Aeronautical Design Research Articles

Advancements in Lightweight Materials for Aerospace Structures: A Comprehensive Review

The aerospace engineering field is witnessing an evolution towards lightweight materials driven by the unwavering pursuit of improved performance and efficiency. Lightweight materials play a critical role in aerospace structures, and this thorough examination explores their significant influence on mission success, design, and fuel efficiency. Key developments in several material categories such as composites, metals, and polymers are methodically examined in this study, revealing their special qualities and potential uses. The historical viewpoint lays out a chronology of the development of materials, charting significant turning points that have influenced the use of lightweight materials in aerospace. The following sections delve into each lightweight material in great detail, explaining composites, alloys (including titanium, aluminium, and high-strength steel), and sophisticated polymers, along with their features, production methods, and uses. An examination of particular varieties and production nuances in the context of aerospace composite materials highlights their benefits in achieving unmatched strength-to-weight ratios. By elucidating their qualities and expanding uses in aircraft constructions, advanced metallic alloy research reveals the most recent advancements in materials like titanium and aluminium. A thorough examination of polymeric materials and nanocomposites reveals their critical role in the creation of lightweight structures. Their distinctive qualities and new uses are emphasized, highlighting their role in the ongoing revolution in aeronautical design. With a comprehensive examination of additive manufacturing and sophisticated machining methods essential to the realization of lightweight aircraft structures, innovative manufacturing technologies take center stage. Additionally, the assessment thoroughly evaluates the longevity and structural integrity of lightweight materials, addressing issues related to corrosion, fatigue, and other crucial elements. Investigations from actual applications provide concrete instances of lightweight materials being successfully used in aerospace projects, shedding light on the materials' performance and tangible advantages in various situations. Looking ahead, the paper's conclusion forecasts forthcoming developments in lightweight materials and clarifies possible obstacles and future research avenues that may influence the course of aerospace engineering. To underscore the critical role that lightweight materials play in aeronautical constructions, this paper synthesizes a variety of knowledge. It highlights the revolutionary potential of lightweight materials in influencing the future of aeronautical engineering, not only synthesizing current knowledge but also laying out a path for further study and innovation.

A Nonlinear Beam Finite Element with Bending–Torsion Coupling Formulation for Dynamic Analysis with Geometric Nonlinearities

Vibration analysis of wing-box structures is a crucial aspect of the aeronautic design to avoid aeroelastic effects during normal flight operations. The deformation of a wing structure can induce nonlinear couplings, causing a different dynamic behavior from the linear counterpart, and nonlinear effects should be considered for more realistic simulations. Moreover, composite materials and aeroelastic tailoring require new simulation tools to include bending–torsion coupling effects. In this research, a beam finite element with bending–torsion coupling formulation is used to investigate the effects of the deflection of beam structures with different aspect ratios. The nonlinear effects are included in the finite element formulation. The geometrical effect is considered, applying a deformation dependent transformation matrix. Stiffness effects are introduced in the stiffness matrix with Hamilton’s Principle and a perturbation approach. The results obtained with the beam finite element model are compared with numerical and experimental evidence.

Handling Qualities Assessment and Performance Evaluation for Unmanned Aerial Systems and Pilots

When fly-by-wire controls first appeared, much research focused on how to evaluate control laws and bare airframes for airworthiness given the reliance on electronic augmentation. Similarly, handling qualities and methods of evaluation for novel flying vehicles have been discussed whenever novel designs are developed. In the last 20 years, with the proliferation of unmanned aircraft systems (UAS), much research has focused on transferring existing methods of performance evaluation and airworthiness assessment to accommodate the unique feature of many UAS. However, the changes in sensory information and pilot experience levels require examining the aircraft and pilots together in a holistic manner. In this work, the authors present the results of a broad study focused on evaluation of both pilot skill and aircraft performance in a holistic way. In this study, the skill of the remote pilot is considered as well as the effectiveness of the electronic flight control system because the evaluation is conducted on the system at-large as opposed to considering each piece individually. An evaluation approach using mission-task-elements (MTEs), like that used within Aeronautical Design Standard-33 Handling Qualities Requirements for Military Rotorcraft (ADS-33), is developed and presented for UAS. In the study, new UAS pilots were evaluated before, during, and after an intensive training program using qualitative measures (like Cooper–Harper rating) and quantitative measurements (like elapsed time) of their performance while flying the prescribed MTEs. The techniques described can provide insight into pilot performance, airframe airworthiness, and effectiveness of stability systems in an efficient test program and the results are inherently easy to understand in the context of MTEs.

Automatic separation of laminar-turbulent flows on aircraft wings and stabilisers via adaptive attention butterfly network

Many of the laminar-turbulent flow localisation techniques are strongly dependent upon expert control even-though determining the flow distribution is the prerequisite for analysing the efficiency of wing & stabiliser design in aeronautics. Some recent efforts have dealt with the automatic localisation of laminar-turbulent flow but they are still in infancy and not robust enough in noisy environments. This study investigates whether it is possible to separate flow regions with current deep learning techniques. For this aim, a flow segmentation architecture composed of two consecutive encoder-decoder is proposed, which is called Adaptive Attention Butterfly Network. Contrary to the existing automatic flow localisation techniques in the literature which mostly rely on homogeneous and clean data, the competency of our proposed approach in automatic flow segmentation is examined on the mixture of diverse thermographic observation sets exposed to different levels of noise. Finally, in order to improve the robustness of the proposed architecture, a self-supervised learning strategy is adopted by exploiting 23.468 non-labelled laminar-turbulent flow observations.

The Importance of Patents in Aeronautical Design

The Importance of Patents in Aeronautical Design

Development and Flight Validation of Proposed Unmanned Aerial System Handling Qualities Requirements

Unmanned aerial systems, commonly known as drones, present new opportunities to perform autonomous tasks. Handling qualities requirements for manned vertical lift aircraft have been well defined and documented. The need to define handling qualities requirements for vertical take-off and landing (VTOL) unmanned aerial systems (UAS) to meet mission demands is of paramount importance for all potential operators and procurement agencies. One way to relate handling qualities specifications of large-scale manned and subscale unmanned aircraft is through Froude dynamic scaling. Froude dynamic scaling based on hub-to-hub distance has shown great promise in relating the natural frequencies of scaled multicopters. There have been recent efforts to develop a VTOL-UAS handling qualities standard by scaling mission task elements and rating their performance through a Trajectory, Tracking, and Aggression (TTA) score. This paper proposes a new performance standard adapted from the TTA scoring method, along with a modified Cooper–Harper scale as a VTOL-UAS handling qualities framework that is consistent with the spirit of Aeronautical Design Standard 33 (ADS-33). These newly proposed performance standards were then validated through simulation and flight testing on a small hexacopter UAS, flown at the University of Portland. A key outcome of this work is the flight verification of a key dynamic response metric, the disturbance rejection bandwidth, and associated validation of Froude scaling for predicted handling qualities metrics.

Control surface design for radio-controlled aircraft. Case: SAE Aero Design Micro-class prototype

This research article presents a design methodology for primary control surfaces (Ailerons, Rudder and Elevator) for experimental unmanned radio-controlled aircraft. The methodology is based on the proposal and standardization of the required mechanical and aerodynamic analysis for each control surface sizing, considering the SAE Aero Design competition objectives within Micro Class. It is used on empirical results previously described in references about aeronautical design, computerized fluids dynamics (CFD) software, and aircraft controllability regulations in order to obtain the design variables. Based on this information, the iteration sequences required for design were automated by a C++ language code to obtain the optimal characteristics for each surface, thereby reducing the possibility of calculation errors, overall time, and workload invested in the design process. The application of the methodology to the latest aircraft design reduced the total control systems weight to the aircraft’s empty weight ratio to a minimum of 3.4%.

Large eddy simulation of aircraft at affordable cost: a milestone in computational fluid dynamics

Abstract While there have been numerous applications of large eddy simulations (LES) to complex flows, their application to practical engineering configurations, such as full aircraft models, have been limited to date. Recently, however, advances in rapid, high quality mesh generation, low-dissipation numerical schemes and physics-based subgrid-scale and wall models have led to, for the first time, accurate simulations of a realistic aircraft in landing configuration (the Japanese Aerospace Exploration Agency Standard Model) in less than a day of turnaround time with modest resource requirements. In this paper, a systematic study of the predictive capability of LES across a range of angles of attack (including maximum lift and post-stall regimes), the robustness of the predictions to grid resolution and the incorporation of wind tunnel effects is carried out. Integrated engineering quantities of interest, such as lift, drag and pitching moment will be compared with experimental data, while sectional pressure forces will be used to corroborate the accuracy of the integrated quantities. Good agreement with experimental $C_L$ data is obtained across the lift curve with the coefficient of lift at maximum lift, $C_{L,max}$ , consistently being predicted to within five lift counts of the experimental value. The grid point requirements to achieve this level of accuracy are reduced compared with recent estimates (even for wall modelled LES), with the solutions showing systematic improvement upon grid refinement, with the exception of the solution at the lowest angles of attack, which will be discussed later in the text. Simulations that include the wind tunnel walls and aircraft body mounting system are able to replicate important features of the flow field noted in the experiment that are absent from free air calculations of the same geometry, namely, the onset of inboard flow separation in the post-stall regime. Turnaround times of the order of a day are made possible in part by algorithmic advances made to leverage graphical processing units. The results presented herein suggest that this combined approach (meshing, numerical algorithms, modelling, efficient computer implementation) is on the threshold of readiness for industrial use in aeronautical design.

Additive Manufacturing and Augmented Reality as New Production Technologies in the Aviation Industry

Abstract: The image of the global aviation industry is dramatically changing. This derives in the first instance from dynamic development of the military and civil aircraft market, where a significant growth in demand and an increase in airliner deliveries over the next 15 years by at least 80% was forecasted. Aircraft manufacturers' revenues in services business, including maintenance, repair and overhaul (MRO) are boosting, too. All this provide favorable conditions for the development of new production technologies in the aviation sector, including Additive Manufacturing (AM) and Augmented Reality (AR). Though the research and development in the field of AM an AR began in the 1980s, only in the last decade AM and AR technologies have reached the necessary level of maturity to be widely used in design, manufacturing and assembly processes in aeronautics, including civil and military aircraft. There are good prospects for their use in aircraft’ maintenance, repair and overhaul as well. The transition from the initial period of formation of AM and AR technologies to the stage of technological growth and rapid development of relevant markets is evidenced by a number of factors. First of all, they include establishment of "dominant" technological designs based on AM and AR (certified additive production methods, new materials based on AM and machines for their production, special Augmented Reality headsets, etc.), as well as beginning of serial production of many AM-components and AR-platforms for the aviation industry. The participation of major aircraft manufacturers such as Boeing and Airbus in AM and AR R&D projects, the formation of "new" supply chains, the development of public-private partnerships (e.g. NAMII in the U.S.), as well as the formation of consortia and alliances of companies that develop and produce systems and parts for aircraft based on additive technologies and augmented reality, are also indicators of the transition to a new stage of development of these technologies and markets.

Design parameters and associated quantitative damage analyses of an asphalt concrete airfield runway

Design parameters and evaluation of associated mechanical behavior of an airfield runway asphalt concrete pavement structure is reported. French aeronautical design methodology was taken as reference. Field and laboratory procedures were employed to determine constituent materials of the designed structure. Stationary linear elastic and dynamic viscoelastic numerical damage analyses were developed and compared, using computerized tools based on 3D Finite Element Methods. Results indicate that viscoelastic analyses provide more discriminating assessment of damage phenomena along the depth of pavement layers, and that landing gear geometric characteristics are more diagnostic than aircraft gross weight for cumulative damage propagation.

Comparative study of symmetrical Vs asymmetrical Vs semi-symmetrical airfoils

Airfoils are the cross-section of the wing or blade. Extensive research in the maximum L/D ratio is crucial as faster travel is the need of the hour for developing faster and more efficient aircraft, for the military as well as transportation purposes. Hence to find the best aerodynamic property, we will study the 3 types of airfoils. Through this paper, the intention is to find out the best airfoil which can be applied for use. In this study, the comparison between symmetric, anti-symmetric, and semi symmetric airfoil characteristics are made using ANSYS Fluent. ANSYS Fluent offers us a platform to make simulations. Codes have been fed into the MATLAB software to generate the required coordinates. Airfoil design upholds great importance in modern-day design in aeronautics. The airfoils were designed using NACA guidelines and compared. This paper aims to find the advantages and disadvantages of the 3 different airfoils. The airfoils examined are made using coordinates derived from the NACA 4-digit series. Four different pitch angles were used: 0°, 2°, 4°, 8° to best replicate real-life applications. The main purpose of this is to find which of the 3 airfoils is the best based on Cd and Cl values for different attack angles. The Reynolds Number for each simulation will be the same for uniformity in the experiment. A high value of Reynold’s Number will be taken in the scale 106. Each airfoil cross-section was studied.

Теплообмен и трение в тонком воздушном ламинарном пограничном слое над поверхностью полусферы

A qualitative solution to the problem of calculating convective heat transfer can be obtained only by numerically integrating the differential equations of the boundary layer, which is associated with overcoming a number of computational problems. Consequently, it is important to develop relatively simple, but fairly high-precision calculation methods. As a first approximation to solving this problem, we can consider the use of the effective length method. From the practical point of view, this method is characterized by satisfactory accuracy of calculating convective heat transfer, which has led to its widespread use in aeronautical design engineering. However, this method is also characterized by a relatively high complexity, although it is much lower than that in numerical integration of the differential equations of the boundary layer. The most effective approach to solving heat transfer and friction problems in engineering practice is to use simple algebraic formulae obtained on the basis of approximating the results of rigorous numerical calculations, or experimental studies. Unfortunately, there is no information in literary sources about the accuracy of these formulae under various conditions of product functioning. This problem is solved on the basis of a systematic numerical calculation of the equations of the boundary layer in the most rigorous theoretical calculation, as well as a detailed analysis of the accuracy of the obtained algebraic formulae and their literary analogues

Incremental Nonlinear Dynamic Inversion for the Apache AH-64 Helicopter Control

Incremental nonlinear dynamic inversion (INDI)-based controller is a promising technique that can be adopted to control dynamic systems with high nonlinearities and extended cross-coupling effects. This paper presents the incremental strategy adopted as a sensor-based controller approach for the Apache AH-64D Longbow helicopter. The strength of the INDI sensor– based approach is that it does not require a detailed vehicle model as it uses only a control effectiveness model and estimates of the vehicle angular accelerations replacing the rest of the model. The weakness is its sensitivity to measurement and actuator delays, demanding additional estimations of model parameters and control effectiveness tuning. Using the Boeing FLYRT Apache model to simulate the vehicle dynamics, the paper has developed three adaptation schemes connecting the INDI sensor–based approach to the Apache partial control authority set as ±20% authority in all axes. The goal was to redesign the existing Apache's flight control systems and demonstrate handling qualities improvements for hover and low-speed flight in normal and degraded visual environment. Implementing the attitude command attitude hold and translational rate command response types in the system through the INDI controller, the paper demonstrates that improvements from Level 2 to Level 1 handling qualities can be achieved when flying the Aeronautical Design Standard-33 (ADS-33E-PRF) hover and pirouette maneuvers in a degraded visual environment.

Investigation of Material Properties Effect on the Ovalization Phenomenon in the Tube Bending Produced by RDB

Rotating draw twisting (RDB) is among the best-known techniques utilized for cylinder shaping. Twisting profiles are utilized in most mechanical fields, including car design, aeronautic design, plant building, fluid transport, heat exchangers and many other sectors. Ovalization affects the nature of cylinder bowing. It occurs in the cross segment of the cylinder in the wake of bowing when the cylinder has twisted without a mandrel, or with a change of mandrel structure. This paper examines the ovalization phenomenon in cylinder bowing with turning draw twisting procedure and utilizing distinctive material properties (types of material: 1.4301(2x40), 1.0036(2x40), 6060T7(2.5x40), 1.4301(4x40), 1.0038(4x40), 1.5415(7.1x51) and 1.7380(7.1x51)). The finite element method (FEM) and experimental tests are applied to compute the ovalization proportions. This investigation helps to distinguish the impact of the material properties.

An automatic system for a helicopter autopilot performance evaluation

PurposeThe purpose of this paper is to elaborate and develop an automatic system for automatic flight control system (AFCS) performance evaluation. Consequently, the developed AFCS algorithm is implemented and tested in a virtual environment on one of the mission task elements (MTEs) described in Aeronautical Design Standard 33 (ADS-33) performance specification.Design/methodology/approachControl algorithm is based on the Linear Quadratic Regulator (LQR) which is adopted to work as a controller in this case. Developed controller allows for automatic flight of the helicopter via desired three-dimensional trajectory by calculating iteratively deviations between desired and actual helicopter position and multiplying it by gains obtained from the LQR methodology. For the AFCS algorithm validation, the objective data analysis is done based on specified task accomplishment requirements, reference trajectory and actual flight parameters.FindingsIn the paper, a description of an automatic flight control algorithm for small helicopter and its evaluation methodology is presented. Necessary information about helicopter dynamic model is included. The test and algorithm analysis are performed on a slalom maneuver, on which the handling qualities are calculated.Practical implicationsDeveloped automatic flight control algorithm can be adapted and used in autopilot for a small helicopter. Methodology of evaluation of an AFCS performance can be used in different applications and cases.Originality/valueIn the paper, an automatic flight control algorithm for small helicopter and solution for the validation of developed AFCS algorithms are presented.

다항식을 이용한 비행경로생성 및 추종제어에 관한 연구

In this paper, we have studied on the flight path generation using polynomial and the flight path tracking control using guidance law, speed hold system, ACAH (Attitude Command Attitude Hold) system. The modeling section of the flight path is divided into five regions, and each region is modeled by a 7SUPth/SUP order polynomial. The flight paths were defined as maneuver library. MTEs (Mission Task Elements) of aeronautical design standard (ADS)-33 have been used to construct the Maneuver library. The Line-of-Sight(LOS) method and classical control method were applied to design the guidance law, speed hold system, and ACAH system for tracking the flight path. Simulation was performed to show that it is possible to generate mission flight path by combining the maneuver libraries. Also, it is shown that the trajectory tracking control is possible. Therefore, since the results of this study enable the real-time trajectory generation and the tracking control, it will be useful to improve the probability of mission success and survivability of UAV (Unmanned Aerial Vehicle).

Damage tolerance of an impacted composite laminate

Composites are known to be vulnerable to out-of-plane loading such as impact. Investigating laminate's residual properties in function of damage detection is the main purpose of impact damage tolerance design in aeronautics. As a good alternative to experimental campaigns, numerical approaches would lead to saving of time. The model developed in Institut Clement Ader over the last years enables to represent the behavior of composite laminates subjected to low velocity/low energy impact - including permanent indentation - and Compression After Impact. Damages such as permanent indentation, fiber failures, matrix cracks and delamination are taken into consideration at each step thanks to a discrete ply modelling. The work presented here deals with the use of this model to make a composite laminate design optimization according to impact damage tolerance design. A method to improve optimization by reducing computation time is also proposed, based on a “best candidates” selection.

Comparative study and optimization of the mechanical behavior of sandwich beams loaded in three point bending

The sandwich material presents a certain interest in term of rigidity and specific resistance for the aeronautic structure design. The study of this material meets always the choice problem of their constituents (coating and core) in order to find the optimal mechanical characteristic. The aim of this work is to do a comparative study of the mechanical behavior of the sandwich beams loaded in three point bending. The structures considered consist of two skins of composite material with unidirectional fibers of six plies Glass/epoxy, Carbon/epoxy or Kevlar/epoxy of stacking sequence [0°/90°]3s and [45°/-45°]3s and the core is in Alporas , Corecel, PVC, or Polyurethane foams. The different results obtained from the Matlab code showed that the correct choice of the material of the coatings and of the core that improves the mechanical behavior of the sandwich beam. In order to increase the performance of sandwich beams, in three points bending, an optimization program based on the principles of genetic algorithms has been developed to maximize the tensile strength of face yielding and face wrinkling failure modes. The equations used to evaluate the individuals in population results from the classical laminate theory with transverse shear stresses and discrete variables. Operators of genetic algorithms (selection, crossover and mutation) are applied to the children of a hundred generations. To achieve optimal solutions, the result appeared effective despite all the non-deterministic nature of genetic algorithms. But, to achieve maximum effectiveness, it’s important to choose smartly the parameters of genetic algorithms depending on the nature of the problem studied and the mechanical characteristics of the function to be optimized.

Numerical simulation of flexible aircraft structures under ditching loads

Aircraft certification requires demonstrating an aircraft’s structural capacity to withstand hydrodynamic loads as experienced during an emergency landing on water known as ditching. Currently employed means to analyze ditching comprise comparison with previously certified aircraft, sub-scale experimental testing, and semi-analytical as well as uncoupled computational methods; all of these are subject to simplifications that limit their predictability and accuracy. Therefore, there is the motivation to employ advanced, coupled numerical simulations to enhance the analysis capabilities. This paper presents a numerical simulation approach combining Smoothed Particle Hydrodynamics and Finite Element method, which permits investigating the structural behavior under ditching loads within one simulation. Comprehensive validation studies based on comparison with experimental results from novel guided ditching experiments of generic panels in aeronautical design have been undertaken and high accuracy has been achieved regarding acting force and strain time histories. Additionally, the profound analysis of the structural behavior of flexible panels allows assessing the main mechanisms that cause the acting hydrodynamic loads to increase significantly when the structure is being deformed. Presented results extend the fundamental knowledge in this field. The validated simulation approach is finally applied to analyze the structural behavior of a detailed stringer-frame-reinforced panel representing a generic aircraft bottom fuselage structure. Comparison between the structural behavior of the generic panels and the aft fuselage structure is established. Furthermore, conclusions with regard to ditching simulations involving larger or even full aircraft structures are drawn.

Streamlining cross-organisation product design in aeronautics

Aircraft development programmes generally involve collaboration in engineering between different organisations, in order to develop innovative products efficiently, to involve necessary skills from the supply chain, and to spread risks and costs among the partners. The size and complexity of the programmes, the market demands and the contexts of competition all require the collaboration to be effective and efficient. Advances in information technology provide new capabilities to support collaborative design but a step change is needed to harness and coordinate this support to be effective and efficient. The extended enterprises in which the collaborative engineering activities take place span the partner organisations. Engineers wishing to cooperate are however facing security constraints. For example, technical security measures such as firewalls and proxy servers hamper smooth exchange of engineering data and seamless execution of collaborative workflows. The restrictions assist organisations in protecting their assets and in remaining compliant with legislation and regulations. From a programme technical point of view, effective and efficient collaboration in this world full of security and the resulting connectivity constraints is a major challenge. This paper describes the usefulness, necessity and challenges of collaboration between multi-disciplinary specialists in aerospace engineering. It presents the ‘Brics’ technology that supports the realisation of cross-organisation collaborative workflows. The technology supports aircraft manufacturers and their supply chains in facing the challenges and in performing analyses of innovative aircraft designs collaboratively. This technology has emerged from past research projects, and has been further developed and successfully demonstrated in the Thermal Overall Integrated Conception of Aircraft project, a research and technology development project carried out in the Seventh Framework Programme funded by the European Union. The developed technology is illustrated in the context of a multi-partner analysis and optimisation study, which has been conducted as part of a pylon design that is subject to thermal constraints.