**Aerodynamic Characteristics and Longitudinal Stability of Tube Launched Tandem-Scheme UAV of Tube Launched Tandem-Scheme UAV**

**Aerodynamic Characteristics and Longitudinal Stability** 

DOI: 10.5772/intechopen.70228

Illia S. Kryvokhatko and Oleksandr M. Masko Additional information is available at the end of the chapter

Illia S. Kryvokhatko and Oleksandr M. Masko

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.70228

#### **Abstract**

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Tube launched unmanned aerial vehicles (UAV) are often implemented with aerodynamic scheme with forward and rear wings (so-called tandem-scheme). Specificity of such UAV is that immediately after launch, they have a flight path in which wings are turned from position along the fuselage to flight position in which sweep angles are about zero. UAV aerodynamic characteristics for different wing rotation angles were researched by computational fluid dynamics (CFD) methods (Ansys 16 software). Quantitative results prove that UAV is unstable with wings rotation angles up to 60° because rear wings produce lift ahead of center of gravity. Therefore, low time of wings unfolding is required. For high angles of wings rotation (low sweep angles), UAV model is stable in a wide range of angles of attack. Local aerodynamic defects were found in the area of the rotation units of both wings. Longitudinal vortex along the left side of fuselage was observed, but it does not result in significant roll moment. Further research might include UAV dynamics modelling based on calculated aerodynamics characteristics or flight tests.

**Keywords:** tandem-scheme UAV, tube launch, aerodynamic performance, flow separation, longitudinal static stability, computational fluid dynamics, Ansys software

## **1. Introduction**

Tube launched unmanned aerial vehicles (UAV) are often implemented with so-called tandem-scheme, i.e., an aerodynamic scheme with forward and rear wings (**Figure 1**). It allows decreasing of the UAV size in folded state inside the tube, e.g., wingspan might be 30–40% <1 for a conventional aerodynamic scheme. So this aerodynamic scheme has become quite widespread in the twenty-first century [1–3].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

**Figure 1.** Tube launched UAVs: "Switchblade," "Sokil-2," "Trident" (in folded state).

Specificity of such UAVs is that immediately after launch, they have a flight path in which wings are turned from the position along the fuselage to flight position with sweep angles equal to about zero [4].

The **goal** of this work is the determination of the aerodynamic characteristics of tube launched tandem-scheme UAV after its start, at the time of wings' unfolding.
