# Design, Manufacturing, and Flight Testing of an Experimental Flying Wing UAV

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## Abstract

**:**

## 1. Introduction

## 2. Aircraft Conceptual Design

#### 2.1. Stall Speed

_{s}) and the maximum lift coefficient (${C}_{{L}_{\mathrm{max}}}$), the wing loading is calculated as:

#### 2.2. Maximum Speed at Cruising Altitude

_{max}) and the efficiency of the propeller must be equal to the power required (P

_{req}) under the maximum constant speed condition. Because the engine output power decreases with increasing flight altitude, the relationship between engine power and altitude is considered based on the air density. According to the maximum speed (V

_{max}) required at cruising altitude, the power loading at sea level can be calculated as:

_{pr}is the propeller efficiency and σ is the ratio of the cruising altitude density to the sea level density.

#### 2.3. Absolute Ceiling

_{pr}is the propeller efficiency and σ

_{AC}is the ratio of the ceiling density to the sea level density.

#### 2.4. Turn Radius

_{pr}is the propeller efficiency, σ is the ratio of the cruising altitude density to the sea level density, V

_{turn}is the specific speed at the turning radius, and R is the turning radius.

#### 2.5. Matching Plot

^{2}.

- The maximum lift coefficient is 1.2 and the stall speed at sea level is 9 m/s. The left area of the vertical black dashed line (1) in Figure 2 satisfies the stall speed.
- At cruising altitude (100 m), the cruising speed is 1.15 times the maximum lift-to-drag ratio speed and the maximum speed is 1.2 times the cruising speed. The area below the blue solid line (2) in Figure 2 satisfies the requirement of the maximum speed at cruising altitude.
- The absolute ceiling is 500 m. The absolute ceiling demand is achieved by the area below the red solid line (3) in Figure 2.
- At cruising altitude (100 m), the turn radius is 15 m at speed of 10 m/s. The area below the purple dashed line (4) in Figure 2 satisfies the requirement of the turning radius at a specific speed (10 m/s) at cruising altitude.

## 3. Weight Estimation for an Electric UAV

#### 3.1. Battery Weight Estimation with Endurance Requirement

_{battery}is calculated as:

_{others}= 0.1·P

_{RMin}, the amount of aircraft power required between the start and end of flight includes take off and climb.

_{RMin}is:

_{RMin}) occurs when $({C}_{L}{}^{3/2}/{C}_{D})$ is maximum [5].

#### 3.2. Battery Weight Estimation with Range Requirement

_{0}and flight end position R

_{1}, and it can be expressed as:

#### 3.3. Weight Estimation for a Specific Payload and Endurance

^{2}. The estimated total weight of the electric UAV is 6.5 kg, empty weight is 2.62 kg, and battery weight is 1.38 kg.

## 4. Aircraft Aerodynamic and Stability Design

#### 4.1. Aerodynamic Configuration and Stability Design

#### 4.2. Design of Experimental Flying Wing UAV

^{2}and total weight of 63.7 Nt (total mass of 6.5 kg), the wing area is calculated to be 1.07 m

^{2}; aerodynamic design and static stability design are based on this wing area. Figure 3b shows the s5010 airfoil profile. The aerodynamic characteristics are estimated using XFLR5 [17] and DATCOM software. The cruise speed is 17.6 m/s, root chord is 0.54 m, tip chord is 0.22 m, wingspan is 2.83 m, aspect ratio is 7.48, sweep angle is 30°, twist angle is −4°, dihedral angle is 2°, and flight angle of attack is 4°.

## 5. Manufacturing Experimental Flying wing UAV

## 6. Flight Test

## 7. Discussion

^{2}. The performance of our flying wing UAV is as follows.

- The maximum lift coefficient is still assumed to be 1.2, and the stall speed at sea level is 11.77 m/s.
- At cruising altitude (100 m), the cruising speed is 23.06 m/s and cruising power is 113 W. The maximum speed at cruising altitude is 25.36 m/s and maximum power demand is 192 W.
- The absolute ceiling is still 500 m.
- At cruising altitude (100 m), the turning factor (load factor) is 1.21, and the turning radius is 25.13 m at flight speed of 12.94 m/s.

## Supplementary Materials

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 5.**Relationship between the lift coefficient and the angle of attack and relationship between the pitching moment coefficient and the angle of attack.

**Figure 9.**(

**a**) Predesigned size of Styrofoam mold (fuselage) and (

**b**) design size of mold consisting of Styrofoam, glass fiber, and epoxy resin (fuselage).

**Figure 13.**(

**a**) Main structural modules (left and right wings) and secondary structural modules (wing tip) and (

**b**) experimental flying wing UAV.

Parameter | Symbol | Value |
---|---|---|

Propeller efficiency | η_{Pr} | 0.7 |

Motor Efficiency | η_{motor} | 0.8 |

Battery Discharge Efficiency | η_{discharge} | 0.95 |

Empty mass density per Wing Surface Area | ρ_{Empty} | 2.44 Kg/m^{2}23.91 Nt/m ^{2} |

Depth of Discharge | f_{DOD} | 0.9 |

Battery Power density | ρ_{Battery} | 243 (Wh/Kg) 24.80 (Wh/Nt) |

Parameter | Symbol | Value |
---|---|---|

Zero lift drag coefficient | ${C}_{{D}_{0}}$ | 0.009 |

Induced drag factor | K | 0.0516 |

Cruising speed | V | 17.6 m/s |

Maximum speed | V_{Max} | 21.15 m/s |

Wing area | A | 1.07 m^{2} |

Wing root chord | Cr | 0.54 m |

Wing tip chord | Ct | 0.22 m |

Wing span | b | 2.83 m |

Wing aspect ratio | AR | 7.48 |

Wing sweep angle | Λ | 30 deg |

Wing twist angle | α_{twist} | −4 deg |

Wing dihedral angle | Γ | 2 deg |

Wing attack angle | α | 4 deg |

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**MDPI and ACS Style**

Chung, P.-H.; Ma, D.-M.; Shiau, J.-K.
Design, Manufacturing, and Flight Testing of an Experimental Flying Wing UAV. *Appl. Sci.* **2019**, *9*, 3043.
https://doi.org/10.3390/app9153043

**AMA Style**

Chung P-H, Ma D-M, Shiau J-K.
Design, Manufacturing, and Flight Testing of an Experimental Flying Wing UAV. *Applied Sciences*. 2019; 9(15):3043.
https://doi.org/10.3390/app9153043

**Chicago/Turabian Style**

Chung, Pei-Hsiang, Der-Ming Ma, and Jaw-Kuen Shiau.
2019. "Design, Manufacturing, and Flight Testing of an Experimental Flying Wing UAV" *Applied Sciences* 9, no. 15: 3043.
https://doi.org/10.3390/app9153043