Development, Model Generation and Analysis of a Flying V Structure Concept

Abstract

The Flying V, a concept aircraft configuration, has been proposed by Airbus and TU Berlin. The initial indications of potential improvements in performance over conventional aircraft gave rise to a continuation of the research. For this, the mass characteristics of the configuration must be explored.

A primary structure concept is conceived based on expected load paths. The original dual-tube fuselage configuration is replaced with an oval cabin concept, in which various constant-curvature arcs are adjoined. Residual forces at their connection are carried by straight members. A parametrisation is set up, for which both aerodynamic and structure concept considerations are taken into account. A CAD model for the structure concept is generated in ParaPy , a KBE framework with CAD integration and coupling to various aerodynamic and structure analysis tools.

A numerical sizing method is selected due to the complexity of the airframe geometry. A model generatoris developed in ParaPy , a KBE-framework with integration of a meshing algorithm and coupling to aerodynamic and structural analysis tools. A CAD model is obtained from the model generator using
a mission parameter set similar to that of an Airbus A350. The model is meshed using the SALOME algorithm for a finite element analysis.

The mesh is exported to Patran for a Nastran analysis. Between ParaPy and Patran, mesh element IDs are altered. This disables a feedback-enabled design loop. Analysis results cannot be interpreted in ParaPy . Automated design is foregone.

Patran mesh verification highlights critical and non-critical mesh errors due to the chosen geometry generation procedure. The flawed elements are redefined manually. Point and distributed loads are applied. Aerodynamic loads are obtained from Airbus’ LatticeBeta full-potential 3D panel method. Uniform material properties are assigned. Due to the thin-shelled nature of the model, out-of-plane element bending stiffness is low. Excessive deformations are observed under transverse load application and in-plane panel compression. A bending stiffness correction is applied.

The model is sized for material failure and local buckling by Airbus’ in-house structure sizing tool ZORRO. A validation is set up using outboard wing cross-sections. These are sized using analytical relations given the numerical procedure loads. From this it is concluded individual regions can only be assessed qualitatively due to the bending stiffness correction applied in the numerical model. Wrongly designed structure regions and load path propagation can be interpreted. Quantitative results are not omitted
from the result interpretation.

An unforeseen load path is identified in the wing transition between the outboard wing front spar and root plane trailing edge. The integration of tapered fuselage within the wing transition is feasible, although the fuselage attracts more loads than anticipated.

The fuselage transition behaves as expected. Integration of the oval cabin concept into a the Flying V configuration is shown to be feasible and beneficial to volume efficiency and planform design flexibility. However, the existing implementation of the cabin concept must be altered for better adaptation in existing regulations.

The assumed static stability as optimised for by Faggiano shows large discrepancy with respect to the determined static margin. Part of this is caused by the incorrect quantitative sizing results. However, it is expected that the aerodynamic profile may be significantly altered in a multi-disciplinary design
procedure.

In order to obtain a correct mass estimation, a new model generation procedure is recommended in detail. This takes multiple facets into account. Geometric model continuity is ensured. A straightforward implementation of stiffener elements is enabled by introducing a foundation for this on the
top-level fuselage model definition. This also adds more possibilities for designing the aft half of an aerodynamic profile for the fuselage section of the planform.

Feasible design automation consequently enables multidisciplinary optimisation. The main hurdles to overcome towards realising design automation are development of a complete model generator, further development of ParaPy ’s geometry generation and Nastran coupling functionalities and feedback between analysis results and model generation. Realising these aspects in future research will finally allow solid conclusions regarding the Flying V performance to be drawn.