Box Wing Aircraft Research Articles

Preliminary Performance Analysis of Medium-Range Liquid Hydrogen-Powered Box-Wing Aircraft

This paper proposes a performance analysis of a medium-range airliner powered by liquid hydrogen (LH2) propulsion. The focus is on operating performance in terms of achievable payload and range. A non-conventional box-wing architecture was selected to maximize operating performance. An optimization-based multidisciplinary design framework was developed to retrofit a baseline medium-range box-wing aircraft by designing and integrating the fuel tanks needed to store the LH2; several solutions were investigated for tank arrangement and layout by means of sensitivity analyses. As a main outcome, a performance analysis of the proposed LH2-powered box-wing aircraft is provided, highlighting the impact of the introduction of this energy carrier (and the integration of the related tank systems) on aircraft operating performance; a comparative study with respect to a competitor LH2-retrofitted tube-and-wing aircraft is also provided, to highlight the main possible operating differences between the two architectures. The findings reveal that the retrofitted box-wing can achieve long-range flights at the cost of a substantially reduced payload, mainly due to the volume limitations imposed by the installation of LH2 tanks, or it can preserve payload capacity at the expense of a significant reduction in range, as the trade-off implies a reduction in on-board LH2 mass. Specifically, the studied box-wing configuration can achieve a range of 7100 km transporting 150 passengers, or shorter ranges of 2300 km transporting 230 passengers. The competitor LH2-retrofitted tube-and-wing aircraft, operating in the same category and compatible with the same airport apron constraints, could achieve a distance of 1500 km transporting 110 passengers.

Performance enhancement of a Box-Wing airliner with the application of riblets

The rapid growth of the commercial aviation sector in recent years, as well as the ambitious emission reduction targets, necessitate the investigation of novel methods to improve the aerodynamic efficiency of future airliners. With increasing passenger demand and evolving industry requirements, innovative designs, like the Box-Wing aircraft configuration, and flow control techniques, such as riblets, are essential to enhance efficiency, reduce fuel consumption and emissions, and meet future aviation needs. In this work, the performance enhancement of a novel Box-Wing airliner with the application of riblets is investigated through CFD modeling. The riblets are small, streamwise grooves aligned with the airflow, which when applied correctly, can reduce the turbulent skin friction drag. The riblets installed on the aircraft are modeled through a dedicated surrogate model, based on the cross-section area of their groove. In this study, both optimal size riblets, as well as constant size riblets, have been examined, assessing the performance degradation associated with the practical application limitations. The results show that the riblets can improve the aircraft’s aerodynamic characteristics, with a maximum drag reduction of 60 drag counts, as well as the overall flight performance, providing a maximum increase of 6.4% in payload and 13.3% in range.

Preliminary Analysis of the Stability and Controllability of a Box-Wing Aircraft Configuration

This paper presents a study on the aeromechanical characteristics of a box-wing aircraft configuration with a focus on stability, controllability, and the impact of aeromechanical constraints on the lifting system conceptual design. In the last decade, the box-wing concept has been the subject of several investigations in the aeronautical scientific community, as it has the potential to improve classic aerodynamic performance, aiming at reducing fuel consumption per unit of payload transported, and thus contributing to a reduction in aviation greenhouse emissions. This study characterises the aeromechanical features of a box-wing aircraft, with a specific focus on the correlations between the aeromechanical constraints and the (main) aircraft design parameters. The proposed approach provides specific insights into the aeromechanical characteristics of the box-wing concept, both in the longitudinal and lateral plane, which are useful to define some overall design criteria generally applicable when dealing with the conceptual design of such an unconventional aircraft configuration.

Introducing the Box-Wing Airframe for Hybrid-Electric Regional Aircraft: A Preliminary Impact Assessment

The combination of new airframes with electric and hybrid-electric propulsion is a potential solution to decarbonize aviation. In this context, recent studies have proven that the box-wing airframe, if integrated on a hybrid-electric aircraft belonging to the regional category, can provide significant reductions in fuel consumption. In light of these promising results, this paper aims to present a broader comparison between the box-wing aircraft and the conventional tube-and-wing aircraft, in the context of regional hybrid-electric air transport. An economic analysis is assessed, and the effects deriving from the box-wing introduction, in terms of direct operating costs, are quantitatively evaluated by applying cost models that consider the integration of hybrid-electric propulsion. In parallel, a comparative analysis of greenhouse emissions is proposed, considering both flight- and production-related emissions. The environmental, economic, and operating improvements that the introduction of the box-wing configuration may provide in the context of future regional hybrid-electric aviation are critically detailed. In this regard, the proposed results show that a box-wing hybrid-electric aircraft can reduce cost and emission without affecting compliance with current airport aprons. Finally, a general summary is presented, providing a solution that represents a practical, incremental, and technological step in the path of commercial aviation decarbonization.

A CFD-Based Collaborative Approach for Box-Wing Aircraft Aerodynamic Assessment: The PARSIFAL Study Case

This article presents a detailed aerodynamic investigation on a transport aircraft with a box-wing lifting system. The aerodynamic development of this configuration is presented through the description of the collaborative and multi-fidelity design approach that took place within PARSIFAL, an European project aiming to develop the box-wing configuration for a civil transonic aircraft. The article starts from an accurate description of the collaborative methodological framework employed and offers an overview of the development of the box-wing aerodynamics together with the highlight on its most significant characteristics and aerodynamic features identified. The design development is detailed step by step, with specific focus on the challenges faced, starting from the conceptual investigations up to the most advanced evaluations. Significant focus is given to the assessment of the aerodynamic performance in transonic flight for the box-wing lifting system, and to the design solutions provided to overcome issues related to this flight regime, such as drag rise and flow separation. In addition, the high-fidelity shape optimisation techniques employed in the advanced stage of the design process are detailed; these allow to define a final configuration with improved aerodynamic performance.

An Analysis of Aerodynamic Design Issues of Box-Wing Aircraft

An Analysis of Aerodynamic Design Issues of Box-Wing Aircraft

Engine Placement Effects on the Flutter of a Medium-Range Box-Wing Aircraft

Engine Placement Effects on the Flutter of a Medium-Range Box-Wing Aircraft

Experimental and CFD Investigation of Directional Stability of a Box-Wing Aircraft Concept

This study aimed to explore the directional stability issues of a previously studied light box-wing aircraft model with a pusher propeller engine in the fuselage aft section. Earlier configurations have included the use of fuselage together with a lifting system consisting of two wings joined together at their wingtips with vertical stabilizers. However, these side vertical surfaces failed to provide the aircraft with sufficient directional stability, thus prompting the quest in this study for novel solutions that would exclude the need for a fuselage extension and a typical fin. Solutions included the use of a ducted propeller and few configurations of small “fishtail” vertical fins, which formed part of the aft fuselage itself and coupled with vortex generators on the fuselage surface to improve their interference and heal flow separation at the fuselage aft cone. The results of wind tunnel testing were supported with CFD simulations to explain the flow behavior of each of the studied solutions. Tuft visualization and computed flow patterns allowed identification of the sources of the observed low efficiency in terms of directional stability of the fishtail against a simple idle duct without a propeller. A final configuration with a duct and a modified version of the fuselage fins was achieved that provides enough yaw stability margins for a safe flight.

Prediction of Maximum Lift Coefficient of Box-Wing Aircraft through the Combination of an Analytical Adaptation of the DATCOM Method and Vortex-Lattice Simulations

Prediction of Maximum Lift Coefficient of Box-Wing Aircraft through the Combination of an Analytical Adaptation of the DATCOM Method and Vortex-Lattice Simulations

Computational Investigation of a Novel Box-Wing Aircraft Concept

With regard to the current needs for greener aviation, this study focuses on a novel concept of Box-Wing Aircraft (BWA). Labelled SmartLiner (BWA/SL), this conceptual aircraft comes as a triplane comprising backward and forward swept wings. The aerodynamic performance and structural characteristics of this BWA/SL aircraft are here explored through numerical simulation, using Computational Fluid Dynamics (CFD) and Fluid-Structure Interaction (FSI). The computational approach is first validated using NASA’s Common Research Model (CRM) aircraft, which is then taken as a reference solution against which to compare the aero-structural merits of the BWA/SL concept. Results show that, although its design is still preliminary and lacks optimization, the BWA/SL aircraft exhibits very decent aerodynamic performance, with higher lifting capacities and a reasonable lift-to-drag ratio. Moreover, thanks to the closed frame of its peculiar planform, it demonstrates superior structural characteristics, including under extreme loading scenarios. Based on this preliminary analysis and considering the room left for its further optimization, this conceptual aircraft thus appears as a potentially promising alternative for the development of more environmentally friendly airliners.

EXPERIMENTAL ANALYSIS OF DOUBLE BOX WING UAV.

In an attempt to reduce the induced drag on a wing, Prandtl found that induced drag reduced significantly by highly increasing the number of vertically offset wings. The same result could be obtained by joining the wingtips of two vertically offset wings. This helped increase payload capacity and also reduced fuel consumption and emissions. Such a wing configuration came to be known as Prandtl’s box wing. In this work, the design and analysis of a box wing aircraft model has been carried out. The preliminary analysis is performed using XFLR5, and the computational analysis is done with the help of ANSYS 18.2. The values of experiments are computed with the help of MATLab R2017. The box wing model has shown a nearly 53.74% reduction in drag as compared with conventional wing models. The computational results of drag have been compared and validated with the results of analytical and the experimental results from the wind tunnel and found to be within 10% of the computational result. Since the drag of the box wing is significantly lesser than the conventional wings the box wing is a feasible configuration which can be used to design various aircrafts including Unmanned Aerial Vehicles and Commercial Planes.

Flutter Analysis of a 3D Box-Wing Aircraft Configuration

The aim of this paper is to present a flutter analysis of a 3D Box-Wing Aircraft (BWA) configuration. The box wing structure is considered as consisting of two wings (front and rear wings) connected with a winglet. Plunge and pitch motions are considered for each wing and the winglet is modeled by a longitudinal spring. In order to exert the effect of the wing-joint interactions (bending and torsion coupling), two ends of the spring are located on the gravity centers of the wings tip sections. Wagner unsteady model is used to simulate the aerodynamic force and moment on the wing. The governing equations are extracted via Hamilton’s variational principle. To transform the resulting partial integro-differential governing equations into a set of ordinary differential equations, the assumed modes method is utilized. In order to confirm the aerodynamic model, the flutter results of a clean wing are compared and validated with the previously published results. Also, for the validation, the 3D box wing aircraft configuration flutter results are compared with MSC NASTRAN software and good agreement is observed. The effects of design parameters such as the winglet tension stiffness, the wing sweep and dihedral angles, and the aircraft altitude on the flutter velocity and frequency are investigated. The results reveal that physical and geometrical properties of the front and rear wings and also the winglet design have a significant influence on BWA aeroelastic stability boundary.

A trim problem formulation for maximum control authority using the Attainable Moment Set geometry

This paper presents a generic trim problem formulation, in the form of a constrained optimization problem, which employs forces and moments due to the aircraft control surfaces as decision variables. The geometry of the Attainable Moment Set (AMS), i.e. the set of all control forces and moments attainable by the control surfaces, is used to define linear equality and inequality constraints for the control forces decision variables. Trim control forces and moments are mapped to control surface deflections at every solver iteration through a linear programming formulation of the direct Control Allocation algorithm. The methodology is applied to an innovative box-wing aircraft configuration with redundant control surfaces, which can partially decouple lift and pitch control, and allow direct lift control. Novel trim applications are presented to maximize control authority about the lift and pitch axes, and a “balanced” control authority. The latter can be intended as equivalent to the classic concept of minimum control effort. Control authority is defined on the basis of control forces and moments, and interpreted geometrically as a distance within the AMS. Results show that the method is able to capitalize on the angle of attack or the throttle setting to obtain the control surfaces deflections which maximize control authority in the assigned direction. More conventional trim applications for minimum total drag and for assigned angle of elevation are also explored.

Sustainable Technology on Aircraft Design: A Review

Next-generation air transportation is a key to influence the environment, safety, and the economy. Several programs strive to create emerging innovation towards sustainability, system integrity, and alternative fuels to guarantee a reduction of its environmental effect as greenhouse gas. Nowadays, the aerospace industry is looking forward to aviation sustainable developments across the globe. Few initiatives through a novel configuration of aircraft is established like Blended Wing Body, Flying V aircraft, Box wing Aircraft, and Double bubble Aircraft to enhance the cargo and passenger volume occupancy and cut-off the fuel burn percent. With the use of disruptive technologies, researchers are progressing the revolutionary airframe for transportation. A systematic overview and comprehensive survey of passenger-based aircraft are investigated. The objective study is to examine fuel burn and its impact on the environment by types of aircraft. In-depth literature review studies on four pillar strategies used to design an efficient airplane. In addition, this paper also serves on advancement in evolutionary technologies used in jet transport aircraft. Reflecting the benefits and challenges of different aircraft designs technologies were also highlighted. This paper highlights the future implications and managerial insights for future aircraft designers.

A Physics-Based Multidisciplinary Approach for the Preliminary Design and Performance Analysis of a Medium Range Aircraft with Box-Wing Architecture

The introduction of disruptive innovations in the transport aviation sector is becoming increasingly necessary. This is because there are many very demanding challenges that the transport aviation system will have to face in the years ahead. In particular, the reduction in pollutant emissions from air transport, and its impact on climate change, clearly must be addressed; moreover, sustainable solutions must be found to meet the constantly increasing demand for air traffic, and to reduce the problem of airport saturation at the same time. These three objectives seem to be in strong contrast with each other; in this paper, the introduction of a disruptive airframe configuration, called PrandtlPlane and based on a box-wing lifting system, is proposed as a solution to face these three challenges. This configuration is a more aerodynamically efficient alternative candidate to conventional aircraft, introducing benefits in terms of fuel consumption and providing the possibility to increase the payload without enlarging the overall aircraft wingspan. The development and analysis of this configuration, applied to a short-to-medium range transport aircraft, is carried out through a multi-fidelity physics-based approach. In particular, following an extensive design activity, the aerodynamic performance in different operating conditions is investigated in detail, the structural behaviour of the lifting system is assessed, and the operating missions of the aircraft are simulated. The same analysis methodologies are used to evaluate the performance of a benchmark aircraft with conventional architecture, with the aim of making direct comparisons with the box-wing aircraft and quantifying the performance differences between the two configurations. Namely, the CeRAS CSR-01, an open-access virtual representation of an A320-like aircraft, is selected as the conventional benchmark. Following such a comparative approach, the paper provides an assessment of the potential benefits of box-wing aircraft in terms of fuel consumption reduction and increase in payload capability. In particular, an increase in payload capability of 66% and a reduction in block fuel per pax km up to 22% is achieved for the PrandtlPlane with respect to the conventional benchmark, while maintaining the same maximum wingspan.

A Control Allocation approach to induce the center of pressure position and shape the aircraft transient response

This paper presents a Control Allocation formulation aimed at altering the dynamic transient response of an aircraft by exclusive means of the aerodynamic effectiveness of its control effectors. This is done, for a given Flight Control System architecture and, optionally, closed-loop performance, by exploiting the concept of Control Center of Pressure, i.e. the center of pressure due to only aerodynamic control forces. Two formulations are proposed, and their advantages and disadvantages presented. The first is based on the straightforward augmentation of the control effectiveness matrix, the second on a weighting matrix to prioritize control effectors. The latter is implemented in three application studies on a box-wing aircraft configuration with redundant control surfaces: a simple pull-up maneuver, a trajectory tracking task, and an altitude holding task in turbulent atmosphere. Results show that the proposed formulation can significantly impact performance metrics that are closely related to the aircraft transient response. In the best case scenario, the aircraft is able to completely cancel the non-minimum phase behavior typical of pitch dynamics, hence achieving a sharp initial response to longitudinal commands. If compared to a standard Control Allocation algorithm, the proposed formulation results in improved tracking precision, better disturbance rejection, and a measurably improved feeling of comfort on board.

Aircraft turnaround time estimation in early design phases: Simulation tools development and application to the case of box-wing architecture

This work deals with the problem of estimating the turnaround time in the early stages of aircraft design. The turnaround time has a significant impact in terms of marketability and value creation potential of an aircraft and, for this reason, it should be considered as an important driver of fuselage and cabin design decisions. Estimating the turnaround time during the early stages of aircraft design is therefore an essential task. This task becomes even more decisive when designers explore unconventional aircraft architectures or, in general, are still evaluating the fuselage design and its internal layout. In particular, it is of paramount importance to properly estimate the boarding and deboarding times, which contribute for up the 40% to the overall turnaround time. For this purpose, a tool, called SimBaD, has been developed and validated with publicly available data for existing aircraft of different classes. In order to demonstrate SimBaD capability of evaluating the influence of fuselage and cabin features on the turnaround time, its application to an unconventional box-wing aircraft architecture, known as PrandtlPlane, is presented as case study. Finally, considering standard scenarios provided by aircraft manufacturers, a comparison between the turnaround time of the PrandtlPlane and the turnaround time of a conventional competitor aircraft is presented.

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.

Innovative Box-Wing Aircraft: Emissions and Climate Change

The PARSIFAL project (Prandtlplane ARchitecture for the Sustainable Improvement of Future AirpLanes) aims to promote an innovative box-wing aircraft: the PrandtlPlane. Aircraft developed adopting this configuration are expected to achieve a payload capability higher than common single aisle analogues (e.g., Airbus 320 and Boeing 737 families), without any increase in the overall dimensions. We estimated the exhaust emissions from the PrandtlPlane and compared the corresponding impacts to those of a conventional reference aircraft, in terms of Global Warming Potential (GWP) and Global Temperature Potential (GTP), on two time-horizons and accounted for regional sensitivity. We considered carbon dioxide, carbonaceous and sulphate aerosols, nitrogen oxides and related ozone production, methane degradation and nitrate aerosols formation, contrails, and contrail cirrus. Overall, the introduction of the PrandtlPlane is expected to bring a considerable reduction of climate change in all the source regions considered, on both the time-horizons examined. Moreover, fuel consumption is expected to be reduced by 20%, as confirmed through high-fidelity Computational Fluid Dynamics (CFD) simulations. Sensitivity of data, models, and metrics are detailed. Impact reduction and mitigation strategies are discussed, as well as the gaps to be addressed in order to develop a comprehensive Life Cycle Assessment on aircraft emissions.

An Investigation of the Longitudinal Dynamic Stability of a Box-Wing Aircraft

This study was undertaken to identify the longitudinal dynamic characteristics of the Box-Wing Aircraft. Research on the Box Wing aircraft gained traction following increasing demand for an environmental friendly aircraft that would reduce noise and pollutant emissions. The Box-Wing Aircraft is renowned for its potential aerodynamics advantages over conventional aircraft. However, due to its departure from conventional configuration, the stability dynamics of the Box Wing has not been fully explored. This study investigates the longitudinal dynamic stability characteristics of a Box Wing Aircraft at the conceptual design level using the J2 Aircraft Dynamics Software. The study integrates empirical mass estimation methods and aerodynamic data generated from a vortex lattice tool into J2 Aircraft Dynamics Software Suite. This was done to assess the Short Period Oscillation and Phugoid responses of a Box Wing Aircraft and a conventional cantilever wing aircraft. For a 2s step input, the short period oscillation induced on the Box Wing was damped out after 19s resulting in damping ratio of 0.68 and the undamped natural frequency is 1.8 <i>rad/s</i>. In the Phugoid mode, the Box Wing Aircraft gives a damping ratio of 0.006 and undamped natural frequency of 0.07 <i>rad/s.</i> On the other hand, the SPO induced on the reference conventional aircraft settles after 14s producing a damping ratio of 0.76 and undamped natural frequency of 3.12 <i>rad/s</i>. The damping ratio and undamped natural frequency for the Phugoid mode of the reference conventional aircraft were however 0.001 and 0.07 <i>rad/s</i> respectively. These results indicate that the reference conventional cantilever wing aircraft possesses acceptable longitudinal dynamic stability characteristics while the Box Wing Aircraft would require stability augmentation systems to improve its flying and handling qualities.