Multidisciplinary Aircraft Design Research Articles

Multidisciplinary optimization methodology for truss-braced wing aircraft using high-fidelity structure sizing

In this research, a method is developed to optimize the truss-braced wing aircraft configuration in a multidisciplinary design framework. Physics-based high-fidelity methods, that can capture the nature of the configuration changes, are employed for the disciplines where the existing classical methods are not reliable. High-fidelity geometry modeling, structure loading, structure optimization, and aeroelastic sizing methods are integrated into the aircraft multidisciplinary design and optimization. The developed algorithm is applied for the multi-objective optimization of a regional jet aircraft to minimize the cost and weight. The results demonstrate that the cost-optimum solution converges to a higher aspect ratio wing equipped with a higher bypass ratio engine, and a 7.94% reduction in the direct operating cost can be achieved. On the other hand, the weight-optimum wing planform tends to a slightly lower aspect ratio wing with a lower bypass ratio engine, while a 6.18% reduction in take-off weight is achieved. In addition to that, the findings of this study highlight the considerable effect that the engine technology has on the optimum layout, which suggests that the engine technology and its performance should also be a part of the design optimization process. The developed modular framework offers further optimization potential for the truss-braced wing aircraft, as more detailed models can be integrated.

A Framework for Aircraft Conceptual Design and Multidisciplinary Optimization

In this research, the architecture and the functionalities of the LAMBDA (Laboratory of Aircraft Multidisciplinary Knowledge-Based Design and Analysis) framework for the design, analysis, and optimization of civil aircraft are presented. The framework is developed in MATLAB R2022a and comprises a modular architecture, which gives the potential for the use of different methods and fidelities for each discipline. The methods can be selected from a set of built-in methods or custom user-defined scripts. Disciplinary modules of the LAMBDA are Requirements, Weight, Sizing, Geometry, Aerodynamics, Engine, Performance, Cost, Emission, and Optimization. This framework has been used for different types of design and optimization problems. When it is applied for the design and optimization of a novel regional TBW (Truss-Braced Wing) aircraft, the operating cost has been reduced by 7.7% in the optimum configuration compared to the base configuration.

Integrating Nonlinear Controllability into a Multidisciplinary Design Process

Even in multidisciplinary aircraft design, most aspects of nonlinear controllability are only considered in later design phases. Hence, control considerations are not used to inform the overall design of the airframe. This paper presents a control-aware controller-agnostic design optimization framework that integrates nonlinear controllability constraints, which are informed by the solutions to optimal control problems, into the multidisciplinary design process. To implement the optimization, procedures to evaluate the sensitivity of the controllability constraint to variations in the design variables are defined. A supersonic aircraft case study illustrates the methodology and the steps involved in the process. The proposed approach enables the integration of control-related constraints into gradient-based design optimization.

Practical Appropriate Fidelity Optimization for Large-scale Multidisciplinary Aircraft Design

Practical Appropriate Fidelity Optimization for Large-scale Multidisciplinary Aircraft Design

A Fast Aerodynamic Model for Aircraft Multidisciplinary Design and Optimization Process

A multidisciplinary design analysis and optimization process is developed at ONERA for the design of tube and wing and blended wing–body aircraft configurations. This process is composed of different disciplinary modules (geometry, propulsion, aerodynamics, structure, handling qualities and flight mission), and the overall process considers different fidelity levels for these modules at each step of the design process. This article describes the low-fidelity aerodynamic module used during the preliminary design optimization process. Analytical formulations retained for lift and drag components are presented in the first part. Then, the performances estimated by the aerodynamic module on some reference configurations are compared with both numerical and experimental data, showing a quite good agreement for both tube and wing and blended wing–body configurations not only for global performance but also for individual drag components.

COMPARISON OF TWO METHODS TO CALCULATE EXTERNAL LOADS AT FLIGHT IN CONTINUOUS TURBULENCE

The external loads from the continuous turbulence on the elastic high aspect ratio wing of the transport category aircraft are calculated by Dynamics of Turbulence Air (DTA) and Interactive Multidisciplinary Aircraft Design (IMAD) methods. The response to continuous turbulence was determined taking into account the requirements of CS-25.341(b). The model of the aircraft structure is directed by symmetrical spatial beam schematization. Determination of aerodynamic forces and moments was performed using the methods of linear computational aerodynamics: the panel method of Doublet-Lattice and Constant Pressures (DLM/CPM) and the method of circulation. Comparison of the results of load determination showed that, in general, the values of the loads calculated using IMAD are lower than the values calculated using DTA. Therefore, when designing an aircraft, it is advisable to combine these methods: calculate the loads using IMAD, as a more functional method, and then the loads obtained in the critical points of the calculated flight area should be confirmed using the DTA method. Thus, this study determined the difference between the results of the calculation of loads from the continuous turbulence on the elastic wing of the transport category aircraft using DTA and IMAD methods.

Regional jet retrofitting through multidisciplinary aircraft design

Multidisciplinary collaborative aircraft design is applied to a 90 passengers regional jet aircraft retrofit, highlighting the impact on costs and performance. Two retrofitting packages have been considered: the re-engining of conventional power-plant platform with advanced geared turbofan and the on-board-system modernization, considering different level of electrification. Starting from a reference existing aircraft, the impact of retrofitting process has been carefully evaluated on capital costs and savings at industrial level through a developed methodology. At aircraft level, masses, performance, noise, and emissions have been computed with dedicated competences increasing the estimation reliability. Overall process is implemented in the framework of the AGILE 4.0 research project in a collaborative remote multidisciplinary approach. Results show that such retrofitting activities are expensive and must be evaluated since the design stage with a bottom-up approach requiring competences coming from designer experience to correctly define the process work-breakdown-structure and its implications.

Multifidelity Sensitivity Study of Subsonic Wing Flutter for Hybrid Approaches in Aircraft Multidisciplinary Design and Optimisation

A comparative sensitivity study for the flutter instability of aircraft wings in subsonic flow is presented, using analytical models and numerical tools with different multidisciplinary approaches. The analyses build on previous elegant works and encompass parametric variations of aero-structural properties, quantifying their effect on the aeroelastic stability boundary. Differences in the multifidelity results are critically assessed from both theoretical and computational perspectives, in view of possible practical applications within airplane preliminary design and optimisation. A robust hybrid strategy is then recommended, wherein the flutter boundary is obtained using a higher-fidelity approach while the flutter sensitivity is computed adopting a lower-fidelity approach.

Collaborative Architecture supporting the next generation of MDAO within the AGILE paradigm

The AGILE project has developed the next generation of aircraft Multidisciplinary Design and Optimization processes providing significant reductions in aircraft development costs and time to market - ultimately leading to more cost-effective and greener aircraft solutions. A novel product development methodology is formulated, enabling collaborative, large scale design and optimization processes. The main elements enabling the developed “AGILE Paradigm” are the Knowledge Architecture and the Collaborative Architecture. The Knowledge Architecture formalizes setting up the product development process. It guides the engineers in formulating the design problem and choosing the appropriate solution strategy. This paper focuses on the Collaborative Architecture, which at its turn formalizes the way in which the involved agents interact within the product development process and enables cross-organizational and cross-the-nation integration of design competences. The principles of the architecture are of a non-intrusive nature and allow legacy processes to be connected in fully automated cross-organization collaborative design workflows. Within the project, it is used to seamlessly integrate the capabilities of nineteen project partners located in nine different countries. A realistic aircraft design use case – addressing an automated systems-of-systems analysis involving the design competences of multiple project partners – demonstrates a working implementation of the Collaborative Architecture. The effective interconnection of simulation capabilities between organizations allows the agents to spend more time on creative, knowledge-intensive design tasks - opening new possibilities for collaboratively resolving the future challenges faced by the aerospace and other industries.

AGILE Paradigm: The next generation collaborative MDO for the development of aeronautical systems

The research and innovation EU funded AGILE project has developed the next generation of aircraft Multidisciplinary Design and Optimization (MDO) processes, which target significant reductions in aircraft development costs and time to market, leading to more cost-effective and greener aircraft solutions. 19 industry, research and academia partners from Europe, Canada and Russia have developed solutions to cope with the challenges of collaborative design and optimization of complex aeronautical products. In order to accelerate the deployment of large-scale, collaborative multidisciplinary design and optimization, a novel approach, the so-called “AGILE Paradigm”, has been conceived. The AGILE Paradigm is defined as a “blueprint for MDO”, accelerating the deployment and the operations of collaborative “MDO systems” and enabling the development of complex products practiced by multi-site and cross-organizational design teams, having heterogeneous expertise. A set of technologies has been developed by the AGILE consortium to enable the implementation of the AGILE Paradigm principles, thus delivering not only an abstract formalization of the approach, but also an applicable framework. The collection of all the technologies constitutes the so-called “AGILE Framework”, which has been applied for the design and the optimization of multiple aircraft configurations. The ambition of the AGILE Paradigm was set to reduce the lead time of 40% with respect to the current state-of-the-art. This work reviews the evolution of the MDO systems, underlines the open challenges tackled by the AGILE project, and introduces the main architectural concepts behind the AGILE Paradigm. Thereafter, an overview of the application design cases is presented, focusing of the main challenges and achievements. The AGILE technologies enabled the consortium to formulate and to solve in 15 months 7 MDO applications in parallel for the development of 7 novel aircraft configurations, demonstrating time savings beyond the 40% goal.

Performance bookkeeping for aircraft configurations with fuselage wake-filling propulsion integration

The aim of this research is the identification of a unified bookkeeping and evaluation scheme for the integrated performance analysis of a boundary layer ingesting (BLI) concept in the conceptual design phase. A thorough review and classification of existing performance bookkeeping schemes suits as a basis for the derivation of a bookkeeping scheme suitable for the initial sizing as well as detailed design analysis during the conceptual phase of a BLI concept. Figures of merit for the concept performance assessment are evaluated with regard to the requirements of aircraft multidisciplinary conceptual design. Based on the survey, the most practical integral momentum conservation approach is deduced and its application to integrated conceptual sizing and a subsequent design analysis is evaluated. The proposed scheme is universally applicable to coupled airframe–propulsion aircraft concepts, compatible with standard aircraft and propulsion system sizing tools and, under certain assumptions, deployable for low- and high-fidelity evaluation methods. Finally, several figures of merit are selected to cover a range of design aspects in the BLI evaluation.

Impact of mission requirements on the design of low observable UCAV configurations

PurposeThe purpose of this paper is to characterise the effects of mission and performance parameters on the design space of low observable subsonic unmanned combat aerial vehicles (UCAVs) operating in typical Hi-Lo-Hi ground strike missions.Design/methodology/approachConceptual design methodologies appropriate to low observable, tailless UCAVs have been integrated into a multidisciplinary aircraft design environment, GENUS, developed at Cranfield University’s aircraft design group. A basic Hi-Lo-Hi mission is designed and a baseline configuration is established through the GENUS framework. Subsequently, an evolutionary optimiser and a robust gradient-based optimiser are used to obtain convergent design solutions for various leading edge sweep angles, mission ranges, cruise Mach numbers and other operational constraints.FindingsThe results indicate that performance constraints, specifically in the form of specific excess power (SEP), have a large influence on the overall sizing of subsonic tailless UCAVs. This requirement drives the engine sizing, which represents a considerable proportion of the empty and gross mass of the vehicle. Cruise Mach number studies show that no significant advantages exist for operating at low speeds while maintaining performance requirements consistent with combat missions. There is a drastic increase in the vehicle’s mass and thrust requirements for flight speeds above Mach 0.8, with low sweep configurations showing a more pronounced effect. Increases in the range are not overly dependent on the leading edge sweep angle. Top-level radar cross section (RCS) results also favour configurations with higher leading edge sweep angles, especially from the nose-on aspect. Finally, research and development costs are shown to be directly linked to engine size.Originality/valueThis research shows the use of an integrated aircraft design environment that incorporates aerodynamics, performance, packaging and low observability aspects into the optimisation loop. Through this methodology, this study supports the efforts towards characterising and establishing alternate visions of the future of aerial warfare through the use of low cost, survivable unmanned platforms in network-centric cooperative tasks.

Proof-of-concept analysis of a supplemental solar power system for aircraft

PurposeThis paper aims to analyze the viability of a solar power system as a supplemental power source for commercial and business aircraft.Design/methodology/approachFirst, a model is established to estimate the potential available power from suitable aircraft surfaces for various meteorological conditions, ground and flight mission characteristics. A proposed aircraft system architecture and an associated parametric conceptual sizing model are presented. This supplemental solar power system sizing model is integrated into an aircraft multidisciplinary design optimization environment to evaluate the aircraft-level impact on mission fuel burn. A parametric study for a business jet aircraft is performed to analyze various solar cell types and power densities for converters. Trade-off studies are performed between efficiency and weight.FindingsConsidering today’s efficiency and power-to-weight ratio of the system components, overall fuel burn reduction can be achieved. Therefore, the technology development work can start now to target short to mid-term applications. In addition, promising system integration scenarios are identified, such as the use of solar power for autonomous operation of the air conditioning system on ground, which yield potential further benefit. In conclusion, a supplemental solar power system seems a promising candidate for more efficient aircraft operation.Originality/valueThe presented novel supplemental solar power system architecture concept and its foreseen aircraft integration show potential benefits for near term applications. The results show that the break even for this technology is already reached and therefore build the foundation to further investigate the technology integration challenges. Clear directions for future research and development are outlined enabling the advancement of the technology readiness level.

Efficient Aircraft Multidisciplinary Design Optimization and Sensitivity Analysis via Signomial Programming

This paper proposes a new methodology for physics-based aircraft multidisciplinary design optimization (MDO) and sensitivity analysis. The proposed architecture uses signomial programming (SP), a type of difference-of-convex optimization that is solved iteratively as a series of log-convex problems. A requirement of SP is that all constraints and objective functions must have explicit signomial formulas. The SP MDO architecture facilitates the low-cost computation of optimal sensitivities through Lagrange duality. The specific example of commercial aircraft MDO is considered. Using SP, a small-, medium-, and large-scale benchmark problem is solved 16, 39, and 26 times faster, respectively, than Transport Aircraft System Optimization (TASOPT), a comparable and widely used aircraft MDO tool. The SP solution times include computation of all optimal parameter and constraint sensitivities, a feature unique to the presented architecture. The reliability of SP is demonstrated by converging a commercial aircraft MDO problem for a number of different objective functions and evaluating both traditional and nontraditional aircraft configurations. While the presented example is commercial aircraft MDO, the SP MDO architecture is applicable to a range of engineering optimization problems.

Multidisciplinary analysis of subsonic stealth unmanned combat aerial vehicles

In this paper, the GENUS multidisciplinary aircraft design and analysis environment is presented in its application to the conceptual design of tailless, low-observable unmanned combat aerial vehicles (UCAVs). Analysis disciplines comprise a variety of low to medium fidelity, physics-based and empirical methodologies, as well as higher order panel method aerodynamic analysis. Stealth considerations have been included in terms of a radar cross section analysis through a physical optics approximation method, with results verified against a well-known radar cross section prediction code. Preliminary results show good agreement for gross and empty masses when compared to several existing UCAV demonstrators and conceptual designs. A further validation of the presented methodologies is evaluated through the design, analysis, and optimisation of an unmanned strike fighter concept.

Exploring Vehicle Level Benefits of Revolutionary Technology Progress via Aircraft Design and Optimization

It is always a strong motivation for aeronautic researchers and engineers to reduce the aircraft emissions or even to achieve emission-free air transport. In this paper, the impacts of different game-changing technologies together on the reduction of aircraft fuel consumption and emissions are studied. In particular, a general tool has been developed for the technology assessment, integration and also for the overall aircraft multidisciplinary design optimization. The validity and robustness of the tool has been verified through comparative and sensitivity studies. The overall aircraft level technology assessment and optimization showed that promising fuel efficiency improvements are possible. Though, additional strategies are required to reach the aviation emission reduction goals for short and medium range configurations.

Application of Signomial Programming to Aircraft Design

Due to the coupled nature of aircraft design, it is important to consider all major subsystems when optimizing a configuration. This is difficult when each individual subsystem model can be arbitrarily complex. By restricting an optimization problem to have a certain mathematical structure, significantly more effective and tractable solution techniques can be used. Geometric programming, one such technique, guarantees finding a globally optimal solution. Although it has been shown that geometric programming can be used to solve some aircraft design problems, the required formulation can prove too restrictive for certain relationships. Signomial programming is a relaxation of geometric programming that offers enhanced expressiveness. Although they do not guarantee global optimality, solution methods for signomial programs are disciplined and effective. In this work, signomial programming models are proposed for optimal sizing of the wing, tail, fuselage, and landing gear of a commercial aircraft. These models are combined together to produce a system-level optimization model. Signomial programming’s formulation allows it to handle some key constraints in aircraft design, and therefore an improvement in fidelity over geometric programming models is achieved. A primary contribution of this work is to demonstrate signomial programming as a viable tool for multidisciplinary aircraft design optimization.

Mission-Based Multidisciplinary Aircraft Design Optimization Methodology Tailored for Adaptive Technologies

Aircraft design is an inherently multidisciplinary undertaking, which motivates the quest for increasingly optimized solutions using distributed design optimization architectures. In this study, a mission-based aircraft preliminary design optimization methodology tailored for the assessment of adaptive technologies is presented. Its most distinguishing feature relies on each subspace representing a different mission stage instead of the traditional aircraft design disciplines. It is tailored for the assessment of adaptive solutions where the optimum design is mission stage dependent. Low-fidelity models have been used for the aircraft design disciplines. The enhanced collaborative optimization architecture has been used, with the concepts of weighting coefficient and dynamic compatibility parameter being presented and duly assessed. Benchmarking case studies results are discussed, using wingspan, wing mean chord, propeller diameter, propeller pitch, flap relative chord, and flap deflection as design variables. A quantitative analysis of the profitability of variable span wing, variable camber flap, and variable pitch propeller is also featured.

Multi-disciplinary optimization in aeronautical engineering

Nowadays, optimization is a very popular tool used to improve existing projects. The optimization covers different disciplines by linking them into multidisciplinary process of design. Existing software tools allow to very effectively solve particular problems giving high quality solutions which were previously very hard to achieve. Aeronautical engineering is a domain/field which links many disciplines: aerodynamics, stability, control, structural analysis, materials, propulsion systems, avionics, etc. Therefore, the multidisciplinary optimization results in very significant progress not only in aircraft design but also in air transport, which links technical aspects with economical questions. The paper presents selected aspects of using the multidisciplinary optimization in aeronautical engineering with special focus on multidisciplinary aircraft design.

LMI–based robust controller design approach in aircraft multidisciplinary design optimization problem

This article proposes a linear matrix inequality–based robust controller design approach to implement the synchronous design of aircraft control discipline and other disciplines, in which the variation in design parameters is treated as equivalent perturbations. Considering the complicated mapping relationships between the coefficient arrays of aircraft motion model and the aircraft design parameters, the robust controller designed is directly based on the variation in these coefficient arrays so conservative that the multidisciplinary design optimization problem would be too difficult to solve, or even if there is a solution, the robustness of design result is generally poor. Therefore, this article derives the uncertainty model of disciplinary design parameters based on response surface approximation, converts the design problem of the robust controller into a problem of solving a standard linear matrix inequality, and theoretically gives a less conservative design method of the robust controller which is based on the variation in design parameters. Furthermore, the concurrent subspace approach is applied to the multidisciplinary system with this kind of robust controller in the design loop. A multidisciplinary design optimization of a tailless aircraft as example is shown that control discipline can be synchronous optimal design with other discipline, especially this method will greatly reduce the calculated amount of multidisciplinary design optimization and make multidisciplinary design optimization results more robustness of flight performance.