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Extensive research in recent years has focused on improving the current loss-of-control prevention systems and developing new strategies for safe path planning of the impaired aircraft. Success in developing such systems requires a comprehensive perception of the influence of damage on the aircraft’s dynamic behaviour and performance, and the effect of various failure degrees on the flight envelope confinement and the remaining safe maneuvers. This paper comprehensively describes the effects of lateral control surface failure on the NASA Generic Transport Model (GTM) flight envelope, defined by a set of attainable steady-state maneuvers herein referred to as trim points. The study utilises a large database of high-fidelity maneuvering flight envelopes computed for the unimpaired case and wide ranges of the aileron and rudder failure cases at different flight conditions. Flight envelope boundary is rigorously investigated, and the key parameters confining the trim points at different boundary sections are identified. Trend analyses of the impaired flight envelopes and the corresponding limiting factors demonstrate the effect of various failure degrees on the remaining feasible trim points. Results can be employed in emergency path planning with potential uses in the development of aircraft resilient control and upset recovery systems.
This work investigates the propeller’s influence on the stability of High Altitude Long Endurance aircraft, incorporating all resultant loads at the propeller hub, propeller slipstream, and gyroscopic loads. Such effects are usually neglected in the aeroelastic simulation of HALE aircraft. For that goal, a previously developed framework, which couples a geometrically nonlinear structural solver with an Unsteady Vortex Lattice method (uVLM) for lifting surfaces and a Viscous Vortex Particle (VVP) method for propeller slipstream, was employed to generate time-data series. Also, a method, based on a combination of Proper Orthogonal Decomposition and system identification, to extract dynamic information (frequencies, damping, and modes) of the aircraft from a time-series signal is proposed and successfully tested for a purely structural case, for which reference data is available. The method is then applied to investigate the stability of aeroelastic cases. The results demonstrate that the presence of propellers can influence the aeroelastic stability of a Very Flexible Aircraft.
In the present study, fuzzy uncertainty and reliability analysis of aeroelastic aircraft wings are investigated. The uncertain air speed and structural parameters are represented by fuzzy triangular membership functions. These uncertainties are propagated through the wing model using a fuzzy interval approach, and the uncertain flutter speed is obtained as a fuzzy variable. Further, the reliability of the wing flutter is based on the interference area in the pyramid shape defined by the fuzzy flutter speed and air speed. The ratio between the safe region volume and the total volume of the pyramid gives the reliability value. Two different examples are considered—a typical wing section, and a clean wing—and the results are given for various wind speed conditions. The results show that the approach considered is a low-cost but suitable method to estimate the reliability of the wing flutter speed in the presence of uncertainties.
Aircraft conflict resolution is an important part of air traffic control operations. This study presents a mixed integer linear programming model (MILP) using a space discretisation technique to deal with aircraft conflict resolutions in en-route flight operations. The purpose of space discretisation is to concentrate on only the significant points of the airspace. The model integrates the multi entry point approach with an airspeed adjustment technique in the horizontal plane. The model aims to generate conflict-free trajectories while minimising the total changes in entry points and airspeed values. A new heuristic algorithm was developed due to the complexity of the problem. The computational results demonstrated that the proposed approach resolved aircraft conflicts for 450 different traffic scenarios in less than a minute. Considerable fuel savings were achieved with no significant increase in delay or flight time compared to conventional vectoring techniques in a fixed entry point airspace structure.
This paper focuses on the problem of skin corrosion on the upper wing surfaces of rib-stiffened aircraft. For maritime and military transport aircraft this often results in multiple co-located repairs. The common approach to corrosion damage in operational aircraft is to blend out the corrosion and rivet a mechanical doubler over the region. In particular this paper describes the results of a combined numerical and experimental investigation into the ability of the additive metal technology, Supersonic Particle Deposition (SPD), to restore the load-carrying capacity of rib-stiffened wing planks with simulated skin corrosion. The experimental results reveal that unrepaired skin corrosion can result in failure by yielding. The experimental results also reveal that SPD repairs to skin corrosion can restore the stress field in the structure, and can ensure that the load-carrying capability of the repaired structure is above proof load.
This paper presents a review of the various aeronautical air conditioning systems that are currently available and discusses possible system configurations in the context of the aeronautical environmental control systems. Descriptions of the standard vapor compression cycle and air cycles are provided. The latter includes, simple-cycle, bootstrap-cycle, simple-bootstrap cycle (3-wheel) and condensing cycle (4-wheel). Water separation and air recirculation systems are also explored. A comparison between vapor compression cycles and air cycles is provided, as well as a comparison between different air cycles. Air cycle units are far less efficient than vapor compression cycle units, but they are lighter and more reliable for an equivalent cooling capacity. Details regarding the aircraft conceptual design phase along with general criteria for the selection of an air conditioning system are provided. Additionally, industry trends and technological advances are examined. Conclusions are compiled to guide the systems engineer in the search for the most appropriate design for a particular application.
The range of small, electrically powered UAVs is still limited by the mass specific energy of batteries. This paper investigates the idea that, in cases where multiple aircraft must transit to the same location, savings in mass or an extension of achievable range are possible when they join wingtip-to-wingtip. The viability of joined flight is investigated by quantifying the relative magnitude of savings resulting from increased aerodynamic efficiency and that of penalties due to the increased structural and component weights. Through a parametric analysis the level of savings achievable is found to be greatly dependent on the proportion of the flight spent in a joined configuration and aircraft design parameters such as wing loading, aspect ratio and the added weight of the joining mechanism. A custom, multidisciplinary UAV sizing algorithm is presented and utilised to design several sample aircraft, featuring two different joining mechanism architectures. The results verify the findings of the parametric study and indicate that mass savings are possible only for moderate to low aspect ratios, with semi-permanent magnetic joining mechanism performing better than rigid structural ones, even when the joined fight segment accounts for only 30% of the total airborne time.
Exergy efficiency can be used as an objective function in order to improve systems efficiency. Thus, the most efficient regions for the operation parameters can be searched easily. Exergy efficiency data of a turboprop engine’s components that have been calculated using basic engine parameters in the previous studies are modeled using cubic spline curve fitting methodology. Spline curves are on the two dimensional plane, where x axis is the input parameter and y axis is the exergy efficiency of the component. A spline curve is defined by the points subject to arbitrary selection of number and position. Initially positions of the points are located with two different methods and then in order to obtain better accuracy point positions are improved by ‘Ant colony’ and ‘Goldsection’ optimisation methods. Sum of Squares of the errors between the fitted value and data value was used as the fitness function. Least square error of 5 × 10−9 is assumed as acceptable accuracy which yields to a minimum R = 0.9998 linear correlation coefficient. In the optimisation step, independent engine variable versus calculated engine performance parameters were checked against spline fitted values. Improvement of the fitness function is observed as the number of fitting points is increased. Ant colony optimisation in engine exergy efficiency parametric modeling is a new approach in authors’ point of view.
The ever-growing need to improve manufacturing processes has led recently to an increase in the number of automation solutions used to assemble aircraft structural elements. A process of interest to this industry is the alignment of fuselage sections, which is currently done either manually or by complex, expensive automated systems. The manual method introduces a significant production delay and most automated systems have limited flexibility. This article presents an integration solution implemented in an alternative low-cost, high-flexibility alignment robotic cell. The performance of an optical coordinate measuring machine (CMM) as feedback source for the adaptive control of a conventional industrial manipulator is assessed. Laser interferometry readings are used as reference. The contribution of the work lies in the execution of experiments based on the EN ISO 9283 standard (Manipulating industrial robots - performance criteria and related test methods) to determine the adequacy of the commercial off-the-shelf system to the tolerances and requirements of the fuselage alignment process at hand. The optimal configuration of the integrated system attained the nominal alignment position with an average accuracy of 0.16mm and
, partially meeting the required tolerances, and the obtained values are nearly 16x better compared to a baseline, open-loop manipulator. These results serve as reference for the aerospace industry in the development of the next generation of tools and automated assembly processes.
This paper deals with the study of the power matching of the propulsion system and on-board systems changing the on-board systems’ electrification level. In particular, four system architectures have been studied, each one with a different level of electrification starting from the More Electric Aircraft (MEA) to the All Electric Aircraft (AEA) systems. The mass and the power requirement of each system architectures have been analysed together with the change in engine specific fuel consumption. Then, these results have been used to quantify the influences of engine and systems power matching to the entire aircraft. In particular, the beneficial effect of system electrification has been evaluated as an increment of aircraft range. Moreover, two reference aircraft – a regional jet and a short/medium range liner – have been selected to understand the variance of the power matching changing aircraft dimensions and mission range. The study is carried out using a distributed and collaborative Multi-Disciplinary Design Analysis and Optimization (MDAO) environment. The results show a beneficial effect of systems electrification on systems mass and engine specific fuel consumption. At aircraft level, the results point out an increment of aircraft range up to 7.7% with a different trend for the two studied cases.
Aircraft full-scale fatigue tests are expensive and time-consuming to conduct but are a critical item on the certification path of any aircraft design or modification. This paper outlines a proposal that trades cycling hours for increased detail in the teardown of a metallic test article. A method for determining the equivalent demonstrated crack size (and crack growth curve) at the mandated test life utilising the lead crack framework is demonstrated. It is considered that the test duration can be significantly reduced, whilst still achieving all the desired outcomes of a certification program.
The WTO concluded in 2012 that subsidized aeronautical research and development (R&D) gave Boeing a head start in product development that caused serious prejudice to the interests of Airbus but later, in 2019, it could not decide how long that head start had lasted. Meanwhile, the WTO concluded in 2018 that launch aid for Airbus aircraft led to innovations that also improved later aircraft models, thereby contributing to serious prejudice to the interests of Boeing. Both conclusions relied on a causation analysis that considered the effects of technological innovation, which makes subsidies used for R&D particularly vulnerable to challenge. This novel analysis may be too broad for the actionable subsidy disciplines of the SCM Agreement.
This study is aimed at establishing a linear holding (LH) procedure instead of a conventional air holding stack to minimize the effects of airborne delays in terms of air traffic management and fuel consumption. This paper uses both actual flight data and the Base of Aircraft Database (BADA) model to obtain fuel consumption for level flight and descent segments, separately.
The total fuel savings obtained by using actual flight data (16%) and the BADA model (10%) indicate that the LH is found to be more advantageous compared to a conventional holding procedure. Furthermore, the recommended LH procedure could be a promising solution for keeping aircraft in a narrow area that could be considered to be an effective method for airspace usage.
The increasing environmental requirements in the air transport sector pose great challenges to the aviation industry and are key drivers for innovation. Besides various approaches for increasing the efficiency of conventional gas turbine engines, electric propulsion systems have moved into the focus of aviation research. The first electric concepts are already in service in general aviation. This study analyses the potentials of electric and turbo hybrid propulsion systems for commercial aviation. Its purpose is to compare various architectures of electrical powertrains with a conventional turboprop on a regional aircraft, similar to the ATR 72, on engine and flight mission levels. The considered architectures include a turbo-electric (power controlled and direct driven), hybrid-electric (serial and parallel) and a pure electric concept. Their system weights are determined using today’s technology assumptions. With the help of performance models and flight mission calculations the impact on fuel consumption, CO
emissions and aircraft performance is evaluated.
One of the challenges of modern engineering design is the amount of data that designers must keep track while performing system analysis and synthesis. This task is particularly important in the design process of complex systems such as novel aerospace systems where Modeling and Simulation play an essential role. The Agile philosophy stems from the field of Software Engineering and describes an approach to development in which requirements and solutions gradually develop through collaboration between self-organising cross-functional teams and end users. Agile Model-Based System Engineering (AMBSE) is the application of the Agile philosophy to Model-Based System Engineering. In this paper, AMBSE is accomplished through the application of the Object-Oriented System Engineering Method (OOSEM). OOSEM employs a top-down scenario-driven process that adopts System Modeling Language (SysML) and leverages the object-oriented paradigm to support the analysis, specification, design, and verification of systems. AMBSE assisted by mathematical modelling and safety assessment techniques is applied to the first design iterations of the main aircraft systems, allowing a comprehensive design exploration. The flight control system was chosen to illustrate the procedure in detail, emphasising the synthesis of a six-degrees-of-freedom model augmented by dynamic inversion control for a hypothetical supersonic transport aircraft satisfying class II MIL-F-8785C handling qualities. It is concluded that AMBSE presents promising properties to support future aircraft development within the current regulatory framework for aircraft design, while enabling a smooth transition from conceptual to preliminary design.
Usage of composite materials is ubiquitous in the modern world. While global tonnages are still well below those of steel, they now find a wider range of applications and their value is starting to become comparable to that of steel products. As low weight and energy efficiency become increasingly important, this trend is likely to accelerate. In this chapter, the objective is to identify some of the issues involved in commercial exploitation of composites. This is done by means of case studies drawn from various industrial sectors. The examples cover a range of composite type, engineering complexity, manufacturing route, market size and competitive position relative to more traditional materials.
An important prerequisite for the design, assessment and certification of aircraft and their associated control systems is a quantitative specification of the environment in which the aircraft is intended to operate, for example, atmospheric gust. Gust loads on aircraft may induce detrimental influences such as increased aerodynamic and structural loads, structural deformation and decreased flight dynamic performance. This paper presents a systematic and comprehensive overview of important concepts and applications of gust loads on aircraft. This overview includes a brief research background, concepts, research techniques, influences and load alleviation measures of gust. Finally, we summarise some potential improvements in the future work. It is also recommended to learn from previous experiences to avoid aviation accidents due to flight through atmospheric gusts and turbulence.
System software subsystems in an unmanned aircraft system share hardware resources due to space, weight, and power constraints. Such subsystems have different criticality, requirements, and failure rates, and can cause undesired interference when sharing the same hardware. A component with high failure rate can reduce the reliability of the system unless a fault containment mechanism is adopted.
This work proposes an asymmetric multiprocessor architecture to establish isolation at the hardware level for distributed implementation of safety-critical subsystems along with user defined payload subsystems on the same hardware with minimally reduced reliability of the system. To achieve that, subsystems are strategically segregated in separate processors, connected to an on-chip protective interconnect for inter-processor communications. A custom watchdog and reset mechanism are implemented to reset a specific processor without affecting the entire system if required. The architecture is demonstrated on a FPGA chip. In addition, an example of an optimised distribution is provided for a specific flight control system with five subsystems.
Aeronautic Pitot probes (PPs) are extremely important for airspeed and altitude measurements in aviation. Failure of the instrument due to clogging caused by ice formation can lead to dangerous situations. In this work, a commercial aeronautic PP was characterised experimentally regarding its inner composition, material properties and its thermal performance in a climatic wind tunnel. Performance runs were taken out in order to analyse the thermal response of the PP under various operating conditions with a particular emphasis on the cooling process in the case of a heating element failure. Data for the thermal conductivity, diffusivity and specific heat for each material forming the PP were obtained. A numerical model to simulate the thermal behaviour of the PP was created using Comsol Multiphysics (CM). Experimental data were compared with their numerical counterparts for model validation purposes. After the model was validated, the operation of the PP in flight conditions was simulated. The failure of the conventional heating system was analysed to obtain the time until the PP reaches a tip temperature where ice formation can be expected. The tip temperature undercut the zero degrees Celsius mark 165 seconds after the heating element was switched off. The data collected in this work can be used to implement and validate mathematical models in order to predict the thermal performance of Pitot probes in flight conditions.
Generally, earth rotating and non-spherical perturbation of the earth in re-entry motion model are simplified using the standard trajectory guidance method. The re-entry motion is also simplified to horizontal motion and vertical motion and controlled, respectively. The simplification of re-entry motion model will lead to loss of motion accuracy and location accuracy. The direct decomposition will lead to the reduction of control accuracy because the horizontal motion and the vertical motion are coupled in re-entry. To improve the standard trajectory guidance method, the standard trajectory guidance method based on decoupling control variables and waypoint is proposed in this paper. The proposed guidance method will not simplify earth rotating and non-spherical perturbation of the earth in motion equation or decompose the re-entry motion to horizontal motion and vertical motion. Trajectory waypoint is adopted to reduce the change frequency of tracking states, because tracking states change frequently if the entire standard trajectory is tracked in real time.