Comparison of box-wing and conventional aircraft mission performance using multidisciplinary analysis and optimization

Unconventional aircraft for civil aviation: A review of concepts and design methodologies

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

State-of-the-art models in preliminary wing design apply physics-based methods for primary structures while using empirical correlations for secondary structures. Using those methods, a detailed optimization such as e.g. rear spar positions or flap size is only possible within a limited design space. Novel structural concepts such as multi-spar flap layouts or the introduction of composite materials cannot be analyzed using statistical methods and require extended higher level structural modeling.

Therefore, a flexible wing modeling and physical mass estimation system for early aircraft design stages is developed – the WINGmass system. The core of the interdisciplinary tool chain is a central model generator that automatically generates all analysis models from the DLR aircraft data format CPACS (Common Parametric Aircraft Configuration Scheme). For the automatic model generation, a large amount of engineering rules are implemented in the model generator, to reduce the amount of required input parameters and therefore to relieve the aircraft designer. Besides the multi-model generator, the tool chain consist of a structural finite element model (incl. wing primary structures, flaps, flap tracks, ailerons, engine pylon and landing gear), a structural sizing algorithm and loads models for aerodynamic, fuel, landing gear and engine loads.

The wing mass estimation system is calibrated against real mass values of the wing primary structures and the trailing edge devices of the Airbus A320 and A340-200. The results of the calibrated tool chain are compared to the masses of the primary structures of the B747-100 and the aluminum baseline version of the MD-90-40X. The calibration factors for composite primary structures are derived from the composite version of the MD-90-40X.

Finally, the benefits of the extended physics-based modeling and the application of the WINGmass system in an interdisciplinary aircraft design environment are shown in an aircraft design study. The objective of this study is to compute the optimal wing shape in terms of mission fuel as a function of the take-off field length. Therefore, a parameter variation of the wing and flap geometry is performed, the engine scaled correspondingly and the mission fuel evaluated.

Application of a Flexible Wing Modeling and Physical Mass Estimation System for Early Aircraft Design Stages

Box-wings are a subset of nonplanar wing designs which have shown promise as a configuration for future transport aircraft. This configuration has been the subject of several studies seeking to determine the optimal wing configuration. However there is uncertainty as to the sensitivity of the wing’s aerodynamic performance, represented as a lift to drag ratio, to changes in some of the its geometric parameters. Specifically, the effects of the stream-wise stagger and the relative area of the two wings are not clear. This study seeks to identify the trends in aerodynamic performance as these parameters are varied while enforcing critical design constraints. Three such constraints are considered: the ability to maintain inherent static stability at cruise, the ability to perform a maneuver without stalling, and the ability to generate sufficient lift to support the aircraft at cruise conditions. A better understanding how the design parameters affect the aerodynamic performance of feasible box-wing designs will provide a better understanding of the sensitivities of such designs and will enable more meaningful analysis of the results from more comprehensive multidisciplinary studies.

Parametric Study of Box-Wing Aerodynamics for Minimum Drag Under Stability and Maneuverability Constraints

This paper presents a multi-disciplinary analysis methodology for a box-wing aircraft configuration optimised for a given mission scenario. This conceptual design methodology and associated toolchain combines well-established vortex lattice analysis and a newly developed structural analysis tool called WingMASS, allowing the design space to be explored from a combined aerodynamics and structural design perspective. For a given mission scenario, the method optimises a box-wing configuration and compares it with an equivalent conventional configuration. This study shows that, for a given mission, a boxwing configuration can lead to a fuel burn reduction of up to 5% by optimising aspect ratio, horizontal and vertical wing separation.

Multi-disciplinary analysis and optimisation methodology for conceptual design of a box-wing aircraft

The box-wing (or Prandtlplane) aircraft concept presents a non-planar-wing alternative to the conventional aircraft design paradigm which offers potential advantages in aerodynamic efficiency and hence reduced costs and emissions. An aerodynamic and structural design tradeoff was conducted to look at the design space for a 150-seat short-range box-wing aircraft. A number of geometric combinations of wing shape parameters were explored applying low-fidelity methods to establish an understanding of the interaction between the aerodynamic and structural characteristics as function of wing design. A combination of higher vertical separation, low horizontal separation and shorter wingspan was found to be optimal for of a box-wing configuration with respect to maximum specific range.

Preliminary aerodynamic and structural design tradeoff for a box-wing airliner

A multi-disciplinary analysis and optimisation methodology has been developed and applied in a study to compare the fuel burn of a box-wing configuration compared to a conventional aircraft configuration for a given mission. The methodology and toolchain combines Vortex Lattice Method (VLM) with a newly developed structural analysis tool WingMASS, allowing the design space to be explored from an aerodynamics and structures perspective. Three geometric parameters were varied: horizontal and vertical wing separation and aspect ratio. A comparison between te box-wing configuration and its conventional counterpart shows that the box-wing configuration has a potential fuel burn reductioin of about 5%. Changing the horizontal wing separation due to weight and balance and stability and control requirements, still leads to a 3% reduction in fuel burn.

Ishan Roy Salam

Papers

Multi-disciplinary analysis and optimisation methodology for conceptual design of a box-wing aircraft

Preliminary aerodynamic and structural design tradeoff for a box-wing airliner

A Methodology for Multi-Disciplinary Analysis of the Box Wing Concept