Method for Improving the Natural Lateral-Directional Stability of Flying Wings

et al. 2022

AEAT

Self Cite

Purpose Unlike conventional aircraft, birds can glide without a vertical tail. The purpose of this paper is to analyse the influence of dihedral angle spanwise distribution on lateral-directional dynamic stability by the simulation, calculation in the development of the bird-inspired aircraft and the flight testing. Design/methodology/approach The gliding magnificent frigatebird (Fregata magnificens) was selected as the study object. The geometric and mass model of the study object were developed. Stability derivatives and moments of inertia were obtained. The lateral-directional stability was assessed under different spanwise distributions of dihedral angle. A bird-inspired aircraft was developed, and a flight test was carried out to verify the analysed results. Findings The results show that spanwise distribution changing of dihedral angle has influence on the lateral-directional mode stability. All of the analysed configurations have convergent Dutch roll mode and rolling mode. The key role of dihedral angle changing is to achieve a convergent spiral mode. Flight test results show that the bird-inspired aircraft has a well-convergent Dutch roll mode. Practical implications The theory that birds can achieve its lateral-directional stability by changing its dihedral angle spanwise distribution may explain the stability mechanism of gliding birds. Originality/value This paper helps to improve the understanding of bird gliding stability mechanism and provides bio-inspired solutions in aircraft designing.

Section: Introductionmentioning

confidence: 99%

Flight testing verification of lateral-directional dynamic stability of gliding birds due to wing dihedral

Wei

Liu²,

et al. 2022

AEAT

Self Cite

“…On the other hand, it has been proven that the lateral-directional stability of this configuration can be achieved by adjusting the spanwise dihedral layout without installing a stability augment system [15,16]. Instead of focusing on the required lateral-directional stability derivative C lβ or C nβ , a criterion of dynamic stability was included in the aerodynamic design for flying wing, which considered the Dutch roll mode characteristics as the critical element for flight qualities [17]. Moreover, a unified algebraic approach was developed to approximate aircraft lateral-directional modes and predict departure susceptibility [18].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Aircraft Achieving Dutch Roll Mode Stability without Weathercock Stability

International Journal of Aerospace Engineering

Song

et al. 2020

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Weathercock stability is usually considered essential to achieve normal flight, while the Dutch roll mode stability can still be achieved without weathercock stability which has been algebraically proved. This paper proposed a flight experiment to investigate the characteristics of an airplane with Dutch roll mode stability but no weathercock stability. Firstly, the algebraic analysis based on a standard lateral-directional mode approximation was made to demonstrate the effect of yawing stability derivative Cnβ on the Dutch roll mode characteristics. The flight experiment was organized after that using a model glider which was modified to have zero Cnβ but with marginal change on Cyβ. The convergence of Dutch roll mode in flight meets the algebraic and numerical analysis as expected. However, the difference of handling characteristics between the original and modified configurations indicates some other roles the weathercock stability plays in flight as well as some limitations of utilizing mode criterion in flight quality analysis.

“…Because of lack of vertical stabilizer, lateral-directional flying quality of such aircraft becomes increasingly worse. Therefore, its directional stability is very close to neutral and even negative value, which causes divergence of Dutch roll mode of the aircraft in lateral-directional motion (Bolsunovsky et al, 2001;Song et al, 2016). It is undoubtedly this brings great challenge in conceptual design of aircraft with flying wing layout.…”

Section: Introductionmentioning

confidence: 99%

Influences of airfoil profile on lateral-directional stability of aircraft with flying wing layout

Pan

2019

AEAT

Self Cite

Purpose The purpose of this study is to analyze influence of airfoil profile on lateral-directional flying quality of flying wing aircraft. The lateral-directional stability is always insufficient for aircraft with the layout due to the absence of vertical stabilizer. A flying wing aircraft with double-swept wing is used as research object in the paper. Design/methodology/approach The 3D model is established for the aircraft with flying wing layout, and parametric modeling is carried out for airfoil mean camber line of the aircraft to analyze lateral-directional stability of the aircraft with different camber line parameters. To increase computational efficiency, vortex lattice method is adopted to calculate aerodynamic coefficients and aerodynamic derivatives of the aircraft. Findings It is found from the research results that roll mode and spiral mode have a little effect on lateral-directional stability of the aircraft but Dutch roll mode is the critical factor affecting flying quality level of such aircraft. Even though changes of airfoil mean line parameters can greatly change assessment parameters of aircraft lateral-directional flying quality, that is kind of change cannot have a fundamental impact on level of flying quality of the aircraft. In case flat shape parameters are determined, the airfoil profile has a limited impact on Dutch roll mode. Originality/value Influences of airfoil profile on lateral-directional flying quality of aircraft with double-swept flying wing layout are revealed in the thesis and some important rules and characteristics are also summarized to lay a theoretical basis for design of airfoil and flight control system of aircraft with the layout.