Preliminary stability analysis methods for PrandtlPlane aircraft in subsonic conditions

Abstract

The present paper aims to assess the reliability and the limitations of analysing the flight stability of a boxwing aircraft configuration known as PrandtlPlane by means of methods conceived for conventional aircraft and well known in literature. Design/methodology/approach: Results obtained by applying vortex lattice methods to PrandtlPlane configuration, validated previously with wind tunnel tests, are compared to the output of a "Roskam-like" method, here defined in order to model the PrandtlPlane features. Findings: The comparisons have shown that the "Roskam-like" model gives accurate predictions for both the Longitudinal Stability Margin and Dihedral Effect, whereas the Directional Stability is always overestimated. Research limitations/implications: The method here proposed and related achievements are valid only for subsonic conditions. The poor reliability related to lateral-directional derivatives estimations may be improved implementing different models known from literature. Practical implications: The possibility to apply a faster method as the "Roskam-like" here presented has two main implications: 1) it allows to implement faster analyses in the conceptual and preliminary design of PrandtlPlane, providing also a tool for the definition of the design space in case of optimization approaches 2) it allows to implement scaling procedure, in order to study families of PrandtlPlanes or different aircraft categories. Social implications: This paper is part of the activities carried out during the PARSIFAL project, which aims to demonstrate that the introduction of PrandtlPlane as air transport mean can fuel consumption and noise impact, providing a sustainable answer to the growing air passenger demand envisaged for the next decades. Originality/value: The originality of this paper lies in the attempt of adopting analysis method conceived for conventional airplanes for the analysis of a novel configuration. The value of the work is represented by the knowledge concerning experimental results and design methods on the PrandtlPlane configuration, here made available in order to define a new analysis tool.

Computational Investigation of a Novel Box-Wing Aircraft Concept

“…The best aerodynamic performance is reached under the S 3 flight condition (M = 0.7 at 43,000 ft), with an L/D value of 15.5 ~16 (under an angle of attack of zero or slightly negative value). Notably, this L/D ratio is very similar to that of a Boeing B747-400 in cruise [49], albeit somewhat lower than that of more traditional, biplane BWA aircraft [9][10][11][12][13][14][15][16][17][18][19] (e.g., L/D 20). This is rather encouraging, considering that the BWA/SL did not benefit (yet) from any aerodynamic optimization of its planform-as would be needed for its aerodynamic performance to be able to compete with those of more modern aircraft, such as the CRM (whose wings were heavily optimized [46,47]).…”

“…It is claimed that this BWA aircraft would offer a lift-to-drag ratio that would be 16% higher than that of a conventional aircraft, along with reduced noise emissions. One can also mention several large-scale projects conducted under the aegis of the European Commission, namely PARSIFAL [9][10][11][12][13][14][15][16][17] and IDINTOS [18,19]. In particular, the recent EU project PARSIFAL explored rather extensively the so-called Prandtl Plane concept, which was investigated from various angles, including market perspectives [9], conceptual design viewpoints [10][11][12], and more technical aspects (e.g., performance [13], stability [14], aerodynamics [15,16], structures [17]).…”

“…One can also mention several large-scale projects conducted under the aegis of the European Commission, namely PARSIFAL [9][10][11][12][13][14][15][16][17] and IDINTOS [18,19]. In particular, the recent EU project PARSIFAL explored rather extensively the so-called Prandtl Plane concept, which was investigated from various angles, including market perspectives [9], conceptual design viewpoints [10][11][12], and more technical aspects (e.g., performance [13], stability [14], aerodynamics [15,16], structures [17]). Additionally, more specific studies were conducted by several universities, worldwide; several works investigated the BWA concept from design perspectives [20][21][22][23][24][25][26][27] whereas others focused on more specific things such as the aerodynamic efficiency of the box-wing itself [28][29][30][31][32][33][34], as well as structural [35,36] and stability [37][38][39][40] aspects.…”

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

“…Specifically, general aspects of aeromechanical behaviour in the longitudinal plane of box-wing aircraft are extensively reported in [87]; a detailed summary of the design of the lifting system, with a focus on stability and controllability requirements, is given in [56]. The methods used to assess the aeromechanical characteristics of box-wing aircraft are extensively reported in [87]; the approach used in the study involves a multi-fidelity approach, starting from the use of literature models [100], passing through extensive analysis campaigns with VLM solvers [58,74], up to the verification of requirements with CFD [74,88].…”

WAGNER: a new code for parametrical structural study of fuselages of civil transport aircraft

“…WAGNER code has been carried out in the frame work of Parsifal project ( [4], [6], [17], [12]); the input of this code is the internal layout of a fuselage of a civil transport aircraft and the output is the automatic generation of the Finite Element mesh of the complete fuselage, ready for static and dynamic preliminary analysis. In the very preliminary structural analysis, a large amount of structural configurations need to be analysed in order to compare benefits and drawbacks of different layouts, to verify the effects of modifications of geometry and material properties and, finally, to provide a preliminary sizing to be used as a baseline for future and deeper studies; hence, the generation of the FEM model is required to be simple, automatic and small time consuming.…”