which solution is optimal for each category. The objective of this research was to identify and compare possible solutions to the integration of the hydrogen fuel containment system on regional, short/medium- and large passenger aircraft, and to understand why and how the optimal tank integration strategy depends on the aircraft category. This objective was pursued by creating a design and analysis framework for CS-25 aircraft capable of appreciating the effects that different combinations of tank structure, fuselage diameter, tank layout, shape, venting pressure and pressure control generate at aircraft level. Despite that no large differences among categories were found, the following main observations were made: (1) using an integral tank structure was found to be increasingly more beneficial with increasing aircraft range/size. (2) The use of a forward tank in combination with the aft one appeared to be always beneficial in terms of energy consumption. (3) The increase in fuselage diameter is detrimental, especially when an extra aisle is not required and a double-deck cabin is not feasible. (4) Direct venting has, when done efficiently, a small positive effect. (5) The optimal venting pressure varies with the aircraft configuration, performance, and mission. The impact on performance from sizing the tank for missions longer than the harmonic one was also quantified.

SCAN: Scattering Characteristics Analysis Network for Few-Shot Aircraft Classification in High-Resolution SAR Images

Recently, deep learning in synthetic aperture radar (SAR) automatic target recognition (ATR) has made significant progress, but the sample limitation problem in the SAR field is still obvious. Compared with the optical remote sensing images, the SAR images are insufficient, especially those containing the geospatial targets with certain target attitude angles (TAAs). To solve these problems, a novel few-shot learning framework named scattering characteristics analysis network (SCAN) is proposed in this article. First, a scattering extraction module (SEM) is designed to combine the target imaging mechanism with the network, which learns the number and distribution of the scattering points for each target type via explicit supervision. Besides, considering the imaging variability of SAR targets, a TAA-guided metalearning network consisting of an angle self-adaption classifier (ASC) and a frequency embedded module (FEM) is designed. ASC guides the network to focus on the positive sample pairs with different TAAs. FEM combines pulse cosine transform (PCT) with the network training process effectively to enrich frequency-domain information. In addition, a new dataset named SAR aircraft category dataset is constructed for the experiments. Compared with other few-shot SAR target classification approaches, our model efficiently integrates the scattering characteristics with the learning process, and the test accuracy for 5-way 1-shot has been improved by 4.74%. Finally, the experimental results are provided to demonstrate the validity of the proposed method.

Classi-Fly: Inferring Aircraft Categories from Open Data

In recent years, air traffic communication data has become easy to access, enabling novel research in many fields. Exploiting this new data source, a wide range of applications have emerged, from weather forecasting to stock market prediction, or the collection of intelligence about military and government movements. Typically, these applications require knowledge about the metadata of the aircraft, specifically its operator and the aircraft category. armasuisse Science + Technology , the R&D agency for the Swiss Armed Forces, has been developing Classi-Fly, a novel approach to obtain metadata about aircraft based on their movement patterns. We validate Classi-Fly using several hundred thousand flights collected through open source means, in conjunction with ground truth from publicly available aircraft registries containing more than 2 million aircraft. We show that we can obtain the correct aircraft category with an accuracy of greater than 88%. In cases, where no metadata is available, this approach can be used to create the data necessary for applications working with air traffic communication. Finally, we show that it is feasible to automatically detect particular sensitive aircraft such as police and surveillance aircraft using this method.

ASSESSING THE IMPACT OF THE SLOPES ON RUNWAY DRAINAGE CAPACITY BASED ON WHEEL/PATH SURFACE ADHESION CONDITIONS

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.

Empennage sizing with the tail volume complemented with a method for dorsal fin layout

Purpose: Provide good values for the tail volume coefficient and the lever arm as a percentage of the fuselage length. Provide a statistical method for dorsal fin layout. – Methodology: Based on an understanding of flight physics, the statistical correlation of real aircraft parameters is investigated. This is based on the firm conviction that high fidelity parameters for future aircraft need a checked against parameters of existing successful aircraft. – Findings: Typical tail volume coefficients are between 0.5 and 1.0 for the horizontal tail and between 0.03 and 0.08 for the vertical tail depending on aircraft category. Empennage statistics have clear trends. The often weak correlation shows that aircraft design allows for sufficient designer's choice. Only a minority of aircraft feature a dorsal fin. Designers see it as an added surface rather than as part of the vertical tail. It is used to limit the hypothetical risk of vertical tail stall due to high sideslip angles. – Research Limitations: Results obtained from statistics are close to reality, but not a proof to fulfill requirements. – Practical Implications: Methods from the paper can be used for quick initial sizing of a vertical tail with or without dorsal fin or sizing of a horizontal tail. These results can also be used as good starting values for optimization tools in aircraft design. – Originality: Estimation of the tail lever arm is necessary for sizing with the tail volume coefficient, but had not been investigated to any detail. A method for the layout of dorsal fins was missing.

A DoE-based approach for the implementation of structural surrogate models in the early stage design of box-wing aircraft

One of the possible ways to face the challenge of reducing the environmental impact of aviation, without limiting the growth of air transport, is the introduction of more efficient, radically different aircraft architectures. Among these, the box-wing one represents a promising solution, at least in the case of its application to short-to-medium haul aircraft, which, according to the achievement of the H2020 project “PARSIFAL”, would bring to a 20% reduction in terms of emitted CO2 per passenger-kilometre. The present paper faces the problem of estimating the structural mass of such a disruptive configuration in the early stages of the design, underlining the limitations in this capability of the approaches available by literature and proposing a DoE-based approach to define surrogate models suitable for such purpose. A test case from the project “PARSIFAL” is used for the first conception of the approach, starting from the Finite Element Model parametrization, then followed by the construction of a database of FEM results, hence introducing the regression models and implementing them in an optimization framework. Results achieved are investigated in order to validate both the wing sizing and the optimization procedure. Finally, an additional test case resulting from the application of the box-wing layout to the regional aircraft category within the Italian research project “PROSIB”, is briefly presented to further assess the capabilities of the proposed approach.

Aircraft taxi time prediction: Feature importance and their implications

Taxiing remains a major bottleneck at many airports. Recently, several approaches to allocating efficient routes for taxiing aircraft have been proposed. The routing algorithms underpinning these approaches rely on accurate prediction of the time taken to traverse each segment of the taxiways. Many features impact on taxi time, including the route taken, aircraft category, operational mode of the airport, traffic congestion information, and local weather conditions. Working with real-world data for several international airports, we compare multiple prediction models and investigate the impact of these features, drawing conclusions on the most important features for accurately modelling taxi times. We show that high accuracy can be achieved with a small subset of the features consisting of those generally important across all airports (departure/arrival, distance, total turns, average speed and numbers of recent aircraft), and a small number of features specific to particular target airports. Moving from all features to this small subset results in less than a 1 percentage-point drop in movements correctly predicted within 1, 3 and 5 min.

Aircraft Takeoff Performance in a Changing Climate for Canadian Airports

Temperature and wind are major meteorological factors that affect the takeoff and landing performance of aircraft. Warmer temperatures and the associated decrease in air density in future climate, and changes to crosswind and tailwind, can potentially impact aircraft performance. This study evaluates projected changes to aircraft takeoff performance, in terms of weight restriction days and strong tailwind and crosswind occurrences, for 13 major airports across Canada, for three categories of aircraft used for long-, medium- and short-haul flights. To this end, two five-member ensembles of transient climate change simulations performed with a regional climate model, for Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios, respectively, are analyzed. Results suggest that the projected increases in weight restriction days associated with the increases in daily maximum temperatures vary with aircraft category and airfield location, with larger increases noted for airfields in the south central regions of Canada. Although avoiding takeoff during the warmest period of the day could be a potential solution, analysis focused on the warmest and coolest periods of the day suggests more weight restriction hours even during the coolest period of the day, for these airfields. Though RCP8.5 in general suggests larger changes to weight restriction hours compared to RCP4.5, the differences between the two scenarios are more prominent for the coolest part of the day, as projected changes to daily minimum temperatures occur at a much faster rate for RCP8.5 compared to RCP4.5, and also due to the higher increases in daily minimum temperatures compared to maximum temperatures. Both increases and decreases to crosswind and tailwind are projected, which suggest the need for detailed case studies, especially for those airfields that suggest increases. This study provides useful preliminary insights related to aircraft performance in a warmer climate, which will be beneficial to the aviation sector in developing additional analysis and to support climate change adaptation-related decision-making.

저고도 운용 항공기를 위한 기상정보의 필요성에 관한 연구

According to the Ministry of Land, Infrastructure and Transport press release ('18.12.21.) The amendment of the Aviation Business Act will reduce the capital requirements for aviation leisure operators and make it easier to enter aviation leisure businesses by improving regulations on small air transportation business. In addition, as the scale of the UAV(Unmanned Aerial Vehicle) sector is expected to increase globally, the dramatic increase in low altitude operating aircraft, including this, must be taken into account. The low altitude aircraft category is divided into small airplanes, helicopters, light aircrafts and ultra-light aircrafts, and instructors include school instructor pilots and student pilots, military and national helicopter pilots, and aviation leisure operators. In case of low altitude aircraft, there are cases of canceling operations due to low visibility and low clouds, and aircraft accidents due to excessive operation and sudden weather phenomenon. Therefore, in order to prevent low-altitude aircraft accidents, a safe flight plan based on weather conditions and weather forecasts and more accurate and local weather forecasts and weather forecast data are needed to prepare for the rapidly changing weather conditions.

Stochastic Runway Scheduling Problem With Partial Distribution Information of Random Parameters

Air traffic flow management is one of the most important operations in terminal airports heavily relying on advanced intelligence transportation techniques. This work considers a two-stage runway scheduling problem given a set of flights with uncertain arrival times. The first-stage problem is to identify a sequence of aircraft weight classes (e.g., Heavy, Large and Small) that minimizes runway occupying time (i.e., makespan). Then the second-stage decision is dedicated to scheduling the flights as punctually as possible after their arrival times realized, which translates into determining a sequence of flights for each aircraft category such that the total deviation time imposed on the flights is minimized. Instead of an exactly known probability distribution, information on uncertain parameters is limited (i.e., ambiguous), such as means, mean absolute deviations and support set of random parameters derived from historical data. Under this information on the random parameters, an ambiguous mixed-integer stochastic optimization model is proposed. For such a problem, we approximately construct a worst-case discrete probability distribution with three possible realizations per random parameter, and adopt a hybrid sample average approximation algorithm in which genetic algorithms are used to replace commercial solvers. To illustrate the effectiveness and efficiency of the proposed model and algorithm, extensive numerical experiments are carried out.

The prospects of hybrid-electric regional air transport - an assessment of travel time benefits of domestic short-haul flights in Germany with 19-seater aircraft

Aviation policy in the EU aims at improving connectivity and reducing environmental impacts. New propulsion systems that are locally free of emissions, e.g. with battery or hydrogen powered designs may contribute to this objective. Initial research suggests that such innovations are best applied in commuter aircraft with up to 19 seats. However, the market for these aircraft has been steadily declining since the end of the 1990s. In this paper, the authors analyze the prospects of re-vitalizing this aircraft category by applying an innovative business model, using hybrid-electric commuter aircraft designed in a cooperative project between Bauhaus Luftfahrt and the German Aerospace Center (DLR) in order to contribute to both objectives. The aircraft, based on characteristics of the BAe Jetstream 31, features a full electric range of approximately 200 km at a payload of 16 passengers, increasing to 1250 km, when the jet fuel-based range extender is used. The potential use of such a hybrid-electrically powered regional aircraft for regional air transport services from smaller airfields is demonstrated from a demand perspective. Travel time benefits are quantified alongside initial demand potentials, based on forecasts for 2030 at the regional pair level as provided by the German Federal Transport Plan.

Preliminary Design of a Model-Free Synthetic Sensor for Aerodynamic Angle Estimation for Commercial Aviation.

Heterogeneity of the small aircraft category (e.g., small air transport (SAT), urban air mobility (UAM), unmanned aircraft system (UAS)), modern avionic solution (e.g., fly-by-wire (FBW)) and reduced aircraft (A/C) size require more compact, integrated, digital and modular air data system (ADS) able to measure data from the external environment. The MIDAS project, funded in the frame of the Clean Sky 2 program, aims to satisfy those recent requirements with an ADS certified for commercial applications. The main pillar lays on a smart fusion between COTS solutions and analytical sensors (patented technology) for the identification of the aerodynamic angles. The identification involves both flight dynamic relationships and data-driven state observer(s) based on neural techniques, which are deterministic once the training is completed. As this project will bring analytical sensors on board of civil aircraft as part of a redundant system for the very first time, design activities documented in this work have a particular focus on airworthiness certification aspects. At this maturity level, simulated data are used, real flight test data will be used in the next stages. Data collection is described both for the training and test aspects. Training maneuvers are defined aiming to excite all dynamic modes, whereas test maneuvers are collected aiming to validate results independently from the training set and all autopilot configurations. Results demonstrate that an alternate solution is possible enabling significant savings in terms of computational effort and lines of codes but they show, at the same time, that a better training strategy may be beneficial to cope with the new neural network architecture.

Numerical simulation and experimental validation of slender wings flutter behaviour

The flutter instability of high aspect ratio wings is numerically investigated by means of finite element aeroelastic analysis. The effect of static equilibrium deflection as well as the additional differential stiffness was introduced in the calculation by a new procedure based on MSC Nastran™ commercial code. The difference between the classic linear flutter calculation and the new procedure presented has been demonstrated numerically and also experimentally. The main parameters that influence the aeroelastic phenomenon were also highlighted and used to define the aeroelastic similarity model related to a typical aircraft of the high altitude long endurance aircraft category.